Search Results (109)

Türkiye hosts a wide variety of barite deposits that can be broadly classified into two major groups based on their tectonic settings: magmatism-associated and passive margin-hosted deposits. The magmatism-associated deposits include Kızılcaören (F + Ba + REE + Th, Beylikova–Eskişehir), Kirazören (Bulancak–Giresun), and Karacaören (Mesudiye–Ordu). The Kızılcaören deposit formed in relation to the emplacement of a late Oligocene carbonatitic sill, while the Kirazören and Karacaören deposits are associated with the Cretaceous Pontide magmatic arc. Passive margin-hosted deposits occur within various Paleozoic sedimentary lithologies—such as metasandstone, shale, schist, and limestone—and are found in the Taurides and the Arabian Platform. These deposits occur as either concordant or discordant veins. This barite belt extends from Şarkikaraağaç (Isparta), through Hüyük (Konya) and Alanya (Antalya), to Silifke (Mersin), Tordere (Adana), Önsen, Şekeroba (Kahramanmaraş), and Hasköy (Muş). The Paleozoic deposits represent the major barite resources of Türkiye, with an annual production of approximately 300,000 metric tons. Smaller deposits around Gazipaşa (Antalya) contain minor Pb-Zn sulfides. Mesozoic barite deposits are hosted in Triassic dolomites and are associated with Pb-Zn mineralization in the Hakkari region of the Arabian Platform. Pb and Sr isotope data indicate that the barium in these deposits was derived from ancient continental crust. The isotopic compositions of both concordant (stratabound) and discordant (vein-type) barites are generally homogeneous. In northwestern Türkiye, the Sr isotope compositions of the barite deposits align well with those of the Oligocene carbonatite host complex. The ⁸⁷Sr/⁸⁶Sr isotope ratio of the Kızılcaören deposit (0.706‰) is the least radiogenic among Turkish barite deposits, suggesting a mantle contribution. The Kirazören deposit in the Pontide magmatic arc follows with a slightly higher ratio (0.707‰). Triassic barites from the Hakkari region yield ⁸⁷Sr/⁸⁶Sr values around 0.709‰, slightly more radiogenic than coeval seawater. Paleozoic barite deposits show the most radiogenic ⁸⁷Sr/⁸⁶Sr values, including Aydıncık (0.718‰), Şarkikaraağaç (0.714‰), Hasköy (0.713‰), Kahramanmaraş (0.712‰), Tordere, and Hüyük (both 0.711‰), consistent with their respective host rocks. The elevated radiogenic Pb and Sr isotope values in the passive margin-hosted deposits suggest that the barium originated from deeper, barium-enriched rocks, whereas stable sulfur isotope data point to a marine sulfur source. Moreover, Sr and S isotopic signatures indicate that the Paleozoic sediment-hosted deposits formed in association with cold seeps on the seafloor, resembling modern analogs. In contrast, the Mesozoic Karakaya deposit (Hakkari) represents a typical vent-proximal, sediment-hosted deposit with no magmatic signature. Full article

