Origin and Mineralization Mechanism of the Water in Parent Magma of Porphyry Deposit(PDF)
《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]
- Issue:
- 2016年第04期
- Page:
- 473-482
- Research Field:
- 基础地质与矿产地质
- Publishing date:
Info
- Title:
- Origin and Mineralization Mechanism of the Water in Parent Magma of Porphyry Deposit
- Author(s):
- BAO Xin-shang; YANG Li-qiang; HE Wen-yan
- State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China
- Keywords:
- content of magmatic water; origin of magmatic water; plate dehydration; mixing; crystallization differentiation; mineralization mechanism; porphyry deposit
- PACS:
- P58
- DOI:
- -
- Abstract:
- The parent magma rich in water (mass fraction of water is more than 4%) is the critical factor for the enrichment and mineralization of ore-forming elements (Cu, Au, etc.), and one of the key to the formation of magma-hydrothermal systems. The main characteristics include that the occurrence of amphibole phenocrysts, enriched light rare earth elements, depleted middle rare earth elements, and w(Sr)/w(Y)>40 and w(La)N/w(Yb)N>40. The water of porphyry metallogenic system in arc settings is derived from the dehydration melting of oceanic plate or metasomatized lithospheric mantle; however, the water of porphyry metallogenic system in post-collisional settings, which is lack of direct subduction source, is likely to be derived from mixing of water-rich mafic magma with melt at lower and/or upper-crustal depths, or from crystallization differentiation of ore-related magmas themselves. Although the geodynamic background of porphyry metallogenic system and the enrichment mechanism of magmatic water in ore-related parent magma are different, they are still considered as the uniform mineralization mechanism. The higher magmatic water is the necessary conditions of forming magmatic hydrothermal mineralization system. During the process of partial melting, the addition of H2O can reduce the melting point of magma, promote the re-melting of the source containing Cu, Au sulfide, or the extraction of Cu, Au ore-forming elements from rock, or the aggregation of the scattered distribution of metal elements in magma, forming metal-rich magma; after the emplacement of ore-related magma, the water-rich magma will quickly reach saturation, making abundant fluids exsolve from magma and magmatic water with all kinds of halide separate from the melt in the form of independent fluid phase. The high-salinity fluid, which is rich in volatile possessing strong capacity of carrying metals, can prompt copper and gold clathrates, and other metal fractions enriched in the fluid, and provide main ore-forming fluids and metal source for the porphyry mineralization, and generate (or improve) the metallogenic potential of parent magma.
Last Update: 2016-07-19