滇桂交界区印支期增生弧型造山带：兼论与造山作用耦合的盆地演化

INDOSINIAN TURKIC-TYPE OROGEN BORDERING YUNNAN AND GUANGXI：WITH REFERENCE TO COUPLED BASIN EVOLUTION

吴根耀 马力 钟大赉 吴浩若 季建清 邝国敦 徐克定

Wu Genyao Ma Li Zhong Dalai Wu Haoruo Ji Jianqing Kuang Guodun Xu Keding

中国科学院地质与地球物理研究所, 北京 100029 2. 中石化集团公司江苏油田, 江苏, 江都 225261 3. 北京大学地质学系, 北京 100871 4. 广西壮族自治区地质矿产局地质勘查研究院, 广西, 南宁 530023 5. 中国石油天然气总公司浙江石油勘探处, 浙江, 杭州 310013

简要介绍了中越交界处古特提斯缝合线的展布,首次报道了八布-PhuNgu洋壳形成的Sm-Nd等时线年龄328.3Ma.该洋盆自早二叠世至中三叠世一直处于向南西的消减中,不同时期的火山弧和被动大陆边缘的位置指示它为后退式消减,被刮削下来的海台碳酸盐岩和活动大陆边缘的火山-沉积岩增生在越北地块上使后者不断向北东成长.晚三叠世时华南次大陆与增生了的越北地块碰撞,增生的火山-沉积楔仰冲超叠在前者上.讨论了增生弧型造山带的主要特点,以贵州为主要实例探讨了与造山作用耦合的盆地演化,提出油气勘探的有利地区是因下插而掩埋的华南次大陆的海相上古生界和三叠纪前渊-前陆沉积.

The Babu-Phu Ngu ocean bordering China and Vietnam separated the Vietbac Block from the Huanan (South China) Subcontinent,with rifting started from the Devonian.The oceanic crust must have been created in Early Carboniferous,evidenced by the Sm-Nd isochron age of 328.3 Ma from the ophiolite,and in the oceanic basin some submarine plateaus occurred on which the shallow marine carbonate rocks deposited during Late Paleozoic.Beginning from the Early Permian the ocean subducted southwestwards,with the magmatic arc migrating toward the ocean.Correspondingly,the passive continental margin migrated northeastwards.The southwestward subduction and arc migration toward the northeast kept on in Early-Middle Triassic,when the passive continental margin inverted to foredeep where flysch formation well developed in areas bordering Guangxi-Guizhou.During the subduction,the carbonate rocks on submarine plateaus,plus the volcano-sedimentary rocks of active continental margins,were accreted onto the Vietbac Block.In Late Triassic,the accreted Vietbac Block collided the Huanan Subcontinent,and the accreted volcano-sedimentary wedges obducted the latter.The molasse deposits (the Erqiao Formation) occurred accompanying with the collision,but now preserved in the central Guizhou only.The stacking up of crustal wedges resulted in the thickening of continental crust,and the orogenic area uplifted and eroded in Juro-Cretaceous.The lithospheric delamination and related collapse rifting might hardly occurred,since the collision did not occur between two lithospheric plates.In short words,the Paleotethysides bordering Yunnan and Guangxi may have been a Turkic-type orogen,which controlled developing of the coupled basins both in continental margins and intracontinental (intracratoi nic) ones.The examples from Guizhou as well as Hunan and east Sichuan revealed that the change of tectonic regime (from sea-floor spreading to oceanic subducting) resulted in a regional compressive stress field and a group of comtemporaneous folds constraining intracratonic sedimentation.Based on analysis of relation between the orogenesis and coupled basin developing,the potential areas for oil-gas exploration are suggested as follows:1) The underthrust and buried marine Upper Paleozoic deposited on the Huanan Subcontinent,especially,to the northeast side of the Youjiang fracture;2) the buried Triassic sediments in the foredeep and foreland basins,as well as the Upper Paleozoic on the South Guizhou Slope.

国家自然科学基金(编号49572154和49672091);中石化集团公司油田部南方海相油气勘探项目经理部项目

https://doi.org/10.11781/sysydz200101008