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Geology, geochemistry, and mineralogy of the Worthington offset dike; a genetic model for offset dike mineralization in the Sudbury igneous complex

Peter C. Lightfoot and Catharine E. G. Farrow
Geology, geochemistry, and mineralogy of the Worthington offset dike; a genetic model for offset dike mineralization in the Sudbury igneous complex (in A special issue devoted to the mineral deposits of the Sudbury Basin, C. M. Lesher (editor) and P. C. Thurston (editor))
Economic Geology and the Bulletin of the Society of Economic Geologists (November 2002) 97 (7): 1419-1446

Abstract

The Worthington offset dyke extends for approximately 15 km away from the SW margin of the 1850 m.y. Sudbury igneous complex. The dyke is zoned with respect to inclusion and sulphide contents. Marginal chilled quartz diorite is transitional into medium-grained quartz diorite. These rocks are sulphide-undersaturated, contain small inclusions from the wall rocks, and are preserved along much of the dyke. Locally, the dyke contains a core of inclusion-rich quartz diorite, which may be choked with inclusions surrounded by semi-massive to massive sulphide. Differences may have developed in response to the different proportions of Archaean granitic rocks relative to Proterozoic sediments and volcanics that contributed to the melt sheet on the N and S Ranges of the Sudbury igneous complex. The first quartz diorite melt was sulphide-undersaturated and devoid of amphibolite inclusions. The introduction of this melt took place during or shortly after the generation of the melt sheet and represented a very rapid introduction of quartz diorite magma into radial and concentric dykes with local incorporation of metasedimentary inclusions. The second phase of activity involved the introduction of a sulphide-bearing melt into portions of the quartz diorite melt that were not completely crystallized at the centre of the offset dyke; this produced the inclusion-rich quartz diorite. Intersections of the quartz diorite with domains of Sudbury breccia appear to have been important in the Copper Cliff offset dyke and the development of mineralization may be a response to the presence of favourable channels through which magmatic sulphides were introduced into the dyke from the overlying melt sheet. It is suggested that the quantity of sulphide in a dyke is related to the thickness of the overlying melt sheet. The melt sheet thickness was presumably greatest at the Copper Cliff and Frood-Stobie offset dykes, the Worthington offset dyke is located below a thinner melt sheet, and the Manchester and Foy offset dykes developed beneath very thin portions of the melt sheet.


ISSN: 0361-0128
EISSN: 1554-0774
Coden: ECGLAL
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: 97
Serial Issue: 7
Title: Geology, geochemistry, and mineralogy of the Worthington offset dike; a genetic model for offset dike mineralization in the Sudbury igneous complex
Title: A special issue devoted to the mineral deposits of the Sudbury Basin
Author(s): Lightfoot, Peter C.Farrow, Catharine E. G.
Author(s): Lesher, C. M.editor
Author(s): Thurston, P. C.editor
Affiliation: Inco Technical Services, Copper Cliff, ON, Canada
Affiliation: Laurentian University, Department of Earth Sciences, Sudbury, ON, Canada
Pages: 1419-1446
Published: 200211
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
References: 62
Accession Number: 2003-014838
Categories: Economic geology, geology of ore depositsIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 3 tables, geol. sketch maps
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
Update Code: 200305
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