Kalsilite of the Khibiny and Lovozero alkaline plutons,Kola Peninsula

Kalsilite—a typical mineral of ore-bearing zones of the Khibiny and Lovozero plutons—was formed after low-Si and high-K nepheline in one of three ways: (1) by relatively high-temperature replacement of Na with K; (2) due to orthoclase-kalsilite poikiloblastesis in foidolites and overlapping foyaites; or (3) by replacement of nepheline with zeolite.     

Possible mechanism of horizontal overpressure generation of the Khibiny,Lovozero, and Kovdor ore clusters on the Kola Peninsula

The paper discusses questions related to the generation of increasing crustal horizontal compressive stresses compared to the idea of the standard gravitational state at the elastic stage or even from the prevalence of horizontal compression over vertical stress equal to the lithostatic pressure. We consider a variant of superfluous horizontal compression related to internal lithospheric processes occurrin in the crust of orogens, shields, and plates. The vertical ascending movements caused by these motions at the sole of the crust or the lithosphere pertain to these and the concomitant exogenic processes giving rise to denudation and, in particular, to erosion of the surfaces of forming rises. The residual stresses of the gravitational stressed state at the upper crust of the Kola Peninsula have been estimated for the first time. These calculations are based on the volume of sediments that have been deposited in Arctic seas beginning from the Mesozoic. The data speak to the possible level of residual horizontal compressive stresses up to 90 MPa in near-surface crustal units. This estimate is consistent with the results of in situ measurements that have been carried out at the Mining Institute of the Kola Science Center, Russian Academy of Sciences (RAS), for over 40 years. It is possible to forecast the horizontal stress gradient based on depth using our concept on the genesis of horizontal overpressure, and this forecasting is important for studying the formation of endogenic deposits.     

Natisite,Na2TiSiO5, an Indicator Mineral of Hyperagpaitic Hydrothermal Assemblages in the Lovozero and Khibiny Alkaline Plutons,Kola Peninsula: Occurrence,Crystal Chemistry,and Genetic Features

Geology of Ore Deposits - Natisite, a natural tetragonal (P4/nmm) modification of Na2TiSiO5 = Na2TiO(SiO4) is an abundant indicator mineral of relatively low-temperature (no higher than...     

Variations in the composition and origin of hydrocarbon gases from inclusions in minerals of the Khibiny and Lovozero plutons,Kola Peninsula,Russia

Relationships between methane and its homologues mainly contained in fluid microinclusions have been studied in 332 monomineralic fractions from the Khibiny and Lovozero alkaline plutons. Hydrocarbon gases (HCG) were extracted for subsequent chromatographic analysis using the bulk method of sample comminution. The molecular weight distribution (MWD) of gaseous alkanes in the same and associated minerals is different depending on geological setting of the samples. The molecular mass of HCG increases (i) with decrease in temperature and capture of fluid inclusions in the course of transformation of primary magmatic minerals and the formation of late minerals as products of intensified postmagmatic processes; (ii) in the direction from khibinite at the margin and foyaite in the core of the Khibiny pluton to the central ring structure; and (iii) from the bottom to top of the differentiated complex in the Lovozero pluton. The results obtained coupled with other geochemical data suggest multistage generation and transformation of hydrocarbons from the magmatic to the final low-temperature hydrothermal stage. The MWD of hydrocarbon components in gases occluded by minerals can serve as an indicator of conditions characteristic of rock and ore formation, as well as of the consecutive formation and transformation of associated minerals revealing ambiguous and controversial relationships.     

Minerals of zirconolite group from fenitized xenoliths in nepheline syenites of Khibiny and Lovozero plutons,Kola Peninsula

Zirconolite, its Ce-, Nd-, and Y-analogs, and laachite, another member of the zirconolite group, are typomorphic minerals of the fenitized xenoliths in nepheline syenite and foidolite of the Khibiny–Lovozero Complex, Kola Peninsula, Russia. All these minerals are formed at the late stage of fenitization as products of ilmentie alteration under the effect of Zr-bearing fluids. The diversity of these minerals is caused by the chemical substitutions of Na and Ca for REE, Th, and U compensated by substitution of Ti and Zr for Nb, Fe and Ta, as well as by the redistribution of REE between varieties enriched in Ti (HREE) or Nb (LREE). The results obtained can be used in the synthesis of Synroc-type titanate ceramics assigned for the immobilization of actinides.     

