Search Results (299)

The Gabal Um Samra (GUS) compound intrusion in the Eastern Desert of Egypt consists of a co-magmatic series of syenogranite and alkali feldspar granite. Accessory minerals (e.g., zircon, monazite, allanite) are abundant. Geochemically, the GUS intrusion is a classic A-type granite. It is extensively fractionated, enriched in large ion lithophile elements and high field strength elements, and depleted in Ba, Sr, K, and Ti. Normalized rare earth element patterns are nearly flat, without any lanthanide tetrad anomalies, but with distinct negative Eu anomalies (Eu/Eu* = 0.14–0.22) due to feldspar fractionation. Paired Zr-Hf and Y-Ho element systematics indicate igneous rather than hydrothermal processes. The petrogenesis of the comparatively unaltered GUS intrusion offers an opportunity to refine the standard model for post-collisional felsic magmatism in the Neoproterozoic Arabian–Nubian Shield. It is explained by the partial melting of juvenile crust induced by lithospheric delamination, followed by extensive fractional crystallization. A quantitative mass-balance model shows that the granite varieties of the GUS intrusion plausibly represent liquids along a single liquid line of descent; but, if so, the more evolved, later pulses display anomalous enrichment in Rb, Nb, Ta, U, and REE. The most plausible source for this enrichment is the extraction of small-degree residual melts from earlier pulses and the mixing of the melts into the later pulses, an energetically favorable process we call “auto-assimilation”. A quantitative model shows that the residual liquid after 97.5% crystallization of the syenogranite can fit the major oxide and trace element data in the alkali feldspar granite if 0.07% by mass of this melt is added to the evolving system for each 1% crystal fractionation by mass. The GUS intrusion represents an example of moderate rare metal enrichment and concentration to sub-economic grade by auto-assimilation. Similar processes may affect intrusions that feature higher grade mineralization, but the evidence is often obscured by the extensive alteration of those deposits. Full article

The Changning-Menglian suture zone, as the remnant of the main Paleo-Tethyan oceanic basin in its southern segment, lacks direct magmatic evidence constraining the timing of subduction initiation in its northern segment. The petrogenesis and tectonic setting of the newly discovered Early Permian (~280 Ma) Wayao granodiorite in the northern segment remain unclear, hindering our understanding of the timing of subduction initiation and processes of the Paleo-Tethyan Ocean in the Changning-Menglian suture zone. This study presents systematic petrographic, zircon U-Pb geochronological, whole-rock major and trace element geochemical, and Sr-Nd-Hf isotopic analyses on the newly discovered Early Permian granodiorite in the Wayao area, northern segment of the Changning-Menglian suture zone, western Yunnan. Zircon U-Pb dating yields a crystallization age of ca. 280 Ma, confirming its emplacement during the Early Permian. The petrogeochemical characteristics indicate that it belongs to the metaluminous, calc-alkaline series of I-type granite. It is enriched in large-ion lithophile elements (LILEs; e.g., Rb, Th, U, La, Pb) and depleted in high-field-strength elements (HFSEs; e.g., Ba, Nb, Sr, Ti), exhibiting a pronounced negative Eu anomaly. Whole-rock Sr-Nd isotopes (εNd(t) = −5.6–−6.1) and zircon Hf isotopes (εHf(t) = −1.34–−10.01) suggest that the magma was predominantly derived from the partial melting of ancient crustal material (primarily metamorphosed basic rocks, such as amphibolite), with a minor addition of mantle-derived components (magma mixing). Combined with petrogeochemical discriminant diagrams (e.g., Sr/Y vs. Y, Rb vs. Yb + Ta) and the regional geological context, this granodiorite is interpreted to have formed in an active continental margin tectonic setting associated with the eastward subduction of the Paleo-Tethys Ocean (represented by the Changning-Menglian Ocean). This discovery fills the gap in the record of Early Permian subduction-related magmatic rocks in the northern segment of the Changning-Menglian suture zone. It provides crucial petrological evidence constraining that the eastward subduction and consumption of the northern Paleo-Tethys Ocean had already commenced by the Early Permian. Full article

