- journal_title：Geological Magazine
- Contributor：BRIAN ROBINS ; NILS R. SANDSTÅ ; HARALD FURNES ; MAARTEN DE WIT
- Publisher：Cambridge University Press
- Date：2011-
- Format：text/html
- Language：en
- Identifier：10.1017/S0016756810000853
- journal_abbrev：Geological Magazine
- issn：0016-7568
- volume：148
- issue：3
- firstpage：435
- section：Original Article
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.