Polymetamorphism of Aktyuz eclogites (northern Kyrgyz Tien-Shan) deduced from inclusions in garnets
Garnet and omphacite in eclogites from the Aktyuz area, northern Kyrgyz Tien-Shan, preserve evidence of two distinct metamorphic events. Relic polyphase inclusions of Fe-rich staurolite (X<sub>Mg</sub> < 0.29), Mg-taramite, paragonite, and oligoclase (An < 16) contained in garnet cores represent a separate pre-eclogitic amphibolite or epidote-amphibolite facies metamorphism (<i>T</i> = 560-650 °C, <i>P</i> = 4-10 kbar). This relatively low- to medium-pressure metamorphic event probably resulted from the heat of the hot hanging wall at the inception of subduction. Inclusions in the garnet cores and rims and matrix omphacite (glaucophane, sodic-calcic and calcic amphiboles, paragonite, phengite, epidote, albite, rutile, hematite, and quartz) suggest that epidote-blueschist facies conditions (<i>T</i> = 330-570 °C, <i>P</i> = 8-16 kbar) were experienced during the prograde stage of the eclogitic metamorphism. This event occurred within a subduction zone. The estimated peak metamorphic conditions of the eclogites are <i>T</i> = 600-710 °C <i></i>and <i>P</i> = 15-25 kbar. The subsequent retrograde path through epidote-amphibolite and greenschist facies suggests a clockwise <i>P-T</i> path, in contrast to the anticlockwise <i>P-T</i> path proposed by previous work.
- Journal of mineralogical and petrological sciences
Journal of mineralogical and petrological sciences 102(2), 150-156, 2007-04-01