Abstract

Mr I. K. Josey & Mr N. D. Shaw write: Recent mapping by the authors of a layered basic body northeast of Kylestrome in what we term the Maldie Belt leads us to suggest a different origin for many of the features described by Davies (1974)

The Maldie Belt layered basic complex has a similar stratigraphy to that found by Davies 12 km to the north. Basal peridotite pyroxenites are overlain by metagabbros and the whole complex lies at a structural interface between overlying metasediments and underlying granulites or quartzofeldspathic gneisses. There is, however, far less late deformation in this area than in the area mapped by Davies and primary features are better displayed. A flat lying fabric which includes the gneissic banding, the metagabbroic foliation and the rhythmic layers in the peridotites is gently folded on near NE axes to form open synclinal structures. These are locally tightened and deformed in monoclinal folds to take the form of ductile shear zones trending east-southeast. These zones of intense deformation show retrogression of granulite facies mineral assemblages and are more widespread in Davies' area to the north so that the Maldie Belt has better preservation of the early history of the complex.

Despite the apparently simple stratigraphical association of peridotite-pyroxenite underlying metagabbro we have found complications due to repetition by low angle shear zones and mineralogical and chemical discontinuities have been found, especially at the pyroxenite metagabbro boundary. Also six rock analyses of a section through the basal peridotite pyroxenite show

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