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Article

Chemical and Textural Variability of Zircon from Slightly Peralkaline Madeira Albite Granite, Pitinga Magmatic Province, Brazil

by
Karel Breiter
1,*,
Hilton Tulio Costi
2,
Zuzana Korbelová
1 and
Marek Dosbaba
3
1
Institute of Geology, Czech Academy of Sciences, Rozvojová 269, CZ-16500 Praha, Czech Republic
2
Museu Paraense Emílio Goeldi, CP 8608, Belém 66075-100, PA, Brazil
3
TESCAN ORSAY HOLDING, Libušina třída 21, CZ-62300 Brno, Czech Republic
*
Author to whom correspondence should be addressed.
Minerals 2025, 15(8), 863; https://doi.org/10.3390/min15080863
Submission received: 2 July 2025 / Revised: 7 August 2025 / Accepted: 13 August 2025 / Published: 15 August 2025
(This article belongs to the Special Issue Tectono-Magmatic Evolution of the Amazonian and São Francisco Cratons: Insights from Thermochronological and Geochronological Data)
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Versions Notes

Abstract

Zircon is one of the most common accessory minerals in all types of granitoids. Due to its resistance to secondary processes, it preserves information about the composition of magma and conditions at the time of crystallization. Madeira albite granite, Brazil, offers optimum conditions for the study of chemistry and shape of zircon and the relation between the contents of particular trace elements in magma vs. in crystallizing zircon. Textural and chemical zircon data obtained using scanning electron microscopy (BSE) and cathodoluminescence (CL) imaging, automated mineralogy by TESCAN Integrated Mineral Analyzer (TIMA), and electron probe microanalyses (EPMA) enabled us to define four albite granite facies containing zircons of specific structures and chemistry. Zircon in the Madeira albite granite was formed during several, largely temporally and spatially independent episodes. During the crystallization of the common facies, occupying most of the intrusion volume, Zr/Hf value in zircon decreased from 40 to 20. This zircon, in some episodes, incorporated a higher amount of Th, which was later unmixed in the form of thorite inclusions. The pegmatoidal facies, representing crystallization of residual magma, contains zircon without thorite inclusions with a Zr/Hf value from 35 to 5. The Th/U and Y/Yb values during this evolution scattered but generally evolved to Th, Yb-enriched compositions (Th/U up to >10, Y/Yb down to 0.1). The Li-poor facies, located in the center of the stock near the cryolite deposit, contains zircon with comparatively high Zr/Hf = 45–70 and higher U and Y contents. Later, part of the common facies was hydrothermally altered to border facies, but zircon did not change noticeably during this process. The contents of minor elements in all zircon varieties are generally low (U + Th + Y + REE ˂ 0.05 apfu); Y and REE are incorporated exclusively in the xenotime component. Many crystals have low analytical totals, down to 95 wt%, and are enriched in Al, Fe, Mn, Ca, and F but this process does not influence the primary Zr/Hf, Th/U, and Y/Yb ratios. Zircons from other Madeira granite facies, including the neighboring Europa pluton, differ mainly in much higher Y/Yb values and in having (Y + REE) >> P, indicating a different than xenotime substitution mechanism. Zircon from the Madeira albite granite differs from zircons from many metaluminous rare-metal granites in low contents of minor elements and a common assemblage with thorite, instead of forming Zrn–Thr–Xnt solid solutions.

1. Introduction

Zircon is one of the most widespread accessory minerals in intermediate and acid igneous rocks [1,2,3,4,5] including rare-metal granites [6,7,8,9,10,11]. In common S- and I-type granitoids, Zr behaves as a compatible element and zircon is one of the early crystallized minerals. Therefore, the contents of Zr in the melt decrease during the fractionation, which results in lower zircon contents in later rocks facies. In such a situation, Zr mineralization cannot occur. In contrast, in P-poor metaluminous or slightly peralkaline granitoids, Zr is, together with other high field strength elements (HFSE) like Hf, Nb, Th, Y, and REE, progressively concentrated and can reach economically interesting contents [12]. Yet higher concentrations can be reached in strongly peralkaline rocks but most Zr in these rocks is bound to different zirconosilicates [13,14,15,16].
The Madeira pluton, along with the major associated secondary tin deposit [17], is in some parts enriched also in Nb, REE, U, Th, and Zr, which makes it an extremely interesting object both economically and scientifically. Our interest focuses on the slightly peralkaline Madeira albite granite, in which zircon forms a common association with thorite, xenotime, cassiterite, pyrochlore, and cryolite, and which offers optimum conditions to study the chemistry and shapes of zircon grains from different types of magma and to disclose the relation between the contents of particular trace elements in magma vs. in crystallizing zircon. While cassiterite, thorite, pyrochlore, REE phases, and cryolite from Madeira have been studied in detail in the recent past [17,18,19,20,21,22], zircon has received, with the exception of geochronological studies by Costi et al. [23], only a limited attention. The contents of REE and some trace elements in Madeira zircon were analyzed by Nardi et al. [24] using laser ablation inductively coupled mass spectrometry (LA-ICP-MS) which allowed us to determine very low concentrations of trace elements. However, this method does not allow quantitative determination of the contents of F or Zr as the main elements and therefore the determination of the analytical sum for assessing zircon hydration and structural damage due to irradiation. Breiter et al. [12] provided several EPMA analyses of Madeira zircon, stressing its high Hf contents, and recently Lamarao et al. [10] published a textural study of Madeira zircon crystals complemented with an extensive set of semiquantitative (SEM-EDS method) analyses.
We decided to conduct a detailed study of the texture and chemical composition of zircon from all facies of the Madeira albite granite with the objective to (i) define the contents of major and minor elements in zircon in all petrologically distinguishable pluton facies, (ii) compare the chemistry of zircon from albite granite with that from other types of granites of the Pitinga province, and rare-metal granites in general, (iii) construct a genetic model of zirconium mineralization based on a combination of zircon texture and chemistry.

2. Geological Setting and Samples

The Madeira pluton together with the neighboring Água Boa and Europa plutons form the Pitinga magmatic province (1829–1818 Ma, [23], Figure 1), situated in the central part of the Amazon Craton, Brazil [23,25,26,27]. The basement of the Pitinga province is composed of (1) effusive and explosive volcanics of the Iricoumé Group, 1889–1888 Ma in age [23], composed of rhyolites, dacites, and their tuffs and ignimbrites in the NE part of the area [18,28]; (2) comagmatic syenogranites and alkali–feldspar granites of the Mapuera suite E and S of the Madeira pluton (1875 ± 4 Ma, [28]); and (3) contemporaneous calc–alkaline granitoids of the Água Branca suite in the western part of the region [23]. The Madeira suite, being 50 My younger than the basement granitoids, represents a new stage of magmatism with a distinct A-type character [23,28].
The Madeira pluton (60 km2) consists of four principal rock types [17,18,25,29]. The early metaluminous porphyritic amphibole–biotite granite (1824 ± 2 Ma, [23]) contains plagioclase-mantled K-feldspar phenocrysts and is usually referred to as the “rapakivi granite”. The rapakivi granite was followed by somewhat younger metaluminous biotite granite (1822 ± 2 Ma, [23]). Both mentioned granites were later intruded by a stock of peralkaline albite granite, traditionally termed “albite granite”, intercalated with a sheet-like body of porphyritic “hypersolvus granite”.
The albite granite body, 2 × 1.3 km in outcrop, is composed of two principal facies. The inner (deeper) part of the body is peralkaline, enriched in disseminated cryolite, and contains two major zones composed of thick veins and pods of cryolite and a number of nests of intragranitic cryolite-rich pegmatites [18,19,20]. The albite granite is, in some parts, strongly enriched in cassiterite [17], thorite [21], and zircon. The peralkaline facies is supposed to more or less represent the primary magmatic stage of the intrusion and was referred to as the “core facies” [25]. The outer shell of the intrusion of albite granite underwent pervasive hydrothermal alteration; Costi et al. [17,25] termed this facies as “border facies”. For a detailed geological map, see the Supplementary Materials.
A sheet-like body of porphyritic hypersolvus alkali feldspar granite was found outcropping to the west of albite granite; it was also reached by several boreholes below the sheet of albite granite. In outcrop, the hypersolvus granite has a sharp contact with the albite granite, while in boreholes it forms intercalations and interdigitations with the latter. Costi et al. [23] dated the hypersolvus granite at 1818 ± 2 Ma and, based on interactions along their contact, interpreted the albite and hypersolvus granites to be generally coeval.
The Europa pluton, located to the NW of the Madeira pluton, is a homogeneous circular body, 90 km2 in areal extent, formed by peralkaline hypersolvus alkali feldspar granite 1829 ± 1 Ma in age [23].
The relatively large Água Boa pluton (350 km2), 1783–1798 Ma in age [30], situated to the NE, predominately consists of biotite granite with a small proportion of amphibole–biotite granite and topaz-bearing granite [17], followed by greisenization and episyenitization with a distinct Sn mineralization [31,32].
Twenty-two representative samples (five mounts of separated zircon grains and 17 thin sections) from the Madeira albite granite, spread across the entire surface and depth of the pluton, were selected for a detailed study of zircon. Samples from the other Madeira granite facies and the Europa pluton were studied on a small scale for comparison. For the list of studied samples, see Supplementary Table S1.

3. Methods

Back-scattered electron (BSE) and cathodoluminescent (CL) images of isolated zircon crystals/grains were acquired using a TESCAN Mira3 FEG scanning electron microscope (TESCAN ORSAY HOLDING, Brno, Czech Republic) housed at the Museu Paraense Emílio Goeldi, Belém, Brazil.
Back-scattered electron (BSE) images of zircon in thin sections were acquired using TESCAN Vega 3XMU scanning electron microscope (TESCAN ORSAY HOLDING, Brno, Czech Republic) housed at the Institute of Geology of the Czech Academy of Sciences, Praha.
A TESCAN Integrated Mineral Analyzer (TIMA) based on a TESCAN MIRA FEG-SEM platform in the demonstration facility of TESCAN ORSAY HOLDING in Brno, Czech Republic, was used for automated mineralogical, modal, and textural analyses. This included collecting back-scattered electron (BSE) and energy dispersive (EDS) data on a regular grid of 10 μm point spacing. Acceleration voltage of 25 kV and a beam current of 10 nA were used during the data acquisition. The individual points were grouped based on a similarity search algorithm, and areas of coherent BSE and EDS data were merged to produce segments (i.e., mineral grains). The results were plotted as a map showing the distribution of minerals within the sample [33].
Electron probe microanalysis (EPMA) was used to study the chemistry of zircon. Although this method does not allow the determination of trace amounts of elements present, like, for example, laser ablation inductively coupled mass spectrometry (LA-ICP-MS), it is able to accurately determine the contents of major and minor elements including the total analytical sum, also in very inhomogeneous mineral grains. Zircon was analyzed using the Jeol JXA—8230 electron microprobe (Jeol Ltd., Tokyo, Japan) housed at the Institute of Geology of the Czech Academy of Sciences, Praha, Czech Republic, operated in the wavelength-dispersive mode. Elemental abundances of F, Al, Si, P, S, Ca, Sc, Ti, Mn, Fe, As, Y, Zr, Nb, La, Ce, Nd, Sm, Dy, Er, Yb, Hf, W, Pb, Bi, U, and Th in zircon were determined at an accelerating voltage of 15 kV and a beam current of 15 nA and with a beam diameter of 1–2 μm. The counting times on peaks were optimized for individual elements according to their expected concentrations (20–60 s), and twice half that time was used to obtain background counts on both sides of the peak. X-ray lines and background offsets were selected to minimize interference. The following reference materials were used: fluorite (F), corundum (Al), quartz (Si), apatite (P), barite (S), diopside (Ca), metallic Sc (Sc), rutile (Ti), Mn3O4 (Mn), hematite (Fe), gallium arsenide (As), synthetic cubic zirconia (Y, Zr), metallic Nb (Nb), REE glass standard La, Ce, Dy, Er, Nd, Sm, Yb, metallic hafnium (Hf), metallic W (W), crocoite (Pb), metallic Bi (Bi), metallic Th (Th), and metallic U (U). In all minerals, raw data were processed using the PRZ correction procedure (XPP method metal/oxide was applied). Empirically determined correction factors were applied to the overlapping X-ray lines. Detection limits (3 sigma) in wt% are 0.009 (S), 0.012 (P), 0.013 (Ti), 0.015 (Hf), 0.018 (Ca), 0.020 (Nb, Sc), 0.025 (Si), 0.025 (La, U), 0.027 (Pb), 0.028 (F, Ce), 0.035 (Th), 0.040 (As, Ba), 0.048 (Gd, Mn), 0.050 (Er), 0.060 (Al, Fe, Y), 0.065 (Yb), 0.070 (Na), 0.075 (Zr), and 0.110 (Dy).
Empirical formulae were calculated on the basis of four atoms of oxygen in a formula unit (apfu).
Abbreviations of mineral names following [34]: Ab = albite, Amp = amphibole, Ann = annite, Crl = cryolite, Cst = cassiterite, Flr = fluorite, Gn = galena, Hem = hematite, Ilm = ilmenite, Kfs = K-feldspar, Mnz = monazite, Pcl = pyrochlore, Px = pyroxene, Py = pyrite, Rbk = riebeckite, Rt = rutile, Qtz = quartz, Thr = thorite, Xnt = xenotime, Zrn = zircon. Other abbreviations used: REEF = fluoride of REE.

