Dating of volcanism and sedimentation in the Skelton Group, Transantarctic Mountains: Implications for the Rodinia-Gondwana transition in southern Victoria Land, Antarctica

Abstract

The Ross orogen in southern Victoria Land, Antarctica, is composed of Skelton Group metasedimentary rocks and varied plutons of the Granite Harbor intrusives.In the Baronick Glacier area, metasediments are dominated by thick sequences of coarse conglomerate, interbedded with pisolitic limestones. Clasts within metaconglomerates are predominantly volcanic, ranging in composition from basanite to rhyolite. Baronick basaltic clast compositions are mildly alkalic and ocean-island basalt-like, compatible with eruption in a continental-margin rift environment. Sr-Nd isotope ratios suggest rhyolites and quartztrachytes were produced by assimilation and fractional crystallization mechanisms. Two rhyolites yielded U-Pb zircon ages determined by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) of 650.1 ± 4.0 Ma and 648.5 ± 3.2 Ma (both 2σ). Studies of southern Victoria Land Skelton Group metasediments indicate that, although dominated by Grenville-aged detrital zircons, they contain an important component dated between 630 and 680 Ma, overlapping the age of volcanism in both the Baronick Glacier and central Transantarctic Mountain areas. The distribution of 650 Ma, riftrelated volcanism in the southern VictoriaLand segment of the Ross orogen, and the absence of signifi cant older, but post-Grenville, extension-related zircon populations, is interpreted to refl ect initiation of Rodinia fragmentation on the Antarctic margin at this time. It is proposed that rifting along the paleo-Pacifi c margin was diachronous, with the Antarctic segment of the rift opening substantially earlier than in Australia. Based on the dates of subduction-related calc-alkaline plutons formed during the Ross and Delamerian orogenies, the paleo-Pacifi c Ocean in Antarctica may also have closed earlier than in Australia, effectively defi ning the time of Gondwana assembly.

Detrital mineral ages from the Ross Supergroup, Antarctica: Implications for the Queen Maud terrane and outboard sediment provenance on the Gondwana margin

“…These samples are dominated by~1230-1015 Ma (Mesoproterozoic) and~660-550 Ma (late Neoproterozoic-Ediacaran) zircon and muscovite age populations with other subsidiary U-Pb zircon age populations that range from 1725 to 1647 Ma (Paleoproterozoic) (primarily in the LUB2B Taylor Formation sample) and 874-680 Ma (Neoproterozoic). These Paleoproterozoic to Neoproterozoic (Ediacaran) age populations are consistent with erosion and transport of sediment derived from late Mesoproterozoic to early Neoproterozoic mobile belts (Fitzsimons, 2000(Fitzsimons, , 2003, late Neoproterozoic (~670-650 Ma) rift-related magmatic provinces in Antarctica Cooper et al, 2010), late Neoproterozoic to Early Ordovician mobile belts (e.g., Ross orogen) involved in the terminal assembly of Gondwana Table 9 for compositional data. (Boger and Miller, 2004;Goodge et al, 2004b;Squire et al, 2006), and other Paleoproterozoic to early Paleozoic sedimentary or crystalline crust of the East Antarctic shield (Fig.…”

“…Several of the samples (HEN2, LUB2B, RAM1, and RAM2) do contain significant 680-630 Ma zircon age populations. These zircon age populations could be associated with~650 Ma rift magmatism (Cooper et al, 2010), but the~563-502 Ma maximum depositional ages yielded by our zircon age populations preclude correlation of our samples with~670-650 Ma synrift sedimentary rocks of the Beardmore Group of the central Transantarctic Mountains and Skelton Group of southern Victoria Land (Fig. 3a) Cooper et al, 2010) (Fig.…”

“…Previous U-Pb zircon analyses of magmatic rocks found in the central Transantarctic Mountains and southern Victoria Land sectors of the Ross orogen have yielded~670-650 Ma crystallization ages that have been associated with late Neoproterozoic continental rifting along the Gondwana margin Cooper et al, 2010). Several of the samples (HEN2, LUB2B, RAM1, and RAM2) do contain significant 680-630 Ma zircon age populations.…”

“…,Mellish et al (2002),Myrow et al (2002),Read et al (2002),Vogel et al (2002);Goodge et al (2002),Curtis et al (2004),Goodge et al (2004a,b),Paulsen et al (2004),Stump et al (2004),Wysoczanski and Allibone (2004),Cottle and Cooper (2006a,b),Stump et al (2006Stump et al ( , 2007,Talarico et al (2007),Paulsen et al (2008),Cooper et al (2010),Goodge et al (2012), andPaulsen et al (2013).…”

Antarctica and supercontinent evolution: historical perspectives, recent advances and unresolved issues

“…Latest Neoproterozoic-Ordovician subduction under the Ross Orogen was associated with the emplacement of an extensive 590-480 Ma magmatic arc (the Granite Harbour Intrusives), together with deformation, metamorphism and deposition of syn-orogenic sedimentary sequences (Borg & DePaolo 1991;Stump 1995;Encarnación & Grunow 1996;Rocchi et al 1998;Cox et al 2000;Allibone & Wysoczanski 2002;Goodge 2002Goodge , 2007Goodge et al 2002Goodge et al , 2004Goodge et al , 2012Myrow et al 2002;Cooper et al 2011). This event was accompanied by accretion of the Bowers and Robertson Bay terranes to the craton margin along the Lanterman Range of northern Victoria Land by the latest Cambrian or earliest Ordovician (Tessensohn & Henjes-Kunst 2005;Federico et al 2006).…”