非洲中部基巴拉带的地质及构造演化特征  

Geological and tectonic evolution characteristics of the Kibara Belt in central Africa

作　　者：许康康[1] 刘晓阳[1] 何胜飞[1] 孙凯[1] 龚鹏辉[1] XU Kangkang;LIU Xiaoyang;HE Shengfei;SUN Kai;GONG Penghui(Tianjin Centre,China Geological Survey,Tianjin,300170)

机构地区：[1]中国地质调查局天津地质调查中心

出　　处：《地质论评》2019年第4期993-1006,共14页Geological Review

基　　金：中国地质调查局项目(编号:DD20190439)的成果~~

摘　　要：基巴拉带(Kibara Belt)是位于非洲中部的一条中元古代构造带,该带对于重建哥伦比亚和罗迪尼亚超大陆具有重要的地质意义。以古元古代的Ubendian—Rusizi带为界,基巴拉带可分为两部分:北部Karagwe—Ankole带(KAB)和南部Kibaride带(KIB)。其中Karagwe—Ankole带又被Kabanga—Musongati(KM)基性—超基性线性杂岩体分为东部区域(ED)和西部区域(WD),其内分别沉积有Kagera超群和Akanyaru超群,而南部Kibaride带内沉积有Kibaran超群。所有地层开始沉积于乌本迪造山作用之后,且碎屑物主要来源于坦桑尼亚克拉通及周边古元古代的活动带。基巴拉带内发育有不同成因的基性—超基性岩浆作用,年龄为1375~1400 Ma左右,早于或近同期于最早期的花岗质岩浆作用。带内发育的花岗质岩浆从早到晚分为4期:D1期、A型、D2期及含锡花岗岩浆作用,除A型花岗质岩浆作用可能来源于亏损地幔外,其他3期都为变质沉积岩局部熔融的产物。根据地层序列及岩浆活动期次,可以将整个基巴拉带的构造演化划分为:①俯冲作用前沉积阶段:1780 Ma左右的东部区域沉积和1420 Ma左右的西部区域和/或Kibaride带内沉积作用;②俯冲作用阶段:1400~1375 Ma左右的基性—超基性岩浆作用、1375 Ma左右的D1期花岗质岩浆作用和1200 Ma左右的A型花岗质岩浆作用;③陆陆碰撞阶段:1100 Ma左右的D2期岩浆作用;④碰撞晚期和碰撞后阶段:980 Ma左右的含锡花岗质岩浆作用和之后的Itombwe超群沉积。The Kibara Belt is an important Mesoproterozoic tectonic belt in central Africa,which is of great significance for the reconstruction of the Colombia and Rodinia supercontinents.The Kibara Belt can be divided into two parts:the Karagwe-Ankole Belt(KAB) in the north and the Kibaride Belt(KIB) in the south,and the boundary between them is Paleoproterozoic Ubendian-Rusizi Belt.The KAB can be further divided into Western Domain(WD) and Eastern Domain(ED) by Kabanga-Musongati mafic-ultramafic intrusions,in which Kagera Supergroup and Akanyaru Supergroup deposited respectively,whereas the Kibraran Supergroup deposited in KIB.All the lithostratigraphic units began to deposit after the Ubendian orogeny and the debris was mainly derived from the Tanzania Craton and the surrounding Palaeoproterozoic belts.There are mafic and ultra-mafic magmatism of about 1375~1400 Ma in KAB and KIB which have different genesis.The granitic magma is mainly divided into four stages from early to late:D1,A-type granite,D2 tin-granite.The A-type granite may be related to the depleted mantle and the others are the product of partial melting of metamorphic sedimentary rocks.Based on the stratigraphic sequence and the ages of the magma,the tectonic evolution of the Kibara Belt can be divided into:(1) Pre-subduction sedimentary stage:deposition in ED at about 1780 Ma and in WD and/or KIB at about 1420 Ma.(2) Subduction stage:mafic and ultra-mafic magmatism from about 1400 Ma to 1375 Ma,D1 granitic magmatism at about 1375 Ma and A-type magmatism at about 1200 Ma.(3) Continental collision stage:D2 magmatism at about 1100 Ma.(4) Late and post-collision stage:tin-granitic magmatism at about 980 Ma and Itombwe Supergroup deposited later.

关 键 词：地层 基性-超基性岩浆作用 花岗质岩浆作用 构造演化 基巴拉带 非洲 

分 类 号：P542[天文地球—构造地质学] P534.3[天文地球—地质学]