ORE GENESIS - A SHORT OVERVIEW ON HYDROTHERMAL, MAGMATIC AND SURFICIAL PROCESSES

• ORE MINERAL : a mineral from which one or more metal can be extracted

  (Chalcopyrite - Cu, Galena - Pb)

• GANGUE : Unnecessary material associated with ore

• TENOR : Total metal content of an ore

• GRADE : Concentration of metal in an ore

• CUT OFF GRADE : Grade below which it is not possible to mine, i.e lowest grade which will be mine

• HOST ROCK : Rock which contain ore deposits

• COUNTRY ROCK : Rock which surrounds the ore deposits

• BENEFICIATION : Process of removal gangue to produce a high grade ore deposit

• ORE GENESIS : Process of formation of ore deposits

• HYPOGENE

  • Primary mineral deposition

  • ascending hydrothermal solution

• SUPERGENE

  • Secondary mineral deposition

  • descending hydrothermal solution

• SYNGENETIC : Formed during same time of formation of host rock

• EPIGENETIC : Formed after formation of host rock

• STRATIFORM:

  • Reflect stratification

  • Concordant in nature

  • Ex: Stratiform copper, Kupferscheiper

• STRATABOUND:

  • Restricted to a particular lithology

  • Mostly discordant

  • Ex: MVT deposit, Zawar belt , Rajpura dariba

• RESOURCE : Total amount of commodity present in the area, deposits which believe to exist but not exploitable due to some reason

• RESERVE : Ore that are economically feasible to mine, discovered deposits which can be extract profitably

MAGMATIC PROCESS

• CRYSTAL FRACTIONATION

  • Diamond in Kimberlite (Panna, vajrakarur, Majhagawan)

  • Chromite in ultramafic rock (Sukinda, Bushveld, Still water and Great dyke)

  • Fe-Ti in Gabbro Anorthosite

• LIQUID FRACTIONATION

  • Apatite-Magnetite in Andesite or Diorite (Kiruna,Singbhum shear zone)

  • Cu-Ni-PGE (Sudbury)

  • Carbonatite in Cu-U-REE (Ambadongar, Gujurat)

• PEGMATITIC DEPOSIT

  • Mica bearing (Bhilwara, Koderma, Nellore)

  • Sn and Rare metals ( Bastar, Melkangi)

HYDROTHERMAL PROCESS

• MAGMATIC WATER

  • Porphyry copper Cu-Mo-Au (Malanjhkhand)

  • Sn-W in Greisen Granites ( Degana)

• METEORIC WATER

  • VMS DEPOSITS -

    • Cyprus type : Mafic volcanic (MOR)

    • Kuroko type : Felsic volcanic (Subduction zone)

    • Besshi type : Mafic siliclastic (Back arc basin)

    • Bathrust type : Felsic siliclastic

    • Mattabi , Noranda : Mafic-felsic volcanic

  • SEDEX DEPOSITS (Zawar )

• CONNATE WATER

  • MISSISSIPI VALLEY TYPE - epigenetic

METAMORPHIC PROCESS

• REGIONAL : Kyanite, Silimanite, Graphite, Talc, Asbestos (Khasi Hills)

• CONTACT : Skarn deposits (Dewaka, Belka khera)

SURFACE DRIVEN

• CHEMICAL- BIOCHEMICAL PRECIPITATION

  • BIF

  • SEDIMENTARY mn

  • SANDSTONE

  • MAGNESITE

  • BARYTE, PHOSPHORITE

• MECHANICAL CONCETRATION

  • BEACH PLACERS

    • Alluvial

    • Eluvial

    • Beach

• RESIDUAL CONCENTRATION

  • BAUXITE DEPOSITS (East coast, Panchpatmali)

  • Lateritic Ni deposits

  • Sedimentary Mn deposits