胶东焦家金矿床基性脉岩地球化学特征及其与金矿化的关系

Relation between Geochemical Characteristics and Gold Mineralization of Mafic Vein Rocks of Jiaojia Gold Deposit in Jiaodong Area

摘要:

野外观察发现，焦家金矿床中有成矿前和成矿后2期基性脉岩，该文对取自基性岩脉的样品进行了岩相学、主元素、微量元素及S同位素的研究，探讨了脉岩的岩石成因及其与金矿化的关系。研究区基性脉岩包括辉绿玢岩和煌斑岩，其中辉绿玢岩SiO2为47.96%，Na2O+K2O为4.075%，煌斑岩SiO2为44.20%~45.34%，Na2O+K2O为6.407%~6.45%，属玄武岩、粗玄岩和碱玄岩类；TiO2为1.31%~2.40%，Ti/Y为331~913。岩石以富集轻稀土元素（LILE）和大离子亲石元素（LREE）为特征，黄铁矿δ34S范围在（1.0~2.8）×10-3之间。研究表明，成矿前煌斑岩和辉绿玢岩具有高Ti煌斑岩的特征，而成矿后的煌斑岩则类似于低Ti煌斑岩。脉岩的岩浆来源于尖晶石—石榴石转换带软流圈地幔的部分熔融,焦家金矿床形成于高Ti与低Ti煌斑岩不同性质岩浆源区的转化过程。

Abstract:

There are 2 periods of mafic vein rocks before and after mineralization were discovered in Jiaojia gold deposit through field observation. In order to constrain petrogenesis and relation with gold mineralization, geochronology, major element, trace element and S isotope of mafic vein rocks have been studied. Mafic vein rocks include lamprophyre and sillite in Jiaojia gold deposit. And their respective content of SO2 is 47.96% and 44.20%~45.34%, and Na2O+K2O is 4.075% and 6.407%~6.45%, which is belong to tephrite, trachy-basalt and basalt. The content of TiO2 is1.31%~2.40%, and Ti/Y is 331~913. The mafic vein rocks are characterized by enrichment in LREE and LILE. δ34S is 1.0×10-3~2.8×10-3 in prite. It is showed that Lamprophyre and sillite before mineralization have the characteristics of high Ti lamprophyres, while lamprophyre after mineralization is low in Ti. The magma originated from partial melting of asthenosphere mantle in spinel-granet transferring zones. Jiaojia gold deposit was formed in transformation process of high Ti and low Ti lamprophyre magma source.