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Science 1 September 1989:
Vol. 245. no. 4921, pp. 959 - 962
DOI: 10.1126/science.245.4921.959
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Articles

Geological and Geochemical Record of 3400-Million-Year-Old Terrestrial Meteorite Impacts

DONALD R. LOWE 1, GARY R. BYERLY 2, FRANK ASARO 3, and FRANK J. KYTE 4

1 Department of Geology, Stanford University, Stanford, CA 94305.
2 Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803.
3 Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720.
4 Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90024.

Beds of sand-sized spherules in the 3400-million-year-old Fig Tree Group, Barberton Greenstone belt, South Africa, formed by the fall of quenched liquid silicate droplets into a range of shallow-to deep-water depositional environments. The regional extent of the layers, their compositional complexity, and lack of included volcanic debris suggest that they are not products of volcanic activity. The layers are greatly enriched in iridium and other platinum group elements in roughly chondritic proportions. Geochemical modeling based on immobile element abundances suggests that the original average spherule composition can be approximated by a mixture of fractionated tholeiitic basalt, komatiite, and CI carbonaceous chondrite. The spherules are thought to be the products of large meteorite impacts on the Archean earth.

Submitted on April 7, 1989
Accepted on June 30, 1989


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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