| Citation: |
Jian Yang, Sheng-xian Liang, Qiao Wang, Wei Zhang, Jing Guo, Guo-zhong Liao, 2019. Concealed porphyry delineation based on nonlinear three-dimensional density-difference inversion: An example in the Beiya mine area, Western Yunnan, China, China Geology, 2, 342-353. doi: 10.31035/cg2018117
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Concealed porphyry delineation based on nonlinear three-dimensional density-difference inversion: An example in the Beiya mine area, Western Yunnan, China
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Abstract
Intermediate acid-complex rock masses with low-density characteristics are the most important prospecting sign in the Beiya area, of western Yunnan province, and provide a physical basis for good gravity exploration. It is usually difficult to obtaining solutions in connection with actual geological situations due to the ambiguity of the conventional gravity-processing results and lack of deep constraints. Thus, the three-dimensional (3D) inversion technology is considered as the main channel for reducing the number of solutions and improving the vertical resolution at the current stage. The current study starts from a model test and performs nonlinear 3D density-difference inversion called “model likelihood exploration”, which performs 3D inversion imaging and inversion of the known model while considering the topographic effects. The inversion results are highly consistent with those of the known models. Simultaneously, we consider the Beiya gold mine in Yunnan as an example. The nonlinear 3D density-difference inversion technology, which is restricted by geological information, is explored to obtain the 3D density body structure below 5 km in the mine area, and the 3D structure of the deep and concealed rock masses are obtained using the density constraints of the intermediate-acid-complex rock masses. The results are well consistent with the surface geological masses and drilling-controlled deep geological masses. The model test and examples both show that the 3D density-difference nonlinear inversion technology can reduce inversion ambiguity, improve resolution, optimize the inversion results, and realize “transparency” in deeply concealed rock masses in ore-concentrated areas,which is useful in guiding the deep ore prospecting.
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References
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Jian Yang, Sheng-xian Liang, Qiao Wang, Wei Zhang, Jing Guo, Guo-zhong Liao, 2019. Concealed porphyry delineation based on nonlinear three-dimensional density-difference inversion: An example in the Beiya mine area, Western Yunnan, China, China Geology, 2, 342-353. doi: 10.31035/cg2018117
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Figure 1.
Geological map of the Beiya area (modified from Regional Geology of Yunnan Province, 2012).
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Figure 2.
The comparision map of density of alkali-rich porphyry with carbonate rock and Emei basalt
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Figure 3.
Gravity anomaly of Beiya mine. a–Bouguer anomaly; b–residual anomaly; c– regional anomaly
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Figure 4.
Three-dimensional gravity forward modeling cell sketch map
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Figure 5.
Three-dimensional density theory model for inversion.
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Figure 6.
Three-dimensional density model and inversion results. a–Bouguer gravity anomaly; b–Model plane diagram; c–Different depth slices of inversion.
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Figure 7.
Geophysical model of the surface geology.
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Figure 8.
Three-dimensional density structure visualization
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Figure 9.
Surface gravity anomaly of the 3D inversion
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Figure 10.
Three-dimensional density structure of the low-density body. a–Overall structure; b–local structure.
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Figure 11.
Three-dimensional density inversion slice of line 55 in the Hongnitang section. a–3D density structure model; b–inversion profile of line 55.
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Figure 12.
Line55 prospecting line profile map in the Hongnitang section.
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Figure 13.
Three-dimensional density inversion map in the Beiya mine. a–Inversion slice profile; b–Three-dimensional density structure of high-density body
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Figure 14.
Three-dimensional distribution of porphyry in Beiya Location.
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Figure 15.
Three-dimensiona density inversion imaging (ore body).