卷 60, 编号 7 (2018)

The Yalguba Ridge in Karelia is a reference geological object for studying Paleoproterozoic variolitic lavas. F. Yu. Levinson-Lessing—the prominent Russian petrologist—was the first to describe these lavas in detail in 1884. Our paper presents up-to-date results of contemporary mineralogical and geochemical studies. Several generations of pyroxenes with magmatic and metamorphic zoning reflect variations in the chemical compositions and thermodynamic parameters of melts during crystallization. The contents of rock-forming and trace chemical elements are estimated for varioles and the rock matrix. Based on a comparison of the mineralogical and geochemical data, we draw conclusions on the crystallization sequence of immiscible melts and the role of crustal-material contamination of basaltic melts.

The structure, geochemistry, and U–Pb and Lu–Hf isotopic composition of zircon crystals from garnet granulite xenoliths of the lower crust in the Belomorian mobile belt have been studied. It has been established that Early Paleoproterozoic zircon, 2.47 Ga in age, is primary magmatic and formed during crystallization of mafic rocks in the lower crust. Meso- and Neoarchean zircons are xenogenic crystals trapped by mafic melt during its contamination with older crustal sialic rocks. Metamorphic zircon grains have yielded a Late Paleoproterozoic age (1.75 Ga). A Paleozoic age has been established for a magmatic crystal formed due to interaction of xenoliths with an alkaline ultramafic melt, which delivered xenoliths to surface. The U–Pb datings and Lu–Hf systematics of crystals have been used to delineate the stages of formation and transformation of the lower crust in this region.

Epifanovite, NaCaCu₅(PO₄)₄[AsO₂(OH)₂] · 7H₂O, a new natural copper, sodium and calcium arsenate–phosphate, has been found in a quartz–phosphate pocket within greisenized cassiterite-bearing granodiorite of the Kester tin deposit, Sakha (Yakutia) Republic, Russia. The mineral occurs as crusts of tabular pseudotetragonal crystals up to 50 μm across and 10 μm thick. Associated minerals are fluorapatite, pseudomalachite, malachite, a Na-analogue of batagayite, tobermorite, libethenite, arsenolite, native copper and unknown Mg–Zn phosphate. Epifanovite is turquoise-blue with pale blue streak, vitreous luster (dull in crusts), and a Mohs hardness of 3. The mineral is brittle. Cleavage is perfect on (001) and good on (100) and (010). Density measured in the Clerici solution is 3.65(3) g/cm³; the calculated density is 3.73 g/cm³. Epifanovite is optically biaxial (–), α = 1.708(5), β = 1.730(5), γ = 1.735(5). 2Vobs = 40°–45°, 2V_calc = 50°. Optical orientation: X = a, Y = b. The empirical formula calculated on the basis of P + As = 5 is (Na_0.94K_0.06)Σ_1.00(Ca_0.82Na_0.08)Σ_0.90(Cu_5.04Zn_0.06)Σ_5.10(PO₄)₄[(As_0.81P_0.19)Σ_1.00(O_1.92OH_2.06Cl_0.02)Σ_4.00] · 7.37H₂O. The idealized formula is NaCaCu₅(PO₄)₄[AsO₂(OH)₂] · 7H₂O. The Raman spectrum contains the following bands, cm^–1: 293, 359 (ν_1–2, CuO₅); 455, 556, 594, 640, 921, 962, 1002, 1086, 1153 (ν_1–4, PO4), 77, 121, 161, 183, 730, 828, 858 (ν_1–3, AsO₄), 2900, 3200, 3410 (ν₁, OH). The mineral is monoclinic, P2₁/m, a = 9.6912(9), b = 9.7440(9), c = 9.9561(9) Å, β = 102.23 (1)°, V = 918.7(1) ų, Z = 2. The strongest reflections in the powder X-ray diffraction pattern are, I–dÅ–hkl: 100–9.73–001, 35–6.79–110, 12–4.355–021, 43–3.072–130, 24–3.061–221, 24–3.003–\(\bar 222\), 11–2.698–023, 10–1.6775–504. The mineral was named in honor of the Russian geologist Porphyry Prokop’evich Epifanov, who discovered the Ege-Khaya and Kester tin deposits. Epifanovite is structurally close to the lavendulan-group minerals and related species: andyrobertsite, calcioandyrobertsite, mahnertite and richelsdorfite.

