PGC Publishing PCGPCG
download
Back Next Next
Iron Oxide-Cu-Au Deposits: What, Where, When, and Why?
 
by
Murray W. Hitzman, Colorado School of Mines, Golden, CO. USA.

in   Porter, T.M. (Ed), 2000 - Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective, PGC Publishing, Adelaide, v. 1, pp 9-25.

ABSTRACT

   The magnetite-apatite deposits ("Kiruna-type") and the iron oxide-Cu-Au deposits form end members of a continuum. In general the magnetite-apatite deposits form prior to the copper-bearing deposits in a particular district. While the magnetite-apatite deposits display remarkably similar styles of alteration and mineralization from district to district and throughout geologic time, the iron oxide-Cu-Au deposits are much more diverse. Deposits of this family are found in post-Archean rocks from the Early Proterozoic to the Pliocene.
   There appear to be three "end member" tectonic environments that account for the vast majority of these deposits: (A) intra-continental orogenic collapse; (B) intra-continental anorogenic magmatism; and (C) extension along a subduction-related continental margin. All of these environments have significant igneous activity probably related to mantle underplating, high heat flow, and source rocks (subaerial basalts, sediments, and/or magmas) that are relatively oxidized; many districts contain(ed) evaporites. While some of the magnetite-apatite deposits appear to be directly related to specific intrusions, iron oxide-Cu-Au deposits do not appear to have a direct spatial association with specific intrusions.
   Iron oxide-Cu-Au deposits are localized along high- to low-angle faults which are generally splays off major, crustal-scale faults. Iron oxide-Cu-Au deposits appear to have formed by: 1) significant cooling of a fluid similar to that responsible for precipitation of magnetite-apatite; 2) interaction of a fluid similar to that causing precipitation of magnetite-apatite with a cooler, copper-, gold-, and relatively sulfate-rich fluid of meteoric or "basinal" derivation; or 3) a fluid unrelated to that responsible for the magnetite-apatite systems but which is also oxidized and saline, though probably cooler and sulfate-bearing. The variability of potential ore fluids, together with the diverse rock types in which these deposits are located, results in the wide variety of deposit styles and mineralogies.



PorterGeo Home   |   PGC Publishing   |   Volume 1   |   Volume 2   |   Volume 3   |   Volume 4   |   Contact
PGC Logo
Porter GeoConsultancy Pty Ltd
 Ore deposit database
 Conferences & publications
 International Study Tours
     Tour photo albums
 Experience
PGC Publishing
 Our books and their contents
     Iron oxide copper-gold series
     Super-porphyry series
     Porphyry & Hydrothermal Cu-Au
 Ore deposit literature
 
 Contact  
 Site map
 FacebookLinkedin