Special Issue "Accessory Minerals in Silicic Igneous Rocks"

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Geochemistry and Geochronology".

Deadline for manuscript submissions: 30 June 2020.

Special Issue Editor

Dr. habil. Hans-Jürgen Förster
Website
Guest Editor
Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum GFZ, Telegrafenberg, 14473 Potsdam, Germany
Interests: granitoid rocks and associated leucocratic mineral deposits; primary and secondary accessory minerals; micas; Se-bearing minerals; fluid−mineral−rock interactions; lithosphere thermal studies; petrophysical and thermal rock properties
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Although minor in abundance and typically small in size, accessory minerals are of fundamental importance in deciphering the history of magmatic–hydrothermal systems. They may inherit information from magma sources, monitor the evolution of fractionating melts, and record information on mixing/mingling/contamination of melts. Accessory minerals constitute important geochronometers and essentially govern the enrichment/depletion of economically relevant elements. They may act as thermobarometers, and monitor the fluid regime in magmas and expelled fluids. Their textural and compositional patterns constrain the impact of rock–mineral–fluid interaction and how intense such processes have obscured the primary composition of igneous rocks.

This Special Issue invites contributions that deal with accessory minerals and their behaviour during the entire evolution of silicic magmatic–hydrothermal systems, from the time/source of melting through fractionation/mixing/mingling of the generated magma until the time/place of crystallization/solidification, expelling of fluids and eventual generation of mineral deposits. We welcome contributions that use accessory minerals for dating the crystallization and alteration ages of rocks, reconstruct their PTX conditions during magma evolution, and monitor their metallogenic fertility.

Dr. habil. Hans-Jürgen Förster
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Accessory minerals
  • Silicic igneous rocks
  • Granites
  • Rhyolites
  • Pegmatites/Aplites
  • Geochronology
  • PT–X conditions
  • Alteration
  • Metallogenic fertility
  • Rare-earth elements
  • Radioactive elements
  • Ore elements

Published Papers (7 papers)

Order results
Result details
Select all
Export citation of selected articles as:

Research

Open AccessArticle
Allanite Geochemical Response to Hydrothermal Alteration by Alkaline, Low-Temperature Fluids
Minerals 2020, 10(5), 392; https://doi.org/10.3390/min10050392 - 28 Apr 2020
Abstract
Allanite is one of the main rare earth elements (REE)-rich accessory minerals in composite dykes from the granitoid pluton of Karkonosze. These dykes differ in composition from the bulk of the pluton by elevated rare earth elements (REE), Y, Zr, and alkali contents, [...] Read more.
Allanite is one of the main rare earth elements (REE)-rich accessory minerals in composite dykes from the granitoid pluton of Karkonosze. These dykes differ in composition from the bulk of the pluton by elevated rare earth elements (REE), Y, Zr, and alkali contents, suggesting contribution of an additional component. Allanite exhibits complex alteration textures, which can be divided into two stages. The first stage is represented by allanite mantles, formed by fluid infiltration into previously crystallized magmatic allanite. These zones have low totals, are Ca-, Al-, Mg-, and light REE (LREE)-depleted, and Y-, heavy REE (HREE)-, Th-, Ti-, and alkali-enriched. The fractionation between LREE and HREE was caused by different mobility of complexes formed by these elements in aqueous fluids. The second stage includes recrystallized LREE-poor, Y-HREE-rich allanite with variable Ca, Al, Mg, and REE-fluorocarbonates. The alteration products from both stages demonstrate higher Fe3+/(Fe2+ + Fe3+) ratios and a negative Ce anomaly. These features point to the alkaline, low-temperature, and oxidized nature of the fluids. The differences in mobility and solubility of respective ligands show that the fluids from the first stage may have been dominated by Cl, whereas those of the second stage may have been dominated by F and CO2 (and PO4 in case of one sample). The inferred chemistry of the fluids resembles the overall geochemical signature of the composite dykes, indicating a major contribution of the hydrothermal processes to their geochemical evolution. Full article
(This article belongs to the Special Issue Accessory Minerals in Silicic Igneous Rocks)
Show Figures

