四川盆地卤水同位素组成及氘过量参数演化规律  

VARIATION OF ISOTOPE COMPOSITIONS AND DEUTERIUM EXCESS OF BRINES IN SICHUAN BASIN

作　　者：尹观[1] 倪师军[1] 高志友[1] 施泽明[1] 闫秋实 

机构地区：[1]成都理工大学核技术与自动化工程学院地球化学系,四川成都610059

出　　处：《矿物岩石》2008年第2期56-62,共7页Mineralogy and Petrology

基　　金：国家自然科学基金资助(项目编号:40643015)

摘　　要：运用岩石地球化原理对四川盆地卤水的同位素及氘过量参数进行分析,结果发现其具有明显的分布规律特征,盆地内以中三叠世为界同位素的显示出海、陆两大体系,海相沉积含卤层卤水中氢同位素组成均低于海水,而氧同位素则高于海水。卤水(主体)源于海水,不同时期海水的蒸发程度有所差异。由震旦系含卤层卤水分布区向上,经寒武系、二叠系茅口组至三叠系嘉陵江组、雷口坡组,卤水的δD值随时代变新而相对富重同位素。陆相沉积含卤层卤水,源于大气降水,同位素组成落在大气降水线附近。海、陆过渡相含卤层(上三叠系须家河组)卤水,同位素组成落在海相沉积含卤层卤水与大气降水端员之间,系大气降水和蒸发海水的混合。盆地内不同时代的含卤层,卤水的氘过量参数(d值)有明显随含卤层时代变老逐步降低的趋势。三叠系雷口坡组—嘉陵江组、二叠系茅口组、寒武系及震旦系含卤层均系碳酸盐地层,水/岩作用十分强烈,同时显示出卤水的氘过量参数的变化是时间的函数。所有含卤层,凡是分布于盆地周边或处在断裂构造发育或经过长期开采卤资源的卤井,明显受到大气降水渗漏补给的影响,它们的氘过量参数(d)都有不同程度的升高,升高的程度取决于现代大气降水混入的数量。三叠系不同组含卤层的卤水,卤水d值的变化与平面分布和含卤层的埋深有一定的关联,含卤层埋深愈深,卤水的氘过量参数(d)值就愈低。The isotope compositions and parameter of deuterium excess of brines, which were sampled in Sichuan basin, show obvious distribution rule. On the δD-δ18O plot, the oxygen and hydrogen isotope compositions of brines sampled in marine sedimentary brine-bearing strata fall in the right part of the plot,and the hydrogen isotope compositions are lower than SMOW, while oxygen isotope compositions are higher than SMOW. From Sinian stratum,up to Cambrian,Permian Maokou Formation Triassic Jialingjiang Formation, the 8D value of brines gets relatively positive with the strata becoming younger. Brines of terrestrial deposit are considered to be derived from precipitation and the isotope compositions fall in the neighborhood of the globe meteoric water line （GMWL）. Brines of transition between marine and terrestrial deposit （Upper Triassic Xujiahe Formation） have δD and δ18O values falling between the two end members of marine deposit brines and precipitation, implying that the brine is a mixture of precipitation and vaporing seawater. In the basin,water samples from the brine-bearing strata of different ages,show various deuterium excess （d） with evident decreasing tendency as the age of strata gets older. The brinebearing strata of Triassic Leikoupo-Jialingjiang Formations,Permian Maokou Formation,Cambrian and Sinian are all carbonate rocks which have intensive action with water. Having the same lithology,the strata present brines whose deuterium excess essentially change with time. All brinebearing strata surrounding the basin or locating at the faults,as well as those brine wells exploited for resources, have been obviously influenced by precipitation supply. Therefore, the deuterium excesses of their brines have increased to different extents, depending on the amount of mixing precipitation. The change and distribution of d values of the brines from different strata of Triassic are related to the burial of stratum depth. The deuterium excesses of brine become lower with the increase of burial depth of th

关 键 词：四川盆地 卤水 同位素 氘过量参数 特征规律 

分 类 号：P588.121[天文地球—岩石学] U452.11[天文地球—地质学]