东秦岭北部富碱侵入岩岩石化学与分布特征  

Major element characteristics of the alkali-rich intrusive rocks zone and distribution of the subzones in the north ern part of east Qinling, China

作　　者：张正伟[1] 朱炳泉[1] 常向阳[1] 谢静[1] 

机构地区：[1]中国科学院广州地球化学研究所

出　　处：《岩石学报》2002年第4期468-474,共7页Acta Petrologica Sinica

基　　金：国家自然科学基金 (编号 40 0 72 0 0 3 );中科院知识创新工程重要方向项目 ( KZCXZ-SW-12 5 );国家重点基础研究发展规划项目(编号 :G19990 43 2 )资助

摘　　要：在东秦岭北部 ,富碱侵入岩的侵位与空间分布受同一个区域构造带 (华北陆块南缘 )控制 ,构成一个区域性的富碱岩浆岩带。根据岩石学和岩石化学研究 ,岩石类型主要分为三大类 :(1)碱性岩类 ,即含有似长石或碱性暗色矿物的正长岩类 ;(2 )碱性花岗岩类 ,包括钠铁闪石花岗岩及孪生的钾长花岗岩类 ;(3)石英正长岩类 ,包括碱性长石为主的石英正长岩、英碱正长岩和花岗正长 (斑 )岩类。根据富碱岩浆岩带的岩石化学特征 ,自北而南可以划分为三个亚带 :北部碱性岩亚带 ,以 Si O2 饱和而 Al2 O3不饱和出现碱性暗色矿物为特征 ;中部碱性花岗岩亚带 ,以 Si O2 强饱和而 Al2 O3不饱和出现碱性暗色矿物和大量石英为特征 ;南部石英正长岩亚带 ,以 Si O2 和 Al2 O3都饱和但 Ca O强烈亏损 ,缺乏 Ca质斜长石 ,出现碱性长石占长石总量的绝对优势 (一般 >95 % )为特征。三个亚带富碱岩浆在化学成分方面虽有差异 ,但共同具有富碱高钾特征 ,AL K=10～ 15 ,K2 O含量范围 5 %～ 15 % ,K2 O/ Na2 O=1.2 6～ 8.30。The alkali-rich intrusive rocks are mainly located in Luonan-Lushi-Queshan area in the northern part of East Qinling, central China, and their occurrences are controlled by, a regional tectonic zone. Based upon systematic petrographic and geochemical studies, the intrusive rocks are divided into three types: ( 1) The alkaline rock type, that is syenitoid containing foid or alkaline dark minerals; (2) The alkaline granitoid including arfredsonite granite and assemblage moyite; (3) quartz syenite including quartz syenite, nordmarkite and granosyenite(porphyry), which took alkaline feldspars as the dominate factors. All these rocks consisted an alkali-rich magmatic rock belt in space, that can be divided into three subzones according to the features of petrochemistry from north to south: the northern subzone of alkaline rock, middle subzone of alkaline granitoid and southern subzone of quartz syenite (porphyry). The three subzones of alkali-rich intrusive rocks belong to the same category of the high-K, ALK = 10similar to15, K2O = 5%similar to15%, K2O/Na2O = 1.26similar to8.30.

关 键 词：分布特征 富碱侵入岩 岩石化学 东秦岭地区 化学成分 

分 类 号：P588.12[天文地球—岩石学]