4. Results

4.1. Geological Structure of the Madeira Albite Granite

Two facies of albite granite, a generally magmatic core facies, and a hydrothermally strongly altered border facies, were already distinguished in the early stages of pluton exploration [17,18,25,29]. Nevertheless, a closer look at the results of chemical analyses from boreholes and outcrops, and the mineral composition of granite allow us to define at least three subfacies within the core granite, although a graphical 3D expression of their spatial distribution is not yet possible: (i) “common” subfacies, (ii) “pegmatoidal” subfacies, and (iii) “Li-poor” subfacies. The fourth facies remains the previously well-defined border facies. In the following text, we describe zircon consistently according to its affiliation with these four albite granite facies (Figure 2).
The common facies forms a substantial part of the body (samples PHR-82A, 160, 163, 239, 242, 244, and 245). It always contains, besides quartz and feldspars, two micas (lepidolite + annite), alkali pyroxene or amphibole, cryolite and an assemblage of HFSE minerals zircon, thorite, xenotime, pyrochlore etc. This facies is generally strongly fractionated (Zr/Hf = 26, Nb/Ta = 8.9, K/Rb = 7.6; means of 8 analyses) and rich in F (1.6–3.2 wt%), Li (ca. 0.15 wt% Li2O), and many trace elements: 3000–5000 ppm Rb, 800–1200 ppm Nb, 90–260 ppm Y, 62 ppm Yb, 90–200 ppm Ta, 500–800 ppm Pb, 150–750 ppm Sn, 200–300 ppm Hf, 4600–8400 ppm Zr, and 200–1200 ppm Th. All bulk-rock chemical data in this chapter and sample numbers follow [29].
The pegmatoidal facies (samples PHR-127, 128) was documented in outcrops in the northern part of the body. It is texturally highly variable, often layered with pegmatite schlieren (compare pictures in Supplementary Materials). Mineral composition is similar to that of the previous rock type, but the grade of fractionation is even higher: Zr/Hf = 9.8, Nb/Ta = 6, K/Rb = 5.7. The contents of F, Li Hf, Nb, Ta, Th, and Y are similar, the contents of Pb, Rb, Sn, and Zn are higher (5000–7500 ppm Pb, 5000–7500 ppm Rb, 1300–1400 ppm Sn, and 1000–3000 ppm Zn), and the contents of Zr are lower (2000–4600 ppm) than in the common facies.
The third facies (samples PHR-240, 241, 246, 247, 248, and 249) was found in some boreholes near the cryolite-rich nucleus of the intrusion (FC-8, 250N/950W, 250S/500W). This granite type contains Zn, Rb, and Cs-rich annite as the only dark mineral. No bulk-rock data are available, but the lack of Li minerals and the relatively high Zr/Hf value of zircon (see further text) indicate low bulk-rock content of Li and a relatively lower grade of fractionation.
The outer shell of the intrusion of albite granite, referred to as the “border facies” ([25], Figure 2d), underwent pervasive hydrothermal alteration: it is now locally slightly peraluminous (aluminum saturation index ASI = 0.9–1.14) and contains common fluorite instead of cryolite. The HFSE were not very mobile during this alteration and their contents in border albite granite are roughly in the same range as in the most common subfacies of the core albite granite (900–1600 ppm Nb, 90–260 ppm Ta, 500–2500 ppm Sn, 3000–7000 ppm Zr, and 200–400 ppm Hf [29]).
Modal composition of the studied granites is presented in Table 1. Albite granite contains 0.24–2.69 wt% of zircon, usually accompanied by common thorite [21] and pyrochlore [22], and rather scarce xenotime. Up to 3.8 vol% of zircon was reported [25] from the border albite granite, while less than 0.2 wt% of zircon was found in other studied granite types.

4.2. Shape and Structure of Zircon Crystals and Aggregates

The shape and internal structure of zircon in the Madeira albite granite are surprisingly variable but zircon crystals from each of the previously defined granite facies share typical features, as shown in Figure 3, Figure 4, Figure 5 and Figure 6.
Zircon grains up to 1–2 mm across with distinct two-stage evolution are typical for the most widespread common facies (samples PHR-82A, mounts 213 and 214; Figure 3). Most crystals have originally euhedral but later partially resorbed cores, surrounded by one to several (mostly two) zones of euhedral growth (Figure 3a,b). The core is densely sieved with numerous very fine-grained thorite and scarcely also xenotime inclusions. The outer zone/zones is/are free of tiny inclusions but may contain individual larger thorite or pyrochlore grains and common inclusions of albite and cryolite. The thin outermost zone is sometimes enriched in Hf and thus relatively bright in BSE. The zoned structure is better visible on CL images, including a repetition of episodes of euhedral crystallization and resorption. The youngest rim, bright in BSE, is enriched in Hf (Figure 3a). Nevertheless, some grains show a zoning reversal: a spotted zoned euhedral core without inclusions (darker inner core + brighter outer core) is rimmed with relatively BSE-dark overgrowth zone packed with thorite inclusions (Figure 3c,d). Relatively scarce subhedral grains/crystals have a simple two-zone structure with relatively thin CL-brighter (Hf-enriched) rims; these grains are thorite inclusions-free, containing only scarce inclusions of silicates (Figure 3e). However, subhedral to euhedral grains with a predominance of an outer light zone over a darker center were also found (Figure 3f).
Zircon in the locally fluidal pegmatoidal subfacies is more uniform. Most grains are anhedral to subhedral, densely sieved with µ-sized silicate and cryolite inclusions (Figure 4a,b), sometimes with large laths of albite (Figure 4c) but free of inclusions of thorite or xenotime. Occasionally, such cores are rimmed with up to 200 µm thick brighter mottled overgrowths with both silicate and thorite inclusions. Also, here, complicated internal structure is better visualized in CL (Figure 4d). Euhedral crystals with mottled cores with medium-grained albite, K-feldspar and hematite inclusions, and thick homogeneous bright Hf-rich rims were found locally (Figure 4e). Similarly, small euhedral zircon grains embedded, together with thorite, in galena (Figure 4f) are only of mineralogical interest.The Li-poor subfacies contains zircon grains of several types. The first type, sub- to euhedral grains packed with tiny silicate inclusions, is similar to the most common type from previous subfacies (Figure 5a) and is probably of primary magmatic origin. Other zircon grains show signs of subsequent alterations of different degrees. Common are grains with preserved euhedral shapes but with a variable intensity of spotty alteration of the entire volume of the crystal (Figure 5b,c). Zircon grains associated with thorite are often rimmed or replaced with Fe-oxide (Figure 5d,e). The final stage of this process is represented with hematite–cryolite–zircon aggregates (Figure 5f).
The border facies, although macroscopically and petrographically different from the core facies [25], contains zircon very similar to that from the common core subfacies. Sieved cores with many tiny thorite and coffinite inclusions and larger silicate inclusions, either euhedral (Figure 6a–e) or partially resorbed (Figure 6f), are rimmed with mottled or homogeneous outer zone, sometimes distinctly brighter in BSE (Figure 6c). The border between the core and the overgrowth can be sharp (Figure 6a,b,e), in some cases blurry or transient (Figure 6c,d,f). The main difference between this zircon and two-stage zircon from the common core subfacies is the frequent presence of xenotime and thorite inclusions also in the outer zone of the crystal (Figure 6a,c).
Zircon from hypersolvus granite usually forms subhedral, homogeneous, or indistinctly zoned grains 100–200 μm across in an assemblage with rutile, ilmenite, and monazite embedded in biotite (Figure 7a). Small grains sieved with silicate microinclusions with a homogeneous overgrowth, resembling two-phase zircons from the border and “common” core subfacies of albite granite were scarcely found (Figure 7b). Zircons from biotite and amphibole–biotite granites form clusters of small (<100 μm) sub- to euhedral homogeneous or indistinctly zoned crystals, together with other associated accessory minerals, embedded in biotite (Figure 7c,d). Zircon from strongly peralkaline Europa granite usually forms sub- to euhedral homogeneous grains 200–500 μm across, sometimes with tiny thorite inclusions (Figure 7e); however, rare, zoned grains were also found (Figure 7f).

