The fundamental role of asthenospherically-derived, OIB-like magmas in volcanism of the North American Cordillera, 50 Ma to present

Conference · Thu Apr 01 00:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5024527

Wolff, J A; Ellisor, R ^[1]; Davidson, J P ^[2]

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1. UTA, Arlington, TX (United States). Dept. of Geology
2. Univ. of California, Los Angeles, CA (United States). Dept. of Earth and Space Sciences

Excluding the small proportion of magmas that bear a clear mantle lithosphere signature, the geochemistry of basalts erupted in the North American Cordillera, over the past 50 Ma, is broadly consistent with a simple model of crustal contamination of magma derived from a mantle source similar to that which produces ocean-island basalts (OIB). Within any one volcanic field or association, the most mafic lavas bear the closest resemblance to OIB; contamination yields basaltic andesites and andesites having characteristics that resemble those of arc magmas. Despite the smaller volumes of andesite produced since the onset of extension compared to the earlier Cenozoic, the same chemical trends are common to both periods. This conclusion can be refined somewhat by using Weaver's trace element characterization of OIB end-member types. Least-contaminated lavas typically lie on mixing lines between depleted MORB mantle (DMM) and enriched mantle (EM). However, a significant role for EM is precluded by high [sup 143]Nd/[sup 144]Nd in the most mafic lavas. Making the conservative assumption that no magma has completely escaped contamination, most suite trends project to a DMM-HIMU mix, typically with a high proportion of DMM. Thus, the mantle component in Cordilleran lavas is essentially identical to common OIB, and it is legitimate to speculate on the possible role of a vigorous mantle plume (or plume family) as the driving force for Cenozoic Cordilleran magmatism.

• OSTI ID: 5024527
• Report Number(s): CONF-9305259-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
• Country of Publication: United States
• Language: English

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