Khibina Massif Research Articles

Apatite fission track thermochronology of Khibina Massif (Kola Peninsula, Russia): Implications for post-Devonian Tectonics of the NE Fennoscandia

The thermal history of the Kola Peninsula area of NE Fennoscandia remains almost fully unknown because of the absence of any thermochronological data such as apatite and/or zircon fission track or (UTh)/He ages. In order to fill this gap and to constrain the post-Devonian erosion and exhumation history of this region, we present the results of apatite fission track (AFT) dating of eleven samples selected from the cores taken from different depths of the northern part of the Khibina intrusive massif. The RbSr isochron age of this alkaline magmatic complex which is located at the center of Kola Peninsula is 368+6Ma (Kramm and Kogarko, 1994). Samples were analyzed from depths between +520 and −950m and yielded AFT ages between 290 and 268Ma with an age uncertainty (1σ) of between ±19Ma (7%) and ±42Ma (15%). Mean track lengths (MTL) lie between 12.5 and 14.4μm. Inverse time–temperature modeling was conducted on the age and track length data from seven samples of the Khibina massif. Thermal histories that best predict the measured data from three samples with the most reliable data show three stages: (1) 290–250Ma—rapid cooling from >110°C to 70°C/50°C for lower/upper sample correspondingly; (2) 250–50Ma—a stable temperature stage; (3) 50–0Ma—slightly increased cooling rates down to modern temperatures. We propose that the first cooling stage is related to late-Hercynian orogenesis; the second cooling stage may be associated with tectonics accompanying with opening of Arctic oceanic basin. The obtained data show that geothermal gradient at the center of Kola Peninsula has remained close to the modern value of 20°C/km for at least the last 250Myr. AFT data show that the Khibina massif has been exhumed not more then 5–6km in the last 290Myr.

Donnayite-(Y) from the Albyn gold deposit, Russian Far East

515 The rare hydrous Y, Sr, Ca, and Na carbonate don� nayite�(Y) (Sr, Ba) 3(Y,Ca,Na)3[CO3]6 ⋅ 3H2O was first found in a pegmatite dike cutting across syenite of the Mont St.�Hilaire Massif in Quebec, Canada [1]. Until recently the mineral was known to occur only in rocks of alkaline complexes: along with St.�Hilaire, these were the Khibina Massif in the Kola Peninsula and the Vishnevye Gory Massif in the Urals [2, 3]; the mineral was also found in carbonatite in the Khibina and Vuor� ijarvi massifs in the Kola Peninsula [4, 5]. In derivatives of alkaline rocks, donnayite�(Y) is contained together with microcline, calcite, natrolite, aegirine, and more rare Sr, Ba, and REE carbonates. Donnayite is occasionally accompanied by albite, fluo� rite, barite, minerals of the labuntsovite group, and its Ba analogue mackelveyite.

Contact interaction of agpaitic magmas with basement gneisses: An example of the Khibina and Lovozero Massifs

Data on processes that occurred at contacts of large agpaitic syenite intrusions and basement gneisses obtained by the authors by studying and sampling profiles across the contacts and involve the composition of minerals, analysis of mineral assemblages, isotopic dating of the processes, and analysis of the behavior of major, volatile, and trace elements in rocks near the contact. The contact zones of the massifs were determined to consist of products of contact interaction during the early and late magmatic stages and provide a record of successive stages of a continuous process of gneiss transformations, starting with the filling of the magmatic reservoir with melt and ending with late- and postmagmatic processes related to the development of a system of alkaline veins and pegmatite bodies in the gneisses. Early alkaline metasomatic processes in the Khibina Massif were local, controlled by diffusion, and were induced by the immediate thermal and chemical effect of alkaline melts on the gneisses. In the Lovozero Massif, metasomatism was related predominantly to the development of postmagmatic veins at 359 ± 5 Ma, was controlled by infiltration, and proceeded immediately after the consolidation of the main intrusive series. The metasomatic transformations during the early and late magmatic stages under the effect of agpaitic melts on gneisses predetermined different closure conditions and, correspondingly, different behaviors of the Rb-Sr and Sm-Nd isotopic systems during the contact processes: while the interaction of agpaitic melts with gneisses has modified the (87Sr/86Sr)(T = 370 Ma) ratio via the enrichment of radiogenic Sr in the host Archean rocks, the Sm-Nd isotopic characteristics of the syenites in the inner contact zone and veins preserved their mantle values, which corresponded to the average ones for rocks in the central parts of the intrusion. Experimental data, model simulations, and natural observations testify that Nb, Ta, Zr, Hf, and REE were mobile in the contact interaction zone with agpaitic melts. With regard for data on the fluid regime of the agpaitic melts and the concentrations of volatile components in the contact zones, we believe that the main role in the transfer of REE and HFSE during contact metasomatism could be played by their ligands with F−, Cl−, and SO42−.