The Chating Cu-Au and Magushan Cu-Mo deposits in Anhui province are two representative deposits within the recently defined Nanling-Xuancheng ore concentration area in the Middle and Lower Yangtze River Metallogenic Belt (MLYB). Magmatism and mineralization for the area are not well known at present due to a lack of in-depth studies on the petrogenesis of ore-bearing intrusive rocks and their relationship with deposits. Here, the ore-bearing intrusive rocks of the two deposits are investigated through analyses of whole-rock geochemistry and Sr-Nd isotopes, zircon U-Pb ages, and zircon Hf isotopes. The results reflect the two intrusions, both formed in the Early Cretaceous (138.9 ± 0.8 Ma and 132.2 ± 1.3 Ma). They belong to the sub-alkaline high-K calc-alkaline series, while trace elements are enriched in LILEs and LREE and depleted in HFSEs. However, the intrusions of the Chating deposit (I_sr = 0.7064–0.7068; ε_Nd(t) = −8.5–−7.3; ε_Hf(t) = −11.9–−7.0) have obviously different Sr-Nd-Hf isotopic compositions from the intrusions of the Magushan deposit (I_sr = 0.7079–0.7081; ε_Nd(t) = −5.7–−5.4; ε_Hf(t) = −5.4–−3.6). The characteristics indicate that the two intrusions were formed in the same diagenetic ages and tectonic settings and derived from a crust–mantle mixture with predominant mantle-derived materials. But the crust materials of sources are different, which further leads to different metallogenic elements, showing that the Chating deposit is enriched in Cu and Au, while the Magushan deposit is enriched in Mo. Moreover, the characteristics and magma sources of two intrusions and metallogenic elements correspond respectively to the Tongling Cu-Au polymetallic ore concentration area in the MLYB and the southern Anhui Mo polymetallic ore concentration area in the Jiangnan orogen. The correlation implies differences in magmatism and mineralization between the northwestern and southeastern parts of the Nanling-Xuancheng ore concentration area, demarcated by the Jiangnan Deep Fault. These variations were mainly controlled by the Pre-Sinian crustal basement. Full article

The article provides a comprehensive analysis of the Magal Gebreel granitic suites (MGGs) using petrological (fieldwork, petrography, mineral chemistry, and bulk rock analysis) aspects to infer their petrogenesis and emplacement setting. Our understanding of the development of the northern portion of the Arabian Nubian Shield is significantly improved by the Neoproterozoic granitic rocks of the seldom studied MGGs in Egypt’s south Eastern Desert. According to detailed field, mineralogical, and geochemical assessments, they comprise syn-collision (granodiorites) and post-collision (monzogranites, syenogranites, and alkali feldspar rocks). Granodiorite has strong positive Pb, notable negative P, Ti, and Nb anomalies, and is magnesian in composition. They have high content of LREEs (light rare-earth elements) compared to HREEs (heavy rare-earth elements) and clear elevation of LFSEs (low-field strength elements; K Rb, and Ba) compared to HFSEs (high-field strength elements; Zr and Nb), which are in accord with the contents of I-type granites from the Eastern Desert. In this context, the granodiorites are indicative of an early magmatic phase that probably resulted from the partial melting of high K-mafic sources in the subduction zone. Conversely, the post-collision rocks have low contents of Mg#, CaO, P₂O₅, MgO, Fe₂O₃, Sr, and Ti, and high SiO₂, Fe₂O₃/MgO, Nb, Ce, and Ga/Al, suggesting A-type features with ferroan affinity. Their P, Nb, Sr, Ba, and Ti negative anomalies are in accord with the findings for Eastern Desert granites of the A2-type. Furthermore, they exhibit a prominent negative anomaly in Eu and a small elevation of LREEs in relation to HREEs. The oxygen fugacity (fO₂) for the rocks under investigation can be calculated using the biotite chemistry. The narrow Fe/(Fe + Mg) ratio range (0.6–0.75) indicates that they crystallized under moderately oxidizing conditions between ~QFM +0.1 and QFM +1. The A-type rocks were formed by the partial melting of a tonalite source (underplating rocks) in a post-collisional environment during the late period of extension via slab delamination. The lithosphere became somewhat impregnated with particular elements as a result of the interaction between the deeper crust and the upwelling mantle. Full article

