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Geologic units containing gabbro

Arkansas

Olistoliths of Metagabbro and Soapstone-Serpentine (Phanerozoic | Paleozoic)

Olistoliths of Metagabbro and Soapstone-Serpentine - Altered peridotite

Arizona

Early Proterozoic granitic rocks (Early Proterozoic)

Wide variety of granitic rocks, including granite, granodiorite, tonalite, quartz diorite, diorite, and gabbro. These rocks commonly are characterized by steep, northeast-striking foliation. (1600-1800 Ma)

Early Proterozoic metamorphic rocks (Early Proterozoic)

Undivided metasedimentary, metavolcanic, and gneissic rocks. (1600-1800 Ma)

Early Proterozoic metavolcanic rocks (Early Proterozoic)

Weakly to strongly metamorphosed volcanic rocks. Protoliths include basalt, andesite, dacite, and rhyolite deposited as lava or tuff, related sedimentary rock, and shallow intrusive rock. These rocks, widely exposed in several belts in central Arizona, include metavolcanic rocks in the Yavapai and Tonto Basin supergroups. (1650 to 1800 Ma)

Early Tertiary to Late Cretaceous granitic rocks (Late Cretaceous to Early Tertiary)

Porphyritic to equigranular granite to diorite emplaced during the Laramide orogeny. Larger plutons are characteristically medium-grained, biotite +/- hornblende granodiorite to granite. Smaller, shallow-level intrusions are typically porphyritic. Most of the large copper deposits in Arizona are associated with porphyritic granitic rocks of this unit, and are thus named 'porphyry copper deposits'. (50-82 Ma)

Middle Miocene to Oligocene granitic rocks (Oligocene to Middle Miocene)

Granite to diorite representing solidified magma chambers that were the likely source of overlying and nearby volcanic rocks of map unit Tv. The granitic rocks are typically equigranular and fine- to medium-grained. (14-26 Ma)

Proterozoic granitic rocks (Proterozoic)

Undivided Early and Middle Proterozoic granitic rocks (units Xg and Yg). (1400-1800 Ma)

California

Franciscan Complex, unit 1 (Coast Ranges) (Jurassic to Cretaceous)

Franciscan complex: Cretaceous and Jurassic sandstone with smaller amounts of shale, chert, limestone, and conglomerate. Includes Franciscan melange, except where separated--see KJfm.

Mesozoic gabbroic rocks, unit 1 (Trinity Ophiolite) (Ordovician)

Gabbro and dark dioritic rocks; chiefly Mesozoic

Mesozoic gabbroic rocks, unit 2 (undivided) (Triassic to Cretaceous)

Gabbro and dark dioritic rocks; chiefly Mesozoic

Mesozoic granitic rocks, unit 1 (Salinian Block) (Early to Late Cretaceous)

Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite

Mesozoic granitic rocks, unit 3 (Sierra Nevada, Death Valley area, Northern Mojave Desert and Transverse Ranges) (Permian to Tertiary; most Mesozoic)

Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite

Mesozoic granitic rocks, unit 5 (Klamath Mountains) (Jurassic to early Cretaceous)

Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite

Miocene marine rocks and Franciscan schist (Cretaceous(?) to Miocene)

Precambrian granitic rocks, unit 1 (Eastern Mojave Desert) (Early Proterozoic to Miocene)

Precambrian granite, syenite, anorthosite, and gabbroic rocks in the San Gabriel Mountains; also various Precambrian plutonic rocks elsewhere in southeastern California

Precambrian granitic rocks, unit 2, (San Gabriel Mountains Anorthosite) (Middle Proterozoic)

Precambrian granite, syenite, anorthosite, and gabbroic rocks in the San Gabriel Mountains; also various Precambrian plutonic rocks elsewhere in southeastern California

Tertiary intrusive rocks (hypabyssal), unit 9 (Jurassic gabbros along Hayward Fault) (Jurassic)

Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.

Undivided pre-Cenozoic metavolcanic rocks, unit 1 (Southwestern Sierra Nevada) (Ordovician(?) to Permian(?))

Undivided pre-Cenozoic metavolcanic rocks. Includes latite, dacite, tuff, and greenstone; commonly schistose.

Undivided pre-Cenozoic metavolcanic rocks, unit 2 (undivided) (Paleozoic(?) to Mesozoic(?))

Undivided pre-Cenozoic metavolcanic rocks. Includes latite, dacite, tuff, and greenstone; commonly schistose.

Colorado

Alkalic and mafic rocks in small plutons, and diabase and gabbro dikes (Proterozoic | Mesoproterozoic)

Alkalic and mafic rocks in small plutons, and diabase and gabbro dikes

Mafic rocks of 1700-m.y. age group (Proterozoic | Paleoproterozoic)

Gabbro and mafic diorite and monzonite

Connecticut

Buttress Dolerite (Middle? Jurassic)

Buttress Dolerite - Dark-gray to greenish-gray (weathers brown or gray), medium- to fine-grained, commonly porphyritic, generally massive with well-developed columnar jointing, grading from basalt near contacts to fine-grained gabbro in the interior, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine.

