Large pegmatite body/bodies are outcropping in the “Suhata Reka” quarry, near the town of Rakitovo. Their bulk mineral composition with dominant K-feldspar (40%), plagioclase (30%), quartz (25%) and mica (≤ 5%) is complemented by (REE+Y)-bearing association of primary and secondary accessories. Zircon, monazite, xenotime, scarce apatite and noticeable amount of garnet are among the pegmatite primary minerals. The cm-sized almandine-spessartine crystals contain numerous fractures which host secondary (REE+Y)-bearing phosphate (xenotime, cheralite) and silicate minerals (e.g. REE-epidote). Formation of the late-stage REE-mineralization in garnet is due to its hydrothermal alteration and redistribution of REE+Y in the secondary phases.
Abstract Calciodelrioite, ideally Ca(VO 3 ) 2 (H 2 O) 4 , is a new mineral (IMA 2012-031) from the uraniumvanadium deposits of the eastern Colorado Plateau in the USA. The type locality is the West Sunday mine, Slick Rock district, San Miguel County, Colorado. The new mineral occurs on fracture surfaces in corvusite- and montroseite-impregnated sandstone and forms as a result of the oxidative alteration of these phases. At the West Sunday mine, calciodelrioite is associated with celestine, gypsum, huemulite, metarossite, pascoite and rossite. The mineral occurs as transparent colourless needles, bundles of tan to brown needles and star bursts of nearly black broad blades composed of tightly intergrown needles. Crystals are elongate and striated parallel to [100], exhibiting the prismatic forms {001} and {011} and having terminations possibly composed of the forms {100} and {61 }. The mineral is transparent and has a white streak, subadamantine lustre, Mohs hardness of about 2½, brittle tenacity, irregular to splintery fracture, one perfect cleavage on {001} and possibly one or more additional cleavages parallel to [100]. Calciodelrioite is soluble in water. The calculated density is 2.451 g cm – 3 . It is optically biaxial (+) with α = 1.733(3), β = 1.775(3), γ = 1.825(3) (white light), 2V meas = 87.3(9)° and 2Vcalc = 87°. The optical orientation is X = b; Z ≈ a. No pleochroism was observed. Electronmicroprobe analyses of two calciodelrioite samples and type delrioite provided the empirical formulae (Ca 0.88 Sr 0.07 Na 0.04 K 0.01 ) Σ1.00 (V 1.00 O 3 ) 2 (H 2.01 O) 4 , (Ca 0.76 Sr 0.21 Na 0.01 ) Σ0.98 (V 1.00 O 3 )2(H 2.01 O) 4 and (Sr 0.67 Ca 0.32 ) Σ0.99 (V 1.00 O 3 ) 2 (H 2.00 O) 4 , respectively. Calciodelrioite is monoclinic, I2/a, with unit-cell parameters a = 14.6389(10), b = 6.9591(4), c = 17.052(2) Å, β = 102.568(9)°, V = 1695.5(3) Å 3 and Z = 8. The seven strongest lines in the X-ray powder diffraction pattern [listed as d obs Å (I)(hkl)] are as follows: 6.450(100)(011); 4.350(16)(013); 3.489(18)(020); 3.215(17)(022); 3.027(50)(multiple); 2.560(28)( 15,413); 1.786(18)(028). In the structure of calciodelrioite (refined to R 1 = 3.14% for 1216 Fo > 4σF), V 5+ O 5 polyhedra link by sharing edges to form a zigzag divanadate [VO 3 ] chain along a, similar to that in the structure of rossite. The chains are linked via bonds to Ca atoms, which also bond to H 2 O groups, yielding CaO 3 (H 2 O) 6 polyhedra. The Ca polyhedra form a chain along b. Each of the two symmetrically independent VO 5 polyhedra has two short vanadyl bonds and three long equatorial bonds. Calciodelrioite and delrioite are isostructural and are the endmembers of the series Ca(VO 3 ) 2 (H 2 O) 4 –Sr(VO 3 ) 2 (H 2 O) 4 . Calciodelrioite is dimorphous with rossite, which has a similar structure; however, the smaller 8-coordinate Ca site in rossite does not accommodate Sr.
A dyke of alkali rhyolite intrudes the Tsetseg and Zuun Nuruu volcanosedimentary sequence of Ordovician-Silurian age (Hovd Zone, Central Asian Orogenic Belt) at the Botgon bag, Mankhan Soum, Hovd District in Western Mongolia.The rock consists of quartz and K-feldspar phenocrysts set in fine-grained groundmass composed of quartz, K-feldspar, albite, blue alkali amphibole (riebeckite-arfvedsonite containing up to 1.94 wt.% ZrO 2 ), tiny brown radial astrophyllite, annite and accessory zircon, ilmenite, fluorite, monazite, hematite, chevkinite and bastnäsite.Astrophyllite has unusual, highly ferroan composition and occurs as two sharply bound zones of astrophyllite I and II with the average empirical formulae: (K 1.71 Na 0.01 Rb 0.08 Cs 0.01 ) (Na 0.93 Ca 0.07 ) (Fe 2+ 6.52 Mn 0.31 Zn 0.06 ) (Ti 0.84 Zr 0.50 Nb 0.55 ) Si 7.68 Al 0.32 O 26 (OH) 3.78 F 0.66 (astrophyllite I, Zr-Nb-rich); (K 1.52 Rb 0.07 ) (Na 0.81 Ca 0.19 ) (Fe 2+ 6.31 Mn 0.28 Zn 0.06 ) (Ti 1.28 Nb 0.30 Zr 0.28 ) Si 7.68 Al 0.32 O 26 (OH) 2.85 F 0.67 (astrophyllite II).Geochemically, the rhyolite corresponds to strongly fractionated silicic alkaline A-type (ferroan) magmatic rock with 75.5-75.9wt.% SiO 2 , 4.4 wt.% K 2 O, 3.9-4.3wt.% Na 2 O and 1.98-2.23 wt.% Fe 2 O 3 t , poor in CaO (0.26-0.37 wt.%), MgO (0.01-0.11 wt.%), and P 2 O 5 (0.01 wt.%).The rock is enriched in Zr, Nb, Ta, Ga, Sn, Y, Rb, Cs, U and Th, depleted in V, Sr, Ba, Sc, and exhibits a pronounced negative Eu anomaly (Eu/Eu* = 0.03-0.05).The conventional whole-rock K-Ar geochronology yielded an age of 299.9 ± 9.1 Ma (1σ), which indicates latest Carboniferous or early Permian extension associated with the A-type alkaline volcanic activity.