The Permian–Triassic magmatic record in the eastern Central Asian Orogenic Belt (CAOB) provides critical insights into the terminal stages of the Paleo-Asian Ocean (PAO) evolution, including collisional and post-collisional processes following its Late Permian closure. The northeastern China region, tectonically situated within the eastern segment of the CAOB, is traditionally known as the Xingmeng Orogenic Belt (XOR). This study integrates zircon U-Pb geochronology, whole-rock geochemistry, and zircon Hf isotopic analyses of intermediate-acid volcanic rocks and intrusive rocks from the former “Tongjiatun Formation” in the Faku area of northern Liaoning. The main objective is to explore the petrogenesis of these igneous rocks and their implications for the regional tectonic setting. Zircon U-Pb ages of these rocks range from 260.5 to 230.1 Ma, indicating Permian–Triassic magmatism. Specifically, the Gongzhuling rhyolite (260.5 ± 2.2 Ma) and Gongzhuling dacite (260.3 ± 2.4 Ma) formed during the Middle-Late Permian (270–256 Ma); the Wangjiadian dacite (243 ± 3.0 Ma) and Wafangxi rhyolite (243.9 ± 3.0 Ma) were formed in the late Permian-early Middle Triassic (256–242 Ma); the Haoguantun rhyolite (240.9 ± 2.2 Ma) and Sheshangou pluton (230.1 ± 1.7 Ma) were formed during the Late Middle-Late Triassic (241–215 Ma). Geochemical studies, integrated with the geochronological results, reveal distinct tectonic settings during successive stages: (1) Middle-Late Permian (270–256 Ma): Magmatism included peraluminous A-type rhyolite with in calc-alkaline series (e.g., Gongzhuling) formed in an extensional environment linked to a mantle plume, alongside metaluminous, calc-alkaline I-type dacite (e.g., Gongzhuling) associated with the subduction of the PAO plate. (2) Late Permian-Early Middle Triassic (256–242 Ma): Calc-alkaline I-type magmatism dominated, represented by dacite (e.g., Wangjiadian) and rhyolite (e.g., Wafangxi), indicative of a collisional uplift environment. (3) Late Middle-Late Triassic (241–215 Ma): Magmatism transitioned to high-K calc-alkaline with A-type rocks affinities, including rhyolite (e.g., Haoguantun) and plutons (e.g., Sheshangou), formed in a post-collisional extensional environment. This study suggests that the closure of the PAO along the northern margin of the North China Craton (NCC) occurred before the Late Triassic. Late Triassic magmatic rocks in this region record a post-orogenic extensional setting, reflecting tectonic processes following NCC-XOR collision rather than PAO subduction. Combined with previously reported age data, the tectonic evolution of the eastern segment of the CAOB during the Permian-Triassic can be divided into four stages: active continental margin (293–274 Ma), plate disintegration (270–256 Ma), final collision and closure (256–241 Ma), and post-orogenic extension (241–215 Ma). Full article

The Yangtze Block, with its widespread Neoproterozoic mafic–felsic magmatic rock series and volcanic–sedimentary rock assemblages, is one of the key windows for reconstructing the assembly and fragmentation process of Rodinia. This study focuses on the Taoyuan syenogranite from the Micangshan Massif on the northern Yangtze Block, by conducting systematic chronology, mineralogy, and geochemistry analyses to investigate their source, petrogenesis, and tectonic setting. LA-ICP-MS U–Pb geochronology reveals that the medium- to coarse-grained and medium- to fine-grained syenogranites have crystallization ages of 878 ± 4.2 Ma and 880 ± 6.5 Ma, respectively. These syenogranites have aluminum saturation index (A/CNK) values ranging from 0.79 to 1.06, indicating quasi-aluminous to weakly peraluminous compositions, and are classified as calc-alkaline I-type granites. The geochemical indicators of these rocks, including Mg^# (44–48, mean 46), Zr/Hf (40.07), Nb/La (0.4), and zircon εHf(t) values (+9.2 to +10.9), collectively indicate a depleted lithospheric mantle source. The mantle source was metasomatized by subduction-derived fluids and sediment melts prior to partial melting as evidenced by their higher Mg^#, elevated Ba content, and distinctive ratios (Rb/Y, Nb/Y, Th/Yb, Th/Sm, Th/Ce, and Ba/La). Integrating regional data, this study confirms crust–mantle interaction along the northern Yangtze during the early Neoproterozoic, supporting a sustained subduction-related tectonic setting. Full article

