Petrographic and chemical data on Cretaceous granitic rocks of the Big Delta Quadrangle, Alaska

SummaryTwo groups of mafic dikes occur within a terrain of metasomatic granitic rocks and quartzofeldspathic gneiss in the central Bighorn Mountains of Wyoming. The younger group consists of dolerite dikes which possess ophitic, subophitic, hypidio morphic-granular and microporphyritic textures. Mineralogically, the dolerites consist primarily of plagioclase (average An 54), augite (average Ca: Mg: Fe = 41: 43: 16) and uralite. The older dikes are metadolerites which possess granoblastic margins that grade into interiors characterized by relict subophitic and locally, porphyriti texture. Dike margins consist of fresh plagioclase and hornblende primarily. Interiors are principally clouded plagioclase (average An 46), augite (average Ca: Mg: Fe = 39: 54: 7) and uralite and/or hornblende. Textural, mineralogic and chemical data indicate that the meta-dolerites were derived from an earlier generation of mafic dikes comparable to the unmeta-morphosed dolerites in the area. The dikes were metamorphosed under low amphibolite facies conditions during the last regional metamorphic event which affected the country rock. During their metamorphism, minimal amounts of water from the country rock facilitated the total recrystallization of the metadolerite margins and the complete or nearly complete replacement of pyroxene by hornblende in the margins. In general, dike interiors underwent no textural changes other than partial destruction of the original subophitic plagioclase–pyroxene relationship as the pyroxene was replaced peripherally by hornblende. This process was accompanied by diffusion of calcium from the plagioclase to form the hornblende, and by diffusion of iron from the augite to cause the clouding of adjacent plagioclase.

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Radioactivity dosage evaluation of Brazilian ornamental granitic rocks based on chemical data, with mineralogical and lithological characterization

Environmental Geology ◽

10.1007/s00254-005-0066-3 ◽

2005 ◽

Vol 49 (4) ◽

pp. 520-526 ◽

Cited By ~ 6

Author(s):

Humberto Terrazas Salas ◽

Hermínio Arias Nalini ◽

Júlio César Mendes

Keyword(s):

Granitic Rocks ◽

Chemical Data

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Freeze-dried dispersions for automated SEM analysis of individual submicron airborne particulates

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100122447 ◽

1992 ◽

Vol 50 (1) ◽

pp. 408-409

Author(s):

Karen A. Katrinak ◽

David W. Brekke ◽

John P. Hurley

Keyword(s):

Air Pollutants ◽

Size Range ◽

Sem Analysis ◽

Individual Particle ◽

Chemical Data ◽

Particle Analysis ◽

Bulk Analysis ◽

Airborne Particulates ◽

Freeze Dried ◽

Individual Particle Analysis

Individual-particle analysis is well established as an alternative to bulk analysis of airborne particulates. It yields size and chemical data on a particle-by-particle basis, information that is critical in predicting the behavior of air pollutants. Individual-particle analysis is especially important for particles with diameter < 1 μm, because particles in this size range have a disproportionately large effect on atmospheric visibility and health.

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