bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metamorphic differentiation; a mechanism indicated by zoned kyanite crystals in some rocks from the Lukmanier region, Switzerland
Authors: Bramwell M. G. 
Published: December 2006

AbstractTwo samples of garnet-kyanite-staurolite schist from Lukmanier, Switzerland, each contain two chemical varieties of kyanite which occur in texturally distinct areas of the rock. Type 1 form large idiomorphic crystals within an open crenulation cleavage S3. They exhibit a systematic zonation of F2O3, with core values of 0.8% decreasing to 0.3% at the crystal margin. Type 2 form small, much less abundant crystals in areas between S3 cleavage zones, and have a homogeneous distribution of 0.3% Fe2O3 throughout the crystal.It is suggested that the first-nucleated crystals contain the highest core concentration of Fe2O3 and are the largest. A positive correlation between core Fe2O3 values and crystal size is interpreted as a nucleation and growth sequence. This indicates that the first crystals formed preferentially in S3 (Type 1), with Type 2 crystals growing later outside the S3 zones.Concentration of kyanite in S3 zones produces a distinct mineral banding in the rock. A mechanism for the development of metamorphic differentiation by preferred nucleation of kyanite in S3 is proposed.
Refinement of the crystal structure of botallackite
Authors: Hawthorne F. C. 
Published: December 2006

AbstractThe crystal structure of botallackite, Cu2(OH)3Cl, monoclinic, a = 5.717(1), b = 6.126(1), c = 5.636(1)Å, β = 93.07(1)°, V = 197.06(5)Å3, space group P21/m, Z = 1, has been refined to an R index of 3.8% for 350 observed (4σ) reflections, measured with Mo-Kα X-radiation on an automatic four-circle diffractometer. The structure consists of sheets of edge-sharing Cuϕ6 (ϕ = unspecified anion) octahedra of composition Cu2(OH)3Cl; these sheets are // {100}, and are joined by hydrogen bonding between oxygen and chlorine anions, thus accounting for the perfect {100} cleavage and the platy habit of botallackite.
The iron content and optic axial angle in zoisites from Galicia, NW Spain
Authors: Maaskant P. 
Published: December 2006

AbstractElectron probe microanalyses of zoisites from high-grade metamorphic rocks in Galicia, NW Spain have been obtained. The elements Na, Mg, P, K, Ti, and Mn were not detected above the 0.1 wt. % level. Assuming all Fe is present as Fe3+, a clear relation is obtained between the Fe content and the optic axial angle. Zoisite with 1.6 wt. % Fe2O3 proves to be uniaxial at 589 nm; uniaxiality in blue light (470 nm) lies at 1.5 wt. % Fe2O3. A change of the optic sign, from positive to negative, is obtained at 2.9 wt. % Fe2O3. The presence of minor elements greatly affects this relation, as is indicated by analyses of sector-zoned Sr-bearing zoisites of a muscovite-zoisite pegmatite from the same region. Under retrograde conditions Fe-rich α-zoisite reacts to form less Fe-rich α-zoisite or β-zoisite and clinozoisite.
Pseudomesolite is mesolite
Authors: Nawaz Rab , Malone John F. , Din Victor K. 
Published: December 2006

AbstractPseudomesolite from Carlton Peak, described by Winchell (1900), is shown to be mesolite by means of chemical and X-ray data. A proposal to this effect has been accepted by the International Mineralogical Association's Commission on New Minerals and Mineral Names. Electron microprobe analysis revealed variations in the composition of pseudomesolite and showed the presence of faroelite. The X-ray powder diffraction pattern is similar to that of mesolite. Single-crystal Weissenberg photographs showed a twinning intergrowth which is explained by a 90° rotation of 50% of the unit cells about the c-axis, so that the a- and b-axes of rotated cells coincide with the b- and a-axes respectively of the unrotated cells. This twinning can not be detected optically. Mesolite has recently been proved to be orthorhombic, contrary to the long-held view that it is monoclinic.Pseudomesolite from Oregon is also shown to be mesolite by single crystal Weissenberg photographs. A wet chemical analysis shows this material to be extremely silica-rich.
The disposal of radioactive wastes into the marine environment: the presence of hot particles containing Pu and Am in the source term
Authors: Hamilton E. I. 
Published: December 2006

