华东南内陆地区早白垩世中期挤压构造事件及其地质意义

发布时间：2018-08-15 14:49

【摘要】：华东南大陆在中生代时期发育规模宏大的陆内变形和火成岩省,为研究大地构造过程以及陆内变形提供理想研究场所。华东南内陆赣南地区三百山盆地和版石盆地的主体由早白垩世早期武夷群火山岩系组成,它不整合在南华-寒武系变质岩系之上,并被早白垩世晚期罗塘群或晚白垩世圭峰群红色沉积岩系不整合覆盖。在三百山盆地内,南华纪变质岩推覆于武夷群鹅湖岭组火山岩之上,形成多个飞来峰。在版石盆地内,逆冲断层发育,震旦纪变质岩系逆掩于鹅湖岭组火山岩之上,且变质岩系内部发育了逆冲断层以及发生了连续的褶皱变形;武夷群石溪组地层发育褶皱构造,地层产状直立甚至倒转,且泥岩层挠曲构造相当发育,并有硅化变质现象。这些现象表明,赣南地区武夷群火山岩系形成之后发生过强烈的挤压构造事件。不整合在三百山盆地武夷群火山岩系之上的罗塘群白埠组砾岩层和不整合在版石盆地武夷群火山岩系之上的圭峰群河口组底部的砾岩层,具有近源快速堆积的特征,构造变形微弱;版石盆地东侧的会昌盆地罗塘群白埠组红色沉积岩系的构造变形微弱,不仅底部砾岩层具有近源快速堆积的特征,而且其底部夹层粗面岩具有埃达克岩和高压型粗面岩的地球化学特征。这些现象表明,赣南地区的挤压构造事件发生在武夷群火山岩系形成之后,罗塘群红色沉积岩系形成之前。火山岩年代学资料显示,版石盆地内武夷群石溪组的流纹岩以及鹅湖岭组的凝灰岩SHRIMP锆石U-Pb年龄分别为130.8±0.7Ma和142.6±1.0Ma,三百山盆地武夷群鹅湖岭组的粗面岩SHRIMP锆石U-Pb年龄为141.6±0.96Ma,会昌盆地内罗塘群白埠组的粗面岩SHRIMP锆石U-Pb年龄为110.7±1Ma。结合赣南地区普遍缺失早白垩世中期地层,说明挤压构造事件发生在131Ma之后、111Ma之前。构造变质岩年代学资料显示,版石盆地逆掩断层中新生矿物绢云母的K-Ar稀释法年龄为118.21±3.21Ma,三百山盆地变质岩系飞来峰底部的逆掩断层中新生矿物绢云母的K-Ar稀释法年龄为112.90±3.65Ma,指示挤压构造事件发生在118~113Ma之间。华东南内陆早白垩世早期(145-130Ma)广泛发育高钾钙碱性火山-侵入岩,早白垩世晚期-晚白垩世早期(110-90Ma)广泛发育铁镁质火山岩,前者构成火山-侵入岩带的主体,后者常夹于红色沉积岩系的底部。而早白垩世中期(130-110Ma)也是火山-侵入活动的相对宁静期,暗示其构造环境既不同于早白垩世早期由挤压向拉张过渡的构造环境,也与早白垩世晚期-晚白垩世早期强烈拉张的构造环境存在区别。运动学特征显示,华东南内陆早白垩世中期挤压应力方向为NW-SE向,与华东南陆缘早白垩世中期挤压构造事件的挤压应力方向一致,指示早白垩世中期华东南内陆和陆缘的挤压构造事件存在内在的联系。华东南内陆早白垩世中期挤压构造事件的确认,结合前人确认的中侏罗世挤压构造事件,为华东南地区燕山期构造演化具有拉张-挤压“手风琴”式的多旋回特征提供了充实而有力的地质证据,也为成矿构造背景分析应兼顾挤压构造事件的影响提供了依据。
[Abstract]:The Sanbaishan basin and slate basin in southeastern China are composed of volcanic rocks of the early Early Cretaceous Wuyi Group, which are unconformity to the South China-Cambrian system. In Sanbaishan basin, the South China metamorphic rocks were pushed over the volcanic rocks of Ehuling Formation of Wuyi Group, forming several flying peaks. In lithographic basin, thrusting faults developed and the Sinian metamorphic rocks were overturned in Ehuling Formation. Above the volcanic rocks, thrusting faults and continuous folding deformation occurred in the metamorphic rock series. Fold structures developed in the Shixi Formation of the Wuyi Group, and the occurrence of the strata was upright or even inverted. The deflection structures of the mudstone layers were well developed and silicified metamorphism occurred. These phenomena indicate that the volcanic rock series of the Wuyi Group developed after the formation of the southern Jiangxi Province. The Baibu Formation conglomerate of Luotang Group unconformity above Wuyi Group volcanic rock series in Sanbaishan Basin and the bottom conglomerate of Hekou Formation unconformity above Wuyi Group volcanic rock series in Banshi Basin are characterized by rapid accumulation near source and weak tectonic deformation. The tectonic deformation of the red sedimentary rock series of Baibu Formation of Luotang Group is weak, and the conglomerate strata at the bottom are characterized by rapid accumulation near source, and the interbedded trachyte at the bottom has the geochemical characteristics of adakite and high-pressure trachyte. Before the formation of the red sedimentary rock series of Luotang Group, the U-Pb ages of zircon SHRIMP from the rhyolite of Shixi Formation and tuff of Ehuling Formation of Wuyi Group in the slate basin were 130.8 6550 The U-Pb age of zircon SHRIMP from Baibu Formation of Luotang Group in the basin is 110.7 The K-Ar dilution age of Sericite in the overthrust fault at the bottom of Feilaifeng peak of the metamorphic rock series in Sanbaishan basin is 112.90 (+3.65 Ma), indicating that the compressional tectonic event occurred between 118 and 113 Ma. High-K calc-alkaline volcanic-intrusive rocks were extensively developed in the early Early Cretaceous (145-130 Ma) of southeastern China, and the late Early Cretaceous-late Cretaceous. Ferromagnesian volcanic rocks were extensively developed in the early stage (110-90 Ma), the former constituting the main body of the volcanic-intrusive rock zone, and the latter often sandwiched at the bottom of the red sedimentary rock series. The middle stage of the Early Cretaceous (130-110 Ma) was also a relatively quiet period of volcanic-intrusive activity, suggesting that its tectonic environment was different from the tectonic ring transiting from compression to extension in the early Cretaceous. Kinematic characteristics show that the compressive stress direction of the southeastern China inland during the middle stage of the Early Cretaceous is NW-SE, which is consistent with the compressive stress direction of the middle stage of the Early Cretaceous in the continental margin of southeastern China, indicating the southeastern China inland and continental in the middle stage of the Early Cretaceous. There is an intrinsic relationship between the extrusion tectonic events on the margin. The confirmation of the extrusion tectonic events in the middle Early Cretaceous in the southeastern China inland and the predecessor's confirmation of the extrusion tectonic events in the middle Jurassic provide substantial and powerful geological evidence for the Yanshanian tectonic evolution in southeastern China with the multi-cycle characteristics of tension-compression "accordion" and also provide strong geological evidence for it. The analysis of metallogenic tectonic background should give consideration to the influence of extrusion tectonic events.
【学位授予单位】：东华理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P542;P534.53

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