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Neoproterozoic Attunga Eclogite in Eastern Australia Margin
Gondzvnm Resenrciz, V. 2, No. 4, p . 61 6. 0 1999 lnternntionni Associntionjor Gondzvnnn Resenrciz, Inpnn. 1SSN: 1342-937X
GR
Goiiclwaiza Research
Neoproterozoic Attunga Eclogite in Eastern Australia Margin T. Watanabe', C.M. Fanning2, E. Leitch3and T. Morital 'Division of Earth and Planetary Sciences, Hokkaido University, Sapporo, Japan zResearch Scliool of Earth Sciences, Australian National University, Canberra, Australia 3Llniversityof Technology, Sydney, NS W, Australia
The breakup of Rodinia supercontinent occurred at ca.700Ma (Powell, 1994)with separation of the south China block from the Australia continent (Li et al., 1995; Wingate et al., 1998).The eastern margin of Gondwana continent was subsequently formed by Cambrian (cf. Dalziel et al., 1994). Although it is widely accepted that Early Paleozoic compressive regimes (Delamerian and Ross Orogenies) prevailed at the eastern margin of Gondwana supercontinent after breakup (cf. Goodge, 1997; Wingate et al., 1998), the tectonic processes which operated prior to the compressive regime are not fully understood. Hence, the mode of breakup of Rodinia and the fragmentation between Australia and south China (Powell, 1998) are of much interest. Our recent study of the New England Fold Belt in eastern Australia to the east gives new evidence for the tectonic evolution of the eastern margin of Gondwana. Post-eclogite mafic schists occur in serpentinite melange of the New England Fold Belt at Attunga, Port Macquarie and Gleneden. SHRIMP U-Pb zircon dating of the Attunga eclogite yields ca.570 Ma crystallization age and a ca.650 Ma inheritance age, probably of the igneous stage. The eclogite is included in leucogabbro, the SHRIMP age of the latter being ca.460 Ma. Study of zoned garnet indicates initial high pressure and final high temperature metamorphic conditions, probably related to the formation of leucogabbro. The occurrence of the eclogite identifies the presence of late
Neoproterozoic subduction zone along the eastern Gondwana margin, and is therefore an important clue for the reconstruction and mode of breakup of the Rodinia supercontinent.
References Dalziel, C., Vidal, P., Coulon, C., Vellutini, P.-J. and Piquet, P. (1994) Temporal evolution of mantle sources during continental rifting: The volcanism of Dijbouti (Afar). J. Geophys. Res., v. 99, pp. 2853-2869. Goodge, J.W. (1997) Latest Neoproterozoic basin inversion of the Beardmore Group, central Transantarctic Mountains, Antarctica. Tectonics, v. 16, pp. 682-701. Li, Z.X., Zhang, L. and Powell, C.McA. (1995) South China in Rodinia: part of the missing link between Australia-East Antarctica and Laurentia? Geology, v.23, pp. 407-410. Powell, C.McA. (1994) South Australian record of a Rodinian epicontinental basin and its mid-Neoproterozoic breakup (-700Ma) to form the Paleo-Pacific Ocean. Tectonophys., v.237, pp. 1130-1140. Powell, C.McA. (1998) Break-up of Rodinia in Australia: implications for the western margin of Laurentia. Abstract GSA Annual meeting, v. 30, A47. Wingate, M.T.D., Campbell, I.H., Compston, W. and Gibson, G. M. (1998) Ion microprobe U-Pb ages for Neoproterozoic basaltic magmatism in south-central Australia and implications for the breakup of Rodinia. Precamb. Res., v. 87, pp. 135-159.
GR
Goiiclwaiza Research
Neoproterozoic Attunga Eclogite in Eastern Australia Margin T. Watanabe', C.M. Fanning2, E. Leitch3and T. Morital 'Division of Earth and Planetary Sciences, Hokkaido University, Sapporo, Japan zResearch Scliool of Earth Sciences, Australian National University, Canberra, Australia 3Llniversityof Technology, Sydney, NS W, Australia
The breakup of Rodinia supercontinent occurred at ca.700Ma (Powell, 1994)with separation of the south China block from the Australia continent (Li et al., 1995; Wingate et al., 1998).The eastern margin of Gondwana continent was subsequently formed by Cambrian (cf. Dalziel et al., 1994). Although it is widely accepted that Early Paleozoic compressive regimes (Delamerian and Ross Orogenies) prevailed at the eastern margin of Gondwana supercontinent after breakup (cf. Goodge, 1997; Wingate et al., 1998), the tectonic processes which operated prior to the compressive regime are not fully understood. Hence, the mode of breakup of Rodinia and the fragmentation between Australia and south China (Powell, 1998) are of much interest. Our recent study of the New England Fold Belt in eastern Australia to the east gives new evidence for the tectonic evolution of the eastern margin of Gondwana. Post-eclogite mafic schists occur in serpentinite melange of the New England Fold Belt at Attunga, Port Macquarie and Gleneden. SHRIMP U-Pb zircon dating of the Attunga eclogite yields ca.570 Ma crystallization age and a ca.650 Ma inheritance age, probably of the igneous stage. The eclogite is included in leucogabbro, the SHRIMP age of the latter being ca.460 Ma. Study of zoned garnet indicates initial high pressure and final high temperature metamorphic conditions, probably related to the formation of leucogabbro. The occurrence of the eclogite identifies the presence of late
Neoproterozoic subduction zone along the eastern Gondwana margin, and is therefore an important clue for the reconstruction and mode of breakup of the Rodinia supercontinent.
References Dalziel, C., Vidal, P., Coulon, C., Vellutini, P.-J. and Piquet, P. (1994) Temporal evolution of mantle sources during continental rifting: The volcanism of Dijbouti (Afar). J. Geophys. Res., v. 99, pp. 2853-2869. Goodge, J.W. (1997) Latest Neoproterozoic basin inversion of the Beardmore Group, central Transantarctic Mountains, Antarctica. Tectonics, v. 16, pp. 682-701. Li, Z.X., Zhang, L. and Powell, C.McA. (1995) South China in Rodinia: part of the missing link between Australia-East Antarctica and Laurentia? Geology, v.23, pp. 407-410. Powell, C.McA. (1994) South Australian record of a Rodinian epicontinental basin and its mid-Neoproterozoic breakup (-700Ma) to form the Paleo-Pacific Ocean. Tectonophys., v.237, pp. 1130-1140. Powell, C.McA. (1998) Break-up of Rodinia in Australia: implications for the western margin of Laurentia. Abstract GSA Annual meeting, v. 30, A47. Wingate, M.T.D., Campbell, I.H., Compston, W. and Gibson, G. M. (1998) Ion microprobe U-Pb ages for Neoproterozoic basaltic magmatism in south-central Australia and implications for the breakup of Rodinia. Precamb. Res., v. 87, pp. 135-159.