Spatial Modeling of Geometallurgical Properties: Techniques and a Case Study

High-resolution spatial numerical models of metallurgical properties constrained by geological controls and more extensively by measured grade and geomechanical properties constitute an important part of geometallurgy. Geostatistical and other numerical techniques are adapted and developed to construct these high-resolution models accounting for all available data. Important issues that must be addressed include unequal sampling of the metallurgical properties versus grade assays, measurements at different scale, and complex nonlinear averaging of many metallurgical parameters. This paper establishes techniques to address each of these issues with the required implementation details and also demonstrates geometallurgical mineral deposit characterization for a copper–molybdenum deposit in South America. High-resolution models of grades and comminution indices are constructed, checked, and are rigorously validated. The workflow demonstrated in this case study is applicable to many other deposit types.     

Aggregation of Nanogold Particles in the Environment

Nanogold exists widespread in the environment. For example, countless nanogold particles appear in weathered rocks due to chemical decomposition of mineral-concentrators (e.g., pyrite, arsenopyrite, pyrrhotite, and magnetite). Nanogold is usually represented by isolated particles dispersed in minerals and sedimentary rocks, but in certain conditions, Au nanoparticles are able to merge with each other and compose simple or complex aggregates. The mechanisms of aggregation are related to specific geochemical situations in the environment. In addition, superfluous surface energy of metal nanoparticles and their chemical activity essentially contribute to aggregation. There are two main ways of accumulation, namely adsorption on surface of minerals (mainly placer Au grains) and gradual consolidation of separate Au nanoparticles due to natural amalgamation. Aggregation of Au nanoparticles is a natural mechanism of accumulation in sedimentary rocks, which may be reproduced in nanotechnologies.     

Bitumen Prices and Structural Changes in North American Crude Oil Markets

In an earlier report, changes in bitumen prices at Hardesty, Alberta, Canada, were modeled as the responses to changes in monthly prices of Hardesty light/medium crude oil for the period 2000–2006 with a simple error correction econometric model. This note re-examines that price relationship for the period 2009–2014. Over the period 2006–2014, there was also rapid growth in North American light oil production from low-permeability carbonate, sandstone, and shale reservoirs. During that period, Canadian raw bitumen production grew by more than 12% per year and there was significant geographical diversification in its markets. Results of the statistical analysis showed that the change in the dynamic relationships between bitumen prices and Hardesty light oil prices probably reflected, in part, the maturation of bitumen markets and closer integration with North American light oil markets. The analysis also examines the dynamic relationships between bitumen prices and West Texas Intermediate and Brent international benchmark crude oil prices. Ideally, if bitumen prices are found to be closely related to a widely traded benchmark crude oil, the benchmark crude oil price forecasts could be used as a basis for predicting bitumen prices. However, neither of international benchmark crude oils tested had high explanatory power.     

Mid and late Holocene forest fires and deforestation in the subalpine belt of the Iberian range,northern Spain

The conversion of subalpine forests into grasslands for pastoral use is a well-knownphenomenon, although for most mountain areas the timing of deforestation has not been determined. The presence of charcoal fragments in soil profiles affected by shallow landsliding enabled us to date the occurrence of fires and the periods of conversion ofsubalpine forest into grasslands in the Urbión Mountains, Iberian Range, Spain. We found that the treeline in the highest parts of the northwestern massifs of the Iberian Range(the Urbión, Demanda, Neila, and Cebollera massifs) is currently between 1500 and 1600 m a.s.l., probably because of pastoral use of the subalpine belt, whereas in the past it would have reached almost the highest divides(at approximately 2100–2200 m a.s.l.). The radiocarbon dates obtained indicate that the transformation of the subalpine belt occurred during the Late Neolithic, Chalcolithic, Bronze Age, Iron Age, and Middle Ages. Forest clearing was probably moderate during fires prior to the Middle Ages, as the small size of the sheep herds and the local character of the markets only required small clearings, and therefore more limited fires. Thus, it is likely that the forest recovered burnt areas in a few decades; this suggests the management of the forest and grasslands following a slash-andburn system. During the Middle and Modern Ages deforestation and grassland expansion affected most of the subalpine belt and coincided with the increasing prevalence of transhumance, as occurred in other mountains in the Iberian Peninsula(particularly the Pyrenees). Although the occurrence of shallow landslides following deforestation between the Neolithic and the Roman Period cannot be ruled out, the most extensive shallow landsliding processes would have occurred from the Middle Ages until recent times.     

Hydro-hypsometric analysis of tropical river basins,Southwest Coast of India using geospatial technology

The key aspect in planning and management of water resources is to analyze the runoff potential and erosion status of the river basin. For the detailed investigation of hydrological response, freely available Cartosat-1 (IRS-P5) data was used for the preparation of digital elevation model (DEM). The runoff potential and type of erosive process of 22 river basins originating in the global biodiversity hotspot of Western Ghats, was inferred through hypsometric analysis. Several parameters like Hypsometric integral (HI), maximum concavity (Eh), coordinates of slope inflection point (I) given by a* and h* and normalized height of hypsometric curve (h) were extracted from the hypsometric curves and used for understanding the hydrological responses. From the hypsometric curves, the landform evolution processes were inferred. Contribution of diffusive and fluvial processes in slope degradation of the river basins was understood. Basins with lesser area (<100 km²) were found to have a positive correlation between hypsometric integral and basin area, whereas for large basins no such correlation exists. Based on the study, river basins can be prioritized for the appropriate conservation measures.     