Mineral assemblages and genesis of hornfelses in the outer contact zone of the Khibina Massif, Kola Peninsula, Russia

The paper presents materials on the fabric of the western, southwestern, and southern exocontact zones of the Khibina alkaline pluton and metavolcanic rocks of the Il’mozerskaya Formation of the Paleoproterozoic Imandra-Varzuga riftogenic structure. The volcanics of the Imandra-Varzuga structure were originally metamorphosed to the greenschist facies (at temperatures of ≥300°C and pressures of ≥2.0–2.5 kbar) and were afterward metamorphosed to the pyroxene-hornfels facies under the thermal effect the Khibina pluton with the development of a hornfels zone 150–400 m thick. According to their composition, the hornfelses are subdivided into three zones: inner, intermediate, and outer. The inner zone is up to 30 m thick and consists of hornfelses of clinopyroxene-plagioclase composition with olivine as a typomorphic mineral and with variable amounts of amphibole. The intermediate zone occurs at a distance of 30–200 m from the pluton, is separated from the inner zone by the olivine isograde, and consists of amphibole-clinopyroxene-plagioclase hornfelses. The outer zone, 200–400 m away from the contact of the pluton, is made of fine-grained melanocratic hornblende hornfelses. The thermal transformations of the metavolcanics involved the gradual replacement of their low-temperature mineral assemblage (actinolite + albite) by a higher temperature one (clinopyroxene + amphibole + andesinebytownite ± olivine). Our data on the chemical composition of the rock-forming minerals of the hornfelses indicate that the olivine is ferrohortonolite-fayalite, the clinopyroxene belongs to the augite-ferroaugite series, and occasional orthopyroxene grains (which were found only in the intermediate zone) are ferrohypersthene. The amphibole in the hornfelses of the intermediate zone and the outermost (farthest from the contact) part of the inner zone is edenite, a Ca amphibole. The amphibole in hornfelses near the contact is kataphorite of the Na-Ca amphibole group. The plagioclase composition generally corresponds to andesine and bytownite and is albite-oligoclase near the contact with the pluton. The hornfelses adjacent to the contact bear rare sanidine grains. The mineral thermo-and barometry of the hornfelses yielded temperatures of 700–640°C and pressures of 1–1.5 kbar. The temperature determined for the zone exactly at the contact was approximately 700°C, which corresponds to the initial temperature of the rocks in contact with the magma and is close to the crystallization temperature of the nepheline syenites of the Khibina pluton.

