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Title: Mineral chemistry and thermobarometry of a southern Appalachian amphibolite with epidote + quartz symplectite

Abstract

The Uchee belt of the southern Appalachian Piedmont, in west-central Georgia, is a Barrovian metamorphic facies-series terrane that is characterized by a steeper metamorphic gradient than the adjacent Inner Piedmont rocks in Alabama. As a result of bulk compositional differences, amphibolites from the Uchee belt developed high- and low-variance subsets of the assemblage calcium amphibole + plagioclase + quartz + epidote + titanite {plus minus} garnet {plus minus} magnetite {plus minus} ilmenite {plus minus} rutile {plus minus} calcite {plus minus} diopside {plus minus} biotite. Plagioclase compositions change from An{sub 24} to An{sub 88} as a result of continuous reactions during prograde (M1) metamorphism. Thermobarometric studies indicate a maximum pressure of 10 {plus minus} 1 kbar and a temperature of 750 {plus minus} 30C for the prograde (M1) metamorphism followed by retrograde (M2) metamorphism at {approximately}524 {plus minus} 50C and 6 kbar recorded by the symplectites. The low equilibration temperature for symplectite, which is supported by low-pressure estimates calculated from reaction relationships, suggests that the symplectite formed during erosion and uplift along a path of low dP/dT immediately following the maximum P-T conditions. The composition of fluids during metamorphism of the Uchee belt, estimated from devolatilization equilibria, suggests the fluids weremore » heterogeneous during (M1) metamorphism but were dominantly H{sub 2}O rich during retrograde (M2) metamorphism. The textural and compositional characteristics of retrograded amphibolites suggest that H{sub 2}O-rich fluids were important during progress of the symplectite-producing reactions.« less

Authors:
 [1];  [2]
  1. (Auburn Univ., AL (United States))
  2. (Univ. of Washington, Seattle (United States))
OSTI Identifier:
6951575
Alternate Identifier(s):
OSTI ID: 6951575
Resource Type:
Journal Article
Resource Relation:
Journal Name: American Mineralogist; (United States); Journal Volume: 77:5-6
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; AMPHIBOLITES; GEOBAROMETRY; GEOTHERMOMETRY; PETROCHEMISTRY; PETROGENESIS; GEORGIA; GEOLOGIC FORMATIONS; AMPHIBOLE; ANORTHITE; APPALACHIAN MOUNTAINS; EPIDOTES; GEOCHEMISTRY; GEOLOGIC HISTORY; METAMORPHISM; MINERALOGY; QUARTZ; ALKALINE EARTH METAL COMPOUNDS; ALUMINIUM COMPOUNDS; ALUMINIUM SILICATES; CALCIUM COMPOUNDS; CALCIUM SILICATES; CHEMISTRY; DEVELOPED COUNTRIES; FELDSPARS; IRON COMPOUNDS; IRON SILICATES; METAMORPHIC ROCKS; MINERALS; MOUNTAINS; NORTH AMERICA; OXIDE MINERALS; OXYGEN COMPOUNDS; ROCKS; SILICATE MINERALS; SILICATES; SILICON COMPOUNDS; TRANSITION ELEMENT COMPOUNDS; USA 580000* -- Geosciences

Citation Formats

Chalokwu, C.I., and Kuehner, S.M.. Mineral chemistry and thermobarometry of a southern Appalachian amphibolite with epidote + quartz symplectite. United States: N. p., Web.
Chalokwu, C.I., & Kuehner, S.M.. Mineral chemistry and thermobarometry of a southern Appalachian amphibolite with epidote + quartz symplectite. United States.
Chalokwu, C.I., and Kuehner, S.M.. . "Mineral chemistry and thermobarometry of a southern Appalachian amphibolite with epidote + quartz symplectite". United States. doi:.
@article{osti_6951575,
title = {Mineral chemistry and thermobarometry of a southern Appalachian amphibolite with epidote + quartz symplectite},
author = {Chalokwu, C.I. and Kuehner, S.M.},
abstractNote = {The Uchee belt of the southern Appalachian Piedmont, in west-central Georgia, is a Barrovian metamorphic facies-series terrane that is characterized by a steeper metamorphic gradient than the adjacent Inner Piedmont rocks in Alabama. As a result of bulk compositional differences, amphibolites from the Uchee belt developed high- and low-variance subsets of the assemblage calcium amphibole + plagioclase + quartz + epidote + titanite {plus minus} garnet {plus minus} magnetite {plus minus} ilmenite {plus minus} rutile {plus minus} calcite {plus minus} diopside {plus minus} biotite. Plagioclase compositions change from An{sub 24} to An{sub 88} as a result of continuous reactions during prograde (M1) metamorphism. Thermobarometric studies indicate a maximum pressure of 10 {plus minus} 1 kbar and a temperature of 750 {plus minus} 30C for the prograde (M1) metamorphism followed by retrograde (M2) metamorphism at {approximately}524 {plus minus} 50C and 6 kbar recorded by the symplectites. The low equilibration temperature for symplectite, which is supported by low-pressure estimates calculated from reaction relationships, suggests that the symplectite formed during erosion and uplift along a path of low dP/dT immediately following the maximum P-T conditions. The composition of fluids during metamorphism of the Uchee belt, estimated from devolatilization equilibria, suggests the fluids were heterogeneous during (M1) metamorphism but were dominantly H{sub 2}O rich during retrograde (M2) metamorphism. The textural and compositional characteristics of retrograded amphibolites suggest that H{sub 2}O-rich fluids were important during progress of the symplectite-producing reactions.},
doi = {},
journal = {American Mineralogist; (United States)},
number = ,
volume = 77:5-6,
place = {United States},
year = {},
month = {}
}