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1

Ion-microprobe dating of zircon from quartz-graphite veins at the Bristol, New Hampshire, metamorphic hot spot  

SciTech Connect

Detrital zircons entrained in hydrothermal quartz-graphite-rutile veins found near the Bristol, New Hampshire, metamorphic hot spot are overgrown by thin rims. Ion-microprobe analyses of these rims date their growth at 408 {plus minus} 6 Ma. These measurements quantitatively confirm textural evidence that the graphite veins were emplaced during peak metamorphism associated with the Acadian orogeny, and they provide a direct positive test of the hypothesis, based on petrological and stable-isotope evidence, that the hydrothermal systems responsible for the quartz-graphite veins were also responsible for the hot-spot metamorphism.

Zeitler, P.K. (Australian National Univ., Canberra (Australia)); Barreiro, B.; Chamberlain, C.P. (Dartmouth College, Hanover, NH (USA)); Rumble, D. III (Geophysical Laboratory, Washington, DC (USA))

1990-07-01

2

Investigating the strengthening of quartz ceramics by hydrothermal treatment  

Microsoft Academic Search

Increasing application of quartz ceramics is accompanied by an increase in the dimensions of the articles, in the complexity of their shapes, a constant increase in demands placed on dimensional accuracy, and also the need to reduce energy expenditure. As a result of all this, extensive use can be found for precision technology in strengthening the components by hydrothermal treatment

S. M. Itkin; V. V. Vikulin

1993-01-01

3

Emerald mineralization and metasomatism of amphibolite, khaltaro granitic pegmatite - Hydrothermal vein system, Haramosh Mountains, Northern Pakistan  

USGS Publications Warehouse

Emerald mineralization is found within 0.1- to 1-m-thick hydrothermal veins and granitic pegmatites cutting amphibolite within the Nanga Parbat - Haramosh massif, in northern Pakistan. The amphibolite forms a sill-like body within garnet-mica schist, and both are part of a regional layered gneiss unit of Proterozoic (?) age. The 40Ar/39Ar data for muscovite from a pegmatite yield a plateau age of 9.13 ?? 0.04 Ma. Muscovite from mica schist and hornblende from amphibolite yield disturbed spectra with interpreted ages of 9 to 10 Ma and more than 225 Ma, respectively, which indicate that peak Tertiary metamorphism reached 325 to 550??C prior to 10 Ma. Pegmatites were emplaced after peak metamorphism during this interval and are older than pegmatites farther south in the massif. At Khaltaro, simply zoned albite-rich miarolitic pegmatites and hydrothermal veins containing various proportions of quartz, albite, tourmaline, muscovite, and beryl are associated with a 1- to 3-m-thick heterogeneous leucogranite sill, that is locally albitized. The pegmatites likely crystallized at 650 to 600??C at pressures of less than 2 kbar. Crystals of emerald form within thin (0.20, 0.54-0.89 wt%), to pale blue beryl (<0.07, 0.10-0.63%), to colorless beryl (<0.07, 0.07-0.28%). The amphibolite is metasomatized in less than 20-cm-wide selvages that are symmetrically zoned around veins or pegmatites. A sporadic inner zone containing F-rich biotite, tourmaline, and fluorite, with local albite, muscovite, quartz, and rare beryl, gives way to an intermediate zone containing biotite and fluorite with local plagioclase and quartz, and to an outer zone of amphibolite containing sparse biotite and local quartz. The inner and intermediate zones experienced gains of K, H, F, B, Li, Rb, Cs, Be, Ta, Nb, As, Y and Sr, and losses of Si, Mg, Ca, Fe, Cr, V and Sc. The outer alteration zone has gained F, Li, Rb, Cs, and As. Oxygen isotope analyses of igneous and hydrothermal minerals indicate that a single fluid of magmatic origin with ??18OH2O = 8??? produced the pegmatite-vein system and hydrothermal alteration at temperatures between 550 and 400??C. The formation of emerald results from introduction of HF-rich magmatic-hydrothermal fluids into the amphibolite, which caused hydrogen ion metasomatism and released Cr and Fe into the pegmatite-vein system.

Laurs, B. M.; Dilles, J. H.; Snee, L. W.

1996-01-01

4

Formation of Quartz-Carbonate Veins: Evidence From Experimental Supercritical Carbon Dioxide-Brine-Rock System  

NASA Astrophysics Data System (ADS)

Quartz-carbonate veins are common in a variety of moderate temperature hydrothermal systems and ore deposits. Associated fluid inclusions have a wide range of compositions, including liquid carbon dioxide fillings. Examination of chemical and physical conditions which result precipitation of quartz and carbonate in veins raises several key questions about multiphase fluid processes and reaction rates. We have been experimentally investigating physical-chemical reaction processes of mixed brine-carbon dioxide fluids for the shallow crust. Synthetic arkose (microcline + oligoclase + quartz + biotite) plus argillaceous shale were reacted with 5.5 molal NaCl brine. The system was held at 200 C and 200 bars for 32 days to approach steady state, then injected with carbon dioxide and allowed to react for an additional 45 days. In a parallel experiment, the system was allowed to react for 77 days without injection of carbon dioxide. Trace ions initially absent from NaCl brine appeared in solution at mM (K, Ca, and silica) to uM (Mg, Al, Fe and Mn) quantities, reflecting reaction of brine with rock. Without carbon dioxide injection, the silica concentration (2.4 mM) was stable below calculated quartz solubility (3.9 mM). Injection of carbon dioxide resulted in decreased pH and increased silica concentration to a level near calculated chalcedony solubility (5.4 mM). Dissolution of silicate minerals is apparently coupled to the acidity, and concomitant inhibition of the precipitation of quartz (and other silicates). A significant increase in concentration of trace metals is consistent with in-situ pH decrease and increased carbon dioxide dissolved in brine. Multi-phase fluid reaction relationships between supercritical carbon dioxide and brine-rock systems allow formation of carbonate vein precipitates in substantial quantities. Brine and continued rock reactions provide a substantial reservoir for Ca, Mg and Fe components. A separate carbon dioxide liquid allows precipitation from relatively small volumes of total fluid, with coupled increases in pH and mineral stability. The doubling of silica concentration in the experimental system containing acidic brine and supercritical carbon dioxide indicates that precipitation of silica can occur in parallel to carbonate minerals when pH increases. Emplacement of silica super-saturated brine into a rock-dominated reaction system buffered to more neutral pH conditions may enhance precipitation of quartz, chalcedony, or amorphous silica as veins or cements, depending on the permeability structure of the host rock. Phase separation or loss of carbon dioxide with decreasing pressure can substantially shift pH upwards, with potential for creating massive vein or scale formation.

Janecky, D. R.; Kaszuba, J. P.

2003-12-01

5

Carbonaceous matter in sulfide-quartz veins at the Kurultyken base-metal deposit, eastern Transbaikal region, Russia  

NASA Astrophysics Data System (ADS)

The carbonaceous matter filling cavities in sulfide-quartz veins at the Kurultyken hydrothermal base-metal deposit in the Khapcheranga ore district, Transbaikal region, was studied using chromatography/mass spectrometry, X-ray diffraction, thermal and isotopic analyses, and IR spectroscopy. It was established that carbonaceous matter was a maltha composed of polycyclic aromatic hydrocarbons (PAHs). Chrysene, pyrene, and benzpyrelene identified among PAHs are evidence for the hydrothermal origin of the initial carbonaceous matter of maltha. The main mass of carbonaceous matter was synthesized under reductive conditions and at a low temperature, i.e., at the final stage of base-metal ore formation. Nevertheless, the thermometric data indicate that part of the carbonic compounds could have formed at 480°C, i.e., at the high-temperature stage of the postmagmatic process. The contribution of host rocks as a source of carbonaceous matter was minimal.

Kuz'min, M. I.; Troshin, Yu. P.; Boiko, S. M.; Razvozzhaeva, E. A.; Zorina, L. D.; Martikhaeva, D. Kh.

2010-06-01

6

Trace elements and cathodoluminescence of quartz in stockwork veins of Mongolian porphyry-style deposits  

NASA Astrophysics Data System (ADS)

The combination of scanning electron microscope-cathodoluminescence (CL), fluid inclusion analysis and high-resolution electron probe microanalysis of Al, Ti, K and Fe in vein quartz has yielded results permitting a greater understanding of the complex mineralisation of the Central Oyu Tolgoi and Zesen Uul porphyry-style deposits, southern Mongolia. These data demonstrate the relationship between quartz precipitation, dissolution and ore deposition as the mineralising fluid chemistry changed through time. Four major quartz generations are identified in the A-type veins from the stockworks of both the Central Oyu Tolgoi (OTi to OTiv) and Zesen Uul deposits (ZUi to ZUiv). Despite differences in the associated alteration and mineralisation style, the observed CL textures and trace element signatures of the quartz generations are comparable between deposits. The OTi and ZUi stage formed both the primary network of A-type veins and pervasive silicification of the host rock. Using the Ti-in-quartz geothermometer, crystallisation temperatures for OTi and ZUi of between 598°C and 880°C are indicated. The main stage of sulphide mineralisation was accompanied by the dissolution of pre-existing quartz (OTi and ZUi) and precipitation of a weakly luminescent generation of quartz (OTii and ZUii) with a low Ti content, reflected in a calculated temperature drop from approximately 700°C to 340°C in Central Oyu Tolgoi and 445°C in Zesen Uul. OTii and ZUii stage quartzes show high and variable Al concentrations. The next stage of quartz in both deposits (OTiii and ZUiii) forms a fine network of veins in cracks formed in pre-existing quartz. OTiii and ZUiii quartz contain measurable fluid inclusions of moderate salinity (3-17.1 wt.% NaCl eq.), entrapped in the temperature range 256°C to 385°C. OTiii and ZUiii are not related to any sulphide mineralisation. The final OTiv and ZUiv stages are characterised by quartz-calcite micro-breccias that penetrate the A-type veins. Based on the calculated entrapment temperatures, the OTiv/ZUiv stage crystallised between 212°C and 335°C, and the quartz is characterised by elevated but variable Al and Fe contents. The CL and trace element signatures of the OTi to OTiii and ZUi to ZUiii stages of the two Mongolian porphyries show similar features to those observed in porphyry-style deposits from other regions. This suggests that a common sequence of quartz crystallisation occurs during the formation of early veins in many porphyry copper systems.

Müller, Axel; Herrington, Richard; Armstrong, Robin; Seltmann, Reimar; Kirwin, Douglas J.; Stenina, Nina G.; Kronz, Andreas

2010-10-01

7

Geometry and texture of quartz veins in Wadi Atalla area, Central Eastern Desert, Egypt  

NASA Astrophysics Data System (ADS)

Several quartz vein sets with varying orientation, geometry and internal structure were recognized in the Atalla area. The veins were associated with the deformation phases affecting the area. En echelon and extensional veins are the main geometrical types. Syn-kinematic veins associated with the major northeast-over-southwest thrust faults were later boudinaged, folded and re-folded. En echelon veins, fibrous veins, and extensional veins are associated with the NNW SSE faults. Other veins are associated with the NW SE, N S, NE SW and E W faults. Veins are concentrated at the intersection zones between faults. The internal structure of the veins comprises syntaxial, antitaxial, and composite types and reflects a change from a compressive stress regime to an extensional one. Chocolate-tablet structures and synchronous and co-genetic vein networks indicate later multi-directional extension of the area. Interaction between cracking and sealing of fractures is a common feature in the study area indicating that it was easy for the pore pressure to open pre-existing fractures instead of creating new ones. The reopening of pre-existing fractures rather than creating new ones is also indicated by the scattering of vein data around ?3. There is an alteration and change in characteristics of the wall rock due to increase in fluid flow rate. Fault-valving probably is also a cause of the complex geometry of some veins.

Akawy, Ahmed

2007-02-01

8

Archean geodynamics and the Abitibi-Pontiac collision: implications for advection of fluids at transpressive collisional boundaries and the origin of giant quartz vein systems  

NASA Astrophysics Data System (ADS)

Giant quartz vein systems of all ages, from the Archean to Cenozoic, are characterised by similarities of geodynamic setting, local structure, paragenesis, metal budget, P-T-t paths, and chemical, fluid dynamic and isotopic properties that collectively imply a singular hydrothermal process. Such quartz vein provinces form in regional brittle-ductile shear zones that define terrane boundaries, including closure of back-arc basins, and arc-continent or continent-continent collisions. Examples include the SVZ of the Archean Abitibi belt; the Norseman Wiluna belt, Yilgarn block; Kolar schist belt, India; Foothills Metamorphic Belt, California, and Coast Ranges Megalineament, in the Cordillera; and the Cenozoic Monte Rosa district, Insubric line. Evidence for an Archean collisional environment comes from the Abitibi and Pontiac Subprovince tectonic boundary, which hosts giant quartz vein systems. In this region, the amphibolite facies Lacorne tectonic block in the Archean Abitibi greenstone belt is anomalous with respect to the prevalent low-grade supracrustal sequences in neighbouring blocks. The Lacorne block has mature clastic sediments with a zircon provenance age spectrum from 3040-2691 Ma, and two granitic magma series; a late syntectonic monzodiorite-monzonite-granodiorite-syenite series formed over 2685-2670 Ma, similar to Phanerozoic volcanic arc granites, and post-tectonic garnet-muscovite granites emplaced at 2650-2630 Ma, which compositionally resemble Phanerozic collisional S-type granites. The Pontiac subprovince to the south of the Abitibi greenstone belt shares all the above features with the Lacorne block, and collided with and was locally thrust under the Abitibi belt, with differential uplift of the Lacorne block following collision to generate a tectonic window. Following collision of allochthonous terranes, the conjuction of large volumes of subcreted oceanic crust and sediments between accreted terranes, displaced isotherms rise, and metamorphic dehydration are all necessary conditions for forming giant quartz vein systems. Metamorphic fluids are expelled along the terrane boundary structures at deep levels, and focussed into second and higher order splays at mid-crustal levels where quartz and Au precipitation occurs. Hydrothermal fluids that formed the giant quartz veins are remarkably uniform in H, O, C, and Sr isotopic compositions, albeit with small provincial variations. The veins and gold precipitated at 270°-360°C, from fluids with low salinity and moderate CO 2 at 2-3 kbar in the brittle-ductile transition.

Kerrich, R.; Feng, R.

1992-01-01

9

A magmatic-hydrothermal transition in Arkaroola (northern Flinders Ranges, South Australia): from diopside-titanite pegmatites to hematite-quartz growth  

NASA Astrophysics Data System (ADS)

A set of Palaeozoic diopside-titanite veins are present in Mesoproterozoic metagranites and metasediments that constitute the basement (Mt Painter Inlier) of the Adelaide Fold Belt (South Australia). These massive veins (up to 1 m) of pegmatitic nature contain large crystals of diopside, LREE-Y-enriched titanite (up to 40 cm in length) and minor amounts of quartz. They can be used to trace the system’s development from a high-temperature magmatic stage through to a massive hydrothermal event. The pegmatitic origin of these veins is evident from a complex fluid-melt inclusion assemblage, consisting of a highly saline inhomogeneous fluid and relicts of melt. Immiscibility of melt and heterogeneous highly saline fluids (exceeding 61 eq. mass% NaCl) is preserved in primary inclusions in diopside and secondary inclusions in titanite, indicating relatively shallow conditions of formation (510 ± 20°C and 130 ± 10 MPa). Graphic intergrowth of diopside and albite occurs at the contact with granitic pegmatites. The system evolved into hydrothermal conditions, which can be deduced from a later population of only fluid inclusions (homogeneous and less saline, ? 40 eq. mass% NaCl), trapped around 350 ± 20°C and 80 ± 10 MPa. During quartz crystallization, the conditions moved across the halite liquidus resulting in a heterogeneous mixture of brine and halite crystals, which were trapped at 200 ± 20°C and 50 ± 10 MPa. Brecciation and a palaeo-geothermal system overprinted the pegmatitic veins with an epithermal hematite-quartz assemblage and lesser amounts of bladed calcite and fluorite, in an intermittently boiling hydrothermal system of fairly pure H2O at 100-140°C and 1-5 MPa. Remobilization of LREEs and Y from titanite and/or the granitic host rock is evidenced by precipitation of apatite, allanite and wakefieldite in an intermediate stage. Occasional incorporation of radioactive elements or minerals, presumably U-rich, in the fluorite is responsible for radiolysis of H2O to H2.

Bakker, Ronald J.; Elburg, Marlina A.

2006-11-01

10

Laser probe 40 Ar\\/ 39 Ar dating for quartz from auriferous quartz veins in the Shihu gold deposit, western Hebei Province, North China  

Microsoft Academic Search

The Shihu gold deposit is situated in the central shear zone of the Meso-Cenozoic Fuping metamorphic core complex in the middle-northern\\u000a part of the Taihang Mountains. This kind of gold deposits named after ‘Shihu type’ widely occurs in this region. Gold-bearing\\u000a quartz veins are their most important industrial orebodies. Detailed laser 40Ar\\/39Ar geochronology of the mineralized quartz veins in the

Ye Cao; Shengrong Li; Huafeng Zhang; Chong Ao; Zhenzhen Li; Xiaobin Liu

2010-01-01

11

Sheared-bedding parallel quartz vein as an indicator of deformation processes  

NASA Astrophysics Data System (ADS)

Monomineralic veins are well known as good recording of filling and precipitation processes. However, they are also able to register the action of deformation in rocks. We used monomineralic, quartz veins from Quadriláterro Ferrífero, Brazil, to represent how the deformation actuated during the transformation of different structures. They were analyzed using a combination of a u-stage and EBSD. Two main types of quartz aggregates are distinguished: single crystals with subgrain development and strain-free grains of quartz. We interpret the microstructures and textures as the result of a combination of concurrent crystal plasticity, microfracturing, solution transfer and recrystallization. The single quartz grains were deformed by dislocation glide. However, as the c-axis orientation of the grain was not favorable for further glide on basal planes, the deformation was accommodated by microfracturing. New grains were formed along the deformed zones with crystallographic orientations suitable for gliding on basal planes. As the deformation proceeded, the new grains continue to develop until the vein was completely recrystallized into an aggregate of granular grains.

Barbosa, Paola Ferreira; Lagoeiro, Leonardo

2012-09-01

12

Anomalous quartz from the Roter Kamm impact crater, Namibia: Evidence for post-impact hydrothermal activity  

SciTech Connect

Centimeter-sized quartz pebbles have been found on the rim of the Roter Kamm impact crater. The Roter Kamm crater has a diameter of about 2.5 km and is situated in the Namib Desert, SWA/Namibia. Because of the sand coverage, impact products are exposed exclusively in the form of ejecta on the crater rim. The quartz pebbles were found close to the main deposits of the impact breccias and show signs of wind abrasion. Thin sections revealed that the pebbles consist of individual quartz domains that are up to 1 mm in size. Under crossed nicols (polarized light), all individual domains show extinction almost simultaneously within {plus minus}2{degree}, which is a rare phenomenon. Microprobe studies, neutron activation analyses, and X-ray diffractometry confirmed that the material consists of pure quartz. The quartz contains three different types of fluid inclusions: primary inclusions that record the formation conditions of the quartz, very small (<1 {mu}m) secondary inclusions associated with the grain boundaries, and late inclusions of irregular size. Freezing point depression measurements of the primary inclusions indicate fluid salinities between 18.3 and 19.6 wt% NaCl. Homogenization temperatures (T{sub h}) for the primary inclusions range from 165 to 250{degree}C. The quartz and the primary inclusions may provide evidence for a post-impact phase of extensive hydrothermal activity, generated by the residual heat from the kinetic energy of the impact.

Koeberl, C. (Lunar and Planetary Institute, Houston, TX (USA) Univ. of Vienna (Austria)); Fredriksson, K. (Smithsonian Institution, Washington, DC (USA)); Goetzinger, M. (Univ. of Vienna (Austria)); Reimold, W.U. (Univ. of the Witwatersrand, Johannesburg (South Africa))

1989-08-01

13

Static recrystallization of vein quartz pebbles in a high-pressure - low-temperature metamorphic conglomerate  

NASA Astrophysics Data System (ADS)

Microfabrics of quartz pebbles in HP-LT (c. 1 GPa, c. 350 °C) metamorphic conglomerates are investigated. The conglomerate was deformed by dissolution-precipitation creep, while the interior of the pebbles remained undeformed. The different pebbles display a wide variety of quartz microstructures imported from the source rocks. One type of pebble is derived from quartz veins; it shows old grains with numerous fluid inclusions, subgrains, and undulatory extinction, which are partly replaced by new grains devoid of inclusions and substructure. Free dislocation densities are on the order of 1012 m-2 in both grains. We conclude that: (1) the quartz vein underwent inhomogeneous crystal-plastic deformation in the source rock; (2) recrystallization took place by strain-induced grain boundary migration starting from small crystalline volumes poor in defects; (3) recrystallization was purely static and commenced during re-burial of the conglomerate; which (4) was simultaneously deformed by dissolution-precipitation creep at low differential stress, insufficient for crystal-plastic deformation of quartz; (5) fluid inclusions within old grains were eliminated and their fluid content was drained along the migrating high angle grain boundaries; and (6) strain-induced grain boundary migration ceased once the driving force became too low by static recovery (concurrent to recrystallization) within the deformed old grains.

Trepmann, Claudia; Lenze, Annette; Stöckhert, Bernhard

2010-02-01

14

Frictional healing of quartz gouge under hydrothermal conditions: 1. Experimental evidence for solution transfer healing mechanism  

Microsoft Academic Search

Experiments on the frictional properties of quartz gouge under hydrothermal conditions have revealed a new fault healing mechanism that operates only at elevated temperature in the presence of liquid-phase water. This distinguishes it from the well-known “Dieterich-type” healing that also operates at room temperature and depends only on the chemical activity of water and not on its phase. The requirement

Masao Nakatani; Christopher H. Scholz

2004-01-01

15

Some effects of tectonic recrystallisation on fluid inclusions in vein quartz  

Microsoft Academic Search

Filling temperature data obtained from tectonic vein quartz varies according to the state of intracrystalline deformation.\\u000a Strain free domains within grains exhibit abundant primary fluid inclusions, from which internally consistent temperatures\\u000a are recorded. The onset of optical features associated with intracrystalline deformation by dislocation creep is accompanied\\u000a by a decrease in the number of fluid inclusions and an increase of

Robert Kerrich

1976-01-01

16

Geological characteristics, tectonic setting and preliminary interpretations of the Jilau gold–quartz vein deposit, Tajikistan  

Microsoft Academic Search

The southern Tien Shan metallogenic province of Central Asia hosts a number of important gold resources including the Jilau\\u000a gold–quartz vein system in western Tajikistan. These deposits were formed at the late stages of continent–continent collision\\u000a in association with subduction-related magmatism, metamorphism and continental margin deformation attributed to the Central\\u000a Asian Hercynian Orogeny. Jilau is hosted by a Hercynian syntectonic

A. Cole; J. J. Wilkinson; C. Halls; T. J. Serenko

2000-01-01

17

Mineralogy and Geochemistry of Dacitic domes and associated Cu- Fe-Au Veins occurences during hydrothermal processes, Yazd Province, Iran  

NASA Astrophysics Data System (ADS)

The Panah-koh Cu-Fe-Au vein deposit, located 60 km south west of Yazd Province, between Central Iranian Zone and Orumieh-Dokhtar tectnomagmatic belt. The vains result from hydrothermal processes related to a Neogenes volcanism which produced a dacitic to rhyodacitic dome which responsible for most of the altration and mineralization in this area. mineralization occurs in a series of NW-SW trending fault planes and breccia zones in (Early Combrian) and sand stone (Percambrian) rocks. the main ore minerals are Chalcopyrite, Pyrite,Arsenopyrite,Hematite,Limonite,Malachite,Azurite, with Quartz,Calcite,Dolomite,Barite and minor Chlorite as the main qanque phases.The Panah- Koh volcanic domes crystallized from an I-Type magma formed in a volcanic arc setting.the volcanic rocks show geochemical evidence of fractionation of Biotite,Hornblande and Fledspars.altration of the minerals in the host rocks suggests pH<5.5 and oxidized conditions.On variation diagrams, MgO, MnO, TiO2, CaO, P2O5, Fe2O3, display negative correlations suggesting that these volcanic rocks experienced fractionation of early-crystallized Biotite, Magnetite, Apatite and Plagioclase. The concentration of Sr, Ni, Ba and V decrease with increasing SiO2 suggesting fractionation of early formed Biotite, K-Feldspar, Magnetite and Plagioclase. supergene effects, with penetration of surface waters along faults and fractures, has led to the oxidation and leaching of the host rocks and the enrichment of copper. Quartz crystals were deposited as layers in crustification banding and comb structures along the walls of veins or the composition of the mineralizing fluids. shallow level of emplacement and low temprature of magma, shows that the hydrothermal system was not able to form a skarn deposit in the Panah-Koh district.

Sharifi, R.

2009-04-01

18

Origin of vein hydrothermal carbonates in triassic limestones of the Espadán Ranges (Iberian Chain, E Spain)  

Microsoft Academic Search

Dolomitization and Hg bearing veins in the lower Triassic limestones of the Espadán Ranges (Iberian Chain, E of Spain) are related to a hydrothermal event that occurred during the Santonian (late Cretaceous). 87Sr\\/86Sr ratios of unaltered regional dolostones range from 0.70829 to 0.70945, higher than those expected for Triassic diagenetic dolostones. Vein filling is constituted by a brown cloudy calcite

J Tritlla; E Cardellach; Z. D Sharp

2001-01-01

19

Intensity of quartz cathodoluminescence and trace-element content in quartz from the porphyry copper deposit at Butte, Montana  

USGS Publications Warehouse

Textures of hydrothermal quartz revealed by cathodoluminescence using a scanning electron microscope (SEM-CL) reflect the physical and chemical environment of quartz formation. Variations in intensity of SEM-CL can be used to distinguish among quartz from superimposed mineralization events in a single vein. In this study, we present a technique to quantify the cathodoluminescent intensity of quartz within individual and among multiple samples to relate luminescence intensity to specific mineralizing events. This technique has been applied to plutonic quartz and three generations of hydrothermal veins at the porphyry copper deposit in Butte, Montana. Analyzed veins include early quartz-molybdenite veins with potassic alteration, pyrite-quartz veins with sericitic alteration, and Main Stage veins with intense sericitic alteration. CL intensity of quartz is diagnostic of each mineralizing event and can be used to fingerprint quartz and its fluid inclusions, isotopes, trace elements, etc., from specific mineralizing episodes. Furthermore, CL intensity increases proportional to temperature of quartz formation, such that plutonic quartz from the Butte quartz monzonite (BQM) that crystallized at temperatures near 750 ??C luminesces with the highest intensity, whereas quartz that precipitated at ???250 ??C in Main Stage veins luminesces with the least intensity. Trace-element analyses via electron microprobe and laser ablation-ICP-MS indicate that plutonic quartz and each generation of hydrothermal quartz from Butte is dominated by characteristic trace amounts of Al, P, Ti, and Fe. Thus, in addition to CL intensity, each generation of quartz can be distinguished based on its unique trace-element content. Aluminum is generally the most abundant element in all generations of quartz, typically between 50 and 200 ppm, but low-temperature, Main Stage quartz containing 400 to 3600 ppm Al is enriched by an order of magnitude relative to all other quartz generations. Phosphorous is present in abundances between 25 and 75 ppm, and P concentrations in quartz show little variation among quartz generations. Iron is the least abundant of these elements in most quartz types and is slightly enriched in CL-dark quartz in pyrite-quartz veins with sericitic alteration. Titanium is directly correlated with both temperature of quartz precipitation, and intensity of quartz luminescence, such that BQM quartz contains hundreds of ppm Ti, whereas Main Stage quartz contains less than 10 ppm Ti. Our results suggest that Ti concentration in quartz is controlled by temperature of quartz precipitation and that increased Ti concentrations in quartz may be responsible for increased CL intensities.

Rusk, B. G.; Reed, M. H.; Dilles, J. H.; Kent, A. J. R.

2006-01-01

20

Hydrothermal calcium-carbonate veins reveal past ocean chemistry  

Microsoft Academic Search

Records of past ocean chemistry provide an integrated history of fundamental Earth processes, including the evolution of its continents, climate, and life. Here, we describe a recent dramatic shift in appreciation of the value and the application of studies of ocean crustal hydrothermal processes, which can be used to both reconstruct records of past ocean chemistry and decipher the past

Damon A. H. Teagle

2011-01-01

21

Mass transfer during wall-rock alteration: An example from a quartz-graphite vein, Black Hills, South Dakota  

NASA Astrophysics Data System (ADS)

Mass transfer and fluid-rock interaction have been evaluated along two sample traverses in low-sillimanite grade quartz-mica schist adjacent to a synmetamorphic quartz-graphite vein in the southern Black Hills, South Dakota. In an ~ 17 cm halo between apparently unaltered schist and the vein contact is an outer zone of cryptic alteration and three inner zones of visible alteration. The cryptic zone consists of the original prograde metamorphic mineral assemblage (quartz + biotite ± muscovite + plagioclase + microcline) plus anomalously high amounts of tourmaline. The outermost visible zone contains abundant graphite. The second visible zone is defined by intensive bleaching of the schist. The innermost visible zone, immediately adjacent to the vein, is tourmaline + quartz + plagioclase + limonite + graphite. The vein is composed almost entirely of quartz, but also contains trace amounts of graphite. Mass balance calculations indicate that Al was essentially inert. The predominant chemical changes during wall-rock alteration were addition of B and C from the vein-forming fluid along with loss of K from the wall rocks, corresponding to precipitation of tourmaline and graphite, and the progressive destruction of microcline, biotite, and muscovite toward the vein. In addition, the elements V, Cr, Cu, Zn, Pb, As, Sb, W, and Au were introduced into the country rock, whereas Si, Rb, Ba, and Cs were removed. On the basis of a constant Al reference frame, calculations indicate a net volume loss of 21-34% within one centimeter of the vein with little or no volume loss further from the vein. Fluid-rock interaction modeling suggests that between one and four equivalent masses of fluid interacted chemically with the most altered mineral assemblages. In addition, greater than one equivalent mass of reactive fluid penetrated to distances of at least 5 cm from the vein contact.

Galbreath, K. C.; Duke, E. F.; Papike, J. J.; Laul, J. C.

1988-07-01

22

Formation of pure quartz domains: role of fluid-rock reaction and syn-tectonic veining in granitic mylonite  

NASA Astrophysics Data System (ADS)

Pure quartz domains (PQD), also called pure quartz layer (Stunitz & Fitz Gerald, 1993) or pure quartz band (Fliervoet, et al., 1997 Hippett, 1998), are commonly developed in quartzo-feldspathic mylonites. Generally, these foliation-concordant quartz domains are believed to be formed by extreme elongation of large quartz grains or quartz aggregates into ribbons. Here. I present micro-structural and textural evidences to demonstrate that these PQDs are actually foliation-concordant quartz. Oriented samples collected from a metre-scale shear zone cutting across granitoids in the Elbe Zone, Saxony, Germany, show distinct microstructural features when viewed on different sections. On the XZ section (cut parallel to stretching lineation), PQDs appear as polycrystalline foliation-concordant ribbons and extend across the entire thin section. On the YZ section (cut normal to stretching lineation), PQDs can only be described as crack-sealing quartz veinlet. Fibrous quartz crystals show a growing-direction almost perpendicular to vein boundaries, suggesting that foliation-parallel tensile fractures, in which quartz veinlets precipitated, have an opening direction parallel to Z axis of the sample reference system. Boundaries of quartz veinlets show an obvious convergence along the foliation, e.g., the Y axis, which suggests a propagation direction of tensile fractures parallel to the Y axis. Crystallographic data of fibrous quartz are characterised by a strong c-axis concentration around the Y axis, indicating an abnormal growing direction for quartz to be normal to their c-axes. Formation of pure quartz domains in granitic mylonites is due to repeatedly operation of foliation-normal dilatation event induced by fluctuation of fluid pressure in a rock system with high anisotropy during a bulk ductile shearing. Fibrous quartz crystals are growing under a local stress configuration being different from regional stress condition. A fracture model has been proposed.

Jiang, Z.

2011-12-01

23

Quartz precipitation and fluid inclusion characteristics in sub-seafloor hydrothermal systems associated with volcanogenic massive sulfide deposits  

NASA Astrophysics Data System (ADS)

Results of a numerical modeling study of quartz dissolution and precipitation in a sub-seafloor hydrothermal system have been used to predict where in the system quartz could be deposited and potentially trap fluid inclusions. The spatial distribution of zones of quartz dissolution and precipitation is complex, owing to the fact that quartz solubility depends on many inter-related factors, including temperature, fluid salinity and fluid immiscibility, and is further complicated by the fact that quartz exhibits both prograde and retrograde solubility behavior, depending on the fluid temperature and salinity. Using the PVTX properties of H2O-NaCl, the petrographic and microthermometric properties of fluid inclusions trapped at various locations within the hydrothermal system have been predicted. Vapor-rich inclusions are trapped as a result of the retrograde temperature-dependence of quartz solubility as the convecting fluid is heated in the vicinity of the magmatic heat source. Coexisting liquid-rich and vapor-rich inclusions are also trapped in this region when quartz precipitates as a result of fluid immiscibility that lowers the overall bulk quartz solubility in the system. Fluid inclusions trapped in the shallow subsurface near the seafloor vents and in the underlying stockwork are liquid-rich with homogenization temperatures of 200-400°C and salinities close to that of seawater. Volcanogenic massive sulfide (VMS) deposits represent the uplifted and partially eroded remnants of fossil submarine hydrothermal systems, and the relationship between fluid-inclusion properties and location within the hydrothermal system described here can be used in exploration for VMS deposits to infer the direction towards potential massive sulfide ore.

Steele-MacInnis, Matthew; Han, Liang; Lowell, Robert P.; Rimstidt, J. Donald; Bodnar, Robert J.

2012-06-01

24

Trace element geochemistry of scheelite and rutile from metaturbidite-hosted quartz vein gold deposits, Meguma Terrane, Nova Scotia, Canada: genetic implications  

NASA Astrophysics Data System (ADS)

Scheelite and rutile from several metaturbidite-hosted gold-bearing quartz vein deposits of the Meguma Terrane of Nova Scotia were analyzed for trace elements including rare earth elements, niobium and tantalum. Scheelites have high concentrations of Sr, Nb, Y and rare earth elements (REE) with bell-shaped chondrite-normalized REE patterns accompanied by both positive and negative Eu anomalies. They also have high Nb/Ta ratios (80-300). Three distinct trace element types of the scheelites are interpreted to reflect chemical differences in the pulses of hydrothermal fluids. Hydrothermal rutiles have high contents of W (up to 4.2 wt.% WO3), are rich in Ta compared to Nb and have a very low Nb/Ta ratio (~0.3). Hydrothermal fluids which produced both scheelite with a high Nb/Ta and rutile with a low Nb/Ta ratio are an efficient medium for fractionation of this ratio although these two minerals play an important role during the process.

Dostal, Jaroslav; Kontak, Daniel J.; Chatterjee, A. K.

2009-12-01

25

Combining in situ isotopic, trace element and textural analyses of quartz from four magmatic-hydrothermal ore deposits  

NASA Astrophysics Data System (ADS)

This study couples in situ 16O, 17O and 18O isotope and in situ trace element analyses to investigate and characterize the geochemical and textural complexity of magmatic-hydrothermal quartz crystals. Euhedral quartz crystals contemporaneous with mineralization were obtained from four magmatic-hydrothermal ore deposits: El Indio Au-Ag-Cu deposit; Summitville Au-Ag-Cu deposit; North Parkes Cu-Au deposit and Kingsgate quartz-Mo-Bi-W deposit. The internal features of the crystals were imaged using cathodoluminescence and qualitative electron microprobe maps. Quantitative isotopic data were collected in situ using 157 nm laser ablation inductively coupled plasma mass spectrometry (for 40 trace elements in quartz) and sensitive high-resolution ion microprobe (for 3 isotopes in quartz). Imaging revealed fine oscillatory zoning, sector zoning, complex "macromosaic" textures and hidden xenocrystic cores. In situ oxygen isotope analyses revealed a ?18O range of up to 12.4 ± 0.3 ‰ in a single crystal—the largest isotopic range ever ascribed to oscillatory zonation in quartz. Some of these crystals contain a heavier ?18O signature than expected by existing models. While sector-zoned crystals exhibited strong trace element variations between faces, no evidence for anisotropic isotope fractionation was found. We found: (1) isotopic heterogeneity in hydrothermal quartz crystals is common and precludes provenance analysis (e.g., ?D-?18O) using bulk analytical techniques, (2) the trace element signature of quartz is not an effective pathfinder toward noble metal mineralization and (3) in three of the four samples, both textural and isotopic data indicate non-equilibrium deposition of quartz.

Tanner, Dominique; Henley, Richard W.; Mavrogenes, John A.; Holden, Peter

2013-10-01

26

In situ 14C depth profile of subsurface vein quartz samples from Macraes Flat New Zealand  

NASA Astrophysics Data System (ADS)

We present results of measurements of cosmogenic in situ 14C produced in a quartz vein from Macraes Flat, East Otago, New Zealand, where concentrations of in situ produced 10Be and 26Al were previously studied by Kim and Englert [Earth Planet. Sci. Lett. 223 (2004) 113]. 14C was extracted from the quartz samples up to depths of 400 g cm-2 using a low temperature wet extraction method [D. Lal, A.J.T. Jull, Nucl. Instr. and Meth. B 92 (1994) 291]. Based on the results for 10Be and 26Al, we expected that the 14C activity in the samples would be at saturation levels, in equilibrium with erosion. The surface exposure age of this site was found to be about 25 000 years using 10Be and 26Al at the surface, with a surface erosion rate of at least 10-3 cm/y [K.J. Kim, P.A.J. Englert, Earth Planet. Sci. Lett. 223 (2004) 113]. The measured 14C activities were compared with those expected from spallation of Si and O in quartz by energetic neutrons and fast muons, and from capture of negative muons in O in quartz [B. Heisinger, A.J.T. Jull, D. Lal, P. Kubik, S. Ivy-Ochs, K. Knie, E. Nolte, Earth Planet. Sci. Lett. 200 (2002) 357; B. Heisinger, D. Lal, A.J.T. Jull, P. Kubik, S. Ivy-Ochs, S. Neumaier, K. Knie, V. Lazarev, E. Nolte, Earth Planet. Sci. Lett. 200 (2002) 345]. Surprisingly, we found that the 14C activities were significantly greater than those expected, by factors of 2 3, especially in samples of depths <200 g cm-2. We suspect that the excess 14C probably resulted from capture of thermal neutrons in nitrogen present in the fluid inclusions in quartz. This study shows that great care has to be taken in measurements of in situ 14C in quartz, especially in samples exposed near sea level and greater depths, where rates of spallation produced 14C are low.

Kim, K. J.; Lal, D.; Englert, P. A. J.; Southon, J.

2007-06-01

27

Orthomagmatic quartz and post-magmatic carbonate veins in a reported porphyry copper deposit, Andean Intrusive Suite, Livingston Island, South Shetland Islands  

NASA Astrophysics Data System (ADS)

A previously reported porphyry Cu+Mo deposit in an Eocene pluton within the South Shetland Island magmatic arc has been re-interpreted as three distinct hydrothermal assemblages. The oldest assemblage (1) exsolved under confinement from the deep (˜6 km?) cooling magma whereas assemblages (2) and (3) formed during tectonic ± magmatic episodes at depths of <1.5 km in the late Cenozoic. The three assemblages occur over the 5×11 km mapped in Barnard Point tonalite pluton. Assemblage (1) comprises shallowly dipping sheets of aplite, biotite+tourmaline pegmatite, massive ‘grey’ quartz, and quartz+tourmaline+bornite+chalcopyrite+molybdenite veins. Magnetite+tourmaline+ chalcopyrite breccias have associated biotite, K-feldspar and muscovite alteration. Fluid inclusions indicate formation from hot (˜600 °C), saline (40 equivalent weight % NaCl+CaCl2) aqueous-carbonic fluids that exsolved from the partly consolidated magma. The primary control on solution chemistry and nature of fracturing was the depth of pluton emplacement. Assemblage (2) consists of steep, vuggy veins and country-rock breccias, with thick propylitic alteration selvages, cemented by microcrystalline quartz, complex intergrowths of FeMg carbonate, bladed barite and trace amounts of bornite and chalcopyrite. These rocks, previously described as breccia ( sensu‘pebble’) dykes in the porphyry complex, are reinterpreted as an influx of moderately hot (175 330 °C), weak to moderately saline (2 21 EWP NaCl), aqueous-carbonic fluids that underwent isobaric boiling at 0.8 to 1.3 km depth. Assemblage (3) consists of thin, hematitic fault infillings formed during a second episode of brittle faulting.

Armstrong, D. C.; Willan, R. C. R.

1996-05-01

28

The gold content of some Archaean rocks and their possible relationship to epigenetic gold-quartz vein deposits  

Microsoft Academic Search

Gold mineralization in Archaean granite-greenstone environments, especially gold-quartz veins, contributes considerably to the world's gold production. The formation of epigenetic gold mineralization in greenstone belts is generally explained by the metamorphic secretion theory. This theory is based on the assumption that the source of the gold may be komatiitic or tholeiitic lavas, pyritic chemical or clastic sediments and even granitic

M. Meyer; R. Saager

1985-01-01

29

The role of fluid phase immiscibility in quartz dissolution and precipitation in sub-seafloor hydrothermal systems  

NASA Astrophysics Data System (ADS)

A numerical model describing quartz dissolution and precipitation in sub-seafloor hydrothermal systems has been developed that documents the effects of retrograde quartz solubility and fluid phase immiscibility on the transport and deposition of silica in this environment. Rates of dissolution and precipitation increase with increasing permeability and with increasing maximum temperature at the base of the system. At the most optimal conditions considered in this study (425 °C, permeability of 10- 13 m2), quartz is precipitated at rates up to 10- 6 mol/m3·s (equivalent to 700 cm3 of quartz per cubic meter of rock per year). Immiscibility at the base of the system creates a zone in which large amounts of quartz precipitate as a result of phase separation. The high rate of quartz precipitation at the one-fluid-phase/two-fluid phase boundary is consistent with the location of highly silicified zones found beneath volcanogenic massive sulfide deposits. Rapid quartz deposition at this boundary may affect the heat transfer efficiency at the base of the upflow zone and may contribute to immobilizing the brine layer so that it does not rise towards the surface. The process of rapid quartz precipitation at the base of the upflow zone, and its effects on the dynamics of these systems, is only observed under conditions of liquid-vapor immiscibility.

Steele-MacInnis, Matthew; Han, Liang; Lowell, Robert P.; Rimstidt, J. Donald; Bodnar, Robert J.

2012-03-01

30

Crack-seal microstructure evolution in multiphase rocks: an example of quartz-chlorite veins formed at the brittle-ductile transition  

NASA Astrophysics Data System (ADS)

For this study we analyzed core samples from the deep geothermal well RWTH-1 (Aachen-Germany), which intersects Carboniferous to Devonian siliciclastics and carbonates deformed during Variscan thrusting and subsequent normal faulting events. From several successive generations of veins, we focussed on quartz-chlorite +/- calcite veins formed by crack-seal processes in the brittle to ductile transition realm (< 390 °C, 150 - 250 MPa, Lögering, 2008). The veins are common in sections of the well which are interpreted as Variscan thrusts based on image logs and seismic data. Veins are up to 1 cm thick, formed in pull-apart sections of brittle-ductile shear zones. The change in angle (releasing angle = alpha) of the shear fracture is the main factor controlling vein geometry. Two end-member types of vein geometry can be defined. The first type, the "flat" vein is formed when alpha is less than a few degrees, it contains chlorite and quartz ribbons and commonly shows evidence for ductile shearing. The quartz ribbons often show peculiar "blocky-sawtooth" boundaries. The second type, the "fat" vein quartz forms when alpha is large, up to 90 degrees. Here, stretched-crystal-type fibrous veins are common, with irregular grain boundaries between the chlorite and quartz fibres. Chlorite is present as inclusion bands or trails. Multiple crack-seal events are interpreted to be the basic microstructural process in the veins. The clearest evidence for this is found in very thin, incipient veins, where "stretched" host rock grains are common. The length of these stretched crystals increases in wider veins, together with an increasing density of healed fractures as shown by fluid inclusion trails. To understand the microstructural evolution, we extend earlier models of polycrystal growth in fractures (Urai et al, 1991) to the growth of two phases (Quartz and Chlorite) from a supersaturated solution, onto a crack-wall containing both phases. When the relative growth rates of the two phases are different, the grain boundary between the two phases will propagate at an angle (beta) to the fracture boundary. Beta may be rather constant in the rock, or be variable due to local fluctuations in fluid chemistry. Using different combinations of alpha and beta, we carried out a series of 2D geometric simulations of microstructural evolution in these two-phase veins, for both localized and delocalized cracking. Results compare very well with the observed microstructures, for both "flat" and "fat" veins. The "blocky-sawtooth" quartz veins can be explained by a series of micro-pull apart shear cracks crossing the quartz ribbons in a chlorite surrounding, which are systematically healed by quartz instead of chlorite and quartz.

Becker, S.; Urai, J.; Scholz, K.; Kukla, P.

2009-04-01

31

Trace element composition of near-surface silica deposits—A powerful tool for detecting hydrothermal mineral and energy resources  

Microsoft Academic Search

Extensive Paleozoic sinter deposits occur at the surface associated with sub-surface quartz veining and epithermal Au mineralisation in the Drummond Basin, Australia. We investigated the trace element composition of the sinter deposits and quartz veins in an attempt to develop a new geochemical exploration guide for geological resources. The Drummond Basin hydrothermal silica deposits are unique in having anomalously enriched

I. Tonguç Uysal; Massimo Gasparon; Robert Bolhar; Jian-xin Zhao; Yue-xing Feng; Greg Jones

2011-01-01

32

The evolution of the deep flow regime at Soultz-sous-Fore^ts, Rhine Graben, eastern France: Evidence from a composite quartz vein  

Microsoft Academic Search

Drilling at Soultz-sous-Fore^ts, France, conducted as part of the European Hot Dry Rock Project, intersected a fracture lined with vein quartz and actively producing hot (150°C) water at 2174 m depth in the granite basement to the Rhine Graben. At least seven generations of quartz are present within the vein, but fluid inclusion homogenization temperatures show that temperatures remained within

M. P. Smith; V. Savary; B. W. D. Yardley; J. W. Valley; J. J. Royer; M. Dubois

1998-01-01

33

Chemical composition and paramagnetism of vein quartz from the Tasmania gold mine, Beaconsfield, northern Tasmania  

NASA Astrophysics Data System (ADS)

Spot samples of gold bearing quartz from reefs at Beaconsfield have higher Ge, Li, As, Mn, Fe and Al contents, and lower K, S, Na and Cl than barren quartz samples. The gold bearing samples are also more paramagnetic.

Russell, D. W.; Bailey, G. M.; Cohen, D. D.; van Moort, J. C.

1996-04-01

34

Crack-seal microstructure evolution in bi-mineralic quartz-chlorite veins in shales and siltstones from the RWTH-1 well, Aachen, Germany  

NASA Astrophysics Data System (ADS)

In core samples from the deep geothermal well RWTH-1 we studied Variscan quartz-chlorite veins formed by crack-seal processes in siliciclastics at the brittle to ductile transition. These sheared veins are common in sections of the well, which are interpreted as Variscan thrust zones based on image logs and seismic data. Microstructures interpreted to reflect different stages in the evolution of such crack-seal veins suggest the veins started in microcracks sealed by quartz and chlorite, to veinlets crossing multiple grains, and bundles of veinlets evolving by progressive localization into low-angle extensional shear veins and high-angle dilational jog veins. In the sheared veins, chlorite and quartz ribbons show evidence for crack-seal and simultaneous ductile shearing during vein evolution, forming peculiar fin-shaped microstructures in quartz ribbons. In high-angle dilational jogs fibrous crystals of quartz and chlorite point to multiple crack-seal events with simultaneous growth of two different mineral phases. This is interpreted to be the basic microstructural process in the veins. We extend earlier models of polycrystal growth in fractures and present a series of 2D simulations of the kinematics of crystal growth in these bi-mineralic veins for both localized and non-localized cracking. Results are compared with the observed microstructures. We show that when the relative growth rates of the two mineral phases are different, serrated grain boundaries evolve. The similarities between observation and model suggest that the assumption of our model is valid, although many second order processes require a more detailed study. We propose that the principles observed here can be applied to other bi-mineralic crack-seal veins.

Becker, Stephan; Hilgers, Christoph; Kukla, Peter A.; Urai, Janos L.

2011-04-01

35

Investigation of the characteristics of thermoluminescence glow curves of natural hydrothermal quartz from Hakkari area in Turkey  

NASA Astrophysics Data System (ADS)

In this study the dosimetric characteristics of some natural hydrothermal quartz (NHQ) samples collected from Hakkari were investigated by using the thermoluminescence (TL) technique for the purpose of determining whether they are suitable as dosimetric materials or not and calculating the kinetic parameters. The experiments carried out can be outlined as: analyzing TL glow curves of NHQ; determining the annealing conditions; the effects of pre-irradiation annealing procedures on TL sensitivity; the investigation of the characteristics of TL glow curves obtained after annealing the samples; determination of the trap parameters with the computerized glow curve deconvolution (CGCD) method and the peak shape (PS) method. The obtained results showed that the trap depths and the frequency factor values are consistent with the literature. The studied samples have linear dose responses for the absorbed doses ranging between ~6.689 Gy and ~301 Gy. In conclusion, the examined quartz samples can be used as dosimetric materials in high dose applications.

Topaksu, M.; Yüksel, M.; Dogan, T.; Nur, N.; Akkaya, R.; Yegingil, Z.; Topak, Y.

2013-09-01

36

Fluid inclusion and carbon isotope studies of quartz-graphite veins, Black Hills, South Dakota, and Ruby Range, Montana  

NASA Astrophysics Data System (ADS)

Fluid inclusions and graphite are intimately associated in quartz veins that cut high grade metamorphic rocks in the Black Hills, South Dakota, and at the Crystal Graphite Mine in the southwestern Ruby Range, Montana. Measured fluid inclusion compositions and volumetric properties were compared with calculated compositions of graphite-saturated fluids and with estimates of metamorphic P-T conditions and carbon isotope ratios of graphite were measured to evaluate possible sources of carbon in veinforming fluids. Fluid inclusions from the two areas contrast markedly in their reliability as recorders of metamorphic fluid compositions and metamorphic conditions. The ?13C of graphite associated with the veins indicates that the source of carbon was also different in the two areas. In the Black Hills veins, fluid inclusions are dominantly H 2O?CO 2 mixtures with 24-96 mol% CO 2 and a maximum of ˜5 mol% N 2 and ˜ 13 mol% CH 4. Isochores for the highest density inclusions pass near estimated peak metamorphic conditions (550°-600°C, 4.5-6.5 kbar) and fluid inclusion compositions are compatible with thermodynamic predictions for fluids in equilibrium with graphite in the stated P- T range at geologically reasonable ƒ O 2.Graphite in a 12-cm wall-rock alteration zone adjacent to one of the veins has uniform ?13C of -20.8 ± 0.2%., indicating that carbon in the vein-forming fluid was derived largely from reduced organic carbon. In the Ruby Range, peak metamorphic conditions were higher - ˜750°-850°C, 5-8 kbar. In contrast to the Black Hills veins, fluid inclusions are almost all CO 2?CH 4 mixtures (with unknown N 2 content). Many contain > 20 equivalent mol% CH 4 and mixed H 2O?CO 2 inclusions were observed in only one sample. Inclusions in one vein have ˜ 84-97 mol% CH 4. Virtually all inclusion compositions are incompatible with computed graphite equilibria and inclusion isochores likewise do not pass through estimated metamorphic conditions. The density and composition of most, if not all, inclusions have been modified subsequent to original trapping, possibly through H 2O loss. The range of ?13C values of vein graphites (-5.8 to -8.6%.) is nearly indistinguishable from values for graphite in dolomitic marble near the veins (-4.8 to -7.1%.). Carbon was probably mobilized through devolatilization reactions in the marble and precipitated as 13C-rich graphite in the veins at fairly constant temperature and from fluid of fairly constant composition.

Duke, Edward F.; Galbreath, Kevin C.; Trusty, Kane J.

1990-03-01

37

Age and genesis of precious metals deposits, Buffalo Hump district, central Idaho: implications for depth of emplacement of quartz veins.  

USGS Publications Warehouse

Three samples (metamorphic country rock, Idaho batholith granite, and auriferous quartz vein) were dated by the 40Ar/39Ar age spectrum technique. The lode deposits are Cretaceous (71 m.y.); their cooling histories and depths of emplacement, inferred from the age spectra, are evidence for the granite plutons and the lode deposits having been emplaced at the same 40-9 km depth and being genetically related. Thus, the Idaho batholith is not barren, and at least two precious-metal mineralizing events, Cretaceous and Eocene in age, occur in central Idaho. Class differences between the two ages of deposits, of style, alteration and mineralogy, are suggested. -G.J.N.

Lund, K.; Snee, L. W.; Evans, K. V.

1986-01-01

38

The gold content of some Archaean rocks and their possible relationship to epigenetic gold-quartz vein deposits  

NASA Astrophysics Data System (ADS)

Gold mineralization in Archaean granite-greenstone environments, especially gold-quartz veins, contributes considerably to the world's gold production. The formation of epigenetic gold mineralization in greenstone belts is generally explained by the metamorphic secretion theory. This theory is based on the assumption that the source of the gold may be komatiitic or tholeiitic lavas, pyritic chemical or clastic sediments and even granitic rocks from which, as a result of regional metamorphic overprinting, gold was extracted and concentrated in suitable structures. It has been shown that in proposed potential source rocks, gold is predominantly associated with sulfide minerals and thus relatively easily accessible to secretion and reconstitution processes. A large number of various rock types originating from granite-greenstone terranes of the Kaapvaal and the Rhodesian cratons were geochemically investigated, and the following ranges for gold determined: volcanic rocks (komatiitic and tholeiitic): 0.1 372 ppb granitic rocks of the basement: 0.3 7.8 ppb iron-rich chemical sediments: 1.0 667 ppb Statistical treatment of the data reveals that volcanic rocks as well as iron-rich chemical sediments are favorable sources for epigenetic gold mineralization formed by metamorphic secretion, while the granitic rocks make less suitable primary gold sources. This finding explains the close spatial relationship which is common between gold-quartz veins and greenstone belts. The conspicuous abundance of epigenetic gold mineralization in the Archaean, however, is attributed to the unique geologic and metamorphic history of the granite-greenstone terranes.

Meyer, M.; Saager, R.

1985-10-01

39

Hydrothermal fluid evolution and structural control of the Guarim gold mineralisation, Tapajós Province, Amazonian Craton, Brazil  

Microsoft Academic Search

Fluid inclusion and structural studies were carried out at the Guarim gold deposit in the Palaeoproterozoic Tapaj?s province\\u000a of the Amazonian craton. Guarim is a fault-hosted gold deposit cutting basement granitoids. It consists of a quartz vein,\\u000a which is massive in its inner portions, grading laterally either to a massive or to cavity-bearing quartz vein associated\\u000a with hydrothermal breccias. The

Evandro Luiz Klein; Reginaldo Alves dos Santos; Kazuo Fuzikawa; Rômulo Simões Angélica

2001-01-01

40

Velocity-weakening behavior of plagioclase and pyroxene gouges and stabilizing effect of small amounts of quartz under hydrothermal conditions  

NASA Astrophysics Data System (ADS)

We investigated properties of frictional sliding of plagioclase, pyroxene, and their mixture gouges with a small amount of hornblende, biotite, and quartz as accessory minerals, under hydrothermal conditions with an effective normal stress of 200 MPa, pore pressure of 30 MPa, and temperatures from 100°C to 600°C. Axial loading rate was stepped between 0.001 and 0.0001 mm/s to acquire the rate dependence. Both plagioclase and pyroxene gouges showed velocity-weakening behavior in the whole temperature range except the velocity-strengthening behavior of pyroxene at 200°C. For temperatures above 400°C, both plagioclase and pyroxene gouges showed oscillatory slips, as a result of small dc values of 3-4 µm which make the critical stiffness rise remarkably and approach the system stiffness. Above 300°C, the direct effect of plagioclase shows an increasing trend with temperature, indicating control of the deformation process by thermally activated mechanisms. As the difference of a and b values here are only 20% at most, this trend also applies to the evolution effect. Our analytical derivation based on the theory of pressure solution shows a log-linear contact area growth with time that corresponds to an evolution effect, and estimations based on this encompass the plagioclase data, though the identification of actual mechanisms is not easy. Finally, it is found that a little quartz (3-5%) added to the plagioclase (60-62%)-pyroxene (35%) mixture has a strong stabilizing effect, leading to a transition from velocity weakening to velocity strengthening. These results may help constrain the depth range of seismic slips on deep faults in the lower crust of gabbroic composition.

He, Changrong; Luo, Li; Hao, Quan-Ming; Zhou, Yongsheng

2013-07-01

41

Fracture and permeability analysis in magma-hydrothermal transition zones in the Samail ophiolite (Oman)  

NASA Astrophysics Data System (ADS)

Many numerical models have stressed the key importance of processes operative within magma-hydrothermal transition zones of spreading centers, but few studies have attempted a geologic characterization of the key physical parameters of this zone. With this in mind, fracture-related data have been collected in the Samail ophiolite (Oman) within gabbro/dike transition zones and major plagiogranite plutons, and at each site the nature, abundance, orientation, filling, and attitude of the fractures were determined. Two main hydrothermal vein groups can be distinguished: an amphibole vein system and a quartz-epidote-sulfide vein system. Amphibole veins are restricted to the gabbro, whereas quartz-epidote-sulfide veins mainly appear in the sheeted-dike complex and plagiogranite. The amphibole vein system is strongly anisotropic (perpendicular to the layering and subparallel to the sheeted dikes) and heterogeneous. The quartz-epidote-sulfide veins,too, are subparallel to the sheeted dikes. they are characterized by a sharp density decrease of macrosopic veins: from an average 0.5/m (sheeted dikes) to 0.2/m (transition zone) to less than 0.01/m (gabbro). In plagiogranite, where no concentric or radiating vein systems were seen, they are 0.1 to 0.3/m. The ubiquitous presence of ridge parallel hydrothermal veins implies a major contribution of regional tectonic stresses associated with spreading in addition to other mechanisms involved in fracture generation: thermal cracking, volatile-rich magma expansion, differential expansion of pore fluids.

Nehlig, P.

