摘要
临沧花岗岩侵入体是一个多期次侵入活动所形成的复式岩基，其主要岩石类型为黑云母二长花岗岩。岩基形成的构造环境，早期为岛弧环境；晚期系大陆碰撞造山环境。根据同位素物源定量模拟，反映出岩基岩浆物质来源的不均匀性和复杂性，岩浆物源成分主要为上地壳、下地壳及一定量的上地幔等组分。临沧岩基经历了较长时间的形成演化，不同构造环境迁移变化，并经过后期构造作用的强烈改造，其现今产状为一巨大的花岗岩推覆体。据现有研究程度，按照岩基的基本特征，可将岩基划分为三个“岩基段”或“岩体”，即晓街、临沧及勐海等三个岩段，其简要特征如下：（１）临沧岩段形成于晋宁期，处于岛弧环境，形成岛弧型花岗岩，主要显示Ⅰ型花岗岩特征，系早期洋壳板块俯冲作用的产物。继后其构造环境转化为碰撞造山环境，早期成分受到后期构造—岩浆作用的强烈改造，因而岩段内含有较多的华力西期、印支期，可能还有加里东期的侵入体。（２）晓街、勐海两岩段分别系印支期，华力西晚期—印支期的产物，两岩段是本区主构造作用期所形成之大规模碰撞型花岗岩，主要显示Ｓ型花岗岩特征。
Lincang granite intrusive body is a composite batholith formed by polyphasic intrusion,whose main rock type is the biotite adamellite.The structural environment of it is an island arc earlier and a land colliding orogenetic environment later.According to the quantitative model of isotopic origin,the magmatic origin of batholith is uneven and complicated.The magmatic compostion is mainly origindted from the upper crust,the lower crust,and the upper mantle in some extent. The Lincang body has experienced a long formation evioution,move and change in different structural environments,and the intensive reformation by the late structural activity.The present occurrence of it is a great granite nappe.Basing upon the present research work,this batholith can be divided into 3' botholith members'or'bodies'according to the basic characteristics of it,ie Xialjie, Lincang and Menghia 3 members.The brief characteristics are as follows.(1)The Lincang member was formed in an island arc ij Jinning stage.It is the granite of island arc type, mainly shows the characteristics of I type granite,resulted from the subduction of the earlier ocean crust plate.Later,the structural environment changed into a colliding orogenetic one, the earlier composition was intensively reformed by the later structural-magmatic action,so that there are more Variscan,Indosinian, probably also Caledonian intrusive bodies in the rock member.(2)Xiaojie and Menghai rock members were separately formed in Indosinian, Late Variscan-Indosinian.They are the colliding type granite in large scale formed in the mainstructural stage of this area and mostly show the characteristics of S type granite.
出处
《云南地质》
1996年第1期1-18,共18页
Yunnan Geology
基金
地质矿产部八五计划重点地质科研项目