Late Paleozoic to Early Mesozoic granitoids in the East Kunlun Orogenic Belt (EKOB) provide critical insights into the complex and debated relationship between Paleo–Tethyan magmatism and tectonics. This study presents integrated bulk-rock geochemical and zircon isotopic data for the Xingshugou monzogranite (MG) to address these controversies. LA-ICP-MS zircon U-Pb dating constrains the emplacement age of the MG to 247.1 ± 1.5 Ma. The MG exhibits a peraluminous and low Na₂O A₂-type granite affinity, characterized by high K₂O (4.69–6.80 wt.%) and Zr + Nb + Ce + Y (>350 ppm) concentrations, coupled with high Y/Nb (>1.2) and A/CNK ratios (1.54–2.46). It also displays low FeO^T, MnO, TiO₂, P₂O₅, and Mg^# values (26–49), alongside pronounced negative Eu anomalies (Eu/Eu* = 0.37–0.49) and moderately fractionated rare earth element (REE) patterns ((La/Yb)_N = 3.30–5.11). The MG exhibits enrichment in light rare earth elements (LREEs) and large ion lithophile elements (LILEs; such as Sr and Ba), and depletion in high field strength elements (HFSEs; such as Nb, Ta, and Ti), collectively indicating an arc magmatic affinity. Zircon saturation temperatures (T_Zr = 868–934 °C) and geochemical discriminators suggest that the MG was generated under high-temperature, low-pressure, relatively dry conditions. Combined with positive zircon ε_Hf(t) (1.8 to 4.7) values, it is suggested that the MG was derived from partial melting of juvenile crust. Synthesizing regional data, this study suggests that the Xingshugou MG was formed in an extensional tectonic setting triggered by slab rollback of the Paleo-Tethys Oceanic slab. Full article

The South Tianshan records the latest accretionary and collisional events in the southwestern Altaids, but the internal subduction-related processes are controversial. This study provides an integrative analysis of a newly identified Late Carboniferous adakitic granodiorite from the South Tianshan, incorporating geochronological, zircon U-Pb and Lu-Hf isotopic, whole-rock geochemical, and Sr-Nd isotopic data. Zircon U-Pb analysis indicates that the granite was emplaced at 310 ± 2.5 Ma. Based on major element compositions, the granodiorite belongs to medium-K calc-alkaline weakly peraluminous series (A/CNK = 0.95–1.09). The samples exhibit typical high-silica adakitic affinity, as evidenced by the elevated contents of SiO₂ (67.75–69.27 wt.%), Al₂O₃ (15.29–15.90 wt.%), Sr (479–530 ppm), and Ba (860–910 ppm); low concentrations of Yb (0.43–0.47 ppm) and Y (7.12–7.44 ppm); high Sr/Y ratios (67–72); and slight Eu anomalies (δEu = 0.89–1.03). The sodium-rich composition (K₂O/Na₂O = 0.48–0.71) is comparable to adakitic rocks from slab-derived melts. Elevated concentrations of Ni (22.12–24.25 ppm), Cr (33.20–37.86 ppm), Co (6.32–6.75 ppm), and V (30.33–32.48 ppm), along with high Mg# values (55–57), suggest melt–mantle interaction during magma ascent. The slightly enriched isotopic signatures, characterized by higher initial ⁸⁷Sr/⁸⁶Sr ratios (0.706086–0.706205) and lower ε_Nd(t) (−3.09 to –2.47) and ε_Hf(t) (−3.11 to +7.66) values, point to notable sedimentary contributions, potentially through source contamination and/or shallow-level crustal contamination. By integrating the new results with previously published data, we consider that the adakitic granodiorite was generated by partial melting of the subducted oceanic crust, triggered by asthenospheric upwelling associated with the southward rollback of the north-dipping South Tianshan oceanic lithosphere. Our data provide new insights into Late Carboniferous retreating subduction along the southern active margin of the Yili-Central Tianshan and the accretionary architecture of the southern Altaids. Full article

The Yanbian area of Jilin Province is situated in the eastern segment of the southern margin of the Xing-Meng Orogenic Belt, representing a region that has been superimposed and reworked by the Paleo-Asian Ocean and Circum-Pacific tectonic event. To determine the emplacement age and petrogenesis of the quartz diorite in the Fudong area of Yanbian, Jilin Province, and to investigate its tectonic setting, petrographic studies, zircon U-Pb geochronology, whole-rock Sr-Nd isotopic analysis, zircon Hf isotopic analysis, and detailed geochemical investigations of this intrusion were carried out. The results indicate that the Fudong quartz diorite has: (1) A weighted mean zircon U-Pb age of 186 ± 1.7 Ma, corresponding to the Late Early Jurassic; (2) geochemically high concentrations of Sr (average: 1146 ppm) and Ba (average: 1213 ppm), and enrichment of light rare earth elements (LREE), along with notably high Th/Yb and Rb/Y ratios; (3) geochemically, the quartz diorite is enriched in large-ion lithophile elements (LILEs; e.g., Ba, K) and light rare earth elements (LREEs), while being depleted in high-field-strength elements (HFSEs; e.g., Ta, Ti). These features are consistent with magma formed in a subduction-related setting. In summary, the Fudong quartz diorite formed within an active continental margin tectonic environment associated with the subduction of the Paleo-Pacific Plate. Its primary magma likely originated from an enriched lithospheric mantle that had been metasomatized by fluids released from the subducted slab. Full article

