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A356 Aluminium Alloy-Zircon composites were synthesized through the stir casting technique by introducing different volume fractions of zircon particles (3, 6, and 9 %). Stir casting process was carried out at the stirring speed of 600 rpm and stirring time of 10 minutes. The microstructure of the composites showed an even distribution of zircon particles. The composites' hardness improved with an increase in vol.% of zircon constituent part. Wear loss against different sliding distances and load was investigated through a Pinon-Disc wear testing apparatus with an L16 orthogonal array. Taguchi's parameter optimization demonstrated that material loss was influenced to a significant extent by adding Zircon. Wear resistance of the synthesized composite was investigated and verified using Analysis of Variance (ANOVA). Zircon content (39.33%) was found to be the most influencing factor on wear loss, followed by the applied load (36.80%) and sliding distance (21.54%). Zircon improves the properties of the composite through restricting the growth of dendritic arms in A356 alloy. In addition, reinforcement particles enhanced the strengthening of the composites through Orowan mechanism by inhibiting the movement of dislocations. ANOVA technique was successfully used to examine the effect of individual parameters on wear loss of A356 alloy-Zircon composites MMCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Jinkeng deposit formed in two stages (∼147 Ma and ∼141 Ma, respectively). • Different metallogenic potential for the two granitic rocks. • The regional compression occurred in the range of 147–144 Ma. The Jinkeng Sn-Cu polymetallic deposit in South China consists of two different types of orebodies: 1) NE-striking skarn- and vein-type Cu-Pb-Zn-Sn orebodies in volcanic rocks suffering subsequent ductile shear deformation, and 2) NW-striking quartz-cassiterite-sulfide veins filled in the faults at the porphyritic granodiorite outward from the fine-grained granite which does not exhibit deformation. The relationships among Sn-Cu polymetallic mineralization, regional magmatism, and deformation metamorphism are still controversial. To address it, the geochronological, whole-rock and mineral geochemical research along with the detailed field investigation were conducted in this study. Our zircon U-Pb dating results show that the volcanic rocks formed at 158–162 Ma, earlier than the porphyritic granodiorite which yields the emplacement age of 146–147 Ma. In-situ LA-ICP-MS U-Pb dating of cassiterite from the deformed skarn ores indicates the early-stage mineralization occurred at 146 ∼ 148 Ma, which is similar to the emplacement age of the porphyritic granodiorite, but earlier than the formation of quartz-cassiterite-sulfide veins and the fine-grained granite (141∼144 Ma). Further, the whole-rock and biotite geochemistry, and zircon Hf isotope compositions suggest that the porphyritic granodiorite exhibits a lower degree of magma differentiation, higher oxygen fugacity, higher Cl and lower F contents than the fine-grained granite. The porphyritic granodiorite might provide the most Cu-Pb-Zn budget accompanied by minor Sn for early-stage mineralization. Overall, our study suggests that the Jinkeng Sn-Cu polymetallic deposit formed in two scenarios where the early dominated Cu-Pb-Zn and minor Sn mineralization related to the emplacement of the porphyritic granodiorite is superimposed by the late vein-type Sn-dominated mineralization related to the emplacement of the fine-grained granite. The two isolated mineralizing events (∼147 Ma and ∼141 Ma, respectively) in Jinkeng were probably responded to the regional magmatic activities triggered by the tectonic transformation where two extensional tectonic events were separated by a short contractional event (147–144 Ma). [ABSTRACT FROM AUTHOR]

The Sm–Nd isotopic system has been broadly utilized for dating and tracing in earth and planetary sciences. However, low Nd+ ionization efficiency permanently hinders precise and accurate measurements on small amounts of Nd samples. So far, isotopic measurement of micro-amount Nd sample via thermal ionization mass spectrometry (TIMS) Nd+ mode was mostly performed on Nd reference solutions, but less on natural rock or mineral samples. In the present study, analytical procedures to measure isotopic composition via the TIMS Nd+ mode were designed for natural rock powders by using 1–5 ng pure Nd. The analytical technique was refined through low-blank sample digestion, small-column chemistry for Nd extraction from matrix elements, loading Nd using purified H 3 PO 4 solution, and careful heating of filaments before data acquisition. Measurements on small Nd amounts (1 ng–5 ng) of either the JNdi-1 reference solution or four reference rock powders yielded satisfactory results of 143Nd/144Nd value with respect to precision and accuracy. The analytical results agree well with the recommendation values of the reference materials within analytical errors and the internal precision is better than ±0.005 % (2RSE). When using 1 ng or 2 ng Nd amounts, 144Nd ion flow can remain stable in a signal intensity of >100 mV, and without the assistance of an additional ionization enhancer. Therefore, the analytical procedure, featured by low procedural blank (about 10–22 pg), high Nd+ ionization efficiency, and easy operation, has broad prospects for the application of Nd isotope in single-grain minerals or micro-samples. An easily-operated methodology to measure Nd isotopic composition of natural rocks using small amount of Nd (1–5 ng) via the TIMS Nd+ mode. [Display omitted] • Measurement method by the TIMS Nd + mode is given for micro-sample of rock. • Nd isotopic ratio using small Nd amounts of 1–5 ng was successfully achieved. • Vapor digestion of rock powder was employed to reduce procedural Nd blank. [ABSTRACT FROM AUTHOR]

The Shuikoushan ore field is one of the largest Pb-Zn-Au polymetallic magmatic hydrothermal system in South China and hosts a significant metallogenic potential. The Kangjiawan gold deposit is a low-temperature hydrothermal vein-type gold deposit developed on the periphery of the ore field. Geological chronology suggests that the gold mineralization of the Kangjiawan deposit is coeval with the emplacement of the Shuikoushan granodiorite and related Pb-Zn mineralization. In addition, trace elements characteristics and a narrow δ34S range of -2.94‰ ∼ +3.03 ‰ of pyrite, indicate that ore-forming materials were mainly derived from granitic magmas. Based on the spatial distribution between the ore deposits and granitic intrusions, it is suggested that the Kangjiawan Au deposit is probably as the distal products of magmatic-hydrothermal systems of the deep concealed granitic pluton. The deep parts of the Kangjiawan Au deposit have potential for high-temperature skarn-type mineralization associated with concealed intrusion. Conversely, there is potential for low-temperature Au mineralization linked to the Shuikoushan Granodiorite in the periphery of the Shuikoushan ore field. [Display omitted] • Calcite U-Pb data support that gold mineralization at Kangjiawan occurred at 151.7 ± 5.4 Ma in late Jurassic. • Trace element analysis and S isotope compositions reflect that Kangjiawan gold deposit is genetically linked to granitic magmas. • The Kangjiawan deposit represents distal products of magmatic-hydrothermal systems associated with a deeply concealed granitic pluton. (Meta)sedimentary rock-hosted gold (Au) deposits are globally important Au resources, of which ore genesis and mineral exploration have been attracted considerable attention. However, the precise dating of Au mineralization of those Au deposits remains challenging due to the absence of suitable dating minerals, thus impeding a comprehensive understanding of their genesis. The Kangjiawan Au deposit, situated in the southern Hunan Province, South China, is one of representative (meta)sedimentary rock-hosted Au deposits. Due to the lack of mineralization age, the genesis of Kangjiawan Au deposit is still a matter of debate. Here we report the data of in situ calcite U-Pb dating, in situ trace elements and sulfur isotope analysis of pyrite, to further constrain the mineralization timing and the sources of ore-forming materials of the Kangjiawan Au deposit. Based on the detailed field investigation and petrographic observations, three mineralization stages have been identified: pyrite (Py1) + quartz (Stage I), gold-bearing pyrite (Py2) + polymetallic sulfides + quartz + calcite (Stage II), and gold-bearing pyrite (Py3) + calcite (Stage III). The results of mineralogical and trace elemental analyses indicate that Au are mainly hosted in Py2 (average 14.19 ppm) and Py3 (average 4.80 ppm), primarily as the form of "invisible gold". In situ LA-ICP-MS U-Pb dating on calcite intergrowth with the gold-bearing pyrite (Py3) yields a Tera-Wasserburg lower intercept age of 151.7 ± 5.4 Ma. This age is well consistent with the published zircon U-Pb age (158.3 ± 1.2 Ma) of the nearby Shuikoushan granodiorite, the molybdenite Re-Os age (157.8 ± 1.4 Ma) of the Laoyachao skarn Pb-Zn deposit in the Shuikoushan ore field, and the garnet U-Pb age (159.1 ± 1.9 Ma) of the skarn Pb-Zn ore in depth of the Kangjiawan Au deposit. These suggested that the Au mineralization of the Kangjiawan deposit is coeval with the emplacement of the Shuikoushan granodiorite and Laoyachao Pb-Zn mineralization, which are important parts of the large-scale Middle-Late Jurassic Cu-Au-Pb-Zn Metallogenic event of the Qin-Hang Metallogenic Belt, South China. In addition, trace elemental contents, such as relative low Co, Ni, and Se (i.e., <0.01 to 100 ppm), and a narrow δ34S range of −2.94 ‰ ∼ +3.03 ‰ of pyrite, indicate that ore-forming materials were mainly derived from granitic magmas. Integrated with previous studies, it is suggested that the Au mineralization in the Kangjiawan deposit is genetically associated with the late Jurassic granitic magmatism and is probably as the distal products of the deep-seated concealed granitic intrusions and related proximal skarn Pb-Zn ore. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three types of cobalt minerals and four types of nickel minerals are identified in Dulenggou Cu-Co deposit. • In-situ U-Pb dating of monazite yielded an age of 467 ± 17 Ma for mineralization. • Dulenggou deposit is a SEDEX-type Cu-Co deposit in the East Kunlun orogenic belt. The East Kunlun region in western China stands out as an important polymetallic metallogenic belt hosting economically significant Au, Cu, Fe, Pb, Zn, Sn, Co, Ni and Cr resources. Within this belt lies the Dulenggou deposit, a notable Cu-Co deposit. Three cobalt minerals (cobaltine, siegenite, and glaucodot) and four nickel minerals (ullmannite, gerdorffite, violarite, and millerite) coexisting with chalcopyrite and pyrite were identified in the Dulenggou deposit. The mineralization of Co and Ni primarily occurs in the form of sulfarsenides (cobaltine and gersdorffite) rather than sulfides (siegenite and ullmannite). Sulfides are commonly associated with chalcopyrite, whereas sulfarsenides coexist with chalcopyrite occasionally within the host rocks. The presence of organic-rich surrounding sedimentary rocks reduces oxygen fugacity, and the increase in arsenic content may influence the paragenetic association of minerals. The sequence of mineral formation is Py0 (host rocks) → PyI + Ccp + Co-Ni minerals (the major mineralization stage) → PyII. The mineralization age of the Dulenggou deposit has been determined by in situ U–Pb dating of hydrothermal monazite in closely association with chalcopyrite and Co–Ni minerals, yielding an age of 467 ± 17 Ma. The δ34S values of sulfides (pyrite and chalcopyrite) from ores and host rocks range widely from 1.9 ‰ to 22.1 ‰. From Py0 to PyI to PyII to chalcopyrite, the δ34S values change from 17.6 ‰ to 22.1 ‰, from 9.1 ‰ to 14.6 ‰, from 1.9 ‰ to 7.7 ‰, and from 9.6 ‰ to 13.4 ‰, respectively. The positive δ34S values suggest that the primary sulfur source possibly originated from seawater and/or the host rocks. Based on the geological and geochemical characteristics, the Dulenggou copper-cobalt deposit is identified as a syngenetic sea floor sedimentary exhalative deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] • The duration of causative magmatism at Huanggang is ∼ 9 m.y. • Degassing caused the elevation of magma oxygen fugacity. • Fractionation of reduced and S-poor magma controlled the enrichment of Fe and Sn. • Enrichment of metals in the ore-forming fluid could be recorded by apatite. The large-scale Huanggang Skarn Fe-Sn deposit is located in the southern part of the Great Xing'an Range (SGXR), NE China. The causative granitic rocks in the Huanggang ore district are characterized by consistently high SiO 2 contents, low Eu N /Eu N * (0.02–0.24) and Sr/Y (0.2–1.9). The pre-ore granite porphyry and syn -ore syenogranite have been dated through zircon and monazite U-Pb dating at 144.6 ± 1.4 Ma and 138.6 ± 1.3 to 135.9 ± 0.8 Ma, respectively. The U-Pb dating of garnet from ore-associated skarn reveals that the mineralization was happened at 136.5 ± 1.3 Ma, which is consistent with the emplacement age of the ore-related syenogranite. Zircon geochemistry shows that the pre-ore granite porphyry has relatively low oxygen fugacity (average zircon Ce4+/Ce3+ = 14.74), whereas the syn -ore syenogranite is more oxidized (average zircon Ce4+/Ce3+ = 178.9). We suggest that the elevation of oxygen fugacity was most likely caused by degassing. The textural features indicate that apatite crystals from the pre-ore granite porphyry are magmatic in origin. In contrast, textural and chemical characteristics of apatite grains from syn -ore syenogranite reveal that they have been modified by hydrothermal fluids in different degrees. The apatite in both pre- and syn -ore granites display relatively high F and low Cl contents, and very low SO 3 concentrations (i.e., <0.032 wt%), indicate extremely low content of S in the causative magma. Apatite from syn -ore syenogranite display more strong and variable enrichment of LREE relative to HREE compared to those from pre-ore granite porphyry. The extensive present of new REE mineral inclusions (monazite and xenotime) in the altered apatite suggests that the concentrations of Ca and Na must be low in the ore-forming fluid. Apatite from syn -ore syenogranite have higher concentrations of Mo, W, Zn, Sn, and Be than those from pre-ore granite porphyry. Combined with zircon and apatite geochemistry, and whole rock components of the ore-related granites in the Huanggang deposit, we propose that the ore-forming magma has undergone long-term evolution under relatively reduced conditions with extensive fractional crystallization of plagioclase. The reduced and S-poor evolved magma could have promoted the enrichment of Sn and prevented Fe from precipitating as sulfide. This study also reveals that the compositional characteristics of ore-forming fluid, such as the enrichment of ore-forming materials, could be revealed by altered apatite geochemistry. [ABSTRACT FROM AUTHOR]

