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1

Hydrothermal deformation of granular quartz sand  

Microsoft Academic Search

Isotropic and triaxial compression experiments were performed on porous aggregates of St Peter quartz sand to explore the influence of temperature (to 225°C). During isotropic stressing, samples loaded at elevated temperature exhibit the same sigmoidal stress-strain curves and non-linear acoustic emission rates as have previously been observed from room temperature studies on sands, sandstones, and soils. However, results from our

Stephen L. Karner; Andreas K. Kronenberg; Frederick M. Chester; Judith S. Chester; Andrew Hajash Jr

2008-01-01

2

Repeated hydrothermal quartz crystallization and cataclasis in the Bavarian Pfahl shear zone (Germany)  

NASA Astrophysics Data System (ADS)

Field and microstructural data of the Pfahl shear zone in north-eastern Bavaria (Germany) reveal the intimate spatial-temporal connection between fragmentation, fluid influx and quartz crystallization. These processes and their interaction led to complex-structured quartz units: (i) a dense network of early quartz veins, (ii) two domains of fine-grained reddish to grayish quartz masses, (iii) an extended central zone of massive white quartz, and (iv) late cross-cutting closely spaced parallel fractures and partly open quartz veins. The fine-grained quartz domains result from repeated and coeval cataclasis, fluidization and quartz precipitation. Material transport in these domains is at least partly governed by the flow of mobile fluid-quartz-particle suspensions. The complex internal meso-to microstructures of the massive white quartz are generated by repeated processes of fragmentation and grain growth. In general, the brittle part of the Pfahl shear zone represents a key example of cyclic dissolution/precipitation and fragmentation on large scale.

Yilmaz, Tim I.; Prosser, Giacomo; Liotta, Domenico; Kruhl, Jörn H.; Gilg, H. Albert

2014-11-01

3

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

4

Gold-quartz veins in metamorphic terranes and their bearing on the role of fluids in faulting  

Microsoft Academic Search

Gold-quartz vein fields in metamorphic terranes such as greenstone belts provide evidence for the involvement of large volumes of fluids during faulting and may be products of seismic processes near the base of the seismogenic regime. In the Val d'Or district of the Abitibi greenstone belt, Canada, quartz-tourmaline-carbonate veins from a vein field (30×15 km) in the hanging wall of

François Robert; Anne-Marie Boullier; Karima Firdaous

1995-01-01

5

Monazite as an indicator of formation conditions of quartz veins at the Zhelannoe deposit, the Subpolar Urals  

NASA Astrophysics Data System (ADS)

At the Zhelannoe quartz deposit, the content of monazite attains 0.5 wt % in unaltered sericitolite and 18 wt % in hydrothermally altered sericitolite. Two monazite generations, including four varieties, characterize the sequence of formation and alteration of sericitolite bodies at the Zhelannoe deposit. Monazite of the first generation occurs in unaltered sericitolite as prismatic and tabular crystals characterized by (Nd,Ce) > La and enrichment in HREEs and ThO2 (5-16 wt %). Its formation is accompanied crystallization of milk white quartz. Monazite of the second generation occurs in altered sericitolite as the product of recrystallization of the first-generation monazite. The large drusy crystals of second-generation monazite were formed similarly with Alpine-type veins. Monazite of the second generation is characterized by Ce > (La,Nd), low contents of HREEs and ThO2 (0.5-7 wt %) and high contents of CaO and SO3 (up to 3-5 wt %). Monazite of the second generation appeared as a result of local superimposed processes and is a characteristic feature of the Zhelannoe deposit.

Repina, S. A.

2008-12-01

6

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

7

Tectonic conditions of hydrothermal polymetallic vein-type mineralization, Sainte Marie-aux-Mines, France  

NASA Astrophysics Data System (ADS)

The Sainte-Marie-aux-Mines (SMM) mines host one of the most famous and oldest silver deposits in Europe. The SMM district is located in the central part of the Vosges mountains, France, within gneiss and granites of the Moldanubian zone. The SMM district includes the Neuenberg E-W vein-type Cu-Ag-As/Pb-Zn deposit and the Altenberg N-S vein-type Pb-Zn-Ag deposit. Deposition of the SMM hydrothermal mineralization occurred under a brittle tectonic regime that might be connected to neo-Variscan and/or post-Variscan tectonics, in a similar way as the polymetallic vein deposits of the Black Forest, Germany. A structural study was done in the Neuenberg area, in the vicinity of the Saint-Jacques vein, and within the Gabe Gottes mine, considering the orientation, extent, chronology and density of faults as well as the nature of the infilling minerals. In the Gabe-Gottes mine, the Saint-Jacques vein comprises multiple successive, sub-parallel subvertical veinlets with gangue minerals, mostly carbonates and quartz, and metal-bearing phases, sulfides and sulfosalts. The veinlets are 2 to 50 cm thick and strike N80° to N110°, the earlier veins slightly dipping towards the north, and the latest one, to the south. Seven systems of faults were identified, which may be classified into three major groups formed respectively before, during and after the main stage of ore deposition: a) Pre-mineralization faults - These consist of sinistral NE-SW strike-slip faults, and NW-SE and NE-SW steeply dipping normal faults. These could be related to Carboniferous events considering their relationships with the granitoid intrusives present in the mine area (Brézouard leucogranite ~329 Ma), and the extensional tectonics developed during exhumation processes. b) Faults associated with the main ore-deposition - These faults could be related to late-Hercynian processes from compressional to extensional tectonic regimes. Mineralization controlling faults consist of dextral and sinistral E-W strike-slip faults. Early strike-slip movements are assessed by the presence of striated iron oxides, the crystallization of which is considered to be early during the ore deposition process. Mineralizing fluids were probably fluorine-rich as F-bearing minerals, sericite, chlorite and apatite are present in the chlorite zone associated with early sulphide-rich ores. The E-W mineralized faults are only easily compatible with the tectonics known in Permian times. c) Late-stage faults - These could be related to the numerous changes in plate configuration which occur during the Mesozoic and Cenozoic times, in accordance with the creation of the Paris basin, the opening of Atlantic ocean and Rhine Graben, as well as with the Tethys closure. For example, the vertical lineation superposed on an horizontal lineation observed on mineralized rocks indicate reactivation of the former E-W mineralized veins under a normal movement. The latter may correspond to an extensive regime known during Oligocene times. On the other hand, one of the major late-stage faults strikes N-S and is related to a dextral strike-slip system, which could be considered as Miocene. It is expected that fluid remobilization occurred during fault reactivation, a process which could have led to successive ore deposition following the emplacement of the major E-W mineralized veins. A fluid inclusion study in the gangue minerals of the Gabe Gottes is now under investigation. This together with isotopic studies will help to determine the source of the mineralizing fluids, as well as the conditions of ore deposition. Keywords: Faults, polymetallic mineralization, variscan orogeny, Gabe-Gottes, Sainte-Marie-aux-Mines, Vosges, F-rich fluids.

Hafeznia, Y.; Bourlange, S.; Ohnenstetter, M.

2012-04-01

8

Volcanogenic-related origin of sulfide-rich quartz veins: evidence from O and S isotopes at the Géant Dormant gold mine, Abitibi belt, Canada  

Microsoft Academic Search

The Géant Dormant gold mine is a sulfide-rich quartz vein gold deposit hosted by a volcano-sedimentary sequence and an associated\\u000a felsic endogenous dome and dikes. The auriferous quartz-sulfide veins were preceded by two synvolcanic gold-bearing mineralizing\\u000a events: early sulfidic seafloor-related and later disseminated pyrite in the felsic dome. This deposit differs from classical\\u000a Archean auriferous quartz vein deposits by the

D. Gaboury; R. Daigneault; G. Beaudoin

2000-01-01

9

Colorado quartz: occurrence and discovery  

USGS Publications Warehouse

The many varieties and associations of quartz found throughout the state rank it as one of the premier worldwide localities for that species. This paper briefly outlines the historical importance of the mineral, the mining history and the geological setting before discussing the varieties of quartz present, its crystallography and the geological enviroments in which it is found. The latter include volcanic rocks and near surface igneous rocks; pegmatites; metamorphic and plutonic rocks; hydrothermal veins; skarns and sedimentary deposits. Details of the localities and mode of occurrence of smoky quartz, amethyst, milky quartz, rock crystal, rose quartz, citrine, agate and jasper are then given. -S.J.Stone

Kile, D.E.; Modreski, P.J.; Kile, D.L.

1991-01-01

10

Geology, Ore-microscopy and Fluid inclusion study on Auriferous Quartz Veins at the Gidami Gold Mine, Eastern Desert of Egypt  

NASA Astrophysics Data System (ADS)

The gold deposits are represented by auriferous quartz veins and aplitic dykes that are cutting through granitic rocks. The main lode of gold is confined to two principal veins occupying fracture zones and fissures. The main auriferous vein is striking mainly NNW-SSE with dipping 85° NE, it extends up to 450 m with an average thickness 120 cm. The second vein is striking NW-SE and dipping 60° E, it extends for 150 m with an average thickness 35 cm. The gold bearing veins are made up of fine grained quartz that is always massive, milky-white with reddish or greenish tint. They commonly include vugs, some of them are occasionally filled with iron oxides, carbonate and clay minerals. Sometimes the quartz veins enclose remnants of altered wall rock materials as an indication for the metamorphic or syntectonic nature of the veins. Brecciation, comb layering, swelling and nodules manganese dendrites are usually detected. The microscopic examination for thin and polished sections of auriferous quartz veins revealed that quartz and calcite are the predominant minerals commonly associated with accessory minerals (fluorite, apatite, zircon, muscovite and sericite). Ore mineral assemblage is found as disseminated sulfide minerals (pyrite, sphalerite, chalcopyrite, molybdenite, pyrrhotite covellite, galena and pentlandite). Ilmenite and goethite are the main iron oxide mineral phases. Gold most commonly occurs as small inclusions within pyrite or goethite. Gold also occurs as tiny grains scattered within quartz vein (in close proximity to the sulfides) or as disseminated grains in the altered wall rocks. Hydrothermal alteration includes silicification, kaolinitization, sericitisation, carbonatisation confined to a delicate set of veins. Petrography and microthermometry of fluid inclusions revealed that the majority of inclusions are of primary/pseudosecondary nature that occur in clusters and along growth zones or along intra-granular planar trails (pseudosecondary inclusions). Two types of samples were taken from the auriferous quartz vein; samples from the outer zone (Rim) and samples from the inner zone (Core). With respect to number of phases present at the room temperature (20 °C) there are two main groups of fluid inclusions can be recognized in both zones: A) two-phase - aqueous inclusions (Type I) and B) three-phase - carbonic-rich inclusions (Type II). Type I inclusions could be further subdivided into two sub-types (H2O-NaCl±KCl) and (H2O-NaCl±MgCl2) systems, based mainly on the eutectic temperature (Teu). For (H2O-NaCl±KCl) system, eutectic temperatures range from -22.1 °C to -23.9 °C at the rim and from -22.7 °C to -23.5 °C at the core. Values of homogenization temperatures (Th) are between (190.4 °C - 273.1 °C) at the rim and between (217 °C - 281.1 °C) at the core. Salinity has a range of (0.73 to 4.7 mass% of NaCl) at the rim and (0 to 1.65 mass% of NaCl) at the core. For (H2O-NaCl± MgCl2) system, eutectic temperatures range from -32.7 °C to -35 °C at the rim and from -33.9 °C to -34.2 °C at the core. Values of homogenization temperatures are up to 376.1 °C at the rim and between (310.6 °C - 480.2 °C) at the core. Salinity has a range of (2.15 to 3.8 mass% of NaCl) at the rim and (2.15 to 3.65 mass% of NaCl) at the core. Type II inclusions of (H2O-NaCl-CO2±CH4) system, most of them were homogenized to liquid state and the other were homogenized to vapour or rarely to critical state. The total homogenization temperature ranges between (260 °C - 340 °C) at the rim with low salinity (0 - 4.2 mass% NaCl equiv.) and density of range (0.49 - 0.86 g/cc). Within core samples, the total homogenization temperature ranges between (299.9 °C - 408.8 °C) with salinity (3.73 - 4.78 mass% of NaCl equiv.) and density of range (0.61 - 0.87 g/cc). These data are consistent with transportation of gold as a bisulphide complex, likely due to decreases in sulphur activity accompanying fluid unmixing.

Abd El Monsef, Mohamed; Salem, Ibrahim; Slobodnik, Marek

2013-04-01

11

Metamorphic origin of ore-forming fluids for orogenic gold-bearing quartz vein systems in the North American Cordillera: Constraints from a reconnaissance study of ??15N, ??D, and ??18O  

USGS Publications Warehouse

The western North American Cordillera hosts a large number of gold-bearing quartz vein systems from the Mother Lode of southern California, through counterparts in British Columbia and southeastern Alaska, to the Klondike district in central Yukon. These vein systems are structurally controlled by major fault zones, which are often reactivated terrane-bounding sutures that formed in orogens built during accretion and subduction of terranes along the continental margin of North America. Mineralization ages span mid-Jurassic to early Tertiary and encompass much of the evolution ofthe Cordilleran orogen. Nitrogen contents and ??15N values of hydrothermal micas from veins are between 130 and 3,500 ppm and 1.7 to 5.5 per mil, respectively. These values are consistent with fluids derived from metamorphic dehydration reactions within the Phanerozoic accretion-subduction complexes, which have ??15N values of 1 to 6 per mil. The ??18O values of gold-bearing vein quartz from different locations in the Cordillera are between 14.6 and 22.2 per mil but are uniform for individual vein systems. The ??D values of hydrothermal micas are between -110 and -60 per mil. Ore fluids have calculated ??18O values of 8 to 16 per mil and ??D values of -65 to -10 per mil at an estimated temperature of 300??C; ??D values of ore fluids do not show any latitudinal control. These results indicate a deep crustal source for the ore-forming fluids, most likely of metamorphic origin. Low ??DH2O values of -120 to -130 per mil for a hydrous muscovite from the Sheba vein in the Klondike district reflect secondary exchange between recrystallizing mica and meteoric waters. Collectively, the N, H, and O isotope compositions of ore-related hydrothermal minerals indicate that the formation of these gold-bearing veins involved dilute, aqueous carbonic, and nitrogen-bearing fluids that were generated from metamorphic dehydration reactions at deep crustal levels. These data are not consistent with either mantle-derived fluids or granitoid-related magmatic fluids, nor do they support a model involving deeply circulated meteoric water.

Jia, Y.; Kerrich, R.; Goldfarb, R.

2003-01-01

12

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

13

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

Microsoft Academic Search

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 -

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

2009-01-01

14

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

15

Blue, complexly zoned, (Na,Mg,Fe,Li)-rich beryl from quartz-calcite veins in low-grade metamorphosed Fe-deposit Skály near Rýma?ov, Czech Republic  

NASA Astrophysics Data System (ADS)

Syn-tectonic quartz-calcite veins containing blue beryl are enclosed in hematite > magnetite-rich portions of the low-grade metamorphosed Fe-deposit Skály near Rýma?ov, Czech Republic. Aggregates of pale to deep blue beryl, up to 2 cm in diameter, are associated with euclase, clinochlore, hematite, albite and dravite. Complexly zoned beryl crystals consist of skeletal aggregates of beryl I randomly distributed within volumetrically dominant beryl II with narrow rims of beryl III. All types of beryl have similar contents of Na (0.32-0.49 apfu) and Mg (0.31-0.41 apfu) but variable contents of Fetot (0.05-0.34 apfu) and Al (1.20-1.62 apfu). The LA-ICP-MS study yielded elevated contents of Li, up 1,314 ppm (0.28 wt.% Li2O) in beryl I. The quartz-calcite veins represent an unusual type of low-T metamorphic-hydrothermal vein related to Fe-ore deposit characterized by single-stage fracturing and mobilization in a closed system at T~200-300°C and CO{3/2-} as a major complexing agent for the mobility of Be.

Novák, Milan; Gadas, Petr; Filip, Jan; Vaculovi?, Tomáš; P?ikryl, Jan; Fojt, Bohuslav

2011-10-01

16

Microfabric memory of vein quartz for strain localization in detachment faults: A case study on the Simplon fault zone  

NASA Astrophysics Data System (ADS)

This manuscript deals with the adaptation of quartz-microfabrics to changing physical deformation conditions, and discusses their preservation potential during subsequent retrograde deformation. Using microstructural analysis, a sequence of recrystallization processes in quartz, ranging from Grain-Boundary Migration Recrystallization (GBM) over Subgrain-Rotation Recrystallization (SGR) to Bulging Nucleation (BLG) is detected for the Simplon fault zone (SFZ) from the low strain rim towards the internal high strain part of the large-scale shear zone. Based on: (i) the retrograde cooling path; (ii) estimates of deformation temperatures; and (iii) spatial variation of dynamic recrystallization processes and different microstructural characteristics, continuous strain localization with decreasing temperature is inferred. In contrast to the recrystallization microstructures, crystallographic preferred orientations (CPO) have a longer memory. CPO patterns indicative of prism and rhomb glide systems in mylonitic quartz veins, overprinted at low temperatures (?400 °C), suggest inheritance of a high-temperature deformation. In this way, microstructural, textural and geochemical analyses provide information for several million years of the deformation history. The reasons for such incomplete resetting of the rock texture is that strain localization is caused by change in effective viscosity contrasts related to temporal large- and small-scale temperature changes during the evolution of such a long-lived shear zone. The spatially resolved, quantitative investigation of quartz microfabrics and associated recrystallization processes therefore provide great potential for an improved understanding of the geodynamics of large-scale shear zones.

Haertel, Mike; Herwegh, Marco

2014-11-01

17

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

18

Tectonic and fluid inclusion constraints on the origin of quartz veins with giant crystals in the Tocantins structural province (Cristalândia, central Brazil)  

Microsoft Academic Search

Large, lens-shaped quartz veins between the Cristalândia and Pium settlements (Tocantins, Brazil) occur in a N–S-oriented, up to 3km wide, dextral, orogen-parallel strike-slip shear zone. Formation PT conditions recorded by multiphase brine inclusions in quartz crystals from drusy cavities correspond to 280–400°C and up to 300MPa, as indicated by high-density CO2 bubbles (up to 0.96g\\/cm3) observed in some brine inclusions.

Frantisek Marko; Vratislav Hurai; Marian Dyda; Gervalino Almeida; Walter Prochaska; Rainer Thomas

2006-01-01

19

Lazulite and Ba, Sr, Ca, K-rich phosphates–sulphates in quartz veins from metaquartzites of Tribe? Mountains, Western Carpathians, Slovakia: Compositional variations and evolution  

Microsoft Academic Search

The phosphate–sulphate mineralization occurs in quartz veins in Lower Triassic metaquartzites of the Tribe? Mts., Central Western Carpathians, Slovakia. The mineralization comprises of lazulite, Ba, Sr, Ca, K-rich phosphates–sulphates and barite in an association with muscovite, hematite, locally rutile, zircon, chlorite and tourmaline. The most widespread lazulite forms up to 10 cm large pale to deep blue aggregates in massive quartz.

Pavel Uher; TomᚠMikuš; Rastislav Milovský; Adrian Biron; Ján Spisiak; Jozef Lipka; Ján Jahn

2009-01-01

20

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

Microsoft Academic Search

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

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

2011-01-01

21

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

Microsoft Academic Search

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

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

2011-01-01

22

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)

Eclogite-hosted garnet-spinel-corundum-quartz-bearing titanohematite veins and lenses (10-20 cm in width) are described for the first time in the Sulu ultrahigh-pressure metamorphic terrane. Some of the lenses were aligned parallel to the foliation of the host eclogite, suggesting that they were the product of ductile deformation of one titanohematite layer. A vein composed of titanohematite + ilmenite + hematite + spinel + garnet + corundum + quartz + K-feldspar + albite was studied in detail. Ti-Fe oxides account for up to >80% and Al-rich phases for ˜15% of the total volume of this vein. Electron microprobe analyses show that the titanohematite solid solution was made up of 0.75 hematite + 0.25 ilmenite. The unusual mineral assemblage of garnet + spinel + corundum + quartz implies that this vein could have experienced high temperatures (>900 °C). Although the garnets showed well-defined Mg and Mn diffusion zoning in the rim as a result of the high temperature event, slight Mg and Mn growth zoning was preserved in the core. Thus, we suggest that the Sulu UHP terrane could have experienced a short-lived, high-temperature (>900 °C) stage during exhumation. Garnets in the titanohematite vein were characterized by extremely low trace-element contents. Petrological and geochemical features of the veins suggest that they could be metamorphic products of igneous cumulates composed of magnetite + plagioclase ± clinopyroxene.

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

2011-09-01

23

Hydrothermal Synthesis of Monodisperse Single-Crystalline Alpha-Quartz Nanospheres  

PubMed Central

Uniformly-sized, single-crystal alpha-quartz nanospheres have been synthesized at 200°C and 15atm under continuous stirring starting from uniform, amorphous Stöber silica colloids and using NaCl and alkali hydroxide as mineralizers. Quartz nanosphere size is controlled by the colloid particle size via direct devitrification. Uniform, high-purity nanocrystalline quartz is important for understanding nanoparticle toxicology and for advanced polishing and nanocomposite fabrication. PMID:21629887

Jiang, Xingmao; Jiang, Ying-Bing

2014-01-01

24

The solubility of natural quartz sand at 100?C, and 150?C, 345 bars: an experimental investigation in a flow-through hydrothermal system  

E-print Network

Thesis by GREGORY LEE BURNS Approved as to style and content by: Andrew jash (Chair of Committee) Robert K. Po p (Member) Brann nson r) John H. pan (Head of Department) May 1989 ABSTRACT The Solubility of Natural Quartz Sand at 100'C and 150...'C, 345 bars: An Experimental Investigation in a Flow-Through Hydrothermal System. (May 1989) Gregory Lee Burns, B. A. , Franklin and Marshall College Chair of Advisory Committee; Dr. Andrew Hajash Natural quartz sand was reacted with distilled...

Burns, Gregory Lee

2012-06-07

25

Hydrothermal Quartz Oxygen Isotope Ratios in Altered Post-Collapse Rhyolite at Sevenmile Hole, Grand Canyon of the Yellowstone River, Yellowstone National Park, WY  

NASA Astrophysics Data System (ADS)

The Grand Canyon of the Yellowstone River, Yellowstone National Park, Wyoming, displays regions of pervasively hydrothermally altered rock formed in the shallow, epithermal portions of a hydrothermal system. Hydrothermal fluid circulation causing the alteration is driven by magmatism related to the Yellowstone Caldera thermal anomaly. The protolith, the Tuff of Sulfur Creek, is a 480 ka high silica, low ?18O rhyolitic tuff that erupted after the Yellowstone caldera collapse at 640 ka. Incision of the canyon has exposed 350 vertical meters in the Sevenmile Hole vicinity. Hydrothermal mineralogy determined by standard XRD powder techniques and PIMA on over 90 samples shows both vertical and lateral variation. A vertical transition occurs from kaolinite at depths less than about 100 meters below the present day canyon rim, to illite in deeper exposures. This transition may correspond to a temperature of 150°C, based on a similar transition in the active Yellowstone hydrothermal system. A lateral variation of mineral assemblages in the altered tuff suggests temperatures that may range up to 330°C. Alteration was most likely caused by a liquid due to the presence of pyrite throughout. Local zones of suspected hydrothermal fluid upwelling correspond to the most intense silicification and highest temperature mineral assemblages. This alteration includes quartz + illite ± hyalophane, slawsonite, and buddingtonite. At similar depths outside inferred fluid upwelling zones, lower temperature assemblages are quartz + illite/smectite ± alunite and buddingtonite. At shallow depths, the lowest temperatures are suggested by the presence of quartz + kaolinite ± alunite and opal. Dickite, a kaolinite polymorph, may indicate locally higher temperatures in the shallow kaolinite zones. Oxygen isotope ratios of silica phases were measured for approximately 50 samples using laser fluorination techniques with an error of ±0.2‰. Hydrothermal quartz displays ?18O signatures more negative (ranging from -5.1 to -0.7 ‰) than quartz phenocrysts in the unaltered tuff (typically 1.7 ‰). Relict quartz phenocrysts in altered tuff have an average value of 0.5 ‰ (n=23, ?=0.7), suggesting minimal oxygen exchange with the hydrothermal fluid. Paragenetically later prismatic vug-filling quartz yielded the lowest average values of -4.5 ‰ (n=5, ?=0.4) while earlier massive quartz in the same vugs range up to -1.0 ‰. The variation shows that the fluid ratio and/or temperature evolved as the vug crystallized inward. Matrix silicification produced quartz ?18O values averaging -4.1 ‰ (n=11, ? =0.8). The low hydrothermal silica signatures suggest that they formed in equilibrium with a fluid that was dominantly meteoric water. There is obvious disequilibrium between open space filling hydrothermal quartz and matrix silicification that may be due to the timing of interaction with circulating waters, progressing water-rock ratios, and/or variable temperatures of alteration. Higher temperature mineral assemblages appear to correspond laterally with the more negative quartz ?18O values. Water-rock interaction was likely greater in these areas and they may mark the location of intense hydrothermal fluid upflow and/or higher temperatures.

Phillips, A. R.; Larson, P. B.; John, D. A.; Pauley, B. M.

2008-12-01

26

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

27

Orthogonal fracture formation in the South Wales coalfield: implications from a field study and fluid overpressure of quartz veins  

NASA Astrophysics Data System (ADS)

Orthogonal fractures can easily make networks in geological formations and are of great importance for permeability and fluid transport in subsurface reservoirs. Despite many studies focusing on the formation of orthogonal fractures, no clear and generally accepted model has been established as yet although their formation is widely believed to occur during crustal uplift or exhumation. Here we provide new insights into their mechanism of formation based on the results of a fieldwork and analytical study of orthogonal fractures and quartz veins in alternating sand-shale layers in the South Wales coalfield, which is one of foreland basins developed in relation with north-south compression of the Variscan Orogeny. More than 3,000 fractures were measured at various localities extending from southern end to northern end of the basin. Most of the fractures in the sandstone layers, are extension fractures (mode I cracks), and become arrested at contacts with shale layers. The fractures strike north-south and east-west. Some fractures are filled with shale, probably supplied from adjacent shale layers, suggesting the shale behaved as semi-ductile material at the time of fracture formation. A remarkable observation is that most of the fractures are perpendicular to bedding planes throughout the basin. This is despite the fact that the beds are strongly folded as a result of the Variscan Orogeny. The perpendicular attitude suggests that the fracture formation somewhat predates or coincides with that of folding. This implies that the orthogonal fractures in this area did not form during crustal uplift/exhumation but rather during basin growth at the time of regional north-south convergence and associated compression of the Variscan Orogeny. By using aspect (length/thickness) ratios of quartz veins of the same geometry as the orthogonal fractures, fluid overpressure (driving pressure) at the time of fracture formation is estimated at around 33 MPa for fractures striking north-south and 18 MPa for those striking east-west. Although the thick Dinantian Carbonates immediately underlie the sandstones of the Coal Measure Group, carbonate minerals are absent in the veins, suggesting that the main driving stress for fracture formation may not have been buoyancy related to a deeper fluid source in the underlying carbonates but rather local stress concentrations, resulting in differential stresses, in the sandstones. These conditions imply that both north-south and east-west extensional stress fields were induced in the sandstones during the basin growth under the regional north-south compression. The process responsible for the north-south extension within the sandstones is, at this stage, not entirely clear. One possibility is that cyclic stress and strain concentration in thrust zones could induce tensile stresses during stress relaxation of syn- and post-slip period of major thrusts. Viscous behaviour of the shale in the study area may have generated the north-south tensile stress fields in the sandstones that resulted in fracture formation.

