青藏高原现代湖泊沉积物碳酸盐矿物氧同位素组成特征及影响因素  

OXYGEN ISOTOPIC COMPOSITIONS OF CARBONATES OF MODERN SURFACE LACUSTRINE SEDIMENTS AND THEIR AFFECTING FACTORS IN TIBET PLATEAU

作　　者：王宁[1] 刘卫国[1] 徐黎明[2] 安芷生[1] 

机构地区：[1]中国科学院地球环境研究所黄土与第四纪地质国家重点实验室 [2]中国科学院青海盐湖研究所,西宁810008

出　　处：《第四纪研究》2008年第4期591-600,共10页Quaternary Sciences

基　　金：国家重点基础研究发展规划项目(批准号:2004CB720200);国家自然科学基金项目(批准号:40599422和40121303)资助

摘　　要：选择青藏高原14个代表性现代湖泊的表层沉积物为研究对象,它们是冷湖、大苏干湖、小苏干湖、大柴旦湖、小柴旦湖、托素湖、尕海、茶卡湖、唐古拉-1、错鄂、乃日平错、纳木错、空姆错和普莫雍错,探讨这些湖泊碳酸盐矿物组成及相应氧稳定同位素组成的影响因素。XRD结果显示这些湖泊的碳酸盐矿物多以方解石为主,并含白云石。其中冷湖以白云石为主,尕海还含有一定量的文石。碳酸盐氧同位素分析结果显示总碳酸盐δ18O在-15.9‰到2.6‰范围变化,方解石δ18O变化范围为-16.2‰~3.9‰,白云石δ18O变化在-15.3‰^-5.4‰范围内。通过氧同位素与湖区环境因素的相关性分析,认为总碳酸盐δ18O受湖水δ18O组成、温度、降水量/蒸发量、盐度、海拔和纬度多种因素影响;方解石δ18O主要受湖水δ18O、温度、盐度、海拔和纬度的影响;白云石δ18O受降水量/蒸发量和盐度的影响。总碳酸盐δ18O对湖水δ18O、温度、海拔和纬度的响应是以方解石为载体而体现的;总碳酸盐δ18O对降水量/蒸发量的响应则归因于白云石δ18O对其的响应结果;另外总碳酸盐δ18O通过方解石和白云石δ18O的叠加作用响应于盐度。该研究初步建立了总碳酸盐、方解石和白云石氧同位素与环境各个指标之间的响应关系,对于揭示过去青藏高原地区环境变化有重要意义。14 typical lakes in Tibet Plateau were taken as our study object. They were Leng Lake, Dasugan Lake, Xiaosugan Lake, Dachaidan Lake, Xiaochaidan Lake, Tuosu Lake, Gahai Lake, Chaka Lake, Tangula Lake, Cuo＇e Lake, Nairiping Co, Nam Co, Kongmu Co and Pumoyum Co. Their modern surface lacustrine sediment samples were collected. Carbonate mineral compositions and the environmental significance of their δ18O were investigated. The result of XRD analysis showed that dominate calcite and lower content dolomite was universal in all lakes except for Leng Lake in which dolomite was dominate. Also a little amount of aragonite was found only in the Gahai Lake. The result of oxygen isotope analysis showed the variation ranges of δ18O of bulk carbonate, calcite, and dolomite corresponding to - 15.9‰ ~ 2.6‰, - 16. 2‰ ~ 3.9‰, and - 15.3‰ ~ - 5.4‰ respectively. Correlation analysis between δ18O and corresponding environmental indicators around each lake showed that the δ18O of bulk carbonate was affected by multi-factors such as the δ18O of lake water, temperature, precipitation/ evaporation,salinity,altitude and latitude. The δ18O of calcite was mainly controlled by the δ18O of lake water, temperature, salinity, altitude and latitude and the δ18O of dolomite was in response to precipitation/evaporation and salinity. Calcite was responsible for the relationship between δ18O of bulk carbonate and the δ18O of lake water, temperature, altitude and latitude. Via dolomite,the δ18O of bulk carbonate was linked to precipitation/evaporation. The response of the δ18O of bulk carbonate to salinity was due to both calcite and dolomite. This study constructed the primary, relationship between the δ18O of bulk carbonate, calcite and dolomite and environmental indicators. It may have important significance to the investigation of the past environmental change.

关 键 词：青藏高原 现代湖泊 总碳酸盐 方解石 白云石 氧同位素 影响因素 

分 类 号：P588.245[天文地球—岩石学] P941.74[天文地球—地质学]