固原硝口岩盐矿区及其周缘断裂体系与特征

Fault System and Characteristics of Rock Salt Deposit and Its Peripheral in Xiaokou,Guyuan

固原地区硝口岩盐矿为宁夏境内已发现的大型沉积型岩盐矿床,局部已进入成熟开发阶段,已有钻探成果表明,构造对岩盐矿的分布具有明显的控制作用,但对于矿区断裂的展布特征认识仍存在较大争议,制约着岩盐矿下一步的开发利用。本文以1∶5万区域重力资料为基础,辅以钻孔资料、CSAMT剖面资料对硝口岩盐矿区周缘构造体系进行了厘定,精细地刻画了硝口矿区构造的展布特征。结果显示:自喜马拉雅造山运动开始,受到青藏高原块体持续挤压作用,矿区及周缘先后形成了北西向与北东向两组不同性质、不同展布特征的断裂体系;硝口岩盐矿发育四条北西走向断裂正断层与两条北东向走滑断层,内部的两条北北西向断裂将硝口岩盐矿区分为西部堑块、中部垒块与东部堑块三个构造单元。

The Xiaokou rock salt deposit in Guyuan area is a large-scale sedimentary rock salt deposit discovered in Ningxia,which has entered a mature development stage locally.The drilling results show that the structure has obvious control effect on the distribution of rock salt deposits,but there is still a big controversy about the distribution characteristics of faults in the mining area,which restricts the further development and utilization of rock salt mines.Based on 1∶50,000 regional gravity data,supplemented by borehole data and CSAMT profile data,this paper determines the peripheral structural system of the Xiaokou rock-salt mining area,and finely describes the structural distribution characteristics of the Xiaokou mining area.The results show that since the beginning of the Himalayan orogeny,two sets of NW-trending and N-E-trending fault systems with different properties and different distribution characteristics have been formed in the mining area and its peripherydue to the continuous compression of the Qinghai-Tibet Plateau blocks;four NW-trending normal faults and two NE-trending strike-slip faults were developed in Xiaokou rock salt deposit.The two internal NW-trending faults divide the Nikou rock salt deposit into three structural units:the western graben block,the central barrier block,and the easterngraben block.