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Long‐Term Geochemical and Geodynamic Segmentation of the Paleo‐Pacific Margin of Gondwana: Insight From the Antarctic and Adjacent Sectors
Author(s) -
Nelson D. A.,
Cottle J. M.
Publication year - 2017
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1002/2017tc004611
Subject(s) - geology , gondwana , zircon , orogeny , geochronology , continental arc , geochemistry , back arc basin , paleontology , rift , permian , carboniferous , supercontinent , devonian , subduction , tectonics , craton , structural basin
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.