Crystalline Limestone Research Articles

Engineering geology study of Lingquansi Cave Temple, People's Republic of China

The Lingquansi Cave Temple, in the Henan Province of China, is a cultural heritage relic of national importance. Exquisitely cut in the rock mass, the images of Buddha in low relief, the inscriptions and the Buddhist scriptures are all stone carving art treasures of the Sui Dynasty. The cave temple was constructed on intact and compacted crystalline limestone between the fifth and tenth centuries A.R. Heavy geological deterioration and other factors have resulted in various degrees of damage to the temple's grottoes and stone carvings over the centuries such that protection and renovation are urgently required. Dazhu Grotto and the biggest and best stone carvings are the main concerns of the engineering geological study discussed here. Detailed investigations of the nature of deterioration have been carried out and proposals for remedial/preservation works are presented.

Kinoite from Fuka, Okayama Prefecture, Japan.

Kinoite was found in a dump at the Fuka mine, Okayama Prefecture, Japan. It occurs as aggregates of flaky crystals, and rarely as subhedral platy crystals up to 1 mm wide in a vein cutting into crystalline limestone. Associated minerals are stringhamite, calcite and an unidentified mineral. The empirical formula of the mineral is (Ca2.00Mg0.02)Σ2.02(Cu1.92Fe0.04Co0.04)Σ2.00Si2.98O10·2.25H2O on the basis of O=10 (anhydrous). The unit cell parameters are a=6.989 (1), b=12.904 (2), c=5.659 (1)A, and β=96.15 (2)°. The mineral is optically biaxial negative with refractive indices α=1.642 (2), β=1.662 (2), and γ=1.675 (2). The Vickers microhardness is 536 kg mm−2 (50 g load) and the density is 3.14 g cm−3. It is likely that kinoite at the Fuka mine was formed as a primary mineral by a reaction of Cu- and Si-bearing fluids with limestone.

Experimental hydrocyclone roping models

Hydrocyclone roping has not been studied and modeled in true grinding circuits. The paper discusses experiments made with a pilot size closed grinding circuit treating 0.5–1.0 t/h crystalline limestone. The equations found in the literature did not all describe roping very well. The best results were obtained by predicting the underflow solids volume flow. Equations based on underflow particle size did not give good results. Roping had mixed effects on the performance of the grinding circuit depending upon how it was obtained. Experiments were made by initiating roping through increasing mill feed rate or decreasing cyclone apex diameter. Varying responses are discussed in the paper. The estimation given in literature, that a circuit has the optimal operational point close to roping, was also confirmed for this set-up.

Molar-Tooth Carbonates: Shallow Subtidal Facies of the Mid- to Late Proterozoic: Discussion

From field work in northern Canada and many other examples documented in the literature, James et al. (1998) highlighted the potential use of molar-tooth structures (i.e., a series of spar-filled cracks) as a stratigraphic indicator for the Mesoproterozoic and Neoproterozoic. These authors also stated that all known occurrences where molar-tooth structures are volumetrically significant are from shallow-water carbonates. Although these are comprehensive statements, considering that most molar-tooth structures reported so far are from shallow-water Mesoproterozoic and Neoproterozoic deposits, I am concerned about such proposed temporal and environmental constrictions, which are not supported by the field data, summarized in the following. Detailed field work in the Grajau Basin, northern Brazil, revealed that structures similar to the ones reported by James et al. (1998) are volumetrically widespread in the Codo Formation. This is a lacustrine lithostratigraphic succession formed during the early stages of the South Atlantic rifting in the Aptian (e.g., Petri and Fulfaro 1983). The sedimentary features described here occur in lime mudstone to grainstone, ostracodal grainstone, and crystalline limestone interbedded with shales strongly affected by penecontemporaneous deformation, as indicated by a variety of complex convolute folds, small faults, fissures, and bed collapses. The molar-tooth structures occur throughout these beds, although they substantially increase in volume downward, where evidence for soft-sediment deformation diminishes. These …