The tectono‐stratigraphic evolution of the Austral Basin and adjacent areas against the background of Andean tectonics,southern Argentina,South America

The Austral Basin (or Magallanes Basin) in southern Argentina is situated in a highly active tectonic zone. The openings of the South Atlantic and the Drake Passage to the east and south, active subduction in the west, and the related rise of the Andes have massively influenced the evolution of this area. To better understand the impacts of these tectonic events on basin formation to its present‐day structure we analysed 2D seismic reflection data covering about 95 000 km² on‐ and 115 000 km² offshore (Austral ‘Marina’ and Malvinas Basin). A total of 10 seismic horizons, representing nine syn‐ and post‐ rift sequences, were mapped and tied to well data to analyse the evolution of sedimentary supply and depocenter migration through time. 1D well backstripping across the study area confirms three main tectonic stages, containing (i) the break‐up phase forming basement graben systems and the evolution of the Late Jurassic – Early Cretaceous ancient backarc Austral/Rocas Verdes Basin (RVB), (ii) the inversion of the backarc marginal basin and the development of the foreland Austral Basin and (iii) the recent foreland Austral Basin. Synrift sedimentation did not exceed the creation of accommodation space, leading to a deepening of the basin. During the Early Cretaceous a first impulse of compression due to Andes uplift caused rise also of parts of the basin. Controlling factors for the subsequent tectonic development are subduction, balanced phases of sedimentation, accumulation and erosion as well as enhanced sediment supply from the rising Andes. Further phases of rock uplift might be triggered by cancelling deflection of the plate and slab window subduction, coupled with volcanic activity. Calculations of sediment accumulation rates reflect the different regional tectonic stages, and also show that the Malvinas Basin acted as a sediment catchment after the filling of the Austral Basin since the Late Miocene. However, although the Austral and Malvinas Basin are neighbouring basin systems that are sedimentary coupled in younger times, their earlier sedimentary and tectonic development was decoupled by the Rio Chico basement high. Thereby, the Austral Basin was affected by tectonic impacts of the Andes orogenesis, while the Malvinas Basin was rather affected by the opening of the South Atlantic.     

TRACE ELEMENT DISTRIBUTION AND IMPLICATIONS IN SEDIMENTS ACROSS THE ALLERØD–YOUNGER DRYAS BOUNDARY IN THE NETHERLANDS AND BELGIUM

In the Northern Hemisphere, the Younger Dryas cooling occurred between 12.8 and 11.7 ka bp . This cooling is thought to have been the result of an abrupt change in atmospheric and oceanic circulations. One of the hypotheses explaining such a change suggests that just before the onset of the Younger Dryas cooling, multiple airbursts/impacts occurred over the Northern Hemisphere. We studied the late Pleistocene sediments from the Netherlands and Belgium to check whether a sudden short event might have taken place just before the onset of the Younger Dryas cooling. The geochemical features revealed suggest that such events might have occurred. The presence of products of biomass burning is suggested on the basis of trace element features of sediments from the lower Younger Dryas boundary. The presence of a volcanic component and a component resulting from extensive biomass burning in the sediments of c. 12.9 ka bp are indicated on the basis of trace element features. The volcanic component may be related to the Laacher See volcano eruption, whereas the cause of the extensive biomass burning remains unclear.     

On the problem of the scale and composition of Paleozoic and Mesozoic granitoid magmatism in the Khilok–Vitim fold belt of Central Transbaikalia

The paper presents a study of the gneissic granitoids of the Malkhan Complex and the intruisve granitoids of the Daur and Bichur complexes developed within the Khilok–Vitim fold belt of Central Transbaikalia. In the state geological map, these complexes have been attributed to the Early and Late Paleozoic. New ⁴⁰Ar/³⁹Ar geochronological data indicate that these rocks are Mesozoic rather than Paleozoic in age, which suggests the much broader manifestation of the Mesozoic granitoid complexes in this area. The studied Mesozoic granitoid massifs exhibit temporal and compositional zoning reflected in a westward decrease in age (from Early to Late Mesozoic) and increase in total alkalinity and potassium content at the appropriate trace-element characteristics. The obtained results of study of the Khilok–Vitim Belt are interpreted in the framework of the model of the formation of domal–cupola structures by the multiple activity of deep thermochemical plumes.     

Sources and formation conditions of ferromanganese mineralization of the Bureya and Khanka massifs,Russian Far East

The geochemical features of typical representatives of ferromanganese deposits are studied in the eastern Bureya and Khanka massifs (Russian Far East). Based on the major-, trace-, and rare-earth element distribution, the hydrothermal–sedimentary (with hydrogenic component) nature of their mineralization is established and the geodynamic setting and depth of ore formation are estimated. The differences in the depth and redox conditions of ore formation resulted in the metallogenic zonation of the Khingan block (Bureya Massif), which is expressed in a westward change in ore composition from the magnetite ores of the Kosten’ga–Kimkan zone to the hematite–magnetite and iron–manganese ores of the South Khingan zone. The conclusions about the participation of hydrothermal sources in the formation of ore mineralization of the studied deposits and the specifics of their localization require revision of the strategy of exploration and evaluation of ferromanganese ores in the southern Far East.