Isotope evolution of strontium in carbonate cements from the Stevens Sandstone: Implications for calcium mass transfer in the San Joaquin basin, California

Conference · Fri Feb 01 04:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5211008

Schultz, J L; Boles, J R; Tilton, G R ^[1]

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1. Univ. of California, Santa Barbara (United States)

Strontium isotopes have been used as geochemical tracers of calcium mass transfer and pore water evolution in the south-central San Joaquin basin, California. Carbonate cements in the Miocene Stevens sandstone record a systematic decrease in the {sup 87}Sr/{sup 86}Sr ratios of the pore water with time (temperature) since deposition in response to plagioclase alteration, and indicate three phases in the evolution of central basin pore waters: (1) Early dolomite cements (< 35C) have Sr ratios consistent with their formation from entrapped seawater. (2) Early calcites (35 to 75C) record decreasing Sr ratios with increasing temperature. {sup 87}Sr/{sup 86}Sr values of the earliest calcites vary significantly by geographic location, progressing from lower, more evolved water ratios in the deeper central parts of the basin 0.7080 at 40C, Coles Levee field, to higher, less evolved values toward the flanks (0.7087 at 40C near Fruitvale). This eastward progression toward higher ratio pore waters may be recording a flux of more evolved water from the center of the basin upward and outward toward the flanks. At Coles Levee, the input of low ratio Sr implies large-scale mass transfer, as at least 1 km of additional depth is required to reach temperatures at which plagioclase alteration occurs. (3) At > 80C, all calcite cements have ratios in the 0.7072-0.7075 range, and appear strongly influenced by plagioclase alteration. At Coles Levee, this low-ratio Sr can be accounted for by local plagioclase dissolution, and implies a significant decrease in regional mass transfer in the later stages of the basin's history.

• OSTI ID: 5211008
• Report Number(s): CONF-9103128--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Journal Volume: 75:2
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
ANORTHOSITES
CALCITE
CALCIUM
CALIFORNIA
CARBONATE MINERALS
CENOZOIC ERA
CHEMISTRY
DEVELOPED COUNTRIES
DIAGENESIS
DISSOLUTION
DOLOMITE
ELEMENTS
GABBROS
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GROUND WATER
HYDROGEN COMPOUNDS
IGNEOUS ROCKS
INTERSTITIAL WATER
ISOTOPE APPLICATIONS
ISOTOPE RATIO
ISOTOPES
MASS TRANSFER
METALS
MINERALOGY
MINERALS
MIOCENE EPOCH
NORTH AMERICA
OXYGEN COMPOUNDS
PLUTONIC ROCKS
ROCK-FLUID INTERACTIONS
ROCKS
SANDSTONES
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
STRONTIUM ISOTOPES
TERTIARY PERIOD
TRACER TECHNIQUES
USA
WATER