Fluid variability in 2 GPa eclogites as an indicator of fluid behavior during subduction

Article Abstract:

Fluid activity ratio calculations indicate that fluid compositional variations existed between millimeter- to centimeter-scale layers in the banded eclogites at pressures of about 2 GPa. Moreover, the heterogeneities represent different saline brines, carbonic fluids or different pairs of immiscible fluids in the various layers. Lastly, data are presented, showing both the complex nature of high-pressure fluids in natural samples and the potential for generating immiscible fluid pairs during subduction.

Research, Subduction zones (Geology), Subduction zones

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Metamorphism, isotopic ages and composition of lower crustal granulite xenoliths from the Cretaceous Salta Rift, Argentina

Article Abstract:

Geologic investigations of the crustal xenoliths of the continental sediments of the Cretaceous Salta Rift at Provincia Salta, Argentina revealed a granitoid composition with quartz-plagioclase-garnet-rutile and K-feldspar. Its Sm-Nd mineral isochron ages were estimated using thermobarometric calculations to be 95.1 +/- 10.4 Ma, 91.5 +/- 13.0 Ma, 89.0 +/- 4.2 Ma in granitoid xenoliths and 110.7 +/- 23.6 Ma in mafic xenolith.

Geology, Stratigraphic, Stratigraphy, Cretaceous period, Salta, Argentina

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Eclogites of the D'Entrecasteaux Islands

Article Abstract:

An analysis of eclogitic rocks of the D'Entrecasteaux Islands in Papua New Guinea is presented. It is shown that the rocks can be classified as true eclogites, retrogressed or S-stage eclogites and eclogites with jadeitic diopside-based clinopyroxene. The three eclogitic types all equilibrated at temperature rangesfrom 530 to 840 degrees Celsius and at pressures of 12 to 24 kbar.

Analysis, Papua New Guinea, Rocks

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