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The Tiegelongnan porphyry-epithermal deposit (2089 Mt @ 0.53% Cu, 0.08 g/t Au) is host to a large variety of Cu-sulfide minerals, mainly chalcopyrite, bornite, covellite, digenite, enargite, and tennantite. We used LA-ICP-MS to investigate the trace element geochemistry of the Tiegelongnan Cu-sulfides, as well as pyrite, to understand the correlation between sulfides and trace elements, gold in particular, in the porphyry and epithermal systems. Porphyry mineralization consists of stage 1 chalcopyrite-pyrite ± molybdenite, stage 2 chalcopyrite-bornite, and stage 3 covellite. Epithermal sulfides form stage 4 pyrite-alunite, stage 5 digenite-bornite-chalcopyrite, and stage 6 enargite-tennantite ± tetrahedrite. Stage 2 chalcopyrite (S2 Ccp, median = 9.7 ppm Au) is the primary porphyry Au host, and stage 6 tennantite in alunite veins (S6 Tnt-s, median = 98.0 ppm Au) is the major epithermal Au host. These Au-rich sulfides formed under higher oxidation conditions, suggesting that a high oxidation state favors the incorporation of Au in Cu-sulfides. Gold contents in coeval chalcopyrite and bornite are positively correlated to temperature, and Au is enriched in chalcopyrite over bornite at low temperatures (< 350 ℃). Positive correlations between Au and As and Te in covellite and chalcopyrite result from the reaction of As3+ + (Au+/Ag+) + Te2− ↔ 4Cu+ + S2−. Epithermal chalcopyrite and bornite contain more As and Pd than that in porphyry stages, and high contents of As, Sn, Cd, Zn, Sb, Te, Au, and Bi in epithermal enargite and tennantite are likely the result of partitioning of these elements in sulfides at low epithermal temperatures. Epithermal overprinting likely leached Cu from earlier porphyry stage sulfides to precipitate high Cu-grade epithermal mineralization. The Cu-sulfides and related trace elements show a spatial distribution, potentially useful for the exploration of overprinted porphyry-epithermal systems. [ABSTRACT FROM AUTHOR]

The study of the petrogenesis of some magmatic rocks with special geochemical attributes provides effective information for us to explore the deep geodynamic background of their formation. A series of granitic porphyry dykes have been found in the mélange zone of the Asa region in southern Tibet, whose genesis may be closely related to the evolution of the Meso-Tethyan Ocean. Regional geodynamic evolution is investigated by whole-rock geochemical analysis, zircon U–Pb dating and Lu–Hf isotopic analysis of two porphyritic granites. The Asa porphyritic granites have high SiO2 (74.29–78.65 wt %) and alkalis (Na2O + K2O = 6.51–9.35 wt %) contents, and low Al2O3 (11.60–14.51 wt %), CaO (0.04–0.19 wt MgO (0.01–0.10 wt %) contents. They are enriched in Zr, Nb, Ce, Y and Hf and depleted in Ti, Ba, Sr and P, consistent with A-type granites. The samples are relatively rich in LREEs, with LREE/HREE ratios of 1.73–3.04. They display negative Eu anomalies (Eu/Eu* = 0.24–0.28) and obvious Ce anomalies in some samples. Zircon U–Pb analyses show that the porphyritic granites formed in late Early Cretaceous time, 107.4 to 105.5 Ma. Zircon εHf(t) values are in the range of 6.9 to 12.0. These data indicate that the porphyritic granites were sourced from interaction between mantle-derived and juvenile lower crust-derived melts, with the addition of oceanic sediment-derived melts. This occurred when the subducting Bangong–Nujiang oceanic crust split to create a slab window. Rising asthenosphere triggered re-melting of lower crust basalts, resulting in the formation of the late Early Cretaceous A-type granites around Asa. [ABSTRACT FROM AUTHOR]