Fukunari, Tetsuzo; Gudmundsson, Agust

2014-05-01

28

Geology and geochemistry of the Bulong quartz–barite vein-type gold deposit in the Xinjiang Uygur Autonomous Region, China  

Microsoft Academic Search

The Bulong gold deposit, located in Akqi County, Southwest Tianshan, China, occurs in Upper Devonian fine-grained clastic rocks. Gold mineralization is controlled by a series of gently tilted fractured zones. Four ore-bearing quartz–barite veins have been recognized in the Bulong ore district. These range in length from 15 to 660 m and are up to 1 m thick. On the

Fuquan Yang; Jingwen Mao; Yitian Wang; Frank P. Bierlein

2006-01-01

29

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  

Microsoft Academic Search

Summary  In the area of the Ghundao Hill (Northern Frontier Province, Pakistan) an orange-yellow to cherry-red topaz is found in calcite,\\u000a quartz, white mica veins crosscutting the schistosity of probably Silurian to Devonian gray limestones. Topaz with such a\\u000a range of colours is traded as Imperial Topaz. Low fluorine contents of about 15?wt.%, oxygen isotope thermometry, K\\/Ar age\\u000a determination on white

G. Morteani; A. Voropaev

2007-01-01

30

Investigation of the long-term performance of betafite and zirconolite in hydrothermal veins from Adamello, Italy  

SciTech Connect

Betafite and zirconolite occur in Ti-rich hydrothermal veins emplaced within dolomite marble in the contact aureole of the Adamello batholith, northern Italy. Zirconolite contains up to 18 wt% ThO{sub 2} and 24 wt% UO{sub 2}, and exhibits strong compositional zoning. Some zirconolite grains were corroded by the hydrothermal fluid. Betafite, the Ti-rich member of the pyrochlore group, often occurs as overgrowths on zirconolite. The betafite is weakly zoned and contains 29--34 wt% UO{sub 2}. In terms of end-members, betafite contains approximately 50 mole percent CaUTi{sub 2}O{sub 7} and is the closest known natural composition to the pyrochlore phase proposed for use in titanate waste forms. Amorphization and volume expansion of the betafite caused cracks to form in the enclosing silicate mineral grains. Backscattered electron images reveal that betafite was subsequently altered along crystal rims, particularly near the cracks. EPMA data reveal little difference in composition between altered and unaltered areas, except for lower totals, suggesting that alteration is primarily due to hydration. The available evidence demonstrates that both betafite and zirconolite retained actinides for approximately 40 million years after the final stage of vein formation. During this time, betafite and zirconolite accumulated a total alpha-decay dose of 3--4 x 10{sup 16} and 0.2--2 x 10{sup 16} {alpha}/mg, respectively.

Lumpkin, G.R.; Day, R.A.; McGlinn, P.J.; Payne, T.E.; Giere, R.; Williams, C.T.

1999-07-01

31

Transport processes at quartz-water interfaces: constraints from hydrothermal grooving experiments  

NASA Astrophysics Data System (ADS)

We performed hydrothermal annealing experiments on quartzite at temperatures of 392 to 568 °C and fluid pressures of 63 to 399 MPa for up to 120 h during which hydrothermal grooves developed on the free surfaces of the samples. Analysis of surface topology and groove characteristics with an atomic force microscope revealed a range of surface features associated with the simultaneous and successive operation of several processes partly depending on crystal orientation during the various stages of an experiment. Initially, dissolution at the quartzite-sample surface occurs to saturate the fluid in the capsule with SiO2. Subsequently, grooving controlled by diffusion processes takes place parallel to dissolution and precipitation due to local differences in solubility. Finally, quench products develop on grain surfaces during the termination of experiments. Average groove-root angle amounts to about 80° and slightly depends on temperature, run duration, and misorientation between neighboring grains. The grooving is thermally activated, i.e., groove depth ranging from 5 nm to several micrometers for the entire suite of experiments generally increases with temperature and/or run time. We use Mullins' classical theories to constrain kinetics parameters for the transport processes controlling the grooving. In the light of previous measurements of various diffusion coefficients in the system SiO2-H2O, interface diffusion of Si is identified as the most plausible rate-controlling process. Grooving could potentially proceed faster if the fluid were not convecting in the capsule. Characteristic times of healing of microfractures in hydrous environments constrained from these kinetics parameters are consistent with the order of magnitude of time scales over which healing occurs in-situ according to geophysical surveys and of recurrence intervals of earthquakes.

Klevakina, K.; Renner, J.; Doltsinis, N.; Adeagbo, W.

2013-04-01

32

Transport processes at quartz-water interfaces: constraints from hydrothermal grooving experiments  

NASA Astrophysics Data System (ADS)

We performed hydrothermal annealing experiments on quartzite samples at temperatures of 392 to 568 °C and fluid pressures of 63 to 399 MPa for up to 120 h, during which hydrothermal grooves developed on the free surfaces of the samples. An analysis of surface topology and groove characteristics with an atomic force microscope revealed a range of surface features associated with the simultaneous and successive operation of several processes partly depending on crystal orientation during the various stages of an experiment. Initially, dissolution at the quartzite-sample surface occurs to saturate the fluid in the capsule with SiO2. Subsequently, grooving controlled by diffusion processes takes place parallel to dissolution and precipitation due to local differences in solubility. Finally, quench products develop on grain surfaces during the termination of experiments. The average groove-root angle amounts to about 160°, varying systematically with misorientation between neighboring grains and depending slightly on temperature and run duration. The grooving is thermally activated, i.e., groove depth ranging from 5 nm to several micrometers for the entire suite of experiments generally increases with temperature and/or run time. We use Mullins' classical theories to constrain kinetic parameters for the transport processes controlling the grooving. In the light of previous measurements of various diffusion coefficients in the system SiO2-H2O, interface diffusion of Si is identified as the most plausible rate-controlling process. Grooving could potentially proceed faster by diffusion through the liquid if the fluid were not convecting in the capsule. Characteristic times of healing of microfractures in hydrous environments constrained from these kinetic parameters are consistent with the order of magnitude of timescales over which postseismic healing occurs in situ according to geophysical surveys and recurrence intervals of earthquakes.

Klevakina, K.; Renner, J.; Doltsinis, N.; Adeagbo, W.

2014-08-01

33

Formation of parting in quartz  

NASA Astrophysics Data System (ADS)

This paper presents hydrothermal quartz with macroscopic planar parting from the Mesoproterozoic Modum complex in southern Norway. Similar macroscopic parting in hydrothermal quartz with macroscopic planar structures has only been described from two localities in the world; Madagascar (Flörke et al., 1981) and Southern California (Murdoch et al., 1938). The study area consists of well foliated and banded sillimanite- garnet- amphibolite- mica gneiss that is cut at high angle by hydrothermal veins containing albite, chlinoclore, hornblende, hydroxyl apatite and quartz. The rim of the veins is generally made up of almost pure end-member euhedral albite. Then there is vugs with euhedral hornblende (10-25cm long) and euhedral hydroxyl apatite with size ranging from mm scale to several cm. Some places the quartz encloses apatite and hornblende. The quartz is anhedral, inequigranular with undulose extinction bordering sub grain rotation. It has large planar penetrative parting faces with pearly luster; however this is not consistent throughout the outcrop and some places the penetrative faces disappears and the quartz has a conchoidal fracture. The planar faces continue throughout the specimens with a few mm spacing. Thin sections oriented perpendicular to the most pronounced planar structure show lamellas that extinguishes at small angles (2 degrees) to each other. EBSD mapping of the planar faces shows two orientations {0-111} and {1-101}, corresponding to the r- and z-faces respectively, separated by irregular boundaries. The misorientation between these two crystallographic orientations on the parting is a 60 degree rotation on [0 0 1] in correspondence to the dauphiné twin law. Investigations conducted on thin sections cut orthogonal to the parting shows that the parting cuts and offsets the dauphiné twins, indicating a late genesis of the parting. However some internal stress induced movement of the twins are visible. SEM-CL documents three generations of quartz and two, possibly three, planar structures; two evident, one more obscure. The most prominent of the three appears to cut across the recrystallization, offsetting the recrystallization textures with varying distances. We propose a very late formation of the parting due to its crosscutting relationship with all features, such as recrystallized quartz, secondary fluid inclusion trails and twins. The parting develops in crystals that are optimally oriented with respect to ?1 in a fast, low temperature deformation event.

Jørgen Kjøll, Hans; Eske Sørensen, Bjørn

2014-05-01

34

Direct measurement of asperity contact growth in quartz at hydrothermal conditions  

NASA Astrophysics Data System (ADS)

Room-temperature friction and indentation experiments suggest fault strengthening during the interseismic period results from increases in asperity contact area due to solid-state deformation. However, field observations on exhumed fault zones indicate that solution-transport processes, pressure solution, crack healing and contact overgrowth, influence fault zone rheology near the base of the seismogenic zone. Contact overgrowths result from gradients in surface curvature, where material is dissolved from the pore walls, diffuses through the fluid and precipitates at the contact between two asperities, cementing the asperities together without convergence normal to the contact. To determine the mechanisms and kinetics of asperity cementation, we conducted laboratory experiments in which convex and flat lenses prepared from quartz single crystals were pressed together in an externally heated pressure vessel equipped with an optical observation port. Convergence between the two lenses and contact morphology were continuously monitored during these experiments using reflected-light interferometry through a long-working-distance microscope. Contact normal force is constant with an initial effective normal stress of 1.7 MPa. Four single-phase experiments were conducted at temperatures between 350 and 530C at 150 MPa water pressure, along with two controls: one single phase, dry at 425C and one bimaterial (qtz/sapphire) at 425C and 150 MPa water pressure. No contact growth or convergence was observed in either of the controls. For wet single-phase contacts, however, growth was initially rapid and then decreased with time following an inverse squared dependence of contact radius on aperture. No convergence was observed over the duration of these experiments, suggesting that neither significant pressure solution nor crystal plasticity occurred at these stresses and temperatures. The formation of fluid inclusions between the lenses indicate that the contact is not uniformly wetted. The contact is bounded by small regions of high aperture, reflecting local free-face dissolution as the source for the overgrowth, a definitive indication of diffusion-limited growth. Diffusion-limited growth is also consistent with the inverse squared aperture dependence. However, the apparent activation energy is ~125 kJ/mol, much higher than expected for silica diffusion in bulk water; at present we do not have a complete explanation for the high activation energy. When our lab-measured overgrowth rates are extrapolated to the 5 to 30 micron radius contacts inferred from near-field recordings of M-2 sized earthquakes in deep drill holes and mines (i.e., SAFOD and NELSAM), we predict rates of contact area increase that are orders of magnitude faster than seen in dry, room-temperature friction experiments. This suggests that natural strength recovery should be dominated by fluid-assisted processes at hypocentral conditions near the base of the seismogenic zone.

Beeler, N. M.; Hickman, S. H.

2008-12-01

35

Partitioning and Leaching Behavior of Actinides and Rare Earth Elements in a Zirconolite- Bearing Hydrothermal Vein System  

SciTech Connect

Chemical extraction techniques and scanning electron microscopy were used to study the distribution and behavior of actinides and rare earth elements (REE) in hydrothermal veins at Adamello (Italy). The six samples discussed in this paper were from the phlogopite zone, which is one of the major vein zones. The samples were similar in their bulk chemical composition, mineralogy, and leaching behavior of major elements (determined by extraction with 9 M HCl). However, there were major differences in the extractability of REE and actinides. The most significant influence on the leaching characteristics appears to be the amounts of U, Th and REE incorporated in resistant host phases (zirconolite and titanite) rather than readily leached phases (such as apatite). Uranium and Th are very highly enriched in zirconolite grains. Actinides were more readily leached from samples with a higher content of U and Th, relative to the amount of zirconium. The results show that REE and actinides present in chemically resistant host minerals can be retained under aggressive leaching conditions. (authors)

Payne, Timothy E.; Hart, Kaye P.; Lumpkin, Gregory R.; McGlinn, Peter J. [Australian Nuclear Science and Technology Organisation, PMB 1, Menai, 2234 (Australia); Giere, Reto [Mineralogisch-Geochemisches Institut, Albert-Ludwigs-Universitaet, Freiburg, D-79104 (Germany)

2007-07-01

36

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

37

Characteristics of gold bearing quartz veins at the historic Morning Star mine, Preservation Inlet, SW Fiordland, New Zealand  

Microsoft Academic Search

The Morning Star mine is one of numerous historically mined gold-quartz lodes in the Preservation Inlet goldfield of southwest Fiordland. The mine is hosted in Early Ordovician metasedimentary rocks that are composed predominantly of psammitic and pelitic lithologies. These rocks still contain their primary depositional features and are characterised by upper greenschist facies metamorphic grade. The Morning Star mine lies

M. J. Begbie; D. Falconer; D. Craw

38

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

NASA Astrophysics Data System (ADS)

Hydrothermal synthesis process of tobermorite (5CaO·6SiO 2·5H 2O) 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.

Kikuma, J.; Tsunashima, M.; Ishikawa, T.; Matsuno, S.; Ogawa, A.; Matsui, K.; Sato, M.

2011-08-01

39

Tectonic and fluid inclusion constraints on the origin of quartz veins with giant crystals in the Tocantins structural province (Cristalândia, central Brazil)  

NASA Astrophysics Data System (ADS)

Large, lens-shaped quartz veins between the Cristalândia and Pium settlements (Tocantins, Brazil) occur in a N-S-oriented, up to 3 km wide, dextral, orogen-parallel strike-slip shear zone. Formation PT conditions recorded by multiphase brine inclusions in quartz crystals from drusy cavities correspond to 280-400 °C and up to 300 MPa, as indicated by high-density CO 2 bubbles (up to 0.96 g/cm 3) observed in some brine inclusions. The estimated crystallization pressures correspond to approximately 10-12 km of overburden, assuming a lithostatic load. The high salinity brines (up to 48 wt%) cannot be correlated with halite-fractionated seawater due to the low Br concentrations. Similarly, the high salt concentrations cannot be attributed to magmatic fluid released during crystallization of a silicic magma at such great pressures. The brines likely were liberated from a hydrated oceanic crust and cover sediments of the Goiás Ocean, subducting beneath the Amazonian plate during the Neoproterozoic Brasiliano orogenic cycle. Fluids derived from the hydrated crust have been trapped in en échélon-arranged tension gashes during a superimposed transtensional/extensional orogenic stage.

Marko, František; Hurai, Vratislav; Dyda, Marian; Almeida, Gervalino; Prochaska, Walter; Thomas, Rainer

2006-07-01

40

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

41

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

42

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

43

Genesis of the hydrothermal gold deposits in the Canan area, Lepaguare District, Honduras  

NASA Astrophysics Data System (ADS)

The Canan area (Honduras) is characterized by a gold-bearing ore deposit that is associated with quartz-veined shear zones. Gold mineralization occurs in low-to medium-grade metamorphic host-rocks (graphitic and sericitic schists). Hydrothermal fluids, which are associated with the emplacement of Cretaceous-Tertiary granodioritic intrusions, are responsible for the formation of quartz veins and the hydrothermal alteration of wall-rocks. Three main altered zones have been detected in the wall-rocks as far as 150 cm from the quartz veins. The distal zone (up to 50-cm thick) contains quartz, chlorite and illite. The intermediate zone is the thickest (up to 80 cm) and is marked by quartz, muscovite, sulphides, kaolinite and native elements such as Au and Ag. The proximal zone, which is close to the quartz veins, is rather thin (up to 25 cm) and contains clay minerals, Al-oxides-hydroxides and sulphides. The transition from the distal to the proximal zone is accompanied by the enrichment of SiO2 and the depletion of all other major elements, except for Fe2O3(tot). Precious metals occur in the highest concentrations in the intermediate zone (Au up to 7.6 ppm and Ag up to 11 ppm). We suggest that gold was transported as a reduced sulphur complex and was precipitated from the hydrothermal solution by the reaction of the sulphur complexes with Fe2+ from the alteration of the mafic minerals of the host-rock. Fluid-wall-rock interactions seem to be the main cause of gold mineralization. Genetic relationships with a strike-slip fault system, hydrothermal alteration zones within the metamorphic wall-rocks, and an entire set of geochemical anomalies are consistent with orogenic-type gold deposits of the epizonal class.

Mattioli, Michele; Menichetti, Marco; Renzulli, Alberto; Toscani, Lorenzo; Salvioli-Mariani, Emma; Suarez, Pedro; Murroni, Alessandro

2014-04-01

44

Oxygen three-isotope fractionation lines in terrestrial silicate minerals: An inter-laboratory comparison of hydrothermal quartz and eclogitic garnet  

NASA Astrophysics Data System (ADS)

Geochemical—and perhaps biochemical—processes may yield tell-tale proxies in rocks and minerals on the Earth or other planetary bodies, in the form of distinctive slopes of linear fractionation arrays on the oxygen three-isotope plot. It is generally recognized that kinetic and equilibrium fractionation processes are described by different mass fractionation laws. We show that coupled laser fluorination, dual-inlet IRMS procedures for oxygen three-isotope analysis of silicates, at high precision, gave reproducible accuracy for the slope value as measured independently by two different laboratories, using replicates of the same silicate samples. As far as we are aware, this is the first such inter-laboratory comparison. Hydrothermal quartz (together with one chalk flint sample) with a range in ? 18O of 31‰ gave respective slope ? values of 0.5240 ± 0.0010 and 0.5242 ± 0.0010, using Prism III and MAT 253 mass spectrometers, respectively, at the Open University (OU). Errors were computed from weighted linear regression and are reported at the 95% confidence level. The comparable result obtained at the Geophysical Laboratory (GL), Carnegie Institution of Washington, was 0.5240 ± 0.0015. A MAT 252 mass spectrometer was used for the latter measurements and the oxygen extraction and purification procedures differed in detail from those used at the OU. In contrast, slopes measured for replicates of seven garnet samples, metamorphosed under high-temperature, high-pressure conditions, and spanning 20‰ in ? 18O, gave 0.5262 ± 0.0008 at OU (Prism III analyses) and 0.5266 ± 0.0012 at GL.

Rumble, D.; Miller, M. F.; Franchi, I. A.; Greenwood, R. C.

2007-07-01

45

Hydrothermal Quartz Oxygen Isotope Ratios in Altered Post-Collapse Rhyolite at Sevenmile Hole, Grand Canyon of the Yellowstone River, Yellowstone National Park, WY  

Microsoft Academic Search

The Grand Canyon of the Yellowstone River, Yellowstone National Park, Wyoming, displays regions of pervasively hydrothermally altered rock formed in the shallow, epithermal portions of a hydrothermal system. Hydrothermal fluid circulation causing the alteration is driven by magmatism related to the Yellowstone Caldera thermal anomaly. The protolith, the Tuff of Sulfur Creek, is a 480 ka high silica, low delta18O

A. R. Phillips; P. B. Larson; D. A. John; B. M. Pauley

2008-01-01

46

Hydrothermal Synthesis of Quartz Nanocrystals  

E-print Network

. Bosworth, and Vicki L. Colvin* Department of Chemistry, Rice UniVersity, 6100 Main Street, Houston, Texas and size selected by dialysis, filtration, and centrifugation. Transmission electron microscopy and X-ray

47

Unravelling the deep fluid composition in the Taupo Volcanic Zone: insight into the magmatic-hydrothermal transition  

NASA Astrophysics Data System (ADS)

The Ngatamariki Geothermal Field represents the only location in the Taupo Volcanic Zone where geothermal well drilling has intercepted intrusive rocks with a high temperature alteration halo. Thus it presents the perfect opportunity to study the magmatic-hydrothermal transition in the TVZ by characterising the nature of the deep magmatic fluids inferred to be linked to the geothermal heat source. In addition to the calc-alkaline Ngatamariki diorite (encountered in a 1985 drillhole; Wood, 1986), recent (2012) geothermal drilling encountered a quartz-phyric tonalite. After emplacement, these intrusions cooled, degassed, and produced a high temperature alteration halo, associated with intense quartz-illite/muscovite-pyrite alteration and pervasive quartz replacement of the overlying tuff-breccia. This alteration zone contains abundant high temperature quartz veins, similar to quartz veining stockwork characteristic of Porphyry Cu (±Au-Mo) systems. The recently encountered quartz-phyric tonalite contains common phenocrysts of quartz and pseudomorphs of plagioclase and minor ferromagnesian minerals (predominantly amphiboles) in a medium-grained, magnetite-bearing felsic groundmass. Quartz phenocrysts are generally rounded and embayed quartz eyes (?1 cm diam.), or skeletal crystals. SEM-CL imaging was used to map the crystallisation history of the phenocrystic quartz in the tonalite and the quartz veins cross-cutting the diorite and overlying pyroclastic rocks. The quartz eyes show a complex growth history with zones of dissolution and recrystallisation. Skeletal quartz crystals also have complex zoning and are outlined by myrmekitic textures and/or dendritic overgrowths with the groundmass (granophyric textures). These features form in granites due to undercooling during shallow magmatic emplacement and are often associated with the exsolution of a volatile phase. Cathodoluminescence indicates that the edges of the quartz veins are lined by euhedral crystals, perpendicular to the vein wall that crystallised early in the vein history. A second generation of mosaic anhedral quartz fills the vein centres. Intermediate density (defined by a salinity of 12 wt% NaCl) pseudo-secondary fluid inclusions trapped in quartz phenocrysts and silicification zone, homogenised at temperatures >500C, and ~400C, respectively. They are inferred to represent subsolvus fluid conditions. Vapour-rich inclusions (containing liquid with ~1 wt% NaCl) and high density (48 wt% NaCl) fluid inclusions with homogenisation temperatures >500C are present in the quartz phenocrysts and veins, and are inferred to represent the transition across the solvus into the two-phase field. The presence of intermediate density, brines and vapour-rich fluids inclusions in vein quartz and phenocrysts is consistent with the intrusion becoming volatile-saturated and exsolving a rising supercritical fluid. This subsequently cooled, boiled, and formed a vein stockwork system at >500C and ~ 500bars. These trapped fluids can perhaps be used as analogues of the deep fluids sustaining TVZ geothermal systems.

Chambefort, I. S.; Lewis, B.; Boseley, C.; Begue, F.; Rae, A.

2012-12-01

48

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

49

Effects of dissolution-precipitation processes on the strength and mechanical behavior of quartz gouge at high-temperature hydrothermal conditions  

Microsoft Academic Search

Laboratory experiments on simulated quartz gouges at a temperature of 927°C, a confining pressure of 300 MPa, and a pore water pressure of 200 MPa demonstrate the interactions between cataclastic and dissolution-precipitation processes and their effects on the strength and mechanical behavior. Significant porosity reduction and microstructures, including grain interlocking, grain interpenetration, and widespread growth of euhedral-shaped grains, indicate the

Kyuichi Kanagawa; Stephen F. Cox; Shuqing Zhang

2000-01-01

50

Reconstruction of the hydrothermal history of the Cu–Ag vein-type mineralisation at Dikulushi, Kundelungu foreland, Katanga, D.R. Congo  

Microsoft Academic Search

The Kundelungu foreland, north of the Lufilian arc in the Democratic Republic of Congo, contains a number of various vein-type and stratiform copper mineralisations. The geodynamic context and metallogenesis of these mineral occurrences remain enigmatic. Currently, the vein-type Cu–Ag ore deposit at Dikulushi is the most significant deposit in the region. Mineralisation at Dikulushi comprises two major styles: 1) a

Stijn Dewaele; Philippe Muchez; Wouter Heijlen; Amanda Boutwood; Terry Lemmon; Roger Tyler

2006-01-01

51

The Benedikt hydrothermal system (north-eastern Slovenia)  

NASA Astrophysics Data System (ADS)

Deep welling in the Benedikt area has proven the existence of recently active hydrothermal system in pre-Tertiary basement composed of banded gneiss, marble and schist originating from a regionally metamorphosed sequence of clastic sediments. Two aquifers with very high fracture porosity were tapped—at depths between 1,485-1,530 and 1,848-1,857 m, where the welling stopped owing to a technical failure. The water temperature exceeds 90°C, while the yield of 100 l/s is limited only by the well performances. The Na-HCO3 dominated water is classified as a CO2-rich healing mineral water suitable for drinking, bottling and balneology. The free degassing gas is almost pure CO2 (99.9 %) and its ?13C composition indicates volcanic origin. The tapped water is relatively old, probably of Pleistocene age at least, and the planned exploitation must consider reinjection in order to protect this valuable natural resource from overexploitation. This recent hydrothermal system is characterised by dominating vertical circulation of waters and is superimposed on older, already inactive hydrothermal system(s), recognised by veins of either metal sulphides and quartz, or calcite. These vein minerals precipitated from hydrothermal fluids migrating from a deeper source towards the ancient surface through a fracture system, which is now self-sealed already. The distribution of metal sulphides indicates that the source might have been a deep-seated Neogene pluton genetically related to the tonalites and quartz diorites that outcrop in the Pohorje Mountains, or a subvolcanic-level volcanic body related to the Neogene volcanic activity in the Graz Basin.

Kralj, Peter; Eichinger, Lorenz; Kralj, Polona

2009-10-01

52

Evolution of the Bucium Rodu and Frasin magmatic-hydrothermal system, Metaliferi Mountains, Romania  

NASA Astrophysics Data System (ADS)

The Miocene Bucium Rodu and Frasin maar-diatreme structures and related Au-Ag epithermal low sulfidation with passing to mesothermal mineralizations are located in the Bucium-Rosia Montana-Baia de Aries metallogenetic district, within so called the "Golden Quatrilaterum", in the northeastern part of the Metaliferi Mountains. These structures are situated at about 5 km southeast from Rosia Montana, the largest European Au-Ag deposit. The total reserves for Bucium Rodu-Frasin are estimated at 43.3 Mt with average contents of 1.3 g/t Au and 3 g/t Ag. The Miocene geological evolution of Bucium Rodu and Frasin magmatic-hydrothermal system took place in closely relationships with tectonic, magmatic and metallogenetic activity from Bucium-Rosia Montana-Baia de Aries district in general, and adjacent areas, in special. The hydrothermal alteration is pervasive; adularia followed by phyllic, carbonatization and silicification alterations, usually show a close relationship with the mineralizations. Propylitic alteration occurs dominantly towards the depth; argillic alteration shows a local character. The mineralization occurs in veins, breccias, stockworks and disseminations and is hosted within two volcanic structures emplaced into a sequence of Cretaceous sediments in closely genetically relations with the Miocene phreatomagmatic fracturing and brecciation events. Within Rodu maar-diatreme structure the mineralizations follow especially the contact between the diatreme and Cretaceous flysch. The vein sets with low, moderately and near vertical dippings, cover 400x400m with N-S trend. The most important mineralization style is represented by veins, accompanied by hydrothermal breccias and disseminations. The veins spatial distribution relives as "en echelon" tension veins. They carry gold, minor base metal sulphides (pyrite, chalcopyrite, sphalerite, galena, tetrahedrite, arsenopyrite). Gangue is represented by carbonates (calcite, dolomite, ankerite, siderite, rhodochrosite) and quartz. In contrast, in Frasin maar-diatreme structure, the mineralizations are focused especially along the northeastern contact between the andesite dome and polimictic breccias. Stockwork is the main style of mineralization and consists of pyrite, small amounts of chalcopyrite, sphalerite, galena, arsenopyrite and gold within a gangue of quartz and carbonates similar to Rodu mineralizations. The ore minerals deposition from hydrothermal fluids have pulsated character with a three stage evolution and mineral assemblages: 1) magnetite (hematite) - pyrite (marcasite) - quartz in the first stage, epithermal low sulfidation with passing to mesothermal; 2) arsenopyrite (Au) - (-base metal sulfides) - quartz, "Chinga" (pyrite (Au)-quartz-adularia) - carbonates (calcite, aragonite, dolomite, ankerite, ± rhodochrosite ± kutnahorite) - quartz - adularia in the second stage, epithermal low sulfidation and 3) pyrite - marcasite - carbonates - quartz, (Au) - carbonates (dominant rhodochrosite) - quartz - adularia and alabandite - rhodochrosite - quartz in the third stage, epithermal low sulfidation. The mineralizing hydrothermal fluids had near neutral pH with the gold transported probably as a bisulfide complex; boiling seems to be the main way of gold precipitation.