4.3. Chemical Composition of Zircon

In total, 330 EPMA analyses of zircon from the Madeira albite granite and 67 EPMA analyses of zircon from other Madeira granite facies and neighboring Europa pluton were performed. Typical analyses are shown in Table 2. Relations among major chemical constituents are presented in Figure 8 and Figure 9.
Analytical totals for zircons from all subfacies of the Madeira albite granite varied between 101 and 94 wt%. Values lower than 98 wt% can no longer be attributed to analytical inaccuracy but reflect changes in chemistry due to structural damage [35]. In all facies of the Madeira pluton, nearly half of all analyses fall within this interval. In the Madeira biotite granite and the neighboring Europa pluton, 60% of the analyzed grains show analytical totals < 98 wt%, commonly down to 88 wt%, i.e., indicating a strong structural damage. Spots with low analytical totals indeed correlate with higher abundances of radioactive elements U + Th (Figure 8a). A decrease in analytical sum below 97 wt% is also accompanied by a strong increase in F contents (up to 0.9 wt%, i.e., 0.1 apfu F, Figure 8b).
Hf is the third most common element in zircon after Zr and Si (Figure 8c). Hf is chemically similar to Zr and replaces Zr in the crystal lattice of zircon without restriction, forming a fully isomorphic zircon–hafnon series [36]. The highest Hf contents up to 12–14 wt% HfO2 (0.11–0.13 apfu Hf) were found in grains from the pegmatoidal subfacies of albite granite and in thin crystal rims in the border facies. Much lower contents of up to 10.7 wt% HfO2 (0.095 apfu) were found in crystal rims in the common albite granite subfacies, while contents in the range of 1.5–2.0 wt% HfO2 (around 0.02 apfu Hf) are common in other granite types. The sum of Zr and Hf in the Madeira albite granite is close to 1 apfu, indicating relative purity of this zircon: max. 0.01 apfu of other elements at the Zr + Hf site were found in the analyzed zircon grains from the border facies and mostly <0.02 apfu in all core subfacies, while 0.1–0.3 apfu impurities or vacations were found in the Madeira biotite granite and Europa riebeckite granite.
Y and HREE are common minor constituents of zircon: 1–8 and 0.5–4 wt% Y2O3 (up to 0.17 apfu Y) were found in zircon from the Madeira biotite granite and Europa riebeckite granite, respectively. In contrast, zircon from the Madeira albite granite contains less than 0.5 wt% Y2O3. Among the monitored HREE, the highest values in the range of 0.2–0.6 wt%, occasionally up to 1.4 wt% Yb2O3 (0.015 apfu Yb) and up to 1.1 wt% Yb2O3, were found in zircon from the pegmatoidal albite granite and altered Li-poor granite, respectively. The contents of Dy and Er are lower, usually ˂0.2 wt% Er2O3 and Dy2O3. Due to their broad variability, HREE contents cannot be used for the classification here. However, distinct differences were found in the case of Y/Yb values (Figure 8d).
Table 2. Chemical compositions (wt%) and empirical formulae (apfu) of zircon. For the locations of the analyses see Figure 3, Figure 4, Figure 5, Figure 6 and Figure 7.
Table 2. Chemical compositions (wt%) and empirical formulae (apfu) of zircon. For the locations of the analyses see Figure 3, Figure 4, Figure 5, Figure 6 and Figure 7.
PlutonMadeira
Rock TypeAlbite Granite, Border Facies
Sample215
Crystal3637
PositionUnmixed CoreUnmixed CoreRimRimRimRimUnmixed CoreRimRimRimRim
Spot589590591592593594566567568569570
P2O50.200.320.280.160.210.290.430.370.200.270.40
As2O50.000.010.000.000.000.000.000.010.000.000.00
Nb2O50.000.000.000.000.000.000.000.000.000.000.00
SiO231.8630.5731.8332.1531.9031.1830.0830.1231.8931.4831.61
TiO20.000.000.000.000.000.000.000.000.000.000.00
ZrO263.2361.4162.3362.4862.6356.2661.6461.1561.6456.5355.09
HfO23.983.095.055.655.1211.043.033.315.2511.7912.87
ThO20.000.140.060.000.030.060.140.030.050.080.02
UO20.040.190.010.030.000.000.110.120.020.020.00
Y2O30.050.320.130.040.140.120.470.250.060.120.26
Dy2O30.060.000.080.000.010.000.000.000.000.000.00
Er2O30.070.080.040.070.080.040.190.160.120.100.23
Yb2O30.210.400.380.260.340.540.450.350.260.460.89
Al2O30.000.050.000.000.000.000.040.000.000.000.00
Sc2O30.000.020.000.000.000.000.000.000.000.000.00
Bi2O30.010.000.000.000.020.000.000.010.030.000.01
MnO0.000.190.000.000.000.000.070.140.020.000.03
FeO0.050.810.000.000.000.000.861.160.000.020.04
CaO0.000.240.010.000.010.000.130.330.010.010.00
PbO0.000.040.010.010.000.050.050.000.000.000.01
SO30.000.000.000.000.000.000.000.000.000.000.00
F0.000.000.000.000.000.000.000.000.000.000.00
Total99.7797.87100.22100.85100.5099.5797.6897.5099.55100.89101.47
P0.0050.0090.0070.0040.0050.0080.0120.0100.0050.0070.011
As0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Nb0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Si0.9930.9760.9920.9970.9921.0010.9650.9681.0001.0011.004
Ti0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Zr0.9610.9560.9480.9450.9500.8810.9640.9580.9420.8760.853
Hf0.0350.0280.0450.0500.0450.1010.0280.0300.0470.1070.117
Th0.0000.0010.0000.0000.0000.0000.0010.0000.0000.0010.000
U0.0000.0010.0000.0000.0000.0000.0010.0010.0000.0000.000
Y0.0010.0050.0020.0010.0020.0020.0080.0040.0010.0020.004
Dy0.0010.0000.0010.0000.0000.0000.0000.0000.0000.0000.000
Er0.0010.0010.0000.0010.0010.0000.0020.0020.0010.0010.002
Yb0.0020.0040.0040.0020.0030.0050.0040.0030.0020.0040.009
Al0.0000.0020.0000.0000.0000.0000.0020.0000.0000.0000.000
Sc0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Bi0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Mn0.0000.0050.0000.0000.0000.0000.0020.0040.0010.0000.001
Fe0.0010.0220.0000.0000.0000.0000.0230.0310.0000.0010.001
Ca0.0000.0080.0000.0000.0000.0000.0040.0110.0000.0000.000
Pb0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
S0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
F0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Zr/Hf27.1433.9521.0918.8920.908.7134.7531.5620.068.197.31
Y/Yb0.381.380.600.280.730.391.811.240.410.440.51
Th/U0.000.754.720.07 1.310.272.513.82
PlutonMadeira
Rock TypeCore Albite Granite Pegmatoidal
SamplePHR-128212
Crystal3a3b11
PositionCoreRimCoreRimRimCoreCoreCoreRimRim
Spot4748495051632633634635636
P2O50.270.360.040.470.260.990.910.390.750.79
As2O50.000.000.000.000.000.000.010.000.000.00
Nb2O50.000.000.000.000.000.000.000.000.000.31
SiO231.6531.5132.0631.3330.4430.7529.8531.3830.9325.87
TiO20.000.000.000.000.000.000.000.000.000.00
ZrO262.5962.5562.8160.8152.8461.3360.0864.1860.8051.38
HfO24.865.264.485.2213.993.473.564.605.465.86
ThO20.090.040.000.110.150.020.020.000.311.97
UO20.000.020.030.020.000.000.090.020.000.05
Y2O30.150.280.000.360.260.580.360.100.561.20
Dy2O30.020.050.050.000.080.050.000.010.120.40
Er2O30.040.210.000.180.190.410.260.100.320.67
Yb2O30.230.480.000.450.570.891.020.531.001.25
Al2O30.000.000.000.000.000.000.000.000.000.46
Sc2O30.020.000.000.000.000.000.010.000.000.00
Bi2O30.010.000.040.000.010.000.000.010.000.00
MnO0.000.010.000.000.010.020.070.000.000.01
FeO0.040.070.000.070.230.020.550.000.000.89
CaO0.000.000.010.010.000.010.080.010.020.06
PbO0.000.000.000.000.020.000.120.010.042.67
SO30.000.000.000.000.000.000.000.000.000.00
F0.000.000.000.000.000.000.000.000.001.85
Total99.98100.8499.5399.0399.0698.5497.01101.35100.3095.68
P0.0070.0100.0010.0120.0070.0260.0250.0100.0200.024
As0.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Nb0.0000.0000.0000.0000.0000.0000.0000.0000.0000.005
Si0.9890.9811.0010.9900.9990.9720.9640.9710.9730.920
Ti0.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Zr0.9530.9500.9560.9370.8460.9450.9460.9690.9330.891
Hf0.0430.0470.0400.0470.1310.0310.0330.0410.0490.059
Th0.0010.0000.0000.0010.0010.0000.0000.0000.0020.016
U0.0000.0000.0000.0000.0000.0000.0010.0000.0000.000
Y0.0020.0050.0000.0060.0050.0100.0060.0020.0090.023
Dy0.0000.0000.0000.0000.0010.0000.0000.0000.0010.005
Er0.0000.0020.0000.0020.0020.0040.0030.0010.0030.007
Yb0.0020.0050.0000.0040.0060.0090.0100.0050.0100.014
Al0.0000.0000.0000.0000.0000.0000.0000.0000.0000.019
Sc0.0010.0000.0000.0000.0000.0000.0000.0000.0000.000
Bi0.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Mn0.0000.0000.0000.0000.0000.0010.0020.0000.0000.000
Fe0.0010.0020.0000.0020.0060.0010.0150.0000.0000.026
Ca0.0000.0000.0000.0000.0000.0000.0030.0000.0010.002
Pb0.0000.0000.0000.0000.0000.0000.0010.0000.0000.026
S0.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
F0.0000.0000.0000.0000.0000.0000.0000.0000.0000.208
Zr/Hf22.0020.3123.9519.906.4530.1928.8323.8319.0214.98
Y/Yb1.081.04 1.400.791.140.620.330.971.68
Th/U 3.04 6.30 0.210.00 42.68
PlutonMadeira
Rock TypeCommon Core Albite Granite
Sample213214
Crystal2218
PositionUnmixed CoreRimRimRimCoreCoreCoreUnmixed RimUnmixed Rim
Spot511512513514642643644645646
P2O50.320.200.270.540.180.360.070.530.24
As2O50.030.040.000.000.000.000.000.000.00
Nb2O50.000.000.000.000.000.010.000.110.00
SiO230.8030.2331.3531.0832.0028.9432.1328.2530.07
TiO20.000.000.000.000.000.040.000.070.03
ZrO261.7561.7262.0559.7462.4658.4164.0058.2261.95
HfO23.093.284.177.484.643.014.951.762.12
ThO20.470.050.030.070.070.280.010.880.43
UO20.110.070.020.000.000.090.010.350.15
Y2O30.270.210.040.350.120.700.000.970.22
Dy2O30.000.000.000.010.000.000.000.000.00
Er2O30.150.030.030.150.050.120.060.150.00
Yb2O30.340.180.410.630.280.360.090.590.20
Al2O30.060.090.030.000.000.700.000.610.38
Sc2O30.000.000.030.010.010.000.010.010.00
Bi2O30.000.010.000.010.000.040.000.000.00
MnO0.130.350.090.010.000.690.030.700.44
FeO0.451.110.460.020.031.320.001.321.28
CaO0.010.040.030.030.010.150.000.070.08
PbO0.060.070.000.000.000.070.000.160.12
SO30.000.000.000.000.000.000.000.000.00
F0.000.080.000.000.000.660.000.740.07
Total98.0397.7599.02100.1299.8495.96101.3695.5197.77
P0.0090.0050.0070.0140.0050.0100.0020.0150.007
As0.0000.0010.0000.0000.0000.0000.0000.0000.000
Nb0.0000.0000.0000.0000.0000.0000.0000.0020.000
Si0.9810.9690.9870.9820.9980.9530.9900.9400.962
Ti0.0000.0000.0000.0000.0000.0010.0000.0020.001
Zr0.9590.9650.9530.9210.9500.9380.9620.9450.966
Hf0.0280.0300.0370.0670.0410.0280.0440.0170.019
Th0.0030.0000.0000.0000.0010.0020.0000.0070.003
U0.0010.0010.0000.0000.0000.0010.0000.0030.001
Y0.0050.0040.0010.0060.0020.0120.0000.0170.004
Dy0.0000.0000.0000.0000.0000.0000.0000.0000.000
Er0.0010.0000.0000.0010.0000.0010.0010.0020.000
Yb0.0030.0020.0040.0060.0030.0040.0010.0060.002
Al0.0020.0030.0010.0000.0000.0270.0000.0240.014
Sc0.0000.0000.0010.0000.0000.0000.0000.0000.000
Bi0.0000.0000.0000.0000.0000.0000.0000.0000.000
Mn0.0030.0100.0030.0000.0000.0190.0010.0200.012
Fe0.0120.0300.0120.0000.0010.0360.0000.0370.034
Ca0.0000.0020.0010.0010.0000.0050.0000.0030.003
Pb0.0010.0010.0000.0000.0000.0010.0000.0010.001
S0.0000.0000.0000.0000.0000.0000.0000.0000.000
F0.0000.0080.0000.0000.0000.0680.0000.0780.007
Zr/Hf34.1432.1525.4213.6423.0033.1522.0956.5149.92
Y/Yb1.402.020.190.990.723.440.022.861.87
Th/U4.390.681.28 3.251.032.553.05
PlutonMadeira
Rock TypeLi-Poor Core Albite GraniteLi-Poor Core Albite Granite Altered
SamplePHR-249PHR-240PHR-241
Crystal262
Rem.PatchyAlteredPatchy Altered
Spot83083183283365666745464748
P2O50.070.060.140.160.670.550.110.120.060.070.15
As2O50.020.000.000.000.000.000.000.000.000.000.00
Nb2O50.000.000.000.000.000.000.000.000.000.000.00
SiO231.6531.7130.1029.8129.2429.1831.1030.7132.1032.0630.41
TiO20.020.010.000.000.000.000.000.000.000.000.00
ZrO265.4666.0762.4860.6059.7157.3563.1562.3964.7565.3162.14
HfO21.831.741.581.561.712.322.201.361.431.251.42
ThO20.000.000.020.020.060.410.110.000.010.000.00
UO20.030.010.230.280.260.340.160.240.030.000.16
Y2O30.050.000.110.190.660.760.070.030.060.000.05
Dy2O30.000.000.000.000.070.190.040.000.000.000.00
Er2O30.000.000.020.100.300.210.000.060.000.040.02
Yb2O30.060.020.260.251.010.790.190.080.000.000.16
Al2O30.020.000.290.440.420.520.050.240.000.000.27
Sc2O30.010.020.010.020.000.020.010.000.000.000.00
Bi2O30.000.000.000.030.000.000.010.000.000.000.01
MnO0.030.010.380.620.410.510.070.440.040.000.39
FeO0.000.010.651.161.512.181.350.720.050.000.83
CaO0.010.020.040.060.080.080.000.050.000.000.08
PbO0.040.020.050.100.060.060.010.040.000.010.07
SO30.000.000.000.000.000.000.010.000.000.000.00
F0.000.000.010.180.230.600.000.130.000.000.07
Total99.3199.7296.3595.5996.4296.0898.6496.6098.5498.7496.22
P0.0020.0020.0040.0050.0180.0150.0030.0030.0020.0020.004
As0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Nb0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Si0.9850.9830.9700.9710.9520.9600.9800.9831.0000.9960.978
Ti0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Zr0.9930.9980.9820.9630.9480.9200.9710.9740.9830.9900.975
Hf0.0160.0150.0150.0150.0160.0220.0200.0120.0130.0110.013
Th0.0000.0000.0000.0000.0000.0030.0010.0000.0000.0000.000
U0.0000.0000.0020.0020.0020.0020.0010.0020.0000.0000.001
Y0.0010.0000.0020.0030.0110.0130.0010.0000.0010.0000.001
Dy0.0000.0000.0000.0000.0010.0020.0000.0000.0000.0000.000
Er0.0000.0000.0000.0010.0030.0020.0000.0010.0000.0000.000
Yb0.0010.0000.0030.0020.0100.0080.0020.0010.0000.0000.002
Al0.0010.0000.0110.0170.0160.0200.0020.0090.0000.0000.010
Sc0.0000.0010.0000.0000.0000.0010.0000.0000.0000.0000.000
Bi0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Mn0.0010.0000.0100.0170.0110.0140.0020.0120.0010.0000.011
Fe0.0000.0000.0170.0320.0410.0600.0360.0190.0010.0000.022
Ca0.0000.0010.0020.0020.0030.0030.0000.0020.0000.0000.003
Pb0.0000.0000.0000.0010.0010.0010.0000.0000.0000.0000.001
S0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
F0.0000.0000.0010.0190.0240.0620.0000.0130.0000.0000.007
Zr/Hf61.1164.8767.5566.3659.6542.2349.0478.3777.3589.2674.76
Y/Yb1.550.300.721.321.141.680.640.61 0.56
Th/U0.000.000.080.090.241.230.70 0.22
PlutonMadeiraEuropa
Rock TypeAmp-Bt GraniteBt GraniteHypersolvus GraniteRbk Granite
SampleF13.50 mPHR-96PHR-176PHR-191PHR-197
Spot1415612133443444546
P2O50.020.010.110.100.270.070.210.090.140.06
As2O50.000.010.010.000.000.000.000.000.000.00
Nb2O50.000.000.000.000.000.000.000.000.000.00
SiO230.4831.5428.5031.7929.0730.5529.8131.6030.0631.55
TiO20.020.020.000.060.100.000.010.000.000.00
ZrO262.4264.7660.4367.0561.1362.1160.7666.6060.8066.25
HfO21.261.221.551.571.532.600.921.241.141.26
ThO20.100.000.180.000.210.000.110.000.060.00
UO20.080.050.350.070.130.170.140.010.170.00
Y2O30.120.000.300.060.730.032.490.261.390.25
Dy2O30.030.000.000.030.090.000.220.040.140.04
Er2O30.020.030.000.020.000.050.290.030.190.04
Yb2O30.090.100.120.000.080.050.390.080.310.02
Al2O30.030.001.290.010.670.070.010.000.220.00
Sc2O30.000.000.000.010.000.000.000.000.000.00
Bi2O30.130.110.020.020.000.020.000.000.000.00
MnO0.080.021.280.000.700.310.070.000.200.00
FeO0.460.222.000.331.450.630.460.030.810.16
CaO1.170.020.260.010.110.020.580.011.140.01
PbO0.010.010.000.000.000.000.080.020.000.00
SO30.010.000.010.000.000.000.000.010.030.01
F0.390.010.490.000.210.000.000.000.000.00
Total97.2198.5496.90101.1396.4896.6896.54100.0396.8099.66
P0.0010.0000.0030.0020.0070.0020.0060.0020.0040.002
As0.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Nb0.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Si0.9780.9900.9270.9740.9430.9820.9660.9770.9670.978
Ti0.0000.0010.0000.0010.0020.0000.0000.0000.0000.000
Zr0.9760.9910.9591.0010.9670.9740.9601.0040.9531.002
Hf0.0120.0110.0140.0140.0140.0240.0080.0110.0100.011
Th0.0010.0000.0010.0000.0020.0000.0010.0000.0000.000
U0.0010.0000.0030.0000.0010.0010.0010.0000.0010.000
Y0.0020.0000.0050.0010.0130.0000.0430.0040.0240.004
Dy0.0000.0000.0000.0000.0010.0000.0020.0000.0010.000
Er0.0000.0000.0000.0000.0000.0010.0030.0000.0020.000
Yb0.0010.0010.0010.0000.0010.0000.0040.0010.0030.000
Al0.0010.0000.0500.0000.0260.0030.0000.0000.0080.000
Sc0.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
Bi0.0010.0010.0000.0000.0000.0000.0000.0000.0000.000
Mn0.0020.0010.0350.0000.0190.0080.0020.0000.0050.000
Fe0.0120.0060.0540.0090.0390.0170.0130.0010.0220.004
Ca0.0400.0010.0090.0000.0040.0010.0200.0000.0390.000
Pb0.0000.0000.0000.0000.0000.0000.0010.0000.0000.000
S0.0000.0000.0000.0000.0000.0000.0000.0000.0010.000
F0.0400.0010.0500.0000.0220.0000.0000.0000.0000.000
Zr/Hf84.6390.9066.6072.9668.2540.81113.1491.7591.2789.82
Y/Yb2.490.024.2422.9216.060.9011.265.357.8621.64
Th/U1.35 0.54 1.58 0.83 0.37
The contents of Th and U in the studied zircon grains are generally very low. Usually, ˂0.5 wt% ThO2 in the Europa and ˂0.2 wt% ThO2 in all facies of the Madeira pluton were found. Higher Th values were found only occasionally in the Madeira biotite granite (up to 10 wt% ThO2, ca. 0.1 apfu Th). The contents of U were 0.5–1.2 wt% UO2 in the Europa riebeckite and Madeira biotite granites and <0.1 wt% UO2 in the core albite granite. In the latter, a local enrichment up to 0.6 wt% UO2 was found in altered crystals/aggregates in the pegmatoidal facies (Figure 8e).
The contents of P2O5 were mostly in the range of 0.2–0.5 wt%, rarely reaching 2.7 wt% in Y-rich zircon grains from the Madeira biotite granite. The ratio of P and Y + HREE is approaching one in all albite granite facies indicating a zircon–xenotime substitution. In other granite types, Y + HREE highly prevail over P, and another substitution mechanism must be expected (Figure 9a).
The contents of Ti reached up to 0.15 wt% TiO2 in the Europa riebeckite and Madeira biotite granites but are usually below the detection limit in the albite granite. The contents of Pb are generally lower than 0.05 wt% PbO with the exception of several crystals in sample PHR-127 (pegmatoidal core subfacies) with up to 0.30 wt% PbO in association with galena. The contents of W, Nb, Bi, and Sc only rarely exceed the detection limits of EPMA.
Elements like Al, Mn, Fe, and Ca, whose ion radius and charge do not fit into the structure of zircon, were still found in significant quantities. The highest contents of Al and Mn (up to 2.5 wt% Al2O3 and 1.25 wt% MnO) are typical for zircon from the Madeira biotite granite; the highest contents of Ca (up to 1.25 wt% CaO) were found in the Madeira biotite and amphibole–biotite granites and also in the Europa riebeckite granite. Zircons from all varieties of albite granite are comparatively Al, Mn, and Ca-poor. In contrast, a strong enrichment in Fe (2–2.6 wt% FeO) was found in some zircon grains in all investigated rock types, i.e., also in albite granite. The contents of all these elements, also called non-formula elements, correlate well with the decrease in analytical totals, i.e., with the increasing structural damage (Figure 9b–e).

