Long‐Term Geochemical and Geodynamic Segmentation of the Paleo‐Pacific Margin of Gondwana: Insight From the Antarctic and Adjacent Sectors. Issue 12 (22nd December 2017)

• Record Type: Journal Article
• Authors: Nelson, D. A.; Cottle, J. M.
• Is Part Of: Tectonics. Volume 36:Issue 12(2017)
• Page Start: 3229
• Page End: 3247
• Publication Date: 2017-12-22
• Subjects: zircon -- U‐Pb geochronology -- Hf isotopes -- geodynamics -- Antarctica; Geology, Structural -- Periodicals; 551.8
• DOI: 10.1002/2017TC004611
• Languages: English
• ISSNs: 0278-7407

Abstract

Abstract: Combined zircon geochemistry and geochronology of Mesozoic volcaniclastic sediments of the central Transantarctic Mountains, Antarctica, yield a comprehensive record of both the timing and geochemical evolution of the magmatic arc along the Antarctic sector of the paleo‐Pacific margin of Gondwana. Zircon age populations at 266–183 Ma, 367–328 Ma, and 550–490 Ma correspond to episodic arc activity from the Ediacaran to the Jurassic. Zircon trace element geochemistry indicates a temporal shift from granitoid‐dominated source(s) during Ediacaran to Early Ordovician times to mafic sources in the Devonian through Early Jurassic. Zircon initial ε Hf shifts to more radiogenic Hf isotope compositions following the Ross Orogeny and is inferred to reflect juvenile crustal growth within an extensional arc system during progressive slab rollback. These new ages and Hf isotopic record are similar to those from the Australian sector, indicating that these regions constituted an ~3, 000 km laterally continuous extensional arc from at least the Carboniferous to the Permian. Conversely, the South American sector records enriched zircon Hf isotopic compositions and compressional/advancing arc tectonics during the same time period. Our new data constrain the location of this profound along‐arc geochemical and geodynamic "switch" to the vicinity of the Thurston Island block of West Antarctica. Key Points: Zircon geochronology and geochemistry indicate an extensional arc system within the Antarctic sector of the Gondwana margin The extensional arc system in the Antarctic sector is a continuation of the extensional arc system in the adjacent Australian sector An along‐arc switch to advancing arc tectonics in South America is located in the vicinity of the Thurston Island block of West Antarctica