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1
Lee, T., V. Tremblay-Dionne, and LS Ko. "Ground effect on a slender reverse delta wing with anhedral." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 4 (February 8, 2018): 1516–25. http://dx.doi.org/10.1177/0954410017754147.
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The ground effect on the lift and drag forces and vortices generated by a slender reverse delta wing with different anhedrals was investigated experimentally. The study was inspired by the Lippisch-type RFB X-114 WIG (wing-in-ground effect) craft for which a reverse delta wing planform with anhedral was employed. The results show that, by positioning the trailing edges of the anhedraled reverse delta wing parallel to the ground, the lift and drag coefficients were found to increase persistently with increasing anhedral as the ground was approached (for ground distances within 40% chord). The observed lift augmentation was also accompanied by an ever-increasing rotational speed and total circulation of the vortices generated by the anhedraled wing. The vortices were also found to be displaced more outboard as the ground was approached, which further suggests their little relevance to the lift generation of the anhedraled reverse delta wing.
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Lee, T., LS Ko, and V. Tremblay-Dionne. "Effect of anhedral on a reverse delta wing." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 232, no. 12 (July 11, 2017): 2317–25. http://dx.doi.org/10.1177/0954410017715047.
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The effect of anhedral on the vorticity flowfield and aerodynamic loadings of a slender reverse delta wing was studied experimentally. The addition of anhedral always led to a reduced lift and lift-to-drag ratio in comparison with their clean-wing counterparts. The drag was increased with increasing anhedral compared to the clean wing at the same lift condition. The reverse delta wing vortex retained its regularity to a higher angle of attack as the anhedral was increased. The persistent outboard location of the reverse delta wing vortex suggests that the lift force was mainly produced by the pressure exerted on the bottom surface of the wing. The anhedral also led to an increased vorticity level and tangential velocity.
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Lee, T., D. Huitema, and P. Leite. "Ground effect on a cropped slender reverse delta wing with anhedral and Gurney flaplike side-edge strips." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 7 (June 8, 2018): 2433–44. http://dx.doi.org/10.1177/0954410018779504.
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The ground effect on the aerodynamic coefficients of a cropped slender reverse delta wing equipped with anhedral and Gurney flaplike side-edge strips was investigated experimentally at Re = 3.82 × 105. In a free stream, the 30% cropping was found to cause a minor reduction in lift CL and drag CD coefficients but a promoted stall compared to the noncropped wing. The anhedral caused further CL decrease and CD increase. Meanwhile, the application of side-edge strips produced a significantly increased CL and CD with a minor change to the CL/ CD ratio as compared to the baseline wing. In ground effect, the cropped wing was, however, found to generate more lift compared to the noncropped wing as the ground was approached. The joint anhedral and SES produced a great increment in both CL and CD but a virtually unchanged CL/ CD ratio compared to their outside ground effect counterparts. The larger the side-edge strips’ height the larger the increase in CL. In short, the cropping led to a weight reduction while the addition of anhedral and SES produced a large lift augmentation of the Lippisch-type wing-in-ground effect craft.
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Brugger, C. R., and J. E. Hammer. "Prevalence of growth twins among anhedral plagioclase microlites." American Mineralogist 100, no. 2-3 (February 1, 2015): 385–95. http://dx.doi.org/10.2138/am-2015-4809.
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Traub, L. W., R. Waghela, and K. A. Bordignon. "Characterisation of a highly staggered spanwise cambered biplane." Aeronautical Journal 119, no. 1212 (February 2015): 203–28. http://dx.doi.org/10.1017/s0001924000010344.
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AbstractAn investigation is presented to elucidate the performance of a staggered, spanwise cambered biplane. The spanwise camber yielded wings forming a ‘∧’ or ‘∨’ when viewed streamwise. The configuration is examined in terms of its aerodynamic and stability characteristics. The feasibility of negating the requirement for a conventional empennage is explored. Geometric variation encompassed front and back wing anhedral/dihedral angles yielding 49 combinations. Evaluation of the geometry was accomplished using both wind tunnel testing and numerical simulation. The results indicated that front wing dihedral in conjunction with aft wing anhedral was most beneficial, such that the benefit of wake spacing was maximised. Aerodynamic benefit was indicated compared to a conventional empennage geometry. The greatest disparity in behaviour of the fore and aft wing anhedral/dihedral distribution was in the high lift regime, where the nature of the stall varied. Simulations to establish the viability of the geometry in terms of controllability were also conducted and indicated that the configuration is viable.
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Kumar, M. Rohin, and C. Venkatesan. "Effects of rotor blade-tip geometry on helicopter trim and control response." Aeronautical Journal 121, no. 1239 (April 10, 2017): 637–59. http://dx.doi.org/10.1017/aer.2017.15.
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ABSTRACTFor performance improvement and noise reduction, swept and anhedral tips have been incorporated in advanced-geometry rotor blades. While there are aerodynamic benefits to these advanced tip geometries, they come at the cost of complicated structural design and weight penalties. The effect of these tip shapes on loads, vibration and aeroelastic response are also unclear. In this study, a comprehensive helicopter aeroelastic analysis which includes rotor-fuselage coupling shall be described and the analysis results for rotor blades with straight tip, tip sweep and tip anhedral shall be presented and compared. The helicopter modelled is a conventional one with a hingeless single main rotor and single tail rotor. The blade undergoes flap, lag, torsion and axial deformations. Tip sweep, pretwist, precone, predroop, torque offset and root offset are included in the model. Aerodynamic model includes Peters-He dynamic wake theory for inflow and the modified ONERA dynamic stall theory for airloads calculations. The complete 6-dof nonlinear equilibrium equations of the fuselage are solved for analysing any general flight condition. Response to pilot control inputs is determined by integrating the full set of nonlinear equations of motion with respect to time. The effects of tip sweep and tip anhedral on structural dynamics, trim characteristics and vehicle response to pilot inputs are presented. It is shown that for blades with tip sweep and tip anhedral/dihedral, the 1/rev harmonics of the root loads reduce while the 4/rev harmonics of the hub loads increase in magnitude. Tip dihedral is shown to induce a reversal of yaw rate for lateral and longitudinal cyclic input.
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Kim, Ki‐Chung, and Inderjit Chopra. "Aeroelastic Analysis of Swept, Anhedral, and Tapered Tip Rotor Blades." Journal of the American Helicopter Society 37, no. 1 (January 1, 1992): 15–30. http://dx.doi.org/10.4050/jahs.37.15.
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Barker, William W., and Vernon J. Hurst. "Freeze etch replication of extracellular bacterial polymers adsorbed onto kaolinite." Proceedings, annual meeting, Electron Microscopy Society of America 51 (August 1, 1993): 52–53. http://dx.doi.org/10.1017/s0424820100146102.
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Freeze etch replication of experimental mixtures of euhedral kaolinite and pure cultures of polysaccharide and protein-producing bacteria reveals that surface textures formed by adsorption of extracellular bacterial polymers onto kaolinite surfaces resemble structures observed in natural estuarine clay rich sediments, where anhedral 0.1 micrometer clay surfaces are covered by anhedral masses and fibrous elements of organic material.All samples, were cryofixed in a Balzers QFD101 propane jet and replicated in a Balzers 360M freeze etch device. Etching occurred at −100°C for 45 sec. and replicas were created with 15 nm Pt @ 45 °, 15 sec. C @ 90°. Following 24 h digestion in cone. HF, replicas were mounted on Formvar-coated 100 mesh Cu grids, carbon-coated for thermal stability, and examined in a Philips STEM 400.Anionic mucopolysaccharide produced by pure cultures of encapsulated Klebsiella pneumoniae (ATCC 8044) readily adsorbed to both the basal (negative charge) and edge (positive charge) surfaces of kaolinite (Fig. 1).
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Traub, Lance W. "Effects of Anhedral and Dihedral on a 75-deg Sweep Delta Wing." Journal of Aircraft 37, no. 2 (March 2000): 302–12. http://dx.doi.org/10.2514/2.2594.
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Barakos, G. N., and A. Jimenez Garcia. "CFD analysis of hover performance of rotors at full- and model-scale conditions." Aeronautical Journal 120, no. 1231 (June 13, 2016): 1386–424. http://dx.doi.org/10.1017/aer.2016.58.