Figure 1

Open AccessArticle
Towards Identification of Zircon Populations in Permo-Carboniferous Rhyolites of Central Europe: Insight from Automated SEM-Mineral Liberation Analyses
Minerals 2020, 10(4), 308; https://doi.org/10.3390/min10040308 - 30 Mar 2020
Abstract
Zircon is a main mineral used for dating rhyolitic magmas as well as reconstructing their differentiation. It is common that different populations of zircon grains occur in a single rhyolitic sample. The presence of both autocrystic and antecrystic zircon grains is reflected in [...] Read more.
Zircon is a main mineral used for dating rhyolitic magmas as well as reconstructing their differentiation. It is common that different populations of zircon grains occur in a single rhyolitic sample. The presence of both autocrystic and antecrystic zircon grains is reflected in their strongly varied chemical compositions and slight spread of ages. However, postmagmatic processes may induce lead loss, which is also recorded as a spread of zircon ages. Therefore, new approaches to identify different zircon populations in rhyolitic rocks are needed. In this study, we suggest that detailed examination of zircon positions in the thin sections of rhyolitic rocks provides valuable information on zircon sources that can be used to identify autocrystic and antecrystic zircon populations. Automated Scanning Electron Microscope (SEM) analyses are of great applicability in determining this, as they return both qualitative and quantitative information and allow for quick comparisons between different rhyolite localities. Five localities of Permo-Carboniferous rhyolites related to post-Variscan extension in Central Europe (Organy, Bieberstein, Halle, Chemnitz, Krucze) were analyzed by automated SEM (MLA-SEM). The samples covered a range of Zr whole rock contents and displayed both crystalline and glassy groundmass. Surprisingly, each locality seemed to have its own special zircon fingerprint. Based on comparisons of whole rocks, modal composition and SEM images Chemnitz ignimbrite was interpreted as containing mostly (or fully) antecrystic zircon, whereas the Bieberstein dyke was shown to possibly contain both types, with the antecrystic zircon being associated with disturbed cumulates. On the other hand, Organy was probably dominated by autocrystic zircon, and Krucze contained dismembered, subhedral zircon in its matrix, whereas Halle zircon was located partly in late veins, filling cracks in laccolith. Both localities may, therefore, contain zircon populations that represent later stages than the crystallization of the main rhyolitic body. Full article
(This article belongs to the Special Issue Accessory Minerals in Silicic Igneous Rocks)
Show Figures

Figure 1

Open AccessArticle
Further Characterization of the RW-1 Monazite: A New Working Reference Material for Oxygen and Neodymium Isotopic Microanalysis
Minerals 2019, 9(10), 583; https://doi.org/10.3390/min9100583 - 26 Sep 2019
Cited by 3
Abstract
The oxygen (O) and neodymium (Nd) isotopic composition of monazite provides an ideal tracer of metamorphism and hydrothermal activity. Calibration of the matrix effect and monitoring of the external precision of monazite O–Nd isotopes with microbeam techniques, such as secondary ion mass spectrometry [...] Read more.
The oxygen (O) and neodymium (Nd) isotopic composition of monazite provides an ideal tracer of metamorphism and hydrothermal activity. Calibration of the matrix effect and monitoring of the external precision of monazite O–Nd isotopes with microbeam techniques, such as secondary ion mass spectrometry (SIMS) and laser ablation-multicollector-inductively coupled plasma-mass spectrometry (LA-MC-ICPMS), require well-characterized natural monazite standards for precise microbeam measurements. However, the limited number of standards available is impeding the application of monazite O–Nd isotopes. Here, we report on the RW-1 monazite as a potential new working reference material for microbeam analysis of O–Nd isotopes. Microbeam measurements by electron probe microanalysis (EPMA), SIMS, and LA-MC-ICPMS at 10–24 µm scales have confirmed that it is homogeneous in both elemental and O–Nd isotopic compositions. SIMS measurements yield δ18O values consistent, within errors, with those obtained by laser fluorination techniques. Precise analyses of Nd isotope by thermal ionization mass spectrometry (TIMS) are consistent with mean results of LA-MC-ICPMS analyses. We recommend δ18O = 6.30‰ ± 0.16‰ (2SD) and 143Nd/144Nd = 0.512282 ± 0.000011 (2SD) as being the reference values for the RW-1 monazite. Full article
(This article belongs to the Special Issue Accessory Minerals in Silicic Igneous Rocks)
Show Figures