1994-01-01

42

Episodic fluid action during exhumation of deeply subducted continental crust: Geochemical constraints from zoisite-quartz vein and host metabasite in the Dabie orogen  

NASA Astrophysics Data System (ADS)

A combined study of mineral compositions and zircon U-Pb ages was carried out for a zoisite?quartz vein and its host retrograded eclogite in the Dabie orogen. The results reveal two episodes of fluid action during exhumation of the deeply subducted continental crust. The vein has a mineral paragenesis of quartz + zoisite + epidote + white mica + garnet + rutile + zircon + apatite, which is almost the same as that of the host retrograded eclogite characterized by symplectites after omphacite and/or garnet in the eclogite. Residues of magmatic zircon in the vein are similar to those in the eclogite, suggesting local sources of the metamorphic fluid for veining and physical transport of the tiny accessory mineral from the host rock to veins. There are significant differences in major and trace elements between vein-forming minerals, which are attributed to two episodes of fluid action for veining. Metamorphic zircon from the vein yields concordant U-Pb ages of 215 ± 4 to 218 ± 4 Ma. Trace element analysis indicates its precipitation from aqueous fluid during two distinct episodes under eclogite-facies and amphibolite-facies conditions, respectively. Ti-in-zircon and Zr-in-rutile thermometries yield variable temperatures from 537 to 683 °C. Thus the veining postdates the UHP metamorphic event at 225-240 Ma and took place during transition from HP eclogite-facies recrystallization to amphibolite-facies retrogression during the exhumation. The host eclogite was also retrograded in this stage to form metabasites such as amphibole eclogite to garnet amphibolite. The abundant occurrence of zoisite, epidote and phengite in the vein suggests that the metamorphic fluid is rich in Si, Al, Ca and K. The fluid composition is estimated in terms of zoisite composition and zoisite/fluid partition coefficients. The results suggest strong enrichment of LREE, Th, U, Pb, Sr, Rb and Ba, moderate enrichment of HREE, but significant depletion of HFSE. In this regard, the occurrence of metamorphic zircon and rutile in the vein suggests very local saturation of Zr and Ti in the Zo-Qtz vein-forming fluid. Therefore, the two episodes of fluid action would occur at the transition from eclogite to amphibolite facies during the exhumation and proceed with different fluid compositions and different flow behaviors. One was channelized under the eclogite-facies conditions, whereas the other is pervasive under the amphibolite-facies conditions. This provides robust constraints on the time, origin and property of metamorphic fluid during the exhumation of deeply subducted continental crust.

Chen, Ren-Xu; Zheng, Yong-Fei; Hu, Zhaochu

2012-12-01

43

Numerical modelling of mechanical controls on coeval steep and shallow dipping auriferous quartz vein formation in a thrust zone, Macraes mine, New Zealand  

NASA Astrophysics Data System (ADS)

The Hyde-Macraes Shear Zone (HMSZ) is a regionally continuous, low-angle, NE dipping (~15°) late-metamorphic thrust zone in the Mesozoic Otago Schist. The shear zone, which is host to large volumes of mineralised schist, consists of foliated fissile schist with some massive schist pods. Two sets of quartz veins are found within the HMSZ: thrust-related, shallowly dipping veins that were emplaced parallel or sub-parallel to the shears and swarms of steeply dipping extensional veins, which cut across the metamorphic foliation. The latter are restricted to the massive schist pods. Mutual cross-cutting relationships occur between steep extensional veins and shallow-dipping veins, suggesting that they formed contemporaneously. The co-existence of these two vein types locally implies local rotation of the principal stress axes to produce extensional veins within a regional thrust setting. The steep extensional veins are spatially related to lateral and oblique ramps within the HMSZ. Three-dimensional mechanical models show that these lateral or oblique ramps can produce favourable conditions for extensional vein formation when combined with a high fluid pressure and oblique convergence. Mechanical requirements include a reduced differential stress, a positive volumetric strain and an increase in the horizontal shear stress. Our models show that under certain conditions, it is possible for extension-related structures to form during shortening because of local changes in the stress state without the need for a regional scale switch in the imposed stress field. The convergence direction across the HMSZ during formation of the steep extensional veins was ~WNW.

Upton, Phaedra; Begbie, Mike; Craw, Dave

2008-01-01

44

Effects of quartz particle size and water-to-solid ratio on hydrothermal synthesis of tobermorite studied by in-situ time-resolved X-ray diffraction  

SciTech Connect

Hydrothermal synthesis process of tobermorite (5CaO.6SiO{sub 2}.5H{sub 2}O) has been investigated by in-situ X-ray diffraction using high-energy X-rays from a synchrotron radiation source in combination with a purpose-build autoclave cell. Dissolution rates of quartz were largely affected by its particle size distribution in the starting mixtures. However, the composition (Ca/Si) of non-crystalline C-S-H at the start of tobermorite formation was identical regardless of the quartz dissolution rate. An effect of water-to-solid ratio (w/s) was investigated for samples using fine particle quartz. Tobermorite did not occur with w/s of 1.7 but occurred with w/s higher than 3.0. Surprisingly, however, the dissolution curves of quartz were nearly identical for all samples with w/s from 1.7 to 9, indicating that the dissolution rate is predominated by surface area. Possible reaction mechanism for tobermorite formation will be discussed in terms of Ca and/or silicate ion concentration in the liquid phase and distribution of Ca/Si in non-crystalline C-S-H. - Graphical abstract: Time-resolved XRD data set was obtained at up to 190 deg. C under a saturated steam pressure. Tobermorite (5CaO.6SiO{sub 2}.5H{sub 2}O) formation reaction was investigated in detail for several different starting materials. Highlights: > Hydrothermal formation of tobermorite was monitored by in-situ XRD. > Ca/Si of C-S-H at the start time of tobermorite formation was determined. > The Ca/Si value was identical regardless of the quartz particle size in the starting mixture.

Kikuma, J., E-mail: kikuma.jb@om.asahi-kasei.co.jp [Analysis and Simulation Center, Asahi-KASEI Corporation, 2-1 Samejima Fuji, Shizuoka 416-8501 (Japan); Tsunashima, M.; Ishikawa, T.; Matsuno, S. [Analysis and Simulation Center, Asahi-KASEI Corporation, 2-1 Samejima Fuji, Shizuoka 416-8501 (Japan); Ogawa, A.; Matsui, K. [Construction Materials Laboratory, Asahi-KASEI Construction Materials Corporation, Sakai-machi, Ibaraki 306-0493 (Japan); Sato, M. [Industrial Application Division, SPring-8/JASRI, Sayo, Hyogo 679-5198 (Japan)

2011-08-15

45

Quartz veins deformed by diffusion creep-accommodated grain boundary sliding during a transient, high strain-rate event in the Southern Alps, New Zealand  

NASA Astrophysics Data System (ADS)

The crystallographic preferred orientations (CPOs) and microstructures of deformed quartz veins were measured for four samples in the hanging-wall of the Alpine Fault in the Southern Alps, New Zealand. Their deformation and exhumation has occurred since 4 Ma. The quartz veins have been ductilely sheared to finite shear-strains of 5 15 in late Cenozoic shear zones at 450±50 °C, 310±90 MPa and strain-rates between 2×10-11 and 2×10-9 s-1. The sheared veins have a polygonal microstructure with few subgrains and an average grain-size of ˜100 ?m. The CPO of the veins is random to very weak within the shear zones. We suggest that dislocation creep accommodated initial shear deformation, at high stresses and strain-rates. The deformation must have created a strong CPO and concomitant dynamic recrystallization reduced the grain-size significantly. Dissipation of stresses during initial deformation lead to a stress and strain-rate drop required for a switch to diffusion creep-accommodated grain boundary sliding (GBS). Continued shearing accommodated by GBS destroyed the CPO. Post-deformational grain growth gave rise to a final polygonal microstructure with a similar grain size in veins and in the wall rocks. Analysis of existing experimental data suggest that this sequence of events is possible in the time available. Rates of all processes may have been enhanced by the presence of a water-rich fluid within the shear zones. These observations of naturally deformed rocks provide a model for the processes that may occur during short-lived deformation at transiently-high stresses at mid-crustal depths or deeper.

Wightman, Ruth H.; Prior, David J.; Little, Timothy A.

2006-05-01

46

An X-ray excited optical luminescence study of a zoned quartz crystal from an emerald-bearing quartz vein, Hiddenite, North Carolina, USA  

NASA Astrophysics Data System (ADS)

The optical luminescence excited with synchrotron radiation along a preferential orientation of a quartz crystal has been investigated. It is found that the crystal is composed of two distinct regions, only one of which luminesces upon X-ray excitation. This luminescence is generally uniform and exhibits emission bands in the blue (470 nm with a shoulder at 522 nm) and in the UV (340 nm) regions of the spectrum. The branching ratio for the intensity of these bands is sensitive to the excitation energy across the Si K-edge. XANES spectra collected by partial luminescence yield (PLY) suggest that both emission bands originate from the de-excitation of Si atoms in the quartz. The possible defect sites within the crystal structure that could account for the observed luminescence are investigated and discussed. Additional experiments are proposed to verify this assignment of the optical emission bands.

Jürgensen, Astrid; Anderson, Alan J.; Sham, Tsun-Kong

2009-04-01

47

Secondary tungsten minerals in quartz veins in the Ishidera area, Wazuka, Kyoto Prefecture, Japan: anthoinite, mpororoite, and Fe-free hydrokenoelsmoreite  

NASA Astrophysics Data System (ADS)

Secondary minerals of tungsten that are the products of alteration of scheelite present in quartz veins in the Ishidera area, Wazuka, Kyoto Prefecture, have been examined using XRD, SEM-EDS, EPMA, and XRF. From the results, three tungsten minerals were identified: anthoinite, mpororoite, and hydrokenoelsmoreite. The two former minerals have not been reported to be found in Japan. This is, therefore, the first discovery of anthoinite and mpororoite in Japan. The two minerals form a white powdery mixture with pseudomorphing scheelite. Chemical analysis of the mixture shows that the Al/W ratio is approximate to 1 and that the Fe2O3 content is very low, suggesting that the ideal formulae of anthoinite and mpororoite are WAlO3(OH)3 and WAlO3(OH)3·2H2O, respectively, even though the original mpororoite had a high content of Fe2O3 substituting for Al2O3. In addition to these two minerals, another tungsten mineral was also found within the scheelite-pseudomorphs. It occurs as aggregates of regular octahedral crystals up to 50 ?m in length. The XRD data are in good agreement with those for hydrokenoelsmoreite, but chemical analysis shows that the major components are WO3, Al2O3, and H2O with no Fe2O3. Up to this time, only Fe-containing hydrokenoelsmoreite, once termed ferritungstite according to the old nomenclature, has been widely reported to be found in Japan. This paper is the first to report the occurrence of such an Fe-free hydrokenoelsmoreite in Japan. It is likely that these three secondary minerals of tungsten at Wazuka were formed in an environment where the supply of H2O and Al2O3 and the leaching of calcium ions from scheelite took place simultaneously. The source of Al is ascribed to the decomposition of muscovite in the quartz veins.

Shimobayashi, Norimasa; Ohnishi, Masayuki; Tsuruta, Kenji

48

Magmatic 87Sr/86Sr relicts in hydrothermally altered quartz diorites (Brabant Massif, Belgium) and the role of epidote as a Sr filter  

NASA Astrophysics Data System (ADS)

The porphyritic quartz diorites of the Caledonian Brabant Massif have been totally altered. Ca, Rb, Sr, Zr, Ce, Y measurements and Sr-Nd isotopic analyses were performed on the Quenast plug and the Lessines sill, in an attempt to study the relative mobility of Sr and evaluate the extent, direction and magnitude of the 87Sr/86Sr alterations. Sr electron microprobe analyses of epidote were also carried out to assess its role in the Sr distribution. The initial 87Sr/86Sr ratio is shown to have had an unsteady behaviour during the studied water/rock interactions since it has been sometimes enhanced, sometimes depressed and occasionally not modified. The possibility and magnitude of the 87Sr contamination turn out to be strictly related to the degree of Sr accommodation in the secondary minerals. Epidote in particular has proved to be the main trap for the hydrothermal Sr and this mineral is thus regarded as the major controlling factor of 87Sr hydrothermal contamination. The epidote-poor rocks (albite+chlorite-rich rocks) seem to have been unaffected by any Sr interchange with the aqueous solutions. Therefore, as alteration quickly follows the crystallization of the magma, their initial 87Sr/ 86Sr ratio, which is deduced from an isochron, might be a primary petrogenetic feature enabling interpretation of the genesis of their parental magmas. On the other hand, in the epidote-rich rocks, this ratio has been readily altered; it could thus generally be used only to trace the origin of the hydrothermal solutions. As a consequence, these rocks should not be selected for dating an alteration event by the Rb-Sr method.

André, Luc; Deutsch, Sarah

1986-01-01

49

Native gold and ore mineral inclusions in detrital zircon and quartz from the early precambrian quartzites and quartz gravelstones of the Karelian Craton  

NASA Astrophysics Data System (ADS)

The study of solid mineral inclusions in detrital hydrothermal and hydrothermally altered zircons and quartz from Archaean and Palaeoproterozoic (Sumian and Jatulian) terrigenous quartz-rich clastic rocks of the Karelian Craton on a VEGA II LSH-TESKAN microanalyzer has revealed, for the first time, micron-sized native gold inclusions and associated syngenetic inclusions of ore minerals, such as galena, sphalerite, pyrite, chalcopyrite, molybdenite, molybdoscheelite, native bismuth and cerussite, as well as barite and complex hydroaluminophosphates of the goyacite-gorceixite-florencite-plumbogummite group. This mineral association in detrital material could indicate the ore-forming nature of its quartz vein source. These data, together with the earlier results of the local isotopic (SHRIMP-II and LA-ICP-MS) dating of these and similar heterogeneous detrital zircons, are indicative of several hydrothermal events, dated at 3.3, 3.15-2.9 and 2.76-2.65 Ga, which occurred in the region in Archaean time. The two latter ages are consistent with the time of formation of quartz vein ore systems with some of which gold ore-forming processes were associated.

Kozhevnikov, V. N.; Safronov, A. N.

2012-05-01

50

Mineralogy and geochemistry of a Late Permian coal in the Dafang Coalfield, Guizhou, China: Influence from siliceous and iron-rich calcic hydrothermal fluids  

USGS Publications Warehouse

This paper describes the influence of siliceous and iron-rich calcic low-temperature hydrothermal fluids (LTHF) on the mineralogy and geochemistry of the Late Permian No. 11 Coal (anthracitic, Rr =2.85%) in the Dafang Coalfield in northwestern Guizhou Province, China. The No. 11 Coal has high contents of vein ankerite (10.2 vol.%) and vein quartz (11.4 vol.%), with formation temperatures of 85 and 180 ??C, respectively, indicating that vein ankerite and vein quartz were derived from low-temperature calcic and siliceous hydrothermal fluids in two epigenetic episodes. The vein quartz appears to have formed earlier than vein ankerite did, and at least three distinct stages of ankerite formation with different Ca/Sr and Fe/Mn ratios were observed. The two types of mineral veins are sources of different suites of major and trace metals. Scanning electron microscope and sequential extraction studies show that, in addition to Fe, Mg, and Ca, vein ankerite is the dominant source of Mn, Cu, Ni, Pb, and Zn in the coal, and the contents of these five elements are as high as 0.09% and 74.0, 33.6, 185, and 289 ??g/g, respectively. In contrast, vein quartz is the main carrier mineral for platinum-group elements (PGEs) Pd, Pt, and Ir in the coal, and the contents of Pd, Pt, and Ir are 1.57, 0.15, and 0.007 ??g/g, respectively. Sequential extraction showed a high PGE content in the silicate fraction, up to 10.4 ??g/g Pd, 1.23 ??g/g Pt, and 0.05 ??g/g Ir, respectively. It is concluded that the formation of ankerite and quartz and the anomalous enrichment of trace elements in the No. 11 Coal in the Dafang Coalfield, Guizhou, result from the influx of calcic and siliceous low-temperature hydrothermal fluids. ?? 2004 Elsevier B.V. All rights reserved.

Dai, S.; Chou, C. -L.; Yue, M.; Luo, K.; Ren, D.

2005-01-01

51

The pink topaz-bearing calcite, quartz, white mica veins from Ghundao Hill (North West Frontier Province, Pakistan): K/Ar age, stable isotope and REE data  

NASA Astrophysics Data System (ADS)

In the area of the Ghundao Hill (Northern Frontier Province, Pakistan) an orange-yellow to cherry-red topaz is found in calcite, quartz, white mica veins crosscutting the schistosity of probably Silurian to Devonian gray limestones. Topaz with such a range of colours is traded as Imperial Topaz. Low fluorine contents of about 15 wt.%, oxygen isotope thermometry, K/Ar age determination on white mica, fluid inclusion data and mineral textures indicate that the topaz from Ghundao Hill crystallized at temperatures of about 230 °C during the Eocene Himalayan tectonothermal event and not from a late to postmagmatic granite-related fluid. The pink Topaz from Ghundao Hill shares the coexistence with carbonates, low fluorine content and a crystallization at low temperature and pressure during a regional tectonothermal event with the Imperial Topaz from Ouro Preto (Brazil) and from the Sanarka/Kamenka rivers (South Urals, Russia). The efficiency of topaz to remove fluorine from fluids at low temperature explains how topaz can be formed from metamorphic fluids that are typically poor in fluorine. High CO2 activity produced in the fluids by metamorphic decarbonatisation reactions and Al buffering by white mica prevented fluorination of carbonates stabilising topaz relative to fluorite.

Morteani, G.; Voropaev, A.

2007-01-01

52

Origin of the CO 2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisation  

Microsoft Academic Search

The Carará gold deposit, located in the Ipitinga Auriferous District, south-eastern portion of the Guiana Shield, northern Brazil, is a typical orogenic, greenstone-hosted, auriferous quartz vein. Mineralisation was post-metamorphic and syn-tectonic in relation to the host Palaeoproterozoic (ca. 2.03Ga) shear zone developed close to the tectonic boundary between a Palaeoproterozoic continental arc and an Archaean block. The deposit style is

Evandro L. Klein; Kazuo Fuzikawa

2010-01-01

53

Cathodoluminescence characteristics of Archean volcanogenic massive sulfide related quartz: Noranda, Ben Nevis and Matagami districts, Abitibi Subprovince, Canada  

NASA Astrophysics Data System (ADS)

The cathodoluminescence (CL) of quartz from ore, stockwork, veins, and interstitial fillings between lava pillows from the ˜2.7 Ga Noranda, Ben Nevis and Matagami volcanogenic massive sulfide (VMS) districts, Abitibi greenstone belt, has been investigated using the "hot cathode" technique (HC1-LM system) to assess the potential of these various sample types to host primary, seafloor VMS-related fluids trapped as inclusions in minerals with primary depositional morphologies. The CL responses indicate that the various quartz types are of hydrothermal origin, and are therefore a potential host for primary hydrothermal fluid inclusions. Most notable is a transient (t < 120 s) blue CL, characteristic of hydrothermal quartz, observed in most samples. CL characteristics are similar over ˜250 km indicating coherent, nonrandom behavior. Furthermore, in ore and stockwork material from the Matagami and Noranda districts respectively, CL reveals primary concentric growth zoned quartz that predates pulses of sulfide deposition-clear evidence that the quartz is undeformed and directly related to VMS mineralization. These growth zones are not apparent in transmitted light. In addition, ore and stockwork quartz commonly show a very unstable (t < 30 s) yellow CL coincident with microfractures and grain boundaries, defining areas affected by secondary hydrothermal activity. In ore from Matagami, local zones of nontransient brown CL may reflect strain zones associated with the deformation and recrystallization of the massive sulfide mound and indicate that such modifications can be recognized and are minor in the investigated cases. CL clearly reveals pseudo-hexagonal, apparently zoned structures in sulfide-mineralized breccia pipe quartz from the Ben Nevis area. These structures and their host quartz, characterized by a very unstable (t < 20 s) bright yellow CL, are interpreted as recrystallized quartz that has undergone rapid growth from a strongly supersaturated solution and noncrystalline precursor. The CL also clearly reveals colloform/crustiform textures indicative of open-space filling; these textures are not visible optically.

Ioannou, S. E.; GöTze, J.; WeiershäUser, L.; Zubowski, S. M.; Spooner, E. T. C.

2004-02-01

54

Microbeam Analyses of Rare-Earth Element (REE) and Sr Isotopes of Anhydrite Veins From the PACMANUS Hydrothermal System  

Microsoft Academic Search

Ocean Drilling Program Leg 193 drilled into areas of focused and diffuse venting from the PACMANUS hydrothermal field along Pual Ridge, eastern Manus Basin. Pual Ridge is primarily composed of fresh dacite that is pervasively altered to argillaceous (illite-chlorite) and overprinting acid-sulfate (pyrophyllite-anhydrite) and siliceous secondary mineral assemblages. Anhydrite is an abundant precipitate in all cores recovered beneath the active

P. R. Craddock; W. Bach

2004-01-01

55

Hydrothermal evolution of the Sar-Cheshmeh porphyry Cu Mo deposit, Iran: Evidence from fluid inclusions  

NASA Astrophysics Data System (ADS)

The Sar-Cheshmeh porphyry Cu Mo deposit is located in Southwestern Iran (˜65 km southwest of Kerman City) and is associated with a composite Miocene stock, ranging in composition from diorite through granodiorite to quartz-monzonite. Field observations and petrographic studies demonstrate that the emplacement of the Sar-Cheshmeh stock took place in several pulses, each with associated hydrothermal activity. Molybdenum was concentrated at a very early stage in the evolution of the hydrothermal system and copper was concentrated later. Four main vein Groups have been identified: (I) quartz+molybdenite+anhydrite±K-feldspar with minor pyrite, chalcopyrite and bornite; (II) quartz+chalcopyrite+pyrite±molybdenite±calcite; (III) quartz+pyrite+calcite±chalcopyrite±anhydrite (gypsum)±molybdenite; (IV) quartz±calcite±gypsum±pyrite±dolomite. Early hydrothermal alteration produced a potassic assemblage (orthoclase-biotite) in the central part of the stock, propylitic alteration occurred in the peripheral parts of the stock, contemporaneously with potassic alteration, and phyllic alteration occurred later, overprinting earlier alteration. The early hydrothermal fluids are represented by high temperature (350 520 °C), high salinity (up to 61 wt% NaCl equivalent) liquid-rich fluid inclusions, and high temperature (340 570 °C), low-salinity, vapor-rich inclusions. These fluids are interpreted to represent an orthomagmatic fluid, which cooled episodically; the brines are interpreted to have caused potassic alteration and deposition of Group I and II quartz veins containing molybdenite and chalcopyrite. Propylitic alteration is attributed to a liquid-rich, lower temperature (220 310 °C), Ca-rich, evolved meteoric fluid. Influx of meteoric water into the central part of the system and mixing with magmatic fluid produced albitization at depth and shallow phyllic alteration. This influx also caused the dissolution of early-formed copper sulphides and the remobilization of Cu into the sericitic zone, the main zone of the copper deposition in Sar-Cheshmeh, where it was redeposited in response to a decrease in temperature.

Hezarkhani, Ardeshir

2006-12-01

56

Garnet-spinel-corundum-quartz-bearing titanohematite veins in eclogite from the Sulu ultrahigh-pressure terrane: Imprint of a short-lived, high-temperature metamorphic stage  

NASA Astrophysics Data System (ADS)

Mineral assemblage of spinel + corundum + quartz was reported in the Sulu UHP belt. Unusual spinel + corundum + quartz assemblage implies a high-T condition (>900 °C). Growth zoning preserved in the garnet implies that high-T stage is short-lived. High-T could have induced granulite-facies metamorphism and partial melting.

Zong, Keqing; Liu, Yongsheng; Gao, Changgui; Hu, Zhaochu; Gao, Shan

2011-09-01

57

Hydrothermal alteration and REE-Th mineralization at the Rodeo de Los Molles deposit, Las Chacras batholith, central Argentina  

Microsoft Academic Search

REE (rare-earth-element) and Th mineralization at the Rodeo de Los Molles deposit occurs within an elliptical body of hydrothermally altered rocks (fenite) located in a biotite monzogranite of the Las Chacras batholith. Ore assemblages are found as isolated patches of intergrown britholite, allanite, apatite, bastnaesite, fluorite, sphene, quartz, and aegirine-augite, as well as nodules of uranothorite and late-stage veins of

Raul Lira; Edward M. Ripley

1992-01-01

58

Fluid chemistry and evolution of hydrothermal fluids in an Archaean transcrustal fault zone network: The case of the Cadillac Tectonic Zone, Abitibi greenstone belt, Canada  

USGS Publications Warehouse

Detailed fluid geochemistry studies on hydrothermal quartz veins from the Rouyn-Noranda and Val-d'Or areas along the transcrustal Cadillac Tectonic Zone (CTZ) indicate that unmineralized (with respect to gold) sections of the CTZ contained a distinct CO2-dominated, H2S-poor hydrothermal fluid. In contrast, both gold mineralized sections of the CTZ (e.g., at Orenada #2) and associated higher order shear zones have a H2O-CO2 ?? CH4-NaCl hydrothermal fluid. Their CO2/H2S ratios indicate H2S-rich compositions. The Br/Cl compositions in fluid inclusions trapped in these veins indicate that hydrothermal fluids have been equilibrated with the crust. Oxygen isotope ratios from hydrothermal quartz veins in the CTZ are consistently 2??? more enriched than those of associated higher order shear zones, which are interpreted to be a function of greater fluid/rock ratios in the CTZ and lower fluid/rock ratios, and more efficient equilibration of the hydrothermal fluid with the wall rock, in higher order shear zones. An implication from this study is that the lower metal endowment of the transcrustal CTZ, when compared with the higher metal endowment in higher order shear zones (ratio of about 1 : 1000), may be the result of the lack of significant amounts of H2O-H2S rich fluids in most of the CTZ. In contrast, gold mineralization in the higher order shear zones appear to be controlled by the high H2S activity of the aqueous fluids, because gold was likely transported in a bisulfide complex and was deposited during sulfidation reactions in the wall rock and phase separation in the quartz veins. ?? 2007 NRC Canada.

Neumayr, P.; Hagemann, S. G.; Banks, D. A.; Yardley, B. W. D.; Couture, J. -F.; Landis, G. P.; Rye, R.

2007-01-01

59

Magnesiochloritoid-talc-garnet assemblages from the Tauern Window, Eastern Alps, Austria: high pressure metamorphosed oceanic hydrothermal veins  

NASA Astrophysics Data System (ADS)

Magnesiochloritoid is a comparatively rare phase typically formed at pressures >2.0 GPa in Mg-rich meta-igneous and meta-sedimentary bulk compositions. While this phase has been described from a number of localities in the Western Alps including the Zermatt-Saas and Monviso ophiolites and the Monte Rosa Massif, only one locality from the Eastern Alps has been known so far which is located in the eclogite zone of the Tauern Window. Here, magnesiochloritoid was found in a fine-grained massive eclogite as large postkinematic poikiloblasts up to 5 mm in size that overgrow a mylonitic assemblage of garnet + omphacite + kyanite + talc + chlorite + rutile + paragonite + calcic amphibole, the latter two phases being products of retrogressive breakdown of kyanite + omphacite. In addition, magnesiochloritoid is present as decimeter-size segregations coexisting with talc + kyanite ± chlorite ± rutile ± paragonite. Magnesiochlorioid has an XMg of 0.63 which is well within the XMg range of 0.61--0.85 reported from the Western Alps. Omphacite appears in two generations: (1) large corroded and strongly zoned grains with rel. Al-poor and Fe-rich cores (jd37, XMg = 0.83) and Al-rich and Fe-poor rims (jd42-46, XMg = 0.91--0.94) and (2) small idomorphic grains (jd46-48, XMg = 0.96--0.98) similar in composition to rims of large corroded grains. Garnet, too, is strongly zoned with Mg-poor cores (alm62py15gross17) and discontinuous Mg-rich rims (alm42py39gross16). This zoning is attributed to recrystallization as a result of deformation under increasing pressure. Peak metamorphic conditions of 2.04 ± 0.16 GPa at temperatures of 623 ± 17^oC were derived from the equilibrium chlorite + kyanite = magnesiochloritoid + talc and the Fe-Mg exchange between garnet and clinopyroxene which is in good agreement with PT-data from mafic eclogites of the Tauern Window. The Mg-rich and Ca-poor bulk composition (11.6 wt% MgO, 7.8 wt% CaO) responsible for the presence of magnesiochloritoid and its occurrence in segregations associated with talc can be explained by Mg-metasomatism with attendant Ca-depletion as a result of ocean-floor hydrothermal activity that led to an enrichment of chlorite and/or smectite (cf. Widmer 1996). Trace element and isotopic whole rock data indicate an E-type MORB affinity. The absence of negative Nb-Ta-Ti anomalies precludes a subduction-modified and/or any significant crustal source component. Lit.: Widmer, T. et al., (2000) Schweiz. Mineral. Petrogr. Mitt. 80, 63--73

Miller, C.; Konzett, J.

2003-04-01

60

Iceland Deep Drilling Project (IDDP): (IV) Fluid Inclusion Microthermometry of the Geitafell Hydrothermal System - a Possible Analog of the Active Krafla System  

NASA Astrophysics Data System (ADS)

The Miocene Geitafell volcanic complex in southeast Iceland hosts an extinct high temperature hydrothermal system that provides an excellent opportunity for study of the interior of an analog to the Krafla and Hengill active systems, which will be penetrated by IDDP drilling. The Geitafell volcano formed on the central Icelandic rift zone at approximately 5-6 Ma. Glacial erosion has exposed the deep interior of the volcano, revealing a complex of tholeitic lavas, hyaloclastites and rhyolites, cut by 12 intrusive phases and a sequence of seven related vein sets with distinct vein fillings and alteration haloes. Mineralogical studies by Fridleifsson (1983) show that when Geitafell was active, it hosted a supercritical hydrothermal system with fluids exceeding 400°°C at pressures up to 300 bar. We have begun fluid inclusion microthermometry studies of this system with the goal to define the specific relationship of the vein sequence to vein temperatures and alteration haloes, and thereby improve the understanding of supercritical hydrothermal systems . We have sampled veins in a basaltic lava from Fridleifsson's vein sets 2 and 3, and a quartz-filled amygdale tied to vein set 2. Vein set 2 is bordered by a narrow (5-10mm) dark alteration halo of chlorite and albite; set 3 veins have cm-scale epidote-rich envelopes. Fluid inclusions were not visible in the quartz and epidote of vein set 3, but quartz in vein set 2 contains abundant fluid inclusions 5 to 15 micrometers in size with vapor bubbles ranging from 10 to 60 vol%. In the amygdale, fluid inclusions are 5 to 30 micronmeters in size with vapor bubbles ranging from 25 to 60 vol%. The average freezing point depression for vein set 2 and amygdale inclusions is 0.1°°C, indicating a salinity of 0.2 wt% NaCl equivalent--largely fresh water. Fluid inclusions homogenize to liquid or to vapor at temperatures ranging from approximately 300 to 394°°C. Most liquid-dominated inclusions homogenize between 300 and 380°°C. The coexisting vapor rich and liquid rich inclusions and the homogenization behavior indicate a boiling hydrothermal system at a temperature of at least 380°°C.

Troyer, R.; Reed, M. H.; Elders, W. A.; Fridleifsson, G. O.

2007-12-01

61

Two-phase separation of fossil hydrothermal fluids in the Mid-Indian Ridge ophiolites  

NASA Astrophysics Data System (ADS)

Rocks of the ophiolite suite were dredged from the axis of the Mid-Indian Ridge at 1 °N. Three stages of their hydrothermal alteration were identified: (1) actinolite-epidote-albite (420-450°C), (2) epidote-chlorite-quartz, and (3) chlorite-smectite (190°C). Epidote-chlorite-quartz veins cutting basaltic breccias include an opaque, amorphous, Na-bearing silica rock that grades into cryptocrystalline quartz. Sometimes it contains rare transparent microcrystalline inclusions, which may be inferred from their high Na, Cl, and Si contents to be quartz intergrown with halite. The specific bulk composition, structure, and texture of the matter allow the interpretation that it is a lithified fossil colloid, precipitated from a highly saline hydrothermal solution as a result of phase separation in the Na?Si?Cl?H 2O system at elevated PT-conditions. The phase separation of hydrothermal fluids is proposed as a mechanism generating supersaturated salt-silicate solutions with simultaneous precipitation of ore components. The latter is confirmed by the negligible Fe and Mn concentrations in both the colloidal matrix and the microcrystalline inclusions in the presence of disseminated ore mineralization in the examined basalt breccias.

Plyusnina, L. P.; Vysotsky, S. V.

1994-05-01

62

Silica Transport and Distribution in Saline, Immiscible Fluids: Application to Subseafloor Hydrothermal Systems  

Microsoft Academic Search

Quartz is a nearly ubiquitous gangue mineral in hydrothermal mineral deposits, most often constituting the bulk of hydrothermal mineralization. The dissolution, transport and precipitation of quartz is controlled by the solubility of silica; in particular, in hot hydrothermal fluids in contact with quartz, silica saturation can generally be assumed, as rates of dissolution and precipitation are generally much faster than

M. Steele-Macinnis; R. J. Bodnar; R. Lowell; J. D. Rimstidt

2009-01-01

63

Fate of trace elements during alteration of uraninite in a hydrothermal vein-type U-deposit from Marshall Pass, Colorado, USA  

NASA Astrophysics Data System (ADS)

Alteration of uraninite from a hydrothermal vein-type U-deposit in Marshall Pass, Colorado, has been examined by electron microprobe analysis in order to investigate the release and migration of trace elements W, As, Mo, Zr, Pb, Ba, Ce, Y, Ca, Ti, P, Th, Fe, Si, Al, during alteration, under both reducing and oxidizing conditions. The release of trace elements from uraninite is used to establish constraints on the release of fission product elements from the UO2 in spent nuclear fuels. Uraninite occurs with two different textures: (1) colloform uraninite and (2) fine-grained uraninite. The colloform uraninite contains 1.04 1.75 wt% of WO3, 0.16 1.70 wt% of As2O3, 0.06 0.88 wt% of MoO3; whereas, the fine-grained uraninite retains 2.25 4.93 wt% of WO3, up to 5.76 wt% of MoO3, and 0.26 0.60 wt% of As2O3. The near constant concentration of incompatible W in the colloform uraninite suggests W-incorporation into the uraninite structure or homogeneous distribution of W-rich nano-domains. Incorporation of W and Mo into the uraninite and subsequent precipitation of uranyl phases bearing these elements are critically important to understanding the release and migration of Cs during the corrosion of spent nuclear fuel, as there is a strong affinity of Cs with W and Mo. Zoning in the colloform texture is attributed to variation in the amount of impurities in uraninite. For unaltered zones, the calculated amount of oxygen ranges from 2.08 to 2.32 [apfu, (atom per formula unit)] and defines the stoichiometry as UO2+x and U4O9; whereas, for the altered zones of the colloform texture, the oxygen content is 2.37 2.48 [apfu], which is probably due to the inclusion of secondary uranyl phases, mainly schoepite. The supergene alteration resulted in precipitation of secondary uranyl minerals at the expense of uraninite. Four stages of colloform uraninite alteration are proposed: (i) formation of an oxidized layer at the rim, (ii) corrosion of the oxidized layer, (iii) precipitation of U6+-phases with well-defined cleavage, and (iv) fracture of the uraninite surface along the cleavage planes of the U6+-phases.

Deditius, Artur P.; Utsunomiya, Satoshi; Ewing, Rodney C.

2007-10-01

64

Hydrothermal clinopyroxenes of the Skaergaard intrusion  

Microsoft Academic Search

Magmatic augites reacted with high temperature aqueous solutions to form secondary calcic pyroxenes during the subsolidus cooling of the Skaergaard intrusion. Secondary, hydrothermal clinopyroxenes replace wall rock igneous augites at the margins of veins filled with calcic amphibole. These veins are up to several millimeters wide and tens of meters in length. Hydrothermal clinopyroxenes are a ubiquitous and characteristic phase

Craig E. Manning; Dennis K. Bird

1986-01-01

65

Hydrothermal alteration, ore fluid characteristics, and gold depositional processes along a trondhjemite-komatiite contact at Tarmoola, Western Australia  

USGS Publications Warehouse

Tarmoola is a structurally controlled Archean orogenic gold deposit hosted in greenschist facies metamorphosed komatiite and trondhjemite in the Leonora district of the Eastern Goldfields province, Yilgarn craton. High-grade (>1 g/t Au) orebodies are located in komatiite wall rock adjacent to the eastern and northeastern margins of the asymmetrical, north-south-striking, Tarmoola trondhjemite intrusion. Gold-bearing veins post-date trondhjemite emplacement (ca. 2700 Ma), quartz diorite dikes (ca. 2667 Ma), and regional greenschist facies metamorphism. Textures and crosscutting relationships in gold-bearing veins indicate two stages of hydrothermal fluid infiltration associated with a single gold-related hydrothermal event: a volumetrically dominant, but gold-poor, stage I fluid and a gold-rich stage II fluid. Gold-bearing veins contain stage I milky quartz and pyrite that are overprinted by stage II quartz-ankerite-muscovite-chalcopyrite-sphalerite-galena-gold-tellurides ?? albite ?? chlorite ?? fuchsite ?? epidote ?? scheelite. Stage I hydrothermal alteration assemblages are different in trondhjemite and komatiite due to contrasting reactions between a common ore fluid and disparate wall-rock chemistry. Stage II fluid-wall rock interaction was minor compared to stage I and is indicated by the overprinting of stage I mineral assemblages by stage II microveins. Wall-rock alteration proximal to veins in trondhjemite is characterized by replacement of igneous plagioclase, amphibole, biotite, and metamorphic chlorite by hydrothermal quartz, muscovite, ankerite, calcite, pyrite, chalcopyrite, sphalerite, galena, tellurides, and gold, whereas in proximal alteration in komatiite, metamorphic chlorite and talc are replaced by ankerite, quartz, muscovite, albite, chlorite, fuchsite, pyrite, chalcopyrite, sphalerite, galena, tellurides, and gold. The stage II fluid was enriched in H2O, CO2, Si, Ca, K, Na, S, Au, Ag, Cu, Pb, W, Bi, As, Mo, Zn, and Te. Based on fluid inclusion studies and stage II mineral equilibria, gold deposited from a homogeneous, neutral to slightly alkaline (pH 5.1-5.5), reduced, low-salinity (<5.5 wt % NaCl equiv) fluid that had a bulk composition of 78 mole percent H2O and 21 mole percent CO2, and trace amounts of CH4, C2H6, H2, Ar, H2S, and He. Gold deposition occurred at 300?? ?? 50??C and 0.5 to 3.0 kbars. Assuming lithostatic fluid pressures, gold precipitated at a 2- to 10-km depth. Stage II gray quartz ??18Ofluid values range from 5.9 to 7.5 per mil, whereas ??Dfluid values calculated from the dehydration of muscovite grains and measured directly from bulk fluid inclusion analyses of stage II gray quartz have ranges of -9 to -35 and -27 to -28 per mil, respectively. Hydrothermal ore fluids were transported from greater crustal depths to the site of gold deposition during the district-scale D3 event by shallowly W dipping, reverse brittle-ductile shear zones in supracrustal rock and along the steeply east dipping trondhjemite contact. Associated subhorizontal east-west shortening caused the reactivation of the eastern trondhjemite margin and subparallel foliation, which facilitated the transport of hydrothermal fluids and the generation of gold-bearing veins and hydrothermal alteration zones in komatiite. East-west-striking fractures in trondhjemite aided the lateral migration of ore fluids away from trondhjemite margins and the formation of east-west-striking gold-bearing veins and broad alteration zones. Gold was most likely transported in the stage II fluid as bisulfide complexes. The sulfidation of trondhjemite and komatiite wall rock by the stage II fluid caused the destabilization of An bisulfide complexes and gold deposition. Potassium, Ca, and CO2 metasomatism of komatiite wall rock may have enhanced gold deposition via the acidification of the stage II fluid. The physicochemical characteristics of the Tarmoola ore fluid and relative timing of gold mineralization are consistent with the Yilgarn-wide,

Duuring, P.; Hagemann, S. G.; Cassidy, K. F.; Johnson, C. A.

2004-01-01

66

P-T-X conditions of late Hercynian fluid penetration and the origin of granite-hosted gold quartz veins in northwestern Iberia: A multidisciplinary study of fluid inclusions and their chemistry  

NASA Astrophysics Data System (ADS)

Quartz veins hosted by late Hercynian granites and their host rocks occur across the Variscides of the northern Iberian peninsula, and locally display Au-As mineralization. Four separate occurrences at Corcoesto, Tomino, Penedono, and Pino have been investigated to determine P-T-X conditions of formation and likely fluid sources. Special attention has been paid to fluid chemistry using a multidisciplinary investigation of fluid inclusion gases by Raman spectroscopy (individual fluid inclusion analysis) and mass spectrometry (bulk analysis), and ion chemistry using microthermometry and bulk leachate chemical analysis. Two major changes in the chemical and physical environment have been identified: (1) a progressive change in the bulk chemical composition from early CO 2-rich, C-H-O-(N) fluids, equilibrated with graphitic metamorphic host rocks, to late H 2O-dominated fluids, inferred from their halogen signature to result from an influx of meteoric or upper crustal fluids affecting the basement at the end of Variscan orogenesis, and (2) changes in the P-T conditions from early stage sulphide deposition in quartz veins, at ca. 450 °C and 150-300 MPa, towards epithermal conditions, ca. 260-310 °C and <75 MPa, at the stage of gold mineralization. Several chemical trends are shown by the fluid inclusions: (1) dilution of the early volatile-rich fluids, (2) a break of graphite buffering activity demonstrated by the CH 4 content increase in the volatile fraction of the latest As mineralizing fluids, and (3) increasing contribution of a relatively oxidizing fluid enriched in sulphate and bromide during the latest stages of fluid percolation (Au stage). These latest fluid stages are interpreted as indicative of extended fluid penetration downward in the crust enhanced by late brittle deformation and decompression, and played an important role in mass transfer at the end of the Hercynian orogeny, especially in transport of metals. Gold ores have formed mostly in granites because main fluid pathways developed in the main structurally active zones which favoured the emplacement of the granites. However, there is no evidence of genetic link between gold ores and their enclosing granites.

Boiron, M.-C.; cathelineau, M.; Banks, D. A.; Yardley, B. W. D.; Noronha, F.; Miller, M. F.

1996-01-01

67

Hydrothermal factors in porosity evolution and caprock formation at the Geysers steam field, California--insight from the Geysers Coring Project  

SciTech Connect

The Department of Energy (DOE)/geothermal industry-sponsored Geysers Coring Project (GCP) has yielded 236.8 m of continuous core apparently spanning the transition between the uppermost Geysers steam reservoir and its caprock. Both zones in the corehole are developed in superficially similar, fractured, complexly veined and locally sericitized, Franciscan (late Mesozoic) graywacke-argillite sequences. However, whereas the reservoir rocks host two major fluid conduits (potential steam entries), the caprock is only sparingly permeable. This discrepancy appears to reflect principally vein texture and mineralogy. Two types of veins are common in the core--randomly-oriented, Franciscan metamorphic quartz-calcite veins; and high-angle, late Cenozoic veins deposited by The Geysers hydrothermal system. The older veins locally contain hydrothermal carbonate-dissolution vugs, which, although concentrated at the larger fluid conduit, are scattered throughout the core. The younger veins, commonly with intercrystalline vugs, consist dominantly of euhedral quartz, calcite, K-feldspar, wairakite, and pyrite--those in the reservoir rock also contain minor epidote and illite. The corresponding caprock veins are devoid of epidote but contain abundant, late-stage, mixed-layer illite/smecite (5-18% smectite interlayers) with minor chlorite/smectite (40-45% smectite interlayers). We suggest that clots of these two expandable clays in the caprock clog otherwise permeable veins and carbonate-dissolution networks at strategic sites to produce or enhance the seal on the underlying steam reservoir. Illite/smectite geothermometry indicates that the SB-15-D caprock clays were precipitated in the approximate temperature range 180-218 C, and those in the reservoir at about 218-238 C. These temperatures, along with occurrence of the clays on commonly etched calcite, K-feldspar, or wairakite, suggest that the clays were precipitated from mildly acidic steam condensate under conditions similar to those now prevailing.

Hulen, Jeffrey B.; Nielson, Dennis L.

1995-01-26

68

Mineralogy and stable isotope geochemistry of hydrothermally altered oceanic rocks  

USGS Publications Warehouse

Mineralogical and isotopic variations observed in altered glassy and crystalline rocks from the East Pacific Rise and the Mid-Atlantic Ridge provide information about the temperatures of alteration and seawater/rock ratios for various hydrothermal regimes within the oceanic crust. A systematic increase in alteration temperature is evident for the glassy rocks in the sequence: (1) nontronite and celadonite vesicle fillings (35??C), (2) saponite-rich pillow breccias (130-170??C), (3) calcite-rich greenstone breccias and epidote-rich greenstone (200-350??C). These results include the highest temperatures thus far reported for saponite formation. The "seawater-dominated" hydrothermal alteration process that formed the saponite-rich pillow breccias is characterized by high water/rock ratios (>50:1), low to moderate temperatures, a seawater origin of most of the carbon in vein calcites (??13 C ??? 0) and the predominance of Fe-rich saponite and calcite as secondary phases. Greenstones (chlorite-quartz-epidote) and greenstone breccias (chlorite-quartz-albite-calcite) are altered in a "rock-dominated" system with lower water/rock ratios (50:1 to < 1:1), higher temperatures, and vein calcites with carbon that is principally of magmatic origin (??13 C ??? -4). The crystalline rocks (diabase, gabrro, and metagabbro) are affected to varying degrees by pervasive high-temperature seawater interactions that commence soon after solidification, producing varying proportions of fine-grained secondary minerals including talc, smectite, chlorite, vermiculite, actinolite, and sodic plagioclase. Hydrothermal solutions, derived from alteration of the crystalline rocks, are of the appropriate temperature and isotopic composition to alter the overlying glassy rocks to the observed mineralogies as well as being the source of metal-rich deposits associated with the oceanic spreading centers. ?? 1982.

Stakes, D. S.; O'Neil, J. R.

1982-01-01

69

Geology, alteration, age, and origin of iron oxide-apatite deposits in Upper Eocene quartz monzonite, Zanjan district, NW Iran  

NASA Astrophysics Data System (ADS)

Iron oxide-apatite deposits are present in Upper Eocene pyroxene-quartz monzonitic rocks of the Zanjan district, northwestern Iran. Mineralization occurred in five stages: (1) deposition of disseminated magnetite and apatite in the host rock; (2) mineralization of massive and banded magnetite ores in veins and stockwork associated with minor brecciation and calcic alteration of host rocks; (3) deposition of sulfide ores together with potassic alteration; (4) formation of quartz and carbonate veins and sericite, chlorite, epidote, silica, carbonate, and tourmaline alteration; and (5) supergene alteration and weathering. U-Pb dating of monazite inclusions in the apatite indicates an age of 39.99 ± 0.24 Ma, which is nearly coeval with the time of emplacement of the host quartz monzonite, supporting the genetic connection. Fluid inclusions in the apatite have homogenization temperatures of about 300 °C and oxygen isotopic compositions of the magnetite support precipitation from magmatic fluids. Late-stage quartz resulted from the introduction of a cooler, less saline, and isotopically depleted fluid. The iron oxide-apatite deposits in the Tarom area of the Zanjan district are typical of a magmatic-hydrothermal origin and are similar to the Kiruna-type deposits with respect to mineral assemblages, fabric and structure of the iron ores, occurrence of the ore bodies, and wall rock alteration.

Nabatian, Ghasem; Ghaderi, Majid; Corfu, Fernando; Neubauer, Franz; Bernroider, Manfred; Prokofiev, Vsevolod; Honarmand, Maryam

2013-09-01

70

Characterization and timing of the different types of fluids present in the barren and ore-veins of the WSn deposit of Panasqueira, Central Portugal  

Microsoft Academic Search

The Panasqueira W-Sn deposit is the largest quartz-vein type deposit of the Iberian Peninsula and the most important wolframite deposit in Western Europe. The ore-veins are almost exclusively sub-horizontal. Besides ore-bearing sub-horizontal veins, the Panasqueira mine also contains barren quartz veins. There are essentially two generations of barren quartz: quartz, contemporaneous with the earliest regional metamorphism (QI), and recrystallized quartz,

F. Noronha; A. Doria; J. Dubessy; B. Charoy

1992-01-01

71

Petrology of hydrothermal alteration in the Vargeão basaltic impact structure (South Brazil)  

NASA Astrophysics Data System (ADS)

Impact cratering process is of primary importance in the evolution of solid bodies of the Solar System. But craters on basaltic rocks, which are the best analog for the surface of other planets and satellites, are rare on Earth. Most studies to date were done in the Lonar crater, a simple crater 1.8 km in diameter, formed on the basaltic flows of the Deccan Province (India). Recently, one medium-size complex crater was identified on volcanic rocks of the Paraná basin (south Brazil) and may provide additional analog to the craters of most rocky planets and satellites. The 12 km wide Vargeão is a very well-preserved impact structure formed on basaltic and subordinately rhyodacites flows of the Serra Geral Formation (about 133-131 Ma), which are locally intertrapped by eolian-sandstones of Botucatu Formation. The impact-related features are represented by shatter cones, breccia-veins and planar deformation features in quartz (few occurrence in the sandstones). This work is focused on the petrogenesis of the centimeter breccia-veins that are found in all lithologies. We conducted a detailed petrological study (petrography, microprobe, SEM, Raman spectroscopy, Spectroscopy of reflectance and XRD) on these veins and their host-rocks. Our results show that the veins were strongly affected by the post-impact hydrothermal fluids. The hydrothermal alteration varies geographically in the structure. On the rim area this alteration consists of total or partial substitution of the melt matrix by quartz, calcite, iron oxides and clay minerals. At the central area, the alteration mineral assembly is composed of quartz, iron oxides, zeolites, clay minerals and rarely calcite. Usually, the alteration shows a zoned setting, which also varies locally. The nature of occurrence of second mineral identified in the context of post-impact hydrothermal alteration of impact craters on basalt represent a critical interpretation to interpret alteration signature of impact craters and the old Noachian terrains of Mars. The interpretation of these signature remain controversial. These signature may result from the excavation of globally altered volcanic material during a warm and wet Mars, or alternatively may be more or less exclusively the results of impact-associated hydrothermal alteration. Our results at Vargeão may be used to assess these different hypotheses.

Yokoyama, E.; Nédélec, A.; Trindade, R. I.; Baratoux, D.; Berger, G.

2011-12-01

72

Stratigraphic development and hydrothermal activity in the Central Western Cascade Range, Oregon  

NASA Astrophysics Data System (ADS)

Two volcanic sequences bounded by erosional unconformities compose the stratigraphy of the North Santiam mining district, Western Cascade Range, Oregon. Diorite, granodiorite, and leucocratic quartz porphyry dikes, stocks, and sills intrude the breccias, flows, and tuffs of a volcanic center in the older Sardine Formation. Tourmaline-bearing breccia pipes are associated with the porphyritic granodiorite intrusions. An erosional unconformity separates the Sardine Formation from the overlying Elk Lake formation. The alteration patterns in the two formations are consistent with the development of hydrothermal systems during the eruption of each formation. However, the development of the two hydrothermal systems is separated by a period of erosion of the older volcanic pile. Early formation of mineralization that resembles porphyry copper deposits occurred within the Sardine Formation, and later, after eruption of the Elk Lake formation, epithermal veins and alteration developed along faults, fractures, and the margins of dikes in the Sardine Formation.

Cummings, Michael L.; Pollock, J. Michael; Thompson, Gordon D.; Bull, Marilyn K.

1990-11-01

73

Quartz Crystal.  

National Technical Information Service (NTIS)

Electronic-grade quartz crystal is single-crystal silica that is free of all macroscopic defects and has piezoelectric properties that permit it to be used in electronic circuits for accurate frequency control, timing, and filtration. These uses generate ...

J. E. Ferrell

1985-01-01

74

Geology of the epithermal Ag-Au Huevos Verdes vein system and San José district, Deseado massif, Patagonia, Argentina  

NASA Astrophysics Data System (ADS)

The San José district is located in the northwest part of the Deseado massif and hosts a number of epithermal Ag-Au quartz veins of intermediate sulfidation style, including the Huevos Verdes vein system. Veins are hosted by andesitic rocks of the Bajo Pobre Formation and locally by rhyodacitic pyroclastic rocks of the Chon Aike Formation. New 40Ar/39Ar constraints on the age of host rocks and mineralization define Late Jurassic ages of 151.3 ± 0.7 Ma to 144.7 ± 0.1 Ma for volcanic rocks of the Bajo Pobre Formation and of 147.6 ± 1.1 Ma for the Chon Aike Formation. Illite ages of the Huevos Verdes vein system of 140.8 ± 0.2 and 140.5 ± 0.3 Ma are 4 m.y. younger than the volcanic host rock unit. These age dates are among the youngest reported for Jurassic volcanism in the Deseado massif and correlate well with the regional context of magmatic and hydrothermal activity. The Huevos Verdes vein system has a strike length of 2,000 m, with several ore shoots along strike. The vein consists of a pre-ore stage and three main ore stages. Early barren quartz and chalcedony are followed by a mottled quartz stage of coarse saccharoidal quartz with irregular streaks and discontinuous bands of sulfide-rich material. The banded quartz-sulfide stage consists of sulfide-rich bands alternating with bands of quartz and bands of chlorite ± illite. Late-stage sulfide-rich veinlets are associated with kaolinite gangue. Ore minerals are argentite and electrum, together with pyrite, sphalerite, galena, chalcopyrite, minor bornite, covellite, and ruby silver. Wall rock alteration is characterized by narrow (< 3 m) halos of illite and illite/smectite next to veins, grading outward into propylitic alteration. Gangue minerals are dominantly massive quartz intergrown with minor to accessory adularia. Epidote, illite, illite/smectite, and, preferentially at deeper levels, Fe-chlorite gangue indicate near-neutral pH hydrothermal fluids at temperatures of >220°C. Kaolinite occurring with the late sulfide-rich veinlet stage indicates pH < 4 and a temperature of <200°C. The Huevos Verdes system has an overall strike of 325°, dipping on average 65° NE. The orientations of individual ore shoots are controlled by vein strike and intersecting north-northwest-striking faults. We propose a structural model for the time of mineralization of the San José district, consisting of a conjugate shear pair of sinistral north-northwest- and dextral west-northwest-striking faults that correspond to R and R' in the Riedel shear model and that are related to master faults (M) of north-northeast-strike. Veins of 315° strike can be interpreted as nearly pure extensional fractures (T). Variations in vein strike predict an induced sinistral shear component for strike directions of >315°, whereas strike directions of <315° are predicted with an induced dextral strike-slip movement. The components of the structural model appear to be present on a regional scale and are not restricted to the San José district.

Dietrich, Andreas; Gutierrez, Ronald; Nelson, Eric P.; Layer, Paul W.

2011-05-01

75

Geology of the epithermal Ag-Au Huevos Verdes vein system and San José district, Deseado massif, Patagonia, Argentina  

NASA Astrophysics Data System (ADS)

The San José district is located in the northwest part of the Deseado massif and hosts a number of epithermal Ag-Au quartz veins of intermediate sulfidation style, including the Huevos Verdes vein system. Veins are hosted by andesitic rocks of the Bajo Pobre Formation and locally by rhyodacitic pyroclastic rocks of the Chon Aike Formation. New 40Ar/39Ar constraints on the age of host rocks and mineralization define Late Jurassic ages of 151.3 ± 0.7 Ma to 144.7 ± 0.1 Ma for volcanic rocks of the Bajo Pobre Formation and of 147.6 ± 1.1 Ma for the Chon Aike Formation. Illite ages of the Huevos Verdes vein system of 140.8 ± 0.2 and 140.5 ± 0.3 Ma are 4 m.y. younger than the volcanic host rock unit. These age dates are among the youngest reported for Jurassic volcanism in the Deseado massif and correlate well with the regional context of magmatic and hydrothermal activity. The Huevos Verdes vein system has a strike length of 2,000 m, with several ore shoots along strike. The vein consists of a pre-ore stage and three main ore stages. Early barren quartz and chalcedony are followed by a mottled quartz stage of coarse saccharoidal quartz with irregular streaks and discontinuous bands of sulfide-rich material. The banded quartz-sulfide stage consists of sulfide-rich bands alternating with bands of quartz and bands of chlorite ± illite. Late-stage sulfide-rich veinlets are associated with kaolinite gangue. Ore minerals are argentite and electrum, together with pyrite, sphalerite, galena, chalcopyrite, minor bornite, covellite, and ruby silver. Wall rock alteration is characterized by narrow (< 3 m) halos of illite and illite/smectite next to veins, grading outward into propylitic alteration. Gangue minerals are dominantly massive quartz intergrown with minor to accessory adularia. Epidote, illite, illite/smectite, and, preferentially at deeper levels, Fe-chlorite gangue indicate near-neutral pH hydrothermal fluids at temperatures of >220°C. Kaolinite occurring with the late sulfide-rich veinlet stage indicates pH < 4 and a temperature of <200°C. The Huevos Verdes system has an overall strike of 325°, dipping on average 65° NE. The orientations of individual ore shoots are controlled by vein strike and intersecting north-northwest-striking faults. We propose a structural model for the time of mineralization of the San José district, consisting of a conjugate shear pair of sinistral north-northwest- and dextral west-northwest-striking faults that correspond to R and R' in the Riedel shear model and that are related to master faults (M) of north-northeast-strike. Veins of 315° strike can be interpreted as nearly pure extensional fractures (T). Variations in vein strike predict an induced sinistral shear component for strike directions of >315°, whereas strike directions of <315° are predicted with an induced dextral strike-slip movement. The components of the structural model appear to be present on a regional scale and are not restricted to the San José district.

Dietrich, Andreas; Gutierrez, Ronald; Nelson, Eric P.; Layer, Paul W.

2012-03-01

76

A hydrothermal system associated with the Siljan impact structure, Sweden--implications for the search for fossil life on Mars.  

