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柴达木盆地大浪滩梁ZK02孔早—中更新世石盐纯液相流体包裹体均一温度及其对钾盐成矿的约束

Homogenization temperature of fluid inclusions in Early-Middle Pleistocene halite from Liang Hole ZK02 in Dalangtan area,Qaidam Basin and its constraints on potash mineralization
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摘要 运用低温冷冻成核方法,对柴达木盆地大浪滩地区梁ZK02孔早—中更新世石盐样品的纯液相流体包裹体进行均一温度测试,获得158个均一温度数据。所测石盐样品的镜下形貌显示有石盐“人”字晶特征,其内部流体包裹体呈负立方体晶形,且测试均一温度数据与包裹体粒度相关性不明显,指示了测试石盐及包裹体原生性良好,其最大均一温度可代表古代夏季气温。最大均一温度测试结果表明:(1)早更新世最大均一温度主要分布于25~30℃温度区间,高泥质、粉砂岩性特征指示早期气候较为温和,淡水补充相对丰富;晚期盐类矿物含量升高,反映干旱程度升高;个别时间段夏季温度高于40℃,呈高温干旱特征。(2)中更新世温度位于30~35℃温度区间,出现了更新世以来最高温度50.6℃,包裹体最大均一温度与高含量盐类矿物共同指示了高温干旱环境特征。与早更新世相比,中更新世环境温度总体呈升高趋势,蒸发盐含量升高,干旱程度增加,温度波动加剧,显示出中更新世更加不稳定的气候特点,与世界范围内中更新世总体气候特征一致,且盐类分布显示这种气候不稳定性在大浪滩地区自早更新世晚期就开始显现了。结合石盐包裹体古温度研究成果,对阿尔金山前砂砾岩孔隙含钾卤水矿成矿模式进行补充:早更新世较为温和湿润的环境下,风化盐分和N_(2)^(2)古盐发生溶滤,汇聚形成含盐卤水,赋存于阿尔金山前冲洪积扇砂砾岩孔隙中,历经中更新世的高温蒸发,最终形成KCl砂砾岩孔隙储层卤水矿床。 Using the cryogenic nucleation method we obtained 158 homogenization temperature measurements of fluid inclusions(pure liquid)in Early to Middle Pleistocene rock salt samples from Liang Hole ZK02 in Dalangtan area,Qaidam Basin.Micromorphological examination revealed inverted cubic fluid inclusions in chevron salt crystals,and no significant correlation was observed between the measured homogenization temperature and inclusion size.The results indicated the samples under investigation contained primary rock salt and fluid inclusions,and the maximum homogenization temperature can represent ancient summer temperatures.Subsequent testing suggested the maximum homogenization temperature in the Early Pleistocene ranged between 2530℃,while high mud and sand contents in the salt rock implied the climate was mild with abundant fresh water injection in the early stage.In the late stage the salt content increased,reflecting intense drought;and at times when summer temperatures were higher than 40℃,high temperature and drought were evident.In the Middle Pleistocene,the temperature ranged largely between 3035℃,and the highest temperature reached 50.6℃.Together,the range of maximum homogenization temperature and high salinity are indicative of high temperature and drought.Compared to the Early Pleistocene,the Middle Pleistocene saw increasing ambient temperature,salt content and drought severity,with aggravated temperature fluctuation,indicating a more unstable climate consistent with the general climate characteristics of the Middle Pleistocene worldwide.The salt distribution showed the climate instability in the Dalangtan area began to appear since the late Early Pleistocene.The metallogenic model of potassium-bearing brine from the pore of sandstone conglomerate in the Altun Mountain can be revised using the paleotemperature of fluid inclusions obtained from this study:In the mild,humid environment of the Early Pleistocene,weathered salt and N_(2)^(2) ancient salt were dissolved and filtered together to form brine in the sandstone pores,and high temperature evaporation in the Middle Pleistocene eventually led to the formation of brine deposit of the KCl sandstone conglomerate pore reservoir.
作者 樊馥 侯献华 郑绵平 孟凡巍 杨振京 苗青 FAN Fu;HOU Xianhua;ZHENG Mianping;MENG Fanwei;YANG Zhenjing;MIAO Qing(MNR Key Laboratory of Saline Lake Resources and Environments,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008,China;Institute of Hydrogeology and Environmental Geology,Chinese Academy of Geological Sciences,Shijiazhuang 050803,China)
出处 《地学前缘》 EI CAS CSCD 北大核心 2021年第6期105-114,共10页 Earth Science Frontiers
基金 国家重点研发计划项目(2017YFC0602802)。
关键词 柴达木盆地 大浪滩地区 早—中更新世 流体包裹体 均一温度 Qaidam Basin Dalangtan area Early Middle Pleistocene homogenization temperature of fluid inclusions
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