Origin of the Tongshankou porphyry-skarn Cu-Mo deposit, eastern Yangtze craton, Eastern China: geochronological, geochemical, and Sr-Nd-Hf isotopic constraints.

Li, J-W., Zhao, X-F., Zhou, M-F., Vasconcelos, Paulo M.d., Ma, C-Q., Deng, X-D, de Souza, Z.S., Zhao, Y-X. and Wu, G. (2008) Origin of the Tongshankou porphyry-skarn Cu-Mo deposit, eastern Yangtze craton, Eastern China: geochronological, geochemical, and Sr-Nd-Hf isotopic constraints.. Mineralium Deposita, 43 3: 315-336. doi:10.1007/s00126-007-0161-3


Author Li, J-W.
Zhao, X-F.
Zhou, M-F.
Vasconcelos, Paulo M.d.
Ma, C-Q.
Deng, X-D
de Souza, Z.S.
Zhao, Y-X.
Wu, G.
Title Origin of the Tongshankou porphyry-skarn Cu-Mo deposit, eastern Yangtze craton, Eastern China: geochronological, geochemical, and Sr-Nd-Hf isotopic constraints.
Journal name Mineralium Deposita   Check publisher's open access policy
ISSN 0026-4598
Publication date 2008-03-01
Year available 2007
Sub-type Critical review of research, literature review, critical commentary
DOI 10.1007/s00126-007-0161-3
Open Access Status DOI
Volume 43
Issue 3
Start page 315
End page 336
Total pages 22
Editor Lehmann, B.
Williams, P.J.
Place of publication Germany
Publisher Springer
Language eng
Subject 970104 Expanding Knowledge in the Earth Sciences
040303 Geochronology
Abstract The Tongshankou Cu–Mo deposit, located in the westernmost Daye district of the Late Mesozoic Metallogenic Belt along the Middle-Lower reaches of the Yangtze River, eastern China, consists mainly of porphyry and skarn ores hosted in the Tongshankou granodiorite and along the contact with the Lower Triassic marine carbonates, respectively. Sensitive high-resolution ion microprobe zircon U–Pb dating constrains the crystallization of the granodiorite at 140.6 ± 2.4 Ma (1σ). Six molybdenite samples from the porphyry ores yield Re–Os isochron age of 143.8 ± 2.6 Ma (2σ), while a phlogopite sample from the skarn ores yields an 40Ar/39Ar plateau age of 143.0 ± 0.3 Ma and an isochron age of 143.8 ± 0.8 Ma (2σ), indicating an earliest Cretaceous mineralization event. The Tongshankou granodiorite has geochemical features resembling slab-derived adakites, such as high Sr (740–1,300 ppm) and enrichment in light rare earth elements (REE), low Sc (<10 ppm), Y (<13.3 ppm), and depletion in heavy REE (<1.2 ppm Yb), and resultant high Sr/Y (60–92) and La/Yb (26–75) ratios. However, they differ from typical subduction-related adakites by high K, low MgO and Mg#, and radiogenic Sr–Nd–Hf isotopic compositions, with (87Sr/86Sr) t  = 0.7062–0.7067, ɛ Nd(t) = −4.37 to −4.63, (176Hf/177Hf) t  = 0.282469–0.282590, and ɛ Hf(t)  = −3.3 to −7.6. The geochemical and isotopic data, coupled with geological analysis, indicate that the Tongshankou granodiorite was most likely generated by partial melting of enriched lithospheric mantle that was previously metasomitized by slab melts related to an ancient subduction system. Magmas derived from such a source could have acquired a high oxidation state, as indicated by the assemblage of quartz–magnetite–titanite–amphibole–Mg-rich biotite in the Tongshankou granodiorite and the compositions of magmatic biotite that fall in the field between the NiNiO and magnetite–hematite buffers in the Fe3+–Fe2+–Mg diagram. Sulfur would have been present as sulfates in such highly oxidized magmas, so that chalcophile elements Cu and Mo were retained as incompatible elements in the melt, contributing to subsequent mineralization. A compilation of existing data reveals that porphyry and porphyry-related Cu–Fe–Au–Mo mineralization from Daye and other districts of the Metallogenic Belt along the Middle-Lower reaches of the Yangtze River took place coevally in the Early Cretaceous and was related to an intracontinental extensional environment, distinctly different from the arc-compressive setting of the Cenozoic age that has been responsible for the emplacement of most porphyry Cu deposits of the Pacific Rim.
Keyword porphyry Cu-Mo deposit
Geochronology
Sr-Nd-Hf isotopic constraint
Eastern China
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Critical review of research, literature review, critical commentary
Collection: School of Earth Sciences Publications
 
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Created: Fri, 17 Apr 2009, 07:51:05 EST by Ms Christine Sinclair on behalf of School of Earth Sciences