Variation of lithium isotope composition in the marine environment: A preliminary report
- Louisiana State Univ., Baton Rouge (USA)
The Li isotopic compositions of ocean waters, lake water, hydrothermal solutions, altered and unaltered basalts have been determined using the technique of thermal ionization mass spectrometry of lithium tetraborate. Seawater appears to be homogeneous in Li isotopic composition. The mean {delta}{sup 6}Li value is {minus}32.3 {plus minus} 0.5{per thousand}, relative to an isotopic standard. Three lakes studied (Lake Tanganyika, Caspian Sea and Dead Sea) yield {delta}{sup 6}Li similar to the seawater isotopic composition. A fresh basalt glass from 21{degree}N, East Pacific Rise displays a {delta}{sup 6}Li value of {minus}4.7{per thousand}. A hydrothermal solution from a 21{degree}N vent field has {delta}{sup 6}Li of {minus}10{per thousand}, indicating incomplete extraction of Li from the igneous minerals or partial retention in secondary phases. The alteration margin of a basalt from the Mid-Atlantic Ridge has {delta}{sup 6}Li of {minus}8.4{per thousand}. The isotope data of submarine basalts suggest preferential removal of {sup 6}Li from seawater into alteration minerals during low temperature weathering. The {delta}{sup 6}Li values of two hydrothermal solutions from Guaymas Basin were found to be {minus}5{per thousand} and {minus}10{per thousand}. The results can be interpreted as the net effect of Li addition from basalt and sediments and incorporation in hydrothermal precipitates as the hydrothermal fluids interact with basin sediments. The observed enrichment of {sup 7}Li in seawater relative to submarine hydrothermal solutions, its principal Li input, is tentatively attributed to isotopic fractionation associated with low temperature alteration of sea floor basalt and incorporation in authigenic sediments. It appears that the Li isotope system may have characteristics that can resolve the mass balance of Li in the ocean.
- OSTI ID:
- 5596493
- Journal Information:
- Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 52:6; ISSN GCACA; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580400* -- Geochemistry-- (-1989)
ALKALI METAL COMPOUNDS
ALKALI METAL ISOTOPES
ATLANTIC OCEAN
BASALT
CHEMICAL COMPOSITION
CHEMISTRY
COMPARATIVE EVALUATIONS
ENERGY SYSTEMS
FLUIDS
FRACTIONATION
GEOCHEMISTRY
GEOLOGIC STRUCTURES
GEOTHERMAL FLUIDS
GEOTHERMAL SYSTEMS
HYDROGEN COMPOUNDS
HYDROTHERMAL SYSTEMS
IGNEOUS ROCKS
ION EXCHANGE
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
LITHIUM 6
LITHIUM 7
LITHIUM COMPOUNDS
LITHIUM ISOTOPES
MASS BALANCE
MID-ATLANTIC RIDGE
NUCLEI
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
OXYGEN COMPOUNDS
PACIFIC OCEAN
PRECIPITATION
ROCKS
SEAS
SEAWATER
SEDIMENTARY BASINS
SEDIMENTS
SEPARATION PROCESSES
STABLE ISOTOPES
SURFACE WATERS
VOLCANIC ROCKS
WATER