华南的格林威尔造山带及其坍塌:在罗迪尼亚超大陆演化中的意义

华南的格林威尔造山运动始自约1200MaB.P.,在约1000～950MaB.P.扬子与湘赣—华夏微大陆发生碰撞 ,继之以岩石圈的拆沉作用和造山带的快速坍塌 ,在仰冲板片和下插板片上分别形成华南裂谷的北支和南支 ,部分地区可能有新生洋壳出现。裂谷以北地区的造山活动持续到约740MaB.P.,碰撞高原控制了长安冰期的沉积 ,至南沱冰期沉积时它已近剥蚀夷平。文章重塑了新元古代时华南裂谷的演化 ,探讨了它在罗迪尼亚超大陆裂解中的意义

GRENVILLE OROGENS IN SOUTH CHINA AND THEIR COLLAPSE: IMPLICATIONS FOR EVOLUTION OF THE SUPERCONTINENT RODINIA

Tectonically,the South China area must have been attached to the world wide Grenville orogens.The subduction occurred from 1200 Ma B.P.,and the Xianggan Cathaysia Microcontinent collided with the Yangtze Microcontinent in 1000～950 Ma B.P.,followed by the lithosphere delamination and orogens' collapse in the collisional area.The rifts consist of the North Branch and the South Branch of the Huanan Rift in the overthrusting(the Yangtze)and the underthrusting(the Xianggan Cathaysia)plates respectively.The both might be connected by some transcurrent troughs,and some impactogens stretched into the collisional plateau.The new formed oceanic crust might be created at some localities in the collapse rift,for example,the central Jiangxi and north Guangxi along the North Branch of the Huanan Rift.The island arc related basalts and granitoids might comprehend the oceanic crust appearing in the South Branch which separated the Xianggan from the Cathaysia Microcontinents,although no ophiolite has been discovered so far. A tectonic differentiation occurred in the South China area in 850～800 Ma B.P. The orogeny kept on in the southern area of the Yangtze,and the compressional stress field might result from the further extension of the Huanan Rift and the subduction of the new formed oceanic crust.The latter is evidenced by the calc-alkine volcanic rocks,the arc related granitism and the high pressure metamorphism.The molasse sedimentation ended in about 740 Ma B.P.,then the collisional plateau controlled the distribution of glacial deposits in the Chang'an ice age.The deposits of the Nantou ice age distributed much wider,indicating the collisional plateau was eroded and peneplained,followed by the sediments of marine cover in the Doushantuo Dengying stages and Cambrian.In the area of lithosphere delamination,a violent extension and rifting occurred during this period.The developing of the Huanan Rift continued to the Early Paleozoic,which was once called the Chengjiang-Caledonian geosyncline.Owing to the volcanic exhalation and hydrothermal solution supporting the metallogenic materials,the Xinyu type iron ore deposit was created in the interval period of glaciations. The Grenville orogeny created a supercontinent,the Rodinia,and the South China area must have been a part of the supercontinent.The Neoproterozoic delamination related rifting resulted in the Rodinia breaking up,namely,the main boundaries among the microcontinents may have been created in the Phanerozoic,and the tectonic or geochemical boundaries formed in the Grenville orogeny have been buried of reprinted.It is revealed that the East Asian continent is a composite one,with most microcontinents being of Gondwana origin during the Phanerozoic.The Gondwana may originate from some relicts of the broken Rodinia.The creation and disruption of the supercontinent Rodinia is a key to understand,in the light of mobilism,the tectonic evolution of China continent during the Proterozoic.