Genesis and compositional characteristics of natural γ-CrOOH

Natural γ-CrOOH was first found and studied in rischorrite of the Khibina Massif, in which this mineral is associated with gonardite, natrolite, phillipsite, and saponite and usually forms microcrystallites in a matrix of amorphous CrOOH hydrogel or, more rarely, occurs as fine-crystalline, thin acicular, and lumpy aggregates of a green and emerald-green color. X-ray powder diffraction data indicate that crystalline blocks consist of a mineral with a rhombohedral unit cell, Cmcm, a = 3.86 A, b = 12.78 A, and c = 3.04 A. Chromium oxyhydroxide from the Khibina Massif is isostructural with γ-CrOOH from the Iksinskoe deposit, but significantly differs from it in bearing low Al concentrations. The empirical formula of the Khibina γ-CrOOH is (Cr0.94Mg0.03Al0.02Ti0.01Fe0.01)1.01O(OH) · nH2O. The Cr oxyhydroxide and associated zeolites crystallized from low-temperature hydrothermal solutions rich in Na. The most probable source of Cr for the γ-CrOOH in the Khibina Massif was titanomagnetite in xenoliths of ultrabasic rocks in the rischorrites affected by postmagmatic alterations.

THE CRYSTAL CHEMISTRY OF SHCHERBAKOVITE FROM THE KHIBINA MASSIF, KOLA PENINSULA, RUSSIA

The crystal structure of shcherbakovite from Mount Rasvumchorr, Khibina massif, Kola Peninsula, Russia, ideally K2 Na Ti 4+ 2 O (OH) (Si4O12), a 8.1538(4), b 10.5569(5), c 13.9882(6) A, V 1204.1(2) A 3 , space group Imma, Z = 4, Dcalc 3.194 g/cm 3 , has been refined to R1 = 3.2% for 960 unique (Fo > 4� F) reflections collected on a Bruker single-crystal P4 diffractometer equipped with a CCD detector and MoKX-radiation. Shcherbakovite occurs in late (hydrothermal) shallowly dipping veins of natrolite and is associated with natrolite, aegirine, K-feldspar, strontian apatite, titanite, spherulitic baryllite and rare pyrrhotite and chalcopyrite. Electron-microprobe analysis gave SiO2 40.57, TiO2 18.87, Fe2O3 1.05, MnO 0.06, BaO 6.7, CaO 0.20, K2O 13.22, Na2O 5.59, Nb2O5 10.49, SrO 0.08, ZrO2 0.84, Ta2O5 0.06, (H2O)calc 0.73, sum 97.83 wt.%. The amount of H2O was determined from crystal-structure analysis. There is one tetrahedrally coordinated T site, 1.607 A, occupied by Si. There are two octahedrally coordinated sites, M(1), occupied by (Ti0.68 Nb0.32 1.00), with = 2.016 A, and M(2), occupied by (Ti0.72 Nb0.15 Fe 3+ 0.08 Zr0.04 1.01), with = 1.999 A. The M(1) and M(2) sites are separated by 0.477 A, and hence cannot be occupied simultaneously at a local level. There are three interstitial A sites: the A(1) site is (9)-coordinated and is occupied by (K0.66 Ba0.23 Na0.07 Ca0.02), with = 2.952 A; the A(2) site is (8)-coordinated and is occupied by K, with = 2.861 A, and the A(3) site is (6)-coordinated and is occupied by Na, with = 2.493 A. Shcherbakovite is a K-analogue of batisite, ideally Ba Na2 Ti 4+ 2 O2 (Si4O12). Shcherbakovite is related to batisite by substitution of K for Ba and K for Na. Noonkanbahite, ideally Ba K Na Ti 4+ 2 O2 (Si4O12), has never been approved by the IMA as a new mineral species. Based on the crystal chemistry of this structure type, the general formula of these minerals may be written as A B C M2 � 2 (Si4O12), with the following end-member compositions: batisite A = Ba, B = Na, C = Na; shcherbakovite, A = K, B = K, C = Na; noonkanbahite, A = Ba, B = K, C = Na; unnamed, A = K, B = Na, C = Na.

