The role of organic matter in processes of ore deposition has been the subject of many recent meetings and symposia. For most deposits it is still unknown whether organic matter plays an active or passive part in determining the site and mechanism of precipitation of ore minerals. The proposed research is designed to determine the influence of organic matter on the geochemical evolution of the sediment-hosted gold deposit at Alligator Ridge is the only large deposit of this type but Alligator Ridge is the only large deposit where heating has not obliterated the original organic record. Preliminary analyses using "Rock-Eval" and aliphatic hydrocarbon extracts demonstrate that organic matter was not inert but was oxidized by mineralizing solutions. Numerous oxidation reactions are possible (to CO2, ether, carbonyl, or other groups), however, and preliminary thermo- dynamic calculations show that they occur over a wide range of oxidation-reduction conditions. It is proposed to determine the nature of oxidation and mineralizing reactions by (1) extract and Infrared analyses of kerogen to identify oxidized compounds; and (2) thermodynamic calculations to compare the redox state of organic matter to that of ore and alteration mineralization. Successful completion of the proposed research will lead to deeper insight into the influence of organic matter on the site and mechanism of gold deposition and may lead to more cost- effective schemes for discovering new deposits.