The Karamaili Granite Belt (KGB) in the southern margin of the Eastern Junggar is the most important tin metallogenic belt in the southwestern Central Asian Orogenic Belt. The plutons in the western part have a close genetic relationship with tin mineralization. The zircon U-Pb ages of the Kamusite, Laoyaquan, and Beilekuduke plutons are 315.1 ± 3.4 Ma, 313.6 ± 2.9 Ma, and 316.5 ± 4.6 Ma, respectively. The plutons have high silica (SiO₂ = 75.53%–77.85%), potassium (K₂O = 4.43%–5.42%), and alkalis (K₂O + Na₂O = 8.17%–8.90%) contents and low ferroan (Fe₂O₃^T = 0.90%–1.48%), calcium, and magnesium contents and are classified as metaluminous–peraluminous, high-potassium, calc-alkaline iron granite. The rocks are enriched in Rb, Th, U, K, Pb, and Sn and strongly depleted in Ba, Sr, P, Eu, and Ti. They have strongly negative Eu anomalies (δEu = 0.01–0.05), 10,000 Ga/Al = 2.87–4.91 (>2.6), showing the geochemical characteristics of A-type granite. The zircon U/Pb ratios indicate that the above granites should be I- or A-type granite, which is generally formed under high-temperature (768–843 °C), low-pressure, and reducing magma conditions. The high Rb/Sr ratio (a mean of 48 > 1.2) and low K/Rb ratio (53.93–169.94) indicate that the tin-bearing plutons have undergone high differentiation. The positive whole-rock εNd(t) values (3.99–5.54) and the relatively young Nd T_2DM model ages (616–455 Ma) suggest the magma is derived from partially melted juvenile crust, and the underplating of basic magma containing mantle materials that affected the source area. The results indicate the KGB was formed in the tectonic transition period in the late Carboniferous subduction post-collision environment. Orogenic compression influenced the tin-bearing plutons in the western part of the KGB, forming highly differentiated and reduced I, A-type transition granite. An extensional environment affected the plutons in the eastern sections, creating A-type granite with dark enclaves that suggest magma mixing with little evidence of tin mineralization. Full article

The Great Xing’ an Range is located in the eastern part of the Xing’ an-Mongolian Orogenic Belt, which is an important component of the Central Asian Orogenic Belt. To determine the emplacement age and petrogenesis of the granitoids in the Gegenmiao and Taonan areas of the central Great Xing’an Range, 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 the following, in relation to the granitoids in the study areas: (1) The zircon U-Pb dating of the granitic rocks in the study areas yields ages ranging from 141.4 ± 2.0 Ma to 158.7 ± 1.9 Ma, indicating their formation during the Late Jurassic to Early Cretaceous; (2) the geochemical characteristics indicate that these rocks belong to the calc-alkaline series and peraluminous, classified as highly fractionated I-type granites with adakite features; (3) the Sr-Nd isotopic data show that the εNd(t) values of Gegenmiao granitic rocks are 2.8 and 2.1, while those of Taonan granitic rocks range from −1.5 to 0.7; (4) the Zircon εHf(t) values of the granitic rocks from Gegenmiao and Taonan vary from 2.11 to 6.48 and 0.90 to 8.25, respectively. They are interpreted to have formed through partial melting of thickened lower crustal material during the Meso-Neoproterozoic. The Gegenmiao and Taonan granitic rocks were formed in a transitional environment from post-orogenic compression to extension, which is closely associated with the Mongolia–Okhotsk tectonic system. 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

This study contributes new mineralogical, whole-rock geochemical, and magnetic susceptibility data to the well-established petrogenesis of the Miocene of Limnos volcanic rocks in the Aegean region. The combined examination of volcanic samples from the Katalakon, Romanou, and Myrina units demonstrates that they belong to a genetically related high-K calc-alkaline to shoshonitic suite that was formed by fractional crystallization in a continental arc setting and derived from a subduction-modified mantle source, contaminated by continental sediments. Different magmatic processes and crystallization conditions are reflected in modest compositional differences in magnetite (Ti, Al substitution) and ilmenite (Mg, Al, Fe–Ti ratios), as well as variations in trace elements between the units (e.g., elevated Nb–Zr in Romanou, high LREE in Myrina, and Ba in Katalakon). According to the magnetic data, bulk magnetic susceptibility is largely determined by magnetite abundance, whereas magnetic domain states are influenced by the grain size and shape, as euhedral grains are associated with stronger responses. The coupled geochemical and magnetic results indicate the diversified and transitional character of the Agios Ioannis Subunit in the Katalakon Unit. Full article

