Journal article

Gold deposits related to reduced granitic intrusions

Thompson J, Newberry R ...see all

Reviews in Economic Geology, vol. 13 (2000) pp. 377-400

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Abstract

The role of intrusions in the formation of many types of gold deposits has been widely debated. Magmatic-hydrothermal processes are proposed by some authors for gold-rich porphyry systems, while many other authors claim that intrusions only serve as convective heat engines or structural hosts for mesothermal gold deposits. Based largely on well-documented examples from Alaska and the Yukon Territory, we recognize a class of deposits that display a spatial and temporal relation to reduced (low f (sub O2) granitoids. Most intrusion-hosted and intrusion-proximal deposits and prospects of this class display a consistent and striking Au-Bi-Te-As (W,Mo,Sb) metal association; evidence for a series of alteration and mineralization events spanning a significant range of temperatures (>500 degrees -1 kbar generally lack evidence for rapid magmatic water exsolution (e.g., porphyritic textures, random stockworks, magmatic breccias). Deposits horizontally and vertically distal from intrusions within a given belt or district typically lack the strong Au-Bi association of proximal deposits and contain higher As, Sb, and base metals and only yield evidence for relatively low-temperature and low-salinity fluids. These latter types possess some characteristics of orogenic (mesothermal), epithermal, or Carlin-type deposits; however, their spatial and temporal association with the higher-temperature deposits suggests a common origin. Although the clearest examples of these reduced intrusion-related deposits (e.g., Fort Knox, Alaska; Dublin Gulch, Yukon Territory) are only of moderate size (

Author-supplied keywords

  • alaska
  • alteration
  • arsenic
  • australasia
  • australia
  • bismuth
  • canada
  • carbon dioxide
  • central europe
  • czech republic
  • deposits
  • dublin gulch
  • europe
  • fluid inclusions
  • fort knox alaska
  • genesis
  • geologic barometry
  • gold ores
  • granites
  • igneous rocks
  • inclusions
  • intrusions
  • kazakhstan
  • kidston australia
  • magmatism
  • mesothermal processes
  • metal ores
  • metals
  • mineral
  • mineralization
  • mokrsko czech republic
  • murantau
  • plutonic rocks
  • porphyry
  • structural controls
  • tellurium
  • united states
  • western canada
  • yukon territory

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Authors

  • John F. H. Thompson

  • Rainer J. Newberry

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