Preliminary Results about the Catastrophic Earthquake of 7 September 1999 in Athens, Greece

The catastrophic earthquake that hit the metropolitan area of Athens, Greece on 7 September, 1999 at 11:56:50.5 GMT has already been considered as the most important earthquake event in the modern history of Greece. In fact, it is the first moderate-to-strong shock ( Ms = 5.9) ever reported to have occurred at such a small epicentral distance (D ≈ 18 km) from the historical center of the city and the first shock in the long history of Athens to cause casualties within its urban area. About 100 buildings collapsed, causing 143 casualties, while another 800 were injured. Search and rescue operations were conducted in more than twenty-five different locations. Preliminary estimations indicate that the number of buildings classified as “red”, “ yellow”, and “green” after official inspection were 13,000, 62,000, and 110,000, respectively. “Red” indicates buildings either damaged beyond repair or heavily damaged but repairable; “yellow” indicates repairable, seriously damaged buildings; and “green” means not seriously damaged buildings. During the first days after the shock about 100,000 people were rendered homeless. More than 50 municipalities were affected, while the tangible loss caused is roughly estimated equal to about $3b U.S. From the point of view of economic loss it is the worst natural disaster reported in the modern history of Greece. First reports about the earthquake were published by Papadopoulos et al. (1999) and Pavlides et al. (1999, 2000), while Tselentis and Zahradnik (2000) prepared a preliminary report on the aftershock monitoring. Here we present more detailed though still preliminary results. In the remainder of this report the 7 September 1999 shock is referred to as “the Athens earthquake” for reasons of brevity. The basement rocks in the active region are Paleozoic shales and sandstones in altered phylites and quartz conglomerates, Triassic-Jurassic crystalline limestones, dolomites, and a few outcrops …

Physical deterioration of sedimentary rocks subjected to experimental freeze-thaw weathering

Ten types of sedimentary rock were subjected to repeated cycles of freezing and thawing. In addition to monitoring sample weight loss throughout testing, a detailed graphic record was made of deterioration mode and its relationship to pre-existing rock flaws. Results suggest that the presence or absence of rock flaws alone does not control deterioration mode, but rather that it is the coupled relationship between these flaws, and rock strength and textural properties which exerts greatest influence. While some pre-existing flaws such as syndepositional deformation structures do not appear to influence breakdown, others such as incipient fractures, cavities and minor lithological boundaries frequently coincide with concentrations of deterioration. A characteristic mode of deterioration which is independent pre-existing flaws tends to develop in sandstones, indicating the influence, in this case, of rock texture. Particularly strong rocks such as crystalline limestone and metasediment tend to fracture preferentially along distinct linear weaknesses such as mineral veins, stylolites and incipient fractures. Particularly weak rocks, such as low-density chalk, break down in a random fashion without regard to pre-existing flaws. In addition to providing some insight into the role of pre-existing flaws in rock deterioration, this work also has practical implications for (i) the study of landform development due to weathering, and (ii) the selection of representative rock samples in durability testing for building stone. Copyright (C) 2000 John Wiley and Sons, Ltd.

Three–Dimensional Isotopic Characteristics of Crystalline Limestone around the Sakonishi Zn Ore Bodies in the Kamioka Mining District, Japan