Iatan, Elena Luisa; Berbeleac, Ion; Visan, Madalina; Minut, Adrian; Nadasan, Laurentiu

2013-04-01

53

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

54

Hydrothermal uranium deposits containing molybdenum and fluorite in the Marysvale volcanic field, west-central Utah  

USGS Publications Warehouse

Uranium deposits containing molybdenum and fluorite occur in the Central Mining Area, near Marysvale, Utah, and formed in an epithermal vein system that is part of a volcanic/hypabyssal complex. They represent a known, but uncommon, type of deposit; relative to other commonly described volcanic-related uranium deposits, they are young, well-exposed and well-documented. Hydrothermal uranium-bearing quartz and fluorite veins are exposed over a 300 m vertical range in the mines. Molybdenum, as jordisite (amorphous MoS2, together with fluorite and pyrite, increase with depth, and uranium decreases with depth. The veins cut 23-Ma quartz monzonite, 20-Ma granite, and 19-Ma rhyolite ash-flow tuff. The veins formed at 19-18 Ma in a 1 km2 area, above a cupola of a composite, recurrent, magma chamber at least 24 ?? 5 km across that fed a sequence of 21- to 14-Ma hypabyssal granitic stocks, rhyolite lava flows, ash-flow tuffs, and volcanic domes. Formation of the Central Mining Area began when the intrusion of a rhyolite stock, and related molybdenite-bearing, uranium-rich, glassy rhyolite dikes, lifted the fractured roof above the stock. A breccia pipe formed and relieved magmatic pressures, and as blocks of the fractured roof began to settle back in place, flat-lying, concave-downward, 'pull-apart' fractures were formed. Uranium-bearing, quartz and fluorite veins were deposited by a shallow hydrothermal system in the disarticulated carapace. The veins, which filled open spaces along the high-angle fault zones and flat-lying fractures, were deposited within 115 m of the ground surface above the concealed rhyolite stock. Hydrothermal fluids with temperatures near 200??C, ??18OH2O ~ -1.5, ?? -1.5, ??DH2O ~ -130, log fO2 about -47 to -50, and pH about 6 to 7, permeated the fractured rocks; these fluids were rich in fluorine, molybdenum, potassium, and hydrogen sulfide, and contained uranium as fluoride complexes. The hydrothermal fluids reacted with the wallrock resulting in precipitation of uranium minerals. At the deepest exposed levels, wall-rocks were altered to sericite; and uraninite, coffinite, jordisite, fluorite, molybdenite, quartz, and pyrite were deposited in the veins. The fluids were progressively oxidized and cooled at higher levels in the system by boiling and degassing; iron-bearing minerals in wall rocks were oxidized to hematite, and quartz, fluorite, minor siderite, and uraninite were deposited in the veins. Near the ground surface, the fluids were acidified by condensation of volatiles and oxidation of hydrogen sulfide in near-surface, steam-heated, ground waters; wall rocks were altered to kaolinite, and quartz fluorite, and uraninite were deposited in veins. Secondary uranium minerals, hematite, and gypsum formed during supergene alteration later in the Cenozoic when the upper part of the mineralized system was exposed by erosion.

Cunningham, C. G.; Rasmussen, J. D.; Steven, T. A.; Rye, R. O.; Rowley, P. D.; Romberger, S. B.; Selverstone, J.

1998-01-01

55

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

56

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

57

Quartz rheology from field observations and numerical modelling  

NASA Astrophysics Data System (ADS)

The mechanical properties of quartz strongly influence the strength of the continental crust and therefore the depth of the brittle-ductile transition and the nucleation depth of major earthquakes. Despite quartz being one of the most abundant minerals constituting the crust, natural examples to constrain quartz rheology are rare. Here, we present a brittle-ductile fault array in the Southern Alps, New Zealand, and use it as a natural laboratory into the rheology of deformed quartz rocks. The faults formed in the hanging wall of the Alpine Fault during the late Cenozoic at ? 21 km depth. They are near-vertical, systematically and closely spaced, extend laterally and vertically over tens of metres, and strike sub-parallel to the Alpine Fault. They consistently express both dextral and NW-up senses of slip. The faults displace quartzofeldspathic meta-greywacke (Alpine Schist) through predominantly brittle processes. Brittle shearing usually ceases where the faults intersect centimetre-thick quartz veins that are hosted by the Alpine Schist and that are discordant to the dominant schist foliation. In these quartz veins shearing is variably ductile to brittle, with ductile shear strains of up to ~15 over shear zone widths of ~3 cm. We use field-observed geometrical scaling relationships related to the sheared quartz veins, such as ductile shear zone width vs. ductile slip, and interactions between brittle faults and ductilely deforming quartz veins that intersect them to produce a set of viable numerical models reflecting the field observations. Quartz rheology is modelled by linear or power law creep, and the material parameters extracted for the quartz veins, together with viscous and brittle strength ratios between vein quartz and schist. The results indicate that under the prevailing deformation conditions, the dominant deformation mechanism in the quartz veins was dislocation creep, resulting in a non-linear viscous quartz flow behaviour.

Grigull, Susanne; Ellis, Susan M.; Little, Timothy A.; Hill, Matthew P.; Buiter, Susanne J. H.

2013-04-01

58

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

2014-02-01

59

Fault rocks and differential reactivity of minerals in the Kanawa Violaine uraniferous vein, NE Nigeria  

NASA Astrophysics Data System (ADS)

The Kanawa Violaine uraniferous vein occurs in a narrow granitic shear zone. Mylonitic fault rocks at the centre of the vein grade outwards into cataclasites and fault breccias. The mineralization is associated with pervasive silicification and phyllosilicate alteration of the feldspar phases. The uranium mineralization occurs as uraninite-rich veinlets within brittle structures. Feldspars were the phenocryst phases most affected by alteration during the brittle-ductile deformation of the host rock. Plagioclase was extensively altered to micas, chlorite ± epidote, ±albite. Alkali-feldspar deformed mainly by transgranular fracturing as a result of shearing to yield clasts with lensoid shape. Quartz shows little evidence of brittle deformation but extensive in situ recrystallization. A mylonitic foliation is defined by monomineralic lenses. Microcracks in the feldspar are oblique to this foliation. The greenschist-facies secondary mineral assemblage, pervasive silicification, deformation mode of alkali-feldspar and the presence of quartz subgrains point to deformation of granites in the epizone by simple shearing within a hydrothermal-fluid-infiltrated medium. Alteration temperatures did not exceed 250 °C. The hydrothermal fluid remobilized and subsequently concentrated the uranium. This fluid was enriched in Si 4+, Na + and K +, possibly derived from plagioclase alteration. This lead to association of the ore with phyllosilicate and silicification alterations.

Suh, C. E.; Dada, S. S.

1997-08-01

60

Mineralogy, geochemistry and fluid evolution of a fossil hydrothermal system in the Paleogene Mendejin volcanic sequence, East Azarbaijan, Iran  

NASA Astrophysics Data System (ADS)

The Mendejin area is one prominent hydrothermal alteration zone in association with Paleogene volcano-sedimentary sequences in NW Iran. The volcanic sequence at Mendejin ranges in composition from basalt to andesite, dacite and rhyolite. Sulfide mineralization and related hydrothermal alteration is associated with the late Mendejin pluton that discordantly intrudes into this cogenetic volcanic sequence. The common hypogene hydrothermal alteration types observed at Mendejin include; phyllic, propylitic, carbonatization, sulfidation, silicification (veins) and argillic types with locally abundant calcite, quartz, tourmaline, sericite, chlorite, kaolinite, illite, alunite, jarosite, and gypsum. Phyllic alteration (without calcite and epidote) is paragenetically early and it is followed by propylitic alteration (with epidote and little calcite) and carbonatization (with high calcite and no epidote) reflecting a gradual increase of CO2 in the hydrothermal system. Mass balance of the hydrothermal alteration within the various volcanic rocks indicates that most elements released during alteration were locally fixed in the low-temperature hydrothermal minerals. As a result, geochemical changes are not as prominent as mineralogical transformations. There is no net mass change during phyllic, argillic, silicic vein and carbonate alteration of andesite and basalt. However, propylitic alteration and carbonatization of dacite caused net mass additions of 8% and 17%, respectively. The high-field-strength elements (HFSE) like Ti, Zr, Hf, Th, Nd, Y, La, Ce, Sm and Lu were the immobile elements during hydrothermal alteration at Mendejin. However, the rare-earth elements (REE) were mobilized during carbonate alteration. Fluid inclusions in quartz and calcite from various assemblages show that hydrothermal minerals were deposited from a low salinity (0.35 to 4.34 wt% equivalent NaCl) hydrothermal solution at 385°C to 150°C. Fluid-wall rock reactions along with boiling of hydrothermal solution and mixing of relatively saline fluid (4.34 wt% equivalent NaCl) with a low-salinity groundwater (0.35 wt% equivalent NaCl) resulted in the extensive alteration of the volcanic country rocks and precipitation of hydrothermal assemblages at Mendejin.

Karimzadeh Somarin, A.; Lentz, D. R.

2008-09-01

61

Role Of Hydrothermal System At Shallower Depth In 2.77 Ga Alteration Of Mt. Roe Basalt, Pilbara, Western Australia  

NASA Astrophysics Data System (ADS)

The sericite-chlorite alteration zone of the 2.77 Ga Mt. Roe basalt near Whim Creek, Pilbara, Western Australia, has been attracting attention if it is paleo-weathering profile (paleosol) formed under anoxic atmosphere or if it is hydrothermally altered zone by reduced fluid. It is also interesting in the standpoint of biological activity at late-Archean era, as it has been reported that the black veins in alteration zone and the sediment above it are characterized by the organic carbons with d13C values of methanogen and methanotroph. A fresh and consecutive core of Mt Roe basalt including alteration zones, which was drilled by ABDP (Archean Biosphere Drilling Project) in July 2003, gives new and more detailed insight into this concern. The core is ca. 300 m long, and is composed of amygdaloidal/massive basaltic lavas and tuffs with clastic sediments interbedded. About seventy selected samples were studied mineralogically using microscope, XRD, XGT and EPMA, and were analyzed chemically for major and trace elements using XRF and ICP-mass. The results show that (1) the core is composed of at least three lava/tuff units with different Ti/Zr and Zr/Hf ratios which are separated by thick sedimentary units, (2) the sedimentary units are comprised of sandstone, siltstone and shale, all of which are black-colored and rich in organic carbon, (3) the strongly sericitized horizons of several meters were recognized just below these sedimentary units, (4) thin sericitized layers are interbetted in amygdaloidal basalt and tuff horizons, the major part of which is associated with the fine-grained, black and organic carbon-rich quartz vein, (5) in some parts of sericitized zone, sulfide, Zn-rich and Ti-REE veins were observed, (6) all of the sericitized zone is characterizes by the depletion of Fe, Mg, Ca, Na and P and the enrichment of K, (7) several other kinds of veins, such as quartz, calcite, and chlorite, distribute across the basalt horizon, (8) organic carbons in black vein show d13C values of -40 to -50 per mil (PDB), and (9) methane was the only gas detected from the fluid inclusions in quartz vein. These observations suggest the followings, (1) there might be at least two stages of alteration; (2) the first one could be responsible for the alteration of plagioclase to calcite and mafic minerals to chlorite, for the calcite and chlorite veins, and for filling up amygdules; (3) the second one might relates to submarine hydrothermal activity at shallower depth, (4) the hydrothermal fluid might circulate through depositing sediment and top of erupted basalt/tuff, (5) methanogene could inhabitate in hydrothermal vein producing methane and made the fluid strongly reducing, and (6) methanotroph could inhabitate around seafloor. As the black hydrothermal vein was not observed in uppermost massive lava unit, the timing of this alteration would have been essentially concurrent with the volcanic activity. This is concordant with the previously reported SHRIMP age of around 2.8 Ga for euhedral apatite minerals in hydrothermal vein.

Nedachi, Y.; Nedachi, M.; Taguchi, S.; Ohmoto, H.

2004-12-01

62

Spider Veins  

MedlinePLUS

... damaged Skin Unwanted Hair Unwanted Tattoos Varicose Veins Vitiligo Wrinkled Skin Treatments and Procedures Ambulatory Phlebectomy Blepharoplasty ... damaged Skin Unwanted Hair Unwanted Tattoos Varicose Veins Vitiligo Wrinkled Skin Treatments and Procedures Ambulatory Phlebectomy Blepharoplasty ...

63

Hydrothermal alteration features in the Vargeão basaltic impact structure (South Brazil): Implications about the presence of liquid water in Mars  

NASA Astrophysics Data System (ADS)

This study presents new petrological data about the hydrothermal fluid percolation in impact craters. Impact cratering process is of primary importance in the evolution of solid bodies of the Solar System. However, impact craters on basaltic rocks, which are the best analog for the surface of other planets and satellites, are rare on Earth. Recently, one medium-size complex crater was identified on volcanic rocks of the Paraná basin (south Brazil), providing an additional analog for the craters of most rocky planets and satellites. The 12 km wide Vargeão is a complex impact structure formed on volcanics rocks of the Serra Geral Formation (about 133-131 Ma), which are locally intertrapped by aeolian-sandstones of Botucatu Formation. Vargeão is morphologically characterized by a well-preserved rim and a smoothed central uplift. The rim region is characterized by concentric gravitational faults that affect tholeiitic basalt flows hundreds of meters thick and rhyodacites few tens of meters thick. Associated with these faults occur the formation of local networks of small red breccia veins. The central uplift has fractured basaltic rocks that contain a lot of red oxidized breccias veins cutted by some white veins. This study is focused on the petrogenesis of these centimeter breccia veins that are found in all lithologies. We conducted a detailed petrological study (petrography, microprobe, SEM, Raman spectroscopy, Magnetic data, 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, zeolites 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 minerals 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 this signature remains controversial. It may result from the excavation of globally altered volcanic material in a warm and wet Mars, or alternatively it may result from impact-associated hydrothermal alteration. Our results at Vargeão may be used to assess these different hypotheses.

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

2013-05-01

64

Stratigraphic development and hydrothermal activity in the central western Cascade Range, Oregon  

SciTech Connect

Two volcanic sequences bounded by erosional unconformities compose the stratigraphy of the North Santiam mining district, Western Cascade Range, Oregon. Diorite, grandodiorite, 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, M.L.; Bull, M.K. (Portland State Univ., Oregon (USA)); Pollock, J.M. (Reed Coll., Portland, OR (USA)); Thompson, G.D. (Pioneer Metals Corp., Ruidoso, NM (USA))

1990-11-10

65

Vein Problems Related to Varicose Veins  

MedlinePLUS

... varicose veins include venous lakes, reticular veins, and hemorrhoids. Venous lakes are varicose veins that appear on ... flat blue veins often seen behind the knees. Hemorrhoids are varicose veins in and around the anus. ...

66

Characteristics of hydrothermal alteration mineralogy and geochemistry of igneous rocks from the epithermal Co-O mine and district, Eastern Mindanao (Philippines)  

NASA Astrophysics Data System (ADS)

Detailed petrographic as well as hyperspectral analyses using PIMA (Portable Infrared Mineral Analyser) and geochemical (major, trace and rare earth elements) studies were conducted on samples of the epithermal, low sulfidation Co-O mine (47,869 ounces gold produced in 2009 with an average grade of 13.3 g/t gold) and district in Eastern Mindanao (Philippines). The aims of the study were to unravel the petrogenetic origin of the various volcanic (host rocks) and intrusive rocks (potential fluid driver) as well as their relationship and influence on the hydrothermal alteration zoning and fluid chemistry. The auriferous veins at the Co-O mine were formed during two hydrothermal stages associated with the district wide D1 and D2 deformation events. Gold in stage 1 quartz veins is in equilibrium with galena and sphalerite, whereas in stage 2 it is associated with pyrite. Auriferous quartz veins of stage 1 reflect temperatures below 250° C or strong variations in pH and fO2 at higher temperatures, due to potential involvement of acidic gas or meteoric water. Cathodoluminescense studies revealed strong zonation of quartz associated with Au, presumably related to changes in the Al content, which is influenced by the pH. Plumose textures indicate times of rapid deposition, whereas saccharoidal quartz grains are related to potential calcite replacement. The geology of the Co-O mine and district is dominated by Miocene volcanic rocks (basic to intermediate flows and pyroclastics units), which are partly covered by Pliocene volcanic rocks and late Oligocene to Miocene limestones. The Miocene units are intruded by diorite (presumably Miocene in age). The epithermal mineralization event may be related to diorite intrusions. The geochemistry of all igneous rocks in the district is defined by a sub-alkaline affinity and is low to medium K in composition. Most units are related to a Miocene subduction zone with westward subduction, whereas the younger Pliocene rocks are related to the currently active east dipping subduction zone. At the Co-O mine the proximal hydrothermal alteration zone is defined by phyllic to argillic alteration displayed in sericitized to carbonated feldspar, quartz and chloritized amphiboles surrounded by a distal alteration halo displaying propylitic alteration. The alteration geochemistry of these hydrothermal altered rocks is defined by an increase in K2O and Na2O and decrease in Al2O3. However, adularia usually associated with hydrothermal alteration in low epithermal Au quartz veins, has so far not been described, which points to a K-poor magma system. PIMA hydrothermal alteration studies indicate the dominant presence of smectite rather than white mica, which supports the involvement of a K-poor hydrothermal fluid. The epithermal Co-O mine and district displays low to medium potassic magma series and a hydrothermal alteration mineralogy that is K-poor. However, the Co-O mine hosts significant amounts of epithermal gold mineralization. The recognition of poor K melts and hydrothermal alteration mineralogy associated with distinct low-sulfidation epithermal gold mineralization has important implication for exploration in the Co-O district and, potentially, also in other areas in the Philippines and worldwide.

Sonntag, Iris; Hagemann, Steffen

2010-05-01

67

Weathering of post-impact hydrothermal deposits from the Haughton impact structure: implications for microbial colonization and biosignature preservation.  

PubMed

Meteorite impacts are among the very few processes common to all planetary bodies with solid surfaces. Among the effects of impact on water-bearing targets is the formation of post-impact hydrothermal systems and associated mineral deposits. The Haughton impact structure (Devon Island, Nunavut, Canada, 75.2 °N, 89.5 °W) hosts a variety of hydrothermal mineral deposits that preserve assemblages of primary hydrothermal minerals commonly associated with secondary oxidative/hydrous weathering products. Hydrothermal mineral deposits at Haughton include intra-breccia calcite-marcasite vugs, small intra-breccia calcite or quartz vugs, intra-breccia gypsum megacryst vugs, hydrothermal pipe structures and associated surface "gossans," banded Fe-oxyhydroxide deposits, and calcite and quartz veins and coatings in shattered target rocks. Of particular importance are sulfide-rich deposits and their associated assemblage of weathering products. Hydrothermal mineral assemblages were characterized structurally, texturally, and geochemically with X-ray diffraction, micro X-ray diffraction, optical and electron microscopy, and inductively coupled plasma atomic emission spectroscopy. Primary sulfides (marcasite and pyrite) are commonly associated with alteration minerals, including jarosite (K,Na,H(3)O)Fe(3)(SO(4))(2)(OH)(6), rozenite FeSO(4)·4(H(2)O), copiapite (Fe,Mg)Fe(4)(SO(4))(6)(OH)(2)·20(H(2)O), fibroferrite Fe(SO(4))(OH)·5(H(2)O), melanterite FeSO(4)·7(H(2)O), szomolnokite FeSO(4)·H(2)O, goethite ?-FeO(OH), lepidocrocite ?-FeO(OH) and ferrihydrite Fe(2)O(3)·0.5(H(2)O). These alteration assemblages are consistent with geochemical conditions that were locally very different from the predominantly circumneutral, carbonate-buffered environment at Haughton. Mineral assemblages associated with primary hydrothermal activity, and the weathering products of such deposits, provide constraints on possible microbial activity in the post-impact environment. The initial period of active hydrothermal circulation produced primary mineral assemblages, including Fe sulfides, and was succeeded by a period dominated by oxidation and low-temperature hydration of primary minerals by surface waters. Active hydrothermal circulation can enable the rapid delivery of nutrients to microbes. Nutrient availability following the cessation of hydrothermal circulation is likely more restricted; therefore, the biological importance of chemical energy from hydrothermal mineral deposits increases with time. Weathering of primary hydrothermal deposits and dissolution and reprecipitation of mobile weathering products also create many potential habitats for endolithic microbes. They also provide a mechanism that may preserve biological materials, potentially over geological timescales. PMID:21767151

Izawa, M R M; Banerjee, Neil R; Osinski, G R; Flemming, R L; Parnell, J; Cockell, C S

2011-01-01

68

Role of hydrothermal activity in uranium mineralisation in Palnad Sub-basin, Cuddapah Basin, India  

NASA Astrophysics Data System (ADS)

Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad Sub-basin, Cuddapah Basin. Several evidences of hydrothermal activity exist in both basement granite and the cover sediments in Koppunuru and Rallavagu Tanda (R.V. Tanda) uranium prospects of Palnad Sub-basin. Profuse development of fracture filled veins consisting of epidote-quartz, chlorite-quartz and quartz is observed at various depths above and below unconformity. Fluid-rock interaction during the formation of these veins has resulted in the alteration of feldspars and mafic minerals of granite and arkosic quartzite into a mineral assemblage consisting of various proportion of illite, chlorite, muscovite and pyrite, with the intensity of alterations being highest near to the unconformity. Pyrite is often associated with illite dominant alteration zone. We infer that circulation of basinal brine through basement granite and cover sediments was responsible for mobilising uranium from granite and its precipitation at favourable locations in cover sediments. Increase in pH of ore fluid due to illitisation and chloritisation of wallrock together with availability of carbonaceous matter and pyrite as reductant have controlled the localisation of uranium mineralisation in Banganapalle Formation.

Thomas, P. K.; Thomas, Tresa; Thomas, Jugina; Pandian, M. S.; Banerjee, Rahul; Ramesh Babu, P. V.; Gupta, Shekhar; Vimal, Rajiv

2014-09-01

69

The Thermal Evolution of the Ouachita Orogen, Arkansas and Oklahoma from Quartz-Calcite Thermometry and Fluid Inclusion Thermobarometry  

E-print Network

To understand the fluid temperature and pressure during the Ouachita orogeny, we used isotopic analysis of syntectonic veins and adjacent host material, quartz-calcite oxygen isotope thermometry and fluid inclusion analysis. The veins were...

Piper, Jennifer

2012-02-14

70

Reconstructing the oxygen isotope composition of late Cambrian and Cretaceous hydrothermal vent fluid  

NASA Astrophysics Data System (ADS)

Oxygen isotope analyses (?18O) of 16 quartz-epidote pairs from late Cambrian (Betts Cove and Mings Bight, Newfoundland), Ordovician (Thetford Mines, Québec, Canada) and Cretaceous (Troodos, Cyprus) ophiolites are used to calculate the ?18O of the hydrothermal fluids from which they crystallized. We combine these with 3 quartz-fluid inclusion measurements and 3 quartz-magnetite measurements from the Cambrian ophiolites to explore how the range in the ?18O of submarine hydrothermal vent fluid has varied between the late Cambrian, Cretaceous and today. The range of calculated ?18O values of vent fluid (-4 to +7.4) is larger than that of modern seafloor hydrothermal vent fluid (0 to +4). We employ two numerical models to ascertain whether this range is most consistent with changes in paleo-seawater ?18O or with changes in the reactive flow path in ancient hydrothermal systems. A static calculation of the vent fluid oxygen isotope composition as a function of the water-rock ratio suggests that in an ocean with a lower ?18O than today, the range of vent fluid ?18O should be larger. Our data, however, show little evidence that the ?18O of the ocean was much lower than the global ice-free value of -1.2. A dual porosity model for reactive flow through fractured and porous media is used to model the relative evolution of the 87Sr/86Sr and ?18O of vent fluid in contact with rock. Our 87Sr/86Sr and ?18O for Cretaceous epidotes suggest the strontium concentration of the Cretaceous oceans may have been much higher than at present. The 87Sr/86Sr and ?18O data from Cambrian epidotes are strikingly different from the younger samples, and are difficult to model unless fluid-rock interaction in the Cambrian hydrothermal systems was substantially different. It is also possible that some of the quartz-epidote veins have been reset by obduction-related metamorphism. Our data suggest that the high calcium-to-sulfate ratio in early (and Cretaceous) seawater may have affected the degree of strontium isotope exchange, causing hydrothermal fluids to have 87Sr/86Sr closer to that of seawater than in modern systems.

Turchyn, Alexandra V.; Alt, Jeffrey C.; Brown, Shaun T.; DePaolo, Donald J.; Coggon, Rosalind M.; Chi, Guoxiang; Bédard, Jean H.; Skulski, Thomas

2013-12-01

71

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  

NASA Astrophysics Data System (ADS)

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 faulting event. The ore minerals occur in quartz and calcite of stage I, associated with fracturing and healing of veins. Hydrothermal wall-rock alteration minerals of stage I include Fe-rich chlorite (Fe/(Fe+Mg) ratios 0.74-0.81), muscovite, illite, K-feldspar, and minor arsenopyrite, pyrite, and carbonates. Sulfide minerals deposited along with electrum during this stage include arsenopyrite, pyrite, pyrrhotite, sphalerite, marcasite, chalcopyrite, galena, argentite, pyrargyrite, and argentian tetrahedrite. Only calcite was deposited during stage II. Fluid inclusions in quartz contain three main types of C-O-H fluids: CO2-rich, CO2-H2O, and aqueous inclusions. Quartz veins related to early sulfides in stage I were deposited from H2O-NaCl-CO2 fluids (1,500-5,000 bar, average 3,200) with T htotal values of 200°C to 383°C and salinities less than about 7 wt.% NaCl equiv. Late sulfide deposition was related to H2O-NaCl fluids (140-1,300 bar, average 700) with T htotal values of 110°C to 385°C and salinities less than about 11 wt.% NaCl equiv. These fluids either evolved through immiscibility of H2O-NaCl-CO2 fluids as a result of a decrease in fluid pressure, or through mixing with deeply circulated meteoric waters as a result of uplift or unloading during mineralization, or both. Measured and calculated sulfur isotope compositions (?34SH2S = 1.5 to 4.8‰) of hydrothermal fluids from the stage I quartz veins indicate that ore sulfur was derived mainly from a magmatic source. The calculated and measured oxygen and hydrogen isotope compositions (?18OH2O = -5.9‰ to 10.9‰, ?D = -102‰ to -87‰) of the ore-forming fluids indicate that the fluids were derived from magmatic sources and evolved by mixing with local meteoric water by limited water-rock exchange and by partly degassing in uplift zones during mineralization. While most features of the Samgwang mine are consistent with classification as an orogenic gold deposit, isotopic and fluid chemistry indicate that the veins were genetically related to intrusions emplaced during the Jurassic to Cretaceous Daebo orogeny.

