Abstract
The Machangqing complex is composed of early syenitic-monzonitic porphyry and late granite-porphyry. Geochemically, they are similar in major and trace element characteristics, and are characterized by relatively low TiO2 ( < 0.5) and P2O5 (< 0.4) and high alkali contents (K2O + Na2O > 8% ), with K2O/Na2O > 1, the absence of significant Eu anomaly and pronounced negative anomalies in Nb, Ta, Ti, and enrichment in large-ion lithophile elements and light rare-earth elements. Zircon U-Th-Pb ELA-ICP-MS age determination of the Machangqing complex has revealed two discrete igneous events. The syenitic-monzonitic porphyry has an age of 35. 6 ±3 Ma, MSWD = 2. 80 ; the granite-porphyry, 35. 0 ±0.2 Ma, MSWD =2.91. The lifespan of magmatic activities of the Machangqing complex associated with Cu + Mo mineralization is about 0.6 Ma. The late-stage ore-bearing granite-porphyry has higher Ce4+ /Ce3+ ratios (264) than the early-stage barren syenitic-monzonitic porphyry (102). The increase of zircon Ce4+ /Ce3+ ratios from the early-to late-stage porphyries indicates that the oxidation state of the magmas associated with copper mineralization increases with time.
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This work was financially supported jointly by NSFG ( No. 40472049), and CAS Key Project ( KZCX2-SW-117 and GIGCX-04-03).
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Huaying, L., Hengxiang, Y., Cehui, M. et al. Zircon LA-ICP-MS U-Pb age, Ce4+ /Ce3+ ratios and the geochemical features of the Machangqing complex associated with copper deposit. Chin. J. Geochem. 25, 223–229 (2006). https://doi.org/10.1007/BF02840415
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DOI: https://doi.org/10.1007/BF02840415