 Economic Minerals – minerals that can be extracted, processed, and marketed at a profit. Factors: -interest in the mineral, -size of the deposit, -mineral concentration, -mineral depth below the surface -market value.  An ore is a natural material with a high concentration of economically valuable minerals that can be mined for a profit

 1) Magmatic Deposits  accumulations of metals associated with magma that forms igneous rocks  Certain metals are enriched in certain magmas and further concentrated during cooling of the magma

 Magmatic Deposits: A) Layered  Gravitational Settling  heavy minerals that crystallize early, settle and concentrate on the bottom of the magma chamber this results in a layered deposit. High-density minerals sink to the bottom of the magma chamber.

 Magmatic Deposits: B) Disseminated  Deposits in which the metal is evenly distributed in generally low concentrations throughout large masses of igneous rock. Ex: porphyry copper deposit  (e.g. Sudbury, Ontario and Voisey’s Bay, Newfoundland and Labrador) A sample of nickel-bearing rock from Sudbury.

 Diamonds  Most diamonds are found in unique ultramafic igneous rocks called kimberlites  Magma generated by partial melting of asthenosphere below 150 kilometres and then rises quickly to the surface, picking up diamonds from solid lithospheric mantle

22) Hydrothermal Deposits aany concentration of metallic minerals formed by the precipitation of solids from hot mineral-rich water (hydrothermal solution).  hot water dissolves and transport minerals, interconnected openings in the rock allows the solutions to move, and chemical reaction result in deposition. Deposition can be caused by boiling, by a drop in temperature, by mixing with a cooler solution, or by chemical reactions between the solution and a reactive rock. pproduce vein deposits.

 Hydrothermal Deposits  Can occur as disseminated deposits, which are distributed throughout the rock body, rather than concentrated in veins; called porphyry deposits = (low grade; large volume)

33) Sedimentation SSecondary enrichment AA class of residual deposits formed by both the removal of valueless material in solution and the solution and redeposition of valuable ore minerals. BBecause solution and redeposition occurs the process is known as a secondary enrichment.

 Weathering  Secondary enrichment  Bauxite  Principal ore of aluminum  Forms in rainy tropical climates from chemical weathering and the removal of undesirable elements by leaching

 Stratiform Deposits  Copper-bearing brines moving through coarse- grained sedimentary rock are forced upward through oxygen-poor, sulphide-rich mud, which promotes precipitation of minerals

 Sedimentary Deposits  Banded Iron Formations  Conditions during the early Precambrian resulted in large quantities of ferrous iron in solution  At some point, photosynthesizing bacteria generated sufficient oxygen to precipitate iron oxide minerals. Ex: Bell Island Deposit

 4) Placer deposits  – formed when heavy metals are mechanically concentrated by currents  Examples:  Gold, Platinum, Diamonds

 5) Metamorphic Deposits  Many of the most important metamorphic ore deposits are produced by contact metamorphism.  Sphalerite (zinc)  Galena (lead)  Chalcopyrite (copper)