化学元素三角图版法在砂岩命名中的应用:以鄂尔多斯盆地南部镇泾地区延长组为例

Application of the Triangle Chart Method of Chemical Elements for Classifying Sandstone Types:A Case Study of the Yanchang Formation in the Zhenjing Region of Southern Ordos Basin

对于物理性质发生变化的细小粉末状岩石,难以利用常规方法获取岩石信息,但是其化学元素组成及元素含量未发生变化,因此,通过找出特定区域化学元素与矿物学的相关性及评价方法,能够形成利用化学元素进行岩性识别、岩石命名的应用方法体系。本文以鄂尔多斯盆地南部镇源-泾川地区延长组为研究对象,在沉积背景分析基础上,对同一砂岩样品分别进行普通薄片鉴定和化学元素分析。结果表明,砂岩中的Si、Na和K+Ti元素含量变化可代表石英、长石、岩屑颗粒组分的含量变化;Si、Na和K+Ti元素三角图版法与传统Q-F-R图版法拟合度较好,采用化学元素三角图版进行砂岩命名的方法具有一定可行度。

Information of fine powdery rocks with varied physical properties can’t be obtained using the conventional methods.As chemical element compositions and element contents of those fine powdery rocks are not changed,we could establish a system of application method to identify lithology and to classify rock type by finding and evaluating the correlations between the specific chemical elements and minerals of those rocks.In this paper,sandstone samples of the Yanchang Formation in the Zhenyuan-Jingchuan region of the southern Ordos Basin have been made thin sections for identifying their rock types and powdered for analyzing their contents of chemical elements based on the analysis of their deposition background.The results show that the variation of Si,Na,and K+Ti contents can represent the change of quartz,feldspar,debris particle percentages in rocks.The triangle chart method of Si,Na and K+Ti elements has better degree of fitting than the Q-F-R Chart Method.Therefore,the triangle chart method of chemical elements has certain feasibility for classifying types of sandstone.