The Use of Typomorphic Features of Placer Gold of the Anabar Region for Determining Its Sources

Abstract

Typomorphic features of placer native gold of the Anabar region were studied as predictive-exploration criteria. The target of the study was to determine the typomorphic features of placer gold related to the intermediate sources (paleo-placers) and the supposed nearby primary ore occurrences. Two varieties of placer native gold were identified. The first variety is well-rounded high-grade lamellar gold with a highly modified internal structure. This gold is associated with intermediate sources, Neogene–Quaternary watershed pebble beds. The second type includes slightly rounded gold with a wide variation in fineness (494‰–999‰). Its indicator is a block heterophase internal structure. The set of typomorphic features of this variety of gold indicates the vicinity of the primary source, what was the prerequisite for constructing prospecting traverses in order to find ore occurrences. As a result of these studies, hydrothermal-metasomatic formations with gold-sulfide mineralization were identified. The main primary substrate for them is fractured near-fault carbonate rocks of the Cambrian and Vendian–Cambrian age. Along with this, hydrothermalites developed on slightly cemented fine-pebble quartz conglomerates of the Middle Permian age were found in the core of exploration wells. Two types of metasomatic rocks are identified: quartz-potassium feldspar and jasperoid. The main ore minerals were galena and pyrite, different ratios by sites were revealed. Gold was identified in the form of small particles in the carbonate and siliceous substrate of hydrothermal-metasomatic formations. The lithological factor was one of the leading favorable factors for the ore formation due to the presence of near-fault highly permeable fractured carbonate and slightly cemented terrigenous rocks. The structural control of the studied ore occurrences is determined by their localization in the Mayat–Logoy and Dogoy–Kuoy faults of the Molodo–Popigay system of discontinuous faults. We assume a two-stage formation of the gold ore occurrences: during the first stage, the ore components in the form of primary hydrothermal-sedimentary ores in the near-gault zones were formed. The second stage was related to the processes of the Mesozoic tectonic-magmatic activation, when the intrusion of basite dikes initiated the mobilization of ore components the gold-sulfide occurrences were formed in the near-fault zone as a result of silicic-potassic metasomatosis of the carbonate and terrigenous rocks.

Anomalous Gold Concentrations in Hypersaline Wetland Sediments (Laguna Honda, South Spain) Caused by Nanoparticles Used in Agricultural Practices: Environmental Transformation

“…Folded edges, striations, randomly orientated scratches, and pitted cavities are commonly indicative of alluvial transport [ 41 ]. With increasing fluvial transport, particles acquire battered and roughened or rounded surface morphologies [ 41 , 42 , 43 ]. The lack of these morphological features in the Laguna Honda homoaggregates suggests a short transport process.…”

Typomorphic Features and Source of Native Gold from the Sykhoi Log Area Placer Deposits, Bodaibo Gold-Bearing District, Siberia, Russia

“…The close connection between the geochemical signatures of the gold from quartz lodes (Figure 14, field I) and gold alloys from the Nygri placer (Figure 14, field V) indicates that the gold in the placer is largely a result of erosion of this type of primary bedrock mineralization [52,53].…”

Editorial for the Special Issue “Native Gold as a Specific Indicator Mineral for Gold Deposits”

“…Several articles focus on the typomorphic features and sources of native gold placer deposits [12][13][14][15][16][17][18][19]. Becerra et al [12] studied the morphology, composition, and mineral inclusions in native gold from terraced placers in the Pureo Area (Southern Chile).…”

“…The paper by Gerasimov [17] focuses on the typomorphism of native gold from two modern placer occurrences, "Billyah" and "Nebaibyt", in the Anabar Region northeast of the Siberian platform, Russia. The results of this study indicate that the native gold in these modern placers comes from two different sources: paleo-placers and nearby "primary" ores.…”