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Increasing Magmatic Oxidation State from Paleocene to Miocene in the Eastern Gangdese Belt, Tibet: Implication for Collision-Related Porphyry Cu-Mo Au Mineralization

2014; Volume: 109; Issue: 7 Linguagem: Inglês

10.2113/econgeo.109.7.1943

1554-0774

Rui Wang, Jeremy P. Richards, Zheng-Qian Hou, Zhiming Yang, Zhengbin Gou, S. Andrew DuFrane,

earthquake and tectonic studies

Research Article| November 01, 2014 Increasing Magmatic Oxidation State from Paleocene to Miocene in the Eastern Gangdese Belt, Tibet: Implication for Collision-Related Porphyry Cu-Mo ± Au Mineralization* Rui Wang; Rui Wang † 1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada †Corresponding author: e-mail, rw5@ualberta.ca Search for other works by this author on: GSW Google Scholar Jeremy P. Richards; Jeremy P. Richards 1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada Search for other works by this author on: GSW Google Scholar Zeng-qian Hou; Zeng-qian Hou 2Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China Search for other works by this author on: GSW Google Scholar Zhi-ming Yang; Zhi-ming Yang 2Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China Search for other works by this author on: GSW Google Scholar Zheng-bin Gou; Zheng-bin Gou 2Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China Search for other works by this author on: GSW Google Scholar S. Andrew DuFrane S. Andrew DuFrane 1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Rui Wang † 1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada Jeremy P. Richards 1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada Zeng-qian Hou 2Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China Zhi-ming Yang 2Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China Zheng-bin Gou 2Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China S. Andrew DuFrane 1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada †Corresponding author: e-mail, rw5@ualberta.ca Publisher: Society of Economic Geologists Received: 02 Dec 2013 Accepted: 03 Mar 2014 First Online: 09 Mar 2017 Online ISSN: 1554-0774 Print ISSN: 0361-0128 © 2014 Society of Economic Geologists. Economic Geology (2014) 109 (7): 1943–1965. https://doi.org/10.2113/econgeo.109.7.1943 Article history Received: 02 Dec 2013 Accepted: 03 Mar 2014 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Rui Wang, Jeremy P. Richards, Zeng-qian Hou, Zhi-ming Yang, Zheng-bin Gou, S. Andrew DuFrane; Increasing Magmatic Oxidation State from Paleocene to Miocene in the Eastern Gangdese Belt, Tibet: Implication for Collision-Related Porphyry Cu-Mo ± Au Mineralization. Economic Geology 2014;; 109 (7): 1943–1965. doi: https://doi.org/10.2113/econgeo.109.7.1943 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Abstract In the Gangdese belt of southern Tibet, Paleocene-Eocene magmas record the final stage of Neo-Tethyan subduction and are associated with few economic porphyry deposits. In contrast, magmas formed during later stages of the India-Asia collision in the Oligo-Miocene are associated with several large porphyry Cu-Mo ± Au deposits, especially in the eastern part of the belt (~89°E–93°E). In a previous study, we showed that these Oligocene-Miocene magmas were more hydrous than the earlier Paleocene-Eocene magmas. In this study, we show that the later magmas were also more oxidized. Paleocene-Eocene rocks from the eastern Gangdese belt are characterized by low zircon Ce4+/Ce3+ ratios (mostly 50; 32.3–141.9, average = 74.3 ± 30.1, n = 33) and higher fO2 values (ΔFMQ 0.8–2.9, average = 1.8 ± 0.8, n = 6; estimated from magnetite-ilmenite pairs).Estimates of magmatic oxidation state from amphibole compositions also show an increase from ΔFMQ 1.2 to 2.1 (average = 1.6 ± 0.2, n = 40) in the Paleocene-Eocene to 2.0 to 2.8 (average = 2.5 ± 0.2, n = 58) in the Miocene. Sparse whole-rock Fe3+/Fe2+ ratios show the same general trend. The amphibole results are systematically shifted to higher ΔFMQ compared to data from magnetite-ilmenite pairs, but their trend is internally consistent.The higher oxidation states (and water contents) of Miocene igneous rocks from the eastern Gangdese belt may explain their unique association with large porphyry deposits in Tibet, because it has been shown from other studies that the potential for hydrous calc-alkaline magmas to transport Au is maximized near ΔFMQ 1.0, and Cu at higher fO2 (ΔFMQ > 1.0). In comparison, the somewhat less oxidized and less hydrous Paleocene- Eocene magmas would have been less fertile for the formation of such deposits.We suggest that these differences reflect the tectonomagmatic evolution of the Cenozoic Gangdese collisional orogen, from early collision-related magmatism in the Paleocene-Eocene to late collisional magmatism in the Miocene. Asthenospheric upwelling following slab breakoff in the Miocene caused interaction between mantle-derived magmas and previously subduction modified Tibetan lithosphere. The resultant evolved magmas had high oxidation states and water contents, which are favorable properties for the subsequent formation of magmatic-hydrothermal porphyry Cu-Mo ± Au deposits. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.