Buttress Dolerite (uncertain) (Middle? Jurassic)

Buttress Dolerite (uncertain)- Dark-gray to greenish-gray (weathers brown or gray), medium- to fine-grained, commonly porphyritic, generally massive with well-developed columnar jointing, grading from basalt near contacts to fine-grained gabbro in the interior, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine.

Hampden Basalt (Lower Jurassic)

Hampden Basalt - Greenish-gray to black (weathers bright orange to brown), fine- to medium-grained, grading from basalt near contacts to fine-grained gabbro in the interior, composed of pyroxene and plagioclase with accessory opaques and locally olivine or devitrified glass.

Holyoke Basalt (Lower Jurassic)

Holyoke Basalt - Greenish-gray to black (weathers bright orange to brown), fine- to coarse-grained, grading from basalt near contacts to gabbro in the interior, composed of pyroxene and plagioclase with accessory opaques and locally olivine or devitrified glass.

Lebanon Gabbro (Devonian)

Lebanon Gabbro - Dark, speckled, coarse-grained, massive but locally sheared gabbro, composed of hornblende, labradorite, and opaques. Some bodies contain biotite, and quartz; some smaller ones are nearly pure hornblende with local augite.

Preston Gabbro (Middle Ordovician or older)

Preston Gabbro - Dark, medium- to coarse-grained, mainly massive gabbro, composed of labradorite, augite, and opaques, generally with hornblende, locally hypersthene, or olivine or both.

Preston Gabbro plus Quinebaug Formation (Middle Ordovician or older)

Preston Gabbro plus Quinebaug Formation - Preston Gabbro - Dark, medium- to coarse-grained, mainly massive gabbro, composed of labradorite, augite, and opaques, generally with hornblende, locally hypersthene, or olivine or both. Quinebaug Formation - Medium- to dark-gray, commonly greenish, medium-grained, well-layered gneiss, composed of hornblende, andesine, biotite, and epidote, commonly with quartz or garnet, interlayered with amphibolite.

Talcott Basalt (Lower Jurassic)

Talcott Basalt - Greenish-gray to black (weathers bright orange to brown), fine- to medium-grained, grading from basalt near contacts to fine-grained gabbro in the interior, composed of pyroxene and plagioclase with accessory opaques and locally olivine or devitrified glass. Pillows in many places; volcanic breccia with fragmentary pillows in others.

West Rock Dolerite (Lower Jurassic)

West Rock Dolerite - Dark-gray to greenish-gray (weathers bright orange to brown), medium- to fine-grained, grading from basalt near contacts to fine-grained gabbro in the interior, generally massive with well-developed columnar jointing, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine.

West Rock Dolerite (uncertain) (Lower Jurassic)

West Rock Dolerite (uncertain) - Dark-gray to greenish-gray (weathers bright orange to brown), medium- to fine-grained, grading from basalt near contacts to fine-grained gabbro in the interior, generally massive with well-developed columnar jointing, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine.

Delaware

Gabbro (Paleozoic)

Gabbro - gabbro

Georgia

Amphibolite / gabbro (Precambrian-Paleozoic)

Amphibolite / gabbro

Gabbro (Precambrian-Paleozoic)

Gabbro

Idaho

Amphibolite after gabbro, diabase, and diorite; Middle Proterozoic sill-like intrusions; southern and northern Belt provinces (Middle Proterozoic)

Younger or Intermediate Precambrian age intrusive rock undifferentiated; Intrusive rock of eastern Idaho; appears older than Cretaceous, possibly Precambrian; Highly metamorphosed rock of central Idaho; age and origin of rock questionable.

Basalt, andesite, diorite, lamprophyre intrusions; Tertiary to Cretaceous, undivided; northern Idaho, central Idaho (Cretaceous or Eocene)

Eocene intrusions including large granitic plutons and dike swarms of central Idaho

Diorite, gabbro, and granite; Jurassic to Triassic plutons; western Idaho, Blue Mountains island-arc complex (Jurassic to Triassic)

Lower Mesozoic intrusions; localized near the Snake Canyon of western Idaho.

Gabbro, diorite, amphibolite, lamprophyre; Tertiary to Late Proterozoic, undivided; northern Idaho (Tertiary to Late Proterozoic)

Younger Precambrian dioritic and amphibolitic sills of northern Idaho.

Gabbro, diorite, quartz diorite, aplite; Late to Middle Proterozoic sills injected into sedimentary strata of the Belt Basin; northern Belt province (Late to Middle Proterozoic)

Younger Precambrian dioritic and amphibolitic sills of northern Idaho; basaltic or mafic; as gabbro.

Gabbroic intrusions; probably Cretaceous; mostly satellitic to the Idaho batholith (Cretaceous )

Cretaceous plutons; basaltic or mafic; as gabbro; probably includes unmapped older and younger crystalline bodies.