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ABSTRACTAnalysis of the performance of a 1/4.71 model-scale and full-scale Sikorsky S-76 main rotor in hover is presented using the multi-block computational fluid dynamics (CFD) solver of Glasgow University. For the model-scale blade, three different tip shapes were compared for a range of collective pitch and tip Mach numbers. It was found that the anhedral tip provided the highest Figure of Merit. Rigid and elastic full-scale S-76 rotor blades were investigated using a loosely coupled CFD/Computational Structural Dynamics (CSD) method. Results showed that aeroelastic effects were more significant for high thrust cases. Finally, an acoustic study was performed in the tip-path-plane of both rotors, showing good agreement in the thickness and loading noise with the theory. For the anhedral tip of the model-scale blade, a reduction of 5% of the noise level was predicted. The overall good agreement with the theory and experimental data demonstrated the capability of the present CFD method to predict rotor flows accurately.
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Kumar, M. Rohin, and C. Venkatesan. "Effects of blade configuration parameters on helicopter rotor structural dynamics and whirl tower loads." Aeronautical Journal 120, no. 1224 (February 2016): 271–90. http://dx.doi.org/10.1017/aer.2015.11.
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ABSTRACTThe influence of the blade geometric parameters on the structural dynamic characteristics, response and loads of a helicopter rotor under hover condition in a whirl tower was investigated. A general geometry was considered for the rotor blade which included configuration parameters like root offset, torque offset, pre-twist, pre-cone, pre-droop, pre-sweep, tip-sweep and tip-anhedral. The option of placing concentrated masses at any location on the blade was also included. Natural frequencies and the corresponding mode shapes of the rotating blade were obtained by solving the linear, undamped structural dynamics model in the finite element domain. For calculating the response and loads on the rotor, the complete aeroelastic equation was solved in modal space. Aerodynamic models used in the aeroelastic loads calculations were Peters-He dynamic wake theory for inflow and themodifiedONERA dynamic stall theory for airloads calculations. From the study, the blade structural dynamic characteristics are found to be sensitive to variation in blade geometric parameters. Tip-sweep was found to have significant effects on root oscillatory moments. The moments at the tip junction with the straight portion of the blade were found to be substantially affected by tip-sweep and tip-anhedral.
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Clarke, D. B. "Cordierite in felsic igneous rocks: a synthesis." Mineralogical Magazine 59, no. 395 (June 1995): 311–25. http://dx.doi.org/10.1180/minmag.1995.059.395.15.
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AbstractCordierite is a characteristic mineral of many peraluminous felsic igneous rocks. A combination of T-P-X parameters, which overlap the stability conditions for felsic magmas, control its formation. Critical among these parameters are relatively low T, low P, and typically high (Mg+Fe2+), Mg/Fe2+, A/CNK, aAl2O3, and fO2. Spatial and textural information indicate that cordierite may originate in one of three principal ways in felsic igneous rocks: Type 1 Metamorphic: (a) xenocrystic (generally anhedral, many inclusions, spatial proximity to country rocks and pelitic xenoliths); (b) restitic (generally anhedral, high-grade metamorphic inclusions); Type 2 Magmatic: (a,b) peritectic (subhedral to euhedral, associated with leucosomes in migmatites or as reaction rims on garnet); (c) cotectic (euhedral, grain size compatibility with host rock, few inclusions); (d) pegmatitic (large subhedral to euhedral grains, associated with aplite-pegmatite contacts or pegmatitic portion alone); and Type 3 Metasomatic (spatially related to structural discontinuities in host, replacement of feldspar and/or biotite, intergrowths with quartz). Of these, Type 2a (peritectic) and Type 2c (cotectic) predominate in granitic and rhyolitic rocks derived from fluid-undersaturated peraluminous magmas, and Type 2d (pegmatitic) may be the most common type in fluid-saturated systems.
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Kogarko, Lia, and Troels F. D. Nielsen. "Chemical Composition and Petrogenetic Implications of Eudialyte-Group Mineral in the Peralkaline Lovozero Complex, Kola Peninsula, Russia." Minerals 10, no. 11 (November 20, 2020): 1036. http://dx.doi.org/10.3390/min10111036.
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Lovozero complex, the world’s largest layered peralkaline intrusive complex hosts gigantic deposits of Zr-, Hf-, Nb-, LREE-, and HREE-rich Eudialyte Group of Mineral (EGM). The petrographic relations of EGM change with time and advancing crystallization up from Phase II (differentiated complex) to Phase III (eudialyte complex). EGM is anhedral interstitial in all of Phase II which indicates that EGM nucleated late relative to the main rock-forming and liquidus minerals of Phase II. Saturation in remaining bulk melt with components needed for nucleation of EGM was reached after the crystallization about 85 vol. % of the intrusion. Early euhedral and idiomorphic EGM of Phase III crystalized in a large convective volume of melt together with other liquidus minerals and was affected by layering processes and formation of EGM ore. Consequently, a prerequisite for the formation of the ore deposit is saturation of the alkaline bulk magma with EGM. It follows that the potential for EGM ores in Lovozero is restricted to the parts of the complex that hosts cumulus EGM. Phase II with only anhedral and interstitial EGM is not promising for this type of ore. Nor is the neighboring Khibiny complex despite a bulk content of 531 ppm of Zr. Khibiny only has interstitial and anhedral EGM. The evolution of the Lovozero magma is recorded in the compositions EGM up through a stratigraphy of 2400 m in Phase II and III of the complex, and distinct in elements like rare earth elements (REE), Sr, Ba, Th, U, Rb, Mn, Fe. The compositional evolution reflects primarily fractional crystallization processes within the magma chamber itself in combination with convective magma flow and layering by precipitation of minerals with different settling velocities. The suggested mechanism for the formation of the EGM deposits is flotation of very small, suspended EGM crystals in the convective magma and concentration below the roof of the magma chamber. Phase III EGM is enriched in total REE (1.3%) and in HREE (Ce/Yt = 8.8) and constitutes a world class deposit of REE in the million tons of Phase III eudialyte lujavrites.
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DIX, GEORGE R. "Origin of anhedral Sr-rich calcite in deep-water mixed sediment, north-east Australia." Sedimentology 42, no. 5 (October 1995): 711–24. http://dx.doi.org/10.1111/j.1365-3091.1995.tb00404.x.
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Roy, D., Priyank Kumar, and Sudip Das. "Effect of Anhedral–Dihedral Angles on 76-40° Double-Delta Wing at Low Speeds." Journal of Aerospace Engineering 32, no. 6 (November 2019): 04019091. http://dx.doi.org/10.1061/(asce)as.1943-5525.0001079.
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Bryon, D. N., M. P. Atherton, M. J. Cheadle, and R. H. Hunter. "Melt movement and the occlusion of porosity in crystallizing granitic systems." Mineralogical Magazine 60, no. 398 (February 1996): 163–71. http://dx.doi.org/10.1180/minmag.1996.060.398.11.
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AbstractPorosity occlusion has been studied in a granodiorite rock from the Peruvian Coastal Batholith. The texture of the granodiorite is characteristic of Cordilleran I-type rocks, and the textural relations and modelled crystallization path within the quaternary An-Ab-Or-Qz system indicate alkali feldspar was the last major phase to start crystallizing. In thin section, alkali feldspar crystals occur both as large anhedral ‘plates’ containing numerous inclusions, and small interstitial cuneiform ‘pockets’. The alkali feldspar pockets are interpreted as late stage nucleation and growth of new crystals in pores that became isolated from the larger crystals during the latter stages of crystallization. Their geometry therefore mirrors that of the pores immediately after isolation.From the modal abundance of the interstitial pockets, and taking into account contemporaneous growth of the other major phases, it is suggested that crystallization in isolated pores involved solidification of the final 3–4% of liquid. Alkali feldspar growth on the rims of the large anhedral plates prior to pore isolation is evidence for the localised (mm-cm scale) diffusion of chemical species within the interconnected melt phase. However, Rayleigh number calculations indicate that the separation of melt from crystals by compositional convection is unlikely to have occurred during interstitial crystallization.
