This thesis reviews heavy mineral separation techniques for red-bed heavy mineral provenance studies. It demonstrates the effectiveness of automated mineralogy for mineral comparisons and targeted mineral analysis, resulting in new provenance history conclusions for the Permo-Triassic of SW England. The methodology was developed to remove iron-oxide coatings from grains and provide optimal separation of heavy mineral concentrates in comparison to hydroseparation and panning. Step-wise methodology iterations were validated at each stage using the QEMSCAN (Quantitative Evaluation of Minerals by SCANing electron microscopy). The QEMSCAN works in a similar way to the SEM (scanning electron microscope) and electron-microprobe. Four EDS (energy dispersive spectroscopy) detectors measured X-rays, secondary electrons and back-scattered electrons from the sample. The software allocated these to defined geochemical SIP (species identification protocol) categories. The SIP was back-validated using the electron-microprobe, XRD (X-ray diffraction), microscopy and SEM. QEMSCAN was the primary analysis technique. The results included false colour mineral maps and semi-quantitative statistics for the SIP categories. This enabled targeted mineral analysis with supporting techniques. The methodology was applied to the Permo-Triassic of SW England. The QEMSCAN was able to pick up small scale and large scale heavy mineral provenance trends. Case study 1 showed regional heavy mineral trends and allowed lithological correlation of outliers. Case study 2 used heavy minerals to confirm contemporaneous structural evolution and the base of the Upper Permian in South Devon. Case study 3 allowed a re-evaluation of the base Triassic. Case study 4 targeted biotite minerals at Corbyn's Head. Case study 5 reviewed local vertical and horizontal trends in comparison to regional trends. This has significant oil and gas exploration implications as it gives confidence in correlating deposits over 10s km and can be applied to North Sea barren red-beds. Finally, some mineral firsts, including rammelsbergite and a topaz rhyolite were identified.

This paper presents the results of a mineralogical and metallurgical study of supergene ores at the Mike Cu-Au(-Zn) deposit on the Carlin trend of Nevada, USA, currently held by Newmont Gold Corporation. With a metal endowment totaling >8.5 M oz. Au, 1027 M lbs. Cu, and 809 M lbs. Zn, Mike is one of the largest deposits on the Carlin trend, but it is currently uneconomic to develop. It contains an unusual and complicated suite of metals and ore minerals. This study was undertaken as a first step to investigate process options for recovering both its Cu and Au by 1) comparing the metal recoveries achieved from the supergene ores by six different lixiviants, and 2) identifying which minerals failed to dissolve in each lixiviant. The reagents selected were sulfuric, sulfurous, and methanesulfonic acids, to recover Cu, and cyanide, thiourea, and glycine, to recover Cu and Au. QEMSCAN and SEM study of six samples of different ore types and grades indicate that the Au occurs as varieties of native gold, including auricupride and electrum. Major Cu minerals are native Cu, cuprite, malachite, chrysocolla, and conichalcite (Ca-Cu arsenate), with locally significant Cu in jarosite and goethite. Gangue mineralogy is dominated by quartz, sericite, chlorite, alunite, smectite and kaolinite, K-feldspar, jarosite, and iron oxides. Bottle roll testing indicates that no single-step leaching process is likely to provide economic recovery of both Cu and Au. Sulfuric and methanesulfonic acid both recovered > 70% of the Cu except from the samples dominated by conichalcite, which was not leached effectively by any of the reagents tested. Only cyanide and thiourea recovered significant Au. Reagent consumption for cyanide, sulfuric acid, and methanesulfonic acid was generally within acceptable levels. Glycine and sulfurous acid are both uneconomic based on low recovery. Further work will focus on developing an economic process in two steps. Mineralogical study of QEMSCAN residue indicates that the non-leaching ore minerals are conichalcite and Cu-bearing Fe oxides. In addition, native Cu and cuprite do not leach well in glycine and chrysocolla does not leach well in thiourea or cyanide. Other observed mineralogical changes include the total loss of dolomite and partial loss of alunite and iron oxide from all samples, with apparent gains in jarosite.

The Nkout (Cameroon) and Putu (Liberia) oxide facies iron ore deposits comprise fresh magnetite banded iron formation (BIF) at depth, which weathers towards the surface, forming high grade martite–goethite ores. This study aimed to improve the mineralogical understanding of these deposits in order to predict their metallurgical responses. It concentrated on developing the QEMSCAN® technique and testing its application to these ore types, but also used a variety of other analysis methods. The QEMSCAN® species identification protocol was developed to include three goethite entries: goethite/limonite, phosphorus-bearing and aluminium-bearing goethite. QEMSCAN® was also used to distinguish between the iron oxides using their backscattered electron signals. To test the correlation between the mineralogy and metallurgical characteristics, magnetic separations were carried out. The samples were divided into 4 main groups based on their whole rock Fe content, determined by XRF analysis, and their degree of weathering: enriched material, weathered magnetite itabirite, transitional magnetite itabirite and magnetite itabirite. Quartz and Al oxide and hydroxide minerals such as gibbsite are the major gangue minerals in the magnetite BIF and martite–goethite ores respectively. From the QEMSCAN® analysis it was concluded that the iron oxides are closely associated and liberation of them individually is poor. Liberation increases when they are grouped together as iron oxide. Chamosite concentrations > 6 wt. % significantly lower liberation of the iron oxides. From the metallurgical testing, it was concluded that iron oxide modal mineralogy gives an indication of iron recovery but other QEMSCAN® data such as mineral association and liberation could be important especially if the iron oxide minerals are not liberated. Grain size and instrument characteristics also affect recovery of iron minerals. There is no evidence to show that there is any structural control on the BIF mineralisation at Nkout because metamorphism has significantly affected the lithological characteristics. The BIF mineralised zones occur as stacks with no particular stratigraphic relationship. Alteration and stratigraphy are the main controls on the martite–goethite ores. These results are applicable to most other BIFs so that as direct shipping ores are exhausted, the approach used here can help to develop the lower grade portions of the deposits.