5. Discussion

5.1. Comparison of the EPMA and LA-ICP-MS Data of Madeira Zircon

In 2012, Nardi et al. [24] analyzed zircon from the Madeira pluton using LA-ICP-MS. Although LA-ICP-MS and EPMA are fundamentally different methods both in terms of detection limits and the analyzed volume of material, the determined element contents and their ratios are in good agreement. In the case of core albite granite (83 EPMA vs. 45 LA), a very good agreement was found for the average values of Yb (3300 vs. 3546 ppm), the Th/U value (6.3 vs. 5.3), and the Zr/Hf value (13.0 vs. 12.4). EPMA yielded lower values for Y (1700 vs. 3316 ppm) and Nb (<300 vs. 834 ppm). The observed differences are more likely due to the uneven distribution of elements in the F-rich and strongly fluid-influenced core albite granite than to analytical problems.

5.2. Basic Chemical Characteristics of Zircon from the Madeira Albite Granite

First, we will point out general specifics of albite granite zircon that will facilitate the following discussion:
  • Zircons from all varieties of albite granite are nearly poor (Zr, Hf)SiO4 with Zr + Hf > 0.95 apfu. Zircons from the Madeira biotite granite and from the Europa pluton contain much more impurities (up to 0.3 apfu, Figure 8c).
  • Zircons from all varieties of albite granite are relatively rich in HREE, best represented by Yb. The average Y/Yb atomic value in zircon here is as low as 1, and in nearly all cases < 3. This separates the Madeira albite granite from all other granite types in the area (Figure 8d), as well as from other weakly peralkaline to subaluminous A-type rare-metal granites [12].
  • In albite granite, REE and Y enter the zircon crystal lattice as the xenotime component, i.e., (REE + Y)/P = 1, while REE + Y distinctly prevail over P in zircons from all neighboring granites (Figure 9a).
  • Although a number of zircon analyses from albite granite yielded low analytical totals down to 95 wt%, the contents of non-formula elements (Al, Ca, Fe) are significantly lower than in zircons from the surrounding granites (Figure 9b–e).
  • The atomic Zr/Hf value of 40 may serve as a threshold dividing Madeira zircons into two groups with different grades of fractionation (Figure 10). The great majority of zircon data from the Li-poor core albite granite subfacies together with zircons from the Madeira Amf-Bt and hypersolvus granites and from the Europa granite are relatively less evolved (Zr/Hf = 40–100), while all zircon analyses from the border albite granite and pegmatoidal core albite granite, and nearly all from the common core albite granite are more fractionated, with Zr/Hf < 40. Zircon from the Madeira Bt granite with Zr/Hf values of 30–50 has a transitional position. Each of the groups of analyses also contains several spots with significantly above-group average Zr/Hf values. These data may represent old inherited zircon cores or a local Hf deficit during the crystallization.

5.3. Evolution of Zircon from the Madeira Albite Granite

The different textures clearly visible in BSE, and even better in CL, indicate that zircon in the albite granite crystallized under different conditions that varied with time and position in the pluton. Distinct inclusion-rich cores (Figure 3a,c and Figure 6a,e) and common signs of partial resorption of crystal surface prior to the crystallization of the following zone (Figure 6c,f) indicate abrupt alternations in the dissolution/crystallization episodes. “Reversed” zoning of some crystals from the common core facies (Figure 3d) denotes a repetition of specific P-T-X conditions or movement of individual crystals through different domains of the intruding magma.
Let us assess to what extent textural diversity corresponds to chemical changes. The most striking textural feature is the presence of often automorphic cores filled with inclusions (i.e., solid solution unmixtures) in the centers of zircon grains from the border and common core facies. Table 3 shows medians of contents of the most common elements in these cores vs. their medians in the following rims. In zircons from both granite facies, the contents of Hf and Yb distinctly increase from cores to rims, while the contents of Th, U, and Y decrease very slightly in the same direction. This is in good agreement with the common behavior of these elements during pronounced crystallization fractionation. Furthermore, the table shows a good agreement in the compositions of the cores and the rims from the two facies, suggesting that their zircons underwent an identical evolution before the strong hydrothermal overprint of the border facies. In other words, the border facies was formed by the transformation of the common core facies.
The Zr/Hf values are stable during the post-magmatic (hydrothermal) processes, successfully illustrating the progress in the fractionation and the order of solidification of individual areas in the pluton (granite facies). Zircon forming the cores of composite grains from the border and common core facies, with Zr/Hf values mostly in the range of 30–40, represents the first episode of zircon crystallization from the intruding albite granite magma. The originally high Th contents in zircon are evidenced by numerous thorite unmixtures; this zircon must have crystallized from a Th-rich magma, i.e., before the onset of crystallization of abundant thorite. Zircon forming the rims of composite grains, showing Zr/Hf values mostly in the range of 20–40, must have crystallized after a time gap, highlighted by the significant resorption of some cores. Zircon grains from the pegmatoidal subfacies are similar to the mentioned “rims” but the lack of zircon cores here indicates that this domain of magma started its crystallization relatively later and from pure melt segregated from crystal mush (including early zircon crystal cores) of the previous facies.
Zircon from the Li-poor subfacies has above-average values of Zr/Hf, mostly 45–70, which suggests a distinct decoupling of Zr/Hf fractionation in the albite granite intrusion. This facies is most rich in F, Rb, Zn, and Cs (mineralogically rich in cryolite and Rb, Zn, Cs-rich annite, Table 1) and, at the same time, poor in Li and “primitive” in terms of its Zr/Hf values. Due to its macroscopic similarity with the common core subfacies, its extent and 3D position cannot be resolved yet, but it was found near cryolite pegmatite bodies in the deeper central part of the intrusion. Local conditions in the differentiation of the late melt (Zr/Hf = 20–30) into a pegmatite liquid rich in Al, Na, F, Y, REE, and a residual granitic melt (rich in K, Fe, Rb, and Zn) probably led to a strong fractionation of Zr and Hf. Cryolite pegmatites have extremely low bulk-rock Zr/Hf values (<10 [20]) whereas granites of the Li-poor subfacies were relatively Hf-depleted in this process, containing zircon with unexpectedly high Zr/Hf values.

5.4. Changes in Zircon Chemistry During Magma Evolution

Changes in the bulk-rock K/Rb value, i.e., its reduction, are generally supposed to be the most reliable indicator of fractionation of all feldspar-dominated igneous rocks [37,38]. The Zr/Hf ratio can play the same role, with the added advantage of much greater resistance to possible changes during alteration [5,9,11,39,40]. Major hosts of K and Rb, i.e., K-feldspar and micas, easily undergo changes during post-magmatic alteration while Zr and Hf, dominantly hosted by resistant zircon, keep their initial ratio. With the exception of strongly peralkaline rocks containing common zirconosilicates [14,41], zircon is a very dominant carrier of Zr and Hf in magmatic rocks. As a result, the Zr/Hf ratio of the bulk rock and the zircon contained in the rock are expected to be the same or at least very close [9]. Figure 11 confirms that the K/Rb and Zr/Hf element ratios evolved indeed conformably, definitely in rocks with K/Rb < 200, which is the case of the vast majority of granitoids. So, the Zr/Hf ratio can be reliably used as a marker of the degree of magmatic fractionation of the studied plutons.
Elements Y, HREE, Th, and U are the most common minor constituents of zircon [5,6,12,39,55,56]. Their contents varied in a broad interval. Nevertheless, ratios between Y and HREE (mostly presented as the Y/Yb value) and the Th/U ratio may indicate different styles of magma evolution [40,56].
The bulk-rock Y/Yb value is sensitive to the peraluminosity of the magma: it often increases during the fractionation of strongly peraluminous S-suites but typically decreases during the fractionation of A-suites. During the crystallization of strongly peralkaline plutons, the bulk-rock Y/Yb values usually remain stable, similarly to the Zr/Hf values. The Madeira albite granite is notable for its low values (Y/Yb < 5) throughout most of its fractional crystallization path (Figure 12a).
The evolution of the Y/Yb values in mineral zircon is a combination of the starting Y/Yb value of magma and the composition of other co-crystallizing HREE minerals, like xenotime or thorite. Despite the wide scatter of values, zircon from all rock types tends to evolve to somewhat lower Y/Yb values: mostly from 20 to 5 in S-types, mostly from 10 to 0.5 in A-types, and mostly from 20 to 2 in peralkaline rocks. In this comparison, zircon from the Madeira albite granite generally shows the lowest values (mostly from 2 to 0.2, Figure 12b), i.e., the highest relative Yb enrichment.
Within the Madeira pluton, zircon from the slightly peralkaline albite granite significantly differs in its low Y/Yb values < 3 from the other, subaluminous, facies of the Madeira pluton and from the peralkaline Europa pluton (mostly Y/Yb > 5). Albite granite zircon keeps the low Y/Yb value across the whole Zr/Hf interval of 5–80 (Figure 12c). The extremely low Y/Yb value in zircon from the Madeira albite granite resulted from a simultaneous crystallization of Y-enriched thorite having relatively high Y/Yb values 13–16 [21].
The behavior of the Th/U values is different: the bulk-rock ratio always strongly decreases in S-type suites but remains scattered in broad intervals with no clear trend in subaluminous A-type suites, peralkaline rocks, and also in the Madeira pluton (Figure 12d).
In mineral zircon, the Th/U value fluctuates within a range of several orders of magnitude. It is almost always <1 (down to 0.01) in zircon from S-suites, which corresponds well with the published mean of more than 10,000 measured zircons from common not-fractionated granites worldwide [40]. The Th/U values in zircon from A-suites and peralkaline rocks are higher, mostly in the range of 0.1–10, with a tendency to increase with increasing fractionation in A-type rocks. The Th/U values in zircons from all components of the Madeira pluton are similar, mostly <3; an exception is Th-enriched zircon from the most fractionated pegmatoidal core subfacies, showing Th/U up to 40, and occasional values from other facies, in all cases associated with the relatively lowest Zr/Hf value, i.e., the most fractionated sample within each facies (Figure 12f).
Taken together, zircon from the most evolved slightly peralkaline Madeira albite granite has a strong preference for Th and Yb compared to U and Y, respectively; this is similar to zircon from subaluminous rare-metal granites of A-type like Cínovec, Erzgebirge [8]; Wiborg batholith, Finland [12]; Eastern Desert, Egypt [60]; or Orlovka (Siberia, unpublished author’s data).