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CAMPOS, THOMAS, ANA MARGARIDA NEIVA, LAURO VALENTIM STOLL NARDI, LUCIANO SCHAEFFER PEREIRA, LEONARDO FRAGA BONZANINI, REINALDO PETTA, and FRANZ MICHAEL MEYER. "Magmatic Epidote and Amphibole from the Rio Espinharas Hybrid Complex, Northeastern Brazil." Pesquisas em Geociências 32, no. 2 (December 31, 2005): 41. http://dx.doi.org/10.22456/1807-9806.19545.
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The petrography and chemistry of epidote and amphibole from the Rio Espinharas hybrid complex (REHC), northeastern Brazil are reported. The Rio Espinharas complex is composed of an intimate association of diorite to shoshonitic metaluminous quartzmonzonite to slightly peraluminous syenogranite. The epidote shows four textural relationships: three are primary and one is resulting from sub-solidus reaction. Euhedral epidote is dispersed and associated mainly with biotite and amphibole. In some cases euhedral crystals of the epidote contain allanite cores, which are subhedral to anhedral and constitute in average less than 20% of the whole grain. The contact between primary epidote and plagioclase is corroded, suggesting reaction with the host-magma. Secondary anhedral epidote is rare and results from plagioclase alteration. The preservation of magmatic epidote in granitic rocks emplaced in the upper crust is attributed to rapid magma ascent, which implies fast upward transport probably by dyking associated to shear zone. The REHC occurs between two transcurrent faults that impose an elongated shape, suggesting that magma filled fractures. The time of 14 years required for dissolution zones of 0.15 mm width of epidote on porphyritic quartz monzonite, corresponds to an average ascent rate of ≥ 700 m year-1 from 7.1 to 2.9 kbar.
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Uluocak, Sinem, Mustafa Perçin, and Oğuz Uzol. "Experimental investigation of tip anhedral effects on the aerodynamics of a model helicopter rotor in hover." Aerospace Science and Technology 113 (June 2021): 106671. http://dx.doi.org/10.1016/j.ast.2021.106671.
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Erdmann, Saskia, D. Barrie Clarke, and Michael A. MacDonald. "Origin of chemically zoned and unzoned cordierites from the South Mountain and Musquodoboit Batholiths, Nova Scotia." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 95, no. 1-2 (March 2004): 99–110. http://dx.doi.org/10.1017/s026359330000095x.
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ABSTRACTTextural relations and chemical zoning of cordierites in granites act as sensitive recorders of the conditions of their crystallisation history and underlying magma chamber processes. In this contribution, we present new data on texturally distinct and variably zoned cordierites from the late-Devonian, granitic South Mountain and Musquodoboit Batholiths, and infer the conditions of their formation. Using a combined textural (grain size, grain shape and inclusion relationships) and chemical (major element composition and compositional zoning) classification, we recognise the following six cordierite types: CG1/TT1, anhedral to subhedral macrocrysts with random inclusions and patchy normal zoning; CG2a/TT2, euhedral to subhedral macrocrysts with random inclusions and normal zoning; CG2b/TT2, euhedral to subhedral macrocrysts with random or oriented inclusions, and oscillatory zoning; CG3a/TT3, subhedral to euhedral microcrysts with no inclusions and reverse zoning; CG3b/TT4, euhedral macrocrysts with no inclusions and no zoning; and CG4/TT5, anhedral macrocrysts with random inclusions and normal zoning. The textural criteria suggest that these cordierites formed as a product of cotectic crystallisation from a melt, or as the result of a peritectic reaction involving country-rock material. The combined chemical and textural criteria suggest that: (1) normal zoning results from cotectic crystallisation during cooling, cotectic overgrowths on grains formed in a peritectic reaction with country-rock material, or cation exchange with a fluid; (2) oscillatory zoning results from cotectic crystallisation during variations in XMg of the silicate melt following magma replenishment; (3) reverse zoning results from crystallisation during pressure quenching; and (4) the unzoned cordierite results from cotectic crystallisation under fluid-rich conditions.
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Novoselov, K. A., E. V. Belogub, and I. A. Blinov. "Te-canfieldite from the lunnoe au-u deposit (Aldan region, Republic of Yakutiya)." МИНЕРАЛОГИЯ (MINERALOGY) 5 (July 16, 2019): 49–56. http://dx.doi.org/10.35597/2313-545x-2019-5-2-49-56.
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Te-canfeldite was found in assemblage with pyrite, marcasite, hessite, and Tl sulfosalts in the ores of the Fedorovskaya vein zone of the Lunnoe Au-U deposit, Aldan shield (Yakutia). The mineral forms anhedral inclusions in vein matrix. Its refection spectrum is characterized by weak normal dispersion, the dispersion curve is almost parallel to the canfeldite curve, but the refectivity value is signifcantly higher. A sustained S:Te ratio of Te-canfldite is consistent with the analytical data for most mineral localities (Lengenbach, Sirotan, Nikolayevskoye, Uryakh). It is suggested that Te-canfeldite is formed in a wide range of geological settings.
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Uitterdijk Appel, Peter W. "Al-rich warwickite from lnglefield Land, North-West Greenland." Mineralogical Magazine 61, no. 408 (October 1997): 693–98. http://dx.doi.org/10.1180/minmag.1997.061.408.08.
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AbstractWarwickite constitutes about 5% of an outcrop of metamorphosed ultramafic rocks of Precambrian age in North-West Greenland. It occurs as slender grains, several millimetres long, and in anhedral grains up to 5 mm in size, together with forsterite, pleonaste, phlogopite, magnetite ± tourmaline. Post-metamorphic alteration of warwickite produced a network of boron-rich minerals and magnetite. The warwickite, containing up to 9.72% Al2O3, displays a significantly different chemical composition from warwickite elsewhere, such as that in recrystallized limestones from the type locality Warwick, New York, and in lamproitic and carbonatite-like rocks at Jumilla, Spain.
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Piccoli, Philip, Philip Candela, and Mark Rivers. "Interpreting magmatic processes from accessory phases: titanite—a small-scale recorder of large-scale processes." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 91, no. 1-2 (2000): 257–67. http://dx.doi.org/10.1017/s0263593300007422.
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In this study we examined variations in ore and other trace-metal concentrations in titanite, a ubiquitous product of magmatic (and subsequent sub-solidus) crystallisation in oxidised silicic magmas. Accessory titanite occurs in the Tuolumne Intrusive Suite (TIS), Sierra Nevada Batholith, as euhedral to anhedral, poikilitic, or interstitial grains. Zoned crystals of titanite were analysed by electron microprobe and synchrotron X-ray fluorescence for major and trace elements. Backscatter electron images reveal zoning, with bright areas correlating positively with total REE concentrations. REE concentrations generally decrease toward the edge of titanite crystals; however, some crystals are reversely zoned, and others exhibit oscillatory or patchy zoning; some grains contain discrete anhedral cores. Most elements in magmatic titanite decrease in concentration towards crystal rims, independent of host rock composition.At least one major reduction event in the magma chamber(s) transiently stabilised ilmenite, now present only as inclusions in titanite, and resulted in a reduction in the REE concentration in titanite. We suggest the hypothesis that the reduction in the REE concentration in these zones is due to the diminished activity of the (REE)Fe3+Ca−1Ti−1exchange component; however, the scatter in the data, together with the operation of other exchange vectors for Fe and Al, did not allow us to test this hypothesis herein. Secondary (i.e. sub solidus, hydrothermal) titanite can be recognised on the basis of its chemistry, sometimes by its anhedral form, and by its position as an alteration rim around primary magmatic phases; however, secondary titanite growth on primary titanite crystals may be harder to discern. Secondary titanite rims on magnetite contain higher Cr, Zr and Mo, and lower REE, relative to magmatic titanite. U/Th ratios increase toward the rim of most titanite grains; however, Th decreases in concentration from core to rim. This is due, most likely, to complications resulting from the coupled substitutions necessary for replacement of Ca by tetravalent Th; factors of this sort are commonly overlooked in trace element analysis.The analysed titanites are from rocks of the normally zoned TIS which ranges in87Sr/86Sri, from 0·7059 (tonalite and quartz-diorite) to 0·7066 (granite). Many element ratios in the titanites exhibit little to no functional dependence on87Sr/86Sri. However, log Mo/W increases with increasing87Sr/86Sri, of the host unit from the equigranular quartz-diorite and tonalite, to the interior granodiorites, possibly reflecting the greater crustal contribution to the interior, more felsic units. Neither Mo nor W increase significantly from core to rim in titanite. If these trends are indicative of the general behaviour of these elements duringin-situfractionation, then these data suggest that Mo and W are not strongly incompatible, and indeed may behave compatibly, in some titaniteand magnetite-bearing granodioritic magmas.
