新疆罗布泊盐湖深部钾盐找矿新进展

摘要

罗布泊是世界最大干盐湖之一，罗布泊超大型钾盐矿床从1995年发现至今，经历了找钾远景预测、勘查、系统科学研究、扩大找矿及开发利用快速推进的过程，浅部（200m 以浅）钾盐资源量已基本查明，但没有一个穿透第四系的较深地质科学钻井。通过区域气候条件、盐类矿物分布、碎屑岩层储卤等方面与柴达木盆地西部的对比分析以及罗布泊地堑式断陷带储卤的发现，提出罗布泊深部具有钾盐成矿远景。在罗布泊罗北凹地西北部实施盐湖深部钾盐找矿第一深井（LDK01井），首次发现钾芒硝、钾锶矾、红钾铁盐等盐类矿物；在深部地层碎屑岩层中发现钾盐矿物钾石盐、光卤石等，地层中 KCl 含量高达2•86％，揭示地层深部存在低品位固体钾矿，确定为一种新类型钾矿，即碎屑岩型钾矿，为罗布泊深部钾盐找矿拓展了方向和空间；深层碎屑岩地层储集卤水，卤水 KCl 平均品位1•50％，揭示出罗布泊盐湖深部存在富钾卤水。重力探测发现罗布泊盆地西部发育次级凹地，初步确定凹地中心第四系沉积厚度大于1200m。结合地质分析，预测库鲁克塔格山前断陷盆地和罗北盆地为进一步寻找深部隐伏钾盐矿床的重要靶区。综合遥感、物探、物性特征等资料及研究成果，估算罗北凹地深部钾盐预测资源量为1•60×108 t，并提出罗北凹地西部及附近区域的深部地层中还蕴藏有丰富的钾盐资源，罗布泊深部找钾潜力巨大。该成果对深化认识罗布泊盐湖的形成演化及满足钾肥生产企业大规模开发均具有重要意义。%LopNur lake is one of the largest dry salt lakes in the world.Since Lop Nur.is discovered in 1995, potassium prospecting,survey,systematic research,exploitation and utilization has been developed to the huge potassium ore.The potash resources in shallow layer (less than 200m)have been investigated. However,no deep quaternary geological well has ever been drilled in the region.From comparison with west Chaidamu basin in climate condition,saline mineral distribution and brine reservoir in clastic stratum, in combination with the brine reservoir discovery in graben fault depression,the paper proposes that the deep stratum in Lop Nur has potassium prospecting.The deep potash resources are investigated in Northwest Luobei depression of Lop Nur.And the first deep well (well LDK01)to prospect potassium in Lop Nur lake is implemented, in which potassium mineral including glaserite, Kalistrontite and erythrosiderite are discovered for the first time.The potassium mineral including sylvite,carnallite etc. are discovered in deep clastic stratum,in which the maximum proportion of KCL is 2.86%,which reveals that low grade solid potash resources are reserved in deep stratum.A new type of potassium mineral, clastic potassium is discovered,which expand orientation and space for potassium prospecting in Lop Nur. The average grade of KCL in deep clastic stratum is 1.5%,which reveals that there is potassium-rich brine in deep Lop Nur lake.Gravity detecting found that secondary depression is developed in west Lop Nur basin.it’s preliminary estimated that the quaternary sedimentary thickness is more than 1200m.From geological analysis,it ’s predicted that the fault basin in front of Kuruketag mountain and Luobei depression are key target for deep potassium prospecting.In combination of remote sensing,geophysical and physical property data,it’s estimated that the potash resources in deep Luobei depression can be up to 160million ton.The paper also proposes that rich potash resources are reserved in deep stratum in west of Luobei depression and surrounding region.There is large potash potential in deep Lop Nur lake.This discovery has important significance for further studying the formation and evolution of Lop Nur lake and large scale of potash production for potash fertilizer enterprise.