5.5. Relations of Zircon to Xenotime, Thorite and Coffinite

Fractionated subaluminous or slightly peralkaline A-type granites are usually enriched in a group of chemical elements Zr, Hf, Th, U, Y, and HREE that preferably form tetragonal minerals zircon, thorite, coffinite, and xenotime. The Madeira albite granite, containing 500–6000 ppm Zr, 20–360 ppm Hf, 50–1200 ppm Th, 25–700 ppm U, and 30–400 ppm Y [26,29], is a very typical example. The distribution of the mentioned elements is quite irregular, but most samples dominate in Zr + Hf. This is also reflected in the higher modal contents of zircon compared to those of thorite: up to 2.69 and 0.15 wt% in the measured samples, respectively (compare Table 1). Xenotime is represented much less here because Y and HREE are mostly bound in fluorite and gagarinite, while coffinite is rare because U is dominantly bound as a minor constituent in thorite [21] and pyrochlore [22].
The as yet proposed partition coefficients (KD) of Th, U, Y, and Yb (representing HREE) between zircon and silicate melt vary a lot [66,67,68] but all authors agree that these elements are highly compatible in zircon and their KD increase with the decreasing crystallization temperature. It was generally accepted that tetragonal minerals zircon, xenotime, thorite, and coffinite show a very limited miscibility with one another [3,69]. However, zircon with very high contents of thorite, coffinite, and xenotime components was found in A-type granites from Jordan and from German Erzgebirge by Förster [70]. Shortly thereafter, Breiter et al. [57] found mineral phases nearly completely filling the zircon–xenotime–thorite + coffinite triangle at Hora svaté Kateřiny in the Bohemian Erzgebirge (Figure 13). In the mentioned A-type granites from the Erzgebirge, Th, U, Y, HREE-rich zircon, or (seemingly) homogeneous hydrated (low analytical totals, down to 90 wt%) mixed phases are the only primary minerals of these elements; pure xenotime is rare, thorite and coffinite are totally absent. The associated secondary U, Th, and REE phases are minerals of synchysite and bastnaesite type. Förster [70] interpreted that the PT conditions and the high concentrations of F-rich fluid at the time of the Erzgebirge granites formation allowed the crystallization of a single mixed phase, which is probably metastable in the long term. A different situation occurred at Madeira: although it was also a water- and fluorine-rich system, zircon and thorite crystallized simultaneously in two, often closely associated minerals. In her detailed study of Madeira thorite, Hadlich [21] reported only very rare grains of mixed compositions with max. 0.3 apfu Zrn + 0.11 apfu Xnt in thorite and 0.2 apfu Thr in zircon but she did not pay much attention to them. The 300 EPMA analyses of zircon performed in this work did not find more than 0.05 apfu of Th + U + Y + HREE. Nevertheless, the cores (Figure 3a and Figure 4a) and outer zones (Figure 3d) of some zircon grains from the common core and the border facies containing numerous thorite inclusions indicate that in some episodes of crystallization, the original composition of zircon may have contained 10%–30% thorite in solid solution. Because xenotime inclusions are rare, the original composition of the mixed phase must have been close to the Zrn–Thr junction with an estimated composition between Zrn90–Thr10 and Zrn70–Thr30.
Both the Madeira magmatic system and the rare-metal A-type granites in the Erzgebirge were strongly water- and F-enriched. The reason why demixing occurred at Madeira, while the mixed phases are still stable in the Erzgebirge, remains unclear and is a challenge for further research.

5.6. Relations of Zircon to Nb,Ta-Minerals

The contents of Nb in zircon, similarly as in the case of Ta, W, Sn, As, and Bi, are only rarely reported. The as yet published partition coefficients (KD) reflect the somewhat higher compatibility of Ta compared to Nb but strongly diverge in their absolute magnitudes: while Nardi et al. [68] reported averages of KD = 2.9 and 1.6, respectively, and Van Lichtervelde et al. [7] proposed KD = 1.5 for Ta and “less” for Nb, Thomas et al. [66] found KD = 236 for Nb (Ta was not measured). This scatter may be due to different methodologies (crystal vs. bulk-rock, crystal vs. melt inclusion, and melting experiments) but it also certainly reflects differences between the crystallization conditions in common granite melt and volatile-saturated melt.
Comparing the situation in the Madeira pluton with published data, a similar situation can be observed as stated above for Th, U, Y, and REE: zircon from Madeira is poor in Nb (below the detection limit of EPMA, 834 ppm reported by [24]), and simultaneously pyrochlore and columbite group of minerals (CGM) are mostly free of Zr with only scarce exceptions which probably represent accidental hits of zircon micro inclusions [22]. In contrast, zircon from Cínovec and other A-type granites in the Erzgebirge [71] and from the Orlovka A-type granite (Siberia, for geological information see [47]) commonly contain 0.1–1 wt% Nb2O5, and the associated pyrochlore and CGM contain 0.1–0.2 wt% ZrO2 (unpublished author’s data). Also in this case, an assemblage of end-member minerals crystallized at Madeira while solid solutions are common in some other A-type granites.

5.7. Constraints on the Genetic Model

Based on the detailed research of the textures and chemistry of Madeira zircon, basic constraints on its genetic model can be stated:
  • The initial magma of albite granite was already strongly fractionated, showing K/Rb~7 and Zr/Hf~25, and enriched in F, Th, and HREE. Th-rich cores of zircon grains from the common core and border facies crystallized from this magma as one of the earliest minerals, i.e., prior to the main crystallization of thorite.
  • After further crystallization of magma associated with partial dissolution of primary zircon during the emplacement, a new population of Th-poor and Hf-enriched crystals and outer parts of already existing zircon grains crystallized. Due to the uneven crystallization of zircon and thorite and the uneven movement of crystal mush, Th-rich zircon crystallized again in some magma domains, forming rims of composite crystals.
  • Before the complete crystallization of magma, residual melt of the pegmatoidal subfacies separated, and zircon rich in Hf and slightly enriched in Yb and Th crystallized from this melt. In other facies, Hf-rich compositions form only the thin outermost rims.
  • Zircon with the locally highest Zr/Hf values crystallized from the Li-poor subfacies, which represented residual melt after decoupling with cryolite-rich pegmatite liquid.
  • The outer part of the albite granite intrusion was strongly altered by post-magmatic fluids and transformed to the border facies. It is possible that it was at this stage that thorite inclusions were unmixed from the Th-rich parts of the zircon crystals.

6. Conclusions

The main results of this study can be summarized as follows:
Four facies differing in their chemical and modal compositions and in the structure and chemistry of zircon were distinguished within the Madeira albite granite intrusion:
  • Common core subfacies, occupying most of the intrusion volume, contains mostly composite zircon crystals with euhedral cores rich in thorite inclusions and with zoned, inclusions-free, Hf-enriched rims; the Zr/Hf value decreased from 40 to 20 during the crystallization.
  • Pegmatoidal subfacies, representing crystallization of residual magma, contains zircon without thorite inclusions but rich in albite and cryolite inclusions with Zr/Hf value from 35 to 5. The Th/U and Y/Yb values evolved into Th, Yb-enriched compositions (Th/U up to >10, Y/Yb down to 0.1) during the fractionation from the common to the pegmatoidal facies.
  • A Li-poor subfacies was found in the central part of the stock near cryolite nests and pegmatites. This facies most probably represents granitic residuum after unmixing of a F-rich liquid forming cryolite pegmatites. Zircon from this facies is patchy, inhomogeneous, without regular zoning, and with comparatively high Zr/Hf values of 45–70 and elevated U and Y contents.
  • The pericontact part of the common facies was later hydrothermally altered to border facies but zircon did not change noticeably during this process.
Apart from the features typical for the individual facies, zircon from the Madeira albite granite displays the following general properties:
-
Many crystals yielded low analytical totals, down to 95 wt%, and are enriched in Al, Fe, Mn, Ca, and F, but this process does not influence the primary Zr/Hf, Th/U, and Y/Yb values.
-
Cores or outer zones rich in thorite inclusions indicate that a solid solution Zrn–Thr phase crystallized during certain episodes. It was later almost completely unmixed. The actual contents of HFSE minor elements in all zircon varieties are generally low (U + Th + Y + REE ˂ 0.05 apfu).
-
Y and REE are incorporated into zircon exclusively in the form of the xenotime component.
-
The contents of Hf, usually in the range of 1.5–2 wt% HfO2, increase in crystals rims in the pegmatoidal subfacies up to 14 wt% HfO2 (0.13 apfu Hf), which is a relatively high value but still significantly lower than the maxima found in some subaluminous A-type granites with up to 35 wt% HfO2 [59].
-
Zircon from albite granite evolved to a strong relative enrichment in Th and Yb, reaching extreme values of Y/Yb = 0.5–1 and Th/U = 0.1–0.5.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/min15080863/s1, Table S1: List of samples; File S1: Supplementary geological material.

Author Contributions

Conceptualization, K.B.; Data curation, Z.K. and M.D.; Investigation, K.B. and H.T.C.; Methodology, Z.K.; Writing—original draft, K.B.; Writing—review and editing, K.B. and H.T.C. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported by RVO 67985831 in Geological Institute of the Czech Academy of Sciences.

Data Availability Statement

Data are included in Table 2.

Acknowledgments

Editors and reviewers are thanked for all comments improving this manuscript.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of this study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results. Marek Dosbaba is employed by TESCAN ORSAY HOLDING. This paper reflects the views of the scientists and not the company.