[Display omitted] • REE mineralization in the Lala deposit primarily formed at ca. 850 Ma. • The host rocks and contemporaneous felsic magmatic rocks serve as the primary sources of REE metallogenic materials. • Na, CO 2 , and F-rich magmatic waters aid REE mineralization, mixing with meteoric waters, leaching the REE from host rocks and early ores. The Lala deposit in the Kangdian metallogenic province is one of the most important iron oxide copper–gold (IOCG) deposits in South China. Rare earth element (REE) activation, migration, and redistribution occurred during late-stage Cu mineralization in the deposit. However, the geological characteristics of REE mineralization and the genetic mechanism of this deposit remain poorly understood. The goal of this study was to investigate REE mineralization and the ore-forming process in the Lala deposit by employing a comprehensive approach that included techniques in petrography, mineralogy, and geochemistry. Mineralogical analysis indicated that the REE-bearing minerals in this deposit include bastnäsite, monazite, parisite, xenotime, apatite, and fluorite. Apatite was observed to have high concentrations of REE (ΣREE ranging from 7,409 to 18,739 ppm). The results of U-Pb isotope dating of bastnäsite and xenotime suggest that the REE mineralization in the Lala deposit primarily formed at ca. 850 Ma, aligning with the Neoproterozoic magmatism in this region. The chondrite-normalized REE pattern of apatite is similar to that of host rocks and contemporaneous magmatic rocks; the ε Nd(t) values of bastnäsite and xenotime (calculated at ca. 850 Ma) ranged from −12.2 to −7.0, which is comparable to the values obtained for contemporaneous country rock (−8.7 to −6.4) and felsic intrusive rocks (−9.6 to 4.4). This similarity indicates that the host rocks and contemporaneous felsic magmatic rocks serve as the primary sources of REE metallogenic materials. The ∼ 850 Ma REE mineralization overprints the early stage Fe-Cu mineralization and is associated with a Neoproterozoic magmatic event. During this process, Na, CO 2 , and F-rich magmatic water mixes with meteoric water and leaches REE from host rocks and early-stage ores. Under the disintegration of REEs, F-complex in hydrothermal fluids, REE minerals (e.g., monazite, bastnäsite, parisite, and xenotime) precipitate together with apatite and fluorite in the Fe-Cu ores. [ABSTRACT FROM AUTHOR]