On the problem of the formation and geochemical role of bituminous matter in pegmatites of the Khibiny and Lovozero alkaline massifs, Kola Peninsula, Russia

Solid bituminous matter (SBM) typically occurs in the late hydrothermal assemblages of pegmatites of the Khibiny and Lovozero massifs, being confined to a microporous framework Ti-, Nb-, and Zr-silicates, which are sorbents of small molecules and efficient catalysts of the polymerization, reforming, and selective oxidation of organic matter. Bituminous matter from the pegmatites of the Lovozero Massif typically have elevated contents of aliphatic hydrocarbons, sulfur, and sodium, but are depleted in oxygen and trace elements. SBM from the pegmatites of the Khibiny Massif are depleted in sulfur and enriched in oxygen-bearing derivatives of polycyclic aromatic hydrocarbons. Being complexing agents for Th, REE, Ba, Sr, and Ca, they play a key role in the transfer and accumulation of Th and in the accumulation of alkali earth and rare earth elements during the hydrothermal stage of mineral formation. Oxidized SBM bearing rare and alkali earth elements are complex microheterogenous systems, which contain mineral (Th silicates, calcite, etc.), metalorganic (with REE, Ca, Sr, Ba), and predominantly organic phases formed by the exsolution of initial metalorganic material with decreasing temperature.     

氟铈硅磷灰石—产自加拿大Mont St.Hilaire的新矿物

新矿物氟铈硅磷灰石产自加拿大魁北京省的ＭｏｎｔＳｔ．Ｈｉｌａｉｒｅ地区，赋存于霞石正长岩、大理岩捕虏体，方钠石正长岩捕虏体和伟晶岩岩墙中。     

U-Pb SHRIMP-II ages of titanite and timing constraints on apatite-nepheline mineralization in the Khibiny and Lovozero alkaline massifs (Kola Peninsula)

Results of this study of titanite samples collected from silicate rocks and apatite-nepheline-(sphene) ores from Paleozoic polyphase alkaline nepheline syenite complexes of the Khibiny and Lovozero massifs revealed the possibility of their in-situ U-Pb dating using sensitive high-resolution ion microprobe SHRIMP-II with an accuracy of 1.0-1.5%, which is comparable with that of U-Pb zircon analysis. Employing different approaches to age determination of the formation of the U-Pb system of titanites, the combined isochrons and mixing lines were plotted from the data obtained from the differentiated complex samples (121 analyses of five Khibiny samples and 52 analyses of one Lovozero sample) and apatite-nepheline ores (120 analyses of five Khibiny samples and 88 analyses of three Lovozero samples). They indicate synchronous crystallization of titanite in silicate rocks throughout the complexes: 374.1 ± 3.7 Ma for the Khibiny massif and 380.9 ± 4.5 Ma for the Lovozero massif, and attest to the later formation of phosphate-rare-metal ores: 371.0 ± 4.2 and 361.4 ± 3.2 Ma, respectively. The relatively delayed ore mineralization specific to the Lovozero massif can be accounted for the significantly lower volumes of magmatic melt and ore fluid involved, different thermal conditions, and the pattern of the investigated mineralization. As such, the obtained U-Pb data from titanite make it possible to limit significantly the time interval (most likely, not exceeding 15-20 Ma) comprising the evolution and activity of the ore-magmatic system of major agpaitic complexes, which is probably associated with plume magmatism.     

