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Carlin-type gold deposits are among the most important gold-bearing hydrothermal ore systems and are mainly located in Nevada, USA, and southwestern China. However, the source and evolution of the ore-forming fluids for these deposits remain controversial, especially those found within China. In this study, lithium and oxygen isotopic analyses of quartz-hosted fluid inclusions are used to elucidate the source and evolution of the giant Shuiyindong Carlin-type gold deposit. Fluid inclusions trapped in quartz of three distinct genetic stages have low salinity (0.8–6.3wt% NaCl equiv.) and moderate temperature (154–343 °C), but display variable Li and O isotope signatures. The Li and O isotopes of stage I fluids (δ7Li values from + 5.1 to + 9.1‰; δ18O values from + 6.3 to + 10.0‰) indicate predominantly a magmatic source for the initial ore-forming fluids. The large variations of Li and O isotopes of stage II fluids (δ7Li values from + 9.3 to + 16.0‰; δ18O values from + 0.1 to + 7.7‰) suggest that the fluids are controlled by mixing of magmatic fluids and meteoric water, which in turn triggered the precipitation of gold-bearing sulfides. The isotopic compositions of stage III fluids (δ7Li values from + 15.5 to + 22.8‰; δ18O values from − 5.4 to − 2.8‰) confirm that the final fluids are dominated by meteoric water. Furthermore, this work demonstrates that the combined Li–O isotopic analysis of fluid inclusions is a powerful tracer to decode the source and evolution of ore-forming fluids in hydrothermal mineralizing systems. [ABSTRACT FROM AUTHOR]

The formation of Carlin-type gold deposits is poorly constrained, mainly due to the lack of accurate ages for gold mineralization. The Youjiang basin, SW China, represents the world's second-largest Carlin-type gold province after NV, USA. In this paper, we use hydrothermal apatite U–Th–Pb dating to systemically determine the mineralization ages of five Carlin-type gold deposits, namely, Shuiyindong, Jinfeng, Zimudang, Linwang, and Jinya, in the Youjiang basin. The hydrothermal apatite is characterized by intimate intergrowth with gold-bearing sulfides, presence of primary fluid inclusions, irregular morphology and cathodoluminescence zoning, and MREE-enriched composition patterns, indicating that it is clearly associated and coeval with gold mineralization. The concentrations of lattice-bound U and Th in the apatite are highly variable, making it suitable for in situ secondary ion mass spectrometry (SIMS) U–Th–Pb dating. The dating results of hydrothermal apatite from the five deposits show that they formed at ca. 150–140 Ma, contemporary with the widespread felsic magmatism and associated W–Sn mineralization to the east of the Youjiang basin, probably in response to slab breakup of the Paleo-Pacific oceanic plate beneath the South China continental plate. Our case story suggests that hydrothermal apatite could be a robust chronometer for age dating of sedimentary rock-hosted gold mineralization worldwide. [ABSTRACT FROM AUTHOR]

Gold in Carlin-type gold ores is commonly hosted in the arsenian pyrite rim, but the formation of arsenian pyrite and its contribution to Au adsorption are poorly understood. Based on our previous NanoSIMS Au mapping, we conducted SEM and HR-TEM analyses to examine the Au deportment and nanoscale texture of individual auriferous arsenian pyrite grains from the giant Carlin-type Lannigou gold deposit, SW China. The results indicate that the arsenian pyrite rim is composed of numerous nanoparticulate pyrite grains (rather than a single crystal), and gold nanoparticles (Au0) occur mainly in sub-rim with the highest Au content, which are porous and have lower degrees of order. We propose that nanoparticulate arsenian pyrite attachment and aggregation is the main mechanism for the arsenian pyrite rim growth, and such mechanism is crucial for the Au efficient enrichment for this giant gold deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple (Fe, Mn) or coupled (Cu, Ag coupled with In, Sb, Ga, Ge, Sn) substitution for Zn was observed in sphalerite. • The Zhaxikang is a magmatism-related medium to low-temperature hydrothermal vein deposit. • The sulfur in the Zhaxikang deposit is predominantly sourced from Jurassic marine sulfate or evaporite rocks. • The metals for the Zhaxikang deposit primarily originated from the basement metamorphic rocks (gneiss) of the Greater Himalayan Crystalline complex. The metallogenesis of collisional orogen has been a significant research topic for comprehending the linkage between magmatism, metamorphism, hydrothermalism and ore deposition. In Southern Tibet, the Zhaxikang deposit is a super-large Pb-Zn-Sb-Ag polymetallic deposit with metal reserves of 2.367 Mt Zn + Pb (average grade of 6.43 %), 0.2552 Mt Sb (average grade of 1.14 %), and 2960.6 t Ag (average grade of 101.64 g/t), constituting the largest deposit within North Himalayan Metallogenic Belt. However, the metal sources of the ore-forming material and mineralization process in this deposit remain a subject of controversy due to previous studies primarily relying on a bulk analysis of sulfides, which record the mixed results of multistage mineralization and intergrown minerals of different stages. The objective of this study is to constrain the sources and mineralization process of the Zhaxikang deposit through in-situ analyses of trace elements and sulfur isotopes in sphalerite. Based on ore textures and mineral paragenesis, four mineralization stages and three generations of sphalerite deposited respectively in stage 1 (Sp1), stage 2 (Sp2), and stage 4 (Sp3), were identified. The Pb and Zn mineralization mainly occurred in stage 2, while Sb and Ag were dominantly in stage 4. The trace elements characteristics (Cd, Fe, In, Ga, Ag, Cu, Co, and Mn) observed in sphalerite indicate that the Zhaxikang deposit could be a hydrothermal vein-type deposit associated with magmatism. The δ34S values of sulfides (7.7–18.4 ‰) in the deposit generally exhibit a slight elevation compared to those (4.1–12.9 ‰) of the Jurassic Ridang Formation slate, indicating that the sulfur of the deposit primarily originated from seawater sulfate in the slate through thermochemical sulfate reduction, although a small amount of contribution from mafic rocks also existed in stage 4. The Pb isotopes in stage 2 range from 19.662 to 19.705, 15.852 to 15.865, and 40.214 to 40.283 for the ratios of 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb, respectively, indicating that the metals primarily from the Greater Himalayan Crystalline complex (GHC) with a minor contribution from host rocks. While, the Pb isotopes in stage 4 range from 19.687 to 19.849 for 206Pb/204Pb, from 15.86022 to 15.885 for 207Pb/204Pb, and from 40.261 to 40.414 for 208Pb/204Pb, respectively, indicating that the metals originated from sulfides in the earlier stage as well as the more radiogenic GHC. [ABSTRACT FROM AUTHOR]

The reduced nature of the subducting slab has been used to explain the relatively poor endowment of economic porphyry copper deposits in Paleo-Tethyan arc systems. The presence of numerous porphyry Cu deposits in the southern Yidun terrane potentially challenges this model, because these deposits are thought to be the product of Paleo-Tethyan subduction. To investigate this, two representative deposits (i.e., Pulang and Songnuo porphyry Cu deposits) from the southern Yidun terrane have been studied. Zircon U-Pb ages of pre- and syn-mineral porphyries in Pulang are 221 ± 2 Ma (MSWD = 0.89) and 215 ± 2 Ma (MSWD = 1.50), respectively. Zircon and garnet U-Pb ages of the Songnuo syn-mineral porphyry are 217 ± 2 Ma (MSWD = 1.15) and 223 ± 5 Ma (MSWD = 0.97), respectively. The Pulang and Songnuo porphyries both have high whole-rock Sr/Y ratios with minor or no negative Eu anomalies, consistent with derivation from hydrous magmas that underwent minor early plagioclase crystallization but abundant amphibole fractionation. The two porphyry intrusions are characterized by high large-ion-lithophile elements (LILE: Th, U, Ba, Rb) abundances, and low concentrations of high-field-strength elements (HFSE: Nb, Ta, Ti, Zr, Hf). They have similar initial Sr isotope ratios from 0.7055 to 0.7073, ƐNd (t) values from − 4.3 to − 1.6 and zircon ƐHf (t) values of − 1.81 ± 1.34 (n = 47) that are distinct from published results for the Permian–Early Triassic Paleo-Tethyan arc granitoids in the Sanjiang region but similar to the Neoproterozoic arc intrusions in the nearby western Yangtze craton. The Pulang and Songnuo porphyries have relatively high zircon EuN/EuN* ratios (0.59 ± 0.04, n = 52) and calculated Δ log fO2 (FMQ) values (1.61 ± 0.23, n = 52), consistent with relatively oxidized magmas. This feature is similar to the published data for the Neoproterozoic arc intrusions (EuN/EuN* = 0.55 ± 0.08; Δ log fO2 (FMQ) = 2.14 ± 0.60), but distinct from the published data for the reduced normal Paleo-Tethyan arc magmas (EuN/EuN* = 0.29 ± 0.10; Δ log fO2 (FMQ) = − 0.68 ± 0.88). Given that the most recent tectonic reconstruction models suggest that the Paleo-Tethys Ocean closed before ~ 220 Ma, we propose that the Pulang and Songnuo porphyries Cu deposits were formed in a postsubduction setting from oxidized melts generated by reactivating the Neoproterozoic arc root, unrelated to Paleo-Tethyan subduction. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Jinding deposit contains high content of associated critical metal Cd, Tl, Ag. • The enrichment of Fe assists incorporation of components Ge + Mn + Pb + As + Tl. • The enrichment of Cd assists incorporation of components Cu + Ag + Sb. • Cd and Fe zonation at sphalerite indicate a potential exploration deposit. The Jinding deposit is well-known to contain high concentrations of metals Zn, Pb, Cd, Tl, Ag, etc. in the world. The associated critical metals and their substitution mechanisms were wildly concerned. This study investigated and compared sphalerites using a combination of textural, trace element, and sulfur isotopic analyses to give insights into element substitution mechanisms and possible sources of ore-forming fluids and to constrain processes involved in ore genesis of the world-class Jinding sediment-hosted Zn-Pb deposit. LA-ICP-MS analyses reveal chemical zoning in the sphalerites together with the coupling of two main groups of trace elements substitution mechanisms: one is Fe + Ge + Mn + Pb + As + Tl and vacancies to substitute Zn, and the other is Cd + Cu + Ag + Sb to substitute Zn. The incorporation of trace elements is facilitated by the replacement of Zn by Cd and Fe. These two group elements have distinct color oscillatory zonation and are intertwined in the trace element LA-ICP-MS element maps. The sulfur isotopic values show high isotope fractionation in the sphalerite from −28.4 to −0.5 ‰, suggesting a bacteriogenic sulfur origin at Jinding. Sphalerite sample has observed that sulfur isotope is correlated with Fe concentration and anti-correlated with Cd concentration. These variations in isotope fractionation and trace element disequilibrium partitioning were interpreted as the effects of temperature and pH with less influence from sulfur activity. These variability zones of sphalerite alternately enriched in Cd- and Fe-related elements suggested that ore fluids may flow from metal-fertile sedimentary/basement sequences during their ascent, and colloform sphalerite was likely formed by a high degree of supercooling, over-saturation, and rapid mixing between bacteriogenic sulfur and metal-rich in spaces of collapse dome. Based on our observations, we suggested that these variability zones of layered sphalerite alternately enriched in Cd and Fe would likely provide useful insight for a potential economic Zn-Pb and associated critical metals mineral exploration deposit. [ABSTRACT FROM AUTHOR]

