Macraes Orogenic Gold Deposit (New Zealand): Origin and by Dave Craw, Doug MacKenzie

By Dave Craw, Doug MacKenzie

This ebook describes the character and beginning of the Macraes gold deposit. It additionally files the major good points of this extraordinary deposit for a variety of pros within the source geology neighborhood. This world-class gold deposit has been a marvelous geological and fiscal luck tale, because it has constructed from a small old gold mine in discontinuous quartz veins measuring simply meters to a large-scale mine in deposits spreading over kilometres in vast disseminated gold-bearing rock.

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Additional resources for Macraes Orogenic Gold Deposit (New Zealand): Origin and Development of a World Class Gold Mine

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2). However, laterally continuous extensional flat veins, such as those in Fig. 2a–c, are rare, and most flat veins are traceable for less than 20 m. The extensional sites in which the flat veins have formed have been filled mainly with quartz, commonly with several sub-parallel vein generations (Fig. 1a). 5–5 m thick (Figs. 2). Hydrothermal replacement reactions have caused widespread silicification of breccias within the veins, and silicification of some adjacent rocks, contributing to overall vein © The Author(s) 2016 D.

Flat veins are either horizontal or gently dipping (Fig. 1), typically <20° to the northeast, and lie sub-parallel to the shear zone as a whole. The veins have formed parallel or sub-parallel to the metamorphic foliation and the syn-mineralisation shears that have been controlled by that foliation, and veins commonly follow shears as they anastomose around more competent rock types (Chap. 3). Most of the veins occur within shears, and they are commonly called “shear veins”. However, some of these flat veins extend beyond shears into less-mineralised rocks between shears (Fig.

The pod has evolved to form a competent rock mass around which more micaceous schists have become sheared. a Overall geometry of the pod. b Internal structure and sheared margins. c Close view of microsheared margin schists and black sheared rock, so that even these fissile rocks became silicified and added to the width of the siliceous pods (Fig. 1b). At small scales (centimetres to microns), microshears developed in deforming quartz-rich rocks, allowing hydrothermal fluids to penetrate and react, causing some recrystallisation and replacement of the pre-existing rocks.

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