Where does hydrothermal alteration occur?
Hydrothermal alteration may occur within the crust associated with hot rock or magmatic activity as well as at the Earth’s surface.
What does hydrothermal alteration mean during volcanic eruption?
Hydrothermal Alteration Hydrothermal alteration is a general term embracing the mineralogical, textural, and chemical response of rocks to a changing thermal and chemical environment in the presence of hot water, steam, or gas (Henley and Ellis, 1983).
Is hydrothermal alteration a metamorphism?
Chemical change in rocks due to interaction with hot water is called hydrothermal alteration. Metamorphic reactions involve the release of fluids as minerals change, and chemical reactions with locally-derived fluids.
What causes metasomatism?
In the metamorphic environment, metasomatism is created by mass transfer from a volume of metamorphic rock at higher stress and temperature into a zone with lower stress and temperature, with metamorphic hydrothermal solutions acting as a solvent.
What are alteration zones?
Alteration zones can be created around a number of the structural features (faults, shear zones, plugs, dykes and unconformities), and are defined as either alteration haloes, where the pre-existing rock property values are enhanced or depleted, or as replacement zones, where the original rock property values ar …
Where does metasomatism occur?
Metasomatism takes place in some rocks adjacent to igneous intrusions (see Contact (thermal) metamorphism; Skarn). It may also affect extensive areas (regional metasomatism), with the introduction of fluids possibly related to partial fusion at depth.
What are the types of alteration?
Types of alterations
- Potassic alteration.
- Phyllic (sericitic) alteration.
- Propylitic alteration.
- Argillic alteration.
Where can you find skarn?
Skarn can form in almost any lithology type such as shale, granite and basalt but the majority of skarns are found in lithology containing a limestone or a dolomite. It is common to find skarns near plutons, along faults and major shear zones, in shallow geothermal systems, and on the bottom of the sea floor.
What are hydrothermally altered rocks?
Hydrothermal alteration of volcanic host rocks involves the replacement of primary igneous glass and minerals (pla- gioclase, orthoclase, quartz, biotite, muscovite, amphibole, pyroxene, titanomagnetite) with alteration minerals stable at the conditions of alteration, generally in the temperate range of 150–400 °C.
What color is skarn?
This rock comes from a location in eastern Siberia known for the incredible blue color. The rock is a skarn, the term for a type of metamorphic rock commonly found when a magma chamber forms next to a limestone deposit.
What is epidote alteration?
Epidote is a very common hydrothermal alteration mineral. This alteration process, if it happens with feldspars, is known as epidotization. Saussuritization is a hydrothermal alteration of plagioclase feldspar which yields epidote. It is usually found in mafic igneous rocks. Epidotic alteration on a gneiss boulder.