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

Journal Article · · American Mineralogist; (United States)

OSTI ID:6951575

Chalokwu, C I ^[1]; Kuehner, S M ^[2]

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1. Auburn Univ., AL (United States)
2. Univ. of Washington, Seattle (United States)

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.

• OSTI ID: 6951575
• Journal Information: American Mineralogist; (United States), Journal Name: American Mineralogist; (United States) Vol. 77:5-6; ISSN AMMIA; ISSN 0003-004X
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
AMPHIBOLE
AMPHIBOLITES
ANORTHITE
APPALACHIAN MOUNTAINS
CALCIUM COMPOUNDS
CALCIUM SILICATES
CHEMISTRY
DEVELOPED COUNTRIES
EPIDOTES
FELDSPARS
GEOBAROMETRY
GEOCHEMISTRY
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GEORGIA
GEOTHERMOMETRY
IRON COMPOUNDS
IRON SILICATES
METAMORPHIC ROCKS
METAMORPHISM
MINERALOGY
MINERALS
MOUNTAINS
NORTH AMERICA
OXIDE MINERALS
OXYGEN COMPOUNDS
PETROCHEMISTRY
PETROGENESIS
QUARTZ
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
USA