柴达木盆地一里坪盐湖富锂卤水干冷气候成矿的流体包裹体证据  

Ore genesis of the lithium-rich brine deposit from Yiliping Salt Lake,Qaidam Basin under dry-cold climate:Evidence from fluid inclusions.

作　　者：胡宇飞[1] 赵艳军[1] 汪明泉[1,2] 焦鹏程[1] HU YuFei;ZHAO YanJun;WANG MingQuan;JIAO PengCheng(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,CAGS,Beijing 100037,China;China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国地质科学院矿产资源研究所,自然资源部成矿作用与资源评价重点实验室,北京100037 [2]中国地质大学(北京),北京100083

出　　处：《岩石学报》2023年第7期2185-2196,共12页Acta Petrologica Sinica

基　　金：国家重点研发计划(2019YFC0605200、2018YFC0604801)资助.

摘　　要：柴达木盆地中部一里坪盐湖含有大量的富锂卤水,其锂品位是柴达木盆地各盐湖中最高的。柴达木盆地富锂卤水的成矿机理特别是古气候对盐湖卤水演变的控制作用是一个热点问题。本文选取一里坪盐湖HC2105钻孔的石盐样品为研究对象,开展石盐铀系定年和石盐流体包裹体均一温度测试,确定石盐析出时盐湖卤水的温度,研究富锂卤水形成与古气候变化的耦合关系。通过石盐铀系定年,推算出了HC2105钻孔上层石盐开始沉积的时间大约为40ka,下层石盐沉积时间约在120~100ka之间。通过石盐流体包裹体均一温度的测试,获得一里坪盐湖石盐析出时盐湖卤水温度介于8.8~30.1℃,平均值温度为20.4℃,所有样品最大值在21.4~30.1℃之间,说明石盐析出时盐湖卤水温度是频繁波动的。结合石盐铀系定年的结果,表明一里坪盐湖发生的两次较为明显的降温过程与石盐的析出相对应,说明在柴达木盆地整体干旱的气候环境下,盐湖卤水持续蒸发浓缩,降温的发生不仅减少了物质来源的补给,而且还降低了石盐的溶解度,使石盐大量析出,进一步加剧卤水蒸发浓缩程度,有助于富锂卤水成矿。The Yiliping Salt Lake located in the middle part of Qaidam Basin(QB)hosts a great quantity of Li-rich brine,whose Li grade is the highest among all the salt lakes in QB.The metallogenic mechanism of Li-rich brines in QB,especially the control of paleoclimate on the evolution of salt lake brines,is a hot issue.This study aims to quantify the precipitation temperature of halites,investigate the coupling relationship between ore formation and paleoclimate variation based on the analyses of U-series dating and homogenization of fluid inclusions of halite samples from borehole HC2105 in the Yiliping Salt Lake.The results show that the deposition of upper and lower salt-bearing layers from borehole HC2105 commenced at ca.40ka and 120~100ka,respectively.The homogenization temperature of halite show that the temperature of ore-forming brine range from 8.8 to 30.1℃,with an average of 20.4℃,the maximum values of all halite samples range from 21.4 to 30.1℃,indicating a frequent variation with respect to brine temperature.Data of homogenization temperature and U-series dating suggest that there were two major temperature descending events which corresponded with halite accumulation.This proves that relatively cool and dry climate of the QB resulted in continuous evaporation,reduced supplement of material,and lowered solubility of halite,which caused the precipitation of halites and further concentrated the brines,thus facilitating the formation of Li rich brines.

关 键 词：富锂卤水 流体包裹体 石盐 铀系定年 一里坪盐湖 

分 类 号：P597.3[天文地球—地球化学] P611.42[天文地球—地质学] P618.71