Geochemistry and Sr-Nd-Pb Isotopes of the Granites from the Hashitu Mo Deposit of Inner Mongolia, China: Constraints on Their Origin and Tectonic Setting

D. Chengwu, D. Pan, Leon Bagas, N. Fengjun, J. Sihong, W. Junhao, D. Chengzhen, Z. Pengfei, Z. Ke

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    Abstract

    © 2016 Geological Society of China. The Hashitu molybdenum deposit is located in the southern part of the Great Hinggan Range, NE China. Molybdenum mineralization is hosted by and genetically associated with monzogranite and porphyritic syenogranite. Sr-Nd-Pb isotopes of the intrusions show that the porphyritic syenogranite has initial 87Sr/86Sr ratios of 0.70418-0.70952, eNd(t) values of 1.3 to 2.1 (t=143 Ma), 206Pb/204Pb ratios of 19.191-19.573, 207Pb/204Pb ratios of 15.551-15.572, and 208Pb/204Pb ratios of 38.826-39.143. The monzogranite has initial 87Sr/86Sr ratios of 0.70293-0.71305, eNd(t) values of 1.1 to 2.0 (t=147 Ma), 206Pb/204Pb ratios of 19.507-20.075, 207Pb/204Pb ratios of 15.564-15.596, and 208Pb/204Pb ratios of 39.012-39.599. The calculated Nd model ages (TDM) for monzogranite and porphyritic syenogranite range from 866 to 1121 Ma and 795 to 1020 Ma, respectively. The granitic rocks in the Hashitu area have the same isotope range as granites in the southern parts of the Great Hinggan Range. The isotope composition indicates that these granites are derived from the partial melting of a juvenile lower crust originating from a depleted mantle with minor contamination by ancient continental crust. The integrating our results with published data and the Late Mesozoic regional tectonic setting of the region suggest that the granites in the Hashitu area formed in an intra-continent extensional setting, and they are related to the thinning of the thickened lithosphere and upwelling of the asthenosphere.
    Original languageEnglish
    Pages (from-to)106-120
    Number of pages15
    JournalActa Geologica Sinica
    Volume90
    Issue number1
    DOIs
    Publication statusPublished - 2016

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