Duration of high-pressure metamorphism and cooling during the intraplate Petermann Orogeny

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• 作者：A.K. Walsh ; T. Raimondo ; D.E. Kelsey ; M. H ; H.L. Pfitzner ; C. Clark
• 关键词：Central Australia ; Petermann ; Musgrave Province ; Intraplate ; SHRIMP U&ndash ; Pb geochronology
• 刊名：Gondwana Research
• 出版年：2013
• 出版时间：November, 2013
• 年：2013
• 卷：24
• 期：3-4
• 页码：969-983
• 全文大小：3423 K

文摘

The Ediacaran-Cambrian Petermann Orogeny, central Australia, is an exceptional example of intraplate orogenesis. It involved sub-eclogite facies metamorphism and extreme basin inversion during the exhumation of Musgrave Province basement from beneath the formerly contiguous Centralian Superbasin. Sensitive High Resolution Ion Microprobe (SHRIMP) U-Pb geochronology of zircon, titanite and rutile, along with Ti-in-zircon thermometry from meta-igneous samples, have been used to determine the timing and duration of high-pressure metamorphism and subsequent cooling associated with this orogenic event. Peak metamorphic temperatures of 720-760 ¡ãC were attained at 544 ¡À 7 Ma (U-Pb zircon). Subsequent cooling to 600-660 ¡ãC by ~ 521 Ma occurred at a rate of ~ 2.6-7.0 ¡ãC Myr^? 1, as recorded by the closure of Pb diffusion in titanite. Further cooling to 585-560 ¡ãC by 498-472 Ma occurred at a rate of 0.9-4.8 ¡ãC Myr^? 1, as recorded by Pb closure in rutile. The duration of tectonism was long-lived (> 40 Myr) across the central and western parts of the orogenic system, and deformation occurred in a comparatively warm and weak portion of crust, characterised by regional thermal gradients of 17-26 ¡ãC km^? 1. This proposed duration of tectonism is much longer than that permitted by a shear heating mechanism, which requires an exceptionally short duration of tectonism, and additionally, an overall cold lithosphere characterised by geothermal gradients of ~ 9 ¡ãC km^? 1.