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Research Collection Journal Article New detrital zircon age and trace element evidence for 1450 Ma igneous zircon sources in East Antarctica Author(s): Paulsen, Timothy; Deering, Chad; Sliwinski, Jakub; Bachmann, Olivier; Guillong, Marcel Publication Date: 2017-10 Originally published in: Precambrian Research 300, http://doi.org/10.1016/j.precamres.2017.07.011 Rights / License: In Copyright - Non-Commercial Use Permitted This page was generated automatically upon download from the ETH Zurich Research Collection. For more information please consult the Terms of use. ETH Library Precambrian Research 300 (2017) 53–58 Contents lists available at ScienceDirect Precambrian Research journal homepage: www.elsevier.com/locate/precamres New detrital zircon age and trace element evidence for 1450 Ma igneous zircon sources in East Antarctica ⇑ Timothy Paulsen a, , Chad Deering b, Jakub Sliwinski c, Olivier Bachmann c, Marcel Guillong c a Department of Geology, University of Wisconsin Oshkosh, Oshkosh, WI 54901, USA b Department of Geological and Mining Engineering and Sciences, Michigan Technological University, Houghton, MI 49931, USA c Institute of Geochemistry and Petrology, Department of Earth Sciences, ETH Zurich, Zurich 8092, CH, Switzerland article info abstract Article history: U-Pb detrital zircon age and trace element data from a Devonian sandstone sample of the Beacon Received 25 November 2016 Supergroup provide new evidence for 1450 Ma zircon sources in Antarctica. These grains yield a Revised 11 July 2017 dominant 1450 Ma (Mesoproterozoic, Calymmian) age probability peak with U/Th ratios suggesting they Accepted 13 July 2017 primarily formed from magmatic processes, also consistent with the presence of grains with oscillatory Available online 14 July 2017 zonation. Determination of zircon parent rock types using trace element proxies reveals that the zircon grains are likely predominantly derived from granitoid rocks, with subsidiary, yet significant contribu- Keywords: tions from mafic and alkaline igneous rocks. These results are consistent with a ca. 1440 Ma Detrital zircon (Mesoproterozoic, Calymmian) granitoid glacial erratic and similar aged detrital zircon found elsewhere U-Pb age Trace element in the Transantarctic Mountains that suggest a continuation of the trans-Laurentian A-type granitoid belt Rock type into Antarctica and, therefore, a 1400 Ma SWEAT-like reconstruction of the continental landmasses. Supercontinent Ó 2017 Elsevier B.V. All rights reserved. 1. Introduction to those found in the trans-Laurentian 1400 Ma (Mesoprotero- zoic, Calymmian) A-type granitoid belt (Fig. 1A) (Goodge and U-Pb detrital zircon age analyses yielded a surprising result Vervoort, 2006; Goodge et al., 2008). The possible continuation of when first applied to thick sequences of continental-derived sand- this granitoid belt into the East Antarctic shield assumes regional stone found along the Pacific-Gondwana margin (Ireland et al., significance because it potentially provides a critical piercing point 1998; Goodge et al., 2002). Instead of confirming that many of for Proterozoic supercontinental reconstructions like the SWEAT these sandstone units are late Neoproterozoic (750–650 Ma) rift hypothesis (Dalziel, 1991; Hoffman, 1991; Moores, 1991). Support to passive margin sedimentary deposits (Goodge et al., 2002; for a granitoid provenance for some of the 1400 Ma detrital zircon Cooper et al., 2011) – a notion that forms part of the basis from grains comes from the discovery of a glacially transported 1440 Ma continental reconstructions in which East Antarctica was con- (Mesoproterozoic, Calymmian) A-type granite cobble recovered nected to Laurentia in the Late Precambrian, for example, the along the edge of the East Antarctic ice sheet in the central SWEAT (Southwest United States-East Antarctica) hypothesis Transantarctic Mountains (Fig. 1)(Goodge et al., 2008). This clast (Moores, 1991; Stump, 1992) – these authors found that many of also possesses an epsilon-hafnium initial value of +7 and an the sedimentary successions are too young and instead represent epsilon-neodymium initial value of +4 making it similar to plutonic flysch derived from late Neoproterozoic-early Paleozoic (650– rocks within the Laurentian intrusive belt (Goodge et al., 2008). 