摘要
垫江凹陷位于四川盆地东部,是四川盆地三叠纪时期重要的成盐凹陷之一,但当时古卤水是否达到钾盐沉积阶段,是否具备形成海相钾盐的良好条件,一直存在争议。本文通过对垫江凹陷长平3井、高探1井和ZK001井嘉陵江组岩盐样品进行化学成分分析,以及对长平3井典型岩盐样品进行氯同位素分析来判断古卤水沉积阶段和成钾条件。结果发现垫江凹陷三叠系嘉陵江组岩盐δ37 Cl值均为负值,均小于-0.32‰,最低达到-1.18‰,绝大部分岩盐样品溴氯系数大于0.31,有很大一部分样品溴氯系数超过0.45,进一步表明垫江凹陷在嘉陵江期古卤水浓缩已达到钾石盐析出阶段,与岩盐包裹体成分分析结果一致。综合气候-物源-构造因素,认为垫江凹陷三叠纪嘉陵江期气候条件炎热,物质来源丰富,存在次级凹陷,古构造条件优越,具备良好的成钾潜力。
The Dianjiang depression of eastern Sichuan basin is one of the most important salt basins in the Triassic. However, there exist some disputes about whether the paleo-brine reached potash deposition and whether preferential metallogenic conditions for marine potash formed. In this paper, we carried out chemical analysis for salt samples from Changping well 3, Gaotan well 1, and ZK001 Jialingjiang Formation in the Dianjiang depression, and chlorine isotopic analysis for the salt samples from Changping well 3 to determine depositional stage of paleo-brine and formation condition. The results indicate that all chlorine isotopic values o the Triassic Jialingjiang halite are negative, lower than --0.32%0, with the lowest value of --1.18%~, and most Br/C1 ratios are higher than 0.31, with coefficient of bromine chloride in some samples exceeding 0.45. There features imply that during the Jialingjiang period paleo-brine in the Dianjiang depression had reached the precipitation stage of sylvinites, which is consistent to analysis result of inclusions in halite. Combined with analysis of climate, provenance and tectonic factors, it can be concluded that the Dianjiang depression was hot, abundant in potash source, existence of sub-depression, and excellent tectonic condition, all of which determined the great potential for the formation of marine potash.
作者
唐清敏
张雄
朱正杰
魏玉燕
刘永旺
刘振
TANG Qingmin;ZHANG Xiong;ZHU Zhengjie;WEI Yuyana;LIU Yongwang;LIU Zhen(Chongqing Key Laboratory of Exogenic Mineralization and Mine Environment,Chongqing Institute of Geology and Mineral Resources,Chongqing,400042;Chongqing Research Center of State Key Laborary of Coal Resources and Safe Mining,Chongqing,400042;Geochemistry Exploration Brigade of Sichuan Bureau of Exploration and Development of Geology and Minerals Resources,Deyang,Sichuang,618000)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2018年第8期1671-1679,共9页
Acta Geologica Sinica
基金
重庆市国土资源和房屋管理局科技项目(编号CQGT-KJ-2017010)
重庆市科委基础科学与前沿技术研究项目(编号cstc2017jcyjAX0364)
国家重点基础研究计划973项目(编号2011CB403007)资助
关键词
垫江凹陷
三叠系
氯同位素
溴氯系数
钾盐
Dianjiang depression
Triassic
chlorine isotope
Br/Cl ratios
marine potash