The North Qilian Orogen experienced a series of late Neoproterozoic to early Paleozoic tectonic events, including the opening and closure of the Proto-Tethyan Qilian Ocean, as well as post-subduction processes. This study investigated the Shandan adakites in the Longshoushan area of the North Qilian Orogen, focusing on zircon U–Pb geochronology, whole-rock geochemistry, and Sr–Nd–Hf–O isotopic compositions. The Shandan adakites yield ages of ca. 446–440 Ma, suggesting they crystallized during the collision between the Alxa and Qilian blocks following the closure of the Proto-Tethyan North Qilian Ocean. High Sr/Y (40.9–117) ratios and enrichments in light rare earth elements indicate that the Shandan adakites were formed by partial melting of thickened magnesian lower crust. They have relatively rich ε_Nd (t) (−7.66 to −6.32), ε_Hf(t) (3.30 to −12.4), and δ¹⁸O (5.34‰–7.52‰). Zircon Hf–O and whole-rock Sr–Nd isotopes confirm significant contributions from the ancient crust and mantle-derived melts, suggesting complex crust–mantle interactions in their magma sources. We propose that the Shandan adakites formed during the (early) post-collisional stage of orogenesis. Based on regional geological evidence and previous studies, we suggest the Alxa and Central Qilian blocks collided during ca. 446–440 Ma, leading to the thickening of the lower crust. After ca. 440 Ma, the tectonic setting of the Northern Qilian Orogen transitioned from a collisional to a post-collisional stage. Full article

The Zaghouan Fluorite Province (ZFP) encloses F-Ba(Pb-Zn) ores hosted within Jurassic carbonate series, in northeastern Tunisia. Critical breakthroughs on the Jebel Stah fluorite deposits, an MVT-style F-mineralization, have been made within the Lower Jurassic limestones along the Zaghouan Fault, which is a major target for mineralization. This study presents the first REE-Y analyses conducted by LA-ICP-MS on fluorites in Tunisia, and specifically on the fluorites of Jebel Stah deposit. This analytical technique provides highly accurate insights into the geochemical regime of mineralizing fluids and the related scavenging sources. Distinct geochemical characteristics between two fluorite generations (G1 and G2) were revealed. Fluorites (Fl2) from the early generation (G1) showed low ΣREE + Y (36.3 and 39.73 ppm, respectively). When normalized to chondrites, early fluorite G1 displayed a bell-shaped REE + Y pattern with a depletion in LREE relative to HREE and a slight MREE hump. Late fluorite (Fl3) generation (G2) displayed higher ΣREE + Y concentrations (77.43 ppm), but an almost similar REE pattern. Ce/Ce* ratios demonstrated strong negative Ce anomalies in all fluorites, while Eu/Eu* ratios indicated weak negative Eu anomalies. The positive Y anomaly observed in the REE + Y patterns of fluorites G1 and G2 suggests Y-Ho fractionation in the fluid system. Moreover, significant degrees of differentiation between terbium (Tb) and lanthanum (La) have been observed in all fluorite samples. The plot of fluorites from both fluorite generations on the Tb/La–Tb/Ca diagram gives evidence of the sedimentary hydrothermal origin of the ore-forming fluids in the Jebel Stah F-deposit. Sr isotopes show that the mineralizing fluids are radiogenic and deeply sourced basinal brines, whereas the small variation in ⁸⁷Sr/⁸⁶Sr ratios suggests a similar source for Sr in fluorites G1 and G2. These results allow us to conclude that the economic fluorite (G1) ore of Jebel Stah was deposited due to the interaction of the deeply sourced hydrothermal fluid with the carbonated host rocks (dolomitization, an increase in pH, and Ca activity), whereas the late fluorite (G2) is an accessory and could have resulted from the mixing of the hydrothermal fluid with shallow meteoric waters. Full article

