The Kramer deposit of southern California--Preliminary insights on the origins of zoned lacustrine evaporite borate deposits

Conference · Wed Jan 01 00:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5690765

Swihart, G H ^[1]; McBay, E H; Smith, D H ^[2]; Siefke, J W ^[3]

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1. Memphis State Univ., TN (United States). Dept. of Geological Sciences
2. Oak Ridge National Lab., TN (United States)
3. Borax and Chemical Corp., Boron, CA (United States)

Lacustrine evaporite borate deposits span the range from mineralogically unzoned or poorly zoned to concentrically or complexly zoned types. Deposits often contain an inner ulexite or probertite (Na-Ca borates) zone and an outer colemanite (Ca borate) zone. A few deposits contain an innermost borax (Na borate) zone. Boron isotopic analyses of core material from the zoned borax-ulexite-colemanite Kramer deposit have been made with the aim of providing a better understanding of the processes of zone formation. Samples from 6 depths over a 63 foot interval in the borax zone yield a [delta] B-11 range of +0.1 to +2.3 permil. Two samples in the portion of the ulexite zone below the borax zone, vertically separated from one another by 20 feet, yield identical results of [delta]B-11 = [minus]2.1 permit. Three ulexite samples from a 10 foot interval above the borax zone produced results in the range [delta]B-11 = [minus]4.6 to [minus]5.5 permil. A number of possible origins for ulexite at Kramer have been proposed: (1) primary precipitation from the lake brines; (2) postdepositional alteration of the borax zone margin by Ca-rich groundwater; (3) mixing of seeping lake brines and Ca-rich groundwater in muds around the lake. Given the small variation in B isotopic composition exhibited in the borax zone, mechanisms 1 and 2 would produce upper and lower portions of the ulexite zone with similar isotopic compositions. In the third scenario, the difference in composition of the upper and lower ulexites could be due to distance from the lake and relative proportions of seeped lake brine (B-11-rich) and clay adsorbed B (B-10-rich). Furthermore, the cotton ball form of the ulexite in this core is identical to that of ulexite forming today just beneath the surface of dry lakes in NV and CA.

• OSTI ID: 5690765
• Report Number(s): CONF-921058-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALIFORNIA
GEOLOGIC DEPOSITS
ORIGIN
BORATES
BORAX
BORON 11
BRINES
CALCIUM COMPOUNDS
EVAPORITES
GROUND WATER
ISOTOPE RATIO
MIXING
PRECIPITATION
SODIUM COMPOUNDS
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
BORON COMPOUNDS
BORON ISOTOPES
DEVELOPED COUNTRIES
HYDROGEN COMPOUNDS
ISOTOPES
LIGHT NUCLEI
NORTH AMERICA
NUCLEI
ODD-EVEN NUCLEI
OXYGEN COMPOUNDS
ROCKS
SEDIMENTARY ROCKS
SEPARATION PROCESSES
STABLE ISOTOPES
USA
WATER
580000* - Geosciences