Ultramafic to mafic granulites from the Larsemann Hills, East Antarctica: Geochemistry and tectonic implications

• Published in: Journal of Asian Earth Sciences
• Main Authors: Tong, Laixi, Jahn, Bor-Ming, Liu, Xiaohan, Liang, Xirong, Xu, Yi-Gang, Ionov, Dmitri
• Other Authors: Guangzhou Institute of Geochemistry, National Taiwan University, Institute of Tibetan Plateau, Beijing, Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: Ultramafic to mafic granulites; Geochemistry; Rayner orogeny; Larsemann Hills; East Antarctica; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; Prydz Bay; Rayner; Antarc*; Antarctica
• Online Access: https://hal.archives-ouvertes.fr/hal-01622589; https://doi.org/10.1016/j.jseaes.2017.06.012

International audience The Larsemann Hills area is part of a reworked early Neoproterozoic metamorphic terrain in southwestern Prydz Bay, East Antarctica. Ultramafic and mafic granulites, whose origins remain controversial, occur as lenses, boudins or layered bodies within the para- and ortho-gneiss in the region. The ultramafic and mafic granulites show spinel-olivine-bearing and two-pyroxene-bearing mineral assemblages recrystallized at 860–900 °C. Their bulk rock analyses indicate an origin as igneous cumulates, with high Mg# (molar MgO/(MgO + FeO)) from 0.73 to 0.84 for ultramafic granulite and from 0.46 to 0.78 for mostly mafic granulite as well as high Cr and Ni contents ([Cr] and [Ni] up to 1826 ppm and 1400 ppm respectively for ultramafic granulite and [Cr] of 1460 ppm for mafic granulite). Trace element patterns show pronounced negative Nb anomalies, suggesting a subduction-related tectonic setting for their precursors, consistent with derivation from arc basalts, also suggested by low TiO2 and K-enrichment in mafic granulites. The ultramafic to mafic granulites may have been formed in a subduction-related continental back-arc basin environment simultaneously with peak metamorphism associated with arc-continent collision during the early Neoproterozoic (990–900 Ma) Rayner orogeny.