What is hydrothermal gold deposit?
Gold-only hydrothermal deposits are thus environments in which gold is very effectively fractionated from other metals, presumably as a consequence of gold’s unique chemical properties, such as high electronegativity and the tendency to form bonds with strong covalent character (e.g. Crerar et al.
What is an epithermal deposit?
Epithermal deposits are a type oflode deposit. They contain economic concentrations from a precious metal such as gold andsilver, and in some casesbase metals such as copper,lead, iron ore andzinc.
Where are hydrothermal ore deposits found?
The deposits are hosted in limestone or dolomite that was deposited on shallow marine platforms in a tectonically stable intraplate environment. As expected in such an environment, volcanic rocks, folding and regional metamorphism are absent as a general rule.
What are hydrothermal vein deposits?
Gem Minerals From Hydrothermal Veins Hydrothermal deposits refer to the accumulation of minerals in fractures and cavities resulting from the circulation of hot waters in the Earth’s crust. Magma releases hot fluids (water and gases) as it cools but can also heat circulating groundwater.
What is the difference between magmatic and hydrothermal deposit?
Ore deposits that form in and around igneous rock units as a result of mineral precipitation from aqueous solutions or hydrothermal fluids are hydrothermal ore deposits. Magmatic-hydrothermal ore deposits are hydrothermal ore deposits in which the aqueous solutions were derived from magma.
What is the best known placer deposit?
The Witwatersrand Basin, South Africa is the largest gold deposit in the world and is considered a paleo-placer, it has produced over 1.5 billion ounces of gold. The Witwatersrand Basin is considered an ancient alluvial placer.
Where are epithermal gold deposits?
These deposits are accompanied by large amounts (over 100’s of metres or even km) of rock that have been altered to clays by hot water. Deposits occur in the North Island, mainly in the Coromandel Peninsula and Taupo Volcanic Zone (see map above).
How are epithermal gold deposits formed?
HOW ARE EPITHERMAL GOLD DEPOSITS FORMED? ➢ Shallow bodies of magma rise to several km below the surface of the earth and give off or emanate super-hot magmatic fluids (Figure 4). rocks, porous layers and other channels (the plumbing system), they react chemically with the country (or host) rocks.
What are four ways that ore deposits can form?
What are four ways that ore deposits can form? Subsurface mining (under the earths surface), Surface mining (on top the earth’s surface), Placer mining (shallow water dredging) and Undersea mining (deep sea). Name the two ways ore can be formed by Contact Metamorphism.
How does a gold vein form?
Gold may occur as deposits called lodes, or veins, in fractured rock. It may also be dispersed within Earth’s crust. Most lode deposits form when heated fluids circulate through gold-bearing rocks, picking up gold and concentrating it in new locations in the crust.
What are magmatic deposits?
Summary. Magmatic ore deposits, also known as orthomagmatic ore deposits, are deposits within igneous rocks or along their contacts in which ore minerals crystallised from a melt or were transported in a melt.
What are hydrothermal gold deposits?
Hydrothermal gold deposits (epithermal, Carlin-type, and orogenic) have accounted for >75% of lode-gold production. Although these deposits form in distinctly different geologic settings and by different ore-forming processes, they have a number of geochemical similarities.
What are hydrothermal replacement deposits?
Hydrothermal replacement depositsare a form of hydrothermal metamorphism or metasomatism. Hydrothermal deposits are categorised according to the depth and temperature at which they formed. Some mineral species crystallize mainly at preferred temperatures and pressures.
What is the mechanism of precipitation of gold?
The change of physicochemical conditions such as temperature, pressure, oxygen fugacity, and sulfur fugacity are effective mechanisms for gold precipitation. Gold tends to be concentrated in the vapor phase of fluids at high temperatures and pressures. The Au–As and Au–Sb associations are common in gold deposit.
What is the mechanism of gold deposition?
Gold mostly occurs as AuCl−2 in a system with temperature higher than 400 °C ( Gammons and Williams-Jones, 1997 ), and with decreasing temperature being the primary mechanism causing gold deposition.