It has been well established that metal and sulfur sources in mineral deposits can be very difficult to identify, especially for ore deposits hosted in sedimentary rocks. Using the world's largest Sb deposit at Xikuangshan in southern China as a case study, this study combined Hg isotopes and in situ sulfur isotope measurements to constrain the sources of Sb and sulfur. A variation of 1.1‰ in δ202Hg (0.04 to 1.15‰) was observed in stibnite ore samples, suggesting that mass-dependent fractionation of Hg isotopes occurred during the formation of the deposit. Significant mass-independent fractionation of Hg isotopes, with △199Hg ranging from − 0.03 to − 0.17‰, was also observed in the ore samples, suggesting that Hg transported by the ore fluids was inherited from Proterozoic basement metamorphic rocks as these rocks show similar △199Hg signatures (− 0.03 to 0.07‰). In situ sulfur isotope measurements yielded δ34S values that cluster in the range of + 6.8 to + 10.2‰, providing evidence that sulfur contained in ore fluids may also have been dominantly derived from underlying Proterozoic basement metamorphic rocks (δ34S = +5.6 to + 11.5‰). Using the new results from Hg and S isotopes, we proposed that deep-circulated meteoric water mobilized Sb, Hg, and S from the Proterozoic metamorphic basement, ascended along deep faults, and subsequently deposited Sb at favorable structural zones as a result of boiling of the hydrothermal fluids, generating the world-class Xikuangshan Sb deposit. This study also highlights the combined use of Hg-S isotopes as a novel method to provide new and additional insights into the source regions of ore materials for sedimentary-hosted Sb deposits. [ABSTRACT FROM AUTHOR]

The Xikuangshan Sb deposit in central Hunan, South China is the largest Sb deposit in the world, which has supplied more than 50% of the world's Sb and with total Sb metal reserves of about 2.5 Mt. However, the age of this deposit is still not well constrained due to a lack of suitable minerals for reliable radiometric dating, which hampered the generation of a generally accepted genetic model of mineralization. Since the fluid-inclusion data suggest that the temperature of ore-forming fluids in the Xikuangshan deposit is up to 360 °C, zircon (U-Th)/He thermochronometry with the closure temperature of 160–200 °C was chosen here to elucidate the age of Sb mineralization. Detrital zircons in the altered host rocks from the Xikuangshan deposit yielded two (U-Th)/He age populations of 156–117 and 97–86 Ma. The older age population (156–117 Ma), which is well in accordance with previous Sm-Nd dating on hydrothermal calcite (156–124 Ma), probably represents the timing of main-stage Sb mineralization in the Xikuangshan Sb deposit, while the younger zircon (U-Th)/He ages may result from partial loss of He in zircon caused by the distal effect of deep-seated intrusions beneath the deposit. This study demonstrates that the (U-Th)/He dating of zircon in altered host rocks can be viable for constraining the timing of low-temperature mineralization. [ABSTRACT FROM AUTHOR]

The Huichizi granite complex is the largest Paleozoic I-type intrusion located in the North Qinling orogenic belt (NQB). In this study, we present systematic geochemical element data, zircon U-Pb ages, Lu-Hf isotopic data, and Sr-Nd isotopic data for the Huichizi granites. In terms of mineral and chemical compositions, these granites are biotite monzonitic and alkali-feldspar granites, both of which are characterized by high TiO2 and total alkali contents and low MgO, TiO2, and TFeO contents. These granites are weakly peraluminous (A/CNK values are 1-1.06 for biotite monzonitic granites and 1.04-1.09 for alkali-feldspar granites) and possess the geochemical characteristics of adakitic rocks, e.g., high Sr contents (319 ppm-633 ppm), Sr/Y ratios (18.5-174), and (La/Yb)N ratios (17.6-57) and low MgO (0.04 wt.%-0.83 wt.%), Y (3.0 ppm-17.2 ppm), and heavy rare-earth element (HREE) contents. This indicates that these rocks were most likely derived from the partial melting of a thickened lower crust. In situ zircon U-Pb dating of these granites yields Early Caledonian ages (437 Ma for biotite monzonitic granites and 424 Ma for alkali-feldspar granites), indicating that the Huichizi granitic complex is the product of multi-periodic magmatism. The positive but varying zircon εHf(t) values (+0.6 to +8.5) suggest that this thickened lower crust was mainly juvenile, i.e., accreted from depleted mantle during the Neo-Mesoproterozoic Period, but involved the ancient recycled crust. Biotite monzonitic granites formed during crust thickening at the extrusion stage, whereas the alkali granites formed during crust thickening at the extension stage (post extrusion). The Huichizi granite complex witnessed the process of extrusion to extension because of the collision between the NCB and the Qinling microcontinent in the Caledonian. [ABSTRACT FROM AUTHOR]

Sulfur isotope signatures of Au-bearing pyrite from Lannigou Au deposit, a typical Carlin-type Au deposit in SW China, provide valuable information about the origin of the ore-forming minerals. Analysis by NanoSIMS was used to determine S isotope compositions of Au-bearing pyrite and to map the grain-scale distributions of Au, Cu, As and S in pyrite from the deposit. Based on different textural pattern of pyrites revealed by back-scattered electron (BSE) images, they are divided into three types: Py-1 diagenetic pyrite without core-rim structure, Py-2 pyrite with an Au-free core and a rhythmically-zoned Au-bearing rim, Py-3 Au-bearing pyrite with rhythmic zoning across the entire grain. The element distributions and S isotope compositions of four paragenetic stages are recognized on the basis of textural observation. Py-1 grains and the Au-free homogeneous cores of zoned crystals were formed in Stage 1 while the Au-bearing rims of the zoned crystals with rhythmic zonation of As and Cu, and to a lesser degree Au, were formed in two superimposed stages: stage 2 formed the inner zone that is enriched in As alone; and stage 3 formed the outer zone that is enriched in both Au and As. Other sulfides such as realgar, cinnabar and stibnite are formed in the last stage. The relationship between Au and As distributions in pyrite rim is complicated, changing from coupled to decoupled at the nanoscale. Such complexity is interpreted to reflect fluctuation of fluid composition and temperature with time, which in turn affect the modes of occurrence of As and Au. It is inferred that As mainly occurs in the crystal lattice replacing S whereas Au is mainly present as nanoparticles that were trapped in pyrite during crystal growth. The Au-bearing rims of the zoned pyrite crystals are characterized by highly variable δ 34 S values from 1.1 to 18.1‰, which exceed the values of the Triassic calcareous host rocks (10–14‰). In contrast, the δ 34 S values of the Au-free cores of zoned pyrite crystals vary over a narrower interval and are mainly between 6 and 12‰, close to the values of pyrite crystals in the sedimentary country rocks. Our new analyses also reveals that the δ 34 S values of the Au-bearing fluids generally increase during the formation of the deposit. The observed S isotope variations are consistent with mixing between a magmatic-related fluid with mantle-like δ 34 S value (∼0‰) and a sedimentary or deep basin brine fluid with elevated δ 34 S value (>18‰), with an increasing contribution from the latter with time. The notably varied values of δ 34 S and the disseminations of Au and other trace elements such as As and Cu in pyrite crystals indicate that the process responsible for Au precipitation in this deposit occurred in an open hydrothermal system. [ABSTRACT FROM AUTHOR]

The contiguous region between Guangxi, Guizhou, and Yunnan, commonly referred to as the Golden Triangle region in SW China, hosts many Carlin-type gold deposits. Previously, the ages of the gold mineralization in this region have not been well constrained due to the lack of suitable minerals for radiometric dating. This paper reports the first SIMS U-Pb age of hydrothermal rutile crystals for the Zhesang Carlin-type gold deposit in the region. The hydrothermal U-bearing rutile associated with gold-bearing sulfides in the deposit yields an U-Pb age of 213.6 ± 5.4 Ma, which is within the range of the previously reported arsenopyrite Re-Os isochron ages (204 ± 19 to 235 ± 33 Ma) for three other Carlin-type gold deposits in the region. Our new and more precise rutile U-Pb age confirms that the gold mineralization was contemporaneous with the Triassic W-Sn mineralization and associated granitic magmatism in the surrounding regions. Based on the temporal correlation, we postulate that coeval granitic plutons may be present at greater depths in the Golden Triangle region and that the formation of the Carlin-type gold deposits is probably linked to the coeval granitic magmatism in the region. This study clearly demonstrates that in situ rutile U-Pb dating is a robust tool for the geochronogical study of hydrothermal deposits that contain hydrothermal rutile. [ABSTRACT FROM AUTHOR]

