四川盆地东部垫江盐盆三叠系嘉陵江组成钾远景分析

垫江盐盆位于四川盆地东部,是四川盆地三叠纪时期重要的成盐盆地之一,但本区是否具备形成海相钾盐的良好条件,一直存在争议。本文通过对四川盆地东部垫江盐盆长寿地区高探1井和长平3井嘉陵江组四段二亚段岩盐样品进行光薄片鉴定、扫描电镜、X粉晶衍射及化学成分分析,发现长平3井岩芯岩盐样品K~+含量最高达到3.82%,在2749~2778m岩盐段发现大量杂卤石和少量钾石盐矿物。两个钻孔岩盐样品溴氯系数均显示其达到钾盐析出阶段。通过对长寿地区气候-物源-构造条件分析,发现长寿地区三叠纪嘉陵江时期古海水温度较高,气候条件炎热,有利于钾盐矿形成;成盐和成钾物质主要来自海水,物质来源丰富;保合村一带可能存在次级凹陷,古构造条件优越,有利于钾盐的形成和保存,是寻找钾盐矿的有利区。

Prospect Analysis of Potash Forming of the Triassic Jialingjiang Formation in the Dianjiang Salt Basin in Eastern Sichuan

The Dianjiang salt basin, located in the eastern part of Sichuan basin, is one of the most important Triassic salt basins in eastern Sichuan basin. However, the metallogenic condition of marine potash formation has long been in dispute. This paper carried out an analysis for the halite samples from Gaotan well 1 and Changping well 3 in the Changshou area using microscopic observation, scanning electron microscope, X- ray power diffraction and chemical components. The results show that the core samples from Changping well 3 contain high K+ concentration up to 3.82% and a large number of polyhalite and minor amount of sylvinite were found at depth between 2749 meter to 2778 meter in Changping well 3. Br×103/Cl coefficients of the samples from two wells suggest that the brines reached the deposition state of sylvinite. Study of the paleoclimate conditions, materials source and tectonic conditions in the Changshou area shows that this area was characteristic of high paleo- seawater temperature and hot climate during the early Middle Triassic, both of which were beneficial to the formation of potash deposit. The materials of potassic salt were mainly derived from seawater, which provided plentiful sources for potassium ion. There might exist a secondary sag in Baohe village. Good structural condition helped the formation and preservation of potash deposits. Therefore, this area will be the target for exploration of potash deposits.