Sedimentary Facies Of The Cambrian Evaporates In The Upper Yangtze Area And Their Conditions For Halite And Potash Finding

Wide distribution of Cambrian salt-bearing basins is a prominent feature of older strata in Asia.In comparison with salt-forming intensities on other continents,salt-forming intensity of the Cambrian system of Asia and there occur large-scale rock salt and super large-scale potash deposits;so this phenomenon is thought to be called the "Asian phenomenon".The Cambrian salt-bearing sequences are mainly distributed in East Siberia of Russia,Iran,Oman,India,Pakistan,and China.The Cambrian was one of the most important epochs of potash deposition in the world.Potash salts are found in East Siberia,Iran,India,and Pakistan,and,among them,one of the largest potash deposits in the world-the Siberian Nepa potash basin-formed in the Early Cambrian.The Cambrian was also one of the most important epochs of rock gypsum and salt deposition in China.Gypsum deposits occur in all the three major continental blocks of China(Yangtze block,North China block,and Tarim block),forming four large marine salt-bearing basins.This article is based on the "Asian phenomenon" of distribution for Cambrian evaporation basins,carrying out more in-depth study for upper Yangtze Cambrian evaporite basins.This paper,through the Paleoclimate and basement tectonic background,revealed the condition of halite and potash finding.Based on the lithofacies-paleogeographic research,the distribution of rock salt and gypsum,carbonate and oxygen isotope of carbonate,major and trace elements,it elaborated the evolution of Cambrian salt basins in the upper Yangtze area.The geochemical of rock salt and brine hydrochemical manifestation evaluated the potash potential.Based on the distribution for Cambrian evaporation basins and basement tectonic background,we deem that the upper Yangtze area locate in a quasi-stable region,a favorable for potash concentration.By paleomagnetic and the collided and cracking process of ancient continent,understanding that the upper Yangtze area located in the low-and mid-latitude zones near the equator during the Cambrian,where the climate was hot and dry,favorable for evaporation and salt deposition.According to the characteristics of the stratigraphic position of salt-bearing strata and spatial distribution of salt-bearing basins,the region is broadly divided into two subbasins:the southeastern Sichuan subbasin and northeastern Chongqing subbasin.The main salt-bearing horizon in southeastern Sichuan subbasin is mainly the Lower Cambrian Qingxudong Formation;the salt-bearing horizon in northeastern Chongqing subbasin is mainly the Middle Cambrian Qinjiamiao Formation.Combining the study of carbonate and oxygen isotope of carbonate,elaborated that the sedimentary evolution of Cambrian salt basins in the upper Yangtze area is from southeastern Sichuan subbasin to northeastern Chongqing subbasin.By comparing the geochemical of rock salt and brine hydrochemical manifestation,the two subbasins both show a good hydrochemical indication and have favorable potash prospects;and,according to the brine hydrochemical manifestation of Chongqing Wuxi region,It is considered that the salinity is relatively high and potassium ion content is relatively large,some samples can be extracted for a separate standard.It is thought that the brine has the possibility of dissolving Potassium salt and potash,the northeastern Chongqing subbasin have favorable potash prospects;so they merit a further study.