柴达木盆地西部中更新世气候转型期的古水温:来自SG-1钻孔石盐流体包裹体的证据  

Paleotemperature during the Mid-Pleistocene Transition in western Qaidam Basin:Evidence from fluid inclusions in halite from drill hole SG-1

作　　者：倪艳华 李明慧[1,2] 方小敏 孟凡巍[4] 颜茂都 刘迎新[5] NI Yanhua;LI Minghui;FANG Xiaomin;MENG Fanwei;YAN Maodu;LIU Yingxin(Institute of Tibetan Plateau Research,Chinese Academy of Sciences,Beijing 100101,China;CAS Center for Excellence in Tibetan Plateau Earth Sciences,Beijing 100101,China;University of Chinese Academy of Sciences,Beijing 100049,China;Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008,China;School of Gemmology,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国科学院青藏高原研究所,北京100101 [2]青藏高原卓越中心,北京100101 [3]中国科学院大学,北京100049 [4]中国科学院南京地质古生物研究所,江苏南京210008 [5]中国地质大学(北京)珠宝学院,北京100083

出　　处：《地学前缘》2021年第6期115-124,共10页Earth Science Frontiers

基　　金：国家重点研发计划项目(2017YFC0602803);中国科学院战略性先导专项(XDA20070201,XDA20070101,XDA20020100);第二次青藏科考项目(2019QZKK0707,2019QZKK0202);国家自然科学基金项目(41620104002,41831177,41561144009)。

摘　　要：中更新世气候转型事件(MPT)是全球性冷气候事件,在柴达木盆地也有记录,但关于该事件形成时的古温度数据较少。石盐原生流体包裹体形成于浅水环境,其均一温度可直接反映晶体形成时的卤水温度,是恢复古温度常用的指标之一。本文选择柴达木盆地西部钻孔SG-1中1.22~0.88 Ma期间的石盐晶体进行流体包裹体均一温度测试,共获得390个石盐流体包裹体数据。其均一温度最高为50℃,最低为6.8℃,90%以上温差值在10℃以内,且石盐流体包裹体大小与温度没有明显线性相关关系,这说明SG-1钻孔石盐流体包裹体被捕获后没有受到后期热液的改造。均一温度数据反映了石盐沉积时的古水温特征。石盐晶体主要在暖季析出,原生流体包裹体恢复的古水温可能是暖季节的温度。均一温度的最高值可能受到热液和气候的共同作用。MPT时期,石盐流体包裹体均一温度(中位值T_(h,med))接近于现代盆地7月份大气温度的平均值,高于盆地的全年温度及MPT时期的全球气温,与MPT时期地中海的海水表面温度相当,均一温度的平均值(T_(h,avg))高于以上温度。SG-1钻孔记录的柴达木盆地MPT事件最冷期出现在约1.165~1.0 Ma。The Mid-Pleistocene Transition(MPT)is a global cold event and also recorded in the Qaidam Basin,but the paleotemperature data is rather lacking.Halite is generally formed in shallow water environment,and the homogenization temperature(T_(h))of primary fluid inclusions in halite can directly reflect the brine temperature at halite crystallization and can be used to reconstruct paleotemperature of brine.This study selected primary halite samples from the 1.220.88 Ma section of drill hole SG-1 in the western Qaidam Basin and collected data on 390 fluid inclusions.The maximum and minimum homogenization temperatures were 50℃and 6.8℃,respectively,with temperature fluctuations mostly(>90%)within 10℃;there is no obvious linear correlation between the size of fluid inclusions in halite and the homogenization temperature.This result indicates that fluid inclusions in halite from hole SG-1 have not been modified by the later hydrothermal solution and the T_(h) data can directly relate to paleotemperature at halite deposition.The reconstructed paleotemperature in this study may be the brine temperature in warm season as halite generally deposits in warm season,while the maximum value of T_(h) may be affected by hydrothermal solution and climate.During the MPT period,the homogenization temperature of palaeo-water(mean value,T_(h,med))is similar to the average temperature in present-day July in the Qaidam Basin or the surface water temperature in the Mediterranean Sea during the same period,but it is much higher than the annual temperature in the Qaidam Basin or the global average temperature during MPT.The average homogenization temperature(T_(h,avg))is higher than all the above temperatures.The coldest climate in the Qaidam Basin during MPT occurred at~1.1651.0 Ma.

关 键 词：石盐 流体包裹体 均一温度 气候变化 

分 类 号：P571[天文地球—矿物学] P578.32[天文地球—地质学]