Timing of emplacement and deformation of the Tia Granodiorite,southern New England Fold Belt,NSW: Implications for the metamorphic history |
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| Authors: | P H G M Dirks R Offler W J Collins |
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| Institution: | 1. Department of Geology , Un?versity of Newcastle , Shortland, NSW, 2308, Australia;2. Institute of Earth Sciences , University of Utrecht , 3508 TA, Utrecht, The Netherlands;3. Department of Geology , Un?versity of Newcastle , Shortland, NSW, 2308, Australia |
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| Abstract: | The Tia Granodiorite, a Hillgrove Suite pluton in the southern New England Fold Belt, intruded complexly deformed metasediment and metabasite belonging to the Tia Complex, which at the time of intrusion had already been affected by two deformation events at low‐T moderate‐P metamorphic conditions and two overprinting deformation events at high‐T low‐P metamorphic conditions. Emplacement took place during D5 thrusting associated with limited uplift as low‐P amphibolite facies metamorphism prevailed. Large‐scale warping during D6 was followed by a second penetrative thrusting event (D7) that caused further uplift and was initiated under lower amphibolite facies conditions. The granodiorite has been dated at ～ 300 Ma using magmatic zircon, an age which is thought to approximate the emplacement age and thus D5. Biotite grains associated with D7 uplift yield a Rb/Sr age of 264±1.3 Ma. D5 and D7 appear to have formed during one extended high‐T metamorphic event because intervening retrogression is lacking in spite of extensive hydrous fluxing, as indicated by numerous syn‐D6 quartz veins. This thermal event coincided with the opening of the extensional Permian basins. |
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| Keywords: | extensional basins Hillgrove Suite New England New England Fold Belt thermal collapse Tia Complex Tia Granodiorite |
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