Search Results (77)

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 granitic rocks and the Dokhan Volcanics at the transect between Safaga and Qena, the Egyptian Northern Eastern Desert represent the northern termination of the Arabian–Nubian Shield (ANS), which, in turn, represents the northern part of the East African Orogeny (EAO). The geochronological development of the magmatic activities that constructed the ANS is critical in understanding these orogenies. The ANS was constructed through pre-collisional, syn-collisional, and post-collisional magmatic phases. The transition between these magmatic phases marks tectonic shifting from subduction to compressional and extensional tectonic settings, respectively. The chronological constraints of these tectonic–magmatic phases are still questionable. Our study aims to refine these chronological constraints through the dating of four calc-alkaline granitic rocks (722 ± 5 Ma–561 ± 4 Ma), five alkaline granitic rocks (758 ± 5 Ma–555 ± 4 Ma), and three Dokhan Volcanic rocks (618 ± 5 Ma–606 ± 5 Ma). Our results suggest the absence of any pre-collisional rocks. The syn-collisional magmatism extended here from 758 ± 5 Ma to 653 ± 7 Ma, demonstrating the chronological domination of the syn-orogenic compressional regime in the NED. The Dokhan Volcanic activity marked the shifting of the tectonic setting from a compressional to an extensional regime at 618 ± 5 Ma. Post-collisional plutonism dominated between 583 ± 5 Ma and 555 ± 4 Ma in the studied region, suggesting that ANS magmatic activity was extended to the Phanerozoic edge. These findings refute the classical interpretations of older magmatism as calc-alkaline granitoids and younger magmatism as alkaline granitoids. Pre-Neoproterozoic (pre-ANS) xenocrysts with ages of 1879 ± 22, 1401 ± 25, 1385 ± 12, 1232 ± 27, 1210 ± 18, and 1130 ± 15 Ma were yielded, which might support a local reworked ancient magmatic source. Full article

The Youjiang Basin is situated at the junction between the Tethyan and Pacific tectonic domains, and its Permian–Triassic volcanic rocks provide important geological archives recording the tectonic evolution and collisional interactions between the South China and Indochina blocks. This study employed LA-ICP-MS zircon U-Pb geochronology and whole-rock geochemistry to investigate interbedded Triassic felsic volcanics. Felsic volcanic rocks in Youjiang Basin were erupted during the Early–Middle Triassic period (ca. 241~251 Ma) and are situated within the strata of the Beisi, Baifeng, and Banba Formations. These rocks in the Daqingshan area are rich in SiO₂ (66.8~72.7 wt%), K₂O (1.4~5.1 wt%), U (5.2~6.7 ppm), and Th (26~32.1 ppm). Conversely, they are depleted in MgO (0.6~1.4 wt%), TiO₂ (0.5~0.9 wt%), Cr (13.1~19.7 ppm), Ni (7.3~10.1 ppm), and negative Eu anomalies (Eu/Eu* = 0.41~0.52), and they also exhibit negative zircon ε_Hf(t) values. It is inferred that these Triassic felsic volcanics originated from the partial melting of crustal rocks in high-pressure environments such as the garnet stability zone within the deep mantle. These felsic volcanic rocks were likely generated during the transitional stage from island arc subduction to syn-collisional settings. Notably, the syn-collisional interaction between South China and Indochina blocks exerted significantly greater tectonic control on the Youjiang Basin than oceanic subduction. Full article

This study focuses on the Fourque massif, one of the thirty Variscan plutons outcropping along the Axial zone of the Pyrenees. It hosts a significant tungsten deposit that was actively mined until 1986. However, since the closure of the mine, no detailed geochemical or geochronological studies have been conducted until recent investigations in 2019, leaving a significant gap in our understanding of this intrusion. This lack of research, along with the ongoing debate and uncertainties regarding the timing and magmatic processes of Variscan plutonism in the Pyrenees, underscores the importance of further investigations. To address these gaps, we present new zircon U–Pb geochronology, whole-rock and zircon geochemistry (X-ray fluorescence and LA-ICP-MS), and Ti-in-zircon thermometry. Our study compares nine new whole-rock geochemistry samples with the limited previous dataset from 1987, refining the petrogenetic interpretation of the intrusion. These efforts are framed within the ongoing debate surrounding the different Variscan intrusions in the Pyrenees, including the discussions on their emplacement age, magmatic context, type, and origin. Geochronological data indicate an age ranging from 304.6 ± 2.3 to 308.4 ± 2.6 Ma, with crystallization temperatures ranging from 700 to 800 °C. The granodiorite is characterized by differentiated petrogenetic facies, related to successive batches of magma rising from a deeper source. The granodiorite exhibits high ASI ratios (>1.3), classifying it as strongly peraluminous. While I-type granites are typically metaluminous to weakly peraluminous, such elevated ASI values suggest a significant influence of crustal assimilation during magmatic evolution. The geochemical signature of the intrusion is enriched in large ion lithophile elements (LILE) and light rare earth elements (LREEs) while showing depletion in heavy rare earth elements (HREEs), consistent with a high-K calc-alkaline, magnesian, syn-orogenic setting. Whole-rock and zircon trace element data suggest that the magma source involved partial melting of the continental crust, with evidence of interaction with a subduction-modified mantle component. By applying methods previously unapplied to this pluton, this study provides new data on its geochemistry and geochronology, revealing significant differences from previous interpretations. These findings offer deeper insights into the emplacement and evolution of the Fourque granodiorite, refining its role within the broader context of Variscan orogenesis in the Pyrenean Axial Zone and similar plutonic systems worldwide. Full article

