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

Conference · Tue Dec 31 23:00:00 EST 1991 · 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--
• 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

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