The South China Craton was formed by amalgamation of the Yangtze and Cathaysia Blocks during the Neoproterozoic. During the Mesozoic, voluminous granitic plutons and associated W-Sn polymetallic deposits were formed in the Cathaysia Block. The giant South China low-temperature metallogenic domain (LTMD) includes an area of ∼500,000 km 2 in the Yangtze Block and is composed of the Chuan-Dian-Qian Pb-Zn, Youjiang Au-As-Sb-Hg and Xiangzhong Sb-Au metallogenic provinces. The Chuan-Dian-Qian Pb-Zn province contains numerous MVT Pb-Zn deposits, whereas the other two provinces are characterized by Carlin-type Au deposits and vein-type Sb, Hg and As deposits. These epigenetic deposits, which formed under low temperature conditions (∼100–250 °C), are typically hosted in sedimentary rocks and are locally controlled by faults and fractures. The deposits formed dominantly at 200–230 Ma and 130–160 Ma, corresponding to Indosinian (Triassic) and Yanshanian (Jurassic to Cretaceous) orogenies, respectively. Indosinian mineralization is recognized in all three provinces, but Yanshanian mineralization occurred only in the Youjiang and Xiangzhong provinces. The Indosinian orogeny, which involved collision of the Indochina Block with the South China Craton, resulted in circulation of basinal brines that leached ore-forming elements from adjacent sedimentary strata to form the Chuan-Dian-Qian Pb-Zn province. Deep-seated granitic magmas generated during this orogeny caused extensive circulation of meteoric water that mobilized ore-forming elements from the sedimentary strata to form the Carlin-type Au deposits in the Youjiang province, and the Sb-Au deposits in the Xiangzhong province. The Indosinian orogeny was the key factor in establishing the metallogenic framework of the LTMD. It produced widespread mineralization in the three metallogenic provinces, each of which has unique features reflecting differences in the nature and composition of the basement rocks. The Yanshanian metallogeny was less important and overprinted the older ore deposits in the Youjiang and Xiangzhong provinces. [ABSTRACT FROM AUTHOR]

Magnetite is a very common mineral in various types of iron deposits and some sulfide deposits. Recent studies have focused on the use of trace elements in magnetite to discriminate ore types or trace ore-forming process. Germanium is a disperse element in the crust, but sometimes is not rare in magnetite. Germanium in magnetite can be determined by laser ablation ICP-MS due to its low detection limit (0.0X ppm). In this study, we summary the Ge data of magnetite from magmatic deposits, iron formations, skarn deposits, iron oxide copper-gold deposits, and igneous derived hydrothermal deposits. Magnetite from iron formations contains relatively high Ge (up to ∼250 ppm), whereas those from all other deposits mostly contains Ge less than 10 ppm, indicating that iron formations can be discriminated from other Fe deposits by Ge contents. Germanium in magmatic/hydrothermal magnetite is controlled by a few factors. Primary magma/fluid composition may be the major control of Ge in magnetite. Higher oxygen fugacity may be beneficial to Ge partition into magnetite. Sulfur fugacity and temperature may have little effect on Ge in magnetite. The enrichment mechanism of Ge in magnetite from iron formations remains unknown due to the complex ore genesis. Germanium along with other elements (Mn, Ni, Ga) and element ratios (Ge/Ga and Ge/Si raios) can distinguish different types of deposits, indicating that Ge can be used as a discriminate factor like Ti and V. Because of the availability of in situ analytical technique like laser ablation ICP-MS, in situ Ge/Si ratio of magnetite can serve as a geochemical tracer and may provide new constraints on the genesis of banded iron formations. [ABSTRACT FROM AUTHOR]

A study using whole-rock major-trace elements and Sr–Nd isotopes as well as zircon U–Pb dating has been carried out on Early Cretaceous mafic–ultramafic intrusions from the Gan–Hang tectonic belt (GHTB), South China, to understand the origin of mantle sources and the sequential evolution of the underlying Late Mesozoic lithospheric mantle of this area. The study focused on two intrusions, one at Quzhou and the other at Longyou (see Fig. 1 ). They are primarily composed of mafic–ultramafic rocks with wide range of chemical compositions. The Quzhou mafic rocks have relatively narrow ranges of SiO 2 (48.94–51.79 wt%), MgO (6.07–7.21 wt%), Fe 2 O 3 (10.48–11.56 wt%), CaO (8.20–8.81 wt%), and Mg # (51.7–56.5) with relatively low K 2 O (0.56–0.67 wt%) and Na 2 O (3.09–3.42 wt%). By contrast, the ultramafic rocks from Longyou have distinct lower SiO 2 (41.50–45.11 wt%) and higher MgO (9.05–9.90 wt%), Fe 2 O 3 (12.14–12.62 wt%), CaO (8.64–10.67 wt%), and Mg # (59.5–61.1) with relatively higher K 2 O (1.32–1.75 wt%) and Na 2 O (4.53–5.08 wt%). They are characterized by Ocean Island Basalts (OIB)-type trace element distribution patterns, with a significant enrichment of light rare earth elements (LREE), large ion lithophile elements (LILE, i.e., Rb, Ba, K, and Sr) and high field strength elements (HFSE, i.e., Nb, Ta), and slight depletion of Th, U, Ti, and Y. The intrusions exhibit relatively depleted Sr–Nd isotope compositions, with ( 87 Sr/ 86 Sr) i range of 0.7035 to 0.7055 ( 143 Nd/ 144 Nd) i of 0.51264 to 0.51281 and ε Nd ( t ) values of + 3.0 to + 6.6. Zircon U–Pb dating of Longyou and Quzhou intrusions yields consistent magma emplacement ages of 129.0 ± 3.9 to 126.2 ± 2.4 Ma, respectively. The dating results are consistent with the peak of extension in Early Cretacerous throughout the Gan–Hang tectonic belt. Their magmas were principally derived from near-solidus partial melting of pyroxenites with different content of silica, and the pyroxenites were resulted from a juvenile SCLM peridotite metasomatized by adakitic and felsic melts under a subducted oceanic crust-lithospheric mantle in Neoproterozoic. During the subduction of the oceanic crust, the juvenile SCLM can be sandwiched by the ancient SCLM above and the pyroxenites below and stored for hundreds of millions of years until Late Mesozoic. Then partial melting of the pyroxenites was triggered during the peak of extension in response to the tectonic reactivation of the GHTB in Early Cretaceous. It is clear that fault reactivation and structural constraints within the GHTB had played an important role in its magmatic evolution. [ABSTRACT FROM AUTHOR]

The Paleo-Tethyan arc belt is host to a small number of porphyry Cu deposits the key controls on which remains poorly understood. It has been hypothesized that the Paleo-Tethyan arc magmas were reduced and therefore less fertile for porphyry Cu formation but few studies have been conducted to directly assess the magmatic oxygen fugacity. We investigate the magma fertility of eastern Paleo-Tethyan arc igneous rocks in the Sanjiang region, SW China, represented by the Maoding (268.3 ± 2.3 Ma), Suwalong (275.6 ± 1.4 Ma to 264.7 ± 1.4 Ma) and Baimaxueshan (255.7 ± 1.5 Ma to 249.3 ± 1.1 Ma) granitoids. They have geochemical features consistent with typical continental arc rocks, formed from partial melting of the mantle wedge, with increasing contamination of crust-derived melts over time. The presence of amphibole, high Sr/Y ratios (35 ± 20, n = 17), and lack of negative Eu anomalies (Eu N /Eu N ⁎ = 1.04 ± 0.3, n = 17) are consistent with derivation from hydrous magmas. Zircons from the intrusive rocks have relatively low Eu N /Eu N ⁎ (mostly <0.4) ratios and calculated ΔFMQ values (−2.1 ± 1.2, n = 86). Combined with apatite microphenocrysts with extremely low sulfur contents (< 0.12 wt% SO 3), it suggests that the intrusions originated from water-rich but reduced arc magmas, that were less fertile for porphyry Cu formation. Our study highlights that magmatic f O 2 is probably a critical control on the prospectivity of arc systems and confirms that zircon and apatite compositions can be used to evaluate porphyry Cu fertility. • The Paleo-Tethyan arc igneous rocks were dated from ~275 to 249 Ma. • They were derived from partial melting of mantle wedge during MASH processes. • These arc magmas were reduced and less fertile for porphyry Cu formation. • Zircon and apatite compositions can be used to evaluate porphyry Cu fertility. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyrite of Carlin-type Au deposits in the Youjiang Basin were analyzed by Nano-SIMS. • The δ34S values Au-bearing pyrite of Linwang vary inversely with Au concentrations. • Initial auriferous fluids of Linwang were sourced from magmatic-hydrothermal systems. • Reduced sulfur in ore-forming fluids of Badu was dominated by sedimentary sulfur. • Sedimentary sulfur contamination result in variable δ34S values of Au-bearing pyrite. The Youjiang Basin in Southwest China is the world's second largest Carlin-type gold (Au)-producing region. However, the source of reduced sulfur that accounts for Au transport in ore-forming fluids remains controversial. Finely characterizing the sulfur isotopic compositions (δ34S values) in micron-scale zonation of Au-bearing pyrite is the key to clearly identify sulfur source. Here, we used high-resolution nanoscale secondary ion mass spectrometry (Nano-SIMS) to characterize the temporal variation in δ34S values and its relationship with metal contents across Au-bearing pyrite from the Linwang and Badu deposits in the Youjiang Basin, with the aim of monitoring the source and evolution of reduced sulfur in auriferous fluids. The Au-bearing pyrite rims in the Linwang deposit contain three growth stages that record episodic injections of Au- and As-rich fluids. Within these rims, the δ34S values vary inversely with Au concentrations. The inner rims with the high Au contents have δ34S values of −1.7‰ to +3.3‰ that are comparable to those of magmatic sulfur. The outer rims with decreasing Au contents have δ34S values of +1.3‰ to +15.7‰ that gradually approach those of pre-ore pyrite in the host rock. Such a variation indicates that the reduced sulfur in the initial Au-bearing ore-forming fluids was primarily originated from deep magmatic-hydrothermal systems while the host rock-derived 34S-enriched sulfur increasingly dominated through fluid-rock interactions during mineralization. In contrast, Au-bearing pyrite from the Badu deposit has positive δ34S values ranging from +9.0‰ to +25.8‰, which overlap those of diagenetic pyrite in the Devonian sedimentary rocks. Combining the intimate spatial association between Au mineralization and the Devonian strata, we propose that the initial ore-forming fluids have leached substantial sulfur from the Devonian strata. Significant contaminations of sedimentary sulfur erased the primary sulfur isotopic signals of the initial auriferous fluids. Our interpretations of these two deposits may also apply to other Carlin-type Au deposits in the Youjiang Basin, where δ34S values of Au-bearing pyrite show host rock-dependent variations. This study demonstrates that high-resolution Nano-SIMS sulfur isotope and elemental analysis of Au-bearing pyrite is a potent tool for tracing the source and evolution of reduced sulfur in ore-forming fluids for sedimentary-host Au deposits worldwide. [ABSTRACT FROM AUTHOR]

