A petrographic and geochemical model for the origin of calcite cap rock at Damon Mound salt dome, Texas, U.S.A.

doi:10.1016/0009-2541(88)90147-7

Chemical Geology

Volume 74, Issues 1–2, 30 December 1988, Pages 67-97

https://doi.org/10.1016/0009-2541(88)90147-7 Get rights and content

Abstract

Calcite cap rock at Damon Mound, Texas, consists of five calcite generations recognizable through standard petrography and cathodoluminescence. Stage-IA calcite formed by dissolution of anhydrite followed by calcite precipitation and was partly replaced by stage-IB calcite. Stage II formed above stage-IA and -IB substrates either filling open voids or cementing breccia fragments. Stage-IIIA and -IIIB calcites fill late fractures that crosscut all previously formed generations.

Microprobe analysis indicates that each calcite generation is geochemically distinct. Sr/Mg ratios indicate that calcite precipitated from variable proportions of formation water, meteoric water, and/or seawater.

Wide variation in calcite fluid-inclusion compositions (1.0–9.4 eq.wt.% NaCl) indicates mixing of high-salinity water and low-salinity meteoric water. The single-phase nature of most fluid inclusions and the homogenization temperatures indicate that calcite precipitated at temperatures of <70°C.

Calcite δ¹³C-values range from −31.1 to −14.4‰ (PDB), generally decrease with depth, and are most similar to crude-oil δ¹³C-values. Calcite δ¹⁸O-values range from −7.6 to −4.8‰ (PDB), generally increase with depth, and are compatible with derivation from local meteoric water or formation water at high temperature. Late-stage calcite can be either isotopically heavier or lighter than adjacent early-stage calcite with regard to both carbon and oxygen, and because isotopic values vary with depth, it appears that fluid mixing is the mechanism most responsible for isotopic variations.

Although δ¹³C- and δ¹⁸O-values of stage-I calcite are similar to adjacent stage-II and -III calcite, $^{87} Sr^{86} Sr$ ratios of adjacent calcite pairs are generally different, indicating that each formed from different fluids or a fluid whose $^{87} Sr^{86} Sr$ composition varied through time due to mixing.

Isotopic modeling indicates that calcite cap rock formed from either of two fluid mixtures: (1) formation water and meteoric water between 40° and 80°C, the source of light carbon being either thermogenic CH₄ or liquid hydrocarbons; or (2) formation water, meteoric water and seawater between 50° and 70°C with thermogenic CH₄ being the light carbon source. Sr was contributed by both anhydrite and fluid. Overall, it appears that calcite cap rock formed from top to base from mixtures of formation water, containing isotopically light carbon and heavy oxygen, and seawater and/or meteoric water, containing isotopically heavy carbon and light oxygen. During this progression the contributions of formation water increased at the expense of seawater and/or meteoric water. The correlation between δ¹⁸O and δ¹³C probably indicates that separate fluid pulses had different carbon abundances and/or slightly different δ¹³C-values.

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A petrographic and geochemical model for the origin of calcite cap rock at Damon Mound salt dome, Texas, U.S.A.

Abstract

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Chem. Geol.

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Appl. Geochem.

Org. Geochem.

Chem. Geol.

Geochim. Cosmochim. Acta

Stable isotopes of oxygen and carbon and their application to sedimentologic and paleoenvironmental problems

General geology of Damon Mound

Organic Geochemistry in Petroleum Exploration

Am. Assoc. Pet. Geol., Educ. Course Note Ser.

The Damon Mound oil field, Texas

Am. Assoc. Pet. Geol. Bull.

On the solubility of anhydrous calcium sulfate and of gypsum in concentrated solutions of sodium chloride at 25°C, 30°C, 40°C, and 50°C

Can. J. Chem.

Life at high temperature

Science

Variation of seawater 87Sr86Sr throughout Phanerozoic time

Geology

Preliminary report on the origin and chemical evolution of lead- and zinc-rich oil field brines in central Mississippi

Econ. Geol.

Concentration and isotopic composition of methane, and light hydrocarbon ratios in West Florida Escarpment seep sediments

Am. Geophys. Union Trans.

Geology of Damon Mound salt dome, Texas: evidence of Oligocene to Post-Pleistocene episodic diapir growth

Univ. Texas at Austin, Bur. Econ. Geol. Geol. Circ.

The Geochemistry of Natural Waters

Damon Mound, Texas

Houston Geol. Soc., Guideb.

Origin of Gulf Coast salt dome sulfur deposits

Am. Assoc. Pet. Geol. Bull.

Diagenetic history of Eocene Wilcox Sandstone and associated formation water, south-central Texas

Practical petrographic classification of limestones

Am. Assoc. Pet. Geol. Bull.

The natural history of crystalline calcium carbonate: effect of magnesium content and salinity

J. Sediment. Petrol.

Variation of seawater $^{87} Sr^{86} Sr$ throughout Phanerozoic time