| 云南江城勐野井钾盐成矿新认识 |
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| 关键词:Mengyejing potash Tethys salt- and potash-forming setting Jurassic salt diapirism “two-storey pot-ash-forming model” |
| 基金项目:国地质调查局“钾盐资源调查评价”计划项目(包括工作项目“油钾兼探实施方案和调查评价综合研究”(编号: 1212011085524); “滇西南古近纪盐盆地钾盐资源调查评价”(编号: 1212011085517))和NSFC-云南联合重点基金项目(编号: U0833601) |
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| A New Viewpoint concerning the Formation of the Mengyejing Potash Deposit in Jiangcheng, Yunnan |
| Through an intensive analysis of the data obtained from previous geological survey and study in southwestern Yunnan, the authors found some doubtful points. Starting with the salt-forming setting of the restricted sea formed in Neo-Tethys and the specific and complex geological and structural conditions of southwestern Yunnan and based on considerable ground geological surveys and sedimentary facies, salt structure and hydrochemical studies, the authors infer that the horsetail potash beds in the Mengyejing Formation of Mengyejing area were squeezed up and flowed in the plastic form through faults from the deep Jurassic potassic rocks onto the surface. In this study, light, portable and practical geophysical means such as the low-frequency magnetotelluric method (EH4) and high-precision method for detecting the electromagnetic spectrum (MES) were used; in addition, the previously-used gravity survey (1:100,000) was also employed. An integrated analysis indicates that there exist several salt beds at the depth. For the purpose of verifying the above-mentioned new idea of potash search, two potash intermediately deep boreholes were drilled, and the drilling results are consistent with this idea. Of the two boreholes, one (MK-1) has been completed and encountered a 70 m thick potash-bearing halite bed in the central part of the Middle Jurassic Huakaizuo Formation, and the other (MK-2) has intersected a gypsum-bearing sequence in the upper part of the Huakaizuo Formation. Meanwhile, Sr isotope study, inclusion thermometry and analyses of the structure and sedimentary features of the salt body were carried out. In summary, the authors demonstrate the formation mechanism of the Mengyejing potash deposit and put forward a “two-storey potash-forming model”, i.e., Jurassic salt body lies in the deep part and diapirism in the shallow part. Guided by this model, the authors deployed regional, high-precision gravity survey (1:50,000), MES spectrum and shallow drilling engineering, thus expanding prospects of potash exploration in the deep and shallow parts of the Lanping-Simao salt-forming belt. |
| ZHENG Mian-ping,ZHANG Zhen,YIN Hong-wei,TAN Xiao-hong,YU Chang-qing,SHI Lin-feng,ZHANG Xue-fei,YANG Jian-xu,JIAO Jian,WU Guo-peng.2014.A New Viewpoint concerning the Formation of the Mengyejing Potash Deposit in Jiangcheng, Yunnan[J].Acta Geoscientica Sinica,35(1):11-24. |
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