The Lanping basin, Yunnan province, SW China, is located at the juncture of the Eurasian and Indian Plates in the eastern part of the Tibetan Plateau. The Lanping basin, in the Sanjiang Tethyan metallogenic province, is a significant Cu-Ag-Zn-Pb mineralized belt in China that includes the largest sandstone-hosted Zn-Pb deposit in the world, the Jinding deposit, as well as several Ag-Cu deposits (the Baiyangping and Jinman deposits). These deposits, with total reserves of over 16.0 Mt Pb + Zn, 0.6 Mt Cu, and 7,000 t Ag, are mainly hosted in Meso-Cenozoic clastic rocks and are dominantly controlled by two Cenozoic thrust systems developed in the western and eastern segments of the basin. The Baiyangping, Babaoshan, and Hetaoqing ore deposits are representative of the epithermal base metal deposits in the Lanping basin. The microthermometric data show that the ore-forming fluids for these deposits were low temperature (110-180 °C) and had bimodal distribution of salinity at moderate and mid to high salinities (approximately 2-8 wt.% and 18-26 wt.% NaCl equivalent). The C and O isotope data indicate that the ore-forming fluids were related to hot basin brines. We present new He and Ar isotope data on volatiles released from fluid inclusions contained in sulfides and in barite in these three deposits. 3He/4He ratios of the ore-forming fluids are 0.01 to 0.14 R/Ra with a mean of 0.07 Ra (where R is the 3He/4He ratio and Ra is the ratio for atmospheric helium). This mean value is intermediate to typical 3He/4He ratios for the crust (R/Ra = 0.01 to 0.05) and the ratio for air-saturated water (R/Ra = 1). The mean ratio is also significantly lower than the ratios found for mantle-derived fluids (R/Ra = 6 to 9). The 40Ar/36Ar ratios of the ore-forming fluids range from 298 to 382 with a mean of 323. This value is slightly higher than that for the air-saturated water (295.5). The 3He/4He ratios of fluids from the fluid inclusions imply that the ore-forming fluid for the Baiyangping, Babaoshan, and Hetaoqing deposits was derived from the crust and that any mantle-derived He was negligible. The content of the radiogenic Ar ranges between 0.2 to 20.4%, and the proportion of air-derived 40Ar averages 94.1%. This indicates that atmospheric Ar was important in the formation of these deposits but that some radiogenic 40Ar was derived from crustal rocks. Based on these observations coupled with other geochemical evidence, we suggest that the ore-forming fluids responsible for the formation of the Ag-Cu-Pb-Zn polymetallic ore deposits in the Baiyangping area of the Lanping basin were mainly derived from crustal fluids. The fluids may have mixed with some amount of air-saturated water, but there was no significant involvement of mantle-derived fluids. [ABSTRACT FROM AUTHOR]

Miaoershan (MES) uranium ore field is one of the most important uranium sources in China, hosts the largest Chanziping carbonaceous-siliceous-pelitic rock type uranium deposit in South China together with many other granite-hosted uranium deposits. The Shazijiang (SZJ) uranium deposit is one of the representative granite-hosted uranium deposits in the MES uranium ore field, situated in the Ziyuan, Guangxi Province, South China. Uranium mineralization in the SZJ deposit mainly occurs as uraninite with quartz and calcite veins that is spatially associated with mafic dykes in the region. The hydrothermal alteration includes silicification, carbonation and hematitization. New uraninite chemical U-Pb geochronology and petrographic evidences provide the timing constraints and new insights into the formation of the SZJ uranium deposit. The results show that the first stage of uranium mineralization formed at 97.5±4.0 Ma, whereas another stage of uranium mineralization occurred at 70.2±1.6 Ma. Two stages of uranium mineralization are fairly consistent with two episodic crustal extensions that occurred at ~100 and ~70 Ma throughout South China. This study indicates that there are two uranium mineralization events in SZJ uranium ore field controlled by mafic dyke, supporting that mafic dykes play an important topochemical role in uranium concentration and/or mobilization. Therefore, geochemical U-Pb age firstly reinforces that ore-forming age of the SZJ uranium deposit mainly yields at 97.5±4.0 and 70.2±1.6 Ma. Additionally, geochemical age method is particularly useful for interest samples which record information on multi-stage uranium mineralizations in South China. [ABSTRACT FROM AUTHOR]

Triassic granites crop out extensively in central Hunan Province, South China. Representative granites include the Baimashan, Weishan, and Ziyunshan plutons. Lithologically, these granites mainly comprise biotite monzogranite, two-mica granites, hornblende-biotite granite, hornblende-biotite monzogranite, and garnet-muscovite granite. These granites havein situzircon secondary ion mass spectrum U–Pb ages between 223.2 ± 3.3 and 209.3 ± 4.0 Ma, indicating that they likely formed predominantly in the Late Triassic. These granitic plutons have similar zircon Hf and O isotopic compositions, withεHf(t) values of −0.8 to −9.0, two-stage depleted mantle model ages (TDM2) of 1.81–1.31 Ga, and weighted mean ofδ18OZrcvalues of 8.53 ± 0.58‰ to 9.12 ± 0.28‰. Combined with U–Pb dating and Hf isotopic data, the elevated and variableδ18O andεHf(t) values of the individual granites indicate that these Triassic granites were likely produced by partial melting of upper Paleoproterozoic to lower Mesoproterozoic metasedimentary rocks and are S-type granites. The variable proportions of inherited zircons in certain samples with U–Pb ages of 627–992 Ma indicate the involvement of lower–middle Neoproterozoic crustal materials during magma crystallization through wall-rock contamination, which resulted in the wide range of isotopic compositions. Underplating of mantle-derived magma may have provided the thermal energy for partial melting of the upper Paleoproterozoic and lower Mesoproterozoic basements, thereby generating these late Triassic granites. The lack of positiveεHf(t) values and highδ18OZrcvalues indicate that the contribution of mantle-derived magmas to these granites may be insignificant. [ABSTRACT FROM AUTHOR]

[Display omitted] • The differences in mineral composition were related to temperature, alteration and hydrothermal fluid. • Ag ranges n*103 ∼ n*104 ppm in galena, n*10 ~ n*103 ppm in sphalerite and pyrite. Sphalerite has higher Au and Ag. • Silver occurs as a solid solution in samples with massive textures and as micro-inclusions in alteration samples. • The minor and trace elements are typical characteristics of massive sulfide deposits in the LSKD. Sphalerite, pyrite and galena are common sulfide minerals in Zn–Pb–(Ag) deposits, containing minor and trace elements that can be used to constrain the ore-forming processes. The Lengshuikeng Ag–Pb–Zn deposit (LSKD) is one of the largest silver deposits in China. The mode of silver occurrence in sulfides remains unclear except for individual silver minerals. In this study, we analyzed the minor and trace element contents of sulfide minerals from massive, vein, and veinlet-disseminated ores by in-situ laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS). The elemental compositions of sulfide minerals are variable. Combining petrographic observations and previous studies, we suggest that the sulfide minerals from two types of mineralization (porphyry and strata-bound types) were formed in a same hydrothermal system, and their content of minor and trace elements mainly is influenced by temperature, alteration of wall rocks and composition change of hydrothermal fluid. The Ag content in galena ranges n*103 ∼ n*104 ppm, whereas that in both sphalerite and pyrite ranges from n*10 ∼ n*103 ppm. Except for galena, a higher content of gold (mean = 0.76 ppm) and silver (mean = 151 ppm) occurs in sphalerite compared with the content of gold (mean = 0.26 ppm) and silver (mean = 69.9 ppm) in pyrite. Generally, altered samples display higher Ag and Au contents in pyrite and sphalerite. Silver occurs in the form of a solid solution in sulfides from samples with massive textures, and as micro-inclusions in sulfides from altered samples. The contents of minor and trace elements (e.g. Cd and In) and their ratios (Ga/In, Zn/Cd and Cd/Fe) are not always sensitive to the temperature and processes of deposit formation. We suggest that sulfides from samples with massive texture and limited alteration are suitable for determining the genetic type of the deposit. Our results show that the hydrothermal fluid is a magmatic fluid related to porphyry granite in the LSKD. [ABSTRACT FROM AUTHOR]

Highlights: [•] New geochronology data to constrain the duration of magmatic-hydrothermal activity. [•] Two stages cooling history, early rapid cooling and late slow cooling. [•] Hydrothermal fluid circulation related to multiple stages of magma emplacement. [ABSTRACT FROM AUTHOR]

Post-orogenic mafic rocks from Northeast China consist of swarms of dolerite dikes. We report a new U–Pb zircon age, as well as whole-rock geochemical and Sr–Nd–Hf isotopic data. Laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) U–Pb zircon analysis yielded an age of 210.3 ± 1.5 million years (i.e. Triassic) for these mafic dikes. Most Dalian mafic rocks exhibit low K2O + Na2O contents, and span the border between alkaline and calc-alkaline rock associations in the total alkali–silica diagram. The investigated dikes are also characterized by relatively high (87Sr/86Sr)i ratios (0.7061–0.7067) and negative ϵNd (t) (−4.7 to −4.3) and ϵHf (t) values (−4.1 to −1.1), implying that they were derived from an enriched lithospheric mantle source. The mafic dikes are characterized by relatively low MgO (4.65–5.44 wt.%), Mg# (41–44), and compatible element content [such as Cr (89.9–125 ppm) and Ni (56.7–72.2 ppm)], which are the features of an evolved mafic magma. No evidence supports the idea that the mafic rocks were affected by significant assimilation or crustal contamination during emplacement. We conclude that the dolerites formed in a post-orogenic extensional setting, related to lithospheric delamination or ‘collapse’ of the Central Asian Orogenic Belt (CAOB), also termed the Xingmeng Orogenic Belt in China. [ABSTRACT FROM AUTHOR]