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

2010-02-01

72

Varicose veins  

PubMed Central

Introduction Varicose veins are caused by poorly functioning valves in the veins, and decreased elasticity of the vein wall, allowing pooling of blood within the veins, and their subsequent enlargement. Varicose veins affect up to 40% of adults, and are more common in obese people, and in women who have had more than two pregnancies. Methods and outcomes We conducted a systematic review and aimed to answer the following clinical question: What are the effects of treatments in adults with varicose veins? We searched: Medline, Embase, The Cochrane Library and other important databases up to January 2010 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). Results We found 39 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. Conclusions In this systematic review we present information relating to the effectiveness and safety of the following interventions: compression stockings, endovenous laser, injection sclerotherapy, radiofrequency ablation, self-help (advice, avoidance of tight clothing, diet, elevation of legs, exercise), and surgery (stripping, avulsion, powered phlebectomy). PMID:21477400

2011-01-01

73

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

74

Bedding parallel veins and their relationship to folding  

NASA Astrophysics Data System (ADS)

Laminated bedding parallel veins hosted in turbiditic sandstone shale sequences from central Victoria, Australia, consist of stacked, millimetre thick, sub-parallel sheets of quartz separated by micaceous layers, wall rock slivers and pressure solution seams. They have very high length to thickness ratios, are laterally continuous over tens to hundreds of metres, and have relatively uniform thickness compared to other vein types. They are intimately associated with and folded by chevron folds, and the quartz grain shape elongation lineation is commonly orthogonal to mesoscopic and macroscopic fold hinge lines. The bedding parallel veins have two morphological forms. Type I are thin (commonly 5-10 cm) laminated veins which have complex microstructures dominated by phyllosilicate inclusion surfaces, related to oblique opening along bedding with varying rates of deposition (opening) relative to shear displacement (slip) along the bedding surfaces. More common are Type II, thicker (generally <20 cm), banded veins of alternating milky-white quartz with wall rock inclusion laminae (formerly fragments) bounded by stylolitic partings parallel to both bedding and the vein margins. The inclusion surfaces in Type I veins track the opening direction during vein formation. Vein opening-sense criteria suggest cyclical pore fluid pressure fluctuations which predate the amplification and propagation of the host chevron folds; i.e. prior to attainment of significant limb dip. Different layer parallel shortening and amplification rates for individual layers within the sedimentary sequence may lead to bedding parallel veins with an opening sense unrelated to the flexural slip folds which eventually follow.

Jessell, M. W.; Willman, C. E.; Gray, D. R.

1994-06-01

75

Oxygen, hydrogen, and sulfur isotope studies in the Juneau gold belt, southeastern Alaska: constraints on the origin of hydrothermal fluids  

USGS Publications Warehouse

The ??18O values of gold-bearing quartz from the Juneau gold belt range from 15.2 to 20.8???, indicating that ore fluid values ranged from 7.2 to 12.8??? at an estimated temperature of 300??C. Hydrothermal micas from many of the deposits are characterized by ??D values of -75 to -53???, and ore fluids were calculated to have values of -35 to -15???. In contrast, extracted fluid inclusion waters have a broad range of ??D values, from -48 in relatively undeformed quartz to about -110??? for some of the more deformed quartz veins. This range of more than 60??? reflects various mixtures from inclusions containing isotopically heavy, primary ore fluids and those containing low-temperature, isotopically light meteoric waters that were trapped in late fractures during uplift of the veins to shallow crustal levels. These results indicate a deep crustal source for the ore fluids, most likely of metamorphic origin. The provinciality of ??34S data suggests a regional metamorphic fluid of approximately -6??? that acquired much of its sulfur from lithologies near sites of ore deposition. -from Authors

Goldfarb, R.J.; Newberry, R.J.; Pickthorn, W.J.; Gent, C.A.

1991-01-01

76

Hydrothermal rare earth mineralisation in carbonatites of the Tundulu complex, Malawi: Processes at the fluid/rock interface  

NASA Astrophysics Data System (ADS)

The Tundulu carbonatite complex in southeastern Malawi was intruded during the late Jurassic to early Cretaceous over three episodes. During the first and second episodes, the major rock types were calcite carbonatites, ankerite carbonatites, and apatite carbonatites. These rocks experienced hydrothermal alteration at the close of the second episode, during which quartz-baryte veins containing a significant level of rare earth fluorocarbonates were deposited. Veins in calcite carbonatites contain abundant synchysite [(La, Ce, Nd)Ca(CO 3) 2)F] with subordinate amounts of parisite [(La, Ce, Nd) 2Ca(CO 3) 3F 2] and bastnäesite [(La, Ce, Nd)CO 3F], crystallising in the order synchysite parisite ? bastnäesite. Some of the parisite is retrograde in origin, having formed as an alteration product from synchysite. Only synchysite has been identified in veins hosted by apatite carbonatites. However, bastnäesite predominates the hydrothermal assemblage in ankerite carbonatites. Parisite and synchysite have been found only as a fibrous fringe between wallrock ankerite and bastnäesite. The crystallisation sequence seen in calcite carbonatites represents a progressive depletion of both Ca 2+ and CO 2-3 in the fluids from which this mineral suite precipitated, with Ca 2+- and CO 2-3-poor phases precipitating last. Clearly, the predominance of bastnäesite in veins hosted by ankerite carbonatites suggests insufficient Ca 2+ and CO 2-3 in the fluids for the ubiquitous precipitation of synchysite and parisite. These observations are consistent with a model in which hydrothermal fluids reacted with the various wallrocks, which then released different amounts of Ca 2+ and CO 2-3, that subsequently reacted with REEs in the fluid to form the various fluorocarbonates. As such, the Tundulu carbonatites provide a natural laboratory in which compositional phase relationships of rare earth fluorocarbonates can be related to variations in the activities of Ca 2+ and CO 2-3 within the Ln(CO 3)F-CaCO 3-F 2(CO 3) -1 system.

Tendelo Ngwenya, Bryne

1994-05-01

77

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

78

Salinity of oceanic hydrothermal fluids: a fluid inclusion study  

Microsoft Academic Search

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

Pierre Nehlig

1991-01-01

79

Hydrothermal Processes  

Microsoft Academic Search

What is Hydrothermal Circulation?Hydrothermal circulation occurs when seawater percolates downward through fractured ocean crust along the volcanic mid-ocean ridge (MOR) system. The seawater is first heated and then undergoes chemical modification through reaction with the host rock as it continues downward, reaching maximum temperatures that can exceed 400 °C. At these temperatures the fluids become extremely buoyant and rise rapidly

C. R. German; K. L. von Damm

2003-01-01

80

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

81

Towards a quantitative description of fracture sealing: Phase-field modeling of mineral precipitation in veins  

NASA Astrophysics Data System (ADS)

Alongside with calcite the growth of quartz establishes the most important mineralization processes in fractures and determines the fluid-rock interaction in the earth's crust. Tectonically caused deformation, fracturing and fluid transport leaves clear detectable traces in the microstructure of the mineralized veins. The underlying physical processes such as diffusion, advection, heat transport and crystal growth have to be captured at the mesoscale (or pore/grain scale). Any analysis is complicated by the facts that these processes are highly nonlinear, and geological boundary conditions as well as many of the kinetic growth parameters are not precisely known. As the microstructures and compositional inhomogeneity of veins could be used to enravel the history of the rock deformation process and the fluid pathways through former fracture networks, spatio-temporal models of vein mineral growth are of special interest. Different from previous approaches to simulate vein growth, we adapt a thermodynamically consistent phase-field model (PFM) which combines irreversible thermodynamics of interfaces and bulk phases with a kinetic growth law and mass transport equations (Wendler et al. 2011). Here, we study the simplest case where preexisting grains of a fracture surface are the seeds for epitaxial overgrowth. Each grain in a 3D domain is captured by a phase field with individual orientation. The model evolves in discrete time steps using a finite difference algorithm on a regular grid, optimized for large grain assemblies. In the present study we provide a brief overview, how the PFM is configured using thermodynamic data from established models for growth and dissolution, kinetic information from in and ex situ microstructural observations and dihedral angles from equilibration experiments. In the case of quartz, previously conducted hydrothermal batch flow growth experiments were analysed to calibrate the model (Okamoto & Sekine 2011). Results from 3D simulations conducted in the limit of low Damköhler numbers explain the observed transition regime in competitive crystal growth for blocky-elongate veins. A mechanism for the initial formation of quartz needles is proposed. For virtual fractured rock samples we study the influence of fracture shape and opening aperture in the evolution of syntaxial (blocky-elongated vs. stretched) veins. In the case of calcite, the chemical variability of the growth process in real systems strongly influences the crystal growth kinetics and limits the significance of quantitative predictions. On the basis of the numerical studies and known parameter uncertainties, we give an assessment of the variabilities of sealing times and vein microstructures. References: F. Wendler, C. Mennerich and B. Nestler, J. Cryst. Growth 327 (2011), 189-201. A. Okamoto and K. Sekine, J. Struct. Geol. 33 (2011) 1764-1775. Three time steps in the sealing of a flat fracture with calcite, only liquid phase evolution is shown.

Wendler, F.; Blum, P.; Thaler, H.; Nestler, B.; Okamoto, A.

2013-12-01

82

Impact-generated hydrothermal regimes within the Manicouagan crater: Terrestrial analog studies relevant to Mars  

NASA Astrophysics Data System (ADS)

The 90 km diameter, 214 Ma Manicouagan impact structure, Canada, is one of the best preserved complex impact craters on Earth. Recent field-based observations (2010 and 2011 seasons), drill core investigations and laboratory studies reveal evidence for the existence of distinct impact-induced hydrothermal regimes at Manicouagan. Four main spatial regimes have been identified: (1) intra-melt sheet cooling cells, (2) sub-melt sheet cells, (3) a central uplift convection system, and (4) peripheral hot springs associated with the collapsed rim. An overlying supra-melt sheet system (i.e., within fallback breccias) may have existed, but no evidence of this remains due to removal by erosion of the uppermost levels of the crater stratigraphy. Epidote, prehnite, chlorite and titanite are also present in fracture systems at Manicouagan, but it is not yet clear whether these are associated with the 1 Ga Grenvillian tectonometamorphic event that predates the impact. Regimes 1 and 2 are generated directly during cooling of the superheated impact melt sheet, which has an average thickness of 300 m, but locally attains thicknesses of more than 1 km. Intra-melt sheet cooling cells include both clast-laden and clast-bearing impact melt variants. Typical hydrothermal minerals present in these regimes are zeolites (e.g., natrolite, analcime) and quartz. Quartz is common in vesicles, while zeolites primarily occur in vein/fracture systems pervading the impact melt. Amethyst is also found in vesicles associated with quartz in certain locations, especially near the base of the impact melt-sheet. These regimes indicate precipitation temperatures of 100-250 °C and favor a pervasive (bulk) hydrothermal influence. Within the anorthositic central uplift, which is estimated to have been 250-300 °C when elevated from depths of 8-10 km due to the impact, zeolites are present as the predominant hydrothermal phases. These typically occupy fractures (up to 1 cm wide). The peripheral hot springs are located at the collapsed rim and terrace zone of the crater, where stilbite-Ca and chabazite-Ca are locally developed, especially where hosted by brecciated gneisses. Good exposures of the breccia-hosted regime occur in the western sector of the crater where they are related to fault-fracture-breccia systems associated with rim collapse. Temperatures of 75-100 °C are indicated by these assemblages. The relatively high (regimes 1-3) and low (regime 4) temperature hydrothermal regimes may have hosted hyperthermophile (80-122 °C) and extreme thermophile (75-90 °C) organisms, respectively. Future work aims to search for evidence of hydrothermal-associated biogenic activity within the Manicouagan impact regime. This has important implications for the potential for similar impact-hydrothermal systems facilitating biogenic activity on Mars, especially during the Noachian. In this respect, our aim is to use Manicouagan as a guide for targeting potential hydrothermal regimes within martian craters for evidence of life.

Paisarnsombat, S.; Thompson, L. M.; Spray, J. G.

2011-12-01

83

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

84

Sweeping quartz crystals  

Microsoft Academic Search

Sweeping is a purification process that removes certain impurities and thereby improves the radiation sensitivity of quartz crystals. The major steps of a typical sweeping process consist of applying electrodes to the Z-surfaces of a lumbered quartz bar; applying voltage to the electrodes to produce an electric field of approximately 1 kV\\/cm; heating the bar slowly either in air, vacuum,

John G. Gualtieri

1989-01-01

85

Deep Vein versus Pseudo Deep Vein Thrombosis  

PubMed Central

An acutely swollen, painful calf is usually caused by deep vein thrombosis or pseudo deep vein thrombosis; however, the differential diagnosis and management of these 2 entities can prove difficult and even hazardous unless a careful, systematic approach is used. This article describes the use of 2 invasive techniques (ascending venography and arthrography) and several noninvasive methods (magnetic resonance imaging, computerized axial tomography, and non-Doppler ultrasound) to differentiate between deep vein thrombosis and pseudo deep vein thrombosis. The author discusses a practical, cost-effective approach to diagnosing and managing the acutely swollen, painful calf. (Texas Heart Institute Journal 1989;16:280-6) Images PMID:15227382

Ansari, Azam

1989-01-01

86

Optociliary veins and central retinal vein occlusion  

Microsoft Academic Search

In a follow up of 94 patients with central retinal vein occlusion (CRVO) whose onset had taken place less than 1 year earlier, optociliary veins (OCVs) were found in 7.4% at first examination. Among the 79 eyes in which the fundus of the eye was very visible after a follow up of more than 1 year OCVs were found in

G Giuffrè; C Palumbo; G Randazzo-Papa

1993-01-01

87

Orogenesis, high-T thermal events, and gold vein formation within metamorphic rocks of the Alaskan Cordillera  

USGS Publications Warehouse

Mesothermal, gold-bearing quartz veins are widespread within allochthonous terranes of Alaska that are composed dominantly of greenschist-facies metasedimentary rocks. The most productive lode deposits are concentrated in south-central and southeastern Alaska; small and generally nonproductive gold-bearing veins occur upstream from major placer deposits in interior and northern Alaska. Ore-forming fluids in all areas are consistent with derivation from metamorphic devolatilisation reactions, and a close temporal relationship exists between high-T tectonic deformation, igneous activity, and gold mineralization. Ore fluids were of consistently low salinity, CO2-rich, and had ??18O values of 7 ???-12??? and ??D values between -15??? and -35???. Upper-crustal temperatures within the metamorphosed terranes reached at least 450-500??C before onset of significant gold-forming hydrothermal activity. In southern Alaska, gold deposits formed during latter stages of Tertiary, subduction-related, collisional orogenesis and were often temporally coeval with calc-alkaline magmatism. -from Authors

Goldfarb, R.J.; Snee, L.W.; Pickthorn, W.J.

1993-01-01

88

What Are Varicose Veins?  

MedlinePLUS

... Gets Them? Varicose veins are more common in women, and people are more likely to get them as they get older. These veins can be genetic (say: juh-NEH-tik). That means that if your mom or your sister ... veins. Sometimes women who are pregnant get them, too. If someone ...

89

Comparison of metasomatic reactions between a common CO2-rich vein fluid and diverse wall rocks: intensive variables, mass transfers, and Au mineralization at Alleghany, California  

USGS Publications Warehouse

The gold deposits at Alleghany, California, are typical of many epigenetic gold-bearing hydrothermal vein systems in metamorphic terranes worldwide. Detailed analyses of alteration halos in serpentinite, mafic amphibolite, and granite wall rocks at Alleghany indicate that widely contrasting deposit types, ranging from fuchsite-carbonate schists to pyrite-albitites, resulted when different wall rocks interacted with the same externally derived CO2-rich hydrothermal vein fluid. Patterns of element redistribution within halos and among lithologic units suggest a complex process involving fluid flow along vein fractures and diffusion (?? infiltration) normal to the veins. Wall rocks locally controlled both the directions and magnitudes of chemical fluxes across vein walls. -from Author

Böhlke, J.K.

1989-01-01

90

Conjugate Oblique-Extension Veins in Shear and Tensile Fracture Systems at the Komis Gold Mine and Mufferaw Gold Prospect, Northern Saskatchewan  

Microsoft Academic Search

Quartz veins at the Mufferaw gold prospect and Komis gold deposit, northern Saskatchewan, are examples of oblique-extension veins that crystallized in shear and tensile frac- tures, which propagated and then opened oblique to their walls during a single continuous deforma- tion event. The Mufferaw gold prospect consists of an interlinked mesh of conjugate shear fractures, tensile fractures, and veins. Oblique-extension

BRUNO LAFRANCE

2004-01-01

91

Stibnite vein from D?bowina near Bardo (polish Sudetes)  

NASA Astrophysics Data System (ADS)

In the contact zone of the Bardo Structure and K?odzko-Z?oty Stok Intrusion and K?odzko Metamorphic, metasomatic orebearing quartz-carbonate veins rich in Sb, Zn, Cu, Ag, Au, Pb are present. In 1771 the mine ,,Reiche Silber Gluck” within stibnite vein was founded in D?bowina near Bardo. Its entrance was discovered again in 2007. The stibnite vein is mainly build of stibnite and sphalerite and of quartz and dolomite rich in Mn. Stibnite crystallizes as columnar or forming radiate centres and aciculars. Its crystals reach size to 2 mm. Sphalerite appears as individual anhedral and polymineralic grained concentrations reaching size to 2,5 mm. Earlier pyrite and arsenopyrite crystallized - they occur locally in this deposit. There were found also in the deposit tetrahedrite rich in Ag, what wasn't reported earlier in studies from the mine in D?bowina.

Kotula, Piotr

2013-09-01

92

Fluid inclusions in quartz crystals from South-West Africa.  

NASA Technical Reports Server (NTRS)

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 substance or a combination of substances. These substances include organic liquid, moderately saline aqueous liquid, dark-colored solid, and a 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.

Kvenvolden, K. A.; Roedder, E.

1971-01-01

93

Timing and duration of hydrothermal activity at the Los Bronces porphyry cluster: an update  

NASA Astrophysics Data System (ADS)

New geochronological data from the Los Bronces cluster of the Río Blanco-Los Bronces mega-porphyry Cu-Mo district establish a wide range of magmatism, hydrothermal alteration, and mineralization ages, both in terms of areal extent and time. The northern El Plomo and southernmost Los Piches exploration areas contain the oldest barren porphyritic intrusions with U-Pb ages of 10.8 ± 0.1 Ma and 13.4 ± 0.1 Ma, respectively. A hypabyssal barren intrusion adjacent northwesterly to the main pit area yields a slightly younger age of 10.2 ± 0.3 Ma (San Manuel sector, U-Pb), whereas in the Los Bronces (LB) open-pit area, the present day mineral extraction zone, porphyries range from 8.49 to 6.02 Ma (U-Pb). Hydrothermal biotite and sericite ages are up to 0.5 Ma younger but consistent with the cooling of the corresponding intrusion events of each area. Two quartz-molybdenite B-type veins from the LB open pit have Re-Os molybdenite ages of 5.65 ± 0.03 Ma and 5.35 ± 0.03 Ma consistent with published data for the contiguous Río Blanco cluster. The San Manuel exploration area within the Los Bronces cluster, located about 1.5-2 km southeast of the open-pit extraction zone, shows both the oldest hydrothermal biotite (7.70 ± 0.07 Ma; 40Ar/39Ar) and breccia cement molybdenite ages (8.36 ± 0.06 Ma; Re-Os) registered in the entire Río Blanco-Los Bronces district. These are also older than those reported from the El Teniente porphyry Cu(-Mo) deposit, suggesting that mineralization in the late Miocene to early Pliocene porphyry belt of Central Chile commenced 2 Ma before the previously accepted age of 6.3 Ma.

Deckart, K.; Silva, W.; Spröhnle, C.; Vela, I.

2014-06-01

94

Pyrite Recrystallization Experiments With Circulating Hydrothermal Solution  

NASA Astrophysics Data System (ADS)

Pyrite is one of the most common sulfide minerals found in hydrothermal deposits and sea-floor sediments from hydrothermal fumaroles. Hydrothermal fluid flow plays an important role in crystallization of sulfide minerals. In this study, we tried to reproduce pyrite crystallization with one-way flowing hydrothermal fluid. We designed a circuit circulating hydrothermal fluid by thermal convection. A rectangular circuit (42.6 cm by 17.3 cm) of SUS316 pressure tubes with 5 mm in inner diameter was used as a reaction vessel. In the circuit, pyrite dissolves to acidic fluid in upstream region. Then, pyrite will crystallize again in downstream region as temperature decreases. The rectangular plane was held to be 20 degrees inclination to generate thermal convection. One of the long sides of the rectangular was heated by an electric furnace. Starting materials were put in a tube to be heated. Upper half, approximately 20 cm, of the tube was filled with quartz sand. Next quarter was filled with equivalent mass mixture of quartz sand and powdered pyrite crystals. The lowest quarter was filled with mixture of quartz sand, pyrite, anhydrite and sulfur, those mass are equivalent. The solution was a mixture of 0.5mol/l HCl and 3.0mol/l NaCl. Maximum temperature was controlled to approximately 350°C at the center of the heated tube. Experimental durations were up to 9 days. Fluid pressure increased to approximately 6 MPa as heating. After the experiments, the run products were fixed with resin in a sample tube, and vertical sections were observed by SEM. In the run products, pyrite dissolved at the lower part of the starting material. In the upper half of the sample tube, pyrite crystals precipitated on quartz surface. Crystallization density depends on temperature gradient of the fluid. Predominant morphology of the pyrite crystals consists (100) plains. Tiny framboidal aggregates and crystals with (210) plains also occur. In the run products of longer than 3 days run durations, platy elongated crystals with (100) plains occur. Platy crystals are almost parallel to the surface of the host quartz grains. High temperature fluid flow and condensation of vapor phase may control nucleation density, crystal morphology and growth habit of pyrite crystals in hydrothermal fluid.

Isobe, H.; Abe, A.; Tanaka, K.

2007-12-01

95

Nanofabricated quartz cylinders for angular  

E-print Network

Nanofabricated quartz cylinders for angular trapping: DNA supercoiling torque detection Christopher nanofabricated quartz cylinders well suited for torque application and detection in an angular optical trap. We that nanofabricated quartz cylinders, when used with an angular trapping instrument, allow direct and simultaneous

Wang, Michelle

96

Hydrothermal Processes  

NASA Astrophysics Data System (ADS)

What is Hydrothermal Circulation?Hydrothermal circulation occurs when seawater percolates downward through fractured ocean crust along the volcanic mid-ocean ridge (MOR) system. The seawater is first heated and then undergoes chemical modification through reaction with the host rock as it continues downward, reaching maximum temperatures that can exceed 400 °C. At these temperatures the fluids become extremely buoyant and rise rapidly back to the seafloor where they are expelled into the overlying water column. Seafloor hydrothermal circulation plays a significant role in the cycling of energy and mass between the solid earth and the oceans; the first identification of submarine hydrothermal venting and their accompanying chemosynthetically based communities in the late 1970s remains one of the most exciting discoveries in modern science. The existence of some form of hydrothermal circulation had been predicted almost as soon as the significance of ridges themselves was first recognized, with the emergence of plate tectonic theory. Magma wells up from the Earth's interior along "spreading centers" or "MORs" to produce fresh ocean crust at a rate of ˜20 km3 yr-1, forming new seafloor at a rate of ˜3.3 km2 yr-1 (Parsons, 1981; White et al., 1992). The young oceanic lithosphere formed in this way cools as it moves away from the ridge crest. Although much of this cooling occurs by upward conduction of heat through the lithosphere, early heat-flow studies quickly established that a significant proportion of the total heat flux must also occur via some additional convective process (Figure 1), i.e., through circulation of cold seawater within the upper ocean crust (Anderson and Silbeck, 1981). (2K)Figure 1. Oceanic heat flow versus age of ocean crust. Data from the Pacific, Atlantic, and Indian oceans, averaged over 2 Ma intervals (circles) depart from the theoretical cooling curve (solid line) indicating convective cooling of young ocean crust by circulating seawater (after C. A. Stein and S. Stein, 1994). The first geochemical evidence for the existence of hydrothermal vents on the ocean floor came in the mid-1960s when investigations in the Red Sea revealed deep basins filled with hot, salty water (40-60 °C) and underlain by thick layers of metal-rich sediment (Degens and Ross, 1969). Because the Red Sea represents a young, rifting, ocean basin it was speculated that the phenomena observed there might also prevail along other young MOR spreading centers. An analysis of core-top sediments from throughout the world's oceans ( Figure 2) revealed that such metalliferous sediments did, indeed, appear to be concentrated along the newly recognized global ridge crest (Boström et al., 1969). Another early indication of hydrothermal activity came from the detection of plumes of excess 3He in the Pacific Ocean Basin (Clarke et al., 1969) - notably the >2,000 km wide section in the South Pacific ( Lupton and Craig, 1981) - because 3He present in the deep ocean could only be sourced through some form of active degassing of the Earth's interior, at the seafloor. (62K)Figure 2. Global map of the (Al+Fe+Mn):Al ratio for surficial marine sediments. Highest ratios mimic the trend of the global MOR axis (after Boström et al., 1969). One area where early heat-flow studies suggested hydrothermal activity was likely to occur was along the Galapagos Spreading Center in the eastern equatorial Pacific Ocean (Anderson and Hobart, 1976). In 1977, scientists diving at this location found hydrothermal fluids discharging chemically altered seawater from young volcanic seafloor at elevated temperatures up to 17 °C ( Edmond et al., 1979). Two years later, the first high-temperature (380±30 °C) vent fluids were found at 21° N on the East Pacific Rise (EPR) (Spiess et al., 1980) - with fluid compositions remarkably close to those predicted from the lower-temperature Galapagos findings ( Edmond et al., 1979). Since that time, hydrothermal activity has been found at more than 40 locations throughout the Pacific, North Atlanti

German, C. R.; von Damm, K. L.

2003-12-01

97

Quartz crystal growth  

DOEpatents

A process for growing single crystals from an amorphous substance that can undergo phase transformation to the crystalline state in an appropriate solvent. The process is carried out in an autoclave having a lower dissolution zone and an upper crystallization zone between which a temperature differential (.DELTA.T) is maintained at all times. The apparatus loaded with the substance, solvent, and seed crystals is heated slowly maintaining a very low .DELTA.T between the warmer lower zone and cooler upper zone until the amorphous substance is transformed to the crystalline state in the lower zone. The heating rate is then increased to maintain a large .DELTA.T sufficient to increase material transport between the zones and rapid crystallization. .alpha.-Quartz single crystal can thus be made from fused quartz in caustic solvent by heating to 350.degree. C. stepwise with a .DELTA.T of 0.25.degree.-3.degree. C., increasing the .DELTA.T to about 50.degree. C. after the fused quartz has crystallized, and maintaining these conditions until crystal growth in the upper zone is completed.