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Müller, Axel, Alfons M. van den Kerkhof, Hans-Jürgen Behr, Andreas Kronz, and Monika Koch-Müller. "The evolution of late-Hercynian granites and rhyolites documented by quartz – a review." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 100, no. 1-2 (March 2009): 185–204. http://dx.doi.org/10.1017/s1755691009016144.
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ABSTRACTThe potential of igneous quartz for providing a better understanding of magmatic processes is demonstrated by studying late-Hercynian rhyolites and granites from central and western Europe. Cathodoluminescence (CL) reveals growth patterns and alteration structures within igneous quartz reflecting the magma crystallisation history. The relatively stable and blue-dominant CL of zoned phenocrysts is principally related to variations in the Ti concentration, which is a function of the crystallisation temperature. The Al/Ti ratio of igneous quartz increases with progressive magma differentiation, as Ti is more compatible, compared to Al, Li, K, Ge, B, Fe, P during magma evolution. The red-dominant CL of the anhedral groundmass quartz in granite is unstable during electron bombardment and associated with OH- and H2O-bearing lattice defects. Thus, CL properties of quartz are different for rocks formed from H2O-poor and H2O-rich melts. Both groundmass and phenocrysts in granites are rich in alteration structures as a result of interaction with deuteric fluids during cooling, whereas phenocrysts in extrusive rocks do not usually contain such structures. The combined study of trace elements along with the analysis of quartz textures and melt inclusion inventories may reveal detailed PTX-paths of granite magmas. This study shows that quartz is a sensitive indicator for physico-chemical changes during the evolution of silicarich magmas. Common growth textures show a wide variety in quartz phenocrysts in rhyolites and some granites. This paper presents a classification of textures, which formed as a result of heterogeneous intra-granular lattice defects and impurities. The alternation of growth and resorption microtextures reflects stepwise adiabatic and non-adiabatic magma ascent, temporary storage of magma in reservoirs and mixing with more mafic, hotter magma. The anhedral groundmass quartz overgrowing early-magmatic phenocrysts in granites is free of growth zoning.
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Roberts, A. C., W. H. Paar, M. A. Cooper, D. Topa, A. J. Criddle, and J. Jedwab. "Verbeekite, monoclinic PdSe2, a new mineral from the Musonoi Cu-Co-Mn-U mine, near Kolwezi, Shaba Province, Democratic Republic of Congo." Mineralogical Magazine 66, no. 1 (February 2002): 173–79. http://dx.doi.org/10.1180/0026461026610020.
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AbstractVerbeekite, ideally PdSe2, monoclinic with space-group choicesC2/m,C2 orCm;a= 6.659(7),b= 4.124(5),c= 4.438(6) Å, ß = 92.76(3)°,V= 121.7(4) Å3;a:b:c= 1.6147:1:1.0761, Z = 2, is a new, very rare, primary mineral, intimately associated with secondary oosterboschite {(Pd,Cu)7Se5}, from the Musonoi Cu-Co-Mn-U mine, near Kolwezi, Shaba Province, Democratic Republic of Congo. Additional associated minerals are Cu- and Pd-bearing trogtalite {(Co,Cu,Pd)Se2}, Se-bearing digenite and Se-bearing covellite. The strongest five lines of the X-ray powder-diffraction pattern {din Å (I) (hkl)} are: 4.423(30)(001), 3.496 (30)(110), 2.718(100)(111), 1.955(50)(310 and 1.896(50)(l̄12). The mineral has also been identified, as a single anhedral 25 µm-sized grain, from Hope's Nose, Torquay, Devon, England where it is associated with native gold, chrisstanleyite Ag2Pd3Se4, oosterboschite(?), unnamed Pd2HgSe3and cerussite. At Musonoi, altered verbeekite grains do not exceed 200 µm in size and are anhedral, black, with a black streak and a metallic lustre. The mineral is opaque, brittle, has an uneven fracture, and lacks discernible cleavage. The VHN5ranges 490–610, mean 550 kp/mm2(2 indentations), roughly approximating a Mohs' hardness of 5Ý.Dcalc.= 7.211 g/cm3for the ideal formula. Electron-microprobe analyses (mean of 4 spot analyses) yielded Pd 39.6, Cu 0.5, Se 58.8, total 98.9 wt.%. The empirical formula is (Pd0.99Cu0.02)σ1.01Se1.99, based on Pd+Cu+Se = 3. In plane-polarized reflected light, the mineral is a nondescript grey and is neither pleochroic nor perceptibly bireflectant. Anisotropy is moderate with rotation tints in varying shades of brown. Reflectance spectra and colour values are tabulated. The name honours Dr Théodore Verbeek (1927–1991) who was the first geoscientist to study the Musonoi palladium mineralization in the Democratic Republic of Congo (1955–1967) and who co-discovered this new mineral phase.
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Maurice, Yvon T. "The significance of various garnet types in surficial materials in southeastern Gaspé Peninsula, Quebec." Canadian Journal of Earth Sciences 32, no. 6 (June 1, 1995): 730–40. http://dx.doi.org/10.1139/e95-062.
Full textAbstract:
The distribution patterns of four types of garnet in surficial materials of southeastern Gaspé Peninsula are interpreted in terms of the glacial history of the area, the lithostratigraphy of the bedrock, and mineral occurrences. Each type is derived from a distinct source, and all have undergone at least some southeastward glacial dispersion. Type 1 garnets, anhedral Ca-garnet fragments, are from the McGerrigle granite metamorphic aureole and were brought into the region by the same ice flow that caused the well-documented southward dispersal of granite debris. Their distribution within the study area depicts the southern part of this important dispersal train with an improved degree of precision. Type 2 garnets, Ca-garnet crystals, seem to be related to skarns within the boundaries of the study area; some patterns cannot be linked to any known source, thus providing challenging exploration opportunities. Type 3 garnets, colored pyralspite garnet crystals, are related to a tectonic breccia within the Maquereau–Mictaw contact zone. Type 4 garnets, Grenville-type anhedral garnets, were not brought into the region by Laurentide ice, as one might suspect, but rather seem to be related to specific horizons within the Silurian Lower Chaleurs Group. On the basis of a palinspastic reconstruction of southern Gaspé Peninsula and a plate tectonic model for the Paleozoic of eastern North America, we propose that these garnets were derived from the erosion of a metamorphic Grenvillian terrane, which presently forms the Northwestern Highlands Zone of Cape Breton Island. The distribution data for this garnet type also lends support to the concept put forth in a previous study whereby a local Late Wisconsinan ice mass penetrated some 5–6 km into the region from the southeast near Saint-Godefroi.
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Pollard, W. H., and H. M. French. "The Internal Structure and Ice Crystallography of Seasonal Frost Mounds." Journal of Glaciology 31, no. 108 (1985): 157–62. http://dx.doi.org/10.1017/s0022143000006407.
Full textAbstract:
AbstractThe crystal character of the ice core within frost blisters supports the hypothesis that groundwater injection into residual zones of the active layer followed by rapid freezing is the primary growth mechanism for these features. The ice core is characterized by an upper zone of relatively small randomly arranged equigranular ice crystals which change with increasing depth to columnar anhedral crystals, commonly exceeding 200 mm in length, and with crystal diameters ranging between 25 and 35 mm. Petrofabric analyses show that thec-axis orientations are normal to crystal elongations, with crystal growth along the basal plane in ana-axis direction. These observations eliminate ice segregation as a possible growth mechanism, thereby distinguishing seasonal frost mounds from palsas.
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Pollard, W. H., and H. M. French. "The Internal Structure and Ice Crystallography of Seasonal Frost Mounds." Journal of Glaciology 31, no. 108 (1985): 157–62. http://dx.doi.org/10.3189/s0022143000006407.