Mineral thermometry and the composition of fluids of the sodalite syenites of the Lovozero alkaline massif

In order to determine the conditions of mineral formation, a suite of sodalite syenite samples was investigated from the differentiated complex and in part from the eudialyte lujavrite complex of the Lovozero alkaline massif. The compositions of major and accessory minerals were analyzed using an electron microprobe. Various mineral geothermometers (Bt-Cpx, Amph-Cpx, and Amph-Bt) were applied to estimate the temperature of formation of clinopyroxene-bearing assemblages from the sodalite syenites. The temperature varied from ～990 to 595–630°C, which reflects various stages of crystallization. The temperatures of formation of sodalite assemblages were estimated from the compositions of coexisting sodalite phases as 625–530°C and appeared to be in good agreement with estimates obtained by other mineral geothermometers. Based on the data on the composition and crystallization temperature of sodalites, the minimum concentration of salts (NaCl and Na₂SO₄) in the mineral-forming fluid was estimated as 10–20 wt % NaCl eq. for the two-sodalite assemblages and 1.5–3.0 wt % NaCl eq. for the nosean-bearing assemblages. The molar fraction of sulfur in the fluid was also estimated: 0.02 for the two-sodalite assemblages and 0.04–0.27 for the nosean-bearing assemblages.     

新疆东天山中段金铜成矿系统研究

依据海岸带的定义,选择陆地和海域的7个特征因子,对中国大陆海岸带26个区段进行Q型聚类分析,定量划分海岸带的类型、研究它们的分布特征。对7个特征因子作R型聚类分析和因子分析,确定影响海岸带发育的主要营力和各种营力之间的关系。数据分析显示,陆地地质作用是控制海岸带形成、发育和演化的主要营力,海洋营力只起改造作用。海岸带陆地地表水流特征既决定海岸的地形地貌和岩性,也控制了海域部分的水下地形地貌和底质岩石成分。从海岸带环境水文地质学角度,中国大陆海岸带可划分为松散岩类和基岩类海岸带两大类型和较粗颗粒底质、细颗粒底质、水动力条件与岩性复杂类等3个松散类海岸带亚类;砾砂粗粒底质、砂砾石台地、水下岸坡或台地等3个基岩类海岸带亚类。     

Mineral types of hydrothermal alteration zones in the Dukat ore field and their relationships to leucogranite and epithermal gold-silver ore,northeastern Russia

The paper considers the localization of potassic and propylitic hydrothermal alteration zones in the domal volcanic-plutonic structure controlling the position of the Dukat ore field with the eponymous unique epithermal Au-Ag deposit. Comprehensive mineralogical and geochemical data on rocks and minerals in hydrothermal alteration zones and associated intrusions have shown that quartz-jarosite-sericite, quartz-pyrite-sericite, and quartz-adularia-chlorite alterations were formed with the participation of fluid flows related to a fingerlike projection of a high-K leucogranite porphyry intrusion with large phenocrysts. These hydrothermal alterations developed in the rifted graben under conditions of divergent plate boundaries, whereas quartz-clinozoisite-calcite, epidote-chlorite, and garnet-calcite-chlorite alterations were linked to K-Na leucogranite intrusive bodies and developed under conditions of convergent plate boundaries reactivated as a result of formation of the marginal Okhotsk-Chukotka volcanic belt. Phase separation and coagulation of specific portions of ascending fluids resulted in the formation and stabilization of small-sized particles of native silver and other ore components, which enabled involvement in flows of secondary geothermal solutions and ore-forming fluids. The Sr, Nd, and Pb isotopic compositions of rocks and minerals from the hydrothermal alteration zones, associated intrusions, and economic orebodies at the Dukat deposit indicate that their components have been derived from the juvenile continental crust, which was altered in pre-Cretaceous periods of endogenic activity. The components of gangue minerals of potassic and propylitic hydrothertmal alterations and associated intrusions have been taken from deep sources differing in 87Sr/86Sr and 143Nd/144Nd at similar U/Pb and Th/Pb ratios. Chalcophile lead in products of hydrothermal activity and melanocratic inclusions in leucogranite has been taken from regions with elevated U/Pb and Th/Pb ratios.     

