Academic literature on the topic 'Lead-arsenic mineralisation'

Lead isotope studies indicate an age of 680 ± 65 Ma for syn-diagenetic stratiform copper mineralisation in the Upper Proterozoic Eleonore Bay Supergroup (EBS) sediments. Metals in EBS-hosted veins were remobilised from local host rocks, or derived from underlying Middle Proterozoic gneisses. Tungsten-arsenic skarns associated with Caledonian granites intruded into the EBS incorporated lead mobilised from the basement gneisses mixed with Caledonian granite lead. Isotopic compositions of trace lead in sparse sulphide occurrences in North-East Greenland point to Late Archaean – Early Proterozoic sources, comparable to the local basement gneisses. Base metal mineralisation in Upper Palaeozoic – Mesozoic rocks in central East Greenland shows a limited range. in lead isotope compositions, suggesting that a large, homogeneous crustal reservoir supplied the metals, or that metals from different sources were effectively mixed. Mineralisation in Tertiary igneous rocks in the Kangerdlugssuaq area of southern East Greenland shows lead isotope evidence for contamination by material from lower crustal Archaean sources.

The mineral potential of the Karrat Group in West Greenland became important after exhaustion in 1990 of the Black Angel lead-zinc mine situated within this supracrustal unit. It consists of shelf and turbidite type metasediments and subordinate metavolcanics deposited in an epicontinental marginal basin. Known mineralization comprises the Black Angel deposit and a number of other marble-hosted lead-zinc occurrences, as well as extensive sulphide facies iron formations and vein type base and precious metals mineralisation in quartzites and metagreywackes. Further areas with anomalously high contents of both base metals and gold-arsenic-tungsten are indicated by drainage geochemistry. The mineral potential of the Karrat Group is for massive base metal sulphide deposits hosted in marbles or clastic metasediments, and turbidite hosted gold-bearing veins and shear zones.

Geoscientists have extensively used machine learning for geological mapping and exploring the mineral prospect of a province. However, the interpretation of results becomes challenging due to the complexity of machine learning models. This study uses a convolutional neural network (CNN) and Shapley additive explanation (SHAP) to estimate potential locations for gold mineralisation in Rengali Province, a tectonised mosaic of volcano-sedimentary sequences juxtaposed at the interface of the Archaean cratonic segment in the north and the Proterozoic granulite provinces of the Eastern Ghats Belt in Eastern India. The objective is to integrate multi-thematic data involving geological, geophysical, mineralogical and geochemical surveys on a 1:50 K scale with the aim of prognosticating gold mineralisation. The available data utilised during the integration include aero-geophysical (aeromagnetic and aerospectrometric), geochemical (national geochemical mapping), ground geophysical (gravity), satellite gravity, remote sensing (multispectral) and National Geomorphology and Lineament Project structural lineament maps obtained from the Geological Survey of India Database. The CNN model has an overall accuracy of 90%. The SHAP values demonstrate that the major contributing factors are, in sequential order, antimony, clay, lead, arsenic content and a magnetic anomaly in CNN modelling. Geochemical pathfinders, including geophysical factors, have high importance, followed by the shear zones in mineralisation mapping. According to the results, the central parts of the study area, including the river valley, have higher gold prospects than the surrounding areas. Gold mineralisation is possibly associated with intermediate metavolcanics along the shear zone, which is later intruded by quartz veins in the northern part of the Rengali Province. This work intends to model known occurrences with respect to multiple themes so that the results can be replicated in surrounding areas.

AbstractHigh-quality and accurate environmental investigations are essential for the evaluation of contamination and subsequent decision-making processes. A combination of environmental geochemical indices, multivariate analyses and geographic information system approach was successfully used to assess contamination status and source apportionment of trace elements (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, V and Zn) in surface stream sediments from the Oued Rarai basin in north-western Tunisia, containing various metal and metalloid ores. The contamination level reported in this study indicates a non-negligible potential ecological risk, mainly related to sediment transport along the river. Antimony (concentrations ranged from 0.02 to 297 mg kg−1 and Igeo > 5), arsenic (from 0.5 to 1490 mg kg−1 and Igeo > 5), lead (from 2.9 to 5150 mg kg−1 and Igeo > 5) mercury (from 0.05 to 54.4 mg kg−1 and Igeo > 5) and silver (from 0.05 to 9.4 mg kg−1 and Igeo > 5) showed the most crucial contamination. Besides, potential ecological risk index values were maximum for arsenic with a median of 302, indicating a very high to serious ecological risk (> 160). Results from correlation analysis and principal component analysis revealed three main geochemical associations related to lithologic, tectonic and anthropogenic sources. V, Cr and Cu mainly originated from natural bedrock and soil. Ag and Cd were more controlled by both natural and mining enrichments. Mercury and Pb were mostly influenced by the ancient ore-related activities at the Oued Rarai site and north-east–south-west trending faults. Finally, Sb, As, Ni and Zn were largely controlled by the siliciclastic continental Neogene sequences. Finally, the physical and chemical dynamics of the watershed system, lithological properties, mineralisation, tectonic settings and mobilisation of subsurface sediments largely controlled both concentrations and spatial patterns of trace elements in the study basin. These results need to be considered in the strategies of suitable environmental management at former and current mining sites in north-western Tunisia.

On etudie les trois principales phases de deformations hercyniennes dans le minervois grace aux differents plissements. Les mineralisations synsedimentaires sont localisees dans des paleostructures distensives synchrones de la formation du proto-atlantique (paleozoique inferieur)