摘要
据３３３个白云母ｂ０值，结合区域地层和构造的研究成果，提出：（１）原称昌宁－孟连变质带解体为西盟－勐统变质带（加里东期中压变质带）和澜沧双变质带的高压亚带，两期高压变质作用分别与海西－印支期的洋壳消减和陆－陆碰撞有关；（２）石鼓变质带是三个逆冲岩片的叠置，各岩片内岩石的变质作用各具特色；（３）金沙江洋盆为地块间小洋盆，其消减及嗣后的弧－弧碰撞可能不产生高压变质作用。在此基础上探讨了白云母ｂ０值在造山带研究中的意义。
Based on 333 bo values of white micas in meta-pelites from West Yunnan,as well as recent contributions of the regional stratigraphy add structural geology, the following knowledges are presented (1)The originally Changning-Menglian metamorphic belt must be separated into two ones : the Ximeng-Mengtong metamorphic belt and the high-pressure srb-belt of Lancang paired metamorphic belts. The former is a Caledonian medium-prssure one,with average Bo value of white micas 9.010 A.(2)Two generation of metamorphism, with average bo values of white micas 9.045 A and 9.070 A respectively,are metamorphic belts,which should be related to subdtiction of oceanic crust and continent-continent collision respectively, The datings of 279 Ma,215 Ma and193.4 Ma from the blueschist indicate that the subduction and collision occur in Farly Permian and Late Triassic-Early Jurassic respectively.(3 ) The Shigu metamorphic belt is composed of three overlapped slabs, one is Jinningian medium-pressure metamorphic belt with average bo value of white micas 9.012 A;the second is Caledonian medium-and high-pressure one,bo values ranging from 9.006 A to 9.070A;and the third Variscan low-pressure and high-temperature metamorphic belt,bo value being 8.994 A.(4)the Jinshajiang Oceanic Basin might be an inter-arc small one,its closure and followed arc-arc collision may not be accopanied with high-pressure metamorphism. Tectonically,the West Yunnan area is a part of the Sanjiang Indosinides,the geostructure being very complicated. A study of bo values of white micas will be helpful for structural analysis and stratigraphic work of an orogenic collage. In addition to the Shigu metamorphic belt,the high-pressure sub-belt of Lanchang paired metamorphic belts can furnish another example. TZie Upper Proterozoic is characterized with early medium-pressure metamorphism overprinted by late high-pressure one, and the Upper Paleozoic with high-pressure metamorphism; in the sub-belt some rocks which are only experienced medium-pressure metamorphism might be once a part of the Ximeng-Mengtong metamorphic belt and overthrusted eastwards in the Himalayan orogenesis during Tertiary. To study orogenic collage should be a multi-disciplinally synthetic work,and research On bo values of white micas from greenschist facies-meta-pelites might play a role in such a work.
出处
《大地构造与成矿学》
EI
CAS
CSCD
1996年第4期310-318,共9页
Geotectonica et Metallogenia
基金
国家自然科学重大基金
国家自然科学基金
关键词
泥质岩
白云母
b0值
地质构造
地质意义
b_0 values of white micas,metamorphic geology, Sanjiang Indosinides,West Yunnan area