A new mineral was discovered in Cr–V-bearing marbles of the Sludyanka Complex from the Pereval marble quarry, Sludyanka district, southern Baikal region, Russia. It was named vanadio-pargasite as vanadium-bearing analog of pargasite according to the amphibole supergroup classification and CNMNC recommendations. Black Cr–V-spinel (magnesiocoulsonite–magnesiochromite), red Cr–V-bearing spinel, calcite, dolomite, Cr–V-bearing diopside and chlorite, phlogopite, and forsterite are associated minerals. Vanadio-pargasite occurs as subhedral long- and short-prismatic crystals 0.10–0.8 × 0.05–0.10 mm in size, with (110) and (010) faces and perfect cleavage by (110). Macroscopically, the new mineral is bright green to emerald green with vitreous luster; in thin sections and powder, it is pale green, without pleochroism. The new mineral is biaxial, positive, 2V = 86° ± 2°, γ = 1.659(2), β = 1.651(2), α = 1.643(2). The Mohs hardness is ~ 6, average VHN50;100 is 795; range 752–824 kg/mm2. The measured and calculated density is 3.05(5) and 3.112 g/cm3, respectively. In a thermogram over the range 654–1081°С, H2O is released with a endothermic effect. Over the range 900–1183°C, the main endothermic effect is caused by water and, possibly, F release, as well as melting of the mineral (1020°C). The absorption bands in the IR spectrum are, cm–1: 3445, 1633, 980, and 469. Vanadio-pargasite is monoclinic, space group 2C/m; the unit cell parameters are: a = 9.914(3), b = 18.003(2), c = 5.300(2) Å, β = 105.69(3)°, V = 910.7(5) ų, Z = 2. The strongest reflections in the X-ray diffraction pattern are [d, Å (I) (hkl)]: 8.98 (15) (020), 8.43 (40) (110), 3.27 (30) (240), 3.14 (100) (310), 2.82 (35) (330), 2.70 (18) (151), 2.34 (15) (\(4.10\bar 1\)), 1.898 (15) (510), 1.445 (25) (4.101). The average chemical composition (528 point analyses) is, wt %: 42.75 SiO₂, 0.14 TiO₂, 12.75 A1₂O₃, 0.44 Cr₂O₃, 5.92 V₂O₃, 19.15 MgO, 0.03 FeO, 0.01 MnO, 12.52 CaO, 3.45 Na₂O, 0.41 K₂O, 0.74 F (wet chem.) 1.75 H₂O (calc.); the total is 99.91. The simplified formula is K_0.1Na_0.9Ca_2.0Mg_4.0V_0.7Al_0.3(Si_6.1Al_1.9)8.0O22(OH_1.7F_0.3)_2.0. Holotype material has been deposited at the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia (registration nos. 5035/1, 5035/2, and 5035/3).

A wide range of model temperature, which is typical for dodecahedroids from placer deposits in the Urals, Brazil, and the northern Yakutia diamond province has been identified in diamond crystals of the Ichetyu Ural-type diamonds deposit, Central Urals. Plates were cut from six crystals; it have been studied with cathodoluminescence and infrared and photoluminescence spectroscopy. Octahedral zoning predominates in the internal structure of rounded dodecahedroids, and growth layers are cut by the surface. Surface pigmentation spots are exhibited in the cathodoluminescent images of all plates. The nitrogen concentration in Ichetyu diamonds ranges from 100 to 2200 ppm and its proportion as B1 defects varies from 0 to 100%. The maximum absorption coefficient of hydrogen band is 56 cm^–1 with an average value of 0.8 cm^–1.

A number of rare phosphates have been found in specimens from the Chalotskoe pegmatite deposit, Transbaikal region, Russia: väyrynenite, MnBe[PO₄](OH,F); parascholzite, CaZn₂[PO₄]₂ · 2H₂O; messelite, Ca₂(Fe²⁺,Mn)[PO₄]₂ · 2H₂O; eosphorite, MnAl[PO₄](OH)₂ · H₂O; moraesite, Be₂[PO₄](OH)4H₂O; and fluorapatite. Väyrynenite forms pink grains 2–3 mm in size, less frequent prismatic crystals up to 0.8 × 3.0 cm, and spheres up to 3 mm in diameter. Parascholzite occurs as pockets up to 0.6 × 1.0 cm composed from snow-white small grains. Messelite forms pale yellow honeycomb grains and poorly shaped crystals up to 1 mm. Eosphorite has been seen in the Chalotskoe pegmatites before, but it has not been studied in detail. It occurs as red-brown prismatic crystals up to 8 cm in length, occasionally forming openbook- like aggregates and pink to pale pink grains up to 5 mm in size. Moraesite forms snow-white fibrous aggregates up to 5 × 6 mm, together with white spheres and short prismatic crystals of fluorapatite up to 1 mm. Microcline, albite, quartz, muscovite, beryl, schorl, almandine-spessartine, columbite-(Fe), and bertrandite are associated minerals. Väyrynenite and parascholzite are found for the first time in Russia.