Abstract: Predominant Zn‐rich ore bodies were found to a deep part of the Sakonishi area in the Kamioka mining district, Japan. The ore mineralization was recognized at 230 to 300m above sea level in the Sakonishi area. Since crystalline limestone is broadly distributed over the area, and the variation in isotopic composition is easily detected, the isotopic prospecting should be powerful in surveying of the extent of the ore bodies and the related hydrothermal system. Although isotopic anomalies have been extracted two‐dimensionally so far, three‐dimensional information is possibly more powerful.In this paper, Zn‐rich ore bodies in the Sakonishi area are treated as hydrothermal ore deposits, and the importance of the activity of hydrothermal fluids during mineralization is emphasized. Oxygen and carbon isotopic ‘iso–surfaces’ are three‐dimensionally calculated for the Sakonishi area. The δ18O values of crystalline limestone from the surface and from the drill holes range from +8. 1 to +21. 1% and from –2. 7 to +20. 4%, respectively. The δ13C values of crystalline limestone from the surface and from the drill holes range from –1. 0 to +5. 3% and from –7. 7 to +4. 6%, respectively. The oxygen and carbon iso‐topic ratios at the mineralization level are extremely low, but there are exceptions as to carbon isotopes. The oxygen isotopic ratios of crystalline limestone may decrease by isotopic exchange reaction with a hydrothermal fluid, while the carbon isotopic ratios slightly change. Since the precipitated calcite from a hydrothermal fluid has low carbon isotopic ratio and various oxygen isotopic ratio depending on the formation temperature, the bulk sample of crystalline limestone containing the precipitated calcite has oxygen and carbon isotopic ratios of relatively low values accordingly. Thus the decrease mechanism for carbon isotopic ratio of crystalline limestone is different from that for oxygen isotopic ratio. Samples with the carbon isotopic ratio of –4 to –8% are considered to be crystallized from hydrothermal fluids.Since the oxygen and carbon isotopic ratios of crystalline limestone at the ore mineralization level are low, the ore bodies are considered to have formed by a prominent hydrothermal activity. Thus oxygen and carbon isotopic ratios of crystalline limestone can be used as an indicator of the related hydrothermal activity. The alteration such as chloritization is intense near fractures in the Sakonishi area, showing that the hydrothermal system is controlled by a fracture system. It is assumed that the decreased isotopic ratios indicate the high degree of reactivity with hydrothermal fluids, and the depleted zone in oxygen and carbon isotopes may correspond to the conduit of the hydrothermal fluids.

Genesis of the Kamioka Skarn Deposits: An Important Role of Clinopyroxene Skarn and Graphite‐bearing Limestone in Precipitating Sulfide Ore

Abstract: A genetical relationship between skarn formation and mineralization is investigated for the Kamioka skarn deposits which are the largest Zn‐Pb producer in Japan. In the Mozumi deposit, one of main deposits in the Kamioka mining area as well as Tochibora and Maruyama, clinopyroxene skarn was generally subjected to later replacement by garnet or magnetite–calcite–quartz during the Zn‐Pb mineralization. The replacement of hedenbergitic clinopyroxene by andraditic garnet resulted in the formation of diopsidic clinopyroxene relicts. With the progress of replacement, the S/So value (So: an estimated area occupied by an original clinopyroxene grain in a thin section, S: a total area of relict clinopyroxene fragments) which is an index of the degree of replacement decreases from 0. 7 to 0. 1, and the hedenbergite mole percent of relict clinopyroxene decreases drastically from about 65 to less than 40. A close association of andraditic garnet and sphalerite suggests that heden‐bergitic clinopyroxene skarn played an important role to reduce the relatively oxic ore‐forming fluid enriched in Zn2+ and SO42– and to precipitate sphalerite from the fluid. Ferrous iron in the hedenbergitic clinopyroxene skarn was oxidized to form andraditic garnet. Besides this garnet formation, the mineral assemblage of magnetite–calcite–quartz replaced the clinopyroxene skarn at the time of mineralization. In both cases, the reduction of relatively oxic ore‐forming fluid by hedenbergitic clinopy‐roxene skarn at the later stage brought about the precipitation of sulfide minerals.In contrast, these types of later replacement are not found in the Tochibora deposit. Instead, graphite‐bearing crystalline limestone and relatively fresh clinopyroxene skarn are common. Mineralized clinopyroxene skarn has high graphite carbon contents relative to barren one, suggesting that the amount of graphite in the skarn was an important controlling factor for mineralization. It is very likely that the graphite played a role of reducing agent during the mineralization in the Tochibora deposit.