西非金矿床类型及时空分布规律

西非素有"黄金海岸"之称, 近年西非金矿勘查和产量不断突破新高, 已超过南非成为非洲最重要的产金区。通过系统总结西非156个有储量数据的金矿山信息发现, 西非已发现金矿储量全球占比超7%, 未来可能成为全球金矿开采与供应的重要一极。成因类型上以造山型金矿为主, 且成矿流体具有富水含碳为特征。砾岩型金矿次之, 独居特色, 其他类型矿床数量较少。西非金矿时间分布上具有广泛分布、高度集中的特点。古元古代埃布尼造山运动(2.2.~2.0 Ga)对金矿的形成具有绝对控制作用, 其他时期金矿数量相对较少。西非金矿空间分布广泛, 且具有明显的丛聚性分布特征, 集中分布于西非克拉通内的莱奥地盾区, 其他地区零星出露。根据西非金矿成矿地质背景与空间分布规律, 划分了23个Ⅳ成矿带。上述研究不仅有助于深入了解西非金矿成矿地质条件及矿床分布规律, 也对该区下步的找矿勘查部署具一定的指示意义, 更可能为该区金矿理论研究提供启示。     

Thorium mineralization in hyperalkaline pegmatites and hydrothermalites of the Lovozero pluton,Kola Peninsula

The Lovozero pluton (Kola Peninsula, Russia) is an unique object from the standpoint of the abundance, diversity, and originality of Th mineralization. In contrast to other igneous rocks and to such chemical elements as Ca, REE, U, and Na, Th in the hyperalkaline pegmatites and hydrothermalites of the Lovozero pluton commonly occurs as its own mineral phases. Umbozerite Na₃Sr₄Th(Mn,Zn,Fe,Mg)[Si₈O₂₄](OH) (7 samples), Ti-Th silicate Na_0–7Sr_0–1ThTi_1–2Si₈O_22–23(OH) · nH₂O (8 samples), Na-Th silicate (Na,K)₄Th₃[Si₈(O,OH)₂₄] · nH₂O (6 samples), thorite (2 samples), steenstrupine-(Ce)-thorosteenstrupine series minerals (5 samples), and Th phosphate (Th,Na,K,Ca,Mg,U,Sr,Ba)[(P,Si, Al)₁O₄] · nH₂O (1 sample) were investigated in this study. Ti-Th silicates and Th phosphate have been described for the first time. All of the above-mentioned minerals have been examined with electron microprobe, IR spectroscopy, powder diffraction, thermogravimetric and optical methods. High-Th minerals such as steenstrupine, umbozerite, Th phosphate, and Na-Th silicates crystallized mainly during the ussingite stage of the pegmatite-forming process. At the early hydrothermal high-alkaline stage, steenstrupine was replaced with REE and Th aggregates (belovite, vitusite, seidite, Na-Th silicates, Ti-Th silicates, etc.). Thorite, Ti-Th silicates, and minerals of the rhabdophane and monazite groups were formed at the late hydrothermal low-alkaline stage. Despite the metamict features of almost all samples, stoichiometric ratios of cations in umbozerites and Ti-Th silicates remain stable. Clear relationships have been revealed between umbozerites and Ti-Th silicates, on the one hand, and seidite-(Ce), a Ti-silicate that has a zeolite-like structure, on the other. This implies that, under certain conditions, these minerals may be regarded as potential suppliers of Th to the environment due to the leaching of Th from zeolite channels.     