The Qushi rhyolites, situated in the eastern sector of the Tengchong terrane, are critical to understanding the Early Cretaceous tectono-magmatic evolution of the Eastern Tethyan Tectonic Domain. Zircon LA-ICP-MS U-Pb geochronology indicates crystallization ages of 118.3–120.5 Ma, with Ti-in-zircon temperatures of 641–816 °C (mean = 716 °C), representing the Early Cretaceous magmatic activity in the Tengchong terrane. Inherited zircons within the rhyolites yield a zircon age of ca. 198.5 Ma, with corresponding Ti-in-zircon temperatures of 615–699 °C (mean = 657 °C), implying the potential presence of an Early Jurassic igneous basement beneath the Qushi region. Geochemically, the rhyolites are classified as calc-alkaline and weakly to moderately peraluminous (A/CNK = 1.07–2.86). These rocks display signatures typical of acidic magmas, marked by significant enrichments in light rare earth elements (LREE: La and Ce) and large ion lithophile elements (LILE: Rb, K, Th and U) while simultaneously exhibiting depletions in high-field-strength elements (HFSE: Nb, Ta, Ti, and P) and heavy rare earth elements (HREE). Trace element signatures further reveal marked depletions in Sr (12.4–244.7 ppm) and Ba while displaying enrichments in Zr and Hf. These geochemical features, including the huge range of the Sr content and A/CNK ratios, suggest both I-type and S-type granite affinities. The Early Cretaceous volcanism of the Qushi rhyolites is likely attributed to the combined effects of subduction and the closure of the Meso-Tethyan Ocean (MTO). This volcanic activity is interpreted to result from subduction-related processes associated with the MTO, potentially involving slab rollback, slab break-off, and subsequent asthenospheric upwelling. The formation of these rhyolites may also be linked to the final closure of the MTO, characterized by the Late Cretaceous collision and amalgamation of the Burma and Tengchong terranes. 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

Fersmite ([Ca,Ce,Na][Nb,Ta,Ti]₂[O,OH,F]₆) from the Mount Brussilof magnesite deposit, British Columbia, Canada occurs as accessory brittle, black, submetallic to vitreous lustre, acicular to platy crystals up to 2 cm long, developed in sparry dolomite, which lines cavities in sparry magnesite. Fersmite also occurs as smaller crystals (<3 mm) enclosed by dolomite, where it is commonly fractured or broken, formed during the final stage of dolomite crystallisation. Electron microprobe (WDS) major element data indicate that the grains confirmed to be fersmite by X-ray diffraction contain >50% Nb and are atypically Ta-poor. Fersmite contains significant U and Th (up to 4700 ppm and 6 wt.%, respectively) and therefore is a viable mineral for U-Pb geochronology. A series of laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) spot analyses and maps were collected on fersmite grains. Although the fersmite grains have considerable common Pb and have experienced Pb loss, the U-Pb spot data suggest growth or pervasive resetting at ca. 190 Ma. Some ⁴⁰Ar/³⁹Ar ages (two of four samples) are consistent with the ~190 Ma U-Pb date. Electron microprobe and LA-ICP-MS mapping indicate that the fersmite is middle to heavy rare earth element-rich. The ~190 Ma fersmite age estimate provides an approximate upper time constraint on the age of sparry magnesite mineralisation, sparry dolomitisation, and, indirectly, on the formation of MVT deposits in the Kicking Horse Rim area and possibly elsewhere in southeastern British Columbia. Full article

