Each claim states how it is known and cites its evidence.
Established0.1–10 cm
In porphyry environments wall-rock alteration is intimately linked to narrow veins, commonly 0.1 to 10 centimetres wide, which typically make up less than 1 to 5 volume percent of the mineralised rock — while the alteration they drive extends through a far larger volume.
- precision note: The value carried is the vein width. The volume fraction, less than 1 to 5 percent, is stated in the claim; the relation between a small vein volume and a large altered volume is the point.
Evidence support: Supported by the cited evidence · one source
Evidence: John 2010 · Primary authority
InferredDissolution, transport and precipitation by hot aqueous fluid.
Hot aqueous fluids move elements without melting anything: they dissolve material where conditions favour solution and precipitate it where conditions do not, transporting elements between rock volumes and altering the rock they pass through.
- method: The cited source states that metamorphism can proceed by reaction with hot mineral-rich fluids entering the rock and that new minerals form by those reactions; the transport role follows.
- precision note: Phase 2 records the physical and chemical bridge only. Ore-forming fluid systems belong to a later phase and are not asserted here.
Evidence support: Supported by the cited evidence · 2 sources, multiple sources, independence unknown
Evidence: U.S. Geological Survey n.d. · Primary authority; John 2010 · Primary authority
EstablishedMetasomatic change of composition, mineralogy and texture by a hot aqueous fluid.
Hydrothermal alteration is a set of metasomatic processes that change the composition, mineralogy and texture of a rock: alkali metasomatism, hydrolytic or acidic reactions, oxidation-reduction reactions including sulfidation, solubility-induced precipitation such as quartz deposition, and hydration and carbonation reactions in which water or carbonate is added.
- precision note: Defined here in the context of porphyry copper systems by the source, but the processes named are general to hydrothermal alteration and are recorded as such.
Evidence support: Supported by the cited evidence · 2 sources, multiple sources, independence unknown
Evidence: John 2010 · Primary authority; U.S. Geological Survey n.d. · Primary authority