Hydrothermal Alteration of Limestone and Mineral Exploration of Zn‐Pb Skarn Deposits in the Sako‐nishi Area of the Kamioka Mine, Central Japan

Abstract: Crystalline limestone of the Sako‐nishi area in the Kamioka Zn‐Pb mine, central Japan, is depleted in 18O and 13C toward the center of mineralization due to interaction with hydrothermal fluids with a dominant meteoric water component. The relationship between isotopic composition and mineral assemblage, texture, the chemical composition of the minerals, and the bulk chemical composition in the limestone was examined. A decrease in the δ18OSMOW value correlated with: (1) increase of fine‐grained calcite which is enriched in Mn and exhibits a bright cathodoluminescence, (2) progressive hy‐drothermal alteration of clinopyroxene in the original limestone into tremolite within the weakly‐altered zone, and into chlorite and actinolite within the strongly‐altered zone, (3) dominance of hydrothermal chlorite in altered limestone having δ18O values of less than 10%. This chlorite was enriched in Fe compared to mafic minerals in the unaltered limestone. The enrichment of Fe and Mn was more conspicuous in calcite and chlorite in skarn deposits. The occurrence and chemical composition of hydrothermal minerals in the limestone, skarn, and ore indicate that the 18O–depleted zones were formed in the later stage from fluids, which were responsible for mineralization and skarnization, and for Fe and Mn enrichment.The Al, Mn, and Fe contents, and the ratios of Mg/(Mg+Mn+Fe), Al/Mg, and Mn/Sr in the hydrochloric acid leachate of limestone varied with decreasing δ18O and δ13C values, reflecting increases in high‐Mn calcite and high‐Fe chlorite. These indexes were useful for the identification of hydrothermally altered limestone. Furthermore, the potential score weighted by each index was more effective and accurate means of detecting promising mineralization zones. An anomalous potential score due to the presence of hydrothermal minerals in the outcropping limestone occurred along the Atotsu–1GO fault. This structure indicates that the skarn deposits of the Sako‐nishi area belong to Mozumi‐type Zn–Pb skarn deposits, in which fissures and faults served as major passages for the hydrothermal fluid. High‐Mn carbonate and high‐Fe chlorite widely occur in base‐metal vein deposits and Zn‐Pb type skarn deposits. Leaching of altered rock with hydrochloric acid in addition to stable isotope composition and cathodoluminescence imaging is effective for geochemical exploration for hydrothermal deposits because it makes possible the detection of the elemental composition of hydrothermal minerals such as chlorite and carbonate and because of the rapidity and convenience of analysis.

