Revised three-dimensional geometry of the platiniferous Hekeia Gabbro, Longwood Range, Southland.

The Hekeia Gabbro in the Longwood Range of Southland, New Zealand, is prospective for platinum group element mineralisation. Recently acquired geological and isotopic data, combined with reinterpreted aeromagnetic data, provide new constraints on the three-dimensional extent and internal structure of the gabbro. Direct observations of in situ subvertical igneous layering give confidence that most curvilinear aeromagnetic patterns are largely caused by macroscopic primary igneous layering. Steep magnetic gradients can be used to reliably define the areal limits of the Hekeia Gabbro and show that it extends to depths of over 1 km. Neodymium isotope ratios distinguish Hekeia Gabbro from younger gabbros and confirm the presence of at least two surface outcrops of Hekeia Gabbro a few kilometres west of the main body. Hekeia Gabbro is interpreted to be part of a 5 km thick Late Permian lopolith that was subsequently deformed and intruded by Triassic plutons. (Authors.)
The Hekeia Gabbro in the Longwood Range of Southland, New Zealand, is prospective for platinum group element mineralisation. Recently acquired geological and isotopic data, combined with reinterpreted aeromagnetic data, provide new constraints on the three-dimensional extent and internal structure of the gabbro. Direct observations of in situ subvertical igneous layering give confidence that most curvilinear aeromagnetic patterns are largely caused by macroscopic primary igneous layering. Steep magnetic gradients can be used to reliably define the areal limits of the Hekeia Gabbro and show that it extends to depths of over 1 km. Neodymium isotope ratios distinguish Hekeia Gabbro from younger gabbros and confirm the presence of at least two surface outcrops of Hekeia Gabbro a few kilometres west of the main body. Hekeia Gabbro is interpreted to be part of a 5 km thick Late Permian lopolith that was subsequently deformed and intruded by Triassic plutons. (Authors.)