Full textAbstract:
AbstractThe crystal character of the ice core within frost blisters supports the hypothesis that groundwater injection into residual zones of the active layer followed by rapid freezing is the primary growth mechanism for these features. The ice core is characterized by an upper zone of relatively small randomly arranged equigranular ice crystals which change with increasing depth to columnar anhedral crystals, commonly exceeding 200 mm in length, and with crystal diameters ranging between 25 and 35 mm. Petrofabric analyses show that the c-axis orientations are normal to crystal elongations, with crystal growth along the basal plane in an a-axis direction. These observations eliminate ice segregation as a possible growth mechanism, thereby distinguishing seasonal frost mounds from palsas.
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Mitchell, Roger H., and Henry O. A. Meyer. "Niobian K–Ba–V titanates from micaceous kimberlite, Star mine, Orange Free State, South Africa." Mineralogical Magazine 53, no. 372 (September 1989): 451–56. http://dx.doi.org/10.1180/minmag.1989.053.372.04.
Full textAbstract:
AbstractCompositional data are presented for Nb-Ba-K-V titanates from micaceous kimberlite (Star mine, S. Africa). These data significantly extend the previously known range of solid solutions in naturally occurring members of the hollandite group. Two distinct suites of crystals occur. One is a suite of primary groundmass prismatic crystals that are Ba-K-V-rich and represent solid-solutions from the priderite series towards mannardite. The second suite consists of anhedral xenocrysts that are Ba-free. In this suite relatively Nb-rich varieties (>4.0% Nb2O5) represent solid-solution towards a niobian-bearing potassian analogue of mannardite, whereas relative Nb-poor (<3.0% Nb2O5) varieties are Nb-bearing vanadian priderites. These hollandite-group minerals have compositions that differ significantly from priderites found in lamproites.
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Kaur, Gurmeet, and R. H. Mitchell. "Mineralogy of the P2-West ‘Kimberlite’, Wajrakarur kimberlite field, Andhra Pradesh, India: kimberlite or lamproite?" Mineralogical Magazine 77, no. 8 (December 2013): 3175–96. http://dx.doi.org/10.1180/minmag.2013.077.8.11.
Full textAbstract:
AbstractA detailed mineralogical examination of representative material from the P2-West 'kimberlite' located in the Wajrakarur Kimberlite Field (India) demonstrates that significant differences exist between these rocks and archetypal hypabyssal kimberlite. The intrusion consists of an olivine-phyric facies which has been transected by, and includes clasts of, a consanguineous phlogopite-rich pegmatitic facies. The olivine-rich parts of P2-West are relatively fresh and consist of euhedral-to-subhedral microphenocrystal olivine set in a groundmass of fine-grained anhedral monticellite, amoeboid apatite, and subhedral-to-euhedral perovskite within a partially chloritized-to-fresh phlogopite-rich mesostasis. The rock lacks the abundant olivine macrocrysts characteristic of kimberlite. Monticellite crystals are commonly partially or completely replaced by pectolite and hydrogarnet. Similar material occurs as irregular aggregates randomly scattered throughout the groundmass. The groundmass, in contrast to that of hypabyssal kimberlites, is relatively poor in spinels. Atoll spinels are absent, with the majority of spinels occurring principally as mantles upon microphenocrystal olivine. Disaggregated cumulate-like assemblages of intergrown anhedral perovskite and spinel are common. Spinel compositions are unlike those of kimberlites and their evolutionary trend is similar to that of lamproite and lamprophyre spinels. The pegmatitic facies of the intrusion are highly and pervasively altered, and characterized by the presence of large clasts, veins, and irregular aggregates consisting of large (1–5 mm) crystals of pinkish-bronze Al-poor phlogopite intergrown with and/or including: apatite; pectolite-hydrogarnet pseudomorphs after an unidentified euhedral phase; chlorite laths; barytolamprophyllite; perovskite; tausonite; diverse Sr-Ba-carbonates; and baryte. The presence of barytolamprophyllite and tausonite are typical of potassic undersaturated alkaline rocks and have never been reported from kimberlite; however, neither feldspar nor feldspathoids are present in P2-West. Micas in fresh and altered rocks are Al2O3- and BaO-poor, and exhibit compositional evolutionary trends towards tetraferriphlogopite rather than kinoshitalite. On the basis of these mineralogical data it is suggested that P2-West represents an unusual lamproite-like intrusion which has undergone extensive hydrothermal deuteric alteration and should not be considered a bona fide kimberlite.
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Kasatkin, A. V., and R. Škoda. "Terrywallaceite from the Kochkar Au Deposit, South Urals: First Find in Russia." МИНЕРАЛОГИЯ (MINERALOGY) 6, no. 1 (March 30, 2020): 47–57. http://dx.doi.org/10.35597/2313-545x-2020-6-1-4.
Full textAbstract:
Terrywallaceite, AgPb(Sb,Bi)3S6, a rare sulfosalt of the lillianite homologous series, was found in a sample from the Kochkar Au deposit (Chelyabinsk oblast). It occurs as anhedral grains up to 0.4 × 0.3 mm and is associated with Sb-bearing bismuthinite, tetrahedrite-(Fe), arsenopyrite and minerals of the tintinaite–kobellite series. Its average empirical formula based on eight analyses is as follows: (Ag0.97Cu0.07)Σ1.04(Pb0.94Cd0.02)Σ0.96(Bi1.84Sb1.17)Σ3.01(S5.99Se0.01)Σ6.00.The monoclinic unit cell dimensions are a = 6.992(2), b = 19.328(4), c = 8.381(10) Å, β = 107.68(7)°, V = 1079(1)ų. This is the first reliable find of the mineral in Russia. Figures 3. Tables 3. References 24. Key words: terrywallaceite, Kochkar Au deposit, South Urals, first find of mineral in Russia, lillianite homologous series.
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Cardenes, Victor, Raúl Merinero, Álvaro Rubio-Ordoñez, Veerle Cnudde, Javier García-Guinea, and Iain K. Pitcairn. "A Morphological and Size-Based Study of the Changes of Iron Sulfides in the Caples and Torlesse Terranes (Otago Schist, New Zealand) during Prograde Metamorphic Evolution." Minerals 10, no. 5 (May 19, 2020): 459. http://dx.doi.org/10.3390/min10050459.
Full textAbstract:
It is widely accepted that metamorphism induces a remobilization of iron sulfides, sweeping away original ones while creating new ones. This paper analyzes size distributions of iron sulfides in several samples from the Caples and Torlesse terranes from the Otago Schist (New Zealand) using high-resolution X-ray computed tomography, which allows all iron sulfides larger than the resolution at which X-ray scans were performed to be characterized. Framboids and clusters of framboids are common in unmetamorphosed samples, but disappear in greenschist/amphibolite facies samples, where iron sulfides have anhedral habits. By contrast, the size and standard deviation of the new iron sulfides both remain within the same range. The results illuminate the evolution of iron sulfides throughout metamorphism, proposing boundaries for the metamorphic processes based on the shape of these iron sulfides.
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Keep, Myra, and J. K. Russell. "Mesozoic alkaline rocks of the Averill plutonic complex." Canadian Journal of Earth Sciences 29, no. 11 (November 1, 1992): 2508–20. http://dx.doi.org/10.1139/e92-197.
Full textAbstract:
The 150 Ma Averill alkaline plutonic complex is situated in southern British Columbia within the Intermontane Belt of the Canadian Cordillera. It comprises concentrically arranged phases of pyroxenite, monzogabbro, monzodiorite, monzonite, and syenite. Gradational changes in the modal composition of the phases contrast with an abrupt change in crystallinity from euhedral mafic minerals in the ultramafic–mafic phases to an anhedral, interstitial habit for mafic minerals in the syenite. Whole-rock compositions have clear alkaline affinities (e.g., feldspathoid normative) and indicate a chemical discontinuity between the ultramafic–mafic phases and the late syenite phases. Melanite garnet is an important accessory mineral of the syenite and is characteristic of silica-undersaturated alkaline intrusions. Clinopyroxene, feldspar, amphibole, biotite, melanite, and titanite compositions compare closely with those of other alkaline complexes in the western Cordillera.
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Kotula, Piotr. "Stibnite vein from Dębowina near Bardo (polish Sudetes)." Contemporary Trends in Geoscience 2, no. 1 (September 1, 2013): 28–33. http://dx.doi.org/10.2478/ctg-2014-0004.
