Sedimentary Characteristics Of The Cretaceous-paleogene Evaporates In Yarkand Basin, Xinjiang Northwestern China And Implications For Potash Information

Potash is one of China’s shortage mineral resources, looking for ancient marinesolid potash deposit is fundamental way to resolve the potash resources shortage.Yarkand basin of XinJiang is located in the central Asia Salt Lake Chain. There arehuge amounts of potassium resources have been founded in the central Asia Salt LakeChain, but there is still no breakthrough in Yarkand basin. So, Whether has thepossibility into potassium in Yarkand basin? If so, which is advantage position forpotash,where it is, and so on. To clarify these problems will be important for the nextstep of potash exploration work, and also has important significance in theory andpractical. Based on "structure-climate-source" as the main line, we study uppercretaceous-palaeocene formation sedimentary characteristics, characteristics ofgeochemical in salt, characteristics of sulfur isotope from gypsum. Within the analysisthat the source material of salt and palaeogeographic characteristicsis of lithofaciesduring this period,we have some understanding in below.(1) The upper cretaceous-paleocene evaporite are mainly come from tuyiluokeformation and aertashi formation in Yarkand basin. Evaporites of aertashi formationare given priority to gypsum rock, thickness gradually thinning from the west to theeast along the Kunlun mountains piedmont belt. Rock salt are mainly distributed intuyiluoke formation, the range is relatively small, arranged some zone as a string ofbeads in secondary sag in the kunlun mountains piedmont, the number of halite inwuparr (one of secondary sags) is biggest.(2) The evaporite minerals in Yarkand basin are mainly gypsum, rock salt,anhydrite, glauberite, lapis lazuli, barite, etc. It can be seen from the mineralassemblage: the ancient lake have evolved to a stage of salt during late cretaceous-paleocene in Yarkand basin, some parts and even reached the rich potassiummagnesium phase, has great potential into potassium.(3) Chemical analysis was carried out for evaporite minerals on the Yarkandbasin found that a number of rich potash trends taken during upper cretaceous–Paleocene. They mainly concentrated in the tuyiluoke formation and lower part of theaertashi formation.(4) Sulfur isotope analysis for late cretaceous-paleogene gypsum rock inyarkand basin found, the isotope values fall in the scope of marine evaporitic rocks, itshows that evaporites for marine origin. (5) Through comprehensive analysis, we think upper cretaceous-paleoceneevaporites form in dry and hot climate conditions in Yarkand basin, the main materialsources from the western Tethys, Basin’s tectonic evolution and basal structure patternin late cretaceous-paleocene are advantageous to the accumulation of salts materialdifferentiation. This suggests that the basin during this period has the geologicalconditions of forming potash. Combining with the output type of evaporites, mineralcombinations, and lithofacies paleogeographic evolution characteristics in basin, putforward that tuyiluoke formation and the bottom of aertashi formation are favorableformations to find potash, Such as Wupaer,one of representative secondary salt lakeare favorable parts to find potash.