[Display omitted] • First direct timing constraints on the Jiaoxi and Anglonggangri W mineralization. • Garnet-muscovite granite provided most Fe in Anglonggangri ore-forming metals. • Varied fluid component and redox state in wolframite and scheelite precipitation. • Highly-evolved granites play critical roles on the Fe-rich wolframite formation. Critical factors controlling Fe-enriched wolframite formation in the quartz vein-type wolframite deposit are in controversy. The Jiaoxi and Anglonggangri are typical examples of quartz vein-type wolframite mineralization found in western Lhasa terrane. The Jiaoxi wolframite comprise dominantly early hübnerite with late ferberite, whereas, the Anglonggangri wolframite are mainly ferberite. Wolframite U-Pb dating yields direct timing of 11.0 ± 0.2 Ma and 9.7 ± 0.2 Ma for Jiaoxi and Anglonggangri tungsten mineralization, respectively. Ages together with enrichment of Nb, Ta, Ti, and Sc and depletion of Sr and most Eu anomaly within Anglonggangri wolframite confirm that metals and fluids were mainly derived from the ore-forming garnet-muscovite granite. Iron and Mn mapping of garnet in the garnet-muscovite granite suggests this granite has changed from the early Mn-enriched to late Fe-rich affinity. Therefore, initial ore-forming fluids exsolved from garnet-muscovite granite have Fe-rich composition, that was significantly modified during tungsten mineralization. Positive trend between Mg and Fe/(Fe + Mn) of wolframite indicates biotite breakdown from country rock of biotite-muscovite granite to add Fe and Mg into fluid during greisenization. Meanwhile, decomposition of plagioclase and K-feldspar provided Ca, Sr, and Eu to form late scheelite. Enrichment of Sr with positive Eu anomaly and decline of REE, Nb, and Ta are typical features of the highly evolved and modified fluid. Positive and negative Eu anomalies within the same wolframite grains reveal the oxidized character and fluctuating composition of fluid during wolframite precipitation. By contrast, negative Eu anomaly and low Mo abundance of scheelite indicate the reducing fluid during scheelite crystallization. Identification of metal and fluid sources for Anglonggangri ferberite highlights the evolved granites play more crucial roles on ferberite formation than early hübnerite crystallization and Fe addition from country rocks during hydrothermal interaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Exhalative-syngenetic process and ductile–brittle deformation contributing to Co mineralization. • Two episodes of Co mineralization occurred at ca. 453 Ma and 190 Ma, respectively. • Tectonic-hydrothermal overprinting event raising the tenor of primary ore. Stratiform Cu-Co deposits hosted in (meta-) sedimentary and volcaniclastic rocks contribute two-thirds of the global Co supply. However, the mechanisms driving Co remobilization during tectonic-hydrothermal overprinting events remain poorly understood. As a dominant Co repository, pyrite can provide valuable insights into mineralization history due to its refractory nature. Here, we present the first micro-analytical investigation of pyrite from the Tuolugou Co(–Au) deposit in East Kunlun Orogenic Belt. Ore textures indicate that Co mineralization is attributed to two distinct stages: primary enrichment and subsequent overprinting processes. The former is characterized by pyrite (PyI with up to 3.92 wt% Co) remnants exhibiting oscillatory zones, while the latter is marked by deformation of pyrite (PyII) ores. Three overprinting episodes, namely Da, Db, and Dc, are further distinguished according to varying extents of deformation and mineral assemblages. The Da is characterized by synkinematic PyIIa (up to 4.18 wt% Co) augens, which were most likely formed via pressure–solution mechanism. The Db is represented by polygonal PyIIb (up to 4.75 wt% Co) and siegenite with 120° triple–point junctions. The random orientation and rare intragrain misorientation of cobaltiferous sulfides at Db suggest their formation by recrystallization without plastic strains. The Dc resulted in the formation of Co ± As–rich PyIIc (up to 5.36 wt% Co) along with minor occurrence of cobaltite–gersdorffite, pyrrhotite (up to 1.25 wt% Co), and marcasite (up to 1.28 wt% Co). The PyIIc replacing PyI underscores the role of fluid-coupled dissolution and precipitation during fluid–rock interactions in the formation of these cobaltiferous sulfide assemblages at Dc. The presence of PyIIc infilling within the PyI fissures, in conjunction with the transition from siegenite to cobaltite–gersdorffite, suggests a shift towards low f O2 and low temperature conditions under relatively brittle setting. There is a discernible disparity in sulfur isotope compositions between the two mineralization stages. The PyI exhibits a narrow range of δ34S V–CDT values from –2.14 to 1.35 ‰, indicating a magmatic sulfur origin. In contrast, PyII displays a wide δ34S V–CDT range of –5.22 to 6.16 ‰, suggesting an involvement of strata sulfur during the overprinting stage. Monazite U-Pb dating has effectively constrained two mineralization events. The ca. 453 Ma age implies a potential correlation of the primary Co mineralization with the Late Ordovician to Early Silurian exhalative-syngenetic processes in a Proto–Tethyan-related post–collisional extension setting. Conversely, the ca. 190 Ma age indicates that Co remobilization was instigated by the early Mesozoic ductile–brittle deformation associated with the Paleo-Tethyan orogenesis. Finally, geochemical modeling was performed by simulating the interaction of a Co-rich acidic, reducing fluid with typical quartz-albitite rocks. The simulations demonstrate the appearance of independent Co minerals such as Co-pentlandite during the reaction progression, greatly supporting ore upgrading via tectonic-hydrothermal overprinting. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new type clay-Li deposit is found in southern Hubei Province, China. • This deposit was formed by fault-controlled hydrothermal alteration. • Hydrothermal apatite U-Pb dating indicates an age of 135.2 ± 13.9 Ma. • The Li enrichment is related to the Mufushan granitic magmatism. Clay-Li deposits are among the major Li deposits in the world and occur mainly in sedimentary and/or volcanic-sedimentary strata. The Li orebodies are generally stratiform and stratibound, and Li is mainly hosted in various clay minerals. Here, we report a new type of clay-Li deposit that occurs along fault zones developed in metasedimentary rocks with significant alteration, and Li is also hosted in clay minerals in the Jinyinshan area in Xianning, southern Hubei Province, China. The study area has no granitic rock outcrops, but approximately 15 km south is the Mufushan granite batholith, where large-scale rare metal mineralization, such as Li, Be, Nb and Ta granitic pegmatites, developed in the internal and outer contact zones of the granite batholith. In this study, high-Li clay minerals, including chlorite, kaolinite and smectite, were identified. The enrichment of Li is closely related to hydrothermal activity along the F9 fault in the region. Hydrothermal apatite coexisting with Li-clay in the orebody along the fault zone yielded an in situ U–Pb age of 135.2 ± 13.9 Ma, which is in good agreement with the ages of granites and Li-pegmatites around the Mufushan batholith. Petrographic, geochemical, and chronological evidence suggests that the ore-forming fluids and Li were likely sourced from the Mufushan granite batholith or a similar blind granite at the depth of the study area; that is, the granite-derived ore-forming fluids can travel long distances along fault zones, and during this pathway, Li from the metasedimentary rocks (i.e., the Lengjiaxi Group) may also have been leached by the fluids and contributed to the Li mineralization in the Jinyinshan clay-Li deposit. The close spatial relationships among different clay minerals indicate that fluid physical–chemical conditions (changes in temperature) may play a crucial role in controlling the formation of Li-rich clay minerals. Our study indicates that the Mufushan area has great potential for hydrothermal clay-Li mineralization occurring in the Lengjiaxi Group metasedimentary rocks around the Mufushan batholith. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two hydrothermal mineralization events in this deposit are identified: quartz-sericite-pyrite-native gold (I) stage and chlorite-quartz-sericite-chalcopyrite-electrum (stage II). • This study provides additional age constraints on the host rocks (Caledonian granitic rocks) in the Hebaoshan area, with ages ranging from 441 to 446 Ma, as well as two mineralization events at approximately 238.46 ± 2.01 Ma and 179.54 ± 7.28 Ma. • The combination of ages and geological evidence suggests that the first mineralization event is associated with the intracontinental orogeny of the Yangtze Block and Cathaysia Block, as well as the flat subduction of the Paleo-Pacific Plate. The second mineralization event is related to the extensional tectonic activity following the collision between the Yangtze Block and Huaxia Block. The Hebaoshan gold deposit (41.5 t Au @ 3.5 g/t) is located in the southeastern region of the South China Block, central part of the Wuyishan metallogenic belt. The ore-hosting rocks in this area are predominantly Precambrian metasedimentary rocks and Caledonian granitic rocks. Two hydrothermal mineralization stages can be distinguished: a quartz-sericite-pyrite-native gold (stage I) and a chlorite-quartz-sericite-chalcopyrite-electrum (stage II), with hydrothermal monazite and rutile are firstly identified in separate stages. The complex geological history of the region has resulted in ongoing debates regarding the age of gold mineralization and the genesis of the major gold deposits in this area. In order to precisely constrain the mineralization age of the deposit and further establish a genetic model for the ore deposit, LA-ICP-MS U-Pb dating and trace element analysis on accessory minerals were conducted. Based on the textures mineral assemblages, and geochemical features of the accessory minerals, magmatic apatite, hydrothermal rutile, and both magmatic and hydrothermal monazite were identified. The U-Pb ages of magmatic apatite and monazite are determined to be 445.3 ± 15.80, 441.3 ± 15.10 Ma and 446.57 ± 1.03 Ma, respectively, suggesting that these ages represent the emplacement ages of the Caledonian intrusive rocks. The ages of hydrothermal monazite and hydrothermal rutile are determined to be 238.46 ± 2.01 Ma (single-mineral analysis), 238.46 ± 2.01 Ma (in-suit analysis) and 179.54 ± 7.28 Ma, respectively, suggesting that represent two mineralization events during the Late Triassic to early Jurassic in the Hebaoshan area. These data provide new constraints on the mineralization process in the Hebaoshan deposit and excludes the link between gold mineralization and the intrusion of the Caledonian granites. Regionally, It is speculated that the two mineralization events at Hebaoshan are respectively associated with intracontinental orogenic movements between the Yangtze Block and Cathaysia Block, the flat-slab subduction of the Paleo-Pacific Plate (stage I), and the subsequent extensional tectonics related to the collision between the Yangtze Block and Cathaysia Block (stage II). Our study indicates that the timing of multiple episodic mineralization can be constrained by analysis of accessory minerals, which provides a geological basis for better genetic model for the deposit and provide geological evidence for unraveling the relationships between magmatic activities and mineralization events in the region. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magmatic/hydrothermal cassiterites are identified in the Yuanlinzi Sn-Cu deposit. • Tin mineralization in the Yuanlinzi Sn-Cu deposit occurred at ca. 139 Ma. • An ore-forming environment with increasing oxygen fugacity is proposed. • Sc/V ratio of cassiterite may monitor redox state of its related melt/fluid. Microtextural, U–Pb isotopic, and trace element analyses were conducted on magmatic and hydrothermal cassiterites from the Yuanlinzi Sn–Cu deposit (NE China) to determine the timing of mineralization and investigate the ore-forming process. Magmatic cassiterites are disseminated in pegmatite, while hydrothermal cassiterites can be classified into three types: cassiterite-bearing stockworks in pegmatite, disseminated cassiterite in wall rock, and cassiterite-quartz-feldspar veins. U–Pb dating of the four types of cassiterite yields a similar age of ∼ 139 Ma, which is consistent with the ages of regional tin mineralization and granites within the mining district. These results suggest a strong association between Early Cretaceous magmatism and tin mineralization. The four types of cassiterite exhibit comparable textural features, characterized by alternating oscillatory CL zonation and dark homogeneous bands, with the latter commonly enriched in W, Nb, Ta, and U. The direct substitution of tetravalent ions, including Zr, Hf, Ti, and V, with Sn4+ and the coupled substitutions of Fe3+ + OH– = Sn4+ + O2– or Fe3+ + H+ = Sn4+, 2Sb3+ + U6+ = 3Sn4+ and Sc3+ + V5+ = 2Sn4+ are responsible for the incorporation of these elements in cassiterite. The enrichment of W, Nb, Ta, and U in the dark domains of cassiterite is related to the coupled substitution of W + U and Nb + Ta, while the excess of Nb and Ta in the oscillatory-zoned domains may be attributed to the substitution of 4(Nb, Ta)5+ + □ = 5Sn4+. The trace element variations observed in the four types of cassiterite, particularly Al, Sc, Ti, V, and Fe, reflect the ongoing enhancement of the water–rock reaction during the mineralization process. The examination of redox-sensitive elements such as Fe, U, and V suggested that tin mineralization in the Yuanlinzi deposit occurred in an oxidizing environment where oxygen fugacity gradually increased. Additionally, we proposed that the Sc/V ratio of cassiterite could serve as an indicator of the redox state of the associated melt/fluid. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrothermal apatite U–Pb age (208.1 ± 6.5 Ma) is coeval with peripheral intrusions. • C–O–S–Pb isotopes indicate a magmatic source for the ore fluid and material. • The Qukuleke is classified as a sediment-hosted intrusion-related deposit. • Intrusion-related Au ore system is a valuable target for regional exploration. Genetic classification of sediment-hosted Au deposits is often disputed in many orogenic belts around the world. The marine sediment-hosted Qukuleke Au deposit (>5 t Au) is an example of this, which has been attributed to orogenic or intrusion-related type. This paper addresses its metallogeny through detailed geologic and petrographic studies, together with apatite U–Pb dating and C–O–S–Pb isotopes. The hydrothermal paragenesis at Qukuleke is divided into three stages (I to III): Stage I (pre-ore) sheeted quartz veins; Stage II (main ore) pervasive sericite ± carbonate ± apatite ± pyrite ± arsenopyrite alteration associated with quartz–calcite ± stibnite veins; Stage III (post-ore) barren calcite veins. LA-ICP–MS hydrothermal apatite U–Pb dating on Stage II disseminated Au ore yielded 208.1 ± 6.5 Ma, coeval with the Late Triassic post-collisional intrusions from the periphery of Qukuleke deposit. Carbon–oxygen isotopes of Au–Sb ore-related hydrothermal calcite show that the hydrothermal fluids were derived from the marine carbonate ore host with considerable magmatic input. Lead–sulfur isotopes of the Au–Sb ore-related are consistent with those of coeval intrusions around the deposit, but different from those of the local sedimentary strata. Our age and geochemical data suggest the presence of a magma source that supplied the hydrothermal fluids, sulfur and metals for the mineralization. Combining the low sulfide content and the Au–As–W–Sb–Mo assemblage characteristics, the Qukuleke is best classified as a sediment-hosted intrusion-related Au deposit. Considering also the discovery of the large coeval Qukukekedong Au deposit nearby, we propose that Late Triassic intrusion-related Au system is a high-potential exploration target in the western EKOB. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu–Pb–Zn skarn related granodiorite and diorite formed at 245–243 Ma. • Phlogopite Ar–Ar dating constrains that skarn mineralization occurs at 240 ± 1 Ma. • Middle Triassic ore-related granodiorite and diorite formed by magma mixing. • Mantle-derived magma plays a vital role in the formation of skarn mineralization. The skarn is one of the most significant Cu–Pb–Zn mineralization worldwide. The timing of the magmatic-hydrothermal activity is of importance for understanding the Cu–Pb–Zn mineralization process. The Cu–Pb–Zn skarn mineralization has been recognized in the northwestern section of the Wulonggou gold ore field, Eastern Kunlun Orogen (EKLO), NW China. However, no precise geochronological data has been measured for the Cu–Pb–Zn mineralization, and the source of ore-forming materials is also not well studied. In this study, we present new LA-ICPMS U–Pb ages and Sr–Nd–Hf isotopic compositions for granodiorite and diorite in the northern section of the Wulonggou gold ore field, as well as an Ar–Ar age for phlogopite and Pb isotopic compositions for sulfides and intrusions, further to constrain the ages of mineralization and magmatism, and the source of ore-forming materials. Two granodiorite samples yield mean ages of 245 ± 2 to 243 ± 2 Ma and a diorite has a mean age of 245 ± 2 Ma. A phlogopite sample, which is associated with Cu–Pb–Zn mineralization, has been chosen to precisely date the formation of Cu–Pb–Zn ores by Ar–Ar method and yields a well–defined plateau age of 240.4 ± 1.2 Ma. These results indicate that the Cu–Pb–Zn skarn mineralization formed in the Middle Triassic and is closely related to the coeval magmatism. The ε Hf (t) values of the ore-related granodioritic and dioritic rocks range from −2.8 to +2.5, whereas an un-mineralized granodiorite sample (WHFG–1) shows lower ε Hf (t) values of –9.3 to –3.4, indicating that these magmatic rocks are derived from the mixing of magma with different proportions of mantle- and crust-components. A mixing model with ∼40–70 % mantle contribution involved in the formation of ore-related granodiorite and diorite was revealed by Sr–Nd–Hf isotopic compositions. Combined with Pb isotopic compositions for sulfides, feldspar, and bulk rocks, we consider a common source for the ore-forming materials and magmatism. In addition, higher ε Hf (t) and ε Nd (t) values for ore-related magmatism implicate that mantle-derived melts show a vital role in the Cu–Pb–Zn skarn mineralization process. [ABSTRACT FROM AUTHOR]

