U-Pb and oxygen isotope characteristics of Timanian- and Caledonian-age detrital zircons from the Brooks Range, Arctic Alaska, USA

Abstract

The Devonian connection between the Brooks Range of Alaska, USA, with the continental margin of Arctic Canada and its subsequent Jurassic–Cretaceous counterclockwise rotation to form the Amerasian Basin, is a highly debated topic in Arctic tectonics. This resource-rich region was assembled from terranes that formed part of Laurentia or Baltica, or were juvenile oceanic arcs in the early Paleozoic that were brought together during Caledonian Orogenesis and the subsequent collision that formed Pangea (Uralide Orogeny). Elements of these orogens, as well as older ones, are predicted to occur in the Brooks Range of Arctic Alaska. This study presents the first combined zircon U-Pb and oxygen data from six Brooks Range metasedimentary units with assumed Neoproterozoic to Devonian ages. Three distinct detrital zircon patterns are identified in these units: (1) those with Neoproterozoic maximum depositional ages characteristic of the Timanide Orogen of northern Baltica and adjacent parts of Siberia, (2) an almost unimodal Siluro–Ordovician (443.5 ± 2.3 Ma) detrital zircon population consistent with the oceanic Apoon arc believed to have existed off shore of northern Laurentia and to have accreted to the North Slope subterrane during the Caledonian event, and (3) those with Middle Devonian maximum depositional ages consistent with post-accretion extension during the final (Scandian) phase of Caledonian Orogenesis. Oxygen isotopes from the same zircons reveal minor to significant crustal contamination with approximately two thirds (n = 255/405) having δ18O values >5.9‰ (above the mantle field of 5.3 ± 0.6‰). Pattern 1 units exhibit a progressive increase in δ18O values throughout the Proterozoic (5.99 to 9.29‰) indicative of increasing crustal growth and Timanide age zircons yield average δ18O values of 7.18 ± 0.64‰ (n = 26) suggestive of more crustal influence than Caledonian age zircons, possibly reflecting northern Baltica signatures. The unimodal population in Pattern 2 yields average δ18O values of 5.49 ± 0.66‰ (n = 17) and 6.02 ± 0.27‰ (n = 23) prior to and during, respectively, the main Caledonian event and suggest derivation from Devonian juvenile arc sources possibly representing the initiation of the collision between Laurentia and Baltica. Similar to Pattern 1, the δ18O values associated with Pattern 3 show a progressive increase in δ18O values throughout the Proterozoic (5.00 to 9.39‰). However, Pattern 3 also exhibits a distinct juvenile fingerprint (6.13 ± 0.24‰, n = 51) during the main Caledonian event and a slight increase to 7.12 ± 1‰ (n = 7) in post-Caledonian zircons possibly suggest correlating with a post-accretion phase in which proximally sourced zircon-bearing detritus was deposited in extension-related basins marking the joining of Laurentia and Baltica.

Pre-Mississippian Stratigraphic Architecture of the Porcupine Shear Zone, Yukon and Alaska, and Significance in the Evolution of Northern Laurentia

“…Due to the presence of ca. 500-740 Ma igneous rocks and abundant detrital zircons in metasedimentary units of the southwestern subterranes of the Arctic Alaska-Chukotka microplate [69,140,[148][149][150][151] this composite terrane is often invoked as a source of Neoproterozoic detritus to the Ellesmerian clastic wedge [8,[137][138][139] (Figure 13(c)). The presence of these Cryogenian-Ediacaran igneous ages and the similarities in provenance to portions of northern Baltica led to the proposed restoration of the Arctic Alaska-Chukotka microplate adjacent to the ca.…”

“…These early Paleozoic U-Pb age populations are abundant in strata of the Ellesmerian clastic wedge (Figure 13(c); [8,[137][138][139]), as well as the Clarence River Group of the North Slope subterrane (e.g., [20]) and a wide variety of Devonian(?) metasedimentary units throughout the southwestern subterranes of the Arctic Alaska-Chukotka microplate (e.g., [35,69,151]). The Ordovician-Silurian signature reflects ties to arc magmatism in the circum-Arctic realm, which is locally preserved in the Pearya terrane [162], Doonerak arc of the Arctic Alaska-Chukotka microplate ( [35] and references therein), and the Descon Formation of the Alexander terrane (e.g., [163,164]).…”

Metal-rich organic matter and hot continental passive margin: drivers for Devonian copper-cobalt-germanium mineralization in dolomitized reef-bearing carbonate platform

“…3a and 3b) (Fig. 3a and 3b;Hitzman 1983Hitzman , 1986Hitzman et al 1986;Till et al 2008;Rohr et al 2018;Robinson et al 2019).…”

“…Our interpretations focus on (1) the first-order controls on the flow, pulses, and redox evolution of mineralizing basinal brines, and (2) the specific metal endowment of the RCB deposit in critical metals (e.g., Co, Ge, Ni) as a consequence of the breakdown of metal-rich algal-bacterial organic matter during dolomitization and sulfide mineralization. The Scandian phase of the northern evolution of the Caledonian orogeny marked the final collision between Baltica and Laurentia (Miller et al 2011;Gee et al 2013;Robinson et al 2019;Fig. 3a).…”

Supplemental Material: ‘Taters versus Sliders: Evidence for a Long-Lived History of Strike-Slip Displacement along the Canadian Arctic Transform System (CATS)

“…Gehrels, inhouse program at Arizona LaserChron Center) and (C) Shepard plot(Saylor et al, 2017) of U-Pb data shown in Fig.2Aof the text. U/Pb and Hf data is from select Arctic and northern Cordilleran terranes including the Svalbard terranes(Pettersson et al, 2009(Pettersson et al, , 2010Gasser and Andresen, 2013;Beranek et al, 2020); Franklinian basin(Beranek et al, 2013a;Hadlari et al, 2014;Dewing et al, 2019); Pearya terrane(Hadlari et al, 2014;Beranek et al, 2015;Malone et al, 2014Malone et al, , 2019Estrada et al, 2018;Dewing et al, 2019; Beauchamp et al, 2019); Canadian Arctic Islands clastic wedge(Anfinson et al, 2012a, b); Arctic Alaska terrane including the North Slope subterrane(Macdonald et al, 2009;Strauss et al, 2013Strauss et al, , 2017Strauss et al, , 2019aGottlieb et al, 2014;McClelland et al, 2015;Cox et al, 2015;Johnson et al, 2016;Lane et al, 2016;Colpron et al, 2019), Seward Peninsula (Amato et al, 2009Till et al, 2014;Dumoulin et al, 2018a), Southwestern subterranes(Strauss et al, 2017;Hoiland et al, 2017;Robinson, et al, 2019), Doonerak(Strauss et al, 2017) and Whale Mountain Allochthon(Johnson et al, 2016(Johnson et al, , 2018Strauss et al, 2019b); Farewell and Mystic terranes(Bradley et al, 2014;Malkowski et al, 2014; Dumoulin et al, 2018a, b); Alexander terrane(Beranek et al, 2013b,c; Tochilin et al, 2014; White et al, 2016); and Yukon-Tanana terrane in southeastern Alaska…”