Due to the unclear tectonic setting of the Jurassic ophiolites within the Bangong-Nujiang suture, how and when intra-oceanic subduction initiated within the Bangong Meso-Tethys remain controversial. Based on the new petrological, geochemical, and geochronological data reported in this paper, ∼190–180 Ma MORB-like ophiolites and OIB-like mafic rocks were identified from the Shiquanhe ophiolitic complex in the western Bangong-Nujiang suture. The MORB-like gabbros exhibit strong light rare earth elements (LREEs) and heavy rare earth elements (HFSEs) depletion and were derived from partial melting of a highly refractory depleted mantle source with limited slab-derived fluids. The OIB-like mafic rocks are enriched in LREEs and HFSEs and were originated from the melting of upwelling asthenospheric mantle without subduction additions. The data for the MORB-like ophiolites reported in this paper and previously published data demonstrate the formation of Early Jurassic fore-arc ophiolites in response to the Early Jurassic intra-oceanic subduction initiation within the Bangong-Nujiang suture. The Early Jurassic OIB-like rocks formed in the extensional tectonic setting, together with regional geological evidence, suggest that the Early Jurassic initial subduction event within the Bangong Meso-Tethys resulted in broad upper plate extension. Our study not only reveals the intra-oceanic subduction initiation age of the Bangong Meso-Tethys but also implies that subduction initiation can cause strong extension in a wider region of the upper plate in the Tethys oceanic system, not just in the fore-arc region. • Discovery of MORB-like fore-arc ophiolite (190–185 Ma) in the Shiquanhe area. • Identifying of OIB-like gabbro-monzonite (185–180 Ma) in the Shiquanhe melange. • Confirming Early Jurassic intra-oceanic subduction initiation in Bangong Ocean. [ABSTRACT FROM AUTHOR]

Conclusion: In the northwest of China, the prevalence of mutations of the three prominent deafness-related genes, GJB2, SLC26A4, and mitochondrial DNA (mtDNA) 12S rRNA, among Tibetan, Tu nationality, and Mongolian subjects is high, at 19%, 28.57%, and 21.05%, respectively. Molecular genetic screening for these mutations and genetic counseling are effective methods to prevent the occurrence of hereditary hearing loss. Objective: To analyze the prevalence of the three common deafness genes GJB2, mtDNA, and SLC26A4 gene mutations in Tibetan, Tu nationality, and Mongolian patients with nonsyndromic hearing impairment in the Northwest region of China. Methods: Genomic DNA was extracted from a total of 189 Tibetan, Tu nationality, and Mongolian probands from the northwest of China. PCR and direct sequencing were used to analyze the coding region of GJB2, mtDNA, and SLC26A4 genes. Results: The mutant allele rate of GJB2 gene was 6.2% in Tibetan and 11.22% in Tu nationality patients, c.235delC was the most prevalent mutation, accounting for 75% of the mutant GJB2 alleles. Mutant allele frequency of SLC26A4 in Tibetan, Tu nationality, and Mongolian subjects was 4.54%, 6.12%, and 15.79% respectively; p.IVS7-2A>G was the most common form. Mongolian cases were significantly higher than Tibetan cases (χ2 = 7.281, p = 0.007 and p < 0.05). mtDNA A1555G mutation was detected in six Tibetan, five Tu nationality, and one Mongolian subject; one Tibetan patient carried the C1494T mutation. [ABSTRACT FROM AUTHOR]

We studied the ranging pattern of the wild black-and-white snub-nosed monkeys ( Rhinopithecus bieti) at Xiaochangdu, Tibet from June 2003 to March 2005. Using the map grid cell method, the group home range were 16.75 km in summer, 10.50 km in winter, and 21.25 km total over two years. The daily travel length (DTL) averaged 765 m with a range of 350-3500 m. The results showed that DTL in winter was significantly shorter than those of in summer and spring. Temperature, rainfall, food availability, and human disturbance correlated positively with DTL. According to the maximum observed group size and estimated total home range, population density and biomass of R. bieti were 9.1 individuals/km and 88.6 kg/km, respectively. The temporal and spatial variations of food resources and patterns of human disturbance largely determine the ranging behavior of R. bieti at Xiaochangdu. [ABSTRACT FROM AUTHOR]

As a part of the Bangong-Nujiang suture, the Shiquanhe-Namco ophiolite mélange belt (SNM), together with the Bangong-Nujiang ophiolite mélange belt (BNM), records the evolutionary history of the Mesotethys. In terms of the closure of the Mesotethys, previous sedimentological research has focused on the BNM, while the SNM remains insufficient. On the basis of detrital zircon dating and sedimentologic data, in this study, we determined the existence of Aptian deep-marine turbidites in the Zhongcang and Lhakorco areas of the SNM. Sandstone petrographic and detrital zircon analysis combine to show that the Zhongcang turbidites provide records of the recycled from the accretionary complex and Triassic-Jurassic strata in the southern Qiangtang margin, with the minor addition of Qiangtang magmatic arc rocks, while sediments in the Lhakorco turbidites were derived mainly from recycled orogen source and Late Jurassic-Early Cretaceous magmatic arc in the Lhasa Terrane. Further analysis suggests that the Aptian turbidites were deposited in a deep-marine oceanic basin of Mesotethys and this oceanic basin prevented Qiangtang-derived sediments transported onto the Lhasa terrane. The Mesotethys experienced diachronic closure from east to west during the Early Cretaceous, and the final closure was most likely completed along the SNM after Aptian. • Discovery of the Aptian deep-marine fan turbidities in SNM • Featuring the Aptian Qiangtang and Lhasa source separation along SNM • Implications for diachronous closure of the Mesotethys [ABSTRACT FROM AUTHOR]

