川东北普光地区新型杂卤石钾盐矿的物源:Sr、S同位素证据

新型杂卤石钾盐矿是近年来发现于四川盆地东北部早—中三叠世的一种可溶性海相固体钾盐,因其可利用性及低成本可开采特征,及其对海相找钾实现突破性进展提供的指示意义,引起了工业界及学术界的广泛关注。但当前以新型杂卤石钾盐矿为载体的海相成钾理论研究尚处于探索阶段,本文聚焦川东北普光地区中下三叠统新型杂卤石钾盐矿,将锶、硫同位素研究方法应用于杂卤石碎屑、石膏及"绿豆岩"等样品,以探讨新型杂卤石钾盐矿中不同组分的物源特征。分析结果显示,杂卤石碎屑和矿层底部硬石膏样品具有相似的δ³⁴S和⁸⁷Sr/⁸⁶Sr同位素特征,δ³⁴S分布在27.9‰~28.9‰之间,⁸⁷Sr/⁸⁶Sr介于0.70826~0.70829之间。该研究结果与同时期全球海相硫酸盐的δ³⁴S和全球海水的⁸⁷Sr/⁸⁶Sr的可对比性表明上述组分的主要物源应为同时期海水。该研究结果为进一步新型杂卤石钾盐矿成矿模型的建立及海相成钾理论的补充和完善提供了一定的参考。

The source material for a new type of polyhalite potassium ore in the Puguang area,northeast Sichuan:evidence from Sr and S isotopes

A new type of polyhalite potassium ore,characterized by the distribution of clastic polyhalite in the halite,is located in the marine evaporite of the lower Triassic Jialingjiang Formation and the Middle Triassic Leikoupo Formation in the Puguang area of Northeast Sichuan.In order to study its source materialand to provide a reference for such research in the future,the strontium and sulfur isotopic techniques are applied to the polyhalite,and the experimental results are compared with the gypsum and mungbean rocks in the Sichuan Basin.The results show that except for the high δ³⁴S and ⁸⁷Sr/⁸⁶Srvalues of clay rich anhydrite samples,theδ³⁴S and ⁸⁷Sr/⁸⁶Srcharacteristics of the new type of detrital polyhalite and its bottom anhydrite samples are similar.Theδ³⁴S are 27.9‰~28.9‰and ⁸⁷Sr/⁸⁶Srare 0.70826~0.70829,respectively,which are homologous,and similar to theδ³⁴S characteristics of global marine sulfate and ⁸⁷Sr/⁸⁶Srcomposition of global seawater in the same period.Therefore,its material source is seawater of the same period.The determination of its provenance has undoubtedly narrowed the scope of discussion of the metallogenic model and provides a framework for future research.