新疆罗布泊盐湖氢氧锶硫同位素地球化学及钾矿成矿物质来源

HYDROGEN, OXYGEN,STRONTIUM AND SULFUR ISOTOPIC GEOCHEMISTRY AND POTASH FORMING MATERIAL SOURCES OF LOP SALT LAKE, XINJIANG

罗布泊罗北凹地第四系上部盐层中蕴藏丰富的卤水，卤水中则富含钾（ＫＣｌ平均品位为１．４０％）。文章通过对罗布泊卤水氢、氧、锶及硫同位素等分析及与塔里木盆地（河流）、柴达木盆地等地区对比研究，确定了罗布泊富钾卤水源于地表水，可能主要是塔里木盆地南北缘河流水；卤水中的硫钾等物质组分主要来源于南天山、塔里木盆地西北、西南部中新生代石膏钙芒硝石盐矿床或地层及其古代地层卤水。由于第四纪期间塔里木盆地西部抬升，东部罗布泊地区则发生沉降，这些物质组分被地表水溶解并最终汇集于罗布泊，从而造成了该区水体中钾硫等背景值较高，使卤水在蒸发浓缩至钙芒硝阶段时钾就富集成矿。

Plenty of brine exists in Upper Quaternary and Holocene salt strata of Luobei depression, Lop Lake, Xinjiang. The brine is rich in potassium, whose average content is 1 40% (KCl), higher than the industrial tenor of 1%. The brine hosting matter is mainly glauberite characterized by well developed pores. Nevertheless, the conditions seem to be different from the general formation regularity of potash deposits: potash deposits were formed before the crystallization and precipitation of large quantities of halite as a result of the evaporation of brine. Based on a comparative study of hydrogen, oxygen and sulfur and strontium isotopes of underground brine and saline minerals in Tarim and Qaidam basins, it is considered that (1) the K rich brine of Luobei depression originated from surface water, mainly from the rivers distributed over the south and north margins of Tarim basin, (2) sulfur and potassium and other elements of brine were derived from gypsum and glauberite and halite deposits and ancient brine in Cenozoic strata distributed in South Tianshan Mountains and the northwestern and southwestern parts of Tarim basin. The western part of Tarim basin was elevated while the eastern part, especially Lop Lake, subsided during Quaternary. Some of these strata were dissolved and lots of potash forming materials were eventually brought into Lop lake. As a result, the backdground contents of potassium and sulfur in lake water are relatively high, and potash deposits were formed during the crystallization and deposition of glauberite through the evaporation of the lake water.