Zircon LA-ICP-MS U-Pb age, Ce4+ /Ce3+ ratios and the geochemical features of the Machangqing complex associated with copper deposit

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• 作者：Liang Huaying (1)
  Yu Hengxiang (2)
  Mo Cehui (3)
  Zhang Yuquan (1)
  Xie Yingwen (1)
  
• 关键词：igneous petrology ; porphyry copper ; geochronology ; Yunnan
• 刊名：Chinese Journal of Geochemistry
• 出版年：2006
• 出版时间：September 2006
• 年：2006
• 卷：25
• 期：3
• 页码：223-229
• 全文大小：996KB
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• 作者单位：Liang Huaying (1)
  Yu Hengxiang (2)
  Mo Cehui (3)
  Zhang Yuquan (1)
  Xie Yingwen (1)
  
  1. Key Laboratory for Metallogenic Dynamics, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640, Guangzhou, China
  2. Guilin Institute of Technology, 541004, Guilin, China
  3. Department of Environmental Engineering, Ji-nan University, 510623, Guangzhou, China
  
• ISSN：1993-0364

文摘

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.