Baughman, Richard J. (Albuquerque, NM)

1992-01-01

98

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

99

Crustal faults exposed in the Pito Deep Rift: Conduits for hydrothermal fluids on the southeast Pacific Rise  

NASA Astrophysics Data System (ADS)

The escarpments that bound the Pito Deep Rift (northeastern Easter microplate) expose in situ upper oceanic crust that was accreted ˜3 Ma ago at the superfast spreading (˜142 mm/a, full rate) southeast Pacific Rise (SEPR). Samples and images of these escarpments were taken during transects utilizing the human-occupied vehicle Alvin and remotely operated vehicle Jason II. The dive areas were mapped with a "deformation intensity scale" revealing that the sheeted dike complex and the base of the lavas contain approximately meter-wide fault zones surrounded by fractured "damage zones." Fault zones are spaced several hundred meters apart, in places offset the base of the lavas, separate areas with differently oriented dikes, and are locally crosscut by (younger) dikes. Fault rocks are rich in interstitial amphibole, matrix and vein chlorite, prominent veins of quartz, and accessory grains of sulfides, oxides, and sphene. These phases form the fine-grained matrix materials for cataclasites and cements for breccias where they completely surround angular to subangular clasts of variably altered and deformed basalt. Bulk rock geochemical compositions of the fault rocks are largely governed by the abundance of quartz veins. When compositions are normalized to compensate for the excess silica, the fault rocks exhibit evidence for additional geochemical changes via hydrothermal alteration, including the loss of mobile elements and gain of some trace metals and magnesium. Microstructures and compositions suggest that the fault rocks developed over multiple increments of deformation and hydrothermal fluid flow in the subaxial environment of the SEPR; faults related to the opening of the Pito Deep Rift can be distinguished by their orientation and fault rock microstructure. Some subaxial deformation increments were likely linked with violent discharge events associated with fluid pressure fluctuations and mineral sealing within the fault zones. Other increments were linked with the influx of relatively fresh seawater. The spacing of the faults is consistent with fault localization occurring every 7000 to 14,000 years, with long-term slip rates of <3 mm/a. Once spread from the ridge axis, the faults were probably not active, and damage zones likely played a more significant role in axial flank and off-axis crustal permeability.

Hayman, Nicholas W.; Karson, Jeffrey A.

2009-02-01

100

Hydrothermal mineralogy and fluid inclusions chemistry to understand the roots of active geothermal systems  

NASA Astrophysics Data System (ADS)

An integrated study to link magmatic textures, magmatic mineral compositions, hydrothermal alteration zoning, hydrothermal mineral chemistry, and fluid inclusion compositions has been undertaken to link an intrusive complex and its degassing alteration halo with their surface equivalent in an active geothermal system. Ngatamariki geothermal system, New Zealand, presents a unique feature in the Taupo Volcanic Zone (TVZ). Drilling intercepted an intrusive complex with a high temperature alteration halo similarly to what is observed in magmatic-derived ore deposits. Thus it presents the perfect opportunity to study the magmatic-hydrothermal transition of the TVZ by characterizing the nature of the deep magmatic fluids link to the heat source of the world known geothermal fields. The record of magmatic-hydrothermal fluid-rock interactions preserved at Ngatamariki may be analogous of processes presently occurring at depth beneath TVZ geothermal systems. The intrusive complex consists of over 5 km3 of tonalite, diorite, basalt and aplitic dykes. Evidence of undercooling subsolidus magmatic textures such as myrmekite and skeletal overgrowth are commonly observed and often linked to volatile loss. The fluids released during the crystallization of the intrusive complex are interpreted to be at the origin of the surrounding high temperature alteration halo. Advanced argillic to potassic alteration and high temperature acidic assemblage is associated with high-temperature quartz veining at depth and vuggy silica at the paleo-surface. Major element compositions of the white micas associated with the high temperature halo show a transition from, muscovite to phengite, muscovitic illite away from the intrusion, with a transition to pyrophyllite and/ or topaz, and andalusite characteristic of more acidic conditions. Abundant high-density (up to 59 wt% NaCl eq and homogenization temperatures of 550 degree Celsius and above) coexist with low-density vapor fluid inclusions. This inferred heterogeneous entrapment represents the phase separation condition at the magmatic-hydrothermal conditions. Microthermometry measurements revealed the common presence of CO2, NaCl, KCl and CaCl2 species. Chemical compositions of the trapped fluids represent the closest equivalent of the magmatic fluids exsolving at depth feeding the deep roots of the geothermal fields. This study brings new constraints on the chemical conditions to model deep fluid-rock interactions in active geothermal systems.

Chambefort, I. S.; Dilles, J. H.; Heinrich, C.

2013-12-01

101

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

102

Vein of Galen Aneurysms  

PubMed Central

Summary Eleven patients with so-called “vein of Galen aneurysms ” are reported, six of whom presented with vein of Galen aneurysmal malformations (four with choroidal type and two with mural type malformations). The remaining five patients presented with vein of Galen aneurysmal dilatations secondarily due to an arteriovenous malformation in one patient, an arteriovenous fistula in another, dural arteriovenous fistulas in two patients, and a varix in another. Treatments for these patients were individualised with consideration given to the clinical manifestations and the angioarchitecture of their lesions. Endovascular intervention played a critical role in the treatment of these vein of Galen aneurysms. PMID:20663385

Komiyama, M.; Nakajima, H.; Nishikawa, M.; Yamanaka, K.; Iwai, Y.; Yasui, T.; Morikawa, T.; Kitano, S.; Sakamoto, H.; Nishio, A.

2001-01-01

103

Preventing Deep Vein Thrombosis  

MedlinePLUS

... birth control methods that contain estrogen or hormone therapy for menopause symptoms • Certain illnesses, including heart failure, inflammatory bowel disease, and some kidney disorders • Obesity • Smoking • Varicose veins • ...

104

The timing of sub-solidus hydrothermal alteration in the Central Zone, Limpopo Belt (South Africa): Constraints from titanite U Pb geochronology and REE partitioning  

NASA Astrophysics Data System (ADS)

In the Central Zone of the Limpopo Belt (South Africa), Palaeoproterozoic granulite-facies metamorphism was superimposed on an earlier Archaean orogenic history. Previously determined ages of ˜ 2030-2020 Ma obtained from high-temperature chronometers (zircon, garnet, monazite) are generally thought to provide the best estimate of the peak of Palaeoproterozoic granulite-facies metamorphism in the Central Zone, whereas ages as young as ˜ 2006 Ma from late melt patches suggest that temperatures remained above the wet solidus for an extended period. We present a new MC-ICP-MS 207Pb- 206Pb age of 2030.9 ± 1.5 Ma for titanite found in amphibolite- to greenschist-facies alteration zones developed adjacent to quartz vein systems and related pegmatites that cut a strongly deformed Central Zone metabasite. This age could potentially date cooling of rocks at this locality to temperatures below the wet solidus. Alternatively, the titanite could be inherited from the metabasite host, and the age determined from it date the peak of metamorphism. Integration of the geochronology with LA-ICP-MS trace element data for minerals from the metabasite, the hydrothermal vein systems and comparable rocks elsewhere shows that the titanite formed during the amphibolite-facies hydrothermal alteration, not at the metamorphic peak or during the greenschist-facies phase of veining. This suggests that high-grade rocks in the Central Zone have cooled differentially through the wet solidus, and provides timing constraints on when Palaeoproterozoic reworking in the Central Zone began. This study illustrates the potential of combined geochronological and high-resolution geochemical studies to accurately match mineral ages to distinct crustal processes.

Buick, Ian S.; Hermann, Jörg; Maas, Roland; Gibson, Roger L.

2007-10-01

105

Origin of the color in cobalt-doped quartz  

NASA Astrophysics Data System (ADS)

Synthetic Co-doped quartz was grown hydrothermally in steel autoclaves at the Technological Center of Minas Gerais (CETEC), Brazil. The quartz samples, originally yellow in the as-grown state acquired blue coloration after prolonged heat treatment times at 500°C near the alpha-beta transition temperature. UV-VIS-NIR absorption spectroscopy shows the characteristic spectra of Co3+ before heat treatment. After heat treatment, the optical absorption spectrum is dominated by two split-triplet bands the first in the near infrared region centered at about 6,700 cm-1 (1,490 nm) and the second in the visible spectral range at about 16,900 cm-1 (590 nm). Both split-triplet bands are typical for Co2+ ions in tetrahedral coordination environments. From the absence of electron paramagnetic resonance (EPR) spectra, we conclude that the Co2+ found in the optical absorption spectra of the blue quartz is not due to an isolated structural site in the quartz lattice. Instead, the blue color is associated with electronic transitions of Co2+ in small inclusions in which the Co site has tetrahedral symmetry. The non-observation of polarization-depend optical absorption spectra is also in agreement with this model. The results for Co2+ in quartz are different from Co-bearing spinel and staurolite and other silicates like orthopyroxene, olivine, and beryls. The formation process of the color center is discussed.

de Miranda Pinto, Luiz Carlos B.; Righi, Ariete; Lameiras, Fernando Soares; da Silva Araujo, Fernando Gabriel; Krambrock, Klaus

2011-09-01

106

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.

107

Mixing of fluids in hydrothermal ore-forming (Sn,W) systems: stable isotope and rare earth elements data  

NASA Astrophysics Data System (ADS)

Experimental and physico-chemical modeling data witness to important role of mixing of different type of fluids during tin and tungsten ore formation in hydrothermal systems. Mixing of magmatogeneous fluids, exsolved from granite melts, with exogenic, initially meteoric waters in hydrothermal ore-forming systems may change chemical composition of ore-forming fluid, causing cassiterite and/or wolframite precipitation (Heinrich, 1990; Sushchevskaya, Ryzhenko, 2002). We studied the process of genetically different fluids mixing for two economic Sn-W deposits, situated in the Iultin ore region (North-East of Russia, Chukotka Penninsula). The Iultin and Svetloe deposits are located in the apical parts of close situated leucogranite stocks, formed at the final stage of the Iultin complex emplacement. Both deposits are composed of a series of quartz veins among the flyschoid rocks (T 1-2), cut by the dikes (K1) of lamprophyre, granodiorite porphyre and alpite. The veins of the deposits are dominated by the productive quartz-wolframite-cassiterite-arsenopyrite-muscovite mineral assemblage. Topaz, beryl, fluorite, and albite occur sporadically. The later sulfide (loellingite-stannite-chalcopyrite) and quartz-fluorite-calcite assemblages show insignificant development. The preore quartz veinlets in host hornfels contain disseminated iron sulfides, chalcopyrite, muscovite. Isotopic (H, O, Ar) study of minerals, supplemented by oxygen isotope data of host granites and metamorphic rocks gave us possibility to conclude, that at the Iultin and the Svetloye deposits fluid mixing was fixed on the early stages of deposit formation and could be regarded as probable cause of metal (W, Sn) precipitation. During postore time the intensive involvement of isotopically light exogenic waters have changed: a) the initial character of oxygen isotope zonality; b) the initial hydrogen isotope composition of muscovites, up to meteoric calculated values for productive fluid (while the ?18O values of quartz from productive association remained rather high). The intense mixing of magmatic and meteoric waters was sponsored by the location of the hydrothermal systems in a permeable zone at the contact of the leucogranite cupolas with hornfels and sandstones, cut by dykes and subsequently developing ore-hosting fissures. REEs data, which also may describe the process of fluid mixing, have been obtained for the minerals and rocks with the help of ICP MS analysis. The REEs concentrations in mineral- forming fluids have been obtained: a) from total analysis of fluid inclusion solutions and b) from calculations of REEs values for such minerals, as fluorite, wolframite, sheelite with mineral-fluid partitioning coefficients (Raimbault et al., 1985). REEs distribution in host rocks was studied for the cross sections, previously analysed for oxygen isotopic zonality (Sushchevskaya et al., 2008). Interpretation of these results favours the view, that ore-forming fluids are of mixing genesis.

Sushchevskaya, T. M.; Popova, J. A.; Velivetskaya, T. A.; Ignatiev, A. V.; Matveeva, S. S.; Limantseva, O. A.

2012-04-01

108

Zonation of Hydrothermal Alteration in the Central Uplift of the Puchezh-Katunki Astrobleme  

NASA Astrophysics Data System (ADS)

The giant (D = 80 km) Puchezh-Katunki astrobleme [1,2] is the site of widespread hydrothermal alteration. It occurs mainly in the central uplift composed of brecciated archean rocks and overlain by allogenic breccia, suevites, and coptomict gravelites (the latter is the lowest bed of crater-lake deposits). Distribution and vertical zonation of secondary minerals is controlled by the thermal gradient during cooling of authigenic breccia massif, while the degree of alteration depends on the intensity of brecciation and fracturing of basement rocks. Three types of hydrothermal mineralization are distinguished on the basis of different crystallization conditions: (1) mixed hydrothermal-diagenetic, in coptomict gravelites; (2) metasomatic, including formation of Fe-Mg hydrous phyllosilicates in shocked and thermally altered gneisses and amphibolites; and (3) veins, represented by mineral associations filling fractures and voids in basement rocks, allogenic breccia, and suevites. The second and third types occur together and each displays characteristic zonations, thus several zones may be distinguished in vertical section (zones 2-4 below). The uppermost zone corresponds to mixed hydrothermal-diagenetic conditions described in (1) above. In general, four zones are distinguished, from top downward, as follows. 1. Zone of hydrothermal-diagenetic alteration in coptomict gravelites. In this zone, replacement of impact glass fragments by assemblage of montmorillonite, calcite, and pyrite, and formation of alkali zeolites and calcite as a cement are observed establishing a temperature of alteration of less than 100 degrees C. 2. Zone of low-temperature (100 degrees-200 degrees C) mineralization comosed of suevites, allogenic breccia, and the upper part of authigenic breccia down to 2.5 km. Fe-saponite develops in shocked and recrystallized basement rocks, and various zeolites, apophylite, calcite, anhydrite, and pyrite fill vugs and fractures; in addition, calcite-nontronite veinlets occur locally. The distribution of zeolites is characterized by their own zonation [3]. 3. Zone of moderate-temperature (200 degrees-300 degrees C) mineralization in basement at a depth of 2.5-4.2 km. Chlorite (of diabantite-pictochlorite series) is a common metasomatic phase associated with pyrite, and also with albite, epidote, and calcite locally. In veinlets, Ca-Fe silicates (andradite, salite, epidote, prehnite) together with pyrite, chlorite, and, very rarely, quartz, are found in a laumontite-anhydrite matrix. 4. Zone of low-moderate-temperature (150 degrees - 250 degrees C?) mineralization at a depth below 4.2 km. Prehnite, anhydrite, calcite, and pyrite are present. Absence of Ca-Fe silicates may indicate a decrease in crystallization temperature compared with the upper zone, while disappearance of hydrous phases seems to be a result of the fall of P(sub)H2O at this depth. The decrease in degree of alteration outward from the impact center and the change in zeolite composition to lower-temperature varieties as well as crystallization of gypsum instead of anhydrite are evidence of lateral hydrothermal zonation in the crater. Thus the zones may have an ellipsoidal shape corresponding to isotherms during circulation. The generalized chronological order of hydrothermal crystallization is the following: Ca-Fe silicates, chlorite (smectites)-calcite, pyrite-anhydrite- zeolites, apophyllite-calcite, nontronite. This reflects a continually decreasing temperature during the process of hydrothermal alteration. Spatial segregation of minerals is caused by change of parameters (pH, f(sub)CO2, temperature, etc.) of solutions moving in the thermogradient field, where the source of heat is a result of the thermal history of the central uplift [4]. Nevertheless, the role of endogenic heat and mass transfer in impact-induced hydrothermal circulation processes cannot be ruled out. References: [1] Masaitis V. L. and Mashchak M. S. (1990) Meteoritics, 25, 383a. [2] Pevzner L. A. et al. (1992) LPS XXIII, 1063-1064. [3] Naumov M. V. (1992) LPS XXIII, 967-968. [4] M

Naumov, M. V.

1993-07-01

109

Multiple episodes of hydrothermal circulation, thermal metamorphism, and magma injection beneath The Geysers steam field, California. [Abstract only  

SciTech Connect

Thermal metamorphic and hydrothermal mineral assemblages in drill cores and cuttings, K-Ar ages, and regional geologic relations indicate that The Geysers has been a locus of multiple intrusion and heat rejuvenation for more than 2.0 My, probably as the result of episodic crustal extension within the San Andreas fault system. Early episodes of magma injection beneath the steam field are indicated by hypabyssal rhyolitic and dacitic rocks that intruded to within a kilometer of the surface, dated by the Union Oil Co. at 1.6 to 2.5 My; and by small rhyolite extrusive bodies dated by the US Geological Survey at about 2.0 My. Later intrusion of magma is indicated by the rhyolite and dacite domes and flows on nearby Cobb Mountain, which are dated at 1.0 to 1.1 My. Episodes of magma injection were accompanied in the subsurface by fracturing of the intruded wallrocks and tourmalinization (probably at greater than or equal to 350/sup 0/C) in contact zones around the intrusions. High-temperature (greater than or equal to 290/sup 0/C) hot water circulation below 920 m is indicated by vein assemblages of epidote +- pyrrhotite. At depths as shallow as 100 m, lower temperature (greater than or equal to 210/sup 0/C) hot-water circulation is suggested by later veins of quartz +- adularis +- chlorite +- white mica +- pyrite; the paragenetically late adularia is dated at 0.69 +- 0.03 My. These lower temperature shallower vein assemblages were followed locally by deposition of datolite, pyrite, galena, sphalerite, minor cinnabar, and calcite in veinlets, cavities, and vugs. This latest hydrothermal mineral assemblage may record an increase in temperature or decrease in pressure, possibly associated with flipover to a vapor-dominated system. These data suggest that the present vapor-dominated system at The Geysers evolved from a hot water system in which the periodic influx of magma has sustained hydrothermal circulation for at least 0.7 My.

McLaughlin, R.J.; Moore, D.E.; Sorg, D.H.; McKee, E.H.

1983-03-01

110

Trace Elements in the Si Furnace. Part I: Behavior of Impurities in Quartz During Reduction  

NASA Astrophysics Data System (ADS)

Quartz and carbonaceous materials, which are used in the production of silicon as well as electrodes and refractories in the silicon furnace, contain trace elements mostly in the form of oxides. These oxides can be reduced to gaseous compounds and leave the furnace or stay in the reaction products—metal and slag. This article examines the behavior of trace elements in hydrothermal quartz and quartzite in the reaction of SiO2 with Si or SiC. Mixtures of SiO2 (quartz or quartzite), SiC, and Si in forms of lumps or pellets were heated to 1923 K and 2123 K (1650°C and 1850°C) in high purity graphite crucibles under Argon gas flow. The gaseous compounds condensed in the inner lining of the tube attached to the crucible. The phases present in the reacted charge and the collected condensates were studied quantitatively by X-ray diffraction (XRD) and qualitatively by Electron Probe Micro Analyzer (EPMA). Contaminants in the charge materials, reacted charge and condensate were analyzed by Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS). Muscovite in the mineral phase of quartz melted and formed two immiscible liquid phases: an Al-rich melt at the core of the mineral, and a SiO2-rich melt at the mineral boundaries. B, Mn, and Pb in quartz were removed during heating in reducing atmosphere at temperature above 1923 K (1650°C). Mn, Fe, Al and B diffused from quartz into silicon. P concentration was under the detection limit. Quartzite and hydrothermal quartz had different initial impurity levels: quartzite remained more impure after reduction experiment but approached purity of hydrothermal quartz upon silica reduction.

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

2013-04-01

111

Cryogenic quartz crystal microbalance  

NASA Technical Reports Server (NTRS)

A radiatively cooled Cryogenic Quartz Crystal Microbalance designed to monitor highly volatile contaminants on the shuttle is described. Measurements are made with two 15-MHz microbalances having removable, optically polished sensors mounted in a radiant cooler. One sensor operates below the freezing point of water and monitors contamination including that of water vapor. The second sensor is heated and monitors the contamination background. It provides a reference from which the density of the water vapor cloud enveloping the shuttle is determined. The design incorporates a low-power dissipation oscillator, heaters for ice removal, and a method for attaching second-surface mirrors to the radiator employing an indium type solder instead of a room temperature vulcanizer.

Mckeown, D.; Sonnenschein, G.; Fox, M. G.

1975-01-01

112

Modeling Low Density Porous Quartz  

Microsoft Academic Search

Extensive Hugoniot data have been published for quartz over a wide range of initial porosities. One remarkable feature of shock-particle velocity data for large initial distensions is the absence of a manifestation of the phase change that figures so prominently in the low distension and solid material Hugoniots. Attempts to model a large distension porous quartz with a homogeneous material

Marlin Kipp

2001-01-01

113

Crystallization pressure versus “crack seal” as the mechanism for banded veins  

NASA Astrophysics Data System (ADS)

Banded fibrous veins are often pointed to as evidence for episodic crack opening driven by oscillations in fluid pressure or bulk strain. Advances in understanding the geochemistry of precipitation, data on veins, and experiments suggest that pressure due to growing crystals may be an alternate explanation for many observations on these types of veins. We propose that some veins originate at sites of precipitation and then propagate due to the pressure exerted by the crystal growth. As materials precipitate, the vein walls are pushed apart. The resulting veins have shapes typical for mode I cracks except that, mechanically, crystallization pressure replaces the role of internal fluid pressure in their propagation. A nonzero remote differential stress serves to align veins. Mechanical and geochemical considerations suggest that this process will be most important in fine-grained rocks such as greenschist-grade pelites where diffusion from sites of dissolution rather than advection is the dominant mass-transport process. Veins may owe their orientation to tectonism, but their initiation and growth are due to processes that supersaturate the pore fluid. Veins formed by this mechanism involve cracking to the extent that precipitation forces an original flaw to extend during precipitation. Cyclic quartz-mica bands may indicate geochemical self-organization at the vein wall driven by pressure-solution-enhanced supersaturation in the pore fluid and nonlinear precipitation kinetics at the vein wall.

Wiltschko, David V.; Morse, John W.

2001-01-01

114

Geology and mineralogy of the Santo Nino Ag-Pb-Zn vein, Fresnillo District, Mexico  

SciTech Connect

The Santo Nino Ag-Pb-Zn vein is the major producer of the Fresnillo District, located 750 km NW of Mexico City. It is over 2.4 km long, more than 480 m in vertical extent, more than 2.5 m wide overall, and has average grades of >600 gm/t Ag and <2% combined Pb and Zn. The vein is hosted by a tilted sequence of Cretaceous graywackes, shales and andesitic volcanics and extends upward into a Lower Tertiary conglomerate. Up to 5 separate opening events occurred along the vein, resulting in discontinuous stages of brecciation and crustiform banding. Ore mineral zonation is well developed both vertically and laterally and closely reflects metal and metal ratio distributions. Ore minerals are sphalerite, galena, pyrite, chalcopyrite, arsenopyrite, marcasite, pyrrhotite, acanthite, native silver, and three coexisting solid solution series, pyrargyrite-proustite, polybasite-arsenopolybasite, and tetrahedrite-tennantite in a gangue of quartz, calcite, clay, sericite,and chlorite. A 5-stage paragenetic sequence can be established: 1) pyrite, arsenopyrite, quartz, 2) sphalerite, galena, chalcopyrite, quartz, 3) tetrahedrite, pyrargyrite, polybasite, quartz, 4) acanthite, native silver, calcite, quartz, and 5) calcite. Preliminary microprobe analyses indicate that the Ag-rich solid solution series are Sb-rich in the central and upper portions of the vein and As-rich at deeper levels.

Gemmell, J.B.; Zantop, H.; Birnie, R.W.

1985-01-01

115

Hydrothermal Biogeochemistry  

NASA Astrophysics Data System (ADS)

Life in hot spring ecosystems is confronted with diverse challenges, and the responses to those challenges have dynamic biogeochemical consequences over narrow spatial and temporal scales. Within meters along hot spring outflow channels at Yellowstone, temperatures drop from boiling, and the near-boiling conditions of hot chemolithotrophic communities, to those that permit photosynthesis and on down to conditions where nematodes and insects graze on the edges of photosynthetic mats. Many major and trace element concentrations change only mildly in the water that flows through the entire ecosystem, while concentrations of other dissolved constituents (oxygen, sulfide, ammonia, total organic carbon) increase or decrease dramatically. Concentrations of metals and micronutrients range from toxic to inadequate for enzyme synthesis depending on the choice of hot spring. Precipitation of minerals may provide continuous growth of microbial niches, while dissolution and turbulent flow sweeps them away. Consequently, microbial communities change at the meter scale, and even more abruptly at the photosynthetic fringe. Isotopic compositions of carbon and nitrogen in microbial biomass reflect dramatic and continuous changes in metabolic strategies throughout the system. Chemical energy sources that support chemolithotrophic communities can persist at abundant or useless levels, or change dramatically owing to microbial activity. The rate of temporal change depends on the selection of hot spring systems for study. Some have changed little since our studies began in 1999. Others have shifted by two or more units in pH over several years, with corresponding changes in other chemical constituents. Some go through daily or seasonal desiccation cycles, and still others exhibit pulses of changing temperature (up to 40°C) within minutes. Taken together, hydrothermal ecosystems provide highly manageable opportunities for testing how biogeochemical processes respond to the scale of temporal, spatial, and compositional changes.

Shock, E.; Havig, J.; Windman, T.; Meyer-Dombard, D.; Michaud, A.; Hartnett, H.

2006-12-01

116

Quartz crystal fabrication facility  

NASA Astrophysics Data System (ADS)

The report describes the design and operation of a five chamber, interconnected vacuum system, which is capable of cleaning, plating, and sealing precision quartz crystal units in ceramic flatpack enclosures continuously in a high vacuum environment. The production rate design goal was 200 units per eight hour day. A unique nozzle beam gold deposition source was developed to operate for extended periods of time without reloading. The source puts out a narrow beam of gold typically in the order of 2 1/2 deg included cone angle. Maximum deposition rates are in the order of 400 a/min at 5.5 in. 'throw' distance used. Entrance and exit air lock chambers expedite the material throughput, so that the processing chambers are at high vacuum for extended periods of time. A stainless steel conveyor belt, in conjunction with three vacuum manipulators, transport the resonator components to the various work stations. Individual chambers are normally separated from each other by gate valves. The crystal resonators, mounted in flatpack frames but unplated, are loaded into transport trays in a lid-frame-lid sequency for insertion into the system and exit as completed crystal units. The system utilizes molybdenum coated ball bearings at essentially all friction surfaces. The gold sources and plating mask heads are equipped with elevators and gate valves, so that they can be removed from the system for maintenance without exposing the chambers to atmosphere.

Ney, R. J.

1980-05-01

117

Hydrogen speciation in synthetic quartz  

USGS Publications Warehouse

The dominant hydrogen impurity in synthetic quartz is molecular H2O. H-OH groups also occur, but there is no direct evidence for the hydrolysis of Si-O-Si bonds to yield Si-OH HO-Si groups. Molecular H2O concentrations in the synthetic quartz crystals studied range from less than 10 to 3,300 ppm (H/Si), and decrease smoothly by up to an order of magnitude with distance away from the seed. OH- concentrations range from 96 to 715 ppm, and rise smoothly with distance away from the seed by up to a factor of three. The observed OH- is probably all associated with cationic impurities, as in natural quartz. Molecular H2O is the dominant initial hydrogen impurity in weak quartz. The hydrolytic weakening of quartz may be caused by the transformation H2O + Si-O-Si ??? 2SiOH, but this may be a transitory change with the SiOH groups recombining to form H2O, and the average SiOH concentration remaining very low. Synthetic quartz is strengthened when the H2O is accumulated into fluid inclusions and cannot react with the quartz framework. ?? 1984 Springer-Verlag.

Aines, R.D.; Kirby, S.H.; Rossman, G.R.