480 Ma) Gondwana mobile belts (Ireland et al., 1998; Goodge However, importantly, there is a general paucity of information et al., 2002; Myrow et al., 2002). However, these studies also dis- about the existence of such rock types outside of the central covered a subsidiary ca. 1400 Ma (Mesoproterozoic, Calymmian) Transantarctic Mountains. The intent of this research note is to zircon age population that was postulated to have been derived present new detrital zircon U-Pb age and trace element data for from proximal source rocks of the East Antarctic shield, which pre- a Devonian Beacon Supergroup sandstone sample from the south sently lies underneath the East Antarctic ice sheet (Fig. 1)(Goodge Victoria Land sector of the Transantarctic Mountains that expands et al., 2002). These detrital zircon grains yielded Hf isotopic values the area over which significant 1450–1400 Ma (Mesoproterozoic, suggestive of an origin from eroded granitoid rocks that are similar Calymmian) zircon age populations are known to occur (Fig. 1). We also present an analysis of trace element data from these zircon grains with the purpose of identifying the most likely source rock ⇑ Corresponding author. E-mail address: [email protected] (T. Paulsen). types within which the detrital zircon grains crystallized. The http://dx.doi.org/10.1016/j.precamres.2017.07.011 0301-9268/Ó 2017 Elsevier B.V. All rights reserved. 54 T. Paulsen et al. / Precambrian Research 300 (2017) 53–58 Fig. 1. (A) Continental reconstruction following the SWEAT hypothesis (Moores, 1991; Dalziel, 1997) showing the trans-Laurentian A-type granitoid belt (white dots) and their possible continuation into Antarctica. White dot in Antarctica shows the location of a previously discovered ca. 1440 (Mesoproterozoic, Calymmian) granitoid glacial erratic; star symbol in Antarctica shows the approximate location of the sample locality for the sandstone analyzed in this paper. Figure modified from Hoffman (1991) and Goodge et al. (2008). (B) Physiographic map of the Antarctic continent showing the location of previous discoveries of ca. 1440 Ma (Mesoproterozoic, Calymmian) granitoid glacial erratic and detrital zircon grains within the central Transantarctic Mountains. Also shown is the location of the Devonian sandstone sample that yielded a significant population of ca. 1450 Ma (Mesoproterozoic, Calymmian) detrital zircon analyzed in this paper. Light gray areas are ice shelves, whereas dark gray indicates rock outcrop. Contours are in meters. White arrow near PRR32746 sample locality shows general paleoflow to the northeast from the East Antarctic shield recorded by the Aztec Siltstone. Image modified from public domain NASA figure available at https://commons.wikimedia.org/wiki/File:Antarctica.svg. results have the potential to better inform future studies that from the Devonian Aztec Siltstone of the Taylor Group a few aspire to constrain supercontinental reconstructions (e.g., Zhao meters below an unconformity that separates it from the overlying et al., 2004; Goodge et al., 2008; Li et al., 2008, 2014). Permian Weller Coal Measures of the Victoria Group (personal The methods used for zircon separation, U-Pb age analyses, and communication). The Taylor Group is a sequence of Devonian sili- trace element analyses are presented as supplementary text in ciclastic sedimentary rocks deposited within intermontane or suc- Appendix A. Supplementary Tables 1 and 2 list the new U-Pb age cessor basins upon the Kukri Erosion Surface, which developed and trace element analytical data for grains that yielded age anal- during a period of post-orogenic uplift and erosion that marked yses that are <15% discordant (by comparison of 206Pb/238U and the terminal stages of the 590–480 Ma (Neoproterozoic- 206Pb/207Pb ages) or <5% reverse discordant. We use the 2015 Inter- Ordovician) Ross orogeny (Isbell, 1999; Goodge et al., 2004; national Chronostratigraphic Chart timescale (Cohen et al., 2013) Rossetti et al., 2011; Hagen-Peter et al., 2016). in the discussion of the results below. Zircon grains from the sample are typically subrounded, and dis- play either oscillatory zoning or patchy and unzoned interiors by cathodoluminescence image analysis; occasional xenocrystic cores 2. Results were also found (Fig. 2). The zircon population shows a polymodal age spectrum indicating derivation from an age-varied source Sample PRR32746 is a fine- to medium-grained sandstone col- (Fig. 3A) or from a provenance with many ages. The cumulative lected by Anne Grunow in 1988 from the Devonian-Jurassic Beacon zircon age suite (n = 195) from the sample ranges from 2847 Ma Supergroup on the southeast ridge of Aztec Mountain (À77.802 °S, (Mesoarchean) to 514 Ma (Cambrian, Series 2). The dominant age 160.552 °E) near the head of Taylor Glacier (http://research.bpcrc. cluster ranges from 1722 to 1039 Ma (Paleoproterozoic-Mesoproter osu.edu/rr/collection/object/46093). The sample was collected ozoic, Stenian; n = 148). This age cluster has four peaks in age T. Paulsen et al. / Precambrian Research 300 (2017) 53–58 55 Fig. 2. Representative cathodoluminescence image of zircon grains with laser spots analyzed from sample PRR32746 and their U-Pb ages. probability at 1665 Ma (n = 9), 1450 Ma (n = 81),