ALBERT

Description: The syenite-associated Beattie deposit (measured and indicated resources of 60.9 Mt grading 1.59 g/t Au, and inferred resources of 29.7 Mt grading 1.51 g/t Au), located in the Abitibi greenstone belt, consists of two styles of gold mineralization: lithology controlled and structure controlled. Lithology-controlled mineralization is hosted by the syenite intrusion and associated with iron carbonate and sericite alteration. Lithology-controlled mineralization is low grade (1–2 g/t Au) and associated with arsenian pyrite and arsenopyrite, with gold being in solid solution within the spongy As-rich cores of pyrite. Structure-controlled mineralization is present within fault zones that are within the syenite intrusion and adjacent to its margins. This type of ore consists of high-grade mineralization (5 g/t Au) in silicified breccia with both hydraulic and tectonic features, cherty veins, and polymetallic veins. In this facies gold is visible as electrum filling microfractures of brecciated pyrite. The deposit has a distinct paragenesis. The initial stage of alteration involved hematite alteration due to deuteric oxidation. This was followed by a shift toward more reducing conditions, triggered by the introduction of CO 2 -rich hydrothermal fluids that led to sulfide precipitation and gold deposition in As-rich pyrite and arsenopyrite. A later-stage alteration event implies the input of silica-rich fluids that produced sulfide brecciation and their redistribution in the fault zones and gold remobilization in microfractures of brecciated pyrite. Calculated composition for 18 O and measured composition for D on quartz veins associated with this late event are respectively 6.9 to 10.8 and –53 to –83, indicating a potential magmatic-metamorphic fluid mixing. This event is associated with enrichment in Te, Hg, Mo, As, Au, Se, Ag, and Sb. In the Beattie deposit, interaction between magmatic and hydrothermal activities, coupled with external fluid ingress, led to a multistage process of sulfide and gold deposition.

Description: Training geologists for a career in the mining industry has changed over the years. It has become at the same time more specialized and with a broader approach. The modern resource geologist needs to understand new styles of ore deposits, the impact of energy transition on the types of deposits and to implement mining processes, the increasing number of mining regulations, and the shift toward educating populations in countries that are new to mining. Based on observation and imagination, rooted in fundamental science, the education of a resource geologist has been transformed by the digital revolution and the integration of the principles of sustainable development. Training future resource geologists means changing the role of teachers to better develop the imaginations of their students and to increasing what students know about the social impact of mining.

Description: The Jbel Tirremi fluorite-barite ± sulfide deposit in northeastern Morocco is hosted in a Jurassic-aged structurally high carbonate platform known as the Jbel Tirremi dome. The host rocks consist of unmetamorphosed, flat-lying early Jurassic dolomitized limestones, locally intruded by Eocene lamprophyre dikes. The orebodies consist mostly of fluorite and barite, and occur as open-space fillings and partial to massive replacement of the enclosing medium- to coarse-grained dolomitized limestones. The ore mineralogy is dominated by fluorite of different colors and habits, barite, and, to a lesser extent, sulfides. Rare earth element compositions along with fluid inclusion, halogen and isotopic data suggest that the fluorite barite mineralization and the spatially associated Eocene alkaline magmatism are petrogenetically unrelated, pointing instead to the regional circulation of hydrothermal basinal brines mixed to various degrees with meteoric water in a dominantly closed rock-buffered system at progressively higher temperatures and fluid/rock ratios. In this respect, fluid inclusion microthermometric measurements show that the ore-bearing hydrothermal system developed in two separate stages of fluorite-barite mineralization, as also revealed by isotopic data. Both stages precipitated from saline fluids at shallow crustal levels (i.e., 〈5 km), and were related, in varying degrees, to different stages of basin evolution and salt dome growth (salt mobilization and mineralization). During the first stage, the ore fluid was a highly saline aqueous brine with a total salinity up to 44.2 wt % NaCl + KCl equiv, at temperatures ≥82°C and possibly up to 218°C, whereas in the second stage the mineralizing fluid had a similar temperature range, but lower salinities (~20–10 wt % NaCl equiv). The recorded high salinities are interpreted to represent the involvement of a mixture of halite dissolution water and evaporated seawater component. Oxygen ( 18 O = 21.7 to 29.6 V-SMOW) and carbon ( 13 C = –7.9 to 0.2 V-PDB) isotope data along with strontium ( 87 Sr/ 86 Sr = 0.70300–070789) and lead ( 206 Pb/ 204 Pb = 17.961–20.96, 207 Pb/ 204 Pb = 15.511–15.697, 208 Pb/ 204 Pb = 37.784–39.993) isotope ratios suggest the involvement of a mixture of oil-bearing fluids, basinal brines, and meteoric fluids that interacted extensively with the early Jurassic host carbonates, the underlying Triassic salt-bearing diapir, associated siliciclastic rocks, and the highly fractionated and greisenized Hercynian granitic crystalline basement, resulting in the release of fluoride, metals, and other constituents to form the Jbel Tirremi deposit. Petroleum-bearing fluid, released from overpressured portions of the Guercif Basin at lithostatic pressures, and bittern brines dominated the first stage of mineralization. Mixing of saline, oxidized, CaCl 2 - and sulfate-rich bittern brine with oil-bearing fluid resulted in fluorite precipitation of stage I. Conversely, during the second stage of mineralization, the hydrothermal system was open to the influx of oxidized meteoric water as a consequence of the upward migration of the Triassic salt-bearing diapir and associated pressure decrease. The shift from stage I to stage II is associated with the evolution of the system from lithostatic to mostly hydrostatic pressure conditions. Stage I mineralization is thought to have occurred during the Late Miocene in response to rapid sedimentation and high subsidence rates and subsequent hydrocarbon migration associated with the outward migration of the Rif thrust front. Conversely, stage II mineralization occurred coevally with the uplift phase during Tortonian time.