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The Metalliferous Mineralization Associatied with Adakitic Rocks

WANG Qiang, TANG Gong-jian, JIA Xiao-hui, ZI Feng, JIANG Zi-qi, XU Ji-feng, ZHAO Zhen-hua   

  1. Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry,Chinese Academy of Sciences, Guangzhou 510640, China
  • Received:2008-09-20 Revised:2008-09-20 Online:2008-09-20 Published:2008-09-20

Abstract: Adakitic rocks have important implications for the metalliferous mineralization. This paper introduces the nomenclature of“ adakitic rocks”, the distribution and tectonic settings of the adakitic rocks associated with metalliferous mineralization. The factors that the adakitic rocks are favorable for the metalliferous mineralization are discussed in detail at last. Similar to a subducted oceanic crust-derived adakite, the“adakitic rocks”are characterized by the following geochemical characteristics: SiO2≥56wt%, Al2O3≥15 wt%, depleted Y (≤18×10-6 ) and heavy rare earth element contents ( Yb≤1.9×10-6 ), high Sr (rarely<400×10-6 ), negligibly positive Eu and Sr anomalies, and depleted high field strength element contents. They can be generated in different tectonic settings and by different mechanisms. The favorable tectonic settings for the metalliferous mineralization include arc, within-continent extension, and active collisional orogenic belt between different continents. Many large and giant are closely associated with adakitic rocks, indicating that they have a huge metalliferous potential. In the arc and within-continent extension settings, the interaction between subducted basaltic oceanic crust, or sediments, or delaminated continental crust-derived melts, or released super critical fluids with mantle causes contamination of melts by mantle peridotites on the one side, and metasomatism of mantle peridotites by the melts or fluids with high Fe2O3 on the other side. Thus, the raised oxygen fugacity in the mantle causes metal sulfides to be decomposed, which is favorable for the Cu-Au mineralization.