Structural analysis of the little Broken Hill area, New South Wales

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Abstract
The structure of the Archaean rocks south of Broken Hill, New South Wales, is superficially simple, with little variation in the strike and dip of layering. Detailed examination, however, reveals a complex history with two generations of folds (B2 and B3) common in the high‐grade rocks. An earlier generation (B1) is postulated on the evidence of the mapped distribution of rock types, and folds in one small outcrop. Later, post‐B3, deformation is related to zones of retrograde schists. Both the B1 and B2 deformation have resulted in transposition of the original layering, the B2 transposition being penetrative on all scales including the regional scale. It is not possible to determine the geometry of the original layering because of the repeated transposition. It is suggested that this complex history may also apply in the vicinity of the Broken Hill orebody, and that there may be an earlier generation of folds than recognised by previous workers. Thus another barrier is added to the interpretation of the relationship of the orebody to the original layering.