Post-orogenic mafic dikes are widespread across eastern Shandong Province, North China Craton, eastern China. We here report new U–Pb zircon ages and bulk-rock geochemical and Sr–Nd–Pb isotopic data for representative samples of these rocks. LA-ICP-MS U–Pb zircon analysis of two mafic dike samples yields consistent ages of 118.7 ± 0.25 million years and 122.4 ± 0.21 million years. These Mesozoic mafic dikes are characterized by high (87Sr/86Sr) i ranging from 0.7082 to 0.7087, low ϵNd(t) values from −17.0 to −17.5, 206Pb/204Pb from 17.14 to 17.18, 207Pb/204Pb from 15.44 to 15.55, and 208Pb/204Pb from 37.47 to 38.20. Our results suggest that the parental magmas of these dikes were derived from an ancient, enriched lithospheric mantle source that was metasomatized by foundered lower crustal eclogitic materials prior to magma generation. The mafic dikes underwent minor fractionation during ascent and negligible crustal contamination. Combined with previous studies, these findings provide additional evidence that intense lithospheric thinning beneath eastern Shandong occurred at ∼120 Ma, and that this condition was caused by the removal/foundering of the lithospheric mantle and lower crust. [ABSTRACT FROM PUBLISHER]

The Xihuashan tungsten deposit, Jiangxi province, China, is a world-class vein-type ore deposit hosted in Cambrian strata and Mesozoic granitic intrusions. There are two major sets of subparallel ore-bearing quartz veins. The ore mineral assemblage includes wolframite and molybdenite, with minor amounts of arsenopyrite, chalcopyrite, and pyrite. There are only two-phase aqueous-rich inclusions in wolframite but at least three major types of inclusions in quartz: two- or three-phase CO-rich inclusions, two-phase pure CO inclusions and two-phase aqueous inclusions, indicating boiling. Fluid inclusions in wolframite have relatively higher homogenization temperatures and salinities (239-380°C, 3.8-13.7 wt.% NaCl equiv) compared with those in quartz (177-329°C, 0.9-8.1 wt.% NaCl equiv). These distinct differences suggest that those conventional microthermometric data from quartz are not adequate to explain the ore formation process. Enthalpy-salinity plot shows a linear relationship, implying mixing of different sources of fluids. Although boiling occurred during vein-type mineralization, it seems negligible for wolframite deposition. Mixing is the dominant mechanism of wolframite precipitation in Xihuashan. δS values of the sulfides range from −1.6 to +0.1‰, indicative of a magmatic source of sulfur. δO values of wolframite are relatively homogeneous, ranging from +4.8‰ to +6.3‰. Oxygen isotope modeling of boiling and mixing processes also indicates that mixing of two different fluids was an important mechanism in the precipitation of wolframite. [ABSTRACT FROM AUTHOR]

Geochronological, geochemical, and whole-rock Sr–Nd isotopic analyses were performed on a suite of Palaeozoic nepheline syenites from Zijinshan to characterize their ages and petrogenesis. Laser ablation inductively coupled plasma-mass spectrometry U–Pb zircon analyses yield consistent ages of 525.7 ± 2.8 million years for a sample (HYK01). These intrusive rocks belong to the foid syenite magma series in terms of K2O + Na2O contents (14.3–15.2 wt.%) and to the shoshonitic series based on their high K2O contents (5.42–5.61 wt.%). The nepheline syenites are further characterized by high light rare earth element contents [(La/Yb) N  = 29.1–36.1]; show modest negative Eu anomalies (δEu = 0.5–0.6) and positive anomalies in Rb, Th, U, Pb, Zr, and Hf; are depleted in Ba and high field strength elements (P and Ti). In addition, all the nepheline syenites in this study display relatively low radiogenic Sr (87Sr/86Sr) i (0.7042–0.7043) and positive ϵNd (t) (0.7–0.8). These results suggest that the nepheline syenites were derived from depleted continental crust. The parent magmas likely experienced fractional crystallization of plagioclase, Ti-bearing oxides (e.g. rutile, ilmenite, and titanite), apatite, and zircon during ascent, with negligible crustal contamination before final emplacement at a high crustal level. [ABSTRACT FROM PUBLISHER]

Mesozoic mafic dikes in the Gan-Hang tectonic belt (GHTB) provide an opportunity to explore both the nature of their mantle source(s) and the secular evolution of the underlying Mesozoic lithospheric mantle in the region. The geochronology and primary geochemical and Sr–Nd–Pb isotopic compositions of Group 1 (middle section of GHTB) and Group 2 (the rest of the section) dolerite dikes spanning the GHTB were investigated. K–Ar ages indicate that dikes of both groups were emplaced during the Cretaceous (131–69 Ma). The dikes are doleritic in composition and are enriched in both large ion lithophile elements (LILEs; e.g. Rb, Ba, and Pb) and light rare earth elements (LREEs), with a wide range of Eu anomalies, but are depleted in high field strength elements (HFSEs; e.g. Nb, Ta, and Ti) and heavy rare earth elements (HREEs). Dikes sampled in the middle section of the GHTB (Group 1) show more pronounced REE differentiation and a greater contribution from crustal material than those from the east and west sections (Group 2) and are similar to GHTB volcanic rocks in exhibiting a slight enrichment in LREEs. The dolerites are further characterized by a wide range in 87Sr/86Sr i  = 0.7041–0.7110, 143Nd/144Nd i  = 0.511951–0.512758, ϵNd t  = –10.4 to +5.6, and Pb isotopic ratios (206Pb/204Pb i  = 18.1–18.3, 207Pb/204Pb i ≈ 15.6, and 208Pb/204Pb i  = 38.2–38.7). The dikes have undergone fractional crystallization of olivine, clinopyroxene, plagioclase, and Ti-bearing phases, except for dikes from the Anding area, which possibly experienced fractionation of plagioclase. Geochemically, all the dike samples originated from mantle sources ranging in composition from depleted to enriched that contained a component of foundered lower crust; crustal contamination during the ascent of these magmas was negligible. In the context of the late Mesozoic lithospheric extension across South China, mafic dike magmatism was likely triggered by the reactivation of deep faults, which promoted foundering of the lower crust and subsequent mantle upwelling in the GHTB. [ABSTRACT FROM AUTHOR]

Abstract: Precambrian mafic dykes in the North China Craton (NCC) consist of dolerite. Geochronological, geochemical, and whole-rock Sr–Nd isotopic analyses were performed on this suite of mafic dykes to characterise their ages and petrogenesis. Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) U–Pb zircon analyses yield consistent ages ranging from 837.9±4.8Ma to 2510±18Ma for seven of the mafic dykes (SHS01, TDG01, LJZ01, LQS02, HB02, WJ01, and DST01) from NCC. Based on these, the mafic dykes can be divided into three groupings: ~2.4–2.5Ga, ~1.8–1.9Ga and 0.8–1.0Ga. The studied dykes belong to the alkaline and sub-alkaline magma series in terms of K2O+Na2O contents (2.6–6.2wt.%), and to the Tholeiitic, calc-alkaline and high-K calc-alkaline series based on their K2O contents (0.1–2.1wt.%). The mafic dykes are further characterised by low and variable light rare earth elements (~2.4–2.5Ga mafic dykes, (La/Yb)N =3.83–10.4; ~1.8–1.9Ga mafic dykes, (La/Yb)N =1.45–2.35); 0.8–1.0Ga mafic dykes, (La/Yb) N =0.66–4.27, show variable Eu anomalies (δEu=0.94–1.35, 0.77–1.21; 0.92–1.28, respectively), positive anomalies in Ba, U, La and Pb, and are depleted in Rb and high field strength elements (Nb, Ta, Ti, and minor Zr and Hf). In addition, the studied mafic dykes all display relatively low radiogenic Sr [(87Sr/86Sr)i =0.6747–0.6921; 0.7017–0.7025; 0.7005–0.7049, respectively for the ~2.4–2.5Ga, ~1.8–1.9Ga and 0.8–1.0Ga mafic dyke groups] and large εNd (t) (13.2–13.5; 10.4–11.8; 6.5–8.5, respectively). These results suggest that all the mafic rocks were derived from a depleted mantle source hybridised by foundered lower crust. The parent mafic magmas likely experienced fractional crystallisation of olivine, pyroxene, hornblende, plagioclase and Fe–Ti oxides (e.g., rutile, ilmenite, titanite, etc.) during dyke ascent, with negligible evidence for crustal contamination prior to emplacement at a high crustal level. [Copyright &y& Elsevier]

Abstract: Mesozoic post-collisional andesites occur in the Gerze area within the Qiangtang Terrane of northern Tibet, China. Geochronological, geochemical, and whole-rock Sr–Nd isotopic analyses were performed on this suite of volcanic rocks to characterize their petrogenesis. Laser ablation-inductively coupled plasma-mass spectrometry U–Pb zircon analyses yielded consistent ages ranging from 122.4±0.4Ma to 124.4±0.4Ma for two andesite samples (JC01 and GZ01). The andesites belong to the alkaline and sub-alkaline magma series in terms of K2O+Na2O contents (4.7–10wt.%), and belong to the high-K calc-alkaline and calc-alkaline series on the basis of their high K2O contents (1.0–3.3 wt.%). The volcanic rocks are further characterized by the enrichment of light rare earth elements [(La/Yb)N =7.4–11.5] and large-ion lithophile elements (e.g., Rb), slightly negative Eu anomalies (Eu/Eu* =0.79–0.94), and negative anomalies in high field strength elements (e.g., Nb, Ta, and Ti) relative to primitive mantle. The samples show slightly elevated (87Sr/86Sr)i values that range from 0.7049 to 0.7057, and low ε Nd(t) values of −3.4 to 0.7. These results suggest that the rocks were derived from a compositionally heterogeneous mantle source and that their parent magmas are basalt magma. The parent mafic magmas may have undergone fractional crystallization of olivine, pyroxene, hornblende, and to a lesser extent, plagioclase during ascent through the thickened crustal pile, with minor or no crustal contamination, before the finally erupting as andesites. [Copyright &y& Elsevier]