Abstract The paragenesis and composition of bavenite–bohseite were investigated in fifteen granitic pegmatites from the Bohemian Massif, Czech Republic. Three types distinct in their relation to primary Be precursors, mineral assemblages, morphology and origin were recognised: (1) primary hydrothermal bavenite–bohseite crystallised in miarolitic pockets from residual pegmatite fluids; and secondary bavenite–bohseite in two distinct types: (2) a proximal type restricted spatially to pseudomorphs after a primary Be mineral (beryl > phenakite, helvine–danalite); and (3) a distal type on brittle fractures and fissures of host pegmatite. The mineral assemblages are highly variable: (1) axinite-(Mn), smectite, calcite and pyrite; (2) bertrandite, milarite, secondary beryl, bazzite, K-feldspar, muscovite–illite, scolecite, gismondine-Ca, analcime, chlorite; and (3) muscovite, albite, quartz, epidote, pumpellyite-(Mg), pumpellyite-(Fe 3+ ), titanite and chlorite. Electron microprobe analyses showed, in addition to major constituents (Si, Ca and Al), minor concentrations (in apfu) of Na (≤0.24), Fe (≤0.10), Mn (≤0.10) and F (≤0.36). The type 1 hydrothermal miarolitic bavenite–bohseite is mostly Al-rich (2.00–0.67 apfu) relative to type 2 proximal bavenite–bohseite and bohseite after beryl, phenakite and helvine–danalite (1.56–0.46, 0.70–0.05, 1.02–0.35 apfu, respectively); and type 3 distal bavenite–bohseite typically after beryl (1.63–0.09 apfu). Raman spectroscopy revealed that the distance between the OH – vibrational modes decreases with increasing bohseite component. The Al content of secondary type 2 proximal bavenite–bohseite is controlled by the composition of the Be precursor whereas type 3 distal bavenite–bohseite with beryl as the Be precursor is more variable and the composition is governed mainly by the composition of fluids. Calcium, a crucial component for bavenite–bohseite origins, was derived from residual pegmatite fluids (Vlastějovice, Vepice IV or Třebíč Plutons) or external sources (e.g. Drahonín IV, Věžná I or Maršíkov). Primary type 1 hydrothermal bavenite–bohseite from miarolitic pockets might have crystallised at T ≈ 300–400°C and P ≈ 200 MPa, whereas the secondary type 2 and 3 bavenite–bohseite formed at T ≈ 300–100°C and P ≈ 200–20 MPa.
Calcurmolite is a rare supergene U mineral formed during the alteration-hydration weathering of uraninite and hypogene Mo minerals; its structure has remained unsolved owing to a lack of crystal material suitable for conventional structure analysis.Here, single-crystal precession electron-diffraction tomography shows the calcurmolite (Rabejac, France) structure to be modulated; it is triclinic, crystallizing in the super-space group P1(α00)0, with a = 3.938 Å, b = 11.26Å, c = 14.195Å, α = 84.4°,β = 112.5°,γ = 133.95°and has a modulation vector q = 0.4 a*.Due to the poor quality of diffraction data, only a kinematical refinement was undertaken, although final results were reasonable: R obs /R all = 0.3825/0.3834for 3953/17442 observed/all reflections.The structure of calcurmolite is based upon the infinite uranyl-molybdate sheets with baumoite topology (U : Mo ratio = 1.5) and an interlayer of 6-coordinated Ca 2+ cations with interstitial H 2 O (ligands are apical uranyl O atoms and molecular H 2 O).Adjacent sheets are linked via Ca-O, as well as H-bonds.The structure formula, based on assumed occupancies in the supercell 5a × b × c, is Ca[(UO 2 ) 3 (MoO 4 ) 2 (OH) 4 ](H 2 O) ~5.0 (for Z = 4).
The crystal structure of pseudojohannite from White Canyon, Utah, was solved by charge-flipping from single-crystal X-ray diffraction data and refined to an Robs = 0.0347, based on 2664 observed reflections. Pseudojohannite from White Canyon is triclinic, P1̄, with a = 8.6744(4), b = 8.8692(4), c = 10.0090(5) Å, α = 72.105(4)°, β = 70.544(4)°, γ = 76.035(4)°, and V = 682.61(5) Å3, with Z = 1 and chemical formula Cu3(OH)2[(UO2)4O4(SO4)2](H2O)12. The crystal structure of pseudojohannite is built up from sheets of zippeite topology that do not contain any OH groups; these sheets are identical to those found in zippeites containing Mg2+, Co2+, and Zn2+. The two Cu2+ sites in pseudojohannite are [5]- and [6]-coordinated by H2O molecules and OH groups. The crystal structure of the pseudojohannite holotype specimen from Jáchymov was refined using Rietveld refinement of high-resolution powder diffraction data. Results indicate that the crystal structures of pseudojohannite from White Canyon and Jáchymov are identical.