1984-01-01

118

Calcite veins in northeastern Puente Hills, southern California  

SciTech Connect

Calcite vein fillings are locally exposed in the northeastern Puente Hills, 2 mi southwest of Pomona on the northeast margin of the Los Angeles basin. They occur within northeast- and northwest-trending faults in the middle Miocene Glendora Volcanics and in the Soquel Member of the upper Miocene Puente Formation. The veins range in width from 1 in. to 15 ft, and several can be traced hundreds of feet. The veins exhibit complex banded and brecciated textures and emit a strong hydrocarbon odor when broken. The carbon isotopic composition is light (delta/sup 13/C = -22.1 to -45.6 per thousand PDB). The range of the oxygen isotopic composition (delta/sup 18/O = +21.3 to +31.1 per thousand SMOW) generally compares with those reported for diagenetic carbonates in marine Miocene shales of California and Oregon. Dissolution of unusual local Soquel marine carbonates, now primarily dolomite, and diagenetic cements seems to be the most likely source of the calcite that was deposited incrementally along faults to form the calcite-filled veins. The extremely depleted carbon isotope values represent the addition of carbon derived from the chemical and/or biological oxidation of methane; a petroleum source of the methane is suggested by the presence of solid hydrocarbon inclusions in the vein calcite. The formation temperature of the vein calcite was probably below hydrothermal.

Spira, M.O.; Zenger, D.H.

1986-04-01

119

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

120

Quartz fiber calorimetry and calorimeters  

E-print Network

Quartz fiber calorimetry is a technique the signal generation mechanism of which is based on the Cherenkov effect. In this article we try to give a comprehensive overview of the subject. We start with a general introduction to calorimetry where the basic elements that characterize the development of electromagnetic and hadronic showers are discussed. Then we describe in detail the operation principle and the properties of calorimeters equipped with quartz fibers. The main advantages of this type of calorimeters are the radiation hardness, the fast response and the compact detector dimensions, features that derive from the quartz material and the specific mechanism of operation. A section is devoted to presenting the quartz fiber calorimeters that have been built or planned to in various experiments to operate as centrality detectors, trigger detectors, luminosity monitors or general purpose very forward calorimeters.

G. Mavromanolakis

2004-12-20

121

Petrology, composition, and age of intrusive rocks associated with the Quartz Hill molybdenite deposit, southeastern Alaska.  

USGS Publications Warehouse

A large porphyry molybdenum deposit (Quartz Hill deposit) was recently discovered in the heart of the Coast Range batholithic complex about 70 km E of Ketchikan, SE Alaska. Intrusive rocks associated with the mineral deposit form two composite epizonal to hypabyssal stocks and many dikes in country rocks. All observed metallization and alteration is within the Quartz Hill stock. Molybdenite forms fracture coatings and occurs in veins with quartz. Alteration is widespread and includes development of secondary quartz, pyrite, K-feldspar, biotite, white mica, chlorite, and zeolite. Field relations indicate that the stocks were emplaced after regional uplift and erosion of the Coast Range batholithic complex, and K-Ar data show that intrusion and alteration took place in late Oligocene time, about 27 to 30 Ma ago. Data from the Ketchikan quadrangle indicate that porphyry molybdenum metallization in the Coast Range batholithic complex is associated with regionally extensive but spotty, middle Tertiary or younger, felsic magmatism. -from Authors

Hudson, T.; Smith, J.G.; Elliott, R.L.

1979-01-01

122

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

123

Thermal Effects in the Hydrothermal Regime of Magmatic-Hydrothermal Systems  

NASA Astrophysics Data System (ADS)

Models of conductive and convective cooling of epizonal magma bodies commonly show temperatures in the country rock that are at or below 500 C. Indeed, simple conductive cooling models place the contact temperature below the midpoint of the intrusion and country rock temperatures, which for felsic magmas in cold country rock (cf. Furlong et al., 1991, Rev. in Min. v. 26), is approximately 500 C or lower. However, some vein systems record temperatures e.g. from fluid inclusions or phase equilibria that exceed 500 C. In some cases, as in some deep skarn deposits, high temperatures of ore deposition probably result from high country rock temperatures. Veins may also occur in the already cooled portions of an ore-generative pluton, which can be at any temperature below the solidus. In still other cases, high country rock temperatures may be heated by previous magmatic events (thermal ground preparation). However, high temperatures of mineral alteration or deposition may be produced in initially cold country rock by flux of high temperature magmatic volatile phase from the magma itself. This is a likely explanation when ore is associated with early stages of magmatism at shallow levels in the crust. The mass conservation equations of infiltration theory (cf. Ferry, 1991, Rev. in Min. v. 26), can be used to estimate time-integrated fluid fluxes, q, given changes in quartz solubility with temperature, geothermal and geobaric gradients in shallow magmatic environments, and order of magnitude vein quartz densities in porphyry copper deposits. The change in the silica content of the rock due to quartz veining is then given by: \\Delta cQZ =- \\int Jw dt \\times \

Candela, P. A.

2002-05-01

124

Hydrothermal alteration and mass exchange in the hornblende latite porphyry, Rico, Colorado  

USGS Publications Warehouse

The Rico paleothermal anomaly, southwestern Colorado, records the effects of a large hydrothermal system that was active at 4 Ma. This hydrothermal system produced the deep Silver Creek stockwork Mo deposit, which formed above the anomaly's heat source, and shallower base and precious-metal vein and replacement deposits. A 65 Ma hornblende latite porphyry is present as widespread sills throughout the area and provided a homogenous material that recorded the effects of the hydrothermal system up to 8 km from the center. Hydrothermal alteration in the latite can be divided into a proximal facies which consists of two assemblages, quartz-illite-calcite and chlorite-epidote, and a distal facies which consists of a distinct propylitic assemblage. Temperatures were gradational vertically and laterally in the anomaly, and decreased away from the centra heat source. A convective hydrothermal plume, 3 km wide and at least 2 km high, was present above the stock-work molybdenum deposit and consisted of upwelling, high-temperature fluids that produced the proximal alteration facies. Distal facies alteration was produced by shallower cooler fluids. The most important shallow base and precious-metal vein deposits in the Rico district are at or close to the boundary of the thermal plume. Latite within the plume had a large loss of Na2O, large addition of CaO, and variable SiO2 exchante. Distal propylitized latite samples lost small amounts of Na2O and CaO and exchanged minor variable amounts of SiO2. The edge of the plume is marked by steep Na2O exchange gradients. Na2O exchange throughout the paleothermal anomaly was controlled by the reaction of the albite components in primary plagioclase and alkali feldspars. Initial feldspar alteration in the distal facies was dominated by reaction of the plagioclase, and the initial molar ratio of reactants (alkali feldspar albite component to plagioclase albite component) was 0.35. This ratio of the moles of plagioclase to alkali feldspar albite components that reacted evolved to 0.92 as the reaction progressed. Much of the alkali feldspar albite component in the proximal facies reacted while the, primary plagioclase was still unreacted, but the ratio for these assemblages increased to 1.51 when the plagioclase entered the reaction paragenesis. Plagioclase reaction during distal propylitic alteration resulted in pseudomorphic albite mixed with illite and a loss of Na2O. CaO is lost in the distal facies as hornblende reacts to chlorite, although some calcium may be fixed in calcite. CaO is added to the proximal facies as the quantity of chlorite replacing hornblende increases and epidote and calcite are produced. ?? 1994 Springer-Verlag.

Larson, P.B.; Cunningham, C.G.; Naeser, C.W.

1994-01-01

125

Mercury isotope fractionation in fossil hydrothermal systems  

NASA Astrophysics Data System (ADS)

The Hg isotopic compositions of samples throughout the vertical extent of two fossil hydrothermal systems were analyzed by multicollector inductively coupled plasma mass spectrometry. Results show >5‰ (?202Hg/198Hg; relative to NIST 3133) fractionation, more than 50 times greater than the 0.1‰ (2?) external reproducibility of the analyses. The Hg isotope compositions from both hydrothermal systems can be grouped by dominant mineralogy and position; ?202Hg/198Hg values at the tops of the systems are -3.5‰ to -0.4‰ in cinnabar-dominant sinter and -0.2‰ to +2.1‰ in metacinnabar-dominant sinter, and the underlying veins have ?202Hg/198Hg values of -1.4‰ to +1.3‰. These differences probably resulted from the combination of boiling of the hydrothermal fluid, oxidation near the surface, and kinetic effects associated with mineral precipitation. The natural variation in Hg isotopic compositions observed in this study is higher than that expected from the trend of decreasing mass-dependent fractionation with increasing mass extrapolated from stable isotope systems up to Z = 26 (Fe), confirming that even the heaviest elements undergo significant stable isotope fractionation in hydrothermal systems.

Smith, Christopher N.; Kesler, Stephen E.; Klaue, Björn; Blum, Joel D.

2005-10-01

126

Hydrothermal Alteration in the Logatchev Hydrothermal Field: Implications From Secondary Mineral Assemblages and Mineral Chemistry  

NASA Astrophysics Data System (ADS)

We present new data on secondary mineral assemblages, clay and whole rock chemistry and clay mineral strontium and lithium isotopic compositions of altered rocks and sediments from the active, ultramafic-hosted Logatchev hydrothermal field reflecting various alteration conditions (e.g. fluid mixing, water-rock interaction). The altered ultramafic rocks are mainly consist of lizardite, chrysotile whereas magnetite and pyrite are minor minerals. Chlorite, chlorite-smectite mixed-layer (e.g., corrensite), smectite and talc are additional common phases in the clay fraction of most of these samples.Iron-hydroxides and iron sulfides are the main components of the hydrothermal crusts, with some amounts of pyroxene, chlorite, illite and pyrite. The hydrothermal sediments beneath the crusts are characterized by quartz, smectite and chlorite as main minerals. Analyses of clay separates representing a variety of alteration styles demonstrates that significant and characteristic changes in the bulk rock chemical composition are associated with various alteration conditions. The elements Cr, Cu, Pb and U appears to have a general enrichment in the lizardite and chlorite concentrates in comparison to a depleted mantle. 87Sr/86Sr ratios of clay concentrates vary between 0.7083 and 0.7096 suggesting that the clays either formed as a result of seawater alteration or hydrothermal alteration with various portions of seawater. The strontium isotopic ratio of a chlorite sample from hydrothermal sediments beneath the hydrothermal crust is much lower than the isotopic data reported for the lizardites suggesting precipitation from fluid with lower seawater content. The Li isotopic composition (?7Li) of the clay separates varies between -5.4 and +6.4‰. Thus, the clays are enriched in 6Li relative to both seawater (~31‰) and hydrothermal vent fluids from the Logatchev field (~6‰) suggesting that 6Li is preferentially retained in alteration products. When considered together with the Sr isotope data, these Li isotope data may be used to estimate the temperature of formation of the clay concentrates.

Lackschewitz, K. S.; Augustin, N.; Devey, C. W.; Eisenhauer, A.; Garbe-Schoenberg, D.; James, R.

2005-12-01

127

Sericitic alteration at the La Crocetta deposit (Elba Island, Italy): interplay between magmatism, tectonics and hydrothermal activity  

NASA Astrophysics Data System (ADS)

The La Crocetta mine near Porto Azzurro (Elba Island, Tuscany, Italy) is an important producer of raw material for the ceramic industry. Exploitation focuses on a pervasively sericitized porphyritic aplite of the Tuscan Magmatic Province, locally known as "eurite", which underwent significant potassium enrichment during sericitic alteration. Eurites are located along the hanging wall of the Elba Centrale Fault, a low-angle extensional lineament of regional significance. A later carbonatization stage, apparently associated with high-angle extensional tectonics, locally overprinted the sericitized facies. It is expressed by carbonate ± pyrite ± quartz veins, with adverse effects on ore quality. Sericitization was accompanied by addition of potassium, and loss of Na (± Ca, Fe). Rubidium was not enriched along with potassium during sericitization, contrary to what would be expected for interaction with late-magmatic fluids. New 40Ar-39Ar data from eurites provide an isochron age of about 6.7 Ma for the sericitization, whereas the age of the unaltered protolith is ca. 8.8 Ma. Field evidence indicates the Elba Centrale Fault to be the main channel for the hydrothermal fluids. On the other hand, the involvement of heat and/or fluids contributed by the Porto Azzurro pluton, which crops out in the La Crocetta area, is ruled out by field, geochemical and geochronological data (40Ar-39Ar age of Porto Azzurro =5.9 Ma, i.e. significantly younger than the sericitization event). Fluid inclusion studies suggest that sericitization was associated with a low-temperature (<250 °C) hydrothermal system. Fluids were locally boiling, of variable salinity (4-17 wt% NaCl equiv.), and contained some CO2 ( XCO2?0.027). Their ultimate source is not unequivocally constrained; meteoric and/or magmatic contributions may be possible. Low-salinity (?2.6 wt% NaCl equiv.), low-temperature (<250 °C) fluids are associated with the late carbonate veining. They are considered to be of dominantly meteoric nature because of their low salinity. In summary, sericitization at La Crocetta is regarded as the product of a detachment fault-related, low temperature hydrothermal system, resulting from the structurally controlled focusing of meteoric and possibly magmatic fluids. Hence, potential targets for exploration for similar resources are represented by aplitic bodies located in the hanging wall of Elba Centrale Fault. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00126-002-0279-2.

Maineri, Cinzia; Benvenuti, Marco; Costagliola, Pilar; Dini, Andrea; Lattanzi, Pierfranco; Ruggieri, Giovanni; Villa, Igor M.

2003-01-01

128

Mineralization in the Bonser Vein, Coniston, English Lake District: Mineral Assemblages, Paragenesis, and Formation Conditions  

Microsoft Academic Search

The Bonser vein, one of the most productive sources of copper in the English Lake District, contains a mineral assemblage comprising quartz, chlorite, calcite, dolomite, stilpnomelane, magnetite, pyrrhotine, pyrite, marcasite, native bismuth, bismuthinite, laltakarite, joseite, arsenopyrite, chalcopyrite, sphalerite, galena, and cosalite. The phases pyrrhotine, sphalerite, arsenopyrite, laitakarite, joseite, and cosalite were analysed by electron microprobe. The occurrence of laitakarite is

C. J. Stanley; D. J. VAUGHAN

1982-01-01

129

[Sclerosis in varicose veins].  

PubMed

The authors report their experience in the sclerotherapy of varicose veins. They have used the technique of French school: with the patient half sitting, direct puncture not far from the gulf of saphena without tourniquet, on a weekly basis. PMID:9835187

Perilli, G; Scioscia, P; Ferretti, L

1998-10-01

130

Hydrothermal crystallization of silica gel. [Chalcedonic spherulites; 3kb, 100 to 300°C  

Microsoft Academic Search

Under hydrothermal conditions (3 kb, 100° to 300°C, 25 to 5,200 hr), freshly solidified silica gel crystallized to quartz, predominantly in the form of chalcedonic spherulites. No intermediate crystalline phases in the transition from amorphous silica to quartz were detected. Chalcedony that made up the synthetic spherulites was either length-slow, length-fast, or both, depending on the experimental conditions. These findings

Oehler

1976-01-01

131

Dislocation Creep of Dry Quartz  

NASA Astrophysics Data System (ADS)

Small scale shear zones formed during heterogeneous, amphibolite facies condition in the Truzzo granite in the Penninic Tambo nappe. Magmatic quartz grains recrystallized dynamically by subgrain rotation and grain boundary migration. The presence of a monoclinic shape fabric and a crystallographic preferred orientation are typical for deformation by dislocation creep. Dynamically recrystallized mean grain sizes vary between 200 and 750 ?m which indicate deformation at relatively low differential stresses (5 - 30 MPa). Fourier-Transform-Infrared (FTIR) spectroscopy reveals water contents mostly below 200 H/10^6 Si in the interior of recrystallized grains (in the form of discrete OH peaks and very little broad band absorption). This water content is in the range of values reported for dry Brazil quartz. Primary magmatic quartz grains contain fluid-inclusion-rich areas with a broad absorption band and higher water concentrations. Recrystallized grains are dry, except for postkinematic inclusion trails. These measurements present the first data on strictly intragranular water contents of dynamically recrystallized quartz in nature. Dry quartz is extremely strong and does not deform by dislocation creep in deformation experiments at the low differential stress levels that would correspond to natural deformation. In contrast, deformation experiments on wet polycrystalline quartz have produced flow laws that can be extrapolated to natural conditions, which yield satisfying results. This is in contrast with our data of the dry quartz deforming by dislocation creep at relatively low differential stresses at natural strain rates. Contrary to the conventional concept of recovery, our data and observations imply that quartz would be hardening as a consequence of grain boundary migration because fluid inclusions are expelled. The drainage of fluid inclusions and microstructures in the feldspar-mica matrix indicate that water during deformation was at least present in the grain boundary region. FTIR measurements of natural deformed quartz reported in literature include grain boundaries and usually yield concentration of up to several 1000s H/10^6 Si. Therefore it is concluded that either introduction of water into the deforming grains must have been transient or that the intragranular water concentrations which are rheologically effective in the naturally deformed Truzzo granite are much lower than those previously reported in the literature.

Kilian, R.; Heilbronner, R.; Stunitz, H.

2011-12-01

132

Modeling Low Density Porous Quartz  

NASA Astrophysics Data System (ADS)

Extensive Hugoniot data have been published for quartz over a wide range of initial porosities. One remarkable feature of shock-particle velocity data for large initial distensions is the absence of a manifestation of the phase change that figures so prominently in the low distension and solid material Hugoniots. Attempts to model a large distension porous quartz with a homogeneous material model (e.g., P-alpha) result in a Hugoniot in which the phase change remains a distinct feature, and also lead to Hugoniot states where the temperature is much too high accompanied by a correspondingly low density (a consequence of excessive energy dissipation). An alternate modeling approach explicitly inserts void into the material to create the proper initial density, then uses an Eulerian calculation that allows the code to do the pore collapse explicitly, requiring only the equation of state for the solid quartz. With a tabular (Sesame) equation of state, which includes the phase transformation, for the competent quartz in the Eulerian code CTH, the resulting calculated Hugoniot pressure-density states for low initial density porous quartz are in excellent agreement with data, and the corresponding temperature states are in accord with published theoretical values.

Kipp, Marlin

2001-06-01

133

Sublingual vein injection in rodents  

Microsoft Academic Search

SUMMARY A simple and rapid technique for intravenous IllJection into the sub- lingual veins of common laboratory rodents is described. No prior pre- paration other than light anaesthesia is required and repeated injections can be made into the same vein. 35 The major problem associated with intravenous administration in common laboratory rodents is the inaccessibility of the veins. In most

H. B. Waynforth; R. Parkin

1969-01-01

134

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

135

METEORIC-HYDROTHERMAL SYSTEMS.  

USGS Publications Warehouse

This paper summarizes the salient characteristics of meteoric-hydrothermal systems, emphasing the isotopic systematics. Discussions of permeable-medium fluid dynamics and the geology and geochemistry of modern geothermal systems are also provided, because they are essential to any understanding of hydrothermal circulation. The main focus of the paper is on regions of ancient meteoric-hydrothermal activity, which give us information about the presently inaccessible, deep-level parts of modern geothermal systems. It is shown oxygen and hydrogen isotopes provide a powerful method to discover and map fossil hydrothermal systems and to investigate diverse associated aspects of rock alteration and ore deposition.

Criss, Robert, E.; Taylor, Jr. , Hugh, P.

1986-01-01

136

Cierco Pb-Zn-Ag vein deposits: Isotopic and fluid inclusion evidence for formation during the mesozoic extension in the pyrenees of Spain  

USGS Publications Warehouse

The Cierco Pb-Zn-Ag vein deposits, located in the central Pyrenees of Spain, crosscut Paleozoic metasedimentary rocks and are in close proximity to Hercynian granodiorite dikes and plutons. Galena and sphalerite in the deposits have average ??34S values of -4.3 and -0.8 per mil (CDT), respectively. Coexisting mineral pairs give an isotopic equilibration temperature range of 89?? to 163??C which overlaps with the 112?? to 198??C range obtained from primary fluid inclusions. Coexisting quartz has a ??18O value of 19 ?? 1 per mil (VSMOW). The fluid which deposited these minerals is inferred to have had ??18OH2o and ??34SH2s values of 5 ?? 1 and -1 ?? 1 per mil, respectively. Chemical and microthermometric analyses of fluid inclusions in quartz and sphalerite indicate salinities of 3 to 29 wt percent NaCl equiv with Na+ and Ca2+ as the dominant cations in solution. The Br/Cl and I/Cl ratios differ from those characteristic of magmatic waters and pristine seawater, but show some similarity to those observed in deep ground waters in crystalline terranes, basinal brines, and evaporated seawater, Barite, which postdates the sulfides, spans isotopic ranges of 13 to 21 per mil, 10 to 15 per mil, and 0.7109 to 0.7123 for ??34S, ??18O, and 87Sr/86Sr, respectively. The three parameters are correlated providing strong evidence that the barites are products of fluid mixing. We propose that the Cierco deposits formed along an extensional fault system at the margin of a marine basin during the breakup of Pangea at some time between the Early Triassic and Early Cretaceous. Sulfide deposition corresponded to an upwelling of hydrothermal fluid from the Paleozoic basement and was limited by the amount of metals carried by the fluid. Barite deposition corresponded to the waning of upward flow and the collapse of sulfate-rich surface waters onto the retreating hydrothermal plume. Calcite precipitated late in the paragenesis as meteoric or marine waters descended into the fault system, possibly during a regression in the overlying basin. There are other deposits resembling Cierco elsewhere in the Iberian peninsula. Taken as a group, they are evidence that hydrothermal circulation systems were widespread during Mesozoic extension. Differences among the deposits can be related to the fact that H2S and other solutes had local and variable sources.

Johnson, C.A.; Cardellach, E.; Tritlla, J.; Hanan, B.B.

1996-01-01

137

Extrahepatic portal vein aneurysm.  

PubMed

Portal vein aneurysms (PVAs) are usually incidental on imaging and asymptomatic. If it is symptomatic or associated with a pathologic finding, a treatment is recommended. We report a case of a 75-year-old Caucasian man presenting with symptomatic and size-increasing portosplenomesenteric aneurysms. Interventional radiology was not indicated because of the large size. A surgical approach was chosen for the patient. Surgical technique consists of an aneurysmorrhaphy in the first time and in the second time, a Goretex prosthesis placement involving the vein. Early complication was treated with a radiologic approach. Six months after surgery, patient had no more symptoms. PVA management remains a surgical challenge for surgeon, for timing and type of treatment. PMID:24456867

Levi Sandri, Giovanni Battista; Sulpice, Laurent; Rayar, Michel; Bosquet, Elise; Boudjema, Karim; Meunier, Bernard

2014-07-01

138

Portal vein thrombosis  

Microsoft Academic Search

Opinion statement  Portal vein thrombosis (PVT) can be a difficult clinical problem to assess and manage. A high index of suspicion is needed\\u000a for a PVT diagnosis given the subtle presentation and potentially serious long-term complications. It should be considered\\u000a a clue to the presence of one or several underlying disorders, including prothrombotic disorders, whether or not a local precipitating\\u000a factor

Hector Rodriguez-Luna; Hugo E. Vargas

2007-01-01

139

Chemical, mineralogical, and mass-change examinations across a gold bearing vein zone in the Akoluk area, Ordu, NE Turkey  

NASA Astrophysics Data System (ADS)

Chemical changes associated with gold mineralization in the Akoluk field in the western part of the eastern Pontides are investigated. The eastern Black Sea region hosts several Kuroko-type, massive sulfide deposits and, therefore, has drawn the attention of numerous workers. Acidic intrusions play an important role and structurally controlled zones of alteration are widespread thus leading to a great potential for epithermal gold deposits in this region. Rocks in the study area are part a volcano-sedimentary sequence. Vein-type mineralization occurs along fault systems in dacitic tuffs of upper Cretaceous age. These rocks are cut by a N45-50oE trending fault system, which is partly truncated by another N55-60oW extending fault system. Mineralization is observed in areas where these fault systems intersect. Native gold, zinckenite, stibnite, orpiment, realgar, cinnabar, pyrite, marcasite, sphalerite, and galena are the main ore minerals. Gangue minerals are quartz, barite and dolomite. Mineralization occurs as a replacement type in the wall rock, and filling type in fracture zones where voids are filled mostly by realgar, orpiment, zincenite, stibnite, quartz, barite, and sericite. The presence of framboidal and colloidal ore minerals and textures indicate that mineralization occur at low temperatures in an epithermal system. Zonal alteration is observed along the fault systems. Outward from the fault alteration types change from silicification through illitization, smectization to carbonatization. As a result of alteration, wall rock has undergone a total mass loss of 2.19%. Almost all the major oxide contents decreased to certain levels. Due to alteration of feldspar and hornblende, the concentrations of Na, Ca and Fe significantly decreased while silica and ore-forming elements were added to the host rocks. Development of carbonate minerals at the fringe of the fracture zone in the host rock indicates relatively alkaline conditions for the hydrothermal fluids in the beginning. However, absence of these carbonate minerals, sericitization of plagioclases and increase in pyrite content towards the quartz-barite with time, became slightly acidic and were enriched in silica.

Yaylal?-Abanuz, Gülten; Tüysüz, Necati

2010-05-01

140

Origin of the quartz in Antrim Shale  

SciTech Connect

Study of the macroscopic and microscopic properties of the Antrim Shale indicated an important anomaly, the quartz. The Antrim Shale (Devonian, Michigan Basin) contains a large, but quantitatively undertermineable volume of authigenic quartz. The shale contains approximately 50% quartz by weight of which, in the >500 mesh size fraction, 56% is polycrystalline. This is approximately 2X the amount of quartz in most shales and 10X the amount of polycrystalline quartz in the silt-size fraction of sandstones and shales. Scanning electron microscopy reveals an authigenic surface composed of hexagonal tabular plates which coalesce to form smooth grain surfaces. These plates have not been previously reported on quartz grains. Oxygen isotopes of quartz and carbonate phases are interpreted to indicate a gradual isotopic lightening of the pore fluids, from approximately -4/sup 0///sub 00/. Most of the authigenic quartz has a delta/sup 18/O = 22/sup 0///sub 00/ (SMOW).

Hathon, C.; Sibley, D.; Cambray, F.W.

1980-02-15

141

Quartz Solubility and Thermodynamics Above the Upper Critical End Point  

NASA Astrophysics Data System (ADS)

Silica is among the most abundant solutes in crustal and mantle fluids, especially at conditions nearing the upper critical end point of the SiO2-H2O system (~10 kbar, 1080 °C). However, the solubility of silica is not well determined at higher pressures. In addition, the thermodynamic mixing relations of the supercritical SiO2-H2O system are poorly known. We made new measurements on quartz solubility in H2O at 15 and 20 kbar at 900-1100 °C. At SiO2 mole fraction below 0.1, solubility was determined by weight loss of single crystals equilibrated with H2O. At higher SiO2 concentrations, solubility was determined by bracketing the presence of absence of quartz in charges with known bulk SiO2 concentration. The measured solubilities imply that there is a solubility minimum above 1050 °C between 10 and 20 kbar. Quartz solubility measurements from Manning (1994), Newton and Manning (2003; 2008), Nakamura (1975) and this study were fitted to a modified sub-regular solution model. A term representing the Gibbs free energy (?Gr) of the reaction 1/2 H2O + 1/2 O2- = OH- (the depolymerization reaction that occurs when silica is dissolved in water) was added to the free energy of mixing parameterization. Thirteen independent parameters describe the T and P variation of the weak sub-regular interaction terms (Ws and Wh) and the strong interaction term (?Gr). Nine of the parameters are linear in T and P, and the other four are quadratic: Ws and ?Gr vary with P2, and ?Gr also varies with T2 and PT. The average error between the data and the model is 5%. Because the Gibbs free energy change of the depolymerization reaction is included in the fit, the model predicts an average state of aqueous silica polymerization of solutions in equilibrium with quartz at P between 10 and 20 kbar and T above 500 °C. The results also highlight what can be inferred from the steep hydrothermal melting curve of quartz - that while pressure does determine whether the system is subcritical or supercritical, it has a comparatively minor effect on the transition from an H2O-rich fluid to an SiO2-rich fluid. Whether due to melting or complete miscibility, the composition of a fluid in equilibrium with quartz increases dramatically between 900 and 1100 °C.

