What is advanced argillic alteration?
Advanced Argillic alteration forms at higher temperatures and lower pH conditions (e.g. the acid-steam condensate zone of a hydrothermal system). It consists primarily of kaolinite + dickite clay minerals at lower temperatures and pyrophyllite + andalusite minerals at temperatures > 300°C.
What is hydrothermal alteration?
Hydrothermal alteration is defined as any alteration of rocks or minerals by the reaction of hydrothermal fluid with preexisting solid phases.
What is albite alteration?
Context 1. of albite (I) corresponds to the initial stage of sodic hydrothermal alteration of the Bacuri deposit and results in white-to-pinkish colour in altered portions of the Serra Dourada granite (Figs. 6A and 6B) and Bacuri Porphyry in distal zones of the deposit (Fig. 6C).
What causes sericite alteration?
Sericitic alteration or sericitization is a process of mineral alteration caused by hydrothermal fluids invading permeable country rock.
What is dickite mineral?
Description: Dickite is a clay mineral having the same formula as kaolin, nacrite and halloysite but a different crystal structure. It is found intergrown with other clay minerals. Dickite can occur in soils, shales, and as a hydrothermal precipitate.
Where is alunite found?
It is currently mined at Tolfa, Italy. In the United States it is found in the San Juan district of Colorado; Goldfield, Nevada; the ghost town of Alunite, Utah near Marysvale; and Red Mountain near Patagonia, Arizona. The Arizona occurrence lies appropriately above a canyon named Alum Gulch.
Which is a common type of alteration?
Alteration types
| Alteration assemblage | |
|---|---|
| Alunite, kaolinite, opal, amorphous clay, hematite, geothite, jarosite | Quartz, alunite, kaolinite, pyrophylite, dickite, diaspore, zunyite, topaz |
What is Albitisation?
albitization The partial or complete replacement of pre-existing plagioclase feldspar or alkali feldspar by albite. There are a number of ways in which this can be achieved. A common process involves the residual water-rich vapour released during the final stages of crystallization of a granite body.
What does Albitization mean?
: a process in which albite replaces the plagioclase feldspar of an igneous rock.
How do you identify sericite?
Usually found as micaceous flakes or tablets with irregular outlines, tabular parallel to {001}. Sericite is name given to very fine, ragged grains and aggregates of white mica – usually muscovite – produced by the alteration of feldspars or other minerals.
Is sericite a mineral?
Sericite is a common alteration mineral of orthoclase or plagioclase feldspars in areas that have been subjected to hydrothermal alteration typically associated with copper, tin, or other hydrothermal ore deposits. Sericite also occurs as the fine mica that gives the sheen to phyllite and schistose metamorphic rocks.
What kind of minerals are found in argillic alteration?
More distal and downwards, advanced argillic alteration gradually evolves into phyllic assemblages dominated by quartz and sericite. Zunyite, along with various amounts of quartz, alunite, aluminum phosphate–sulfate minerals (APS), diaspore, kaolinite, and minor pyrophyllite, are the main minerals in the advanced argillic alteration.
What are the assemblages of Advanced argillic alteration?
Veins with assemblages characteristic of advanced argillic alteration consistently offset veins associated with sericitic alteration. Most of the advanced argillic assemblages at Resolution formed at relatively low temperatures, stable with kaolinite and dickite.
Who is the author of argillic alteration and ore deposits?
George Melvin Schwartz; Argillic alteration and ore deposits. Economic Geology 1956;; 51 (5): 407–414. doi: https://doi.org/10.2113/gsecongeo.51.5.407 The prominence of clay minerals in the hydrothermally altered rocks of many mineral deposits has been emphasized in recent years.
Where does argillic alteration occur in a hydrothermal system?
Advanced Argillic alteration forms at higher temperatures and lower pH conditions (e.g. the acid-steam condensate zone of a hydrothermal system). It consists primarily of kaolinite + dickite clay minerals at lower temperatures and pyrophyllite + andalusite minerals at temperatures > 300°C.