Characteristics of porphyry Cu mineralization at Waisoi (Namosi District), Viti Levu, Fiji

Akira Imai, Yukiko Ohbuchi, Takayuki Tanaka, Seiya Morita, Kentaro Yasunaga

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The porphyry Cu deposits at Waisoi in Namosi district, Viti Levu are separated into two deposits: the Waisoi East deposit and the Waisoi West deposit. In the Waisoi East deposit, quartz porphyry is exposed and in the Waisoi West deposit, diorite porphyry is sporadically exposed in addition to a small body of quartz porphyry. The mineralization in the Waisoi East deposit is characterized by the bornite-chalcopyrite-pyrite assemblage associated with traces of molybdenite and native gold. Polyphase fluid inclusions in stockwork quartz veinlets show homogenization temperatures ranging from 210 to >500°C. The high-grade Cu mineralization in the Waisoi West deposit is characterized by the bornite-chalcopyrite-pyrite assemblage accompanied with sheeted and stockwork quartz veinlets. Polyphase fluid inclusions occasionally containing hematite flakes in quartz veinlets in the center of the Waisoi West deposit homogenize at temperatures ranging from 450°C to >500°C. However, fluid inclusions in stockwork quartz veinlets in the periphery, homogenize at lower temperatures around 210°C. Both in the Waisoi East and Waisoi West deposits, primary bornite-chalcopyrite-pyrite assemblage in the high Cu-grade zone was deposited at the upper stability limit of chalcopyrite with respect to sulfur fugacity. Thus, the principal Cu mineralization at the Waisoi deposits occurred at a relatively high sulfur fugacity, that is, in a high-sulfidation environment.

Original languageEnglish
Pages (from-to)374-385
Number of pages12
JournalResource Geology
Volume57
Issue number4
DOIs
Publication statusPublished - Dec 1 2007

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Quartz
porphyry
mineralization
quartz
chalcopyrite
bornite
fluid inclusion
pyrite
Sulfur
Quartz deposits
Fluids
fugacity
sulfur
molybdenite
Gold
Temperature
diorite
hematite
gold
temperature

All Science Journal Classification (ASJC) codes

  • Geology
  • Geochemistry and Petrology

Cite this

Characteristics of porphyry Cu mineralization at Waisoi (Namosi District), Viti Levu, Fiji. / Imai, Akira; Ohbuchi, Yukiko; Tanaka, Takayuki; Morita, Seiya; Yasunaga, Kentaro.

In: Resource Geology, Vol. 57, No. 4, 01.12.2007, p. 374-385.

Research output: Contribution to journalArticle

Imai, Akira ; Ohbuchi, Yukiko ; Tanaka, Takayuki ; Morita, Seiya ; Yasunaga, Kentaro. / Characteristics of porphyry Cu mineralization at Waisoi (Namosi District), Viti Levu, Fiji. In: Resource Geology. 2007 ; Vol. 57, No. 4. pp. 374-385.
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