滇西兰坪古近系盆地硼元素法定量恢复古盐度及其意义

Boron Element Method for Quantitative Recovery Paleosalinity and its Significance of Paleogene Lanping Basin in the Western Yunnan

中文关键词:  兰坪盆地  钾盐  古盐度  硼元素法

英文关键词:Lanping basin  Potassium  Palaeosalinity  Boron element method

中文摘要:

      通过对兰坪盆地古近纪野外剖面中含盐泥岩-泥质粉砂岩-粉砂岩微量和常量元素的测定,利用Adams和Couch古盐度计算公式、Walker“相当硼”判别法及锶钡比值法定量-半定量地分析了本区古盐度特征,结果表明古盐度在6.5‰~22.05‰之间,盐度变化明显,以半咸水沉积为主,其次为淡水沉积。沉积中心主要分布在云龙县-兰坪县一带,古盐度值最高,平面上表现为从沉积中心向盆地周缘盐度逐渐降低,并与其所伴生的沉积环境表现出良好的对应关系。结合盆地沉积相、古环境及古地理特征,综合分析认为,云龙县-兰坪县一带含盐系地层具有优越的钾盐成矿前景。

英文摘要:

      Though the analysis of major and trace elements of the Paleogene saline clay-argillaceous siltstone-siltstone samples collected from field outcrops in Lanping basin, palaeosalinity character of these regions was revealed by quantitative semiquantitative analysis involving calculation using Adams and Couch palaeosalinity formula, equivalent boron determinate method suggested by Walker and strontium-barium ratio method. The results indicate the palaeosalinity changes obviously, in the range of 6.5‰~22.05‰, and display that the majority of samples show semisaltwater sedmientary environment and freshwater environment is secondary. The sedimentary center is mainly distributed in Yunlong and Lanping County with higher paleosalinity values. In plane view, the paleosalinity values debase as far away from the sedimentary center to the peripheral basin, and its associated sedimentary environment show good corresponding relation. According to the basin sedimentary facies, paleoenvironment and paleogeographic characteristics, the author considers that the salt-bearing stratum of Yunlong - Lanping County has a superior potassium metallogenic prospect.