The development of the SW Pacific Margin of Gondwana: Correlations between the Rangitata and New England Orogens

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Abstract
Prior to formation of the Tasman Sea, the Late Paleozoic‐Mesozoic Rangitata Orogen of New Zealand and New Caledonia abutted the Paleozoic New England Orogen of eastern Australia. Comparison of the record of Permian‐Cretaceous igneous and deformational events from the two orogens suggests that their tectonic evolution was interrelated and is a consequence of convergent plate interaction along the southwest Pacific margin of Gondwana. The following relations are proposed: (1) termination of arc volcanism and widespread sedimentation in New England, together with the onset of regional deformation and crustal anatexis were synchronous with the commencement of volcanism and sedimentation within the Rangitata Orogen; (2) Early Permian andesitic volcanism in eastern New England represents an along‐strike extension of the Brook Street terrane of New Zealand; (3) Late Permian regional deformation in New England coincides with both a break in subduction‐related igneous activity in the New England and Rangitata Orogens and a shift in the locus of this activity; (4) Late Permian‐Triassic calc‐alkaline igneous activity in New England correlates with a phase of relatively continuous accumulation of pyroclastic material in the forearc basin of the Rangitata Orogen; (5) cessation of plutonism in New England corresponds with commencement of formation of the Esk Head Melange in New Zealand and the probable commencement of juxtaposition of the Te Anau and Alpine Assemblage; (6) Late Cretaceous epizonal plutons intruded into the New England Orogen are similar in character and age to those emplaced during the final phases of Rangitata orogenesis, and both appear to mark initial stages of rifting associated with formation of the Tasman Sea. The generation of Permian and Triassic igneous activity in eastern New England by convergent plate interaction results, on present reconstructions of the Gondwana margin, in an excessively wide arc‐trench gap succession, for the position of the trench is constrained to east of New Caledonia from the Permian onward. This suggests there may have been some rearrangement of tectonic elements along the margin resulting in widening of the Lord Howe Rise between Australia and New Caledonia in the period between termination of igneous activity in New England and formation of the Tasman Sea in the Late Cretaceous.