The Yangtze River is the largest river in Asia, and its evolution has been a subject of debate for more than a century. The formation of the First Bend is widely recognized as a key drainage reorganization event that led to the birth of the modern Yangtze River. In this study, we use new detrital rutile U Pb ages to constrain the sedimentary provenance of the Cenozoic deposits in the Jianchuan Basin. Our results show that detrital rutile U Pb ages of the Eocene sandstones from the Jianchuan Basin are similar to those of the Yalong River and Jinsha River, indicating that the upper Yangtze is likely to have flowed through the Jianchuan Basin in the late Eocene. Moreover, the characteristic zircon age signature of the Yalong and Jinsha Rivers also appear in the Jianchuan Basin, which is consistent with the rutile data. Our new rutile data and previous detrital zircon data suggest that the upper Yangtze River is likely to connect the Red River via the Jianchuan Basin since the late Eocene. [Display omitted] • New detrital rutile results indicate Cenozoic sediment in the Jianchuan Basin source from upper Yangtze (Yalong and Jinsha rivers). • The characteristic zircon age signature of the Yalong and Jinsha rivers are also appearance in the Jianchuan Basin, which is consistent with the rutile data. • The upper Yangtze is likely to flow southwards into the Red River through the Jianchuan Basin prior to ∼36 Ma. [ABSTRACT FROM AUTHOR]

Typical stratiform-like cassiterite–sulfide orebodies formed at 160–150 Ma cut by a steep hydrothermal vein-type orebody were discovered in the Xianghualing tin–polymetallic orefield, which implied a new phase of magmatism and mineralization later than the Late Jurassic stage. Hence, a systematic study of the characteristics and genesis of the concealed Laohuya granite, including U–Pb age, trace elements, Lu–Hf isotopes of zircons, and whole-rock major- and trace-elements, is examined in this paper. The zircon U–Pb dating yielded a Concordia age of 87.75 ± 1 Ma, confirming the existence of Late Cretaceous magmatism in the Xianghualing tin–polymetallic orefield. The Laohuya granite is classified as syenogranite and belongs to the peraluminous, high K calc-alkaline series. It is a highly evolved A2-type granite with εHf(t) values ranging from −14.97 to −7.59 and two-stage model ages (TDM2) ranging from 2939 to 2280 Ma. Combining chronology, petrochemistry, isotopic geochemistry, and previous tectonic studies, we believe that the Laohuya granite originated from the partial melting of a reworked ancient crust composed of TTGs, and its weathered sediments formed in subduction or collision zones at 2.5 Ga, controlled by the reactivation of the Chenzhou–Linwu deep fault in the extensional setting of South China during the Late Cretaceous. [ABSTRACT FROM AUTHOR]

BACKGROUND: Apatite is a common U - bearing accessory mineral with a U - Pb closure temperature of ~500℃, making U - Pb dating of apatite a potentially valuable thermochronometer. However, its low U concentration, high common lead concentration and lack of reference material has limited widespread application to LA-ICP-MS dating. OBJECTIVES: To develop a technique for U-Pb dating of apatite using laser ablation sector field inductively coupled plasma-mass spectrometry (LA-HR-ICP-MS). METHODS: The U-Pb isotope ratio in apatite samples was determined by LA-HR-ICP-MS, with apatite MAD2 as the external standard to correct U - Pb and Pb - Pb elemental fractionation directly without a common Pb correction. RESULTS: Long-term U-Pb analysis of Madagascar apatite sample (MAD2) showed homogeneous distribution of U, Pb and U-Pb isotope ratios, with average contents of U and Pb ~ 23. 8×10 -6 and ~ 13. 5×10 -6, respectively and weighted average 207 Pb / 206 Pb and 206 Pb / 238U ratios of 0. 0941±0. 0006 and 0. 0794±0. 0004, respectively. Taking MAD2 apatite as a reference mineral, combined with 207 Pb-correction method, the ages of apatite samples, McClure Mountain (521±5Ma), Tory-Hill-apt (1021±16Ma), a Durango (30. 7±1. 5Ma) and Fagnshan diorite apatite (~131Ma) can be determined accurately. CONCLUSIONS: The Madagascar apatite sample (MAD2) can be used to calibrate apatite U-Pb isotope ratio measured by LA-ICP -MS directly, without common-Pb correction, similar to the calibration strategy in zircon U-Pb dating. The method greatly reduces the difficulty of data processing during apatite U-Pb dating by LA-ICP -MS, which is conducive to the wide application of the method. [ABSTRACT FROM AUTHOR]

Khondalite belts are of special importance is delimiting old suture zones and in palaeocontinental reconstruction of Precambrian terrains. In the South‐American Platform, khondalitic rocks surround cratonic areas and Archean blocks reworked in the Neoproterozoic, an example of which being the Ceará Khondalite Belt (CKB). Located in the northern portion of the Borborema Province in NE Brazil, CKB is here described by means of its petrographic, structural, and LA‐SF‐ICP‐MS zircon and monazite U–Pb geochronological characteristics. CKB constitutes an E‐W to NE–SW striking belt comprising migmatitic spinel (hercynite)‐ and graphite‐bearing cordierite‐garnet‐sillimanite‐biotite gneisses, small granulitic boudins, garnet‐biotite quartzite, lenses of garnet amphibolite, calc‐silicate rock, gondite, and mylonitized leucogneiss. Relicts of Palaeoproterozoic island and continental arcs surrounding CKB are represented by tonalitic and dioritic gneiss, respectively. The contact between CKB and the Neoproterozoic Independência Unit is marked by a transpressional shear zone to the north, whereas the contact between CKB and Archean and Palaeoproterozoic rocks to the south is via a N‐verging thrust fault. The metamorphic peak is given by the parageneses: spinel (hercynite)‐quartz, spinel (hercynite)‐cordierite, and cordierite‐sillimanite‐garnet, possibly stable under UHT conditions. Crystallization ages of 2,086 ± 8 Ma and 2,063 ± 9 Ma were obtained by dating CKB migmatitic dioritic orthogneisses using the zircon U–Pb method. The CKB para‐derived rocks yielded detrital zircon U–Pb age peaks at 2,190, 2,130, and 2,060 Ma. Three metamorphic stages are identified in the Palaeoproterozoic via U–Pb dating of zircon rims and monazite at 2,094 ± 4 Ma, 2,055 ± 5 Ma, and 1,958 ± 3 Ma. A fourth metamorphic event with associated migmatization in shear zones took place in the Neoproterozoic between 595 ± 6 Ma and 573 ± 15 Ma, as indicated by dating zircon rims and monazite, respectively. Our study shows that the metamorphic events occurring in CKB in the Palaeoproterozoic share similarities with those that affected the khondalitic rocks bordering the São Francisco and the North China cratons, which suggests the existence of a continuous orogen during the Rhyacian‐Orosirian related to the Columbia Supercontinent amalgamation. [ABSTRACT FROM AUTHOR]

A Mesoproterozoic granite covering about 5 km2 is firstly recognized in the Zhusileng area, which is located between the northern Alxa Block and the South Gobi microcontinent. New geochronological data from this area provide new insight for understanding the Precambrian crustal evolution of the middle segment of the southern Central Asian Orogenic Belt (CAOB). Based on the crystal shapes, internal textures, and high Th/U ratios, the zircons from this Mesoproterozoic granite are interpreted as magmatic origin. Meanwhile, LA‐ICP‐MS zircon U–Pb dating shows that it was emplaced at 1458 ± 7.5 Ma. Published geochronological data and Sr–Nd isotopic compositions of igneous rocks from the Zhusileng area and its vicinity are also compiled in this study. The Late Palaeozoic granitoids from the Zhusileng area have strongly negative εNd(t) values (−0.1 to −10.8), high (87Sr/86Sr)i (0.69657–0.73423) and old Nd model ages (0.9–1.8 Ga), suggesting the existence of Precambrian microcontinent in the Zhusileng area. Furthermore, the statistical analysis (or isotopic mapping) of Sr–Nd isotopic compositions of Palaeozoic granitoids from the middle segment of the southern CAOB also displays similar εNd(t) values and relatively old Nd model ages along the Hanshan Block, Zhusileng, Tsaggan Uul terrane, and Hutag Uul terrane. Therefore, we propose that those units may share a common basement during Mesoproterozoic to Early Neoproterozoic. [ABSTRACT FROM AUTHOR]

The Tan–Lu Fault zone (TLFZ) is the largest fault zone in eastern China and a typical and representative structure of the Circum–Pacific tectonic domain. The Late Mesozoic tectonic evolution of the TLFZ is greatly significant, since it revealed the Jurassic–Cretaceous tectonic evolution of eastern China and the subduction history of the Palaeo–Pacific Plate. However, its tectonic evolution in the Early Cretaceous remains controversial. Based on geological mapping, microstructural analysis, and LA–ICP–MS zircon U–Pb dating, we constrained the deformation history of the Feidong Segment of the TLFZ in the Early Cretaceous. Results showed that the Feidong Segment of the TLFZ experienced a strong sinistral strike–slip movement at the beginning of the Early Cretaceous (~143 Ma); it was subsequently subjected to normal faulting during the Early Cretaceous (135–102 Ma), which controlled the strong magmatic activities within the Feidong area. At the end of the Early Cretaceous (~100 Ma), a weak sinistral strike–slip movement occurred again along the TLFZ. The deformation temperatures of the two sinistral strike–slip shearing stages were 500–550°C and 400–450°C, respectively. The regional comparison indicated that the Early Cretaceous tectonic evolution of the TLFZ was actually the epitome of the contemporaneous tectonic evolution of eastern China and was the result of strain localization in the Cretaceous tectonic framework of eastern China. [ABSTRACT FROM AUTHOR]

The Kongling terrane (Huangling dome) outcrops Precambrian metamorphic basement of the Yangtze craton. However, the Precambrian tectonic evolution of the southern Kongling terrane remains poorly constrained. In this contribution, we report zircon geochronology of the metasedimentary rocks from southern Kongling terrane of the Yangtze craton. Zircon U‐Pb dating results yielded magmatic age clusters at ca. 3,000 Ma, ca. 1,520 Ma, ca. 1,150 Ma, ca. 860 Ma, 900–920 Ma, and 980 Ma, and metamorphic age at ca. 2,900 Ma. These data display that the southern Kongling terrane witnessed Mesoarchean magmatism and metamorphic event, Mesoproterozoic and Neoproterozoic magmatism. In combination with previous studies, it is proposed that the Precambrian metamorphic basement of the Yangtze craton was amalgamated by the multi‐stage subduction‐collision processes at ca. 3,000–2,900 Ma, ca. 2,000–1,800 Ma, and ca. 1,100–940 Ma. In addition, the Proterozoic processes were related to the assembly and breakup of Columbia and Rodinia supercontinents. Key Points: The southern Kongling terrane of the Yangtze craton witnessed ca. 3,000 Ma magmatic and ca. 2,900 Ma metamorphic eventsThe SKT experienced Mesoproterozoic and Neoproterozoic magmatism causing by the breakup and amalgamation of the Precambrian supercontinentsThe Precambrian metamorphic basement of the Yangtze craton was formed by multi‐stage subduction‐collision processes [ABSTRACT FROM AUTHOR]

