# tblAlterationType

AlterationTypeDesc:
Chemical +/- mineralogical change in wallrock or vein as a result of hydrothermal alteration


AlterationTypeDesc:
Key mins. topaz-musc.  Localised high-T alteration associated with peraluminous granites and related mineralisation.  Syn; Fluorine metasomatism


AlterationTypeDesc:
Key mins. chl, epi, alb, cc~wair.  Commonly forms the outermost alteration zone at intermediate to deep levels in porphyry sys. or in epithermal environment.  Syn; zeolitic


AlterationTypeDesc:
Key min. orthoclase.  Wallrock alteration of plagioclase around veins, fractures and permeable zones AND selective replacement of plagioclase  in alteration envelopes.


AlterationTypeDesc:
Key min. tour. Pervasive replacement of footwall strata below massive sulphide.  Assoc. w abundant dissem. sulphide in shallow footwall. Ltd to feldspathic strata


AlterationTypeDesc:
Key min. qz.  Complete replacement of lmst and occassionally other rock types, by fine grnd qtz; often assoc. w brecciation.


AlterationTypeDesc:
Key mins. biot (phlogopite), feld, mag. Form of wall rock alteration char. by  formation of potash feldspar and/or biotite (biotitisation) and anhydrite.  Gen. found in the core of porphyry deposits, partic. those hosted by mafic intrusives or wallrx


AlterationTypeDesc:
Key mins. alb, chl, mus.  Metasomatic replacement of an existing min. (usually fspar) by albite. Characterised by pervasive replacement of feldspathic strata and massive sulphide, typically along structures and around mafic intrusions.


AlterationTypeDesc:
Char. by progressive alteration of wall rock from sericite to mixed layer clays; occurs as texturally destructive clay-rich wallrock alteration around veins and replacement zones in permeable lithologies.


AlterationTypeDesc:
Key mins. alun~kaol-dick~qz~pyro~cris. Intense clay alteration in upper part of porphyry systems & alteration halos in epithermal setting.  Low-mid pH/shallow to deep crustal envir. Syn; acid sulphate (in intrusion-related setting)


AlterationTypeDesc:
An irregularly-shaped, replacement ore deposit, usu. formed at high temps in metamorphosed, carbonate-rich seds. at the contacts w med.-large ore bodies.


AlterationTypeDesc:
Key mins. gnt, cpx, woll.  Generally forms replacement zones in wallrx (exoskarn - typ. in lmst. or occassionally mafic to intermediate vol. rx.) or within intrusives (endoskarns)


AlterationTypeDesc:
Key mins. forst, diop OR serp, talc.  Developed as metasomatic replacements of dolomitic lmst.  High-T Mg-skarns are characterised by forst+diop & low-T Mg-skarns contain serp+talc


AlterationTypeDesc:
Key mins. cc, chl.  Commonly replaces earlier skarn alteration but may also affect adjacent wallrock lmst.


AlterationTypeDesc:
Key mins: cc, ank~sid~qz.  Wallrock alteration in and around veins or shear zones, extensive repl. of UM to mafic rx & disseminated in the shallow FW below massive sulphide & baritic facies


AlterationTypeDesc:
Key mins. qtz, cal.  Replacement of ultramafic rx in the shallow parts (low temperature) of geothermal systems.


AlterationTypeDesc:
Key mins. dol, sid.  Occurs as disseminated alteration, commonly over extensive lateral & stratigraphic intervals.  Composition of carbonates may change with distance from ore zones


AlterationTypeDesc:
A type of wallrock alteration involving an increase in quartz or cryptocrystalline silica in the altered rock.


AlterationTypeDesc:
Typically occurs in structural zones or as replacement bodies in permeable lithologies, usu. in the core of zones of advanced argillic alteration.  Common in upper parts of porphyry systems (telescoped) but more common in epithermal environment


AlterationTypeDesc:
Key mins. qz, cc.  Replacement of ultramafic rx in the shallow parts (low T) of geothermal systems


AlterationTypeDesc:
The alteration of ultramafic rx such as dunite, perioditite and pyroxenite into serpentinite


AlterationTypeDesc:
Key mins. ser, qz. Pervasive replacement of rocks in footwall below massive sulphide lenses; concentrated in stockwork feeder zones, common in intermediate to felsic volcanics


AlterationTypeDesc:
Temporary group for different classes of seicitic alteration

AlterationTypeCom:
'sericitic' captured for lots mines as @ 9/8/01


AlterationTypeDesc:
Key mins. ill-smec~kaol-dick~mont~chl. May be present as alteration zone bw. advanced argillic & propylitic alteration particularly in high sulphidation epithermal settings and porphyry systems. Mid pH/shallow to mid crustal environment. Syn; ser-chl-clay


AlterationTypeDesc:
Key min. chl. Wall rock alteration in and around veins & shear zones, particularly in mafic volcanic/volcaniclastic sed. rx. & pervasive replacement of rocks in footwall  below massive sulphide deposits


AlterationTypeDesc:
Key mins. ser, qtz, pyr.  Wide spread.  Most commonly associated with sulphide ore. Forms peripheral halo around porphyry deposits.  Mid-high pH/mid to deep crustal environment. Syn: sericitic


AlterationTypeDesc:
Key mins. biot, K-spar (orthoclase), mag.  Generally found in the core of porphyry deposits, particularly those hosted by more mafic intrusions (diorite, monzonite, granodiorite) or mafic to intermediate volcanoclastic wallrocks.


AlterationTypeDesc:
Key mins. K-spar (orthoclase or microcline).  Found in the core of porphyry systems, particularly hosted by felsic intrusions (granodiorite-qtz monzonite, granite, syenite)


AlterationTypeDesc:
felpdsar alteration leading to formation of zoisites and other minerals


AlterationTypeDesc:
A 'rust-like' hydrated oxide of iron produced by the weathering of iron minerals


AlterationTypeDesc:
Introduction of,or replacement by pyrite.  A common process of hydrothermal alteration


