Discovery,breakthrough and prospect of"new type polyhalite potash deposit"in the Puguang area,northeastern Sichuan basin
Globally,the majority of proven potassium salt resources are ancient marine soluble solid deposits(sylvine,carnallite).In contrast,China's proven potassium salt resources mainly originate from modern salt lake brines.Despite decades of exploration,breakthroughs in marine soluble solid potassium salt prospecting in ancient salt basins have remained elusive.The Sichuan basin,a major marine potassium-forming basin in China,harbors significant polyhalite deposits associated with or interbedded with anhydrite and dolomite in the Middle and Lower Triassic series.However,these deposits are generally buried at depths exceeding 2000 m,posing significant challenges for development and utilization.Since 2017,core reviews from brine exploration wells(HC2 and HC3)in the Xuanhan salt basin of the Puguang area in the northeastern Sichuan basin have revealed a type of polyhalite-type potassium-bearing ore.This"new type polyhalite potassium ore"is characterized by the abundant fragmented polyhalite dispersed in the salt matrix and exhibiting a converted KCl content exceeding industrial grade thresholds.This type of polyhalite,known as"new type polyhalite potassium ore,"differs from sylvite,carnallite,and the polyhalite associated or interbedded with anhydrite and dolomite(anhydrite-type polyhalite)discovered by predecessors.Small-and medium-scale tests show that this"new type polyhalite potassium ore"can be dissolved by water injection through butt wells;therefore,it is a"live ore"that can be developed and utilized on a large scale.It is also a new type of sulfate-chloride composite marine soluble solid potassium salt deposit.A thick industrial layer of"new type polyhalite potassium ore"with a thickness of 29.46 m and an average KC1 content of 12.03％(reaching a maximum of 20.5％)was discovered in the"potassium-lithium exploration"reference well CXD 1.This discovery,based on the"double controlled compound"metallogenic theory,marks a substantial breakthrough in marine soluble solid potassium salt prospecting in China.Furthermore,a quantitative prediction model for K content and density parameters of the ore was established by fitting measured core sample data and logging interpretation data.Utilizing the"gas-potassium exploration"method and data from 33 wells,the KCl resource of the"new type polyhalite potassium ore"was preliminary estimated using the"geometric method,"referring to the ancient solid salt exploration code(2020).The estimated inferred resource is 245 million tons(super-large scale),with potential resources reaching 465 million tons,totaling 710 million tons.This discovery lays the foundation for establishing China's first 100-million-ton-class marine potassium salt base in Xuanhan County,Dazhou City,northeastern Sichuan Province,and represents a major breakthrough in China's search for marine soluble solid potassium ore.
new type polyhalite potash depositmarine faciescompound soluble new type of solid potassium depositMiddle-Lower TriassicPuguang area,northeastern Sichuan basin
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