Quartz diorite, tonalite, granodiorite, orthogneiss, migmatite; Cretaceous to Jurassic quartz dioritic plutons; western Idaho, Blue Mountains island-arc complex (Early Cretaceous to Late Jurassic)

Lower Cretaceous to Upper Jurassic intrusions in west-central Idaho.

Quartzite and biotite schist in fault contact; Middle Proterozoic metasedimentary rocks; southern Belt province (Middle Proterozoic)

Intermediate Precambrian age metasediments; dominantly quartzite with minor micaceous layers and mica schists of northern Idaho

Syenite, granite, quartz syenite, and gabbro; Ordovician to Cambrian plutons; east-central Idaho (Ordovician to Cambrian)

Intrusive rock of eastern Idaho; appears older than Cretaceous; possibly Precambrian

Syenite, quartz syenite, monzodiorite, quartz diorite, gabbro, pyroxenite, and hornblendite; Late Proterozoic plutons; east-central Idaho (Late Proterozoic)

Younger or Intermediate Precambrian age intrusive rock undifferentiated.

Massachusetts

Cooleyville Granitic Gneiss (Devonian)

Cooleyville Granitic Gneiss - Biotite tonalite to granite in composition, strongly foliated and lineated; contains inclusions of Dpgb; intrudes Dl.

Diorite and gabbro (Proterozoic Z)

Diorite and gabbro - Complex of diorite and gabbro, subordinate metavolcanic rocks and intrusive granite and granodiorite.

Gabbro (Proterozoic Z)

Gabbro - Hornblende gabbro and hornblende-pyroxene gabbro metamorphosed in part to hornblende gneiss and amphibolite.

Holyoke Basalt (Lower Jurassic)

Holyoke Basalt - Thick, columnar quartz tholeiite containing local gabbroic segregations, thinks eastward; interpreted as one or more thick ponded lava flows. Assigned to Newark Supergroup (Robinson and Luttrell, 1985).

Hornblende-olivine gabbro (Precambrian to Paleozoic)

Hornblende-olivine gabbro - Intrudes Dl.

Metamorphosed mafic to felsic flow, and volcaniclastic and hypabyssal intrusive rocks (Proterozoic Z)

Metamorphosed mafic to felsic flow, and volcaniclastic and hypabyssal intrusive rocks - Includes some diorite and gabbro north and northwest of Boston.

Nahant Gabbro and gabbro at Salem Neck (Ordovician)

Nahant Gabbro and gabbro at Salem Neck - Labradorite-pyroxene gabbro, hornblende gabbro and hornblende diorite. Intrudes CAbw. Nahant Gabbro intrudes Early Cambrian Weymouth Formation at Nahant and thus is younger than gabbroic or dioritic rocks intruded by Late Proterozoic Dedham Granite or Topsfield Granite. Unrecognized equivalents to Nahant Gabbro at Nahant and at Salem Neck may be present within unnamed gabbro and diorite units shown on MA State geologic map (Zen and others, 1983). Mapped as three facies at Nahant, following usage of Bell (1977): pyroxene gabbro, olivine gabbro, and quartz diorite. Biotite from olivine gabbro was analyzed by Rb-Sr and K-Ar methods and yielded an Ordovician age (450 +/-13 Ma by Rb-Sr methods, 483 +/-21 Ma by K-Ar methods). Quartz diorite phase may be a more mafic phase of Dedham Granite (Wones and Goldsmith, 1991).

Prescott Complex (Devonian)

Prescott Complex - Hornblende gabbro (formerly Prescott Diorite of Emerson, 1917).

Sharon Syenite (Proterozoic Z)

Sharon Syenite - Gray to dark-gray syenite containing microperthite, oligoclase and clinopyroxene, mixed with ferro-gabbro. Proterozoic Z Sharon Syenite forms long narrow mass along southeast side of Norfolk basin. Consists of gray to dark-gray syenite and minor ferrogabbro. Both rock types are intruded by Proterozoic Z Dedham Granite, but relationship to other Proterozoic Z gabbros is unknown. Near Sharon, unit is intruded by unnamed Proterozoic Z diorite (Wones and Goldsmith, 1991).

Maryland

Baltimore Gabbro Complex (Late Precambrian (?) - Early Paleozoic )

Baltimore Gabbro Complex - Hypersthene gabbro with subordinate amounts of olivine gabbro, norite, anorthositic gabbro, and pyroxenite; igneous minerals and textures well preserved in some rocks, other rocks exhibit varying degrees of alteration and recrystallization with a new metamorphic mineral assemblage.

Georgetown Mafic Complex (Late Precambrian (?) - Early Paleozoic )

Georgetown Mafic Complex - Poorly exposed complex of tonalite, dark quartz diorite, gabbro, amphibolite, and undifferentiated basic rocks.

Metagabbro and Amphibolite (Early Paleozoic (?))

