Geochronology, geochemistry and petrogenesis of the tungsten-bearing porphyritic granite in the Dahutang tungsten deposit, Jiangxi Province
The porphyritic granite containing high tungsten content (typically several hundreds of × 10-6) is discovered in the Dahutang area,Jiangxi Province,South China.The tungsten content is dozens to hundreds of times higher than the normal barren granites.In this paper,we reported detailed studies on the LA-ICP-MS zircon U-Pb dating,major elements,trace elements,zircon Hf isotopic compositions and whole-rock Nd isotopic compositions of the tungsten-bearing porphyritic granite.The studies of petrography and geochemistry of this rock indicate that it is highly fractional S-type granite,possessing the characteristics of silica-rich,high alkalinity,high Ga/Al ratios,low zircon saturation temperatures,enrichment in LILEs and depletion in HFSEs and significant negative Eu anomalies.Hence,this rock belongs to peraluminous granite.Its εNd(t) and εHf(t) values varied from-7.45 to-8.20 and from -2.43 to-8.23,respectively,and the calculated two-stage model ages (tDMC) of Nd and Hf isotopes are as 1534 ～ 1595Ma and 1312 ～ 1677Ma,respectively.Coupled with the values of CaO/Na2O (＜ 0.3),these data suggest that pelitic metasediments of Proterozoic Shuangqiaoshan Group may be the source rocks for the porphyritic granite.The porphyritic granite shows typical geochemical features of Li-,and Rb-rich,Ba-,Zr-,and ΣREE-depletion,with the GCI values ＞0.The values of Ba/Rb ＜ 0.6 and Rb/Zr ＞ 6 can be used to distinguish the tungsten-bearing granite from the barren granite.It is likely that the magma had extracted tungsten from the tungsten-rich Shuangqiaoshan Group metasedimentary rocks during partial melting of these source rocks.Extreme fractional crystallization resulted in further enrichment of tungsten in the evolved granitic magma which led to later precipitation of tungsten from the magmatic-hydrothermal fluids.
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万方数据
维普
