Field Guides Research Papers - Academia.edu (original) (raw)

The Ingalls Ophiolite Complex is a suprasubduction-zone ophiolite formed largely in a fracture-zone setting. Mantle tectonites are cut by a large, high-T shear zone overprinted by sheared serpentinite. Mafi c complexes of ca. 161 Ma... more

The Ingalls Ophiolite Complex is a suprasubduction-zone ophiolite formed largely in a fracture-zone setting. Mantle tectonites are cut by a large, high-T shear zone overprinted by sheared serpentinite. Mafi c complexes of ca. 161 Ma gabbro, sheeted dikes, and pillow lava occur as large blocks in the sheared serpentinite. An overlying Late Jurassic argillite unit contains minor chert, graywacke, and pebble conglomerate, along with lenses of ophiolite breccias. Detrital serpentinite forms some of these breccias, and mafi c blocks in other breccias range up to hundreds of meters in diameter. Older basement is locally present in the ophiolite complex, including (1) phyllite, metachert, and pillow basalt of the undated De Roux unit overlain by (2) Early Jurassic pillow lava, basalt breccia, and minor chert and oolitic limestone of the Iron Mountain unit (fossil seamount). This older basement indicates that at least part of the ophiolite is polygenetic. The presence of a high-T mantle she...