Geochemistry and tectonic setting of the ophiolitic Ingalls Complex,North Cascades, Washington; implications for correlations of JurassicCordilleran ophiolites
Metzger, Ellen P; Miller, Robert B; Harper, Gregory D (2002) Geochemistry and tectonic setting of the ophiolitic Ingalls Complex,North Cascades, Washington; implications for correlations of JurassicCordilleran ophiolites. Journal of Geology, vol.110, no.5, pp.543-560, Sep 2002
| Authors | Metzger, Ellen P; Miller, Robert B; Harper, Gregory D |
|---|---|
| Year | 2002 |
| Title | Geochemistry and tectonic setting of the ophiolitic Ingalls Complex,North Cascades, Washington; implications for correlations of JurassicCordilleran ophiolites |
| Source | Journal of Geology, vol.110, no.5, pp.543-560, Sep 2002 |
| Publisher | University of Chicago Press, Chicago, IL, United States (USA) |
| ISSN | 0022-1376 |
| GeoRef | 2002-073284 |
| Keywords | back-arc basins; basins; Cascade Range; Chelan County Washington;chrome spinel; complexes; Cordilleran Orogeny; discriminant analysis;dunite; geochemistry; harzburgite; igneous rocks; Ingalls Complex;Jurassic; Kittitas County Washington; lava; lithogeochemistry; maficmagmas; magmas; major elements; Mesozoic; metals; ophiolite; oxides;peridotites; pillow lava; plutonic rocks; rare earths; statisticalanalysis; subduction zones; tectonics; trace elements; ultramafics;United States; volcanic rocks; Washington |
| DOI | 10.1086/341759 |
Abstract
This study synthesizes new and existing chemical data to interpret thetectonic setting of the Late Jurassic Ingalls Complex of the NorthwestCascades, Washington, and to compare it with other Cordilleranophiolites of similar age. Mafic rocks of the Ingalls Complexrepresent a spectrum of magma types including normal-type and enrichedmidocean ridge basalt, within-plate basalt, and island arc basalt.Based on mafic magma chemistry, compositions of Cr-spinels inassociated peridotite, and field relations, the Ingalls Complex is asuprasubduction zone ophiolite formed in a back-arc basin cut by anoceanic fracture zone. Regional tectonic relations also support thishypothesis. Our synthesis of available chronologic, geochemical, andstratigraphic data for all Jurassic Cordilleran ophiolites shows thatthe Ingalls Complex has similarities and differences with each. Themost compelling likeness is between the Ingalls Complex and Josephineophiolite, both of which exhibit a wide range of magmatic affinities,Cr-spinel compositions that are consistent with a suprasubduction zoneorigin in a back-arc basin setting, and positions inboard of a coevalJurassic arc.