Structure and metamorphism of the Calliope Volcanic Assemblage: Implications for middle to Late Devonian orogeny in the northern New England Fold Belt |
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| Authors: | V J Morand |
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| Institution: | 1. Department of Geology , James Cook University of North Queensland , Townsville, Qld, 4811, Australia;2. Department of Geology , Batlarat University College , PO Box 663, Ballarat, Vic., 3353, Australia |
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| Abstract: | The Late Silurian to Middle Devonian Calliope Volcanic Assemblage in the Rockhampton region is deformed into a set of northwest‐trending gently plunging folds with steep axial plane cleavage. Folds become tighter and cleavage intensifies towards the bounding Yarrol Fault to the east. These folds and associated cleavage also deformed Carboniferous and Permian rocks, and the age of this deformation is Middle to Late Permian (Hunter‐Bowen Orogeny). In the Stanage Bay area, both the Calliope Volcanic Assemblage and younger strata generally have one cleavage, although here it strikes north to northeast. This cleavage is also considered to be of Hunter‐Bowen age. Metamorphic grade in the Calliope Volcanic Assemblage ranges from prehnite‐pumpellyite to greenschist facies, with higher grades in the more strongly cleaved rocks. In the Rockhampton region the Calliope Volcanic Assemblage is part of a west‐vergent fold and thrust belt, the Yarrol Fault representing a major thrust within this system. A Late Devonian unconformity followed minor folding of the Calliope Volcanic Assemblage, but no cleavage was formed. The unconformity does not represent a collision between an exotic island arc and continental Australia as previously suggested. |
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| Keywords: | Calliope Volcanic Assemblage Devonian Hunter‐Bowen Orogeny New England Fold Belt thrust fault |
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