The tectonic evolution of the Paleo-Pacific Ocean and the destruction mechanism of the North China Craton (NCC) are still controversial. In this study, we conducted zircon U-Pb dating, whole-rock geochemistry, and Sr-Nd-Hf isotope analyses on the Weiyuanpu mafic–ultramafic intrusions in the eastern segment of the northern margin of the NCC to discuss their petrogenesis and tectonic implications. The Weiyuanpu mafic–ultramafic intrusions consist of troctolite, hornblendite, hornblende gabbro, gabbro, and minor diorite, anorthosite, characterized by cumulate structure. The main crystallization sequence of minerals is olivine → pyroxene → magnetite → hornblende. The zircon U-Pb ages of hornblendite, hornblende grabbro, and diorite are ~170Ma. Geochemical characteristics exhibit low-K tholeiitic to calc-alkaline series, enriched in light rare-earth elements (LREE) and significant large-ion lithophile elements (LILE), and depleted in high-field-strength elements (HFSE). Sr-Nd isotopic compositions are I_Sr = 0.7043–0.7055, εNd(t) = −0.7 to +0.9, and zircon εHf (t) values range from +3.4 to +8.7. These results suggest that the source region was a phlogopite-bearing garnet lherzolite mantle metasomatized by subduction fluids. The study reveals that the northeastern margin of the NCC was in a back-arc extensional setting due to the subduction of the Paleo-Pacific Ocean during the Middle Jurassic, which caused lithosphere thinning and mantle melting in this region. Full article

The North China Craton (NCC) experienced extensive destruction and modification of its subcontinental lithospheric mantle during the Mesozoic, a period marked by intensive tectonism, magmatism, and mineralization. Among the key manifestations of this event are the Shizhuzi magmatic complex (SMC) and related Mo-Cu-Au deposits in the Liaodong Peninsula. This study presents new zircon U-Pb ages and Hf isotope data, along with whole-rock major and trace element geochemical data. Meanwhile, by incorporating published datasets, the magmatism and mineralization of the SMC are discussed. Two-stage magmatic activity is identified in the SMC as follows: (1) Stage I (130–126 Ma) associated with mineralization, and (2) Stage II (121–117 Ma), both corresponding to the peak destruction of the NCC. The mineralized granitoids exhibit I-type affinities and formed in an extension setting. Quartz diorites within this suite were derived from the partial melting of an enriched mantle source, and the high-temperature thermal underplating associated with this process subsequently triggered partial melting of the basaltic lower crust, leading to the generation of granodiorites and monzonitic granites. These rocks experienced limited fractional crystallization (dominated by plagioclase + biotite) and are linked to Mo-Cu-Au mineralization. In contrast, the non-mineralized granitoids are high-K calc-alkaline, peraluminous A-type granites, which developed in an extremely extensional tectonic setting. They were derived from partial melting of ancient lower crust and display characteristics of highly fractionated granites, having undergone extensive crystallization differentiation involving plagioclase + K-feldspar during magmatic evolution. The mineralized and non-mineralized granitoids exhibit distinct differences in lithology, major/trace element characteristics, Hf isotopes, and degree of fractional crystallization. Our proposed two-stage magmatic model—coupled with a mineralization phase—provides significant insights into both magmatic processes and metallogenesis in the Liaodong Peninsula. It further offers key perspectives into the Early Cretaceous decratonization of the NCC in terms of its tectonic–magmatic–mineralization evolution. Full article

Multiple occurrences of adakitic rocks, with crystallization ages clustering around ~160 Ma, have been documented in the Zhuxi district, northeast Jiangxi Province, South China. This research identifies a new adakitic biotite granite porphyry within the Zhuxi W-Cu polymetallic deposit. Zircon U-Pb geochronology of this porphyry yields a crystallization age of 161.6 ± 2.1 Ma. Integrated with previously published data, the adakitic rocks in the study area—comprising diorite porphyrite, biotite quartz monzonite porphyry, and the newly identified biotite granite porphyry—are predominantly calc-alkaline and peraluminous. They exhibit enrichment in light rare-earth elements (LREEs) and depletion in heavy rare-earth elements (HREEs), with slight negative Eu anomalies. The trace element patterns are characterized by enrichment in Ba, U, K, Pb, and Sr, alongside negative Nb, Ta, P, and Ti anomalies, indicative of arc-like magmatic signatures. Comparative analysis of geological and geochemical characteristics suggests that these three rock types are not comagmatic. Petrogenesis of the Zhuxi adakitic suite is linked to a dynamic tectonic regime involving Mesozoic crustal thickening, subsequent delamination, and lithospheric extension. Asthenospheric upwelling likely triggered partial melting of the overlying metasomatized lithospheric mantle, generating primary mantle-derived magmas. Underplating and advection of heat by these magmas induced partial melting of the thickened lower crust, forming the biotite granite porphyry. Partial melting of delaminated lower crustal material, interacting with the asthenosphere or asthenosphere-derived melts, likely generated the diorite porphyrite. The biotite quartz monzonite porphyry is interpreted to have formed from mantle-derived magmas that underwent assimilation of, or mixing with, silicic crustal melts during ascent. The ~160 Ma crystallization ages of these adakitic rocks are broadly contemporaneous with W-Mo mineralization in the Taqian mining area of the Zhuxi district. Furthermore, their geochemical signatures imply a prospective metallogenic setting for Cu-Mo mineralization around this period in the Taqian area. Full article

