华夏地块显生宙的变质作用期次和特征

华夏地块主要存在四期变质作用。加里东期变质作用呈北东向展布于华夏的大部分地区，变质作用可达麻粒岩相，且麻粒岩断续分布平行于造山带，此期变质作用是在挤压造山构造背景下发生，很可能与扬子地块向冈瓦那大陆北缘聚合–碰撞，造成大陆边缘沉积物变形–变质有关。根据粤东梅县片麻岩和兴宁混合岩的LA–ICPMS锆石U–Pb定年以及邻区独居石U–Pb年代学的研究，海西的变质作用主要发生在260~280 Ma，年轻于欧洲典型的海西期造山时代。华夏地块的海西期变质作用分布局限，它们可能形成于拉张构造背景。印支期变质岩在华夏有较广泛的分布，西南端大容山—十万大山的印支期变质作用可达麻粒岩相，其他地区的变质作用具有中低压相系的特征，记录了造山后期伸展构造背景。LA–ICPMS锆石U–Pb定年指示华夏中部粤中地区的印支期变质作用发生在231~232 Ma。燕山期变质岩主要分布于东南沿海和台湾中央山脉，显示了双变质带的特点，表明与太平洋板块向东南沿海俯冲作用密切相关。从印支期到燕山期，变质带的方向发生了转变，说明影响华夏地块变质作用的构造域发生了改变。

Phanerozoic Metamorphic Episodes and Characteristics of Cathaysia Block

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.