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Mineral Resources > Online Spatial Data > Geology > by state > Minnesota Geology

Geologic units in Lake county, Minnesota

[Additional scientific data in this geographic area]

Mafic metavolcanic rocks (Late Archean) at surface, covers 4 % of this area

Mafic metavolcanic rocks - Dominantly basalt that contains thin sedimentary units, including iron-formation. Includes parts of the Ely Greenstone and the Newton Lake Formation in northeastern Minnesota. Also includes metabasalt exposed in the Minnesota River Valley.

Lithology: basalt; sedimentary rock; iron formation; meta-basalt

North Shore Volcanic Group; Schroeder-Lutsen basalts (Middle Proterozoic) at surface, covers 0.2 % of this area

North Shore Volcanic Group; Schroeder-Lutsen basalts - Predominantly ophitic olivine tholeiitic basalt unconformably over older, normally polarized volcanic rocks. Based on its stratigraphic position and geochemical affinities, the unit may be correlative with the Lake Shore traps of northern Michigan

Lithology: basalt

Multiphase intrusions of hornblende-pyroxene-bearing and biotite-bearing monzonite, monzodiorite, diorite, syenite, and granodiorite (Late Archean) at surface, covers 0.4 % of this area

Multiphase intrusions of hornblende-pyroxene-bearing and biotite-bearing monzonite, monzodiorite, diorite, syenite, and granodiorite - Typically postdates regional metamorphism and deformation associated with the Algoman orogen.

Lithology: monzonite; monzodiorite; diorite; syenite; granodiorite

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) at surface, covers 0.4 % of this area

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

Lithology: gabbro; diorite; peridotite; ultramafitite (komatiite)

North Shore Volcanic Group; Normally polarized volcanic rocks, undivided (Middle Proterozoic) at surface, covers 15 % of this area

North Shore Volcanic Group; Normally polarized volcanic rocks, undivided - Basalt, andesitic basalt, rhyolite and related volcanogenic interflow sedimentary rocks along and inland from the North Shore of Lake Superior.

Lithology: basalt; rhyolite; clastic

Granite-rich migmatite (Late Archean) at surface, covers 2 % of this area

Granite-rich migmatite - Granitic gneiss, paragneiss, schist, and migmatite in the Vermillion Granitic Complex, and other parts of extreme northern Minnesota. Grades into granitoid rocks.

Lithology: gneiss; schist; migmatite

Saganaga Tonalite of northeastern Minnesota (Late Archean) at surface, covers < 0.1 % of this area

Saganaga Tonalite of northeastern Minnesota - Emplaced more-or-less contemporaneously with deposition of metasedimentary and metavolcanic rocks

Lithology: tonalite

Duluth Complex; Felsic series (Middle Proterozoic) at surface, covers 3 % of this area

Duluth Complex; Felsic series - Granophyric granite and related felsic rocks

Lithology: granite

Subvolcanic mafic rocks, undivided; Beaver Bay Complex and other named and unnamed gabbroic-troctolitic intrusions (Middle Proterozoic) at surface, covers 18 % of this area

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.

Lithology: gabbro; troctolite

Duluth Complex; Anorthositic series (Middle Proterozoic) at surface, covers 27 % of this area

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

Lithology: anorthosite; gabbro

Metasedimentary rocks, undivided (Late Archean) at surface, covers 6 % of this area

Metasedimentary rocks, undivided - Graywacke, slate, local units of conglomerate, arenite, graphitic slate, fine-grained felsic volcanogenic, and volcaniclastic rocks, lean oxide iron-formation and its metamorphic equivalents. Includes the Knife Lake Group and the Lake Vermilion Formation in northeastern Minnesota.

Lithology: graywacke; slate; metasedimentary rock; felsic metavolcanic rock; iron formation

Syntectonic to pretectonic granitoid rocks (Late Archean) at surface, covers 5 % of this area

Syntectonic to pretectonic granitoid rocks - Granite and granodiorite of the Vermilion Granitic Complex, the Giants Range and Bemidji batholiths, as well as smaller intrusions of tonalite and monzonite of the Algoman orogen in northern Minnesota. Also includes the Odessa, Sacred Heart, and Fort Ridgely Granites exposed along the Minnesota River Valley in southwestern Minnesota.

Lithology: granite; granodiorite; tonalite; monzonite

Duluth Complex; Troctolitic and gabbroic cumulate rocks (Middle Proterozoic) at surface, covers 15 % of this area

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

Lithology: troctolite; gabbro

Subvolcanic mafic rocks, undivided; Selected granophyric and leuco-granitic phases of troctolitic-gabbroic intrusions in the Beaver Bay Complex (Middle Proterozoic) at surface, covers 3 % of this area

Subvolcanic mafic rocks, undivided; Selected granophyric and leuco-granitic phases of troctolitic-gabbroic intrusions in the Beaver Bay Complex

Lithology: granite