Pyroxene exsolution in mafic granulites from the Grove Mountains, East Antarctica: constraints on Pan-African metamorphic conditions

Exsolution textures were observed in clinopyroxenes in mafic granulites from the Grove Mountains, East Antarctica. The first generation of exsolution occurs only in subcalcic augite megacrysts, in which coarse orthopyroxene lamellae exsolved parallel to the (100) plane. Electron microprobe reintegra...

Full description

Bibliographic Details
Published in:European Journal of Mineralogy
Main Authors: Liu, XC, Zhao, ZR, Zhao, Y, Chen, J, Liu, XH
Other Authors: Liu, XC (reprint author), Chinese Acad Geol Sci, Inst Geomech, Beijing 100081, Peoples R China., Chinese Acad Geol Sci, Inst Geomech, Beijing 100081, Peoples R China., Chinese Acad Geol Sci, Inst Geol, Beijing 100037, Peoples R China., Peking Univ, Elect Microscopy Lab, Beijing 100871, Peoples R China., Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China.
Format: Journal/Newspaper
Language:English
Published: european journal of mineralogy 2003
Subjects:
pyroxene exsolution
inverted pigeonite
mafic granulite
metamorphic conditions
Pan-African
Grove Mountains
OPTIMAL PHASE BOUNDARIES
LARSEMANN-HILLS
EXPERIMENTAL CALIBRATION
CRUSTAL EVOLUTION
HIGH-TEMPERATURE
ENDERBY-LAND
PRYDZ-BAY
GARNET
LAMELLAE
PRESSURE
East Antarctica
Larsemann Hills
Prydz Bay
Antarc*
Antarctica
Enderby Land
Online Access:https://hdl.handle.net/20.500.11897/400953
https://doi.org/10.1127/0935-1221/2003/0015-0055
Description
Summary:Exsolution textures were observed in clinopyroxenes in mafic granulites from the Grove Mountains, East Antarctica. The first generation of exsolution occurs only in subcalcic augite megacrysts, in which coarse orthopyroxene lamellae exsolved parallel to the (100) plane. Electron microprobe reintegration of such augites yields a pre-metamorphic igneous temperature of ca. 970degreesC. The second generation of exsolution develops in both igneous and metamorphic clinopyroxenes. In metamorphic clinopyroxenes, two sets of very narrow pigeonite lamellae, subsequently inverted to orthopyroxene, exsolved parallel to (100) and (001) planes, respectively with 0degrees and 113degrees deviation to c-axis of the host. A peak metamorphic temperature of ca. 850degreesC was obtained from the reintegrated compositions of exsolved clinopyroxene, and an exsolution temperature of 740-770degreesC from the orientations of exsolved lamellae. The preservation of augite megacrysts and appearance of equilibrium assemblages suggests that mafic granulites from the Grove Mountains were formed during a single episode of high-grade metamorphism. Temperature estimates for original pyroxene crystallization and pigeonite exsolution from clinopyroxene host provide a good constraint on the peak conditions for this metamorphic event. In contrast with the Prydz Bay area, it is proposed that the Pan-African metamorphism in East Antarctica had reached a higher temperature of ca. 850degreesC, and later underwent a slow cooling process, which probably resulted from the magmatic underplating of the lower crust. Mineralogy SCI(E) 15 ARTICLE 1 55-65 15

Similar Items