Heavy metals (HMs) from industrial pollution are bioaccumulated in plant tissues, but we lack information on their spatial variability in forest ecosystems. Picea abies L. needles, bark, and litter were collected at 17 sites along a 1000-m-wide altitudinal gradient in southern Romania to measure concentrations of mineral nutrients, non-toxic metals, and toxic metals. Isotopic ratios (^206/207Pb, ^87/86Sr) were used to infer contamination origins. We found significant differences in needle versus bark and litter elements’ concentrations, indicating that needles are sensitive biomarkers in tracking air pollution. We found high Fe, Mn, Zn, and Cu concentrations, which can be involved in the low Na, Mg, and P content in needles. The mole ratios indicate a negative relationship with As concentrations in needles. Several environmental health and ecological risk assessment indices document that Cd levels can represent a moderate risk for most sites. Our study shows that P. abies presented an elevated bioaccumulation potential for Fe, Zn, Cu, Ni, and Cr, respectively, and it only absorbed Na, Sr, Cd, and Li. The methodology and results presented herein may serve as a reference for future studies and provide a foundation to develop management strategies to mitigate heavy metal pollution in forest ecosystems. Full article

The Kongco area of Nima in the northern part of the Lhasa terrane has a suite of alkaline granitic porphyry dykes associated with Early Cretaceous granites and accompanied by Cu/Mo mineralization. LA-ICP-MS ²⁰⁶Pb/²³⁸U zircon geochronology performed on the dykes produced an age of 104.15 ± 0.94 Ma (MSWD = 0.98), indicating the Early Cretaceous emplacement of the dykes. The dykes exhibit high silica (SiO₂ = 76.22~77.90 wt.%), high potassium (K₂O = 4.97~6.21 wt.%), high alkalinity (K₂O + Na₂O = 8.07~8.98 wt.%), low calcium (CaO = 0.24~0.83 wt.%), low magnesium (MgO = 0.06~0.20 wt.%), and moderate aluminum content (Al₂O₃ = 11.93~12.45 wt.%). The Rieterman index (σ) ranges from 1.93 to 2.34. A/NK (molar ratio Al₂O₃/(Na₂O + K₂O)) and A/CNK (molar ratio Al₂O₃/(CaO + Na₂O + K₂O)) values of the dykes range from 1.06 to 1.18 and 0.98 to 1.09, respectively. The dykes are relatively enriched in Rb, Th, U, K, Ta, Ce, Nd, Zr, Hf, Sm, Y, Yb, and Lu, and they show a noticeable relative depletion in Ba, Nb, Sr, P, Eu, and Ti, as well as an average differentiation index (DI) of 96.42. The dykes also exhibit high FeO_T/MgO ratios (3.60~10.41), Ga/Al ratios (2.22 × 10⁻⁴~3.01 × 10⁻⁴), Y/Nb ratios (1.75~2.40), and Rb/Nb ratios (8.36~20.76). Additionally, they have high whole-rock Zr saturation temperatures (884~914 °C), a pronounced Eu negative anomaly (δEu = 0.04~0.23), and a rightward-sloping “V-shaped” rare earth element pattern. These characteristics suggest that the granitic porphyry dykes can be classified as A2-type granites formed in a post-collisional tectonic environment and that they are weakly peraluminous, high-potassium, and Calc-alkaline basaltic rocks. Positive ε_Hf(t) values = 0.43~3.63 and a relatively young Hf crustal model age (T_DM2 = 826~1005 Ma, ⁸⁷Sr/⁸⁶Sr ratios = 0.7043~0.7064, and ε_Nd(t) = −8.60~−2.95 all indicate lower crust and mantle mixing. The lower crust and mantle mixing model is also supported by (²⁰⁶Pb/²⁰⁴Pb)t = 18.627~18.788, (²⁰⁷Pb/²⁰⁴Pb)t = 15.707~15.719, (²⁰⁸Pb/²⁰⁴Pb)t = 39.038~39.110). Together, the Hf, Sr and Pb isotopic ratios indicate that the Kongco granitic porphyry dykes where derived from juvenile crust formed by the addition of mantle material to the lower crust. From this, we infer that the Kongco granitic porphyry dykes are related to a partial melting of the lower crust induced by subduction slab break-off and asthenospheric upwelling during the collision between the Qiangtang and Lhasa terranes and that they experienced significant fractional crystallization dominated by potassium feldspar and amphibole. These dykes are also accompanied by significant copper mineralization (five samples, copper content 0.2%), suggesting a close relationship between the magmatism associated with these dykes and regional metallogenesis, indicating a high potential for mineral exploration. Full article

