Hostname: page-component-cd9895bd7-mkpzs Total loading time: 0 Render date: 2024-12-25T17:16:04.555Z Has data issue: false hasContentIssue false

The Jurassic gabbroic intrusions of Utpostane and Muren: insights into Karoo-related plutonism in Dronning Maud Land, Antarctica

Published online by Cambridge University Press:  20 May 2003

SAKU K. VUORI
Affiliation:
Department of Geology, University of Helsinki, FIN-00014 Helsinki, Finland
ARTO V. LUTTINEN
Affiliation:
Department of Geology, University of Helsinki, FIN-00014 Helsinki, Finland

Abstract

Middle Jurassic continental flood basalts of Vestfjella, western Dronning Maud Land are cut by gabbroic intrusions that represent rare exposures of Karoo-related mafic plutons in Antarctica. The gabbros and numerous associated dolerites indicate high magmatic activity along the continental margin of Dronning Maud Land during the break-up of Gondwana. The scattered nunataks of Utpostane (∼25 km2) are dominated by olivine gabbronorite and olivine mela-gabbronorite, which can be grouped into four zones. The Utpostane intrusion exhibits inclined sheet-like geometry, is at least ∼3 km thick and shows moderate enrichment of incompatible element contents from its base towards the exposed roof contact (e.g. Zr from ∼15 to ∼60 ppm). High MgO contents (∼8–36 wt%) indicate that the parental magma of Utpostane was more primitive than a typical Karoo tholeiite (MgO ∼6 wt%). At Muren, gabbroic outcrops record a cross section of a ∼1.3 km thick inclined sheet-like intrusion. The intrusion can be divided to two main units, the upper and lower zones, which are dominated by olivine gabbro and gabbronorite, respectively. Parental melts of the geochemically differentiated upper zone and the homogeneous lower zone of Muren were typical low-MgO Karoo tholeiites, but they were chemically distinct and were emplaced as separate magma pulses.

Type
Research Article
Copyright
© Antarctic Science Ltd 2003

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)