Abstract
The study of lithological features and tectonic evolution related to mineralization in the eastern Tian Shan is crucial for understanding the ore-controlling mechanism. In this paper, the lithological features and ore-controlling structure of the Huangshan Ni–Cu ore belt in the eastern Tian Shan are documented using advanced spaceborne thermal emission and reflection radiometer (ASTER) multispectral data based on spectral image processing algorithms, mineral indices and directional filter technology. Our results show that the algorithms of b2/b1, b6/b7 and b4/b8 from ASTER visible and near-infrared (VNIR)- shortwave infrared (SWIR) bands and of mafic index (MI), carbonate index (CI) and silica index (SI) from thermal infrared (TIR) bands are helpful to extract regional pyroxenite, external foliated gabbro bearing Ni–Cu ore bodies as well as the country rocks in the study area. The detailed interpretations and analyses of the geometrical feature of fault system and intrusive facies suggest that the Ni–Cu metallogenic belts are related to Carboniferous arc intrusive rocks and Permian wrench tectonics locating at the intersection of EW- and NEE-striking dextral strike-slip fault system, and the emplacement at the releasing bends in the southern margin of Kanggur Fault obviously controlled by secondary faults orthogonal or oblique to the Kanggur Fault in the post-collision extensional environment. Therefore, the ASTER data-based approach to map lithological features and ore-controlling structures related to the Ni–Cu mineralization are well performed. Moreover, a 3D geodynamic sketch map proposes that the strike-slip movement of Kanggur Fault in Huangshan-Kanggur Shear Zone (HKSZ) during early Permian controlled the migration and emplacement of three mafic/ultramafic intrusions bearing Ni–Cu derived from partial mantle melting and also favored CO2-rich fluids leaking to the participation of metallogenic processes.
Highlights
The exploration and assessment of mineral resources are one of the primary tasks of remote sensing applications
The grayscale image of ASTER band ratio (BR) b2/b1 shows that area in the vicinity of Huangshan-Kanggur Shear Zone (HKSZ) and western intrusion of HSX-II display BR value higher than 1.0 because partial limestone, granitoids and Quaternary sediments have an abundance of ferric oxide minerals corresponding to the stronger absorption at ASTER band 1, while principal mafic/ultramafic intrusions including pyroxenite show low values of ASTER BR b2/b1
The higher values of ASTER b6/b7 and b4/b8 are located in the western HSX-II, which possibly illustrates that both HSX-I and HSX-II intrusions are separated from an earlier intrusion by faulting action
Summary
The exploration and assessment of mineral resources are one of the primary tasks of remote sensing applications. As an important part of the central Asian orogenic belt (CAOB), the Tian Shan is a metallogenic belt with large areas, high-grade and good prospects because of the multi-stage metallogenic processes in the Proterozoic, Paleozoic and Mesozoic periods [1,2,3,4]. Shan orogenic belt and contains a series of mineralized zones and lodes (e.g., Au, Fe, Cu, Ni) [2,5,6,7,8,9]. The lithological features and regional tectonics related to regional mineralization is still a principal problem to understand the ore-controlling mechanism. Previous studies have reported the application of multispectral
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