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Abstract

abstract

Aspects of the geology and geochemistry of the layered rocks at Annandagstoppane (72�'S, 06發6'W) and Juletoppane (72�'S, 05�'W) in the Giaeverryggen, western Dronning Maud Land, are discussed. The mafic rocks in the two areas have been divided into a 'main suite' and a 'younger suite'. The main suite rocks comprise medium-grained gabbros, gabbronorites and anorthositic gabbros. Lenticular and discontinuous rhythmic layers are present. The younger suite comprises basaltic dykes at Annandagstoppane, and a dolerite sill and small pods of fine-grained gabbroic bodies at Juletoppane. Petrographic and geochemical aspects of main suite rocks in the two areas show close similarities, and indicate that pyroxene and plagioclase were the primocrysts in the orthocumulate assemblages. The preliminary results suggest that the Annandagstoppane and Juletoppane gabbroic rocks may either constitute a single layered intrusion, or reflect outcrops of intrusions of several ages, their magmas having been derived from compositionally similar mantle sources. The close chemical similarities of the younger suite with the main suite suggest that all the mafic phases in the two areas are genetically related.