Calcium isotopes in igneous rocks and the origin of granite
Journal Article
·
· Geochimica et Cosmochimica Acta; (USA)
- Univ. of California, Los Angeles (USA)
The K-Ca radioactive parent-daughter system provides a tool for tracing the origins of igneous rocks. It is complementary to other isotopic systems because as stoichiometric constituents of major minerals, the concentrations of K and Ca, and the K/Ca ratio in rocks, are simply related to mineralogy. In this paper the authors report the first high-precision calcium isotopic analyses of continental granitic rocks, island arc rocks, and mid-ocean ridge basalts. These data show that mid-ocean ridge basalts have the low {sup 40}Ca/{sup 42}Ca ratios expected for the Earth's mantle, but that island arc rocks have slightly higher {sup 40}Ca/{sup 42}Co ratios indicative of crustal calcium in their magma sources. Many granitic rocks have high initial {sup 40}Ca/{sup 42}Ca ratios, and in conjunction with independent evidence for the age of the crustal sources, these ratios provide constraints on the K/Ca ratios, and in turn on the silica contents and residual mineralogy, of the deep crustal magma sources.
- OSTI ID:
- 5127117
- Journal Information:
- Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 53:4; ISSN GCACA; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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Wed Dec 31 23:00:00 EST 1986
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Tue Dec 31 23:00:00 EST 1991
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OSTI ID:5479231
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Mon Dec 31 23:00:00 EST 1984
· Geol. Soc. Am., Abstr. Programs; (United States)
·
OSTI ID:6650013