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Geology of the Tenke-Fungurume Sediment-Hosted Strata-Bound Copper-Cobalt District, Katanga, Democratic Republic of Congo*

By
Wolfram Schuh
Wolfram Schuh
1
Freeport McMoRan Exploration, 10861 N. Mavinee Drive, Tucson, Arizona 85737
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Richard A. Leveille
Richard A. Leveille
2
Freeport McMoRan Exploration, 333 North Central Avenue, Phoenix, Arizona 85004
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Isabel Fay
Isabel Fay
3
Department of Geosciences, University of Arizona, Tucson, Arizona 85721
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Robert North
Robert North
1
Freeport McMoRan Exploration, 10861 N. Mavinee Drive, Tucson, Arizona 85737
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Published:
January 01, 2012

Abstract

Tenke-Fungurume is one of the world's premier copper deposits with almost 17 billion pounds (7.7 million metric tons, Mt) of contained copper as reserves and mineralized material at a combined average grade exceeding 3 wt % Cu identified by Freeport McMoRan Copper and Gold, Inc. (Freeport). It is also the world's largest known resource of potentially mineable cobalt. Tenke-Fungurume lies within the Central African Copperbelt, which straddles the border between the Democratic Republic of Congo (DRC) and Zambia. The Central African Copperbelt is the largest copper- and cobalt-producing belt in Africa and one of the three most important copper regions in the world. The belt also contains half of the world's cobalt reserves.

The Tenke-Fungurume district consists of over 120 separate mineralized tectonic blocks, 30 of which have been drilled by Freeport to resource definition level with mineable reserves defined within 14 of those. Since 2006, Freeport has drilled approximately 350,000 m in over 2,000 diamond drill holes defining recoverable proven and probable reserves of 141 Mt at 3.00% Cu + 0.32% Co (8.4 billion lbs Cu and 860 million lbs Co) with an additional 105 Mt at 3.31% Cu and 0.307% Co as mineralized material adding a further 7.6 billion lbs of contained copper. Production is by open-pit mining and agitated leach processing at a current rate of 281 million lbs copper and 25 million lbs cobalt per year. Tenke-Fungurume is the third largest copper mine in Africa and the largest cobalt mine in the world.

All current production and reserves are from oxide ores with oxidation typically extending to depths of 80 to 150 m. Main oxide ore minerals include up to 91% malachite and up to 9% pseudomalachite and libethenite; oxide cobalt is mainly heterogenite. The oxide zone is underlain by a 50- to 200-m-thick zone of mixed ore characterized by pink cobaltoan dolomite, chrysocolla, and chalcocite. Sulfide mineralization below the mixed ore has been drilled to a 1,900-m depth. Sulfide minerals are chalcocite, bornite, carrollite, chalcopyrite, and scant pyrite.

The Central African Copperbelt coincides with the Neoproterozoic Lufilian arc, a platform sedimentary sequence of the Katanga Supergroup deposited between 880 and 570 Ma. Extension was followed by the 560 to 500 Ma compressional Lufilian orogeny that folded and thrust the ore-hosting sediments to the northeast.

The large majority of the copper-cobalt ores in Tenke-Fungurume are strata bound, hosted in the Mines Series of the Roan Group. The bulk of the ore occurs directly above a regional stratigraphic contact between red, oxidized hematitic beds below, and gray, reduced carbonate beds above. The former are reddish Roches Argileuses Talqueuses (RAT) lilas, the latter are gray algal dolomites of the Mines Series. This major redox boundary underlies copper-cobalt mineralization everywhere in the Central African Copperbelt.

Field and petrographic observations indicate that hypogene copper-cobalt mineralization took place in two main phases; an initial diagenetic event formed strata-bound, disseminated to fine laminated copper sulfides, and a second overprinting sulfide event generated crosscutting epigenetic veins related to the Lufilian orogeny. Deep supergene oxidation during the Tertiary formed the oxide orebodies.

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Contents

Special Publications of the Society of Economic Geologists

Geology and Genesis of Major Copper Deposits and Districts of the World: A Tribute to Richard H. Sillitoe

Jeffrey W. Hedenquist
Jeffrey W. Hedenquist
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Michael Harris
Michael Harris
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Francisco Camus
Francisco Camus
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Society of Economic Geologists
Volume
16
ISBN electronic:
9781629490410
Publication date:
January 01, 2012

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