滇西兰坪-思茅盆地成钾地质条件分析

Geologic Settings of the Potassium Formations in the Lanping-Simao Basin, Yunnan Province

滇西兰坪-思茅盆地是我国重要的成钾盆地。本文通过综合分析盆地的构造演化、岩相古地理特征、古气候环境特征、以及盆地含盐沉积分布、微量元素Br及Sr的地球化学特征等条件,以期探讨盆地的成盐潜力和成盐时代,认为盆地具有良好的海相成钾环境和成钾潜力,Br和Sr同位素特征反映成盐物质主要来源于海水。根据盆地地质条件和含盐显示的对比,提出晚三叠世与侏罗纪是盆地重要的成盐时代,可能在盆地底部或深部沉积有巨厚的源盐层,甚至是钾盐层。通过典型的江城勐野井钾盐矿床Sr同位素比值(87Sr/86Sr)资料分析,我们认为勐野井钾盐矿床成矿物质可能来源于深部中生代侏罗纪源盐层,建议滇西南找钾工作应该加强对深部海相盐层的探索。

The Lanping-Simao Basin is an important potash basin in western Yunnan province. In this paper, we study the potash deposit potential of the basin by systemic analysis of the tectonic evolution, paleogeography, paleoclimate, distribution of salt deposition and geochemical characteristics. The geochemical characteristics of Br and 87Sr/86Sr reflect that the salts maybe originated from sea water. Based on geological setting analysis, we suggest that the Late Triassic and Jurassic are important salt-forming eras of the Lanping-Simao Basin, and there may be a thick layer of source salt at the depth of the basin, with huge potash potential. With analysis of 87Sr/86Sr ratio, we argue that the potassium deposits in the Mengyejing area were sourced from the deep buried Mesozoic evaporate strata. We suggest that attention should be paid to the deep buried Mesozoic evaporate strata in the future potash exploration in Southwestern Yunnan.