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Geologic units containing peridotite

California

Ultramafic rocks, chiefly Mesozoic, unit 1 (Trinity Ophiolite) (Ordovician)

Ultramafic rocks, mostly serpentine. Minor peridotite, gabbro, and diabase. Chiefly Mesozoic unit 1

Ultramafic rocks, chiefly Mesozoic, unit 2 (Western Sierra Nevada and Klamath Mountains) (Late Proterozoic(?) to Early Jurassic)

Ultramafic rocks, mostly serpentine. Minor peridotite, gabbro, and diabase. Chiefly Mesozoic unit 2

Ultramafic rocks, chiefly Mesozoic, unit 3 (Coast Ranges and Western Klamath Mountains) (Middle to Late Jurassic)

Ultramafic rocks, mostly serpentine. Minor peridotite, gabbro, and diabase. Chiefly Mesozoic unit 3

Kentucky

Peridotite intrusion (Permian)

Peridotite intrusion; in northeastern corner of Elliot County

Massachusetts

Belchertown Complex (Devonian)

Belchertown Complex (intrudes De) - Hornblende peridotite.

Monson Gneiss (Ordovician, Cambrian, or Proterozoic Z)

Monson Gneiss - Lenses of peridotite, variously altered.

Mount Mineral Formation (Proterozoic Z)

Mount Mineral Formation (Probably correlates with Poplar Mountain Gneiss but is more aluminous) - Lenses of partially serpentinized harzburgite containing abundant veins of anthophyllite.

Serpentinized peridotite stocks (Ordovician to Proterozoic Z)

Serpentinized peridotite stocks - Intrudes Yw and Ygg.

Maryland

Ultramafic Rocks (Early Paleozoic - Late Precambrian (?))

Ultramafic Rocks - Chiefly serpentinite with partly to completely altered dunite, peridotite, pyroxenite, and massive to schistose soapstone; talc-carbonate rock and altered gabbro are common in some bodies.

Michigan

Gabbroic rocks of Keweenawan affinity (Middle Proterozoic)

Gabbroic rocks of Keweenawan affinity - gabbro, anorthosite, granite, peridotite

Minnesota

Gabbro, diorite, peridotite, and associated komatiitic flows of the Deer Lake sequence in Itasca County and the upper part of the Newton Lake Formation in Lake and St. Louis Counties (Late Archean)

Gabbro, diorite, peridotite, and associated komatiitic flows of the Deer Lake sequence in Itasca County and the upper part of the Newton Lake Formation in Lake and St. Louis Counties

Post-tectonic mafic intrusions (Late Archean)

Post-tectonic mafic intrusions - Gabbro, peridotite, pyroxenite, and their metamorphic equivalents. Unit also includes small intrusive complexes of anorthosite, gabbroic anorthosite, and anorthositic gabbro. Generally characterized by pronounced magnetic signatures.

New York

Olivine pyroxenite (Upper Ordovician)

Olivine pyroxenite - in part with poikilitic hornblende; local peridotite.

Oregon

Gabbro and ultramafic rocks associated with granitic plutons (Cretaceous and Jurassic) (Late Jurassic and Early Cretaceous)

Predominantly hornblende gabbro, gabbro, and olivine gabbro, but includes pyroxenite, hornblende pyroxene, and minor peridotite, dunite, and serpentinite (Smith and others, 1982)

Ultramafic and mafic intrusive rocks and serpentinized equivalents (Triassic and Paleozoic) (Paleozoic to Triassic)

Peridotite, pyroxenite, gabbro, and norite. Light-green, gray, and black serpentine, mostly derived from peridotite; commonly highly sheared; in places includes some metavolcanic rocks and metamorphosed inclusions of keratophyre and chert. Includes ultramafic and mafic phases of the ophiolitic Canyon Mountain Complex of Thayer (1963; 1977) and Brown and Thayer (1966), alpine mafic rocks of Wolff (1965), gabbro of Ashley (1967), and serpentinite-matrix melange of Brooks and others (1983) and Ferns and others (1983):

Ultramafic and related rocks of ophiolite sequences (Jurassic) (Paleozoic(?), Triassic(?), and Jurassic)

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

Pennsylvania

Ultramafic rocks (Probably lower Paleozoic)

Ultramafic rocks - Includes serpentine, steatite, and other products of alteration of peridotites and pyroxenites.

Tennessee

Intrusive igneous rocks (Precambrian)

Intrusive Igneous Rocks - Mica peridotite plugs (two in Union County), intrude Sneedville Limestone; metadiorite and metagabbro sills and dikes in Sevier County, intrude Great Smoky Group.

Virginia

Valley and Ridge Igneous Intrusions; Peridotite (Jurassic-Tertiary)

Valley and Ridge Igneous Intrusions; p: Peridotite - Dikes in Augusta and Rockingham Counties: nepheline syenite, teschenite-syenite, and teschenite-picrite. Igneous bodies in Highland County: andesite and basalt.

Vermont

Ultramafic Rocks (Ordovician)

Ultramafic Rocks - Dunite, peridotite, and serpentinite

Washington

Pre-Tertiary basic intrusive rocks (Triassic-Permian)

Predominantly gabbro and metagabbro; includes hornblendite, peridotite, and pyroxenite. In Nighthawk district and near 49th Parallel in Okanogan County and in Orient district of Stevens County.

Pre-Tertiary ultrabasic intrusive rocks (Late-Jurassic)

Peridotite and pyroxenite; generally altered partly or completely to serpentine. Includes serpentinite and saxonite on Sumas Mountain, Whatcom County.

Wisconsin

Gabbroic rocks of Keweenawan affinity (Middle Proterozoic)

Gabbroic rocks of Keweenawan affinity - gabbro, anorthosite, granite, peridotite

Wyoming

Peridotite intrusive rocks (Archean)

PERIDOTITE INTRUSIVE ROCKS--In Laramie Mountains.