Metagabbro and Amphibolite - Weakly to strongly lineated metagabbro and epidote amphibolite.

Quartz Gabbro and Quartz Diorite Gneiss (Paleozoic)

Quartz Gabbro and Quartz Diorite Gneiss - Mixed rock zone of greenish-black, uralitized, quartz-bearing gabbro to dark gray, weakly gneissic, pyroxene-hornblende-biotite quartz diorite.

Ultramafic and Gabbroic Rocks (Early Paleozoic (?))

Ultramafic and Gabbroic Rocks - Mixed metagabbro, serpentinite, metapyroxenite, and actinolite-, chlorite-, and epidote-bearing schists.

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.

Maine

Cambrian gabbro/diorite/ultramafic rocks (Cambrian)

Cambrian gabbro/diorite/ultramafic rocks

Cambrian Hurricane Mountain Formation, metagabbro (Cambrian)

Cambrian Hurricane Mountain Formation, metagabbro

Carboniferous gabbro/diorite/ultramafic rocks (Carboniferous)

Carboniferous gabbro/diorite/ultramafic rocks undivided

Cretaceous gabbro/diorite/ultramafic rocks (Cretaceous)

Cretaceous gabbro/diorite/ultramafic rocks

Cretaceous quartz diorite - gabbro/diorite/ultramafic rocks (Cretaceous)

Cretaceous quartz diorite - gabbro/diorite/ultramafic rocks - Cretaceous biotite quartz diorite and gabbro/diorite/ultramafic rocks

Devonian gabbro (Devonian)

Devonian gabbro

Devonian gabbro/diorite/ultramafic rocks (Devonian)

Devonian gabbro/diorite/ultramafic rocks

Devonian gabbro/diorite/ultramafic rocks - quartz diorite (Devonian)

Devonian gabbro/diorite/ultramafic rocks - quartz diorite - Devonian gabbro/diorite/ultramafic rocks to biotite quartz diorite - gabbro, diorite, ultramafic rocks, biotite monzodiorite, biotite syenite, and biotite quartz diorite.

Devonian gabbro - ultramafic rocks (Devonian)

Devonian gabbro - ultramafic rocks

Mesozoic gabbro/diorite/ultramafic rocks (Mesozoic)

Mesozoic gabbro/diorite/ultramafic rocks

Ordovician gabbro/diorite/ultramafic rocks (Ordovician)

Ordovician gabbro/diorite/ultramafic rocks

Silurian gabbro/diorite/ultramafic rocks (Silurian)

Silurian gabbro/diorite/ultramafic rocks

Michigan

Gabbroic rocks of Keweenawan affinity (Middle Proterozoic)

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

Mafic metavolcanic rocks (Early Proterozoic)

Mafic metavolcanic rocks - Dominantly tholeiitic basalt and basaltic andesite flows and tuffs; associated with sheet dikes, massive and layered metagabbro, and ultramafic rocks. In northeastern Wisconsin, rocks have been named the Quinnesec Formation.

Minnesota

Anorthosite, gabbroic anorthosite, and anorthositic gabbro of the Mentor mafic intrusive complex in Polk County (Late Archean)

Anorthosite, gabbroic anorthosite, and anorthositic gabbro of the Mentor mafic intrusive complex in Polk County

Duluth Complex; Anorthositic series (Middle Proterozoic)

Duluth Complex; Anorthositic series - Plagioclase-rich gabbroic cumulates and related rocks

Duluth Complex; Early gabbros (Middle Proterozoic)

Duluth Complex; Early gabbros - Gabbro and related rocks in northeastern Minnesota that have petrologic affinities to the Logan Intrusions

Duluth Complex; Troctolitic and gabbroic cumulate rocks (Middle Proterozoic)

Duluth Complex; Troctolitic and gabbroic cumulate rocks - Constitute at least nine named and several unnamed intrusions

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

Logan Intrusions (Middle Proterozoic)

Logan Intrusions - Diabase, porphyritic diabase, gabbro, and related felsic sills and dikes.

Post-tectonic intrusions of the Penokean orogen (Early Proterozoic)

Post-tectonic intrusions of the Penokean orogen - Small stocks of olivine pyroxenite in Morrison County; small plutons of hornblende-rich diorite and gabbro that contain layers and lenses of nelsonite, pyroxenite, and anorthosite in Todd County.

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.

Subvolcanic mafic rocks, undivided; Beaver Bay Complex and other named and unnamed gabbroic-troctolitic intrusions (Middle Proterozoic)

Subvolcanic mafic rocks, undivided; Beaver Bay Complex and other named and unnamed gabbroic-troctolitic intrusions - Includes a number of other intrusions in a variety of dikes and sills such the Endion sill and the Pigeon River intrusions.

