Potassic alteration and veining and the age of copper emplacement at Mount Isa, Australia

Melissa J. Gregory*, Andy R. Wilde, Bruce F. Schaefer, Reid R. Keays

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contribution

Abstract

Preliminary Re-187/Os-188 dating of whole rocks and sulphide separates from the Mount Isa copper orebody has generated an isochron age of 1367 +/- 80 Ma (MSWD = 49; n = 6). This age is approximately 150 myr younger than published biotite Ar-40/Ar-39 ages previously assumed to date the copper-forming event at ca. 1523 Ma. These older ages are from rocks in which biotite is likely to be metamorphic rather than hydrothermal in origin. Unambiguous potassic alteration related to copper formation is characterised by biotite replacement of metabasalt (brownstones) and potassium feldspar replacement of meta-tuffs. Previous Ar-40/Ar-39 dating of biotite from brownstone yields 1352 Ma to 1385 Ma ages, while Rb-87/Sr-86 dating of potassium feldspar altered tuffs gives 1323 Ma. Muscovite from the Buck Quartz Fault, considered a conduit for copper mineralising fluids, yields an Ar-40/Ar-39 age of 1324 Ma. We suggest that these ages more accurately reflect the age of copper emplacement, whereas the older Ar-40/Ar-39 ages more likely relate to cooling from peak metamorphism.

Original languageEnglish
Title of host publicationMineral deposit research
Subtitle of host publicationmeeting the global challenge
EditorsJ Mao, FP Bierlein
PublisherSpringer, Springer Nature
Pages755-758
Number of pages4
Volume1 and 2
ISBN (Print)3540279458
Publication statusPublished - 2005
Event8th Biennial SGA Meeting - Beijing, China
Duration: 18 Aug 200521 Aug 2005

Conference

Conference8th Biennial SGA Meeting
CountryChina
CityBeijing
Period18/08/0521/08/05

Keywords

  • Mount Isa
  • re-os
  • potassic alteration
  • MINERALIZATION
  • QUEENSLAND
  • OREBODIES
  • METAMORPHISM
  • DEFORMATION
  • SYSTEM
  • FLUID

Cite this