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Ore forming process
The document discusses three main types of ore forming processes: magmatic, sedimentary, and metamorphic. It focuses on magmatic processes, describing early and late magmatic processes like dissemination, segregation, injection, and residual liquid segregation and injection. Immiscible liquid segregation and injection are also discussed. Pegmatite deposits and contact metasomatic deposits near invading magmas are summarized. A variety of ore deposits can form from these magmatic processes depending on temperature and pressure conditions during crystallization and cooling of magma.
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Ore forming process
- 1. Ore Forming Process By Abdul BariQanit M.Sc. Geology
- 2. The processes offormation of mineral deposits are grouped into three main types: a. Magmatic Process b. Sedimentary Process c. Metamorphic Process.
- 3. Mineral deposits formeddue to the various processes associated with magmatic activities are called 'Primary-Mineral Deposits'. Mineral deposits arising out of the processes of weathering, and activities of several geological agents are called 'Secondary Mineral Deposits'. These are closely associated with the sedimentary processes of formation. Metamorphic mineral deposits are the out- come of metamorphic processes acting upon an earlier formed mineral deposits or rocks.
- 5. • Charnockite •Gneiss • Sandstone beds
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- 7. As we know,magma consists of a multitude of constituents, which are in mutual solution. As the magma approaches the earth's surface its temperature and the external pressure drop, with the result of crystallization and differentiation of minerals in a definite sequence. The formation temperature of different magmatic deposits varies from 1500'C to 300C°.
- 10. Magmatic Process Early MagmaticLate Magmatic Dissemination Residual Liquid Segregation Segregation Residual Liquid Injection Injection Immiscible Liquid Segregation Immiscible Liquid Injection
- 11. Early Magmatic Process Theearly magmatic deposits are believed to have been formed simultaneously with the host-rock. (or) Where the Ore Deposits formed in the Early stage of Magmatic periods.
- 12. Late Magmatic Process Thelate magmatic deposits are formed towards the close of the magmatic deposits. For example Titaniferous magnetite,
- 13. Magmatic Dissemination Magmatic Dissemination(Simple crystallization without concentration). It involves simple crystallization whereby early formed crystals are found
- 14. Diamond formation inKimberlite Pipes
- 15. Magmatic Segregation This typeof magmatic concentration is often due to the gravitative crystallization of early formed heavy minerals for, e.g., Bushveld chromite deposits (South Africa), chromite deposits of Keonjhar (Orissa).
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- 17. Magmatic Injection In thiscase, the metallic concentrates instead of remaining -at the place of their original accumulation, get injected into the adjacent solid rock-masses It occurs at the residual magmatic stage, e.g., Magnetite deposits of Kiruna (Sweden).
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- 19. Immiscible Liquid Segregation Sometimesmagma of an ore-and- silicate composition breaks down during cooling into two immiscible fractions which accumulate to form liquid segregation deposits e.g. Sulphide minerals Deposits.
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- 21. Immiscible Liquid Injection Theimmiscible liquid accumulations before consolidation when subjected to disturbances, get injected into the surrounding rocks, forming immiscible liquid-injection. A nickeliferous Sulphide deposit of Sudbury (U.S.A.) is
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- 23. Residual Liquid Segregation Basicmagmas undergoing differentiation may sometimes become enriched in iron and titanium. This heavy residual liquid may segregate and crystallize within the parent igneous mass. Such ore bodies commonly occur in form of parallel bands. The host rocks are usually anorthosite, norite, gabbro etc, e.g.. Titaniferous magnetite bands of
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- 25. Residual Liquid Injection Insuch cases, residual liquid be squeezed out towards places of less pressure into the neighboring rock mass forming late magmatic injections, e.g., Titaniferous magnetite deposits Adirondack region of New York.
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- 28. These are formedtowards the very end of consolidation of the magma, in which the residual fraction is highly enriched with volatile constituents. Pegmatitic liquids may be squeezed out to fill in the cracks and fissures in the parent igneous body or the adjoining country rocks, and form pegmatite veins or dykes. These are usually formed between 500°C to 800"C.
- 29. Deposits of mica,feldspar, beryl, lithium minerals, Gemstones and tin mineral like cassiterite are included in the pegmatite deposits.
- 30. multicolor tourmaline crystalin the Himalaya pegmatite
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- 33. In the neighborhoodof invading magmas, alteration and replacement of the country rocks due to invasion of magmatic emanations may sometimes lead to the development of mineral deposits of economic importance.
- 34. In this case,the enclosing country rock is altered by the heat and other chemical constituents of the invading intrusive magma forming new minerals under conditions of high temperature and pressure. The deposits are usually resulted in calcareous rocks. The temperature of formation ranges from 400°C to 1000°C.
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