Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Geology

Supervisor

Banerjee, Neil R.

2nd Supervisor

Van Loon, Lisa L.

Co-Supervisor

Abstract

The Monument Bay Project is located in the Archean Stull Lake Greenstone Belt, in Northern Manitoba, Canada. This thesis focuses on the geometallurgy and gold mineralization of the Monument Bay Deposit in order to better understand the multiple gold mineralizing events and provide a pathfinder to gold mineralization. Traditional microscopy is used in combination with geochemical and mineralogical analytical techniques (Electron Probe Microanalysis (EPMA) and Energy-dispersive X-ray Spectroscopy (EDS)/(WDS) element map) and synchrotron geochemical techniques (synchrotron X-ray Diffraction (SR-XRD), synchrotron micro X-ray fluorescence (SR-µXRF) mapping, X-ray Absorption Near-edge Structure (XANES) Spectroscopy). Metallic gold (Au0) exists as free gold and inclusion gold, and no refractory gold (Au+1) has been found in the selected samples. As-1, which is the non-toxic form of arsenic, occurs in arsenopyrite and is the only form of arsenic in the samples. Free gold and inclusion gold have been found in porphyritic dacite and metasediments. Only free gold exhibit in metavolcanic rocks. Microscopic gold distribution is related to sulphide morphology. There is evidence for four sulphide generations identified from microscopy and EDS/WDS element maps: Ⅰ. Arsenopyrite 1 (Apy1); Ⅱ. Pyrite 1 (Py1) and Arsenopyrite 2 (Apy2); Ⅲ. Chalcopyrite (Ccp), Galena (Gn), and Sphalerite (Sp); Ⅳ. Pyrite 2 (Py2) and Arsenopyrite 3 (Apy3). The various Au/Ag and Au/Sb ratios identified using EDS point analysis suggest an episode of Au remobilization during sulphide formation because of changes in temperature and pressure. The spatial distribution of different types of sulphides in different veining events suggests there were three main gold mineralizing events. The majority of the gold was deposited as metallic gold in episode Ⅱ. This information is being applied by Yamana to understand the multi-episodic fluid history and environmental characterization of the Monument Bay project and will lead to a better understanding of the mineralogical expression of gold mineralization and geometallurgy at the Monument Bay Project.

Summary for Lay Audience

Because of the appearance and properties of gold, it is a store of value and widely used in various fields, like technology, manufacturing, jewellery, and investment. The main source of gold supply is mine production. Canada has a rich gold endowment and was the fifth largest producer of gold worldwide in 2019. Orogenic gold deposits make up 35% of world gold production and are the most typical gold deposit type in Canada. One such deposit is the Monument Bay Project which is located in northeastern Manitoba.

Nowadays, more and more geoscientists are trying to apply new techniques to be more efficient and effective at exploration in order to locate gold deposits and figure out how gold formed. Synchrotron X-ray technology is one of the cutting-edged techniques. Although this technique is well established in environmental sciences, the applications for mineral exploration and production are underdeveloped. This research combines traditional geological methods with innovative synchrotron techniques to enhance the understanding of the gold formation, type, location, and distribution of possible toxic elements in rocks.

Generally, gold is strongly associated with sulphides in orogenic gold deposits. The typical and common sulphides are pyrite and arsenopyrite. The characteristics and distribution of sulphids can reflect the history of gold formation. Apart from that, Au presents as metallic gold (Au0) and refractory gold (Au+1) in gold deposits. Metallic gold is easier to extract, and the process is more environmentally friendly. But the refractory gold is the opposite. Arsenic has three possible oxidation states: -1, +3, and +5. -1 and +5 are not toxic, but +3 is toxic and harmful to the environment. As a result, confirming the types of gold and arsenic is important in making decision on looking for gold and producing gold.

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