The Biggenden gold-bearing Fe skarn deposit in southeast Queensland, Australia, is a calcic magnetite skarn that has been mined for Fe and gold (from the upper portion of the deposit). Skarn has replaced volcanic and sedimentary rocks of the Early Permian Gympie Group, which formed in different tectonic settings, including island arc, back arc, and mid-ocean ridge. This group has experienced a hornblende-hornfels grade of contact metamorphism due to the intrusion of the Late Triassic Degilbo Granite. The intrusion is a mildly oxidized I-type monzogranite that has geochemical characteristics intermediate between those of granitoids typically associated with Fe-Cu-Au and Sn-W-Mo skarn deposits. The skarn mineralogy indicates that there was an evolution from prograde to various retrograde assemblages. Prograde garnet (Adr_11-99Grs_1-78Alm_0-8Sps_0-11), clinopyroxene (Di_30-92Hd_7-65Jo_0-9), magnetite, and scapolite formed initially. Epidote and Cl-bearing amphibole (mainly ferropargasite) were the early retrograde minerals, followed by chlorite, calcite, actinolite, quartz, and sulfides. Late-stage retrograde reactions are indicated by the development of nontronite, calcite, and quartz. Gold is mainly associated with sulfide minerals in the retrograde sulfide stage. The fluids in equilibrium with the ore-stage calcites had δ¹³C and δ¹⁸O values that indicate deposition from magmatically derived fluids. The calculated δ¹⁸O values of the fluids in equilibrium with the skarn magnetite also suggest a magmatic origin. However, the fluids in equilibrium with epidote were a mixture of magmatic and meteoric water, and the fluids that deposited chlorite were at least partly meteoric. δD values for the retrograde amphibole and epidote fall within the common range for magmatic water. Late-stage chlorite was deposited from metasomatic fluids depleted in deuterium (D), implying a meteoric water origin. Sulfur isotopic compositions of the Biggenden sulfides are similar to other skarn deposits worldwide and indicate that sulfur was most probably derived from a magmatic source. Based on the strontium (⁸⁷Sr/⁸⁶Sr) and lead (²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb) isotope ratios, the volcanic and sedimentary rocks of the Gympie Group may have contributed part of the metals to the hydrothermal fluids. Lead isotope data are also consistent with a close age relationship between the mineralization at Biggenden and the crystallization of the Degilbo Granite. Microthermometric analysis indicates that there is an overall decrease in fluid temperature and salinity from the prograde skarn to retrograde alterations. Fluid inclusions in prograde skarn calcite and garnet yield homogenization temperatures of 500 to 600 °C and have salinities up to 45 equivalent wt % NaCl. Fluid inclusions in quartz and calcite from the retrograde sulfide-stage homogenized between 280 and 360 °C and have lower salinities (5–15 equivalent wt % NaCl). In a favored genetic model, hydrothermal fluids originated from the Degilbo Granite at depth and migrated through the shear zone, intrusive contact, and permeable Gympie Group rocks and leached extra Fe and Ca and deposited magnetite upon reaction with the adjacent marble and basalt. Full article

