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Xie H.,CAS Guangzhou Institute of Geochemistry | Xie H.,University of Chinese Academy of Sciences | Wu G.,Chinese Academy of Geological Sciences | Wu G.,Lingbao Jinyuan Mining Ltd Liability Company | And 5 more authors.
Earth Science Frontiers | Year: 2013

The zircon U-Pb geochronology, major and trace elements and Sr-Nd isotopes determination of the Lamasu intrusion in western Chinese Tianshan were conducted to understand its petrogenesis and geodynamic setting. The Lamasu intrusion is mainly composed of quartz monzodiorite, granodiorite porphyry and tonalite porphyry. Among them the quartz monzodiorite was formed in 394.8±4.9 Ma, while the granodiorite porphyry and tonalite porphyry were intruded in 380.9±3.9 Ma. The rocks display the adakitic affinity and show a calc-alkaline and high-K calc-alkaline differentiation trend. They display REE patterns characterized by relative enrichment of LREE ((La/Yb)N: 3.55-15.52) with slightly negative or positive Eu anomalies (δEu: 0.53-1.12). They have high Sr ((322-808)×10-6) and low Y contents ((12.90-18.86)×10-6) and also enriched in LILE but depleted in HFSE with negative Nb, Ta and Ti anomalies. Initial Sr-Nd isotopic compositions are εNd(t)=-4.29 to 0.75 and ISr=0.706052 to 0.708263. The Nd model ages vary from 1.03 to 1.46 Ga. The Pb isotopic ratios of granodiorite porphyry and tonalite porphyry are 206Pb/204Pb=18.500-19.044, 207Pb/204Pb=15.575-15.626, 208Pb/204Pb=38.443-38.864, while the quartz monzodiorite are 206Pb/204Pb=18.694-18.711, 207Pb/204Pb=15.622-15.630, 208Pb/204Pb=38.648-38.660. All these geochemical data demonstrate that the Lamasu intrusion is likely derived from the partial melting of oceanic crust, with the subsequent melts interacted during their uplift with the overlying mantle wedge metasomatized by the subducted sediments and subordinately contaminated by ancient crust. The Lamasu intrusion was emplaced in a continental arc setting during the southward subduction of the Junggar Remnant Ocean Basin in the Late Devonian and are closely related with Cu (Au) mineralization of that region.

Zhu M.,CAS Institute of Geology and Geophysics | Wu G.,Chinese Academy of Geological Sciences | Wu G.,Lingbao Jinyuan Mining Ltd Liability Company | Xie H.,CAS Guangzhou Institute of Geochemistry | And 2 more authors.
Acta Petrologica Sinica | Year: 2011

Kekesai intrusion, located in the north of the Sayram block of western Tianshan, Xinjiang, is composed of monzogranite porphyry of high-K calc-alkaline series. This paper presents the new major and trace element geochemistry and Sr-Nd isotopic compositions of the monzogranite porphyry. The contents of SiO 2 (70.56% -71.46%), Al 2O 3(15.27% -16.01%), MgO(0.77% ∼1.02%), Sr (363 ×10 -6∼577 ×10 -6), Y (7.40×10 -6 ∼8.50 × 10 -6) , Yb (0.60×10 -6 ∼0.72× 10 -6) together with the strongly fractionated REE patterns ((La/Yb) N: 14.99∼23.69) and weak negative-, or positive-Eu anomalies (δEu; 0.88∼1.21) indicate that the monzogranite porphyry shows characteristics of adakitic rock. The rocks have low I Sr(0.705078 ∼0.705572) , positive ε Nd(0 values (2.82 ∼3.56) and young two-stage Nd-model age (774 ∼ 835Ma). The LA-MC-ICP-MS zircon U-Pb age of the monzogranite porphyry indicates that the intrusion was emplaced at the end of the Late Carboniferous (301.9 ± 1.8Ma). Element and isotope data demonstrate that the Kekesai intrusion was produced by the partial melting of juvenile Neoproterozoic lower crust and associated with initial stage of post-collision process.

Wu G.,Chinese Academy of Geological Sciences | Wu G.,CAS Guangzhou Institute of Geochemistry | Wu G.,Lingbao Jinyuan Mining Ltd Liability Company | Chen Y.,Chinese Academy of Geological Sciences | Chen Y.,Pelting University
Acta Petrologica Sinica | Year: 2010

A lot of epithermal gold deposits and occurrences, such as Arharlei and Wurenkebulake deposits, have been found in the northeastern Kazakhstan Tianshan, which is one of the important epithermal gold metallogenic belts in the Central Asian Orogenic Belt Whereas, the metallogenetic chronology study of the gold deposits is poor. To time the mineralization, the authors dated andesite and andesitic basalt from the host rocks of the Arharlei and Wurenkebulake deposits, respectively, using high-resolution laser-ablation 40Ar/ 39 Ar method. Twenty analyses of andesites from the Arharlei deposit yielded a 40Ar/39 Ar isochron age of 304 ± 7Ma ( MSWD =6) , and 21 of andesitic basalts from the Wurenkebulake deposit deposit yielded a 40Ar/39 Ar isochron age of 280 ± 6Ma (MSWD =2.4). This shows that the gold deposits in the northeastern Kazakhstan Tianshan have been formed between end Late Carboniferous and Early Permian. Petrology and geochemistry primarily studied by the authors show that the volcanic rocks related to these epithermal gold deposits in this region are mainly of high-K calc-alkaline and shoshonite series, and comprise mainly rhyolite, trachyandesite, basaltic trachyandesite, basaltic andesite, trachybasalt and basalt, with hi modu I features. The epithermal gold deposits of the end Late Carboniferous might be formed in a transitional period from continent-continent collision to rift environments, whilst the Permian epithermal gold deposits were formed in an irilraeonlmental rift setting.

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