PubMed

The Siljan ring structure (368 +/- 1.1 Ma) is the largest known impact structure in Europe. It isa 65-km-wide, eroded, complex impact structure, displaying several structural units, including a central uplifted region surrounded by a ring-shaped depression. Associated with the impact crater are traces of a post-impact hydrothermal system indicated by precipitated and altered hydrothermal mineral assemblages. Precipitated hydrothermal minerals include quartz veins and breccia fillings associated with granitic rocks at the outer margin of the central uplift, and calcite, fluorite, galena, and sphalerite veins associated with Paleozoic carbonate rocks located outside the central uplift. Two-phase water/gas and oil/gas inclusions in calcite and fluorite display homogenization temperatures between 75 degrees C and 137 degrees C. With an estimated erosional unloading of approximately 1 km, the formation temperatures were probably not more than 10-15 degrees C higher. Fluid inclusion ice-melting temperatures indicate a very low salt content, reducing the probability that the mineralization was precipitated during the Caledonian Orogeny. Our findings suggest that large impacts induce low-temperature hydrothermal systems that may be habitats for thermophilic organisms. Large impact structures on Mars may therefore be suitable targets in the search for fossil thermophilic organisms. PMID:14582511

Hode, Tomas; von Dalwigk, Ilka; Broman, Curt

2003-01-01

77

AGE AND ORIGIN OF BASE- AND PRECIOUS-METAL VEINS OF THE COEUR D'ALENE MINING DISTRICT, IDAHO  

SciTech Connect

Ore-bearing quartz-carbonate veins of the Coeur d'Alene mining district yield {sup 87}Sr/{sup 86}Sr ratios of 0.74 to >1.60 for low-Rb/Sr, carbonate gangue minerals, similar to current ranges measured in Middle Proterozoic, high-Rb/Sr rocks of the Belt Supergroup. Stable-isotope and fluid-inclusion studies establish a genetic relationship between vein formation and metamorphic-hydrothermal systems of the region. These extraordinary {sup 87}Sr/{sup 86}Sr ratios require accumulation of radiogenic {sup 87}Sr in a high Rb/Sr system over an extended period prior to incorporation of Sr into the veins by hydrothermal processes. Evaluation of the age and composition of potential sources of highly radiogenic Sr indicates that the ore-bearing veins of the Coeur d'Alene district formed within the last 200 Ma from components scavenged from sedimentary and metasedimentary rocks of the Belt Supergroup, the primary host-rocks of the district. These results are consistent with a Cretaceous or Early Tertiary age for these veins. Pb-Zn deposits that yield Pb isotope, K-Ar, and Ar-Ar results indicative of a Proterozoic age probably formed during deposition or diagenesis of the Belt Supergroup at 1350-1500 Ma, possibly as Sullivan-type syngenetic deposits. K-Ar and Rb-Sr apparent ages and {delta}{sup 18}O values of Belt Supergroup rocks decrease southward from the Coeur d'Alene district toward the Idaho batholith, normal to the trends of metamorphic isograds, fold axes, foliation, and the major reverse faults of the district. Isoclinal folding, thrust faulting, high-temperature metamorphism, granitic plutonism, and regional-scale metamorphic-hydrothermal activity is documented in the region between 140 Ma and 45 Ma, but no similar combination of events is recognized for Late Proterozoic time. Combined with Sr results from the veins, the evidence strongly favors formation of the ore-bearing carbonate veins of the district by fluids related to a complex metamorphic-hydrothermal system during Cretaceous and/or early Tertiary time. Proterozoic Pb-Zn deposits were probably deformed, remobilized along younger structures, and incorporated into the younger hydrothermal deposits during this event.

Fleck, R J; Criss, R E; Eaton, G F; Cleland, R W; Wavra, C S; Bond, W D

2000-11-07

78

Hydrothermal brecciation in the Jemez fault zone, Valles Caldera, New Mexico: Results from continental Scientific Drilling Program core hole VC-1  

NASA Astrophysics Data System (ADS)

An unusual breccia sequence penetrated in the lower 30 m of Continental Scientific Drilling Program core hole VC-1 (total depth 856 m) records a complex hydrothermal history culminating in hydraulic rock rupture and associated alteration at the edge of the Quaternary Valles caldera. The breccias, both tectonic and hydrothermal in origin, were formed in the Jemez fault zone, near the intersection of this major regional structure with the caldera's ring-fracture margin. Tectonic breccias in the sequence are contorted, crushed, and sheared. Coexisting hydrothermal breccias lack such frictional textures but display matrix flow foliation and prominent clast rounding, features characteristic of fluidization. These hydrothermal breccias were intensely altered, during at least five major stages, to quartz-illite-phengite-pyrite aggregates; traces of molybdenite occur locally. This assemblage indicates interaction with hydrothermal fluid at temperatures in excess of 200°C. The extrapolated present maximum temperature of 184°C in the breccia zone therefore represents considerable cooling since these phases were formed. Fluid inclusions in the breccias also preserve evidence of the prior passage of hotter fluids. The inclusions are principally two phase, liquid rich, secondary in origin, and concentrated in hydrothermal quartz. Older, high-salinity inclusions, unrelated to brecciation, homogenize in the temperature range 189°-246°C. Younger inclusions, in part of interbreccia origin, are low-salinity and homogenize in the temperature range 230°-283°C; locally coexisting liquid- and vapor-rich inclusions document periodic boiling of the dilute fluids. These fluid-inclusion data, along with the probable age of the hydrothermal breccias (<1.5 Ma), the assumed depth at which they developed (about 515 m), and the contemporaneous state of stress (extensional) can be combined to model hydrothermal brecciation at the VC-1 site. The minimum fluid pressure (Pfr) required to hydrofracture these rocks was probably about 7.5 MPa (0.0146 MPa/m). A boiling point versus depth curve based on these Pfr values graphically defines the physical conditions prevailing when the breccias were formed. When fluid pressure at the assumed depth of brecciation exceeded that curve, in response to rapid release of confining pressure possibly augmented by renewed heating, flashing hydrothermal fluid fractured the enclosing rock. Large overpressures, most likely induced by sudden seismic cracking of a hydrothermally sealed portion of the Jemez fault zone, led to local fluidization of the resulting breccias. Late quartz veining, hydrothermal alteration, and molybdenite mineralization were probably produced by the fluids responsible for brecciation.

Hulen, Jeffrey B.; Nielson, Dennis L.

1988-06-01

79

Raman and micro-thermometric investigation of the fluid inclusions in quartz in a gold-rich formation from Lepaguare mining district (Honduras, Central America)  

NASA Astrophysics Data System (ADS)

Fluid inclusions in the quartz crystals present in gold-rich veins from central Honduras have been studied by means of micro-thermometry and micro-Raman spectroscopy in order to provide information on the physico-chemical conditions and chemical composition of the mineralizing fluids. The use of a confocal micro-Raman apparatus allowed to obtain information on the fluid composition, in particular on the gas phase, minimizing the contributions of the host matrix to the Raman signal. The samples studied were collected from an area (Lepaguare mining district, Northern-Central Honduras) rich in ore deposits due to the Cenozoic magmatic activity, where the gold and sulphide mineralization is connected with a system of quartz veins (few decimetres thick) occurring in low-grade metamorphic rocks and produced by hydrothermal fluids. The quartz crystals present in the gold-rich veins often contain fluid inclusions. Four types of fluid inclusions have been observed, but their assemblage in the same clusters and fracture systems, as well as their comparable salinity and homogenization data, suggest that they have the same origin. Micro-thermometry and Raman spectroscopy provide a composition of the mineralizing fluids attributable to the system H 2O-NaCl-KCl-CO 2-CH 4, with temperature and pressure intervals of 210-413 °C and 1050-3850 bar, respectively. These data agree with an epigenetic origin of the gold deposit (depth < 6 km) related to granitoid or granodiorite intrusions associated to orogenic environments.

Bersani, D.; Salvioli-Mariani, E.; Mattioli, M.; Menichetti, M.; Lottici, P. P.

2009-08-01

80

Chabazite in spodumene-bearing Alpine-type fissure veins from Hiddenite, North Carolina, USA  

NASA Astrophysics Data System (ADS)

Alpine-type fissure vein mineralization in the Hiddenite area of western North Carolina, USA consists mostly of quartz, but locally contains Cr-bearing beryl (emerald) or Cr-bearing spodumene (hiddenite). These gem minerals occur in mineral-lined cavities and may be accompanied by euhedral crystals of quartz, calcite, muscovite, rutile, albite, pyrite, siderite and dolomite. Chabazite-Ca occurs as a late stage phase in spodumene-bearing veins, but is absent in emerald-bearing veins. Chabazite-Ca occurs as simple penetrating twins of pseudocubic rhombohedra and as the lens-shaped variety, phacolite. Chabazite-Ca from Hiddenite contains minor amounts of Na, Mg, Fe and K. Phacolitic chabazite-Ca shows Fe-enriched but Mg-depleted cores relative to the rims. Chemical zoning is absent in rhombohedral chabazite. The Hiddenite chabazite apparently precipitated under low temperature (< 250°C) and low pressure (< 2 kbar) conditions during the waning stages of crystallization of an alkaline hydrothermal fluid.

Wise, Michael A.

2009-07-01

81

Age of tin ore from the Solnechnoe quartz-tourmaline-cassiterite deposit, the Khabarovsk krai, Russia from the results of Rb-Sr dating of quartz and adularia  

NASA Astrophysics Data System (ADS)

The age of the main productive phase of ore formation at the large Solnechnoe tin deposit has been estimated for the first time based on the study of the Rb-Sr isotopic system of hydrothermal quartz and adularia from ore veins and metasomatic rocks. The Rb-Sr isochron age (84 ± 1 Ma) of mineralization coincides with the age of intrusive rocks pertaining to the third phase of the Silinka Complex, which control tin mineralization. The 87Sr/86Sr ratios of ore-forming solution and granitic rocks of the final intrusive phase are close to each other, indicating that the granitic melt was most likely one of the main sources of metals. The long and multistage formation history of the deposit could have been caused by complex geodynamic evolution of the Sikhote-Alin accretionary fold region in the Cretaceous.

Chugaev, A. V.; Bortnikov, N. S.; Gonevchuk, V. G.; Gorelikova, N. V.; Korostelev, P. G.; Baranova, A. N.

2012-05-01

82

Trace Element Analyses of Quartz-Two Wrongs Don't Make a Right  

Microsoft Academic Search

Microanalysis of trace elements in hydrothermal quartz can improve understanding of the chemical dynamics of ore-forming systems. Quartz is expected to vary in composition because of the wide range of formation temperatures and parent fluid compositions. Compositional variations are evident in the variations in cathodoluminescence (CL) intensity of precipitated quartz, which is a result of structural defects including those caused

H. Lowers; B. Rusk; A. Koenig

2007-01-01

83

Hydrothermal Processing  

Microsoft Academic Search

This chapter is a contribution to a book on Thermochemical Conversion of Biomass being edited by Prof. Robert Brown of Iowa State University. It describes both hydrothermal liquefaction and hydrothermal gasification of biomass to fuels.

Douglas C

2011-01-01

84

Characterization and modeling of illite crystal particles and growth mechanisms in a zoned hydrothermal deposit, Lake City, Colorado  

USGS Publications Warehouse

Mean thickness measurements and crystal-thickness distributions (CTDs) of illite particles vary systematically with changes in hydrothermal alteration type, fracture density, and attendant mineralization in a large acid-sulfate/Mo-porphyry hydrothermal system at Red Mountain, near Lake City, Colorado. The hydrothermal illites characterize an extensive zone of quartz-sericite-pyrite alteration beneath two deeply rooted bodies of magmatic-related, quartz-alunite altered rock. Nineteen illites from a 3000 ft vertical drill hole were analyzed by XRD using the PVP-10 intercalation method and the computer program MudMaster (Bertaut-Warren-Averbach technique). Mean crystallite thicknesses, as determined from 001 reflections, range from 5-7 nanometers (nm) at depths from 0-1700 ft, then sharply increase to 10-16 nm at depths between 1800-2100 ft, and decrease again to 4-5 nm below this level. The interval of largest particle thickness correlates strongly with the zone of most intense quartz-sericite-pyrite alteration (QSP) and attendant high-density stockwork fracturing, and with the highest concentrations of Mo within the drill core. CTD shapes for the illite particles fall into two main categories: asymptotic and lognormal. The shapes of the CTDs are dependent on conditions of illite formation. The asymptotic CTDs correspond to a nucleation and growth mechanism, whereas surface-controlled growth was the dominant mechanism for the lognormal CTDs. Lognormal CTDs coincide with major through-going fractures or stockwork zones, whereas asymptotic CTDs are present in wallrock distal to these intense fracture zones. The increase in illite particle size and the associated zone of intense QSP alteration and stockwork veining was related by proximity to the dacitic magma(s), which supplied both reactants and heat to the hydrothermal system. However, no changes in illite polytype, which in other studies reflect temperature transitions, were observed within this interval.

Bove, D. J.; Eberl, D. D.; McCarty, D. K.; Meeker, G. P.

2002-01-01

85

Varicose Veins  

MedlinePLUS

... Veins Explore Varicose Veins What Are … Related Vein Problems Causes Who Is at Risk Signs & Symptoms Diagnosis Treatments Prevention Living With Clinical Trials Links Spanish Version Related Topics Overweight and Obesity How the Heart Works Related Media Videos Widgets Quizzes Send a link to NHLBI ...

86

Formation of jasper and andradite during low-temperature hydrothermal seafloor metamorphism, Ongeluk Formation, South Africa  

NASA Astrophysics Data System (ADS)

Andradite and andradite-grossular solid solutions have repeatedly been described as minor constituents of weakly metamorphosed ocean-floor metabasites and associated calcareous or siliceous sediments. The conditions of garnet formation, however, have remained rather elusive. Here, wedescribe the discovery of andradite as a minor but widespread constituent of chert and jasper closely associated with only very weakly metamorphosed basaltic andesites of the Early Paleoproterozoic Ongeluk Formation, Transvaal Supergroup, South Africa.The andradite is most commonly fine-grained and forms skeletal crystals that poikilotopically enclose and replace quartz and hematite. Macroscopically coarse-grained andradite is scarce and was recognized at one locality only. Up to 3-mm largeandradite grains occur closely associated with quartz in short veins that crosscut thin beds of andradite-bearing jasper. The cogenetic association of quartz and andradite was studied in detail to constrain the conditions of garnet formation. Our results indicate that andradite crystallized at temperatures well below 200 °C in the sub-seafloor environment in siliceous sediments of hydrothermal origin that provided an ample source of SiO2 and Fe2O3. Andradite formed when hydrothermally modified seawater introduced Ca that was leached when seawater interacted with plagioclase and clinopyroxene in the surrounding volcanic pile. Other important preconditions for garnet formation were the lack of mixing between the hydrothermal fluid and cold seawater and low fCO2. It appears reasonable to extend the findings of this study to other recorded occurrences of andradite in modern and ancient ocean-floor metabasites.

Gutzmer, J.; Pack, A.; Lüders, V.; Wilkinson, J. J.; Beukes, N. J.; Niekerk, H. S.

87

Hydrothermal heat flow near the Main Central Thrust, central Nepal Himalaya  

NASA Astrophysics Data System (ADS)

In central Nepal hot springs are common in a broad zone where deeply incised river gorges cross the MCT along steep stream reaches. The chemistry of the hydrothermal fluids is distinct from that of the rivers, enabling the use of chemical mass balance to estimate the hydrothermal flux. Spring exit temperatures are 25-70 °C. We combine mass balance estimates of spring flux with observed T to estimate hydrothermal power dissipation of springs at the surface of 500 MW across the Narayani basin. Estimates of reservoir T and a simple conductive cooling model indicate an additional 1260 MW is transferred to the uppermost crust by fluid flow, for a total heat transfer of 1760 ± 953 MW. Fluid inclusions from post-ductile quartz veins yield T = 301 ± 6 °C, P = 1056 ± 110 bars, and imply a geothermal gradient 75 ± 7.8 °C km- 1. Simple models of thermal balance suggest that hydrothermal circulation is a major mechanism of heat loss from this region of steep geothermal gradient. A 1-D model of rock advection and radiogenic heating indicates that coupled erosion-rock uplift is the major source for heat in the upper crust, and is consistent with the observed magnitude of hydrothermal heat transfer. On a more local scale, a simple porous media flow model appears to predict observed T-depth relationships in the zone of active meteoric fluid flow, and implies T ? 100 °C at depths only on the order of 100 m. These very shallow isotherms have the potential to influence low T thermochronometers.

Derry, L. A.; Evans, M. J.; Darling, R.; France-Lanord, C.

2009-08-01

88

Thermodynamics of hydrothermal systems with oxalate ion  

NASA Astrophysics Data System (ADS)

The geochemical and industrial significance of oxalates have led to great interest in the behavior of oxalate ion in hydrothermal systems. On the basis of a study by G.B. Naumov et al (1971) of gaseous-liquid inclusions it is shown that whewellite (CaC2O4•H2O) which was found in quartz-calcite-fluorite veins in the uranium ore deposit of the Eastern Transbaikal region was formed at temperatures about 150°C and pressure CO2 of 600-860 atm. The isotopic composition of carbon for these hydrothermal whewellite samples was determined by Galimov et al (1975): Delta13C from -1.56 to -2.22%. In a continuation of the study of organic-acid-water-rock interactions the thermodynamics of hydrothermal equilibriums for the systems Ox-H, Ox-H-Ca, Ox-H-Mg (where Ox = C2O42-), are described up to 200°C. The key network reactions and compounds related to the aqueous ion C2O42- are discussed and used to define the key values. The critical evaluation of thermodynamic properties for this ion is a part of the development of the new key values system for the joint thermodynamic database in the Internet. The evaluation involves the analysis of the enthalpy changes, Gibbs energy changes, and the entropy calculations for all key substances in the key network. A consistent set of thermodynamic property values is given for ?-H2C2O4(cr), ?-H2C2O4(cr), H2C2O4•H2O(cr), CaC2O4(cr), CaC2O4•H2O(cr,whewellite), NaC2O4(cr,natroxalate), MgC2O4•2H2O(cr,glushinskite) and aqueous species C2O42-, HC2O4-, H2C2O4°, CaC2O4°. This study was funded by Russian Foundation for Basic Research (project N 07-05-01108).

Khodakovsky, I. L.; Devina, O. A.

2009-04-01

89

Nickel Electrobonded Quartz Blanks.  

National Technical Information Service (NTIS)

Problems associated with the use of conventional bonding materials for quartz resonators are reviewed briefly along with the properties of nickel films deposited from nickel sulfamate solutions. The experimental procedure for bonding quartz blanks to stai...

J. M. Stanley

1971-01-01

90

Evolution of hydrothermal regime along a crustal shear zone, Tinos Island, Greece  

Microsoft Academic Search

Structural cathodoluminescence and SIMS ?18O analyses of quartz-calcite veins are combined to constrain the evolution in space and time of fluid infiltration in an exhuming detachment shear zone (Tinos Island, Cyclades, Greece). Careful description of vein arrays shows that the plumbing system evolved into an interconnected network just beneath the ductile-to-brittle transition. Microtextures of quartz and calcite infilling veins display

V. Famin; P. Philippot; L. Jolivet; P. Agard

2004-01-01

91

Preliminary mineralogical data on epithermal ore veins associated with Rosia Poieni porphyry copper deposit, Apuseni Mountains, Romania  

NASA Astrophysics Data System (ADS)

Rosia Poieni is the largest porphyry copper (±Au±Mo) deposits associated with Neogene magmatic rocks from the South Apuseni Mountains, being located approximately 8 km northeast of the town of Abrud. During a recent examination of some epithermal mineralized veins, crosscutting the porphyry mineralization from the Ro?ia Poieni deposit, two species of tellurides and one tellurosulfide minerals were identified. The studied samples were collected from the + 1045 m level, SW side of the open pit and are represented by epithermal veins, crosscutting the porphyry copper mineralized body. The thickness of the veins is almost 4 cm. Following reflected-polarized light microscopy to identify the ore-mineral assemblages, the polished sections were studied with a Scanning Electron Microscope (SEM) equipped with a back-scattered electron (BSE) detector to study fine-sized minerals. Quantitative compositional data were determined using a Cameca SX 50 electron microprobe (EMP). Based on optical microscopy, SEM and EMPA three mineral associations have been separated inside the epithermal vein, from the margins to the centre: 1. quartz+tennantite-tetrahedrite+goldfieldite+pyrite+sphalerite; 2. quartz+pyrite+tellurobismutite; 3. chalcopyrite+hessite+vivianite. Goldfieldite occurs in anhedral grains and it is associated with tennantite-tetrahedrite and quartz. The electron microprobe analysis gave a variable content in Te between 13.28-13.39 wt.%, 43.34 wt.% Cu, 0.1 wt. % Fe, 0.2 wt.% Zn, 14.68 wt.% As, 4.35 wt.% Sb and 24.84 wt.% S. The calculated formula for the goldfieldite is Cu11.8Te1.8(Sb,As)4S13.4. The EPM analyses on tetrahedrite-tennantite revealed a low content in Te (0.02-0.03 wt.%) and 42.23 wt.% Cu, 2.67 wt.% Fe, 7.34 wt.% Zn, 0.04 wt.% Sb, 19.28 wt.% As and 28.4 wt.% S. The calculated formula is Cu9.8(Fe,Zn)2.4(Sb,As,Te)3.8S13. The variable ratio of the Te content may reflect a variable content of Te in the hydrothermal fluids from which the tellurian tetrahedrite precipitated. Hessite lies close to the grain boundary between the calchopyrite grains, which is associated with vivianite. Electron microprobe analysis gave 57.73 wt.% Ag and 42.27 wt.% Te with calculated stoichiometric formula Ag1.9Te1.1 . Tellurobismuthite it forms irregular grains and it is associated with quartz and pyrite. Electron microprobe analysis gave 57.20 wt.% Bi and 42.80 wt.% Te with calculated stoichiometric formula Bi2.2Te2.8. Based on the mineral assemblages separated inside the ore vein and on the ratio of the Te content for the different identified tellurium bearing minerals, we can conclude that the Te content of the fluids from which they precipitated, increased from the margins to the centre of the vein. In summary, this study of specimens from Rosia Poieni porphyry copper deposit, has resulted in the recognition of some tellurium-bearing minerals, not reported by previous workers. These minerals are represented by tellurobismutite, hessite and goldfieldite and they are associated with epithermal vein mineralization (pyrite, chalcopyrite, sphalerite, tennantite-tetrahedrite, quartz, vivianite). The presence of tellurium indicates the transition between porphyry-style mineralization to epithermal vein mineralization. Acknowledgements: This work was supported by the strategic grant POSDRU/89/1.5/S58852, Project "Postdoctoral program for training scientific researches" co-financed by the European Social Found within the Sectorial Operational Program Human Resources Development 2007-2013".

Iatan, E. L.; Popescu, Gh. C.

2012-04-01

92

Stable isotopic and fluid inclusion indications of large-scale hydrothermal paleoflow, boiling, and fluid mixing in the Keno Hill Ag-Pb-Zn district, Yukon Territory, Canada  

NASA Astrophysics Data System (ADS)

The Keno Hill vein system of the central Yukon is restricted predominantly to the highly fractured, graphitic Keno Hill Quartzite unit of Mississippian age. Hydrothermal mineral zoning is related spatially to a Cretaceous granitic pluton which intrudes the quartzite. During mineralization, the quartzite acted as a district-scale aquifer. Subsequent erosion has exposed a 40-km long vein system, from its plutonic roots, outward to polymetallic Ag-Pb-Zn veins, and further to assemblages of epithermal character. The ?18O quartz values from veins near the pluton increase outwards from +10.6 to +20.1%. as a result of cooling of the hydrothermal fluids and exchange with the quartzite. Contours of isotope values outline broad paths of fluid movement within the quartzite. Proceeding further from the pluton, ?18O quartz values decrease to +10.5%. at the outer edge of the system. The presence of meteoric water is indicated here, where late stage quartz has ?18O SMOW values as low as -7.l%. The outward decreasing trend appears to have been established by mixing of isotopically light meteoric water with exchanged fluids that were in isotopic equilibrium with the quartzite. Fluid inclusions from quartz in the orebodies demonstrate an evolving H 2O-CO 2-NaCl-CH 4 system. Loss of CO 2 and CH 4 during water vaporization coincides with increasing salinity and decreasing temperature resulting from high enthalpy steam loss. Depressurization during active faulting is the principal mechanism. Late stage fluids are represented by dilute aqueous inclusions with lower homogenization temperatures. Quartz from silver-rich veins has been shifted to higher ?18O values, by up to 4%. relative to adjacent silver-poor veins, the result of a minimum 10-25% adiabatic boiling and fractionation dominated by water vaporization and associated cooling. Graphite initially buffered the hydrothermal fluids to a high CO 2 content, with variable CH 4. Involvement of organic carbon from the host rocks is indicated by the negative ?13CPDB values for the carbonates, from -4.0 to -12.9%. Variations in the carbon isotopes result from fluctuating CO 2/CH 4 ratios, reflecting the contrasting volatility of the gas pair. Siderite formed as a late-stage product of the boiling event, and its formation coincides with a decreasing 18O trend in the water created by the equilibration of graphite and water in replacing exsolved CO 2. The formation of CH 4 during this stage had a reducing effect on the fluid, resulting in an increase in ?13C siderite values in association with the decreasing ?18O siderite values. A closed-system boiling model, together with calculations of water consumption during post-boiling CO 2 and CH 4 formation, indicates that greater than 50% of the original water in the ore fluid was removed. Relatively saline mineralizing fluids resulted.

Lynch, J. V. G.; Longstaffe, F. J.; Nesbitt, B. E.

1990-04-01

93

Varicose vein stripping  

MedlinePLUS

... called the superficial saphenous vein is thick and rope-like. Vein stripping usually takes about 1 to ... high blood pressure in a vein (lipodermatosclerosis) Large, rope-like veins that cannot be treated with other, ...

94

Fluids in deeply subducted continental crust: Petrology, mineral chemistry and fluid inclusion of UHP metamorphic veins from the Sulu orogen, eastern China  

Microsoft Academic Search

The complex vein associations hosted in southern Sulu ultrahigh-pressure (UHP) eclogites contain quartz±omphacite (or jadeite)±kyanite±allanite±zoisite±rutile±garnet. These minerals have chemical compositions similar to those of host eclogites. Inclusions of polycrystalline quartz pseudomorphs after coesite were identified in vein allanite and garnet, and coesite inclusions were found in vein zircon. These facts suggest that the veins together with host eclogites have been

Ze-Ming Zhang; Kun Shen; Wei-Dong Sun; Yong-Sheng Liu; J. G. Liou; Cao Shi; Jin-Li Wang

2008-01-01

95

Why calcite can be stronger than quartz  

NASA Astrophysics Data System (ADS)

Calcite and quartz are two of the most common minerals in the continental crust and it is therefore not surprising that these minerals have been extensively studied since the very beginning of laboratory rock mechanics experiments. Extending such laboratory data to geological deformation rates around 10-14 s-1 requires an extrapolation of more than 7 orders of magnitude, with correspondingly large uncertainties. Extrapolation is based on the assumption that flow parameters are constant with changing conditions and that parameters not included in the flow law have a negligible influence on the creep properties. The validity of this extrapolation can only be tested, at least semi-quantitatively, by comparison with naturally deformed rocks. Observations generally indicate that quartz is significantly stronger than calcite in natural rocks, with quartz forming porphyroclasts in calcite marble mylonites, or with quartzite layers being folded or boudinaged within a weaker calcite marble matrix. However, in the Neves area (Tauern Window, Eastern Alps), shearing of Alpine coarse grained quartz-calcite veins under hydrous amphibolite facies conditions (ca. 550Ë? C) produced quartz mylonites containing asymmetric cm-scale single crystal calcite porphyroclasts. Under these conditions, coarse calcite is clearly stronger than the surrounding polycrystalline, dynamically recrystallized, quartz matrix. The important parameter controlling this difference in observed natural behaviour is the grain size of the calcite. Although there is considerable variation, uncertainty and even contradiction in the published experimental results, we show that extrapolation of laboratory creep data on calcite single crystals and coarse marbles, together with the corresponding data for wet quartzites, is indeed consistent with these natural observations. Extrapolation indicates an inversion in the relative strength of coarse calcite and quartz at a strain rate around 10-11 s-1, corresponding to a differential flow stress of ca. 50 MPa. At lower strain rates and stresses, wet quartz should be weaker than coarse calcite crystals. Field evidence (flow of quartz-rich layers even for orientations with very low resolved shear stress) and the preserved microstructure (lack of recrystallized or bulged twins in the calcite porphyroclasts) in the Neves area are also consistent with flow stresses of less than ca. 50 MPa. These low values during deformation under water-rich amphibolite facies conditions are in marked contrast to the much higher differential stresses reported for the flow (and fracture) of quartz-rich rocks under dry conditions in the middle to lower crust.

Mancktelow, N. S.; Pennacchioni, G.

2009-04-01

96

Numerical Modelling of Vein Microstructures  

NASA Astrophysics Data System (ADS)

Mineral veins occur in a variety of forms (syntaxial, antitaxial, etc.), and with various microstructures (fibrous, stretched crystals, vuggy, etc.). These structures can, if correctly interpreted, provide useful insight into the geological and tectonic conditions at which the veins formed (Oliver and Bons 2001). Durney and Ramsay (1973) defined the base for the modern classification and interpretation of vein (micro-) structures. Numerical modelling, not available then, has since been added as a tool to better understand the formation of vein (micro-) structures, focussing on three aspects in particular: 1) What determines the habit of growing vein crystals? In particular, what determines the formation of a fibrous habit? (Bons 2001, Hilgers et al. 2001) 2) The formation of fibrous pressure fringes. The complex internal structures of the fringes appear mostly the result of the relative rotation of object and fringes (Koehn et al. 2001). 3) Competition between growing crystals, which for example explains the development of a conical c-axes CPO in zeolite films (Bons and Bons 2003). References: Bons, P.D. 2001. Development of crystal morphology during unitaxial growth in a progressively widening vein: I. The numerical model. Journal of Structural Geology 23, 865-872. Bons, A.J., Bons, P.D. 2003. The development of oblique preferred orientations in zeolite films and membranes. Microporous and Mesoporous Materials 62, 9-16. Durney DW, Ramsay JG (1973) Incremental strains measured by syntectonic crystal growths. In: Gravity and Tectonics (eds De Jong KA, Scholten K), John Wiley and Sons, New York, pp. 67-96. Hilgers, C., Koehn, D., Bons, P.D., Urai, J.L. 2001. Development of crystal morphology during unitaxial growth in a progressively widening vein: II. Numerical simulations of the evolution of antitaxial fibrous veins. Journal of Structural Geology 23, 873-885. Koehn, D., Aerden, D.G.A.M., Bons, P.D., Passchier, C.W. 2001. Computer experiments to investigate complex fibre patterns in natural antitaxial strain fringes. Journal of Metamorphic Geology 19, 217-232. Oliver, N.H.S., Bons, P.D. 2001. Mechanisms of fluid flow and fluid-rock interaction in fossil metamorphic-hydrothermal systems inferred from vein-wallrock patterns, geometry, and microstructure. Geofluids 1, 137-163.

Bons, P. D.

2005-12-01

97

Gold-Bearing Veining in Transcrustal Fault Zone in the Transantarctic Mountains (Northern Victoria Land, Antarctica): Implications for the Paleo-Pacific Margin of Gonwana  

NASA Astrophysics Data System (ADS)

Paleozoic gold mineralizations occur all along the former Pacific margin of Gondwana, for instance in eastern Australia, the South Island of New Zealand and southern South America. Here we describe syntectonic gold- bearing veins in northern Victoria Land (Antarctica) that was part of this margin during the Paleozoic: this is the first gold occurrence signalled in the Transantarctic Mountains of Antarctica. Northern Victoria Land can be subdivided into three NW-SE trending domains known as the Wilson, Bowers and Robertson Bay terranes. The terrane arrangement is increasingly interpreted as a fossil arc-trench system resulting from a westward-directed subduction at the paleo-Pacific margin of Gondwana during the Early Paleozoic Ross Orogeny and therefore the three terranes should represent the continental magmatic arc, the forearc/back- arc and the trench sedimentary sequence, respectively. The mineralized veins occur inside the Bowers terrane, not far from the contact with the outboard Robertson Bay terrane. The veins are hosted primarily by greenschist to low-greenschist metabasalts with interlayers of metasandstones of Middle Cambrian age. Gold occurs as coarse-grained native gold, associated with silver, arsenopyrite and an ironarsenic compound. Regional structural setting is characterized by a NW-SE-trending fold belt, cut by NW-SE and N-S fault systems linked to a transpressional regime of deformation. Quartz-carbonate veins occurs in a brittle-ductile high strain zone superimposed on the earlier regional metamorphic foliation and folds. The high strain zone is characterized by foliated fault rocks with S-C structures, widespread veining, and hydrothermal alteration of the host rocks. The vein network is surrounded by a zoned alteration halo approximately up to 500 m wide. Chlorite thermometry provides temperature estimates ranging from 270 to 280° C in the chlorite-altered metabasalts and from 290 to 310° C in the more altered samples. 39Ar-40Ar dating on sericites provides Carboniferous ages for the mineralization event.

Crispini, L.; Capponi, G.; Federico, L.; Talarico, F.

2008-12-01

98

Hydrothermal growth of well-aligned TiO 2 nanorod arrays: Dependence of morphology upon hydrothermal reaction conditions  

Microsoft Academic Search

Well-aligned TiO2 nanorod arrays (TNAs) were prepared on pretreated quartz substrates via hydrothermal method. The effect of the different\\u000a preparation conditions on the growth morphologies of TNAs was systematically investigated by X-ray diffraction (XRD) and field-emission\\u000a scanning electron microscopy (FE-SEM). The photocatalytic properties were tested by photodegradation of a methyl blue solution.\\u000a It is demonstrated that the hydrothermal reaction conditions,

Yuxiang Li; Mei Zhang; Min Guo; Xidong Wang

2010-01-01

99

Borehole plugging by hydrothermal transport. Final report  

Microsoft Academic Search

Calcium silicate--and aluminosilicate--compositions based on mixtures of fine grained quartz with various cements or calcium silicate compounds have been investigated under hydrothermal conditions in the temperature range 110-250°C and pressure range 1,000-10,000 psi, pressures which are always in excess of that required to maintain liquid HO, and approximate the confining pressures which might be anticipated in deep boreholes. All silicate

D. M. Roy; W. B. White

1976-01-01

100

Pingüino In-bearing polymetallic vein deposit, Deseado Massif, Patagonia, Argentina: characteristics of mineralization and ore-forming fluids  

NASA Astrophysics Data System (ADS)

The Pingüino deposit, located in the low sulfidation epithermal metallogenetical province of the Deseado Massif, Patagonia, Argentina, represents a distinct deposit type in the region. It evolved through two different mineralization events: an early In-bearing polymetallic event that introduced In, Zn, Pb, Ag, Cd, Au, As, Cu, Sn, W and Bi represented by complex sulfide mineralogy, and a late Ag-Au quartz-rich vein type that crosscut and overprints the early polymetallic mineralization. The indium-bearing polymetallic mineralization developed in three stages: an early Cu-Au-In-As-Sn-W-Bi stage (Ps1), a Zn-Pb-Ag-In-Cd-Sb stage (Ps2) and a late Zn-In-Cd (Ps3). Indium concentrations in the polymetallic veins show a wide range (3.4 to 1,184 ppm In). The highest indium values (up to 1,184 ppm) relate to the Ps2 mineralization stage, and are associated with Fe-rich sphalerites, although significant In enrichment (up to 159 ppm) is also present in the Ps1 paragenesis associated with Sn-minerals (ferrokesterite and cassiterite). The hydrothermal alteration associated with the polymetallic mineralization is characterized by advanced argillic alteration within the immediate vein zone, and sericitic alteration enveloping the vein zone. Fluid inclusion studies indicate homogenisation temperatures of 308.2-327°C for Ps1 and 255-312.4°C for Ps2, and low to moderate salinities (2 to 5 eq.wt.% NaCl and 4 to 9 eq.wt.% NaCl, respectively). ?34S values of sulfide minerals (+0.76‰ to +3.61‰) indicate a possible magmatic source for the sulfur in the polymetallic mineralization while Pb isotope ratios for the sulfides and magmatic rocks (206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of 17.379 to 18.502; 15.588 to 15.730 and 38.234 to 38.756, respectively) are consistent with the possibility that the Pb reservoirs for both had the same crustal source. Spatial relationships, hydrothermal alteration styles, S and Pb isotopic data suggest a probable genetic relation between the polymetallic mineralization and dioritic intrusions that could have been the source of metals and hydrothermal fluids. Mineralization paragenesis, alteration mineralogy, geochemical signatures, fluid inclusion data and isotopic data, confirm that the In-bearing polymetallic mineralization from Pingüino deposit is a distinct type, in comparison with the well-known epithermal low sulfidation mineralization from the Deseado Massif.

Jovic, Sebastián M.; Guido, Diego M.; Schalamuk, Isidoro B.; Ríos, Francisco J.; Tassinari, Colombo C. G.; Recio, Clemente

2011-03-01

101

The Third Dimension of an Active Back-arc Hydrothermal System: ODP Leg 193 at PACMANUS  

NASA Astrophysics Data System (ADS)

This first sub-seafloor examination of an active hydrothermal system hosted by felsic volcanics, at a convergent margin, obtained drill core from a high-T "smoker" site (penetrated to sim200 mbsf) and a low-T site of diffuse venting (~400mbsf). We aimed to delineate the lateral and vertical variability in mineralisation and alteration patterns, so as to understand links between volcanological, structural and hydrothermal phenomena and the sources of fluids, and to establish the nature and extent of microbial activity within the system. Technological breakthroughs included deployment of a new hard-rock re-entry system, and direct comparison in a hardrock environment of structural images obtained by wireline methods and logging-while-drilling. The PACMANUS hydrothermal site, at the 1700m-deep crest of a 500m-high layered sequence of dacitic lavas, is notable for baritic massive sulfide chimneys rich in Cu, Zn, Au and Ag. Below an extensive cap 5-40m thick of fresh dacite-rhyodacite, we found unexpectedly pervasive hydrothermal alteration of vesicular and flow-banded precursors, accompanied by variably intense fracturing and anhydrite-pyrite veining. Within what appears one major hydrothermal event affecting the entire drilled sequence, there is much overprinting and repetition of distinctly allochemical argillaceous (illite-chlorite), acid-sulfate (pyrophyllite-anhydrite) and siliceous assemblages. The alteration profiles include a transition from metastable cristobalite to quartz at depth, and are similar under low-T and high-T vent sites but are vertically condensed in a manner suggesting higher thermal gradients beneath the latter. The altered rocks are surprisingly porous (average 25%). Retention of intergranular pore spaces and open vesicles at depth implies elevated hydrothermal pressures, whereas evidence from fluid inclusions and hydrothermal brecciation denotes local or sporadic phase separation. A maximum measured temperature of 313 degC measured 8 days after drilling (360 mbsf at the diffuse venting site), if indicative of thermal gradient, suggests the presence of a very shallow ( ~1.5 km below seafloor) magmatic heat source. While isotopic characteristics of anhydrite suggest an irregularly varying component of magmatic fluid, the abundance of this mineral implies a substantial role for circulating seawater within the subsurface hydrothermal system. Other than the near-ubiquitous, fine grained disseminated pyrite in altered rocks, we found little sulfide mineralisation. Pyritic vein networks and breccias are extensive in the rapidly penetrated, but poorly recovered, interval down to 120 mbsf within our "high-T end-member" hole spudded on a mound surmounted by active (280 degC) chimneys. Anhydrite and open cavities possibly dominate this interval, from which a possible example of subhalative semi-massive sulfide containing chalcopyrite and some sphalerite was recovered near 30 mbsf. At the low-T and high-T vent sites respectively, anaerobic microbes were recorded by direct counting at depths down to 99 and 78 mbsf, and in 90 degC cultivation experiments at 69-107 and 99-129 mbsf. >http://www-odp.tamu.edu/publications/prelim/193

Binns, R.; Barriga, F.; Miller, D.

2001-12-01

102

Coupled stress and pore fluid pressure changes in the middle crust: Vein record of coseismic loading and postseismic stress relaxation  

Microsoft Academic Search

The structural, microstructural, and fluid inclusion record of late-stage quartz veins in metamorphic rocks of southern Evia (Greece) is analyzed and a mechanical model is proposed. The veins are monogenetic. They developed in a single stage from tensile cracks at temperatures similar to 300°C. The orientation of the veins is uniform on the kilometer scale and indicates an extensional tectonic

J. A. Nüchter; B. Stöckhert

2008-01-01

103

Temporal relations of volcanism and hydrothermal systems in two areas of the Jemez volcanic field, New Mexico  

SciTech Connect

Two hydrothermal alteration events (8.07 Ma, one sample; 6.51-5.60 Ma, six samples) related to the waning stages of late Miocene volcanism ({ge} 13 to {le} 5.8 Ma) are recognized at the Cochiti district (southeast Jemez Mountains). Most of the K/Ar dates (0.83 {plus minus} 0.11-0.66 {plus minus} 0.21 Ma, four samples) in the hydrothermally altered, caldera-fill rocks of core hole VC-2A at Sulfur Springs, Valles caldera, indicate post-Valles caldera hydrothermal alteration. A sample from acid-altered landslide debris of postcaldera tuffs from the upper 13 m of the core hole was too young to be dated by the K/Ar method and is possibly associated with current hot-spring activity and the youngest pulses of volcanism. Oxygen-isotope data from illite/smectite clays in the Cochiti district are zonally distributed and range from {minus}2.15{per thousand} to {plus}7.97{per thousand} (SMOW), depending upon temperature, extent of rock-fluid interaction, and composition. The samples from VC-2A get lighter with depth ({minus}0.20{per thousand} to {plus}1.62{per thousand}). The K/Ar and oxygen-isotope data provide strong evidence that the epithermal quartz-vein-hosted gold-silver mineralization at Cochiti and the sub-ore grade molybdenite at VC-2A were deposited in the late Miocene (5.99-5.60 Ma) and mid-Quaternary ({approximately}0.66 Ma), respectively, by hydrothermal fluids composed primarily of meteoric water.

WoldeGabriel, G.; Goff, F. (Los Alamos National Laboratory, NM (USA))

1989-11-01

104

Hydrothermal systems in two areas of the Jemez volcanic field: Sulphur Springs and the Cochiti mining district  

SciTech Connect

K/Ar dates and oxygen isotope data were obtained on 13 clay separates (<2 ..mu..m) of thermally altered mafic and silicic rocks from the Cochiti mining district (SE Jemez Mountains) and Continental Scientific Drilling Project (CSDP) core hole VC-2A (Sulphur Springs, Valles caldera). Illite with K/sub 2/O contents of 6.68%--10.04% is the dominant clay in the silicic rocks, whereas interstratified illite/smectites containing 1.4%--5.74% K/sub 2/O constitute the altered andesites. Two hydrothermal alteration events are recognized at the Cochiti area (8.07 m.y., n = 1, and 6.5--5.6 m.y., n = 6). The older event correlates with the waning stages of Paliza Canyon Formation andesite volcanism (greater than or equal to13 to less than or equal to8.5 m.y.), whereas the younger event correlates with intrusions and gold- and silver-bearing quartz veins associated with the Bearhead Rhyolite (7.54--5.8 m.y.). The majority of K/Ar dates in the hydrothermally altered, caldera-fill rocks of core hole VC-2A (0.83--0.66 m.y., n = 4) indicate that hydrothermal alteration developed contemporaneously with resurgence and ring fracture Valles Rhyolite domes (0.89--0.54 m.y.). One date of 0 +- 0.10 m.y. in acid-altered landslide debris of postcaldera tuffs from the upper 13 m of the core hole probably correlates with Holocene hydrothermal activity possibly associated with the final phases of the Valles Rhyolite (0.13 m.y.).

WoldeGabriel, G.

1989-03-01

105

Hydrothermal alteration in research drill hole Y-2, Lower Geyser Basin, Yellowstone National Park, Wyoming  

SciTech Connect

Y-2, a US Geological Survey research diamond-drill hole in Lower Geyser Basin, Yellowstone National Park, was drilled to a depth of 157.4 meters. The hole penetrated interbedded siliceous sinter and travertine to 10.2 m, glacial sediments of the Pinedale Glaciation interlayered with pumiceous tuff from 10.2 to 31.7 m, and rhyolitic lavas of the Elephant Back flow of the Central Plateau Member and the Mallard Lake Member of the Pleistocene Plateau Rhyolite from 31.7 to 157.4 m. Hydrothermal alteration is pervasive in most of the nearly continuous drill core. Rhyolitic glass has been extensively altered to clay and zeolite minerals (intermediate heulandite, clinoptilolite, mordenite, montmorillonite, mixed-layer illite-montmorillonite, and illite) in addition to quartz and adularia. Numerous veins, vugs, and fractures in the core contain these and other minerals: silica minerals (opal, ..beta..-cristobalite, ..cap alpha..-cristobalite, and chalcedony), zeolites (analcime, wairakite, dachiardite, laumontite, and yugawaralite), carbonates (calcite and siderite), clay (kaolinite and chlorite), oxides (hematite, goethite, manganite, cryptomelane, pyrolusite, and groutite), and sulfides (pyrhotite and pyrite) along with minor aegirine, fluorite, truscottite, and portlandite. Interbedded travertine and siliceous sinter in the upper part of the drill core indicate that two distinct types of thermal water are responsible for precipitation of the surficial deposits, and further that the water regime has alternated between the two thermal waters more than once since the end of the Pinedale Glaciation (approx. 10,000 years B.P.). Alternation of zones of calcium-rich and sodium- and potassium-rich hydrothermal minerals also suggests that the calcium-rich and sodium- and potassium-rich hydrothermal minerals also suggests that the water chemistry in this drill hole varies with depth.

Bargar, K.E.; Beeson, M.H.

1981-05-01

106

Vein filter  

US Patent & Trademark Office Database

A vein filter having improved collectability of chyme blood or thrombi and stability of indwelling. The filter includes at least 3 wires radially spreading backward of a head member and connected such that the intervals between any adjacent two wires are connected with threads of an equal length at a substantially equal distance from the head member. At respective connection parts where the threads are connected to the wires, hook parts to be hooked on the inner wall of a blood vessel are provided. The head member is on the apex of a shaft extending back and the rear end of each wire is connected to a slide member slidable along the shaft. The wires are preferably made of shape memory alloy or stainless spring steel.

Okada; Masayosi (Osaka, JP)

2003-05-06

107

Silica Transport and Distribution in Saline, Immiscible Fluids: Application to Subseafloor Hydrothermal Systems  

NASA Astrophysics Data System (ADS)

Quartz is a nearly ubiquitous gangue mineral in hydrothermal mineral deposits, most often constituting the bulk of hydrothermal mineralization. The dissolution, transport and precipitation of quartz is controlled by the solubility of silica; in particular, in hot hydrothermal fluids in contact with quartz, silica saturation can generally be assumed, as rates of dissolution and precipitation are generally much faster than fluid flow rates. The solubility of silica in aqueous fluids can be used to understand the evolution of hydrothermal systems by tracing the silica distribution in these systems through time. The solubility of quartz in an aqueous fluid is dependent upon the pressure, temperature and composition (PTX) of the fluid. Silica solubility in pure water as a function of pressure and temperature is well understood. However, natural fluids contain variable amounts of dissolved ionic species, thus it is necessary to include the effects of salinity on silica solubility to accurately predict quartz distribution in hydrothermal systems. In particular, addition of NaCl results in enhanced quartz solubility over a wide range of PT conditions. Furthermore, if phase separation occurs in saline fluids, silica is preferentially partitioned into the higher salinity brine phase; if vapor is removed from the system, the bulk salinity in the system evolves towards the brine end member, and overall silica solubility is enhanced. There is abundant evidence from natural fluid inclusions for fluid immiscibility in hydrothermal ore deposits. Additionally, recent hydrothermal models that include fluid phase equilibria effects predict that phase separation may be an important control on the distribution of dissolved components in seafloor hydrothermal systems. An empirical equation describing the solubility of silica in salt-bearing hydrothermal solutions over a wide range of PTX conditions has been incorporated into a multiphase fluid flow model for seafloor hydrothermal systems to predict the evolution of silica distribution in time and space in these systems. Preliminary runs illustrate a significant effect of salinity in the evolving and boiling system on silica solubility. The model predicts that silica solubility is progressively enhanced in the two-phase liquid-plus-vapor region as brine is concentrated by the preferential loss of vapor. The model also predicts that there is a narrow region of intense quartz deposition in the deep part of the upflow zone, where the fluid reenters the one-phase field. The model currently treats the wallrock as an infinite quartz reservoir, but future work will fully couple the quartz solubility and fluid flow models, to allow porosity adjustment and resultant permeability evolution by quartz dissolution and precipitation. This work was supported in part by the Institute for Critical Technology and Applied Sciences (ICTAS) at Virginia Tech

Steele-Macinnis, M.; Bodnar, R. J.; Lowell, R.; Rimstidt, J. D.

2009-05-01

108

Silicon\\/quartz bonding and quartz deep RIE for the fabrication of quartz resonator structures  

Microsoft Academic Search

In this paper, silicon\\/quartz bonding and quartz deep RIE (DRIE) processes have been developed to fabricate micromechanical quartz resonator structures. A low temperature (< 300degC), plasma-assisted silicon\\/quartz bonding condition that can provide the maximum bonding shear strength of 10 MPa has been experimentally constructed. The bonded silicon wafer was first applied to an etch mask of quartz, and thick quartz

Hyoung-Kyoon Jung; Young-Suk Hwang; Ik-Jae Hyeon; Yong-Kweon Kim; Chang-Wook Baek

2008-01-01

109

HYDROTHERMAL MINERALOGY OF RESEARCH DRILL HOLE Y-3, YELLOWSTONE NATIONAL PARK, WYOMING.  

USGS Publications Warehouse

The approximate paragenetic sequence of hydrothermal minerals in the Y-3 U. S. Geological Survey research diamond-drill hole in Lower Geyser Basin, Yellowstone National Park, Wyoming, is: hydrothermal chalcedony, hematite, pyrite, quartz, clay minerals (smectite and mixed-layer illite-smectite), calcite, chlorite, fluorite, pyrite, quartz, zeolite minerals (analcime, dachiardite, laumontite, stilbite, and yugawaralite), and clay minerals (smectite and mixed-layer illite-smectite). A few hydrothermal minerals that were identified in drill core Y-3 (lepidolite, aegirine, pectolite, and truscottite) are rarely found in modern geothermal areas. The alteration minerals occur primarily as vug and fracture fillings that were deposited from cooling thermal water. Refs.

Bargar, Keith, E.; Beeson, Melvin, H.

1984-01-01

110

Subsurface structure of a submarine hydrothermal system in ocean crust formed at the East Pacific Rise, ODP/IODP Site 1256  

NASA Astrophysics Data System (ADS)

ODP/IODP Hole 1256D penetrates an in situ section of ocean crust formed at the East Pacific Rise, through lavas and sheeted dikes and ˜100 m into plutonic rocks. We use mineralogy, oxygen isotopes, and fluid inclusions to understand hydrothermal processes. The lavas are slightly altered at low temperatures (<150°C) to phyllosilicates and iron oxyhydroxides, with a stepwise increase in grade downward to greenschist minerals in the upper dikes. This resulted from generally upwelling hydrothermal fluids in the dikes mixing with cooler seawater solutions in the lavas, also producing minor metal sulfide mineralization in the upper dikes. Alteration grade increases downward in the dikes, with increasing recrystallization to amphibole and loss of metals at higher temperatures (>350°C up to ˜600°C). Intrusion of gabbro bodies into the lower dikes resulted in contact metamorphism to granoblastic hornfels at 850°C-900°C, representing a thermal boundary layer between the axial melt lens and the overlying hydrothermal system. Downward penetration of hydrothermal fluids led to rehydration of granoblastic dikes and plutonic rocks at ˜800°C down to <300°C. Fluid inclusion and oxygen isotope data show that vein quartz formed at ˜300°C to >450°C from hydrothermal fluids that were affected by supercritical phase separation. Fluids had variable salinities and were enriched in 18O (+0.4‰ to +3.5‰) relative to seawater, similar to seafloor vent fluids. Dike margins are brecciated and mineralized, suggesting hydrothermal activity coeval with magmatism. Anhydrite formed mainly in the upper dikes when partly reacted seawater fluids were heated as they penetrated deeper into the system. Low-temperature alteration of the volcanic section continued as cold seawater penetrated along fluid pathways, forming minor iron oxyhydroxides in the rocks. Hydrothermal processes at Site 1256 fit with current models whereby greenschist alteration of dikes at low water/rock ratios is overprinted by fracture-controlled alteration and mineralization by upwelling hydrothermal fluids, a conductive boundary layer above gabbroic intrusions, leaching of metals from dikes and gabbros in the deep "root zone," and stepped thermal and alteration gradients in the basement. The Site 1256 section, however, is intact and retains recharge effects (anhydrite), allowing an integrated view of processes in the subsurface.

Alt, Jeffrey C.; Laverne, Christine; Coggon, Rosalind M.; Teagle, Damon A. H.; Banerjee, Neil R.; Morgan, Sally; Smith-Duque, Christopher E.; Harris, Michelle; Galli, Laura

2010-10-01

111

Fluid composition and origin in the hydrothermal system of the Nezhdaninsky gold deposit, Sakha (Yakutia), Russia  

NASA Astrophysics Data System (ADS)

Petrochemical characteristics of igneous, sedimentary, and metasomatic rocks; chemical and isotopic compositions of minerals and fluids; and PT parameters of mineral formation at the Nezhdaninsky deposit are reported. A model of hydrothermal system formation is developed on this basis. In addition to decreasing Ba/Rb and Li/Mg ratios in the course of the hydrothermal process, resulting in the formation of ore-bearing metasomatic rocks, increasing K/Ba and diminishing K/Cs ratios indicate the probable participation of magmatic fluid in the ore deposition. The agreement of the K/Rb and K/Ba ratios with the values typical of the main trend of igneous rocks (MT) implies that the K, Rb, and Ba contents were distributed in the ore-forming hydrothermal fluid according to the ratios in the source magmatic chamber. The K/Rb ratios in metasomatic rocks correspond to the MT and approach the pegmatitic-hydrothermal trend and the composition of orthomagmatic fluid of Mo-W greisen. Similar REE patterns of igneous and terrigenous rocks do not allow the REE source to be constrained unequivocally. The lithological control of lithophile element distribution testifies to the supply of host rock components to the hydrothermal system. All studied rocks and minerals are enriched in LREE. The REE total and the contribution of HREE decrease from preore to synore metasomatic rocks, from preore to regenerated carbonates, and from older to younger scheelite. A similar tendency is noted in granitoids of the Kurum pluton. The ?18O values of quartz range from +10.3 to +12.6‰ in Au-Mo-W zones, from +15.9 to +16.4‰ in metasomatic rocks, from +14.8 to +16.6‰ in gold-ore veins, and from +13.5 to +16.9‰ in silver-base-metal ore mineralization. The estimates of ? ^{18} O_{H_2 O} suggest that water was supplied from a magmatic source (?18O = +(5.5-9.0‰)) and as a product of sedimentary rock dehydration. High-temperature (up to 390°C) and highly concentrated (up to 31 wt % NaCl equiv) fluids participated in the mineral formation. The phase separation of the fluid into H2O-CO2 liquid and predominantly carbon dioxide gas was combined with mixing of a high-temperature and relatively highly concentrated chloride solution with a low-temperature and poorly mineralized fluid. The redox conditions varied from equilibrium with CH4-bearing fluid at the gold-molybdenum-tungsten stage to equilibrium with CO2-bearing fluid during the gold-ore stage.

Bortnikov, N. S.; Gamyanin, G. N.; Vikent'eva, O. V.; Prokof'ev, V. Yu.; Alpatov, V. A.; Bakharev, A. G.

2007-04-01

112

CO2 DRIVEN HYDROTHERMAL ERUPTIONS IN GEOTHERMAL SYSTEMS OF TURKEY  

Microsoft Academic Search

Substantial CO2 degassing occurs from geothermal waters in Turkey as evident from ongoing deposition of recent terrace travertines and emplacement of significant travertine vein and breccia deposits representing hydrothermal eruption products. Geochemical data indicate rapid ascent of CO2- bearing fluids without significant interaction with basement and host rocks. High-precision U-series dates of most travertine veins coincide with times of cold\\/dry

I. Tonguç Uysal; Jian-xin Zhao; Yue-xing Feng; Suzanne D. Golding

2009-01-01

113

Hydrothermal alteration minerals in Aluto Langano geothermal wells, Ethiopia  

SciTech Connect

Aluto Langano geothermal field is characterized by alteration mineral assemblages of calcite, quartz, chlorite, undifferentiated clays, hematite, biotite and epidote. The presence of garnet and sphene is also reported for one of the wells. The measured temperature for the reservoir is above 300/sup 0/C. Permeability of the reservoir is highly influenced by the deposition of hydrothermal minerals.

Gebregzabher, Z.

1986-01-01

114

Outgassing of quartz  

Microsoft Academic Search

The outgassing of quartz crystal plates was measured with a high resolution mass spectrometer using thermal desorption techniques. As the quartz was heated from 40°C to 1200°C in a vacuum, the mass spectrometer identified several types of gases. The primary species that appeared were NH3, OH, and H2O. The bonding sites of the OH and H2O are discussed, including the

D. E. Pierce; R. A. Murray; R. Lareau; S. Laffey; J. R. Vig

1994-01-01

115

Predicting Contaminant Transport along Veins and Fractures in Saprolite Above the Water Table.  

National Technical Information Service (NTIS)

This study evaluated the time of travel (TOT) of a Br(-) solute through quartz-diorite and mica-schist saprolites that contained quartz veins. Following saturation of the saprolite, a Br(-) tracer and dye were applied for a specific time period. The drain...

M. J. Vepraskas

1995-01-01

116

Internal vein texture and vein evolution of the epithermal Shila-Paula district, southern Peru  

NASA Astrophysics Data System (ADS)

The epithermal Shila-Paula Au-Ag district is characterized by numerous veins hosted in Tertiary volcanic rocks of the Western Cordillera (southern Peru). Field studies of the ore bodies reveal a systematic association of a main E-W vein with secondary N55-60°W veins—two directions that are also reflected by the orientation of fluid-inclusion planes in quartz crystals of the host rock. In areas where this pattern is not recognized, such as the Apacheta sector, vein emplacement seems to have been guided by regional N40°E and N40°W fractures. Two main vein-filling stages are identified. stage 1 is a quartz-adularia-pyrite-galena-sphalerite-chalcopyrite-electrum-Mn silicate-carbonate assemblage that fills the main E-W veins. stage 2, which contains most of the precious-metal mineralization, is divided into pre-bonanza and bonanza substages. The pre-bonanza substage consists of a quartz-adularia-carbonate assemblage that is observed within the secondary N45-60°W veins, in veinlets that cut the stage 1 assemblage, and in final open-space fillings. The two latter structures are finally filled by the bonanza substage characterized by a Fe-poor sphalerite-chalcopyrite-pyrite-galena-tennantite-tetrahedrite-polybasite-pearceite-electrum assemblage. The ore in the main veins is systematically brecciated, whereas the ore in the secondary veins and geodes is characteristic of open-space crystallization. Microthermometric measurements on sphalerite from both stages and on quartz and calcite from stage 2 indicate a salinity range of 0 to 15.5 wt% NaCl equivalent and homogenization temperatures bracketed between 200 and 330°C. Secondary CO2-, N2- and H2S-bearing fluid inclusions are also identified. The age of vein emplacement, based on 40Ar/39Ar ages obtained on adularia of different veins, is estimated at around 11 Ma, with some overlap between adularia of stage 1 (11.4±0.4 Ma) and of stage 2 (10.8±0.3 Ma). A three-phase tectonic model has been constructed to explain the vein formation. Phase 1 corresponds to the assumed development of E-W sinistral shear zones and associated N60°W cleavages under the effects of a NE-SW shortening direction that is recognized at Andean scale. These structures contain the stage 1 ore assemblage that was brecciated during ongoing deformation. Phase 2 is a reactivation of earlier structures under a NW-SE shortening direction that allowed the reopening of the preexisting schistosity and the formation of scarce N50°E-striking S2-cleavage planes filled by the stage 2 pre-bonanza minerals. Phase 3 coincides with the bonanza ore emplacement in the secondary N45-60°W veins and also in open-space in the core of the main E-W veins. Our combined tectonic, textural, mineralogical, fluid-inclusion, and geochronological study presents a complete model of vein formation in which the reactivation of previously formed tectonic structures plays a significant role in ore formation.

