Changes in stable isotope ratios of metapelites and marbles during regional metamorphism, Mount Lofty Ranges, South Australia: implications for crustal scale fluid flow

Article Abstract:

The metamorphic conditions, as measured isotopically, during the formation of the Mount Lofty Ranges in South Australia increased from the biotite to the migmatite grade parallel to the lithological strike of the rocks. As the metamorphic grade increases, the amount of oxygen-18 isotope in the metapelites increases and amount of isotope in marbles decreases. This change in the content of the oxygen isotope is due to the along-strike up-temperature fluid flow towards the granite pluton during regional metamorphosism. The fluid in the metapelite is formed by the devolatization of the rocks at low metamorphic grades but the fluid in the marble is partly formed from the siliceous rocks.

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Resetting of oxybarometers and oxygen isotope ratios in granulite facies orthogneisses during cooling and shearing, Adirondack Mountains, New York

Article Abstract:

Geochemical analysis of the granitic and syenitic orthogneisses of Diana and Stark complexes of the northwest Adirondacks in New York revealed the highly variable nature of resetting of mineralogic and isotopic systems. It has also provided a clearer picture of the granulite-facies metamorphism through shearing and retrogression of the two complexes. It was suggested that oxygen isotope fractionations indicated recrystallization and fluid infiltration processes as shown by the differential setting between sheared and unsheared rocks of the Adirondack complexes.

Oxygen, Natural history, Oxygen isotopes, Adirondack Mountains

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Permeability generation and resetting of tracers during metamorphic fluid flow: Implications for advection-dispersion models

Article Abstract:

Fluid infiltration is important in contact and regional metamorphism. Fluid advection-dispersion models have been developed in hydrogeology. The way in which a fluid-saturated medium needed for the application of advection-dispersion models may arise is discussed. The differing patterns of isotopic, mineralogical and major element resetting if rocks were fluid absent are considered.

Observations, Composition, Dispersion, Dispersion (Optics), Permeability, Rocks

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