Figure 1

Open AccessArticle
Geochronology and Geochemistry of Uraninite and Coffinite: Insights into Ore-Forming Process in the Pegmatite-Hosted Uraniferous Province, North Qinling, Central China
Minerals 2019, 9(9), 552; https://doi.org/10.3390/min9090552 - 13 Sep 2019
Cited by 1
Abstract
The biotite pegmatites in the Shangdan domain of the North Qinling orogenic belt contain economic concentrations of U, constituting a low-grade, large-tonnage pegmatite-hosted uraniferous province. Uraninite is predominant and ubiquitous ore mineral and coffinite is common alteration mineral after initial deposit formation. A [...] Read more.
The biotite pegmatites in the Shangdan domain of the North Qinling orogenic belt contain economic concentrations of U, constituting a low-grade, large-tonnage pegmatite-hosted uraniferous province. Uraninite is predominant and ubiquitous ore mineral and coffinite is common alteration mineral after initial deposit formation. A comprehensive survey of the uraninite and coffinite assemblage of the Chenjiazhuang, Xiaohuacha, and Guangshigou biotite pegmatites in this uraniferous province reveal the primary magmatic U mineralization and its response during subsequent hydrothermal events. Integrating the ID-TIMS (Isotope Dilution Thermal Ionization Mass Spectrometry) 206Pb/238U ages and U-Th-Pb chemical ages for the uraninites with those reported from previous studies suggests that the timing of U mineralization in the uraniferous province was constrained at 407–415 Ma, confirming an Early Devonian magmatic ore-forming event. Based on microtextural relationships and compositional variation, three generations of uranium minerals can be identified: uaninite-A (high Th-low U-variable Y group), uranite-B (low Th-high U, Y group), and coffinite (high Si, Ca-low U, Pb group). Petrographic and microanalytical observations support a three-stage evolution model of uranium minerals from primary to subsequent generations as follows: (1) during the Early Devonian (stage 1), U derived from the hydrous silicate melt was mainly concentrated in primary magmatic uaninite-A by high-T (450–607 °C) precipitation; (2) during the Late Devonian (stage 2), U was mobilized and dissolved from pre-existing uraninite-A by U-bearing fluids and in situ reprecipitated as uraninite-B under reduced conditions. The in situ transformation of primary uraninite-A to second uraninite-B represent a local medium-T (250–450 °C) hydrothermal U-event; and (3) during the later low-T (100–140 °C) hydrothermal alteration (stage 3), U was remobilized and derived from the dissolution of pre-existing uraninite by CO2- and SiO2-rich fluids and interacted with reducing agent (e.g., pyrite) leading to reprecipitation of coffinite. This process represents a regional and extensive low-T hydrothermal U-event. In view of this, U minerals evolved from magmatic uraninite-A though fluid-induced recrystallized uraninite-B to coffinite, revealing three episodes of U circulation in the magmatic-hydrothermal system. Full article
(This article belongs to the Special Issue Accessory Minerals in Silicic Igneous Rocks)
Show Figures

Figure 1

Open AccessArticle
Pyrochlore-Group Minerals in the Granite-Hosted Katugin Rare-Metal Deposit, Transbaikalia, Russia
Minerals 2019, 9(8), 490; https://doi.org/10.3390/min9080490 - 15 Aug 2019
Abstract
Pyrochlore group minerals are the main raw phases in granitic rocks of the Katugin complex-ore deposit that stores Nb, Ta, Y, REE, U, Th, Zr, and cryolite. There are three main types: Primary magmatic, early postmagmatic (secondary-I), and late hydrothermal (secondary-II) pyrochlores. The [...] Read more.
Pyrochlore group minerals are the main raw phases in granitic rocks of the Katugin complex-ore deposit that stores Nb, Ta, Y, REE, U, Th, Zr, and cryolite. There are three main types: Primary magmatic, early postmagmatic (secondary-I), and late hydrothermal (secondary-II) pyrochlores. The primary magmatic phase is fluornatropyrochlore, which has high concentrations of Na2O (to 10.5 wt.%), F (to 5.4 wt.%), and REE2O3 (to 17.3 wt.%) but also low CaO (0.6–4.3 wt.%), UO2 (to 2.6 wt.%), ThO2 (to 1.8 wt.%), and PbO (to 1.4 wt.%). Pyrochlore of this type is very rare in nature and is limited to a few occurrences: Rare-metal deposits of Nechalacho in syenite and nepheline syenite (Canada) and Mariupol in nepheline syenite (Ukraine). It may have crystallized synchronously with or slightly later than melanocratic minerals (aegirine, biotite, and arfvedsonite) at the late magmatic stage when Fe from the melt became bound, which hindered the crystallization of columbite. Secondary-I pyrochlore follows cracks or replaces primary pyrochlore in grain rims and is compositionally similar to the early phase, except for lower Na2O concentrations (2.8 wt.%), relatively low F (4 wt.%), and less complete A- and Y-sites occupancy. Secondary-II pyrochlore is a product of late hydrothermal alteration, which postdated the formation of the Katugin deposit. It differs in large ranges of elements and contains minor K, Ba, Pb, Fe, and significant Si concentrations but also low Na and F. Its composition mostly falls within the field of hydro- and keno-pyrochlore. Full article
(This article belongs to the Special Issue Accessory Minerals in Silicic Igneous Rocks)
Show Figures