Chauvet, Alain; Bailly, Laurent; André, Anne-Sylvie; Monié, Patrick; Cassard, Daniel; Tajada, Fernando Llosa; Vargas, Juan Rosas; Tuduri, Johann

2006-07-01

117

An experimental study of the diffusion of oxygen in quartz and albite using an overgrowth technique  

Microsoft Academic Search

Diffusion rates of18O tracer in quartz (? c, 1 Kb H2O) and Amelia albite (? 001, 2 Kb H2O) have been measured, using Secondary Ion Mass Spectrometry (SIMS). A new technique involving hydrothermal deposition of labelled materials has removed the possibility of pressure solution-reprecipitation processes adversely affecting the experiments. Reported diffusion constants are:ß-quartz (? c),\\u000a$$D_0 = 3.4\\\\left( {\\\\begin{array}{*{20}c} {

S. C. Elphick; P. F. Dennis; C. M. Graham

1986-01-01

118

The origin and evolution of base metal mineralising brines and hydrothermal fluids, South Cornwall, UK  

Microsoft Academic Search

A fluid inclusion geochemical study has been carried out on quartz from post-Variscan quartz ± carbonate ± base metal sulphide ± anhydrite ± fluorite veins hosted by Palaeozoic basement (Porthleven, Menheniot, Cornwall) and Permo-Triassic sediments (Western Approaches). Data indicate that the base metal mineralising fluids have a similar bulk chemical composition to the saline fluids found in the Permo-Triassic basinal

S. A. Gleeson; J. J. Wilkinson; F. M. Stuart; D. A. Banks

2001-01-01

119

Sources and drains: Major controls of hydrothermal fluid flow in the Kokanee Range, British Columbia, Canada  

Microsoft Academic Search

Vein fields are fractured domains of the lithosphere that have been infiltrated by hydrothermal fluids, which deposited minerals in response to changing physico-chemical conditions. Because oxygen is a major component of the infiltrating fluid and the surrounding rock matrix, the oxygen isotope composition of minerals found in veins is used to decipher ancient fluid flow within the lithosphere. We use

Georges Beaudoin; René Therrien

1999-01-01

120

Fluid inclusions and hydrothermal alteration on the Dixie Valley Fault, Nevada  

NASA Astrophysics Data System (ADS)

Footwall rocks of the 1954 rupture segment of the Dixie Valley fault show extensive hydrothermal alteration related to fluids that were present on the fault during tectonic events. Hydrothermal alteration of granitic host rocks consists of temporally and spatially overlapping mineral assemblages. An early, biotite-feldspar assemblage is followed by later Fe-chlorite and epidote. Both chlorite and epidote are replaced by hydrothermal sericite and cross-cut by calcite-hematite and quartz-calcite veins. Biotite is partially replaced by prehnite. The latest hydrothermal minerals are stilbite, laumontite, kaolinite, alunite, smectite, illite, and pervasive replacement of rock units with fine grained quartz, chalcedony, and opal. Secondary fluid inclusions trapped in healed microfractures in igneous quartz include type I inclusions that contain a moderate salinity aqueous liquid and vapor, type II inclusions that contain a moderate salinity aqueous liquid and CO2; type III inclusions that show eutectic melting temperatures below the NaCl-H2O eutectic and contain substantial CaCl2, and type IV inclusions containing halite and other daughter minerals. Microthermometric measurements on these inclusions yield variable compositions and homogenization temperatures. Salinities of type I inclusions vary from 0.1 to 12.9 wt % NaCl with the mode in the interval 0 to 1%. Salinities of type II CO2 bearing inclusions range from 0.62 to 6.81 wt % NaCl relative to H2O, and salinities of type III inclusions with low eutectic melting temperatures are 12.9 to 25.3 NaCl equivalent wt %. Salinities of halite-bearing inclusions are 30.1 to 39.2 wt % NaCl. Homogenization temperatures span the range 120° to 400°C. The processes of isochemical cooling with upward displacement of the footwall, mixing of cool low-salinity water with hotter components, and mixing of cool, evaporite brine with hotter components could be responsible for variable fluid inclusion compositions, homogenization temperatures, and densities. The P-T path of the fault fluids is established by mineral equilibria and fluid inclusion characteristics. The path includes a lithostatic fluid pressure at 305°C and 1570 bars. Along with cooling and escape of CO2 from fluids, the fluid P-T path probably approaches hydrostatic pressure conditions at lower temperatures. Hydrothermal alteration product minerals, fluid temperatures, pressures, and compositions in the footwall of the Dixie Valley fault constrain minimum fault age to 20 to 25 Ma, displacement to 6 km with about 3 km of pre-10 to 13 Ma and 3 km of post-10 Ma uplift. Fluid compositions and P-T data suggest the following mechanism for rupture initiation and arrest. Ruptures may be initiated as a result of high fluid pressures, then opening of dilatant fractures causes drastic decrease in fluid pressure, separation of steam and CO2. The drastic reduction in fluid bulk modulus that accompanies volatile phase separation permits propagation of the ruptures even though fluid pressure is reduced. In areas where fluid pressure reduction is not accompanied by phase separation, fractures are arrested by dilatant hardening.

Parry, W. T.; Hedderly-Smith, D.; Bruhn, R. L.

1991-11-01

121

Ancient water on asteroid 4 Vesta: evidence from a quartz veinlet in the Serra de Magé eucrite meteorite  

Microsoft Academic Search

The meteorite Serra de Magé, a eucrite inferred to be from the asteroid 4 Vesta, contains quartz veinlets. They are identical to antitaxial or ‘crack-seal’ quartz veinlets in terrestrial rocks, and are extraterrestrial and ancient because they pre-date a 4.40 Ga metamorphism. The quartz was likely deposited from liquid water solutions (as are terrestrial veins); other potential solvents or transport

Allan H. Treiman; Antonio Lanzirotti; Dimitrios Xirouchakis

2004-01-01

122

Hydrothermal Manganese Mineralization Near the Samoan Hotspot  

NASA Astrophysics Data System (ADS)

The thickest beds of hydrothermal manganese oxides recovered to date from the global ocean were collected from a volcanic cone in the south Pacific. In April 2005, samples were dredged aboard the R.V. Kilo Moana from a volcanic cone on the lower flank of Tulaga seamount (about 2,700 m water depth; 14° 39.222' S; 170° 1.730' W), located 115 km SW of Vailulu'u, the volcanically and hydrothermally active center of the Samoan hotspot. Additional hydrothermal manganese samples were collected off Ofu Island (dredge Alia 107), 72 km to the WSW of Vailulu'u. Manganese-oxide beds up to 9 cm thick are composed of birnessite and 10 Å manganates. Some layers consist of Mn-oxide columnar structures 4 cm long and 1 cm wide, which have not been described previously. The mean Mn and Fe contents of 18 samples are 51 weight percent and 0.76 weight percent, respectively. Elevated concentrations of Li (mean 0.11 wt. percent) are indicators of a hydrothermal origin, and distinguishes these samples, along with the high Mn and low Fe contents, from hydrogenetic Fe-Mn crusts. Other enriched elements include Ba (mean 0.14 percent), Cu (249 ppm), Mo (451 ppm), Ni (400 ppm), Zn (394 ppm), V (214 ppm), and W (132 ppm). Chondrite-normalized REE patterns show large negative Ce anomalies and LREE enrichments, both characteristic of hydrothermal Mn deposits. Small negative Eu anomalies are not typical of hydrothermal deposits and can be explained either by the absence of leaching of plagioclase by the hydrothermal fluids or by the precipitation of Eu-rich minerals, such as barite and anhydrite, at depth. The high base-metal contents indicate that sulfides are not forming deeper in the hydrothermal system or that such deposits are being leached by the ascending fluids. Textures of the thickest Mn deposits indicate that the Mn oxides formed below the seabed from ascending fluids during multiple phases of waxing and waning hydrothermal pulses. The deposits were later exposed at the seafloor by erosional or mass wasting events; subsequently a thin layer of hydrogenetic Fe-Mn oxides accreted on the exposed surface. Mn-oxide filled veins may represent part of a feeder system. The thick sediment-free Mn-oxide layers locally grade into Mn-oxide cemented volcaniclastic beds. Our results indicate the extensive production of hydrothermal Mn on a regional basis, probably from multiple hydrothermal sources within the Samoan chain, and from the Tonga arc/back-arc system immediately to the west, as determined in previous studies.

Hein, J. R.; Staudigel, H.; Koppers, A.; Hart, S. R.; Dunham, R.

2006-12-01

123

Geology and geochemistry of epithermal precious metal vein systems in the intra-oceanic arcs of Palau and Yap, western Pacific  

USGS Publications Warehouse

The Palau and Yap arcs are part of an intra-oceanic island-arc-trench system which separates the Pacific and Philippine plates in the western Pacific Ocean. The 350-km-long Palau arc consists of over 200 islands while the 400-km-long Yap arc located to the north has only four major islands exposed. Four of the largest islands in Palau are composed primarily of early Eocene to mid-Miocene volcanic rocks and the four islands comprising Yap contain only Miocene volcanic rocks. Basalt and basaltic andesites of the Babelthuap Formation are the oldest volcanic rocks in Palau and are characterized by high MgO, Ni and Cr and low TiO2 and have a boninitic affinity. They form the central and southeastern parts of Babelthuap Island. Oligocene arc tholeiite flows having an age of 34-35.5 Ma comprise most of the three smaller volcanic islands in Palau and the western part of Babelthuap. The youngest volcanic rocks are dacitic intrusions having an age of 22.7-23.2 Ma. The Yap arc is unusual in that metamorphic rocks up to amphibolite grade form most of the islands. These are underlain by a melange composed of igneous and volcanic clasts as well as clasts from a dismembered copper-gold skarn deposit. Miocene volcanic rocks consisting of flows and volcaniclastic deposits overlie the melange and metamorphic complex. An epithermal precious-metal vein system hosted by flows and flow breccias of the Babelthuap Formation occurs in an area 1.5 km by 1 km on the southeast side of Babelthuap Island. Over 50 veins and mineralized breccias ranging up to 2 m in width and having a strike length up to 500 m contain from trace to 13.0 ppm gold. The veins consist of quartz with varying amounts of sulfides and iron oxides after sulfides and the mineralized breccias consist of brecciated country rock cemented by quartz and iron oxides after sulfides. The veins and mineralized breccias generally dip within 15?? of vertical and have two preferred orientations, north-northwest and north-northeast. Hydrothermal alteration of the host rocks consists of a widespread weak to moderately strong propylitic alteration and a more restricted sericitic alteration adjacent to the veins and shear zones. Sulfide minerals in the veins consist primarily of pyrite accompanied by lesser amounts of sphalerite, chalcopyrite, galena, acanthite, native silver, cerargyrite, and iodyrite in partly oxidized parts of the vein system. Gold is typically fine-grained, 1-20 microns, and occurs as native gold, electrum and gold-silver-telluride. Elements correlated with high gold concentrations include molybdenum, tellurium, bismuth, lead, silver, copper, zinc and arsenic. In Yap a similar vein system to that present in Palau is hosted by the Miocene Tomil Volcanics on the islands of Maap and Gagil Tamil. The quartz veins and quartz-cemented breccias contain up to 3.7 ppm gold and trace elements associated with the gold include tellurium, copper, silver and vanadium. Within the mineralized area an unusually iron-rich (3-20%), 4-m-thick, hot-spring deposit contains up to 1.04 ppm gold and high concentrations of tellurium, copper and vanadium. Hydrothermal eruption breccia beds are present within the deposit. The presence of the hot-spring deposit and banded and comb textures of the vein quartz suggest that the vein system presently exposed formed at a shallow level. The vein systems in Palau and Yap have similar textures, geochemical suites and alteration assemblages. Both vein systems formed late in the volcanic evolution of the intra-oceanic arc. Media tested for their effectiveness in geochemical exploration in the tropical, deeply weathered environment of Palau and Yap included stream sediments, heavy-mineral concentrates from stream sediments, and sediment from the mangrove coastal environment which is well developed around most of the islands of Yap and Palau. Geochemical surveys in both Yap and Palau of mangrove sediment show that adjacent to areas of gold mineralization, gold and tellu

Rytuba, J. J.; Miller, W. R.

1990-01-01

124

Fluid immiscibility in late-Alpine gold-bearing veins, Eastern and Northwestern European Alps  

Microsoft Academic Search

Gold-bearing quartz veins fill late-Alpine brittle structures in Pennine nappes of Austria (in the Tauern window) and in northern Italy. The veins formed in the latter stages of uplift of the Alps. Fluid inclusions in veins sampled from Böckstein, Austria, and Valle Anzasca, Italy have a wide variety of compositions, ranging from aqueous brine (about 5 wt% NaCl equiv.) to

D. Craw; D. A. H. Teagle; R. Belocky

1993-01-01

125

Vein development during folding in the upper brittle crust: The case of tourmaline-rich veins of eastern Elba Island, northern Tyrrhenian Sea, Italy  

NASA Astrophysics Data System (ADS)

Detailed structural analysis of tourmaline-rich veins hosted in the contact aureole of the ˜6 Ma Porto Azzurro granite in southeastern Elba Island, northern Tyrrhenian Sea is presented. Using geometric features of the veins, the physical conditions at the time of vein formation are estimated, namely the stress ratio (? = (?2 - ?3)/(?1 - ?3)), driving stress ratio (R? = (Pf - ?3)/(?1 - ?3)) and fluid overpressure (?Po = Pf - ?3). Two vein sets (A veins and B veins) have been recognized based on orientation and thickness distributions and infilling material. Analysis of vein pole distributions indicates ? = 0.57 and R? = 0.24 for the A veins and ? = 0.58 and R? = 0.47 for the B veins, and fluid pressures less than the intermediate stress magnitude. Analysis of geometric features of the veins gives estimated fluid overpressures of between ˜16 MPa (A veins) and ˜32 MPa (B veins). We propose a model for the tectonic environment of vein development, in which formation of secondary permeability in the deforming thermal aureole of the Porto Azzurro pluton was controlled by ongoing development of fracture systems in the hinge zone of a regional NNW-SSE trending fold that favored transport and localization of hydrothermal fluids.

Mazzarini, Francesco; Musumeci, Giovanni; Cruden, Alexander R.

2011-10-01

126

Metasomatic- hydrothermal processes in the Qatruyeh area, Iran: Mineralogy and trace elements geochemistry of metasedimentary rock- hosted iron indices  

NASA Astrophysics Data System (ADS)

The Qatruyeh iron indices are located at about 40 Km northeast of Neyriz, in the eastern edge of the HP-LT Sanandaj-Sirjan metamorphic belt, Zagros Mountain. Qatruyeh indices are contained within the metasedimentary rocks of the Late Proterozoic- early Paleozoic, which consists predominantly of dolomitic limestone, greenschist and quartzite. Field investigations, mineralogical studies and XRD analyses indicate that orebodies are dominated by magnetite. The structures of orebodies are mainly formed as thin layers and massive, which are located between dolomitic limestones and greenschists. Tourmaline, muscovite, chlorite, talc, martite, specularite, goethite, limonite, pyrite and chalcopyrite are present as minor minerals. The area has experienced two different stages of metasomatic- hydrothermal alterations. The iron ores were formed during the metasomatic- hydrothermal processes. Those processes are: (1) Na-Ca alteration and (2) mineralization (Oxidation-Sulfidation). The first stage of alteration follows the attainment of peak regional metamorphic condition (187± 2.6 Ma based on zircon SHRIMP U- Pb). This alteration is accompanied with Low-grade magnetite ores formation (50 % Fe2O3t), replacement textures, gradual transformation between layered ores and host rock. Wet chemistry analyses on magnetite shows that Na-Ca alteration caused increasing Cr and Cu as transition metals and Ni, Co and V were depleted. Metasedimentary rock-hosted iron deposits indicate that Na-Ca alteration increase Cu, Ni, Cr, Co, Zn as immobile elements and Na-Fe, whereas the LILE (Pb, Sr) were depleted. The formation of paragonite-tourmaline is also occurs as a part of iron deposition process in the stage. The second stage of metasomatic- hydrothermal alteration is accompanied with widespread veins and veinlets of High-grade magnetite (75 % Fe2O3t) - hematite- Quartz. Mineralization took place along host rock fractures with passage of saline, hot and oxidized aqueous fluids. Paragonite altered to muscovite in the host-rocks and ores in the stage. Sulfide replacement is generally occurred as a late stage phase.

Rajabzadeh, M. A.; Asadi, S.

2009-04-01

127

Piezoelectric quartz crystal biosensors  

Microsoft Academic Search

Biosensing methods utilize the intrinsic selectivity of a biorecognition process to create relatively simple, low cost, analytical alternatives for a variety of research investigations. Here, biosensor applications of the piezoelectric quartz crystal (PQC) are reviewed. The discussion is divided into sections focusing on the development of PQC based analytical techniques, applications in solution phase sensing pertaining to PQC biosensors, and

Renee L. Bunde; Eric J. Jarvi; Jeffrey J. Rosentreter

1998-01-01

128

Galileo quartz clock  

Microsoft Academic Search

A quartz oscillator for use in the Galileo experiment (orbiter and Probe) for Jupiter mission 1982 are described. This oscillator has achieved significant performance breakthroughs by the use of an SC cut, double rotated, crystal in a titanium dewar flask. Some of the performance parameters as well as the design feature of the oscillator are presented.

M. Block; M. Meirs; M. Rosenfeld; P. C. Garriga

1979-01-01

129

Quartz Crystal Aging Effects.  

National Technical Information Service (NTIS)

The purpose of this research is to improve fabricating procedures and reduce the aging of quartz resonators. Aluminum-plated 5 MHz resonators in the HC-27/U container displayed high negative aging rates when stored at 45C. Successive aging at 45C and 85C ...

R. B. Belser W. H. Hicklin

1968-01-01

130

Quartz Crystal Aging Effects.  

National Technical Information Service (NTIS)

The purpose of this research is to reduce the aging and failure rates of quartz resonators, thereby increasing their reliability. Aging measurements at 85C of 84 resonators distributed among the frequencies, 81.9, 100, 250, 455, and 500 kilocycles, and am...

R. B. Belser W. H. Hicklin

1966-01-01

131

Source and evolution of ore-forming hydrothermal fluids in the northern Iberian Pyrite Belt massive sulphide deposits (SW Spain): evidence from fluid inclusions and stable isotopes  

NASA Astrophysics Data System (ADS)

A fluid inclusion and stable isotopic study has been undertaken on some massive sulphide deposits (Aguas Teñidas Este, Concepción, San Miguel, San Telmo and Cueva de la Mora) located in the northern Iberian Pyrite Belt. The isotopic analyses were mainly performed on quartz, chlorite, carbonate and whole rock samples from the stockworks and altered footwall zones of the deposits, and also on some fluid inclusion waters. Homogenization temperatures of fluid inclusions in quartz mostly range from 120 to 280 °C. Salinity of most fluid inclusions ranges from 2 to 14 wt% NaCl equiv. A few cases with Th=80-110 °C and salinity of 16-24 wt% NaCl equiv., have been also recognized. In addition, fluid inclusions from the Soloviejo Mn-Fe-jaspers (160-190 °C and ?6 wt% NaCl equiv.) and some Late to Post-Hercynian quartz veins (130-270 °C and ?4 wt% NaCl equiv.) were also studied. Isotopic results indicate that fluids in equilibrium with measured quartz (?18Ofluid ?-2 to 4‰), chlorites (?18Ofluid ?8-14‰, ?Dfluid ?-45 to -27‰), whole rocks (?18Ofluid ?4-7‰, ?Dfluid ?-15 to -10‰), and carbonates (?18Oankerite ?14.5-16‰, ?13Cfluid =-11 to -5‰) evolved isotopically during the lifetime of the hydrothermal systems, following a waxing/waning cycle at different temperatures and water/rock ratios. The results (fluid inclusions, ?18O, ?D and ?13C values) point to a highly evolved seawater, along with a variable (but significant) contribution of other fluid reservoirs such as magmatic and/or deep metamorphic waters, as the most probable sources for the ore-forming fluids. These fluids interacted with the underlying volcanic and sedimentary rocks during convective circulation through the upper crust.

Sánchez-España, Javier; Velasco, Francisco; Boyce, Adrian J.; Fallick, Anthony E.

2003-08-01

132

Minerals Yearbook 1991: Quartz Crystal.  

National Technical Information Service (NTIS)

Cultured quartz crystal production was unchanged, and consumption increased in 1991 from levels recorded in 1990. Production and sales of domestic lascas as feedstock for cultured quartz crystal was higher in 1991, and reported consumption was slightly lo...

J. A. Ober

1992-01-01

133

Minerals Yearbook, 1990: Quartz Crystal.  

National Technical Information Service (NTIS)

Cultured quartz crystal production and consumption decreased slightly in 1990 after 3 years of growth. Consumption of domestic lascas as feedstock for cultured quartz crystal decreased also. The single domestic producer of lascas, the raw material from wh...

J. A. Ober

1991-01-01

134

Monolithic Quartz Vibrating Beam Accelerometer.  

National Technical Information Service (NTIS)

A monolithic quartz vibrating beam accelerometer is described. The objective is machining, by chemical etching process, miniature accelerometers suitable for various applications, like guidance systems, and vehicle dynamic control. The monolithic quartz a...

F. Deyzac D. Janiaud S. Muller

1992-01-01

135

Metamorphic fluid flow in the northeastern part of the 3.8 3.7 Ga Isua Greenstone Belt (SW Greenland): A re-evalution of fluid inclusion evidence for early Archean seafloor-hydrothermal systems  

NASA Astrophysics Data System (ADS)

Fluid inclusions in quartz globules and quartz veins of a 3.8-3.7 Ga old, well-preserved pillow lava breccia in the northeastern Isua Greenstone Belt (IGB) were studied using microthermometry, Raman spectrometry and SEM Cathodoluminescence Imaging. Petrographic study of the different quartz segregations showed that they were affected by variable recrystallization which controlled their fluid inclusion content. The oldest unaltered fluid inclusions found are present in vein crystals that survived dynamic and static recrystallization. These crystals contain a cogenetic, immiscible assemblage of CO 2-rich (+H 2O, +graphite) and brine-rich (+CO 2, +halite, +carbonate) inclusions. The gas-rich inclusions have molar volumes between 44.8 and 47.5 cm 3/mol, while the brine inclusions have a salinity of ˜33 eq. wt% NaCl. Modeling equilibrium immiscibility using volumetric and compositional properties of the endmember fluids indicates that fluid unmixing occurred at or near peak-metamorphic conditions of ˜460 °C and ˜4 kbar. Carbonate and graphite were precipitated cogenetically from the physically separated endmember fluids and were trapped in fluid inclusions. In most quartz crystals, however, recrystallization obliterated such early fluid inclusion assemblages and left graphite and carbonate as solid inclusions in recrystallized grains. Intragranular fluid inclusion trails in the recrystallized grains of breccia cementing and crosscutting quartz veins have CO 2-rich assemblages, with distinctly different molar volumes (either between 43.7 and 47.5 cm 3/mol or between 53.5 and 74.1 cm 3/mol), and immiscible, halite-saturated H 2O-CO 2-NaCl(-other salt) inclusions. Later intergranular trails have CH 4-H 2 ( X up to ˜0.3) inclusions of variable density (ranging from 48.0 to >105.3 cm 3/mol) and metastable H 2O-NaCl(-other salt?) brines (˜28 eq. wt% NaCl). Finally, the youngest fluid inclusion assemblages are found in non-luminescent secondary quartz and contain low-density CH 4 (molar volume > 105.33 cm 3/mol) and low-salinity H 2O-NaCl (0.2-3.7 eq. wt% NaCl). These successive fluid inclusion assemblages record a retrograde P-T evolution close to a geothermal gradient of ˜30 °C/km, but also indicate fluid pressure variations and the introduction of highly reducing fluids at ˜200-300 °C and 0.5-2 kbar. The quartz globules in the pillow fragments only contain sporadic CH 4(+H 2) and brine inclusions, corresponding with the late generations present in the cementing and crosscutting veins. We argue that due to the large extent of static recrystallization in quartz globules in the pillow breccia fragments, only these relatively late fluid inclusions have been preserved, and that they do not represent remnants of an early, seafloor-hydrothermal system as was previously proposed. Modeling the oxidation state of the fluids indicates a rock buffered system at peak-metamorphic conditions, but suggests a change towards fluid-graphite disequilibrium and a logf/fO above the Quartz-Fayalite-Magnetite buffer during retrograde evolution. Most likely, this indicates a control on redox conditions and on fluid speciation by ultramafic rocks in the IGB. Finally, this study shows that microscopic solid graphite in recrystallized metamorphic rocks from Isua can be deposited inorganically from a fluid phase, adding to the complexity of processes that formed reduced carbon in the oldest, well-preserved supracrustal rocks on Earth.

Heijlen, Wouter; Appel, Peter W. U.; Frezzotti, Maria-Luce; Horsewell, Andy; Touret, Jacques L. R.

2006-06-01

136

Plastic Deformation of Quartz: Unfinished business?  

NASA Astrophysics Data System (ADS)

Starting at Harvard in the mid-1930's, David Griggs built a series of high pressure machines for experimental rock deformation. One persistent aim was to achieve the plastic deformation of quartz. Each time he built a new machine for higher pressure and/or temperature, one of the first materials he tested would be quartz. This search went on through a 500 MPa liquid-medium machine at temperatures up to 300°C, then with a gas-medium machine for temperatures up to 800°C, and finally with a solid-medium machine for higher pressures and temperatures. Quartz proved stubbornly resistant to deformation except at extremely high stresses until, finally and somewhat serendipitously, it was found possible to deform quartz at relatively low stresses in the presence of water under special conditions. The breakthrough came in an experiment in a 1500 MPa solid-medium apparatus in which talc was used as pressure medium. At the temperature of the experiment, the talc dehydrated and so released water. Under these conditions, natural quartz proved to be very weak and to readily undergo plastic deformation, a phenomenon that became known as "hydrolytic weakening". Soon after this discovery, it was also found that certain synthetic single crystals could be easily deformed ab initio. These crystals were from a particular set that had been grown rapidly under hydrothermal conditions and had incorporated water during growth. Attempts in our laboratory to weaken crystals in a gas-medium apparatus at around 300 MPa by cooking dry quartz in the presence of added water were all unsuccessful, although we could deform wet synthetic crystals. There was considerable speculation about a role of high pressure in promoting hydrolytic weakening, but the dilemma was eventually clarified by electron microscope studies by Fitz Gerald and coworkers. These studies showed that crystals that had been subjected to high pressure and temperature in the solid-medium apparatus were extensively microcracked, presumably due to non-hydrostatic stresses generated from the solid medium during raising the pressure, thus evidently promoting the ingress of water. From our gas-medium experiments it would seem that both the solubility and the rate of diffusion of water-related species in dry quartz must be very low, such that at 300 MPa and around 500 - 1000 °C the water penetrates less than a few micrometres in the course of a few hours. Thus the sluggishness of diffusion and the low equilibrium solubility of water-related species in quartz probably explain the failure to achieve hydrolytic weakening in the gas-medium apparatus. However, the documentation of these properties remains inadequate. The initial, and still current, Frank-Griggs hypothesis for the origin of hydrolytic weakening is that the water plays a role in the breaking of the covalent silicon-oxygen bonds as a dislocation is propagated. It is a corollary that the dislocation must be saturated with water or that the water must migrate with the dislocation as it moves. Heggie and Jones have done a number of ab initio calculations on the role of the water in the migration of dislocations in quartz which support the idea that the motion of dislocations is aided by the presence of water-related species in the dislocation core.

Paterson, M. S.

2011-12-01

137

Ultrasonic abrasion of quartz crystals  

Microsoft Academic Search

In the present work, we investigate the wear mechanisms associated with the ultrasonic abrasion of quartz. Ultrasonic abrasion was carried out in X-, Y-, Z- and AT-cut plates of natural quartz and Z-cut plates of synthetic quartz. The counter bodies, square and cylindrical, were fabricated from stainless steel. The abrasive slurry was made from boron carbide with mean grain size

P. L Guzzo; A. A Raslan; J. D. B De Mello

2003-01-01

138

Genetic environment of germanium-bearing gold-silver vein ores from the Wolyu mine, Republic of Korea  

Microsoft Academic Search

The Wolyu mine is one of the largest vein-type gold-silver-bearing epithermal systems in the Youngdong district and is the first gold-silver deposit in Korea found to contain significant germanium, in the form of argyrodite (Ag8GeS6). Mineralized veins (78.9 ± 1.2 Ma) crosscutting Late Cretaceous hostrock tuff and quartz porphyry (81.5 ± 1.8 Ma) consist of three stages of quartz and

Seong-Taek Yun; Chil-Sup So; Sang-Hoon Choi; Kevin L. Shelton; Ja-Hak Koo

1993-01-01

139

Prototype vein contrast enhancer  

NASA Astrophysics Data System (ADS)

A proof-of-principle prototype Vein Contrast Enhancer (VCE) has been designed and constructed. The VCE is an instrument that makes vein access easier by capturing an infrared image of peripheral veins, enhancing the vein-contrast using software image processing, and projecting the enhanced vein-image back onto the skin using a modified commercial projector. The prototype uses software alignment to achieve alignment accuracy between the captured infrared image and the projected visible image of better than 0.06 mm. Figure 1 shows the prototype demonstrated in our laboratory.

Zeman, Herbert D.; Lovhoiden, Gunnar; Vrancken, Carlos

2004-07-01

140

The compression pathway of quartz  

SciTech Connect

The structure of quartz over the temperature domain (298 K, 1078 K) and pressure domain (0 GPa, 20.25 GPa) is compared to the following three hypothetical quartz crystals: (1) Ideal {alpha}-quartz with perfectly regular tetrahedra and the same volume and Si-O-Si angle as its observed equivalent (ideal {beta}-quartz has Si-O-Si angle fixed at 155.6{sup o}). (2) Model {alpha}-quartz with the same Si-O-Si angle and cell parameters as its observed equivalent, derived from ideal by altering the axial ratio. (3) BCC quartz with a perfectly body-centered cubic arrangement of oxygen anions and the same volume as its observed equivalent. Comparison of experimental data recorded in the literature for quartz with these hypothetical crystal structures shows that quartz becomes more ideal as temperature increases, more BCC as pressure increases, and that model quartz is a very good representation of observed quartz under all conditions. This is consistent with the hypothesis that quartz compresses through Si-O-Si angle-bending, which is resisted by anion-anion repulsion resulting in increasing distortion of the c/a axial ratio from ideal as temperature decreases and/or pressure increases.

Thompson, Richard M.; Downs, Robert T.; Dera, Przemyslaw (Ariz); (UC)

2011-11-07

141

CMS quartz fiber calorimeter  

NASA Astrophysics Data System (ADS)

The CMS will be a general purpose detector for the Large Hadron Collider at CERN. Its quartz fiber calorimeter is designed to provide hermetic measurement of energy flow in the forward rapidity region. The calorimeter must operate under extremely hard radiation conditions and almost without maintenance. Several prototypes have been constructed and tested at the CERN high-energy beam. The cost effective technology of manufacturing of fine sampling absorber modules has been developed.

Gavrilov, V.

2000-10-01

142

Microstructural evolution of syntaxial veins formed by advective flow  

NASA Astrophysics Data System (ADS)

Veins are common in Earth's crust, and are formed by a wide range of processes, which lead to crystal growth in dilation sites. The first-order processes in vein formation have been identified, but it is much less clear how these can be diagnosed from field studies. In order to better understand the microstructural evolution during vein growth, we grew veins of analogue material [alum, KAl(SO4)2·12H2O] in a transmitted-light cell from an advecting supersaturated fluid. Real-time observation shows the effects of flow rate and supersaturation on the evolving microstructure: (1) along-vein trends in growth rate caused by decreasing supersaturation, and (2) growth competition between clear crystals in the absence of nucleation and primary fluid inclusions. Although the overall trends in growth rate are in agreement with previous work, the local effects at the scale of individual grains reported here are less well understood; these new data form a basis for better interpretation of natural microstructures. To explore the possible effects of experimentally observed processes during vein growth, we simulate the growth kinetics of a quartz vein at various conditions of advective flow in Earth's crust. Results show that in general the along-vein changes in growth rate occur at length scales much larger than a typical outcrop.

Hilgers, Christoph; Dilg-Gruschinski, Karin; Urai, Janos L.

2004-03-01

143

Controls on quartz silt formation by crystalline defects.  

PubMed

Silt composed predominately of quartz occurs abundantly in the sedimentary material found in deposits worldwide. Its origin is still the subject of many debates, but one acknowledged source is due to glacial grinding. To examine this problem and test the apparent contradictory evidence in the literature, a series of experiments were performed. In these experiments, the Bromhead ring shear apparatus was used as it can simulate glacial grinding due to its uninterrupted shearing action; hence, it provides an effective reproduction of glacial grinding. Experiments conducted on unweathered sand-sized vein quartz produced little silt, while use of sand from a sedimentary deposit, Leighton Buzzard sand, produced plentiful silt. Experimental results suggest that there is an internal mineralogical control on the formation of quartz silt particles. It is argued that the processes involved in the formation of quartz introduce defects (Moss defects) into the low-quartz crystal structure, demonstrated by the presence of peaks in the particle size curve around 20 microm. This indicates that there is a lithological control for the silt yielded under weathering, and this could explain why a pronounced mode at around 20-60 micirom is commonly observed in silts, such as loess. PMID:16501939

Kumar, R; Jefferson, I F; O'hara-Dhand, K; Smalley, I J

2006-02-24

144

QUARTZ FIBER ELECTROSCOPES  

DOEpatents

This patent pertains to quartz fiber electroscopes of small size for use by personnel to monitor nuclear radiation. The invention resides tn a novel way of charging the electroscope whereby the charging of the electroscope whereby the charging of the electroscope is carried out without obtaining contact with the fiber system or its support and the electroscope can therefore be constructed without a protective cap to prevent wrongful discharge. The electroscope is charged by placing a voltage between an electrode located in close proximity to the element to be charged and the electroscope me metallic case. ABSTRACTS

Henderson, R.P.

1956-04-17

145

Quartz and Cholesterol  

NSDL National Science Digital Library

The WebWare molecules of the month for June are from two articles in this issue. The article, "Cement: Its Chemistry and Properties", featured on the cover, dicusses the constituents of cement. Silica is one of the main components of cement, and the most common form of pure silica (SO2) is α-quartz. In "Bromination and Debromination of Cholesterol: An Inquiry-Based Lab Involving Structure Elucidation, Reaction Mechanism, and 1H NMR", Grant and Latimer describe an experiment suitable for upper-level organic chemistry students.

146

ORIGIN OF QUARTZ IN COAL.  

USGS Publications Warehouse

Both a scanning electron microscope and an electron microprobe (EMP) were used in this study to analyze the cathodoluminescence properties of quartz grains in samples of the Upper Freeport coal bed because quartz grains in coal are small (silt sized) and below the resolution capabilities of a standard luminoscope. Quartz grains were identified by the detection of silicon alone with energy dispersive X-ray units attached to both the SEM and the EMP.

Ruppert, Leslie, F.; Cecil, C. Blaine; Stanton, Ronald, W.

1984-01-01

147

A Model For Syntectonic Fibrous Vein Growth Inferred From Microtextures. Ouachitas Orogen, Arkansas  

NASA Astrophysics Data System (ADS)

Veins from the Lower Ordovician Mazarn Formation in the Arkansas' Ouachitas show two processes of vein growth, 1) continuous localized fracturing and filling and 2) recrystallization, tied to the deformation history of the area under study. Evidence for continuous localized fracturing includes the presence of veinlets near or at the vein-host interface. Veinlets are long and narrow features parallel to the main body of the vein, filled mainly with quartz, between 5 and 25 ?m wide. Veinlets cut and displaced host grains. Displacement of host grains is evident because the material precipitated on veinlets show different luminescence than host grains. Remnants of these veinlets are observed in completely recrystallized fibers. Evidence for recrystallization includes, 1) wide fibers (more than 100 ?m) with fluid inclusion trails parallel to fiber length that span the entire fiber length, 2) luminescence in the central part of the vein is different than luminescence in the external part of the vein (close to host-vein interface), 3) remnants of original luminescence in the central part of the vein suggesting that recrystallization is a later process. We hypothesize that in this region folding followed by flattening gave rise to boudinage of resistant layers accompanying abundant pressure solution providing the vein forming material. Precipitation of material took place along necks of boudins, which fractured repeatedly allowing veins to grow in width and length. Late thrust faults led to open system conditions which gave rise to new vein growth and recrystallization. Recrystallization altered the shape of previously formed veins.

Cervantes, P.; Wiltschko, D. V.

2005-12-01

148

A Palm Vein Recognition System  

Microsoft Academic Search

Palm vein pattern recognition is one of the newest bometric techniques researched today. This paper presents a palm vein recognition system that uses blood vessel patterns as personal identifying factor. The vein information is hard to duplicate since veins are internal to the human body. The design details of the palm vein capture device are researched, and preprocessing and feature

Huan Zhang; Dewen Hu

2010-01-01

149

Development of quartz tuning fork temperature sensors  

Microsoft Academic Search

A temperature sensing technique taking thermal sensitive quartz tuning fork vibration arm as sensitive components and output of digital frequency is presented. In the design of quartz tuning fork temperature sensor, selecting the cut type of quartz tuning fork according to the each anisotropic nature of quartz tuning fork, so that there is a linear relationship between quartz tuning fork

Jun Xu; Bo You; Xue-fei Zhao; Xin Li

2008-01-01

150

Distinguishing shocked from tectonically deformed quartz by the use of the SEM and chemical etching  

USGS Publications Warehouse

Multiple sets of crystallographically-oriented planar deformation features (PDFs) are generated by high-strain-rate shock waves at pressures of > 12 GPa in naturally shocked quartz samples. On surfaces, PDFs appear as narrow (50-500 nm) lamellae filled with amorphosed quartz (diaplectic glass) which can be etched with hydrofluoric acid or with hydrothermal alkaline solutions. In contrast, slow-strain-rate tectonic deformation pressure produces wider, semi-linear and widely spaced arrays of dislocation loops that are not glass filled. Etching samples with HF before examination in a scanning electron microscope (SEM) allows for unambiguous visual distinction between glass-filled PDFs and glass-free tectonic deformation arrays in quartz. This etching also reveals the internal 'pillaring' often characteristic of shock-induced PDFs. This technique is useful for easily distinguishing between shock and tectonic deformation in quartz, but does not replace optical techniques for characterizing the shock features.

Gratz, A. J.; Fisler, D. K.; Bohor, B. F.

1996-01-01

151

Caractérisation des quartz filoniens épithermaux de la zone volcanique de Cabo de Gata (province d'Almería, Espagne) par thermoluminescence basse température; relation avec les textures pétrographiques et les inclusions fluides  

NASA Astrophysics Data System (ADS)

In the area of Cabo de Gata, the quartz samples show a wide variety of petrographic textures, and therefore, a highly complex history of veins, which requires several methods and techniques. In the present paper, the authors propose thermoluminescence (TL) as an interesting method for characterizing the different steps involved in the crystallization of quartz veins, coupled with the microscopic observation and fluid inclusion studies. Two different TL techniques will be presented: auto-photographs of TL emissions which represent an original approach in investigating relationships with petrographic textures, and quartz glow curves, which make possible the attribution of low-temperature TL emission to structural defects produced during quartz growth.

Demoustier, Axelle; Charlet, Jean-Marie; Castroviejo, Ricardo

1999-04-01

152

Comparative study of yttrium and rare-earth element behaviours in fluorine-rich hydrothermal fluids  

Microsoft Academic Search

The mineral ‘fluorite’ is utilized as a probe to investigate the behaviour of the pseudolanthanide yttrium with respect to the lanthanides (rare-earth elements, REE) in fluorine-rich hydrothermal solutions. Hydrothermal vein fluorites are characterized by the close association of Y and REE, but in contrast to igneous and clastic rocks they show variable and nonchondritic Y\\/Ho ratios of up to 200.

Michael Bau; Peter Dulski

1995-01-01

153

Postpartum ovarian vein thrombosis.  

PubMed

Ovarian vein thrombosis is a rare occurrence in the postpartum period. Two cases of postpartum ovarian vein thrombosis are presented. The differential diagnosis is extensive because many diseases can present with similar symptoms. Early diagnosis is essential for appropriate treatment and prevention of the potential sequelae that can occur. Computerized tomography with contrast is the optimal imaging modality for the diagnosis. PMID:8285981

Chawla, K; Mond, D J; Lanzkowsky, L

1994-01-01

154

Montre-bracelet à quartz  

Microsoft Academic Search

Summary Description of the main features of a quartz wrist watch. The quartz resonator oscillates in the fundamental flexural mode at a frequency of 8192 Hz. A single chip of a fully integrated circuit realizes the three main functions of oscillator, frequency devider by a factor of 32 and pulse former. An electromagnetic resonant motor, associated with an indexing mechanism,

H. Oguey

1970-01-01

155

Monolithic quartz vibrating beam accelerometer  

Microsoft Academic Search

A monolithic quartz vibrating beam accelerometer is described. The objective is machining, by chemical etching process, miniature accelerometers suitable for various applications, like guidance systems, and vehicle dynamic control. The monolithic quartz active part includes two vibrating beams, the proof mass, and its articulation in a base. It is obtained by a process similar to the one used in watch

F. Deyzac; D. Janiaud; S. Muller

1992-01-01

156

Geophysical anomalies and quartz microstructures, Eastern Warburton Basin, North-east South Australia: Tectonic or impact shock metamorphic origin?  

NASA Astrophysics Data System (ADS)

The Eastern Warburton Basin, Northeast South Australia, features major geophysical anomalies, including a magnetic high of near-200 nT centred on a ~ 25 km-wide magnetic low (< 100 nT), interpreted in terms of a magmatic body below 6 km depth. A distinct seismic tomographic low velocity anomaly may reflect its thick (9.5 km) sedimentary section, high temperatures and possible deep fracturing. Scanning electron microscope (SEM) analyses of granites resolves microbreccia veins consisting of micron-scale particles injected into resorbed quartz grains. Planar and sub-planar elements in quartz grains (Qz/PE) occur in granites, volcanics and sediments of the > 30,000 km-large Eastern Warburton Basin. The Qz/PE include multiple intersecting planar to curved sub-planar elements with relic lamellae less than 2 ?m wide with spacing of 4–5 ?m. Qz/PE are commonly re-deformed, displaying bent and wavy patterns accompanied with fluid inclusions. U-stage measurements of a total of 243 planar sets in 157 quartz grains indicate dominance of ?{10–12}, ?{10–13} and subsidiary §{11–22}, {22–41}, m{10–11} and x{51–61} planes. Transmission Electron Microscopy (TEM) analysis displays relic narrow ? 1 ?m-wide lamellae and relic non-sub grain boundaries where crystal segments maintain optical continuity. Extensive sericite alteration of feldspar suggests hydrothermal alteration to a depth of ~ 500 m below the unconformity which overlies the Qz/PE-bearing Warburton Basin terrain. The data are discussed in terms of (A) Tectonic–metamorphic deformation and (B) impact shock metamorphism producing planar deformation features (Qz/PDF). Deformed Qz/PE are compared to re-deformed Qz/PDFs in the Sudbury, Vredefort, Manicouagan and Charlevoix impact structures. A 4–5 km uplift of the Big Lake Granite Suite during ~ 298–295 Ma is consistent with missing of upper Ordovician to Devonian strata and possible impact rebound. The occurrence of circular seismic tomography anomalies below the east Warburton Basin, the Poolowana Basin and the Woodleigh impact structure signifies a potential diagnostic nature of circular tomographic anomalies.

Glikson, Andrew Y.; Uysal, I. Tonguç; Fitz Gerald, John D.; Saygin, Erdinc

2013-03-01

157

Dual quartz crystal microbalance  

SciTech Connect

Construction and performance of a dual quartz crystal microbalance is described. The final probe has a dipstick configuration that is particularly suitable for sensing and monitoring applications in viscous and/or conducting liquids. The differential (heterodyned) frequency measurement substantially eliminates the deleterious effects of viscosity, temperature, and conductivity. The corresponding performance coefficients are temperature df/dT = 1.5 Hz/[degree]C, viscosity df/d[eta][sub L] = 103 Hz/cP, and conductivity df/dM = 108 Hz/M, where conductivity is expressed in terms of molarity of sodium chloride. As an example, the etching of a 2000-A-thick layer of aluminum has been monitored as a function of time. 13 refs., 8 figs., 1 tab.

Dunham, G.C.; Benson, N.H.; Petelenz, D.; Janata, J. (Pacific Northwest Lab., Richland, WA (United States))

1995-01-15

158

Hydrothermal solidification of municipal solid waste incineration bottom ash with slag addition.  

PubMed

Hydrothermal solidification of municipal solid waste incineration (MSWI) bottom ash has been carried out under saturated steam pressure (1.56 MPa) at 200 degrees C for up to 24 h by mixing quartz, slaked lime and water-cooled blast furnace slag (WBFS). The strength enhancement for the WBFS addition was best. The strength development was shown to be due mainly to tobermorite formation, and the tobermorite formation densified matrix, thus promoting the strength development. WBFS seemed to have a higher reactivity than the quartz during the initial hydrothermal process, which provided more silica available to harden the solidified specimens. However, a longer curing time (24 h) was favorable to the quartz dissolution for tobermorite formation, which in turn, enhanced the strength for quartz addition. Curing time affected the crystal morphology evolution, and the stubby plate of tobermorite seemed to result in a high strength enhancement in this study. Laboratory leaching tests were conducted to determine the amount of heavy metals dissolved from the final solidified specimens, and the leaching results showed that after hydrothermal processing the heavy metals dissolved from the solidified specimens were reduced effectively. As such, the hydrothermal processing may have a high potential for recycling/reusing MSWI ash on a large scale. PMID:20385479

Jing, Zhenzi; Ran, Xianqiang; Jin, Fangming; Ishida, Emile H

2010-04-10

159

Growth Units and Formation Mechanisms of the Crystals under Hydrothermal Conditions.  

National Technical Information Service (NTIS)

The growth units and formation mechanisms of quartz (SiO2) and barium titanate (BaTiO3) crystals under hydrothermal conditions have been investigated by means of cataphoretic experiments. It is proposed that the growth units of the crystals in hydrotherma...

W. Z. Zhong G. Liu E. Shi S. Hua D. Tang Q. Zhao

1994-01-01

160

Microthermometric analysis of synthetic fluid inclusions in the hydrothermal diamond-anvil cell  

Microsoft Academic Search

The hydrothermal diamond-anvil cell (HDAC) was employed as a pressurized fluid inclusion heating stage to determine temperatures of phase transitions in synthetic fluid inclusions in quartz. Using this technique, the common problem of decrepitation or stretch- ing of inclusions having high internal pressures was eliminated. Homogenization temperatures of pure H2O synthetic inclusions determined in the HDAC are inversely related to

CHRISTIAN SCHMIDT; I-MING CHOU; ROBERT J. BODNAR; WILLIAM A. BASSETT

161

Genetic analysis of quartz from pegmatites of the Mama-Chuya mica belt based on distribuition of isomorphic impurities, Russia  

NASA Astrophysics Data System (ADS)

The effect of the formation conditions of pegmatites in the Mama-Chuya mica belt on the distribution of isomorphic Al, Ti, and Ge impurities in quartz detected by electron paramagnetic resonance (EPR) has been estimated using the isogen method, which takes into account the relationship between this distribution and geological time. It has been revealed that each of the studied types of pegmatite veins is described by special isogens that reflect interrelations between concentrations of various isomorphic impurities. The typification of veins, enrichment of parental melt in water, and other factors affect the isogens. New potentialities of the isogen method for genetic analysis of quartz have been established.

Rakov, L. T.; Tkachev, A. V.; Sakhnov, A. A.

2013-02-01

162

Popliteal vein aneurysm.  

PubMed

The incidence of a popliteal vein aneurysm is extremely low. Two cases of this rare venous anomaly are described. The epidemiology, morphology, and diagnostic methods are discussed and the potentially dangerous complications and treatment methods are presented. PMID:16796307

Falkowski, A; Poncyljusz, W; Zawierucha, D; Kuczmik, W

2006-06-01

163

Acute portal vein thrombosis.  

PubMed

The findings in acute portal vein thrombosis in a patient with chronic calcific pancreatitis and two episodes of pancreatic surgery are described. The diagnosis was made by ultrasound, which showed a dilated portal vein filled with low-level echoes, surrounding hepatic oedema, hypertrophy of the hepatic artery, splenomegaly, collateral vessels and ascites. This was confirmed by computed tomography. The ultrasonic differences in appearance between acute and chronic portal vein thrombosis are discussed, in the context of portal hypertension. The diagnosis of acute portal vein thrombosis should be considered in patients in the appropriate situation who suffer a sudden clinical deterioration with right upper quadrant or abdominal pain. Ultrasound is recommended as the imaging modality of first choice because of the flexibility of its scanning plane and its real time and Doppler capabilities. Computed tomography is valuable in patients with an ileus or heavy pancreatic calcification and for its ability to demonstrate patent vessels on intravenous injection of contrast medium. PMID:3319354

Albertyn, L E

1987-11-01

164

Deep Vein Thrombosis  

MedlinePLUS

... Vein Thrombosis (DVT) Common Signs and Symptoms of PE PE can be fatal, if you experience these signs ... signs and symptoms of these disorders (DVT and PE) can vary by individual and event. Some individuals ...

165

Packaging Precision Quartz Crystal Resonators.  

National Technical Information Service (NTIS)

The causes of aging and thermal hysteresis in quartz resonators are reviewed with emphasis on those aspects which can be influenced by the resonator's packaging. A microcircuit compatible ceramic package design is proposed which is aimed toward optimizing...

E. Hafner J. R. Vig

1973-01-01

166

The First Quartz Electronic Watch  

Microsoft Academic Search

The goal of this paper is to present the history of the quartz electronic watch. The first quartz watch was a Swiss wristwatch\\u000a presented in 1967. It was exactly 20 years after the invention of the transistor. Today Switzerland and Japan are dominant\\u000a on the market of electronic watches. In Switzerland, the competencies in low-power electronics come directly from the

Christian Piguet

2002-01-01

167

Experiments with a quartz resonator  

NASA Astrophysics Data System (ADS)

Experiments with a quartz resonator are described: (i) the frequency response, the quality factor, and the transient processes; (ii) the temperature dependence of the resonance frequency; and (iii) the parameters of the equivalent impedance. A popular quartz resonator designed for generating oscillations of frequency 32?768 Hz (= 215) serves as an example. A new data-acquisition system from PASCO Scientific is used for the measurements. The experiments employ 1 ppm frequency resolution, but are well suited for undergraduate laboratories.

Kraftmakher, Yaakov

2013-09-01

168

Luminescence sensitivity changes in quartz  

Microsoft Academic Search

In the luminescence dating of sedimentary or heated quartz, some heat treatment is usually applied to the sample immediately prior to the measurement of the optically stimulated luminescence. In this paper we report experiments on a 30,000-year-old sedimentary quartz, in which we use the luminescence response to a test dose to monitor the changes in sensitivity that are caused by

A. G. Wintle; A. S. Murray

1999-01-01

169

The role of carboxylic acids in albite and quartz dissolution: An experimental study under diagenetic conditions  

Microsoft Academic Search

Simple water soluble organic acids may promote secondary porosity development in sandstones during diagenesis by increasing feldspar solubility and dissolution rate. To test this hypothesis, Amelia albite and Brazilian hydrothermal quartz were reacted with 0.07 m acetate and 0.07 m acetate-0.005 m oxalate solutions at selected pH values, and distilled water. Pore fluid chemistry was monitored through time at various

Stan P. Franklin; Andrew Hajash Jr.; Thomas A. Dewers; Thomas T. Tieh

1994-01-01

170

Hydrothermal alteration in oceanic ridge volcanics: A detailed study at the Galapagos Fossil Hydrothermal Field  

USGS Publications Warehouse

The Galapagos Fossil Hydrothermal Field is composed of altered oceanic crust and extinct hydrothermal vents within the eastern Galapagos Rift between 85??49???W and 85??55???W. The discharge zone of the hydrothermal system is revealed along scarps, thus providing an opportunity to examine the uppermost mineralized, and highly altered interior parts of the crust. Altered rocks collected in situ by the submersible ALVIN show complex concentric alteration zones. Microsamples of individual zones have been analysed for major/minor, trace elements, and strontium isotopes in order to describe the complex compositional details of the hydrothermal alteration. Interlayered chlorite-smectite and chlorite with disequilibrium compositions dominate the secondary mineralogy as replacement phases of primary glass and acicular pyroxene. Phenocrysts and matrix grains of plagioclase are unaffected during alteration. Using a modification of the Gresens' equation we demonstrate that the trivalent rare earth elements (REEs) are relatively immobile, and calculate degrees of enrichment and depletion in other elements. Strontium isotopic ratios increase as Sr concentrations decrease from least-altered cores to most-altered rims and cross-cutting veins in individual samples, and can be modeled by open system behaviour under low fluid-rock ratio (< 10) conditions following a period of lower-temperature weathering of volcanics within the rift zone. The complex patterns of element enrichment and depletion and strontium isotope variations indicate mixing between pristine seawater and ascending hot fluids to produce a compositional spectrum of fluids. The precipitation of base-metal sulfides beneath the seafloor is probably a result of fluid mixing and cooling. If, as suggested here, the discharge zone alteration occurred under relatively low fluid-rock ratios, then this shallow region must play an important role in determining the exit composition of vent fluids in marine hydrothermal systems. ?? 1994.

Ridley, W. I.; Perfit, M. R.; Josnasson, I. R.; Smith, M. F.

1994-01-01

171

Impact-generated hydrothermal systems on Earth and Mars  

NASA Astrophysics Data System (ADS)

It has long been suggested that hydrothermal systems might have provided habitats for the origin and evolution of early life on Earth, and possibly other planets such as Mars. In this contribution we show that most impact events that result in the formation of complex impact craters (i.e., >2-4 and >5-10 km diameter on Earth and Mars, respectively) are potentially capable of generating a hydrothermal system. Consideration of the impact cratering record on Earth suggests that the presence of an impact crater lake is critical for determining the longevity and size of the hydrothermal system. We show that there are six main locations within and around impact craters on Earth where impact-generated hydrothermal deposits can form: (1) crater-fill impact melt rocks and melt-bearing breccias; (2) interior of central uplifts; (3) outer margin of central uplifts; (4) impact ejecta deposits; (5) crater rim region; and (6) post-impact crater lake sediments. We suggest that these six locations are applicable to Mars as well. Evidence for impact-generated hydrothermal alteration ranges from discrete vugs and veins to pervasive alteration depending on the setting and nature of the system. A variety of hydrothermal minerals have been documented in terrestrial impact structures and these can be grouped into three broad categories: (1) hydrothermally-altered target-rock assemblages; (2) primary hydrothermal minerals precipitated from solutions; and (3) secondary assemblages formed by the alteration of primary hydrothermal minerals. Target lithology and the origin of the hydrothermal fluids strongly influences the hydrothermal mineral assemblages formed in these post-impact hydrothermal systems. There is a growing body of evidence for impact-generated hydrothermal activity on Mars; although further detailed studies using high-resolution imagery and multispectral information are required. Such studies have only been done in detail for a handful of martian craters. The best example so far is from Toro Crater (Marzo, G.A., Davila, A.F., Tornabene, L.L., Dohm, J.M., Fairèn, A.G., Gross, C., Kneissl, T., Bishop, J.L., Roush, T.L., Mckay, C.P. [2010]. Icarus 208, 667-683). We also present new evidence for impact-generated hydrothermal deposits within an unnamed ˜32-km diameter crater ˜350 km away from Toro and within the larger Holden Crater. Synthesizing observations of impact craters on Earth and Mars, we suggest that if there was life on Mars early in its history, then hydrothermal deposits associated with impact craters may provide the best, and most numerous, opportunities for finding preserved evidence for life on Mars. Moreover, hydrothermally altered and precipitated rocks can provide nutrients and habitats for life long after hydrothermal activity has ceased.

Osinski, Gordon R.; Tornabene, Livio L.; Banerjee, Neil R.; Cockell, Charles S.; Flemming, Roberta; Izawa, Matthew R. M.; McCutcheon, Jenine; Parnell, John; Preston, Louisa J.; Pickersgill, Annemarie E.; Pontefract, Alexandra; Sapers, Haley M.; Southam, Gordon

2013-06-01

172

The titanium-in-quartz (TitaniQ) thermobarometer: A critical examination and re-calibration  

NASA Astrophysics Data System (ADS)

Synthetic quartz was grown in rutile-bearing H2O (±NaCl) fluids at 600-800 °C and 1-10 kbar by dissolution and reprecipitation of quartz in a small thermal gradient. Rapid attainment of rutile saturation is proved by the formation of rutile crystals at the contact between old quartz substrate and new quartz overgrowth in several experiments. Titanium concentrations in new quartz correlate positively with the concentrations of Li and Al and depend strongly on quartz growth rate, increasing by up to a factor of 2.5 as the growth rate varied from ˜4 to ˜110 ?m/day. Considering the composition of the most slowly grown quartz samples as most representative we obtain Ti concentrations that are about three times lower than those obtained during earlier calibrations of the TitaniQ thermobarometer. Our data can be fitted by the equation logTi(ppm)=-0.27943·104/T-660.53·(P0.35/T)+5.6459 where T is given in Kelvin and P in kbar. An independent test was made by analyzing igneous quartz from five intrusive and three volcanic magma systems that crystallized at known pressures (0.8-2.7 kbar) and temperatures (675-780 °C). The activity of TiO2 was constrained from the composition of melt inclusions hosted in the analyzed quartz. Although the results depend on the model chosen to calculate aTiO2, they agree much better with our calibration than with previous TitaniQ calibrations. Crystallization pressures calculated based on our calibration agree within 0.1-1.0 kbar with independent pressure estimates, whereas those calculated based on previous calibrations are consistently higher by 3-9 kbar. Slight deviations between our calibration and the natural data are either due to uncertainties in the calculation of aTiO2 of the natural melts or due to failure to synthesize structurally perfect quartz even at our slowest growth rates. Our findings imply that TitaniQ should not be applied to quartz grown from hydrothermal fluids, because growth rates in these environments can be very variable. TitaniQ is more likely to work in igneous quartz, although the present models for TiO2 solubility in quartz and silicate melts may still need to be refined.

