The system Ag-Fe-S: Phase equilibria and mineral assemblages

1970 ◽  
Vol 5 (1) ◽  
Author(s):  
L.A. Taylor
Keyword(s):  
Phase Equilibria ◽  
S Phase ◽  
Mineral Assemblages

The system Pd–Ag–S: phase relations and mineral assemblages

2020 ◽  
Vol 84 (1) ◽  
pp. 125-130
Author(s):  
Anna Vymazalová ◽  
František Laufek ◽  
Alexandr V. Kristavchuk ◽  
Dmitriy A. Chareev
Keyword(s):  
Mineral Assemblage ◽  
Glass Tube ◽  
S Phase ◽  
Mineral Deposits ◽  
Mineral Assemblages ◽  
Pd Alloy ◽  
Stable Association ◽  
Silver Palladium ◽  
New Phase ◽  
Silica Glass Tube

AbstractPhase equilibria in the system Pd–Ag–S were studied using the silica-glass tube method at 400°C and 550°C. In the system we synthesised three ternary phases: coldwellite (Pd3Ag2S), kravtsovite (PdAg2S) and a new phase Pd13Ag3S4. At 400°С, coldwellite forms a stable association with vysotskite (PdS) and vasilite (Pd16S7); vysotskite and kravtsovite; phase Pd4S and a Ag–Pd alloy; it also coexists with a new phase Pd13Ag3S4. Kravtsovite is stable up to 507°C; the presence of kravtsovite in the mineral assemblage reflects its formation below this temperature. The occurrence of coldwellite, vysotskite and Ag2S together in equilibrium reflects the formation of this mineral assemblage above this temperature (507°C). Coldwellite is stable up at 940°С. Mineral assemblages defined in this study can be expected in Cu–Ni–PGE mineral deposits, associated with mafic and ultramafic igneous rocks, in particular in mineralisations with known silver–palladium sulfides.

Phase equilibria and mixed parageneses of metabasites in lowgrade metamorphism

1985 ◽  
Vol 49 (352) ◽  
pp. 321-333 ◽  
Author(s):  
J. G. Liou ◽  
S. Maruyama ◽  
M. Cho
Keyword(s):  
Phase Equilibria ◽  
Model System ◽  
Metamorphic Grade ◽  
Low Grade ◽  
Qualitative And Quantitative ◽  
Basaltic Rocks ◽  
Mineral Assemblages ◽  
The Common ◽  
Invariant Points ◽  
Model Phase

AbstractThe system Na2O-CaO-MgO Al2O3-SiO2-H2O is proposed to model phase equilibria and mineral parageneses for low-temperature metamorphism of basaltic rocks. Univariant reactions marking the transitions between various sub-greenschist facies are identified and some have been experimentally determined. The introduction of Fe2O3 into the model system at fixed FeO/MgO ratio creates continuous reactions for facies boundaries and discontinuous reactions for invariant points of the model system. Both qualitative and quantitative effects on P-T displacement and phase compositions are discussed. The XFe3+ isopleths for epidote were plotted to exemplify the transition from the zeolite through prehnite-pumpellyite to prehnite-actinolite facies. T-XFe3+ relations were established for continuous and discontinuous reactions relating such facies transitions. Because of the common occurrence of two or three Ca-Al hydrosilicates in low-grade metabasites, an isobaric Al-Ca-Fe3+ projection from chlorite may be used to illustrate mineral assemblages and compositions of the coexisting Ca-Al silicates in the presence of quartz, albite, and chlorite. Reported occurrences in several classic burial metamorphic terrains and ocean-floor metabasites in ophiolites are described. Only the composition of a mineral from a buffered assemblage can constrain the intensive properties for metamorphism; previously reported compositional trends for pumpellyite and epidote with increasing metamorphic grade are oversimplified.

Calculated phase equilibria in K2O-FeO-MgO-Al2O3-SiO2-H2O for sapphirine-quartz-bearing mineral assemblages

2004 ◽  
Vol 22 (6) ◽  
pp. 559-578 ◽  
Author(s):  
D. E. Kelsey ◽  
R. W. White ◽  
T. J. B. Holland ◽  
R. Powell
Keyword(s):  
Phase Equilibria ◽  
Calculated Phase ◽  
Mineral Assemblages

Phase Equilibria in the System MgO-Al2O3-SiO2-H2O: Chlorites and Associated Minerals

1973 ◽  
Vol 39 (303) ◽  
pp. 297-312 ◽  
Author(s):  
Bruce Velde
Keyword(s):  
Solid Solution ◽  
Chemical Composition ◽  
Low Temperature ◽  
Phase Equilibria ◽  
Water Pressure ◽  
Positive Slope ◽  
Natural Mineral ◽  
Natural Minerals ◽  
Cell Dimensions ◽  
Mineral Assemblages

SummaryTwenty-six compositions in the system MgO-Al2O3-SiO2-H2O were investigated under conditions of 1 and 2 Kb water pressure and temperatures between 300 and 700°C. The solid solution for 7 Å and 14 Å chlorites has been delimited as well as that of the expanding phases (tri- and dioctahedral montmorillonites and expanding chlorites). Negative slopes were found for the transformation montmorillonite → expanding chlorite, and expanding chlorite → chlorite+quartz and a positive slope for 7Å → 4 Å transformation. The relative positions of the reactions chlorite+quartz → cordierite+talc, chlorite+andalusite → cordierite and chlorite+corundum → cordierite+spinel are located between 500 and 65°C.Cell dimensions of the synthetic chlorites can be correlated with their chemical composition. Solid solution in synthetic minerals compares well with 325 analysis of natural minerals from the literature, indicating that the chemiographic relations between phases in the simplified synthetic system are applicable to natural mineral assemblages. The phase relations indicate that at low temperature the 7Å aluminous chlorite is not stable with quartz or another silica phase.

New insights into the age and metamorphic evolution of the Irumide orogeny in Malawi

2021 ◽  
Author(s):  
Sofia C. Böhme ◽  
Steven D. Boger
Keyword(s):  
Phase Equilibria ◽  
Island Arc ◽  
Zircon Geochronology ◽  
The South ◽  
Metamorphic Evolution ◽  
Temperature Conditions ◽  
The North ◽  
Southern Margin ◽  
Mineral Assemblages

<p>Metapelitic rocks of the Irumide Domain in central Malawi contain detrital and metamorphic zircons. U-Pb zircon geochronology yielded two age populations, which have been dated at c. 1995 Ma and 1050 Ma. The ages demonstrate that the precursor sediments to these rocks were derived from erosion of the Palaeoproterozoic Ubendian Domain, which is adjacent to the north, and at a later stage were affected by the Irumide orogeny. The metapelitic rocks are characterised by garnet + sillimanite + biotite ± muscovite ± K-feldspar mineral assemblages. Phase equilibria modelling shows that they equilibrated under pressure-temperature conditions of about 7 kbar and 700–740˚C.  In combination with the metamorphic ages this is interpreted to record late Mesoproterozoic (c. 1050 Ma) accretion of a juvenile island arc, the South Irumide Domain, to the southern margin of the Tanzania-Congo Craton.</p>

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