Chromium mineralization in the Khibiny alkaline massif (Kola Peninsula,Russia)

This paper presents new data on chromium mineralization in a fenitized xenolith in Mt. Kaskasnyunchorr in the Khibiny alkaline massif (Kola Peninsula, Russia) and summarizes data on Cr mineralogy in the Khibiny Mountains. Protolith silicates that contained Cr³⁺ admixture are believed to be the source of this element in the fenite. Cr-bearing (maximum Cr₂O₃ concentrations, wt %, are in parentheses) aegirine (5.8), crichtonite-group minerals (2.1), muscovite (1.3), zirconolite (1.1), titanite (1.0), fluorine-magnesioarfvedsonite (0.8), biotite (0.8), ilmenite (0.6), and aenigmatite (0.6) occur in the fenite. The late-stage spinellides of the FeTi-chromite-CrTi-magnetite series, which are very poor in Mg and Al and which formed after Crrich aegirine and ilmenite, are the richest in Cr (up to 42% Ct₂O₃). Cr concentrations grew with time during the fenitization process. Unlike minerals in the Khibiny ultramafic rocks where Cr is associated with Mg, Al (it is isomorphic with Cr), and with Ca, chromium in the fenites is associated with Fe, Ti, and V (with which Cr³⁺ is isomorphic) and with Na in silicate minerals. Cr³⁺ Mobility of Cr³⁺ and the unique character of chromium mineralization in the examined fenites were caused by high alkalinity of the fluid.     

Corundum-group minerals in rocks of the Khibiny alkaline pluton,Kola Peninsula

Five minerals of the corundum group have been identified in the Khibiny pluton with certainty. Corundum proper and karelianite occur only in hornfels after volcanic and sedimentary rocks. Xenoliths of hornfels mark the ring faults that bound foidalite within the field of foyaite. Hematite occurs in hydrothermally altered nepheline syenite and crosscutting hydrothermal veins related to the ring faults. Minerals of the ilmenite-pyrophanite series are present in all rocks of the pluton, including veins. Accessory ilmenite in foyaite varies from the manganese variety and pyrophanite in the inner and outer parts of the pluton to manganese-free ilmenite in zone of the Main Ring Fault. In xenoliths of volcanic rocks and alkaline ultramafic rocks, ilmenite is enriched in magnesium. The zoning in distribution of the above-mentioned minerals and the character of variation in their compositions from margins of the pluton to its center are consistent with the petrochemical zoning formed as a result of foyaite alteration of near ring faults.     

Quickclays as products of glacial action: a new approach to their nature,geology, distribution and geotechnical properties

Essentially, quickclays are products of glaciation which accounts for their limited distribution; other modes of development being of lesser importance. Glacial grinding provides the fine silt and clay sizes required to constitute quickclays. Two major factors account for the geotechnical properties, a composition factor related to material comprising the soil system and a leaching factor, the effectiveness of which is related to the clay-mineral content of the soil.Soils can be divided into three types, based on criteria of particle size and type of interparticle bond. Among the latter are long-range active bonds, typical of true clay-mineral systems; and short-range inactive bonds such as are observed between two quartz particles. The three main soil types have: (a) small particles and long-range forces - the bond/weight ratioR is high; (b) small particles and short-range forces ? R > 1 ; and (c) large particles and short-range forces - i.e., the sands, andR < 1. Quickclays fall more conveniently into type (b) than into type (a) in as much as the most important property is a preponderance of inactive bonds in the soil system. This is achieved by a high content of non-clay mineral particles, and also may be assisted by leaching and cementation. If more than a critical proportion of long-range bonds are present, the required very high sensitivity does not occur.The initial failure of the soil might be treated as tensile using a volume failure criterion; the low settling velocity of the very small (≈ 1?2 μm) particles allows the solid-liquid transformation to occur after a modest shock loading. Observations of low thixotropy, lack of secondary settlement and sudden failure in compression tests can be explained by requirements of particle size and material.     