Huang, Ruifang; Audétat, Andreas

2012-05-01

173

Pelvic Vein Embolisation in the Management of Varicose Veins  

SciTech Connect

Pelvic vein incompetence is common in patients with atypical varicose veins, contributing to their recurrence after surgery. Therefore, refluxing pelvic veins should be identified and treated. We present our experience with pelvic vein embolisation in patients presenting with varicose veins. Patients presenting with varicose veins with a duplex-proven contribution from perivulval veins undergo transvaginal duplex sonography (TVUS) to identify refluxing pelvic veins. Those with positive scans undergo embolisation before surgical treatment of their lower limb varicose veins. A total of 218 women (mean age of 46.3 years) were treated. Parity was documented in the first 60 patients, of whom 47 (78.3%) were multiparous, 11 (18.3%) had had one previous pregnancy, and 2 (3.3%) were nulliparous. The left ovarian vein was embolised in 78%, the right internal iliac in 64.7%, the left internal iliac in 56.4%, and the right ovarian vein in 42.2% of patients. At follow-up TVUS, mild reflux only was seen in 16, marked persistent reflux in 6, and new reflux in 3 patients. These 9 women underwent successful repeat embolisation. Two patients experienced pulmonary embolisation of the coils, of whom 1 was asymptomatic and 1 was successfully retrieved; 1 patient had a misplaced coil protruding into the common femoral vein; and 1 patient had perineal thrombophlebitis. The results of our study showed that pelvic venous embolisation by way of a transjugular approach is a safe and effective technique in the treatment of pelvic vein reflux.

Ratnam, Lakshmi A. [St. George's Hospital, Department of Radiology (United Kingdom); Marsh, Petra; Holdstock, Judy M.; Harrison, Charmaine S. [Stirling House, Whiteley Clinic (United Kingdom); Hussain, Fuad F. [Royal Surrey County Hospital, Department of Radiology (United Kingdom); Whiteley, Mark S. [Stirling House, Whiteley Clinic (United Kingdom); Lopez, Anthony, E-mail: consultant@radiologist.co.u [Royal Surrey County Hospital, Department of Radiology (United Kingdom)

2008-11-15

174

Minimum of Creep Strength at Quartz Phase Transition  

NASA Astrophysics Data System (ADS)

In this study, we performed experiments to observe the deformation of quartz around fluid inclusions at elevated temperatures and pressures in a hydrothermal diamond anvil cell (HDAC). Temperature is controlled accurately and pressure is determined from the homogenisation temperature of water, which is used as confining medium. Deformation around the inclusions occurs due to the difference of confining pressure P_c from the pressure in the inclusion P_i. P_i varies with inclusion volume, which changes due to elastic and plastic deformation. This volume change can be calculated from the change in homogenisation temperature of the inclusion fluid. Our experiments show that the pressure difference needed to deform quartz around an inclusion is much smaller at the ?-? transition than in either the ?- or ?-stability fields of quartz. These results demonstrate that transformation plasticity of silicates can indeed cause a considerable localised reduction in the strength of Earth's crust and mantle. To quantify stresses from our experimental data, we use finite element models that have been used to investigate elastic volume changes of fluid inclusions as a function of shape and distance from the free sample surface. Stresses around an inclusion are proportional to the observed pressure differences, and on inclusion shape. One result of this study is that inclusions with shapes close to prolate ellipsoids will experience larger elastic volume changes than those shaped like oblate ellipsoids. The experimental results also follow this trend. By including elastic anisotropy in the models, we expect an even closer match with the experimentally observed volume changes. These models will then be used to calculate the stresses produced in the quartz host under the internal and external pressure conditions that lead to plastic deformation in the HDAC experiments. Ultimately the model will be applied to estimate the drop in strength associated with the ?-? transition.

Bruhn, D.; Schmidt, C.; Burnley, P.

2003-04-01

175

Hydrothermal alteration and sulfide mineralization in gabbroids of the Markov Deep (Mid-Atlantic Ridge, 6° N)  

NASA Astrophysics Data System (ADS)

A new type of sulfide occurrence related to metasomatically altered brecciated gabbroids has been studied at the Sierra Leone site situated in the axial rift valley of the Mid-Atlantic Ridge (Markov Deep, 6° N). Two associations of plutonic, subvolcanic, and volcanic rocks were dredged: (1) mid-ocean ridge basalts (MORB) and their intrusive analogues and (2) rocks of the silicic Fe-Ti-oxide series with dominating gabbronorites and sporadic trondhjemites. Almost all igneous rocks at the Sierra Leone site are enriched in Pb, Cu, U, Ga, Ta, Nb, Cs, and Rb and depleted in Zr, Th, and Hf. The rocks of the Fe-Ti-oxide series are enriched in Zn, Sn, and Mo and depleted in Ni and Cr. The main ore-bearing zone is situated at the foot of the eastern wall of the deep, where it is hosted in cataclastic hornblende gabbro and gabbronorite of the Fe-Ti-oxide series. Ore mineralization in metasomatically altered rocks is composed of quartz-sulfide and prehnite-sulfide veinlets, disseminated sulfide, and veined copper sulfide ore. The ore consists of pyrite, chalcopyrite, sphalerite, pyrrhotite, bornite, chalcocite, and digenite. The ?34S value of sulfides varies from 3.0 to 15.3‰. At the foot of the eastern wall of the Markov Deep, directly downslope from the ore-bearing zone, loose sediments contain grains of native Cu, Pb, Zn, and Sn and intermetallic compounds (isoferroplatinum, tetraferroplatinum, and brass) apparently derived from the ore. Mineral assemblages of ore-bearing metasomatic rocks and fluid inclusions therein were studied. Ore metasomatism developed under a low oxygen potential within a temperature interval from 400 to 160°C, though initial hydrothermal alteration of rocks proceeded at temperatures of 800-450°C. The temperature of stringer-disseminated ore mineralization is estimated at 170-280°C. The hydrothermal fluids are considered to be of magmatic origin; as the hydrothermal system evolved, they became diluted with seawater that was contained in fractured oceanic crust. The ore matter could have been derived from magmatic fluids that were released from water-saturated melts of the Fe-Ti oxide series during their ascent and leached from host gabbroids in the process of metasomatic alteration.

Sharkov, E. V.; Abramov, S. S.; Simonov, V. A.; Krinov, D. I.; Skolotnev, S. G.; Bel'Tenev, V. E.; Bortnikov, N. S.

2007-12-01

176

Reversible water weakening of quartz  

NASA Astrophysics Data System (ADS)

We have performed looped pressure-stepping deformation experiments at the same temperature (800 °C) and strain rate (2×10?6 s?1) on a milky quartz crystal and a quartzite that deform by dislocation creep. Our results demonstrate that flow strengths at fixed water content depend on f, and that the dependence is reversible. Thus, rheology of quartzite can be predicted if f is known. In addition, the effect of f on strength of quartzite is greater than that of the milky quartz single crystal. The differing sensitivities are due to differing effects that water has on deformation and recovery within grain interiors and at (or near) grain boundaries. These results indicate that, as temperature increases with depth and the dominant recovery mechanism of dislocation creep changes from recrystallization at grain boundaries to intragranular recovery, dependence of quartz creep on f may also decrease.

Holyoke, Caleb W.; Kronenberg, Andreas K.

2013-07-01

177

Monolithic quartz vibrating beam accelerometer  

NASA Astrophysics Data System (ADS)

A monolithic quartz vibrating beam accelerometer is described. The objective is machining, by chemical etching process, miniature accelerometers suitable for various applications, like guidance systems, and vehicle dynamic control. The monolithic quartz active part includes two vibrating beams, the proof mass, and its articulation in a base. It is obtained by a process similar to the one used in watch crystal manufacturing, so the potential cost is very low. The simplicity of piezoelectric excitation and the numerical output (frequency signal) are key features to reduce dimensions and cost. The expected accuracy of this sensor is 0.003 in a harsh environment. First experimental results are presented.

Deyzac, F.; Janiaud, D.; Muller, S.

1992-06-01

178

Geology and geothermometry of vein-type W-Sn deposits at Pennaichaung and Yetkanzintaung Prospects, Tavoy Township, Tennasserim Division, southern Burma  

NASA Astrophysics Data System (ADS)

The Pennaichaung and Yetkanzintaung W-Sn Prospects are located in Tavoy Township, Tennasserim Division, southern Burma. The W-Sn mineralization at the Pennaichaung is closely related with a small, satellitic granitoid pluton of presumably Late Mesozoic age, which intruded the metaclastic rocks of Mergui Group (mostly Carboniferous). The mineralized quartz veins at the Pennaichaung penetrated the granitoid-metasedimentary rocks contact. In contrary to the Pennaichaung deposit, the W-Sn veins at the Yetkanzintaung are exclusively in the metasedimentary rocks of slates and quartzites of Margui Group. Mineralized quartz veins in the Pennaichaung area trend NNE-SSW, NW-SE and NE-SW with a maximum thickness of 30 cm, but only quartz veins trending NNE-SSW are found to be productive and contained economically workable wolframite and cassiterite. Majority of the mineralized quartz veins in the Yetkanzintaung area trend approximately N-S with easterly dip of 50° 70°. The thickness of the ore veins in the Yetkanzintaung area are thinner than those of the Pennaichaung and range from 1 cm to 20 cm with an average width of 5 cm. Fluid inclusion studies of the quartz from the ore veins cutting the granitoid in the Pennaichaung area have yielded a filling temperature range of 170° 270°C with a maximum mode of 220°C, while quartz crystals from the ore veins in the nearby metasedimentary rocks gave a filling temperature range of 140° 220°C with a maximum mode of 160°C. Hence, the Pennaichaung deposit was thought to have emplaced under a filling temperature range of 140° 270°C. A similar low filling temperature range was recorded for the Yetkanzintaung deposit. Quartz from the Yetkanzintaung ore veins have yielded filling temperatures of 200° 240°C, whereas the fluorites associated with the mineralized quartz veins gave a temperature range of 140° 160°C. Limited freezing runs indicate a salinity of less than 5 NaCl equivalent weight percent for inclusions in quartz from both orebodies. No fluid inclusion evidence of boiling of ore fluids nor presence of liquid CO2 was observed in this study. Thus, the ore fluids responsible for the W-Sn mineralization at the Pennaichaung and Yetkanzintaung areas were of low temperature, diluted, CO2-deficient, NaCl brines.

Zaw, U. Khin

1984-04-01

179

Preoperative assessment of alternative veins.  

PubMed

Duplex ultrasonography, with or without color flow, has replaced phlebography as the technique of choice to select veins for autogenous bypass grafts. Although anatomic location and length are well-defined by ultrasound, evaluation of the venous wall itself is still imperfect. In situ diameters are less than those of arterialized veins. Ultrasonic search is most valuable in the examination of patients with good veins obscured by a layer of fat. Preoperative knowledge of variant anatomy and location of major veins and their branches facilitates bypass surgery. The preoperative vein mapping should be available in the operating room to guide the placement of incisions for unroofing and exploration directly over veins and vein segments that have a high likelihood of being usable. The finding of a useful vein when none is apparent on physical examination may enable the construction of an autogenous bypass in lieu of a less desirable prosthetic graft or leg amputation. PMID:8564029

Salles-Cunha, S X; Beebe, H G; Andros, G

1995-09-01

180

Elastomechanical properties of bovine veins.  

PubMed

Veins have historically been discussed in qualitative, relative terms: "more compliant" than arteries, subject to "lower pressures". The structural and compositional differences between arteries and veins are directly related to the different functions of these vessels. Veins are often used as grafts to reroute flow from atherosclerotic arteries, and venous elasticity plays a role in the development of conditions such as varicose veins and valvular insufficiency. It is therefore of clinical interest to determine the elastomechanical properties of veins. In the current study, both tensile and vibration testing are used to obtain elastic moduli of bovine veins. Representative stress-strain data are shown, and the mechanical and failure properties reported. Nonlinear and viscoelastic behavior is observed, though most properties show little strain rate dependence. These data suggest parameters for constitutive modeling of veins and may inform the design and testing of prosthetic venous valves as well as vein grafts. PMID:20129420

Rossmann, Jenn Stroud

2009-07-10

181

Retinal Vein Occlusions  

Microsoft Academic Search

Retinal vein occlusion (RVO) is a common cause of vision loss in elderly people. The complex pathogenesis of central RVO (CRVO), hemi-RVO (HRVO) and branch RVO (BRVO) makes it an interdisciplinary task. Treatment of RVO should aim at eliminating the complications and vision-disturbing effects of RVO but also include prophylactic measures in order to avoid recurrence of the disease. Problems

Wolf Buehl; Stefan Sacu; Ursula Schmidt-Erfurth

2010-01-01

182

Bacteria at Hydrothermal Vents  

NSDL National Science Digital Library

This website provides information on thermophiles living in deep-sea vents, including their importance in biotechnology and extraterrestrial life research. The site also contains images of thermophiles at varying scales and a link to the "Hot Topics" main page including numerous links to further information on hydrothermal vents and research conducted in deep-sea environments.

Discover, Expeditions T.; Woods Hole Oceanographic Institution, National S.

183

Hydrothermal pretreatment of coal  

SciTech Connect

We are examining the effects on composition and behavior of Argonne-supplied Wyodak coal under both thermal (no added water/N{sub 2}) and hydrothermal (liquid water/N{sub 2}) conditions at 350{degree}C for periods of 30 min and 5 hr, with emphasis during this period on the longer treatment. Field ionization mass spectrometry (FIMS) of the untreated, thermally treated, and hydrothermally treated coals is conducted at conditions where the samples are heated from ambient to 500{degree}C at 2.5{degree}/min. In the 5 hr work the volatilities of the coals are 24%, 16%, and 25% respectively. Solvent swelling studies with the recovered coals do not demonstrate the expected lower degree of crosslinking in the hydrothermal case. Both the thermal and hydrothermal treatments yield products with a decreased swelling ratio, but the ratio for the product from the aqueous treatment is slightly lower than that from thermal treatment. At present we cannot reconcile this result with our other data. 4 refs., 6 figs.

Loo, Bock; Ross, D.S.

1990-08-14

184

Hydrothermal carbonization of microalgae  

Microsoft Academic Search

Hydrothermal carbonization is a process in which biomass is heated in water under pressure to create a char product. With higher plants, the chemistry of the process derives primarily from lignin, cellulose and hemicellulose components. In contrast, green and blue-green microalgae are not lignocellulosic in composition, and the chemistry is entirely different, involving proteins, lipids and carbohydrates (generally not cellulose).

Steven M. Heilmann; H. Ted Davis; Lindsey R. Jader; Paul A. Lefebvre; Michael J. Sadowsky; Frederick J. Schendel; Marc G. von Keitz; Kenneth J. Valentas

2010-01-01

185

Deep Vein Thrombosis and Pulmonary Embolism  

MedlinePLUS

... A A Fact Sheet: Deep Vein Thrombosis and Pulmonary Embolism Who is at risk for Deep Vein Thrombosis ... vein thrombosis How can Deep Vein Thrombosis and Pulmonary Embolism be prevented? If you're at risk, you ...

186

Hydrothermal systematics, alteration, and mineralization in the Grant Canyon, Bacon Flat, and Blackburn Oil Fields, Nevada - Intriguing Parallels with Carlin-Type gold deposits  

SciTech Connect

Nevada's three known thermally active oil reservoirs-Blackburn, Bacon Flat, and Grand Canyon-share a surprisingly long list of essential attributes with the Carlin-type, low-grade, sediment-hosted gold deposits, particularly those of the Alligator Ridge mining district. Like these rich precious-metal ore bodies, the three fields (1) are hosted by Paleozoic carbonate and calcareous silici-clastic strata; (2) occur in structural or structural/stratigraphic traps sealed beneath shales or hydrothermally argillized and silicified tuffs and epiclastic debris, (3) have undergone intense fracturing and brecciation, as well as massive hydrothermal decalcification as major porosity-creating processes; (4) occupy rocks partly altered to or veined by the secondary-mineral assemblage quartz-kaolin-barite-pyrite-marcasite; (5) have a direct geothermal connection; (6) are enriched in the elements arsenic, antimony, mercury, thallium, and even contain significant traces of gold-up 50 ppb in altered Mississippian Chainmain Shale in the Blackburn field. Moreover, measured temperatures, as well as late-stage, fluid-inclusion homogenization temperatures (T[sub h]) at the fields-all in the range 100-135[degrees]C-fall within the fluid-inclusion T[sub h] span of 90-165[degrees]C recorded for multiple Alligator Ridge deposits. Fracture-controlled live oil and oil-bearing fluid inclusions in some of the Alligator Ridge ores provide further evidence of genetic similarities with the oil reservoirs. The authors suggest that the three oil fields could represent either weakly mineralized analogs of the gold deposits or an incipient phase in their evolution ultimately leading to ore mineralization.

Hulen, J.B.; Nielson, D.L. (Univ. of Utah Research Institute, Salt Lake City, UT (United States))

1993-08-01

187

Hydrothermal Alteration in the PACMANUS Hydrothermal Field: Implications From Secondary Mineral Assemblages and Mineral Chemistry, OPD Leg 193  

NASA Astrophysics Data System (ADS)

Leg 193 of the Ocean Drilling Program investigated the subsurface nature of the active PACMANUS hydrothermal field in the Manus backarc basin near Papua New Guinea. Drilling in different areas on the felsic neovolcanic Pual Ridge, including the high-temperature black smoker complex of Roman Ruins and the low-temperature Snowcap site with diffusive discharge yielded a complex alteration history with a regional primary alteration being overprinted by a secondary mineralogy. The intense hydrothermal alteration at both sites shows significant differences in the secondary mineralogy. At Roman Ruins, the upper 25 m of hydrothermally altered rocks are characterized by a rapid change from secondary cristobalite to quartz, implying a high temperature gradient. From 10 to 120 mbsf the clay mineralogy is dominated by illite and chlorite. The chlorite formation temperature calculated from oxygen isotope data lies at 250° C in 116 mbsf which is similar to the present fluid outflow temperatures of 240-250° C (Douville et al., 1999, Geochim. Cosmochim. Acta, 63, 627-643). Drilling in the Snowcap field recovered evidence for several stages of hydrothermal alteration. Between 50 and 150 mbsf, cristobalite and chlorite are the most abundant alteration minerals while hydrothermal pyrophyllite becomes abundant in some places At 67 mbsf, the isotopic composition of pyrophyllite gives a temperature for ist formation at 260° C whereas at 77 and 116 mbsf the pyrophyllite displays the highest temperatures of formation (>300° C). These temperatures are close to the maximum measured borehole temperatures of 313° C. The appearance of assemblages of chlorite, chlorite-vermiculite, chlorite-vermiculite-smectite and illite-smectite as well as the local development of corrensite below 150 mbsf suggests that the alteration at Snowcap may be more complex than that beneath Roman Ruins. Detailed geochemical studies of the authigenic clay mineral phases will provide further insights into the chemical changes due to hydrothermal alteration.

Lackschewitz, K. S.; Kummetz, M.; Kummetz, M.; Ackermand, D.; Botz, R.; Devey, C. W.; Singer, A.; Stoffers, P.

2001-12-01

188

The Modi Taung–Nankwe gold district, Slate belt, central Myanmar: mesothermal veins in a Mesozoic orogen  

Microsoft Academic Search

The recently discovered quartz–gold veins comprising the Modi Taung–Nankwe gold district in central Myanmar are largely hosted by mudstones of the late Palaeozoic Slate belt. Mesozoic rocks of the Paunglaung–Mawchi zone separate the Slate belt from the Shan Scarp and Shan Plateau to the east. At Modi Taung 5 km of exploration adits indicate that the veins, within steeply dipping

A. H. G. Mitchell; C. A. Ausa; L. Deiparine; T. Hlaing; N. Htay; A. Khine

2004-01-01

189

Geology and geochemistry of the Mammoth breccia pipe, Copper Creek mining district, southeastern Arizona: Evidence for a magmatic-hydrothermal origin  

USGS Publications Warehouse

The Copper Creek mining district, southeastern Arizona, contains more than 500 mineralized breccia pipes, buried porphyry-style, copper-bearing stockworks, and distal lead-silver veins. The breccia pipes are hosted by the Copper Creek Granodiorite and the Glory Hole volcanic rocks. The unexposed Mammoth breccia pipe, solely recognized by drilling, has a vertical extent of 800 m and a maximum width of 180 m. The pipe consists of angular clasts of granodiorite cemented by quartz, chalcopyrite, bornite, anhydrite, and calcite. Biotite 40Ar/ 39Ar dates suggest a minimum age of 61.5??0.7 Ma for the host Copper Creek Granodiorite and 40Ar/39Ar dates on hydrothermal sericite indicate an age of 61.0??0.5 Ma for copper mineralization. Fluid inclusion studies suggest that a supercritical fluid with a salinity of approximately 10 wt.% NaCl equiv. condensed to a dilute aqueous vapor (1-2.8 wt.% NaCl equiv.) and a hypersaline brine (33.4-35.1 wt.% NaCl equiv.). Minimum trapping temperatures are 375??C and trapping depths are estimated at 2 km. Sulfur isotope fractionation of cogenetic anhydrite and chalcopyrite yields a temperature of mineralization of 469??25??C. Calculated oxygen and hydrogen isotope values for fluids in equilibrium with quartz and sericite range from 10.2??? to 13.4??? and -60??? to -39???, respectively, suggesting that the mineralizing fluid was dominantly magmatic. Evidence from the stable isotope and fluid inclusion analyses suggests that the fluids responsible for Cu mineralization within the Mammoth breccia pipe exsolved from a gray porphyry phase found at the base of the breccia pipe. ?? Springer-Verlag 2008.

Anderson, E. D.; Atkinson, Jr. , W. W.; Marsh, T.; Iriondo, A.

2009-01-01

190

Geology and geochemistry of the Mammoth breccia pipe, Copper Creek mining district, southeastern Arizona: evidence for a magmatic-hydrothermal origin  

NASA Astrophysics Data System (ADS)

The Copper Creek mining district, southeastern Arizona, contains more than 500 mineralized breccia pipes, buried porphyry-style, copper-bearing stockworks, and distal lead-silver veins. The breccia pipes are hosted by the Copper Creek Granodiorite and the Glory Hole volcanic rocks. The unexposed Mammoth breccia pipe, solely recognized by drilling, has a vertical extent of 800 m and a maximum width of 180 m. The pipe consists of angular clasts of granodiorite cemented by quartz, chalcopyrite, bornite, anhydrite, and calcite. Biotite 40Ar/39Ar dates suggest a minimum age of 61.5 ± 0.7 Ma for the host Copper Creek Granodiorite and 40Ar/39Ar dates on hydrothermal sericite indicate an age of 61.0 ± 0.5 Ma for copper mineralization. Fluid inclusion studies suggest that a supercritical fluid with a salinity of approximately 10 wt.% NaCl equiv. condensed to a dilute aqueous vapor (1-2.8 wt.% NaCl equiv.) and a hypersaline brine (33.4-35.1 wt.% NaCl equiv.). Minimum trapping temperatures are 375°C and trapping depths are estimated at 2 km. Sulfur isotope fractionation of cogenetic anhydrite and chalcopyrite yields a temperature of mineralization of 469 ± 25°C. Calculated oxygen and hydrogen isotope values for fluids in equilibrium with quartz and sericite range from 10.2‰ to 13.4‰ and -60‰ to -39‰, respectively, suggesting that the mineralizing fluid was dominantly magmatic. Evidence from the stable isotope and fluid inclusion analyses suggests that the fluids responsible for Cu mineralization within the Mammoth breccia pipe exsolved from a gray porphyry phase found at the base of the breccia pipe.

Anderson, Eric D.; Atkinson, William W.; Marsh, Timothy; Iriondo, Alexander

2009-02-01

191

Quartz crystal microbalance for immunosensing  

Microsoft Academic Search

An immunosensing system is described for the detection of specific antibodies in human sera using a piezoelectric immunosensor and a flow through system. A quartz crystal microbalance theory, regarding mass and viscoelastic effects in multilayer systems, which is derived from the Mason circuit, gives the theoretical background for the interpretation of measurement data obtained from an oscillator circuit. An acoustic

C. Kößlinger; S. Drost; F. Aberl; H. Wolf

1994-01-01

192

Diffusional crack healing in quartz  

Microsoft Academic Search

Annealing fractured single quartz in the presence of pore fluid at 200 MPa (2 kb) pressure at 400° and 600°C for various periods resulted in the reorganization of intially planar cracks into arrays of spherical and tubular fluid inclusions, a process termed crack healing. Samples heated at 600°C for several days with no added pore fluid showed no optically measurable

David L. Smith; Brian Evans

1984-01-01

193

Microchemical evidence for episodic growth of antitaxial veins during fracture-controlled fluid flow  

NASA Astrophysics Data System (ADS)

The mechanism by which syntectonic hydrothermal veins form is widely debated, with some workers suggesting that certain vein textures are related to specific fluid flow regimes. Central to the debate is whether vein formation involves advective fluid flow, or occurs by local diffusion of material from the surrounding wall rock. To address this issue, we integrated textural observations and microchemical analyses of a hydrothermal vein from the Lachlan Orogen, southeast Australia, to reveal information about vein growth history, changes in fluid chemistry, and the evolution of fluid flow pathways during vein growth. The study area is part of a regional-scale fault-fracture network in an interbedded limestone-shale sequence, which formed at depths of ˜ 5-10 km (˜ 150-200 °C) during late Devonian crustal shortening. This integrated approach demonstrates that the zonation of textures, Sr isotopes, stable isotopes (C, O), and trace and rare earth elements is distinctly asymmetrical about the median growth-line of the vein. ? 18O values in vein calcite (17.0-18.8‰, VSMOW) are lower than those in surrounding unaltered limestones (23-25‰, VSMOW), and vary systematically across the vein. In contrast, ? 13C values are relatively constant across most of the vein, but become markedly depleted ( ca. 4‰) immediately adjacent to the wall rock. This strong depletion in ? 13C was probably caused by the influx of more oxidised fluids during the latest stages of vein growth. Strontium isotope ratios ( 87Sr/ 86Sr) vary between 0.70912 and 0.70931 across the vein. Abrubt changes in 87Sr/ 86Sr, ? 18O, Ce/Ce *, Eu/Eu * and trace element concentrations indicate that vein growth was accompanied by stepwise changes in the fluid flow pathway and consequent variations in fluid chemistry. Taken together, our findings are not consistent with growth of fibrous antitaxial veins by diffusional transfer of material from the surrounding wall rock. Instead, they suggest that externally sourced fluids migrated along episodically changing fracture-controlled flow pathways. This has implications for the dynamics of crustal permeability and mineralisation.

Barker, Shaun L. L.; Cox, Stephen F.; Eggins, Stephen M.; Gagan, Michael K.

2006-10-01

194

Human Greater and Canine Lateral Saphenous Veins  

Microsoft Academic Search

Canine lateral saphenous vein and human greater saphenous vein were studied together to determine similarities and differences. Helical strips of both vessels contracted to norepinephrine with similar sensitivity. Canine veins developed more isometric tension than human veins treated similarly. Histological studies show canine veins to have little connective tissue and a single circular layer of smooth muscle. Human veins have

Michael R. Goldberg; Paul D. Joiner; Albert L. Hyman; Philip J. Kadowitz

1975-01-01

195

Redistribution of Water During Deformation of Milky Quartz  

NASA Astrophysics Data System (ADS)

Dislocation creep of quartz is facilitated by the presence of water, and many key observations regarding mechanisms of water weakening can be attributed to the elegant studies of Mervyn Paterson, his colleagues, and his students. In particular, Paterson and Kekulawala (1979) and Kekulawala et al. (1978, 1981) showed that creep strengths of quartz single crystals depend on the character and distribution of extended water defects and clusters. By comparing mechanical properties and infrared (IR) spectra of hydrothermally grown synthetic quartz, dry natural quartz, amethyst, heat-treated synthetic quartz, and natural milky quartz, they demonstrated a correspondence between the chemical weakening effect of water and the broad, non-freezable OH stretching band expressed most clearly by wet synthetic crystals. However, they also showed that natural milky quartz crystals with freezable fluid inclusions exhibit strengths that are intermediate to those of dry natural and wet synthetic crystals. Micro-IR studies of naturally deformed tectonites have since shown that water is incorporated as coarse, freezable fluid inclusions that may decorate dislocations, subgrain walls, and grain boundaries. Non-freezable OH bands have not been detected in natural quartzites. Following the lead of Paterson and colleagues, we have shortened single crystals of milky quartz at 45° to a and c at T = 800° C, ? = 10-5 s-1 and confining pressures ranging from 400 to 1820 MPa, and we report on the results of (1) micro-thermometry of fluid inclusions before and after deformation, (2) IR absorption measurements of water content, and (3) transmission electron microscopy (TEM) of fine-scale inclusions, subgrain boundaries, and dislocations. Flow strengths measured for Arkansas milky quartz crystals are highly variable (from 300 to 800 MPa at low strains, 5%) and exhibit variable strain softening, corresponding to the heterogeneous initial distribution of fluid inclusions and variations in bulk water content (300 to 7000 ppm). Fluid inclusions measured optically prior to deformation are highly variable in size from 1 to 300 ? m, but they consist of relatively uniform, low salinity brines (melting points of -2° C) with a restricted range of densities (homogenization temperatures of 140° to 170° C). Remarkably few of these optical-scale inclusions survive deformation. Instead, optical microstructures of deformed samples are dominated by heterogeneous deformation bands, undulatory extinction and basal deformation lamellae. IR absorption spectra of deformed samples indicate that little fluid has been lost, and TEM reveals fine-scale (20-500 nm) fluid inclusions that decorate finely spaced (1-3 ? m) low-angle subgrain boundaries. Dense, tangled dislocations, irregular subgrain boundary geometries, and relationships between these boundaries and inclusions suggest complex processes of fluid redistribution during deformation that we do not fully understand. Nevertheless, once redistribution has taken place, mean distances between fluid inclusions are sufficiently small that extrinsic water-related point defects may be introduced throughout the crystal by volume and pipe diffusion.

Kronenberg, A. K.; Lamb, W. M.; Luo, Z.; Neal, L. A.

2001-12-01

196

Investigations of gold films on quartz crystals  

Microsoft Academic Search

Changes at the interface between the metal electrode and the quartz plate have been identified as possible instability mechanisms in high-precision resonators. This study was undertaken to investigate the nature of the gold-quartz interface, if gold diffuses into quartz under \\

Mary Hendrickson; Sally Laffey; John R. Vig

1993-01-01

197

Quantifying Silica Reactivity in Subsurface Environments: Reaction Affinity and Solute Matrix Controls on Quartz and SiO2 Glass Dissolution Kinetics  

Microsoft Academic Search

During the three years of this project, Professor Dove's laboratory made tremendous progress in understanding controls on amorphous silica dissolution kinetics in aqueous solutions. Our findings have already received considerable attention. In hydrothermal and low temperature studies, the work focused on determining quantitative and mechanistic controls on the most abundant silica polymorphs in Earth environments--quartz and amorphous silica. Our studies

Patricia M. Dove

2000-01-01

198

New insights into the relationship between quartz and various post quartz phases  

NASA Astrophysics Data System (ADS)

Atomistic computer simulations are presented which suggest that the pressure-induced transition from low quartz to quartz II at 21 GPa is irreversible. While quartz II is ferroelastic in principle, the transition itself is coelastic, as the shape of the newly formed crystal is predetermined by the handedness of low quartz. Upon releasing the pressure, quartz II remains stable down to 5 GPa, where it transforms into another polymorph of similar symmetry. The shape of the post quartz polymorph can be 'switched' elastically between 'left' and 'right' by passing through an intermittent low quartz phase.

Campana, Carlos; Müser, Martin H.

2004-03-01

199

Peralkaline fluid composition in equilibrium with K-feldspar, muscovite and quartz at 10 kbar and 700°C: Al transport in crustal fluids  

NASA Astrophysics Data System (ADS)

Aluminum is commonly regarded as one of the least soluble elements during metamorphic and metasomatic processes. However, abundant field evidence suggests that aluminum transport can occur in natural hydrothermal processes. For example, late formed aluminumsilicate-bearing and muscovite-bearing veins are widely observed in high-grade metamorphic rocks, and provide a persuasive argument for considerable mobility of aluminum in aqueous fluid. The present study explores the fluid composition coexisting with K-feldspar (K-fsp), muscovite (ms), corundum (co) and quartz (qz) at deep crustal metamorphic conditions, using a piston cylinder device at 10 kbar and 700°C. Starting materials of natural microcline, quartz, synthetic corundum, reagent Al2O3 and KSi3O6.5 glass was used. Ms and K-fsp dissolve incongruently to co + fluid and ms + fluid, respectively. Fluid composition in equilibrium with co + ms and ms + K-fsp were located in experiments with and without qz. In quartz-absent experiments fluid composition with co+ms (I1) is mAl = 0.11, mK = 0.15, mSi = 0.44, and with K-fsp + ms (I2) mAl = 0.18, mK = 0.28 and mSi = 0.81, where mi is molality of the subscripted element. Fluid compositions with qz are: mAl = 0.08, mK = 0.11 and mSi = 1.18 (co + ms + qtz; II1) and mAl = 0.18, mK = 0.29 and mSi = 1.58 for (K-fsp + ms +qtz; II2). Measured fluid compositions are peralkaline (K/Al < 1.4). Bulk solubility of Al in pure H2O at this P and T is reported to be ~0.3 wt% [1], and increase to ~1.9 wt % Al in the presence of SiO2 [2]. This study shows that Al solubility is further enhanced by the presence of K and Si, increasing from ~4.07 wt% for (I1) to ~ 7.14 wt% at (I2). Presence of quartz enhances the bulk solubility from ~ 7.63 wt% (II1) to ~ 12.05 wt % at (II2). Results indicate that substantial aluminum transfer may occur at deep-crust metamorphic conditions in aqueous solutions equilibrated with common crustal bulk compositions such as metapelites and granites. Such high Al mobility is promoted by K and Si. Large-scale Al transfer may explain the formation of aluminumsilicate- and muscovite-bearing veins by replacement of K-feldspar in metamorphic rocks, without appealing to either strongly acid or basic solutions. [1] Tropper and Manning (2007) Chem. Geol. 240, 54-60. [2] Manning (2007) Geofluids 7, 258-269.

Wohlers, A.; Manning, C. E.

2012-04-01

200

Cerebral vein thrombosis  

Microsoft Academic Search

Advances in neuroimaging have modified our knowledge on cerebral vein thrombosis (CVT). This disease is now diagnosed more\\u000a frequently, and increasing evidence as to what are the most common risk factors and on the natural history of the disease\\u000a is becoming available. Most patients with CVT have a benign prognosis: only a minority of patients die during the acute phase

Francesco Dentali; Walter Ageno

2010-01-01

201

Vein of Galen malformation  

Microsoft Academic Search

Since 1984, 43 patients with true vein of Galen ancurysmal malformations have been referred to us and managed according to our patient selection, technique, and follow-up guidelines. Thirty-four were embolized transarterially with bucrilate (isobutyl cyanoacrylate) or enbucrilate (N-butyl cyanoacrylate) embolization. No cutdown or hypotension during or after the embolization was used and no balloon catheter was employed. Forty-seven percent of

P. Lasjaunias; R. Garcia-Monaco; G. Rodesch; K. Ter Brugge; M. Zerah; M. Tardieu; D. Victor

1991-01-01

202

Relative elemental mobility during hydrothermal alteration of a basic sill, Isle of Skye, N.W. Scotland  

NASA Astrophysics Data System (ADS)

In Sconser quarry, Isle of Skye, a thin Tertiary basic sill is cut by vertical veins which formed fluid conduits in a major meteoric-hydrothermal system. In order to study the relative mobility of different elements during hydrothermal metamorphism, sill material adjacent to a large (6 mm wide) vein was cut into slices and subjected to geochemical and isotopic analysis. Isotopic evidence indicates that the basic magma which formed the sill was contaminated by Lewisian (Archaean) gneisses at depth, while material from Torridonian (Proterozoic) sandstone country rocks was introduced by hydrothermal fluids after crystallisation. The behaviour of the different elements during hydrothermal metamorphism divides them into 4 groups. 1. Large-ion low-charge elements Ba, K, Rb and Cs were strongly leached from the wall rock in the vicinity of the vein. 2. Other elements including Sr and Pb were depleted near the vein, but isotopic evidence indicates addition of some material from the fluids. This two-way nuclide transport forms an exchange process. 3. Many high-field-strength elements including the REE are slightly enriched near the vein, but Nd isotope evidence reveals no addition of material from fluids. These elements must have been relatively enriched by the removal of other elements (mainly Si and Al). 4. Ca and Na were added to the wall rock from fluid. The variable mobility of these elements is explained by the differing ease with which they could be incorporated into a new albite-calcite-chlorite-epidote mineralogy. The constitution of this hydrothermal mineralogy was largely determined by the primary igneous mineralogy, though the composition of hydrothermal fluids had a subordinate influence.

Dickin, A. P.; Jones, N. W.

1983-06-01

203

Genesis of jadeite-quartz rocks in the Yorii area of the Kanto Mountains, Japan  

NASA Astrophysics Data System (ADS)

This paper reports the results of U-Pb dating and REE (rare earth element) analysis of zircons separated from jadeite-quartz rocks within serpentinite mélanges in the Yorii area of the Kanto Mountains, Japan. These rocks contain jadeite, albite, and quartz, with minor aegirine-augite, zircon, monazite, thorite, allanite, and titanite. Mineral textures provide evidence of a jadeite + quartz = albite reaction during formation of these jadeite-quartz rocks. Zircon crystals separated from the jadeite-quartz rocks can be split into two distinct types, here named Types I and II, based on their morphology and REE concentrations. Type I zircons are prismatic and have fluid, jadeite, quartz, and albite inclusions. Those show positive Ce and negative Eu anomalies and HREE (heavy rare earth element) enriched chondrite normalized REE patterns and have higher REE concentrations than those generally found in magmatic zircons. Type I zircons would have precipitated from a fluid. Mineralogical observation provides that Type I zircon crystallized at the same timing of the formation of the jadeite-quartz rocks. Type II zircons are porous and have REE patterns indicative of a hydrothermal zircon. Both types of zircons are fluid-related. Type I zircons yield U-Pb ages of 162.2 ± 0.6 Ma, with an MSWD (mean square weighted deviation) of 1.4. At this time, Japan was still a part of the eastern margin of the Asian continent, with the subduction of the oceanic paleo-Pacific Plate leading to the formation of the Jurassic Mino-Tanba-Chichibu accretionary complex in Japan. The age data indicate that the jadeite-quartz rocks formed in a deep subduction zone environment at the same time as the formation of the Jurassic accretionary complex in a shallower near-trench subduction zone environment. The jadeite-quartz rocks contain high concentrations of Zr and Nb, with low LILE (large ion lithophile elements) concentrations, suggesting that the HFSE (high field strength elements) can be concentrated into jadeite-quartz rocks prior to a fluid moving up into the mantle wedge. Typical arc volcanic rocks are depleted in the HFSE, suggesting that the high HFSE concentrations within jadeite-quartz rocks are consistent with fluids being stripped of their HFSE prior to interaction with mantle material during the formation of arc magmas. Although these jadeite-bearing rocks are rare occurrences on the surface exposure, they could be abundant in or above subducted slabs.

Fukuyama, Mayuko; Ogasawara, Masatsugu; Horie, Kenji; Lee, Der-Chuen

2013-02-01

204

Sampling methane in hydrothermal minerals on Earth and Mars  

NASA Astrophysics Data System (ADS)

The source of Martian atmospheric methane is unknown. On Earth, hydrothermal mineral deposits contain ancient methane together with a host of chemical and geological lines of evidence for the mechanism of gas production. Such deposits are therefore potentially attractive sampling sites on Mars. In order to evaluate this potential, hydrothermal calcite veins were sampled across the Caithness region of Scotland and analysed for methane by an incremental-crushing mass spectrometry technique that may be adaptable to Mars rovers. Methane was detected in all samples. Variations in the quantity of methane released were found to relate directly to the geological history of the localities. Calcite particle size was found to affect measurements in a systematic and informative way. Oxidative weathering had no discernable effect on methane recoverability. These results suggest that the technique is sensitive and informative enough to deserve consideration for missions to Mars.

McMahon, Sean; Parnell, John; Blamey, Nigel J. F.

2012-07-01

205

Mineralization, alteration, and hydrothermal metamorphism of the ophiolite-hosted Turner-Albright sulfide deposit, southwestern Oregon  

NASA Astrophysics Data System (ADS)

The Turner-Albright sulfide deposit, part of the Josephine ophiolite, formed on and below the seafloor during Late Jurassic volcanism at a back arc spreading center. Ore fluids were probably localized by faults which were active on the seafloor at the time of sulfide deposition. The uppermost massive sulfide formed on the seafloor at hydrothermal vents, similar to sulfide-depositing hot springs on modern spreading centers. The bulk of the sulfide mineralization formed below the seafloor within olivine basalt hyaloclastite erupted near the time of mineralization. Infiltration of hydrothermal fluid into the hyalo-clastite altered the rock to quartz + Fe-chlorite and quartz + sericite + Fe-chlorite. Intense alteration resulted in replacement of the protolith by quartz + sulfide. The fluid responsible for the hydrothermal alteration was evolved seawater with low pH and Mg and high Fe. Sulfide ?534S values average 4.7‰ and indicate contribution of sulfur from both basalt and seawater sulfate. The average value of sulfide ?34S and the difference between sulfide and contemporaneous seawater sulfate ?34S values are similar to ophiolite-hosted sulfide deposits in Cyprus. Chlorite-rich hydrothermally altered basalt has ?18O values of 3.0-6.8‰ due to high-temperature (250°-350°C) reaction with a seawater-derived ore fluid. Quartz in silicified basalt has higher ?18O values of 12.3-15.5‰, probably reflecting lower-temperature recrystallization of amorphous silica formed during initial alteration of basalt. Mudstone and clinopyroxene basalt above the sulfide horizons were not altered by the ore-transporting hydrothermal fluid, but these rocks were hydrothermally metamorphosed by altered seawater heated by deep circulation into hot oceanic crust. This subseafloor metamorphism produced a mineral assemblage typical of prehnite-pumpellyite facies metamorphism. Exchange with altered seawater increased the whole-rock ?18O of the basalts to values of 9.4-11.2‰.

Zierenberg, Robert A.; Shanks, Wayne C., III; Seyfried, William E., Jr.; Koski, Randolph A.; Strickler, Michael D.

1988-05-01

206

Monolithic quartz vibrating beam accelerometer  

NASA Astrophysics Data System (ADS)

The principles of manufacturing and the operating characteristics of a monolithic quartz vibrating-beam accelerometer are described. The device is obtained by a process similar to the one used in watch crystal manufacturing (i.e., wafer machining using chemical etching process). The monolithic quartz active part includes two vibrating beams, the proof mass, and its articulation on a base. The key features that reduce the accelerometer dimensions and cost are the simplicity of piezoelectric excitation and the numerical output. The expected accuracy is 0.001 in harsh environments. The device exhibited operating frequencies of about 100 kH, a scale factor of 50 Hz/G, a resolution of 10 microG, and residual errors within 50 microG.

Deyzac, F.; Janiaud, D.; Muller, S.

207

Thermionic current measurement in quartz  

NASA Astrophysics Data System (ADS)

The characterization of quartz samples by a thermionic current measurement called Ionic Thermal Current (ITC) is reported. A better understanding of impurity migration, under applied electric field, would enable a more efficient control of the electromigration process used for quartz purification: 'sweeping'. Several blocks originating from the same zone were cut off in the same crystal. The laminas were cut in each of the blocks of perpendicular to the Z or Y axes. Two crystals were studied: one of the I quality (number 272) and the other of standard quality (number 511). The ITC measurements of these two types of crystal are presented. Thermionic currents of laminas cut off more or less further from the nucleus are compared. The effects of 'sweeping' on the ITC current is shown.

Jeandel, G.; Warin, A.; Poignon, C.; Aubry, J. P.; Morlot, G.

1992-06-01

208

Quartz-enhanced photoacoustic spectroscopy.  

PubMed

A new approach to detecting a weak photoacoustic signal in a gas medium is described. Instead of a gas-filled resonant acoustic cavity, the sound energy is accumulated in a high- Q crystal element. Feasibility experiments utilizing a quartz-watch tuning fork demonstrate a sensitivity of 1.2x10(-7) cm(-1) W/ radicalHz . Potential further developments and applications of this technique are discussed. PMID:18033396

Kosterev, A A; Bakhirkin, Yu A; Curl, R F; Tittel, F K

2002-11-01

209

Quartz-enhanced photoacoustic spectroscopy  

Microsoft Academic Search

A new approach to detecting a weak photoacoustic signal in a gas medium is described. Instead of a gas-filled resonant acoustic cavity, the sound energy is accumulated in a high-Q crystal element. Feasibility experiments utilizing a quartz-watch tuning fork demonstrate a sensitivity of 1.2 × 10-7 cm-1 W\\/Hz. Potential further developments and applications of this technique are discussed.

A. A. Kosterev; Yu. A. Bakhirkin; R. F. Curl; F. K. Tittel

2002-01-01

210

Quartz-enhanced photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

A new approach to detecting a weak photoacoustic signal in a gas medium is described. Instead of a gas-filled resonant acoustic cavity, the sound energy is accumulated in a high-Q crystal element. Feasibility experiments utilizing a quartz-watch tuning fork demonstrate a sensitivity of 1.2 × 10-7 cm-1 W/Hz. Potential further developments and applications of this technique are discussed.

Kosterev, A. A.; Bakhirkin, Yu. A.; Curl, R. F.; Tittel, F. K.

2002-11-01

211

Doubly rotated contoured quartz resonators  

Microsoft Academic Search

Doubly rotated contoured quartz resonators are used in the design of temperature-compensated stable clocks and dual-mode sensors for simultaneous measurements of pressure and temperature. The design of these devices is facilitated by models that can predict frequency spectra associated with the three thickness modes and temperature and stress-induced frequency changes as a function of crystalline orientation. The Stevens-Tiersten technique for

Bikash K. Sinha

2001-01-01

212

K-feldspar-muscovite-andalusite-quartz-brine phase equilibria: An experimental study at 25 to 60 MPa and 400 to 550 C  

SciTech Connect

Felsic magmas may evolve one or more water or chlorine-rich fluid phases which can transport heat and solutes into associated hydrothermal systems and can contribute to alteration and ore deposition. To understand the role of a high-salinity aqueous phase in the magmatic hydrothermal environment, the composition of a subcritical, vapor-undersaturated high-salinity liquid phase (brine) in equilibrium with K-feldspar-muscovite-quartz and muscovite-andalusite-quartz was determined for pressures and temperatures ranging from 25 MPa and 400 C to 60 MPa and 550 C, with total Cl (NaCl + KCl + HCl) concentrations ranging from 3.42 to 8.56 (moles of solute/kg solution). Comparison of results with previous studies conducted at higher pressures and lower-salinity aqueous phases show that the mineral stability fields in the K-feldspar-muscovite-andalusite-quartz system shift to lower KCl/KCl values with increasing salinity and decreasing pressure.

Frank, M.R.; Candela, P.A.; Piccoli, P.M. [Univ. of Maryland, College Park, MD (United States)

1998-12-01

213

A demonstration of an affinity between pyrite and organic matter in a hydrothermal setting.  

PubMed

One of the key-principles of the iron-sulphur world theory is to bring organic molecules close enough to interact with each other, using the surface of pyrite as a substrate in a hydrothermal setting. The present paper explores the relationship of pyrite and organic matter in a hydrothermal setting from the geological record; in hydrothermal calcite veins from Carboniferous limestones in central Ireland. Here, the organic matter is accumulated as coatings around, and through, pyrite grains. Most of the pyrite grains are euhedral-subhedral crystals, ranging in size from ca 0.1-0.5 mm in diameter, and they are scattered throughout the matrix of the vein calcite. The organic matter was deposited from a hydrothermal fluid at a temperature of at least 200°C, and gives a Raman signature of disordered carbon. This study points to an example from a hydrothermal setting in the geological record, demonstrating that pyrite can have a high potential for the concentration and accumulation of organic materials. PMID:21299877

Lindgren, Paula; Parnell, John; Holm, Nils G; Broman, Curt

2011-02-07

214

Experimental calibration of a Ti-in-quartz thermobarometer: an overview for applications to mylonites  

NASA Astrophysics Data System (ADS)

During the last decade several trace element thermometers (Ti-in-quartz, Ti-in-zircon, Zr-in-rutile and Zr-in-sphene) were developed at RPI by determining the solubilities of trace elements in minerals as a function of pressure and temperature. The Ti-in-quartz thermometer is of particular interest for potentially estimating the P-T conditions of ductile deformation in crustal rocks because quartz fabric development and microstructural formation has been extensively studied. In this presentation I will discuss the experimental approach and thermodynamic basis used to calibrate trace element solubilities for usage as trace element thermometers, and overview some fundamental considerations necessary to 'take the temperature of ductile deformation'. In our experiments quartz and rutile were crystallized at equilibrium from SiO2- and TiO2-saturated fluids (aqueous solutions, hydrous melts) so that TiO2 activity was unity during quartz crystallization. During growth, Ti4+ substituted for Si4+ on the tetrahedral site in quartz so that the quartz contained the equilibrium concentration of Ti for each P-T condition. In static sub-solidus quartzose systems metamorphosed at high temperature conditions, Ti solubility equilibrium in quartz crystals must be attained by Ti diffusion from a Ti-bearing source (e.g. rutile, garnet, ilmenite, etc.). Due to the low diffusivity of Ti and the timescales of thermal events, Ti solubility equilibrium may not be attained in some systems. There are few studies that have investigated the role of dynamic recrystallization in attaining solubility equilibrium (e.g. Behr and Platt 2011; Grujic et al. 2011; Kidder et al. 2013). Constraining TiO2 activity during deformation is particularly important. The presence of rutile during deformation does not necessarily guarantee unity TiO2 activity unless it crystallized during the deformation event of interest. Behr WM, Platt JP (2011) A naturally constrained stress profile through the middle crust in an extensional terrane. Earth and Planetary Science Letters 303, 181-192 Grujic D, Stipp M, Wooden JL (2011) Thermometry of quartz mylonites: Importance of dynamic recrystallization on Ti-in-quartz reequilibration. Geochemistry, Geophysics, Geosystems 12, doi:10.1029/2010GC003368 Kidder S, Avouac J-P, Chan Y-C (2012) Application of titanium-in-quartz thermobarometry to greenschist facies veins and recrystallized quartzites in the Hsüehshan range, Taiwan. Solid Earth 4, 663-706

Thomas, Jay

2013-04-01

215

Experimental post-entrapment water loss from synthetic CO2-H2O inclusions in natural quartz  

Microsoft Academic Search

Artificial fluid inclusions were hydrothermally synthesized by crack healing in natural Brazilian quartz. Two original experiments E421 and E679 with a H20-CO2 fluid were carried out at 835 K, 200 MPa, over 38 days, and at 856 K, 211 MPa, over 35 days, respectively. In both experiments homogeneous three-phase (a vapor and two liquids) fluid inclusions were synthesized with 22

RONALD J. BAKKER; J. BEN H. JANSEN

1991-01-01

216

Mesozoic hydrothermal alteration associated with gold, mineralization in the Mercur district, Utah  

NASA Astrophysics Data System (ADS)

K/Ar dates and chemical data show that a Mesozoic gold-bearing hydrothermal system altered black shales of the Mississippian Great Blue Limestone throughout an area encompassing the Mercur gold district, Utah. K/Ar dates of illite veins and illite-rich, clay-sized separates of altered shales that are enriched in Au, As, Hg, Sc, and other heavy metals indicate that hydrothermal activity occurred from 193 to 122 Ma. Several ages from within the Mercur district cluster near 160 Ma and may date the minimum age of gold mineralization.

Wilson, Paula N.; Parry, W. T.

1990-09-01

217

Gold-bearing reefs of the Witwatersrand Basin: A model of synsedimentation hydrothermal formation  

Microsoft Academic Search

The current concepts concerning the genesis of the unique ore-bearing reefs of the Witwatersrand Basin and its gold resource\\u000a potential are considered. The results of microscopic examination of ore from the Black, Ventersdorp Contact, Carbon Leader,\\u000a and Vaal reefs, as well as of thermobarometric study of quartz, are presented. A model of synsedimentation hydrothermal origin\\u000a of the reefs in the

Yu. G. Safonov; V. Yu. Prokof’ev

2006-01-01

218

OH-defects in detrital quartz grains: Potential for application as tool for provenance analysis and overview over crustal average  

NASA Astrophysics Data System (ADS)

OH-defects of 95 detrital quartz grains from 4 localities in North-west Germany (2 North Sea beach sands, one Triassic sandstone, and one Carboniferous sandstone) were studied with infrared (IR) microscopy. By applying novel analytical strategies, the water contribution of fluid and mineral inclusions was minimised and the amount of water incorporated as OH-point defects was quantified. The defect water concentration in all studied quartz grains ranges between 0 and 50 wt. ppm H2O with a mean value around 10 wt. ppm. Interestingly, grains from the investigated sandstones exhibit in average nearly three times higher defect water concentrations (18 wt. ppm) than the grains from the North Sea (6.5 wt. ppm). Quartz grains with extreme undulose extinction always exhibit low defect water contents and water-rich grains usually show small undulosity, but also grains with low defect water and low undulosities are common. IR spectra of the detrital quartz grains were compared to reference spectra from samples of known localities and rock types in order to identify potential sources from which the quartz grains were sampled. Most detrital quartz grains exhibit IR signature typical for granites (showing an Al-specific band at 3378 cm? 1) and regional metamorphic rocks, but also absorption bands typical for pegmatites and hydrothermal quartz (showing a Li-specific band at 3480 cm? 1) are observed. In contrast, IR signatures typical for high-pressure origin (i.e., hydrogarnet substitution with an absorption band at 3585 cm? 1) and for tourmaline-bearing rocks (showing a B-specific band at 3595 cm? 1) are subordinate to insignificant. In view of the large scatter of defect water between individual quartz grains the strategy presented here offers an option to estimate the average defect water content of quartz in the Earth's crust.

Stalder, Roland; Neuser, Rolf Dieter

2013-08-01

219

Migration of hydrothermal systems in an evolving collisional orogen, New Zealand  

NASA Astrophysics Data System (ADS)

The Pacific-Australian tectonic plate boundary through the South Island of New Zealand consists of the transpressional Southern Alps mountain belt and the transcurrent Marlborough Fault System, both of which have active tectonically driven hydrothermal systems, with topographically driven meteoric incursion and warm springs. The Southern Alps hydrothermal system is relatively diffuse, with little or no fault control, and is channelled through scattered extensional sites beneath the mountains, where gold mineralisation is occurring locally. The hydrothermal activity along the Marlborough Fault System is controlled by the principal faults in well-defined valleys separated by narrow high ridges. Lateral evolution of Marlborough fault strands southwestwards into the Southern Alps has caused diversion of diffuse Southern Alps hydrothermal activity into the structural superimposition zone, where fluid flow is increasingly being controlled by faults. This hydrothermal diversion was accompanied by major topographic reorientation and river drainage reversal in the late Quaternary. Vein swarms now exposed in the remnants of the Southern Alps north of the superimposition zone formed at shallow levels, with some evidence for fluid boiling, from a mixture of meteoric and deep-sourced fluid. These veins, some of which contain gold, are part of an abandoned <1 million-year-old hydrothermal zone beneath the fossil topographic divide of the Southern Alps that has now been dismembered by lateral incursion of the Marlborough fault strands. Observations on this active plate boundary provide some insights into processes that controlled orogenic gold mineralisation in ancient belts, particularly with respect to relationships between hydrothermal fluid flow, structure and topography.

Craw, D.; Upton, P.; Horton, T.; Williams, J.

2013-02-01

220

Fluid inclusion and isotopic systematics of an evolving magmatic-hydrothermal system  

NASA Astrophysics Data System (ADS)

The Geysers, California, is the site of a long-lived hydrothermal system that initially developed 1.5-2 m.y. ago in response to the intrusion of a hypabyssal granitic pluton. Although wells drilled into The Geysers produce only dry steam, fluid inclusion, isotopic, and mineralogic data demonstrate that the present vapor-dominated regime evolved from an earlier and more extensive, liquid-dominated hydrothermal system. Circulation of these early fluids produced veins characterized by tourmaline ± biotite ± actinolite ± clinopyroxene within the pluton and adjacent biotite-rich hornfels, actinolite ± ferroaxinite ± epidote and epidote ± chlorite within the intermediate parts of the thermal system and calcite in the outer parts. Potassium feldspar and quartz are present in all assemblages. Pressure-corrected homogenization temperatures and apparent salinities of fluid inclusions trapped in vein minerals range from 440°C and 44 wt% NaCl equivalent within the hornfels (<600 m from the pluton) to 325°C and 5 wt% NaCl equivalent at distances of approximately 1500 m from the intrusion. We suggest that the shallow, moderate salinity fluids are connate waters modified by water-rock interactions while the high-salinity fluids are interpreted as magmatic brines. Halite-dissolution temperatures of inclusions in the hornfels and pluton indicate that the magmatic fluids were trapped at lithostatic pressures (300-900 bars). In contrast, homogenization temperatures of the connate fluids suggest trapping under hydrostatic pressures of less than several hundred bars. Whole-rock ? 18O values of samples from The Geysers display systematic variations with respect to depth, location within the field, and grade of alteration. At depths below +610 m relative to mean sea level, the ? 18O values are strongly zoned around a northwest-southeast trending low located near the center of the steam reservoir. As the pluton beneath The Geysers is approached, the ? 18O values decrease from approximately + 14 per mil near the surface to +4 to +7 per mil within the hornfels. The ? 18O values then increase to +8 to + 10 per mil at the intrusive contact, and thereafter, vary little within the pluton. Calculated rock-water fractionation factors suggest that temperature was the dominant control on the vertical decrease in the isotopic values of the reservoir rocks. In contrast, the increase in the ? 18O values within the hornfels suggest equilibration with an isotopically heavy fluid and/or decreasing water:rock ratios. The formation of vapor-dominated conditions is reflected in the abrupt appearance of low salinity (0.0-0.4 wt% NaCl equivalent) fluid inclusions with homogenization temperatures near 265°C. These inclusion fluids are thought to represent steam condensate that formed as the early liquid-dominated system boiled off. Bladed calcite, which is corroded in places, and late-stage clays provide mineralogic evidence of boiling and the formation of an acidic condensate in the upper part of the reservoir and in the overlying caprock. At greater depths, however, clear mineralogic evidence of boiling is lacking. The present vapor-dominated regime at The Geysers consists of two hydraulically connected steam reservoirs. Within the main steam reservoir, pressures are vaporstatic and temperatures are nearly constant at 240°C. Beneath this reservoir in the northwestern third of the field, temperatures as high as 342°C have been encountered. Wells drilled into this deeper reservoir discharge corrosive, Cl-bearing steam.

