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GEOREF RECORD

The magnesite deposit at Main Creek, Savage River, Tasmania

M. T. Frost
The magnesite deposit at Main Creek, Savage River, Tasmania
Economic Geology and the Bulletin of the Society of Economic Geologists (December 1982) 77 (8): 1901-1911

Abstract

The magnesites at Main Creek, a tributary of Savage River in northwestern Tasmania are associated with dolomite and talc-chlorite schist in a mildly metamorphosed belt running northeastward across the area. The nearly vertically dipping lens of magnesite is over 218 m thick, and although the extension to the south and north is very uncertain, reserves most likely exceed 40 million metric tons. As a result, mining is being considered. A further deposit of about equal size is found to the north at Arthur River. The carbonate mineralogy is well characterized by the use of a very sensitive backscattered electron detector which easily distinguishes magnesite and dolomite and also demonstrates the zoning of Mg and Fe in both the magnesite and dolomite. Apart from the thin bands of schist and dolomite, the magnesite ore contains about 5 to 10 percent quartz and 5 to 10 percent dolomite. In the upper dolomite horizons especially, replacement of dolomite by magnesite is evident. Mg metasomatism by dilute MgCl (sub 2) solutions is considered more likely than a sedimentary origin. The amount of FeCO (sub 3) in the magnesite falls steadily from about 3 percent at the surface to less than 1 percent FeCO (sub 3) at 305 m. Experimental studies of Johannes (1970) suggest that a MgCl (sub 2) solution with small amounts of FeCl (sub 2) would be expected to form more Fe-rich magnesite at higher (cooler) horizons and more Mg-rich magnesite at depth. It is also suggested that the Savage River magnesites, which were once dolomites, may be contemporaneous with the Savage River dolomites which lie to the west, outside the Arthur lineament, and which are considered to be early Cambrian in age.


ISSN: 0361-0128
EISSN: 1554-0774
Coden: ECGLAL
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: 77
Serial Issue: 8
Title: The magnesite deposit at Main Creek, Savage River, Tasmania
Author(s): Frost, M. T.
Affiliation: CSIRO, Div. Miner. Chem., Port Melbourne, Vic., Canada
Pages: 1901-1911
Published: 198212
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
References: 26
Accession Number: 1983-005341
Categories: Economic geology, geology of nonmetal deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 11 anal., 6 tables, geol. sketch maps
S41°40'00" - S40°40'00", E144°30'00" - E146°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Society of Economic Geologists
Update Code: 1983
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