ORE DEPOSITS OF SUB AERIAL VOLCANIC ASSOCIATION

 

Volcanic ore deposits include metallic ores, non-metallic oresor industrial minerals (clays, zeolites) and for that matter, water in its natural form (drinking, agricultural) or as geothermal springs.  Ore deposits associated with subaerial volcanism include Ni-Cu PGE (platinum group elements) deposits associated with subaqueous ultramafic flows, and Au-Ag and Zn-Cu-Pb (Au-Ag) deposits associated with subaerial (epithermal deposits) and subaqueous (volcanic-associated massive sulfide) volcanic centres respectively.

There is no doubt that metallic ores of Cu, Ni, Zn, Au, Ag and PGE hosted by volcanic rocks are of great economic significance for many countries such as Canada, Australia and Chile.  Copper and gold has been mined from volcanic rocks in Rome, Cyprus and Turkey around 2500 BC.  Gold ores in volcanic rocks convinced investors to support Columbus’ voyage to the Far East 1n 1492.

Two distinct types of Ni-Cu (PGE) ore deposits occur within komatiitic flow sequences. The different types differ in their morphology, percent sulfide, grade and location within different flow facies.  Komatiite hosted Ni-Cu sulfide ores contain approximately 25 % of the world’s known Ni resources.  

Ore mineral assemblages occurring in volcanic rocks

  1. Cu-Fe-Zn assemblages in volcanic rocks
  2. Stratiforn Sulfide Deposits of marine and marine-volcanic affiliation. These include chemical sedimentation and sulfide pyroclastic concentrations interbedded with some lavas. All these are essentially sea floor volcanic accumulations. A few of these are associated with basaltic and more mafic lavas Eg Cyprus and Japan, whereas a vast majority are associated with andesitic and dacitic rocks. Eg Base metals of Ontario, Mount Isa and McArthur River (Precambrian); Bathurst, New Brunswick and E. Australia (Paleozoic) and Japan (Tertiary).
  3. Mineral deposits associated with flood basalts, for example the copper bearing lavas of the Keweenaw  Peninsula, Lake Superior; copper bearing lavas of the Deccan traps around Bhawani Mandi, Rajasthan.

Notes & Handouts

The Himalayas

Kumaon Himalayas

Askot Basemetals

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