Several Problems of Organic Geochemistry in the Forming of Some Sediment-reformed Deplsits

Both laboratory and field studies show that organic matter could play an important role in the forming of sediment-reformed deposits. 1.Forming sediment source rock Humic and fulvic acids have a strong tendency to complex and to absorb metal elements, one gram fulvic acid can complex and absorb 188mg Cu, 165mg Zn, and 276mg Cd respectively; one gram sea algal fregment can combine 58-78μg Au. Humic and fulvic acids are high molecular- weight, weak acid polyelectrolyts, and they are coagulated by strong electrolyte(sea water); biodetritus and clay mineral usually get to setttl in sea water and fresh water. Then humic matter and metal elements carried by it would be able to deposit and to form source rock. 2.The role in mobilization and migration of metal elements The determining results show that interlayer water and oil-field water were rich in organic acids and cyclic compounds containing O, S, P, N, etc.; while their character is simillar with ore-forming solution(called low temperature ore-forming solutions). The experimental studies suggest:(1) The solubility of mineral(sphalerite and galena) is much higher in solutions containing dissolved organic compounds than in inorganic solutions(generally 4-17 times);(2) the four complexes studied, lactic acid-Zn complex, EDTA-Zn and fulvic acid-Zn have high thermal stability, their thermal decomposition temperatures are in the rang of 140-240℃. 3.The migration and accumulation of metal elements in crud oil(waterree system) Experimental results suggest that crude oil has a strong tendency of extracting metal elements from aquous solutions, 54-90% of Au, Cu, Pb, Zn can be extracted solubility of mineral in mineral-crude oil-solution system is much higher than that of single aquous solution. The authors suggest that some mud-rock and shale had ever ben "double source rock", metal elements were mobilized. When petroleum was formed and migrated.