Inherited crustal features and tectonic blocks of the Transantarctic Mountains: An aeromagnetic perspective (Victoria Land, Antarctica)

摘要

Aeromagnetic images coverings a sector of the Transantarctic Mountains in Victoria Land as well as the adjacent Ross Sea are used to study possible relationships between tectonic blocks along the Cenozoic and Mesozoic West Antarctic rift shoulder and prerift features inherited mainly from the Paleozoic terranes involved in the Ross Orogen. The segmentation between the Prince Albert Mountains block and the Deep Freeze Range-Terra Nova Bay region is related to an inherited NW to NNW ice-covered boundary, which we name the "central Victoria Land boundary." It is interpreted to be the unexposed, southern continuation of the Ross age back arc Exiles thrust system recognized at the Pacific coast. The regional magnetic high to the west of the central Victoria Land boundary is attributed to Ross age calc-alkaline back arc intrusives forming the in-board Wilson "Terrane," thus shifting the previously interpreted Precambrian "shield" at least 100 km farther to the west. The high-frequency anomalies of the Prince Albert Mountains and beneath the Polar Plateau show that this region was extensively effected by Jurassic tholeiitic magmatism; NE to NNE trending magnetic lineations within this pattern could reflect Cretaceous and/or Cenozoic faulting. THe western and eastern edges of the Deep Freeze Range block, which flanks the Mesozoic Rennick Graben, are marked by two NW magnetic lineaments following the Priestley and Campbell Faults. The Campbell Fault is interpreted to be the reactivated Wilson thrust fault zone and is the site of a major isotopic discontinuity in the basement. To the east of the Campbell Fault, much higher amplitude magnetic anomalies reveal mafic-ultramafic intrusives associated with the alkaline Meander Intrusive Group (Eocene-Miocene). These intrusives are likely genetically linked to the highly uplifted Southern Cross Mountains block. The NW-SE trends crossing the previously recognized ENE trending Polar 3 Anomaly offshore of the Southern Cross Mountains are probably linked to Cenozoic reactivation of the Paleozoic Wilson-Bowers suture zone as proposed from recent seismic interpretations. The ENE trend of the anomaly may also be structural, and if so, it could reflect an inherited fault zone of the cratonal margin.