The Geology of the Argyle (AK1) Diamond Deposit,Western Australia
Date
2018
Authors
Rayner, Murray J.
Jaques, Alan
Boxer, G. L.
Smith, C. B.
Lorenz, Volker
Moss, Stephen W.
Webb, Kimberley
Ford, D.
Journal Title
Journal ISSN
Volume Title
Publisher
Society of Economic Geologists
Abstract
The Argyle (AK1) pipe in the Kimberley region of Western Australia is the world’s largest source of natural
diamonds, and it has produced more than 835 million carats since mining began in 1983. The ~1.2 Ga olivine
lamproite pipe lies within the Paleoproterozoic Halls Creek orogen at the southeastern margin of the Kimberley
craton, and it was emplaced during a period of extension associated with large-scale, NNE-trending strikeslip
faulting of the orogen.
AK1 is composed of four coalesced, steep-sided diatremes aligned along an NNE-trending fault and tapering
to narrow feeder zones at depth. The body is infilled by volcaniclastic olivine lamproite and cut by late olivine
lamproite dikes. Two distinct groups of volcaniclastic rocks are present. The dominant type comprises mainly
quartz-rich lapilli tuffs and coarse ash tuffs formed by numerous phreatomagmatic eruptions, when olivine
lamproite magma was erupted through water-rich sands and silts of the Carr Boyd Group. In contrast, latestage
olivine lamproite lapilli tuffs, devoid of accidental quartz grains, fill the center of the northern diatreme.
Following emplacement, the body was tilted 30° to the north and extended north-south by the sinistral northnorthwest–south-southeast
Gap fault system and east-northeast–west-southwest by the dextral Razor Ridge fault.
The Razor Ridge fault offsets the most southerly diatreme (southern tail) from the main part of AK1. Reversal
of structural offsets affecting AK1 reveals a geometry which closely resembles that of other ultramafic diatremes.
Variations in diamond grade and quality within AK1 indicate that at least two distinct magmas with unique
diamond contents have been emplaced at Argyle.
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Source
Special Publication Number 20
Type
Book chapter
Book Title
Geoscience and Exploration of the Argyle, Bunder, Diavik, and Murowa Diamond Deposits
Entity type
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Restricted until
2037-12-31