TPost-orogenic intrusive complexes from the Sulu belt of eastern China consist of pyroxene monzonites and dioritic porphyrites. We report new U-Pb zircon ages, geochemical data, and Sr-Nd-Pb isotopic data for these rocks. Laser ablation-inductively coupled plasma-mass spectrometry U-Pb zircon analyses yielded a weighted mean 206Pb/238U age of 127.4 ± 1.2 Ma for dioritic porphyrites, consistent with crystallization ages (126 Ma) of the associated pyroxene monzonites. The intrusive complexes are characterized by enrichment in light rare earth elements and large ion lithophile elements (i.e. Rb, Ba, Pb, and Th) and depletion in heavy rare earth elements and high field strength elements (i.e. Nb, Ta, P, and Ti), high (87Sr/86Sr)i ranging from 0.7083 to 0.7093, low εNd(t) values from ε14.6 to - 19.2, 206Pb/204Pb = 16.65-17.18, 207Pb/204Pb = 15.33-15.54, and 208Pb/204Pb = 36.83-38.29. Results suggest that these intermediate plutons were derived from different sources. The primary magma-derived pyroxene monzonites resulted from partial melting of enriched mantle hybridized by melts of foundered lower crustal eclogitic materials before magma generation. In contrast, the parental magma of the dioritic porphyrites was derived from partial melting of mafic lower crust beneath the Wulian region induced by the underplating of basaltic magmas. The intrusive complexes may have been generated by subsequent fractionation of clinopyroxene, potassium feldspar, plagioclase, biotite, hornblende, ilmenite, and rutile. Neither was affected by crustal contamination. Combined with previous studies, these findings provide evidence that a Neoproterozoic batholith lies beneath the Wulian region. [ABSTRACT FROM AUTHOR]

Abstract: Post-orogenic granitic and associated mafic rocks from northeastern (NE) China consist of granodiorite and gabbro intrusions. We report here upon new U–Pb zircon ages, geochemical data and Sr–Nd–Hf isotopic data for these rocks. LA-ICP-MS U–Pb zircon analysis yields an age of 262.8±1.0Ma for the granitic rocks, and a uniform age of 262.1±0.7Ma for the gabbro. Most of the granitic and mafic rocks are characterised by low K2O+Na2O, and pertain to the subalkaline series in the total alkali–silica diagram. The granodiorite samples show low (87Sr/86Sr) i ranging from 0.700 to 0.705, positive ε Nd(t) values from +0.3 to +0.8, and large variation in ε Hf(t) values of between −4.0 and +2.5, indicating that both newly underplated basalt (70–80%) and ancient lower crustal sources (20–30%) contributed to their origin. Furthermore, positive ε Hf(t) values with two-stage model ages (T DM2) of 1123–1260Ma, together with Nd model ages (960–1000Ma), suggest an important episode of crustal growth during the Meso-Neoproterozoic beneath the Songliao Block. In contrast, the investigated gabbro is characterised by relatively high (87Sr/86Sr) i ratios (0.707–0.708), negative ε Nd(t) (−5.9 to −5.3) and ε Hf(t) values (−5.0 to −2.3), implying that this was derived from an enriched mantle source. The geochemical data indicate that the granitic magmas underwent separation of clinopyroxene, hornblende, K-feldspar, plagioclase, Ti-bearing phases (e.g., rutile, ilmenite, titanite), apatite and zircon during their evolution. Whereas the gabbro is characterised by low MgO (2.92–3.92wt.%), Mg# (35–41) and compatible elements content, such as Cr (10–68ppm), Co (16–31ppm) and Ni (5.7–33ppm), features of a more evolved mafic magma. There is no evidence that the granitic and mafic rocks were affected by crustal contamination during emplacement. Our interpretation is that the two coeval intrusive suites were both formed in a post-orogenic extensional setting, related to lithospheric delamination or ‘collapse’ of the Central Asian Orogenic Belt (CAOB) (Xingmeng orogenic Belt in China). [Copyright &y& Elsevier]

Abstract: Late Mesozoic (122.5–127 Ma) mafic dykes (dolerite-porphyries) in the Beibo gold district, Shandong Province, eastern North China Craton, can be subdivided into two groups (high-K and low-K) based upon K2O content. They are characterised by enrichment in light rare earth element (LREE) and some large ion lithophile elements (LILEs) (e.g., Rb, Ba and Sr), similar concentrations of heavy rare earth elements (HREEs), high (87Sr/86Sr) i ranging from 0.7094 to 0.7101, low ε Nd(t) values from −15.3 to −13.9, 206Pb/204Pb=16.98–17.70, 207Pb/204Pb=15.47–15.55 and 208Pb/204Pb=37.61–37.89. In addition, the high-K dolerite-porphyries are distinguished by negative Eu, Nb, Ta, P anomalies in chondrite-normalised REE and primitive-mantle-normalised trace element diagrams. These features suggest that they were derived from a common, enriched garnet-lherzolite mantle beneath the North China Craton, and that this was metasomatised by multiple enrichment events induced by hybridism of foundering lower crust at mantle depths. The low-K dolerite-porphyries were produced by 10–15% partial melting of the garnet-lherzolite source that had undergone metasomatism by carbonate-rich fluids producing secondary phlogopite and amphibole, whereas the high-K group was derived by relatively low-degree (3–5%) partial melting of a source that had experienced metasomatism by a carbonate-rich fluid with crystallisation of only secondary amphibole. The Pd-subgroup platinum-group element (PPGE) (Rh, Pt and Pd) enrichment and Ir-subgroup platinum-group element (IPGE) (Ir and Ru) depletion of these mafic dykes suggest derivation from an S-unsaturated magma. Geochemical and PGE features indicate that fractionation of olivine, clinopyroxene, hornblende, plagioclase, ilmenite, titanite, apatite, laurite and Os–Ir–Ru alloys was important in the formation of the high-K mafic magma. Additionally, separation of all the above phases with the exception of plagioclase and apatite played an important role in the origin of low-K dolerite-porphyries. Minor crustal contamination also occurred during ascent of these mafic magmas. [Copyright &y& Elsevier]

Abstract: Herein we present new U–Pb zircon ages, whole-rock geochemical data and Nd–Sr–Hf isotopic data for an Early Palaeozoic monzogranite batholith from the Tengchong–Baoshan Block, Western Yunnan Province, China. Mineralogical and geochemical features suggest that this granitoid is a high-K, calc-alkaline, I-type granite. SHRIMP and laser ablation ICP-MS (LA-ICP-MS) analysis of zircon yields ages of between 499±5Ma and 502±5Ma, for three samples from the batholith. The monzogranite is characterised by high initial 87Sr/86Sr (0.7132–0.7144), negative ε Nd(t) (−9.7 to −9.40) and ε Hf(t) (−10 to −13.1), and is interpreted to derive from remelting of pre-existing Palaeoproterozoic, high-K, metabasaltic rocks of the upper crust. The granitoid magma underwent extensive fractional crystallisation of biotite±hornblende, ilmenite, titanite, K-feldspar and plagioclase during emplacement. The crystallisation temperature of the magma lies in the range 633–733°C, however, there is no evidence to suggest crustal assimilation occurred during its ascent. Like the ∼500Ma, I-type granite of this study, there occur numerous granitoid rocks of Early Palaeozoic age (490–470Ma) in adjacent regions across the entire Tengchong–Baoshan Block (). This episode of plutonism is coeval with the widespread granitoid magmatism found throughout the Indian Plate and the Himalayan Orogenic Belt that are both subordinate parts of the ancient, Gondwana supercontinent. We infer, therefore, that the Tengchong–Baoshan Block may also have formed part of Gondwana, and that it separated from this supercontinent along with other crustal blocks during the Late Palaeozoic. Moreover, based on the findings of this study, we document the occurrence of arc-related magmatism in the Tengchong–Baoshan Block during the late Palaeoproterozoic. [Copyright &y& Elsevier]

Abstract: A zircon U–Pb age of adakitic rocks from Jiaodong, the Shandong Province, indicates that the volcanic rocks erupted at 123.6±0.8Ma. The volcanic rocks are composed only of trachyandesite with SiO2 contents ranging from 59 to 62wt.% and Al2O3 contents from 14 to 16wt.%. Their K2O contents range from 3.1 to 3.9wt.% and those of Na2O from 4.2 to 4.9wt.%, indicating that these rocks belong to the alkaline K-rich series. These rocks are characterized by enrichment in light rare earth elements (LREE) and depletion in heavy rare earth elements (HREE). They show strongly positive Ba anomalies and negative Nb, Ta, and Ti anomalies. The trachyandesites have high concentration of Sr, ranging from 919 to 1376ppm, and low Yb (0.92–1.16ppm) and Y contents (13.3–15.0ppm), resulting in high Sr/Y (65–98) and La/Yb ratios (38–51), all of which are characteristics of adakites defined by Defant and Drummond [Defant, M.J., and Drummond, M.S., 1990. Derivation of some modern arc magmas by melting of young subducted lithosphere. Nature 347, 662–665]. Isotopic compositions have high Sr and Pb ratios (87Sr/86Sr=0.7097–0.7099; 208Pb/204Pb=37.71–38.30; 207Pb/204Pb=15.34–15.54; 206Pb/204Pb=16.95–17.19), but low Nd (143Nd/144Nd=0.51150–0.51153; ε Nd(t)=−18.5 to −19.1). These geochemical features suggest a mafic, lower crust magma source. High Sr/Y and La/Yb ratios and negative Nb and Ti anomalies of the adakitic rocks suggest that garnet and amphibole were stable as two residual phases during partial melting, implying that the crustal thickness exceeded 40km in the Early Cretaceous. The present thickness of the crust in the Jiaodong area is only ∼32km, and therefore the crust appears to have been thinned by at least 8–10km since Early Cretaceous times. The high MgO (2.7–3.3wt.%), Cr (93–274ppm), and Ni (60–115ppm) contents and high Mg# (46–52) values in the adakitic rocks favours interaction between the pristine melts and mantle peridotite prior to eruption. [Copyright &y& Elsevier]

