Argillic alteration is hydrothermal alteration of wall rock which introduces clay minerals including kaolinite

Kaolinite

Kaolinite is a clay mineral, part of the group of industrial minerals, with the chemical composition Al2Si2O54. It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra...

, smectite and illite

Illite

Illite is a non-expanding, clay-sized, micaceous mineral. Illite is a phyllosilicate or layered alumino-silicate. Its structure is constituted by the repetition of tetrahedron – octahedron – tetrahedron layers. The interlayer space is mainly occupied by poorly hydrated potassium cations...

. The process generally occurs at low temperature

Temperature

Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

s and may occur in atmospheric condition

Atmosphere

An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...

s. Argillic alteration is representative of supergene

Supergene

A supergene is a group of neighbouring genes on a chromosome which are inherited together because of close genetic linkage and are functionally related in an evolutionary sense, although they are rarely co-regulated genetically....

 environments where low temperature groundwater becomes acid

Acid

An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

ic.

Argillic assemblages include kaolinite

Kaolinite

Kaolinite is a clay mineral, part of the group of industrial minerals, with the chemical composition Al2Si2O54. It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra...

 replacing plagioclase

Plagioclase

Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...

 and montmorillonite

Montmorillonite

Montmorillonite is a very soft phyllosilicate group of minerals that typically form in microscopic crystals, forming a clay. It is named after Montmorillon in France. Montmorillonite, a member of the smectite family, is a 2:1 clay, meaning that it has 2 tetrahedral sheets sandwiching a central...

 replacing amphibole

Amphibole

Amphibole is the name of an important group of generally dark-colored rock-forming inosilicate minerals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures.-Mineralogy:...

 and plagioclace. Orthoclase

Orthoclase

Orthoclase is an important tectosilicate mineral which forms igneous rock. The name is from the Greek for "straight fracture," because its two cleavage planes are at right angles to each other. Alternate names are alkali feldspar and potassium feldspar...

 is generally stable and unaffected. Argillic grades into phyllic alteration at higher temperatures in an ore deposit hydrothermal system.

Advanced argillic alteration occurs under lower pH and higher temperature conditions. Kaolinite and dickite

Dickite

Dickite has molecular weight of 258.16 grams. It is a phyllosilicate clay mineral chemically composed of aluminium, silicon, hydrogen and oxygen contributing 20.90%, 21.76%, 1.56%, and 55.78% each respectively. It has the same composition as kaolinite, nacrite, and halloysite, but with a...

 occur at lower temperatures whereas pyrophyllite

Pyrophyllite

Pyrophyllite is a phyllosilicate mineral composed of aluminium silicate hydroxide: Al2Si4O102. It occurs in two more or less distinct varieties, namely, as crystalline folia and as compact masses; distinct crystals are not known....

 and andalusite

Andalusite

Andalusite is an aluminium nesosilicate mineral with the chemical formula Al2SiO5.The variety chiastolite commonly contains dark inclusions of carbon or clay which form a checker-board pattern when shown in cross-section....

 occur under high temperature conditions (T > 300°C). Quartz

Quartz

Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

 deposition is common. Alunite

Alunite

Alunite is a sulfate mineral that was first observed in the 15th century in Monti della Tolfa, north of Rome, where it was mined for the manufacture of alum. First called aluminilite by J.C. Delamétherie in 1797, this name was contracted by François Beudant in 1824 to alunite.Distinct crystals of...

, topaz

Topaz

Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO42. Topaz crystallizes in the orthorhombic system and its crystals are mostly prismatic terminated by pyramidal and other faces.-Color and varieties:...

, zunyite

Zunyite

Zunyite is a sorosilicate mineral, Al13Si5O2018Cl, composed of aluminium, silicon, hydrogen, chlorine, oxygen, and fluorine.-Occurrence:Zunyite occurs in highly aluminous shales and hydrothermally altered volcanic rocks...

, tourmaline

Tourmaline

Tourmaline is a crystal boron silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is classified as a semi-precious stone and the gem comes in a wide variety of colors...

, enargite

Enargite

Enargite is a copper arsenic sulfosalt mineral with formula: Cu3AsS4. It takes its name from the Greek word enarge, "distinct." Enargite is a steel gray, blackish gray, to violet black mineral with metallic luster. It forms slender orthorhombic prisms as well as massive aggregates...

 and tennantite

Tennantite

Tennantite is a copper arsenic sulfosalt mineral. Its chemical formula is Cu12As4S13. It is grey-black, steel-gray, iron-gray or black in color. A closely related mineral, tetrahedrite has antimony substituting for arsenic and the two form a solid solution series. The two have very similar...

 may also occur. Greisen

Greisen

Greisen is a highly altered granitic rock or pegmatite. Greisen is formed by autogenic alteration of a granite and is a class of endoskarn.Greisens appear as highly altered rocks, partly coarse, crystalline granite, partly vuggy with miarolitic cavities, disseminated halide minerals such as...

alteration is similar.