CHLORBARTONITE, K6Fe24S26(Cl,S), A NEW MINERAL SPECIES FROM A HYDROTHERMAL VEIN IN THE KHIBINA MASSIF, KOLA PENINSULA, RUSSIA: DESCRIPTION AND CRYSTAL STRUCTURE

Chlorbartonite, ideally K 6Fe24S26(Cl,S), is a new potassium iron sulfide chloride found as an accessory mineral in a microcline – pectolite – sodalite – aegirine vein within feldspathic urtite at Mount Koashva, Khibina massif, Kola Peninsula, Russia. The mineral occurs as roundish grains up to 2 cm across included in sodalite and natrolite crystals; it is associated with djerfish erite and rasvumite. Chlorbartonite is weakly magnetic, brittle, and has a conchoidal fracture. Cleavage and parting were not observe d. Macroscopically, the mineral is opaque, brown-black, with a black streak and submetallic luster. In reflected light, it appears optically isotropic, yellowish brown, and without internal reflections; interpolated values of reflectance ( R, %) at the standard wavelengths (nm) are: 10.8 (470), 13.5 (546), 15.1 (589), and 17.2 (650). The hardness VHN 40 is 203–212, average 207 kg/mm 2 ; the Mohs hardness is 4. The density is 3.70 g/cm 3 (measured) and 3.65 g/cm 3 (calculated). The electron-microprobe analysis of six grains gave, as an average composition: S 33.84, Cl 0.99, K 9.62, Fe 54.09, Co 0.04, Cu 0.57, total 99.15 wt.%. The empiric al formula calculated on the basis of a total of 57 atoms is K 6.08(Fe23.93Cu0.22Co0.01)� 24.16S26.00(Cl0.69S0.07)� 0.76, which yields an ideal formula of K6Fe24S26(Cl,S). The mineral is tetragonal, I4/mmm, a 10.3810(8), c 20.614(2) A, V 2221.5(3) A 3 , Z = 2. The strongest eight lines in the X-ray powder-diffraction pattern [ d in A (I)(hkl)] are: 9.25(33)(101), 5.97(65)(112), 3.121(45)(312), 2.986(100)(224), 2.380(38)(332), 2.374(57)(316), 1.834(51)(440), and 1.830(82)(408). The crystal structure has been refined to an R1 of 0.020 (447 unique observed reflections with Fo ≥ 4� Fo). The structure consists of a framework of the Fe 8S14 clusters of eight edge-sharing FeS4 tetrahedra. The framework has large cavities occupied by ClK 6 octahedra. As the name indicates, chlorbartonite is the Cl-dominant analogue of bartonite.

CERITE-(La), (La,Ce,Ca)9(Fe,Ca,Mg)(SiO4)3[SiO3(OH)]4(OH)3, A NEW MINERAL SPECIES FROM THE KHIBINA ALKALINE MASSIF: OCCURRENCE AND CRYSTAL STRUCTURE

