Geology of volcanic rocks in the south half of the Ishpeming greenstone belt, Michigan / by Theodore J. Bornhorst and Rodney C. Johnson.

Format:

Book

Government document

Author/Creator:

Bornhorst, Theodore J., author.

Johnson, R. C. (Rodney C.), author.

Contributor:

Geological Survey (U.S.), issuing body.

Series:

Contributions to Precambrian geology of Lake Superior region ; ch. P.

U.S. Geological Survey bulletin ; 1904-P.

Contributions to Precambrian geology of Lake Superior region ; ch. P

U.S. Geological Survey bulletin ; 1904-P

Language:

English

Subjects (All):

Volcanic ash, tuff, etc--Michigan.

Volcanic ash, tuff, etc.

Geology, Stratigraphic--Archaean.

Geology, Stratigraphic.

Geology--Michigan.

Geology.

Kitchi Formation.

Mona Formation.

Archaean Geologic Period.

Michigan.

Physical Description:

1 online resource (iii, 13 pages) : illustrations, maps.

Distribution:

[Washington, D.C.] : United States Government Printing Office

Other Title:

Ishpeming greenstone belt, Michigan

Volcanic rocks, south half Ispheming greenstone belt, Michigan

Place of Publication:

[Reston, Va.] : U.S. Department of the Interior, U.S. Geological Survey, 1993.

Summary:

The south half of the Ishpeming greenstone belt is domi- nated by a thick succession of subaqueously erupted volcanic rocks. A regional structural interpretation of the belt provides a framework for placing this succession in a stratigraphic order. The south half of the Ishpeming greenstone belt preserves the remnants of overlapping subaqueous volcanic complexes within an arc system. The Kitchi Formation, as redefined herein, comprises the lower half of the volcanic succession and is subdivided into three informal units. The basal basalt flow unit is composed of pillowed, tholeiitic, basalt flows and minor banded iron-formation and dacitic tuff. It is overlain by the second and third units, which are tuff and lahar (volcanic debris flow) units that inter- finger with one another. These units range in composition from calc-alkalic basalt to dacite. The Kitchi Formation represents an evolving tholeiitic, mafic shield to calc-alkalic, mafic to felsic subaqueous volcano. The Mona Formation, which is redefined herein, is in structural contact with the Kitchi Formation, but is likely younger. It is subdivided into three informal units. The base consists of a basalt flow unit, which is composed of pillowed, tholeiitic to magnesium-rich basalt flows and minor amounts of banded iron-formation and tuff. The basalt is overlain by a calc-alkalic dacite to rhyolite lapilli-tuff unit and a laterally continuous upper tuff unit of calc-alkalic basalt to andesite. The Mona Formation represents an evolving tholeiitic, mafic shield to mafic-felsic calc-alkalic, mafic to felsic subaqueous volcano. The Deer Lake Peridotite, an ultramafic sill complex that intrudes the Kitchi Formation, is speculatively interpreted as a subvolcanic ultramafic komatiite base of the Mona Formation.

Notes:

Includes bibliographical references (page 13).

Print version record.

Electronic reproduction. [S.l.] : HathiTrust Digital Library, 2011.

Other Format:

Print version: Bornhorst, Theodore J. Geology of volcanic rocks in the south half of the Ishpeming greenstone belt, Michigan

OCLC:

937435762

Access Restriction:

Use copy Restrictions unspecified