The Solonker-Xar Moron-Changchun-Yanji Suture Zone is the result of the final closure of the Paleo-Asian Ocean (PAO). However, the closure time of the PAO in Northeast China remains controversial. The Hunchun area is located in the easternmost part of the Solonker-Xar Moron-Changchun-Yanji Suture Zone. Tectonism and magmatism in the Hunchun area can provide important information for understanding the late-stage evolution of the PAO. In this study, our zircon U-Pb ages show that the granodiorites and diorites in the Hunchun were formed at 282.3–251.4 Ma. This geochronological evidence suggests prolonged Permian magmatism in the Hunchun area. Whole-rock geochemistry, zircon trace, and Lu-Hf isotope data show that all the intrusive rocks are mainly calc-alkaline series to arc tholeiite series. Granodiorites are I-type granites formed by the partial melting of juvenile lower crust derived from the mantle. Diorites show similar characteristics to the sanukitic high-Mg diorite and are formed by the partial melting of the depleted mantle metasomatized by subduction sediments and/or slab-derived fluids. These results indicate that the Permian diorites and granodiorites in the Hunchun area formed in an active continental margin setting related to the subduction of the PAO plate. Significantly, sudden changes in the whole-rock Sr/Y and (La/Yb)_N ratios and zircon ε_Hf(t) values are observed in the Late Permian-Early Triassic igneous rocks in the eastern Central Asian Orogenic Belt (CAOB). This indicates that the final closure of the PAO in Northeast China likely occurred in the Late Permian-Early Triassic. Full article

The Early Cretaceous intermediate intrusive rocks have important significance in understanding the crust–mantle interaction, iron mineralization, and tectonic evolution in the western Shandong Peninsula. In this study, we present new zircon U–Pb ages, and Hf isotope, whole-rock geochemistry, Sr–Nd isotopes, and the mineral chemistry of the diorite-porphyrite in the southern Xintai area, mid-western Shandong Peninsula. The diorite-porphyrite formed at ca. 125 Ma. They have intermediate SiO₂ (59.57–62.29 wt.%) and MgO (2.78–3.58 wt.%) contents, high Mg# values (53–56), high Sr (589–939 ppm) and low Y (9.2–10.8 ppm) contents, and high Sr/Y ratios (54–94), showing adakitic affinity. The diorite-porphyrite exhibits lower zircon ε_Hf(t) values (−30.1 to 7.5) and whole-rock ε_Nd(t) values (−3.5 to −6.0), with (⁸⁷Sr/⁸⁶Sr)_i ratios of 0.70514–0.70567. We suggest that the diorite-porphyrite was derived from the partial melting of the local delamination of lower continental crust and then by the interaction with the enriched lithospheric mantle. The genesis of diorite-porphyrite may be related to the rollback process of the Paleo-Pacific slab in the Early Cretaceous. This geodynamic process induced the melting of the enriched lithospheric mantle, subducted oceanic crust, and local delamination of lower continental crust, which produced different types of adakitic magmatism in the western Shandong Peninsula. Full article