Full textAbstract:
Abstract In the contact zone of the Bardo Structure and Kłodzko-Złoty Stok Intrusion and Kłodzko Metamorphic, metasomatic orebearing quartz-carbonate veins rich in Sb, Zn, Cu, Ag, Au, Pb are present. In 1771 the mine ,,Reiche Silber Gluck” within stibnite vein was founded in Dębowina near Bardo. Its entrance was discovered again in 2007. The stibnite vein is mainly build of stibnite and sphalerite and of quartz and dolomite rich in Mn. Stibnite crystallizes as columnar or forming radiate centres and aciculars. Its crystals reach size to 2 mm. Sphalerite appears as individual anhedral and polymineralic grained concentrations reaching size to 2,5 mm. Earlier pyrite and arsenopyrite crystallized - they occur locally in this deposit. There were found also in the deposit tetrahedrite rich in Ag, what wasn't reported earlier in studies from the mine in Dębowina.
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Oliveira, F. S., A. F. D. C. Varajão, C. A. C. Varajão, and B. Boulangé. "A comparison of properties of clay minerals in isalteritic and in degraded facies." Clay Minerals 48, no. 5 (December 2013): 697–711. http://dx.doi.org/10.1180/claymin.2013.048.5.03.
Full textAbstract:
AbstractThe mineralogical, geochemical and micromorphological features of an isalteritic clay facies, which originated from weathering of an anorthosite, were compared to those of clay facies derived from the degradation of a bauxite developed from the same rock. The isalteritic clay was formed by the hydrolytic alteration of plagioclase, whereas the degraded clays were formed by decomposition of gibbsite and neoformation of kaolinite. This resilification process resulted from the reintroduction of silica via the oscillation of the phreatic level and/or the decomposition of organic matter on the surface. The degradation process was gradual and yielded two different facies: (a) degraded clays with almost total decomposition of gibbsite, and (b) degraded clays with gibbsite nodules. Morphologically, the isalteritic clays differ from the degraded clays because they contain larger hexagonal and pseudo-hexagonal crystals. The degraded clays have more irregular crystal shapes, ranging from laths to anhedral shapes.
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Yang, Zhijun, Rong Liang, Xiangqing Zeng, and Mingsheng Peng. "A Microscopy and FTIR and PL Spectra Study of Polycrystalline Diamonds from Mengyin Kimberlite Pipes." ISRN Spectroscopy 2012 (April 22, 2012): 1–10. http://dx.doi.org/10.5402/2012/871824.
Full textAbstract:
The results of a microscopy and FTIR and PL spectra study of the natural polycrystalline diamonds from the Mengyin kimberlite pipes show that they can be classified as the euhedral faceted polycrystalline diamonds (EFPCDs) and anhedral rounded polycrystalline diamonds (ARPCDs). Different diamond grains or their points were formed in different conditions or processes. They were not formed in diamond nucleation stage, but in the diamond growth period. They probably originated from the relatively deeper mantle and were formed in the environment like the peridotitic (P) type diamond single crystals. The EFPCDs did not undergo a remarkable dissolution process during their formation and were possibly fast formed shortly before the kimberlite eruption. The ARPCDs not only were formed at a higher temperature than the EFPCDs but also underwent a notable dissolution process and had been stored relatively longer in the mantle. Fluids or melts probably participated in the formation of the ARPCDs or modified them during the period of their storage in the mantle.
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Bauluz, B., M. J. Mayayo, A. Yuste, and J. M. González López. "Genesis of kaolinite from Albian sedimentary deposits of the Iberian Range (NE Spain): analysis by XRD, SEM and TEM." Clay Minerals 43, no. 3 (September 2008): 459–75. http://dx.doi.org/10.1180/claymin.2008.043.3.10.
Full textAbstract:
AbstractThe kaolinite from Albian sedimentary deposits (Escucha and Utrillas Formations) of the Iberian Range (Spain) have been investigated. This research has shown the presence of different types of kaolinites (detrital and diagenetic) along with micaceous phases in these deposits. Detrital kaolinites show anhedral morphology, low crystallinity and a degree of ordering as well as the presence of interstratified smectite layers. They constitute the matrix of the claystones and siltstones and were probably formed as a consequence of intense weathering processes in the source area during the warm period of the early Cretaceous. Diagenetic kaolinites have been recognized in the sandstones and siltstones, with kaolinite growing between ‘expanded’ mica flakes and vermiform and euhedral kaolinite forming the matrix. They have euhedral morphologies, high crystallinity and a high degree of ordering. They grewin situas a response to incipient diagenesis by K-feldspar dissolution and/or organic acid-rich fluids derived from the maturation of organic matter in shales.
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Gaspar, José C., Antônio J. G. Conceição e Silva, and Débora P. de Araújo. "Composition of priderite in phlogopitites from the Catalão I carbonatite complex, Brazil." Mineralogical Magazine 58, no. 392 (September 1994): 409–15. http://dx.doi.org/10.1180/minmag.1994.058.392.06.
Full textAbstract:
AbstractMagnetite grains with exsolved ilmenite lamellae may be replaced by pyrite or carbonate in phlogopitites of the Catalão I carbonatite complex, Goiás State, Brazil. The ilmenite is transformed in part to priderite and sometimes to rutile. Priderite occurs as small anhedral grains (< 0.2mm) or composite crystals associated with ilmenite and rutile. Chalcopyrite, magnetite, monazite, and pyrochlore also occur inside the area of original magnetite grains. The priderite belongs to the K2FeTi7O16-BaFeTi7O16 series with K/(K + Ba) ranging from 1.0 to 0.53. The highest contents for other elements are: V2O3 2.65, Cr2O3 4.1, and Nb2O5 1.98 wt.%. Priderites associated with magnetite have the highest V, Cr, and Nb contents whereas others have the highest Ba content. Zoning characterized by K-Ba substitution is patchy but always present. V-and Cr-poor priderites are similar in composition to priderites from lamproites, and the V- and Cr-rich ones are compositionally similar to hollandite-group minerals found in kimberlites.
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Cheney, Jorn A., Jonathan P. J. Stevenson, Nicholas E. Durston, Masateru Maeda, Jialei Song, David A. Megson-Smith, Shane P. Windsor, James R. Usherwood, and Richard J. Bomphrey. "Raptor wing morphing with flight speed." Journal of The Royal Society Interface 18, no. 180 (July 2021): 20210349. http://dx.doi.org/10.1098/rsif.2021.0349.
Full textAbstract:
In gliding flight, birds morph their wings and tails to control their flight trajectory and speed. Using high-resolution videogrammetry, we reconstructed accurate and detailed three-dimensional geometries of gliding flights for three raptors (barn owl, Tyto alba ; tawny owl, Strix aluco , and goshawk, Accipiter gentilis ). Wing shapes were highly repeatable and shoulder actuation was a key component of reconfiguring the overall planform and controlling angle of attack. The three birds shared common spanwise patterns of wing twist, an inverse relationship between twist and peak camber, and held their wings depressed below their shoulder in an anhedral configuration. With increased speed, all three birds tended to reduce camber throughout the wing, and their wings bent in a saddle-shape pattern. A number of morphing features suggest that the coordinated movements of the wing and tail support efficient flight, and that the tail may act to modulate wing camber through indirect aeroelastic control.
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Shitaoka, Yorinao, Masaya Miyoshi, Junji Yamamoto, Tomoyuki Shibata, Tsuneto Nagatomo, and Keiji Takemura. "Thermoluminescence age of quartz xenocrysts in basaltic lava from Oninomi monogenetic volcano, northern Kyushu, Japan." Geochronometria 41, no. 1 (March 1, 2014): 30–35. http://dx.doi.org/10.2478/s13386-013-0144-3.
Full textAbstract:
Abstract We determined the eruption age of basaltic rocks by application of thermoluminescence (TL) method, which is often used for TL dating, to quartz. Mafic magma only rarely includes quartz because of their mutual disequilibration. The basaltic lavas reported herein include quartz as xenocrysts, as corroborated by their rounded or anhedral shape. The basaltic lava used for this study is from the Oninomi monogenetic volcano in northern Kyushu, Japan. The volcano eruption was estimated as occurring 7.3–29 ka because the lava exists between two widespread tephras: Aira-Tanzawa ash (26–29 ka) and Kikai-Akahoya ash (7.3 ka). We succeed-ed in collecting ca. 200 mg of quartz by decomposition of 30 kg of the lava samples. TL measurements for the lava indicate the eruption age as 15.8 ± 2.5 ka, which is fairly consistent with the stratigraphical estimation. Although the TL method has played a considerable part in constraining the timescale of Quaternary events, its application has been limited to silicic samples. The present result demonstrates the availability of quartz for dating even of mafic rock.