岩石学・地球化学・年代学のリンク 同位体地質温度計と超高温変成作用 特に方解石‐石墨同位体温度計

Isotopic geothermometry is an important tool to clarify the thermal history of the metamorphic events because of independence of pressure. When applying the thermometer, it is necessary that the temperature dependence of the fractionation factors among the rock forming minerals be well calibrated.Carbon isotopic geothermometry between calcite and graphite is the most suitable thermometer to record peak metamorphic temperatures in crystalline limestone, because of the inert property of graphite in an isotopic exchange reaction during retrograde metamorphism. Various authors and approaches have reported fractionation factors in the calcitegraphite system. There is, however, still inconsistency among experimental, theoretical, and empirical results. In particular, the slope of the fractionation curve for temperature dependence still has a discrepancy between theoretical-experimental and empirical data. The causes of this discrepancy may be due to uncertainty in individual approaches, e.g., in experimental studies, uncertainty as to the reaction mechanism due to the inert property of crystalline graphite for isotopic exchange experiments ; in theoretical studies, uncertainty caused by a deficiency of reliable data on the vibrational frequency of calcite and graphite crystals; and, in empirical studies, incomplete crystallinity of carbonaceous matter.According to empirical data on carbon isotopic systematics, in crystalline limestone that metamorphosed at temperatures higher than 400°C, isotopic equilibria have been mostly attained in many cases. At temperatures lower than 400°C, data sets show an increased disequilibrium. Because the carbon isotopic fractionation between calcite-graphite is more than 3‰ at about 700°C, this thermometer has great potential as a tool for determining ultra-high temperature metamorphism. Furthermore, because of the inert property of graphite in an isotopic exchange reaction during retrograde metamorphism, graphite-calcite assemblage is the most probable candidate for preserving the highest temperature condition. Again, carbon isotopic zonation in graphite crystal could provide another tool to clarify the thermal history of polymetamorphic terrains.Oxygen isotopic thermometry was long been widely used to determine the temperatures of metamorphic rocks. It has long been recognized that oxygen isotope thermometers often record discordant temperatures during slowly cooling retrograde metamorphism, because of a relatively rapid diffusion rate during retrograde metamorphism. Revised correction techniques for re-equilibration during a retrograde isotopic exchange reaction under the such high temperatures help in using oxygen isotopic thermometry in deducing thermal history.

Hexahydroborite from Fuka, Okayama Prefecture, Japan.

Hexahydroborite was found in a vein consisting of borate minerals which developed along the boundary between crystalline limestone and skarns at Fuka, Okayama Prefecture, Japan. Hexahydroborite occurred as aggregates of pyramidal crystals up to 2mm wide on the cavity wall, in association with olshanskyite and calcite. Wet analyses and ICP-MS gave the empirical formula Ca1.001B2.102O4.154·5.846H2O on the basis of O=10, which was consistent with the ideal formula Ca[B(OH)4]2·2H2O. The reflections of X-ray powder data for hexahydroborite from Fuka were indexed on the monoclinic cell, a=16.011(2), b=6.688(1), c=7.954(2)A, β=103.81(1)°, determined by single crystal method. The mineral was optically biaxial positive with refractive indices α=1.502(2), β=1.505(2), γ=1.509(2) and had a Mohs hardness of 2.5 and a density of 1.84gcm−3. It is likely that hexahydroborite at Fuka was formed by a reaction of ground water with sibirskite and/or parasibirskite at a low temperature around 25°C.

ＣａＯ‐Ｂ２Ｏ３‐Ｈ２Ｏ系ホウ酸塩鉱物 特に岡山県備中町有賀産の例について

Calcium-borate minerals such as takedaite and parasibirskite have been found in a vein in crystalline limestone near gehlenite-spurrite skarns at Fuka, Okayama Prefecture, Japan. The minerals are plotted in the CaO:B2O3 molar ratio range from 1 : 1 to 3 : 1 and up to 0.25 in the B2O3 ratio in the CaO-B2O3-H2O system. This paper reviews the author's studies on physical and chemical properties and genesis of the borate minerals. The properties show the following characteristics with an increase of water content in the minerals: (1) the refractive indices, birefringence, hardness and density of the minerals decrease; (2) the endothermic peaks on the DTA curve shift remarkably at low temperature; (3) the intensity of IR absorption bands near 3400 cm-1 increases, and the band near 1000 cm-1 shifts toward the lower frequency region. The formation of the minerals may be considered as follows: (1) takedaite was primarily formed by a reaction of boron-bearing fluids with limestone; (2) sibirskite and parasibirskite were formed by hydrothermal alteration of takedaite; (3) a late-hydrothermal solution converted sibirskite and parasibirskite to olshanskyite, frolovite and nifontovite.

