| China became the biggest leopoldite consumption country in the world, however, the known leopoldite resource in our country is very limited, it can not satisify the agricultural demand right now, so the government puts leopoldite on the scarce resource list. Therefore, exploring more leopoldite mineral deposit become the core task for all Chinese geologist. The Sichuan Triassic Basin is one of main complementary sea salt basins in China. Our predecessors already identified that there are six thousand-meter thick saliferous strata growing in Jialingjiang Formation and Leikoupo Formation in Triassic. Besides salts, abundant polyhalites and kainites are also found in mines, which as a herald of leopoldite’s emergence.This paper is based on the 973 project of the Chinese Geological Science Institution of Mineral Resource named “the potash triassic paleotethyan conditions and post-evolutionary mechanism of Sichuan basin” which is attached to the project called“ the research and prediction of the rules of Chinese landmass and potassium”. The samples of brine from Triassic Sichuan basin and the Changping third well in Dianjiang salt basin,the eastern part of Sichuan basin are the objects of this study. Based on the previous studies, this study synthesizes the investigation from the fields of petrology,mineralogy,geochemistry of the flat section of Changping third well salt and the hydrogen and oxygen isotopes found in Brine samples, and tries to explore the reasons of the salification and potash-forming shown by the core and brine exposing.According to the catalog file of changping third well,saliferous strata divided into three salt cycles from top to bottom.The overall performance of the repeated deposition of anhydrite halite anhydrite rock layer- layer and dolomite- anhydrite layers, each salt cycle contains serveral subordinate salt cycles. The system Reflected in the deposition process of the strata in the marine transgression and regression phenomenon repeated,which cause repeated changes in water concentration.Changping third well saliferous strata from top to bottom can be divided into three main salt layers, the thickness of layer run up to 52.37 meters. The main mineral of saliferous strata are halite, anhydrite, polyhalite, dolomite and calcite, through the identifiction and analysis of polyhalite, we find out that the polyhalite particles distributed in halite as a thin bedded shape are from primary precipitation during the water evaporation. and banana leafy polyhalite formed from the early salt forming process after recrystallization.Through the study of salt geochemical bromochloromethane coefficient of Changping third well, found Changping saliferous strata bromochloromethane coefficient is generally high, the numerical part layer display bromochloro precipitation has reached the stage of potassium and magnesium salt. And during the starting period of each deposition layer,Concentrated brine from the basin or other sub basin may provide supply.Through the geochemistry analysis of Triassic brines samples in Sichuan Basin, find out that the main elements is Na Cl, most of the samples show their lackness of Ca2+, Mg2+ and SO42-, among them, 4 samples contain abundent K, which already reach the exploitation and industrial use value. By using work of the Second Geological Brigade(Analysis of hydrogen and oxygen isotope), consider the origin of brines mostly belongs to the marine sedimentary-precipitation superposition type. Its origin not just because the infiltration of atmospheric precipitation, but also connect with water supply. In addition, it always accompanied by active water- rock exchange interaction. |
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