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Science 3 December 1993:
Vol. 262. no. 5139, pp. 1550 - 1554
DOI: 10.1126/science.262.5139.1550
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Articles

A Binary Source Model for Extension-Related Magmatism in the Great Basin, Western North America

William P. Leeman 1 and Dennis L. Harry 1

1 Keith-Wiess Geological Laboratory, Rice University, Houston, TX 77251

Models for extension-related magmatism based on decompression melting of asthenospheric mantle poorly simulate fluxes and bulk compositions of magmas produced during early stages of continental extension. For the Great Basin of western North America, it is proposed that magmatism proceeded in two stages, the first involving melting of lithospheric mantle sources between 40 and sim5 million years ago (Ma), followed (since sim5 Ma) by melting of upwelling asthenospheric mantle in areas where extension has exceeded about 100 percent. This transition in magma sources is diachronous, depending on initial variations in lithosphere thickness and on rates of lithospheric thinning.

Submitted on July 19, 1993
Accepted on September 30, 1993


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