Geologic Significance of Regional magnetic Anomalies in Coats Land and Western Dronning Maud Land

Abstract

Some aspects of the Late-Proterozoic-Early Mesozoic tectonic development of western Dronning Maud Land and Coats Land are examined in this study by using aeromagnetic data.Results of our study neither contradict nor support a postulated connection ofthe Kaapvaal-Zimbabwe Province into western Droning Maud Land but certainly indicate that the Coats Land crustal block has never been part of the African craton; it appears rather to be typical of the East Antarctic Shield.Our interpretation contradicts the suggestion that the Coast Land area is a continuation of the Mazatal-Yavapai-Grenville provinces of North America.Structural relationship of magnetic anomalies in the neighboring terranes (Maudheim Province, Shackleton Range and Coats Land) strongly indicate the existence of an ancient cratonic fragment in Coats Land.Magnetic anomalies related to the Ross orogenie event are very limited in western Dronning Maud Land and not discernible in the Shackleton Range area.This observation together with the geologie data allow us to suggest that a Ress-age suture resulting from Gondwana coalescence is not presented in western Dronning Maud and Coats Lands, apparently it must lie south of the current exposures of the Shackleton Range.Magnetic anomaliesassociated with fragmentation of Gondwana during the Mesozoic are depicted within the ancient Grunehogna cratonic fragment as isolated intrusions and either a linear chain of mafic intrusions or a dcep-seated fault; apparently inherited some ancient inhomogenity in the Precambrian crust and are recognized within the Proterozoic mobile belt (the Maudheim Province) as intrusions of different composition which are predominantly alkalic in nature.Three well-known intrusions are located in the eastern shoulder ofthe Jurassie Jutulstraumen-Penckskket failed rift whose axis is associated with negative magnetic anomalies, suggesting that axial intrusions not developed along the axis of the rift as aprecursor to crustal splitting.