Elpasolite from hyperalkaline pegmatite of the Khibiny pluton, Kola Peninsula. Symmetry of elpasolite

Elpasolite, K₂NaAlF₆, has been found for the first time in a pegmatite related to peralkaline foid syenite at Mt. Koashva, Khibiny alkaline pluton, Kola Peninsula, Russia, as pale pink octahedral crystals up to 2 mm in size within cavities in the natrolite core of pegmatite in association with amicite, sodalite, aegirine, pectolite, catapleiite, sitinakite, lemmleinite-K, and vinogradovite. The chemical composition determined with an electron microprobe is as follows, wt %: 31.53 K; 9.22 Na; 11.20 Al; 47.21 F; total is 99.16. The empirical formula is K_1.96Na_0.98Al_1.01F_6.05. The infrared spectrum is given. The crystal structure has been refined to R = 0.030, space group Fm $ \bar 3 Elpasolite, K₂NaAlF₆, has been found for the first time in a pegmatite related to peralkaline foid syenite at Mt. Koashva, Khibiny alkaline pluton, Kola Peninsula, Russia, as pale pink octahedral crystals up to 2 mm in size within cavities in the natrolite core of pegmatite in association with amicite, sodalite, aegirine, pectolite, catapleiite, sitinakite, lemmleinite-K, and vinogradovite. The chemical composition determined with an electron microprobe is as follows, wt %: 31.53 K; 9.22 Na; 11.20 Al; 47.21 F; total is 99.16. The empirical formula is K_1.96Na_0.98Al_1.01F_6.05. The infrared spectrum is given. The crystal structure has been refined to R = 0.030, space group Fm m, a = 8.092 ?. The result of a special X-ray powder diffraction study confirmed the suggestion made by Morss (1974) that reflections violating space group Fm m in some published X-ray powder patterns of natural elpasolite are Kβ-lines. Original Russian Text ? I.V. Pekov, N.V. Chukanov, N.N. Kononkova, N.V. Zubkova, M.Kh. Rabadanov, D.Yu. Pushcharovsky, 2007, published in Zapiski Rossiiskogo Mineralogicheskogo Obshchestva, 2007, No. 6, pp. 76–84.     

粤东莲花山地区锡矿矿产类型

锡矿是粤东优势矿种之一。在收集分析粤东莲花山地区61个锡矿床（点）成矿特征的基础上,对该地区锡矿床（点）矿产类型进行划分归类,建立了粤东莲花山地区锡矿工业类型,主要有为锡石-硫化物型、锡石-硅酸盐型、锡石-石英脉型、斑岩型4类;对4种不同类型锡矿床所具有的矿物组合进行归纳,并开展各类型代表性矿床综合研究,初步构建了4个类型代表性矿区的成矿模式图,为粤东地区锡矿研究提供了基础资料。     

Mineral matter and the nature of pyrite in some high-sulfur tertiary coals of Meghalaya, northeast India

Coal samples collected from four different sources in the Jaintia Hills of Meghalaya, northeast India, have been investigated for their sulfur content, mineral matter, and to assess their potential behavior upon beneficiation. These coals contain high sulfur which occurs both in organic and inorganic forms. The organic sulfur content is much higher than the inorganic sulfur. Studies on different size and gravity fractions indicated that the mineral phases are concentrated in higher density fractions (d > 1.8) and in general are fine grained (<50 μm). Data of reflected-light optical microscope and electron probe micro-analysis (EPMA) revealed that minerals in these coals are sulfides-pyrite, marcasite, sphalerite, pentlandite; sulfates-barite, jarosite; oxides-hematite, rutile; hydroxides-gibbsite, goethite; phosphate-monazite; carbonate-calcite, siderite and silicates-quartz, mica, chlorite, and kaolinitic clay. The disulfides of iron occur in two modes — mainly pyrite and occasionally marcasite with wide size ranges and in various forms, such as: framboid, colloidal precipitate, colloform-banded, fine disseminations, discrete grains, dendritic (feathery), recrystallized, nuggets, discoidal, massive, cavity-fracture- and cleat-fillings. Framboidal pyrite has formed primarily due to biological activities of sulfur reducing bacteria in the early stages of coalification. Massive and other varieties have formed at later stages due to coalescence and recrystallization of the earlier formed pyrites. Sulfur isotopic values indicate a biogenic origin for the pyrites. Association of trace metals, such as Ni, and Zn has been recorded in these pyrites. Given the large fractions of organic sulfur present, these coals can be upgraded only partially to reduce the sulfur content by beneficiation.