Table of Contents
What are epigenetic mineral deposits?
The epigenetic mineral deposits are formed later after the enclosing or host rocks have been formed in filled or opened fissures in the country rocks and such ore bodies are called lodes or veins.
What is hypogene and supergene?
Supergene is a term used to describe near-surface processes and their products, formed at low temperature and pressure by the activity of descending water and gas. The opposite term is hypogene, formed by ascending water and gas at high temperature and pressure.
What is a mineral deposit called?
A mineral deposit that is sufficiently rich to be worked at a profit is called an ore deposit, and in an ore deposit the assemblage of ore minerals plus gangue is called the ore.
What is Syngenetic in geology?
In economic geology, the term syngenetic has traditionally been used to refer to ore deposits formed at the same time as the enclosing rock as opposed to epigenetic that describes mineral deposits formed later.
How are mineral deposits formed?
Deposits of minerals form when a medium that contains and transports mineral-making ore releases and deposits the ore. Magma is one such medium that transports ores. When magma or lava cools, the magma and ore carried within it crystallize to form tiny minerals in the newly-created igneous rock.
What are supergene deposits?
In ore deposit geology, supergene processes or enrichment are those that occur relatively near the surface as opposed to deep hypogene processes. Supergene processes include the predominance of meteoric water circulation (i.e. water derived from precipitation) with concomitant oxidation and chemical weathering.
What is hypogene deposit?
Hypogene ore deposits are formed under the influence of deep-seated endogene (=hypogene) geologic processes by the action of ascending solutions. Such solutions and conditions of ore formation are also called hypogene. The temperature and pressure are higher in hypogene than in supergene conditions.
What are the four mineral deposits?
9.36), copper–lead–zinc, and platinum–chromium–nickel–cobalt. Figure 9.36. The multiple-mineral deposits are composed of more than one ore-forming mineral commodities in different ratios to make the deposit economic. The deposits include chalcopyrite, galena, and sphalerite.
Are hydrothermal deposits epigenetic?
The hydrothermal theory of the origin of epigenetic mineral deposits has had a long gestation and has many variants. Hydrothermal origin without qualifiers means simply transport and deposition of the mineral matter of veins and similar deposits by and from hot waters.
What is epigenetic geology?
In geology, epigenesis is the modification of minerals in rocks after formation. Epigenesis often happens near the surface of the Earth due to exposure to oxygen, carbon dioxide and water. Epigenesis is responsible for the formation of secondary minerals in ore deposits.
Where are stratiform deposits found?
Stratiform chromite deposits are found throughout the world, but the chromitite seams of the Bushveld Complex, South Africa, are the largest and most intensely researched.
What is hypogene mineralization?
The term hypogene is mainly used in the field of ore geology. It describes mineralization within and below the Earth’s crust that is caused by ascending thermal fluids which derive from a magmatic source.
What minerals are found in hydrothermal deposits?
They often occur in clusters. Chalcopyrite (Cu), sphalerite (Zn), galena (Pb), silver and gold. The dominant gangue minerals are quartz, pyrite and pyrrhotite. Lenses of barite (BaSO4), gypsum or anhydrite are associated with the sulfides in some deposits.
Where are hydrothermal mineral deposits found?
Typical hydrothermal deposits form below the seawater/sediment interface and are called stratabound deposits—more rarely these deposits can form on the seafloor as chimneys, mounds, caprock, or Fe-rich muds.
What are stratiform deposits?
In mineral deposit: Stratiform deposits. A final class of hydrothermal deposit is called stratiform because the ore minerals are always confined within specific strata and are distributed in a manner that resembles particles in a sedimentary rock.
What is the difference between epigenetic and syngenetic deposits?
Much of the disagreement over “epigenetic” and “syngenetic” deposits is semantic; some ores and altered rocks are in part syngenetic and in part epigenetic and for them the term “diplogenetic” is proposed.
What is epigenetic mineral formation?
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.
What is epigenetic deposition?
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. If a mineral deposit formed much later than the rocks which enclose it, it is said to be epigenetic.
What are the different types of genetic deposits?
Such deposits could be derived from syngenetic, diplogenetic, or epigenetic deposits through the action of metamorphic, hydrothermal, supergene or other solutions.