Moore, Joseph N.; Gunderson, Richard P.

1995-10-01

221

The Riviera Deposit: Endo-skarn and Vein-hosted W-MO-REE Mineralization in I-type Granites of the Cape Granite Suite, South Africa  

NASA Astrophysics Data System (ADS)

The blind Riviera deposit is located in the western Cape Province and was discovered by stream sediment sampling in the mid 1970's. Resources total 46 million metric tons assaying 0,216 per cent tungsten and 200 parts per million molybdenum, a marginal grade that has prohibited development into an open cast mine. Mineralization is mainly hosted by granitoids of the Riviera Pluton which intruded the regionally metamorphosed volcano-sedimentary Malmesbury Group. These granitoids form part of the Cape Granite Suite, a series of batholiths and plutons with S-, I- and A-type characteristics. The composite Riviera Pluton comprises a suite of metaluminous to slightly peraluminous granitoids. The rocks least affected by hydrothermal alteration are granodioritic to adamelitic in composition whereas the more altered host rocks include quartz-monzonite, granite and quartz syenite. As a whole the suite is subalkaline to K-calcalkaline and conforms to the characteristics of I-type granites. The pluton was emplaced into a dome-shaped interference structure, late in the Neoproterozoic Saldanian orogenic cycle. Alteration, particularly prevalent in the roof or cupola of the pluton, occurs as zones of pervasive sericitization, argillization, silicification and potassic alteration. Their spatial and temporal relationship is complex and indicates several superimposed alteration events. Wall rocks display limited alteration and have acted as an impermeable cap. The cross-cutting granitoid intrusions produced wall rock xenoliths of various dimensions consisting mainly of meta-carbonates displaying various stages of digestion. Economic concentrations of scheelite are spatially linked to these assimilations, particularly proximal to the wall rock contact. The occurrence of diagnostic minerals such as vesuvianite, hornblende, hedenbergite, grandite garnets define a typical endo-skarn association. Accessory minerals include pyrite, pyrrhotite, chalcopyrite, sphalerite and the LREE enriched mineral allanite. Scheelite and molybdenite occurs as fine disseminations, but also as coarse grains within cross-cutting, late stage quartz and calcite veins in the granite and the wall rocks. No spatial or paragenetic correlation exists between the concentration of tungsten and molybdenum, suggesting that their distribution is related to sequential introduction of multiple magmatic phases and associated mineralizing fluids.

Rozendaal, A.; Moyen, J.

2009-05-01

222

Chronic retinal vein occlusion in glaucoma  

Microsoft Academic Search

Asymptomatic chronic retinal vein occlusion that occurs in chronic simple glaucoma is described. The condition is characterized by marked elevation of retinal vein pressure with collateral vessels and vein loops at the optic disc in cases of central vein occlusion, or retinal veno-venous anastomoses along a horizontal line temporal and nasal to the disc in hemisphere vein occlusion. No patient

R A Hitchings; G L Spaeth

1976-01-01

223

Does Hydrothermal Circulation Matter?  

NASA Astrophysics Data System (ADS)

Determining Earth's energy budget and the sources and mechanisms for heat transfer within it depends largely on assumptions of the heat loss from the formation and cooling of oceanic lithosphere, which covers about 60% of Earth's surface. Recently Hofmeister and Criss (2005) have suggested that the total global heat flow is about 30 TW, about 25% less than previously estimated by Pollack et al. (1993). The main difference between the two estimates is whether the effects of heat transfer by hydrothermal circulation are included. Thermal models describe the evolution of the lithosphere by the conductive cooling of hot material as it moves away from spreading centers. The frequently used half-space (boundary layer) and "plate" models generally successfully represent heat flow, depth, and geoid values with age, and depth-dependent properties such as flexural thickness, maximum depth of intraplate earthquakes, and lithospheric thickness. However, such models overpredict the measured heat flow from ridge crest to about 65 Myr crust. This difference is generally assumed to reflect water flow in the crust transporting heat, as shown by the spectacular hot springs at midocean ridges. If so, the observed heat flow is lower than the model's predictions, which assume that all heat is transferred by conduction. Because hydrothermal heat transport is hard to quantify, heat flow is about 50% larger than directly measured. This estimate is consistent with observations of hydrothermal circulation which indicate that the discrepancy is largely a result of the water fluxing along the oceanic basement and upwelling at isolated basement highs and outcrops. Detailed studies at such areas often show high heat flow near these outcrops and low heat flow in the surrounding areas. Hence isolated measurements are biased towards lower values and underpredict the total heat flow.

Stein, C. A.; Stein, S.; von Herzen, R. P.; Fisher, A. T.

2006-05-01

224

Biocatalytic transformations of hydrothermal fluids  

NASA Astrophysics Data System (ADS)

The occurrence of copious animal populations at deep-sea vents indicates an effective microbial chemosynthetic biocatalysis of hydrothermal fluids on their emission into oxygenated ambient seawater. The large metabolic and physiological diversity of microbes found at these sites, including anaerobic and aerobic hyperthermophiles, reflects an even higher variety of biocatalytic or enzymatic reactions that greatly influence deep-sea hydrothermal geochemistry.

Jannasch, H. W.

225

Hydrothermal Liquefaction of Biomass  

SciTech Connect

Hydrothermal liquefaction technology is describes in its relationship to fast pyrolysis of biomass. The scope of work at PNNL is discussed and some intial results are presented. HydroThermal Liquefaction (HTL), called high-pressure liquefaction in earlier years, is an alternative process for conversion of biomass into liquid products. Some experts consider it to be pyrolysis in solvent phase. It is typically performed at about 350 C and 200 atm pressure such that the water carrier for biomass slurry is maintained in a liquid phase, i.e. below super-critical conditions. In some applications catalysts and/or reducing gases have been added to the system with the expectation of producing higher yields of higher quality products. Slurry agents ('carriers') evaluated have included water, various hydrocarbon oils and recycled bio-oil. High-pressure pumping of biomass slurry has been a major limitation in the process development. Process research in this field faded away in the 1990s except for the HydroThermal Upgrading (HTU) effort in the Netherlands, but has new resurgence with other renewable fuels in light of the increased oil prices and climate change concerns. Research restarted at Pacific Northwest National Laboratory (PNNL) in 2007 with a project, 'HydroThermal Liquefaction of Agricultural and Biorefinery Residues' with partners Archer-Daniels-Midland Company and ConocoPhillips. Through bench-scale experimentation in a continuous-flow system this project investigated the bio-oil yield and quality that could be achieved from a range of biomass feedstocks and derivatives. The project was completed earlier this year with the issuance of the final report. HydroThermal Liquefaction research continues within the National Advanced Biofuels Consortium with the effort focused at PNNL. The bench-scale reactor is being used for conversion of lignocellulosic biomass including pine forest residue and corn stover. A complementary project is an international collaboration with Canada to investigate kelp (seaweed) as a biomass feedstock. The collaborative project includes process testing of the kelp in HydroThermal Liquefaction in the bench-scale unit at PNNL. HydroThermal Liquefaction at PNNL is performed in the hydrothermal processing bench-scale reactor system. Slurries of biomass are prepared in the laboratory from whole ground biomass materials. Both wet processing and dry processing mills can be used, but the wet milling to final slurry is accomplished in a stirred ball mill filled with angle-cut stainless steel shot. The PNNL HTL system, as shown in the figure, is a continuous-flow system including a 1-litre stirred tank preheater/reactor, which can be connected to a 1-litre tubular reactor. The product is filtered at high-pressure to remove mineral precipitate before it is collected in the two high-pressure collectors, which allow the liquid products to be collected batchwise and recovered alternately from the process flow. The filter can be intermittently back-flushed as needed during the run to maintain operation. By-product gas is vented out the wet test meter for volume measurement and samples are collected for gas chromatography compositional analysis. The bio-oil product is analyzed for elemental content in order to calculate mass and elemental balances around the experiments. Detailed chemical analysis is performed by gas chromatography-mass spectrometry and 13-C nuclear magnetic resonance is used to evaluate functional group types in the bio-oil. Sufficient product is produced to allow subsequent catalytic hydroprocessing to produce liquid hydrocarbon fuels. The product bio-oil from hydrothermal liquefaction is typically a more viscous product compared to fast pyrolysis bio-oil. There are several reasons for this difference. The HTL bio-oil contains a lower level of oxygen because of more extensive secondary reaction of the pyrolysis products. There are less amounts of the many light oxygenates derived from the carbohydrate structures as they have been further reacted to phenolic Aldol condensation products. The bio-oil

Elliott, Douglas C.

2010-12-10

226

Cody hydrothermal system  

SciTech Connect

The hot springs of Colter's Hell are the surface manifestations of a much larger hydothermal system. That system has been studied to define its extent, maximum temperature, and mechanism of operation. The study area covers 2700 km/sup 2/ (1040 mi/sup 2/) in northwest Wyoming. Research and field work included locating and sampling the hot springs, geologic mapping, thermal logging of available wells, measuring thermal conductivities, analyzing over 200 oil and gas well bottom-hole temperatures, and compiling and analyzing hydrologic data. These data were used to generate a model for the hydrothermal system.

Heasler, H.P.

1982-01-01

227

Fluid source and pressure temperature conditions of high-salinity fluids in syn-tectonic veins from the Northeastern Apuan Alps (Northern Apennines, Italy)  

NASA Astrophysics Data System (ADS)

Structural studies on syn-tectonic veins cropping out in the northeastern sector of the Apuan Alps metamorphic complex (Northern Apennines, Italy) revealed two sets of veins: (1) type A fibrous veins within the “Scisti sericitici Formation”, related to a late-D1 tectonic phase; (2) B-veins, within the “Diaspri Formation” that developed between late-D1 and D2 tectonic phases. The mineralogy of the A (quartz, chlorite, hematite with minor amounts of apatite, allanite-(Ce), thorite and synchysite) and B-veins (quartz only) reflects the mineralogical composition of the host-rocks: quartz, chlorite, white mica and accessory minerals (apatite, zircon, titanite) occur in the “Scisti sericitici Formation”, while quartz is the main phase in the “Diaspri Formation”. The study of fluid inclusions trapped in quartz crystals of the syn-tectonic veins shows that the inclusions are always oversaturated in NaCl at room temperature and their salinities range from 29.5 to 37 wt.% NaCl equiv. The isochore of the earliest trapped fluid inclusions (type IA; primary inclusions in fiber quartz of A veins), coupled with mineralogical geothermometric data, constrains the pressure temperature conditions to around 325 300 MPa and 370 380 °C during the late-D1 phase. Subsequent trapping of inclusion types IIA, IIB, IIIA, IIIB and VB in the two vein sets probably occurred during a pressure temperature decrease (down to 220 245 MPa and 260 270 °C) at a lithostatic thermal gradient of 30 °C/km. Type IVB inclusions, on the other hand, were probably trapped at lower pressure (between lithostatic and hydrostatic conditions) during a transient pressure drop resulting from fault-valve action. SEM/EDS analyses on salts precipitated within opened inclusions confirmed the NaCl-rich compositions of the trapped fluids and also revealed the presence of minor amounts of Ca, K and Mn in the salts. A fluid circulation model, based on mineralogical and fluid inclusion data, was proposed for the high-salinity fluids found in the syn-tectonic veins: the high-salinity and NaCl-rich nature of the trapped fluids suggest that the original metamorphic fluids interacted with evaporite levels present at the base of the Tuscan Nappe, overlying Apuan Alps metamorphic Units. These fluids then infiltrated downward, possibly through shear zones crosscutting the stratigraphic sequence, into the syn-tectonic veins and interacted with the host-rocks to produce a local element mobilization and their precipitation in the vein minerals; as a result the latter reflect the mineralogy of the host-rocks.

Montomoli, Chiara; Ruggieri, Giovanni; Carosi, Rodolfo; Dini, Andrea; Genovesi, Marianna

228

Coexisting serpentine and quartz from carbonate-bearing serpentinized peridotite in the Samail Ophiolite, Oman  

NASA Astrophysics Data System (ADS)

Tectonically exposed mantle peridotite in the Oman Ophiolite is variably serpentinized and carbonated. Networks of young carbonate veins are prevalent in highly serpentinized peridotite, particularly near low-temperature alkaline springs emanating from the peridotite. An unusual feature in some samples is the coexistence of serpentine and quartz, which is not commonly observed in serpentinites. This assemblage is unstable with respect to serpentine + talc or talc + quartz under most conditions. Serpentine in the carbonated serpentinites in this study is more iron rich than in most serpentinites reported in previous studies, and samples with co-existing quartz contain the most iron-rich serpentines. Calculations of thermodynamic equilibria in the MgO-SiO2-H2O-CO2 system suggest that serpentine + quartz may be a stable assemblage at low temperatures (e.g., <~15-50 °C) and is stabilized to higher temperatures by preferential cation substitutions in serpentine over talc. Based on these calculations, serpentine + quartz assemblages could result from serpentinization at near-surface temperatures. Clumped isotope thermometry of carbonate veins yields temperatures within error of the observed temperatures in Oman groundwater for all samples analyzed, while the ?18O of water calculated to be in equilibrium with carbonate precipitated at those temperatures is within error of the observed isotopic composition of Oman groundwater for the majority of samples analyzed. As groundwater geochemistry suggests that carbonate precipitation and serpentinization occur concomitantly, this indicates that both hydration and carbonation of peridotite are able to produce extensive alteration at the relatively low temperatures of the near-surface weathering environment.

Streit, Elisabeth; Kelemen, Peter; Eiler, John

2012-11-01

229

Selenium minerals in gold-bearing veins of the North Urals  

NASA Astrophysics Data System (ADS)

The gold-bearing veins of the North Urals contain rare mineral selenium phases such as kawazulite, clausthalite, bohdanowiczite, volynskite, soucekite, naumannite, and eucairite, new for this region. They are largely observed as the finest inclusions in copper sulfides and closely associate with bismuth and tellurium minerals. Selenides were formed at the final oregenesis stages. Selenium was likely taken from the host rocks in the course of hydrothermal metasomatic processes initiated by granite intrusions.

Kuznetsov, S. K.; Sokerina, N. V.; Filippov, V. N.; Sokerin, M. Yu.; Zharkov, V. A.

2012-01-01

230

Surface and interfacial free energies of quartz  

Microsoft Academic Search

Water and electrolytes cause significant changes in brittle fracture strength and subcritical fracture propagation velocities in quartz and quartz rocks. The changes may be caused, in part, by changes in surface free energy. Experimental fracture surface energies of quartz range from about 400 mJ m⁻² to about 11.5 J m⁻². Thermodynamic surface free energies are likely to be lower than

George A. Parks

1984-01-01

231

Volatile evolution of ore fluids in Coeur D'Alene veins during metamorphism of the Belt Basin  

SciTech Connect

Two major vein types are recognized in the Coeur d'Alene district, Idaho and Montana. Early Zn-rich veins fill axial plane shears of WNW-trending folds in competent lithologies of Prichard Fm. and Ravalli Group metasediments. Later, Ag-rich veins occur predominantly in upper Revett Fm. quartzite in east- to northeast-trending fractures. Both vein types were deposited from fluids generated during regional greenschist grade metamorphism. Volatile composition of individual fluid inclusions in quartz and sphalerite from these veins were estimated using microthermometry and laser Raman spectroscopy. A high-sensitivity quadrupole mass spectrometer was used to obtain quantitative analyses of fluid extracted from whole crystals. Fluid inclusions from both vein types generally contain less than 10 mole % total gases and 5-10 eq. wt. % NaCl. However, fluid inclusion in Zn-rich veins contain greater concentrations of CH/sub 4/, short chain hydrocarbons, and N/sub 2/ compared to Ag-rich veins in which CO/sub 2/ is the dominant volatile component. The observed change in volatile compositions during metamorphism is consistent with a shift from relatively reducing to oxidizing conditions. The change from Zn- to Ag-rich veins may reflect the combined effects of a) volatile evolution of the metamorphic fluids through time, b) episodic development of large fractures with different orientations, and c) different lithologies contributing metamorphic fluids to these fractures.

Hofstra, A.H.; Landis, G.P.; Leach, D.L.

1985-01-01

232

Eclogite-facies vein systems in the Marun-Keu complex (Polar Urals, Russia): textural, chemical and thermal constraints for patterns of fluid flow in the lower crust  

Microsoft Academic Search

Metasomatic amphibole-eclogite sequences grew in selvages of quartz veins from the Marun-Keu complex (Polar Urals, Russia) during high-pressure metamorphism. Relicts of a pre-metasomatic eclogite-facies assemblage are present in the wallrock layers as irregular patches. Wallrock interstitial quartz trails lying at a high angle to reaction fronts provide evidence for grain-scale pore channelisation which may be produced by intergranular-fluid compositional gradients

José F. Molina; Stefano Poli; Håkon Austrheim; Johannes Glodny; Anatolij Rusin

2004-01-01

233

An experimental study of the diffusion of oxygen in quartz and albite using an overgrowth technique  

NASA Astrophysics Data System (ADS)

Diffusion rates of18O tracer in quartz (? c, 1 Kb H2O) and Amelia albite (? 001, 2 Kb H2O) have been measured, using Secondary Ion Mass Spectrometry (SIMS). A new technique involving hydrothermal deposition of labelled materials has removed the possibility of pressure solution-reprecipitation processes adversely affecting the experiments. Reported diffusion constants are: ?-quartz (? c),D_0 = 3.4left( {begin{array}{*{20}c} { + 4.8} \\ { - 2.0} \\ } right)x 10^{ - {text{13}}} {text{m}}^{text{2}} {text{s}}^{ - {text{1}}} , Q=98±7 KJ mol-1 (600 825° C, 1 Kb); Amelia albite (? 001),D_0 = 1.0left( {begin{array}{*{20}c} { + 2.0} \\ { - 0.7} \\ } right)x 10^{ - {text{13}}} {text{m}}^{text{2}} {text{s}}^{ - {text{1}}} , Q=85±7 KJ mol-1, (400 600° C, 2 Kb). Measured quartz18O diffusivities decrease discontinuously at the ?- ? transition, reflecting strong structural influences. The reported albite data agree with previously recorded studies, but ?-quartz data indicate significantly lower activation energies. Possible causes of this discrepancy, and some geological consequences, are noted.

Elphick, S. C.; Dennis, P. F.; Graham, C. M.

1986-09-01

234

Frictional strengths of talc-serpentine and talc-quartz mixtures  

USGS Publications Warehouse

Talc is a constituent of faults in a variety of settings, and it may be an effective weakening agent depending on its abundance and distribution within a fault. We conducted frictional strength experiments under hydrothermal conditions to determine the effect of talc on the strengths of synthetic gouges of lizardite and antigorite serpentinites and of quartz. Small amounts of talc weaken serpentinite gouges substantially more than predicted by simple weight averaging. In comparison, mixtures of quartz and talc show a linear trend of strength reduction at talc concentrations 15 wt % and enhanced weakening at higher concentrations. All of the strength data are fit by a modified version of the Reuss mixing law that allows for the dominance of one mineral over the other. The difference in the behavior of serpentinite-talc and quartz-talc mixtures at low talc concentrations is a reflection of their different textures. Lizardite, antigorite, and talc all have platy habits, and displacement within gouges composed of these minerals is localized to narrow shears along which the platy grains have rotated into alignment with the shear surfaces. The shears in the mixed phyllosilicate gouges maximize the proportion of the weaker mineral within them. When mixed with a strong, rounded mineral such as quartz, some minimum concentration of talc is needed to form connected pathways that enhance strength reductions. The typical development of talc by the reaction of Si-rich fluids with serpentinite or dolomite would tend to localize its occurrence in a natural fault and result in enhanced weakening.

Moore, D. E.; Lockner, D. A.

2011-01-01

235

Design of a tuning-fork gyro made of quartz  

Microsoft Academic Search

Based on piezoelectric effect of quartz, a design of tuning- fork gyroscopes made of quartz was presented in this paper. The gyroscope is a kind of micro-machined quartz angular rate sensor. Its structure is similar to a tuning fork in quartz watch. In the gyroscope, the piezoelectric effect in quartz is used both to excite a reference vibration in the

Yubin Jia; Yunan Sun; Bingkun Qin; Fang Cui; Gang Chen

1998-01-01

236

Bismuth tellurides and sulphosalts from the Larga hydrothermal system, Metaliferi Mts, Romania: Paragenesis and genetic significance  

Microsoft Academic Search

Intermediate levels of the Larga-FataB a?ii field, Metaliferi Mts., Romania, are host to epithermal vein mineralization, small skarn-like bodies and 'geode'-like replacement ores, that together form a complex hydrothermal system rooted in the subjacent andesite stock. Silver-Pb-Bi sulphosalts, some with Sb and\\/or Se, are intimately associated with hessite and a range of Bi-tellurides with Bi\\/(Te+S+Se) 41 (tetradymite, tellurobismuthite, tsumoite, Pb-free

N. J. Cook; C. L. Ciobanu

2004-01-01

237

(U+Th)–He evidence of Jurassic continuous hydrothermal activity in the Schwarzwald basement, Germany  

Microsoft Academic Search

(U+Th)–He model and isochron ages of 21 botryoidal hematites collected from the Hohberg base-metal vein system in the Triberg granite complex, Mittelschwarzwald (Germany), cover most of the Jurassic period. The possibility of quantitative 4He loss triggered by successive hydrothermal events, although conceivable for individual hematites — based on a 4He retentivity study and calculated opening temperatures of hematite for 4He

Rolf S Wernicke; Hans J Lippolt

1997-01-01

238

Hydrothermal processes at seafloor spreading centers,  

SciTech Connect

This chapter discusses the initial entry of hydrothermal seawater into deep levels of the oceanic crust, the effectiveness of hydrothermal circulation in cooling the crust, the geometry of hydrothermal circulation, the relationship between the hydrothermal circulation and the magma chamber, the reaction of the oceanic crust with the seawater, and the identification of the hydrothermal fluid which alters a rock sample. Topics considered include the crack front, observation relevant to the crack front, the limitations of the crack front hypothesis, the observed pattern of hydrothermal alteration, the nature of the hydrothermal fluid, the physics of large scale convection, and convection through crack zones. Knowledge of hydrothermal circulation at the ridge axis is based on sampling of the hydrothermal fluid, indirect geophysical measurements of the oceanic crust, and studies of rocks which are believed to have undergone hydrothermal alteration at the ridge axis. Includes 2 drawings.

Sleep, N.H.

1983-01-01

239

Frictional slip of granite at hydrothermal conditions  

USGS Publications Warehouse

To measure the strength, sliding behavior, and friction constitutive properties of faults at hydrothermal conditions, laboratory granite faults containing a layer of granite powder (simulated gouge) were slid. The mechanical results define two regimes. The first regime includes dry granite up to at least 845?? and wet granite below 250??C. In this regime the coefficient of friction is high (?? = 0.7 to 0.8) and depends only modestly on temperature, slip rate, and PH2O. The second regime includes wet granite above ~350??C. In this regime friction decreases considerably with increasing temperature (temperature weakening) and with decreasing slip rate (velocity strengthening). These regimes correspond well to those identified in sliding tests on ultrafine quartz. The results highlight the importance of fluid-assisted deformation processes active in faults at depth and the need for laboratory studies on the roles of additional factors such as fluid chemistry, large displacements, higher concentrations of phyllosilicates, and time-dependent fault healing. -from Authors

Blanpied, M. L.; Lockner, D. A.; Byerlee, J. D.

1995-01-01

240

Geometric Analysis of Vein Fracture Networks From the Awibengkok Core, Indonesia  

NASA Astrophysics Data System (ADS)

Fracture network systems within rocks are important features for the transportation and remediation of hazardous waste, oil and gas production, geothermal energy extraction and the formation of vein fillings and ore deposits. A variety of methods, including computational and laboratory modeling have been employed to further understand the dynamic nature of fractures and fracture systems (e.g. Ebel and Brown, this session). To substantiate these studies, it is also necessary to analyze the characteristics and morphology of naturally occurring vein systems. The Awibengkok core from a geothermal system in West Java, Indonesia provided an excellent opportunity to study geometric and petrologic characteristics of vein systems in volcanic rock. Vein minerals included chlorite, calcite, quartz, zeolites and sulphides. To obtain geometric data on the veins, we employed a neural net image processing technique to analyze high-resolution digital photography of the veins. We trained a neural net processor to map the extent of the vein using RGB pixel training classes. The resulting classification image was then converted to a binary image file and processed through a MatLab program that we designed to calculate vein geometric statistics, including aperture and roughness. We also performed detailed petrographic and microscopic geometric analysis on the veins to determine the history of mineralization and fracturing. We found that multi-phase mineralization due to chemical dissolution and re-precipitation as well as mechanical fracturing was a common feature in many of the veins and that it had a significant role for interpreting vein tortuosity and history of permeability. We used our micro- and macro-scale observations to construct four hypothetical permeability models that compliment the numerical and laboratory modeled data reported by Ebel and Brown. In each model, permeability changes, and in most cases fluctuates, differently over time as the tortuosity and aperture of veins are affected by the precipitation, dissolution, and re-precipitation of minerals, and also by mechanical fracturing. In all of our cases we interpret a first-phase mineral dissolution stage where permeability gradually declines as the vein is blocked by inward growing minerals. Hereafter, permeability may briefly increase with the onset of internal fracturing within the vein or by a phase of mineral dissolution opening up new pathways for fluid flow. Eventually we infer that permeability will decline again as second stage minerals are deposited in the fluid flow pathways.

Khatwa, A.; Bruhn, R. L.; Brown, S. R.

2003-12-01

241

Hydrothermal sediment alteration at a seafloor vent field: Grimsey Graben, Tjörnes Fracture Zone, north of Iceland  

NASA Astrophysics Data System (ADS)

An active seafloor hydrothermal system subjects the background sediments of the Grimsey Graben (Tjörnes Fracture Zone) to alteration that produces dissolution of the primary volcaniclastic matrix and replacement/precipitation of sulfides, sulfates, oxides, oxyhydroxides, carbonates and phyllosilicates. Three types of hydrothermal alteration of the sediment are defined on the basis of the dominant hydrothermal phyllosilicate formed: smectite, kaolinite, chlorite. The most common alteration is near-total conversion of the volcaniclastic material to smectite (95-116°C). The dominant smectite in the deepest sediments sampled is beidellite, which is replaced by montmorillonite and an intimate mixture of di- and tri-octahedral smectite up core. This gradual vertical change in smectite composition suggests an increase in the Mg supply upward, the result of sediment alteration by the ascending hydrothermal fluids mixing with descending seawater. The vertical sequence kaolinite ? kaolinite-smectite mixed-layer ? smectite from bottom to top of a core, as well as the distinct zonation across the veins (kaolinite in the central zone ? kaolinite-smectite in the rim), suggests hydrothermal transformation of the initially formed smectite to kaolinite through kaolinite-smectite mixed-layer (150-160°C). The cause of this transformation might have been an evolution of the fluids toward a slightly acidic pH or a relative increase in the Al concentration. Minor amounts of chamosite fill thin veins in the deepest sections of some cores. The gradual change from background clinochlore to chamosite across the veins suggests that chamosite replaces clinochlore as Fe is made available from hydrothermal dissolution of detrital Fe-containing minerals. The internal textures, REE distribution patterns and the mode of occurrence of another magnesian phyllosilicate, kerolite, suggest that this mineral is the primary precipitate in the hydrothermal chimneys rather than an alteration product in the sediment. Kerolite precipitated after and grew on anhydrite in the chimneys. Oxygen isotope ratios are interpreted to reflect precipitation of kerolite at temperatures of 302° to 336°C. It accumulated in the hydrothermal mounds following the collapse of the chimneys and subsequent dissolution of anhydrite, thereby forming highly permeable aquifer layers underlying the vent field. Some kerolite was redeposited in the near vent field sediments by turbidity flows. The altered sediments are depleted in Mn, Rb and Sr, and enriched in U, Mo, Pb, Ba, As, Bi, Sb, Ag, Tl and Ga, as a result of leaching and precipitation, respectively. Conservative elements (Ti, Zr, Hf, Sc, Cr, Nb and Sn) are depleted or enriched in the altered sediments because of passive (precipitation or leaching of other phases) rather than active (because of their mobility) processes.

Dekov, Vesselin; Scholten, Jan; Garbe-SchöNberg, Carl-Dieter; Botz, Reiner; Cuadros, Javier; Schmidt, Mark; Stoffers, Peter

2008-11-01

242

Learning from the pulmonary veins.  

PubMed

The purpose of this article is to review the basic embryology and anatomy of the pulmonary veins and the various imaging techniques used to evaluate the pulmonary veins, as well as the radiologic findings in diseases affecting these structures. Specific cases highlight the clinical importance of the imaging features, particularly the findings obtained with multidetector computed tomography (CT). Pulmonary vein disease can be broadly classified into congenital or acquired conditions. Congenital disease, which often goes unnoticed until patients are adults, mainly includes (a) anomalies in the number or diameter of the vessels and (b) abnormal drainage or connection with the pulmonary arterial tree. Acquired disease can be grouped into (a) stenosis and obstruction, (b) hypertension, (c) thrombosis, (d) calcifications, and (e) collateral circulation. Pulmonary vein stenosis or obstruction, which often has important clinical repercussions, is frequently a result of radiofrequency ablation complications, neoplastic infiltration, or fibrosing mediastinitis. The most common cause of pulmonary venous hypertension is chronic left ventricular failure. This condition is difficult to differentiate from veno-occlusive pulmonary disease, which requires a completely different treatment. Pulmonary vein thrombosis is a rare, potentially severe condition that can have a local or distant cause. Calcifications have been described in rheumatic mitral valve disease and chronic renal failure. Finally, the pulmonary veins can act as conduits for collateral circulation in cases of obstruction of the superior vena cava. Multidetector CT is an excellent modality for imaging evaluation of the pulmonary veins, even when the examination is not specifically tailored for their assessment. PMID:23842969

Porres, Diego Varona; Morenza, Oscar Persiva; Pallisa, Esther; Roque, Alberto; Andreu, Jorge; Martínez, Manel

243

Transparent ultrananocrystalline diamond films on quartz substrate  

Microsoft Academic Search

Highly transparent ultrananocrystalline diamond (UNCD) films were deposited on quartz substrates using microwave plasma enhanced chemical vapor deposition (MPECVD) method. Low temperature growth of high quality transparent UNCD films was achieved by without heating the substrates prior to the deposition. Additionally, a new method to grow NCD and microcrystalline diamond (MCD) films on quartz substrates has been proposed. Field emission

P. T. Joseph; Nyan-Hwa Tai; Yi-Chun Chen; Hsiu-Fung Cheng; I-Nan Lin

2008-01-01

244

The Quartz Analog Watch: A Wonder Machine.  

ERIC Educational Resources Information Center

|Summarizes how a quartz watch works. Discusses the quartz crystal, its form, and how its frequency is set to a standard; the integrated circuit chip that drives the crystal in vibration, scales its frequency down, and forms pulses that turn the motor; and the motor that drives the gear train that turns the hands. (ZWH)|

Crane, H. Richard, Ed.

1993-01-01

245

Fused quartz substrates for microchip electrophoresis  

Microsoft Academic Search

A fused quartz microchip is fabricated to perform capillary electrophoresis of metal ions complexed with 8-hydroxyquinoline-5-sulfonic acid (HQS). The channel manifold on the quartz substrate is fabricated using standard photolithographic, etching, and deposition techniques. By incorporating a direct bonding technique during the fabrication of the microchip, the substrate and cover plate can be fused together below the melting temperature for

Stephen C. Jacobson; Alvin W. Moore; J. Michael. Ramsey

1995-01-01

246

Quartz Growth on X-Seeds.  

National Technical Information Service (NTIS)

This invention concerns itself with a method for producing single crystal, seed material for use in growing synthetic quartz crystals. This seed material comprises a Z-faced seed crystal cut or sliced from the X-plus growing region of a synthetic quartz, ...

A. F. Armington

1983-01-01

247

U-Pb and Ar-Ar geochronology of the Fujiawu porphyry Cu-Mo deposit, Dexing district, Southeast China: Implications for magmatism, hydrothermal alteration, and mineralization  

NASA Astrophysics Data System (ADS)

The Fujiawu porphyry Cu-Mo deposit is one of several porphyry Cu-Mo deposits in the Dexing district, Jiangxi Province, Southeast China. New zircon SHRIMP U-Pb data yield a weighted mean 206Pb/238U age of 172.0 ± 2.1 and 168.5 ± 1.4 Ma from weakly altered granodiorite porphyry and quartz diorite porphyry, respectively. Two hydrothermal biotites from granodiorite porphyry give an Ar-Ar step-heating plateau age of 169.9 ± 1.8 and 168.7 ± 1.8 Ma. Hydrothermal apatite exsolved from altered biotite yields an isotope dilution thermal ionization mass spectrometry isochron age of 164.4 ± 0.9 Ma. The apatite age is similar to the ages obtained from hydrothermal rutile (165.0 ± 1.1 and 164.8 ± 1.6 Ma) and indicates that the magmatism and hydrothermal activity in the Fujiawu deposit occurred in the Middle Jurassic. Hydrothermal fluid circulation related to multiple stages of magma emplacement resulted in Cu-Mo mineralization in the Fujiawu porphyry deposit. The zircon SHRIMP U-Pb ages and the published molybdenite Re-Os age (170.9 ± 1.5 Ma) represent the timing of magma crystallization and Mo mineralization, whereas the rutile and apatite U-Pb ages reflect the timing of Cu mineralization following quartz diorite emplacement. The data suggest slow cooling after emplacement of the quartz diorite porphyry.

Li, Xiaofeng; Hu, Ruizhong; Rusk, Brian; Xiao, Rong; Wang, Cuiyun; Yang, Feng

2013-09-01

248

Cathodoluminescence of Shocked Quartz at the Cretaceous-Tertiary Boundary.  

National Technical Information Service (NTIS)

Empirical studies have documented an association between rock type and the cathodoluminescence color of constituent quartz grains. Quartz from extrusive igneous sources luminesces uniform pale blue. Quartz from intrusive igneous and high-grade metamorphic...

M. R. Owen M. H. Anders

1988-01-01

249

Modeling Hydrothermal Vents on Europa  

NASA Astrophysics Data System (ADS)

Simulations of potential hydrothermal vents at Europa's ocean floor are presented. The effects of differing initial rock composition and temperature are explored with respect to mineral formation and vent fluid composition.

Gavin, P.; Vance, S.

2012-03-01

250

Autoclaved cement-quartz pastes: The effects on chemical and physical properties when using ground quartz with different surface areas Part I: Quartz of wide particle size distribution  

Microsoft Academic Search

The effects of different surface area of ground quartz in 24 hour precured and autoclaved cement-quartz pastes, at CS of 0.5, were investigated. Portlandite production and calcium silicate hydrate formation increased during procuring in the presence of ground quartz, while the compressive strength increased with increasing quartz surface area. Autoclaving for 8 hours at 177 °C under saturated steam yielded

Danielle S. Klimesch; Abhi Ray; Brian Sloane

1996-01-01

251

Inflammation in Retinal Vein Occlusion  

PubMed Central

Retinal vein occlusion is a common, vision-threatening vascular disorder. The role of inflammation in the pathogenesis and clinical consequences of retinal vein occlusion is a topic of growing interest. It has long been recognized that systemic inflammatory disorders, such as autoimmune disease, are a significant risk factor for this condition. A number of more recent laboratory and clinical studies have begun to elucidate the role inflammation may play in the molecular pathways responsible for the vision-impairing consequences of retinal vein occlusion, such as macular edema. This improved understanding of the role of inflammation in retinal vein occlusion has allowed the development of new treatments for the disorder, with additional therapeutic targets and strategies to be identified as our understanding of the topic increases.

Deobhakta, Avnish; Chang, Louis K.

2013-01-01

252

ESR dating of fault movement using various defect centres in quartz; the case in the western South Fossa Magna, Japan  

NASA Astrophysics Data System (ADS)

The dates of movements of the Itoigawa-Shizuoka Tectonic Line (I-S T.L.) and Minobu Fault in the western South Fossa Magna have been obtained by ESR dating. Measurements were made on various lattice defects of the OHC, Ge, Al and E' centres in quartz grains of fault clay and quartz veins intruded at the time of movement. All the dates obtained from these centres in quartz grains from two localities of the I-S T.L. and two localities of the Minobu Fault fall in the range of 0.30-0.55 Ma; this suggests that all the centres were annihilated completely, and that the obtained age can be admitted as the actual data of the latest fault movement. Meanwhile, ESR dates of,quartz vein and fault clay in other localities (locations 3, 6, 7) are divided into 0.30-0.55 Ma and 1.5-2.0 Ma, which suggest incomplete resetting. The dates of 0.30-0.55 and 1.5-2.0 Ma might correspond to the clino-unconformities observed in Plio-Pleistocene sequence of this region.

Fukuchi, Tatsuro; Imai, Noboru; Shimokawa, Koichi

1986-05-01

253

The effect of redox on the relative solubilities of copper and iron in Cl-bearing aqueous fluids at elevated temperatures and pressures: An experimental study with application to subseafloor hydrothermal systems  

Microsoft Academic Search

A series of hydrothermal experiments were performed to evaluate the role of redox, temperature, and fluid chemistry on the solubility of Cu- and Fe-bearing sulfide minerals in Na-K-Cl aqueous fluids. The experiments made use of potassic aluminosilicate minerals + quartz to maintain fluid pH at values generally appropriate for subseafloor hydrothermal systems. To avoid uncertainties in pH resulting from non-ideal

W. E. Seyfried Jr.; K. Ding

1993-01-01

254

Carbon isotopes and petrography of kerogens in ~3.5-Ga hydrothermal silica dikes in the North Pole area, Western Australia 1  

NASA Astrophysics Data System (ADS)

More than 600 specimens of ~3.5 Ga-old hydrothermal silica dikes from the North Pole area, Pilbara craton, Western Australia, have been studied petrographically. The kerogens in 44 samples have been analyzed isotopically (C and N) and chemically (C, N, and H). The silica dikes are composed mainly of fine-grained silica (modal abundance: >97%) and are classified into two types by minor mineral assemblages: B(black)-type and G(gray)-type. The B-type silica dikes contain kerogen (0.37 to 6.72 mgC/g; average 2.44 mgC/g, N = 21) and disseminated sulfides, dominantly pyrite and Fe-poor sphalerite. In some cases, carbonate and apatite are also present. Their silica-dominated and sulfide-poor mineral assemblages suggest precipitation from low-temperature reducing hydrothermal fluid (likely 100-200°C). On the other hand, the G-type silica dikes are sulfide-free and concentrations of kerogen are relatively low (0.05 to 0.41 mgC/g; average 0.17 mgC/g, N = 13). They typically contain Fe-oxide (mainly hematite) which commonly replaces cubic pyrite and rhombic carbonate. Some G-types occur along secondary quartz veins. These textures indicate that the G-type silica dikes were formed by postdepositional metasomatism (oxidation) of the B-types, and that the B-types probably possess premetasomatic signatures. The 13 C values of kerogen in the B-types are -38.1 to -33.1 (average -35.9 , N = 21), which are ~4 lower than those of the G-types (-34.5 to -30.0 ; average -32.2 , N = 19), and ~6 lower than bedded chert (-31.2 to -29.4 ; average -30.5 , N = 4). This indicates the preferential loss of 12 C during the metasomatism (estimated fractionation factor: 0.9985). Considering the metasomatic effect on carbon isotopes with probably minor diagenetic and metamorphic overprints, we conclude that the original 13 C values of the kerogen in the silica dikes would have been heterogeneous (~5 ) and at least some material had initial 13 C values of -38 . The inferred 13 C-depletions of organic carbon could have been produced by anaerobic chemoautotrophs such as methanogen, but not by aerobic photoautotrophs. This is consistent with the estimated physical and chemical condition of the hydrothermal fluid, which was probably habitable for anaerobic and thermophilic/hyperthermophilic chemoautotrophs. Alternatively, the organic matter may have been possibly produced by abiological reaction such as Fischer-Tropsch Type (FTT) synthesis under the hydrothermal condition. However, the estimated condition is inconsistent with the presence of the effective catalysts for the FTT reaction (i.e., Fe-Ni alloy, magnetite, and hematite). These lines of evidence suggest the possible existence of biosphere in the ~3.5 Ga sub-seafloor hydrothermal system.

Ueno, Yuichiro; Yoshioka, Hideyoshi; Maruyama, Shigenori; Isozaki, Yukio

2004-02-01

255

Destruction of a fluvial reservoir by hydrothermal activity (Cameros Basin, Spain)  

NASA Astrophysics Data System (ADS)

This study provides an example of a high-quality fluvial hydrocarbon reservoir that was completely destroyed by hydrothermal processes. The reservoir unit was deposited in the Cameros Basin, located in the NW sector of the Iberian Chain (Spain). The basin was filled with clastic fluvial deposits (sandstones and conglomerates) between Late Berriasian and Early Aptian times. Provenance of sands was mainly from coarse crystalline rocks. A humid tropical climate produced intense weathering of K-feldspar during transport from source to basin. Thus, a mineralogically mature rigid framework with high porosity existed at the time of deposition, which would have constituted a high-quality hydrocarbon reservoir. At present however, the porosity of the reservoir is negligible. Porosity was reduced by a sequence of diagenetic processes: (1) mechanical compaction (i.e. crushing of metamorphic lithic grains) and chemical compaction, (2) kaolinite and siderite cementation, and (3) early quartz cementation. Hydrocarbon emplacement probably occurred between phases (2) and (3). A low-grade metamorphic (hydrothermal) event, reaching greenschist facies, took place during the Late Cenomanian. It dramatically reduced the remaining porosity of the reservoir and destroyed the hydrocarbon charge. Hydrothermal processes which affected the sandstones include (1) re-compaction; (2) late quartz cementation and silicification of remaining feldspars; (3) carbonate cementation; (4) chloritization of feldspars, metamorphic lithic fragments and intrabasinal argillaceous grains; and (5) growth of pyrite and chloritoid crystals on argillaceous material of intrabasinal, extrabasinal or even diagenetic origin. Hydrocarbons that migrated to the margins of the basin escaped these hydrothermal modifications and were preserved. The results of this study may be used to predict the diagenetic and hydrothermal evolution of other potential reservoirs in similar tectonic settings.

Ochoa, M.; Arribas, J.; Mas, R.; Goldstein, R. H.

2007-11-01

256

Seismic cycles recorded in late Quaternary calcite veins: Geochronological, geochemical and microstructural evidence  

NASA Astrophysics Data System (ADS)

Southwest Turkey is seismically active as a result of the Hellenic subduction process in the Eastern Mediterranean. We conducted high-resolution micro-sampling, high-precision U-series dating and microchemical analysis on an extensional vein system in a tectonically active but non-hydrothermal area. U/Th age data and microscopic observations provide evidence of repeated fracturing of a previously sealed crack system followed by a new increment of veining. Repeated injection of veinlets suggests that the vein system was formed by the crack-seal mechanism. Four major U/Th age groups for the emplacement of the vein system fall between 23.9 ± 0.2 ka and 23.2 ± 0.4 ka, 21.7 ± 0.4 ka and 19.2 ± 0.2 ka, 17.3 ± 0.1 ka and 16.2 ± 0.3 ka, and at 11.8 ± 0.2 ka. Stable and Sr isotope geochemistry of the calcite vein samples indicates that surface water interacting with the soil cover was the major component of the groundwater system from which the extensional veins precipitated. Trace element and O isotope data of the vein system are interpreted to reflect carbonate precipitation associated with seismic cycles involving fluids with different trace element compositions and CO2 contents. Initial carbonate precipitation during a single seismic cycle occurred from CO2-dominated fluids that were degassed from the original CO2-water mixture. This was followed consecutively by carbonate precipitation from the remaining water, which was relatively impure with higher trace element contents. Millimetre to submillimetre-scale U-series dating in conjunction with geochemistry of carbonate veins related to active tectonism offers an innovative means of constraining the absolute timing of late Quaternary seismic and inter-seismic events.

Uysal, I. Tonguç; Feng, Yue-Xing; Zhao, Jian-Xin; Bolhar, Robert; I?ik, Veysel; Baublys, Kim A.; Yago, Anya; Golding, Suzanne D.

2011-02-01

257

The roles of magmatic and hydrothermal processes in PGE mineralization, Ferguson Lake deposit, Nunavut, Canada  

NASA Astrophysics Data System (ADS)

The Ferguson Lake Ni-Cu-Co-platinum-group element (PGE) deposit in Nunavut, Canada, occurs near the structural hanging wall of a metamorphosed gabbroic sill that is concordant with the enclosing country rock gneisses and amphibolites. Massive to semi-massive sulfide occurs toward the structural hanging wall of the metagabbro, and a low-sulfide, high-PGE style of mineralization (sulfide veins and disseminations) locally occurs ~30-50 m below the main massive sulfide. Water-rock interaction in the Ferguson Lake Ni-Cu-Co-PGE deposit is manifested mostly as widespread, post-metamorphic, epidote-chlorite-calcite veins, and replacement assemblages that contain variable amounts of sulfides and platinum-group minerals (PGM). PGM occur as inclusions in magmatic pyrrhotite and chalcopyrite in both the massive sulfide and high-PGE zones, at the contact between sulfides and hornblende or magnetite inclusions in the massive sulfide, in undeformed sulfide veins and adjacent chlorite and/or epidote halos, in hornblende adjacent to hydrothermal veins, and in plagioclase-chlorite aggregates replacing garnet cemented by sulfide. The PGM are mostly represented by the kotulskite (PdTe)-sobolevskite (PdBi) solid solution but also include michenerite (PdBiTe), froodite (PdBi2), merenskyite (PdTe2), mertieite II (Pd8[Sb,As]3), and sperrylite (PtAs2) and occur in variety of textural settings. Those that occur in massive and interstitial sulfides, interpreted to be of magmatic origin and formed through exsolution from base metal sulfides at temperatures <600°C, are dominantly Bi rich (i.e., Te-bearing sobolevskite), whereas those that occur in late-stage hydrothermal sulfide/silicate veins and their epidote-chlorite alteration halos tend to be more Te rich (i.e., Bi-bearing kotulskite). The chemistry and textural setting of the various PGM supports a genetic model that links the magmatic and hydrothermal end-members of the sulfide-PGM mineralization. The association of PGM with magmatic sulfides in the massive sulfide and high-PGE zones has been interpreted to indicate that PGE mineralization was initially formed through exsolution from base metal sulfides which formed by magmatic sulfide liquid segregation and crystallization. However, the occurrence of PGM in undeformed sulfide-bearing veins and in their chlorite-epidote halos and differences in PGM chemistry indicate that hydrothermal fluids were responsible for post-metamorphic redistribution and dispersion of PGE.

Campos-Alvarez, Nelson O.; Samson, Iain M.; Fryer, Brian J.

2012-04-01

258

Trace Elements in the Si Furnace-Part II: Analysis of Condensate in Carbothermal Reduction of Quartz  

NASA Astrophysics Data System (ADS)

Silicon feedstock for production of solar-grade silicon should be as pure as possible to decrease the cost of manufacturing of solar cells. Impurities in quartz, carbonaceous materials, electrodes, and refractories are mostly present in the form of oxides. These oxides can be reduced to volatile gaseous compounds in presence of SiO(g) and CO(g) atmosphere and potentially leave the furnace or stay in the condensed reaction products, metal, and slag. This work investigates the conditions under which volatile impurities report to the gas phase in laboratory experiments with lumpy and pelletized mixtures of SiO2, SiC, and Si at 1923 K and 2123 K (1650 °C and 1850 °C), respectively, were carried out. The volatile compounds were generated by the reduction of quartz and collected in the form of condensate. The effects of the reaction temperature, quartz type, charge composition, pellets, and lumps on the composition of the condensate were studied. The trace elements in the charge input, reacting charge, and condensate were analyzed using inductively coupled plasma (ICP)-mass spectroscopy (MS) and X-ray diffraction (XRD). CO(g) and SiO(g), which are the major components in reduction reactions, formed four types of condensate: white, brown, green, and orange. The condensate constituents were amorphous SiO2, 3C:SiC, Si, and ?-quartz. Each impurity present in the quartz charge entered the gas phase during quartz reduction and was detected in the condensate. Al and Fe show limited volatility. The volatility of Mn, P, and B depends on the charge mix: a higher PCO enhances the concentration of these elements in the gas phase. Fluid inclusions, common in hydrothermal quartz, enhance the distribution of the contaminants to the gas phase. Industrial campaigns on Si and Fe-Si production confirm the experimental results.

Dal Martello, Elena; Tranell, Gabriella; Ostrovski, Oleg; Zhang, Guangqing; Raaness, Ola; Larsen, Rune Berg; Tang, Kai; Koshy, Pramod

2013-04-01

259

Gold and platinum group elements in cobaltarsenide ores: Hydrothermal concentration from a serpentinite source-rock (Bou Azzer, Morocco)  

Microsoft Academic Search

Summary The cobalt-arsenide ores of Bou Azzer are located along the borders of serpentinite massifs (Upper Proterozoic ophiolite complex) in carbonate-quartz lenses resulting from hydrothermal carbonate alteration of serpentinite. The cobalt ores contain an average gold content of 5–20 ppm; gold is mainly located in skutterudite (120 ppm av.), whereas the Fe-arsenide (loellingite) contains < 1 ppm Au. Similarly the

M. Leblanc; W. Fischer

1990-01-01

260

Homogenization Temperature Measurements in Hydrothermal Diamond-Anvil Cell for Melt and Fluid Inclusions from the Jiajika Pegmatite Deposit, China  

Microsoft Academic Search

We measured the total homogenization temperatures (Th) of volatile-rich melt and fluid inclusions under elevated external pressures in a hydrothermal diamond-anvil cell (HDAC) to understand fluid evolution in the Jiajika pegmatite deposit in China, the largest spodumene deposit in Asia. Three types of inclusions were investigated: 1. CH4-H2O (~10 vol. %) bearing aluminosilicate melt inclusions hosted in quartz from granite;

J. Li; I. Chou; S. Yuan; R. C. Burruss

2009-01-01

261

Mapping hydrothermally altered rocks with the airborne imaging spectrometer (AIS) and the airborne visible\\/infrared imaging spectrometer (AVIRIS)  

Microsoft Academic Search

The airborne imaging spectrometer (AIS) and the airborne visible\\/infrared imaging spectrometer (AVIRIS) were used to map the alteration mineralogy of a hydrothermal system in the northern Grapevine Mountains of Nevada and California, using detailed spectral characteristics. Areas of quartz-sericite-pyrite (QSP) alteration were identified based on the presence of sericite (fine-grained muscovite) spectral features near 2.2 microns. Areas of argillic alteration

Fred A. Kruse; Dan L. Taranik

1989-01-01

262

Mapping Hydrothermally Altered Rocks with the Airborne Imaging Spectrometer (ais) and the Airborne Visible\\/infrared Imaging Spectrometer  

Microsoft Academic Search

The Airborne Imaging Spectrometer (AIS), and the Airborne Visible\\/Infrared Imaging Spectrometer (AVIRIS) were used to map the alteration mineralogy of a hydrothermal system in the Northern Grapevine Mountains, Nevada and California using detailed spectral characteristics. Areas of quartz-sericitepyrite (QSP) alteration were identified based on the presence of sericite (fine-grained muscovite) spectral features near 2.2 !.lID. Areas of argillic alteration were

Fred A. Kruse; D. L. Taranik

1989-01-01

263

The Iceland Deep Drilling Project (IDDP): (6) Hydrothermal minerals record CO2 partial pressures in the Reykjanes Geothermal System, Iceland  

Microsoft Academic Search

The Reykjanes Geothermal system, a target site for drilling by the IDDP, is located on the Reykjanes Peninsula in southwest Iceland, the landward extension of the Mid-Atlantic Ridge spreading center. Seawater penetrates the coastal Reykjanes geothermal system at depth, mixing with magmatic volatiles and reacting with the basaltic host rock to form secondary hydrothermal minerals. Within this system, epidote-prehnite-calcite- quartz-fluid

A. J. Freedman; D. K. Bird; S. Arnórsson; T. Fridriksson; W. A. Elders; G. O. Fridleifsson

2009-01-01

264

Fluid inclusions in quartz crystals from South-West Africa  

USGS Publications Warehouse

Quartz crystals from calcite veins of unknown age in Precambrian metasedimentary rocks at Geiaus No. 6 and Aukam farms in South-West Africa contain both primary and secondary inclusions filled with one or a variable combination of: organic liquid, moderately saline aqueous liquid, dark-colored solid, and vapor. Analysis of these materials by microscopy and by gas chromatography and mass spectrometry shows the presence of constituents of both low and high molecular weights. The former include CH4, C2H6, C3H8 and possibly C4H10 as well as CO, CO2, H2O, N2 and H2. High molecular weight components are dominantly n-alkanes and isoprenoid hydrocarbons. The n-alkanes range from at least n-C10 to n-C33. Concentrations of n-alkanes larger than n-C17 decrease regularly with increasing carbon number. An homologous series of isoprenoid hydrocarbons ranging from at least C14 to C20 is present in unusually high concentrations. Pristane (C19) is most abundant, and C17 isoprenoid is least abundant. The molecular composition and distribution of hydrocarbons suggest biological precursors for these components. Consideration of data provided by freezing, crushing and heating experiments suggests that the pressures at the time these in part supercritical fluids were trapped probably exceeded 30-40 atm, and the minimum trapping temperature was about 120-160??C. Both primary and secondary inclusions apparently containing only organic materials were trapped by the growth of the host quartz from aqueous solution. The data obtained neither prove nor preclude Precambrian, Paleozoic or younger sources for the organic materials. ?? 1971.

Kvenvolden, K. A.; Roedder, E.

1971-01-01

265

Mineralogy, paragenesis and textures associated with metasomatic- hydrothermal processes, Qatruyeh area, Sanandaj- Sirjan zone, SW Iran  

NASA Astrophysics Data System (ADS)

The Qatruyeh area is located at about 40 Km northeastern of Neyriz region, in the eastern edge of the high P- Low T metamorphic Zagros orogenic belt. The studied area principally includes outcrops of green schist facies metamorphic rocks that are thrusted over the Neotethyan ophiolites. Hydrothermal activities occurred episodically in the Mesozoic era . The textural relationships, mineral assemblages and X- Ray diffractions have recognized two different stages of hydrothermal alteration during mineralization. The Mineralization was largely controlled by striking faults and host rock layers. Three different types of magnetite are distinguished in microscopic investigation. The First is euhedral to subhedral, partly replacement by martite with exsolved ilmenites. The Second reveals myrmekite like textures and the last type includes layered magnetite. All of the types are related to replacement textures such as psedomorphism, widening of a fracture filling, irregulare or vermicular intergrowths, islands of unreplaced host rock, cusp or caries, nonmatching walls or borders of a fracture and rims of one mineral penetrating another along its crystallographic direction. X- Ray analyses indicate oxide minerals (Magnetite, Hematite, Maghemite, Specularite, Goethite, Limonite and Ilmenite), Silicate minerals (Tourmaline-shorl and dravite-, Epidote, Chlorite, Actinolite, Titanite, Paragonite, Talc, Muscovite and Quartz), Carbonate minerals (Siderite and Malachite) and Sulfide minerals (Pyrite and Chalcopyrite-minor-) as major phases. The mineral paragenesis and textures show two different stages of metasomatic- hydrothermal alteration. The first stage alteration (Sodic- Calsic) accompanying with mineral paragenesis of Magnetite+ Tourmaline+ Titanite+ Paragonite and the second stage of alteration (Solfidation- Oxidation) follows with Magnetite+ Hematite+ Quartz

Asadi, S.; Rajabzadeh, M. A.

2009-04-01

266

Improved Thermoelectrically Cooled Quartz Crystal Microbalance.  

National Technical Information Service (NTIS)

Design changes in the thermoelectrically-cooled quartz microbalance, which is used to monitor surface contamination in space simulation chambers, is described in terms of its extended temperature range, increased temperature control, mass sensitivity, and...

W. E. Mckeown W. E. Corbin M. G. Fox

1974-01-01

267

Basic Material Quartz and Related Innovations  

Microsoft Academic Search

Although material quartz is of scientific interest in its own right, its volume of usage and variety of applications dictate\\u000a its technological importance.The technological prominence of ?-quartz stems largely from the presence of piezoelectricity,\\u000a combined with extremely low acoustic loss. It was one of the minerals with which the Brothers Curie first established the\\u000a piezoelectric effect in 1880. In the

A. Ballato

2008-01-01

268

Method of making a quartz resonator  

DOEpatents

A quartz resonator is made from a chemically polished quartz plate. The plate is placed in an enclosure fitted with at least three mounting clips to receive the plate. The plate is secured to the clips with an electrically conductive adhesive capable of withstanding operation at 350 degrees C. The assembly is cleaned and a metallic electrode deposited onto the plate until the desired frequency is reached. The enclosure is then hermetically sealed. The resulting resonator can consistently withstand extremely high shocks.

