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目的探讨南秦岭五龙岩体中暗色微粒包体的成因及源区性质。方法运用岩石学及地球化学方法进行研究。结果暗色微粒包体的野外地质、显微结构、矿物组合等特征显示其曾与寄主岩浆以熔融体状态共存,并经历淬冷作用。包体为闪长质,碱质含量高,在SiO2-K2O图解上所有样品均落入橄榄玄粗岩系列,且Na2O/K2O>1;与寄主岩相比,较富镁、铁、钙、钛;强烈富集LILE和LREE,亏损Nb,Ta等高场强元素。结论暗色包体为镁铁质岩浆侵入长英质岩浆房中并与之发生混合的产物,该镁铁质岩浆源于受俯冲流体/熔体交代的富集岩石圈地幔,其源区中金云母发生熔融,残留金红石、贫Mg角闪石和石榴子石。
Objective To investigate the origin and source region of dark particle inclusions in Wulong rock mass, South Qinling. Methods Using the methods of petrology and geochemistry. Results The field geology, microstructure and mineral assemblage of the dark-colored inclusions show that they co-exist with the host magma as molten bodies and undergo quenching. The inclusions are dioritic and have a high content of alkali. All the samples in the SiO2-K2O diagram fall into the series of olivary rock with Na2O / K2O> 1. Compared with the host rock, the samples are relatively rich in magnesium, iron, calcium, Titanium; strongly enriched LILE and LREE, loss of Nb, Ta field strength elements. Conclusions The dark-colored inclusions are the product of mafic magma intruding into and mixing with the magma chamber. The mafic magma originates from the enriched lithospheric mantle that is subducted by subducting fluids / melts. Its source region, Mica occurs melting, residual rutile, poor Mg amphibole and garnet.