库车盆地古近纪和新近纪构造环境与蒸发岩沉积

库车盆地分布有沉积广厚、层数众多的古近纪和新近纪石盐岩,是我国最有找钾希望的内陆成盐盆地之一。盆地自形成以来一直处于稳定的沉降状态,在古近纪和新近纪成盐期,盆地经历了强-弱-强3个构造演化阶段,其沉降中心由北而南逐渐迁移,沉积中心由北西逐渐向东、南东方向迁移,盆地内的构造分异渐趋明显,形成了一系列次级凹陷。古近纪和新近纪成盐卤水的迁移和聚集、成盐作用的强弱以及整个含盐系的沉积发育明显受到上述构造活动的控制:含盐系的厚度随时间由北西向东、向南逐渐增厚,且厚度分布逐渐趋于复杂化;石盐岩的沉积规模和范围也逐渐向东扩大;古近纪早期和新近纪强烈的构造活动对于成盐作用而言是一种干扰因素,而古近纪中、晚期相对较弱、导致盆地缓慢持续沉降的构造活动对成盐,尤其对成钾作用则极为有利。从盆地的构造分异结果及其控制的含盐系和其中石盐岩的发育特征来看,古近纪和新近纪库车盆地已具备钾盐蒸发岩形成的构造条件。

Paleaogene and Neogene Tectonic Environment and Sedimentation of Evaporite in Kuqa Basin

There are a lot of layers of Palaeogene ang Neogene halite which are widely distributed in Kuqa basin. So Kuqa basin is one of the inland salt basins in which it is the most hopeful to search potash in China. It stably subsided after its formation. During Palaeogene ang Neogene salt-forming, Kuqa basin experienced strong-weak-strong tectonic stages, and its center of subsidence moved gradually from north to south and depocenter from northwest to east and southeast. Because of tectonic differentiation, series of second depression formed in Kuqa basin. The multiphase tectonic activities above clearly controlled the move and gather of salifying brine, the strongth of salt-forming and the deposition of salt-bearing strata. With the pass of time, the salt-bearing strata thickened gradually from northwest to east and southeast, and the distribution of the thickness trended towards complicated; the measurement of the halite deposition extended towards east too; in the early Palaeogene and the Neogene, strong multiphase tectonic activity was a disadvantage to salt-forming, but in the middle and late Palaeogene, weak multiphase tectonic activity, which resulted in slow and sustained subsidence of the basin, was greatly advantaged to it, especially to potash-forming. The result of the basin's tectonic differentiation and the development of the salt-bearing strata indicate that in Palaeogene ang Neogene, the Kuqa basin had already had the tectonic environment in which the potash evaporite formed.