Figure 1

Open AccessArticle
Niobium Mineralogy of Pliocene A1-Type Granite of the Carpathian Back-Arc Basin, Central Europe
Minerals 2019, 9(8), 488; https://doi.org/10.3390/min9080488 - 15 Aug 2019
Cited by 1
Abstract
A1-type granite xenoliths occur in alkali basalts erupted during Pliocene–Pleistocene continental rifting of Carpathian back-arc basin (Central Europe). The Pliocene (5.2 Ma) peraluminous calc-alkalic granite contains unusually high concentrations of critical metals bound in Nb, Ta, REE, U, Th-oxides typical for [...] Read more.
A1-type granite xenoliths occur in alkali basalts erupted during Pliocene–Pleistocene continental rifting of Carpathian back-arc basin (Central Europe). The Pliocene (5.2 Ma) peraluminous calc-alkalic granite contains unusually high concentrations of critical metals bound in Nb, Ta, REE, U, Th-oxides typical for silica-undersaturated alkalic granites, and syenites: columbite-Mn, fergusonite-Y, oxycalciopyrochlore, Nb-rutile, and Ca-niobate (fersmite or viggezite). In contrast, it does not contain allanite and monazite—the main REE-carriers in calc-alkalic granites. The crystallization of REE-bearing Nb-oxides instead of OH-silicates and phosphates was probably caused by strong water deficiency and low phosphorus content in the parental magma. Increased Nb and Ta concentrations have been inherited from the mafic parental magma derived from the metasomatized mantle. The strong Al- and Ca-enrichment probably reflects the specific composition of the mantle wedge modified by fluids, alkalic, and carbonatitic melts liberated from the subducted slab of oceanic crust prior to the Pliocene-Pleistocene rifting. Full article
(This article belongs to the Special Issue Accessory Minerals in Silicic Igneous Rocks)
Show Figures

Figure 1

Open AccessArticle
Sm-Nd Dating and In-Situ LA-ICP-MS Trace Element Analyses of Scheelite from the Longshan Sb-Au Deposit, Xiangzhong Metallogenic Province, South China
Minerals 2019, 9(2), 87; https://doi.org/10.3390/min9020087 - 30 Jan 2019
Cited by 9
Abstract
Longshan is an important Sb-Au ore deposit (3.7 Mt @4.5 wt. % Sb and 4.6 g/t Au) in the Xiangzhong metallogenic province (XZMP), South China. In the present work, trace element composition, Sm-Nd isotope dating, and Sr isotope of scheelite from the Longshan [...] Read more.
Longshan is an important Sb-Au ore deposit (3.7 Mt @4.5 wt. % Sb and 4.6 g/t Au) in the Xiangzhong metallogenic province (XZMP), South China. In the present work, trace element composition, Sm-Nd isotope dating, and Sr isotope of scheelite from the Longshan Sb-Au deposit are used to constrain the genesis of the deposit. Based on mineral assemblages and geological characteristics, two types of scheelites can be distinguished (Sch1 and Sch2). Sch1 is granular and cemented by stibnite, while Sch2 is commonly present in stibnite, pyrite, calcite, and quartz veins, indicating that Sch2 is later than Sch1. The Sm-Nd isochron age defined by Sch1 is 210 ± 2 Ma (MSWD = 1.0, n = 4). This age is interpreted as the age of Sb-Au mineralization and overlaps with the 201–228 Ma granitic rocks in the XZMP. Sch1 exhibits high ΣREE + Y contents (43.5 to 104 ppm), low Sr values (2687 to 6318 ppm, average of 4018 ppm), and a narrow range of 87Sr/86Sr values (0.7209 to 0.7210, average of 0.7209). In contrast, the elevated Sr abundance (4525 to 11,040 ppm, average of 6874 ppm) and wide 87Sr/86Sr ratios (0.7209 to 0.7228, average of 0.7214) in Sch2 were possibly caused by fluid-rock interaction mixing with Sr-enriched basement rocks. Sulfides have a narrow range of δ34S values of −1.8‰ to 3.2‰, with an average value of 1.1‰ (n = 7). Geochronological, geochemical and isotopic data suggest that the Longshan Sb-Au deposit is possible genetically related to the Late Triassic granitic intrusion in the XZMP. Full article
(This article belongs to the Special Issue Accessory Minerals in Silicic Igneous Rocks)
Show Figures

Figure 1

Back to TopTop