The Björkdal gold deposit is situated in the Skellefte mining district, northern Sweden. The ore is mined from a complex system of quartz veins ranging from a few cm to a meter in width. The mineral processing steps at Björkdal comprises a flotation circuit, which performance is dependent on the pH of the ore feed. A total of ten samples from five different ore zones from the underground development was investigated with the purpose of improving the understanding of factors that causes the pH value of rock samples to vary which is deleterious to the metal recovery. The samples were investigated with optical microscopy together with scanning electron microscopy (SEM) and automated mineralogy (QEMSCAN) to carry out the modal mineralogy. The analyses identified a total of 37 different minerals in the samples. Chlorite was identified with significantly higher values in parts of the investigated ore zones and especially in the sample with the highest pH value, suggesting chlorite-hosting shear zones that crosscut the sampled ore zones to be a contributing factor that could be affecting the elevated pH values, resulting in a decreased recovery of gold.

The Aurora zone is an ore zone which was recently discovered in the Björkdal gold mine, northern Sweden, and it has been the main focus of mining and exploration activities for the past few years (Pressacco et al., 2020). The purpose of this project is to determine how gold occurs in the Aurora zone. A three-day long campaign was therefore done at the processing plant at the Björkdal mine where 11 000 tonnes of ore from the drive Aurora 370/1650 E+W were processed. The issue regarding the ore from the Aurora zone is that it has a lower recovery compared to the rest of the mine.  Six chip samples, 12 samples from the ingoing plant feed and two tailing samples were analyzed using optical microscopy, scanning electron microscopy (SEM), and automated mineralogy (QEMSCAN). This was done to determine the mineralogy, grain size distribution, mineral associations, textures and modal mineralogy which all are factors that could influence the metal recovery at the processing plant. The samples were prepared using the cold mounting method and epoxy mounts were created. After cutting, grinding, and polishing, the sections were ready to be examined. Optical microscopy was performed using a Nikon ECLIPSE E600 POL microscope. Ten epoxy mounts were carbon coated and automated mineralogy was performed on nine of them in a ZEISS Sigma 300 VP using a recipe (analysis mode) for “bright phase search”. Manual point-ID analysis was done using a ZEISS MERLIN SEM. Fifty gold grains were identified in this study, 48 of them in the chip samples and two of them in the ingoing-feed samples. 64% of them were associated with silicates, 22% were quartz associated, 12% were associated with bismuth minerals and 2% of them were associated with sulfides. The grain size distribution has a range between 0.7 and 19 μm and the median grain size is 4.8 μm. The gold grains identified from the Aurora zone have a significantly smaller median grain size than gold from other parts of the mine. The majority of the gold grains identified in this study, have a very fine grain size, are mainly associated with silicates and most prominently occur as inclusions. Gold that occurs in this way is typically difficult to recover in the processing plant and it seems like this is the main reason for the lower gold recovery from the Aurora ore zone.  No gold was found in the tailings, suggesting that the mineral process is performing well although no thorough conclusion can be made in regards of the processing. The lack of data for the different sample types in this project is an issue. Gold from the tailings must be identified and examined to draw any clear conclusions regarding the processing. For future work, it is therefore recommended to analyze more tailing samples and to implement hydroseparation at the sample preparation stage, to separate the heavier gold particles from lighter minerals. Then more gold will most likely get detected in the tailing samples.

PALEOFLUID CHEMISTRY OF OROGENIC GOLD DEPOSITS: NOVEL ANALYTICAL METHODS AND CASE STUDIES FROM THE BOHEMIAN MASSIF Tomáš Hrstka1 1 Charles University in Prague, Faculty of Science, Institute of Geochemistry, Mineralogy and Mineral Resources, Albertov 6, Praha 2, CZ-128 43 Abstract of the Ph.D. Thesis Fluid inclusions represent a unique tool for understanding the processes leading to the formation of mineral deposits and fluid-rock interactions in general. Orogenic gold deposits in the central part of the Bohemian Massif (Libčice and Kasejovice deposits) were studied in order to provide a better understanding of their genesis. A multifaceted approach was adopted including a broad spectrum of micro-analytical methods. While traditional methods were used as the basis of this study (e.g., microthermometry, SEM and optical microscopy), the application and improvement/development of modern analytical methods (e.g., LA-ICP- MS and Raman spectroscopy) or introduction of alternative innovative techniques (CLSM, Nano- tomography, QEMSCAN) constituted a significant part of this study. This study reveals the importance of the HCO3 - species in hydrothermal fluids (i.e., >100 řC to ~350 řC). Previously, the prevalence of Cl- and other anions was reported for hydrothermal paleofluids and the majority of studies suggested...