AbstractRadioactive particulate matter (identified as hot particles) is present in the effluent discharged by the British Nuclear Fuels Ltd (BNFL) uranium reprocessing plant at Sellafield, Cumbria, UK. There is very little information on the abundance or chemical and physical forms of solid matter in the effluent; even less is known of the significance of particulate debris in relation to the uptake of radionuclides for non-occupationally exposed people as a result of transfer along marine foodchains. Some observations on the occurrence and abundance of hot particles in the vicinity of Sellafield are reported, with special reference to those that contain transuranic radionuclides (Pu,Am,Cm). Some of the uncertainties are discussed in an evaluation of the significance of hot particles, albeit aggregates of colloids for the smallest particles, and exposure to man from ionizing radiation. There is no evidence that hot particles derived from BNFL and subsequently dispersed into the marine environment represent a hazard to man. However, further studies are required in order to determine whether or not the pathways followed by the particles are significant, or different to those of other radionuclides through which the radiation exposure of man within this region of Cumbria is assessed.
Hydrothermal crystallization of a radioactive waste storage glass
Authors: Savage David , Robbins Jane E. , Merriman Richard J. 
Published: December 2006

AbstractA borosilicate glass, containing 25 wt. % of simulated high-level radioactive waste has been reacted with water at 350°C and 500 bars for 14 and 48 days using large-volume ‘cold-seal’ high-pressure equipment. Under these conditions the glass crystallizes a suite of mineral phases including: albite, NaAlSi3O8; aegirine, NaFeSi2O6; riebeckite, Na2Fe2(Fe,Mg)3Si8O22(OH)2; zektzerite, LiNaZrSi6O15; barium-strontium molybdate, (Ba,Sr)MoO4; stillwellite, (Nd,Ce,La)BSiO5; willemite, Zn2SiO4; smectite; a lithium-sodium borosilicate hydrate; melilite (åkermanite), Ca2MgSi2O7. A description of the morphology of these phases is given, together with a number of chemical analyses. The implications of the incorporation of waste species in these mineral phases to the disposal of high-level radioactive waste is discussed.
The use of zeolites for the treatment of radioactive waste
Authors: Dyer A. , Mikhail K. Y. 
Published: December 2006

AbstractThe uptake of 137-Cs and 90-Sr on to synthetic zeolite A has been studied. The use of a combined barium exchange followed by a relatively mild heat treatment has been shown to fix the isotopes within a collapsed zeolite structure. Leaching experiments using deionized and simulated sea and pond waters were carried out on zeolite compacts and zeolite/cement composites. They demonstrated the effectiveness of the calcination and cement containment. Some comments on the interpretation of leach test data are made.
Geological control of fracture permeability in the Carnmenellis granite, Cornwall: implications for radionuclide migration
Authors: Heath M. J. 
Published: December 2006

AbstractMulti-packer hydraulic tests and radioactive tracer experiments carried out in boreholes in the Carnmenellis granite have shown that the flow of water through the rock is largely confined to narrow zones separated by zones of very low permeability. Correlation of the hydraulic data with geological data from oriented cores has shown that most of the flow is associated with discrete geological features, including pegmatitic and other veins, and elvan (quartz-feldspar porphyry) dykes, characteristic features of the granite of the area. Joints have also been found to conduct water, particularly in the upper 250 m of the granite. The permeability of the granite has been found not to be simply a function of fracture frequency, long sections of highly fractured rock having no associated flow under test conditions. While flow paths have been found to become less frequent with depth, flow rates do not vary over the depths studied, the highest flow rate recorded at the site being associated with a vein at 637 m. Water-conducting fractures have been found to have certain preferred orientations which vary with depth. A set striking 155°C is particularly well developed in the upper 250 m of the granite. This orientation is significant in that it is parallel to the cross-courses in the nearby mineralized belt with which the younger (Tertiary) mineralization tends to be associated and from which thermal brines issue into several local mines. These fractures are also approximately parallel to the maximum horizontal stress which affects the granite and which appears to be responsible for the selective opening of joints of certain orientations.
NaC1 crystallization at the MgCl2/NaC1 solution boundary–a possible natural barrier to the transport of radionuclides
Authors: Sander W. , Herbert H.-J. 
Published: December 2006