Understanding mass transfer associated with fluids circulation and deformation in the Alpine orogeny is often complex due to common multistage crystallization. For example, in two emblematic and historic Pb-Ag deposits of the French Alps, Macôt-la Plagne (MP) and Peisey-Nancroix (PN), a sedimentary or orogenic origin is still debated. To discriminate between the metallogenic models of the two deposits, an integrative methodology combining field, microstructural, mineralogical, thermobarometrical, and geochronological data was here applied for establishing detailed Pressure–Temperature–Time–Deformation (P-T-t-d) mineralization conditions. Both deposits are located in Permo-Triassic quartzite of the External Briançonnais domain along the Internal Briançonnais Front (Internal Western Alps). The ore mainly occurs as veins and disseminated textures containing galena, pyrite, and variable content of tetrahedrite–tennantite and chalcopyrite. Quartz porphyroclasts and sulfide microstructures indicate a dynamic recrystallization of the quartzite during the main fluid mineralization episode. Chlorites and K-white micas (phengite) chemical analysis and thermodynamic modeling from compositional maps indicate an onset of the mineralization at 280 °C, with a main precipitation stage at 315 ± 35 °C and 6.25 ± 0.75 kbar. In situ U-Pb dating on monazite, cogenetic with sulfides, gives ages around 35 Ma for both deposits. The integrative dataset converges for a cogenetic MP-PN Alpine Pb-Ag mineralization during deformation in relation to the thrusting of the "Nappe des Gypses" and the Internal Briançonnais at the metamorphic peak. [ABSTRACT FROM AUTHOR]

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Here we report the first set of thallium (Tl) isotope data in alkaline rocks from the North China Craton to constrain the nature of recycled materials in the metasomatized subcontinental lithospheric mantle. Samples from the Hekanzi and Saima alkaline complexes display Tl isotope compositions (ε205Tl) identical to the present‐day upper mantle and continental crust, suggesting that neither the recycled low‐temperature altered oceanic crust nor the pelagic sediments were involved in their sources. The volcanic rocks from the Liaodong‐Jinan region, whose source was previously proposed to contain recycled low‐temperature altered oceanic crust, also display modern mantle‐like Tl isotope composition, suggesting a significant Tl‐loss in the recycled oceanic crust during the subduction due to the dehydration process. Our Tl isotope data provide complementary constraints to the Sr‐Nd‐Hf‐O isotopes on the nature of metasomatic agent in the subcontinental lithospheric mantle. Plain Language Summary: Recycling of crustal materials into Earth's mantle by subduction causes mantle heterogeneities. The sources of some alkaline rocks contain recycled crustal materials. Pelagic sediments, low‐temperature altered oceanic crust, and continental crust have sharp differences in thallium isotope compositions. Combined with Sr‐Nd‐Hf‐O isotopes, whole‐rock Tl isotopes place a better constraint on the metasomatic sources. Key Points: Thallium isotope compositions of the alkaline rocks were analyzed to track crustal recycling in the subcontinental lithospheric mantleThallium isotope suggested that low‐temperature altered oceanic crust and pelagic sediments were not involved in the investigated sourcesThe O‐Nd‐Hf‐Tl isotope data for the Liaodong‐Jinan volcanics reveal a significant Tl‐loss in the subducted slab during dehydration process [ABSTRACT FROM AUTHOR]

In situ carbonate U-Pb dating studies have proliferated dramatically in recent years. Almost all these studies have targeted relatively young calcite up to Carboniferous in age. To assess the robustness of the carbonate U-Pb chronometer in deep-time, we carried out in situ U-Pb analyses in magnesite-ankerite-calcite carbonates in the martian meteorite Allan Hills (ALH) 84001. Carbonates in ALH 84001 formed at ca. 3.94 Ga, and there is little evidence that much happened to this rock since then, making it an ideal sample to test the robustness of the U-Pb system in old carbonates. We obtained a concordant date of 3941 ± 49/110 Ma (n = 14, MSWD = 2.0), which is identical to the step-leaching Rb/Sr date determined previously. These results thus confirm that old carbonates are amenable to U-Pb dating in samples that have had a relatively simple history post-carbonate formation. [ABSTRACT FROM AUTHOR]

The Cordillera of Canada and Alaska is a type example of an accretionary orogen, but the origin of some terranes remains contentious (e.g., Stikinia of British Columbia and Yukon, Canada). Presented herein are igneous and detrital zircon U/Pb-Hf and trace-element data, as well as the first radiolarian ages from the Asitka Group, the basement to eastern Stikinia. The data are used to evaluate the role of juvenile and ancient crust in the evolution of Stikinia and the tectonic environment of magmatism. Two rhyolites are dated by U-Pb zircon at 288.64 ± 0.21 Ma and 293.89 ± 0.31 Ma, with εHf(t) = +10. Red chert contains radiolarians that are correlated with P. scalprata m. rhombothoracata + Ruzhencevispongus uralicus assemblages (Artinskian-Kungurian). Detrital zircon U/Pb-Hf from a rare Asitka Group sandstone have a mode at ca. 320 Ma and εHf(t) +10 to +16; the detrital zircon suite includes five Paleoproterozoic zircons (~5% of the population). Detrital zircons from a stratigraphically overlying Hazelton Group (Telkwa Formation) volcanic sandstone indicate deposition at ca. 196 Ma with zircon εHf(t) that are on a crustal evolution line anchored from the Asitka Group. Zircon trace-element data indicate that the Carboniferous detrital zircons formed in an ocean arc environment. The Proterozoic detrital zircons were derived from a peripheral landmass, but there is no zircon εHf(t) evidence that such a landmass played any role in the magmatic evolution of eastern Stikinia. The data support that eastern Stikinia formed on Paleozoic ocean floor during the Carboniferous to early Permian. Consistent with previous fossil modeling, zircon statistical comparisons demonstrate that Stikinia and Wrangellia were related terranes during the Carboniferous to Permian, and they evolved separately from Yukon-Tanana terrane and cratonic North America. [ABSTRACT FROM AUTHOR]

The thermal histories of upper crustal magma reservoirs place important constraints on the formation, evolution, and remobilization of crustal magmas, yet quantifying thermal histories remains challenging. We report new in situ plagioclase trace-element data, Sr in plagioclase diffusion timescales, and plagioclase 238U-230Th-226Ra disequilibria data from Mount Saint Helens (MSH) 1980 cryptodome and 2004–2005 dacite domes to evaluate the thermal storage conditions and compositional diversity of recent MSH magmas. This approach allows us to more directly link the thermal (and therefore physical) conditions within the MSH magma reservoir to timescales of storage, thereby constraining the fraction of time 1980–2005 MSH magmas have spent in a mobile state. Plagioclase trace-element data and U-series characteristics reveal a compositionally heterogenous magmatic system beneath MSH and also require multi-stage plagioclase growth histories. The data also show that 2004–2005 dacites contain a different plagioclase population relative to the 1980 cryptodome dacite, comprised of either a compositionally (and possibly temporally) distinct plagioclase component or composed of the same plagioclase components but in significantly different proportions. Discordant plagioclase 238U-230Th and 230Th-226Ra apparent ages require a mixture of young (likely eruption related) and old (>20–40 ka) plagioclase crystals in both 1980 and 2004–2005 dacites. The low (230Th)/(232Th) in all measured 1980 and 2004–2005 plagioclase requires a significant fraction (>10–30%) of the plagioclase to be old (>10s kyr). Maximum modeled Sr diffusion timescales at 750°C range from decades to centuries for both eruptions, with a maximum of ~600 years found in 1980 cryptodome plagioclase. However, partially equilibrated Sr in the innermost exposed parts of some crystals found in both 1980 and 2004–2005 plagioclase indicate that a fraction (>20%) of plagioclase may have experienced a total of >10 kyrs at temperatures ≥750°C. Coupling Sr diffusion timescales with U-series measurements indicates that significant fraction (at least ~40%) of modeled MSH plagioclase spent <5% of their storage time at temperatures ≥750°C and thus in an easily mobilized rheological state. In contrast, the fraction of partially equilibrated plagioclase possibly spent >25–50% of their storage time at hotter conditions. Our data combined with data from other arc magmatic systems (e.g. Mt. Hood) imply that the process of remobilizing magma in arc systems toward successive eruptions requires thermally rejuvenating largely crystalline material, as opposed to sequential tapping of a persistent liquid-dominated magma body, even if successive eruptions are spaced closely in time (decades). In addition, rejuvenation events responsible for successive eruptions may sample spatially localized, but potentially overlapping, portions of the broader magma reservoir. [ABSTRACT FROM AUTHOR]

Determining absolute ages of orogenic faults is critical to understanding the deformation process in the upper crust, but obtaining age remains a problem due to the lack of readily available techniques. Carbonates occur as veins in faults in a range of geological settings, and thus it is a suitable mineral for U-Pb geochronology. Here, we apply the new approach of U-Pb dating on syn-tectonic dolomite veins from the Gelouang gold deposit in the western Qinling Orogen to unravel the absolute timing of the fault formation shedding new light on the regional upper crustal deformation archive. In situ LA-ICP-MS U-Pb dating of dolomite yielding a successful age of 115–112 Ma demonstrates that the dolomite precipitated coeval with tectonic events ascribed to the post-orogenic deformation phase in the Qinling Orogen. This event is possibly correlated with broader intracontinental processes and might be an inevitable response to the extensional deformation of the Qinling Orogen. The presented LA-ICP-MS dolomite U-Pb age successfully represents the age of a specific structure that encompasses the intracontinental process in the Qinling Orogen. Moreover, it demonstrates the utility of the method to decipher a response to complex deformation histories on a regional scale. [ABSTRACT FROM AUTHOR]

The timing of the Lhasa–Qiangtang collision following the closure of the Bangong–Nujiang Tethys Ocean has not been well constrained. An integrated study of whole-rock geochemistry and zircon U–Pb–Hf isotopes was carried out for Early Cretaceous quartz diorite-porphyrites and granites from the Yilashan and Amdo areas, northern Tibet. LA–ICP–MS zircon U–Pb dating reveal that the Yilashan and Amdo granitoids were emplaced at ~121–110 Ma. These granitic rocks display selective enrichment of light rare earth elements, large ion lithophile elements (e.g., Rb, U) and Th, but depletion of Sr and high field strength elements (e.g., Nb, Ta, Ti) compared to its neighboring elements. These new data, combined with regional geological setting, show that these igneous rocks were formed under a geodynamic setting of the Lhasa and Qiangtang (–Amdo) collision with oceanic slab breakoff and asthenospheric upwelling. The BNTO had been closed at ~121–110 Ma in the study area. Yilashan-Amdo granitoids roughly yield high (87Sr/86Sr)i ratios and obvious negative εNd(t) and zircon εHf(t) values along with old Nd TDM and zircon Hf TDM2 ages. Together with their variable U–Pb ages, these features indicate a Precambrian "hidden" crustal source beneath the northern Lhasa and Amdo terranes. The YLSS S-type granophyres were derived from partial melting of Paleoproterozoic lower crustal metagraywackes, whereas the YLSZ quartz diorite–porphyrites and the Amdo I- and A-type granites were mainly derived from partial melting of Paleo–Mesoproterozoic lower crustal mafic rocks with a certain amount of addition of mantle-derived melts. Minor amounts of the materials originated from the Amdo orthogneisses may also be involved in the formation of the YLSZ quartz diorite–porphyrites and the Amdo I-type granites. In addition, the Yilashan ophiolite was intruded by the ~112–108 Ma granophyric and quartz diorite–porphyritic intrusions before its final emplacement into the surrounding strata. [ABSTRACT FROM AUTHOR]

