东秦岭造山带钠长岩的特征、成因及时代  

Characteristics and Genesis of the Albitite in the East Qinling Orogenic Belt

作　　者：李勇[1] 苏春乾[2] 刘继庆[2] 

机构地区：[1]西北大学地质系 [2]西安工程学院区调所

出　　处：《岩石矿物学杂志》1999年第2期121-127,共7页Acta Petrologica et Mineralogica

摘　　要：经１／５万区调填图，作者在东秦岭造山带夹持于竹林关－青山断裂带和山阳－豆腐尖断裂带之间的原划“九里坪组”地层中解体出了一系列规模不大的钠长岩体。通过野外宏观调查和室内测试分析，对这些钠长岩的产状、地质背景、岩石化学和地球化学特征进行了综合研究。提出了这些钠长岩是由深部钠质熔浆沿断裂带上侵到地壳浅部发生侵入－交代作用而形成的观点。其成因模式为：侵入－隐爆－充填交代。这与前人在研究西秦岭造山带钠长岩时所提出的热水沉积成因模式明显不同。另外，还从这些钠长岩体中首次获得全岩铷－锶等时线年龄为３６４９±１０９Ｍａ的资料。对研究整个秦岭造山带钠质流体热事件具有十分重要的意义。The albitite dispersed over the Qinshan_Zhulinguan area consists of a series of small intrusive and metasomatic bodies disintegrated from the “Jiuliping F ormation” which is sandwiched between Zhulinguan-Qinshan fault and Shanyan g-Doufujia n fault in the East Qinling orogenic belt. Comprehensive studies show that the a l bitite was formed by intrusive_metasomatic activity of alkali fluids (a kind of special magma or solution). Rocks of the albitite can be mainly divided into thr ee types, viz., lumpy albitite, breccia of albitite and brecciated albitite. Am ong them, the first type was formed by intrusion and the last two types were for med by cryptoexplosion and filling_metasomatism. Both the lumpy albitite and the brecciated albitite have the same Rb-Sr isochron age of 364.9±10.9 Ma, indicat ing that the activity of the alkali fluids occurred in Devonian.

关 键 词：东秦岭 造山带 钠长岩 岩石特征 岩石成因 

分 类 号：P588.122[天文地球—岩石学]