江西赣州西北部蛤湖地区拆离伸展构造体系

Detachment-extensional tectonic system in the Hahu area,northwestern Ganzhou, Jiangxi

在江西赣州西北部蛤湖地区发现1条韧性拆离断层,宽1～3km,倾向南东。该断层以震旦系砂页岩的构造片岩化和中酸性火山岩的糜棱岩化为特征。其上盘由5～6条铲式正断层组成,正断层的倾向与拆离断层一致,其中最上部的1条正断层控制了箕状断陷盆地的形成和分布;下盘为笔架山穹隆状复式花岗岩杂岩体及其外接触带的震旦系浅变质地层。这些构造构成了一个在成因上与拆离断层形成有关的伸展构造体系。该体系的形成与区域北东向地垒式隆起局部地段的强烈隆升有关,发生于侏罗纪至晚白垩世,其活动对内生成矿起着重要的控制作用。

A ductile detachment fault is found in the Hahu area, northwestern Ganzhou, Jiangxi Province, based on intensive field geological survey. The detachment fault is 1-3 km wide and strikes NE. It is characterized by tectonic foliation of Sinian sandstone-shale and mylonitization of intermediate-acid volcanic rocks. The hanging wall is composed of five to six listric normal faults, which dip parallelly to the dip of the detachment fault. The uppermost normal fault controls the formation and distribution of the dustpan-shaped down-faulted basin. The footwall consists of the Jurassic Bijiashan domal composite granite complex and Sinian low-grade metamorphosed strata in its exocontact zone. These structures form an extensional tectonic system that is genetically related to the formation of the detachment fault. The formation of the system is associated with the strong uplift of some segments of the regional NE-trending horst-type uplift. The system originated during the Jurassic to Late Cretaceous.