Pseudospherulitic fibrous calcite in paleo-groundwater, unconformity-related diagenetic carbonates (Paleocene of the Ager Basin and Miocene of the Madrid Basin, Spain)

ABSTRACT Massive, decimeter-thick intervals formed by mosaics of subspherical calcite crystals displaying an intracrystalline fibrous microfabric have been found in Paleocene and Miocene strata in Spain. The fibrous microfabric is marked by inclusion-defined fibers that radiate from the central parts of the crystals, which can be termed pseudospherulites and not spherulites, because they are single crystals and not polycrystalline aggregates. The horizons of pseudospherulitic calcite appear in meter-scale, laterally persistent levels of crystalline limestones that exhibit complex pseudospar fabrics, they are interbedded with peritidal and/or lacustrine deposits, they grade downward into bedded dolomicrites, and they can be linked to unconformities several meters higher in the section, above intervening unaltered limestones. The pseudospar zones are interpreted as early-diagenetic, paleo-groundwater alteration products after dolomicrites. The pseudospherulites are composed of low-Mg calcite with low contents of Fe and Mn, and they have a stable-isotope composition indicative of precipitation from meteoric water. They form xenotopic mosaics in which goethite, palygorskite, and sepiolite may be present as inclusions and in the intercrystalline matrix. Cathodoluminescence microscopy reveals peripheral growth of the pseudospherulites, which results from several phases of precipitation and even of dissolution. The first phase of crystal growth may show rhombic habits and may contain corroded dolomite inclusions, interpreted as an indication of growth at the expense of dolomicrite by a dissolution/precipitation process. The second phase of crystal growth is fibrous sensu stricto, exhibits lobate growth laminae, and shows indications of displacive growth. The pseudospherulitic fabric is not relict and the pseudospherulites do not represent speleothems, recrystallized Microcodium, or neomorphosed spherulitic carbonate. Instead, they are interpreted as split crystals that grew within dolomicritic host sediments, in part by dissolution-precipitation and in part by displacement. The hypothesis of a dolomicritic host is supported by the geological and diagenetic setting, by the presence of corroded dolomite inclusions within the pseudospherulites, and by the relationship between their growth and the authigenesis of sepiolite, palygorskite, and goethite. The pseudospherulites grew in the shallow subsurface, at or near the water table, from predominantly oxidizing meteoric water, and under periodically fluctuating geochemical conditions (saturation, redox) caused by fluctuations of the water table during periods of subaerial exposure. The presence of fossil bacteria within the pseudospherulites, the anastomosing pattern of the inclusion-defined fibers, and the lobate growth forms of the fibrous calcite suggest some bacterial influence in the genesis of the pseudospherulitic fabric.

Tensile test of poly(vinyl chloride) filled with ground calcium carbonate particles

The fracture behavior of poly(vinyl chloride) filled with ground calcium carbonate particles during a tensile test was studied. The particles were prepared by crushing natural raw crystalline limestone. For this purpose, 10–50 parts of the particles having two different mean sizes (2 and 8 μm) without further surface treatment were mixed with 100 parts of poly(vinyl chloride) and 3 parts of lead stearate as a stabilizer using a mixing roll. A tensile test was carried out using a dumbbell specimen. As a result, the yield stress decreased with increase in the particle content; however, there was no significant influence of particle size. From scanning electron microscopic observations of the specimen's surfaces during the tensile test, it was found that the particle/matrix interfaces were delaminated and formed voids around the particles when the applied stress approached the yield stress, that is, the particles acted as voids and the matrix around the voids was plastically deformed effectively. These observations appear to be the reason for the decrease of yield stress by the incorporation of the particles. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 311–316, 1998

Sibirskite from Fuka, Okayama Prefecture, Japan.

Sibirskite was found in a vein consisting of borate minerals which developed along the boundary between crystalline limestone and skarns at Fuka, Okayama Prefecture, Japan. Sibirskite occurs as aggregates of prismatic crystals up to 0.1 mm long and 0.02mm wide, in association with takedaite, frolovite and calcite. Wet and microprobe analyses of sibirskite from Fuka give the empirical formula Ca1.004H1.071B0.974O3 on the basis of 0=3. The formula, optical properties and X-ray powder data are consistent with those from the type locality. The space group and cell dimensions determined are P21/a, a=8.643(6), b=9.523(2), c=3.567(3) A, β=119.23(3)° and Z=4. The calculated density is 2.59 g cm−3, and agrees with the measured value of 2.58 g cm−3.It is likely that sibirskite at Fuka was formed by late-hydrothermal alteration of takedaite.