Cerite-(La), ideally (La,Ce,Ca) 9 (Fe,Ca,Mg)(SiO 4 ) 3 [SiO 3 (OH)] 4 (OH) 3 , was found in an aegirine – natrolite – microcline vein in foyaite, Mt. Yuksporr, Khibina massif, Kola Peninsula, Russia. It forms porous pseudomorphs (up to 7 cm long) after an unidentified hexagonal prismatic mineral. Within the pseudomorphs, cerite-(La) occurs as a boxwork-like aggregates of equant to tabular crystals (flattened on c , up to 2 mm across), with dominant rhombohedral and pinacoidal faces. Associated minerals are aegirine, anatase, ancylite-(Ce), barylite, catapleiite, cerite-(Ce), chabazite-Ca, edingtonite, fluorapatite, galena, ilmenite, microcline, natrolite, sphalerite, strontianite and vanadinite. The mineral is brittle, with a conchoidal fracture. It is light yellow to pinkish brown with a white streak, and translucent with a vitreous luster. Cleavage and parting were not observed. The Mohs hardness is 5; the density is 4.7(1) g cm −3 (meas.) and 4.74 g cm −3 (calc.). It is uniaxial, optically positive, n o 1.810(5), n e 1.820(5) (for λ = 589 nm). An average result of seven electron-microprobe analyses for seven different crystals (each one reported as an average of 6–10 points from each crystal) gave La 2 O 3 37.57, Ce 2 O 3 23.67, Pr 2 O 3 0.61, Nd 2 O 3 1.48, Sm 2 O 3 0.10, Gd 2 O 3 0.24, SrO 1.97, CaO 5.09, Fe 2 O 3 1.40, MgO 0.51, SiO 2 22.38, P 2 O 5 0.63, H 2 O 3.20 (determined by the Penfield method), total 98.85, which corresponds to the empirical formula (La 4.23 Ce 2.65 Ca 1.37 Sr 0.35 Nd 0.16 Pr 0.07 Gd 0.02 Sm 0.01 ) ∑8.86 (Fe 0.32 Ca 0.30 Mg 0.23 ) ∑0.85 [SiO 4 ] 3 [(Si 0.84 P 0.16 ) ∑1.00 O 3 (OH)] 4 (OH) 2.78 , calculated on the basis of (Si + P) = 7. The mineral is trigonal, R 3 c , with a 10.7493 (6), c 38.318 (3) A, V 3834.36 A 3 , Z = 6. The strongest eight lines in the X-ray powder-diffraction pattern [ d in A( I )( hkl )] are: 3.53(26)(10.10,211), 3.47(40)(122), 3.31(38)(214), 3.10(25)(300), 2.958(100)(02.10), 2.833(37)(128), 2.689(34)(220), 1.949(34)(238,13.13). The crystal structure has been refined on the basis of F 2 for all unique reflections collected using a CCD area detector, to an R 1 of 0.036, calculated for the 1544 unique observed reflections ( F o ≥ 4σ F o ). Cerite-(La) is structurally related to cerite-(Ce). The mineral is named as the La-dominant analogue of cerite-(Ce). The structural formula for these minerals can be written as REE 9 M Ca x [SiO 4 ] 3 [SiO 3 ((OH) 1− x O x )] 3 [SiO 3 (OH)] 1− x (OH) 3 , where REE stands for La or Ce, and where M represents Fe, Mg, Ca.

Structural refinement of a K-rich natrolite: evidence of a new extraframework cation site

The structure refinement of a natural K-rich natrolite from the Kirov mine, Khibina massif (Kola Peninsula), closely intergrown with amicite, was carried out in order to elucidate the relationship between the chemical composition of natrolite and the arrangement of extraframework atoms in the zeolitic cavities. The results of the refinement clearly show the presence of a new extraframework site, occupied by potassium, with a slight occupancy (about 3%). The short distance between the new K site and O w (1.68 Å) prevents the simultaneous presence of K and O w, so that the occupancy of the O w site is accordingly lowered. On the basis of structural refinements of K-exchanged natrolite and gonnardite, a mechanism of Na–K substitution in natrolite is suggested. This substitution produces remarkable changes in the natrolite structure through rearrangement of the ions in the zeolitic channels.

The discovery of the Tomtor Massif in the northern part of the Siberian Platform - Comparison with the Khibina Massif on Kola Peninsula and its potential in REE and Nb

The discovery of the Tomtor Massif in the northern part of the Siberian Platform - Comparison with the Khibina Massif on Kola Peninsula and its potential in REE and Nb

Folded structures in the Khibina apatite deposits

The Kukisvumchorr-Yukspor apatite-nepheline body of the Kola Peninsula is a thick sheet-type lens which dips 28-32° NE. The rich upper zone consists of spotted, spotted-banded, and brecciated ores, whose mean P2MO5 content is 26-28 percent. The lower, of band ed-lens ores together with reticulate and large block types, have a mean P2MO5 content of 16-18 percent. Poikilitic nepheline syenites overlie, and ijolites and urtites underlie the ore body. The apatite-nepheline ore field is an arc-shaped belt at the boundary between foyaites and khibinites in the general structure of the Khibina massif. Mining has shown that the early idea of only minor tectonic activity and little disturbed igneous complexes is wrong. A great variety of internal structure is present and shown in several illustrations. Most prominent are folded structures that in places resemble a highly dislocated sedimentary complex. Variations in the type of folding indicate that the various ore zones were formed at different times. Forms in th...