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The northeast margin of the Otago Schist belt is a complex geological and topographic zone, with a long history of gold mining. The geological evolution of this complex zone began with metamorphism in the Jurassic (>140 million years ago). Initial gold mineralization in the schist occurred about that time. Regional crustal extension in the middle Cretaceous (110-120 million years ago) facilitated uplift and erosion, and more gold mineralization occurred in the schist at that time. Erosion of schist basement and its gold deposits, transferred gold to the alluvial system, primarily in quartz gravels. Extensive recycling of quartz gravels and alluvial gold occurred from the late Cretaceous (about 90 million years ago) to present. The complex geology of the northeast margin of the schist belt has controlled the geology of gold deposits, both schist-hosted and alluvial. The world-class Macraes gold mine (late Jurassic-early Cretaceous) occurs in this structural zone. The following pages give an account of some of the key aspects of this complex geology, and the inter-relationships among them.

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