A Case Study Of The Influx Of Upper Mantle Fluids Into The Crust

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Journal Article: A Case Study Of The Influx Of Upper Mantle Fluids Into The Crust

Abstract
Geochemical and geophysical investigations in the Bohai Gulf and adjacent areas, China, indicate that uplift of the high-conductivity layer in the lithosphere coincides with the area of high heat flow. In this area are distributed abundant oil and gas fields in a Tertiary fault basin and also large quantities of basaltic rocks. Gas fields, mostly CO2 bearing, occur at the basin margins, where a widespread alkaline olivine basalt has high contents of gold. Geochemical prospecting of the surface (soil and soil gas) in the area indicates that there is an anomaly zone of large-scale gold mineralization, and large gold deposits have been found in this area. Isotopic study demonstrates that CO2 in the volcanic rocks and in the CO2-bearing gas deposits are all derived from the mantle. Experiments show that Au- and CO2-bearing hydrothermal fluids separated into vapor phase and liquid phases respectively due to a reduction of pressure and temperature over the temperature range from 250 to 290°C and at 22 M Pa. Au appears in the vapor phase rich in CO2. That proves that it is possible that CO2-bearing aqueous fluids (in gas phase) can carry gold and transport it from deeper parts of lithosphere to the surface.

Authors 
Ronghua Zhang and Shumin Hu








Published Journal 
Journal of Volcanology and Geothermal Research, 2002





DOI 
Not Provided
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Citation

Ronghua Zhang,Shumin Hu. 2002. A Case Study Of The Influx Of Upper Mantle Fluids Into The Crust. Journal of Volcanology and Geothermal Research. (!) .