References

  1. Pupin, J.P. Zircon and granite petrology. Contrib. Mineral. Petrol. 1980, 73, 207–220. [Google Scholar] [CrossRef]
  2. Pupin, J.-P. Granite genesis related to geodynamics from Hf–Y in zircon. Earth Environ. Sci. Trans. R. Soc. Edinb. 2000, 91, 245–256. [Google Scholar]
  3. Speer, J.A. Zircon. Rev. Miner. Geochem. 1980, 5, 67–112. [Google Scholar]
  4. Hanchar, J.M.; Hoskin, P.W.O. Zircon. Rev. Miner. Geochem. 2003, 53, 89–112. [Google Scholar] [CrossRef]
  5. Hoskin, P.W.O.; Schaltegger, U. The composition of zircon and igneous and metamorphic petrogenesis. Rev. Miner. Geochem. 2003, 53, 27–62. [Google Scholar] [CrossRef]
  6. Breiter, K.; Förster, H.-J.; Škoda, R. Extreme P-, Bi-, Nb-, Sc-, U- and F-rich zircon from fractionated perphosphorus granites: The peraluminous Podlesí granite system, Czech Republic. Lithos 2006, 88, 15–34. [Google Scholar] [CrossRef]
  7. Van Lichtervelde, M.; Holtz, F.; Dziony, W.; Ludwig, T.; Meyer, H.-P. Incorporation mechanisms of Ta and Nb in zircon and implications for pegmatitic systems. Am. Miner. 2011, 96, 1079–1089. [Google Scholar] [CrossRef]
  8. Breiter, K.; Škoda, R. Vertical zonality of fractionated granite plutons reflected in zircon chemistry: The Cínovec A-type versus the Beauvoir S-type suite. Geol. Carpathica 2012, 63, 383–398. [Google Scholar] [CrossRef]
  9. Breiter, K.; Škoda, R. Zircon and whole-rock Zr/Hf ratios as markers of the evolution of granitic magmas: Examples from the Teplice caldera (Czech Republic/Germany). Mineral. Petrol. 2017, 111, 435–457. [Google Scholar] [CrossRef]
  10. Lamarão, C.N.; Marques, G.T.; de Oliveira, D.C.; Costi, H.T.; Borges, R.M.K.; Dall’Agnol, R. Morphology and composition of zircons in rare metal granites from Brazilian tin provinces. J. S. Am. Earth Sci. 2018, 84, 1–15. [Google Scholar] [CrossRef]
  11. Zaraisky, G.P.; Aksyuk, A.M.; Devyatova, V.N.; Udoratina, O.V.; Chevychelov, V.Y. Zr/Hf ratio as an indicator of fractionation of rare-metal granites by the example of the Kukulbei Complex, Eastern Transbaikalia. Petrology 2008, 16, 710–736. [Google Scholar] [CrossRef]
  12. Breiter, K.; Lamarão, C.N.; Borges, R.M.K.; Dall’Agnol, R. Chemical characteristics of zircon from A-type granites and comparison to zircon of S-type granites. Lithos 2014, 192–195, 208–225. [Google Scholar] [CrossRef]
  13. Kovalenko, V.I.; Tsaryeva, G.M.; Goreglyad, A.V.; Yarmolyuk, V.V.; Troitsky, V.A. The peralkaline granite-related Khaldzan-Buregtey rare metal (Zr, Nb, REE) deposit, Western Mongolia. Econ. Geol. 1995, 90, 530–547. [Google Scholar] [CrossRef]
  14. Kynicky, J.; Chakhmouradian, A.R.; Xu, C.; Krmicek, L.; Galiová, M. Distribution and evolution of zirconium mineralization in peralkaline granites and associated pegmatites of the Khan Bogd complex, Southern Mongolia. Can. Mineral. 2011, 49, 947–965. [Google Scholar] [CrossRef]
  15. Marks, M.A.; Hettmann, K.; Schilling, J.; Frost, B.R.; Markl, G. The mineralogical diversity of alkaline igneous rocks: Critical factors for the transition from miaskitic to agpaitic phase assemblages. J. Petrol. 2011, 52, 439–455. [Google Scholar] [CrossRef]
  16. Sarangua, N.; Watanabe, Y.; Echigo, T.; Hoshino, M. Chemical characteristic of zircon from Khaldzan Burgedei peralkaline complex, Western Mongolia. Minerals 2018, 9, 10. [Google Scholar] [CrossRef]
  17. Costi, H.T.; Krás Borges, R.M.; Dall’Agnol, R. Depósitos de estanho da mina Pitinga, estado Amazonas. In Caracterizacao de Depósitos Minerais em Distritos Mineiros da Amazónia; Marini, O.J., Queiroz, E.T., Ramos, B.W., Eds.; DNPM-CT/Mineral-ADIMB: Brasília, Brazil, 2005; pp. 395–475. [Google Scholar]
  18. Bastos Neto, A.C.; Pereira, V.P.; Ronchi, L.H.; de Lima, E.F.; Frantz, J.C. The world-class Sn, Nb, Ta, F (Y, REE, Li) deposit and the massive cryolite associated with the albite-enriched facies of the Madeira A-type granite, Pitinga mining district, Amazonas State, Brazil. Can. Mineral. 2009, 47, 1329–1357. [Google Scholar] [CrossRef]
  19. Minuzzi, O.R.R.; Bastos Neto, A.C.; Flores, J.A.A.; Pereira, V.P.; Ferron, J.T.M.M. O dep’osito criolítico maciço e o min’erio disseminado de criolita da mina Pitinga (Amazonas, Brasil). Rev. Bras. Geocienc. 2006, 36, 104–123. (In Portuguese) [Google Scholar] [CrossRef][Green Version]
  20. Paludo, C.M.; Neto, A.C.B.; Pereira, V.P.; Botelho, N.F. Mineralogia e geoquímica de pegmatitos ricos em ETR, F e metais alcalinos associados a facies albita granito no depósito de Sn-Nb-Ta- (F, ETR, U, Th) Madeira (mina Pitinga, AM, Brasil). Pesqui. Geociências 2018, 45, e0747, (In Portuguese, with English Abstract). [Google Scholar] [CrossRef]
  21. Hadlich, I.W.; Neto, A.C.B.; Botelho, N.F.; Pereira, V.P. The thorite mineralization in the Madeira Sn-Nb-Ta world-class deposit (Pitinga, Brazil). Ore Geol. Rev. 2019, 105, 445–466. [Google Scholar] [CrossRef]
  22. Breiter, K.; Costi, H.T.; Korbelová, Z. Pyrochlore-supergroup minerals and their relation to columbite-group minerals in peralkaline to subaluminous A-type rare-metal granites with special emphasis on the Madeira pluton, Amazonas, Brazil. Minerals 2024, 14, 1302. [Google Scholar] [CrossRef]
  23. Costi, H.T.; Dall’Agnol, R.; Moura, C.A.V. Geology and Pb-Pb geochronology of Paleoproterozoic volcanic and granitic rocks of Pitinga province, Amazonian craton, northern Brazil. Int. Geol. Rev. 2000, 42, 832–849. [Google Scholar] [CrossRef]
  24. Nardi, L.V.S.; Formoso, M.L.L.; Jarvis, K.; Oliveira, L.; Neto, A.C.B.; Fontana, E. REE, Nb, U a Th contents and tetrad effect in zircon from a magmatic-hydrothermal F-rich system of Sn-rare metal-cryolite mineralized granites from the Pitinga mine, Amazonia, Brazil. J. S. Am. Earth Sci. 2012, 33, 34–42. [Google Scholar] [CrossRef]
  25. Costi, H.T.; Dall’Agnol, R.; Pichavant, M.; Ramo, O.T. The peralkaline tin-mineralized Madeira cryolite albite-rich granite of Pitinga, Amazonian craton, Brazil: Petrography, mineralogy and crystallization processes. Can. Miner. 2009, 47, 1301–1327. [Google Scholar] [CrossRef]
  26. Lenharo, S.L.R.; Pollard, P.J.; Born, H. Petrology and textural evolution of granites associated with tin and rare-metals mineralization at the Pitinga mine, Amazonas, Brazil. Lithos 2003, 66, 37–61. [Google Scholar] [CrossRef]
  27. Bettencourt, J.S.; Juliani, C.; Xavier, R.P.; Monteiro, L.V.; Neto, A.C.B.; Klein, E.L.; Assis, R.R.; Leite, W.B.; Moreto, C.P.; Fernandes, C.M.D.; et al. Metallogenetic systems associated with granitoid magmatism in the Amazonian Craton: An overview of the present level of understanding and exploration significance. J. S. Am. Earth Sci. 2016, 68, 22–49. [Google Scholar] [CrossRef]
  28. Ferron, J.M.T.M.; Neto, A.C.B.; Lima, E.F.; Nardi, L.V.S.; Costi, H.T.; Pierosan, R.; Prado, M. Petrology, geochemistry, and geochronology of Paleoproterozoic volcanic and granitic rocks (1.89–1.88 Ga) of the Pitinga province, Amazonian craton, Brazil. J. S. Am. Earth Sci. 2010, 29, 483–497. [Google Scholar] [CrossRef]
  29. Costi, H.T.C. Petrologia de Granitos Alcalinos com alto Flúor Mineralisados em Metais Raros: O Examplo do Albita Granito da mina Pitinga, Amazonas, Brazil. Ph.D. Thesis, Universidade Federal do Pará, Belém, Brazil, 2005; p. 345, (In Portuguese with English Abstract). [Google Scholar]
  30. Lenharo, S.L.R. Evolucao Magmática e Modelo Metalogenético dos Granitos Mineralizados da Regiao de PITINGA, Amazonas, Brasil. Ph.D. Thesis, Universidade de Sao Paulo, Escola Politécnica, Departamento de Engenharia de Minas, Sao Paulo, Brazil, 1998; pp. 1–290. (In Portuguese). [Google Scholar]
  31. Borges, R.M.K.; Villas, R.N.N.; Fuzikawa, K.; Dall Agnol, R.; Pimenta, M.A. Phase separation, fluid mixing, and origin of the greisens and potassic episyenite associated with the Água Boa pluton, Pitinga tin province, Amazonian Craton, Brazil. J. S. Am. Earth Sci. 2009, 27, 161–183. [Google Scholar] [CrossRef]
  32. Borges, R.M.K.; Amorim, L.E.D.; Rios, F.J.; dos Santos, G.C.S.; Freitas, M.E.; Lima, T.A.F.D.; Santos, A.; Pedrosa, T.A. Melt-melt immiscibility and implications for the origin of Madeira albite-rich granite, Pitinga mine, Amazonas, Brazil: A melt inclusion study. Braz. J. Geol. 2021, 51, e20210011. [Google Scholar] [CrossRef]
  33. Hrstka, T.; Gottlieb, P.; Skála, R.; Breiter, K.; Motl, D. Automated mineralogy and petrology-applications of TESCAN Integrated Mineral Analyzer (TIMA). J. Geosci. 2018, 63, 47–63. [Google Scholar] [CrossRef]
  34. Warr, L.N. IMA-CNMNC approved mineral symbols. Miner. Mag. 2021, 85, 291–320. [Google Scholar] [CrossRef]
  35. Nasdala, L.; Kronz, A.; Wirth, R.; Váczi, T.; Pérez-Soba, C.; Willner, A.; Kennedy, A.K. The phenomenon of deficient electron microprobe totals in radiation-damaged and altered zircon. Geochim. Cosmochim. Acta 2009, 73, 1637–1650. [Google Scholar] [CrossRef]
  36. Yin, R.; Wang, R.C.; Zhang, A.C.; Hu, H.; Zhu, J.C.; Rao, C.; Zhang, H. Extreme fractionation from zircon to hafnon in the Koktokay No. 1 granitic pegmatite, Altai, Northwestern China. Am. Miner. 2013, 98, 1714–1724. [Google Scholar] [CrossRef]
  37. Goldschmidt, V.M.; Muir, A. Geochemistry; Oxford University Press: Oxford, UK, 1954. [Google Scholar]
  38. Cerny, P.; Meintzner, R.E.; Anderson, A.J. Extreme fractionation in rare-element granitic pegmatites: Selected examples of data and mechanisms. Can. Miner. 1985, 23, 381–421. [Google Scholar]
  39. Hoskin, P.W.O.; Ireland, T.R. Rare earth element chemistry of zircon and its use as a provenance indicator. Geology 2000, 28, 627–630. [Google Scholar] [CrossRef]
  40. Kirkland, C.L.; Smithies, R.H.; Taylor, R.J.M.; Evans, N.; McDonald, B. Zircon Th/U ratios in magmatic environs. Lithos 2015, 212–215, 397–414. [Google Scholar] [CrossRef]
  41. Sheard, E.R.; Williams-Jones, A.E.; Heiligmann, M.; Pederson, C.; Trueman, D.L. Controls on the concentration of zirconium, niobium, and the rare earth elements in the Thor Lake rare metal deposit, Northwest Territories, Canada. Econ. Geol. 2012, 107, 81–104. [Google Scholar] [CrossRef]
  42. Raimbault, L.; Cuney, M.; Azencott, C.; Duthou, J.L.; Joron, J.L. Geochemical evidence for a multistage magmatic genesis of Ta–Sn–Li mineralization in the granite at Beauvoir, French Massif Central. Econ. Geol. 1995, 90, 548–596. [Google Scholar] [CrossRef]
  43. Breiter, K.; Ďurišová, J.; Korbelová, Z.; Vašinová Galiová, M.; Hložková, M. Granite Pluton at the Panasqueira Tungsten Deposit, Portugal: Genetic Implications as Revealed from New Geochemical Data. Minerals 2023, 13, 163. [Google Scholar] [CrossRef]
  44. Pollard, P.J. The Yichun Ta-Sn-Li deposit, South China: Evidence for extreme chemical fractionation in F-Li-P-rich magma. Econ. Geol. 2021, 116, 453–469. [Google Scholar] [CrossRef]
  45. Breiter, K.; Müller, A.; Leichmann, J.; Gabašová, A. Textural and chemical evolution of a fractionated granitic sytem: The Podlesí stock, Czech Republic. Lithos 2005, 80, 323–345. [Google Scholar] [CrossRef]
  46. Breiter, K. Monazite and zircon as major carriers of Th, U, and Y in peraluminous granites: Examples from the Bohemian Massif. Mineral. Petrol. 2016, 110, 767–785. [Google Scholar] [CrossRef]
  47. Badanina, E.V.; Veksler, I.V.; Thomas, R.; Syritso, L.F.; Trumbull, R.B. Magmatic evolution of Li-F rare-metal granites: A case study of melt inclusions in the Khangilay complex, Eastern Transbaikalia (Russia). Chem. Geol. 2004, 210, 113–133. [Google Scholar] [CrossRef]
  48. Haappala, I.; Lukkari, S. petrological and geochemical evolution of the Kymi stock, a topaz granite cupola within the Wiborg rapakivi batholith, Finland. Lithos 2005, 80, 347–362. [Google Scholar] [CrossRef]
  49. Sami, M.; Ntaflos, T.; Farahat, E.S.; Mohamed, H.A.; Hauzenberger, C.; Ahmed, A.F. Petrogenesis and geodynamic implications of Ediacaran highly fractionated A-type granitoids in the north Arabian-Nubian Shield (Egypt): Constraints from whole-rock geochemistry and Sr-Nd isotopes. Lithos 2018, 304–307, 329–346. [Google Scholar] [CrossRef]
  50. Haapala, I.; Frindt, S.; Kandara, J. Cretaceous Gross Spitzkoppe and Klein Spitzkoppe stocks in Namibia: Topaz-bearing A-type granites related to continental rifting and mantle plume. Lithos 2007, 97, 174–192. [Google Scholar] [CrossRef]
  51. Kempe, U.; Möckel, R.; Graupner, T.; Kynický, J.; Dombon, E. The genesis of Zr–Nb–REE mineralisation at Khalzan Buregte (Western Mongolia) reconsidered. Ore Geol. Rev. 2015, 64, 602–625. [Google Scholar] [CrossRef]
  52. Goodenough, K.M.; Upton, B.G.J.; Ellam, R.M. Geochemical evolution of the Ivigtut granite, South Greenland: A fluorine-rich “A-type” intrusion. Lithos 2000, 51, 205–221. [Google Scholar] [CrossRef]
  53. Sami, M.; Osman, H.; Ahmed, A.F.; Zaky, K.S.; Abart, R.; Sanislav, I.V.; Abdelrahman, K.; Fnais, M.S.; Xiao, W.; Abbas, H. Magmatic evolution and rare metal mineralization in Mount El-Sibai peralkaline granites, Central Eastern Desert, Egypt: Insights from whole-rock geochemistry and mineral chemistry data. Minerals 2023, 13, 1039. [Google Scholar] [CrossRef]
  54. McDonough, W.F.; Sun, S. The composition of the Earth. Chem. Geol. 1995, 120, 223–253. [Google Scholar] [CrossRef]
  55. Belousova, E.A.; Griffin, W.L.; O’Reilly, S.Y.; Fisher, N.I. Igneous zircon: Trace element composition as an indicator of source rock type. Contrib. Mineral. Petrol. 2002, 143, 602–622. [Google Scholar] [CrossRef]
  56. Breiter, K.; Kynický, J.; Korbelová, Z. Chemical and textural peculiarities of zircon from peralkaline granites and quartz-bearing syenites. Minerals 2024, 14, 187. [Google Scholar] [CrossRef]
