Econ. Environ. Geol. 2010; 43(5): 429-441

Published online October 31, 2010

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

The Nature of Gold Mineralization in the Archean Sunrise Dam Gold Deposit in Western Australia

Yoo-Hyun Sung1* and Sang-Hoon Choi2

1Research & Development Team, Technical Institute, Korea Resources Corporation
2Department of Earth and Environmental Sciences, Chungbuk National University, Cheongju 361-763, Korea

Correspondence to :

Yoo-Hyun Sung

yhsung@kores.or.kr

Received: October 1, 2010; Accepted: October 20, 2010

Abstract

The Sunrise Dam gold deposit is located approximately 850 km ENE of Perth, in the eastern part of the Yilgarn Craton, Western Australia. The mine has produced approximately 153 t of Au at an average grade of 4.2 g/t, which stands for the most significant gold discoveries during the last decade in Western Australia. The deposit occurs in the Laverton Tectonic Zone corresponding to the corridor of structural complexity in the Laverton greenstone belt, and characterized by tight folding and thrusting. The mine stratigraphy consists of a complexly deformed and altered volcaniclastic and volcanic rocks. These have been overlain by a turbidite sequence containing generally well-sorted siltstones, sandstones and magnetite-rich shales, which are consistently fining upwards. These sequences have been intruded by quartz diorite, ultramafic dikes, and rhyodacite porphyry (Archean), and lamprophyre dikes (Palaeoproterozoic). These rocks constitute the asymmetric NNE-trending Spartan anticline with north-plunging thrust duplication of the BIF unit. The deposit is located on the western limb of this structure. Transported, fluvial-lacustrine and aeolean sediments lie unconformably over the deposit showing significant variation in relief. Gold mineralization occurs intermittently along a NE-trending corridor of ca. 4.5 km length. The 20 currently defined orebodies are centered on a series of parallel, gently-dipping (~30o) and NESW trending shear zones with a thrust-duplex architecture and high-strain characteristics. The paragenetic sequence of the Sunrise Dam deposit can be divided into five hydrothermal stages (D1, D2, D3, D4a, D4b), which are supported by distinctive features of the mineralogical assemblages. Among them, the D4a stage is the dominant episode of Au deposition, followed by the D4b stage, which is characterized by more diverse ore mineralogy including base metal sulfides, sulfosalts, and telluride minerals. The D4a stage contains higher proportions of microscopic free gold (48%) than D4b stage (12%), and pyrite is the principal host for native gold (electrum) followed by tetrahedrite-group minerals in both stages.

Keywords Sunrise Dam gold deposit, Yilgarn Craton, Western Australia

Article

Econ. Environ. Geol. 2010; 43(5): 429-441

Published online October 31, 2010

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

The Nature of Gold Mineralization in the Archean Sunrise Dam Gold Deposit in Western Australia

Yoo-Hyun Sung1* and Sang-Hoon Choi2

1Research & Development Team, Technical Institute, Korea Resources Corporation
2Department of Earth and Environmental Sciences, Chungbuk National University, Cheongju 361-763, Korea

Correspondence to:

Yoo-Hyun Sung

yhsung@kores.or.kr

Received: October 1, 2010; Accepted: October 20, 2010

Abstract

The Sunrise Dam gold deposit is located approximately 850 km ENE of Perth, in the eastern part of the Yilgarn Craton, Western Australia. The mine has produced approximately 153 t of Au at an average grade of 4.2 g/t, which stands for the most significant gold discoveries during the last decade in Western Australia. The deposit occurs in the Laverton Tectonic Zone corresponding to the corridor of structural complexity in the Laverton greenstone belt, and characterized by tight folding and thrusting. The mine stratigraphy consists of a complexly deformed and altered volcaniclastic and volcanic rocks. These have been overlain by a turbidite sequence containing generally well-sorted siltstones, sandstones and magnetite-rich shales, which are consistently fining upwards. These sequences have been intruded by quartz diorite, ultramafic dikes, and rhyodacite porphyry (Archean), and lamprophyre dikes (Palaeoproterozoic). These rocks constitute the asymmetric NNE-trending Spartan anticline with north-plunging thrust duplication of the BIF unit. The deposit is located on the western limb of this structure. Transported, fluvial-lacustrine and aeolean sediments lie unconformably over the deposit showing significant variation in relief. Gold mineralization occurs intermittently along a NE-trending corridor of ca. 4.5 km length. The 20 currently defined orebodies are centered on a series of parallel, gently-dipping (~30o) and NESW trending shear zones with a thrust-duplex architecture and high-strain characteristics. The paragenetic sequence of the Sunrise Dam deposit can be divided into five hydrothermal stages (D1, D2, D3, D4a, D4b), which are supported by distinctive features of the mineralogical assemblages. Among them, the D4a stage is the dominant episode of Au deposition, followed by the D4b stage, which is characterized by more diverse ore mineralogy including base metal sulfides, sulfosalts, and telluride minerals. The D4a stage contains higher proportions of microscopic free gold (48%) than D4b stage (12%), and pyrite is the principal host for native gold (electrum) followed by tetrahedrite-group minerals in both stages.

Keywords Sunrise Dam gold deposit, Yilgarn Craton, Western Australia

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