桐柏-大别山南缘志留纪黄羊山碱性杂岩的暗色矿物  

Diagnostic Mafic Minerals of Huangyangshan Alkaline Complex from the Southern Margin of Tongbai-Dabie Mountains

作　　者：许聘[1] 马昌前[2,3] 

机构地区：[1]中国地质大学研究生院 [2]中国地质大学地球科学学院 [3]中国地质大学地质过程与矿产资源国家重点实验室,武汉430074

出　　处：《地质科技情报》2006年第4期63-68,73,共7页Geological Science and Technology Information

基　　金：国家自然科学基金重点项目"大别山中生代侵入岩类成因;岩浆动力学与构造体制转换"(40334037)

摘　　要：黄羊山碱性杂岩体位于桐柏-大别山南缘,其SHRIMPU-Pb年龄为(439±6)Ma。该杂岩体由石英正长岩和碱性花岗岩组成,其中以石英正长岩为主体,从中心到边缘粒度变化由粗到细。利用电子探针对该杂岩体中的特征暗色矿物的分析结果表明,角闪石和辉石的成分变化较小,角闪石显示出从铁钠透闪石到钠铁闪石的成分演化趋势,辉石主要为霓石,另外岩体中大量出现三斜闪石。根据矿物间的相互接触关系、环带结构、矿物组合的相平衡关系等识别了原生的岩浆矿物组合和次生的岩浆期-岩浆期后矿物组合,建立了矿物结晶顺序,重建了过碱性岩浆或流体的成分、温度、氧逸度的演化历史。从矿物组合的相平衡关系角度表明,黄羊山碱性杂岩体为大陆裂谷环境的产物。The Huangyangshan alkaline complex is located in the southern margin of Tongbai - Dabie Mountains. Emplacement of the complex is dated as （439±6） Ma, using SHRIMP U-Pb method. Rocktypes in the complex include quartz-syenite and alkaline granite. The former is predominant, showing a grain size decrease from the center to the margin of the complex. All the mafic minerals in the rocks are Fe-rich. ＂Detailed studies of amphibole and pyroxene show that their chemical compositions define relatively limited trends. Amphiboles show variation from ferro-richterite to arfvedsonite and pyroxenes are mainly aegirine. Another characteristic is the general presence of aenigmatite. In this study,two stages of the formation of mafic minerals are identified： the primary magmatic assemblage and the secondary post magmatic assemblage, corresponding to the sequence of magma crystallization. This study also rebuilds the evolutive history of the composition, oxygen fugacity, temperature, of the peralkaline magma or fluid. In this study,the phase equlibria illustrates that Huangyangshan alkaline complex is emplaced within the continent rifting settings.

关 键 词：桐柏-大别地区 矿物化学 钠角闪石 三斜闪石 碱性岩 

分 类 号：P588.15[天文地球—岩石学]