Syntectonic intrusions of the Penokean orogen (Early Proterozoic)

Syntectonic intrusions of the Penokean orogen - Includes the Pierz Granite, the Freedhem and Bradbury Creek Granodiorites, and several unnamed intrusions of granite, granodiorite, tonalite, and gabbro in east-central Minnesota

Missouri

DIABASE DIKES AND SILLS (Precambrian [Y])

DIABASE DIKES AND SILLS

Montana

Diabase, metagabbro, and diorite and related rocks (Proterozoic)

Diabase, metagabbro, and diorite and related rocks: dark gray fine to medium grained, mostly in dikes and sills; dominantly mafic but contain alkalai feldspar and micropegmatite in some areas.

Tertiary dikes and sills (Phanerozoic | Cenozoic | Tertiary)

Tertiary dikes and sills: mostly granophyric rocks in west and alkalic rocks in east, but includes some quartz diorite and other rocks. These dikes and sills are in part offshoots of the Tertiary coarse-grained intrusive rocks.

North Carolina

Gabbro of Concord Plutonic Suite (Devonian/Ordovician)

Gabbro of Concord Plutonic Suite (399-479 my) - Barber, Concord, Farmington, Mecklenburg, and Weddington intrusives.

Pee Dee Gabbro (Pennsylvanian)

Pee Dee Gabbro (314 my) - dark gray to black, medium to fine grained, massive.

New Hampshire

Augite-hornblende-biotite gabbro (Cretaceous)

Augite-hornblende-biotite gabbro - Fine- to coarse-grained.

Augite-hornblende diorite and gabbro (Cretaceous )

Augite-hornblende diorite and gabbro - Gray to black, coarse-grained, porphyritic. Found in Mt. Pawtuckaway quadrangle.

Exeter Diorite (Early Devonian)

Exeter Diorite - Includes associated intrusive rocks of southeastern New Hampshire; pyroxene and pyroxene-hornblende diorite and gabbro, along with minor granodiorite and granite.

Gabbro (Jurassic)

Gabbro - Has varying amounts of olivine, augite, and hornblende.

Gabbro and diabase (Middle Ordovician)

Gabbro and diabase - Foliated to nonfoliated and coarse- to fine-grained; includes mafic dikes tentatively correlated with Chickwolnepy intrusions.

Hornblende gabbro (Late Ordovician)

Hornblende gabbro.

Hypersthene-biotite quartz diorite and hornblende or actinolite diorite or gabbro (Early Devonian - Late Devonian)

Hypersthene-biotite quartz diorite and hornblende or actinolite diorite or gabbro - Spatially associated with Spaulding Tonalite plutons.

New Jersey

Gabbro (Middle Proterozoic)

Gabbro - Medium- to coarse-crystalline, medium- to dark-gray foliated rock composed principally of plagioclase (An35) and clinopyroxene. Contains minor amounts of garnet, biotite, and sulfide. The rock is more siliceous than typical gabbros.

Nevada

Diorite (Jurassic to Cretaceous)

Gabbroic complex (Early Jurassic to Middle Jurassic)

GABBROIC COMPLEX (Lower and Middle Jurassic)-Includes gabbro, basalt, and synorogenic quartz sandstone (Boyer Ranch Formation). Churchill and Pershing Counties

Granitic rocks, western Nevada (Jurassic to Cretaceous)

GRANITIC ROCKS, WESTERN NEVADA (Mesozoic)-Mostly quartz monzonite and granodiorite. Inconclusively dated or not dated radiometrically

Intrusive rocks of mafic to intermediate composition (Eocene to Miocene)

INTRUSIVE ROCKS OF MAFIC TO INTERMEDIATE COMPOSITION

New York

Gabbro or norite to hornblende diorite (Upper Ordovician)

Gabbro or norite to hornblende diorite - rock complex with minor pyroxenite; Croton Falls and Peach Lake complexes in New York, and Mt. Prospect Complex in Connecticut.

Oklahoma

Raggedy Mountain Gabbro Group (Phanerozoic | Paleozoic | Cambrian-Early)

LAWTON- Gabbro, anorthosite, and diorite; thickness, as much as 10,000 feet (3,000 m).

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)

Gabbroic rocks (Paleozoic to Triassic)

Most gabbro genetically related to ultramafic rocks, but some probably derived from metamorphism of Triassic and older volcanic rocks

Granite and diorite (Jurassic and Triassic) (Triassic and Jurassic)

Felsic to intermediate, granitoid intrusive rocks. Includes Jurassic muscovite granodiorite, hornblende gabbro, tonalite, and quartz diorite of southwest Oregon (Smith and others, 1982)

Granitic rocks (Cretaceous and Jurassic) (Late Jurassic and Early Cretaceous)

Mostly tonalite and quartz diorite but including lesser amounts of other granitoid rocks. Potassium-argon ages determined on hornblende indicates plutons range in age from 143 to 166 Ma (Hotz, 1971)

Hypabyssal intrusive rocks (Miocene and Miocene?) (Miocene)