AbstractConcentration, conductivity, temperature, and flow logs from sixteen brine-filled shafts in northern Germany have shown that the brines in all former potash salt mines exhibit a very sharp stratification into lower Mg-rich brine, an upper layer of Na-rich brine, and groundwater at the top. Laboratory experiments have shown that, at the MgCl2-brine/NaCl-brine boundary, both solutions become oversaturated with regard to NaCl, due to diffusion processes. NaCl therefore crystallizes from the solutions and forms a salt plug in the boundary region, which considerably reduces further diffusion. It is concluded that the observed effects would also take place in shafts. The backfilling material helps to nucleate the halite crystals and provides a structure on which they might be supported. The results of these experiments show that the density boundaries in the brine bodies act as barriers against transport of matter while the formation of a halite plug growing independently at the MgCl2/NaCl-brine interface acts as an additional barrier.
A survey of white mica crystallinity and polytypes in pelitic rocks of Snowdonia and Llŷn, North Wales
Authors: Merriman R. J. , Roberts B. 
Published: December 2006

AbstractPelitic rocks in North Wales, ranging in age from late Precambrian to Silurian were sampled. XRD analysis was used to determine the mineralogy and white mica crystallinity of separated < 2 µm fractions. Results show that three stages of metapelite recrystallization can be distinguished. Stage I metapelites are uncleaved or feebly cleaved with crystallinities > 0.43Δ°2θ; the 1Md polytype dominates < 2 µm fractions, occurring as K-and Na-micas. Stage II metapelites show variable cleavage development and crystallinities in the range 0.26-0.43Δ°2θ; 1Md and 2M1 polytypes occur and K- and Na-micas are commonly regularly interstratified. Stage III metapelites are strongly cleaved with crystallinities < 0.26Δ°2θ; the 2M1 polytype is dominant, occurring as K-mica and paragonite. Pelites bearing pyrophyllite, rectorite, and corrensite are found close to plug-like intrusions and were contact altered prior to regional metamorphism. 1M mica is common in deeply buried but relatively undeformed volcaniclastic rocks of the Arfon Group.Contours of equal crystallinity (isocrysts) are plotted with metabasite zones on a metamorphic map. This shows that stage I metapelites are equivalent to the subpumpellyite zone (≡?laumontite zone). Stage II metapelites are equivalent to the prehnite-pumpellyite facies and stage III metapelites to the clinozoisite and biotite zones of the greenschist facies.
Phase equilibria and mixed parageneses of metabasites in lowgrade metamorphism
Authors: Liou J. G. , Maruyama S. , Cho M. 
Published: December 2006

AbstractThe system Na2O-CaO-MgO Al2O3-SiO2-H2O is proposed to model phase equilibria and mineral parageneses for low-temperature metamorphism of basaltic rocks. Univariant reactions marking the transitions between various sub-greenschist facies are identified and some have been experimentally determined. The introduction of Fe2O3 into the model system at fixed FeO/MgO ratio creates continuous reactions for facies boundaries and discontinuous reactions for invariant points of the model system. Both qualitative and quantitative effects on P-T displacement and phase compositions are discussed. The XFe3+ isopleths for epidote were plotted to exemplify the transition from the zeolite through prehnite-pumpellyite to prehnite-actinolite facies. T-XFe3+ relations were established for continuous and discontinuous reactions relating such facies transitions. Because of the common occurrence of two or three Ca-Al hydrosilicates in low-grade metabasites, an isobaric Al-Ca-Fe3+ projection from chlorite may be used to illustrate mineral assemblages and compositions of the coexisting Ca-Al silicates in the presence of quartz, albite, and chlorite. Reported occurrences in several classic burial metamorphic terrains and ocean-floor metabasites in ophiolites are described. Only the composition of a mineral from a buffered assemblage can constrain the intensive properties for metamorphism; previously reported compositional trends for pumpellyite and epidote with increasing metamorphic grade are oversimplified.
Low-grade metamorphism and accretion tectonics: Southern Uplands terrain, Scotland
Authors: Kemp A. E. S. , Oliver G. H. J. , Baldwin J. R. 
Published: December 2006