The Cambrian period marks a crucial phase in the initial subduction of the Proto-Tethys Ocean beneath the East Kunlun Orogen. Studying the I-type granites and mafic–ultramafic rocks formed during this period can provide valuable insights into the early Paleozoic tectonic evolution of the region. This paper incorporates petrology, LA-ICP-MS zircon U-Pb geochronology, and whole-rock major and trace element data obtained from the Kekesha intrusion in the eastern section of the East Kunlun Orogen. The formation age, petrogenesis, and magmatic source region of the intrusion are revealed, and the early tectonic evolution process of the subduction of the Proto-Tethys Ocean is discussed. The Kekesha intrusion includes four main rock types: gabbro, gabbro diorite, quartz diorite, and granodiorite. The zircon U-Pb ages are 515.7 ± 7.4 Ma for gabbro, 508.9 ± 9.8 Ma for gabbro diorite, 499.6 ± 4.0 Ma for quartz diorite, and 502.3 ± 9.3 Ma and 501.6 ± 6.2 Ma for granodiorite, respectively, indicating that they were formed in the Middle Cambrian. The geochemical results indicate that the gabbro belongs to the high-Al calc-alkaline basalt series, the gabbro diorite belongs to the medium-high-K calc-alkaline basalt series, the quartz diorite belongs to the quasi-aluminous medium-high-K calc-alkaline I-type granite series, and the granodiorite belongs to the weakly peraluminous calc-alkaline I-type granite series, all of which belong to the medium-high-K calc-alkaline series that have undergone varying degrees of differentiation and contamination. Gabbro and gabbro diorite exhibit significant enrichment in light rare earth elements (LREEs), depletion in heavy rare earth elements (HREEs), and an enhanced negative anomaly in Eu (Europium). Compared to gabbro and gabbro diorite, quartz diorite and granodiorite exhibit more pronounced enrichment in LREEs, more significant depletion in HREEs, and an enhanced negative anomaly in Eu. All four rock types are enriched in large-ion lithophile elements (LILEs) such as Cs, Rb, Th, Ba, and U, and are depleted in high-field-strength elements (HFSEs) such as Nb, Ta, and Ti. This indicates that these rocks originated from the same or similar mixed mantle source regions, and that they are formed in the island-arc tectonic environment. This paper suggests that the gabbro and gabbro diorite are mainly derived from the basic magma formed by partial melting of the lithospheric mantle metasomatized by subducted slab melt in the oceanic crust subduction zone and mixed with a small amount of asthenosphere mantle material. Quartz diorite results from the crystal fractionation of basic magma and experiences crustal contamination during magmatic evolution. Granodiorite forms through the crystal fractionation of basic magma, mixed with partial melting products from quartz diorite. While the lithology of the intrusions differs, their geochemical characteristics suggest they share the same tectonic environment. Together, they record the geological processes associated with island-arc formation in the East Kunlun region, driven by the northward subduction of the Proto-Tethys Ocean during the Early Paleozoic. Based on regional tectonic evolution, it is proposed that the Proto-Tethys Ocean began subducting northward beneath the East Kunlun block from the Middle Cambrian. The Kekesha intrusion formed between 516 and 500 Ma, marking the early stages of Proto-Tethys Ocean crust subduction. Full article