This study presents 13 new U-Pb zircon ages obtained by laser ablation-inductively coupled plasma-mass spectrometry (LAICP- MS) together with whole-rock geochemical, Sr-Nd isotopic and zircon Hf isotopic data for a mafic dike swarm in the southern Qiangtang area of Tibet. These data provide the basis for a new model of the late Paleozoic evolution of the Tethys. Combined with the results of previous zircon U-Pb dating, the magmatic zircon grains extracted from mafic dikes yield latest Carboniferous to Early Permian ages (317-279 Ma). The geochemistry of the southern Qiangtang mafic rocks indicates the presence of low-Ti (QLT) and high-Ti (QHT) suites. The magmas that formed the QLT suite underwent higher degrees of partial melting (>5%) and display evidence of crustal contamination, whereas the QHT suite was derived from magmas generated by low-degree (1%-5%) partial melting of a garnet-bearing mantle source, with a greater extent of fractional crystallization than the QLT suite, and no evidence of crustal contamination. We propose that the QHT and QLT suites may have been derived from magmas from different parts of a single mantle plume. The formation of the southern Qiangtang mafic dikes (latest Carboniferous to Early Permian; 317-279 Ma) may have been related to the northward drift of the Cimmerian continent from the northern Gondwana margin, which resulted in the opening of the Meso-Tethys Ocean. [ABSTRACT FROM AUTHOR]

The oceanic plagiogranites that intruded into the ophiolite suite have received a great deal of attention from researchers. Some of these plagiogranites were controlled by mid-ocean ridge spreading and were formed via crystallization of basaltic magma or partial melting of the mafic gabbroic oceanic crust. The other plagiogranites were controlled by subducted oceanic crust slabs, and their formation mechanism is similar to that of the oceanic island arcs. The identification of different types of oceanic plagiogranites is of great significance for understanding the evolution of ancient ocean basins. In the Shiquanhe–Namtso mélange zone in central Tibet, scholars have recently identified many rock sequences related to intra-oceanic arcs, including MORB-like basalts, boninites, high-Mg andesites, and multiple series of granitic rocks. To further explore the formation mechanism of felsic rocks in oceanic island arcs and their role in the growth of continental crustal material, we sampled a series of Middle and Late Jurassic granitoids exposed in the ophiolitic mélange belt in the Shiquanhe area. Using zircon U-Pb dating, zircon Lu-Hf isotopic testing, whole-rock Sr-Nd isotopic testing and whole-rock major and trace geochemical testing, we determined the magmatic genesis and tectonic history of these samples. According to the test results and our field survey, we divided our samples into three groups. The first group consists of low-K plagiogranites (LKGs). These samples have ages that fall between 163 and 162 Ma. With their low K 2 O/Na 2 O ratios, low La/Yb ratios, low Sr/Y ratios, low Gd/Yb ratios, weak negative Eu anomalies and their significantly depleted zircon isotopic compositions (εHf(t) = 10.0–12.5; εNd(t) = 0.64–1.10), we propose that these samples are the products of partial melting of oceanic gabbro and turbidite at shallow depths in low-pressure and high-temperature conditions. The second group consists of samples from dioritic enclaves within the LKGs. These samples, which are slightly older than the LKG samples (175–173 Ma), have isotopic characteristics that are similar to those of the LKG samples (εHf(t) = 10.4–13.5; εNd(t) = 0.51–0.83). The samples in the second group may be homologous captives that formed during the early crystallization of LKG homologous magmas. The third group consists of samples with compositions of high-K granodiorites (HKGs) and ages similar to those of the LKG group (~163 Ma). With high K 2 O/Na 2 O ratios, relatively high La/Yb ratios, low Sr/Y ratios, low Gd/Yb ratios, negative Eu anomalies, significantly enriched isotopic compositions (εHf(t) = −11.1 to −15.4; εNd(t) = −13.29 to −13.43). Considering the basement exposure and known magmatic characteristics in the Shiquanhe area, we propose that HKGs samples are the result of interaction between continental subduction sediment melts and heterogeneous mantle material in high-temperature and low-pressure conditions. By comparing the oceanic plagiogranites in the Shiquanhe–Namtso mélange zone with those developed in the young, hot intra-oceanic subduction zone, we determined that the oceanic plagiogranites in the Shiquanhe–Lhaguotso–Asa area are forearc granites developed in the forearc area. These plagiogranites were controlled by the young, hot subducting plate and were formed by partial melting of a multi-component source area in a high-temperature and low-pressure environment. • Newly discovered Jurassic (175–162 Ma) granitic intrusions in Shiquanhe area. • These rocks were formed during the intra-oceanic subduction of young oceanic crust. • We define a new type of oceanic plagiogranites: forearc granites. [ABSTRACT FROM AUTHOR]