  57. Breiter, K.; Čopjaková, R.; Škoda, R. The involvement of F, CO2, and As in the alteration of Zr-Th-REE-bearing accessory minerals in the Hora Svaté Kateřiny A-type granite, Czech Republic. Can. Miner. 2009, 47, 1375–1398. [Google Scholar] [CrossRef]
  58. Xie, L.; Wang, R.; Chen, X.; Qui, J.; Wang, D. Th-rich zircon from peralkaline A-type granite: Mineralogical features and petrological implications. Chin. Sci. Bull. 2005, 50, 809–817. [Google Scholar]
  59. Wang, R.C.; Fontan, F.; Shijin, X.; Xiaoming, C.; Monchoux, P. Hafnian zircon from the apical part of the Suzhou granite, China. Can. Mineral. 1996, 34, 1001–1010. [Google Scholar]
  60. Abdalla, H.M.; Helba, H.; Matsueda, H. Chemistry of zircon in rare metal granitoids and associated rocks, Eastern Desert, Egypt. Resour. Geol. 2009, 59, 51–68. [Google Scholar] [CrossRef]
  61. Cheng, W.R.; Fontan, F.; Monchoux, P. Mineraux dissemines indicateurs du caractere pegmatitique du granite Beauvoir, Massif d’Echassieres, Allier, France. Can. Mineral. 1992, 30, 763–770, (In France with English Abstract). [Google Scholar]
  62. Breiter, K.; Ďurišová, J.; Korbelová, Z.; Lima, A.; Galiová, M.V.; Hložková, M.; Dosbaba, M. Rock textures and mineral zoning—A clue to understanding rare-metal granite evolution: Argemela stock, Central-Eastern Portugal. Lithos 2022, 410–411, 106562. [Google Scholar] [CrossRef]
  63. Breiter, K.; Müller, A.; Shail, R.; Simons, B. Composition of zircons from the Cornubian Batholith of SW England and comparison with zircons from other European Variscan rare-metal granites. Miner. Mag. 2016, 80, 1273–1289. [Google Scholar] [CrossRef]
  64. Pérez-Soba, C.; Villaseca, C.; Del Tanago, J.G.; Nasdala, L. The composition of zircon in the peraluminous Hercynian granites of the Spanish Central System batholith. Can. Mineral. 2007, 45, 509–527. [Google Scholar] [CrossRef]
  65. Huang, X.L.; Wang, R.C.; Chen, X.M.; Hu, H.; Liu, C.S. Vertical variations in the mineralogy of the Yichun topaz-lepidolite granite, Jiangxi, Southern China. Can. Mineral. 2002, 40, 1047–1068. [Google Scholar] [CrossRef]
  66. Thomas, J.B.; Bodnar, R.J.; Shimizu, N.; Sinha, A.K. Determination of zircon/melt trace element partition coefficients from SIMS analysis of melt inclusions in zircon. Geochim. Cosmochim. Acta 2002, 66, 2887–2901. [Google Scholar] [CrossRef]
  67. Rubato, D.; Hermann, J. Experimental zircon/melt and zircon/garnet trace element partitioning and implications for the geochronology of crustal rocks. Chem. Geol. 2007, 241, 38–61. [Google Scholar] [CrossRef]
  68. Nardi, L.V.S.; Formoso, M.L.L.; Müller, I.F.; Fontana, E.; Jarvis, K.; Lamarão, C. Zircon/rock partition coefficients of REEs, Y, Th, U, Nb, and Ta in granitic rocks: Uses for provenance and mineral exploration purposes. Chem. Geol. 2013, 335, 1–7. [Google Scholar] [CrossRef]
  69. Speer, J.A. The actinide orthosilicates. Rev. Miner. Geochem. 1982, 5, 113–135. [Google Scholar]
  70. Förster, H.-J. Composition and origin of intermediate solid solutions in the system thorite-xenotime-zircon-coffinite. Lithos 2006, 88, 35–55. [Google Scholar] [CrossRef]
  71. Breiter, K.; Korbelová, Z.; Chládek, Š.; Uher, P.; Knesl, I.; Rambousek, P.; Honig, S.; Šešulka, V. Diversity of Ti–Sn–W–Nb–Ta oxide minerals in the classic granite-related magmatic–hydrothermal Cínovec/Zinnwald Sn–W–Li deposit (Czech Republic). Eur. J. Miner. 2017, 29, 727–738. [Google Scholar] [CrossRef]
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Figure 1. A simplified geological map of the Pitinga magmatic province (a) and the Madeira pluton (b). Compiled according to [23,29].
Figure 1. A simplified geological map of the Pitinga magmatic province (a) and the Madeira pluton (b). Compiled according to [23,29].
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Figure 2. Textures of the Madeira albite granite according to TIMA: (a) core albite granite, common subfacies (samle PHR-82a); (b) core albite granite, pegmatoidal subfacies (sample PHR-128); (c) core albite granite, Li-poor subfacies (sample PHR-247); (d) border albite granite (sample PHR-174). Height of all samples is 35 mm. Color explanation: dark blue—quartz; medium blue—albite; red—K-feldspar; dark green—alkali pyroxene or amphibole; light green—cryolite; light brown—annite; pink—Li-mica; dark red—thorite; yellow—zircon. Some large zircon grains are highlighted by black rings.
Figure 2. Textures of the Madeira albite granite according to TIMA: (a) core albite granite, common subfacies (samle PHR-82a); (b) core albite granite, pegmatoidal subfacies (sample PHR-128); (c) core albite granite, Li-poor subfacies (sample PHR-247); (d) border albite granite (sample PHR-174). Height of all samples is 35 mm. Color explanation: dark blue—quartz; medium blue—albite; red—K-feldspar; dark green—alkali pyroxene or amphibole; light green—cryolite; light brown—annite; pink—Li-mica; dark red—thorite; yellow—zircon. Some large zircon grains are highlighted by black rings.
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Figure 3. Back-scattered electron images (BSE) and cathodoluminescence images (CL) of zircon grains from the Madeira core albite granite, common subfacies: (a) a densely sieved core crowded with thorite inclusions rimmed with zoned and slightly mottled overgrowths without inclusions (BSE, grain 213-22); (b) CL image of the same grain: zircon in green, cryolite and albite in red; (c) a reversely zoned grain with a mottled euhedral inner and outer core and an thin irregular rim with numerous thorite and pyrochlore inclusions (grain 214-28); (d) a reversely zoned grain with a faintly zoned subhedral core and an irregular rim packed with thorite inclusions (grain 214-18); (e) a subhedral grain with a large, slightly mottled core and a thinner outer zone. Both the core and the rim contain silicate inclusions but no thorite inclusions (grain 213-37); (f) a grain with an irregular, darker core with silicate inclusions passing to a brighter rim of a highly variable width and with numerous cracks (grain 213-35). Scale bars 200 μm in all images. Red numbers indicate position of zircon analyses from Table 2.
Figure 3. Back-scattered electron images (BSE) and cathodoluminescence images (CL) of zircon grains from the Madeira core albite granite, common subfacies: (a) a densely sieved core crowded with thorite inclusions rimmed with zoned and slightly mottled overgrowths without inclusions (BSE, grain 213-22); (b) CL image of the same grain: zircon in green, cryolite and albite in red; (c) a reversely zoned grain with a mottled euhedral inner and outer core and an thin irregular rim with numerous thorite and pyrochlore inclusions (grain 214-28); (d) a reversely zoned grain with a faintly zoned subhedral core and an irregular rim packed with thorite inclusions (grain 214-18); (e) a subhedral grain with a large, slightly mottled core and a thinner outer zone. Both the core and the rim contain silicate inclusions but no thorite inclusions (grain 213-37); (f) a grain with an irregular, darker core with silicate inclusions passing to a brighter rim of a highly variable width and with numerous cracks (grain 213-35). Scale bars 200 μm in all images. Red numbers indicate position of zircon analyses from Table 2.
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Figure 4. Back-scattered electron (BSE) and cathodoluminescence (CL) images of zircon grains from the Madeira core albite granite, pegmatoidal subfacies: (a) a subhedral grain with numerous silicate and scarce thorite inclusions, the density of silicate inclusions decreases outwards (grain 212-5); (b) the same grain in CL; (c) a subhedral grain with a dark core and a brighter rim. Large albite and quartz grains are embedded across the zoning. Rare thorite inclusions concentrate especially to the outer rim (grain 212-11); (d) upper part of this grain in CL showing a combination of zoning and patchy texture. The red columnar crystal is albite; (e) two euhedral crystals with silicate inclusions and thin bright Hf-rich rims (grain PHR 128-3); (f) small euhedral zircon crystals embedded, together with thorite, in galena (grain PHR 127-1). Scale bars 200 μm in all images. Red numbers indicate position of zircon analyses from Table 2.
Figure 4. Back-scattered electron (BSE) and cathodoluminescence (CL) images of zircon grains from the Madeira core albite granite, pegmatoidal subfacies: (a) a subhedral grain with numerous silicate and scarce thorite inclusions, the density of silicate inclusions decreases outwards (grain 212-5); (b) the same grain in CL; (c) a subhedral grain with a dark core and a brighter rim. Large albite and quartz grains are embedded across the zoning. Rare thorite inclusions concentrate especially to the outer rim (grain 212-11); (d) upper part of this grain in CL showing a combination of zoning and patchy texture. The red columnar crystal is albite; (e) two euhedral crystals with silicate inclusions and thin bright Hf-rich rims (grain PHR 128-3); (f) small euhedral zircon crystals embedded, together with thorite, in galena (grain PHR 127-1). Scale bars 200 μm in all images. Red numbers indicate position of zircon analyses from Table 2.
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Figure 5. Back-scattered electron images (BSE) of zircon grains from the Madeira core albite granite, Li-poor subfacies: (a) a fresh euhedral crystal with no zoning, densely crowded with silicate microinclusions (grain PHR 245-7); (b) a euhedral mottled crystal with no zoning, with albite inclusions (grain PHR 241-5); (c) a euhedral, intensively mottled crystal with no zoning (grain PHR 249-2); (d) a group of sub- to euhedral zircon crystals together with thorite embedded in annite. Both thorite and zircon are coated with hydrothermal hematite (grain PHR 239-1); (e) a homogeneous zircon together with thorite are replaced by hematite and cryolite (grain PHR 240-3); (f) remnants of zircon grain intensively replaced with hematite, quartz and cryolite (grain PHR 240-6). Scale bars 100 μm in all images. Red numbers indicate position of zircon analyses from Table 2.
Figure 5. Back-scattered electron images (BSE) of zircon grains from the Madeira core albite granite, Li-poor subfacies: (a) a fresh euhedral crystal with no zoning, densely crowded with silicate microinclusions (grain PHR 245-7); (b) a euhedral mottled crystal with no zoning, with albite inclusions (grain PHR 241-5); (c) a euhedral, intensively mottled crystal with no zoning (grain PHR 249-2); (d) a group of sub- to euhedral zircon crystals together with thorite embedded in annite. Both thorite and zircon are coated with hydrothermal hematite (grain PHR 239-1); (e) a homogeneous zircon together with thorite are replaced by hematite and cryolite (grain PHR 240-3); (f) remnants of zircon grain intensively replaced with hematite, quartz and cryolite (grain PHR 240-6). Scale bars 100 μm in all images. Red numbers indicate position of zircon analyses from Table 2.
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Figure 6. Back-scattered electron (BSE) and cathodoluminescence (CL) images of zircon grains from the Madeira border albite granite: (a) a zircon grain composed of a columnar core with numerous thorite microinclusions overgrown with a more homogeneous zone with individual larger silicate, cryolite and thorite inclusions. The outer zone contains larger xenotime inclusions, it is locally altered and became spotted (grain 215-36); (b) upper part of the same grain in CL: early zircon core with granulate texture, rimmed with an irregularly botryoidally zoned rim of late zircon; (c) a triangular euhedral core, rich in thorite inclusions and locally resorbed, rimmed with two zones free of microinclusions but locally mottled, with cracks and an engulfed euhedral xenotime grain. The outer bright zone is enriched in Hf (grain 215-37); (d) the upper part of this crystal in CL showing granulate texture of the core and irregular complex zoning of the rim; (e) a subhedral grain combining a euhedral core crowded with thorite and silicate inclusions, with the outer zone composed of 2–3 zones with no inclusions; the rim is enriched in Hf; (f) a subhedral dark core with numerous thorite inclusions gradually passing to a brighter, inclusion-poor outer zone and a thin, Hf-rich rim (grain 215-38). Scale bars 200 μm in all images. Red numbers indicate position of zircon analyses from Table 2.
Figure 6. Back-scattered electron (BSE) and cathodoluminescence (CL) images of zircon grains from the Madeira border albite granite: (a) a zircon grain composed of a columnar core with numerous thorite microinclusions overgrown with a more homogeneous zone with individual larger silicate, cryolite and thorite inclusions. The outer zone contains larger xenotime inclusions, it is locally altered and became spotted (grain 215-36); (b) upper part of the same grain in CL: early zircon core with granulate texture, rimmed with an irregularly botryoidally zoned rim of late zircon; (c) a triangular euhedral core, rich in thorite inclusions and locally resorbed, rimmed with two zones free of microinclusions but locally mottled, with cracks and an engulfed euhedral xenotime grain. The outer bright zone is enriched in Hf (grain 215-37); (d) the upper part of this crystal in CL showing granulate texture of the core and irregular complex zoning of the rim; (e) a subhedral grain combining a euhedral core crowded with thorite and silicate inclusions, with the outer zone composed of 2–3 zones with no inclusions; the rim is enriched in Hf; (f) a subhedral dark core with numerous thorite inclusions gradually passing to a brighter, inclusion-poor outer zone and a thin, Hf-rich rim (grain 215-38). Scale bars 200 μm in all images. Red numbers indicate position of zircon analyses from Table 2.