Seath folds in a crystalline limestone in Amakusa-shimojima Island, western Kyushu, Japan

九州西部の西彼杵半局, 野母半島および天草下島には低温高圧型の変成作用を受けた結晶片岩類が分布し, それらは「長崎変成岩類」と総称されている (例えば, 唐木田ほか, 1969;服部, 1992など). 著者らは熊本県天草下島の西部において長崎変成岩類の変形構造の調査を進めているが, 最近, シース褶曲 (sheath fold, 鞘状褶曲) の3次元形態を観察できる露頭を発見した, シース褶曲の形成過程については, 変形岩の野外および顕微鏡下での観察やモデル実験などによって解析されている (例えば, Minnigh, 1979; Cobbold and Quinquis, 1980; Skiernaa, 1989など). それらの結果から, シース褶曲の鞘状部の先端の向きは, 褶曲形成時の勢断方向と一致していることが知られている, シース褶曲の形態を記載することは岩石の変形史を知る上で重要である. しかし, 野外では一つの断面しか観察できないことが多いので, 褶曲軸などを正確に測定することは一般には困難である. ここで紹介する露頭では, シース褶曲が発達した岩石のさまざまな方向の断面を観察することができる.

Johnbaumite from Fuka, Okayama Prefecture, Japan.

Johnbaumite was found as a vein-forming mineral in crystalline limestone near gehlenite-spurrite skarns at Fuka, Okayama Prefecture. It is associated with arsenopyrite, lollingite, garnet, magnetite and calcite. Wet chemical analyses and EPMA of the mineral yield an empirical formula (Ca4.961Fe0.005) Σ4.97(As2.991P0.024) Σ3.02 O12(OH0.651F0.278Cl0.071) Σ1.00 on the basis of (O, OH, F, Cl) = 13. The DTA and TG curves, and IR spectrum are measured, and the optical and X-ray diffraction properties agree with previous data.Johnbaumite from Fuka may be formed by reaction of As, Fe, S, etc.- bearing fluids with limestone.

Stratigarphy and Sedimentology of the Kuşçular Formation (Lower Paleocene), the West of Elazığ, Turkey

Stratigraphic and sedimentological aspects of Kuşçular Formation has been firstly recognized in this study which represent in the west of Elazığ. The sediments of this formation consist of seven lithofacies. they are; 1- Massive conglomerates, 2-Stratified conglomerates, 3-Massive sandstones, 4-Horizantel bedded sandstones, 5-Red mudstones, 6-Nodular gypsum, 7-Stratified gypsums. Fine-grained facies are dominant at the lower levels of sequences represent in the prograding alluvial fan envirenments. These successions represent a depositional basin which rapidly filled. Ions necessary for gypsium occurances in the playa deposits are thought to come from the sulfide minerals of Elazığ Complex, crystalline limestone of Keban Metamorphics and Harami Formation.

Mode of Occurrence of Nepheline Syenites in the Gorkha-Ampipal Area, Central Nepal Lesser Himalaya