AbstractPrevious studies of low-grade metamorphism in the Southern Uplands accretionary terrain indicated prehnite-pumpellyite facies/anchizone conditions developed throughout the area, except for local preservation of trench-slope sediments and an accreted seamount at zeolite facies/advanced diagenetic grade. New graptolite reflectance data are presented that show a general northward increase in temperature in the Southern Uplands. The results from two cross-strike traverses in the southern and central belts in contemporaneous sequences, using illite crystallinity, illite lateral spacing (bo) , and graptolite reflectance, indicate the development of systematic accretion-related low-grade metamorphism. Well-developed and constant anchizone conditions occur throughout the NE (Langholm) traverse, associated with common, F1 accretion-related folding and a regionally penetrative S1 cleavage. In the SW (Kirkcudbright) traverse, however, the youngest, last accreted packets are preserved at a transitional diagenetic stage and lack a penetrative S1 cleavage. Illite crystallinity, graptolite reflectance, and bo increase systematically northward through earlier accreted packets, reaching values of the NE traverse only at the northern end. The concomitant increase of bo with illite crystallinity suggests the relatively high P-low T trajectory characteristic of subduction zones. Integration of metamorphic and structural data relates increasing intensity of aceretion-related F1 folding, developmertt of S1 fabric, and onset of later fold phases to grade of metamorphism and structural level within the accretionary pile.
Low-temperature recrystallization of Franciscan greywackes from Pacheco Pass, California
Authors: Maruyama S. , Liou J. G. , Sasakura Y. 
Published: December 2006

AbstractLow-temperature metamorphism of the Franciscan complex at Pacheco Pass occurs at P-T conditions near the so-called jadeite isograd. Along Highway 152 in the Diablo Range, from west to east, four distinct prograde metamorphic zones are defined: (I) albite-quartz zone, (II) albite-rich, albite-quartz-clinopyroxene assemblage, (III) clinopyroxene-rich, albite-quartz-clinopyroxene assemblage, and (IV) clinopyroxene zone. Metamorphic pyroxenes are restricted to zones II, III, and IV in metagreywackes, but metabasites contain augite-rich pyroxenes even in zone I. With increasing grade, the compositions of pyroxene in metagreywackes change in XJd from nearly 100 in zone II to about 60 in zone III. The diopside component has little effect on the XJd of pyroxene. The apparent change of XJd reflects differences in pressure and temperature rather than in bulk rock composition. In metagreywackes, at the onset of zone II, albite breaks down to form Jd100 according to the reaction Ab = Jd+Qz. With increasing grade, this reaction leads to less jadeitic pyroxene. From zones II to III, a continuous reaction is delineated: Qz+2 pyroxenes (Jd80Ac15Aug5)=pyroxene (Jd60Ac30Aug10) + Ab.The metamorphic temperatures are estimated to be about 170°C in zones I and II, and about 230°C in zones II and III. The temperature variation recorded in a single rock is probably less than 30°C The pressure estimate depends on the choice of experimental data for the jadeite-albite-quartz curve; it ranges from 4.5 to 8 kbar. A gently folded thermal structure of the Cretaceous subduction zone metamorphism is postulated for this area.
Significance of illite crystallinity and bo values of K-white mica in lowgrade metamorphic rocks, North Hill End Synclinorium, New South Wales, Australia
Authors: Offler R. , Prendergast E. 
Published: December 2006

AbstractA study of low-grade metamorphism in late Silurian to early Carboniferous rocks in the North Hill End Synclinorium and adjacent anticlinoria has been made by the determination of illite crystallinity and bo values of K-white mica in eighty slates and phyllites. Illite crystallinity values vary from 0.40 Δ°2θ on the Molong Anticlinorium to 0.12 Δ°2θ within the axis of the synclinorium, suggesting anchizonal to epizonal metamorphic conditions. This is in agreement with previous observations on Ca-Al-hydrosilicate assemblages which indicated a change from prehnite-pumpellyite facies in the anticlinoria adjacent to the synclinorium to middle greenschist facies in the axis. Local variations in crystallinity are attributed to variation in ak+ in fluids migrating along cleavage zones.The mean bo value obtained from the pelites is 9.017 Å (σn = 0.008; n = 80) which is in close agreement with that obtained from part of the adjacent Capertee Anticlinorium ( = 9.019 Å; σn = 0.007; n = 52). However, ‘t’ tests indicate that two bo populations are present in the synclinorium ( = 9.019 and 9.022 Å), with the lower values concentrated in the southern portion of this structure. The two populations are considered to be the result of slightly different metamorphic conditions prevailing during the deformation of the rocks in the synclinorium. A higher geothermal gradient affecting rocks giving the lower bo values is attributed to the presence of granitoids at shallower depths than elsewhere in the synclinorium.
Mineralogical and chemical evolution of white micas and chlorites, from diagenesis to low-grade metamorphism; data from various size fractions of greywackes (Middle Cambrian, Morocco)
Authors: Wybrecht E. , Duplay J. , Piqué A. , Weber F. 
Published: December 2006