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Figure 7. Back-scattered electron images (BSE) of zircon grains from other granite types of the Madeira pluton and from the Europa pluton: (a) subhedral, faintly zoned zircon grains associated with rutile, ilmenite, and monazite embedded in biotite from hypersolvus granite (grain PHR 176-1); (b) a zircon grain composed of a colander-like core and a mottled outer zone (hypersolvus granite, grain PHR 191-3); (c) a cluster of small euhedral homogeneous zircon crystals with thorite and ilmenite embedded in biotite and quartz (amphibole–biotite granite, borehole F13, depth 50.4 m); (d) a euhedral, faintly zoned zircon grain associated with fluorite and REE–fluoride, embedded in biotite (biotite granite, grain PHR 96-2), (e) a cluster of euhedral non-zoned zircon crystals with scarce thorite inclusions associated with kenopyrochlore and plumbopyrochlore, embedded in riebeckite (Europa pluton, grain PHR 197-1); (f) a zoned zircon crystal with a small sieved core rimmed with a zoned overgrowth with large silicate inclusions (Europa pluton, grain PHR 197-3). Scale bars 100 μm in all images. Red numbers indicate position of zircon analyses from Table 2.
Figure 7. Back-scattered electron images (BSE) of zircon grains from other granite types of the Madeira pluton and from the Europa pluton: (a) subhedral, faintly zoned zircon grains associated with rutile, ilmenite, and monazite embedded in biotite from hypersolvus granite (grain PHR 176-1); (b) a zircon grain composed of a colander-like core and a mottled outer zone (hypersolvus granite, grain PHR 191-3); (c) a cluster of small euhedral homogeneous zircon crystals with thorite and ilmenite embedded in biotite and quartz (amphibole–biotite granite, borehole F13, depth 50.4 m); (d) a euhedral, faintly zoned zircon grain associated with fluorite and REE–fluoride, embedded in biotite (biotite granite, grain PHR 96-2), (e) a cluster of euhedral non-zoned zircon crystals with scarce thorite inclusions associated with kenopyrochlore and plumbopyrochlore, embedded in riebeckite (Europa pluton, grain PHR 197-1); (f) a zoned zircon crystal with a small sieved core rimmed with a zoned overgrowth with large silicate inclusions (Europa pluton, grain PHR 197-3). Scale bars 100 μm in all images. Red numbers indicate position of zircon analyses from Table 2.
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Figure 8. Chemical compositions of zircon grains from the Madeira and Europa plutons: (a) analytical total vs. Th + U; (b) analytical total vs. F; (c) Zr vs. Hf; (d) Y vs. Yb; (e) Th vs. U.
Figure 8. Chemical compositions of zircon grains from the Madeira and Europa plutons: (a) analytical total vs. Th + U; (b) analytical total vs. F; (c) Zr vs. Hf; (d) Y vs. Yb; (e) Th vs. U.
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Figure 9. Chemical compositions of zircon grains from the Madeira and Europa plutons: (a) P vs. (Y + REE); (b) analytical total vs. Al2O3; (c) analytical total vs. MnO; (d) analytical total vs. CaO; (e) analytical total vs. FeO.
Figure 9. Chemical compositions of zircon grains from the Madeira and Europa plutons: (a) P vs. (Y + REE); (b) analytical total vs. Al2O3; (c) analytical total vs. MnO; (d) analytical total vs. CaO; (e) analytical total vs. FeO.
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Figure 10. Atomic Zr/Hf values in the analyzed zircon grains (397 analyses from this work). In the case of the border and the common core facies of the Madeira albite granite, cores rich in thorite inclusions and their rims + homogeneous grains without thorite are presented separately.
Figure 10. Atomic Zr/Hf values in the analyzed zircon grains (397 analyses from this work). In the case of the border and the common core facies of the Madeira albite granite, cores rich in thorite inclusions and their rims + homogeneous grains without thorite are presented separately.
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Figure 11. Correlation between the bulk-rock K/Rb and Zr/Hf values during the fractionation of the Madeira pluton compared with those in granites of different geochemical affiliation: (a) all samples; (b) detail of samples with K/Rb < 250. Data sources for S-type rock suites: Beauvoir, France [42]; Panasqueira, Portugal [43]; Aqua Boa, Brazil [26]; Yichun, China [44]; Western Erzgebirge, Czech Republic [45], and two-mica granites from the Czech Republic [46]. Data sources for A-type rock suites: Orlovka, Siberia [47]; Eastern Erzgebirge [9]; Kimi, Finland [48]; Abu-Diab, Egypt [49]; Spitzkoppe, Namibia [50]. Peralkaline suites: Khan Bogd, Mongolia [14]; Khalzan Buregte, Mongolia [13,51]; Ivigtut, Greenland [52]; El-Sibai, Egypt [53]. Data from the Madeira pluton taken from [29], chondrite value from [54].
Figure 11. Correlation between the bulk-rock K/Rb and Zr/Hf values during the fractionation of the Madeira pluton compared with those in granites of different geochemical affiliation: (a) all samples; (b) detail of samples with K/Rb < 250. Data sources for S-type rock suites: Beauvoir, France [42]; Panasqueira, Portugal [43]; Aqua Boa, Brazil [26]; Yichun, China [44]; Western Erzgebirge, Czech Republic [45], and two-mica granites from the Czech Republic [46]. Data sources for A-type rock suites: Orlovka, Siberia [47]; Eastern Erzgebirge [9]; Kimi, Finland [48]; Abu-Diab, Egypt [49]; Spitzkoppe, Namibia [50]. Peralkaline suites: Khan Bogd, Mongolia [14]; Khalzan Buregte, Mongolia [13,51]; Ivigtut, Greenland [52]; El-Sibai, Egypt [53]. Data from the Madeira pluton taken from [29], chondrite value from [54].
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Figure 12. Evolution of Y, Yb, Th and U during magma fractionation and zircon crystallization, correlation between the Y/Yb, Th/U and Zr/Hf values: (a) Zr/Hf vs. Y/Yb in granites of different geochemical affiliations; (b) Zr/Hf vs. Y/Yb in zircon from granites of different geochemical affiliations; (c) Zr/Hf vs. Y/Yb in zircon from the Madeira and Europa plutons; (d) Zr/Hf vs. Th/U in granites of different geochemical affiliations; (e) Zr/Hf vs. Th/U in zircon from granites of different geochemical affiliations; (f) Zr/Hf vs. Th/U in zircon from the Madeira and Europa plutons. Note the slow decrease in the Y/Yb values and the steep increase in the Th/U values with increasing fractionation (decreasing Zr/Hf) in the Madeira albite granite zircon, visible in (b,e). For sources of bulk-rock data see Figure 11. Data sources for zircon from A-suites: Redanco, Jamon, Bom Jardin, and Pedra Branca suites, Brazil [12]; Wiborg batholith and Kimi stock, Finland [12]; Eastern Erzgebirge, Czech Republic and Germany [8,12]; Hora svaté Kateřiny, Czech Republic [57]; A-granites from SE China [58]; Suzhou granite, China [59]; granites from Eastern Desert, Egypt [60]; Orlovka, Siberia (unpublished author’s data). For S-suites: Beauvoir, France [8,61]; Western Erzgebirge and two-mica granites of the Bohemian Massif, Czech Republic [6,46]; Panasqueira, Portugal [43]; Argemela, Portugal [62]; Cornwall, England [63]; Variscan granites from Spain [64]; Yichun granite, China [65]. For peralkaline suites: Khan Bogd, Mongolia [56]; Khalzan Buregte, Mongolia [16,56]; Ivigtut, Greenland [56]; El-Sibai, Egypt [53]. Chondrite values were taken from [54].
Figure 12. Evolution of Y, Yb, Th and U during magma fractionation and zircon crystallization, correlation between the Y/Yb, Th/U and Zr/Hf values: (a) Zr/Hf vs. Y/Yb in granites of different geochemical affiliations; (b) Zr/Hf vs. Y/Yb in zircon from granites of different geochemical affiliations; (c) Zr/Hf vs. Y/Yb in zircon from the Madeira and Europa plutons; (d) Zr/Hf vs. Th/U in granites of different geochemical affiliations; (e) Zr/Hf vs. Th/U in zircon from granites of different geochemical affiliations; (f) Zr/Hf vs. Th/U in zircon from the Madeira and Europa plutons. Note the slow decrease in the Y/Yb values and the steep increase in the Th/U values with increasing fractionation (decreasing Zr/Hf) in the Madeira albite granite zircon, visible in (b,e). For sources of bulk-rock data see Figure 11. Data sources for zircon from A-suites: Redanco, Jamon, Bom Jardin, and Pedra Branca suites, Brazil [12]; Wiborg batholith and Kimi stock, Finland [12]; Eastern Erzgebirge, Czech Republic and Germany [8,12]; Hora svaté Kateřiny, Czech Republic [57]; A-granites from SE China [58]; Suzhou granite, China [59]; granites from Eastern Desert, Egypt [60]; Orlovka, Siberia (unpublished author’s data). For S-suites: Beauvoir, France [8,61]; Western Erzgebirge and two-mica granites of the Bohemian Massif, Czech Republic [6,46]; Panasqueira, Portugal [43]; Argemela, Portugal [62]; Cornwall, England [63]; Variscan granites from Spain [64]; Yichun granite, China [65]. For peralkaline suites: Khan Bogd, Mongolia [56]; Khalzan Buregte, Mongolia [16,56]; Ivigtut, Greenland [56]; El-Sibai, Egypt [53]. Chondrite values were taken from [54].
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Figure 13. A ternary diagram of zircon–xenotime–thorite/coffinite. Zircon from the Madeira albite granite (this study) is actually nearly poor (Zr,Hf)SiO4, while some parts of crystals prior to unmixing could contain 10%–30% of the thorite component. Data sources: [57] (Hora sv. Kateřiny), [70] (Erzgebirge), [21] (Madeira thorite and rare mixed phases).
Figure 13. A ternary diagram of zircon–xenotime–thorite/coffinite. Zircon from the Madeira albite granite (this study) is actually nearly poor (Zr,Hf)SiO4, while some parts of crystals prior to unmixing could contain 10%–30% of the thorite component. Data sources: [57] (Hora sv. Kateřiny), [70] (Erzgebirge), [21] (Madeira thorite and rare mixed phases).
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Table 1. Partial modal composition of granites by TIMA (wt%).
Table 1. Partial modal composition of granites by TIMA (wt%).
PlutonEuropaMadeira Pluton
Rock TypeRbk-Bt GraniteAmp-Bt GraniteBt GraniteHypersolvus GraniteHypersolvus GraniteBorder Albite Granite
SamplePHR-195PHR-101PHR-96PHR-176PHR-191PHR-174
Albite26.0332.3823.8428.9536.4839.29
Quartz40.9730.1934.2034.3429.1630.63
Orthoclase26.8228.3237.0830.7627.5025.09
Li-mica/Muscovite0.310.340.520.641.130.34
Annite0.065.052.574.373.340.52
Riebeckite5.190.100.000.001.350.01
Cryolite0.000.000.000.000.070.00
Fluorite0.000.470.650.440.400.69
Zircon0.180.150.090.100.191.78
Thorite + alter. Thorite0.000.020.020.060.010.15
Hematite0.010.500.010.010.090.82
Cassiterite0.000.000.000.000.000.07
Pyrochlore0.000.020.000.000.020.06
Columbite0.000.000.000.000.000.21
Galena0.000.000.000.010.000.01
Sphalerite0.000.000.000.070.000.00
Genthelvite0.000.000.000.000.000.00
Titanite0.000.300.000.000.000.00
Ilmenite0.070.340.000.070.070.00
Apatite0.000.200.000.000.000.00
PlutonMadeira Pluton, Core Albite Granite
FaciesCommonCommonCommonPegmatPegmatPegmatPegmatLi-PoorLi-PoorLi-Poor
SamplePHR-82aPHR-160PHR-163PHR-127PHR-128PHR-159PHR-161PHR-240PHR-247PHR-249
Albite34.7724.0539.2236.7045.3834.4339.4957.6433.1551.29
Quartz25.0033.9026.6220.3621.3829.3825.098.3230.4910.43
Orthoclase28.1019.9725.7234.0223.5625.7523.3727.1121.9025.32
Li-mica2.294.751.711.682.082.142.080.000.000.00
Annite (Rb, Cs, Li, Zn-annite)0.331.221.070.150.711.030.343.123.274.31
Riebeckite1.574.050.462.831.400.871.270.901.340.42
Cryolite4.997.352.891.763.364.064.801.946.586.48
Fluorite0.000.000.000.000.000.000.000.000.000.01
Zircon1.442.551.070.491.120.921.330.242.690.65
Thorite + alter. Thorite0.150.020.110.100.020.020.030.010.030.00
Hematite0.540.750.550.190.290.661.060.650.100.91
Cassiterite0.200.240.170.200.200.060.160.000.030.01
Pyrochlore0.550.860.330.460.380.610.590.040.250.00
Columbite0.050.070.030.120.080.060.110.000.050.00
Galena0.000.010.000.510.000.000.000.000.000.00
Sphalerite0.000.000.000.130.000.000.000.000.000.00
Genthelvite0.000.170.000.000.000.000.170.000.000.00
Table 3. Medians of selected oxides (wt%) in zircon cores with thorite inclusions vs. crystal rims.
Table 3. Medians of selected oxides (wt%) in zircon cores with thorite inclusions vs. crystal rims.
Rock TypeBorder Albite GraniteCommon Core Albite Granite
PositionCoresRimsCoresRims
n29341825
SiO230.9431.1830.7631.08
ZrO262.7761.1562.3561.27
HfO23.134.723.004.00
ThO20.0690.0520.0810.066
UO20.0770.0410.3530.070
P2O50.2530.2870.2660.266
Y2O30.1840.1380.2170.208
Yb2O30.2740.3600.2810.351
Analytical total98.7999.3398.0399.02
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Breiter, K.; Costi, H.T.; Korbelová, Z.; Dosbaba, M. Chemical and Textural Variability of Zircon from Slightly Peralkaline Madeira Albite Granite, Pitinga Magmatic Province, Brazil. Minerals 2025, 15, 863. https://doi.org/10.3390/min15080863

AMA Style

Breiter K, Costi HT, Korbelová Z, Dosbaba M. Chemical and Textural Variability of Zircon from Slightly Peralkaline Madeira Albite Granite, Pitinga Magmatic Province, Brazil. Minerals. 2025; 15(8):863. https://doi.org/10.3390/min15080863

Chicago/Turabian Style

Breiter, Karel, Hilton Tulio Costi, Zuzana Korbelová, and Marek Dosbaba. 2025. "Chemical and Textural Variability of Zircon from Slightly Peralkaline Madeira Albite Granite, Pitinga Magmatic Province, Brazil" Minerals 15, no. 8: 863. https://doi.org/10.3390/min15080863

APA Style

Breiter, K., Costi, H. T., Korbelová, Z., & Dosbaba, M. (2025). Chemical and Textural Variability of Zircon from Slightly Peralkaline Madeira Albite Granite, Pitinga Magmatic Province, Brazil. Minerals, 15(8), 863. https://doi.org/10.3390/min15080863

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