Mitrofanovite, Pt₃Te₄, is a new telluride discovered in low-sulfide disseminated ore in the East Chuarvy deposit, Fedorovo–Pana intrusion, Kola Peninsula, Russia. It forms anhedral grains (up to ~20 μm × 50 μm) commonly in intergrowths with moncheite in aggregates with lukkulaisvaaraite, kotulskite, vysotskite, braggite, keithconnite, rustenburgite and Pt–Fe alloys hosted by a chalcopyrite–pentlandite–pyrrhotite matrix. Associated silicates are: orthopyroxene, augite, olivine, amphiboles and plagioclase. Mitrofanovite is brittle; it has a metallic lustre and a grey streak. Mitrofanovite has a good cleavage, along {001}. In plane-polarised light, mitrofanovite is bright white with medium to strong bireflectance, slight pleochroism, and strong anisotropy on non-basal sections with greyish brown rotation tints; it exhibits no internal reflections. Reflectance values for the synthetic analogue of mitrofanovite in air (R_o,R_e’in %) are: 58.4, 54.6 at 470 nm; 62.7, 58.0 at 546 nm; 63.4, 59.1 at 589 nm; and 63.6, 59.5 at 650 nm. Fifteen electron-microprobe analyses of mitrofanovite gave an average composition: Pt 52.08, Pd 0.19, Te 47.08 and Bi 0.91, total 100.27 wt.%, corresponding to the formula (Pt_2.91Pd_0.02)_Σ2.93(Te_4.02Bi_0.05)_Σ4.07based on 7 atoms; the average of eleven analyses on synthetic analogue is: Pt 52.57 and Te 47.45, total 100.02 wt.%, corresponding to Pt_2.94Te_4.06. The density, calculated on the basis of the formula, is 11.18 g/cm³. The mineral is trigonal, space groupR $\overline 3 $ m, witha= 3.9874(1),c= 35.361(1) Å,V= 486.91(2) ųandZ= 3. The crystal structure was solved and refined from the powder X-ray-diffraction data of synthetic Pt₃Te₄. Mitrofanovite is structurally and chemically related to moncheite (PtTe₂). The strongest lines in the powder X-ray diffraction pattern of synthetic mitrofanovite [din Å (I) (hkl)] are: 11.790(23)(003), 5.891(100)(006), 2.851(26)(107), 2.137(16)(1013), 2.039(18)(0114), 1.574(24)(0120), 1.3098(21)(0027). The structural identity of natural mitrofanovite with synthetic Pt₃Te₄was confirmed by electron backscatter diffraction measurements on the natural sample. The mineral name is chosen to honour Felix P. Mitrofanov, a Russian geologist who was among the first to discover platinum-group element mineralisation in the Fedorova–Pana complex.

The Keivy alkali granite-nepheline syenite complex, Kola Peninsula, NW Russia, contains numerous associated Zr-REE-Y-Nb occurrences and deposits, formed by a complex sequence of magmatic, late-magmatic, and post-magmatic (including pegmatitic, hydrothermal, and metasomatic) processes. The REE-rich lithologies have abundant (some of economic importance) and diverse britholite group minerals. The REE and actinides distribution in host rocks indicates that the emanating fluids were alkaline, with significant amounts of F and CO₂. From chemical studies (REE and F variations) of the britholites the possible fluid compositions in different lithologies are proposed. Fluorbritholite-(Y) and britholite-(Y) from products of alkali granite (mineralized granite, pegmatite, quartzolite) formed under relatively high F activity in fluids with low CO₂/H₂O ratio. The highest F and moderate CO₂ contents are characteristic of fluid from a mineralized nepheline syenite, resulting in crystallization of fluorbritholite-(Ce). Britholite group minerals (mainly fluorcalciobritholite and ‘calciobritholite’) from a nepheline syenite pegmatite formed from a fluid with composition changing from low F and high CO₂ to moderate F and CO₂. An extremely high F content is revealed for metasomatizing fluids emanating from alkali granitic magma and which affected the basic country rocks. The dominant substitution scheme for Keivy britholites is REE³⁺ + Si⁴⁺ = Ca²⁺ + P⁵⁺, showing the full range of ‘britholite’ and ‘calciobritholite’ compositions up to theoretical apatite.

The paper presents results of comprehensive studies of the rock association composing the lower zone of the northeastern part of the Monchetundra mafic massif in the Monchegorsk ore district. The zone consists of orthopyroxenite, plagioorthopyroxenite, and norite, which are variably amphibolized and host numerous gabbroid injections from the upper zone of the massif. The chemical composition of the dominant rock-forming minerals of the rocks was studied. The orthopyroxenes of the lower zone of the Monchetundra massif (LZMM) notably differs from those of the Monchegorsk pluton (Monchepluton) in containing lower aluminum concentrations because of differences in the P–T parameters of their crystallization. According to mineral geothermobarometric data, the LZMM rocks crystallized at 1200–1000°C and approximately 6 kbar, at a depth of about 20 km, whereas the Monchepluton rocks crystallized at an average temperature of 1230°C and a pressure of 3 kbar in shallow conditions. The LZMM rocks are characterized by moderate magnesium and silica contents and by elevated iron and low titanium concentrations, are enriched in the light rare earth elements (LREE) and LILE (Rb, Ba, and Sr) but are depleted by HFSE (Nb and Ta). The behavior of major components in the rocks is similar to that in analogous rocks in the bottom axial part of the Monchetundra massif, lying at its basement. Moreover, all petro- and geochemical parameters of the LZMM rocks are close to those of the analogical rocks of the Monchepluton. The paper presents new U–Pb isotope-geochronological data on individual zircon grains from the LZMM rocks. The age of the orthopyroxenite is 2496.3 ± 2.7 Ma, and that of the norite is 2500 ± 2 Ma, which indicates that these rocks crystallized simultaneously (within the error). The orthopyroxenite has an age of 2452 ± 85 Ma and positive ε_Nd(T) = +1.7, and the model age of the protolith T(DM) is 2.76 Ga according to data on the Sm–Nd of isotopic systematics. The possible parental melt of the rocks may have been komatiite contaminated with crustal material. The obtained results indicate that the Monchetundra massif is a composite intrusion, whose lower zone is similar to the layered intrusions and the upper one is made up of rocks belonging to the gabbro–anorthosite complex. The massif was formed by at least three pulses of magmatic activity (at 2.50, 2.47, and 2.45 Ga).

The Sakharjok Y-Zr deposit in Kola Peninsula is related to the fissure alkaline intrusion of the same name. The intrusion ∼7 km in extent and 4–5 km2in area of its exposed part is composed of...

Minerals of the gadolinite-(Y)-hingganite-(Y) series pertaining to the gadolinite-datolite group have been found in the alkali granite pegmatites of the Kola Peninsula. Gadolinite-(Y) is...