International Geologiical Congress - Oslo 2008

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MRD-01 General contributions to mineral deposits - Part 1

 

Metallogenesis of the tibetan collisional orogen: A review

 

Zengqian Hou, Institute of Geology, Chinese Academy of Geological Sciences (China)
Xuanxue Mo, China University of Geoscience (China)
Zhiming Yang, Institute of Gelogy, Chinese Academy of Geological Sciences (China)
Anjian Wang, Institute of Mineral Resource, Chinese Academy of Geological Sciences (China)
Zhusen Yang, Institute of Mineral Resource, Chinese Academy of Geological Sciences (China)
Xiaoming Qu, Institute of Mineral Resource, Chinese Academy of Geological Sciences (China)
 

 

This paper reviews the metallogenesis that have produced a variety of collision-related deposits and their important metallogenic settings of the Tibetan orogen, created by Indo-Asian collision starting in the early Cenozoic. The synthesized analysis lead us to propose a new conceptual framework for the Tibetan metallogenic systems, which may aid in deciphering inter-relationships among ore types in other collisonal belts. This framework includes three principal metallogenic systems in the orogen, i.e., (1) the main-collisional metallogeny in a convergent setting at 65-41 Ma, (2) the late-collisional metallogeny in a transform structural setting at 40-26 Ma, and (3) the post-collisional metallogeny in the crustal extension setting at 25-0 Ma, each forming more than three distinct types of ore deposits in the Tibetan orogen.
The main-collision of Indo-Asian continents, happened at 65-41 Ma, has formed four principal magma suites, and produced a convergent metallogenic setting characterized by the early-stage intense crustal shorting and thickening and the late-stage stress relaxation. The resulting mineralization formed (1) the Sn deposits, (2) the orogenic Au deposits, (3) the skarn Cu-Mo-Au, and (4) hybrid Au-Cu deposits.
The late-collision, caused by continuous Indo-Asian convergence and low angle underthrusting of India at 40-26 Ma, is characterized by large-scale horizontal terrane movement along the shearing zone. The relevant metallogenesis have produced four significant metallogenic events in a transform structural setting, i.e., (1) the porphyry Cu-Mo(-Au) deposits, (2) the REE deposits associated with carbonatite-alkalic complexes, (3) the sandstone-hosted Pb-Zn and vein-type Ag-Pb-Zn deposits, and (4) the orogenic-type Au deposits. Almost metallogenic events occur in a narrow timing range (40-26 Ma) peaking at 35 Ma, and available isotopic data suggest the formation of some giant deposits involved deep processes, most likely related to upwelling processes of the asthenosphere beneath the east Tibetan plateau.
The post-collision is characterized by crustal shorting in lower structural level and synchronal extension in shallow structural level prior to 18 Ma, and east-west crustal extension with NS-striking normal faulting systems after 18 Ma, regarded to have related to the lithospheric mantle thinning beneath the Tibetan plateau. The relevant metallogenesis occurred in a post-collisional extension setting, and associated ore deposits were mainly developed in the mid-Miocene Gangdese tectono-magmatic belt in Tibet. The resulting metallogenic events include (1) the porphyry Cu mineralization, (2) the vein-type Sb-Au mineralization, and (3) the hydrothermal Ag-Pb-Zn mineralization.
On the basis of the synthesized analysis on metallogeny of the Tibetan orogen, a more complete classification for ore deposit-related to collision was proposed in this paper.

 

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