Abstract: Geogas prospecting is a relatively new technique in exploration for deep-seated and concealed mineral deposits. Now, the technique is to reveal the presence of concealed ore bodies by analyzing the element concentrations of substances that are transported by geogas from concealed ore bodies to the Earth''s surface. However, the element concentrations provide us with limited information about the concealed ore bodies. In our work, to investigate the category, size, shape, chemical component of geogas particles, copper grids for transmission electron microscopy measurement were directly used to capture the geogas-carried solid particles in Quaternary sediments overlying the Changkeng concealed gold deposit, Guangdong Province, South China. In the samples, we found Au, PbSO4, WO3, Fe2O3, SiO2, TiO2, and Al2O3 particles, etc. using a transmission electron microscopy. Of which, gold particles, and Hg-, Zn-, Pb-, W-bearing particles may originate from concealed ore bodies and can provide more direct information than those provided by element concentrations. [Copyright &y& Elsevier]

The Oligocene Yao’an syenite porphyry, associated with gold mineralisation, and the Machangqing alkali granite porphyry–monzonite porphyry, associated with Cu mineralisation, belong to the Red River–Jinshajiang alkaline igneous belt that formed in a continental setting in southwestern China. A study of the mineral chemistry of major silicate minerals in these two mineralised intrusions provides insights into their overall crystallisation conditions. The temperature and pressure conditions, derived from amphibole–plagioclase and perthite–plagioclase geothermometry and Al-in-amphibole barometry, suggest that the Yao’an intrusion crystallised at around 820 ± 50°C and 0.9–1.3 kbar, whereas the Machangqing intrusion crystallised at around 730 ± 50°C and 2.2–2.8 kbar. The higher temperature and lower pressure of crystallisation for the Yao’an intrusion relative to the Machangqing intrusion indicates that it was emplaced at a shallower crustal level. Based on biotite composition, the two intrusions formed under imposed oxygen fugacities above the Ni–NiO buffer (NNO), and the Yao’an intrusion crystallised under more oxidising conditions than the Machangqing intrusion. The results show that the intrusions associated with Cu–Au mineralisation in the Red River–Jinshajiang alkaline igneous belt were emplaced at a relatively high fO2, which, together with the weakly fractionated magma, favoured Au enrichment relative to Cu in the belt. [ABSTRACT FROM AUTHOR]

Abstract: Shuiyindong is one of the largest and highest grade, stratabound Carlin-type gold deposits in China. It is hosted in Permian bioclastic limestone near the axis of an anticline. Hydrothermal calcite is common on the periphery of central zones of ferroan carbonate dissolution that provided the main source of iron that was sulfidized during gold deposition. These calcite veins contain relatively high concentrations of rare earth elements with MREE-enriched patterns, and yield Sm-Nd isochron ages of 134±3 Ma to 136±3 Ma, with significant different initial εNd values of −12.9 and −2.0, respectively. These ages are interpreted to record age of decarbonation and gold deposition during the late stages of Yanshanian Orogeny. The initial Nd isotopic compositions of the calcites suggest that Nd was primarily derived from the Permian Longtang Formation that hosts all ore bodies at the deposit. This study shows that Sm-Nd isotopic compositions of hydrothermal calcites can be used to constrain the age and source of Nd in Carlin-type gold deposits. [Copyright &y& Elsevier]

Abstract: Post-orogenic alkaline intrusions and associated mafic dikes from the Sulu orogenic belt of eastern China consist of quartz monzonites, A-type granites and associated mafic dikes. We report here U–Pb zircon ages, geochemical data and Sr–Nd–Pb–Hf isotopic data for these rocks. The SHRIMP U–Pb zircon analyses yield consistent ages ranging from 120.3±2.1 Ma to 126.9±1.9 Ma for five samples from the felsic rocks, and two crystallization ages of 119.0±1.7 Ma and 120.2±1.9 Ma for the mafic dikes. The felsic rocks and mafic dikes are characterized by high (87Sr/86Sr)i ranging from 0.7079 to 0.7089, low ε Nd(t) values from −15.3 to −19.2, 206Pb/204Pb=16.54–17.25, 207Pb/204Pb=15.38–15.63, 208Pb/204Pb=37.15–38.45, and relatively uniform ε Hf(t) values of between −21.6±0.6 and −23.7±1.0, for the magmatic zircons. The results suggest that they were derived from a common enriched lithospheric mantle source that was metasomatized by foundered lower crustal eclogitic materials before magma generation. Geochemical and isotopic characteristics imply that the primary magma to these rocks originated through partial melting of ancient lithospheric mantle that was variably hybridized by melts derived from foundered lower crustal eclogite. The mafic dikes may have been generated by subsequent fractionation of clinopyroxene, whereas the felsic rocks resulted from fractionation of potassium feldspar, plagioclase and ilmenite or rutile. Both were not affected by crustal contamination. Combined with previous studies, these findings provide new evidence that the intense lithospheric thinning beneath the Sulu belt of eastern China occurred between 119 and 127 Ma, and that this was caused by the removal of the lower lithosphere (mantle and lower crust). [Copyright &y& Elsevier]

Abstract: Mesozoic mafic dykes in western Shandong Province (Luxi), SE, the North China Craton (NCC) provide an opportunity to examine the nature of their mantle source and the secular evolution of the Mesozoic lithospheric mantle beneath SE NCC. Chronological, geochemical and Sr–Nd–Pb isotopic analyses were carried out on two selected Mesozoic mafic dykes from Mengyin and Zichuan in western Shandong, respectively. Detailed SHRIMP zircon U–Pb dating yields emplacement ages of 144±2 Ma for the Mengyin mafic dykes and of 143±2 Ma for the Zichuan mafic dykes. Both are enriched in LILE (Rb, Ba, Sr, Pb) and LREE without Eu anomalies, but are depleted in HFSE (Nb, Ta and Ti). The dykes have relatively radiogenic Sr (87Sr/86Sr)i (0.706~0.707) and negative ε Nd(t) (−6.5 to −4.4), but remarkably unradiogenic Pb (206Pb/204Pb=16.99–18.36). Both dykes may have experienced crystal fractionation of olivine and clinopyroxene. The Mengyin mafic dykes are characterised by high MgO (9.66–17.97 wt.%), Mg# (66–74), Cr (809–1208 ppm) and Ni (171–390 ppm), indicative of derivation from mantle-derived melts with minor fractionation. In contrast, the Zichuan mafic dykes have relatively low MgO (3.38–4.14 wt.%), Cr (24–56 ppm) and Ni (14–24 ppm), suggesting that they may have originated from an extremely evolved magma. There is evidence in support of multiple enrichment events induced by hybridism of foundering lower crust at mantle depths. For example, phlogopite, amphibole and rutile metasomatism may have affected the lithospheric mantle beneath Mengyin, whereas phlogopite and carbonatite metasomatism modified the lithospheric mantle below Zichuan. This study sheds light also on the geodynamic significance of the 144–143 Ma mafic dykes, for example, we propose that lithospheric thinning underneath southeastern NCC of eastern China was caused by the removal of the lower lithosphere (mantle and lower crust). [Copyright &y& Elsevier]

The No. 302 uranium deposit, located in Guangdong Province, is a typical granite-type uranium ore deposit. REE geochemical characteristics of the wall rocks, pitchblende, altered rocks, calcite and fluorite from this deposit have been systematically studied in this paper. The result showed that the alkali-metasomatic granites and other altered rocks have the same REE distribution patterns as Indosinian granites. It is indicated that the hydrothermal ore-forming solution had altered the Indosinian granites, and ore-forming materials may directly originate from the Indosinian granites. Calcite and fluorite of different stages are the products derived from the same source but different stages. The evolution and degassing of the mineralizing solution might induce LREE enrichment to varying degree. Mantle fluid and a large volume of mineralizer may be the crucial factors controlling uranium mineralization, and the hydrothermal solution with mineralizer played an important role in U transport and concentration. Meanwhile, the degassing of CO2 might promote U and REE precipitation. [ABSTRACT FROM AUTHOR]

Abstract: The Wulantuga Germanium Deposit (WGD), hosted in coal seams with Ge resources up to 1600 Mt, is located in the Shengli Coalfield in Xilingol, Inner Mongolia, China. Forty-two channel samples of Ge-bearing lignites of the No. 6-1 coal seam (Lower Cretaceous Bayanhua Formation) were collected and their REE compositions were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The modes of occurrence of REE in selected lignite samples were studied by scanning electron microscope with energy-dispersive X-ray spectrometer (SEM-EDX) and statistical methods. The distribution of REE and Y in all 42 samples from WGD are in accordance with the log normal distribution, the total rare earth element content (∑REE) of most lignite samples from WGD range from 9.02 to 118 ppm, only four samples show relatively higher (149–533 ppm) ∑REE concentration. The average REE contents of 42 lignite samples from WGD are slightly higher than those of the USA coals, world wide coals, sandstone from WGD, and the contemporary Ge-barren lignite from Hongqi Coal Mine. The lignite samples from WGD have shale-like Chondrite or NASC-normalized REE patterns similar to those of sandstone overburden and Ge-barren lignite from Hongqi Coal Mine. REE contents of most lignite samples are highly positive correlated with ash yields, indicating a mainly detrital source and association with syngenetic mineral matter. REE-rich phosphates (monazite) were identified by SEM-EDX in some medium-to high-ash (ash yields range from 23.58% to 38.18%) lignite samples with high ∑REE+Y contents from WGD. REE can be concentrated in the upper and lower proportions of the No. 6-1 coal seam. The vertical profiles of REE mainly follow that of TiO2, and the average REE/TiO2 ratio of lignite sample in three sections is very close to that of the sandstone from WGD or lignite from Hongqi Coal Mine. It was determined that most REE in the lignite from WGD were derived from a detrital source and associated with syngenetic mineral matter. However, when normalized to the overlying sandstone, some lignite samples from WGD display a small but distinct enrichment in middle-to heavy-REE, indicating small quantity of middle-to heavy-REE may be added and/or retained during epigenesis. The lignite samples from WGD are characterized by higher ratios of LREE/HREE and Eu/Eu*, and horizontal NASC-normalized REE patterns, and distinguished from those of the Ge-bearing lignites from Lincang Germanium Deposit, Yunnan, China and Ge deposits of Russian Far East. There is no distinct correlations between Ge and any individual REE or ∑REE+Y content of lignite from WGD. [Copyright &y& Elsevier]

