Diagenesis of calcite cement in Frio Formation sandstones and its relationship to formation water chemistry

Calcite cement is one of the most volumetrically important diagenetic minerals formed during burial of Frio Formation sandstones from the Corpus Christi area of Texas. Syndepositional calcite is restricted to shore-zone sandstones, whereas later, post-quartz-overgrowth, burial-diagenetic calcite is present in both shore-zone and shelf sandstones. The delta ¹⁸ O of burial-diagenetic calcite becomes depleted with depth. Chemical and textural evidence favors partial dissolution and reprecipitation (recrystallization) with consequent isotopic resetting as being responsible for the change in calcite delta ¹⁸ O with progressive burial. The change in calcite ⁸⁷ Sr/ ⁸⁶ Sr with depth also supports progressive recrystallization of calcite. There is a strong relationship between the ⁸⁷ Sr ⁸⁶ Sr and trace element composition of calcite and formation water from individual growth-fault blocks. Significant differences in strontium isotopic and trace element composition exist between adjacent fault blocks, implying that each fault block has behaved as a chemically separate system since the time of calcite precipitation.