Hypabyssal, medium-grained, hornblende diorite and quartz diorite in small stocks and large dikes; includes intrusions of medium- to fine-grained gabbro and plugs and small stocks of medium-grained, holocrystalline, olivine andesite. Also includes medium-grained, commonly porphyritic biotite quartz monzonite and leucocratic granodiorite. Many of these intrusive bodies are moderately to intensely propylitized, as are wallrocks they intrude; locally, along shears, the rocks also are sericitized. Potassium-argon ages on several of these shallow intrusions range from about 8 Ma to about 22 Ma (Wise, 1969; Bikerman, 1970; Sutter, 1978; Power and others, 1981a, b; Fiebelkorn and others, 1983)

Intrusive gabbroic rocks (Oligocene and Eocene) (Eocene to Oligocene)

Sills and dikes of basalt, diabase, gabbro, and granophyric gabbro; locally albitized and zeolitized (Snavely and others, 1976a, b)

Mafic and intermediate intrusive rocks (Miocene) (Miocene)

Dikes, plugs, and sills of basalt, diabase, gabbro, and lesser andesite that fed many of the Miocene basalt and andesite flows in unit Tc. Some intrusions are rootless and are invasive into sedimentary sequences; includes related breccia and peperite. Includes Depoe Bay and Cape Foulweather dikes, sills, and plugs in the Coast Range (Snavely and others, 1976a, b; Wells and others, 1983)

Mafic and intermediate intrusive rocks (Pliocene and Miocene) (Miocene to Pliocene)

Dikes, plugs, and sills of basalt, diabase, gabbro, and lesser andesite that fed many of the Miocene basalt and andesite flows in units Tc and Tba. Some intrusions are rootless and are invasive into sedimentary sequences; includes related breccia and peperite. Includes the Monument dike swarm of northwestern Grant County (OR061), the Chief Joseph dike swarm principally in Baker and Wallowa Counties (OR093), the Steens Mountain dike swarm in Harney County (OR005; OR094; OR095) and numerous isolated intrusive bodies in southern Lake County and several intrusive masses in and near-vent flows in southern Malheur County (OR023;OR024). May also include some lower Pleistocene(?) rocks

Mafic intrusions (Oligocene) (Oligocene)

Sheets, sills, and dikes of massive granophyric ferrogabbro; some bodies strongly differentiated and include pegmatitic gabbro, ferrogranophyre, and granophyre (MacLeod, 1981). Plagioclase and amphibole from unit have yielded K-Ar ages of about 30 Ma (Snavely and others, 1976a)

Melange of Dutchmans Peak (Triassic or Paleozoic) (Paleozoic(?) to Jurassic(?))

Heterogeneous mixture of interlayered metasedimentary and metavolcanic rocks metamorphosed to upper greenschist and (or) almandine-amphibolite facies, and serpentinite, gabbro, and metagabbro (Smith and others, 1982)

Mixed rocks (Mesozoic and Paleozoic) (Paleozoic to Mesozoic)

Intermingled, commonly highly sheared metasedimentary, metavolcanic, and igneous rocks. Includes serpentinite, altered gabbro, chert, siliceous phyllite, greenstone, and limestone

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

Metagabbro (Probably lower Paleozoic)

Metagabbro - Ranges from fine- to medium-grained, altered gabbro to hornblende gneiss.

Rhode Island

Esmond Igneous Suite - mafic/intermediate rock (Late Proterozoic)

Esmond Igneous Suite - mafic/intermediate rock - Dark-gray, purple, or black, medium- to coarse-grained rock that may contain plagioclase, quartz, clinopyroxene, hornblende, olivine, and accessory biotite, epidote, sphene, zircon, apatite, and opaque minerals; secondary chlorite, sericite, and saussurite. Massive to variably foliated. Composition includes tonalite, quartz diorite, diorite, and gabbro. Includes rock mapped formerly as quartz diorite.

gabbro/diorite (Late Proterozoic? to Devonian?)

gabbro/diorite - Dark-gray to black, fine- to medium-grained, equigranular, faintly foliated rock, composed of plagioclase, clinopyroxene, hornblende, biotite, and accessory sphene, apatite, and opaque minerals. Includes quartz diorite, diorite, and gabbro.

Scituate Igneous Suite - diorite/gabbro (Devonian)

Scituate Igneous Suite - diorite/gabbro - Fine- to medium-grained, equigranular, massive to slightly foliated rock, composed of plagioclase, hornblende, clinopyroxene, and quartz, with accessory biotite, sphene, apatite, and opaque minerals; secondary chlorite, epidote, and saussurite. Varieties include quartz diorite, diorite, and gabbro.

