| 华北克拉通太古宙上壳岩早前寒武纪构造变形与变质作用关系——以北京密云沙厂地区为例 |
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| 摘 要： | 沙厂铁矿区上壳岩在太古宙时期经历了麻粒岩相、角闪岩相和绿片岩相的多相变质作用,这种多相变质作用的发生及其分布特点是与本区台怀运动旋回的两幕构造变形的形成有密切关系。本文根据不同变质相的矿物组合与不同变形幕构造片理的相互关系的研究得出角闪岩相退变是与台怀变形序列的第一幕变形相对应,而绿片岩相退变是与第二幕变形有联系的结论。退变质作用的不均匀性,即其强弱的表现与不同变形幕的构造变形有直接关系。
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| 关 键 词： | 太古宙 克拉通 变质作用 变形作用 |
A CASE STUDY LED IN SHACHANG, MIYUN, BEIJING, ON RELATIONSHIP BETWEEN THE EARLY PRECAMBRIAN DEFORMATION AND METAMORPHISM OF THE HIGH-GRADE ARCHEANSUPRACRUSTALS IN THE NORTHERN CHINA CRATON |
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| Authors: | Yang Zhensheng Liu Wuxu |
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| Institution: | Yang Zhensheng Liu Wuxu |
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| Abstract: | Two main deformations in Taihuai Tectonic Cycle of the late Archaean(2700-2500 Ma.)in high-grade supracrustals in the Northern China Craton are identified by a case study led in Shachang,Miyun, Beijing where are recognized two generations of four structural elements,i.e.fault, fold,foliation and lineation. The first deformation (D1) produced recumbent fold(F1)with strong transposition of lithological layers,on their surfaces, and distinct foliation (S1) and lineation with nearly SN horenzantal occurrence as that of the axes of F1. In the second deformation(D2) the structure of the supracrustals was moulded into coaxially superposed large-medium scale open folds (F2) with vertical axial planes and vertically sheared ductile faults.The minerals with preferred orientation,by which the foliations,S1 or S2,are showed, are of two phases,the active phase,formed syntectonicly,and the passive phase,crys-talized before or after deformation.The active phase representing syntectonic metamor-phism shows that the first deformation occurred in an amphibolite facies and the second deformation in green-schist facies rather than in granulite or amphibolite facies. The distribution of the active phases, both in D1 and D2, as well as the distribution of foliation S1 and S2, shows that all the two metamorphisms proceeded strongly only at places where the then synchronous deformations, D1 and D2, were strong.The granulite facies metamorphism taking place around 3000 Ma. ago had been expected to have some particular structural elements but now only banded structures are recognizable. |
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| Keywords: | Archean Craton metamorphism deformation event |
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