Geochemistry of metasedimentary units of the Cambro-Ordovician Ross Orogen in North Victoria Land and Oates Land, Antarctica

• Main Authors: Henjes-Kunst, Friedhelm, Schüssler, Ulrich
• Format: Dataset
• Language: English
• Published: PANGAEA 2003
• Subjects: Aluminium oxide; Area/locality; Barium; Calcium oxide; Cerium; Chromium; Cobalt; Comment; Gallium; Iron oxide; Fe2O3; Lanthanum; LATITUDE; Lithologic unit/sequence; LONGITUDE; Loss on ignition; Magnesium oxide; Manganese oxide; Nickel; Niobium; ORDINAL NUMBER; Phosphorus oxide; Potassium oxide; Rubidium; Sample code/label; Sample comment; Scandium; Silicon dioxide; Sodium oxide; Strontium; Sulfite; Thorium; Titanium dioxide; Vanadium; Yttrium; Zinc; Zirconium; Victoria Land; Bowers; Robertson Bay; Oates Land; Antarc*; Antarctica
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.704725; https://doi.org/10.1594/PANGAEA.704725

Metasediments in the three early Palaeozoic Ross orogenic terranes in northern Victoria Land and Oates Land (Antarctica) are geochemically classified as immature litharenites to wackes and moderately mature shales. Highly mature lithotypes with Chemical Index of Weathering values of >=95 are typically absent. Geochemical and Rb-Sr and Sm-Nd isotope results indicate that the turbiditic metasediments of the Cambro-Ordovician Robertson Bay Group in the eastern Robertson Bay Terrane represent a very homogeneous series lacking significant compositional variations. Major variations are only found in chemical parameters which reflect differences in degree of chemical weathering of their protoliths and in mechanical sorting of the detritus. Geochemical data, 87Sr/ 86Sr t=490 Ma ratios of 0.7120 - 0.7174, epsilonNd, t=490 Ma values of -7.6 to -10.3 and single-stage Nd-model ages of 1.7 - 1.9 Ga are indicative of an origin from a chemically evolved crustal source of on average late Palaeoproterozoic formation age. There is no evidence for significant sedimentary infill from primitive “ophiolitic” sources. Metasediments of the Middle Cambrian Molar Formation (Bowers Terrane) are compositionally strongly heterogeneous. Their major and trace element data and Sm-Nd isotope data (epsilonNd, t=500 Ma values of -14.3 to -1.2 and single-stage Nd-model ages of 1.7 - 2.1 Ga) can be explained by mixing of sedimentary input from an evolved crustal source of at least early Palaeoproterozoic formation age and from a primitive basaltic source. The chemical heterogeneity of metasediments from the Wilson Terrane is largely inherited from compositional variations of their precursor rocks as indicated by the Ni vs TiO2 diagram. Single-stage Nd-model ages of 1.6 -2.2 Ga for samples from more western inboard areas of the Wilson Terrane (epsilonNd, t=510 Ma -7.0 to -14.3) indicate a relatively high proportion of material derived from a crustal source with on average early Palaeoproterozoic formation age. Metasedimentary series in an ...