大容山花岗岩形成的物理化学条件和地质背景推测  

THE PHYSICOCHEMICAL CONDITION AND TEH GEOLOGICAL BACKGROUND IN FORMATION OF DARONGSHAN GRANITES

作　　者：汪绍年 Wang Shaonian

机构地区：[1]广西区域地质调查队

出　　处：《岩矿测试》1983年第1期12-16,共5页Rock and Mineral Analysis

摘　　要：大容山花岗岩体位于桂东南地区,呈北东向巨大长条状岩基产于云开大山后加里东隆起的西北侧晚古生代以来长期活动的北东向断裂带内,为一复式岩体,主体由堇青石黑云母花岗岩组成,可分内部相、过渡相、边缘相,最边缘还有紫苏辉石花岗斑岩出露。岩体以普遍含包体,暗色团块,堇青石、硅线石、石榴石等矿物为特征。 岩体不同部位主要矿物成分变化不大(表1),多属花岗岩.Darongshan granitic body occuring as an elongated batholith is composed of cordierite-biotite granite and monzonitic granite, commonly containing dark enclaves, cordierites, sillimanites and garnets, etc. Most of them are the unmelted restites during the formation of magma and only a part of cordierites crystallized from magma at depth. The granites crystallized from magma at temperature about 680-710℃ under pressure 2-3 Kb and characterized by lower fo2. These show that the granites are the mezo-abyssal intrusions. The magma which make up the Darongshan body is rich in Al and poor in Na and its degree of water suturation is lower than that in common granite. It formed possibly in anatexis of metamorphic sediments riched in Al and Si (high-grade amphibolite facies). According to the compositions of the unmelted restites auther infers that the magma was produced under pres-surs about 4-6 Kb at temperature 680-730℃. Dungwu movement gave rise to the formation of orogentic belts and made a favourable condition for the anatexis. Later the fault movement brought about the formation of magma and resulted it in an emplacement from late Permian to early Triassic period.

关 键 词：黑云母花岗岩 物理化学条件 主要矿物成分 大容山 紫苏辉石 地质背景 花岗岩体 花岗斑岩 

分 类 号：P61[天文地球—矿床学]