Ultramafic and related rocks of ophiolite sequences

Predominantly harzburgite and dunite with both cumulate and tectonite fabrics. Locally altered to serpentinite. Includes gabbroic rocks and sheeted diabasic dike complexes. Comprises Josephine ophiolite of Harper (1980), ophiolites of Onion Mountain, Sexton Mountain, Pearsoll Peak, Rogue River, and Riddle areas (Smith and others, 1982) and Coast Range ophiolite and serpentinite melange of M.C. Blake, Jr. and A.S. Jayko (unpublished data, 1985). In southwest Oregon, locally includes small bodies of early Mesozoic or late Paleozoic serpentinized and sheared ultramafic rocks, mostly in shear zones. Locally, volcanic and sedimentary rocks shown separately
State Oregon
Name Ultramafic and related rocks of ophiolite sequences
Geologic age Paleozoic(?), Triassic(?), and Jurassic
Lithologic constituents
Igneous > Plutonic > Ultramafic > Peridotite (Pluton)Includes basal parts of ophiolites
Metamorphic > Metaigneous > Serpentinite
Igneous > Plutonic > Dioritic > Diorite (Diabase)Includes sheeted dike complexes of ophiolites
Igneous > Plutonic > Gabbroic > Gabbro (Pluton)Includes high-level parts of ophioolites
NGMDB product
Counties Coos - Curry - Douglas - Jackson - Josephine