扬子大陆的陆内俯冲与大陆的缩小

扬子大陆的陆内俯冲与大陆的缩小

邓晋福赵海玲莫宣学刘厚详罗照华

中国地质大学

收稿日期:1995-03-20 修回日期:1995-03-20 出版日期:1995-09-20 发布日期:1995-09-20

INTRACONTINENTAL SUBDUCTION OF THE YANGTZE CONTINENT AND CONTINENT REDUCING—INFERRED FROM MUSCOVITE (TWO MICA) GRANITES

Deng Jinfu, Zhao Hailing, Mo Xuanxue, Liu Houxiang, Luo Zhaohua

China University of Geosciences, Beijing, 100083

Received:1995-03-20 Revised:1995-03-20 Online:1995-09-20 Published:1995-09-20

摘要/Abstract

摘要： 本文简要论述了白云母花岗岩是陆内俯冲的岩石学记录。华南大陆与天水－雅江地带广泛分布中生代二云母花岗岩侵入体，已有的同位素年龄范围为２４５－１２２Ｍａ，与此同时，它们两侧的扬子大陆发育的陆褶皱带，这种成对性及其构造配置表明，扬子大陆华击大卢松潘－甘孜褶皱带发生的过陆内俯冲作用，基于二云母花岗岩带的总宽度，估算扬子大陆最小的总俯冲量至少为６５０ｋｍ，扬子大陆现今宽度的６８０ｋｍ，这样，扬子大陆在中生代时期由于陆内俯冲怍用缩小了约一半；另一可能方案是，消失的主要是夹持于扬子太陆与江南造山带之同的一个微大陆，扬子大陆与秦岭造山带之问的壳内构造边界不具陆内俯冲性质，而是逆冲推复－走滑构造带，在大地构造单元上，江南造山带与龙门山造山带应分属两个上叠大陆，而不属于扬子大陆。华南中生代造山带内侧属于高喜马拉雅型陆内俯冲带(缝合带内无蛇绿岩伴生)，而不是雅鲁藏布江型(缝合带内有蛇绿岩伴生)。陆内俯冲作用是华南大陆形成的主要机制之一。此外，它经受过晚元古代和加里东期陆内俯冲事件，可能属于雅鲁藏布江型。多次陆内俯冲和白云母(二云母)花岗岩的形成导致亲陆壳金属元素富集，可能是华南W-Sn-Sb-Nb-Ta-REE-U 等大型、超大型矿床形成与群集的深部动力学背景。

Abstract: This paper briefly demonstrates that the muscovite (two-mica)granite is a petrological record of intracontinental subduction. The Indosinian-Yanshan Lan (245-122M a) two-mica granites are widely distributed in the South China Continent and the Tianshui-Yajiang region, and the foreland fold-belts are developed on both side of the Yangtze Continent. Such a symmetric feature and their structural setting indicate the intracontinental subduction of Yangtze Continent beneath both the South China Continent and the Songpan-Ganzi fold belt. Based on both the total width of two-mica granite zones on both sides of the Yangtze Continertt (about 650km ),the minimum subducted width of Yangtze continent is estimated to be 650km. The present width of Yangtze continent is about 680km,therefore the Yangtze Continent and is reduced at least to about one half of its original width by the Mesozoic intracontinental subduction. Alternatively, the subducted area may be a m icro-continent situated between the Yangtze Continent and Jiangnan orogenic belt. This paper gives a criterion to recognize and distinguish the intracontinental subduction zone and the thrust tectonic zone. The tectonic boundary between the Yangtze Continent and Qinling orogenic belt is a thrust-strike slip tectonic zone rather than a intracontinental subduction zone. The Jiangnan orogenic belt and Longmenshan orogenic belt a believed to be the overriding continents, rather than to belong to the Yangtze Continent. The inner side of the Mesozoic Southeast orogenic zone is considered to belong to the Higher Himalaya-type in tracontinental subduction zone rather than to the Yarlu Zangbo-(Tsangpo-)type or the Hsu’s (1987) collision orogenic zona-type. The intracontinental subduction is believed to be the main mechanism for the formation of the South China Continent, which underwent both of the Neoproterozoic and the Caledonian intracontinental subduction events resembling the YarluZangbo-type or the Hsu’s (1987) collision orogenic zone type. Both the multiple intracontinental subduction and formation of muscovite granites with consequent concentration of the metallic elements of continental crust affinity may be a favouruble dynamic background for the formation of the large and superlarge W –Sn-Sb-N b-Ta-REE-U ore deposits in the South China Continent

邓晋福赵海玲莫宣学刘厚详罗照华. 扬子大陆的陆内俯冲与大陆的缩小[J]. J4.

Deng Jinfu, Zhao Hailing, Mo Xuanxue, Liu Houxiang, Luo Zhaohua. INTRACONTINENTAL SUBDUCTION OF THE YANGTZE CONTINENT AND CONTINENT REDUCING—INFERRED FROM MUSCOVITE (TWO MICA) GRANITES[J]. J4.