...K. L. Milliken; P. B. Gold; L. S. Land ABSTRACT Alteration of feldspars in the youngest of the Gulf Coast Cenozoic sands and sandstones is dominated by dissolution and albitization. Volumetrically significant amounts of alteration are only observed below burial depths of about 4.5 km in sands...

...Graham J. Borradaile; Don Tarling Abstract Strongly deformed Archean sandstones and conglomerates in northwestern Ontario show extreme heterogeneity of strain, with pebbles deformed more than feldspar grains, which are more deformed than quartz grains. Despite the heterogeneous changes of shape...

... the presence of >3 m of crystal mush. The Klokken Laminated Syenites are slightly more fractionated than Nunarssuit and approach the water-rich termination of fractionation of olivine, clinopyroxene and ternary feldspar. Cumulus phases in Nunarssuit layers are chemically less fractionated than those...

...A. N. Halliday Abstract The exact timing of main stage mineralization in southwest England has never been certain. K-Ar ages for micas and feldspars from a metallized pegmatite are discordant but suggest formation at about 285 m.y. The K-Ar ages of micas from greisens are also discordant...

... and deformation has caused complete recrystallization of the feldspars in parts of the granite. Some of this metamorphism occurred during Permian time, but the effects of earlier episodes cannot be evaluated. Geologic Setting We have studied the Scituate Granite Gneiss (SGG), Hope Valley Alaskite Gneiss (HVA...

...K. Viswanathan; K. Brandt Abstract The crystal structure of a monoclinic ternary barium feldspar with the formula ( Ba 0.19 K 0.59 Na 0.22 ) ( Si 2.82 Al 1.13 Fe 0.05 3 + ) O 8 [ a = 8.516 ( 1 ) , b = 13.023 ( 2 ) , c = 7.206 ( 1 ) Å , β = 115.90 ( 5 ) ∘ ] , space group C 2/ m has been refined to R...

... as: main magmatic, late magmatic, early post-magmatic, and late post-magmatic. Main magmatic stage microveins contain minerals in equilibrium with fractionated intergranular melt existing at this stage of release from the crystal-melt parent system. The assemblage typically will be quartz, K-feldspar...

...STEVEN R. BOHLEN; ERIC J. ESSENE; KAREN S. HOFFMAN Abstract Recently obtained feldspar and oxide temperature data for orthogneiss and paragneiss in the Adirondack Mountains, New York, further constrain and generally support the regional thermometry previously established. Peak metamorphic...

... antipole represents a late Proterozoic remagnetization. We chose biotite and K-feldspars from the available cores — biotite to record high temperature events and K-feldspars to detect any weak late Proterozoic reheating event. The biotite 40 Ar/ 39 Ar age spectrum is flat for 80% of the released Ar...

...George P. Rodgers; Heinrich D. Holland Abstract Tonalite cobbles from moraines in the Tobacco Root Mountains, Montana, have weathering rinds in which the feldspars are altered to clays along microcracks. Energy-dispersive X-ray and X-ray diffraction analyses have shown that microcracks...

...R. J. Stull Abstract Synneusis, the drifting together and systematic attachment of crystals in a melt, is involved in three of the known origins for mantled feldspars: (1) overgrowth, (2) exsolution, and (3) filling of skeletal plagioclase. Quartz latite dikes of the Chocolate Mountains, California...

... of these eruptions from the vertical size grading of feldspar phenocrysts near the base of deep-sea tephra layers. The size grading is a function of the release time of the particles, their settling velocity, the water depth at the site of the ash layer, and the duration of the eruption. The model has been tested...