Eclogite facies rocks along the Paleozoic activemargin ofGondwana are rare. They are limited to isolated segments of Northern Victoria Land (Antarctica), western Tasmania, and southeastern Australia. New petrological data for mafic rocks and their host garnet-kyanite schists from the Franklin Metamorphic Complex (western Tasmania) permit reconstruction of sixmain stages ofmineral growth for the eclogite. Stages I and II occurred at greenschist/ amphibolite-facies conditions (ca. 500–600 °C; 0.55–0.7 GPa for stage II) before attaining high-pressure conditions (at≈600–650 °C; N1.5GPa for stage III). The following stages, IVandV, record the decompression from high-pressure conditions to amphibolite-facies (ca. 500–600 °C; 0.4–1.0 GPa). Finally, stage VI represents the late greenschist-facies retrogression. However, the pelitic schist surrounding the eclogite records only the mediumpressureamphibolite-facies stage. The P–T evolution over time outlines a clockwise path that is quite steep in both the prograde and retrograde segments. The latter shows a nearly isothermal decompression between the eclogite and the high-pressure amphibolite-facies stage IV, which was achieved at deep crustal levels (≈30 km), and a final decrease in both pressure and temperature from deep/intermediate to shallowcrustal levels, with a typical cooling-unloading path. The lack of a complete re-equilibration during the different stages and the high dP/dT for both the prograde and retrograde paths are indicative of a rapid burial and initially rapid exhumation. The similarity of the mafic whole-rock chemical composition, including N, T to E-MORB and of the peak metamorphic age (≈500Ma) betweenthe Tasmanian eclogites and theUHProcks fromNorthern Victoria Land, supports the idea that they formed in the context of the same contractional event. However, the different P–T conditions and dP/dT point to different tectono-metamorphic settings for the two sectors of the paleo-Pacific margin of Gondwana during the Ross/Tyennan orogeny.

Palmeri, R., Chmielowski, R., Sandroni, S., Talarico, F.M., Ricci, C.A. (2009). Petrology of the eclogites from western Tasmania: insights into the Cambro-Ordovician evolution of the palaeo-Pacific margin of Gondwana. LITHOS, 109(3-4), 223-239 [10.1016/j.lithos.2008.06.016].

Petrology of the eclogites from western Tasmania: insights into the Cambro-Ordovician evolution of the palaeo-Pacific margin of Gondwana

Palmeri, R.;Sandroni, S.;Talarico, F. M.;Ricci, C. A.
2009-01-01

Abstract

Eclogite facies rocks along the Paleozoic activemargin ofGondwana are rare. They are limited to isolated segments of Northern Victoria Land (Antarctica), western Tasmania, and southeastern Australia. New petrological data for mafic rocks and their host garnet-kyanite schists from the Franklin Metamorphic Complex (western Tasmania) permit reconstruction of sixmain stages ofmineral growth for the eclogite. Stages I and II occurred at greenschist/ amphibolite-facies conditions (ca. 500–600 °C; 0.55–0.7 GPa for stage II) before attaining high-pressure conditions (at≈600–650 °C; N1.5GPa for stage III). The following stages, IVandV, record the decompression from high-pressure conditions to amphibolite-facies (ca. 500–600 °C; 0.4–1.0 GPa). Finally, stage VI represents the late greenschist-facies retrogression. However, the pelitic schist surrounding the eclogite records only the mediumpressureamphibolite-facies stage. The P–T evolution over time outlines a clockwise path that is quite steep in both the prograde and retrograde segments. The latter shows a nearly isothermal decompression between the eclogite and the high-pressure amphibolite-facies stage IV, which was achieved at deep crustal levels (≈30 km), and a final decrease in both pressure and temperature from deep/intermediate to shallowcrustal levels, with a typical cooling-unloading path. The lack of a complete re-equilibration during the different stages and the high dP/dT for both the prograde and retrograde paths are indicative of a rapid burial and initially rapid exhumation. The similarity of the mafic whole-rock chemical composition, including N, T to E-MORB and of the peak metamorphic age (≈500Ma) betweenthe Tasmanian eclogites and theUHProcks fromNorthern Victoria Land, supports the idea that they formed in the context of the same contractional event. However, the different P–T conditions and dP/dT point to different tectono-metamorphic settings for the two sectors of the paleo-Pacific margin of Gondwana during the Ross/Tyennan orogeny.
2009
Palmeri, R., Chmielowski, R., Sandroni, S., Talarico, F.M., Ricci, C.A. (2009). Petrology of the eclogites from western Tasmania: insights into the Cambro-Ordovician evolution of the palaeo-Pacific margin of Gondwana. LITHOS, 109(3-4), 223-239 [10.1016/j.lithos.2008.06.016].
File in questo prodotto:
File Dimensione Formato  
Palmeri_Lithos_2009_109_223_239.pdf

non disponibili

Tipologia: Post-print
Licenza: NON PUBBLICO - Accesso privato/ristretto
Dimensione 3.07 MB
Formato Adobe PDF
3.07 MB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11365/22551
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo