Tourism, Scientific, and Didactic Potential of the Ultrabasic-Alkaline Intrusion in Afrikanda with Perovskite Mineral (Kola Peninsula, N Russia) and of the Related Built Heritage

The present article is an example of research on the tourism, scientific, and teaching potential of the ultrabasic-alkaline intrusion with perovskite minerals in Afrikanda (Kola Peninsula, North Russia) and the possibility of its development as part of a local geopark site. A proposal to create a protected zone in this site, to expose sites of geological, natural, historical, and tourist interest is presented. Didactic routes and locations of geo-point visitors are proposed. Currently, there are numerous quarries and other mining objects of high historical, technical, and geological value. In the vicinity, there is a trough lake and post-glacial formations that can supplement knowledge about this region and add interest to would-be visitors. The remains of a historical camp for workers and miners are also visible in the intrusion area. In the vicinity of Afrikanda village, there is an international railroad line to Murmansk and St. Petersburg with a working railroad station. The place has high historical and geological potential for tourists and very rare and interesting mineralization. The last is a key value. The location is associated with 30 alkaline intrusions in NE Fennoskandia. There are opportunities to create a museum with a park where, with relatively little funding (most of the existing infrastructure buildings are in good condition), the intrusions can be shown to tourists. We proposed a conservation area with exposures, quarries, mine infrastructure, and historical sites, along with the location of geosites, hiking trails, and a geo-point for visitors. These sites are prospective for the economic revival of Afrikanda village and can protect the unique exposures.

Applied mineralogy of zirconium minerals: a case study of alkaline intrusion in SE-Brazil

Brazil has important zirconium resources when compared with other countries. However, most of the zirconium production in Brazil occurs as coproduct of the mining and processing of heavy mineral sands for the titanium minerals. This paper reports mineral and technological characterization studies associated with an alkaline intrusion in SE-Brazil. The data were obtained in a complex local rock known as “caldasite,” probably formed during hydrothermal alteration associated with post-magmatic events. The results obtained by multi-element analysis and X-ray diffraction analysis, petrography and scanning electronic microscopy indicated that zirconium concentration is about 66 wt%, having zircon and baddeleyite as most relevant minerals; gibbsite and anatase are found in minor proportions. The mineral assemblage developed a complex rock texture and structure associated with hydrothermal fluids percolation indicated by remobilization of zirconium in primary rocks. Caldasite presented concentric growth banding texture, revealed by zircon nucleation and baddeleyite microcrystalline interlaying. Results obtained indicate that caldasite has a high potential as zirconium resource due to concentration and mineral associations. Article Highlights This paper focused on the results of several techniques of mineralogical and technological characterization applied in an enriched-zirconium rock formed during hydrothermal alteration in alkaline intrusion in SE-Brazil. The results showed the rock is found in veins and has a mineral assemblage of zirconium, baddeleyite, gibbsite and anatase presented in a concentric growth banding texture. ZrO2 content is about 66% and preliminary results indicated the rock has a high potential for industry application.

Age and Origin of the Dongping Au-Te Deposit in the North China Craton Revisited: Evidence from Paragenesis, Geochemistry, and In Situ U-Pb Geochronology of Garnet

Dongping is the largest Au-Te vein deposit (~120 t Au) in the North China craton, but its age, origin, and setting remain unsolved. Here, we integrate paragenesis, geochemistry, and in situ U-Pb geochronology of garnet to constrain the timing and possible origin of the Dongping Au-Te deposit. Gold mineralization at Dongping is hosted in the Shuiquangou alkaline complex (ca. 401–390 Ma) and dominated by quartz-sulfide veins with minor ores in adjacent alteration envelopes. Andradite to grossular garnets are recognized in pre-, syn-, and post-ore quartz veins as well as mineralized alteration envelopes and are closely associated with a variety of ore and gangue minerals, mainly including K-feldspar, quartz, specularite, magnetite, pyrite, tellurides, epidote, and calcite. The paragenetic, textural, fluid inclusion, and compositional data suggest that garnets precipitated directly from a low-salinity fluid at 302° to 383°C and 90 to 330 bar. Garnets from various veins and alteration envelopes have similar U contents ranging from 0.80 to 13.89 mg/kg and yield reproducible U-Pb dates of 142 ± 5 to 139 ± 6 Ma (1σ) by laser ablation-inductively coupled plasmamass spectrometry. The dating results suggest that gold mineralization at Dongping occurred in the Early Cretaceous and thus preclude a genetic link between Au-Te mineralization and the ore-hosting alkaline intrusion as commonly suggested. When combined with independent geologic, geochemical, and geochronological studies, the new garnet U-Pb dates allow us to classify the Dongping Au-Te deposit as an oxidized intrusion-related gold deposit, with the causative magma likely derived from melting of an ancient enriched lithospheric mantle source due to destruction of the subcontinental lithospheric keel beneath the North China craton—a catastrophic event induced by the westward subduction of the Paleo-Pacific plate. This study highlights garnet U-Pb dating as a potential robust geochronometer for gold vein deposits elsewhere.

The experimental WSN network for underground monitoring H2 abundance in the mine atmosphere Karnasurt mine Lovozero layered alkaline intrusion

We have developed specialized equipment based on mini-MDM hydrogen sensors and the WSN telecommunication technology for long-term monitoring of hydrogen content in the environment. Unlike existing methods, the developed equipment makes it possible to carry out measurements directly in the explosion zone with high discreteness in time. This equipment was tested at a large rare-earth deposit of the Lovozero Alkaline Pluton Karnasurt in the underground mining tunnel. We observed a short time very high concentration of hydrogen in the atmosphere (more than 3 orders of normal atmosphere concentration). This discovery is very important because at the time of the explosion one can create abnormally high concentrations of explosive mixtures of hydrocarbon gases that can lead to accidents. The high resolving power of the measurement equipment makes it possible to determine the shape of the anomaly hydrogen of such a concentration and to calculate the volumes of hydrogen released from the rocks, at first time in the practice. The shape of the anomaly usually consists of 2-3 additional peaks of the shape - "dragon-head-like peak". We make an first attempt is made to explain this form of anomaly in the article. The aim of the work in the estimation hydrogen emission in mining ore deposit rare earth elements.

Silicate-Carbonate Liquid Immiscibility: Insights from the Crevier Alkaline Intrusion (Quebec)

This contribution explores the petrogenetic relationships between silicate and carbonatitic rocks in the Crevier Alkaline Intrusion (CAI, Québec, Canada). The CAI is located in the Proterozoic Grenville Province and is composed of a suite of undersaturated peralkaline rocks from ijolite to nepheline syenite and carbonatites. Petrogenetic relationships between different undersaturated alkaline igneous rocks, carbonate-bearing and carbonate-free nepheline syenite and carbonatites observed in the CAI suggest that (1) carbonate-bearing and carbonate-free silicate rocks are comagmatic with carbonatite, and that (2) both silicate and carbonatitic liquids are fractionated from an ijolitic parental magma that has undergone liquid immiscibility. One of the observed facies is characterized by spectacular ocelli of carbonate-bearing nepheline syenite in a matrix of carbonatite. The younger nepheline syenite facies can be divided into two groups based on the presence or absence of magmatic carbonates. Both groups are characterized by the presence of pyrochlore-group minerals that carry the Nb–Ta mineralization. We specifically use accessory minerals such as zircon, pyrochlore and apatite to constrain the temporal and physicochemical parameters of the immiscibility process. By coupling (1) mineral textures, (2) trace elements, (3) Ti-in-zircon thermometry, and (4) oxygen isotope compositions, we have traced the crystallization of zircon before, during and after the immiscibility process. The results allowed us to constrain the minimum temperature of this process at ∼815–865°C. In addition, two magmatic populations of pyrochlore are identified through their petrographic and geochemical characteristics within the younger nepheline syenite facies. Pyrochlore from the earlier ocelli facies of carbonate-bearing nepheline syenite follow a Nb–Ta differentiation trend, whereas pyrochlore from the younger carbonate-free nepheline syenite follow a more classical Nb–Ti trend. Following the complete immiscibility between the silicate and carbonatitic liquids, the fractionation between Nb and Ta stopped while a new generation of Nb-rich pyrochlore grew, displaying a more classical Nb–Ti fractionation trend and a higher Nb/Ta ratio in the nepheline syenite.