柴达木盆地西部更新统砂砾型深层卤水钾矿成矿模式与找矿方向探讨

Discussion on metallogenic model and prospecting direction of Pleistocene gravel brine Potassium deposit in western Qaidam Basin

通过对柴达木盆地西部大浪滩—黑北凹地、察汗斯拉图凹地、昆特依凹地和马海凹地发现的新类型砂砾型深层卤水钾盐矿床进行卤水化学成份和微量元素系统测试和分析、相关同位素测试,经综合分析和研究后认为,砂砾型深层卤水钾盐矿床为溶滤—沉积成因类型,其形成受第四纪砂砾层和古近纪以来古岩盐层的控制.其成矿模式为:盆地西部从始新世至上新世干旱条件下不断形成的“盐谷”是物源,早更新世砂砾沉积层是成矿空间,周围高山融水径流至山前地带,长年溶滤古近纪以来沉积的岩盐层中的盐类物质,渗流至砂砾层,在相对封闭的条件下形成高矿化度卤水,富集成为砂砾型深层卤水钾盐矿.在今后柴达木盆地开展砂砾型深层卤水钾盐勘查工作时,应优先选择盆地周缘深大断裂、山前古近纪以来盐类地层和早更新世山前冲洪积扇体同时发育的地区安排布署工作.

After comprehensive analysis and research of the chemical,trace elemental and isotopic composition of the new types of graveled pore brine discovered in Dalangtan-Heibei,Chahan Slatu,Kunteyi and Mahai in the western Qaidam Basin,it is believed that this gravel-type brine bearing potassium deposit belongs to leaching sedimentary model,and its formation is controlled by the Quaternary gravel deposit and the paleo-halite formation since the Paleogene.The metallogenic model is as follows:the “ salt valley” which was continuously formed under drought conditions in the western part of the basin from the Eocene to the Pliocene became the provenance,and then the early Pleistocene sandy-gravel deposit was forming the ore-bearing space.As the surrounding meltwater runoff to the piedmont zone,it would then percolate into the Quaternary gravel deposit with salts that had been leached from the Paleogene halite formation.Under relatively closed conditions,it transformed into high-salinity brine and finally came into gravel-type brine bearing potassium deposit.Therefore,in the future exploration in Qaidam Basin,priority should be given to areas where at the same time developed the deep faults at the periphery of the basin,the Paleogene halite formation and the early Pleistocene alluvial fan bodies.