Abstract: The Wulantuga Germanium Deposit (WGD), hosted in coal seams with Ge resources up to 1600 Mt, is located in the Shengli Coalfield in Xilingol, Inner Mongolia, China. Forty-two channel samples of Ge-bearing lignites of the No.6-1 coal seam in Lower Cretaceous Bayanhua Formation were collected and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The mode of occurrence of elements in selected lignite samples were studied by cluster analysis and scanning electron microscope with energy-dispersive X-ray spectrometer (SEM-EDX). The lignite samples of WGD are distinctly enriched in Be, Ge, Sb, W, and U and depleted in Rb, Nb, Sn, and Ta, compared with the average composition of upper continental crust. The average concentrations of above enriched elements also are higher than those of overlying sandstone of WGD and contemporary Ge-barren lignite of Hongqi Coal Mine in Shenli Coalfield, as well as the average concentration of elements in the USA coals and worldwide coals. With an exception of Sr, most trace elements and ash yields obey the log normal distribution in all 42 lignite samples collected from WGD. The elements in these lignites may be classified into four groups: The first group (Ge–Mo association) contains elements with negative correlation coefficients with ash yields, and they show mainly organic affinity. The elements in the second group (Tl–Ga–Zn–Co association) show negative to moderate correlation coefficients with ash yields, and may also have an organic affinity, but most of them are mainly related to mineral matter (such as sphalerite). The last two groups (Rb–Cs and W–U–Cd–Y–Pb–Cu–Hf–Zr–Th–Sn–Nb–Ta–TiO2–Sb–Ba–Sr–MnO–Be associations) contain elements with moderate to high correlation coefficients with ash yields, much of them associated mainly with mineral matter (such as anatase, manganite, zircon, and barite) as identified by SEM-EDX analysis, and show mainly aluminosilicate affinity. Silver-bearing particles or native silver were identified by SEM-EDX in the lignites from WGD and Hongqi Coal Mine. Germanium and Mo can concentrate in different proportion of coal seam in different sections, while other elements more or less follow the distribution of ash yield. The TiO2-normalized elemental profiles reveal that Be/TiO2, Ge/TiO2, W/TiO2, U/TiO2, Mo/TiO2, Sb/TiO2, Tl/TiO2, and Sr/TiO2 ratios of the lignite samples in three sections of WGD are generally one or two order of magnitude higher than the reference ratios of sandstone from WGD and lignite from Hongqi Coal Mine, much (more than 90%) of these elements (Be, Ge, W, U, Mo, Sb, Tl, and Sr) may be transported into coal seam by solution. The Ge-bearing lignites from WGD are distinctly characterized by lower Rb/Cs ratios, higher U/Th ratios, different from those of the overlying sandstone from WGD and contemporary lignite from Hongqi Coal Mine. Most trace elements in the Ge-bearing lignite of WGD may have been derived from a granitic source, and the enrichment of Be, Ge, Sb, W, and U may be attributed to an epigenetic lateral transferred Ge-bearing solution that leached these elements from the granitic source and transported them into the lignite. [Copyright &y& Elsevier]

The sedimentary-volcanic tuff (locally called "green-bean rock") formed during the early Middle Triassic volcanic event in Guizhou Province is characterized as being thin, stable, widespread, short in forming time and predominantly green in color. The green-bean rock is a perfect indicator for stratigraphic division. Its petrographic and geochemical features are unique, and it is composed mainly of glassy fragments and subordinately of crystal fragments and volcanic ash balls. Analysis of the major and trace elements and rare-earth elements (REE) , as well as the related diagrams, permits us to believe that the green-bean rock is acidic volcanic material of the calc-alkaline series formed in the Indosinian orogenic belt on the Sino-Vietnam border, which was atmospherically transported to the tectonically stable areas and then deposited as sedimentary-volcanic rocks there. According to the age of green-bean rock, it is deduced that the boundary age of the Middle-Lower Triassic overlain by the sedimentary-volcanic tuff is about 247 Ma. [ABSTRACT FROM AUTHOR]

Alkali-rich intrusive rocks in western Yunnan were derived from an enriched lithospheric mantle (EM II) source. The data available indicated they are alkali-rich (K2O + Na2O > 8wt%) and shoshonitic. Although formed in a within-plate environment they exhibit signatures of arc magmatic rocks, such as high amounts of LILE and LREE relative to the HFSE and HREE, and thus high Ba/Nb, Ba/Zr, Sr/Y, La/Yb ratios as well as mimic chondrite-normalized REE and primitive mantle-normalized trace element patterns of subducted sediments, and they fall in the collision- or arc-related tectonic setting field on all discrimination diagrams. This might suggest the enrichment be related to the substantial extent of sediment contamination by the Mesozoic Tethyan subduction processes. [ABSTRACT FROM AUTHOR]

The Cambrian Gezhongwu Formation in Southwest China is the lowest Cambrian phosphorite unit. The Formation belongs to the Meishucun stage with small shelly fossils. Rare-earth element (REE) data from the Gezhongwu phosphorites of Zhijin documented the depositional conditions. The total REE concentrations are high in the Gezhongwu phosphorites, which are especially rich in yttrium. The PAAS-normalized REE patterns of the Gezhongwu phosphorites are characterized by negative Ce anomalies and slight enrichment of MREE, as being ha!-shaped. The hat-shaped patterns suggest that the REE originated from depositional environments rather than from subsequent diagenesis. The negative Ce anomalies indicate that the depositional environments are oxic. The positive Eu anomaly, the high total REE and the hat-shaped REE pattern revealed contributions from the normal marine environment mixed with hydrothermal water to the REE budget of the Gezhongwu phosphorites. [ABSTRACT FROM AUTHOR]

On the basis of an experimental study and thermodynamic calculation, the mechanisms of paragenesis and separation of silver, lead and zinc in the hydrothermal system have been studied. At acidic to nearly neutral pH, their chloride complexes are stable, and among them the chloride complexes of zinc are most stable. And the sulfide complexes are the dominant species at nearly neutral to alkaline pH, while the sulfide complexes of silver are most stable. With decreasing temperature, [Cl-], fO2 and increasing pH, the solubilities of silver, lead and zinc will decrease, leading to their deposition and separation. For sulfide complexes, the concentrations of reduced sulfur and pH are two important factors affecting their stabilities. Complexes of different forms and stabilities respond to the variation of conditions to different extents, which gave rise to the paragenesis and separation of silver, lead and zinc in the whole ore-forming process of dissolution, transport and deposition. [ABSTRACT FROM AUTHOR]

Articulated fossil brachiopod shells have been used extensively to extract primary chemical information of Phanerozoic seawater. Despite the selection of well-preserved shells using trace element, microstructure and cathodoluminescence criteria, there are still concerns as to whether the selected brachiopod shells do indeed contain original seawater signals. Analyzed in-situ by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LAICPMS), Sr, Na, Mg, Mn, B and Ba distribute symmetrically in shell transects of the modern brachiopods Magellania flavescens and Terebratulina septentrionalis. Symmetry of the trace element distribution pattern is considered an intrinsic and original ontogenetic property of the brachiopod shell chemistry. The trace element distribution is symmetrical in a well-preserved shell of the Devonian brachiopod Independatrypa lemma, indicating that the selected shell by the conventional criteria has preserved its original seawater signal for 400 Ma. In another specimen of I. lemma that is considered diagenetically altered, trace element concentrations are asymmetrically distributed in the shell. The agreement between the distribution criteria and the conventional methods indicates the latter can be used to select brachiopod shells with original seawater chemistry. The average element concentration in the whole shell of unaltered brachiopods should be a reflection of the seawater chemistry, while its change in different part of a shell reflects ontogenetic effect, and its high frequent fluctuations in a transect are results of changes in environmental parameters with seasonal or annual characteristics. [Copyright &y& Elsevier]

Reports on scheelite Sm-Nd and quartz Ar-Ar dating for the Woxi Au-Sb-W deposit in western Hunan. High level of Sm and Nd concentrations of scheelite; Finding that the disseminated scheelites demonstrate a good linear array, which corresponds to an isochron age of 402 ± 6 Ma; Indication that the Ar-Ar age spectra for 2 quartz samples show the saddle shape; Overlap in the minimum apparent age, plateau age and isochron age of each quartz sample; Suggestion that the minimum apparent ages of 420 ± 20 and 414 ± 19 Ma coincide with the scheelite Sm-Nd age; Assertion that the Au-Sb-W mineralization at Woxi district took place in the Late Caledonian period, which agrees with the tectonic evolution of the Xuefengshan district and with geochronological data available for Au, Sb and W deposits in this area; Inference from the low initial Nd isotope ratio of scheelites that the fluid responsible for Au-Sb-W mineralization is of deep crustal origin; Suggestion that it originated from the Archacan continental basement rather than the Proterozoic strata.

Focuses on the emplacement ages of lamproites in the Guinzhou Province in China. Influence of the whole-rock Sm-Nd and Rb-Sr isochron methods in constraining the lamproites; Occurrence of intrusive activities of lamproites in the region; Emplacement of the upwelling of hot materials derived from the deep mantle from the Late Cambrian to the Early Ordovician.