Applied Earth Science: Transactions of the Institutions of Mining and Metallurgy

The possibility of using Icelandic basalt for production of continuous fibres with presently known technology was investigated. One hundred and forty-five samples were taken based on selected field and petrographical criteria and further geochemically analysed. Additional sample discrimination using the geochemical results indicates that it may be difficult to find a suitable basalt for such production. However, minor modification to the composition of three samples is adequate to make them suitable. The viscosity of one specimen was further measured and found to be within the known limits for production of continuous fibres. It, therefore, seems possible that selected samples from the collection are suitable for production of continuous basalt fibres.

Mine planning is directly dependent on the lithological features and the definition of contacts between materials. Geological modelling is a continual duty that is performed using observation data, which includes open faces information. New data must be continuously acquired and more details are added to the model. This task can benefit from the automation of lithological detection. Unmanned aerial vehicles (UAVs) are widely used in open pit mining projects, with low risk to the operators, to the aircraft or third parties. Topographic modelling using UAV imagery is now common in the mining industry. The next step, presented here, is to automate the surface feature detection using machine learning (ML) algorithms to classify a complete detailed geological model. An inexpensive aircraft was used on a Brazilian phosphate mine with point spacing as small as 10 cm.

The direct measurement of gases trapped in sulphide minerals shows that samples from gold-bearing deposits in Britain and Ireland are anomalously rich in methane. Chalcopyrite samples in deposits of Palaeozoic age sited in Neoproterozoic basement (Caledonides greenschist), Munster Basin (Variscides greenschist) and the Carboniferous cover (diagenetic) were compared using mass spectrometry of cold-crushed gases. All host sequences contain sources of organic matter. The content of non-aqueous gas is greater in both sets of greenschist-hosted deposits than in the diagenetic-hosted deposits. However, chalcopyrite accompanying gold in the Neoproterozoic is methane-rich, but in the low-gold Munster Basin it is methane-poor. These gas data from opaque minerals complement fluid inclusion data from gangue minerals, and add support to models for the involvement of organic species in orogenic gold mineralisation.

Both Zn–Pb hypogene sulphide and Zn supergene non-sulphide mineralisation types occur in the Mississippi Valley-type deposit of Florida Canyon, located in northern Peru. The geometry and spatial relationship between the two ore types are very complex to interpret, when it comes to mineral resource evaluation. An algorithm using the Zn, Pb and S contents is proposed for the calculation of sphalerite, galena and non-sulphide norms in the block model after its conventional ordinary kriging estimation. Model validation was performed by comparing the results of the calculations with available SEM/EDS-MLA data. The results show good correlation between the calculated and the quantitative values, thus accrediting the proposed methodology. The algorithm is simple and fast to use and can be applied to mineral resource evaluation of Zn–Pb MVT deposits associated with non-sulphide mineralisation.

The Bozymchak Cu-Au skarn deposit is located in the Chatkal – Kurama region, approximately 130 km east from the Almalyk Cu-Au porphyry mine camp. The current paper provides the results from geochemical study and shows that geochemical characteristics of the Bozymchak area granitoids, including the rare-earth elements, are essentially similar to high-K calc-alkaline series magmatism of the Almalyk area. Systematic sampling of the Bozymchak granitoids has revealed the zoned distribution of several elements relative to the Cu-Au skarn. Most markedly, this is expressed by P₂O₅, MgO, Fe₂O₃ and V, whose contents decrease in the granitoids located closest to the skarns. The zoned distribution of base metals Cu, Zn, Pb, Mo, and also As, is less distinct, however, in general, their content decreases away from the skarns. This revealed geochemical zoning appears to represent a hydrothermal halo of Cu-Au bearing skarns and can potentially be used for guiding exploration in the region.

Orogenic gold deposits are the main source of gold for humanity. These deposits formed from the Archaean to Phanerozoic at crustal depths of more than 4 km. The key parameters accounting for their formation remain under discussion. I review these parameters in light of recent scientific advances using a systemic approach, where the relative pertinence of each component of a complex system in time and space is addressed. From the base to the top of the mineralising system, the following components and processes are reviewed: (1) the fluid sources; (2) the appropriate ligands and their sources; (3) the solubility of gold and its potential sources; (4) the function of faults as conduits; and (5) the mechanisms for precipitating gold. This review provides further support for the role of carbon-rich and pyritic sedimentary rocks in the formation of orogenic gold deposits throughout geological time.