Kikiktat volcanics of Arctic Alaska—Melting of harzburgitic mantle associated with the Franklin large igneous province

Abstract

The Kikiktat volcanics (new name) of the northeastern Brooks Range of Arctic Alaska are exceptionally well-preserved Neoproterozoic continental tholeiites. This volcanic suite includes high-temperature picritic compositions, making them an excellent probe of mantle composition and temperature underlying the northern margin of Laurentia during the breakup of Rodinia. Detrital zircons from a volcaniclastic sample directly overlying basaltic flows of the Kikiktat volcanics were dated at 719.47 ± 0.29 Ma by U-Pb chemical abrasion-thermal ionization mass spectrometry. This age suggests that the Kikiktat volcanics are an extension of the Franklin large igneous province. Petrogenetic modeling indicates a simple crystallization sequence of olivine → plagioclase → clinopyroxene, recording anhydrous low-pressure fractionation of a picritic parental melt. The composition of this parental liquid requires melting of harzburgite in the spinel stability field, while temperature estimates of the primary melt indicate elevated mantle potential temperatures. In contrast to the ca. 720 Ma Natkusiak basalts of Victoria Island, the Kikiktat volcanics have very low Ti concentrations, consistent with melting of harzburgitic mantle possibly by thermal conduction of an underlying plume. These data are consistent with Neoproterozoic to early Paleozoic tectonic reconstructions that restore the North Slope of Arctic Alaska to the northeastern margin of Laurentia and not directly adjacent to Victoria Island.

Detrital geochronology of pre-Mississippian strata in the northeastern Brooks Range, Alaska: Insights into the tectonic evolution of northern Laurentia

“…In addition, the compositional and textural immaturity of the Clarence River group sandstone samples highlights proximity to the source region. These observations provide support for recent paleogeographic interpretations that restore the North Slope to northeast Laurentia in the early Paleozoic (e.g., Strauss et al, 2013;Malone et al, 2014;Cox et al, 2015).…”

“…The samples from the northern Sadlerochit Mountains are stratigraphically below the ca. 720 Ma Kikiktat volcanics (Cox et al, 2015) and contain zircon grains as young as ca. 760 Ma, indicating that these units were deposited in the middle Cryogenian (Macdonald et al, 2009;Strauss et al, 2013 group samples are typically assumed to be older than the units from the Neruokpuk Formation (e.g., Dutro et al, 1972;Reiser et al, 1980;Lane et al, 2016) and are possibly correlative with the units in the northern Sadlerochit Mountains (Macdonald et al, 2009;Strauss et al, 2013), indicating that they were likely deposited in the Cryogenian or Ediacaran.…”

“…1), before being deformed in the Early-Middle Devonian Romanzof orogeny (e.g., Lane, 1991Lane, , 2007Moore et al, 1994;Cecile et al, 1999;Colpron and Nelson, 2011;Beranek et al, 2010;Lane et al, 2016). In contrast, others have argued that the North Slope has pre-Mississippian origins in northeast Laurentia, and that it did not attain its pre-Canada Basin position until sometime before the Late Devonian or Early Mississippian (Sweeney, 1982;Dumoulin et al, 2000;Macdonald et al, 2009;Strauss et al, 2013;Cox et al, 2015). Resolving these conflicting interpretations has broad implications for Neoproterozoic-Paleozoic plate reconstructions of the circum-Arctic region and Caledonian-Appalachian orogeny (Strauss et al, 2013); thus, our objective is to present new data pertaining to the structural and stratigraphic evolution of pre-Mississippian rocks in the NE Brooks Range to directly address these competing models.…”

A new rock-based definition for the Cryogenian Period (circa 720 – 635 Ma)

“…Rooney et al, 2014;Strauss et al, 2014;Hoffman et al, 1996). Precise U-Pb zircon maximum age constraints for the onset of glaciation are provided by a pre-glacial age of 726 (±1) Ma for the Leger granite, which predates deposition of the entire Mirbat Group in Oman (Allen, 2007) and 719.5±0.3 Ma for the Kikiktak Volcanics, beneath the Hula Hula Diamictite in Arctic Alaska (Cox et al, 2015). Re-Os isochron ages of 727.3±4.9 Ma for the upper Mwashya Formation, beneath the Grand Conglomerat in Zambia and 732.2±4.7 Ma for the Coppercap Formation beneath the Rapitan Group in NW Canada provide complementary maximum age constraints.…”

Insights into the Assembly of Arctic Alaska: Provenance and Geochemical Data from the Doonerak Fenster and Endicott Mountains Allochthon

“…Latitudinal positions are based on Cocks and Torsvik (2005, 2007, and references therein). The bulk of the North Slope of Arctic Alaska is on the peri-Laurentian margin following Strauss et al (2013), Cox et al (2015), and Johnson et al (2016). (A) Paleogeographic model restoring Doonerak to a position proximal to Baltica in the Late Ordovician, in a setting similar to the Alexand er terrane and exotic portions of the Arctic Alaska-Chukotka microplate.…”