CLASSIFICATION OF ORE DPOSITS

CLASSIFICATION OF ORE DPOSITSBasing on the nature and morphology Basing on the origin/ GenesisBasing on the temperature of formation (PT Conditions)Basing on the mineral compositionCLASSIFICATION BASING ON THE MORPHOLOGY/SHAPERegular Discordant Ore-bodiesTubular mineral deposits, these are ore bodies which are extensive in two dimensions, but have restricted development in their third dimension, e.g. veins.Tubular mineral deposits, these are ore bodies which are relatively short in two dimensions but extensive in third dimension, e.g pipes. Irregular Discordant Orebodies Disseminated deposits, in these deposits, ore minerals are peppered through out the body of host rock in the same way as the accessory minerals are disseminated in the igneous rocks. The ore minerals makes the closely spaced veins called stockworkprospecting, e.g diamonds in kimberlites.Concordant OrebodiesParallel to bedding and limited development perpendicular to it, thus strataform. Not to be confused with stratabound, which refers to type of orebody, concordant or discordant, which is restricted to a particular part of the stratigraphic colomn.Stratiform Deposits

Classification basing on the temperature of formationHydrothermal ore deposit can be classified based on approximate temperatures of formation as;Hypothermal mineral deposits; this is formed at depth of 3 to 15km with temperature ranging from 300-600C.Classification basing on the temperature of formationMesothermal mineral deposits; this is formed at depth of 1 to 4.5km with temperature ranging from 200-300CEpithermal mineral deposits; this is formed at near surface depth 1.5 km with temperature ranging from 50-200C.Classification basing on Origin/GenesisHydrothermal mineral deposits formed in association with magma and hot waters.Magmatic mineral deposits concentrated in igneous rocks (crystallization verses segregation) Sedimentary mineral deposits precipitated from a solution, typically sea water Classification basing on Origin/GenesisPlacer deposits sorted and distributed by flow of water (or ice) and concentrated by gravity Residual mineral deposits formed by weathering reactions at the earth's surfaceMetamorphic mineral deposits, formed by metamorphic processes, both contact and regionalClassification basing on Origin/GenesisSecondary or supergene enrichment where leaching of materials occurs and precipitation at depth produces higher concentrations.Other classificationThe ore deposit can also be classified basing on the formation time relationship with the host rock into;Epigenetic mineral depositSyngenetic mineral deposit Epigenetic mineral depositFormed much later than the rocks which enclose it. If a mineral deposit formed much later than the rocks which enclose it, it is said to be epigenetic. An example is a vein. The first step in the formation of a vein is the fracturing or breaking of rock along a fault zone, at a depth ranging from surface to several kilometers below surface.Epigenetic mineral depositThe rock must be solid (lithified) and brittle, creating open spaces when it breaks.Hydrothermal solutions pass along the fault zone and deposit or precipitate the ore and gangue minerals within the open spaces. Thus, the vein is necessarily younger than the rocks that contain it.Syngenetic mineral deposit A syngenetic mineral deposit is a deposit which formed at the same time as the rocks that enclose it. Magmatic deposits are syngenetic in that the ore minerals crystallize from the same liquid that produces the silicate minerals which form the bulk of the intrusive - they crystallize more or less simultaneously as the melt cools.Syngenetic mineral deposit Deposits which form on the earth's surface in the form of a sedimentary layer are also syngenetic. The rocks which they lie upon were deposited just prior to the mineralizing event, while the overlying rocks were deposited just after - all three layers being deposited at essentially the same time in terms of the geological time frame.