Molybdenite Re–Os and zircon U–Pb isotopic data are first obtained from the stockwork and disseminated-style gold-bearing ores and the fine-grained granite hosting these ores in the Xiawolong gold mine, respectively, which is located within the Muping–Rushan gold metallogenic belt, eastern Jiaodong Peninsula, so as to illustrate the genesis of gold mineralization and its implication for exploration. Four molybdenite samples yield a well-defined Re–Os isochron age of 118.4 ± 2.5 Ma (2σ), which is identical to the weighted average Re–Os model age of 118 ± 1.7 Ma (2σ). Integration of the new geochronologic data with those reported recently from the other gold mines in the Muping–Rushan gold metallogenic belt suggests that a discrete gold event occurred in Xiawolong ca. 4 m.y. older than that for the other gold mineralization at ca. 114 Ma in eastern Jiaodong. In addition, two fine-grained granite samples, measured using the LA-ICP-MS zircon U–Pb method, produce the first precise ages of 118 ± 2 to 117 ± 2 Ma (2σ), identical to the molybdenite Re–Os ages, within the margin of error and obtained in this study. The fine-grained granite has a similar lithology and emplacement age as those of the medium-grained monzogranite consisting of the marginal facies of the Sanfoshan batholith, and is considered to be the crystallization products of Sanfoshan granitic magma in the late stage. Combined with the previous S-Pb-D-O isotope, fluid inclusion and geological studies, which suggest that the ore-forming fluid of Xiawolong gold mineralization is from magmatic water, and the identification that the magnetite coexists with the gold-bearing pyrite and molybdenite in the gold ores, which indicates a high oxygen fugacity (fO₂) of both the magma and resultant hydrothermal fluids, it is logical to infer that the Xiawolong gold deposit is genetically in relation to the Sanfoshan granitic magmatism, which is high in fO₂ and rich in Au at the magmatic–hydrothermal transition stage, and the change in fO₂ mostly likely makes a significant contribution to the precipitation of Au. This result reveals that the late-stage granitic magma with high fO₂, which is crystallized into the fine-grained granite, probably is also rich in Au, except the W–Mo–Cu–Zn–U–Be–Li–Nb–Ta–Sn–Bi-elements. Therefore, based on the extensional tectonic regime for the early Cretaceous Jiaodong gold deposits, we propose that gold exploration in the Jiaodong should not only focus on the fault-hosted Au but also on the fine-grained granite-hosted Au around the apical portions of the late Early Cretaceous small-granitic intrusions with high fO₂. This model could also be important for prospecting in other gold ore districts, which have a similar tectonic 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 giant Changba-Lijiagou (Ch-L) Pb-Zn deposit is in the northeast part of the Xicheng ore cluster, Western Qinling Orogen. The ore genesis remains controversial; it could be either a sedimentary exhalative genetic type or an epigenetic hydrothermal genetic type. Here, in situ titanite U-Pb dating for the two kinds of titanite is presented, yielding ages of 212.8 ± 3.0 Ma in the mineralized skarn ore and 214.6 ± 5.1 Ma in the host rock. These ages conform to the previously reported magmatic zircon age (229–211 Ma) based on the in situ zircon U-Pb dating of plutons in this district and the time of large-scale magmatic–hydrothermal activities in Western Qinling Orogen (229–209 Ma). Titanites occurring in mineralized skarn and those that are calcite-hosted are similar to hydrothermal-origin titanites in major element characteristics. The Eu anomalies in the two types of titanite record oxidizing conditions during the mineralization process. A mineral assemblage of garnet, pyroxene, riebeckite, biotite, and potash feldspar, replacing the albite, is well-developed in the deposit. The mineralogical and geochronological characteristics indicate that the Ch-L Pb-Zn deposit is a distal skarn deposit and the result of intensive tectonomagmatic processes in the Xicheng ore cluster during the process of the Late Triassic orogeny. Full article

Himalayan leucogranite is an excellent target for understanding the orogenic process of the India–Asia collision, but its origin and tectonic significance are still under debate. An integrated study of geochronology, geochemistry, and in situ Sr-Nd-Hf isotopes was conducted for a tourmaline-bearing leucogranite in the eastern Tethyan Himalaya using LA-ICP-MS, X-ray fluorescence spectroscopy, and ICP-MS and LA-MC-ICP-MS, respectively. LA-ICP-MS U-Pb dating of zircon and monazite showed that it was emplaced at ~19 Ma. The leucogranite had high SiO₂ and Al₂O₃ contents ranging from 73.16 to 73.99 wt.% and 15.05 to 15.24 wt.%, respectively. It was characterized by a high aluminum saturation index (1.14–1.19) and Rb/Sr ratio (3.58–6.35), which is characteristic of S-type granite. The leucogranite was enriched in light rare-earth elements (LREEs; e.g., La and Ce) and large ion lithophile elements (LILEs; e.g., Rb, K, and Pb) and depleted in heavy rare-earth elements (e.g., Tm, Yb, and Lu) and high field strength elements (HFSEs; e.g., Nb, Zr, and Ti). It was characterized by high I Sr (t) (0.7268–0.7281) and low ε Nd (t) (−14.6 to −13.2) and ε Hf (t) (−12.6 to −9.47), which was consistent with the isotopic characteristics of the Higher Himalayan Sequence. Petrogenetically, the origin of the leucogranite is best explained by the decompression-induced muscovite dehydration melting of an ancient metapelitic source within the Higher Himalayan Sequence during regional extension due to the movement of the South Tibetan Detachment System (STDS). The significantly high lithium and beryllium contents of the leucogranite and associated pegmatite suggest that Himalayan leucogranites possess huge potential for lithium and beryllium exploration. Full article