South Carolina

Anderson metagabbro (Paleozoic)

Anderson metagabbro

Diorite-gabbro- Clouds Creek pluton (Carboniferous)

Diorite-gabbro- Clouds Creek pluton

Diorite-gabbro- Dutchman's Creek pluton (Carboniferous)

Diorite-gabbro- Dutchman's Creek pluton

Gabbro- Abbeville pluton (Devonian to Silurian)

Gabbro- Abbeville pluton

Gabbro- Buffalo pluton (Devonian to Silurian)

Gabbro- Buffalo pluton

Gabbro- Calhoun Falls pluton (Devonian to Silurian)

Gabbro- Calhoun Falls pluton

Gabbro- Chester pluton (Devonian to Silurian)

Gabbro- Chester pluton

Gabbro- Greenwood pluton (Devonian to Silurian)

Gabbro- Greenwood pluton

Gabbro- McCormick pluton (Devonian to Silurian)

Gabbro- McCormick pluton

Gabbro- Mecklenburg pluton (Devonian to Silurian)

Gabbro- Mecklenburg pluton

Gabbro- Mt. Carmel pluton (Devonian to Silurian)

Gabbro- Mt. Carmel pluton

Gabbro- North York pluton (Devonian to Silurian)

Gabbro- North York pluton

Gabbro- Odgen pluton (Devonian to Silurian)

Gabbro- Odgen pluton

Gabbro of Concord Plutonic Suite (Devonian to Silurian)

Gabbro of Concord Plutonic Suite

Gabbro- Rock Hill North pluton (Devonian to Silurian)

Gabbro- Rock Hill North pluton

Gabbro- Rock Hill South pluton (Devonian to Silurian)

Gabbro- Rock Hill South pluton

Hammett Grove Meta-igneous Suite - metagabbro (Paleozoic or Neoproterozoic)

Hammett Grove Meta-igneous Suite - metagabbro

Metagabbro and minor metadiorite (Middle Paleozoic to Neoproterozoic)

Metagabbro and minor metadiorite

Metagabbro- Big Wateree Creek (Middle Paleozoic to Neoproterozoic)

Metagabbro- Big Wateree Creek: metagabbro and minor metadiorite

Metagabbro- Chester (Middle Paleozoic to Neoproterozoic)

Metagabbro- Chester: metagabbro and minor metadiorite

South Dakota

Metamorphosed Siltstone (Proterozoic | Paleoproterozoic)

Medium-gray to dark-greenish-gray phyllite, slate, and biotite schist containing minor chert and amphibolite. Locally intruded by thin metagabbro sills. Thickness 1,000-3,000 ft (305-914 m).

Tennessee

Bakersville Gabbro (Precambrian)

Bakersville Gabbro - Metagabbro, dark, porphyritic; contains diorite, basalt, anorthosite, and diabase; occurs as thin to massive dikes and lenticular masses.

Intrusive igneous rocks (Paleozoic (?))

Intrusive Igneous Rocks - Metadiorite and metagabbro in Polk County, intrude Great Smoky Group.

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.

Mount Rogers Group including Bakersville Gabbro, Beech Granite, Cranberry Granite, and Roan Gneiss (Precambrian)

Mount Rogers Group - Metavolcanics, typically purplish and reddish; massive lavas and tuffs, altered rhyolites and quartz latites; strongly foliated; interbedded arkose, shale, and conglomerate. Thickness 1,000 to 3,000 feet; Includes Bakersville Gabbro - Metagabbro, dark, porphyritic; contains diorite, basalt, anorthosite, and diabase; occurs as thin to massive dikes and lenticular masses; Beech Granite - Granite, porphyritic, light-gray to reddish; coarse potash feldspar crystals and clustered interstitial mafics (chloritized biotite and hornblende) give spotted appearance; includes Max Patch Granite; Cranberry Granite - Complex of intertonguing rock types including migmatite, granitic gneisses, monzonite, quartz diorite, greenstone, mica and hornblende schists, abundant granitic pegmatite; and Roan Gneiss - Layered hornblende and garnet gneiss and granitic migmatite with zones of mica schist and amphibolite, foliation commonly contorted; contains numerous granitic and gabbroic dikes.

Roan Gneiss (Precambrian)

Roan Gneiss - Layered hornblende and garnet gneiss and granitic migmatite with zones of mica schist and amphibolite, foliation commonly contorted; contains numerous granitic and gabbroic dikes.

Texas

Mafic igneous rocks (preCambrian-Proterozoic)

Mafic igneous rocks

Virginia

Abbeyville Gabbro (Proterozoic)

Abbeyville gabbro

Altered Diorite and Gabbro (Proterozoic)

Altered diorite and gabbro

Amphibole Metagabbro (Cambrian)

Amphibole Metagabbro

Georgetown Intrusive Suite (Cambrian)

Georgetown Intrusive Suite - Tonalite, quartz gabbro, quartz diorite, metapyroxenite, and hornblendite.

Hornblende-plagioclase Gabbro (Proterozoic)

Hornblende Gabbro in Carolina Slate Belt; Hornblende-Plagioclase Gabbro in Central Virginia Volcanic-Plutonic Belt; Gabbro, Hornblendite and Norite in Central Piedmont

Rich Acres Formation (Cambrian)

Rich Acres Formation - Norite, metagabbro, and diorite.

