Source of Silicate and Carbonate Cements During Deep Burial Diagenesis
Prodip K. Dutta
Detrital silicate minerals and silicate cements (formed during shallow burial) of siliciclastic sandstones commonly dissolve during deep burial diagenesis. Quartz, feldspars, mica, and garnet among detrital silicate minerals, and quartz and kaolinite among authigenic silicate minerals show extensive dissolution features during deep burial diagenesis of siliciclastic sandstones of the Gondwana Supergroup, India. No dissolution features were observed in zircon, tourmalene, and rutile among detrital minerals or in chlorite and smectite among early formed authigenic minerals. Dissolution enriched the pore fluids in silica, potassium, sodium, calcium, magnesium, iron, and aluminum. Authigenic cements formed during this stage are illite, quartz, feldspar, iron oxide, and carbon tes of calcium, magnesium, and iron.
Mass-balance calculations show that the source of all silicate cements formed during deep burial diagenesis was internally derived from the dissolution of both detrital and early formed authigenic cements. However, a considerable gap exists between the amounts of cations (calcium, magnesium, and iron) derived internally and the respective amounts of these cations needed to form the various carbonate cements at this stage. Therefore, an outside source for these cations is needed to explain the formation of carbonate cements. A large mass transfer of cations from outside the sediment source seems remote since ground-water movement, which probably carried cement from an external source, is extremely restricted at great burial depths. Therefore, carbonate cements may have been major const tuents during shallow burial diagenesis in Gondwana sandstones. Subsequently, these early formed carbonates were completely dissolved and remobilized as late-stage carbonate cement.
AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.