The Mingshan reservoir of the Dabie Orogen has a number of Neoproterozoic bimodal intrusive rocks. We focused on the zircon U-Pb chronology, Hf isotopes, and bulk-rock geochemistry of these rocks. The results showed the following: (1) The bimodal intrusive rocks mainly consist of monzogranitic gneiss and plagioamphibolite, with zircon U-Pb ages of 785.0 ± 7.1 Ma and 787.3 ± 6.1 Ma, respectively. These ages indicate that they were formed in the late Qingbaikou epoch of the Neoproterozoic era. (2) The monzogranitic gneiss was dominated by peraluminous features and displayed a strong right deviation of REE (rare-earth element) patterns and a negative δEu anomaly. It is enriched in the LILEs (large-ion lithophile elements) Rb, Ba, and K, but slightly depleted in Nb, Sr, P, and Ti, with low 10,000* Ga/Al values, indicating that it is similar to Al-type granite. The plagioamphibolite belongs to the metaluminous, peraluminous series. It has a Mg^# (molar ratio of Mg to Mg + Fe) of 36.1~55.9 and is enriched in the LILEs Rb, Ba, and K, with a slight positive anomaly of Ba, and is depleted in Nb and Sr. (3) The monzogranite shows negative zircon εHf(t) values ranging from −13.4 to −7.2 and a Paleoproterozoic T_DM2(Hf) (two-stage depleted mantle model age) of 1969–2298 Ma. The zircon εHf(t) values and T_DM2(Hf) of the plagioamphibolite were concentrated around 2.9–5.7 and 1257–1410 Ma, respectively. The geochemistry and Hf isotopes show that the monzogranitic gneiss and plagioamphibolite have distinct magmatic sources. The plagioamphibolite formed from mantle and partial continental crustal materials. The monzogranitic gneiss, on the other hand, was formed as a result of the partial melting of the shallow ancient felsic crust caused by mafic rock heating or upwelling. Taking into account regional correlation, the middle Neoproterozoic bimodal intrusive rocks originated in the structural framework of an extensional setting. Full article

In the Huanggangliang–Ganzhuermiao metallogenic belt in the southern Great Xing’an Range, the Haobugao Pb–Zn deposit is the most widespread skarn-type polymetallic deposit. The observed mineralization processes in this area are closely associated with both magmatic and tectonic activity. The zircon U–Pb ages of two granitoid phases are 134.0 ± 0.6 Ma and 133.4 ± 0.9 Ma (Early Cretaceous). High SiO₂ content (average mass fractions of 77.98 wt.% and 73.25 wt.%), high alkalinity (average mass fractions of 6.19 wt.% and 8.78 wt.%), and low CaO levels (average mass fractions of 0.16 wt.% and 0.12 wt.%) are characteristic of these rocks. They are also enriched in high-field-strength elements (HFSEs) (Th, U, Ta, Zr, Hf, etc.) and depleted in large ion lithophile elements (LILEs) (Ba, Sr, etc.). Furthermore, the Nb/Ta ratios (7.80~8.82, 10.00~10.83) point to a crustal origin of the magma. The zircon Hf isotopic compositions suggest that the melting of young crust derived from Meso-Neoproterozoic and Neoproterozoic depleted mantle gave rise to the magma in these granite porphyries. These rocks formed in an extensional environment driven by the subduction and retreat of the Paleo-Pacific plate during the Early Cretaceous. Full article