In the Gorkha-Ampipal area, low-grade metamorphic rocks of the Kuncha Formation are delimited in the north by the Masel Thrust. The Kuncha Formation is characterised by doubly-plunging, en-echelon types of noncylindrical folds which are 2 to 20 km long (essentially in NW-SE direction), and have wavelengths of a few km. Mineral and stretching lineations are gently plunging due NNE or SSW. The hanging wall of the Masel Thrust is represented by garnet-biotite schists and gneisses. The schists and gneisses make up a steeply northward dipping homocline. In contrast to the rocks of the footwall, they are generally gently dipping and constitute several mesoscopic folds. Further north, the homocline is discordantly overlain by the intensely deformed unit of phyllites, graphitic schists, marbles, crystalline limestones, and calcareous quartzites. The Main Central Thrust sharply overrides the latter unit and brings with it gently northward dipping kyanite-garnet-biotite schists, quartzites, feldspathic schists, and mylonitic gneisses.
 There are several nepheline syenite intrusive bodies in the Kuncha Formation in the vicinity of the villages Harmi Bhnnjyang, Ampipal, Chanp Bhanjyang, Bhulbhule Khar, and Luintel Bhanjyang. Two separate bodies are also encountered at the confluence of the Masel Khola and the Daraundi Khola. The nepheline syenite bodies observed in the study area vary widely in their shape, size, and orientation. The largest pluton is observed in the vicinity of the villages Ampipal and Chanp Bhanjyang. It is about 7.5 km long in NNE-SSW direction and about 2 km wide. The second largest body is observed between the villages Bandre and Luintel Bhanjyang. It is about 2.5 km long approximately in east-west direction and 300 m wide. Numerous other smaller bodies ranging in size from hundreds of m to a few cm also occur in the region. The nephelinesyenites show sharp and irregular contacts with the country rock, they are crosscut by numerous dykes, and occasionally the effect of contact metamorphism is also observed in the country rock.
 The northeastern part of the largest nepheline syenite pluton (which occurs between Ampipal and Chanp Bhanjyang) is covered by about 500 m thick band of impure marbles. Rare, thin alternations of impure marble with phyllite as well as large (more than 10 m in diameter) scattered marble boulders areseen on the slopes NE of Chanp Bhanjyang, N of Bhulbhule Khar, at the saddle of Lagamkot, and at Khanigaun. The secondary mineralisation in the marbles is represented by magnetite, actinolite, biotite, and chlorite. There exist a few old iron mine workings in the magnetite mineralisation zones. Similar minerals are also seen in the nepheline syenite suggesting a direct relationship between the mineralisation in the nepheline syenite and the marbles. Generally, the nepheline syenite bodies exhibit the same trends of foliation and lineation as those of the country rock, and therefore, they must be intruded before the development of the secondary structures.
 There are a few hot springs at Bhulbhule Khar, which contain a high amount of H2S gas and sulphur, and are coming through the nepheline syenite. The development of copper as well as other secondary ore minerals and several generations of veins in the country rock, and the presence of hot springs probably indicate a continued hydrothermal activity in that area up to the recent times.

Takedaite, a new mineral from Fuka, Okayama Prefecture, Japan

AbstractTakedaite, Ca3B2O6, has been found in crystalline limestone near gehlenite−spurrite skarns at Fuka, Okayama Prefecture. It occurs as aggregates of granular crystals up to 0.8 mm long and 0.3 mm wide. The mineral is associated with nifontovite, olshanskyite, pentahydroborite, frolovite, sibirskite, calcite and an unidentified mineral, is white or pale gray, and has a vitreous luster. Takedaite is trigonal with space group of Rc, a = 8.638(1), c = 11.850(2)Å, Z = 6. The strongest lines in the X-ray powder pattern [d in A(I)(hkl)] are 2.915(100)(113), 1.895(75)(223), 2.756(61)(104), 2.493(44)(300), 2.044(21) (214,131), 2.160(19)(220), 1.976(18)(006), 1.549(12)(306). The Vickers microhardness is 478 kg mm−2 and the Mohs hardness 4.5. The density is 3.10(2) g cm−3 (meas.) and 3.11 g cm−3 (calc.). Wet chemical analyses give the values CaO 71.13%, B2O3 28.41%, ig. loss 0.14%, and total 99.68%. The empirical formula calculated on the basis of O = 6 is Ca3.053B1.965O6, with the simplified formula of Ca3B2O6.