measured the [delta][sup.66]Zn values of pegmatite (0.25 [per thousand]~0.59 [per thousand]) and some other granitoids (-0.16 [per thousand]~0.21 [per thousand]) and then found there is even no variation in [delta][sup.66]Zn values during fluid exsolution
in some cases.
The dark-appearing veins following fractures in the Gold Sheen sapphires appear to have formed after the exsolution
of Fe-Ti oxides.
%) associated with decreasing temperature, so 200 bars (20 MPa) is a reasonable minimum estimate for [H.sub.2]O exsolution
. The bulk density of the crystallized magma is calculated as 2.5 g/[cm.sup.3].
The galena can contain up to 20% Ag (by weight) and in certain circumstances the gold may also be present as replacement or exsolution
blebs in arsenopyrite or pyrite.
Previous studies have shown three potential fluid formation mechanisms: (1) formation at magmatic temperatures, in which intermediate-felsic magma in a chamber becomes saturated to oversaturated in terms of volatile content through crystallization and separation to a certain extent, forming high- and low-salinity fluids [37, 38]; (2) formation from hydrothermal fluids with low to moderate salinities through liquid immiscibility or decompression boiling resulting from the fracturing of caprocks; or (3) volatile exsolution
from late residual magma associated with crystallization during hypabyssal magmatic emplacement .
There is no kinetic barrier to heterogeneous nucleation of bubbles; therefore, the exsolution
surface (level in the chamber or conduit) is synonymous with the saturation surface because volatiles exsolve during magma ascent (Fig.
The mineral is white and occurs generally interstitial to microcline and quartz, as an exsolution
product within microcline crystals, and in irregular masses as much as 30 cm in maximum dimension.
The chalcopyrite commonly occurs within sphalerite as exsolution
The miscibility gap is narrower at high temperatures, so that under slow cooling conditions, early formed augites and low-Ca pyroxenes develop exsolution
lamellae as low-Ca pyroxene and augite (respectively) are expelled from the structures.
Occurrence: The grains in Indarch probably formed by exsolution
of Si and N from kamacite, perryite and schreibersite during parent-body metamorphism.
The primary ore textures comprise euhedral-anhedral-grained, metasomatic, edge-shared, void-filling, poikilitic, slaty cleavage, skeletal, exsolution
, graphic, crumpled, and cataclastic textures (Figure 4).
In ore from Kipushi, needles and grains of gallite occur in sphalerite and in chalcopyrite as exsolution
Magnetite commonly exhibits an exsolution
texture comprised of intergrown magnetite, hematite, rutile and (rarely) translucent brown euxenite with a yellowish alteration surface.
According to Rodriguez Gallego (1985), structural imperfections in phyllosilicates can be classified into the following groups: 1) point defects; 2) line defects or dislocations; 3) plane defects (polytypism etc.); 4) volume defects (intergrowth, exsolutions
Pyrrhotite occurs as coarse crystals with flame exsolutions
of pentlandite and surrounded by polycrystalline, chain-like pentlandite aggregates, yielding similar textures to those observed in Sudbury ores.