中国北方中新生代盆地砂岩型铀超常富集的驱动力

中国北方中新生代陆相沉积盆地存在大规模的砂岩型铀超常富集的现象,富集的驱动力究竟来自哪里?众所周知,砂岩型铀具有水成性、动态性、易聚散性等特征,非常活跃,这些特征决定了任何一次构造隆升对其超常富集和早期矿床的重置都起关键性作用,尤其是新生代构造的作用更加不容忽视。本文分析了新生代欧亚板块与印度板块、太平洋板块的时空构造特征及其与沿线盆地铀富集的时空关系,结果表明:①欧亚板块与印度板块在古新世开始碰撞,中新世经历快速隆升,形成现今巨型青藏高原和蒙古高原,改造影响了沿线中新生代盆地,形成一系列有利于砂岩型铀富集的大陆斜坡带,沿着北西西构造线昆仑山脉、天山山脉、祁连山脉等所围限的准噶尔、伊犁、塔里木、吐哈、柴达木、银额等盆地内侏罗纪、白垩纪、新近纪沉积地层中发育大规模铀的超常富集现象。②太平洋板块在渐新世-中新世低角度北西西向俯冲于欧亚板块之下,造成大兴安岭-太行山等系列山脉的快速隆升和沿线盆地内部褶皱逆冲断裂构造的形成,在海拉尔、二连、鄂尔多斯、松辽等盆地内侏罗纪、白垩纪、新近纪沉积地层中发育铀富集现象。③北方系列盆地砂岩型铀储层的时代无论是中生代还是新生代,铀成矿时间绝大部分集中在渐新世...

Driving Forces for Sandstone-type Uranium Super-enrichment in Meso-Cenozoic Basins,North China

Large-scale supernormal enrichment and mineralization of sandstone type uranium formed in the Meso Cenozoic continental sedimentary basins in North China,but the driving forces are still unclear.Being hydrous,dynamic and open,the sandstone type uranium deposits are significantly controlled by structural uplifts which may play a key role in the supernormal enrichment and the replacement of pre-existing deposits,especially those in the Cenozoic era.This paper analyzes the space-time evolution of uranium enrichment in basins and its relationship with evolution of the Eurasian,Indian,and Pacific tectonic regimes in the Cenozoic era.The results show that the Asia plate and India plate began to collide in Paleocene,rapid uplift in Miocene,and formed the present giant Qinghai Tibet Plateau and Mongolia Plateau.The tectonic transformation led to the formation of the Meso-Cenozoic basins and a series of continental slope belts that are favorable for uranium enrichment as sandstone type deposits.The large-scale enrichment of uranium in the Junggar,Ili,Tarim,Tuha,Qaidam,Yin’e and other basins was limited by the NWW mountain ranges including the Kunlun Mountains,Tianshan Mountains,and Qilian Mountains.The low angle NW subduction of the Pacific plate under the Eurasian Plate in Oligocene Miocene resulted in the rapid uplift of a series of mountains,such as the Great Xing’an Range-Taihang Mountains,and formed fold thrust fault structures in the basins.The enrichment of uranium occurred in Jurassic,Cretaceous and Neogene sedimentary strata in the Hailaer,Erlian,Ordos,Songliao and other basins.The sandstone type uranium mineralization in Mesozoic or Cenozoic reservoirs mainly took place in Oligocene to Miocene,and mostly in Miocene.We,therefore,suggest that the supernormal enrichment of sandstone-type uranium in the Meso-Cenozoic basins in North China is controlled by the Oligocene Miocene Asia-India continental collision and the tectonic uplift of the basins caused by the subduction of the Pacific plate which provideed driving forces for the enrichment of sandstone type uranium.From the perspective of structural driving force,sandstone type uranium deposits in continental basins in North China can be divided into the Tethys and littoral Pacific metallogenic domains.