幔源岩浆去气形成富二氧化碳含金流体——可能性与现实性

CARBON DIOXIDE RICH AND GOLD-BEARING FLUIDS DEGASSED FROM MANTLE-DERIVED MAGMA--REALITY AND POSSIBILITY

综合国内外研究资料并结合笔者的研究成果 ,评述了幔源岩浆去气形成富二氧化碳含金流体的可能性和现实性。笔者认为 ,在地幔熔融和富集交代过程中可以形成富金和二氧化碳的岩浆 ,进一步在岩浆去气过程中金可以气相形式随二氧化碳排出 ,而一个由深部稳定热源驱动、富含幔源岩浆去气带入的二氧化碳和金并与地壳浅部流体混合的热液环流系统是形成重要金矿化的必要条件。

The reality and possibility of the formation of CO 2 rich and Au bearing fluids by mantle derived magmatic degassing are discussed. Combining with relevant materials, the research indicates that CO 2 rich and Au bearing magma may be formed by mantle melting and metasomatism, volatile Au associated with CO 2 may be degassed from the mantle derived magma and be mixed with or be absorbed by meteoric water, the mantle derived magmatic degassing may contribute large quantities of Au and CO 2 to hydrothermal systems that are responsible for the formation of Au deposits. The Au in the volcanic rocks in CO 2 gas fields in Shengli oil fields in Eastern China may be taken as a good example for the mechanism . Recently, some mantle derived CO 2 gas wells have been found in the Shengli oilfield. The Au content in volcanic rocks in Shengli oilfield has been analyzed. There are significant differences in Au content of the volcanic rocks between CO 2 gas fields and non CO 2 gas fields: the Au content in volcanic rocks in CO 2 gas fields ranges from 0.0031× 10 -6 to 2.15× 10 -6 (the average is 0.327×10 -6 ) , whereas the Au content in volcanic rocks in non CO 2 gas fields ranges from 0.0000×10 -6 to 0.0055×10 -6 (average is 0.0025×10 -6 ).The research also indicates that the mantle derived magmatic degassing may contribute greatly to hydrothermal convection system that was driven by a steady going deep heat source, enriched with volatile Au and associated CO 2 degassed from the magma,and mixed with meteoric water.