Hunt, J. D.; Manning, C. E.

2010-12-01

142

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

2010-01-01

143

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

144

Coupled fluid flow and reaction in mid-ocean ridge hydrothermal systems: The behavior of silica  

SciTech Connect

The authors apply a kinetic model of water-rock interaction to problems of silica mass transfer in mid-ocean ridge hydrothermal systems. A one-component steady state formulation is used to illustrate that the quartz geobarometer must be used with caution in mid-ocean ridge systems because the assumptions required by the technique may not be met. The results of this model suggest that there can be measurable mass transfer between wall rock and fluid in the upwelling zone of even vigorously flowing mid-ocean ridge hydrothermal systems. In addition, they attempt to quantify the effect of conductive cooling in the upwelling zone on the accuracy of the quartz geobarometer. The porosity and permeability fields constitute a critical link between the fluid dynamic equations and the equations describing chemical reactions in water-rock systems. They utilize a quasi-steady state approximation to evaluate the changes in porosity over time due to dissolution and precipitation of quartz along the flow path of a mid-ocean ridge hydrothermal system. There is little doubt that many mid-ocean ridge fluids encounter pressure and temperature conditions in which the solubility of quartz reaches a maximum. Their calculations suggest that precipitation of quartz from fluids passing through the solubility maximum within the oceanic crust may decrease the local porosity on a time scale of decades.

Wells, J.T.; Ghiorso, M.S. (Univ. of Washington, Seattle (United States))

1991-09-01

145

Evolution of the magmatic-hydrothermal acid-sulfate system at Summitville, Colorado: Integration of geological, stable-isotope, and fluid-inclusion evidence  

USGS Publications Warehouse

The Summitville Au-Ag-Cu deposit is a classic volcanic dome-hosted high-sulfidation deposit. It occurs in the Quartz Latite of South Mountain, a composite volcanic dome that was emplaced along the coincident margins of the Platoro and Summitville calderas at 22.5??0.5 Ma, penecontemporaneous with alteration and mineralization. A penecontemporaneous quartz monzonite porphyry intrusion underlies the district and is cut and overlain by pyrite-quartz stockwork veins with traces of chalcopyrite and molybdenite. Alteration and mineralization proceeded through three hypogene stages and a supergene stage, punctuated by at least three periods of hydrothermal brecciation. Intense acid leaching along fractures in the quartz latite produced irregular pipes and lenticular pods of vuggy silica enclosed sequentially by alteration zones of quartz-alunite, quartz-kaolinite, and clay. The acid-sulfate-altered rocks host subsequent covellite+enargite/luzonite+chalcopyrite mineralization accompanied by kaolinite, and later barite-base-metal veins, some containing high Au values and kaolinite. The presence of both liquid- and vapor-rich fluid inclusions indicates the episodic presence of a low-density fluid at all levels of the system. In the mineralized zone, liquid-rich fluid inclusions in healed fractures in quartz phenocrysts and in quartz associated with mineralization homogenize to temperatures between 160 and 390 ??C (90% between 190 and 310 ??C), consistent with the range (200-250 ??C) estimated from the fractionation of sulfur isotopes between coexisting alunite and pyrite. A deep alunite-pyrite pair yielded a sulfur-isotope temperature of 390 ??C, marking a transition from hydrostatic to lithostatic pressure at a depth of about 1.5 km. Two salinity populations dominate the liquid-rich fluid inclusions. One has salinities between 0 and 5 wt.% NaCl equivalent; the other has salinities of up to 43 wt.% NaCl equivalent. The occurrence of high-salinity fluid inclusions in vein quartz associated with mineralization, as well as in the deep stockwork veins, suggests that brines originating deep in the system transported the metals. The ??34S values of sulfides in magnetite (-2.3???) and of sulfate in apatite (5.4???) in unaltered quartz latite indicate that ??34S???S was near 0???. The ??34S values of coexisting alteration alunite and pyrite are 18.2??? to 24.5??? and -8.1??? to -2.2???, respectively. Deep in the system, most of the change in ??34S values occurs in the sulfates, indicating that the fluids were initially H2S-dominant, their redox state buffered at depth by equilibration with igneous rocks. However, in the main alteration zone, most of the change in ??34S values occurs in pyrite, indicating that the fluids moved off the rock buffer and became SO42- -dominant as pyrite precipitated and SO2 disproportionation produced the sulfuric acid requisite for acid leaching. The ??34S values of the late-stage barite and sulfides indicate that the system returned to high H2S/SO42- ratios typical of the original rock-buffered fluid. The ??DH2O of alunite parent fluids was near -45??? and their ??18O ranged from 7??? to -1???, depending on the degree of exchange in the alteration zone at low water-rock ratio, or mixing with unexchanged meteoric water. The low ??D values of some alunite samples are interpreted to result from postdepositional exchange with later ore fluids. Fluid exsolved fr om the magma at depth had ??DH2O and ??18OH2O values near -70??? and 10???, respectively. During and following migration to the top of the magma chamber, the fluid underwent isotopic exchange with the partially crystallized magma and its solid and cooler, but still plastic, carapace just below the transition from a lithostatic to hydrostatic pressure regime. These evolved magmatic fluids had ??DH2O and ??18OH2O values close to -40??? and 5???, respectively, prior to release into the superjacent hydrostatically pressured fracture zone, wherein the fluids separat

Bethke, P.M.; Rye, R.O.; Stoffregen, R.E.; Vikre, P.G.

2005-01-01

146

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

147

JAMA Patient Page: Treatment of Varicose Veins  

MedlinePLUS

... removal of varicose veins just below the skin’s surface. • Sclerotherapy —a solution is injected into the vein causing it to scar down and visibly fade. This therapy is recommended for telangiectasias, reticular veins, or small ...

148

Quartz resources in the Serra de Santa Helena formation, Brazil: A geochemical and technological study  

NASA Astrophysics Data System (ADS)

This study presents an evaluation of Brazilian quartz deposits of Corinto and Olhos D'água, in Minas Gerais State, as potential high purity raw material for the production of silica glass. Both deposits are part of the Serra de Santa Helena formation, which holds other quartz deposits. Several quartz samples from these mines were analyzed to evaluate their chemical purity, by determination of the content of trace elements by ICP-MS after acid digestion. The technological characteristics of the ores after flame-fusion into silica glass were evaluated according to their bubble generation and UV transparency. The results indicate that silica glass with chemistry suitable for crucible applications can be obtained from materials of both mines, and even optical grade silica glass can be manufactured using transparent ore from one of the mines. In addition, this work explores the trace elements composition of each mine, as well as their fluid inclusions, and characterizes the mines as being of hydrothermal origin. Small differences in the physical and chemical characteristics of quartz that could affect the technological behavior of the ores are related to the geological history of the mines and provide interesting insights regarding the exploration of other quartz resources within the same geological formation.

Santos, Murilo Ferreira Marques dos; Fujiwara, Eric; Schenkel, Egont Alexandre; Enzweiler, Jacinta; Suzuki, Carlos Kenichi

2014-12-01

149

Geodiversity of hydrothermal processes along the Mid-Atlantic Ridge and ultramafic-hosted mineralization: A new type of oceanic Cu-Zn-Co-Au volcanogenic massive sulfide deposit  

NASA Astrophysics Data System (ADS)

Several hydrothermal deposits associated with ultramafic rocks have recently been found along slow spreading ridges with a low magmatic budget. Three preferential settings are identified: (1) rift valley walls near the amagmatic ends of ridge segments; (2) nontransform offsets; and (3) ultramafic domes at inside corners of ridge transform-fault intersections. The exposed mantle at these sites is often interpreted to be a detachment fault. Hydrothermal cells in ultramafic rocks may be driven by regional heat flow, cooling gabbroic intrusions, and exothermic heat produced during serpentinization. Along the Mid-Atlantic Ridge (MAR), hydrothermal deposits in ultramafic rocks include the following: (1) sulfide mounds related to high-temperature low-pH fluids (Logatchev, Rainbow, and Ashadze); (2) carbonate chimneys related to low-temperature, high-pH fluids (Lost City); (3) low-temperature diffuse venting and high-methane discharge associated with silica, minor sulfides, manganese oxides, and pervasive alteration (Saldanha); and (4) stockwork quartz veins with sulfides at the base of detachment faults (15°05'N). These settings are closely linked to preferential circulation of fluid along permeable detachment faults. Compared to mineralization in basaltic environments, sulfide deposits associated with ultramafic rocks are enriched in Cu, Zn, Co, Au, and Ni. Gold has a bimodal distribution in low-temperature Zn-rich and in high-temperature Cu-rich mineral assemblages. The Cu-Zn-Co-Au deposits along the MAR seem to be more abundant than in ophiolites on land. This may be because ultramafic-hosted volcanogenic massive sulfide deposits on slow spreading ridges are usually not accreted to continental margins during obduction and may constitute a specific marine type of mineralization.

Fouquet, Yves; Cambon, Pierre; Etoubleau, Joël; Charlou, Jean Luc; Ondréas, Hélène; Barriga, Fernando J. A. S.; Cherkashov, Georgy; Semkova, Tatiana; Poroshina, Irina; Bohn, M.; Donval, Jean Pierre; Henry, Katell; Murphy, Pamela; Rouxel, Olivier

150

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

151

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

152

Hydrothermal Alteration in Submarine Basaltic Rocks from the Reykjanes Geothermal Field, Iceland. (Invited)  

NASA Astrophysics Data System (ADS)

The Iceland Deep Drilling Project (IDDP) is preparing to drill to 4-5 km in the Reykjanes Geothermal Field to sample geothermal fluids at supercritical temperature and pressure for power generation. The Reykjanes geothermal field is the on-land extension of the Reykjanes Ridge spreading center. The upper 1-2 kilometers drilled at Reykjanes are submarine basalts and basaltic sediments, hyalloclastites, and breccias, with an increasing proportion of basaltic intrusive rocks below 2 km depth. Geothermal fluids are evolved seawater with a composition similar to mid-ocean ridge hydrothermal systems. Zn- and Cu-rich sulfide scale, locally enriched in Au and Ag, are deposited in production pipes. The sulfide deposits are compositionally and isotopically similar to seafloor massive sulfides. In anticipation of deeper drilling, we have investigated the mineralogy and geochemistry of drill cuttings from a 3 km deep well (RN-17). The depth zoning of alteration minerals is similar to that described from other Icelandic geothermal fields, and is comparable to observed seafloor metamorphic gradients in ODP drill holes and ophiolites. Chlorite-epidote alteration occurs at depths >400 m and passes downhole through epidote-actinolite alteration and into amphibole facies (hornblende-calcic plagioclase) alteration below 2.5 km. Local zones of high temperature (>800°C), granoblastic-textured, pyroxene hornfels, are interpreted to form by contact metamorphism during dike/sill emplacement. Similar granoblasically altered basalts were recovered from the base of the sheeted dikes in IODP Hole 1256D. Downhole compositional variations of drill cuttings, collected every 50 m, suggest that rocks below ~ 2 km are little altered. Whole-rock oxygen isotope profiles are consistent with low water/rock ratios, but suggest that early stages of hydrothermal alteration included meteoric water-derived fluids. Strontium isotope profiles indicate more extensive exchange with seawater-derived fluids. Drill core collected (100% recovery) at an in situ temperature of 320°C from an inclined off-set hole drilled from RN-17 provides a sharp contrast to the drill cuttings. Original rock textures, including fine-scale banding and quenched crystals in hyalloclastite, are very well preserved, but the core is pervasively altered to amphibole-calcic plagioclase. Fluid inclusions in epidote veins record episodes of seawater boiling, and zonation of strontium isotopes across the veins indicates changing seawater-rock ratios, both of which may relate to dike emplacement. The compositional variation observed in 9 m of drill core far exceeds the compositional variation the lowermost km of drill cuttings. Different areas of the core show addition and depletion of silica, alkalies, and magnesium. The cuttings are highly biased due to selective recovery of relatively fresh igneous plagioclase and pyroxene crystals from intrusive bodies, and resistant alteration minerals such as vein quartz and epidote are more abundant in the cuttings relative to the core. Selective recovery of less altered rock during ocean drilling operations is a known problem, but the recovered core may be less representative of the degree of alteration than is generally appreciated.

Zierenberg, R. A.; Schiffman, P.; Fowler, A. P.; Marks, N.; Fridleifsson, G.; Elders, W. A.

2013-12-01

153

NMR characterization of shocked quartz  

SciTech Connect

We have characterized experimentally and naturally-shocked quartz (both synthetic and natural samples) by solid state nuclear magnetic resonance (NMR) spectroscopy. Relaxation analysis of experimentally-shocked samples provides a means for quantitative characterization of the amorphous/disordered silica component NMR spectra demonstrate that magnetization in both the amorphous and crystalline components follows power-law behavior as a function of recycle time. This observation is consistent with the relaxation of nuclear spins by paramagnetic impurities. A fractal dimension can be extracted from the power-law exponent associated with each phase, and relative abundances can be extracted from integrated intensities of deconvolved peaks. NMR spectroscopy of naturally-shocked sandstone from Meteor Crater, Arizona (USA) led to the discovery of a new amorphous hydroxylated silica phase. Solid state NMR spectra of both experimentally and naturally shocked quartz were unexpectedly rich in microstructural information, especially when combined with relaxation analysis and cross-polarization studies. We suggest solid state NMR as a potentially useful tool for examining shock-induced microstructural changes in other inorganic compounds, with possible implications for shock processing of structural ceramics.

Boslough, M.B.; Cygan, R.T.; Assink, R.A. [Sandia National Labs., Albuquerque, NM (United States); Kirkpatrick, R.J. [Illinois Univ., Urbana, IL (United States)

1994-03-01

154

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

155

Hydrothermal activity Hydrothermal circulation at mid-ocean ridges  

E-print Network

#12;Hydrothermal activity #12;Hydrothermal circulation at mid-ocean ridges After sea water seeps metal-sulphide chimneys. #12;Hydrothermal circulation at mid-ocean ridges Black-smoker Schornsteine am;Distance (km) 10 105 50 2 4 6 8 Depth(km) Moho Transition zone Mush Gabbro Rift Valley · Slow ridges

Siebel, Wolfgang

156

Vein matching using artificial neural network in vein authentication systems  

NASA Astrophysics Data System (ADS)

Personal identification technology as security systems is developing rapidly. Traditional authentication modes like key; password; card are not safe enough because they could be stolen or easily forgotten. Biometric as developed technology has been applied to a wide range of systems. According to different researchers, vein biometric is a good candidate among other biometric traits such as fingerprint, hand geometry, voice, DNA and etc for authentication systems. Vein authentication systems can be designed by different methodologies. All the methodologies consist of matching stage which is too important for final verification of the system. Neural Network is an effective methodology for matching and recognizing individuals in authentication systems. Therefore, this paper explains and implements the Neural Network methodology for finger vein authentication system. Neural Network is trained in Matlab to match the vein features of authentication system. The Network simulation shows the quality of matching as 95% which is a good performance for authentication system matching.

Noori Hoshyar, Azadeh; Sulaiman, Riza

2011-10-01

157

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

158

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

159

REE in fluid inclusions of quartz from gold deposits of north-eastern Russia  

NASA Astrophysics Data System (ADS)

Inductively coupled plasma-mass spectrometry (ICP-MS) has been used to determine rare earth element concentrations in aqueous solutions extracted from fluid inclusions. Quartz has been sampled from ores of three major types of polygenic gold hydrothermal systems of North-Eastern Russia: (1) gold-quartz-sulphide (Au-Q, Nezhdaninsk); (2) gold-antimony (Au-Sb, Sarylakh) and (3) intrusion-related gold-bismuth-siderite-polysulphide (Au-Bi-Sid, Arkachan) large deposits located in terrigenous rocks of the Verkhoyansk fold belt. The total concentration of REE in the fluid inclusions is not high (up to 52 ppm). The contribution of LREE dominates in REE balance (?LREE/?HREE=7.4-112.1). The chondrite-normalized REE patterns of inclusion fluids for the Au-Q and Au-Bi-Sid deposits are characterized by LREE enrichment with a positive or negative Eu anomaly. REE patterns for the regenerated quartz from Au-Sb deposits are characterized by pronounced differentiation between light and heavy lanthanides in fluid inclusions. Significant total REE concentration decreasing (on 1-2 order) from early to late stages of Nezhdaninsk and Arkachan deposits is revealed. The positive correlations of total REE concentrations with Rb, Cs, Li and B contents in fluid inclusions are shown. The REE distribution in fluid inclusions can be used as indicators of the contribution of magmatic fluid in the hydrothermal system.

Vikent'eva, Olga V.; Gamyanin, Gennady N.; Bortnikov, Nikolay S.

2012-06-01

160

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

161

Varicose Veins and Venous Insufficiency  

MedlinePLUS

... flowing toward the heart—against the force of gravity. When the valves do not perform their function, ... the vein, an interventional radiologist inserts a thin tube known as a catheter, about the size of ...

162

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. PMID:23653882

Deobhakta, Avnish; Chang, Louis K.

2013-01-01

163

Benefits of Endoscopic Vein Harvesting  

Microsoft Academic Search

.   The purpose of this study was to evaluate and compare the benefits of endoscopic saphenous vein harvesting (EVH) with the\\u000a traditional incision technique (TIT) for coronary artery bypass grafting (CABG) in respect to the technical procedure and\\u000a clinical outcome. In a prospective nonrandomized, case-matched study the greater saphenous vein was harvested for CABG in\\u000a 22 patients using the endoscopic

Bettina Marty; Ludwig Karl von Segesser; Piergiorgio Tozzi; Juan Guzmann; Philippe Frascarolo; Xavier Muller; Daniel Hayoz

2000-01-01

164

Mixing from below in hydrothermal ore deposits  

NASA Astrophysics Data System (ADS)

Unconformity-related hydrothermal ore deposits typically show indications of mixing of two end-member fluids: (a) hot, deep, rock-buffered basement brines and (b) colder fluids derived from the surface or overlying sediments. The hydromechanics of bringing these fluids together from above and below remain unclear. Classical percolative Darcy-flow models are inconsistent with (1) fluid overpressure indicated by fracturing and brecciation, (2) fast fluid flow indicated by thermal disequilibrium, and (3) strong fluid composition variations on the mm-scale, indicated by fluid inclusion analyses (Bons et al. 2012; Fusswinkel et al. 2013). We propose that fluids first descend, sucked down by desiccation reactions in exhumed basement. Oldest fluids reach greatest depths, where long residence times and elevated temperatures allow them the extensively equilibrate with their host rock, reach high salinity and scavenge metals, if present. Youngest fluids can only penetrate to shallower depths and can (partially) retain signatures from their origin, for example high Cl/Br ratios from the dissolution of evaporitic halite horizons. When fluids are released from all levels of the crustal column, these fluids mix during rapid ascent to form hydrothermal ore deposits. Mixing from below provides a viable hydromechanical mechanism to explain the common phenomenon of mixed shallow and deep fluids in hydrothermal ore deposits. Bons, P.D., Elburg, M.A., Gomez-Rivas, E. 2012. A review of the formation of tectonic veins and their microstructures. J. Struct. Geol. doi:10.1016/j.jsg.2012.07.005 Fusswinkel, T., Wagner, T., Wälle, M., Wenzel, T., Heinrich, C.A., Markl, M. 2013. Fluid mixing forms basement-hosted Pb-Zn deposits: Insight from metal and halogen geochemistry of individual fluid inclusions. Geology. doi:10.1130/G34092.1

Bons, Paul D.; Gomez-Rivas, Enrique; Markl, Gregor; Walter, Bejamin

2014-05-01

165

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

166

A cervelleite-like mineral and other Ag-Cu-Te-S minerals [Ag2CuTeS and (Ag,Cu)2TeS] in gold-bearing veins in metamorphic rocks of the Cycladic Blueschist Unit, Kallianou, Evia Island, Greece  

Microsoft Academic Search

A cervelleite-like mineral, two unnamed silver sulfotellurides in the system Ag-Cu-Te-S [Ag2CuTeS, (Ag,Cu)2TeS], Te-rich polybasite and cadmian tetrahedrite occur in gold-bearing quartz veins in metapelites and faults within brecciated marbles of the Cycladic Blueschist Unit in the Kallianou area (southern Evia Island, Greece). The quartz veins and faults are discordant to syn-metamorphic structures and formed during ductile to brittle deformation

Panagiotis Christos Voudouris; Paul G. Spry; Gregory Aarne Sakellaris; Constantinos Mavrogonatos

2011-01-01

167

GEOCHEMISTRY OF HYDROTHERMAL DEPOSITS  

E-print Network

T. Mackenzie MichaelJ.Mottl #12;iv ABSTRACT Mineralogical composition,major, minor and rare earth elementchemistry,and uranium-seriesradionuclideswere determinedfor hydrothermaliron-rich depositsfrom five hydrothermal vent fields on the summit of Loihi Seamount,Hawai'i. The mineralogy and the major

Luther, Douglas S.

168

Precipitation mechanism of Al-substituted tobermorite using hydrothermal reaction  

NASA Astrophysics Data System (ADS)

We examined the addition of different crystal phases of alumina (?-Al2O3, ?-Al2O3) to slurries consisting of quartz and slaked lime for synthesis of Al-substituted tobermorite. XRD results showed that Al-substituted tobermorite formed after the reaction. It was clear that two kinds of Al-substituted tobermorite synthesized using different alumina crystal phases shows different morphologies. The difference in the reactivity of the Al2O3 had an influence in the hydrothermal reaction environment. The coordination number and chemical bonding-state of Al caused the different morphology of the tobermorite.

Abe, Kazuki; Maeda, Hirotaka; Ishida, Emile H.

2010-11-01

169

Hydrothermal alteration maps of the central and southern Basin and Range province of the United States compiled from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data  

USGS Publications Warehouse

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and Interactive Data Language (IDL) logical operator algorithms were used to map hydrothermally altered rocks in the central and southern parts of the Basin and Range province of the United States. The hydrothermally altered rocks mapped in this study include (1) hydrothermal silica-rich rocks (hydrous quartz, chalcedony, opal, and amorphous silica), (2) propylitic rocks (calcite-dolomite and epidote-chlorite mapped as separate mineral groups), (3) argillic rocks (alunite-pyrophyllite-kaolinite), and (4) phyllic rocks (sericite-muscovite). A series of hydrothermal alteration maps, which identify the potential locations of hydrothermal silica-rich, propylitic, argillic, and phyllic rocks on Landsat Thematic Mapper (TM) band 7 orthorectified images, and geographic information systems shape files of hydrothermal alteration units are provided in this study.

Mars, John C.

2013-01-01

170

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

171

44. HYDROTHERMAL ALTERATION OF BASALTS AND SEDIMENTS AT DEEP SEA DRILLING PROJECT SITE 456, MARIANA TROUGH1  

Microsoft Academic Search

Basalts in two holes spaced 200 meters apart at DSDP Site 456 in the Mariana Trough both show a downward se- quence of nonoxidative and oxidative zones of alteration, each 10 to 15 meters thick, overlying fresh basalts. Basalts in the nonoxidative zone have been extensively chloritized and have vein and vesicle fillings of quartz, opal, chlorite, calcite, and pyrite.

James H. Natland; Roger Hekinian

172

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

PubMed Central

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

2011-01-01

173

Hydrothermal alteration of late-to post-tectonic Lyon Mountain Granitic Gneiss, Adirondack Mountains, New York: Origin of  

E-print Network

Hydrothermal alteration of late- to post-tectonic Lyon Mountain Granitic Gneiss, Adirondack) leucogranites of Lyon Mountain Gneiss (LMG) in the Adirondack Mountains, New York State. Most recent± sillimanite veins and nodules in the Adirondack Mountains (Figs 1 & 2) resulted from alkali leaching by acidic

Soja, Constance M.

174

Fluid circulations and quartz ductile deformation in the depths of accretionary prisms: An integrated cathodoluminescence and infrared study  

NASA Astrophysics Data System (ADS)

To study the processes of deformation in the depths of accretionary prism, we have carried out a study in the Shimanto Belt, in Japan, considered as a fossil accretionary prism. There, the deep metamorphic terranes of the Hyuga and Morotsuka Group were pervasively deformed for conditions of ~300 ° C and 3-5 Kbars. Quartz precipitated at depth was intensely deformed by ductile shearing, enabling to unravel the micro processes of deformation in presence of abundant fluid. Cathodoluminescence (CL) analysis revealed the presence of two distinct kinds of quartz, which we interpret as associated with two distinct fluids. One kind of quartz, blue in CL, precipitates in macro veins. The other kind of quartz, brown in CL, is found in micro veins as well as plastically deformed quartz domains. The distribution and speciation of water studied with FT-IR analysis is correlated to structures. Inherited grains, free from plastic deformation, contain a larger amount of water than strongly elongated grains. In addition, small and equant recrystallized grains contain an even smaller amount of water than elongated grains. In parallel, recrystallized grains are free from optically visible fluid inclusions, which are in contrast densely distributed in inherited and elongated grains. We also observed water speciation with the presence of characteristic picks at 3380 cm and 3480 cm-1attributed to OH associated relatively with Al+3 and Li+1. All samples always show the broad band centered at 3400 cm-1 related to 'liquid-like' molecular water (H2O) in quartz but only the quartz blue in CL, present in veins, registered the signal in secondary picks. FT-IR and cathodoluminescence signals, in good agreement with each other, constitute consistent signatures of the two distinct kinds of fluids circulating at depth. Further study is required to determine the origin of these fluids. In addition, recrystallization plays a large role in redistributing water and impurities during plastic deformation. The effect on quartz rheology is unclear, as recrystallized grains are drier, hence potentially stronger, than inherited grains.

Palazzin, Giulia; Raimbourg, Hugues; Famin, Vincent

2014-05-01

175

Vein deposits hosted by plutonic rocks in the Croesus Stock and Hailey gold belt mineralized areas, Blaine County, Idaho  

USGS Publications Warehouse

Mineral deposits in the Croesus and Hailey gold belt mineralized areas in Blaine County, south-central Idaho, are preciousand base-metal quartz veins that are part of a family of vein deposits spatially and temporally associated with the Idaho batholith. Historic production from these veins has been mainly gold and silver. Host rocks are older border phase plutons of the Idaho batholith that are characterized by more potassium and less sodium as compared to rocks from the main body of the batholith to the west. Host structures are reverse faults that have moderate to shallow dips to the northeast and high-angle normal faults that also strike northwest. The veins are characterized by several generations of quartz and generally sparse sulfide minerals; gold is associated with late-stage comb quartz. The precious-metal ore bodies are in a series of shoots, each of which is as much as 8 ft in width, 400 ft in breadth, and 1,000 ft in pitch length.

Worl, Ronald G.; Lewis, Reed S.