Ta River Metamorphic Suite (Cambrian)

Ta River Metamorphic Suite - Amphibolite gneiss

Vermont

Essexitite (Permian-Triassic)

Essexitite

Hornblende-biotite diorite; gabbro (Permian-Triassic)

Hornblende-biotite diorite; gabbro.

Washington

Basic intrusive rocks, undivided (Jurassic in central Cascades; Oligocene to Eocene in northern Cascades)

Predominantly gabbro; includes some serpentine. Age undetermined.

Mesozoic granitic rocks, undivided (Mostly Cretaceous-Jurassic)

Granite, quartz monzonite, quartz diorite, granodiorite, and trondhjemite. Includes diorite in southeastern Washington; diorite and gabbro near Concunully in Okanogan County; gneiss, schist, and migmatites in areas of Chelan, Colville, and Okanogan batholiths. Includes high-grade metamorphic rocks of Precambrian age in Spokane area.

Mesozoic-Tertiary marine rocks, undivided (Miocene to Eocene)

Dark-gray, massive to poorly bedded gray-wacke of the interior Olympic Peninsula; commonly with interbedded slate, argillite, volcanic rocks, and minor arkosic sandstone. Includes rocks both older and younger than Ev2, some of which may be Paleozoic.

Mesozoic-Tertiary volcanic rocks, undivided (Oligocene to Eocene)

Altered basalt, pillow lavas, and flow breccia of inner volcanic belt of Olympic Peninsula; includes minor interbedded red limy argillite and associated manganese ore.

Pre-Carboniferous crystalline complex (Devonian)

Metahornblendite, amphibolite, gneiss, metadiorite, meta-quartz diorite, and trondhjemite. As klippes along western slope of northern Cascade Mountains.

Pre-Carboniferous intrusive rocks (Paleozoic)

Meta-quartz diorite, hypersthene diorite, and gneissose and directionless quartz diorite of eastern Skagit County. Quartz diorite and diorite in the San Juan Islands. Includes amphibolite and gneiss locally.

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 metamorphic rocks, undivided (Probably Permian)

Schist, gneiss, marble, quartzite, amphibolite, greenstone, metaconglomerate, graywacke; includes metasedimentary, volcanic, and intrusive rocks. Some areas, as on San Juan Islands, show little if any metamorphism.

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.

Pre-Tertiary volcanic rocks, undivided (Probably mostly Jurassic)

Andesite and basalt flows, and greenstone; includes minor interbedded limestone, arkose, quartzite, and chert beds.

Pre-Upper Jurassic metamorphic rocks of the low-grade zone (Jurassic)

Greenschist, phyllite, and slate; includes some limestone, quartzose phyllite, schistose metaconglomerate, breccia, and basic igneous rocks. Includes schist locally.

Pre-Upper Jurassic metamorphic rocks of the medium and high-grade zone (Early Jurassic-Triassic)

Schist, amphibolite, and minor lime-silicate rocks, marble, quartzite, and metaconglomerate.

Tertiary-Cretaceous basic intrusive rocks (Cretaceous-Jurassic)

Diorite and gabbro in western Snohomish County.

Tertiary-Cretaceous granitic intrusive rocks (Early Tertiary-Late Cretaceous)

Granite, granodiorite, trondhjemite, and quartz diorite. Late Cretaceous and/or early Tertiary.

Tertiary dikes, sills, and small intrusive bodies (Middle to Late Tertiary)

Dikes are commonly diabase; plugs and sills are generally andesite porphyry and dacite.

Tertiary granitic rocks (Probably mostly Eocene; ranges from Miocene to Paleocene)

Granite, quartz monzonite, quartz diorite, granodiorite, and trondhjemite. Includes dacite porphyry and granite breccia near Bumping Lake, Yakima County.

Wisconsin

Gabbro (Early Proterozoic)

Gabbro - Massive to layered intrusive gabbroic rocks; weakly metamorphosed and deformed. Exposed in both Pembine-Wausau and Marshfield terranes

Gabbroic rocks of Keweenawan affinity (Middle Proterozoic)

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

Layered metagabbro (Late Archean)

Layered metagabbro - Interlayered gabbro, mafic accumulates, gabbroic anorthosite and anorthosite (Cummings, 1984) in Eau Claire River (T. 27 N., R. 8 W.). Age uncertain, but interpreted as Archean (Sims, 1990).

Mafic metavolcanic rocks (Early Proterozoic)

Mafic metavolcanic rocks - Dominantly tholeiitic basalt and basaltic andesite flows and tuffs; associated with sheet dikes, massive and layered metagabbro, and ultramafic rocks. In northeastern Wisconsin, rocks have been named the Quinnesec Formation.

Mellen Intrusive complex; Olivine gabbro (Middle Proterozoic)

Mellen Intrusive complex; Olivine gabbro

Metagabbro (Early Proterozoic)

Metagabbro - Mafic to ultramafic bodies defined and delineated principally by positive magnetic and gravity anomalies; includes diorite bodies. Comagmatic with unit Xmi