Phase relations in a portion of the granite system, KAlSi3O8‐NaAlSi3O8‐SiO2‐H2O have been studied in the pressure range 4 to 10 kb. At 10 kb, melting begins at 625°C at an isobaric invariant point involving albite + orthoclase + quartz + liquid + vapor. The anhydrous composition of the liquid at this isobaric quaternary eutectic corresponds to 21 orthoclase: 56 albite: 23 quartz in contrast to that at the isobaric quaternary minimum at 0.5 kb, where the liquid corresponds to 31 orthoclase: 30 albite: 39 quartz. This represents a shift of the liquid, in anhydrous projection, almost directly toward NaAlSi with increasing P. The quaternary minimum in this system becomes a eutectic at approximately 3.6 kb. Compositional comparisons among granites, aplites, zoned pegmatites, and the quaternary minimum and eutectic suggest that igneous pegmatites and aplites represent magmas that were saturated or nearly saturated with water when they began to crystallize. Trends in bulk composition among pegmatites further suggest selective losses of alkalies during crystallization, probably by diffusion through aqueous fluids coexisting with the silicate melts and their solid products.

No abstract

No abstract

No abstract

No abstract

Abstract:The alkaline mafic (lamprophyric) Gusinoozerskaya dyke in West Transbaikalia is composed of partially melted granite xenoliths. Among the xenoliths, two melted substrates are observed: (1) plagioclase and quartz, and (2) alkaline feldspar and quartz. Few millimeters thick microfelsite and microgranophiric rims are the products of melting around the granite xenoliths. Ultra-acid glass is observed in the inner parts of the xenoliths at the boundary of quartz and feldspars. A distinctive feature of the fresh melts (regardless of the composition of the protolithic substrate) is an increased content of potassium with K2O/Na2O≥2. Having compared the compositions of the products of contact melting with the experimental data, we conclude that melting took place in the presence of alkaline-chloride and/or alkaline-carbonic fluid released from the crystallizing host alkaline-basic magma. The probable geotectonic conditions for the occurrence of ultrapotassic acid magmas are estimated.

No abstract

Signature of Chairman of Department Committee on Graduate Students..... ,4-.. 9 fold-axis. Some evidence was found indicating that the planes may develop in the tensional direction. Quartz, then, may fail by shear or tensional rupture and in certain oases by deformation which produces lamellae that may be a type of translation-gliding. Failure by rupture along crystallographic directions has been described by one investigator, and has been produced experimentally in the laboratory. These different phenomena are believed to represent failure under varying environmental conditions and the optimum development of any one type of failure depends on such factors as confining pressure, temperature, composition, and the presence (and character) of solutions. If several sets of planes of liquid inclusions develop at different times, the relative ages of the planes can be discerned from the character of the planes. Planes of inclusions that are very "young" appear as extremely thin sheets of liquid, whereas "old" planes are made up of inclusions that are nearly equant, with some of the inclusions having crystal planes as boundaries (negative crystals).