Strata-bound massive sulfide deposits in Silurian-Devonian volcanic rocks at Harborside, Maine

Strata-bound polymetallic massive sulfide ores of Silurian-Devonian age occur within the Coastal volcanic belt of Maine and New Brunswick. This terrain, overprinted by greenschist-facies regional metamorphism, is thought by some to represent volcanism above a consuming plate margin, and by others a...

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Bibliographic Details
Published in:	Economic geology and the bulletin of the Society of Economic Geologists Vol. 79; no. 7; pp. 1693 - 1702
Main Authors:	Bouley, Bruce A, Hodder, Robert W
Format:	Journal Article
Language:	English
Published:	Economic Geology Publishing Company 01-11-1984
Subjects:	Appalachian Phase Appalachian-Caledonian Orogen Appalachians copper ores Devonian economic geology exhalative processes geochemistry Hancock County Maine IGCP Knox County Maine kuroko-type deposits Maine massive deposits metal ores metamorphic rocks metavolcanic rocks mineral deposits, genesis North America ore bodies orogenic belts orogeny Paleozoic Penobscot Bay region Permian polymetallic ores production Silurian stratabound deposits sulfides trace elements United States volcanism Waldo County Maine zinc ores
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Summary:	Strata-bound polymetallic massive sulfide ores of Silurian-Devonian age occur within the Coastal volcanic belt of Maine and New Brunswick. This terrain, overprinted by greenschist-facies regional metamorphism, is thought by some to represent volcanism above a consuming plate margin, and by others a tensional tectonic environment. Along the east side of Penobscot Bay, Maine, volcanic rocks of the Castinc Formation are a well-preserved bimodal assemblage of mafic and felsic lavas, pyroclastites, and volcanogenic sedimentary rocks that record cyclic volcanic episodes.At Harborside, massive bodies of pyrite, sphalerite, and chalcopyrite were mined by Callahan Mining Corporation from open pit and underground workings. From 1968 to 1972, production totaled 800,000 tons of ore averaging 5.5 percent Zn, 1.28 percent Cu, 0.5 percent Pb, and 17.1 g/short ton Au. The massive sulfide bodies are on the flank of a black rhyolite dome and are assorted with Mg-rich rocks including talc, talc-carbonate, and talc-chlorite assemblages. The orebodies are strata-bound within dome-derived oligomictic rhyolite breccias, which are in turn enveloped by coarse polymictic fragmental rocks characteristic of vent facies volcanism. The nature of the volcanism and of the volcanic products, as well as the association of clusters of sulfide bodies about brecciated domes, compares closely with many of the massive sulfide deposits in the Kuroko district, Japan.
ISSN:	0361-0128 1554-0774
DOI:	10.2113/gsecongeo.79.7.1693