Origin and chemical evolution of formation waters from Silurian-Devonian strata in the Illinois basin, USA

Journal Article · Tue Jan 01 04:00:00 EST 1991 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(91)90420-A· OSTI ID:5920692

Stueber, A M ^[1]; Walter, L M ^[2]

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1. Southern Illinois Univ., Edwardsville (USA)
2. Univ. of Michigan, Ann Arbor (USA)

A suite of formation-water samples from Silurian-Devonian reservoirs in the Illinois basin has been analyzed for major, minor, and trace element concentrations and for H, O, and Sr isotopic compositions in order to interpret origin of salinity and geochemical evolution of brine compositions in this evaporite- and shale-poor cratonic basin. Although chloride concentrations range from 2,000 to 137,000 mg/L, Cl/Br ratios (291 {plus minus} 18) are consistent with those of seawater or seawater evaporated short of halite saturation (Cl/Br = 292). Thus, during Silurian-Devonian time, subaerially evaporated, penesaline brine entered the subsurface where it was chemically modified through brine-rock interactions. Cation/Br ratios and mineralogy of associated strata indicate that Na and K were depleted through interaction with clay minerals, Ca was enriched and Mg depleted by dolomitization, and Sr was enriched as a result of CaCO{sub 3} recrystallization and dolomitization. Brine {sup 87}Sr/{sup 86}Sr ratios range from 0.7092 to 0.7108; when these ratios are plotted versus 1/Sr, a two-component mixing trend is suggested, although Sr concentrations have experienced local diagenetic modification. A {sup 87}Sr-enriched fluid may have accompanied petroleum migration from New Albany shales into adjacent Silurian-Devonian carbonates where it mixed with remnant evaporated seawater. This event probably preceded the influx of meteoric water, as {delta}D and {delta}{sup 18}O are not correlated with Sr isotopic compositions of formation waters.

• OSTI ID: 5920692
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 55:1; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALKALINE EARTH ISOTOPES
BETA DECAY RADIOISOTOPES
BRINES
CHEMICAL COMPOSITION
CHEMISTRY
DEVONIAN PERIOD
ELECTRON CAPTURE RADIOISOTOPES
EVEN-ODD NUCLEI
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC STRATA
GEOLOGIC STRUCTURES
HOURS LIVING RADIOISOTOPES
HYDROGEN COMPOUNDS
ILLINOIS BASIN
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPE RATIO
ISOTOPES
MINERALIZATION
NUCLEI
OXYGEN COMPOUNDS
PALEOZOIC ERA
RADIOISOTOPES
ROCK-FLUID INTERACTIONS
SEAWATER
SILURIAN PERIOD
STABLE ISOTOPES
STRONTIUM 87
STRONTIUM ISOTOPES
WATER