Vig, John R. (Colts Neck, NJ); Filler, Raymond L. (Freehold, NJ); Peters, R. Donald (Pinnellas Park, FL); Frank, James M. (Seminole, FL)

1981-01-01

269

Why calcite can be stronger than quartz  

Microsoft Academic Search

In the Neves area (Eastern Alps), calcite forms asymmetric centimeter-scale single-crystal porphyroclasts in quartz mylonites developed during hydrous amphibolite facies metamorphism at ?550°C. Under these conditions, coarse calcite was clearly stronger than the surrounding polycrystalline, dynamically recrystallized, quartz matrix. Experimental results indicate that coarse calcite is less strain rate sensitive than wet quartzite, consistent with an inversion in strength on

Neil S. Mancktelow; Giorgio Pennacchioni

2010-01-01

270

Calibration of quartz tuning fork temperature sensors  

Microsoft Academic Search

This paper presents the results from investigations of thermal sensitivity, thermal response time and long-term stability of a newly miniaturized design of thermal sensitive quartz tuning fork resonator working at flexural mode with ZY-cut at fundamental frequency of 32 kHz. Special attention is given to the methodology and equipment for calibration of quartz tuning fork temperature sensor. To obtain accuracy

Jun Xu; Bo You; Hong-jun Wang; Jing Ma

2008-01-01

271

Quartz optical waveguide by ion implantation  

Microsoft Academic Search

We have shown single-mode surface optical waveguiding in lithium-ion-implanted fused quartz, and multimode buried waveguiding in argon- and lithium-ion-implanted fused quartz. Guide losses are observed to be of the order of 5 dB for the samples investigated for both species of ions. Described in this letter are the experimental procedures and parameters for ion implantation and the measurements for mode

David T. Y. Wei; William W. Lee; Louis R. Bloom

1973-01-01

272

Crystal quartz optical whispering-gallery resonators.  

PubMed

A quality factor exceeding 5x10(9) is obtained in whispering-gallery mode (WGM) resonators fabricated of crystalline quartz. We observe significant electrical tunability of WGMs in x-cut resonators and demonstrate an electro-optic modulator with a submegahertz passband at 12 GHz. We discuss other photonics applications of the crystal quartz WGM resonators in narrowband agile tunable filters, compact narrow linewidth lasers, and microwave and millimeter wave oscillators. PMID:18628800

Ilchenko, Vladimir S; Savchenkov, Anatoliy A; Byrd, Jerry; Solomatine, Iouri; Matsko, Andrey B; Seidel, David; Maleki, Lute

2008-07-15

273

Commercialization of vein contrast enhancement  

NASA Astrophysics Data System (ADS)

An ongoing clinical study of an experimental infrared (IR) device, the Vein Contrast Enhancer (VCE) that visualizes surface veins for medical access, indicates that a commercial device with the performance of the existing VCE would have significant clinical utility for even a very skilled phlebotomist. A proof-of-principle prototype VCE device has now been designed and constructed that captures IR images of surface veins with a commercial CCD camera, transfers the images to a PC for real-time software image processing to enhance the vein contrast, and projects the enhanced images back onto the skin with a modified commercial LCD projector. The camera and projector are mounted on precision slides allowing for precise mechanical alignment of the two optical axes and for measuring the effects of axes misalignment. Precision alignment of the captured and projected images over the entire field-of-view is accomplished electronically by software adjustments of the translation, scaling, and rotation of the enhanced images before they are projected back onto the skin. This proof-of-principle prototype will be clinically tested and the experience gained will lead to the development of a commercial device, OnTarget!, that is compact, easy to use, and will visualize accessible veins in almost all subjects needing venipuncture.

Lovhoiden, Gunnar; Deshmukh, Harshal; Vrancken, Carlos; Zhang, Yong; Zeman, Herbert D.; Weinberg, Devin

2003-07-01

274

Carbon isotope evidence for a magmatic origin for Archaean gold-quartz vein ore deposits  

NASA Astrophysics Data System (ADS)

Sediments from three sites in the Santa Barbara Basin were examined with a 160X power light microscope and TEM equipment to characterize the magnetostatic bacteria (MB) in the samples. Both the free magnetite and the crystals in the MB in the samples had lengths from 40-60 nm in length and increased in size from one end to the next. An intact magnetosome was also observed. Scanning the sediments with saturation isothermal remanent magnetization (SIRM) and altering field demagnetization techniques using a SQUID magnetometer yielded coercivity spectra which showed that the primary remanence carrier in the sediments was single domain magnetite. Although it is expected that the predominance of the bacterial magnetite component will decrease with depth in the open ocean basin, single-domain bacteria as old as 50 Myr have been observed in oceanic sediments.

Burrows, D. R.; Wood, P. C.; Spooner, E. T. C.

1986-06-01

275

The Role of Brines in low Temperature, Fault-related Deformation of Quartz Arenites  

NASA Astrophysics Data System (ADS)

Fluids play an integral role in deformation within the Earth\\'{}s crust over a wide range of physical conditions. At low temperatures (<300° C) the effect is dominantly mechanical, largely through the effects of pore fluid pressure. At higher temperatures (>300° C), chemical processes, such as diffusive mass transfer, advective mass transfer, and hydrolytic weakening dominate. Brines, because of their greater reactivity, enhance certain chemical processes during deformation. In the transition between high and low temperature regimes, both mechanical and chemical processes operate and interact in complex ways. This study investigates the role of brines in the deformation of quartz arenite in a map scale fault zone deformed under conditions transitional between low and high temperature regimes. The fault zone is also known to have been a conduit for fluids thought to be largely basinal brines. The Cove Mountain fault zone in south central Pennsylvania contains several map-scale blocks of quartz arenite which display a wide range of brittle and ductile microstructures. Abundant evidence of fluids is present in the form of quartz veins, microveins, fluid inclusion planes, cataclastic bands, and stylolites. Three different fluids are recognized based on cathodoluminescence color of quartz, and homogenization (Th) and melting temperatures (Tm) from fluid inclusions. Blue-green luminescing quartz has a Th of 185 to 215° C and a Tm of -15 to -17° C; red luminescing quartz has a Th of 165 to 200° C and a Tm of -16 to -20° C; and zoned quartz with both red and blue-green luminescence has a Th of 180 to 220° C and a Tm of -18 to -23° C. The eutectic temperature of all three fluids is approximately -50° C suggesting that CaCl2 is the dominant salt species. Grains adjacent to fluid conduits (microfractures, cataclastic bands, and stylolites) display more crystal plastic microstructures than those farther away. Compared to quartz in veins and in undeformed portions of the rock, which have water contents of ~1,000 and ~12,000 H/106 Si, respectively (determined by FTIR), grains adjacent to fluid conduits have water contents as high as 26,000 H/106 Si indicating that water was able to penetrate these grains and thus promote ductile deformation in a dominantly brittle regime. Access of water to grain centers was provided by both microfracturing and diffusion. Evidence for diffusion is shown by the presence of quartz grains adjacent to fluid conduits which have blue luminescing centers and red rims. Water contents in these grains ranges from 2,000-22,000 H/106 Si with some correlation between water content and luminescence color. The large amount of pressure solution relative to similar rocks in the region is believed to be related to the salinity of the brines. Also, the thick accumulation of goethite in stylolites and fractures precipitated by these fluids is unusual in similar rocks in the region suggesting that the fluid chemistry was atypical. The microstructures in this fault zone indicate that water is important in controlling the operative deformation mechanisms in the transition from low to high temperature deformation. Furthermore, the chemistry of these brines may account for greater solubility of quartz and faster diffusion rates than would be the case with low salinity fluids.

O'Kane, A.; Onasch, C. M.; Farver, J.

2004-12-01

276

Hydrothermal pretreatment of coal  

SciTech Connect

We have examined changes in Argonne Premium samples of Wyodak coal following 30 min treatment in liquid water at autogenous pressures at 150{degrees}, 250{degrees}, and 350{degrees}C. In most runs the coal was initially dried at 60{degrees}C/1 torr/20 hr. The changes were monitored by pyrolysis field ionization mass spectrometry (py-FIMS) operating at 2.5{degrees}C/min from ambient to 500{degrees}C. We recorded the volatility patterns of the coal tars evolved over that temperature range, and in all cases the tar yields were 25%--30% of the starting coal on mass basis. There was essentially no change after the 150{degrees}C treatment. Small increases in volatility were seen following the 250{degrees}C treatment, but major effects were seen in the 350{degrees} work. The tar quantity remained unchanged; however, the volatility increased so the temperature of half volatility for the as-received coal of 400{degrees}C was reduced to 340{degrees}C. Control runs with no water showed some thermal effect, but the net effect from the presence of liquid water was clearly evident. The composition was unchanged after the 150{degrees} and 250{degrees}C treatments, but the 350{degrees} treatment brought about a 30% loss of oxygen. The change corresponded to loss of the elements of water, although loss of OH'' seemed to fit the analysis data somewhat better. The water loss takes place both in the presence and in the absence of added water, but it is noteworthy that the loss in the hydrothermal runs occurs at p(H{sub 2}O) = 160 atm. We conclude that the process must involve the dehydration solely of chemically bound elements of water, the dehydration of catechol is a specific, likely candidate.

Ross, D.S.

1989-12-21

277

Hydrothermal dealumination of faujasites  

SciTech Connect

Two faujasites (USY and REY) were hydrothermally treated at temperatures between 400 and 850/sup 0/C in 100% steam and up to 65 h to induce dealumination. The Al expulsion from the zeolite lattice was followed by X-ray diffraction (XRD) and by /sup 29/Si and /sup 27/Al nuclear magnetic resonance (NMR) spectroscopy. Both techniques showed large changes in crystal structure in less than 30 min while crystallinity losses were kept below 15% at temperatures up to 500/sup 0/C. The Al expulsion from the zeolite lattice is accompanied by Al diffusion through the channel network to the zeolite particle surface. The surface enrichment by Al was quantitatively measured by X-ray photoelectron spectroscopy (XPS or ESCA). The diffusion of Al to the particle surface takes place only in the presence of steam and the migrating species is speculated to be a hydroxylated Al ion. These studies were complemented by secondary ion mass spectrometry (SIMS) and scanning transmission electron microscopy (STEM). SIMS analysis demonstrated a very large enrichment of Al in the top 30 A of steamed zeolites. STEM measurements of Si/Al profiles on 800 A-thick microtomed sections confirmed the SIMS data, but indicated broader, less steep changes in the Si/Al ratio across zeolite particles. Because dealumination causes both structural changes (shrinkage of unit cell) and chemical changes (decrease in acidity) in a zeolite, it has profound implications on catalyst performance and on catalyst deactivation. For instance, dealuminated faujasites exhibit drastically reduced coking rates in the cumene cracking test reaction which is discussed in some detail.

Fleisch, T.H.; Meyers, B.L.; Ray, G.J.; Hall, J.B.; Marshall, C.L.

1986-05-01

278

Cyclic development of igneous features and their relationship to high-temperature hydrothermal features in the Henderson porphyry molybdenum deposit, Colorado  

USGS Publications Warehouse

The Henderson porphyry molybdenum deposit was formed by the superposition of coupled alteration and mineralization events, of varying intensity and size, that were associated with each of at least 11 intrusions. Deposition of molybdenite was accompanied by time-equivalent silicic and potassic alteration. High-temperature alteration and mineralization are spatially and temporally linked to the crystallization of compositionally zoned magma in the apex of stocks. Differences in hydrothermal features associated with each intrusion (e.g., mass of ore, orientation and type of veins, density of veins, and intensity of alteration) correlate with differences in primary igneous features (e.g., composition, texture, morphology, and size). The systematic relations between hydrothermal and magmatic features suggest that primary magma compositions, including volatile contents, largely control the geometry, volume, level of emplacement, and mechanisms of crystallization of stocks. These elements in turn govern the orientations and densities of fractures, which ultimately determine the distribution patterns of hydrothermal alteration and mineralization. -from Authors

Carten, R. B.; Geraghty, E. P.; Walker, B. M.

1988-01-01

279

Salinity of oceanic hydrothermal fluids: a fluid inclusion study  

NASA Astrophysics Data System (ADS)

An extensive microthermometric study of quartz, epidote, plagioclase, anhydrite and sphalerite-hosted fluid inclusions from ophiolitic [Semail (Oman) and Trinity (California) ophiolites] and oceanic (East Pacific Rise hydrothermal vents, Gorringe Bank, ODP Leg 111 Hole 504B) crust has been carried out in order to constrain a model accounting for wide salinity variations measured in the oceanic hydrothermal fluids. Recorded salinities in fluid inclusions vary between 0.3 and 52 wt% NaCl eq. However, more than 60% of the mean (+/- standard deviation) salinities of the samples are within the range 3.2 +/- 0.3 wt% NaCl eq (= microthermometric error) and the mean salinity of all fluid inclusions (without the brines) is 4.0 wt% NaCl eq with a standard deviation of 1.6 wt% NaCl eq. Whereas most samples display slightly higher salinities than seawater, several samples exhibit very high salinities (more than two times that of seawater). These high salinities are restricted to the plagiogranites (Semail and Trinity ophiolites) which mark the top of the fossil magma chamber, in the transition zone between the plutonic sequence and the sheeted dyke complex. The fluid inclusion population studied in the plagiogranites is characterized by the occurrence of four major fluid inclusion families: (1) low- to medium-salinity Liquid/Vapor fluid inclusions which homogenize into the liquid phase; (2) low-salinity Liquid/Vapor fluid inclusions with pseudocritical homogenization; (3) low- to medium-salinity Liquid/Vapor fluid inclusions which homogenize into the vapor phase; and (4) high-salinity Liquid/Vapor/Halite fluid inclusions which homogenize into the liquid phase by halite dissolution and exhibit salinities as high as 52 wt% NaCl eq. These fluid inclusion families are interpreted as resulting from phase separation occurring in hydrothermal or magmatic fluids within the transition zone between the hydrothermal system and the magma chamber at temperatures higher than 500°C. Very low salinities (less than half that of seawater) have been found only in one dioritic sample from the Gorringe Bank. Mineralogical and petrological data from the Semail Ophiolite shows the absence of Cl-rich minerals. Furthermore, hydration of the crust, although very important, cannot account for the large salinity variations. Thus the large salinity variations measured are interpreted as resulting from phase separation and generation of brine-rich fluids at the top of the magma chamber. This phase separation and subsequent phase segregation and brine accumulation may result in a double-diffusive convection of the fluids in the hydrothermal system. Present address: B.R.G.M., SGN/GEO, B.P. 6009, 45060 Orleans Cedex 2, France

Nehlig, Pierre

1991-03-01

280

Subfascial endoscopic perforator vein surgery.  

PubMed

Chronic venous insufficiency is a tremendous health care problem in western societies. Venous disease can affect any combination of the superficial, deep, and perforator venous systems of the lower extremities. Generally the superficial venous deficits are addressed through sclerotherapy, enovenous ablation, stab phlebectomy, and or stripping. Patients with advanced clinical sequelae (lipodermatosclerosis or ulceration) of CVI should also be evaluated for the presence of incompetent perforating veins. Open surgical approached to the calf perforating veins (ie. Linton procedure) were complicated by significant wound complications and have largely been replaced by the less invasive Subfascial Endoscopic Perforator Surgery (SEPS). The use of SEPS in patients with ulceration has been shown to be safe and to reduce the time that patients will have ulcers during follow-up. This chapter will review the pathophysiology, diagnosis, and treatment of incompetent perforating veins of the legs with particular attention to surgical issues. PMID:16387265

Iafrati, Mark D

2005-12-01

281

Hydrothermal oxidation of radioactive combustible waste  

Microsoft Academic Search

A hydrothermal processing system was designed, built and tested for treatment of transuranic combustible material. The operation is performed in a plutonium glovebox. Presented in this paper are results from the study of the hydrothermal oxidation of plutonium and americium contaminated organic wastes. The use of thermal liquefaction, via pyrolysis, to prepare solid materials for hydrothermal processing was tested and

L. A Worl; S. J Buelow; D. M Harradine; R Lanning; D. D Padilla; J. H Roberts; X Shao

2000-01-01

282

Isolated bilateral external iliac vein aplasia.  

PubMed

We present a case of 11-year-old girl with a history of prominent superficial veins over abdomen and thorax since birth. A superficial vein extending from either inguinal region joined in umbilical region and extended up to right supraclavicular region. Other features of Klippel-Trenaunay syndrome like nevus, limb edema were absent. On radiological investigations both external iliac veins could not be visualized and venous return from lower limbs was draining into the right subclavian vein via these superficial veins. Both external iliac veins could not be identified during surgery. PMID:22729029

Onkar, Deepali; Onkar, Prashant; Mitra, Kajal

2012-06-23

283

Hydrothermal Vents: Thar She Blows!  

NSDL National Science Digital Library

In this lesson students will discover how the proximity of hot magma to cold ocean water creates new rocky structures around hydrothermal vents. During this activity, students will demonstrate an understanding of how the processes that result in the formation of hydrothermal vents create new ocean floor and how the transfer of energy effects solids and liquids. This hands-on activity uses online data resources and includes: focus questions, learning objectives, teaching time, audio/visual materials needed, background information, learning procedures, evaluations, extensions, as well as resources and student handouts.

284

Repeated seismic slips recorded in ultracataclastic veins along active faults of the Arima-Takatsuki Tectonic Line, southwest Japan  

NASA Astrophysics Data System (ADS)

Field investigations, combined with meso- and microstructural analyses, reveal that numerous ultracataclastic veins are widely developed within a fault zone (<150 m wide) as simple veins, complex lenses, and networks, along active faults of the Arima-Takatsuki Tectonic Line, southwest Japan. These veins comprise mainly pseudotachylyte-like vein and weakly consolidated to unconsolidated fault gouge that is black, dark-brown, brown, gray, and brownish-red in color. Meso- and microstructural features show that these pseudotachylyte-like and fault gouge veins and networks formed during multiple stages, as earlier veins are generally cut and overprinted by younger veins, indicating that the vein-forming events occurred repeatedly and that ultracataclastic material was injected into networks of faults and fractures in the fault zone. The pseudotachylyte-like and fault gouge veins are characterized by an ultrafine- to fine-grained matrix and angular to subangular fragments of host granitic rocks of various sizes, ranging from submicron to millimeters. SEM-EDS (Scanning Electronic Microscope-Energy Dispersive X-ray) and powder X-ray diffraction analyses show that all the ultracataclastic veins are characterized by crystalline materials composed mainly of quartz and feldspar, similar to the host granitic rocks.The present results support the existing hypothesis that ultrafine- to fine-grained materials formed by comminution can be fluidized and injected rapidly into fracture networks located far from the source fault plane in a solid-fluid-gas system during seismic slip; therefore, such materials provide a record of paleoseismic faulting events that occurred repeatedly within the seismogenic fault zone.

Lin, Aiming; Yamashita, Katsuhiko; Tanaka, Makoto

2013-03-01

285

Sn/SiO2 single crystals growth by the hydrothermal method at high temperatures and pressures  

NASA Astrophysics Data System (ADS)

?-quartz-type materials are of much interest for their use in many applications. The growth of ?-Si1-xSnxO2 single crystals was realized by the hydrothermal method at high temperatures and pressures in a Cr-Ni alloy autoclave. As the mineralizer, a NaOH (1.0?M) solution was used. Nutrient material was prepared from synthetic quartz. Si1-xSnxO2 single crystals with ?-quartz structure were investigated in terms of x-ray diffraction and energy dispersive x-ray analyses. Fourier transform infrared spectroscopy reveals that the optical quality factor, known as the material Q, of Si1-xSnxO2 (x=0.006) single crystals is 3.7×105 and 2.4×105 for wavenumbers of 3410 and 3500?cm-1, respectively.

Miron, I.; Ursu, D. H.; Miclau, M.; Grozescu, I.

2012-05-01

286

The surgical anatomy of varicose veins.  

PubMed

Varicose veins are managed largely in ignorance of important aspects of normal anatomy. In a study of 60 dissected legs the following observations were made: 1. The long saphenous vein--normally lies on the deep fascia enclosed with an envelope of fibrous tissue, which presumably compresses the vein rhythmically on exercise to aid centripetal flow. Thick walled and straight it is never varicose, and, communicating regularly with only one or two of the 60 or so perforating veins in the lower limb, its removal by stripping in operations for varicose veins is unjustifiable. In 18% of legs its femoral part is thin walled, superficial, and sometimes multipartite: in such legs varicose veins are commoner than usual, a point of aetiological interest. 2. The tributaries of the long saphenous vein--below the knee normally drain indirectly into it via an arch vein lying parallel but in a posterior and superficial plane, communicating with it both above and below. To reach it, for instance, the pre-tibial tributaries must cross the long saphenous vein. Varicosities of these tributaries and the arch vein therefore overlie the long saphenous vein and are sometimes attributed to it. Similarly the upper end of the arch vein is often erroneously thought to be the long saphenous vein itself dilated up to an incompetent thigh perforator. 3. Perforating veins--are found all over the limb but mainly at intermuscular septa. Minor ones communicate with small muscle veins, major ones with the main deep veins. The major ones medially above the ankle differ from the rest in running a short (1 cm) and unprotected course from subcutaneous fat to posterior tibial veins through the wide gap between soleus and tibia. They are therefore peculiarly susceptible to damage, and their incompetence is peculiarly direct an its effect, which anatomical weakness may account for the prevalence of medial venous ulceration. PMID:7071165

Thomson, H

287

Irreversibility of the pressure-induced phase transition of quartz and the relation between three hypothetical post-quartz phases  

NASA Astrophysics Data System (ADS)

Our atomistic computer simulations mainly based on classical force fields suggest that the pressure-induced transition from ? quartz to quartz II at 21GPa is irreversible. While quartz II is ferroelastic in principle, the transition itself is coelastic, as the shape of the newly formed crystal is determined by the handedness of ? -quartz. Upon releasing the pressure, our model quartz II remains stable down to 5GPa , where it undergoes an isosymmetric transformation into a less dense polymorph. If the classical force field model of quartz II is compressed quickly to 50GPa , a yet different post-quartz polymorph results, which can probably best be described as an incommensurate modulation of the quartz II structure. We discuss the equation of state and the thermomechanical stability of all four phases. One of the post-quartz phases can be switched elastically by shear between two symmetrically equivalent shapes; however, ? -quartz appears as an intermittent phase.

Campañá, Carlos; Müser, Martin H.; Tse, John S.; Herzbach, Daniel; Schöffel, Philipp

2004-12-01

288

Effect of substitution of fly ash for quartz in triaxial kaolin–quartz–feldspar system  

Microsoft Academic Search

Quartz was progressively replaced by 5, 10 and 15 wt.% fly ash (a byproduct of Indian thermal power plant) in a traditional triaxial porcelain composition consisting of kaolinitic clay, quartz and feldspar. The effects of this substitution upon firing at different temperatures (1150–1300 °C) were investigated by measuring the linear shrinkage, bulk density, porosity and flexural strength. Quantitative estimation of mullite

Kausik Dana; Sukhen Das; Swapan Kumar Das

2004-01-01

289

Chemical potentials of oxygen for fayalite-quartz-lron and fayalite-quartz-magnetite equilibria  

Microsoft Academic Search

The oxygen potentials corresponding to fayalite-quartz-iron (FQI) and fayalite-quartz-magnetite (FQM) equilibria have been\\u000a determined using solid-state galvanic cells: Pt,Fe + Fe2SiO4 + SiO2\\/(Y2O3)ZrO2\\/Fe + \\\\r\\

K. T. Jacob; G. M. Kale; G. N. K. Iyengar

1989-01-01

290

Constraints on Ridge Flank Hydrothermal Fluid Fluxes From Tl Geochemistry  

NASA Astrophysics Data System (ADS)

Hydrothermal circulation of seawater through the ocean crust is a fundamental process in the formation and aging of the ocean crust. It provides a major control on the compositions of the oceans, including the concentrations of many of the geochemical tracers used to decipher past climate variations e.g., 87Sr and 18O. The hydrothermal contribution to ocean chemical budgets depends on the composition and flux of hydrothermal fluids. Heat flow studies indicate that approximately two thirds of convective heat loss occurs at crustal ages greater than 1 Ma by seawater circulation through ridge flanks at significantly lower temperatures than axial black smoker venting. However, fluid fluxes through the ridge flanks are extremely difficult to estimate from heat flow anomalies because the variation in fluid temperature with crustal age is not known. It has previously been demonstrated that thallium (Tl) exhibits different behaviour on and off axis, using samples from Ocean Drilling Program (ODP) Hole 504B. On axis Tl is leached from the sheeted dikes by high-temperature hydrothermal fluids, with no associated fractionation in Tl isotope composition (?205Tl). In contrast, isotopically light Tl is added to the upper crust from seawater during low- temperature off axis circulation. The resulting decrease in Tl concentration and extent of isotopic fractionation with depth can be accounted for using a simple Rayleigh fractionation model. This unique behaviour can be exploited to determine both the axial and off-axial hydrothermal fluid fluxes required to produce the observed shifts in Tl concentration and isotopic composition of the crust by simple mass balance calculations. We present new Multiple Collector-Induced Coupled Plasma Mass Spectrometry (MC-ICPMS) analyses of Tl concentrations and isotopic compositions of upper ocean crust produced at slow- (Macquarie Island), intermediate- (ODP Holes 504B and 896A and the Juan de Fuca Ridge), and fast- (ODP Hole 1256D) spreading rates. Whole rock samples that exhibit different styles of alteration are combined with analyses of vein mineral separates to determine which minerals are responsible for Tl-uptake from seawater. Uppermost basement from ODP Hole 504B has ?205Tl = -20, which given the Tl isotope composition of seawater (?205Tl = -6), indicates that this uptake is associated with a fractionation factor of 0.9986. We combine this fractionation factor with the simple Rayleigh fractionation model to determine the time-integrated fluid flux through the different crustal sections from their profiles of Tl concentration and isotopic composition, to assess the controls on ridge flank fluid fluxes.

Rehkamper, M.; Coggon, R. M.; Teagle, D. A.

2008-12-01

291

Ocean ridge magmatic and hydrothermal geochemical processes  

NASA Astrophysics Data System (ADS)

The ocean ridge system as an interaction site linking the interior of the earth with the lithosphere, biosphere, and hydrosphere is characterized in a critical review of U.S. research from the period 1987-1990. Sections are devoted to magmatic and hydrothermal processes, with particular attention to the chemical variability of MORB, studies of magmatic segmentation in the East Pacific Rise, plans for sampling the Pacific-Antarctic Ridge, regional differences in the extent and pressure of melting, the diversity of oceanic plutonic rocks, observations of active hydrothermal venting, the composition of hydrothermal fluids, models of hydrothermal circulation, and the mineralogy and geochemistry of hydrothermal deposits. A comprehensive bibliography is provided.

Klein, Emily M.

292

Hydrothermal alteration in research drill hole Y-3, Lower Geyser Basin, Yellowstone National Park, Wyoming  

USGS Publications Warehouse

Y-3, a U.S. Geological Survey research diamond-drill hole in Lower Geyser Basin, Yellowstone National Park, Wyoming, reached a depth of 156.7 m. The recovered drill core consists of 42.2 m of surficial (mostly glacial) sediments and two rhyolite flows (Nez Perce Creek flow and an older, unnamed rhyolite flow) of the Central Plateau Member of the Pleistocene Plateau Rhyolite. Hydrothermal alteration is fairly extensive in most of the drill core. The surficial deposits are largely cemented by silica and zeolite minerals; and the two rhyolite flows are, in part, bleached by thermal water that deposited numerous hydrothermal minerals in cavities and fractures. Hydrothermal minerals containing sodium as a dominant cation (analcime, clinoptilolite, mordenite, Na-smectite, and aegirine) are more abundant than calcium-bearing minerals (calcite, fluorite, Ca-smectite, and pectolite) in the sedimentary section of the drill core. In the volcanic section of drill core Y-3, calcium-rich minerals (dachiardite, laumontite, yugawaralite, calcite, fluorite, Ca-smectite, pectolite, and truscottite) are predominant over sodium-bearing minerals (aegirine, mordenite, and Na-smectite). Hydrothermal minerals that contain significant amounts of potassium (alunite and lepidolite in the sediments and illitesmectite in the rhyolite flows) are found in the two drill-core intervals. Drill core y:.3 also contains hydrothermal silica minerals (opal, [3-cristobalite, chalcedony, and quartz), other clay minerals (allophane, halloysite, kaolinite, and chlorite), gypsum, pyrite, and hematite. The dominance of calcium-bearing hydrothermal minerals in the lower rhyolitic section of the y:.3 drill core appears to be due to loss of calcium, along with potassium, during adiabatic cooling of an ascending boiling water.

Bargar, Keith E.; Beeson, Melvin H.

1985-01-01

293

Hydrothermally altered and fractured granite as an HDR reservoir in the EPS-1 borehole, Alsace,  

SciTech Connect

As part of the European Hot Dry Rocks Project, a second exploration borehole, EPS-1, has been cored to a depth of 2227 m at Soultz-sous-Forets (France). The target was a granite beginning at 1417 m depth, overlain by post-Paleozoic sedimentary cover. Structural analysis and petrographic examination of the 800-m porphyritic granite core, have shown that this rock has undergone several periods of hydrothermal alteration and fracturing. More than 3000 natural structures were recorded, whose distribution pattern shows clusters where low-density fracture zones (less than 1 per meter) alternate with zones of high fracture density (more than 20 per meter). Vein alteration, ascribed to paleohydrothermal systems, developed within the hydrothermally altered and highly fractured zones, transforming primary biotite and plagioclase into clay minerals. One of these zones at 2.2 km depth produced a hot-water outflow during coring, indicating the existence of a hydrothermal reservoir. Its permeability is provided by the fracture network and by secondary porosity of the granitic matrix resulting from vein alteration. This dual porosity in the HDR granite reservoir must be taken into account in the design of the heat exchanger, both for modeling the water-rock interactions and for hydraulic testing.

Genter, A.; Traineau, H.

1992-01-01

294

Hepatic vein obstruction (Budd-Chiari)  

MedlinePLUS

Hepatic vein obstruction prevents blood from flowing out of the liver and back to the heart. This blockage can cause liver damage. Obstruction of this vein can be caused by a tumor or growth pressing on the vessel, or ...

295

Retinal Vein Occlusion: Current Treatment  

Microsoft Academic Search

Retinal vein occlusion (RVO) is a pathology noted for more than 150 years. Although a lot has been written on the matter, it is still a frequent condition with multifactorial etiopathogenesis with many unclear aspects. The RVO pathogenesis has varied systemic and local implications that make it difficult to elaborate treatment guidelines. The management of the patient with RVO is

Rosangela Lattanzio; Ana Torres Gimeno; Maurizio Battaglia Parodi; Francesco Bandello

2011-01-01

296

[Complications in varicose vein operations].  

PubMed

Although operations on varicous veins are regarded as easy and low-risk, severe complications with the involvement of arteries, veins and nerves can occur during the course of such operations and, in reconstruction, demand the whole spectrum of vascular surgery. Therefore, surgeons operating on varicous veins and on out-patients should possess sufficient experience in vascular surgery and be able to admit their patients to a centre of vascular surgery in the case of severe complications without unnecessary loss of time. Beside a perfectly done operation sufficient preoperative diagnostic examinations and postoperative care of the patient have to be claimed. The treatment of varicous veins in a hospital must be possible also in the future. The extent of the procedure is usually greater during stationary treatment and bilateral operations are feasible. Therefore, from the economic point of view, a stationary assignment for a few days does not seem more expensive than several single operations with subsequent outpatient treatment and repeated diagnostic examinations in ambulatory settings. PMID:11503468

Balzer, K

2001-07-01

297

Magmatic intrusions and hydrothermal systems  

Microsoft Academic Search

This dissertation investigates the possible role of hydrothermally driven ground-water outflow in the formation of fluvial valleys on Mars. Although these landforms have often been cited as evidence for a past warmer climate and denser atmosphere, recent theoretical modeling precludes such climatic conditions on early Mars when most fluvial valleys formed. Because fluvial valleys continued to form throughout Mars' geological

Virginia Claire Gulick

1993-01-01

298

Hydrothermal alteration facies within the intrusive-hosted Salave gold prospect, NW Spain  

SciTech Connect

The Salave gold prospect occurs within an Hercynian granodioritic complex intruding Cambro-Ordovician metasediments and a heterogeneous gabbroic body. Mineralization consists mostly of disseminated and veinlet pyrite, arsenopyrite, molybdenite, stibnite, and lesser sphalerite associated with a zoned sequence of hydrothermal alteration. Gold occurs as free particles and/or intergrown with the sulfides. Mathematical appraisal of analytical data suggests that the hydrothermal alteration resulted from largely isochemical redistribution processes imposed on the mineralogy of the host granodiorite by influxes of sporadically boiling fluids rich in CO/sub 2/. Hydrothermal alteration is described in terms of a zonal sequence inward from unaltered host rock through (1) chlorite-sericite alteration-(2) propylitic to advanced propylitic alterations-(3)albitites-(4) an auriferous (greater than or equal to 1g/t Au) sericite-carbonate-albite-(+/-)quartz-sulfide cataclastic facies. The zonation corresponds to increasing carbonatization, sericitization, albitization, desilification, and destruction of the original igneous texture. Aventurine alteration is common and is thought to be the product of late stage hydrothermal oxidizing conditions. Potassic alteration in the form of K-feldspar or biotite was occasionally observed.

Harris, M.

1985-01-01

299

A comparison of fluids causing post-depositional hydrothermal alteration in Archaean basement granitoids and the Witwatersrand Basin  

Microsoft Academic Search

Summary Some Archaean granitoids occurring along the north-western and western edge of what is classically known as the Witwatersrand Basin have been hydrothermally altered in two different styles. Both styles - pervasive and vein-controlled alteration - are characterised by sulphide mineralisation as well as by thorium-, uranium-, gold- and REE-rich nodules of carbonaceous material (fly-speck carbon). All of the granitoids

R. Klemd; Universitfit Bremen

1999-01-01

300

Syn-metamorphic gold mineralisation, Invincible Vein, NW Otago Schist, New Zealand  

NASA Astrophysics Data System (ADS)

The Invincible Vein fills a fault zone which strikes northeast and dips steeply southeast in the lower Rees Valley, NW Otago. The vein cuts north striking foliation in lower greenschist facies Otago Schist. Structures associated with the fault zone are both brittle and ductile, and the fault zone has had a complex history of post-mineralisation reactivation. Mineralised vein material filling parts of the fault zone consist of quartz, albite, muscovite, chlorite, calcite, pyrite, arsenopyrite and minor gold. These minerals have been strained and locally recrystallised during ductile deformation. Fluid inclusion homogenisation temperatures (140 175°C) and ice melting temperatures (0 to 1°C) indicate that the mineralising fluid was low salinity, low CO2 water with a density between 0.88 and 0.93 g/cm3. Arsenopyrite geothermometry implies a temperature of mineralisation of 370 ± 70°C. Mineralisation pressure lay between 2 and 5 kbar. Mineralisation pressure-temperature conditions and mineralogy are essentially the same as for metamorphism of the host schist. Vein calcite oxygen isotope ratios (+12 to +15 per mil) are similar to host schist values. Carbon isotope ratios of vein calcite (- 3 to -5 per mil) are distinctly different from ratios in host schist (-7 to -10 per mil). Elevated vein Cr contents, and isotopically depleted carbon data, are consistent with some degree of equilibration with metavolcanic rocks. It is inferred that metavolcanic rocks of the underlying Aspiring Terrane were a significant source for mineralising fluid and metals. Invincible mineralisation occurred in the latter stages of metamorphism, and is the earliest recognised gold-bearing vein system in the Otago Schist.

Hay, R.; Craw, D.

1993-04-01

301

Minerals produced during cooling and hydrothermal alteration of ash flow tuff from Yellowstone drill hole Y-5  

USGS Publications Warehouse

A rhyolitic ash-flow tuff in a hydrothermally active area within the Yellowstone caldera was drilled in 1967, and cores were studied to determine the nature and distribution of primary and secondary mineral phases. The rocks have undergone a complex history of crystallization and hydrothermal alteration since their emplacement 600,000 years ago. During cooling from magmatic temperatures, the glassy groundmass underwent either devitrification to alkali feldspar + ??-cristobalite ?? tridymite or granophyric crystallization to alkali feldspar + quartz. Associated with the zones of granophyric crystallization are prismatic quartz crystals in cavities similar to those termed miarolitic in plutonic rocks. Vapor-phase alkali feldspar, tridymite, magnetite, and sporadic ??-cristobalite were deposited in cavities and in void spaces of pumice fragments. Subsequently, some of the vapor-phase alkali feldspar crystals were replaced by microcrystalline quartz, and the vapor-phase minerals were frosted by a coating of saccharoidal quartz. Hydrothermal minerals occur primarily as linings and fillings of cavities and fractures and as altered mafic phenocrysts. Chalcedony is the dominant mineral related to the present hydrothermal regime and occurs as microcrystalline material mixed with various amounts of hematite and goethite. The chalcedony displays intricate layering and was apparently deposited as opal from silica-rich water. Hematite and goethite also replace both mafic phenocrysts and vapor-phase magnetite. Other conspicuous hydrothermal minerals include montmorillonite, pyrite, mordenite, calcite, and fluorite. Clinoptilolite, erionite, illite, kaolinite, and manganese oxides are sporadic. The hydrothermal minerals show little correlation with temperature, but bladed calcite is restricted to a zone of boiling in the tuff and clearly was deposited when CO2 was lost during boiling. Fractures and breccias filled with chalcedony are common throughout Y-5 and may have been produced by rapid disruption of rock caused by sudden decrease of fluid pressure in fractures, most likely a result of fracturing during resurgent doming in this part of the Yellowstone caldera. The chalcedony probably was deposited as opal or ??-cristobalite from a pre-existing silica floc that moved rapidly into the fractures and breccias immediately after the sudden pressure drop. ?? 1978.

Keith, T. E. C.; Muffler, L. J. P.

1978-01-01

302

Hydrothermal synthesis of amino acids  

SciTech Connect

This study presents further evidence that amino acids can be synthesized rapidly in hydrothermal solutions from reactants that may have been present in primitive environments. Aqueous NH[sub 4]HCO[sub 3] solutions were reacted with C[sub 2]H[sub 2], H[sub 2], and O[sub 2] (formed in situ from CaC[sub 2], Ca, and H[sub 2]O[sub 2]) at 200-275[degrees]C over 0.2-2 h periods to synthesize several amino acids and abundant amines. These amino acid and amine producing reactions were not observed to occur below 150[degrees]C. Amino acids and amines also were synthesized at 210[degrees]C from solutions of NH[sub 4]OH, HCHO, NaCN, and H[sub 2]. When NH[sub 4]OH was replaced by NH[sub 4]HCO[sub 3], the syntheses predominantly confirmed the recent results of Hennet et al. (1992). Additionally, amino acids and amines were observed to form by reactions among NH[sub 4]OH, HCHO, and H[sub 2] at hydrothermal conditions, essentially confirming the results of Fox and Windsor (1970). Inclusion of both carbonate and O[sub 2] in these latter solutions greatly enhanced the production rate of amino acids. The amines synthesized hydrothermally could be significant if they are precursors in the amino acid syntheses either at hydrothermal or later at lower temperatures. These observations provide additional input to the current questions of synthesis, stability, and decomposition of amino acids at hydrothermal conditions, and their possible relevance to the origin of life.

Marshall, W.L. (Oak Ridge National Lab., TN (United States))

1994-05-01

303

An interesting clinical case: variant of the cephalic vein emptying into the internal jugular vein.  

PubMed

This case report describes a 45-year-old patient who was referred to our center for surgical creation of long-term vascular access. Angiographic mapping revealed the left cephalic vein draining directly into the internal jugular vein rather than the axillary vein. The patient was scheduled for an ulnar artery to cephalic vein fistula. PMID:22780845

Lum, Craig; Ladenheim, Eric D

2012-07-11

304

Isotope geochemistry of hydrothermal alteration in East of Esfahan, Central Iran  

NASA Astrophysics Data System (ADS)

In the Cenozoic magmatic belt of Central Iran, the Eocene volcanics and pyroclastics from the East of Esfahan underwent extensive hydrothermal alteration. The Eocene volcanics composed mostly of andesite lava and tuffs have been altered. The survey area is laterally zoned from an inner quartz-sericite alteration zone to an outer propylitic zone. Quartz-sericite alteration is predominant (>95%), but smaller zones of alunite-jarosite and silicified zones are present and superimposed onto a quartz-sericite alteration. In the quartz-sericite zone all altered rocks are light grayish to whitish in color and porphyritic with aphanitic groundmass. Concentrations of alunite and jarosite veinlets and stockworks are dispersed irregularly in this zone. Alunite and jarosite occur also as coatings on fractured rocks. All types of alunite occurrences are brick-red, cream, white and buff in colors, while jarosite is brown to rusty in colors. To verify, chemical composition of alunite and jarosite were identified by X-ray diffraction in mineral assemblages. Major alteration zones show inclusions of propylite, quartz sericite, advanced argillic and silicified zones. These alunites are mainly porcelaneous and their compositions show a solid solution between alunite and jarosite. In alteration zones, the mineral assemblage is characterized by alunite-jarosite + quartz + sericite + alkali feldspars + chlorite ± turquoise ± barite ± iron oxides. There are numerous alunite and jarosite occurrences, mainly as veinlets, in parts of the advanced argillic zone. Alunite ?18O and ? D values range from -1.76 to 8.81‰ and from -52.86 to -129.26‰ respectively. Field observations, mineralogical evidence and results from light element stable isotope data (?18O, ? D and ?34S); indicate that in this area alunitization is supergene in origin.

Taghipour, Sedigheh; Taghipour, Batoul

2010-05-01

305

Splenic vein aneurysm: a rare clinical entity.  

PubMed

A 52-year-old man presented with complaints of generalized malaise along with pain in left hypochondrium and diarrhea. The color Doppler and subsequent contrast enhanced CT scan revealed changes of portal hypertension and saccular dilatation of splenic vein along with partial thrombus in portal vein and superior mesenteric vein. PMID:22733582

Gupta, Amit; Kumar Singhal, Madhu; Maheshwarappa, Ravishanker Pillenahalli; Meena, Mangi Lal

2012-06-26

306

Evolution and paragenetic context of low ?D hydrothermal fluids from the Panasqueira WSn deposit, Portugal: new evidence from microthermometric, stable isotope, noble gas and halogen analyses of primary fluid inclusions  

Microsoft Academic Search

The evolution, paragenetic context and origin of remarkably low ?D hydrothermal fluids from the Hercynian Panasqueira W-Sn-Cu(Ag) deposit have been investigated through a combined microthermometric, stable isotope, halogen and noble gas fluid inclusion study. Large variations in ?D between ?60 ‰ and ?134‰ have been observed in primary fluid inclusions from growth zones in a quartz crystal (Pa66) paragenetically constrained

D. A Polya; K. A Foxford; F. Stuart; A. Boyce; A. E Fallick

2000-01-01

307

Diversity of primary CL textures in quartz from porphyry environments: implication for origin of quartz eyes  

NASA Astrophysics Data System (ADS)

Porphyry-style mineralization is related to the intrusion and crystallization of small stocks, which can be of different compositions (from intermediate to felsic) and can intrude into different host rocks (from magmatic to sedimentary). We used cathodoluminescence and electron probe microanalysis to study the internal textures of more than 300 quartz eyes from six porphyry deposits, Panguna (Papua New Guinea), Far Southeast porphyry (Philippines), Batu Hijau (Indonesia), Antapaccay (Peru), Rio Blanco (Chile) and Climax (USA). Significant diversity of the internal textures in quartz eyes was revealed, sometimes even within a single sample. Quartz grains with Ti-rich cores surrounded by Ti-poor mantles were found next to the grains showing the opposite Ti distribution or only slight Ti fluctuations.We propose that diversity of the internal patterns in quartz eyes can actually reflect in situ crystallization history, and that prolonged crystallization after magma emplacement under conditions of continuous cooling can account for the observed features of internal textures. Formation of quartz eyes begins at high temperatures with crystallization of high titanium Quartz 1, which as the melt becomes more and more evolved and cooler, is overgrown by low Ti Quartz 2. Subsequent fluid exsolution brings about dramatic change in the melt composition: OH - , alkalis and other Cl-complexed elements partition into the fluid phase, whereas Ti stays in the melt, contributing to a rapid increase in Ti activity. Separation of the fluid and its further cooling causes disequilibrium in the system, and the Quartz 2 becomes partially resorbed. Exsolution of the fluid gradually builds up the pressure until it exceeds the yield strength of the host rocks and they then fracture. This pressure release most likely triggers crystallization of Quartz 3, which is higher in Ti than Quartz 2 because Ti activity in the melt is higher and pressure of crystallization is lower. As a result of the reaction between the exsolved fluid and quartz a new phase, a so called `heavy fluid' forms. From this phase Quartz 4 crystallizes. This phase has extremely high metal-carrying capacity, and may give a rise to mineralizing fluids. Finally, on the brink of the subsolidus stage, groundmass quartz crystallizes. Prolonged crystallization under conditions of continuous cooling accounts better for the diversity of CL textures than crystallization in different parts of a deep magma chamber. It is also in a better agreement with the existing model for formation of porphyry-style deposits.

Vasyukova, O. V.; Kamenetsky, V. S.; Goemann, K.; Davidson, P.

2013-10-01

308

Mineralogical, fluid inclusion, and stable isotope constraints on mechanisms of ore deposition at the Samgwang mine (Republic of Korea)—a mesothermal, vein-hosted gold–silver deposit  

Microsoft Academic Search

The Samgwang mine is located in the Cheongyang gold district (Cheonan Metallogenic Province) of the Republic of Korea. It\\u000a consists of eight massive, gold-bearing quartz veins that filled NE- and NW-striking fractures along fault zones in Precambrian\\u000a granitic gneiss of the Gyeonggi massif. Their mineralogy and paragenesis allow two separate vein-forming episodes to be recognized,\\u000a temporally separated by a major

Bong Chul Yoo; Hyun Koo Lee; Noel C. White

2010-01-01

309

Mineralogical, fluid inclusion, and stable isotope constraints on mechanisms of ore deposition at the Samgwang mine (Republic of Korea)---a mesothermal, vein-hosted gold-silver deposit  

Microsoft Academic Search

The Samgwang mine is located in the Cheongyang gold district (Cheonan Metallogenic Province) of the Republic of Korea. It consists of eight massive, gold-bearing quartz veins that filled NE- and NW-striking fractures along fault zones in Precambrian granitic gneiss of the Gyeonggi massif. Their mineralogy and paragenesis allow two separate vein-forming episodes to be recognized, temporally separated by a major

Bong Chul Yoo; Hyun Koo Lee; Noel C. White

2010-01-01

310

Adsorption of goethite onto quartz and kaolinite  

USGS Publications Warehouse

The adsorption of colloidal goethite onto quartz and kaolinite substrates has been studied as a function of pH and NaCl concentration. Goethite adsorption was measured quantitatively by Fourier-transform infrared spectroscopy. The results indicate that adsorption onto both substrates is due primarily to coulombic forces; however, the pH dependence of adsorption is very different for the two substrates. This is explained by the fact that the surface charge on quartz is entirely pH-dependent, while kaolinite has surface faces which carry a permanent negative charge. Adsorption of goethite on to kaolinite increases markedly with increasing NaCl concentration, while adsorption onto quartz is relatively independent of NaCl concentration. This can be explained by the influence of NaCl concentration upon the development of surface charge on the substrates. A method is described for separating surface-bound goethite from free goethite.

Goldberg, M. C.; Weiner, E. R.; Boymel, P. M.

1984-01-01

311

Basic Material Quartz and Related Innovations  

NASA Astrophysics Data System (ADS)

Although material quartz is of scientific interest in its own right, its volume of usage and variety of applications dictate its technological importance.The technological prominence of ?-quartz stems largely from the presence of piezoelectricity, combined with extremely low acoustic loss. It was one of the minerals with which the Brothers Curie first established the piezoelectric effect in 1880. In the early 1920s, the quartz resonator was first used for frequency stabilization. Temperature-compensated orientations (the AT and BT shear cuts) were introduced in the 1930s, and assured the technology's success. By the late 1950s, growth of cultured bars became commercially viable, and in the early 1970s, cultured quartz use for electronic applications first exceeded that of the natural variety. The discovery of cuts that addressed compensation of stress and temperature transient effects occurred in the 1970s, and led to the introduction of compound cuts such as the SC, which hasboth a zero temperature coefficient of frequency, and is simultaneously stress-compensated [1-5]. Between 109 and 1010 quartz units per year were produced by 2000 at frequencies from below 1 kHz to above 10 GHz. Categories of application include resonators, filters, delay lines, transducers, sensors, signal processors, and actuators. Particularly noteworthy are the bulk- and surface-wave resonators; their uses span the gamut from disposable timepieces to highest precision oscillators for position-location, and picosecond timing applications. Stringent high-shock and high-pressure sensor operations are also enabled. Table 2.1 shows the major applications of quartz crystals. These applications are discussed subsequently in greater detail. For general background and historical developments, see [1,6-11].

Ballato, A.

312

Use of autogenous saphenous vein as a conduit for mesenterico-left portal vein bypass.  

PubMed

The authors describe a case of extrahepatic portal vein (EHPV) thrombosis and portal hypertension treated with a variant of mesenterico-left portal vein bypass (MLPVB) or Rex shunt. In this case, a segment of autogenous greater saphenous vein was used to bridge the distance between the left gastric vein inflow and the left portal vein. Use of such nontraditional conduit in similar circumstances may expand the application of portal revascularization/decompression procedures in treating these patients. PMID:17560237

Query, Julie A; Sandler, Anthony D; Sharp, William J

2007-06-01

313

Etiology and Management of Branch Retinal Vein Occlusion  

Microsoft Academic Search

Retinal vein occlusion is one of the vascular disorders affecting vision. Branch retinal vein occlusion and central retinal vein occlusion are the two basic types of vein occlusion. Branch retinal vein occlusion is three times more common than central retinal vein occlusion and is second only to diabetic retinopathy as the most common retinal vascular cause of visual impairment. The

Sadaf Hamid; Sajid Ali Mirza; Ishrat Shokh

314

Model of the porphyry copper and polymetallic vein family of deposits - Applications in Slovakia, Hungary, and Romania  

USGS Publications Warehouse

A tectonic model useful in estimating the occurrence of undiscovered porphyry copper and polymetallic vein systems has been developed. This model is based on the manner in which magmatic and hydrothermal fluids flow and are trapped in fault systems as far-field stress is released in tectonic strain features above subducting plates (e.g. strike-slip fault systems). The structural traps include preferred locations for stock emplacement and tensional-shear fault meshes within the step-overs that localize porphyry- and vein-style deposits. The application of the model is illustrated for the porphyry copper and polymetallic vein deposits in the Central Slovakian Volcanic Field, Slovakia; the Ma??tra Mountains, Hungary; and the Apuseni Mountains, Romania.

Drew, L. J.

2003-01-01

315

Management of varicose veins and venous insufficiency.  

PubMed

Chronic venous disease, reviewed herein, is manifested by a spectrum of signs and symptoms, including cosmetic spider veins, asymptomatic varicosities, large painful varicose veins, edema, hyperpigmentation and lipodermatosclerosis of skin, and ulceration. However, there is no definitive stepwise progression from spider veins to ulcers and, in fact, severe skin complications of varicose veins, even when extensive, are not guaranteed. Treatment options range from conservative (eg, medications, compression stockings, lifestyle changes) to minimally invasive (eg, sclerotherapy or endoluminal ablation), invasive (surgical techniques), and hybrid (combination of ?1 therapies). Ms L, a 68-year-old woman with varicose veins, is presented. She has had vein problems over the course of her life. Her varicose veins recurred after initial treatment, and she is now seeking guidance regarding her current treatment options. PMID:23268520

Hamdan, Allen

2012-12-26

316

Transpressive ductile flow and oblique ramping of lower crust in a two-sided orogen: Insight from quartz grain-shape fabrics near the Alpine fault, New Zealand  

Microsoft Academic Search

The three-dimensional (3-D) grain-shape fabric (GSF) of deformed quartz veins was measured in 30 samples from the hanging wall of the oblique-slip Alpine fault in the central Southern Alps, New Zealand. These record aspects of the neotectonic strain experienced by lower crustal rocks in the Pacific Plate as they were transported through a two-sided orogen. Deformation was nonsteady state: transpression

Timothy A. Little

2004-01-01

317

Septic postpartum ovarian vein thrombosis.  

PubMed

This report describes the clinical findings and outcome of a patient suffering from septic postpartum ovarian vein thrombosis. Treatment modalities are well described and range from hysterectomy and thrombectomy to the use of vena cava filters in combination with anticoagulation and antibiotics. Defervescence with a combination infusion of tissue plasminogen and heparin were used. This treatment approach has been found particularly successful in cases of ilio-femoral, hepatic, renal and vena caval thromboses. PMID:12370730

Rajab, Khalil E; Malik, Neelam; Skirman, Jonathan H

2002-09-01

318

Current treatment of varicose veins  

Microsoft Academic Search

Opinion statement  Varicose veins (VVs) of the lower limbs are a common complaint that can take many forms, ranging from a nonpathologic condition\\u000a to an invalidating chronic disorder. When they have not been neglected, uncomplicated VVs have often been treated by sclerotherapy\\u000a or surgery, with variably successful results. Currently, the best way of assessing VVs has been to carry out routine

François Becker

2006-01-01

319

Method of Chemically Polishing Quartz Crystal Blanks.  

National Technical Information Service (NTIS)

The general object of this invention is to provide a method of chemically polishing quartz crystal blanks. A more specific object is to provide such a method wherein the resulting chemically polished blanks will be suitable for use in resonators and oscil...

R. J. Brandmayr

1985-01-01

320

Friction of Quartz in High Vacuum.  

National Technical Information Service (NTIS)

The purpose of this investigation was to determine the fundamental factors controlling the frictional properties of quartz surfaces, with emphasis on the effects of surface cleanliness. Ultra-high vacuums (to 10 to the minus 10th power torr) and high temp...

L. G. Bromwell

1966-01-01

321

UNDERGROUND DEFORMATION MEASUREMENT USING NEW QUARTZ  

Microsoft Academic Search

This work demonstrates the usage of two new quartz instruments, which are a tiltmeter and an extensometer that we developed lately to measure with high accuracy deformations of structures, volcanoes, tunnels, and ground surface. The stability of an underground quarry, near Paris in France was the subject of the study. The deformation of the quarry under different cases of loading

INSTRUMENTS Bassam Saleh

322

Aqueous Wetting Films on Fused Quartz  

Microsoft Academic Search

Using an image analyzing interferometer, IAI, the interfacial characteristics of an isothermal constrained vapor bubble, CVB, in a quartz cuvette were studied as a precursor to heat transfer research. The effects of pH and electrolyte concentration on the meniscus properties (curvature and adsorbed film thickness) and the stability of the aqueous wetting films were evaluated. The surface potential in the

Rene Reyes Mazzoco; Peter C. Wayner

1999-01-01

323

From hertz to gigahertz - Quartz oscillators  

Microsoft Academic Search

Different types of quartz oscillators are described, including temperature-compensated, frequency-controlled, metrological, and surface wave oscillators. Their applications as frequency standards and sensors and their utilization in clocks and watches are discussed together with their performance. Possible future developments leading to improvements in long and short term stability, frequency, and sensitivity (or insensitivity) to external factors such as temperature, pressure, and

J. J. Gagnepain; J. Uebersfeld

1976-01-01

324

Quartz analog watch with perpetual calendar  

Microsoft Academic Search

The Caliber ETA 252.411 with perpetual calendar, which is similar in dimensions and display to classic quartz watch movements, is described. The main characteristics are: the date display in the window is always correct (until 28 Feb. 2100); the change of time zones is operated without losing minute and second by means of a date correction at each midnight passage;

Eric Favre; Pierre Schmidli; Bruno Erni

1992-01-01

325

The Standardization of Quartz-Crystal Units  

Microsoft Academic Search

Quartz-crystal units have been thrust into enormous production before their engineering treatment as circuit elements has become formalized. As a result, crystals are specified in terms of the desired performance of the set which is to use them rather than in terms of their own properties. The intrinsic properties of crystal units form the ideal basis for their specification. When

K. S. Van Dyke

1945-01-01

326

Historical review of quartz crystal growth  

Microsoft Academic Search

The history of quartz crystal growth is reviewed from the origin to the industrialization. The developing process of growth techniques is divided into the following three stages: (1) The fundamental work based on the mineralogical genetic view point, which was performed in Italy during the end of the 19th to the beginning of the 20th centuries. (2) The works to

Fumiko Iwasaki; Hideo Iwasaki

2002-01-01

327

Quartz crystal microbalance immunosensors for environmental monitoring  

Microsoft Academic Search

This paper presents discussion of quartz crystal microbalance (QCM) immunosensors for environmental monitoring. Factors limiting the practical application of antibodies to analytical problems are also presented. Among several candidates for the QCM immunosensor device, selected QCM devices and oscillating circuits were tested thoroughly and developed to obtain highly stable and sensitive frequency signals. The biointerface of QCM immunosensor was designed

Shigeru Kurosawa; Jong-Won Park; Hidenobu Aizawa; Shin-Ichi Wakida; Hiroaki Tao; Kazuhiko Ishihara

2006-01-01

328

Commercial quartz crystal microbalances – theory and applications  

Microsoft Academic Search

A tutorial review article on the quartz crystal microbalance (QCM) is presented. Following an introduction to the theory and commercial aspects of the QCM the authors present a summary of recent and important prior research in each of the different areas of analytical interest in the QCM.

C. K. O’Sullivan; G. G. Guilbault

1999-01-01

329

Frequency interference between two quartz crystal microbalances  

Microsoft Academic Search

Multichannel quartz crystal microbalances (MQCM) are very attractive for biosensor applications because these devices can be miniaturized using microelectromechanical systems micromachining technology, leading to substantial reductions in cost, diagnostic time, and sample volumes. However, the miniaturization also brings about frequency interference between adjacent microbalances and the measuring accuracy will thus be affected by the extent of frequency coupling. In this

Feng Shen; Kwok Hong Lee; Sean J. O'Shea; Pin Lu; Teng Yong Ng

2003-01-01

330

Quartz Crystal Microbalance for Medical Diagnostics  

Microsoft Academic Search

The research is to develop techniques to improve disease detection using a Quartz Crystal Microbalance (QCM) to induce and detect the Bond Rupture of the antibody-antigen bonds. In this paper a short introduction to QCM is presented and the techniques of how it is used to detect the bond rupture are reviewed. Issues involved in the detection such as frequency

Matthew J. van der Werff; Yong J. Yuan; W. L. Xu

2005-01-01

331

Quartz Dual Axis Rate Sensor (QDARS)  

Microsoft Academic Search

GyroChip ® Quartz MEMS sensors have been used in a wide variety of applications from high volume automotive stability control and rollover prevention systems, to tactical grade Inertial Navigation Systems integrated with Global Positioning Systems (INS\\/GPS). This paper focuses on a recent addition to this range of sensors by introducing an inertial rate sensor capable of sensing angular rate about

Randall Jaffe; Steven Simshauser; Asad M. Madni

2006-01-01

332

Qd: A Quartz Declinometer of Classic Type.  

National Technical Information Service (NTIS)

A declinometer with quartz fibre suspension is described. The magnet is a bar with the mirror fixed on the plane face and the magnet is firmly attached to the stirrup which can be clamped during transport. The theory of the suspended system is described i...