Intra-oceanic subduction is a fundamental process on Earth, the study of which can improve understanding of plate tectonic processes and the history of continental growth. Several studies of the intra-oceanic subduction of the Meso-Tethys Ocean have been published in recent years, particularly relating to the Bangong–Nujiang suture zone (BNSZ) and the Shiquanhe–Nam Tso mélange zone (SNMZ) in central Tibet. Here, we report newly discovered occurrences of Jurassic diorite (161.2–160.6 Ma) and plagiogranite (161.0 Ma) from the western part of the central SNMZ. The diorite samples have moderate SiO 2 and high MgO contents and Mg# values; high Ba/Th and Ba/La ratios; low K 2 O, TiO 2 , and REE contents; low (La/Yb) N , (La/Sm) N , and Th/Yb ratios; and positive ε Hf (t) values, similar to high-Mg diorite formed by partial melting of a subduction-modified mantle wedge. The plagiogranite intrudes gabbro of the ophiolite suite and has high SiO 2 and Na 2 O contents; low Al 2 O 3 , K 2 O, P 2 O 5 , TiO 2 , and total REE contents; and clear negative Eu anomalies, similar to shear-related oceanic plagiogranite, which can be formed by partial melting process of gabbro in the high temperature shear zone near the expansion center. The formation processes of Asa high-Mg diorite and shear-related plagiogranite are consistent with initial subduction within the Meso-Tethys ocean. Based on these data and those for sedimentary and Jurassic magmatic rocks of the region, we propose that, during subduction, the Northern Lhasa terrane was formed from a collage of oceanic island arcs, oceanic plateaus, and accretionary complexes. • Intermediate-acid magmatism in the SNMZ, central Tibet. • High-Mg diorites and shear-type plagiogranite with Late Jurassic ages (161–160 Ma). • The Jurassic intra-Meso-Tethys oceanic subduction event (165–160 Ma). • The generation of the Northern Lhasa terrane by accretion of intra-oceanic arcs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The first identified oceanic core complex in the Bangong-Nujiang suture zone. • The mid-ocean ridge of the Meso-Tethys Ocean moved northward since the Late Triassic. • This ridge was slow spreading during the Early Jurassic. In this paper, we report the first identified oceanic core complex (OCC) in the Saibucuo area of the Bangong-Nujiang suture zone, describe the geology and petrology of this OCC, and present new zircon U-Pb ages and Lu-Hf isotopes, and whole-rock major- and trace-elements and Sr-Nd isotopes for the diabase dikes in this OCC. The Saibucuo OCC consists of serpentinites, serpentinized peridotites, diabase dikes, tectonic breccias, sedimentary breccias, and limestones. The serpentinized peridotites cross-cut by carbonate veins, the sedimentary breccias with simple gravel compositions cut by normal faults, together with the limestones in the cover sequence lead to the conclusion that the Saibucuo OCC is similar to the OCCs of mid-ocean ridge settings. This conclusion is consistent with the E-MORB features of diabase dikes, which are formed by the interaction of the mid-ocean ridge and mantle plume, and the abyssal peridotite features of serpentinized peridotites. Zircon U–Pb ages of the diabase dikes indicate that the Saibucuo OCC was formed at the ca. 190 Ma. Based on these data and regional geological records, the early Mesozoic tectonic evolution of the Meso-Tethys Ocean was restored. The Meso-Tethys Ocean was a broad and mature oceanic basin during the Late Triassic-Early Jurassic. Coeval collision of the Northern and Southern Qiangtang terranes during the Late Triassic initiated the northward subduction of the Meso-Tethys Ocean, and the northward migration of the mid-ocean ridge. Continuous northward subduction of the Meso-Tethys Ocean caused the mid-ocean ridge to gradually approach the northward subduction zone, and eventually to subduct and collide with the northern trench during the Early-Middle Jurassic. The mid-ocean ridge within the Meso-Tethys Ocean was slow spreading during the Early Jurassic. [ABSTRACT FROM AUTHOR]