Sr-S-K同位素示踪思茅盆地深部富钾盐体的物源
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1.中国地质科学院矿产资源研究所,自然资源部盐湖资源与环境重点实验室;2.内生金属矿床成矿机制研究国家重点实验室,南京大学地球科学与工程学院;3.中国地质大学(北京)

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地质调查项目思茅盆地中生代海相钾盐资源调查评价(编号DD20201115, DD20221913)


Sr, S, and K isotopes to tracing material sources of the deep potassium-bearing salt body in the Simao Basin, southwestern China
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1.MNR Key Laboratory of Saline Lake Resources and Environments,Institute of Mineral Resources,CAGS;2.State Key Laboratory for Mineral Deposits Research,School of Earth Sciences and Engineering,Nanjing University;3.School of Earth Sciences and Resources,China University of Geosciences

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    摘要:

    思茅盆地2350 m以深新发现了累计厚度149 m的富钾盐体。为了厘定其成钾物质来源,本文重点分析了15件钾石盐岩样品的Sr、K同位素和7件硬石膏岩样品的Sr、S同位素。结果显示样品的Sr、S、K同位素均具有海水的特征,说明该盐体的成钾物质来源为海水。87Sr/86Sr值分别与δ34SV-CDT值和δ41K值负相关揭示析盐期存在陆源淡水补给蒸发盆地。淡水补给导致样品的87Sr/86Sr值大于母源海水、δ34SV-CDT和δ41K值小于母源海水。混源模拟计算显示钾石盐岩中淡水补给锶元素的比例为3.3%~29.2%,硬石膏岩中淡水补给锶元素的比例不超过35.2%。淡水补给Sr、S、K元素的量较少,不足以影响我们根据相应的同位素指标对盐体母质来源的识别。本项研究综合应用传统的Sr-S同位素与新兴的K同位素示踪思茅盆地深部富钾盐体的物源,为进一步研究其成因机理提供了可靠的数据支撑。

    Abstract:

    A deep potassium-bearing salt body is first discovered in the Simao basin and it is characterized by a cumulative thickness of 149 m and burial depths of more than 2350 m. In this study, Sr, K isotope from 15 sylvinites and Sr, S isotope of the 7 anhydrock have to be analyzed by MC-ICP-MS, respectively, and it aims to determine the material sources of the salt body. The results are shown that all of the 87Sr/86Sr ratios, δ34SV-CDT values, and δ41K values indicate that seawater provided potassium sources for this salt body. The 87Sr/86Sr values were negatively correlated with δ34SV-CDT and δ41K values, respectively, which revealed the presence of terrestrial freshwater recharge to the evaporation basin during the precipitation of salt. Freshwater recharge resulted in samples with 87Sr/86Sr values greater than parental seawater and δ34SV-CDT and δ41K values less than parental seawater. Data obtained by simulation calculation of the mixed source suggest that the proportion of strontium in the freshwater supply in the sylvinite ranges from 3.3% to 29.2%, and the proportion of strontium in the freshwater supply in the anhydrock does not exceed 35.2%. The Sr, S, and K isotopes compositions of the samples still hold characteristics of the seawater, because of terrigenous recharge amount is little and does not disturb the identification of parent source. This study integrates the traditional stable isotopes(Sr-S) with the emerging K isotopes to trace the source of deep potassium-bearing salt body in the Simao basin, providing reliable data to further investigate the genesis mechanism.

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  • 收稿日期:2022-06-12
  • 最后修改日期:2022-07-13
  • 录用日期:2022-07-17
  • 在线发布日期: 2022-11-05
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