The Waxing Mo polymetallic deposit is located in the central part of the Lesser Xing’an–Zhangguangcai Range (LXZR), NE China. The Mo (Cu) mineralization in the deposit is dominantly hosted by quartz veinlets and stockworks and is closely related to silicification and potassic alteration, while the W mineralization is most closely related to greisenization. Zircon samples from granodiorite, biotite monzogranite, granodiorite porphyry, and syenogranite in the Waxing deposit yielded U-Pb ages of 172.3 Ma, 172.8 Ma, 173.0 Ma, and 171.4 Ma, respectively. Six molybdenite samples from porphyry Mo ores yielded a Re-Os isochron age of 172.0 ± 1.1 Ma. The granitoids in the ore district are relatively high in total alkali (Na₂O + K₂O), are metaluminous to weakly peraluminous, and are classified as I-type granitoids. The zircon samples from all granitoids showed a relatively consistent Hf isotopic composition, as shown by positive ε_Hf(t) values (3.1–8.3) and young T_DM2 ages (0.69–1.25 Ga). These results, combined with the whole-rock geochemistry, suggest that the magma source of these rocks most likely derived from partial melting of a juvenile middle-lower continental crust, with a minor contribution from the mantle. These granitoids have compositional characteristics of adakites such as relatively high Sr contents (e.g., >400 ppm) and Sr/Y ratios (e.g., >33), as well as weak Eu anomalies (e.g., Eu/Eu* = 0.8–1.1), indicating extensive fractionation crystallization of a hydrous magma. The apatite geochemistry indicates that the ore-related magma in Waxing is F-rich and has a relatively low content of sulfur. The zircon geochemistry reveals that the granodiorite, biotite monzogranite, and granodiorite porphyry have relatively high oxygen fugacity (i.e., ΔFMQ = +1.1~1.3), whereas the fO₂ values of the granite porphyry and syenogranite are relatively low (i.e., ΔFMQ = +0.1~0.5). The whole-rock and mineral geochemistry suggest that the Mo mineralization in Waxing is probably genetically related to granitoids (i.e., granodiorite, biotite monzogranite, and granodiorite porphyry), with higher oxygen fugacity and a high water content, whereas the magmatic S concentration is not the key factor controlling the mineralization. A comparison of the geochemical compositions of ore-forming and barren stocks for porphyry Mo deposits in the LXZR showed that geochemical ratios, including Eu/Eu* (>0.8), 10,000*(Eu/Eu*)/Y (>600), Sr/Y (>33), and V/Sc (>8), could be effective indicators in discriminating fertile granitoids for porphyry Mo deposits from barren ones in the region. Full article

The Deki Amhare complex is located in central Eritrea, within the Arabian–Nubian Shield (ANS). It consists of an inner core of monzogranite porphyry and diorite enclaves (MMEs), surrounded outwardly by granodiorite and quartz diorite. The zircon U–Pb ages, whole-rock geochemistry, and Sr–Nd–Hf isotopic compositions of the Deki Amhare complex granitoids were used to discuss the Neoproterozoic tectonics of the ANS. The Late Tonian granodiorite and quartz diorite are metaluminous and calc-alkaline to slightly high-K calc-alkaline I-type plutons, with ages of 811.2 ± 4.8 Ma and 811.6 ± 5.7 Ma, respectively. They exhibit positive ε_Hf(t) (7.6–9.5) and ε_Nd(t) (3.9–4.7) values and relatively low (⁸⁷Sr/⁸⁶Sr)_i ratios (0.70374–0.70463), indicating that they derived from the partial melting of a metasomatized mantle wedge during intra-oceanic subduction. The Ediacaran monzogranite porphyry and MMEs are subalkaline to alkaline A₂-type granitoids with ages of 620.0 ± 4.3 Ma and 614.8 ± 3.9 Ma. These display positive ε_Hf(t) (5.3–8.7) and ε_Nd(t) (4.2–4.7) values, as well as low (⁸⁷Sr/⁸⁶Sr)_i ratios (0.70310–0.70480), implying that they formed through crust–mantle magma mixing related to post-collisional slab break-off. Based on these data, three stages of regional tectonic evolution can be described: (1) from ~1200 Ma to ~875 Ma, the mafic oceanic crust was derived from depleted mantle during the opening of the Mozambique Ocean; (2) from ~875 Ma to ~630 Ma, intra-oceanic subduction and arc formation occurred with the development of I-type batholiths; and (3) from ~630 Ma to ~600 Ma, crustal and lithospheric reworking took place post-collision, leading to the formation of A₂-type granitoids. Full article