Age constraints on recycled crustal and supracrustal sources of Archaean metasedimentary sequences, Eastern Goldfields Province, Western Australia: evidence from SHRIMP zircon dating

SHRIMP U-Pb zircon dating of sedimentary, volcanic and subvolcanic-intrusive rocks from unconformity bounded sequences in the Eastern Goldfields province defines maximum depositional ages for those sequences, The Kambalda Sequence, which records a backarc basin, was deposited prior to 2700 Ma and from at least 2715 Ma. The Spargoville Sequence, which records an are-adjacent, volcano-bound basin, was deposited between 2700 and 2683 Ma. The Kalgoorlie Sequence, which records an intra-are rift basin, comprises two tectonic stages with depositional ages of 2681-2670 and 2661 -2655 Ma. Deposition of the Spargoville and Kalgoorlie Sequences overlapped with the intrusion of granitoids, and subvolcanic porphyries, thereby indicating that those granitoids were emplaced during crustal extension. Younger, submarine-fan (Kurrawang Sequence) and braided-fluvial ( Merougil and Jones Creek Sequences) deposits of a remnant-ocean basin were deposited at <2655 Ma, prior to regional compression and metamorphism, which apparently occurred between 2650 and 2630 Ma. When coupled to palaeocurrent data, provenance dating of detrital zircon suites fingerprints southeast-oriented amalgamation of felsie detritus from multiple sources within longitudinal depositional systems, and longitudinal reworking of felsic detritus from single-sourced transverse systems. Most felsic detritus was recycled from coeval volcanoplutonic arcs and the orogen to the remnant-ocean basin sequences, with zircon ages ranging from similar to 2730 to similar to 2660 Ma. Older felsic sources, with age ranges of 3570-3130, 3030-2900, 2870-2770 and similar to 2760 Ma, could have been structural enclaves within the volcanoplutonic arcs or orogen, but were more likely within a distant cratonic basement. When coupled with stratigraphic data, it is concluded that detrital-zircon age distributions preserve evidence for the sedimentary recycling: of coeval volcanoplutonic are or orogenic sources, uplifted basin-floor and disserted-arc successions, and cratonic basement. Virtually all source terrains have apparently vanished, presumably through the combination of tectonic and sedimentary recycling, and tectonic severance. Increased use of detrital zircon suites from Archaean sedimentary sequences is advocated in order to quantify the balance between sedimentary recycling of felsic rocks from contemporaneous volcanoplutonic sources, which themselves document crustal growth in are environments, and fi um relict volcanoplutonic and crustal-basement sources, which document the degree of crustal recycling. (C) 2000 Elsevier Science B.V. All rights reserved.