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Chen Z.-L.,Chinese Academy of Geological Sciences | Zhou Y.-G.,Chinese Academy of Geological Sciences | Han F.-B.,Chinese Academy of Geological Sciences | Chen B.-L.,Chinese Academy of Geological Sciences | And 3 more authors.
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | Year: 2012

The exhumation of ore-bearing rocks after mineralization plays an important role in the ore preservation, and their relation is one of major issues of mineral deposit geology. The number percentage and area proportion of intermediate-acid intrusive bodies are regarded as two indexes of mountain exhumation degree in this paper. The temperature-space distribution of current outcropped deposits in Tianshan range not only is helpful for understanding the relationship between the mountain exhumation with the preservation of early-formed deposits, but also facilitates further ore-prospecting. Statistics results show that there are very few number and little area proportion of intermediate-acid intrusive bodies in Yilianhabigaer mountain in western segment of north Tianshan, Bogeda mountain in middle segment of north Tianshan, and southwest Tianshan, where there are only few outcropped metal ore deposits mainly characterized by epithermal mineralization. And relative deeply intrusive rocks, as well as lots of large to super-large intrusive-rock-related meso-hypothermal ore deposits, are widely exposed in Jueluotage area in southern part of north Tianshan, middle Tianshan unit, and Kuluketage area in eastern segment of south Tianshan. Previous data from fission track dating of apatite shows that Yilianhabigaer mountain, Bogeda mountain, and southwest Tianshan initially uplifted at the end of the Mesozoic, followed by rapid uplift and deformation since about ca.25 Ma. Mountains in middle Tianshan, southern part of north Tianshan, and eastern segment of south Tianshan begun to uplift rapidly and denudate since the Early Jurassic, but only weak uplift occurred in the Cenozoic. The outcropped rocks, the distribution characteristics of metal ore deposits, and the uplift-exhumation process of mountains suggest that superficial volcano-sedimentary rocks are still preserved in Yilianhabigaer mountain, Bogeda mountain, and southwest Tianshan, because of shallow erosion as response to short-time sustained denudation and rapid uplift during the late Cenozoic, leading to exposure of few intermediate-acid intrusive bodies and mostly epithermal metal deposits at the surface. While those superficial volcano-sedimentary rocks in middle Tianshan, southern part of north Tianshan, and eastern segment of south Tianshan probably have already been denudated away due to long-time erosion since the Middle Mesozoic and weak deformation in the Cenozoic, and deeply intrusive rocks and meso-hypothermal ore deposits widely outcropped at the surface as a result. As to the ore-prospecting in distinct units of Tianshan range, it is suggested that various types of deposits with different ore-forming temperature should be focused on at the surface and there is favorable mineralization potential in southwest Tianshan. It also shows that the exhumation diversity of mountain is one of the most important reasons for the popular saying that "large deposits are limited within the national boundary". Source

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