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Lei R.,Chang'an University | Lei R.,Key Laboratory of Western Chinas Mineral Resources and Geological Engineering Ministry of Education | Wu C.,Nanjing University | Qu X.,Bureau of Mineral Resources | And 5 more authors.
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2014

We present a case study of the Early Paleozoic ore-bearing gneiss granite in the Tianhudong iron-molybdenum ore deposit in the central Tianshan in an attempt to provide new insights for the early Paleozoic tectonic setting and tectonic evolution of the central Tianshan. LA-ICP-MS zircon U-Pb dating yields (445.3±4.6) Ma for the studied granite. The granite is composed mainly of biotite, amphibole, quartz, plagioclase and K-feldspar. Geochemical analyses show the granite belongs to subaluminous calc-alkaline granite. The granite is generally enriched in large ion lithophile elements (LILEs) such as Rb, Ba and LREEs, but depleted in typical high field strength elements (HFSEs) such as Nb, Ta, Ti, Y and HREEs, consistent with the geochemical characteristics of typical arc igneous rock. The zircon Hf isotope compositions (εHf(445 Ma)) of the studied granite vary from -6.30 to -1.77, and the TDM2 ranges from 1.538 to 1.825 Ga, indicating the source rocks of the granite contain significant crustal materials. Integrating all the available data, we suggest that the granite is produced by melting of the mainly crustal protolith during a subduction process. Combined with the previous studies and our recent study results, it is suggested that the central Tianshan zone was a magmatic arc tectonic environment during the Early Paleozoic. The mechanism of the Early Paleozoic central Tianshan arc can be ascribed to the southern subduction of the ancient Tianshan ocean located between the Tuha block and Tarim block.

Wang C.,Eastern China Geoexploration and Development Bureau for Non Ferrous Metals | Wang C.,Nanjing University | Wang C.,Northwest University, China | Zhang Z.,Eastern China Geoexploration and Development Bureau for Non Ferrous Metals | And 8 more authors.
Acta Petrologica Sinica | Year: 2010

The Yiwu granitic complex is mainly composed of a monzogranite and an alkali-feldspar granite phases. Zircon LA-ICPMS U-Pb dating gave ages of 284.6 ± 1.4Ma and 284.0 ± 1. 1Ma for the monzogranite and alkali-feldspar granite, respectively, indicating their Early-Permian emplacement in accompany with post-collisional compression-extension transition. Petrological, geochemical and isotopic studies suggest that these rocks were evolution products from the same magma. In comparison with the monzogranite, the alkali-feldspar granite is higher in Si, alkai, DI and Rb/Sr, and richer in Th, U, Nb and Ta, but lower in Al, Sr, P, Ti, Sm, Nb/Ta and Zr/Hf. A continuous differentiation trend is exhibited from monzogranite to alkali-feldspar granite. Model ages (tDM) are calculated to be 693Ma and 763Ma for the monzogranite and alkali-feldspar granite, respectively. Both rock types are higher in εNd(1) ( +4.53 and +4.64, respectively) and lower in (87Sr/86Sr)¡703858 and 0.703855, respectively). It is suggested that the magma for the Yiwu granitic complex was produced by partial melting of a Neoproterozoic depleted-mantle-sourced juvenile mafic crust, and the alkali-feldspar granite represents the residue of the monzogranite parental magma after fractionation of plagioclase, apatite, Ti-Fe-oxides, sphene, monazite, allanite, zircon etc.

Feng H.,Nanjing University | Feng H.,Northwest University, China | Wu C.-Z.,Nanjing University | Wu C.-Z.,Northwest University, China | And 5 more authors.
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2012

The Yangmadian Mo deposit is located in western Liaoning province, eastern part of the Yanshan-Liaoning Mo (Cu) metallogenic belt. The Yangmadian granitic pluton associated with the molybdenum mineralization is composed of three main different lithofacies, porphyraceous granite, coarse-grained granite and fine-grained granite. Their major minerals include quartz (30%-45%), K-feldspar (35%-50%), plagioclase (15%-25%) and biotite (3%-5%). Orebodies of the Yangmadian Mo deposit occur mainly in the fine-grained granite, and minor in the coarse-grained granite and porphyraceous granite. Geochemical researches show that the pluton is rich in Si (w(SiO2)=69.26%-76.44%), alkalis (w(Na2O+K2O)=7.87%-8.81%), poor in Ca (w(CaO)=0.36%-1.33%), Mg (w(MgO)=0.17%-0.61%), Fe (w(FeOT)=1.47%-3.39%), potassic (K2O/Na2O=1.05-1.31) and metaluminous (A/CNK=0.90-1.00). The pluton is generally enriched in Large Ion Lithophile Element (LILE, such as K, Rb, Th and LREE), normal in High Field Strong Element (HFSE, such as Nb, Ta, Zr, Hf and HREE), slightly depleted in Medium REE, and displays a "V" shape chondrite-normalized REE patterns with strong negative Eu anomalies (δEu=0.26-0.76). Both evolution characters of the minerals and geochemical characters of the rocks indicate that the Yangmadian pluton were resulted from different degree fractional crystallization of the common parent magma, which derived from the part melting of lower crust materials under high-pressure granulite facies. The isotopic dating indicates that LA-ICP-MS zircon U-Pb ages are (192.1±1.9) Ma, (189.5±1.4) Ma, and (189.3±3.3) Ma for porphyraceous, coarse-grained and fine-grained granite, respectively. Based on comprehensive researches on existing geological data, it can be conclude that petrogeny and metallogeny of the Yangmadian pluton were resulted from the Early Jurassic reactivation of the residual mantle wedge induced by subduction of the Paleo-Asia Ocean in Paleozoic period.

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