Epidote-amphibolite to amphibolite facies transition in the southern Appalachian Piedmont; P-T conditions across the garnet and calc-silicate isograds

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doi: 10.1130/0091-7613(1989)017<0491:EATAFT>2.3.CO;2
Authors:Chalokwu, Christopher I.
Author Affiliations:Primary:
Auburn Univ., Dep. Geol., Auburn, AL, United States
Volume Title:Geology (Boulder)
Source:Geology (Boulder), 17(6), p.491-494. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613
Publication Date:1989
Note:In English. 22 refs.; illus. incl. geol. sketch maps
Summary:Amphibolites occur in three distinct localities (Hudson Rapids, Davis Mill, and Lindsey Creek) in the west-central Georgia part of the Uchee belt, southern Appalachian Piedmont. Epidote-amphibolite facies assemblage (plagioclase [An24-36] + hornblende + epidote + sphene + quartz) at the Davis Mill occurrence gives way to the amphibolite assemblage (calcic plagio-clase [An33-88] + hornblende + garnet + epidote + ilmenite + quartz) at Hudson Rapids. Mineral chemistries indicate that the transition was controlled by increasing pressure and unusual bulk compositions.Equilibrium mineral assemblages record temperatures ranging from 610 to 780 °C at the garnet isograd, and from 570 to 634 °C close to the calc-silicate isograd. Estimated pressures range from 7 to 9.25 ±2 kbar. These P-T conditions are consistent with a thickened crustal section caused by emplacement of the Piedmont allochthon, followed by isobaric cooling (or isothermal compression), and the formation of symplectites of epidote + amphibole around plagioclase + clinopyroxene. [L.C.H.]
Subjects:Amphibolite facies; Amphibolites; Calc-silicate composition; Facies; Garnet group; Geologic barometry; Geologic thermometry; Isograds; Metamorphic belts; Metamorphic rocks; Metamorphism; Mineral assemblages; Nesosilicates; Orthosilicates; P-T conditions; Petrology; Silicates; Appalachians; Georgia; Harris County Georgia; North America; Piedmont; Southern Appalachians; Talbot County Georgia; United States; Columbus County Georgia; Epidote facies; Uchee Belt; West-central Georgia
Abstract Numbers:90M/2353
Record ID:1989049183
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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001 1989049183
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005 20190221170353.0
008 190110e198906 coua 0 0 eng d
040 |a ViAlAGI  |c ViAlAGI 
072 7 |a 05A  |2 georeft 
100 1 |a Chalokwu, Christopher I.  |e analytic author  |u Auburn Univ., Dep. Geol., Auburn, AL 
245 1 0 |a Epidote-amphibolite to amphibolite facies transition in the southern Appalachian Piedmont; P-T conditions across the garnet and calc-silicate isograds 
300 |a p. 491-494 
500 |a In English. 22 refs. 
500 |a Abstract number: 90M/2353 
500 |a Abstractor: L.C.H. 
500 |a Affiliation: Auburn Univ., Dep. Geol.; Auburn, AL; USA; United States 
500 |a Key title: Geology (Boulder) 
500 |a Source note: Geology (Boulder), 17(6), p.491-494. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 
500 |a Publication type: journal article 
504 |b 22 refs. 
510 3 |a GeoRef, Copyright 2019 American Geosciences Institute. 
520 |a Amphibolites occur in three distinct localities (Hudson Rapids, Davis Mill, and Lindsey Creek) in the west-central Georgia part of the Uchee belt, southern Appalachian Piedmont. Epidote-amphibolite facies assemblage (plagioclase [An<24-36`] + hornblende + epidote + sphene + quartz) at the Davis Mill occurrence gives way to the amphibolite assemblage (calcic plagio-clase [An<33-88`] + hornblende + garnet + epidote + ilmenite + quartz) at Hudson Rapids. Mineral chemistries indicate that the transition was controlled by increasing pressure and unusual bulk compositions.Equilibrium mineral assemblages record temperatures ranging from 610 to 780 °C at the garnet isograd, and from 570 to 634 °C close to the calc-silicate isograd. Estimated pressures range from 7 to 9.25 ±2 kbar. These P-T conditions are consistent with a thickened crustal section caused by emplacement of the Piedmont allochthon, followed by isobaric cooling (or isothermal compression), and the formation of symplectites of epidote + amphibole around plagioclase + clinopyroxene. 
650 7 |a Amphibolite facies  |2 georeft 
650 7 |a Amphibolites  |2 georeft 
650 7 |a Calc-silicate composition  |2 georeft 
650 7 |a Facies  |2 georeft 
650 7 |a Garnet group  |2 georeft 
650 7 |a Geologic barometry  |2 georeft 
650 7 |a Geologic thermometry  |2 georeft 
650 7 |a Isograds  |2 georeft 
650 7 |a Metamorphic belts  |2 georeft 
650 7 |a Metamorphic rocks  |2 georeft 
650 7 |a Metamorphism  |2 georeft 
650 7 |a Mineral assemblages  |2 georeft 
650 7 |a Nesosilicates  |2 georeft 
650 7 |a Orthosilicates  |2 georeft 
650 7 |a P-T conditions  |2 georeft 
650 7 |a Petrology  |2 georeft 
650 7 |a Silicates  |2 georeft 
651 7 |a Appalachians  |2 georeft 
651 7 |a Georgia  |2 georeft 
651 7 |a Harris County Georgia  |2 georeft 
651 7 |a North America  |2 georeft 
651 7 |a Piedmont  |2 georeft 
651 7 |a Southern Appalachians  |2 georeft 
651 7 |a Talbot County Georgia  |2 georeft 
651 7 |a United States  |2 georeft 
653 |a Columbus County Georgia 
653 |a Epidote facies 
653 |a Uchee Belt 
653 |a West-central Georgia 
773 0 |t Geology (Boulder)  |d Boulder, CO : Geological Society of America (GSA), Jun. 1989  |x 0091-7613  |y GLGYBA  |n Geology (Boulder), 17(6), p.491-494. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 Publication type: journal article  |g Vol. 17, no. 6  |h illus. incl. geol. sketch maps 
856 |u urn:doi: 10.1130/0091-7613(1989)017<0491:EATAFT>2.3.CO;2