| Description |
1 online resource (iii, 13 pages) : illustrations, maps. |
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text txt rdacontent |
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computer c rdamedia |
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online resource cr rdacarrier |
| Series |
Contributions to Precambrian geology of Lake Superior region ; ch. P |
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U.S. Geological Survey bulletin ; 1904-P |
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Contributions to Precambrian geology of Lake Superior region ; ch. P.
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U.S. Geological Survey bulletin ; 1904-P.
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| Bibliography |
Includes bibliographical references (page 13). |
| 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. |
| Note |
Description based on print version record. |
| Access |
Use copy Restrictions unspecified star MiAaHDL |
| Reproduction |
Electronic reproduction. [S.l.] : HathiTrust Digital Library, 2011. MiAaHDL |
| System Details |
Master and use copy. Digital master created according to Benchmark for Faithful Digital Reproductions of Monographs and Serials, Version 1. Digital Library Federation, December 2002. http://purl.oclc.org/DLF/benchrepro0212 MiAaHDL |
| Processing Action |
digitized 2011 HathiTrust Digital Library committed to preserve pda MiAaHDL |
| Subject |
Volcanic ash, tuff, etc. -- Michigan.
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Geology, Stratigraphic -- Archaean.
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Geology -- Michigan.
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Archaean Geologic Period. (OCoLC)fst01351718
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Geology. (OCoLC)fst00940627
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Geology, Stratigraphic. (OCoLC)fst00940727
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Volcanic ash, tuff, etc. (OCoLC)fst01168809
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Michigan. (OCoLC)fst01208387
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Kitchi Formation.
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Mona Formation.
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| Chronological Term |
From 2 to 5 billion years ago
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| Added Author |
Johnson, R. C. (Rodney C.), author.
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Geological Survey (U.S.), issuing body.
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| Added Title |
Ishpeming greenstone belt, Michigan |
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Volcanic rocks, south half Ispheming greenstone belt, Michigan |
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Technical Report Archive & Image Library (TRAIL)
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| Other Form: |
Print version: Bornhorst, Theodore J. Geology of volcanic rocks in the south half of the Ishpeming greenstone belt, Michigan (DLC) 92027841 (OCoLC)26404169 |
| Gpo Item No. |
0620 (online) |
| Sudoc No. |
I 19.3:1904-P |
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