摘要:
白马山小岩体位于西秦岭白马山金矿区内,与矿床具有密切的空间关系。通过研究白马山岩体主量、微量及稀土元素地球化学特征及 Sr‐Nd‐Pd 同位素组成特征,探讨其岩石成因。白马山石英闪长岩属高钾钙碱性系列岩石,具有与“C”型埃达克岩相似的地球化学特征。 Sr‐Nd‐Pb 同位素组成特征显示,该小岩体富放射性成因 Pb ,初始(87 Sr/86 Sr)t 比值为0.70637,εNd(t)=-6.75,具有较高的 T DM 值(1.53Ga),说明岩浆主要来自于大陆下地壳,且与耀岭河群的基性火山岩相似,这些“C”型埃达克质岩浆可能源于加厚基性下地壳的部分熔融,其残留相为(角闪)榴辉岩。
Abstract:
The Baimashan small rock body ,related to gold deposit in space ,is located in the Baimashan gold mining field ,western Qinling metallogenic belt .This study conducted geochemical characteristics a‐nalysis of main elements ,trace elements and rare earth elements ,and Sr‐Nd‐Pd isotopic composition so as to understand its petrogensis .The results indicate that these rocks belong to high K calc‐alkalic series and have geochemical compositions similar to the C‐type adakite .Sr‐Nd‐Pb isotopic compositions show that the rock body is characterized by enrichment of radiogenic Pb ,with initial ( 87 Sr/86 Sr)t of 0 .706 ,negativeεNd(t) of ‐6 .75 ,and T DM of 1 .53Ga ,implying that the magmas should derive from lower continental crust and geochemically similar to the mafic rocks of the Yaolinghe Group .It can be concluded that the rock might result from partial melting of thickened mafic lower crust ,with residual phase being amphibole eclo‐gite .
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