E. K. Lauridsen

1981-01-01

333

Quartz Liner Tube Inside Tube Furnace  

NSDL National Science Digital Library

This site, from the American Physical Society, gives a brief description of a furnace at Kansas State University that is used in semiconductor research. An image shows heat radiation from the quartz liner in this furnace, which is used in silicon-doping experiments.

2008-09-10

334

Models of hydrolytic weakening in quartz  

Microsoft Academic Search

Three models of the weakening of quartz by small amounts of water are described and analysed. Attention is confined to the glide of dislocations caused by a double-kink nucleation process. The structure of a double kink on a basal 60° dislocation is described and its formation energy estimated using a short-range interaction potential. The same potential was used to give

M. Heggie; R. Jones

1986-01-01

335

R. F. Sputtered Quartz Dielectric Capacitors.  

National Technical Information Service (NTIS)

Radio frequency sputtering was used to deposit quartz films for use as the dielectric in thin film capacitors. Experiments are described in which the performance of the capacitors was assessed. Capacitances up to 250 microfarads/sq m were achieved with re...

B. J. Franklin

1969-01-01

336

Fused quartz substrates for microchip electrophoresis  

SciTech Connect

A fused quartz microchip is fabricated to perform capillary electrophoresis of metal ions complexed with 8-hydroxyquinoline-5-sulfonic acid (HQS). The channel manifold on the quartz substrate is fabricated using standard photolithographic, etching, and deposition techniques. By incorporating a direct bonding technique during the fabrication of the microchip, the substrate and cover plate can be fused together below the melting temperature for fused quartz. To enhance the resolution for the separation, the electroosmotic flow is minimized by covalently bonding polyacrylamide to the channel walls. A separation length of 16.5 mm and separation field strength of 870 V/cm enable separations to be performed in {<=}15 s. By increasing the concentration of HQS from 5 mM to 20 mM, the separation efficiency improves by approximately 3 times. The low background signal from the fused quartz substrate results in mass detection limits of 85, 61, and 134 amol and concentration detection limits of 46, 57, and 30 ppb for Zn, Cd, and Al, respectively. 30 refs., 6 figs., 2 tabs.

Jacobson, S.C.; Moore, A.W.; Ramsey, J.M. [Oak Ridge National Lab., TN (United States)

1995-07-01

337

Mystery of the Megaplume: Hydrothermal Vent Chemistry  

NSDL National Science Digital Library

In this lesson, students will investigate hydrothermal vents to see how the chemistry of the water they emit provides clues to the location of the vents. They should be able to describe hydrothermal vents and characterize vent plumes in terms of physical and chemical properties; describe data gathering operations in which a towed instrument package ("tow-yo") measures conductivity, temperature, and depth; and interpret temperature anomaly data to recognize a plume emanating from a hydrothermal vent.

338

Extensions of the quartz-crystal-microbalance technique  

Microsoft Academic Search

The high mass sensitivity of the quartz-crystal microbalance is explained by the very high acceleration of the particles on the surface of the quartz resonators. The sensing properties of quartz resonators in contact with a solid, liquid or gas medium are explained within the energy-transfer model. The use of the quartz-crystal microbalance is extended up to the Curie point (573

V. M Mecea; J. O Carlsson; R. V Bucur

1996-01-01

339

A study of adsorption of dodecylamine on quartz surface using quartz crystal microbalance with dissipation  

Microsoft Academic Search

In this study the adsorption characteristics of dodecylamine hydrochloride (DACL) on quartz surface have been investigated using a high sensitivity surface characterization technique referred to as quartz crystal microbalance with dissipation (QCM-D) technique in conjunction with zeta-potential and FTIR analyses. The experimental results have demonstrated the versatility and accuracy of the QCM-D for surface adsorption characterization and for the first

J. Kou; D. Tao; G. Xu

2010-01-01

340

Fabrication of micromachined quartz-crystal resonators using surface activated bonding of silicon and quartz wafer  

Microsoft Academic Search

In this paper, we present the fabrication and the characterization of the cantilever-shaped quartz crystal resonator for high sensitive force sensing. Fabrication process employs low-temperature plasma-activated bonding of silicon to quartz wafer using N2 plasma. Fabricated resonator have thickness of 2~20 mum, fundamental resonant frequency of thickness-shear mode of 76-720 MHz. The 20-mum-thick cantilever exhibits a high quality factor of

Akihiro Takahashi; Takahito Ono; Yu-Ching Lin; M. Esashi

2006-01-01

341

Preservation of arm veins for arterial reconstruction.  

PubMed

The results of surgery for lower extremity salvage have improved steadily over the past decade. One of the principles accounting for this advance is the preferential use of autogenous veins for peripheral bypass surgery. Nonautogenous and prosthetic grafts to the infrageniculate (below knee) level have patency rates significantly lower than autogenous bypasses. Currently, the technical limits of bypass surgery often depend upon the availability of adequate venous conduits. The saphenous vein has been the conduit of choice for distal arterial bypasses. However, some patients lack saphenous veins as a result of previous vein harvesting for coronary or other arterial surgery, phlebitis, variations in venous anatomy, previous vein stripping, or other conditions. In these patients, arm veins (cephalic and basilic) have been used successfully for limb salvage. There are several requirements for the successful use of arm veins. These include a detailed knowledge of the anatomy of the cephalic and basilic veins, education of patients and health care professionals, nursing protocols to preserve arm veins, and the training of surgical nurses in the demanding technical maneuvers for arm vein implantation. This paper will address these subjects. PMID:1599859

Apyan, R L; Schneider, P A; Andros, G

1992-06-01

342

Carrick Range Au and Sb mineralisation in Caples Terrane, Otago Schist, Central Otago, New Zealand  

Microsoft Academic Search

Mineralised zones of the Carrick Range, bearing gold and stibnite veins, constitute one of the rare economically significant mineralised fields in the Caples Terrane. The mineralised zones have a polyphase hydrothermal history. Early low?angle shears are filled by milky quartz, with minor carbonate, sulphides, and gold. These are cut by steeply dipping hydrothermal breccias and veins with prismatic and fine?grained

P. M. Ashley; D. Craw

1995-01-01

343

From Quartz Crystal Microbalance to Fundamental Principles of Mass Measurements  

Microsoft Academic Search

This article reveals that the mass sensitivity of the quartz crystal microbalance (QCM) is acceleration dependent and this feature is not specific to only the QCM, but also is valid in the case of other balances. During quartz crystal vibration a megagravity field is created at the surface of the quartz resonator. The existence of this field is demonstrated using

Vasile Mihai Mecea

2005-01-01

344

Reaction Permeability in Ocean Floor Hydrothermal Systems  

NASA Astrophysics Data System (ADS)

Fracturing is normally assumed to be the only significant mechanism for generating the permeability required for black smoker hydrothermal circulation within oceanic sheeted dykes. We present evidence for reaction-enhanced permeability as an alternative mechanism using data from three diverse settings; epidosites from the Troodos ophiolite, diabase intrusions chilling against fault rocks and altered gabbros in the immediate footwall of a detachment fault at 30 °N in the Atlantic (IODP Site 1309), and the "type section" of Pacific ocean crust in ODP Hole 504b. In each case, freshly broken surfaces were examined in the SEM, revealing euhedral secondary minerals (amphibole or epidote) growing into porosity located in areas formerly occupied by igneous minerals such as pyroxene. Relict porosity is up to 20 ?m in size but may originally have been considerably larger. BSEM and CL imaging of polished surfaces reveals euhedral zoning and resorbtion surfaces in both amphibole and quartz. Amphiboles at IODP site 1309 have a wide range in composition with early zones being exceptionally rich in Ti and Al (temperatures using the Ernst and Liu geothermometer in excess of 800 °C), but later zones and porosity-filling amphibole needles being actinolitic. Key field relations in the Troodos ophiolite show that the most intense alteration is often in the undeformed cores of dykes, and that each successive dyke was epidotised before the next was intruded. Reaction permeability provides a mechanism for concentrating fluid flow into the site of alteration, and can create exceptionally large transient permeabilities before the porosity is occluded by secondary minerals. Mineral solubilities generally peak at P-T conditions close to the critical point for water, so in a diabase cooling from magmatic temperatures the local fluid is always likely to be undersaturated down to the temperature of black smoker venting. A moving fluid will remove material from the cooling diabase, creating porosity. The porosity-filling phases generally represent greenschist facies conditions, consistent with black smoker vent temperatures. Reaction porosity textures have been observed in 8 out of 10 specimens so far examined in broken surface from Atlantic and Pacific dyke rocks. This permeability-generating mechanism may therefore be widespread.

McCaig, A. M.; Cann, J. R.

2011-12-01

345

Epithermal gold-silver deposits in New Zealand: a new wall poster  

Microsoft Academic Search

The epithermal gold-silver deposits wall poster is one in a series of posters on different mineral deposit types being produced by GNS Science to raise awareness of the characteristics of New Zealand mineral deposits and their prospectivity. Epithermal deposits consist of quartz veins, quartz vein stockworks and hydrothermal breccias that are mainly hosted in subaerial andesitic or rhyolitic rocks of

A. B. Christie; R. L. Brathwaite

346

Shifts in leaf vein density through accelerated vein formation in C4 Flaveria (Asteraceae)  

PubMed Central

Background and Aims Leaf venation in many C4 species is characterized by high vein density, essential in facilitating rapid intercellular diffusion of C4 photosynthetic metabolites between different tissues (mesophyll, bundle sheath). Greater vein density has been hypothesized to be an early step in C4 photosynthesis evolution. Development of C4 vein patterning is thought to occur from either accelerated or prolonged procambium formation, relative to ground tissue development. Methods Cleared and sectioned tissues of phylogenetically basal C3 Flaveria robusta and more derived C4 Flaveria bidentis were compared for vein pattern in mature leaves and vein pattern formation in developing leaves. Key Results In mature leaves, major vein density did not differ between C3 and C4 Flaveria species, whereas minor veins were denser in C4 species than in C3 species. The developmental study showed that both major and minor vein patterning in leaves of C3 and C4 species were initiated at comparable stages (based on leaf length). An additional vein order in the C4 species was observed during initiation of the higher order minor veins compared with the C3 species. In the two species, expansion of bundle sheath and mesophyll cells occurred after vein pattern was complete and xylem differentiation was continuous in minor veins. In addition, mesophyll cells ceased dividing sooner and enlarged less in C4 species than in C3 species. Conclusions Leaf vein pattern characteristic to C4 Flaveria was achieved primarily through accelerated and earlier offset of higher order vein formation, rather than other modifications in the timing of vein pattern formation, as compared with C3 species. Earlier cessation of mesophyll cell division and reduced expansion also contributed to greater vein density in the C4 species. The relatively late expansion of bundle sheath and mesophyll cells shows that vein patterning precedes ground tissue development in C4 species.

McKown, Athena D.; Dengler, Nancy G.

2009-01-01

347

Hydrothermal alteration in the Baca Geothermal System, Redondo Dome, Valles Caldera, New Mexico  

NASA Astrophysics Data System (ADS)

Thermal fluids circulating in the active hydrothermal system of the resurgent Redondo dome of the Valles caldera have interacted with their diverse host rocks to produce well-zoned alteration assemblages, which not only help locate permeable fluid channels but also provide insight into the system's thermal history. The alteration shows that fluid flow has been confined principally to steeply dipping normal faults and subsidiary fractures as well as thin stratigraphic aquifers. Permeability along many of these channels has been reduced or locally eliminated by hydrothermal self-sealing. Alteration from the surface through the base of the Miocene Paliza Canyon Formation is of three distinctive types: argillic, propylitic, and phyllic. Argillic alteration forms a blanket above the deep water table in formerly permeable nonwelded tuffs. Beneath the argillic zone, pervasive propylitic alteration is weakly developed in felsic host rocks but locally intense in deep intermediate composition volcanics. Strong phyllic alteration is commonly but not invariably associated with major active thermal fluid channels. Phyllic zones yielding no fluid were clearly once permeable but now are hydrothermally sealed. High-temperature alteration phases at Baca are presently found at much lower temperatures. We suggest either that isotherms have collapsed due to gradual cooling of the system, that they have retreated without overall heat loss due to uplift of the Redondo dome, that the system has shifted laterally, or that it has contracted due to a drop in the water table. The deepest Well (B-12, 3423 m) in the dome may have penetrated through the base of the active hydrothermal system. Below a depth of 2440 m in this well, hydrothermal veining largely disappears, and the rocks resemble those developed by isochemical thermal metamorphism. The transition is reflected by temperature logs, which show a conductive thermal gradient below 2440 m. This depth may mark the dome's neutral plane, which separates an upper permeable zone of extensional fracturing from a lower, less permeable compressional regime. The Baca hydrothermal system is similar to those which have formed ore deposits in other calderas: particularly, Creede (Colorado) type epithermal silver base metal veins and stockworks. Recent scientific drilling has also intersected a deep zone of strong phyllic alteration and molybdenum mineralization in the Valles caldera's ring fracture system, a setting which localized a large stockwork molybdenite orebody in the nearby Questa caldera.

Hulen, Jeffrey B.; Nielson, Dennis L.

1986-02-01

348

Parasitization of a hydrothermal vent limpet (Lepetodrilidae, Vetigastropoda) by a highly modified copepod (Chitonophilidae, Cyclopoida).  

PubMed

The limpet Lepetodrilus fucensis McLean is very abundant at hydrothermal vents on the Juan de Fuca and Explorer Ridges in the northeast Pacific Ocean. This limpet is parasitized by an undescribed chitonophilid copepod throughout the limpet's range. The parasite copepodite enters the mantle cavity and attaches to the afferent branchial vein. The initial invasive stage is a vermiform endosome within the vein that develops an extensive rootlet system causing an enlargement of the afferent branchial vein. Subsequently, an ectosomal female body grows outside the vein to sizes up to 2 mm in width. Once a dwarf male attaches, egg clusters form and nauplii are released. In over 3000 limpets examined from 30 populations, prevalence averaged about 5% with localized infections in female limpets over 25%. After the establishment of limpet populations at new vents, copepod prevalence increased over the succeeding months to 3 years. Host effects were marked and included castration of both sexes and deterioration in gill condition which affected both food acquisition and the gill symbiont. There was a significantly greater parasite prevalence in larger females which likely modifies the reproductive and competitive success of local host populations. PMID:18664307

Tunnicliffe, V; Rose, J M; Bates, A E; Kelly, N E

2008-07-29

349

Mineralogical and geochemical characteristics of hydrothermal alteration and episyenitization in the Königshain granites, northern Bohemian Massif, Germany  

NASA Astrophysics Data System (ADS)

The late-Hercynian granites of Königshain underwent multistage hydrothermal processes. Extensive high-temperature late-magmatic alteration is, for example, indicated by low Zr/Hf and an REE pattern displaying the tetrad effect. Intensive post-magmatic alteration of the granite occurred along brittle structures. At least two main stages of post-magmatic hydrothermal alteration are involved. The first high-temperature stage, which is characterized by albitization and/or quartz leaching (episyenitization), resulted from fluid-rock interaction with late-magmatic fluids that very probably mixed with external low-salinity fluids. Quartz dissolution was triggered by vapour condensation and/or the cooling of these fluids (below 450 °C) along brittle structures. The high porosity resulting from quartz leaching during stage 1 assisted subsequent circulation of low-temperature fluids at stage 2; the latter is characterized by the chloritization and illitization of episyenites. Almost all major and trace elements were enriched or depleted during one of the main alteration stages. However, Zr, Hf, Th, and Ti were immobile during post-magmatic alteration. The significant depletion of LREE and the enrichment of HREE in albitized samples is controlled by the dissolution of monazite and the new formation of HREE-rich polycrase-(Y) or aeschynite-(Y) during post-magmatic stage 1. Negative Ce anomalies of episyenites are associated with illitization and suggest oxidizing conditions during stage 2.

Hecht, L.; Thuro, K.; Plinninger, R.; Cuney, M.

350

Hydrothermal studies in a new diamond anvil cell up to 10 GPa and from -190??C to 1200??C  

USGS Publications Warehouse

The new hydrothermal diamond anvil cell (HDAC) has been designed for optical microscopy and X-ray diffraction at pressures up to 10 GPa and temperatures between -190??C and 1200??C. Laser light reffected from the top and bottom anvil faces and the top and bottom solid sample faces produce interference fringes that provide a very sensitive means of monitoring the volume of sample chamber and for observing volume and refractive index changes in solid samples due to transitions and reactions. Synchrotron radiation has been used to make X-ray diffraction patterns of samples under hydrothermal conditions. Individual heaters and individual thermocouples provide temperature control with an accuracy of ??0.5??C. Liquid nitrogen directly introduced into the HDAC has been used to reduce the sample temperature to -190??C. The ??-?? phase boundary of quartz has been used to calculate the transition pressures from measured transition temperatures. With this method we have redetermined 5 isochores of H2O up to 850??C and 1.2 GPa at which the solution rate of the quartz became so rapid that the quartz dissolved completely before the ??-?? transition could be observed. When silica solutions were cooled, opal spherules and rods formed. ?? 1993 Birkha??user Verlag.

Bassett, W. A.; Shen, A. H.; Bucknum, M.; Chou, I. -M.

1993-01-01

351

Portal vein aneurysm in a dog.  

PubMed

Portal vein aneurysm (PVA) is a rare abnormal dilatation of the portal vein, which has not been reported in dogs. We describe the findings of ultrasound and computed tomography in a case of PVA in a young male toy poodle, with the final diagnosis established by explorative surgical observation. The dog had an aneurysmal fusiform dilatation in the extrahepatic portal vein with portal hypertension and multiple portsystemic shunts. This is the first report of canine PVA. PMID:22571895

Miyawaki, Shingo; Washizu, Makoto; Maeda, Sadatoshi; Shibata, Sanae; Watanabe, Kazuhiro; Yamazoe, Kazuaki

2012-04-27

352

Hemodialysis-associated subclavian vein stenosis  

Microsoft Academic Search

Hemodialysis-associated subclavian vein stenosis. This study was undertaken to evaluate hemodialysis-associated subclavian vein stenosis (SVS) and to clarify treatment of this condition. Forty-seven patients underwent upper arm venography to evaluate fistula dysfunction. Subclavian vein stenosis was documented in 12. Eleven of 12 had elevated venous dialysis pressure (196 ± 8.9 mm Hg), and six had arm edema. All 12 had

Steve J Schwab; L Darryl Quarles; John P Middleton; Richard H Cohan; Moshin Saeed; Vincent W Dennis

1988-01-01

353

Jugular vein thrombosis associated with distant malignancy.  

PubMed Central

We describe two patients who developed internal jugular vein thrombosis associated with primary malignant disease arising outside the neck, and in one patient it was the presenting feature. Computed tomography was performed and the findings characteristic of internal jugular vein thrombosis are illustrated. We conclude that malignant disease should be considered in patients presenting with spontaneous internal jugular vein thrombosis with no other predisposing factors and that computed tomography is of value in confirming the diagnosis. Images Figure 1 Figure 2

Carrington, B. M.; Adams, J. E.

1988-01-01

354

Periorbital rejuvenation: reticular vein treatment.  

PubMed

The safety profile of certain techniques, such as sclerotherapy, is questionable in a region as precarious as the periorbital region, where complications related to vision would be catastrophic. Other safe techniques such as phlebectomy can be performed with successful outcomes but are operator dependent, require a reasonable degree of technical ability, and can result in scarring and other complications. The aim of this article is to explore newer, laser-based treatment of these periorbital veins, discuss the physiology and the therapeutic efficacy, and better delineate the safety profile and evolution of the technique that has led to the present treatment paradigm. PMID:23369597

Chauhan, Nitin; Ellis, David A F

2013-02-01

355

Deep Vein Thrombosis in Children  

PubMed Central

We describe a rare case of deep vein thrombosis (DVT) in children, highlight the importance of early diagnosis of rare disease with potential complications. In a 5 year old boy presented with persistent leg pain without any obvious cause. Detailed investigation led to diagnosis of DVT. As there are common differential diagnoses for leg pain in children, pediatricians usually have a low index of suspicious of DVT in children. This case highlight that paediatricians must consider DVT in their differential diagnosis when children present with leg pain.

Aabideen, Kanakkande; Ogendele, Michael; Ahmad, Ijaz; Amegavie, Laweh

2013-01-01

356

Ovarian Vein and Caval Thrombosis  

PubMed Central

We present an illustrative case of postpartum ovarian vein thrombosis and describe its clinical presentation, differential diagnosis, and management. This pathologic process may produce clinical complications or a catastrophic outcome. These adverse events may be avoided if an expeditious diagnosis is made and appropriate treatment is instituted. This mandates a high index of suspicion, the ability to rule out the presence of other processes that may produce similar symptoms in the postpartum patient, and the appropriate triage of specific patients to either medical or surgical management.

Takach, Thomas J.; Cervera, Roberto D.; Gregoric, Igor D.

2005-01-01

357

Below-the-Belt Dermatological Conditions: Spider Veins, Varicose Veins, Cellulite, Pedicures  

MedlinePLUS

... it comes to treating spider and varicose veins, cellulite and problems stemming from pedicures, there are many ... vein - which is then reabsorbed by the body. Cellulite Cellulite is a hormonally based condition unique to ...

358

Quartz channel fabrication for electrokinetically driven separations  

NASA Astrophysics Data System (ADS)

For well resolved electrokinetic separation, we utilize crystalline quartz to micromachine a uniformly packed separation channel. Packing features are posts 5 micrometers on a side with 3 micrometers spacing and etched 42 micrometers deep. In addition to anisotropic wet etch characteristics for micromachining, quartz properties are compatible with chemical solutions, electrokinetic high voltage operation, and stationary phase film deposition. To seal these channels, we employ a room temperature silicon-oxynitride deposition to form a membrane, that is subsequently coated for mechanical stability. Using this technique, particulate issues and global warp, that make large area wafer bonding methods difficult, are avoided, and a room temperature process, in contrast to high temperature bonding techniques, accommodate preprocessing of metal films for electrical interconnect. After sealing channels, a number of macro- assembly steps are required to attach a micro-optical detection system and fluid interconnects.

Matzke, Carolyn M.; Arnold, D. W.; Ashby, Carol I.; Kravitz, Stanley H.; Warren, Mial E.; Bailey, C. G.

1998-09-01

359

Quartz Channel Fabrication for Electrokinetically Driven Separations  

SciTech Connect

For well resolved electrokinetic separation, we L tilize crystalline quartz to micromachine a uniformly packe Q&iKLmnel. Packing features are posts 5 Vm on a side with:} pm spacing and etched 42 Vm deep. In addition to anisotropic wet etch characteristics for micromachining, quartz propmties are compatible with chemical soiutioits, ekctrokinetic high voltage operation, and stationary phase film depositions. To seal these channels, we employ a room temperature silicon-oxynhride deposition to forma membrane, that is subsequently coated for mechanical stability. Using this technique, particulate issues and global warp, that make large area wafer bon ding methods difficult, are avoided, and a room temperature process, in contrast to high temperature bonding techniques, accommodate preprocessing of metal films for electrical interconnect. After sealing channels, a number of macro-assembly steps are required to attach a micro-optical detection system and fluid interconnects. Keywords: microcharmel, integrated channel, micromachined channel, packed channel, electrokinetic channel, eleetrophoretic channel

Arnold, D.W.; Ashby, C.I.H.; Bailey, C.G.; Kravitz, S.H., Warren, M.E.; Matzke, C.M.

1998-12-01

360

Postimpact hydrothermal alteration of the Manson impact structure  

NASA Astrophysics Data System (ADS)

Core materials from the Manson impact structure (MIS), Manson, Iowa, are examined in order to evaluate postimpact alteration processes. Interpretation of the high-temperature postimpact hydrothermal system is based on mineralogic investigation. MIS rocks from the M1, M7, M8, and M10 cores obtained by the continental scientific drilling project (CSDP) in 1991 and 1992 are used in this study. All lithologies, including the sedimentary clast breccias (SCB), crystalline clast breccias (CCB), and central peak crystalline peaks (CPC), have been described previously. Emphasis is placed on fluid conduits that cross-cut all these lithologies. Analytical techniques include petrography, Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD). The minerals are grouped according to their temperatures of occurrence in modern geothermal systems. The highest temperatures in the MIS are represented by a garnet and ferroactinolite assemblage (assemblage I). Assemblage II contains epidote, prehnite, and wollastonite, which represents slightly lower temperatures in the system. The existence of laumontite, quartz, and adularia defines a third assemblage. Assemblage IV is defined by calcite and clays, and represents the lowest alteration temperature at the MIS. These temperature-sensitive calc-silicates serve to constrain the fluid temperatures of the MIS hydrothermal system. Assemblage I suggests that the system reached over 300 C. Successively decreasing temperatures through time, approaching ambient temperatures, are suggested by the lower temperature assemblages II, III, and IV. A model for the cooling history of the MIS is reported elsewhere. The distribution of these high-temperature minerals points to the central uplift, not the melt sheet, as being the heat source for the system.

McCarville, P.; Crossey, L. J.

1994-07-01

361

Experimental investigation of the solubility of albite and jadeite in H 2O, with paragonite + quartz at 500 and 600 °C, and 1-2.25 GPa  

NASA Astrophysics Data System (ADS)

The solubilities of the assemblages albite + paragonite + quartz and jadeite + paragonite + quartz in H 2O were determined at 500 and 600 °C, 1.0-2.25 GPa, using hydrothermal piston-cylinder methods. The three minerals are isobarically and isothermally invariant in the presence of H 2O, so fluid composition is uniquely determined at each pressure and temperature. A phase-bracketing approach was used to achieve accurate solubility determinations. Albite + quartz and jadeite + quartz dissolve incongruently in H 2O, yielding residual paragonite which could not be retrieved and weighed. Solution composition fixed by the three-mineral assemblage at a given pressure and temperature was therefore bracketed by adding NaSi 3O 6.5 glass in successive experiments, until no paragonite was observed in run products. Solubilities derived from experiments bounding the appearance of paragonite thus constrain the equilibrium fluid composition. Results indicate that, at a given pressure, Na, Al, and Si concentrations are higher at 600 °C than at 500 °C. At both 500 and 600 °C, solubilities of all three elements increase with pressure in the albite stability field, to a maximum at the jadeite-albite-quartz equilibrium. In the jadeite stability field, element concentrations decline with continued pressure increase. At the solubility maximum, Na, Al, and Si concentrations are, respectively, 0.16, 0.05, and 0.48 molal at 500 °C, and 0.45, 0.27, and 1.56 molal at 600 °C. Bulk solubilities are 3.3 and 10.3 wt% oxides, respectively. Observed element concentrations are everywhere greater than those predicted from extrapolated thermodynamic data for simple ions, monomers, ion pairs, and the silica dimer. The measurements therefore require the presence of additional, polymerized Na-Al-Si-bearing species in the solutions. The excess solubility is >50% at all conditions, indicating that polymeric structures are the predominant solutes in the P- T region studied. The solubility patterns likely arise from combination of the large solid volume change associated with the albite-jadeite-quartz equilibrium and the rise in Na-Al-Si polymerization with approach to the hydrothermal melting curves of albite + quartz and jadeite + quartz. Our results indicate that polymerization of Na-Al-Si solutes is a fundamental aspect of fluid-rock interaction at high pressure. In addition, the data suggest that high-pressure metamorphic isograds can impose unexpected controls on metasomatic mass transfer, that significant metasomatic mass transfer prior to melting should be considered in migmatitic terranes, and that polymeric complexes may be an important transport agent in subduction zones.

Wohlers, Anke; Manning, Craig E.; Thompson, Alan B.

2011-05-01

362

Authigenic quartz in the Upper Freeport coalbed, west- central Pennsylvania  

SciTech Connect

Cathodoluminescence petrography was used to examine quartz grains contained in facies of the Upper Freeport coalbed (Middle Pennsylvanian) of west-central Pennsylvania. Samples included ash concentrates, polished blocks of different lithotypes, and standard petrographic pellets of specific gravity separates of facies channel samples. More than 80% of the quartz in mineral and vitrain-rich bands in the polished blocks do not exhibit cathodoluminescence. In specific gravity separates, 100% of the quartz in the lightest gravity separates did not luminesce. In the heaviest gravity separates, which included shale-parting material, 60% of the quartz did not luminesce. In contrast, in a sample of shale directly overlying the coalbed, more than 90% of the quartz luminesced. On the basis of these data and of other published data, quartz in the Upper Freeport coalbed is interpreted to be authigenic in origin. The authigenic quartz grains are postulated to have been derived from phytoclasts.

Ruppert, L.P.

1985-05-01

363

Fission fragment registration in synthetic quartz  

Microsoft Academic Search

Synthetic quartz crystals were irradiated with Cf-fission fragments to study track registration properties in the x-plane. It was found that the properties depend on the sense of the x-plane: the etched-track size is larger and the effective critical angle ?? is higher on the + xx-plane than on the - x-plane and as a result the registration efficiency for fission

Teruko Sawamura; Hastuo Yamazaki

1990-01-01

364

Quartz analog watch with perpetual calendar  

NASA Astrophysics Data System (ADS)

The Caliber ETA 252.411 with perpetual calendar, which is similar in dimensions and display to classic quartz watch movements, is described. The main characteristics are: the date display in the window is always correct (until 28 Feb. 2100); the change of time zones is operated without losing minute and second by means of a date correction at each midnight passage; and the use of nonvolatile memories for information concerning the perpetual calendar allows an easy time resetting after change of battery.

Favre, Eric; Schmidli, Pierre; Erni, Bruno

365

Remodelling of the Superior Caval Vein After Angioplasty in an Infant with Superior Caval Vein Syndrome  

SciTech Connect

An 8-month old girl was presented with superior caval vein syndrome early after cardiac surgery. Angiography showed severe stenosis of the superior caval vein with 50 mmHg pressure gradient. Following balloon angioplasty, the pressure gradient was reduced to 7 mmHg with some residual stenosis of the superior caval vein. When the patient was reevaluated 5 months after the procedure, angiography revealed a normal diameter of the superior caval vein without a pressure gradient.

Mert, Murat [Istanbul University, Institute of Cardiology, Department of Cardiovascular Surgery (Turkey)], E-mail: mmert@superonline.com; Saltik, Levent [Istanbul University, Cerrahpasa Medical School, Department of Pediatric Cardiology (Turkey); Gunay, Ilhan [Istanbul University, Institute of Cardiology, Department of Cardiovascular Surgery (Turkey)

2004-08-15

366

Treatment of central retinal vein occlusion by injection of tissue plasminogen activator into a retinal vein  

Microsoft Academic Search

Purpose: To report the injection of tissue plasminogen activator into a retinal vein to treat central retinal vein occlusion.Methods: An 81-year-old woman with visual loss of the right eye secondary to central retinal vein occlusion developed central retinal vein occlusion and visual loss in her left eye. Treatment of her left eye with topical ocular hypotensive medications, pentoxifylline, and laser

Jeffrey N. Weiss

1998-01-01

367

Frictional slip of granite at hydrothermal conditions  

Microsoft Academic Search

Sliding on faults in much of the continental crust likely occurs at hydrothermal conditions, i.e., at elevated temperature and elevated pressure of aqueous pore fluids, yet there have been few relevant laboratory studies. To measure the strength, sliding behavior, and friction constitutive properties of faults at hydrothermal conditions, we slid laboratory granite faults containing a layer of granite powder (simulated

Michael L. Blanpied; David A. Lockner; James D. Byerlee

1995-01-01

368

Hydrothermal conversion of carbohydrates and related compounds  

NASA Astrophysics Data System (ADS)

The research described in this thesis was aimed at the (partial) elucidation of the chemistry of the major decarboxylation pathways occurring in the hydrothermal conversion of carbohydrates. Knowledge of the chemical background of this hydrothermal decarboxylation might enable more effective processing of biomass with respect to minimizing the oxygen content of hydrothermolysis products.

Luijkx, Gerardus Christianus Antonius

369

Hydrothermal metamorphism in the Larderello Geothermal Field  

SciTech Connect

The various tectonic units underlying the Larderello-Travale geothermal region have undergone hydrothermal metamorphism. The hydrothermal mineral assemblages are generally consistent with the temperatures now measured in the wells, leading to the hypothesis that solid phases deposited from a liquid medium during a hot-water stage that preceded the vapor-dominated one. 61 refs.

Cavarretta, G.; Gianelli, G.; Puxeddu, M.

1980-01-01

370

EFFECTS OF EXTRATERRESTRIAL HYDROTHERMAL PROCESSES IN CHONDRITES  

Microsoft Academic Search

Hydrothermal reactions in terrestrial geological processes may be defined in a simplified form as those that cause numerous alterations of earlier formed rocks and minerals due to the action of hot aqueous solutions, usually in a postmagmatic stage. Under extraterrestrial conditions hydrothermal processes should occur probably less often because of the lack of the environments rich in such solutions. Only

Andrzej MANECK

371

Hydrothermal decomposition of esters under high pressure  

Microsoft Academic Search

The hydrothermal decomposition of two esters (methyl formate and ethyl formate) was studied in the absence of oxygen over the temperature range of 373 – 673 K at pressures from 15 to 35MPa for residence times between 72 and 600s. At hydrothermal conditions, the esters were hydrolyzed to formic acid and the corresponding alcohols in equilibrium yields of more than

Takashi Moriyoshi; Keisuke Sam; Yasuhiro Uosaki

2001-01-01

372

Surface and interfacial free energies of quartz  

NASA Astrophysics Data System (ADS)

Water and electrolytes cause significant changes in brittle fracture strength and subcritical fracture propagation velocities in quartz and quartz rocks. The changes may be caused, in part, by changes in surface free energy. Experimental fracture surface energies of quartz range from about 400 mJ m-2 to about 11.5 J m-2. Thermodynamic surface free energies are likely to be lower than fracture surface energies owing to dissipative energy losses and failure to achieve equilibrium surface structure. Thermodynamic surface free energies are sensitive to environmental composition. Reaction of water vapor with pristine fracture surfaces reduces surface energy by hydroxylation, but the extent of reduction is not known. Adsorption of water vapor on the hydroxylated surface and immersion in liquid water reduce surface energy by 75-230 and 72 mJ m-2 respectively. In an electrolyte, the surface free energy is maximum at the point of zero charge, where adsorption of ionic solutes is least. Adsorption of hydrogen ion, hydroxide ion, and electrolytes reduce surface energy as concentration increases, by tens of mJ m-2. All of these surface energy changes are qualitatively consistent with changes in fracture behavior caused by the same variables.

Parks, George A.

1984-06-01

373

N2 adsorption study on quartz, silver, and carbon nanotube by inductive pulse quartz crystal microbalance  

NASA Astrophysics Data System (ADS)

We utilize an ``inductive pulse'' quartz crystal microbalance method to study N2 adsorption on quartz, silver, and a single wall carbon nanotube at 77 K. This method is based on radio frequency electric pulse excitation and ring-down signal measurements of quartz crystal resonators located in an induction coil. The surface areas and adsorption strength c are estimated by the Brunauer-Emmett-Teller (BET) model. The estimated c for quartz and silver surface are about 1/5 times smaller than that measured by the conventional method. This is explained as suppression of the self-heating effect, by using our inductive pulse method. We suggest a simple theoretical estimation of self-heating effects on conventional and inductive pulse methods. For the intermediate adsorption range, we analyze our data using the generalized Frenkel-Hasley-Hill (FHH) model with fractal dimension. While the quartz and silver have fractal dimensions of about 2.2+/-0.1, single wall carbon nanotube has 1.2+/-0.1, which are explained by its strong adsorptive force.

Park, Jang-Ik; Yu, Insuk; Seo, Yongho

2007-03-01

374

Mineralogy, chemical composition and structure of the MIR Mound, TAG Hydrothermal Field  

NASA Astrophysics Data System (ADS)

The study of samples collected from the surface of the MIR mound (TAG Hydrothermal Field) by video-controlled hydraulic grab allowed identification of a number of mineralogical types. These include pyrite-chalcopyrite (Py-Cp), bornite-chalcopyrite-opaline (Bn-Cp-Op) and sphalerite-opaline (Sp-Op) sulfide chimneys, massive sulfides composed of pyrite (Py), chalcopyrite-pyrite (Cp-Py), marcasite-pyrite-opaline (Mc-Py-Op), sphalerite-pyrite-opaline (Sp-Py-Op) and sphalerite-chalcopyrite-pyrite-opaline (Sp-Cp-Py-Op), as well as siliceous and Fe-Mn oxide hydrothermal deposits. Most of the minor elements (Ag, Au, Cd, Ga, Hg, Sb and Pb) are associated with Zn-rich massive sulfides, Co Bi, Pb, and As with Ferich ones, while Cu-rich sulfides are depleted of trace metals. Cu-enriched assemblages are concentrated in the northern part, Zn-enriched in the center, and siliceous rocks in the south of the MIR mound. According to paragenetic relations, the development of the mound started with the formation of quartz (originally opaline) rocks and dendritic assemblages of melnikovite-pyrite, followed by deposition of chalcopyrite and recrystallization of primary pyrite, subsequent generation of sphalerite-rich assemblages and final deposition of opaline rocks. The late renewal of hydrothermal activity led to local formation of Cu-rich chimneys enriched in Au, Ag, Hg and Pb probably due to their remobilization from inner parts of the deposit.

Stepanova, T. V.; Krasnov, S. G.; Cherkashev, G. A.

375

Mineral-enhanced hydrothermal oligopeptide formation at the second time scale.  

PubMed

Accumulation of biopolymers should have been an essential step for the emergence of life on primitive Earth. However, experimental simulations for submarine hydrothermal vent systems in which high-temperature water spouts through minerals within a short time scale have not been attempted. Here, we show that enhancement of hydrothermal oligopeptide elongation by naturally occurring minerals was successfully verified for the first time by using a mineral-mediated hydrothermal flow reactor system (MMHF). MMHF consists of a narrow tubular reactor packed with mineral particles, and the enhancement or inhibitory activities of 10 types of naturally occurring minerals were successfully evaluated for an elongation reaction from (Ala)(4) to (Ala)(5) and higher oligopeptides in the absence of condensation reagents. It was unexpected that calcite and dolomite facilitated the elongation from (Ala)(4) to (Ala)(5) and higher oligopeptides with 28% yield at pH 7, while tourmaline, galena, apatite, mica, sphalerite, quartz, chalcopyrite, and pyrite did not show enhancement activities. These facts suggest the importance of carbonate minerals for the accumulation of peptide in primitive Earth environments. PMID:21671764

Kawamura, Kunio; Takeya, Hitoshi; Kushibe, Takao; Koizumi, Yuka

2011-06-14

376

Hydrothermal diamond-anvil cell: Application to studies of geologic fluids  

USGS Publications Warehouse

The hydrothermal diamond-anvil cell (HDAC) was designed to simulate the geologic conditions of crustal processes in the presence of water or other fluids. The HDAC has been used to apply external pressure to both synthetic and natural fluid inclusions in quartz to minimize problems caused by stretching or decrepitation of inclusions during microthermometric analysis. When the HDAC is loaded with a fluid sample, it can be considered as a large synthetic fluid inclusion and therefore, can be used to study the PVTX properties as well as phase relations of the sample fluid. Because the HDAC has a wide measurement pressure-temperature range and also allows in-situ optical observations, it has been used to study critical phenomena of various chemical systems, such as the geologically important hydrous silicate melts. It is possible, when the HDAC is combined with synchrotron X-ray sources, to obtain basic information on speciation and structure of metal including rare-earth elements (REE) complexes in hydrothermal solutions as revealed by X-ray absorption fine structure (XAFS) spectra. Recent modifications of the HDAC minimize the loss of intensity of X-rays due to scattering and absorption by the diamonds. These modifications are especially important for studying elements with absorption edges below 10 keV and therefore particularly valuable for our understanding of transport and deposition of first-row transition elements and REE in hydrothermal environments.

Chou, I. -M.

2003-01-01

377

Mineral-Enhanced Hydrothermal Oligopeptide Formation at the Second Time Scale  

NASA Astrophysics Data System (ADS)

Accumulation of biopolymers should have been an essential step for the emergence of life on primitive Earth. However, experimental simulations for submarine hydrothermal vent systems in which high-temperature water spouts through minerals within a short time scale have not been attempted. Here, we show that enhancement of hydrothermal oligopeptide elongation by naturally occurring minerals was successfully verified for the first time by using a mineral-mediated hydrothermal flow reactor system (MMHF). MMHF consists of a narrow tubular reactor packed with mineral particles, and the enhancement or inhibitory activities of 10 types of naturally occurring minerals were successfully evaluated for an elongation reaction from (Ala)4 to (Ala)5 and higher oligopeptides in the absence of condensation reagents. It was unexpected that calcite and dolomite facilitated the elongation from (Ala)4 to (Ala)5 and higher oligopeptides with 28% yield at pH 7, while tourmaline, galena, apatite, mica, sphalerite, quartz, chalcopyrite, and pyrite did not show enhancement activities. These facts suggest the importance of carbonate minerals for the accumulation of peptide in primitive Earth environments.

Kawamura, Kunio; Takeya, Hitoshi; Kushibe, Takao; Koizumi, Yuka

2011-06-01

378

Hydrothermal synthesis of {beta}-nickel hydroxide nanocrystalline thin film and growth of oriented carbon nanofibers  

SciTech Connect

Novel well-crystallized {beta}-nickel hydroxide nanocrystalline thin films were successfully synthesized at low temperature on the quartz substrates by hydrothermal method, and the oriented carbon nanofibers (CNFs) were prepared by acetylene cracking at 750 deg. C on thin film as the catalyst precursor. High resolution transmission electron microscopy (HR-TEM) measurement shows that thin films were constructed mainly with hexagonal {beta}-nickel hydroxide nanosheets. The average diameter of the nanosheets was about 80 nm and thickness about 15 nm. Hydrothermal temperature played an important role in the film growth process, influencing the morphologies and catalytic activity of the Ni catalysts. Ni thin films with high catalytic activity were obtained by reduction of these Ni(OH){sub 2} nanocrystalline thin films synthesized at 170 deg. C for 2 h in hydrothermal condition. The highest carbon yield was 1182%, and was significantly higher than the value of the catalyst precursor which was previously reported as the carbon yield (398%) for Ni catalysts. The morphology and growth mechanism of oriented CNFs were also studied finally.

Zhang Enlei [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China); Tang Yuanhong, E-mail: yhtang2000@163.com [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China) and Powder Metallurgy Research Institute, Central South University, Changsha 410083 (China); Zhang Yong; Guo Chi; Yang Lei [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China)

2009-08-05

379

Hydrothermal synthesis of hydroxyapatite rods  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HAP) rods were synthesized from dicalcium phosphate anhydrous (CaHPO4, DCPA) and calcium carbonate (CaCO3) by the hydrothermal method from 120 to 180 °C. Both cuttlebone (aragonite polymorph of CaCO3) and CaCO3 chemical (calcite polymorph of CaCO3) were used as CaCO3 sources. The nucleation and growth of HAP rods mainly occurred on DCPA particles, while some HAP rods also grew from aragonite particles. The nucleation and growth of ?-tricalcium phosphate (?-TCP) particles on the surface of calcite particles were observed at the beginning of the reaction of DCPA and calcite, and some HAP rods were also found to grow out of ?-TCP particles. After the hydrothermal reaction at 140 °C for 24 h, most products are HAP with a small amount of ?-TCP synthesized as a byproduct. The HAP rods synthesized were ˜200 nm in width and several microns in length. The reaction mechanism and growth process of HAP rods are discussed.

Zhang, Xing; Vecchio, Kenneth S.

2007-10-01

380

Hydrothermal alteration, fluid inclusions and stable isotope systematics of the Alvo 118 iron oxide-copper-gold deposit, Carajás Mineral Province (Brazil): Implications for ore genesis  

NASA Astrophysics Data System (ADS)

The Alvo 118 iron oxide-copper-gold (IOCG) deposit (170 Mt at 1.0 wt.% Cu, 0.3 g/t Au) lies in the southern sector of the Itacaúnas Shear Belt, Carajás Mineral Province, along a WNW-ESE-striking, 60-km-long shear zone, close to the contact of the ~2.76-Ga metavolcano-sedimentary Itacaiúnas Supergroup and the basement (~3.0 Ga Xingu Complex). The Alvo 118 deposit is hosted by mafic and felsic metavolcanic rocks and crosscutting granitoid and gabbro intrusions that have been subjected to the following hydrothermal alteration sequence towards the ore zones: (1) poorly developed sodic alteration (albite and scapolite); (2) potassic alteration (biotite or K-feldspar) accompanied by magnetite formation and silicification; (3) widespread, pervasive chlorite alteration spatially associated with quartz-carbonate-sulphide infill ore breccia and vein stockworks; and (4) local post-ore quartz-sericite alteration. The ore assemblage is dominated by chalcopyrite (~60%), bornite (~10%), hematite (~20%), magnetite (10%) and subordinate chalcocite, native gold, Au-Ag tellurides, galena, cassiterite, F-rich apatite, xenotime, monazite, britholite-(Y) and a gadolinite-group mineral. Fluid inclusion studies in quartz point to a fluid regime composed of two distinct fluid types that may have probably coexisted within the timeframe of the Cu-Au mineralizing episode: a hot (>200°C) saline (32.8‰ to 40.6 wt.% NaCl eq.) solution, represented by salt-bearing aqueous inclusions, and a lower temperature (<200°C), low to intermediate salinity (<15 wt.% NaCl eq.) aqueous fluid defined by two-phase (LH2O + VH2O) fluid inclusions. This trend is very similar to those defined for other IOCG systems of the Carajás Mineral Province. ? 18OH2O values in equilibrium with calcite (-1.0‰ to 7.5‰ at 277°C to 344°C) overlap the lower range for primary magmatic waters, but the more 18O-depleted values also point to the involvement of externally derived fluids, possibly of meteoric origin. Furthermore, sulphide ? 34S values (5.1‰ to 6.3‰), together with available boron isotope and Cl/Br-Na/Cl data provide evidence for a significant component of residual evaporative fluids (e.g., bittern fluids generated by seawater evaporation) in this scenario that, together with magma-derived brines, would be the main sources of the highly saline fluids involved in the formation Alvo 118 IOCG deposit. The restricted high temperature sodic alteration, the pervasive overprinting of the potassic alteration minerals by chlorite proximal to the ore zones, ore breccias with open-space filling textures in brittle structures, microthermometric and stable isotope data indicate, collectively, that the Alvo 118 IOCG system developed at structurally high levels and may be considered the shallower representative of the IOCG systems of the CMP.

Torresi, Ignacio; Xavier, Roberto Perez; Bortholoto, Diego F. A.; Monteiro, Lena V. S.

2012-03-01

381

The Iceland Deep Drilling Project (IDDP): (4) A Quartz Fluid Inclusion Tool for Sampling Supercritical Geothermal Fluids Downhole  

NASA Astrophysics Data System (ADS)

Chemical analyses of in situ samples of supercritical geothermal fluids would provide a uniquely good measure of fluid composition at depth relative to compositions reconstructed from analyses of gas and liquid sampled at wellheads. Fluids sampled at the wellhead are commonly a mixture from multiple aquifers and, in many circumstances, they lack components such as sulfate, sulfide, Ca, Cu, Zn, and Fe that precipitated in scale minerals where the fluids boiled or cooled during their ascent. To circumvent the above problems and the failings of downhole mechanical samplers at temperatures exceeding 300°C and to obtain total fluid samples at supercritical conditions in the IDDP wells, we plan to trap fluids in fluid inclusions formed in fractured quartz that we suspend in a geothermal well on a wireline. In a series of hydrothermal laboratory experiments at 450°C and 600 bar and spanning 6 hr to 5 days in length, thermal shock fractures in natural and synthetic quartz crystals heal, forming ragged fluid inclusions in one day and many well formed inclusions in three days. Amorphous silica is added to the experimental charge, without which, fractures heal little and only 1-2 micron inclusions form. Microthermometry measurements on the inclusions produced in experiments return the run temperature within 20°C at the experimental pressure, indicating that inclusions formed and sealed at the run conditions. The fluid inclusion tool (FIT) consists of a perforated stainless steel pipe containing multiple stainless steel mesh canisters with non-mesh ends to minimize vertical fluid flow. The canisters contain 10mm-scale chunks of fractured quartz surrounded by ground quartz glass. The perforated pipe will be fixed within a one-meter outer perforated stainless steel housing that is suspended on a stainless steel slick line. The FIT is weighed by one or more 10kg lead sinker bars. The entire assembly is lowered into the well from a lubricator fitted on the wellhead, thus enabling sampling under high temperatures and pressures. In the initial field testing runs, the contents of the mesh canisters will be varied to examine the effects of ground glass grain size, and the suitability of clear natural quartz vs synthetic quartz, both with respect to fluid inclusion development and chemical analyses of inclusions. Inclusions will be analyzed by various bulk methods and by LA-ICP-MS on individual inclusions. Once we optimize the fluid inclusion tool configuration in field tests and by analytical results, the volume of sampling quartz can be scaled up as needed to provide for optimum sampling and analyses.

Reed, M. H.; Grist, H.; Fridriksson, T.; Danielsen, P.; Senkovich, D.; Johnston, A.; Elders, W. A.; Fridleifsson, G. O.

2009-12-01

382

Can tuffisite veins help dictate eruption styles?  

Microsoft Academic Search

The ability of magmas to degas during ascent may affect eruption style. The permeability of the magma and\\/or the conduit wall rocks may therefore dictate whether an eruption will be explosive or effusive. Fractures increase permeability. Fractures filled by veins of autoclastic, cataclastic and tuffisitic glass shards and crystal fragments are common in shallow conduit systems. These veins have the

S. Kolzenburg; M. J. Heap; Y. Lavallee; J. K. Russell; P. G. Meredith; D. B. Dingwell

2010-01-01

383

Superficial Dorsal Vein Rupture Imitating Penile Fracture  

PubMed Central

Dorsal vein rupture of the penis is a rare condition, and few cases have been reported in the literature. Herein we report a 41-year-old man who presented with mildly painful and acute swollen penis, which initially imitated a penile fracture but was surgically explored and shown to be a superficial dorsal vein rupture.

Topsakal, Medih; Kavukcu, Ender; Karadeniz, Tahir

2011-01-01

384

Branch Retinal Vein Occlusion: Classification and Treatment  

Microsoft Academic Search

Branch retinal vein occlusion (BRVO) refers to a heterogeneous group of disorders with different clinical aspects, courses, and probably therapy. Depending on the site of the arteriovenous crossing, we can roughly divide BRVO into 3 main groups: major BRVO, hemispheric retinal vein occlusion, and macular BRVO. Main treatment options include laser treatment, corticosteroid administration, anti-VEGF drugs, and sheathotomy with or

Maurizio Battaglia Parodi; Francesco Bandello

2009-01-01

385

[Arteriovenous dissection for branch retinal vein occlusion].  

PubMed

Arteriovenous dissection (AVD) is a surgical maneuver to separate the retinal artery and vein at the crossing site in patients with branch retinal vein occlusion (BRVO). The published studies showed an evidence level 3. AVD seems to be maintainable in patients with recent onset of BRVO and decimal visual acuity < or =0.4. PMID:18317778

Feltgen, N; Hattenbach, L-O; Mirshahi, A; Hansen, L

2008-04-01

386

Postpartum ovarian vein thrombophlebitis: sonographic diagnosis  

Microsoft Academic Search

Background: We describe our experience with sonographic diagnosis of ovarian vein thrombosis, an uncommon but dangerous postpartum complication. Methods: We retrospectively reviewed the medical records of seven patients in our institution who developed postpartum ovarian vein thrombophlebitis within the past 5 years. Results: In all cases the diagnosis was made by ultrasound, which showed tubular hypoechoic masses lateral to the

I. Hadas-Halpern; M. Patlas; D. Fisher

2002-01-01

387

The occurrence of quartz in coal fly ash particles  

SciTech Connect

Quartz is present in both coal and residual ash. Ash originates from combustion of pulverised coal and, once removed from the flue gases by electrostatic precipitators (ESPs), it is called pulverized fuel ash (PFA). Thus, occupational exposure to PFA could also include exposure to silica. However, epidemiological studies did not show evidence of progressive massive fibrosis (PMF). In vitro tests demonstrated that PFA is less toxic than silica, and in vivo data of PFA did not support the importance of silica content for toxicity. Commissioned by the Dutch coal-fired power plants, KEMA has started a research project to determine the quartz content in coal and the corresponding PFA. It appears that on average 50% of the alpha-quartz in coal is found again in the total fraction of PFA (D50(ae) 31 {mu}m, where D50(ae) is the aerodynamically mass median diameter), whereas 16% is found in an even finer fraction (D50(ae) 10 {mu}m). The remaining part of the quartz is embedded in a glass phase. Scanning electron microscopy (SEM) with x-ray microanalyses (XMA) of cross-sections of 11,130 ash particles showed that quartz in PFAis present as unmelted sand particles. These quartz particles are angularly shaped. However, two types are to be distinguished: free coarse angular quartz particles (not respirable) and small angular quartz particles within the PFA particles. From the SEM/XMA results, it has to be concluded that the quartz in the respirable fraction is predominantly present within the original molten PFA particle. Since the effects of quartz are surface related, this elucidates the negative results of quartz-related effects of PFA in epidemiological, in vitro and in vivo studies. Besides, the amount of the total alpha-quartz in the respirable fraction of the ashes studied is less than 0.2%, so probably the Dutch occupational quartz standard of 0.075 mg m{sup 3} will not be exceeded.

Meij R.; Nagengast S.; Winkel H.T.

2000-10-15

388

Geochemistry of hydrothermal plume in the Suiyo Seamount Caldera  

Microsoft Academic Search

Chemical compounds of the hot basalt origin are discharged into the deep ocean via hydrothermal plume by the deep-sea hydrothermal activity. The hydrothermal plume is widely diffused to the ocean by mixing with ambient seawater. Chemical reactions and interactions with microorganisms in the diffusion process of the hydrothermal plume are important to comprehend the oceanic geochemical cycles. Recently, it has

K. Shitashima; Y. Maeda

2002-01-01

389

21 CFR 880.6970 - Liquid crystal vein locator.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Liquid crystal vein locator. 880.6970 Section 880...Miscellaneous Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a device used to...

2013-04-01

390

21 CFR 880.6970 - Liquid crystal vein locator.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Liquid crystal vein locator. 880.6970 Section 880...Miscellaneous Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a device used to...

2009-04-01

391

21 CFR 880.6970 - Liquid crystal vein locator.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Liquid crystal vein locator. 880.6970 Section 880...Miscellaneous Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a device used to...

2010-04-01

392

Enhancing the contrast of subcutaneous veins  

NASA Astrophysics Data System (ADS)

A technique for enhancing the contrast of subcutaneous veins has been demonstrated. This technique uses a near infrared light source and one or more infrared sensitive CCD TV cameras to produce a contrast enhanced image of the subcutaneous veins. This video image of the veins is projected back onto the patient's skin using an LCD vein projector. The use of an infrared transmitting filter in front of the video cameras prevents any positive feedback from the visible light from the video projector from causing instabilities in the projected image. The demonstration contrast enhancing illuminator has been tested on adults, both Caucasian and African-American, and it enhances veins quite well in most cases. Preliminary studies on a 9 month old girl indicate promise for pediatric use.

Zeman, Herbert D.; Lovhoiden, Gunnar

1999-07-01

393

Geothermometry, geochronology, and mass transfer associated with hydrothermal alteration of a rhyolitic hyaloclastite from Ponza Island, Italy  

USGS Publications Warehouse

A rhyolitic hyaloclastite from Ponza Island, Italy, was hydrothermally altered, producing four distinct alteration zones based on X-ray diffraction mineralogy and field textures: (1) nonpervasive argillic zone; (2) propylitic zone; (3) silicic zone; and (4) sericitic zone. The unaltered hyaloclastite is volcanic breccia with clasts of vesiculated obsidian in a matrix of predominantly pumice lapilli. Incomplete alteration of the hyaloclastite resulted in the nonpervasive argillic zone, characterized by smectite and disordered opal-CT. The other three zones exhibit more complete alteration of the hyaloclastite. The propylitic zone is characterized by mixed-layer illite-smectite (I-S) with 10 to 85% I, mordenite, opal-C, and authigenic K-feldspar (akspar). The silicic zone is characterized by I-S with ???90% I, pure illite, quartz, akspar, and occasional albite. The sericitic zone consists primarily of I-S with ???66% I, pure illite, quartz, and minor akspar and pyrite. K/Ar dates of I-S indicate hydrothermal alteration occurred at 3.38 ?? 0.08 Ma. Oxygen isotope compositions of I-S systematically decrease from zones 1 to 4. In the argillic zone, smectite has ??18 O values of 21.7 to 22.0??? and I-S from the propylitic, silicic, and sericitic zones ranges from 14.5 to 16.3???, 12.5 to 14.0???, and 8.6 to 11.9???, respectively. ??18 O values for quartz from the silicic and sericitic zones range from 12.6 to 15.9???. By use of isotope fractionation equations and data from authigenic quartz-hosted primary fluid inclusions, alteration temperatures ranged from 50 to 65 ??C for the argillic zone, 85 to 125 ??C for the propylitic zone, 110 to 210 ??C for the silicic zone, and 145 to 225 ??C for the sericitic zone. Fluid inclusion data and calculated ??18 O water values indicate that hydrothermal fluids were seawater dominated. Mass-transfer calculations indicate that hydrothermal alteration proceeded in a relatively open chemical system and alteration in the sericitic zone involved the most extensive loss of chemical species, especially Si. Systematic gains in Mg occur in all alteration zones as a result of I-S clay mineral formation, and systematic losses of Na, Ca, and K occur in most zones. With the exception of Ca, calculations of mass transfer associated with hydrothermal alteration on Ponza agree with chemical fluxes observed in laboratory experiments involving hydrothermal reactions of rhyolite and seawater. The anomalous Ca loss at Ponza may be due to hydrothermal formation of anhydrite and later low-temperature dissolution. On the basis of Mg enrichments derived from circulating seawater, we estimate the following minimum water/rock ratios: 9, 3, 6, and 9 for the argillic, propylitic, silicic, and sericitic zones, respectively. Hydrothermal fluid pH for the propylitic and silicic zones was neutral to slightly basic and relatively acidic for the sericitic zone as a result of condensation of carbonic and perhaps other acids. Copyright ?? 2003 Elsevier Science Ltd.

Altaner, S. P.; Ylagan, R. F.; Savin, S. M.; Aronson, J. L.; Belkin, H. E.; Pozzuoli, A.

2003-01-01

394

Formation of viable nuclei and particle growth in hydrothermal processing of silicon dioxide wafers: A modeling study of entrance effects  

SciTech Connect

A major problem that besets rapid hydrothermal processing of silicon dioxide wafers is the formation of particles. In this report we have used The