Detrital-zircon U-Pb geochronology is extensively used to imply provenance histories as one of the most common methods to constrain the tectonic evolution of ancient sedimentary systems. The rapid accumulation of detrital-zircon thermochronology data in the eastern Tien Shan region brought great convenience for understanding the basin–mountain evolution in the region. In this work, 41 samples for zircon U-Pb dating from the Jurassic–Cretaceous strata of the Turpan-Hami basin and its adjacent region were compiled. Based on the systematic investigation, comparison, and summarization of Late Mesozoic sources in the eastern Tien Shan region and the quantitative characterization of source variations, we further explored and dissected the Late Mesozoic tectonic evolution of the eastern Tien Shan orogenic belt. Data from detrital-zircon age spectra, KS tests, MDS plots, Monte Carlo simulations, etc., suggested that eastern Tien Shan was also highly active during the Mesozoic, and especially, Bogda was the most remarkable. Moreover, there was a sig-nificant differential segmental exhumation before the Late Jurassic. In general, from the Early Ju-rassic to the Cretaceous, the proportion of Bogda provenance gradually increased, especially the large-scale uplift and denudation that occurred after the development of the Qigu Formation. The provenance of central Tien Shan and Jueluotag gradually stabilized before the Cretaceous. From the Late Jurassic to the Cretaceous, the decreasing tendency of the central-Tien-Shan-provenance percentages decreased, while that of Jueluotag provenance increased. Furthermore, central Tien Shan provenance had a slightly growing trend from the Early Jurassic (38%) to the Middle Jurassic (41.3%) and then gradually decreased to 20.3%. The Central Tien Shan still accounted for a sizeable proportion of the provenance, the genesis of which suggests that it may be that provenance as-cribable to central Tien Shan still crossed the poorly uplifted Jueluotag to the Turpan-Hami basin. Similar to central Tien Shan, the provenance ascribable to Jueluotag gradually decreased from an initial 51.8% to 14.9% in the Late Jurassic, but the proportion of the provenance increased again to 26% during the Cretaceous. These features opened the prelude to the Cenozoic tectonic activities in this region. In addition, the decomposition results revealed that the inverse Monte Carlo mixed model for dissecting the provenance of sandstone samples was subject to large biases in complex geological settings, such as detrital-zircon populations, the age spectra of source areas, contempo-raneous magmatism, and recovered older strata. [ABSTRACT FROM AUTHOR]

The Truong Son orogenic belt (TSOB) is one of the most important orogenic belts in the Indochina block. There are numerous mafic to felsic intrusions in the Early Paleozoic caused by the Tethyan orogeny. However, the tectono-magmatic evolution of the TSOB in the Early Paleozoic is still unclear. In this paper, zircon U-Pb dating, whole-rock geochemistry, and the Sr-Nd isotopic data of the Early Paleozoic magmatic rocks have been systematically investigated to explore the petrogenesis and tectonic significance of these rocks in the TSOB. Based on our new results integrated with previous geological data, four major tectono-magmatic episodes are identified. (1) The Middle Cambrian (~507 Ma) is the early stage of northward subduction of the Tamky-Phuoc Son Ocean. (2) The Early Ordovician to Middle Ordovician (483–461 Ma) is the main subduction stage of the Tamky-Phuoc Son Ocean. The intrusive rock associations imply the closure of the Tamky-Phuoc Son Ocean. (3) The Late Ordovician to Early Silurian (461–438 Ma) is the collision stage of the Kontum massif and Truong Son terrane. (4) The Early Silurian to Late Silurian (438–410 Ma) is the late stage of collision accompanied by slab roll-back. [ABSTRACT FROM AUTHOR]

The Heilongjiang Complex records the evolution history of the Mudanjiang Ocean, which is of great significance to constrain the amalgamation process of the Jiamusi and Songnen‐Zhangguangcai Range massifs. We carried out petrological, chronological, geochemical, mineral chemical and electron backscatter diffraction (EBSD) fabric analyses on the Heilongjiang Complex in the Yilan area. The latest zircon U–Pb dating results show that the protolith ages of the amphibolite are 261.3 ± 3.0 Ma and 261.8 ± 3.3 Ma, while that of the granodioritic mylonite is 207.8 ± 2.2 Ma. The amphibolites and granodioritic mylonite are enriched in large‐ion lithophile elements (e.g., Rb, Ba, and Sr) and light rare earth elements, with depletion in high‐field‐ strength elements (e.g., Nb, Ta, Zr, and Hf), indicating that the formation of the protoliths of the amphibolites and granodioritic mylonite is related to the subduction of the Mudanjiang oceanic plate under the Songnen‐Zhangguangcai Range Massif. The amphibolites and granodioritic mylonite both experienced two periods of metamorphic and deformation events. The metamorphic degree of the early period of metamorphism is low amphibolite facies, which records a clockwise P–T path from early increased temperature and pressure to a late isothermal depressurization. The P–T path reveals that this period of metamorphism is associated with the collision between two massifs. The later period of metamorphism reaches low greenschist facies, accompanied by deformation, which may be related to the rapid exhumation of the Heilongjiang Complex. This study provides a new perspective for exploring the collision and collage process of the Jiamusi and Songnen‐Zhangguangcai Range massifs. [ABSTRACT FROM AUTHOR]

Carbonate U-Pb dating of samples from rift-bounding faults of intracontinental basins in the Borborema province, northeastern Brazil, indicate recurrent tectonic activity during Pangea breakup lasting for >150 m.y. from the Late Triassic to the Paleocene, reactivating inherited strike-slip Neoproterozoic--Cambrian shear zones. Triassic ages indicate that brittle deformation started some 80 m.y. before previously known, most likely related to rifting along the incipient Central Atlantic. The subsequent Cretaceous opening of the South Atlantic caused renewed fault activity during rifting and basin development. Furthermore, recurrent Cenozoic tectonic activity along the rift-bounding faults is indicated, suggesting that structural inheritance of the Neoproterozoic--Cambrian continental-scale Borborema shear zone system has been responsible for accommodation of recurrent tectonic stress from Mesozoic rifting to the present day. [ABSTRACT FROM AUTHOR]

The early Paleoproterozoic was a time of unprecedented change in Earth's climate and surface environment. The key to resolving some of the controversies surrounding the timing and causes of these changes lies with supracrustal sequences, such as the 2.45-2.22 Ga Turee Creek Group in the southern Pilbara craton, northwestern Australia. The group preserves a predominantly siliciclastic sequence; however, its precise age, tectonic setting, and postdepositional history are disputed. Although it is interpreted to have been deposited in a foreland basin setting shortly after 2.45 Ga, the oldest well-recognized deformational event, marked by northward folding and thrusting, is the 2.20-2.15 Ga Ophthalmia orogeny. Evidence for a pre-Ophthalmia fabric-forming tectonic event north of the Archean Sylvania Inlier, southeast Pilbara craton, which is marked by tight to isoclinal folding, has been largely overlooked. In this area, we report in situ U-Pb geochronology of authigenic monazite and xenotime in shale with a well-developed tectonic cleavage from the ca. 2.63 Ga Jeerinah Formation. Monazite porphyroblasts, which are locally wrapped by strain fringes aligned in a tectonic cleavage, yielded weighted mean 207Pb/206Pb ages at 2370 ± 11 Ma and 2312 ± 8 Ma, whereas xenotime, which overprints a crenulation cleavage, gave a weighted mean 207Pb/206Pb age of 2291 ± 11 Ma, constraining fabric development to between 2.31 Ga and 2.29 Ga. Our results confirm the existence of a pre-Ophthalmia deformational event in the southeastern Pilbara craton, herein referred to as the Sylvania orogeny, which is part of an ~300 m.y. interval (2.45-2.15 Ga) of northward-directed compression ("Hamersley orogenic cycle"). This orogenic cycle is marked by east-west and northwest-southeast folding, cleavage development, veining, hydrothermal gold mineralization, and isotopic resetting across the southern Pilbara craton. Our results indicate that the syn--Great Oxidation Event Turee Creek Group was deposited in one or more foreland basins after 2.45 Ga. Our results provide a new tectonostratigraphic and geodynamic framework for understanding the timing and origin of geochemical records in a key succession deposited during an interval of global environmental change. [ABSTRACT FROM AUTHOR]

Southeastern (SE) Yunnan is a major Sn polymetallic province of China, with the Dulong large Sn-Zn polymetallic deposit (in the Laojunshan orefield) being one of the most representative deposits. Our recent work had first identified helvine- group minerals in this deposit. These minerals mainly occur in massive sphalerite ores, and coexist with sphalerite, pyrrhotite, biotite, talc, cassiterite, and fluorite. Raman spectroscopic, X‑ray difraction (XRD), scanning electron microscopic (SEM), and electron probe microanalysis (EPMA) analyses indicate that these helvine-group minerals are oscillatory-zoned helvine-danalite. Both the helvine and danalite zones are mixed with varying proportion of the other helvine-group end-member, and our studies indicate that the oscillatory zoning was formed mainly by periodic fluctuations of the fluid physicochemical conditions (notably fS2 and fO2), but less related to the variation of the fluid Mn, Fe, and Zn contents. The helvine zone was likely formed in a higher fS2 but lower fO2 environment than the danalite zone. In this study, we present the first LA-ICP-MS in situ trace element data for the helvine-danalite minerals from Dulong, and the results indicate that the helvine has considerably high contents and a wide range of trace elements. The helvine is rich in Ca, Al, Sc, and Y, while the danalite is rich in Sn and P (reaching thousands of parts per million). Such trace element enrichments are likely controlled by their respective ionic size and chalcophile behavior. Meanwhile, the fO2 and fS2 conditions during the zoning formation may have also influenced the trace element distributions: trace elements may have mainly entered the helvine-group minerals by substituting into the M-sites in M4[BeSiO4]3S, for instance Al, Sc, and Y substitute for Mn, and Sn and Mg for Fe and Zn. It is noteworthy that the helvine and danalite zones are all HREE-enriched and have distinct negative Eu anomalies. This may be related to the high fluid F-Y-P contents during the mineral formation. High-F-Y fluids can readily incorporate HREEs into helvine-group minerals, and phosphates incorporate HREEs more readily in alkali fluids. Europium occurs as Eu2+ in the fluid, causing the negative Eu anomalies observed. We have also identified grains of cassiterite in the helvine-group minerals and its coexisting sphalerite. U-Pb dating on these cassiterite grains yielded 86.5 ± 1.6 Ma, coeval with the reported sulfide mineralization age. This indicates that both the Be and Sn-Zn polymetallic mineralization occurred in the Cretaceous, and may have been products of the Late Yanshanian Laojunshan magmatic-hydrothermal activity. Considering the close relations with many W(-Be) deposits nearby (e.g., Nanyangtian, Saxi, and Maka), the Laojunshan orefield may also have substantial Be mineralization potential. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Geomechanics is the property of Journal of Geomechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Geomechanics is the property of Journal of Geomechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Geomechanics is the property of Journal of Geomechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

