Diagenetic saline formation waters: Their role in crustal processes
- Univ. of Texas, Austin, TX (United States). Dept. Geology
Formation waters typical of most sedimentary basins are Bi-rich, Na-Ca-Cl brines. High Cl content is due to halite dissolution and high Ca content to albitization of metastable detrital plagioclase deposited in both sands and shales. High Br content is due to halite recrystallization, especially during deformation, and to the conversion of carnallite to sylvite. Minor elements and isotopes are all controlled by mineral/water reactions. Saline formation waters are thus a normal diagenetic product formed during burial. Diagenetic formation waters constitute a previously unrecognized loop in crustal cycling. Transfer of Li, B, S, Cl, Ca, and Br from sediments to brines, and then discharge of brines back to the ocean, explains why these six elements are depleted in the average igneous crust relative to the average sedimentary crust. Diagenetic saline formation waters are limited in volume only by the availability of sedimentary halite and detrital plagioclase. Thus, the volume of fluids available for MVT-type mineralization and late stage sediment diagenesis is much larger than would be true if formation waters were modified surficial brines. Discharge of saline formation waters from sedimentary basins accounts for efficient chloride cycling (225 Ma residence time in the ocean), and for most of the chloride content of the world's rivers not due to aerosols. Expulsion of large volumes of diagenetic formation waters during tectonism can account for rapid excursions in oceanic chemistry, as in the case of [sup 87]Sr/[sup 86]Sr.
- OSTI ID:
- 5707245
- Report Number(s):
- CONF-921058--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 24:7; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
Similar Records
Na-Cl-Br systematics of fluid inclusions from Mississippi Valley-type deposits, Appalachian Basin: Constraints on solute origin and migration paths
Formation waters from Mississippian-Pennsylvanian reservoirs, Illinois basin, USA: Chemical and isotopic constraints on evolution and migration
Related Subjects
580000* -- Geosciences
ALKALI METALS
ALKALINE EARTH METALS
BORON
BRINES
BROMINE
CALCIUM
CHEMISTRY
CHLORINE
CONTINENTAL CRUST
DIAGENESIS
EARTH CRUST
ELEMENTS
GEOCHEMISTRY
GEOLOGIC STRUCTURES
HALOGENS
LITHIUM
METALS
MINERALIZATION
NONMETALS
RECYCLING
ROCK-FLUID INTERACTIONS
SALINITY
SEDIMENTARY BASINS
SEMIMETALS
SULFUR