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Oziegbe, E. J., O. O. Ocan, and A. O. Buraimoh. "Petrography of Allanite-bearing Tonalite from Iwo Region, Osun State, Nigeria." Materials and Geoenvironment 67, no. 2 (July 27, 2020): 79–89. http://dx.doi.org/10.2478/rmzmag-2020-0006.
Full textAbstract:
AbstractPrimary, secondary and accessory minerals in tonalitic rocks from Iwo region of the Precambrian Basement Complex of Southwestern Nigeria were identified and analysed with the aim of determining the various processes involved during the crystallisation of magma. Thin sections of tonalite were prepared and studied with the aid of a petrographic microscope. The mineral assemblages observed are biotite, plagioclase, alkali-feldspar, amphiboles, pyroxene, quartz, muscovite and chlorite. Allanite, titanite, apatite and zircon occur as accessory minerals. Muscovite and chlorite are found to be secondary minerals. The mineral allanite has a characteristic form of zoning and shows evidence of metamictisation, and is surrounded by dark-coloured biotite having radioactive haloes. Titanite is anhedral to subhedral crystals and forms reaction rim round opaque minerals. Plagioclase shows evidence of compositional zoning as well as plastic deformation of the twin lamellae. The allanite observed is primary in nature and has undergone radioactive disintegration; chlorite and muscovite are formed by secondary processes of chloritization and sericitisation, respectively. The tonalite is formed as a result of rapid cooling of magma close to the Earth's surface.
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Sinh, Vuong Bui Thi, Yasuhito Osanai, Christoph Lenz, Nobuhiko Nakano, Tatsuro Adachi, Elena Belousova, and Ippei Kitano. "Gem-Quality Zircon Megacrysts from Placer Deposits in the Central Highlands, Vietnam—Potential Source and Links to Cenozoic Alkali Basalts." Minerals 9, no. 2 (February 1, 2019): 89. http://dx.doi.org/10.3390/min9020089.
Full textAbstract:
Gem-quality zircon megacrysts occur in placer deposits in the Central Highlands, Vietnam, and have euhedral to anhedral crystal shapes with dimensions of ~3 cm in length. These zircons have primary inclusions of calcite, olivine, and corundum. Secondary quartz, baddeleyite, hematite, and CO2 fluid inclusions were found in close proximity to cracks and tubular channels. LA-ICP-MS U-Pb ages of analyzed zircon samples yielded two age populations of ca. 1.0 Ma and ca. 6.5 Ma, that were consistent with the ages of alkali basalt eruptions in the Central Highlands at Buon Ma Thuot (5.80–1.67 Ma), Pleiku (4.30–0.80 Ma), and Xuan Loc (0.83–0.44 Ma). The zircon geochemical signatures and primary inclusions suggested a genesis from carbonatite-dominant melts as a result of partial melting of a metasomatized lithospheric mantle source, but not from the host alkali basalt. Chondrite-normalized rare earth element patterns showed a pronounced positive Ce, but negligible Eu anomalies. Detailed hyperspectral Dy3+ photoluminescence images of zircon megacrysts revealed resorption and re-growth processes.
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Bush, Richard T., and Leigh A. Sullivan. "Pyrite micromorphology in three Australian Holocene sediments." Soil Research 37, no. 4 (1999): 637. http://dx.doi.org/10.1071/sr98113.
Full textAbstract:
The distribution and morphology of pyrite in 3 Holocene estuarine sediments were examined using light microscopy, analytical scanning electron microscopy, and X-ray diffraction. The distribution and morphologies of pyrite were similar with pyrite being dispersed throughout the soil matrices as well as concentrated in root remnants and other macropores. The pyrite occurred in both framboidal and irregularly shaped dense clusters from 4 to 15 µm diameter, and also in loose clusters. Individual crystals in these clusters ranged in size from 1 to 2 µm. Pyrite crystals exhibited octahedral, pyritohedral, and equant anhedral (i.e. rounded globular) habit. Organic matter coatings and clay coatings were common around pyrite at each site. Thin coatings of monosulfide with an acicular morphology occurred around some framboidal clusters at one site. The distribution of framboids and individual crystals in the clayey matrix, root remnants, and other macropores indicates that the pyrite in these sediments has formed in situ. These data have important implications for the rate of sulfide oxidation and acid production from these soils.
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Jones, Brian. "Calcite rafts, peloids, and micrite in cave deposits from Cayman Brae, British West Indies." Canadian Journal of Earth Sciences 26, no. 4 (April 1, 1989): 654–64. http://dx.doi.org/10.1139/e89-056.
Full textAbstract:
Speleothemic deposits from the Oligocene–Miocene Bluff Formation of Cayman Brae include calcite rafts that formed in cave pools. The rafts, which formed at the surface of the cave pools where rapid degassing of CO2 from the surface waters led to the precipitation of the calcite, can be divided into single- or double-sided spar calcite rafts and symmetrical, asymmetrical, or composite micrite – spar calcite rafts. Agitation of the water caused the rafts to sink and accumulate on the floor of the pool.Cavities formed by stacking of the calcite rafts are filled or partly filled with spar calcite, micrite, peloids, and terra rossa glaebules. The micrite laminae, like those in the micrite – spar calcite rafts, probably formed through the merger of peloids, which are formed of either subhedral to euhedral crystals or anhedral to subhedral grains. Available petrographic evidence suggests that the micrite and the peloids formed by precipitation from cave water. This example demonstrates that high-magnesium calcite peloids are not necessarily indicative of early marine diagenesis in reefs.
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Wang, Qing, and Qijun Zhao. "Rotor blade aerodynamic shape optimization based on high-efficient optimization method." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 234, no. 2 (July 26, 2019): 375–87. http://dx.doi.org/10.1177/0954410019865700.
Full textAbstract:
In order to design a high-performance rotor, a high-efficient optimization method is established by coupling Kriging model and sequential quadratic programming with high-accuracy computational fluid dynamics method. In order to obtain the global optimal design point, the initial blade shape is optimized by using the Kriging model coupled with genetic algorithm based on the baseline rotor blade (Helishape 7A rotor). After that, the modified sequential quadratic programming method is employed to search the final blade shape based on the initial blade shape deeply. In the optimal process, the regions of design variables are restricted considering rotor dynamic characteristics. As a result, a new shape of rotor blade with characters of nonlinear twist, variational chord length, complex swept, and anhedral distributions is obtained. Compared with the baseline rotor, blade-tip vortex of the final optimized rotor is significantly weakened, the figure of merit of the final optimized rotor increases about 3.42%, and the peak of sound pressure decreases about 16.9%. At the same time, it is demonstrated that the final optimized rotor has better forward flight characteristics.
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Chang, Shih-Bin R., Clarence R. Allen, and Joseph L. Kirschvink. "Magnetic Stratigraphy and a Test for Block Rotation of Sedimentary Rocks within the San Andreas Fault Zone, Mecca Hills, Southeastern California." Quaternary Research 27, no. 1 (January 1987): 30–40. http://dx.doi.org/10.1016/0033-5894(87)90047-0.
Full textAbstract:
AbstractA 500-m section of the Palm Spring Formation in the southern Mecca Hills, located within the San Andreas fault zone in southeastern California, has been paleomagnetically sampled to determine possible tectonic rotation in this area and to establish time-stratigraphic control. This work was partly stimulated by the fact that 80 km farther south, previous studies demonstrated 35° of postdepositional rotation in the Palm Spring Formation of the Vallecito-Fish Creek basin east of the Elsinore fault. Several lines of evidence suggest that hematite is the main magnetic carrier of the Mecca Hills samples. Large anhedral hematite grains observed in magnetic extracts and a positive fold test imply a detrital origin of the remanence. The polarity reversal patterns, together with earlier vertebrate paleontologic studies, restrict the time span for deposition of this unit to the middle-late Matuyama chron (2.0–0.75 myr ago), thus of uppermost Pliocene and early Pleistocene age. Characteristic directions of best least-squares fit for 73 samples suggest little or no overall rotation, despite the severe late Quaternary tectonic activity demonstrated by the intense deformation of these strata.
