Isotopic characterization of Jurassic evaporites. Aconcagua-Neuquén Basin, Argentina
Isotopic characterization of Jurassic evaporites. Aconcagua-Neuquén Basin, Argentina
复制标题
阿根廷阿空加瓜-内乌肯盆地的同位素特征。
DOI：
--
复制
发表时间：
2005
期刊：
影响因子：
--
通讯作者：
L. R. Ortiz
中科院分区：
文献类型：
--
作者：
Gabriela Lo Forte;F. Cabo;L. R. Ortiz
同位素分析可以用来解释蒸发沉积物的起源。在阿根廷阿空加瓜-内乌昆盆地南门多萨（Mendoza）侏罗系海相蒸发物（Tabanos组和Auquilco组）露头进行了锶、氧和硫的初步同位素研究，作为沉积学综合研究的一部分。分析的剖面位于arroyo Las Lenitas， Canada Ancha和arroyo Blanco。样品单元包括层状、带状和结核状岩相，由硬石膏、次生石膏和方解石组成。采用常规岩相分析和x射线衍射对其矿物学进行了研究。6个样品的87Sr/86Sr比值在0.706793 ~ 0.706839之间，与同年代的海洋硫酸钙数据吻合。10个样品的氧（d18O）和硫（d34S）同位素组成分析也得出了类似的结论：所得值分别在+11.55‰~ +14.42‰和+17.25‰~ +18.48‰之间。沉积地层学证据和同位素数据都表明，塔巴诺斯和奥奎尔科的蒸发岩起源于海洋，而分析上没有发现大陆水或热液溶液的贡献。结果还表明，原生石膏-硬石膏-次生石膏转化过程中未发生同位素分馏。
Isotopic analysis can be used to interpret the origin of evaporitic sediments. A preliminary isotopic study of strontium, oxygen and sulphur has been carried out in Ca-sulphate facies of Jurassic marine evaporates (Tabanos Formation and Auquilco Formation) outcropping in southern Mendoza, Aconcagua-Neuquen Basin (Argentina), as a part of a comprehensive sedimentologic study. The analysed sections are located at arroyo Las Lenitas, Canada Ancha and arroyo Blanco. Sampled units include laminated, banded, and nodular lithofacies, made up of anhydrite, secondary gypsum and calcite. The mineralogy was studied by conventional petrographic analysis and X-ray diffraction. The 87Sr/86Sr ratio was obtained in six samples, with values ranging from 0.706793 to 0.706839, which match marine calcium-sulphate data of the same age. A similar conclusion may be derived from ten samples analysed for oxygen (d18O) and sulphur (d34S) isotopic composition: the obtained values are between +11.55‰ and +14.42‰, and between +17.25‰ and +18.48‰ respectively. The sedimentologic- stratigraphic evidence and the isotopic data both suggest a marine origin for the Tabanos and Auquilco evaporites, without an analytically detectable contribution of continental waters or hydrothermal solutions. The results also suggest that no isotope fractionation occurred during the primary gypsum-to-anhydrite-to-secondary gypsum transformations.