What are hydrothermal alterations?

Hydrothermal alteration is defined as any change in the mineralogic composition of a rock due to the action (by either physical or chemical means) of hydrothermal fluids in an open system.

Where does hydrothermal alteration occur?

geothermal systems
Summary. Hydrothermal alteration occurs in geothermal systems and involves the replacement of the primary mineral assemblage by alteration minerals. Changes in temperature, pressure, and chemistry of the system usually induce extensive alteration of the host rock.

What is Greisenisation?

A process of hydrothermal alteration in which feldspar and muscovite are converted to an aggregate of quartz, topaz, tourmaline, and lepidolite (i.e., greisen) by the action of water vapor containing fluorine.

What are the types of alteration?

Types of alterations

Potassic alteration.
Phyllic (sericitic) alteration.
Propylitic alteration.
Argillic alteration.
Silicification.
Carbonatization.
Greisenization.
Hematitization.

What are hydrothermally altered rocks?

Hydrothermal alteration refers to rocks that have been altered from their original composition through water-rock interactions with a geothermal fluid. Hydrothermal alteration may also refer to the selective removal of minerals by a fluid, as in the case of acid leaching.

What is rock alteration?

Rock alteration usually involves chemical weathering in which the. mineral composition of the rock is changed, reorganized, or redistributed. The rock minerals are exposed. to solution, carbonation, hydration, and oxidation by circulating waters.

What is silicification in geology?

—Silicification is the replacement of original skeletal material accomplished through the concurrent dissolution of calcium carbonate and precipitation of silica. The processes is aided by the nucleation of silica to organic matter which surrounds the mineral crystallites within the shell.

What is Gossan rock?

Gossan (eiserner hut or eisenhut) is intensely oxidized, weathered or decomposed rock, usually the upper and exposed part of an ore deposit or mineral vein.

What are skarn deposits?

Skarn deposits are one of the more abundant ore types in the earth’s crust and form in rocks of almost all ages. Skarn is a relatively simple rock type defined by a mineralogy usually dominated by calcsilicate minerals such as garnet and pyroxene.

What is alteration in rocks?

[… in rocks] Any change in the mineralogic composition of a rock brought about by physical or chemical means, esp. by the action of hydrothermal solutions; also, a secondary, i.e., supergene, change in a rock or mineral.

What is wall rock alteration?

wall-rock alteration A reaction of hydrothermal fluids with enclosing rocks, causing changes in mineralogy that are most marked adjacent to the vein and become less distinct further away.

What is vuggy quartz?

A vug, vugh, or vugg (pronounced /vʌɡ/) is a small to medium-sized cavity inside rock. It may be formed through a variety of processes. Most commonly, cracks and fissures opened by tectonic activity (folding and faulting) are partially filled by quartz, calcite, and other secondary minerals.

What are hydrothermal alterations?