Zircon, with a chemical formula of ZrSiO₄, is a widely used mineral for determining the crystallization age of igneous rocks. It is also used to constrain the timing of metamorphic events from its overgrowth or recrystallized domains. Furthermore, detrital zircon grains can provide information on the sedimentary provenance. Due to the trace amounts of uranium (parent) which decays into its daughter element (Pb), it is a prime geochronometer for the majority of magmatic and metamorphic rocks. With high-precision analytical instruments, such as TIMS, SIMS, and LA-ICP-MS, huge amounts of geochronological and trace element data from zircon have been generated around the globe to date. Target domains within zircon grains are analyzed to extract geochemical and geochronological records using spatially resolved techniques such as ion probes or laser ablation coupled with mass spectrometry. Before any such analysis, the zircon grains are examined for internal structures, growth zoning, and the presence of tiny inclusions. However, many researchers analyze multiple domains within single zircon grains for U-Pb isotope analysis with little regard for their internal structures, particularly crystallographic orientations. Hence, they may obtain mixed ages with variable discordance, leading to imprecise interpretation especially when the growth domains are not well-identified. Particularly, zircon grains that contain multi-growth domains or have local internal deformations within a single grain may not produce geologically meaningful age results if the analyses are conducted on mixed domains. This study presents a brief review on zircon geochronology, how to identify and visualize micro-deformations in metamorphic zircons through the EBSD analysis, and the effects of micro-deformation on age results. Examples from a case study conducted on zircons hosted in the Himalayan high-pressure eclogites are presented that show intra-grain plastically deformed domains and their effects on the corresponding age results. Full article

The Lengjimanda plate is situated in the middle section of the Da Hinggan mountains, in the eastern section of the Tianshan Xingmeng orogenic belt. To determine the formation age of the volcanic rocks in the Longjiang formation in this area, to explore their origin and tectonic background, and to reconstruct the geodynamic evolution of the region, this study conducted petrological, zircon U–Pb geochronological, geochemical, and isotopic analyses of the volcanic rocks in the Longjiang formation. The Longjiang formation’s volcanic rocks are primarily composed of trachyandesite, trachyte trachydacite, and andesite, which are intermediate basic volcanic rocks. They are enriched in large-ion lithophile elements, are depleted in high-field-strength elements, are significantly fractionated between light and heavy rare earth elements, and exhibit a moderate negative Eu anomaly in most samples. The results of the LA–ICP–MS zircon U–Pb dating indicate that the volcanic rocks in this group were formed in the Early Cretaceous period at 129.1 ± 0.82 Ma. The zircon ε_Hf(t) ranges from +1.13 to +43.77, the t_DM2 ranges from +655 to +1427 Ma, the initial Sr ratio (⁸⁷Sr/⁸⁶Sr)_i ranges from 0.7030 to 0.7036, and the ε_Nd(t) ranges from +2.1 to +6.6. Based on the geochemical compositions and isotopic characteristics of the rocks, the initial magma of the volcanic rocks in the Longjiang formation originated from the partial melting of basaltic crustal materials, with a source material inferred to be depleted mantle-derived young crustal. These rocks were formed in a superimposed post-collisional and continental arc environment, possibly associated with the Mongol-Okhotsk Ocean closure and the oblique subduction of the Pacific plate. This study addresses a research gap regarding the volcanic rocks of the Longjiang formation in this area. Its findings can be applied to exploration and prospecting in the region. Full article

The Youjiang metallogenic province (YMP) is a famous ore-concentrating area in South China, known for its substantial Carlin-type gold deposits, antimony deposits, and mercury deposits. Previous studies have yielded conflicting views regarding the ages of mineralization in this area, particularly regarding the occurrence of Yanshanian versus Indosinian ore-forming events during the Mesozoic era. To resolve these discrepancies, this study utilized in situ LA-ICP-MS U-Pb dating on carbonate minerals from the Lannigou Carlin-type Au deposit, the Lanmuchang Hg-(Tl) deposit, and the Sixiangchang Hg deposit to accurately determine their mineralization ages. Our results indicate that the three deposits formed at 137 ± 9 Ma, ~97 Ma, and 454 ± 21 Ma, respectively. By integrating previously reported geochronological data, we propose that the low-temperature Au-As-Sb-Hg-Tl deposits in the YMP were formed during two major periods, Late Triassic and Late Jurassic to Cretaceous, with the latter being more prevalent. Additionally, there was a Paleozoic hydrothermal mercury mineralization event at the northeastern edge of this region. These newly acquired data significantly enhance our understanding of multistage, low-temperature mineralization events in the YMP. Our study also demonstrates that in situ carbonate U-Pb dating is an excellent method for investigating the timing of low-temperature mineralization events. Full article