| 湘西北民乐毗邻区深部电性结构及其地质意义 |
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| 关键词:northwestern Hunan Province magnetotelluric sounding Nanhua Period sedimentary basin manganese ore |
| 基金项目:国家重点研发计划“深地资源勘查开采”重点专项课题(编号: 2017YFC0601506);湖南省自然科学基金“基于中心阻抗响应的大地电磁反演及应用研究”(编号: 2020JJ3136);中国地质调查局“湖南花垣-凤凰地区铅锌矿整装勘查区矿产调查与找矿预测” (编号: 121201004000172201-22) |
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| 摘要: |
| Deep Electrical Structure in the Neighboring Areas of Minle in Northwestern Hunan Province |
| In order to reveal the manganese-bearing sedimentary stratigraphic structure of the Datangpo Formation of Nanhua Period in the neighboring areas of Minle in northwestern Hunan Province, deepen the understanding of the geological space for horst-graben manganese mineralization, and realize the geophysical deep-exploration technology for the Nanhua sedimentary manganese deposit, the authors, according to the prospecting guidance, processed and explained the magnetotelluric sounding profile passing through the Minle manganese deposit in the study area, and inferred the stratigraphic structure of the Nanhua Jigu Basin in combination with geological information. Firstly, the impedance tensor and phase tensor decomposition analysis was carried out by the frequency domain magnetotelluric detection data, which reveals that the Minle area in northwestern Hunan mainly exhibits two-dimensional structural features in the high frequency region (greater than 0.01 Hz); secondly, the authors used Swift decomposition and phase tensor to investigate the decomposition results of the electric spindle analysis of all the survey data of the section. It is judged that the main structural trend of the section was generally 37° eastward; in addition, the apparent resistivity and phase of the two polarization directions of TE and TM were calculated. Finally, for the TE and TM modes, the Occam inversion method was used to perform separate and joint inversion, and the deep electrical distribution of the Minle area was obtained and geological interpretation was carried out. The results show that the shallow to deep electrical structure of Minle area in northwestern Hunan is relatively simple, and the strata are well stratified from new to old. The strata can be roughly divided into six layers, i.e., the middle layer of the Gaotai Formation dolomite and the high-resistance layer of the Qingxudong Group limestone, Shijia Formation–Niuhutang Formation low resistance layer, Liuchapo Formation–Doushantuo Formation higher resistance layer, Nantun Formation–Datangpo Formation low resistance layer, Gucheng Formation and Fulu Formation middle resistance layer. Magnetotelluric inversion shows that the “concave-concave” stratigraphic structure on the contour map of the resistivity model is the main geophysical marker for the ore-forming target area, that the Minle–Huayu area is the transitional phase and the marginal facies of the paleo-natural gas seepage, and that the manganese-bearing strata have the feature that the shallower the depth, the thinner the thickness northeastward. |
| CAO Chuang-hua,ZOU Guang-jun,PENG Jie,LOU Fa-sheng,DENG Ju-zhi,MENG De-bao,KANG Fang-ping,WEN Chun-hua,LI Kun-peng,HAN Zhong-ji.2020.Deep Electrical Structure in the Neighboring Areas of Minle in Northwestern Hunan Province[J].Acta Geoscientica Sinica,41(2):219-229. |
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