After subjecting Zamora building stones to accelerated ageing tests, colour changes were studied, namely: (a) freezing/thawing and thermal shock (gelifraction and thermoclasty), and (b) combination of freezing/thawing plus thermal shock and salt crystallisation (sulphates or phosphates) (gelifraction, thermoclasty and haloclasty). Zamora building stones are silicified conglomerates (silcretes) from the Cretaceous that show marked colour changes due to the remobilisation of iron oxyhydroxides. In this work, four varieties were: white stone; ochreous stone; white and red stone; and purple stone Their micromorphological characterization (skeleton, weathering plasma and porosity/cutan) is formed of grains and fragments of quartz and quartzite as well as by accesory minerals muscovite and feldspar (more or less altered), and some opaque. Quartz, feldspar and illite/mica were part of the skeleton; kaolinite, iron oxyhydroxides, and CT opal were part of the weathering plasma or cutans; their porosity were 11.7–8.7%. Their chromatic data have been statistically analysed (MANOVA-Biplot). They showed higher variations in ΔE*, ΔL*, Δa* and Δb*on combined freezing/thawing plus thermal shock and sulphates crystallisation leading to rapid alteration of the building stones. Chromatic differences between the other two artificial ageing tests were less evident and were not detected in all samples. The global effect of ageing on the Zamora building stones darkened them and reduced their yellowing. The ochreous stone suffered the least variation and the purple stone the most. This study of the colour by statistical analyse may be of interest for the evaluation and monitoring of stone decay, which is an inexpensive, simple, easy and non-destructive technique. [ABSTRACT FROM AUTHOR]

The significance of mineralogical maturity as a provenance indicator has long been debated and we use this study to demonstrate that it can indeed be a powerful tool to track the distribution of sandstone reservoirs. We investigate the cause of the pronounced geographic and stratigraphic differences in mineralogical composition that are found in the Upper Triassic–Lower Jurassic Gassum Formation across the Norwegian–Danish Basin and surrounding areas. Zircon U-Pb dating of 46 sandstone samples including analysis of 4816 detrital grains are combined with quantifications of the detrital mineralogical composition and placed in a sequence stratigraphic framework. The results show that the Gassum Formation can be divided into a southeastern region with high mineralogical maturity and a less mature region to the northwest with more feldspars, rock fragments, micas, and heavy minerals. Both the mineralogical assemblage and the provenance signature have been thoroughly homogenized in the SE region where sediment supplies from the Fennoscandian Shield and the Variscan Orogen are evident. In the NW region, sediment was initially supplied from Fennoscandia only, but the provenance abruptly changed from the Telemarkia Terrane to comprising also the more distant Caledonian Orogen resulting in a different mineralogical assemblage. The change occurred during a basinwide regression and may be caused by tectonic movements in the hinterland that permanently changed the composition of the sediment supplied to the basin. [ABSTRACT FROM AUTHOR]

Granite is a distinctive constituent part of the continental crust on Earth, the formation and evolution of which have long been hot research topics. In this paper, we reviewed the partial melting processes of crustal rocks without or with fluid assistance and summarized the role of fluids and volatiles involved in the formation of granitic melts. As a conventional model, granitoids were thought to be derived from the dehydration melting of hydrous minerals in crustal basement metamorphic rocks in the absence of external fluids. However, the external-fluid-assisted melting of crustal metamorphic rocks has recently been proposed to produce granitoids as extensive fluids could be active in the deep continental crust, especially in the subduction zones. It has been demonstrated experimentally that H2O plays a crucial role in the partial melting of crustal rocks, in which H2O can (1) significantly lower the solidus temperature of the melted rocks to facilitate partial melting; (2) affect the melting reaction process, mineral stability, and the composition of melt; and (3) help the melt to separate more easily from the source area and aggregate to form a large-scale magma chamber. More importantly, dissolved volatiles and salts in the crustal fluids could also lower the solidus temperature of rocks, affect the partitioning behaviors of trace elements between minerals and melts, and facilitate the formation of some distinctive granitoids (e.g., B-rich, F-rich, and high-K granitoids). Furthermore, various volatiles dissolved in fluids could result in elemental or isotopic fractionation as well as the diversity of mineralization during fluid-assisted melting. In-depth studies regarding the fluid-assisted partial melting of crustal rocks will facilitate a more comprehensive understanding of melting of the Earth's crust, thus providing strong theoretical constraints on the genesis and mineralization of granitoids as well as the formation and evolution of the continental crust. [ABSTRACT FROM AUTHOR]

Chemical abrasion is a technique that combines laboratory annealing and partial dissolution in hydrofluoric acid (HF) to selectively remove radiation-damaged portions of zircon crystals prior to U-Pb isotopic analysis, and it is applied ubiquitously to zircon prior to U-Pb isotope dilution thermal ionization mass spectrometry (ID-TIMS). The mechanics of zircon dissolution in HF and the impact of different leaching conditions on the zircon structure, however, are poorly resolved. We present a microstructural investigation that integrates microscale X-ray computed tomography (µCT), scanning electron microscopy, and Raman spectroscopy to evaluate zircon dissolution in HF. We show that µCT is an effective tool for imaging metamictization and complex dissolution networks in three dimensions. We find that most grains do not dissolve predominantly from rim-to-core. Acid frequently reaches crystal interiors via fracture networks spatially associated with radiation damage zoning and inclusions to dissolve higher U zones, material in the vicinity of fractures, and some inclusions. Other acid paths to crystal cores include the dissolution of surface-reaching inclusions and the percolation of acid across zones with high defect densities. In highly crystalline samples dissolution is crystallographically-controlled with dissolution proceeding almost exclusively along the c-axis. Increasing the leaching temperature from 180 °C to 210 °C results in deeper etching textures, wider acid paths, more complex internal dissolution networks, and greater volume losses. We discuss the implications of our findings for zircon ID-TIMS U-Pb geochronology and paired trace element analyses, radiation damage annealing models, and for using µCT for imaging radiation damage zoning for (U-Th)/He thermochronology. [ABSTRACT FROM AUTHOR]

BACKGROUND: The Hetian nephrite belt in Xinjiang is the largest nephrite ore belt in the world, with a length of about 1300 km. In addition to white, gray, black and brown nephrite, the Qiemo—Ruoqiang zone, Xinjiang also produces a yellow-green nephrite. There are few studies on the color origin and characterization of this kind of Hetian nephrite, which affects the understanding of the color and genesis of this kind of Hetian nephrite. OBJECTIVES: To understand the color genesis, genetic types and formation age of the yellow-green nephrite in Qiemo—Ruoqiang deposit. METHODS: Electron probe microanalysis (EPMA), backscattered electron (BSE) image, X-ray fluorescencespectrometry (XRF), and high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS) were used to investigate mineral and chemical composition. The FeO content was determined by titration method to explore its color origin and genetic type, and the zircon U-Pb isotope dating by sensitive high-resolution ion microprobe (SHRIMP) was used to constrain its mineralization age. RESULTS: Yellow-green nephrite in Qiemo—Ruoqiang was predominately composed of apatite, calcite, dolomite, diopside, epidote, sphene and zircon. The yellow-green nephrite whole rock had low total REE (∑REE=2.61-19.1μg/g) with obvious Eu negative anomaly (δEu<0.05), LREE right dipping, and HREE flat pattern. According to the distribution pattern of rare earth and the content of Cr and Ni, it was inferred that it was a magnesia skarn type Hetian nephrite. Compared with other nephrite in the world, the average value of Fe3+/Fe2+ of the yellow-green nephrite in Qiemo—Ruoqiang (average=0.16) overlapped with nephrite in other regions. The ratio is slightly higher (0.07-0.26), while the content of Fe3+ and Fe2+ was not significantly different between the yellow-green nephrite and other color nephrite. The SHRIMP U-Pb dating of zircon in the yellow-green nephrite yielded ages of 461.7±6.1 Ma (MSWD=1.6) and 498.1±4.6 Ma (MSWD=1.16). CONCLUSIONS: The color genesis of the yellow-green nephrite in Qiemo is probably related to the ratio of Fe3+/Fe2+, but not to the content of Fe3+ and Fe2+. The SHRIMP U-Pb dating results of zircon in yellow-green nephrite represent the formation age of the yellow-green nephrite. These new data provide geochronological constraints for the magmatism of Hetian nephrite belt and the tectonic evolution of the West Kunlun orogenic belt. [ABSTRACT FROM AUTHOR]

BACKGROUND: Despite zircon U-Pb dating analysis by LA-ICP-MS receiving wide acceptance, it remains a challenge to obtain results with high accuracy and precision. It is known that gas flow rates of LA system can affect the signal stability of ICP-MS and thus result in impacts on analytical uncertainty of zircon U-Pb dating. However, the exact effects and mechanism of gas flow rates on zircon U-Pb dating analysis are still unclear. OBJECTIVES: To thoroughly understand the influence of gas flow rates on the analytical uncertainty of zircon U-Pb dating, and to provide valuable information to propose a reliable and robust LA-ICP-MS approach for zircon U-Pb dating analysis. METHODS: By applying zircon standard samples of Harvard 91500 and Ple2 ovice as researching subjects, ICP-MS connected to a 193 nm nanosecond laser ablation system was used to investigate the influence of gas flow rate settings on accuracy and precision of U-Pb dating analysis. RESULTS: With fixed make-up gas (Ar) of 1.0 L/min, the average 206Pb/238U ages of Harvard 91500 were found to increase from 1002.0±10.4 Ma (1σ) to 1083.0±6.8 Ma (1σ) with increasing carrier gas (He) from 0.2 to 1.2 L/min. Thus, it was clear that the sample aerosol transportation efficiency can greatly affect the analytical accuracy of zircon U-Pb dating. Furthermore, when the He flow rate was higher than 0.8 L/min, the analytical accuracy and precision of zircon U-Pb dating decreased due to the increased signal intensity oscillations and formation of oxides from the introduction of large particles of sample aerosols. The comparison of the data of Ple2 ovice obtained under 0.95/0.8, 0.80/0.8 and 0.8/0.6 L/min for He/Ar gas flow rate patterns indicated that there were no significant differences in U/Pb weighted average age. However, the relative deviation of 1σ single-point analysis was the smallest (1.4%) when the Ar and He flow rates were both 0.8 L/min. CONCLUSIONS: The analytical accuracy and precision of zircon U-Pb dating by LA-ICP-MS can be improved by optimizing the gas flow rate setting of carrier gas and make-up gas, and highly recommending 0.8 L/min of both Ar and He. [ABSTRACT FROM AUTHOR]