Globally, most skarn deposits show a direct relationship with magmatic activity, indicating a genetic link between the geochemical composition of causative plutons and the metal content of associated skarns. Therefore, this study investigated the Early–Middle Eocene plutonic rocks and their relationship with Fe-Zn skarn deposits in the Esendemirtepe-Koçak and Horoz areas of south-central Türkiye. Despite the regional significance, previous studies have not adequately addressed the petrogenetic evolution of these intrusions and the geochemical characteristics of the related skarns. In particular, the fluid-aided mobility of elements at the contact between the causative plutons and the volcano-sedimentary country rocks remains poorly understood. Therefore, in this study, field studies, petrographic and mineralogical analysis, and whole-rock geochemical analysis were conducted to investigate the genetic link between the plutonic rocks and the skarn deposits. Field studies reveal that the skarn zones are within volcano-sedimentary sequences and marble-schist units intruded by four distinct plutonic bodies: (1) Esendemirtepe diorite, (2) Koçak diorite, (3) Horoz granodiorite, and (4) Çifteköy monzogabbro. These rocks exhibit calc-alkaline, I-type, and metaluminous signatures, except for the Çifteköy monzogabbro, which shows I-type, tholeiitic, and alkaline characteristics. All the plutonic rocks associated with the skarn formation display steep LREE-enriched REE patterns with minor positive Eu anomalies (Eu/Eu* = 0.98–1.35), suggesting a subduction-related volcanic arc setting similar to other granitoids in the Ulukışla Basin. The Horoz skarn exhibits both endoskarn and exoskarn features, while the Esendemirtepe-Koçak deposit is characterized by typical exoskarn features. Dominant ore minerals in both skarn deposits include magnetite, hematite, sphalerite, chalcopyrite, and pyrite, with minor arsenopyrite, galena, and cobaltite. The mineral composition of the skarn also shows the dominance of Na-rich and Mg-rich minerals in both locations. The geochemical compositions of the I-type, metaluminous Esendemirtepe-Koçak, and Horoz plutonic rocks are compatible with Fe-Zn skarn type deposits based on the moderate MgO (0.36–4.44 wt.%) and K₂O (1.38–7.99 wt.%), and Rb/Zr and Sr/Zr ratios. They also show typical volcanic arc features, and the variation in various trace element concentrations shows similarity with Fe-Zn skarn type granitoids. These findings support a strong genetic relationship between the mineralization and the geochemical and mineralogical characteristics of the associated plutonic rocks. Full article

Amphibole-rich cumulates provide crucial information pertaining to the petrogenetic history of suprasubduction zone ophiolites and are, therefore, helpful in constraining the evolution and closure of the Neo-Tethys during the late Cretaceous to the early Tertiary period. Following this, the present contribution examines the meta-hornblendite and meta-hornblende-gabbro lithologies in the Mayudia ophiolite complex (MdOC), NE Himalaya, based on their field and petrographic relations, constituent mineral compositions, whole rock major and trace element chemistry and bulk strontium (Sr)—neodymium (Nd) isotope systematics. MdOC cumulates potentially represent the fossilized record of an island arc root, where amphibole + titanite + magnetite was fractionally crystallized from a super hydrous magma (10.56–13.61 wt.% melt water content) prior to plagioclase in a stable physico-chemical condition (T: 865–940 °C, P: 0.8–1.4 GPa, logfO₂: −8.59–−11.19 unit) at lower crustal depths (30–38 km). Such extreme hydrous nature in the parental magma was generated by the flux melting of the sub-arc mantle wedge with aqueous inputs from the dehydrating slab. A super hydrous magmatic reservoir was, therefore, extant at sub-arc mantle depths in the eastern Neo-Tethys, which has likely modulated the composition of the oceanic crust during intraoceanic subduction. Full article