中国主要高压-超高压变质带的大地构造背景及俯冲/折返机制的探讨  

Tectonic setting of main high-and ultrahigh-pressure metamorphic belts in China and adjacent region and discussion on their subduction and exhumation mechanism.

作　　者：杨经绥[1] 许志琴[1] 张建新[1] 张泽明[1] 刘福来[1] 吴才来[1] 

机构地区：[1]国土资源部大陆动力学重点实验室,中国地质科学院地质研究所,北京100037

出　　处：《岩石学报》2009年第7期1529-1560,共32页Acta Petrologica Sinica

基　　金：中国地质调查局地质调查项目(1212010918013、1212010610105、1212010711816);国家重点基础研究发展规划(973)项目(2003CB716504);国家自然科学基金重大项目(40399141)的资助

摘　　要：造山带中发现超高压矿物柯石英和金刚石,被认为与洋壳或陆壳岩片的深俯冲(>100km)有关。但探讨这些岩片是如何俯冲和折返的?却是一个极具挑战的难题。目前,中国境内含榴辉岩的高压超高压(HP/UHP)变质带已经发现11条,此外,世界各地发现的高压超高压变质带还有至少20条。高压超高压变质带,特别是中国众多的HP-UHP变质带,在什么特定的大地构造条件中形成?又是在怎样的构造背景下折返而剥露地表?中国大陆上为什么出现众多规模可观的HP-UHP变质带?为什么出现洋壳(深)俯冲与陆壳(深)俯冲不同类型的HP-UHP带?这是本文试探讨的问题。根据中国境内的11条高压/超高压变质带形成时代和区域构造背景,将其分为4类:Ⅰ.始特提斯(早古生代)高压/超高压变质带,包括(1)柴北缘-南阿尔金超高压变质带,(2)北祁连-北阿尔金高压变质带,(3)东秦岭超高压变质带;Ⅱ.古特提斯高压/超高压变质带,包括(4)大别高压/超高压变质带,(5)苏鲁高压/超高压变质带,(6)西藏羌塘高压变质带;(7)西藏松多(超)高压变质带;Ⅲ.新特提斯高压/超高压变质带,包括(8)雅鲁藏布江东构造结南迦巴瓦(超)高压变质带;Ⅳ.古亚洲域南缘高压/超高压变质带,包括(9)新疆西南天山超高压变质带,(10)甘肃北山高压变质带,和(11)冀北高压变质带。中国高压/超高压变质带形成的大地构造背景有洋壳(深)俯冲和陆壳(深)俯冲两大成因类型,认为前者大都与始-古特提斯洋盆中微陆块之间的汇聚碰撞有关;后者为大陆块之间剪式碰撞和撕裂式岩石圈舌形板片深俯冲的产物。由于中国(邻区)大陆是三大陆块与许多小陆块聚集构成的巨大拼合体,小陆块在特提斯洋盆(特别是始、古特提斯洋盆)中的独特位置,使陆块之间的刚性洋盆岩石圈得以(深)俯冲插入小陆块之下。而大陆块之间特殊部位的碰撞为陆壳(深)俯冲创造条件�Ultrahigh-pressure minerals, such its coesite and diamond, Which Occur in major orogenic belts provide evidence of deep subduction (> 100km) of both oceanic and continental crust. However, we still do not have a clear understanding of the processes by which this material is subducted and exhumed. Thus far, 11 high-and ultrahigh-pressure metamorphic (HP-UHPM) belts with eclogite facies rocks have been found in China, and at least another 20 belts have been reported elsewhere in the world, indicating that these are important and widespread tectonic features. Despite numerous Studies Over the last 20 years many questions remain, Such as: 1) What specific tectonic settings are required for the formation of the high-and ultrahigh-pressure metamorphic belts; 2) Why are such belts so widespread and well exposed in China and 3) Why are there different types of HP-UHP metamorphic belts and are these differences related to deep subduction of oceanic crust or continental crust.? Based on their ages and regional tectonic settings, the II HP-UHP belts in China can be divided into 4 groups. Group I consists of three Proto-Tethyan (Early Paleozoic) HP-UHPM belts, including the North Qaidam-South Altun UHPM belt, the North Qilian-North Altun HPM belt and the North Qinling UHPM belt. Group 11 includes four Paleo-Tethyan HP-UHPM belts, namely the Dabie HP-UHPM belt, the Sulu HP-UHP belt, the Tibet Qiangtang HPM belt and the Tibet Sumdo (U) HPM belt. The Neo-Tethyan Namche Barwa (U) HP belt in the East Himalayan Syntaxis comprises Group III. Three Paleo-Asian HP-UHPM belts, including the West-South Tianshan UHPM belt in Xinjiang, the Beishan HPM belt in Gansu and the Jibei HPM belt. in Hebei, make up Group IV. The HP-UHPM belts in China formed by (deep) subduction of both oceanic and continental crust. Subduction of oceanic crust may have occurred (luring convergence of mini-continental blocks within the Prototethyan and Paleotethyan oceanic basins. Deep subduction of continental crust probably resulted from scissor-like collision

关 键 词：高压/超高压变质作用 柯石英 金刚石 俯冲作用 折返作用 

分 类 号：P541[天文地球—构造地质学]