Dissolution of ooids in seawater-derived fluids - an example from Lower Permian re-sedimented carbonates, West Texas, USA Academic Article uri icon

abstract

  • Abstract Selective dissolution of metastable minerals and certain pore types, such as moldic and oomoldic pores, are widely accepted to indicate diagenesis by meteoric fluids in carbonate rocks. In this study, oomoldicrich resedimented carbonates from the Happy Field in the Midland Basin, which contain no evidence of subaerial environments, indicate that such pores may form in other settings. Ooid dissolution in the reservoir was evaluated through petrography, scanning electron microscopy, stable isotopes (18O and 13C), elemental geochemistry, and Xray diffraction of bioclasts, ooids and associated cements. Cements are primarily dogtooth and equant lowmagnesium calcite, poikilotopic celestine is present, and latestage lowmagnesium calcite occurs in lesser amounts. Equant low magnesium calcite cements are interpreted to reflect the initial stages of pore filling, synchronous with aragonitic ooid dissolution, thus implying that oomoldic pores and equant cements formed in similar fluids. Although the prominent equant low magnesium calcite cement textures mimic those often associated with meteoric fluids, geochemistry suggests a marine origin. The equant cements have 18O (Vienna Pee Dee Belemnite) ratios between 2.0 and 3.5, and 13C (Vienna Pee Dee Belemnite) ratios between 4 and 5. Magnesium/calcium ratios show values, ranging from 5 to 142mmol/mol (n=223, average 23.2 and SD=20.1). Strontium/calcium ratios present values from 0.3 to 2.6mmol/mol (n=223, average 0.71mmol/mol, SD=0.35). Geochemical data coincide with typical lowlatitude Permian marine carbonate values and further signify diagenesis within the marine phreatic realm. To explain this process, the results indicate that the dissolution of aragonite ooids and precipitation of early cements occurred in environments ranging between the seafloor to shallow burial dominated by undersaturated marine fluids. Undersaturation was triggered by organic matter decomposition occurring at the seafloor and in the shallow subsurface immediately below. These findings have broader implications for marine and burial carbonate diagenesis as well as diagenesis of resedimented deposits.

published proceedings

  • SEDIMENTOLOGY

author list (cited authors)

  • Laya, J. C., Albader, A., Kaczmarek, S., Pope, M., Harris, P. M., & Miller, B.

citation count

  • 5

complete list of authors

  • Laya, Juan Carlos||Albader, Ahmad||Kaczmarek, Stephen||Pope, Michael||Harris, Paul Mitch||Miller, Brent

editor list (cited editors)

  • Betzler, C.

publication date

  • October 2021

publisher