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Števko, Martin, Jiří Sejkora, and Ľudovít Dojčanský. "New data on sulphosalts from hydrothermal siderite-type veins in the Spišsko-gemerské rudohorie Mts. (eastern Slovakia): 1. Nuffieldite and aikinite from Slovinky-Došťavná vein." Bulletin Mineralogie Petrologie 29, no. 1 (2021): 108–14. http://dx.doi.org/10.46861/bmp.29.108.
Full textAbstract:
A new occurrence of nuffieldite was recently discovered in a siderite-type hydrothermal vein with sulphides in Došťavná near Slovinky, Spišsko-gemerské rudohorie Mts., Spišská Nová Ves Co., Košice Region, Slovakia. It forms lead-gray acicular crystals reaching up to 1 cm in size or aggregates up to 2.5 cm, which are enclosed in quartz-siderite matrix together with chalcopyrite, pyrite, tourmaline and chlorite. Nuffieldite is frequently replaced by minor aikinite, galena and native bismuth. The refined unit-cell parameters of nuffieldite (for the orthorhombic space group Pbnm) are: a 14.5313(16) Å, b 21.454(2) Å, c 4.0500(6) Å and V 1262.58(19) Å3. The average (n=145 analyses) empirical formula of nuffieldite from Slovinky-Došťavná based on Pb+Bi+Sb = 5 apfu is corresponding to Cu1.30Pb2.00Bi2.00(Pb0.30Bi0.30 Sb0.40)1.00(S7.12Se0.03)7.15. Aikinite forms microscopic, anhedral to subhedral grains or aggregates replacing nuffieldite. The average (n=29) empirical formula of studied aikinite based on (Cu+Pb)/2+(Sb+Bi) = 8 apfu is Pb3.83Cu3.76(Bi4.12 Sb0.09)4.21(S12.40Se0.03)12.03.
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Jamei, Saeed, Adi Maimun, Rasul Niazmand Bilandi, Nor Azwadi, Simone Mancini, Luigi Vitiello, and Maria De Carlini. "Wake behind a Compound Wing in Ground Effect." Journal of Marine Science and Engineering 8, no. 3 (March 1, 2020): 156. http://dx.doi.org/10.3390/jmse8030156.
Full textAbstract:
Flow structure is a crucial point for the conceptual design of Wing-in-Ground effect (WIG) crafts. In this study, pressure distributions around a compound wing, velocity and the turbulent intensity distribution in the wake area after trailing of the wing, have been investigated numerically. Computational simulations were completed regarding various angles of attack in-ground-effect. Two parts made up the compound wing: The first composed by one rectangular wing in the center, the second composed by a reverse taper wing, consisting of an anhedral angle at the side. A realizable k-ε turbulent model exhibited the flow field in the physical domain about the wing surface. The numerical results of the compound wing were validated using the data provided by wind tunnel tests. The flow structures around the compound wing were compared with that of a rectangular wing for different conditions. It was found that the pressure distribution on the rectangular wing was weaker than at the lower surface for the compound wing. However, the suction effect on the upper surface of the rectangular wing was higher. Also, the velocity defect and the turbulence level in the wake area was greater behind the compound wing.
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Feng, Yonggang, Ting Liang, Xiuqing Yang, Ze Zhang, and Yiqian Wang. "Chemical Evolution of Nb-Ta Oxides and Cassiterite in Phosphorus-Rich Albite-Spodumene Pegmatites in the Kangxiwa–Dahongliutan Pegmatite Field, Western Kunlun Orogen, China." Minerals 9, no. 3 (March 8, 2019): 166. http://dx.doi.org/10.3390/min9030166.
Full textAbstract:
The Kangxiwa–Dahongliutan pegmatite field in the Western Kunlun Orogen, China contains numerous granitic pegmatites around a large granitic pluton (the Dahongliutan Granite with an age of ca. 220 to 217 Ma), mainly including barren garnet-, tourmaline-bearing pegmatites, Be-rich beryl-muscovite pegmatites, and Li-, P-rich albite-spodumene pegmatites. The textures, major element contents, and trace element concentrations of columbite-group minerals (CGM) and cassiterite from three albite-spodumene pegmatites in the region were investigated using a combination of optical microscopy, SEM, EPMA and LA-ICP-MS. The CGM can be broadly classified into four types: (1) inclusions in cassiterite; (2) euhedral to subhedral crystals (commonly exhibiting oscillatory and/or sector zoning and coexisting with magmatic cassiterite); (3) anhedral aggregates; (4) tantalite-(Fe)-ferrowodginite (FeSnTa2O8) intergrowths. The compositional variations of CGM and cassiterite are investigated on the mineral scale, in individual pegmatites and within the pegmatite group. The evolution of the pegmatites is also discussed. The variation of Nb/Ta and Zr/Hf ratios of the cassiterite mimics the Nb-Ta and Zr-Hf fractionation trends in many LCT pegmatites, indicating that these two ratios of cassiterite may bear meanings regarding the pegmatite evolution.
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Elton, N. J., J. J. Hooper, and V. A. D. Holyer. "An occurrence of stevensite and kerolite in the Devonian Crousa gabbro at Dean Quarry, The Lizard, Cornwall, England." Clay Minerals 32, no. 2 (June 1997): 241–52. http://dx.doi.org/10.1180/claymin.1997.032.2.06.
Full textAbstract:
AbstractStevensite has been found at Dean Quarry, The Lizard, Cornwall, associated intimately with the disordered, hydrated variety of talc known as kerolite. Both minerals occur as pseudomorphs after pectolite and as microcrystalline anhedral masses filling cavities and veins in gabbro. Associated minerals include calcite and prehnite. The XRD data show that stevensite occurs as a physical mixture with kerolite, rather than as mixed-layer stevensite-kerolite. Kerolite is unaffected by glycerol treatment whilst stevensite readily expands: this test provides the only reliable distinction between the two minerals. Differences in IR and chemical data for stevensite and kerolite are subtle; data are broadly similar to those in the literature. Both minerals are readily decomposed to amorphous silica by hot concentrated HCl. Stevensite dehydroxylated at 400°C for 1.5 h is virtually indistinguishable from kerolite. The Dean Quarry occurrence is similar to many others worldwide. Stevensite and kerolite formed after prehnite, calcite, analcime, pectolite and natrolite during a phase of decomposition and alteration of these earlier minerals. ‘Stevensite’ from the first British occurrence in the Whin Sill, North Tyne, has been re-examined and appears to be kerolite or ‘hydrated-talc’.
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Eric, S., D. Milovanovic, and D. Babic. "GARNETS OF MICA-SCHISTS FROM CRNI VRH AND RESAVSKI HUMOVI (SERBIA)." Bulletin of the Geological Society of Greece 36, no. 1 (January 1, 2004): 552. http://dx.doi.org/10.12681/bgsg.16752.
Full textAbstract:
Metamorphic rocks of the Crni Vrh and Resavski Humovi area belong to the north-northwestern part of the Serbo-Macedonian Composite Terrane and consist of different types of mica-schists, gneisses and amphibolites. Mica-schists are composed of biotite, muscovite, garnet, staurolite, kyanite, small quantity of Kfeldspar, acid plagioclase and quartz. Accessory minerals are apatite, zircon, tourmaline and ilmenite. Garnets in mica-schists from both localities occur as subhedral to anhedral porphyroblasts from 0.2 to 10mm in size. Most garnets are oriented parallel to the dominant foliation. Garnets from the Crni Vrh mica-schists contain more spesartine component than garnets from Resavski Humovi, while almandine component show opposite tendency. The difference between those garnets is clearly visible, as well as zonality expressed through the increase of almandine component from center to the grain rim. The spesartine component as mentioned above, shows the opposite tendency. Using different geothermometers and geobarometers it was found that mica-schists from Crni Vrh were formed at temperatures from 550-600°C and pressures from 6-6.2 kbar, while micaschists from Resavski Humovi developed at slightly lower temperatures (520-560°C) and at some higher pressures (7-7.3 kbar).