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Mineral Occurrence
ALUNITIC ALUN
ARGILLIC ARGI
Introduction of, or replacement by, ALUNITE. This alteration is caused by extreme hydrolytic leaching of
wallrocks in the presence of sulphate. The conditions are oxidizing with an abundance of sulphate ions. The
most common mineral assemblage is ALUNITE with some form of silica: QUARTZ, CHALCEDONY,
CRISTOBALITE, TRIDYMITE, or OPAL. Other minerals present commonly include KAOLINITE, SERICITE,
DIASPORE, BARITE, JAROSITE, RUTILE, ZUNYITE, PYRITE, and HEMATITE.
Intermediate argillic alteration is the replacement or alteration of feldspars to form predominantly clay
minerals. These include the KAOLINITE group: DICKITE, KAOLINITE, HALLOYSITE, and
METAHALLOYSITE; the SMECTITE (MONTMORILLONITE) group; the ILLITE group; and the amorphous
clays (ALLOPHANE). Mineral assemblages characteristic of advanced argillic alteration caused by
hydrothermal solutions at low and moderate temperatures are dominated by KAOLINITE group clay minerals.
DICKITE, KAOLINITE, DIASPORE, and PYROPHYLLITE may occur with SERICITE, QUARTZ, ALUNITE,
PYRITE, TOURMALINE, TOPAZ, ZUNYITE, and AMORPHOUS CLAYS (ALLOPHANE).
BIOTITE BIOT Introduction of, or replacement by, BIOTITE.
CARBONATE CARB
CHLORITIC CLOR
DEUTERIC
(AUTOMETASOMATISM) DEUT
EPIDOTE EPID
FENITIC FENT
GREISEN GRSN
HEMATITE HEMT
LEACHING LECH
OXIDATION OXID
POTASSIUM SILICATE
(POTASSIC)
KSPA
PROPYLITIC PROP
Introduction of, or replacement by, CARBONATES. Magnesium, iron, calcium, and manganese carbonates
are common. These are CALCITE, DOLOMITE, ANKERITE, and SIDERITE.
The replacement by, conversion into, or introduction of CHLORITE. This alteration may result from a number
of disparate metasomatic processes. Mineral assemblages comprise CHLORITE, with subordinate SERICITE,
QUARTZ, and PYRITE.
A process involving reactions between primary magmatic minerals and the water-rich solutions that separate
from the same body of magma at a late stage in its cooling history. These processes may result in
SILICIFICATION, SODIUM SILICATE (ALBITIZATION), POTASSIUM SILICATE, TOURMALINIZATION and
GREISENIZATION as pervasive, selectively pervasive, cavity filling and/or vein-controlled modes of alteration.
The hydrothermal introduction of EPIDOTE into rocks or the alteration of rocks in which plagioclase feldspar is
albitized, freeing the anorthite molecule for the formation of EPIDOTE and ZOISITE, often accompanied by
chloritization. These processes are characteristically associated with metamorphism.
Widespread alkali metasomatism of quartzofeldspathic country rocks in the environs of carbonatite complexes
and/or alkalic igneous rocks. FENITES are characterized by FELDSPATHOIDS, and ALKALI FELDSPARS
(POTASH FELDSPAR, ALBITE), PYROXENES (AEGERINE, AEGERINE-AUGITE), and AMPHIBOLES
(RIEBECKITE-ARFVEDSONITE series).
A type of alteration whose minerals are enriched in fluorine, boron, and the alkali metals (Na, K, and Li). The
characteristic minerals include TOURMALINE, TOPAZ, MUSCOVITE, ZINNWALDITE, FLUORITE, ALKALI
FELDSPARS, and/or KAOLINITE.
HEMATITE is the principal mineral product and varieties may be granular, specular, or more rarely, earthy.
The latter is generally of supergene origin and is associated with clay minerals. The style of hematite
alteration is pervasive, selectively pervasive, and vein-controlled.
The separation, selective removal, or dissolving-out of soluble constituents from a rock, soil, or orebody by the
natural action of percolating water.
A process whereby an area is modified by surface waters, and/or reaction with oxygen (e.g., sulphides altered
to oxides and carbonates). A GOSSAN represents an oxidized zone formed by the oxidation of sulphides and
the leaching-out of the sulphur and most metals, leaving hydrated iron oxides and rarely sulphates. Minerals
include LIMONITE, HEMATITE, and others.
Hydrothermal alteration resulting from potassium metasomatism, commonly accompanied in calcalkaline
rocks by removal of calcium and sodium. Characteristic major minerals are POTASSIUM FELDSPARS
(ADULARIA, ORTHOCLASE, MICROCLINE), BIOTITE or CHLORITE, SERICITE, and QUARTZ, with
common ALBITE, ANHYDRITE, FE-MG CARBONATE, and APATITE.
The result of low pressure-temperature alteration. The propylitic assemblage consists of EPIDOTE,
CHLORITE, ZOISITE, CLINOZOISITE, SERICITE, MG-FE-CA CARBONATES, PYRITE, and sometimes
ALBITE-ORTHOCLASE, all involved in partial replacement of wallrock minerals. HEMATITE, JAROSITE, and
GOETHITE are also common.
PYRITE PYRT Introduction of, or replacement by, PYRITE. A common process of hydrothermal alteration.
QUARTZ CARBONATE QZCA
LISTWANITE. A mineralogic assemblage that results from the carbonatization of serpentinized ultramafic
rocks. A distinctive alteration suite consisting of green chromium-bearing mica (MARIPOSITE, FUCHSITE)
with QUARTZ, CARBONATE, LIMONITE and MAGNESITE.
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