AbstractFour size fractions have been separated and studied in eight samples of Cambrian greywackes, ranging from non-metamorphic to low metamorphic grade. Chemical study included analyses of each size fraction and comparison with the whole rock analysis. Mineralogical study involved analyses of individual crystals using microprobe (> 6 µm) and STEM (< 6 µm). This showed that in each fraction, a progressive homogenization of the mineralogical composition occurred during the development of metamorphism; that chemical transfers especially of Fe-Mg and K-Na, occurred between fine and coarse fractions and that recrystallization in fine and coarse fractions was simultaneous.
Stable isotope compositions of alteration fluids in low-grade Lower Palaeozoic rocks, English Lake District
Authors: Thomas L. J. , Harmon R. S. , Oliver G. J. H. 
Published: December 2006

AbstractA combination of hydrogen and oxygen isotope analyses and fluid inclusion studies has defined the composition of fluids involved in the metamorphism of Lower Palaeozoic rocks in the English Lake District. Three fluid fields have been defined from secondary phases: 1, syn-burial metamorphic D-enriched fluids from epidote and chlorite at a temperature between 250 and 350°C; D-depleted fluid measured from groundmass and quartz inclusions; 3, a mixed magmatic-meteoric fluid with an intermediate H-isotopic composition estimated from W/R granite data and calculated from illite.
Hydrothermal mineralogy of calcareous sandstones from the Colorado River delta in the Cerro Prieto geothermal system, Baja California, Mexico
Authors: Schiffman Peter , Bird Dennis K. , Elders Wilfred A. 
Published: December 2006

AbstractThe Cerro Prieto geothermal system provides a unique opportunity for the detailed study of calc-silicate mineral transitions between the diagenetic clay-carbonate and greenschist facies within the terrigenous sediments of the Colorado River delta. In this system, progressive devolatization reactions within carbonate-cemented, quartzofeldspathic sediment have produced a distinct hydrothermal mineral zonation at temperatures between 200–370°C and fluid pressures below 0.3 kbar. Descriptive and compositional data are presented for these minerals which include wairakite, epidote, prehnite, actinolite, clinopyroxene, garnet, sphene, biotite, microcline, and calcite. Partitioning of octahedral Fe, Mg, and Al between coexisting authigenic silicates is comparable with data from higher temperature metamorphic rocks and demonstrates an approach to local equilibrium within this system. Calculated fugacities of oxygen at temperatures above 300°C are (with rare exception) more reducing than that defined by the quartz-fayalite-magnetite buffer, a result consistent with the scarcity of hematite and grandite and the ubiquitous presence of organic material in Cerro Prieto sandstones.
Pumpellyite-dominated metadomain alteration at Builth Wells, Wales–evidence for a fossil submarine hydrothermal system?
Authors: Bevins R. E. 
Published: December 2006

AbstractTwo metamorphic alteration styles have been observed in basic lavas and volcaniclastic rocks of the Builth Volcanic Series of Ordovician age exposed at Llanelwedd Quarry, in the Builth lnlier, Wales. The first alteration style is characterized by the development of a mineral assemblage comprising albite+chlorite+ sphene+ pumpellyite ± prehnite ± calcite ± white mica, although original textures are largely preserved. This alteration pattern corresponds with that developed in volcanic and volcaniclastic rocks elsewhere in Wales, and which is attributed to the effects of burial. The second alteration style is characterized by the development of metadomains dominated by pumpellyite or, more rarely, prehnite. In the metadomains no original textures are seen in hand specimen. This alteration pattern has, so far, not been observed elsewhere in Wales, and it is here suggested that it might result from a submarine hydrothermal circulation system.