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Evidence for refilling of previously emptied basaltic pillows in the Hooggenoeg Complex, Barberton Greenstone Belt

Published online by Cambridge University Press:  26 October 2010

BRIAN ROBINS ,
NILS R. SANDSTÅ ,
HARALD FURNES  and
MAARTEN DE WIT
BRIAN ROBINS*
Affiliation:
Department of Earth Science, 5007 University of Bergen, Norway
NILS R. SANDSTÅ
Affiliation:
Norwegian Petroleum Directorate, Post box 600, 4003 Stavanger, Norway
HARALD FURNES
Affiliation:
Department of Earth Science and Centre for Geobiology, 5007 University of Bergen, Norway
MAARTEN DE WIT
Affiliation:
AEON and Department of Geological Sciences, University of Cape Town, Rondebosch 7700, South Africa
*
†Author for correspondence: [email protected]
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Abstract

Some large metabasaltic pillows in the uppermost part of the Palaeoarchaean Hooggenoeg Complex in the Barberton Greenstone Belt, South Africa, exhibit flow-banded margins and homogeneous cores that have a different texture and compositional variation. The margins consist of millimetre to several centimetre thick alternating bands of pale green spherulitic and darker, conspicuously variolitic varieties of non-vesicular and aphyric metabasalt, previously inferred to be due to mingling of two different types of lava. The dark cores have sharp, aphanitic contacts with the flow-banded carapaces. They lack flow banding, have coarse-grained interiors and exhibit well-preserved primary textures with pseudomorphs after prismatic pyroxene set in a groundmass containing skeletal plagioclase. The compositional range of samples from these cores is unlike that of the flow-banded metabasalt but is similar to a 19 m thick lobate metabasalt flow ~150 m stratigraphically further up, at the local top of the Hooggenoeg volcanic sequence. The pillow cores are inferred to result from the later refilling of drained hollow pillows.

Keywords

pillow lavaBarbertonGreenstone beltArchaean
Type
Original Article
Information
Geological Magazine , Volume 148 , Issue 3 , May 2011 , pp. 435 - 441
Copyright
Copyright © Cambridge University Press 2010

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