Phanerozoic Metamorphic Episodes and Characteristics of Cathaysia Block
Phanerozoic Metamorphic Episodes and Characteristics of Cathaysia Block
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发表时间：
2007
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通讯作者：
Shu Liangshu
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作者：
Shu Liangshu
华夏地块经历了多期变质作用。加里东期变质作用在大部分地区发生，变质程度最高达麻粒岩相。麻粒岩分布于华夏地块，北东向平行于造山带。认为变质作用发生在造山环境中，可能是扬子地块与冈瓦大陆北部拼装碰撞，导致冈瓦大陆北部被动大陆边缘沉积物变形变质的结果。根据粤东梅县片麻岩和兴宁混合岩的LA-ICPMS锆石U-Pb定年结果和附近变质岩中独居岩的年代学数据，华夏地块的海西变质作用主要发生在260~280 Ma，比典型的中欧大陆海西造山事件要晚。华夏地块的海西变质作用是局部分布的，可能发生在伸展背景下。华夏地块印支期变质作用范围较广，华夏西南部大荣山-十万大山地区变质程度可能达到麻粒岩相。其他地区的变质作用以中低压面系为特征，可能与印支晚期造山作用的伸展环境有关。La ICPMS锆石U-Pb同位素分析表明，华夏中部印支期变质作用发生在231~232 Ma之间。分布在台湾中国东南部沿海和台湾中部山脉的燕山期变质岩具有成对变质带的特征。这可能表明变质作用与中国东南部的太平洋俯冲有密切关系。印支期至燕山期变质带方向不同，表明影响华夏地块的构造体制在这两幕中发生了转换。
There were several episodes of metamorphism in the Cathaysia Block. The Caledonian metamorphism occurred over the most area, and the highest grade was up to granulite facies. The granulites scatter over the Cathaysia Block with NE direction parallel to orogeny belt. It is proposed that the metamorphism took place in the orogenic setting, which likely resulted from the assembling and colliding of the Yangtze Block to the northern Gondwanaland, leading to deformation and metamorphism of sediments in the passive continental margin of the northern Gondwanaland. According to LA ICP-MS zircon U-Pb dating results of the Meixian gneiss and Xingning migmatite in eastern Guangdong Province and geochronological data of the monazites from nearby metamorphic rocks, the Hercynian metamorphism in the Cathaysia Block mainly took place at 260～280 Ma, younger than the typical Hercynian orogeny event in the central European continent. The Hercynian metamorphism in the Cathaysia Block was locally distributed, and probably occurred under the extension setting. The Indosinian metamorphism was wider in the Cathaysia Block, and the metamorphic grade in the Darongshan-Shiwandashan area at southwestern Cathaysia might reach granulite facies. The metamorphism in other regions was characterized by middle-low pressure faceis series, which might be related with the extension setting in late Indosinian orogeny. LA ICP-MS zircon U-Pb isotope analyses indicate that the Indosinian metamorphism in the central Cathaysia occurred at 231～232 Ma. The Yanshanian metamorphic rocks, which are distributed along the coastal area of southeastern China and Central Range of Taiwan, show the feature of paired metamorphic belts. It probably suggests that the metamorphism be closely related with the subduction of Pacific Ocean under the southeastern China. The directions of metamorphic belt were different from Indosinian to Yanshanian events, indicating that tectonic regime influencing the Cathaysia Block was transformed in these two episodes.