Chemical diversity in convergent margin magmas is a product of igneous differentiation in crustal hot zones, vertically extensive regions characterised by a low-volume (<20%) mobile melt phase dispersed in a crystal-rich mush. Chemical reaction between buoyant, percolating melts and the surrounding mush leads to chemical buffering by the local mineral assemblage. Where this assemblage has low thermodynamic variance (e.g. six mineral phases plus melt and H2O-CO2 fluid) the resultant multiply saturated melts will show limited chemical variability. Plutonic xenoliths from many volcanic arcs, as well as exhumed arc crustal sections, testify to the ubiquity of low-variance, broadly gabbroic, mineral assemblages. Here I use the concept of multiple saturation to explore the chemical consequences of percolative reactive melt flow in crustal hot zones using data from published experimental studies on a wide variety of different starting materials. I show that the common, low-variance hornblende gabbronorite assemblage clinopyroxene-hornblende-orthopyroxene-magnetite-plagioclase-ilmenite (CHOMPI) coexists with fluid-saturated melt over a wide range of pressure (1–10 kb) temperature (800–1050 °C) and fluid composition (molar fraction H2O, X H2O, of 1.0 to 0.3). The CHOMPI stability field is bounded by the following: the appearance of garnet at high pressure, the hydrous haplogranite granite liquidus at low temperature, and amphibole breakdown at high temperature and low pressure. CHOMPI melts cover a wide compositional range (54–74 wt% SiO2; 4.4–0.1 wt% MgO) that can be parameterised in terms of five independent variables: pressure, temperature, f O2, molar CO2/H2O in the fluid and melt K2O content. The compositional diversity and broad stability field of CHOMPI-saturated melts make them extremely common in the rock record. Melt composition parameterisations can be inverted to recover pressure (±1.3 kb), temperature (±16 °C) and fluid molar CO2/H2O (±0.43) of CHOMPI-saturated melts. If a natural magma composition can be shown to lie on or close to the CHOMPI saturation surface then the conditions under which that melt was last in equilibrium with this mineral assemblage can be established. I apply this method of magma source thermobarometry and hygrometry to the most recent eruptions from 15 Cascades arc volcanic centres. Calculated pressures range from 1.3 to 5.8 kb (5–21 km depth) with significant along-arc variation. Temperatures correlate with pressure and match independent estimates of eruption temperatures from mineral thermometry with the exception of two eruptions where significant (≤10°C) cooling occurred during pre-eruptive magma storage. Fluid X H2O is in the range 0.47–0.92 and inversely correlates with pressure. Mineralogical buffering of melt chemistry in hot zones is proposed as an important mechanism of chemical differentiation in volcanic arcs. Mineralogical buffering can operate at the low-melt fractions observed in geophysical surveys of arc crust, providing an alternative to traditional concepts of assimilation-fractional crystallisation and liquid lines of descent that operate most effectively in melt-rich systems. [ABSTRACT FROM AUTHOR]

We collected a debris-rich ice core from a buried ice mass in Ong Valley, located in the Transantarctic Mountains in Antarctica. We measured cosmogenic nuclide concentrations in quartz obtained from the ice core to determine the age of the buried ice mass and infer the processes responsible for the emplacement of the debris currently overlaying the ice. Such ice masses are valuable archives of paleoclimate proxies; however, the preservation of ice beyond 800 kyr is rare, and therefore much effort has been recently focused on finding ice that is older than 1 Myr. In Ong Valley, the large, buried ice mass has been previously dated at > 1.1 Ma. Here we provide a forward model that predicts the accumulation of the cosmic-ray-produced nuclides 10 Be, 21 Ne, and 26 Al in quartz in the englacial and supraglacial debris and compare the model predictions to measured nuclide concentrations in order to further constrain the age. Large downcore variation in measured cosmogenic nuclide concentrations suggests that the englacial debris is sourced both from subglacially derived material and recycled paleo-surface debris that has experienced surface exposure prior to entrainment. We find that the upper section of the ice core is 2.95 + 0.18 / - 0.22 Myr old. The average ice sublimation rate during this time period is 22.86 + 0.10 / - 0.09 m Myr -1 , and the surface erosion rate of the debris is 0.206 + 0.013 / - 0.017 m Myr -1. Burial dating of the recycled paleo-surface debris suggests that the lower section of the ice core belongs to a separate, older ice mass which we estimate to be 4.3–5.1 Myr old. The ages of these two stacked, separate ice masses can be directly related to glacial advances of the Antarctic ice sheet and potentially coincide with two major global glaciations during the early and late Pliocene epoch when global temperatures and CO 2 were higher than present. These ancient ice masses represent new opportunities for gathering ancient climate information. [ABSTRACT FROM AUTHOR]

The large Bayanbaolege Ag polymetallic ore deposit is located in the Tuquan-Linxi Fe (Sn)-Cu-Pb-Zn-Ag-Nb (Ta) polymetallic metallogenic belt, which is an important part of the Great Xing'an Range metallogenic province, northeast China. The sulfide–quartz vein-type orebodies in the deposit are mainly hosted in the Cretaceous granodiorite porphyry and Late Permian Linxi formation. The U-Pb dating of the zircon from the post-ore diorite porphyrite yields an age of 124.8 ± 1.1 Ma, which constrains the mineralization time at the Early Cretaceous. The Sr-Nd isotope values (87Sr/86Sr)i = 0.708576~0.710536; εNd (t) = −0.51~+0.69; the Hf isotope values 176Hf/177Hf = 0.2827278~0.2830095, the εHf (t) = +3.1~+11.2, TDM2 = 615~1341 Ma of the metallogenic granodiorite porphyry. The Hf isotope values 176Hf/177Hf = 0.2828596~0.2829451, and the εHf (t) = +5.7~+8.8 of the diorite porphyrite, TDM2 = 827~1108 Ma, indicating that the ore-forming materials were the possible involvement of heterogeneous juvenile sources including moderately depleted mantle and newly underplated lower crust. The major and trace elements (including REEs) implied that these intrusions are the I-type granite and linked intimately to the westward subduction of the Paleo-Pacific Ocean plate. From these whole-rock major and trace elements and zircon U-Pb ages, as well as Sr-Nd-Hf isotope data, we conclude that the ore-associated I-type granites in the Bayanbaolege deposit formed in an extensional tectonic setting of the Early Cretaceous, and are compactly related to the retreat of the Paleo-Pacific Ocean subducted plate linked intimately to the westward subduction of the Paleo-Pacific Ocean plate rather than the closure of the Mongol–Okhotsk Ocean. Furthermore, by integrating geological background work and previous research work, implying the mineralization age of the Bayanbaolege deposit should have been formed in the 125–130 Ma. [ABSTRACT FROM AUTHOR]

The Qin-Hang Metallogenic Belt (QHMB), an important metallogenic belt in South China, hosts Cu and W–Sn polymetallic deposits. The Tongshanling ore field in the QHMB is characterized by the coexistence of Cu- and W-bearing polymetallic deposits, which are related to granodiorite and granite porphyry. This study examined whole-rock geochemistry, geochronology, and Sr–Nd–Hf isotopes to determine the genetic relationship between diverse ore-related granitoids (i.e., granodiorite and granite porphyry) and Cu–W metallogeny in the Tongshanling ore field. Zircon LA-ICP-MS U–Pb dating shows that the granodiorite and granite porphyry in the Tongshanling ore field were emplaced at 163.7 ± 0.4 Ma to 154.7 ± 0.6 Ma and 161.1 ± 0.3 Ma, respectively. Geochemically, the granodiorites are classified as oxidized I-type, while the highly evolved granite porphyry is reduced A-type. The Lu–Hf isotopic composition of the granodiorites is characterized by εHf(t) values ranging from –10.49 to –4.99 (average = –7.17), with corresponding TDMC ages ranging from 1524 to 1877 Ma (average = 1682 Ma). In contrast, the granite porphyry has higher εHf(t) values (–3.60 to –1.58, average = –2.78) and younger TDMC (1310–1438 Ma, average = 1387 Ma). The εNd(t) values of granodiorite are −8.06 to −7.37 and the two-stage model ages (TDM2) are 1543–1598 Ma, while the granite porphyry has higher εNd(t) values (−3.0 to −3.4) and younger TDM2 ages (1195–1223 Ma). The results show that the granodiorite and granite porphyry were formed from partial melting of different Mesoproterozoic basement rocks under varying degrees of crust–mantle interaction. Granite porphyry underwent well-recorded fractional crystallization. Compared to the Cu-forming granodiorite, the W-forming granite porphyry has a higher differentiation index, higher crystallization temperatures of zircon (average = 708 °C versus 631 °C), and lower oxygen fugacity (median ΔFMQ = –2.21 versus –1.77). [ABSTRACT FROM AUTHOR]

The East Kunlun Orogenic Belt is located in the western part of the Central Orogenic Belt of China, with a large number of Triassic igneous rocks parallel to the Paleo-Tethys ophiolite belt, which provides a large amount of geological information for the tectonic evolution of the Paleo-Tethys Ocean. The granitoids studied in this paper are located in the Ela Mountain area in the eastern part of the East Kunlun Orogenic Belt. Zircon U-Pb dating results show that these different types of granitoids were crystallized in the Triassic. The 247.5 Ma porphyritic granites from Zairiri (ZRR) displayed calc-alkaline I-type granite affinities, with the zircon εHf(t) values being mainly positive (−0.5 to + 3.8, TDM2 of 1309–1031 Ma), indicating that they are derived from the partial melting of the juvenile crust and mixed with ancient crustal components. The 236.8 Ma Henqionggou (HQG) granodiorites and 237.5 Ma Daheba (DHB) granodiorites are high-K calc-alkaline I-type granite, and both have mafic microgranular enclaves (MMEs), showing higher and more varied Mg# (39.73–62.73), combined with their negative Hf isotopes (εHf(t) = −2.6 to −1.6, TDM2 = 1430–1369 Ma), suggesting that their primary magmas were the products of partial melting of the Mesoproterozoic lower crust that mixed with mantle-derived rocks. The 236.4 Ma DHB porphyritic diorites showed characteristics of high-K calc-alkaline I-type granitoids, with moderate SiO2 contents, medium Mg# values (40.41–40.65), with the Hf isotopes (εHf(t) = −2.9 to −0.5; TDM2 = 1451–1298 Ma) indistinguishably relative to contemporaneous host granodiorites and MMEs. The petrographic and geochemical characteristics indicate that the porphyritic diorites are the product of well-mixed magma derived from the Mesoproterozoic lower crust and lithospheric mantle. Based on the results of this paper and previous data, the chronology framework of Late Permian–Triassic magmatic rocks in the eastern part of the East Kunlun Orogenic Belt was constructed, and the magmatic activities in this area were divided into three peak periods, with each peak representing an extensional event in a particular tectonic setting, for example, P1 (slab roll-back in subduction period; 254–246 Ma), P2 (slab break-off in transition period of subduction and collision; 244–232 Ma), P3 (delamination after collision; 230–218 Ma). [ABSTRACT FROM AUTHOR]

Granitoid gneisses dominated by tonalitic–trondhjemitic–granodioritic (TTG) compositions, with metamorphic supracrustal rocks consisting of sedimentary and volcanic rocks, are widely exposed in the Eastern Hebei terrane, North China Craton (NCC). This study presents systematic zircon U–Pb geochronological and whole-rock geochemical data of the Neoarchean granitoid gneisses and supracrustal rocks in Eastern Hebei. Zircon U–Pb isotopic dating for the representative samples reveals that magmatic precursors of granitoid gneisses were emplaced between 2524 ± 7 and 2503 ± 12 Ma, and the protoliths of the pelitic granulites were deposited in the Late Neoarchean era. Both of them have been subjected to granulite facies metamorphism during 2508 ± 10 to 2468 ± 33 Ma, coeval with the intrusion of syenogranitic pegmatite (2488 ± 5 Ma). Zircon ages of 2.45–2.01 Ga obtained from the analyzed samples were considered mixed data from 2.53–2.48 Ga and 1.9–1.8 Ga and were chronologically meaningless. Paleoproterozoic metamorphic zircon ages of 1.9–1.8 Ga were usually neglected because of hardly being obtained from TTG gneisses and supracrustal rocks. The tectonic regime during the Neoarchean era was considered to be dominated by vertical tectonism in the Eastern Hebei terrane. [ABSTRACT FROM AUTHOR]