Geochronology of the Panguna porphyry copper deposit, Bougainville Island, New Guinea

Abstract

K-Ar ages have been determined on the major intrusive and sub volcanic bodies associated with the Panguna copper deposit on Bougainville. The earliest pre-mineraliza-tion intrusive has an age of 4 to 5 m.y., and the mineralized, strongly altered, intrusive bodies are 3.4 ± 0.3 m.y. old. The 3.4 m.y. age is interpreted as the age of mineralization of the Panguna rocks and is not distinguishable from the age of the porphyries themselves. Thus a clear time interval of about 0.5 to 1.5 m.y. is recognized between the initial magmatic emplacement at Panguna and subsequent mineralization associated with the porphyries. One of the intrusives that on field evidence is known to postdate mineralization has an age of 3.5 ± 0.3 m.y., and another such body was emplaced only 1.6 m.y. ago.