2001-01-01

176

Hydrothermal alterations in the Echassières granitic cupola (Massif central, france)  

NASA Astrophysics Data System (ADS)

Detailed petrographic and mineralogic investigations of an albite-lepidolite granite at Echassières (Massif Central, France; scientific deep drill program) shows the existence of hydrothermal stages which are closely related to the magmatic and structural history. According to fluid inclusion data, K-Ar datations and 18O/16O-D/H compositions of secondary minerals, two successive hydrothermal periods have been recognized. The early one (273 268 million years) produced a series of aluminous phyllosilicates: muscovite, pyrophyllite, donbassite, tosudite, kaolinite which are observed as vein deposits (<10 mm wide) and alteration products of primary minerals in wall-rocks. The vein system was sealed by monomineralic assemblages during a cooling period (400 150°C). This early hydrothermal alteration stage was controlled by interactions of rock with low salinity (1 10 wt% NaCl equivalent) fluids expelled from the granitic body during the cooling processes. The chemical properties of these fluids were the following: low pH, very low Mg and Fe and high Li, Na and K contents. Thermodynamic calculations show that the sequence pyrophyllite, Li-bearing donbassite, tosudite is mostly temperature dependent. From the chemical composition of secondary minerals and isotopic data it can be deduced that these fluids, which have a meteoric origin, have been expelled from the granite body during its cooling period and after interaction with it at high temperature. The late hydrothermal stage corresponds to deposits of fluorite and Fe-Mg rich illite (151 million years) in subvertical fractures. Temperature conditions did not exceed 250° C and fluids came through the surrounding metamorphic rocks into the granitic body. IIlite/smectite mixed-layer minerals have been identified in subvertical fractures which were opened during Tertiary periods. In the host micaschists, successive hydrothermal alterations took place during the cooling of the Beauvoir granite. Early magmatic fluids interacted with these micaschists. Locally, the metamorphic assemblage is replaced by a metasomatic one. Secondary topaz and (F, Li)-rich mica crystals were formed over a range of 450 of 150°C. Later hydrothermal fluids reacted with the country rocks to form phengite-biotite, chlorite-illite and kaolinite over a range of 300 to 150°C. Illite/smectite mixed-layer minerals crystallized in the roof micaschists and within the Beauvoir granite during the Tertiary alteration period. Meteoric water invaded open fractures producing supergene alteration mineral assemblages.

Merceron, Thierry; Vieillard, Philippe; Fouillac, Anne-Marie; Meunier, Alain

1992-11-01

177

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

178

Quartz-enhanced photoacoustic spectroscopy: a review.  

PubMed

A detailed review on the development of quartz-enhanced photoacoustic sensors (QEPAS) for the sensitive and selective quantification of molecular trace gas species with resolved spectroscopic features is reported. The basis of the QEPAS technique, the technology available to support this field in terms of key components, such as light sources and quartz-tuning forks and the recent developments in detection methods and performance limitations will be discussed. Furthermore, different experimental QEPAS methods such as: on-beam and off-beam QEPAS, quartz-enhanced evanescent wave photoacoustic detection, modulation-cancellation approach and mid-IR single mode fiber-coupled sensor systems will be reviewed and analysed. A QEPAS sensor operating in the THz range, employing a custom-made quartz-tuning fork and a THz quantum cascade laser will be also described. Finally, we evaluated data reported during the past decade and draw relevant and useful conclusions from this analysis. PMID:24686729

Patimisco, Pietro; Scamarcio, Gaetano; Tittel, Frank K; Spagnolo, Vincenzo

2014-01-01

179

Impurity Content Characterization of Brazilian Quartz Lascas  

NASA Astrophysics Data System (ADS)

Lattice impurities (Al, Li, Fe) free from the influence of cations in inclusion liquid were evaluated by atomic absorption spectrophotometry (AAS) in quartz lascas taken from 10 deposits with known localities in three states, Minas Gerais, Tocantins and Bahia. Levels of Al content and associated Li content depend on the localities of deposits. Quartz deposit regions with high Al content are composed of granite, gneiss, and pegmatite as surrounding rocks. It was concluded that the charge compensation for Al-Si substitution in quartz lascas was realized substantially by the formation of Al-Li and Al-OH centers which were confirmed from the linear relation of Al-Li plots by AAS data and IR spectra due to Al-OH center. The variety in Al-Li and Al-OH correlations was attributed to the fluctuation of growing conditions of quartz in nature.

Iwasaki, Hideo; Iwasaki, Fumiko; Oliveira, Virginia A. R.; Hummel, Daniele C. A.; Pasquali, Maria A.; Guzzo, Pedro L.; Watanabe, Noêmia; Suzuki, Carlos K.

1991-07-01

180

Quartz-Enhanced Photoacoustic Spectroscopy: A Review  

PubMed Central

A detailed review on the development of quartz-enhanced photoacoustic sensors (QEPAS) for the sensitive and selective quantification of molecular trace gas species with resolved spectroscopic features is reported. The basis of the QEPAS technique, the technology available to support this field in terms of key components, such as light sources and quartz-tuning forks and the recent developments in detection methods and performance limitations will be discussed. Furthermore, different experimental QEPAS methods such as: on-beam and off-beam QEPAS, quartz-enhanced evanescent wave photoacoustic detection, modulation-cancellation approach and mid-IR single mode fiber-coupled sensor systems will be reviewed and analysed. A QEPAS sensor operating in the THz range, employing a custom-made quartz-tuning fork and a THz quantum cascade laser will be also described. Finally, we evaluated data reported during the past decade and draw relevant and useful conclusions from this analysis. PMID:24686729

Patimisco, Pietro; Scamarcio, Gaetano; Tittel, Frank K.; Spagnolo, Vincenzo

2014-01-01

181

High capacity cation exchanger by hydrothermal zeolitization of coal fly ash  

Microsoft Academic Search

During; hydrothermal treatment in NaOH medium coal fly ash partially transformed to zeolite P and\\/or hydroxysodalite, while quartz slowly dissolved and mullite remained stable. Residual coal favored the formation of zeolite P. The relative proportion of the two zeolites could be changed by seeding. During fusion of fly ash with NaOH an endothermic reaction at 170–180°C occurred, resulting in formation

V. Berkgaut; A. Singer

1996-01-01

182

Coupled fluid flow and reaction in mid-ocean ridge hydrothermal systems: The behavior of silica  

Microsoft Academic Search

The authors apply a kinetic model of water-rock interaction to problems of silica mass transfer in mid-ocean ridge hydrothermal systems. A one-component steady state formulation is used to illustrate that the quartz geobarometer must be used with caution in mid-ocean ridge systems because the assumptions required by the technique may not be met. The results of this model suggest that

J. T. Wells; M. S. Ghiorso

1991-01-01

183

Mineralogical, geochemical and isotopic characteristics of hydrothermal alteration processes in the active, submarine, felsic-hosted PACMANUS field, Manus Basin, Papua New Guinea  

NASA Astrophysics Data System (ADS)

During ODP Leg 193, 4 sites were drilled in the active PACMANUS hydrothermal field on the crest of the felsic Pual Ridge to examine the vertical and lateral variations in mineralization and alteration patterns. We present new data on clay mineral assemblages, clay and whole rock chemistry and clay mineral strontium and oxygen isotopic compositions of altered rocks from a site of diffuse low-temperature venting (Snowcap, Site 1188) and a site of high-temperature venting (Roman Ruins, Site 1189) in order to investigate the water-rock reactions and associated elemental exchanges. The volcanic succession at Snowcap has been hydrothermally altered, producing five alteration zones: (1) chlorite ± illite-cristobalite-plagioclase alteration apparently overprinted locally by pyrophyllite bleaching at temperatures of 260-310°C; (2) chlorite ± mixed-layer clay alteration at temperatures of 230°C; (3) chlorite and illite alteration; (4) illite and chlorite ± illite mixed-layer alteration at temperatures of 250-260°C; and (5) illite ± chlorite alteration at 290-300°C. Felsic rocks recovered from two holes (1189A and 1189B) at Roman Ruins, although very close together, show differing alteration features. Hole 1189A is characterized by a uniform chlorite-illite alteration formed at ˜250°C, overprinted by quartz veining at 350°C. In contrast, four alteration zones occur in Hole 1189B: (1) illite ± chlorite alteration formed at ˜300°C; (2) chlorite ± illite alteration at 235°C; (3) chlorite ± illite and mixed layer clay alteration; and (4) chlorite ± illite alteration at 220°C. Mass balance calculations indicate that the chloritization, illitization and bleaching (silica-pyrophyllite assemblages) alteration stages are accompanied by different chemical changes relative to a calculated pristine precursor lava. The element Cr appears to have a general enrichment in the altered samples from PACMANUS. The clay concentrate data show that Cr and Cu are predominantly present in the pyrophyllites. Illite shows a significant enrichment for Cs and Cu relative to the bulk altered samples. Considerations of mineral stability allow us to place some constraints on fluid chemistry. Hydrothermal fluid pH for the chloritization and illitization was neutral to slightly acidic and relatively acidic for the pyrophyllite alteration. In general the fluids, especially from Roman Ruins and at intermediate depths below Snowcap, show only a small proportion of seawater mixing (<10%). Fluids in shallow and deep parts of the Snowcap holes, in contrast, show stronger seawater influence.

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

2004-11-01

184

Genesis of the Abu Marawat gold deposit, central Eastern Desert of Egypt  

Microsoft Academic Search

Gold mineralisation at the Abu Marawat mine, central Eastern Desert of Egypt, is related to a system of massive and sheared, milky quartz veins cutting a sequence of Neoproterozoic island arc metavolcanic\\/volcaniclastic rocks and related banded iron formation (BIF). Sulphide-bearing quartz veins and related hydrothermal breccia bodies display a range of textures including sheared, boudinaged and recrystallised quartz, open space

Basem A. Zoheir; Ahmed Akawy

2010-01-01

185

Surgical Access to Jejunal Veins for Local Thrombolysis and Stent Placement in Portal Vein Thrombosis  

SciTech Connect

Portal vein thrombosis is an infrequent entity, which may cause high morbidity and mortality. We report a case of portal vein thrombosis due to benign stenosis following partial pancreatoduodenectomy with segmental replacement of the portal vein by a Gore-tex graft. Using a surgical access to jenunal veins, local thrombolysis, mechanical fragmentation of thrombus, and stent placement were successfully performed.

Schellhammer, Frank, E-mail: frank.schellhammer@med.uni-duesseldorf.d [University Hospital Duesseldorf, Institute of Diagnostic Radiology (Germany); Esch, Jan Schulte am [University Hospital Duesseldorf, Department of General, Visceral and Pediatric Surgery (Germany); Hammerschlag, Sascha [University Hospital Duesseldorf, Institute of Diagnostic Radiology (Germany); Knoefel, Wolfram Trudo [University Hospital Duesseldorf, Department of General, Visceral and Pediatric Surgery (Germany); Fuerst, Guenter [University Hospital Duesseldorf, Institute of Diagnostic Radiology (Germany)

2008-07-15

186

In situ time-resolved X-ray diffraction of tobermorite synthesis process under hydrothermal condition  

NASA Astrophysics Data System (ADS)

Hydrothermal synthesis process of tobermorite (5CaO.6SiO2.5H2O) has been investigated by in situ X-ray diffraction (XRD) using high-energy X-rays from a synchrotron radiation source in combination with a laboratory-made autoclave cell and a photon-counting pixel array detector. Three types of quartz sand having different particle size distributions were used. Not only the dissolution rate of quartz but also that of portlandite (Ca(OH)2) were largely affected by particle size distribution of quartz in starting mixtures. The effect of ?-Al2O3 on quartz dissolution and tobermorite formation was also investigated. In all cases, portlandite dissolved completely before the tobermorite formation, while a certain amount of quartz remained undissolved at the timing for tobermorite to start to be detected (denoted as T0). However, the composition (Ca/Si) of non-crystalline C-S-H at T0 was identical regardless of the quartz dissolution rate. Possible reaction mechanism for tobermorite formation has been discussed in terms of distribution of Ca/Si in non-crystalline C-S-H.

Kikuma, J.; Tsunashima, M.; Ishikawa, T.; Matsuno, S.; Ogawa, A.; Matsui, K.; Sato, M.

2011-03-01

187

TAIL VEIN INJECTION (SOP-7) INTRODUCTION  

E-print Network

TAIL VEIN INJECTION (SOP-7) INTRODUCTION Several techniques can be employed which allow within the vein. If the injection is placed subcutaneously, the tail may also blanch but the resistance, the tail can be warmed under a heat lamp. Warming the tail causes the veins to dilate. 3. Locate the right

Kleinfeld, David

188

Hemodilution therapy in central retinal vein occlusion  

Microsoft Academic Search

Systemic hemorheologic abnormalities may play a part in the pathogenesis of central retinal vein occlusions. A statistically significant elevation of plasma viscosity was found in patients with acute central retinal vein occlusion compared with control patients. Local retinal blood flow parameters including arteriovenous passage time and mean arterial dye bolus velocity were significantly altered in the central retinal vein occlusion

Sebastian Wolf; Oliver Arend; Bernd Bertram; Andreas Remky; Karin Schulte; Kenneth J. Wald; Martin Reim

1994-01-01

189

Cathodoluminescence investigations on quartz cement in the sandstones of Khabour Formation from Iraqi Kurdistan Region, Northern Iraq  

NASA Astrophysics Data System (ADS)

The Ordovician deltaic to shallow marine Khabour Formation in Northern Iraq consists mainly of sandstone with minor siltstone and interbedded shale. The sandstones are pervasively cemented by quartz that resulted in very little preserved primary porosity. Cathodoluminescence and petrographic studies showed that the silica cementation occurred in five successive phases which can be distinguished by their luminescence pattern. The precipitations of two phases have predated the major compaction process while the other phases are younger. The successive phases represent a sequence of changes in silica supply which were classified as very early and early, derived from dissolved biogenic silica that precipitated as opal/microquartz, possibly pre-compactional and of non-luminescent quartz overgrowth type. This was followed by phases whose silica supply derived from pressure solution of quartz, dissolution of feldspar, and hydrothermal fluids related to major thrust fault event. These successive quartz cement phases showed an increase in luminescence and the development of complicated zonation pattern in late-stage quartz cementation.

Omer, Muhamed F.; Friis, Henrik

2014-03-01

190

(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

191

Posterolateral cervical vein as a recipient vein in reconstructive microvascular surgery of the head and neck.  

PubMed

Free flaps are becoming the preferred method of choice for head and neck reconstruction. However, many patients who have undergone radiotherapy and radical neck dissection or who require treatment for recurrent tumor, often present difficulty in choosing recipient vessels. The authors have noted a potential recipient vein coursing vertically along the anterior ridge of the trapezius muscle. They used this vein as the recipient vein in two patients; the two free flaps were transferred successfully without complications. This vein, which they provisionally named the posterolateral cervical vein (PLCV), is considered an important option as a recipient vein in head and neck reconstruction when more commonly used recipient cervical veins are unavailable. PMID:17230316

Yagi, Shunjiro; Nakayama, Bin; Kamei, Yuzuru; Takahashi, Masakathu; Torii, Shuhei

2007-01-01

192

Geochemical investigations and Fluid inclusion studies on iron ores from Qatruyeh area, Sanandaj-Sirjan zone, SW Iran: implications for a hydrothermal-metasomatic genetic model  

NASA Astrophysics Data System (ADS)

The Qatruyeh iron deposits are located in the eastern edge of the NW-SE trending Sanandaj-Sirjan metamorphic zone of southwestern Iran and are hosted by a Late Proterozoic to Early Paleozoic sequence dominated by metamorphosed carbonate rocks. The ores occur as layered bodies, with lesser amounts within disseminated magnetite- and hematite-bearing veins. Geochemical analyses of the high-field strength, large ion lithophile, and rare earth elements (REE) indicate that mineralization within the low-grade layered magnetite ores was related to magmatic process accompanied by Na-Ca alteration. The stage is shown by metasomatic replacement textures, gradational contact between layered magnetite and host rock and mineral assemblages of actinolite + titanite + siderite + tourmaline (dravite) + quartz + paragonite. Chemical analyses on layered magnetite show Zn, Cr, LREE and Co/Ni ratio were enriched, whereas V and HREE were depleted. Subsequent to formation, low-temperature hydrothermal activity produced hematite ores with associated propyllitic-sericitic alteration with hematite (specularite) + chlorite + epidote + muscovite + quartz assemblages. The metacarbonate host rocks are LILE-depleted and HFSE-enriched due to metasomatic alteration. REE were relatively immobile during host rock alterations. Microthermometric analyses generally, have been described and measured only on primary inclusions of two-phase liquid +vapor (type A), and two-phase vapor +liquid with (type B). Type A inclusions are dominated by more than 80 vol % of H2O at room temperature. The first ice temperature of melting (Tm) often occurs around -24.5° to -19.5° C. Salinities determined by last ice Tm were 3.5 to 15 weight percent NaCl equivalent (size of inclusions between 2.5 and 15?m) for inclusions trapped in whole quartz samples. The average of homogenization temperature (Th) values change between 300 and 345°C and Tm measurements range from -11.3° to -3.5°C. Homogenization temperature exists for primary types (A) of fluid inclusion may indicate episodes of hydrothermal activities in mesothermal systems for Fe deposits in this region. Type B inclusions, characterized by much more gas bubble within an aqueous liquid are commonly found in all selected samples. Type B inclusions are dominated by more than 60 vol % H2O-CO2 at room temperature. In the Type B inclusions liquid-CO2 homogenize to vapor in the temperature range 396° to 410°C. A general increase in Th values is observed for Type B inclusions in comparison to Type A. Values of Tm of type B inclusions fall within a narrow range from -54.9 to -55.4oC. Salinities determined by last ice Tm were 2.8 to 3.9 weight percent NaCl equivalent. These fluids consist of mixtures of H2O and CO2, the most common fluids released during metamorphic reactions. Fluid inclusion data indicate that the ore forming fluids at Qatruyeh were CO2-bearing, low to moderately saline, NaCl-MgCl2-CaCl2-H2O rich fluids. Fluid mixing, cooling and effervescence played an important role in the formation of the Qatruyeh deposits. Therefore, The range of homogenization temperatures, presence of CO2 in quartz fluid inclusions and an increase in pH indicate that the mixing of fluids and reaction with dolomitic-marble host rock were the most important mechanisms for deposition of magnetite.

Asadi, Sina; Rajabzadeh, Mohammad Ali

2010-05-01

193

Life at Hydrothermal Vents  

NSDL National Science Digital Library

The first Web site is a NOVA Online Adventure from PBS (1). Into the Abyss decribes the "pitch darkness, poison gas, heavy metals, extreme acidity, and enormous pressure" found at hydrothermal vents, and offers a look at bizarre and fascinating creatures found in this environment. The next Web site from Exploring Earth, an online earth sciences text book, contains video clips taken during research expeditions along the Juan de Fuca Ridge (2). Ocean AdVENTure, a ThinkQuest Web site, offers a comprehensive and well-designed introduction to hydothermal vents from research tools to fauna to unsolved mysteries and more (3). Visitors can choose their own scientific adVENTure to explore hydrothermal vents in this interactive feature from the University of Washington School of Oceonagraphy Exploraquarium (4). Dive and Discover is "an interactive distance learning Web site designed to immerse you in the excitement of discovery and exploration of the deep seafloor." This Web site (5) extends a virtual invitation to join scientists aboard research cruises to the depth of the Pacific and Indian Oceans, providing daily logs, video, and other features for each expedition. The next Web site from the University of California-Berkeley offer a closer look at the "strange tube-dwelling worm" phylum found only near hydrothermal vents (6). Creature Features, provided by the University of Delaware Graduate College of Marine Science, contains descriptions and video clips of tubeworms, vent crabs, Pompeii crabs, and ancient bacteria found at deep sea vents (7). The last Web site (8) is a transcript of a June 1997 PBS NewsHour interview with science writer William Broad. Broad discusses his book The Universe Below: Discovering the Secrets of the Deep Sea, and relates the exciting opportunities for scientific exploration of the sea floor made possible by the end of the Cold War.

Sohmer, Rachel.

2002-01-01

194

The superficial femoral vein: a valuable conduit for a short renal vein in kidney transplantation.  

PubMed

A variety of techniques have been developed to improve the problem with a short renal vein in kidney transplantation. Those techniques range from thorough mobilization of the recipient common and external iliac veins (iliac vein transposition) to donor vein elongation with a saphenous or gonadal vein or a polytetrafluoroethylene graft. Right renal vein extension using the inferior vena cava represents an excellent option for cadaveric kidney transplantation; however, for kidneys from living donors, that is not a suitable alternative. We present two cases where the superficial femoral vein was used as a conduit with good results; there was no additional morbidity for the patient. Although uncommon, renal vein extensions are sometimes needed in kidney transplantation. The superficial femoral vein comes close to representing the ideal conduit for a short renal vein when compared with a synthetic or an autologous graft due to its diameter and harvesting technique. PMID:19545768

Alcocer, F; Zazueta, E; Montes de Oca, J

2009-06-01

195

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

196

Experimental and theoretical investigation of the production of HCl and some metal chlorides in magmatic/hydrothermal systems. Annual report, 1991--1992  

SciTech Connect

In the calculations we have assumed that all apatites are magmatic. The presence of chlorite and altered plagioclase within the granite and quartz-monzodiorite suggests that alteration may play a role in leading to erroneous estimates of initial melt Cl and F for 2 reasons: (1) the apatites may in fact not be magmatic in origin, but are hydrothermal, and (2) the halogen signature of magmatic apatite may be changed due to subsolidus exchange with a hydrothermal fluid. We are currently endeavoring to develop criteria for determining whether apatite composition represents earlier or later stages of magmatic-hydrothermal development.

Not Available

1992-12-31

197

Hydrothermal reactions under mechanochemical treating  

Microsoft Academic Search

The mechanochemical treating of solids containing some amount of free or chemically bound water in high-energetic activators enable the hydrothermal processes (as in autoclaves). Estimations of the optimal value of the water content were carried out. The data on the investigation of the mechanochemical reaction between calcium hydroxide and hydrated silica are presented as the experimental confirmation of the hydrothermal

N. V. Kosova; A. Kh. Khabibullin; V. V. Boldyrev

1997-01-01

198

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.

199

New evidence for persistent impact-generated hydrothermal activity in the Miocene Ries impact structure, Germany  

NASA Astrophysics Data System (ADS)

The extent of impact-generated hydrothermal activity in the 24 km sized Ries impact structure has been controversially discussed. To date, mineralogical and isotopic investigations point to a restriction of hydrothermal activity to the impact-melt bearing breccias, specifically the crater-fill suevite. Here, we present new petrographic, geochemical, and isotopic data of postimpact carbonate deposits, which indicate a hydrothermal activity more extended than previously assumed. Specifically, carbonates of the Erbisberg, a spring mound located upon the inner crystalline ring of the crater, show travertine facies types not seen in any of the previously investigated sublacustrine soda lake spring mounds of the Ries basin. In particular, the streamer carbonates, which result from the encrustation of microbial filaments in subaerial spring effluents between 60 and 70 °C, are characteristic of a hydrothermal origin. While much of the primary geochemical and isotopic signatures in the mound carbonates have been obliterated by diagenesis, a postimpact calcite vein from brecciated gneiss of the subsurface crater floor revealed a flat rare earth element pattern with a clear positive Eu anomaly, indicating a hydrothermal fluid convection in the crater basement. Finally, the strontium isotope stratigraphic correlation of the travertine mound with the crater basin succession suggests a hydrothermal activity for about 250,000 yr after the impact, which would be much longer than previously assumed.

Arp, Gernot; Kolepka, Claudia; Simon, Klaus; Karius, Volker; Nolte, Nicole; Hansen, Bent T.

2013-12-01

200

Hydrothermal alteration of sediments associated with surface emissions from the Cerro Prieto geothermal field  

SciTech Connect

A study of the mineralogical changes associated with these hydrothermal vents was initiated with the aim of developing possible exploration tools for geothermal resources. The Cerro Prieto reservoir has already been explored by extensive deep drilling so that relationships between surface manifestations and deeper hydrothermal processes could be established directly. Approximately 120 samples of surface sediments were collected both inside and outside of the vents. The mineralogy of the altered sediments studied appears to be controlled by the type of emission. A comparison between the changes in mineralogy due to low temperature hydrothermal activity in the reservoir, seen in samples from boreholes, and mineralogical changes in the surface emission samples shows similar general trends below 180 C: increase of quartz, feldspar and illite, with subsequent disappearance of kaolinite, montmorillonite, calcite and dolomite. These mineral assemblages seem to be characteristic products of the discharge from high intensity geothermal fields.

Valette-Silver, J.N.; Esquer P., I.; Elders, W.A.; Collier, P.C.; Hoagland, J.R.

1981-01-01

201

Immunohistochemistry comparing endoscopic vein harvesting vs. open vein harvesting on saphenous vein endothelium  

PubMed Central

Objective The present study attempts to compare the immunohistochemistry (IHC) of von Willebrand factor (vWf) , endothelial cadherin, Caveolin and endothelial Nitric Oxide Synthase (eNOS) in VasoView Endoscopic Vein Harvesting (EVH) versus traditional Open Vein Harvesting (OVH) techniques for Coronary Artery Bypass Graft (CABG) Surgery performed in Javad al Aemeh Hospital of Mashhad, Iran in 2013,. Methods and materials Forty-seven patients were scheduled for CABG (30 EVH and 17 OVH) among whom patients with relatively same gender and similar age were selected. Three separate two cm vein samples were harvested from each patient’s saphenous vein. Each portion was collected from distal, middle and proximal zones of the saphenous vein. The tissues were deparaffinized, and antigen retrieval was done using EZ-retriever followed by an immunohistochemistry evaluation with vWf, e-cadherin, Caveolin and eNOS. In addition, demographic questioner as of Lipid profile, FBS, BMI, and cardiovascular risk factors were collected. Data analyses, including parametric and nonparametric tests were undertaken using the SPSS 16 software. A P value??0.05). Qualitative report of vWf, e-cadherin, Caveolin and eNOS reveals no significant difference between the EVH and OVH (P?>?0.05). Conclusion This study indicates that VasoView EVH technique causes no endothelial damage in comparison with OVH. This study could be a molecular confirmation for the innocuous of EVH technique. PMID:24938544

2014-01-01

202

The Pantelleria caldera geothermal system: Data from the hydrothermal minerals  

NASA Astrophysics Data System (ADS)

This paper proposes, on the basis of petrographic and mineralogic data on cutting and cores from two deep wells ("Pantelleria 1" and "Pantelleria 2"), the first model of the active hydrothermal system of the island of Pantelleria. Phyllosilicates were studied in detail because they are considered key minerals in the identification of hydrothermal processes. The results of these studies emphasize differences between the intracaldera and pericaldera areas of the island. Within the 45 ka caldera there is a high-temperature (240-260 °C at 600-800 m depth) active hydrothermal system with five zones of characteristic alteration minerals with increasing depth. Rocks are unaltered to a depth of 200 m, contain smectite and mixed-layer chlorite-smectite (C/S) between 200 and 380 m, chlorite, illite, chalcedony and quartz from 380 to 500 m, albite, adularia and saponite from 500 to 680 m, mixed-layer biotite-vermiculite from 680 m to the depth drilled (1100). Outside the caldera, but near the rim, a low-temperature and low-permeability (< 140 °C) hydrothermal system is characterized by smectite, dolomite and ankerite at depths of 390 to 650 m, chlorite and calcite at 650-900 m, and mixed layers of chlorite-smectite, illite-smectite and iron carbonates (ankerite, siderite) from 900 m of the well at 1203 m. The superimposition of hydrothermal mineral assemblages is evidence for cooling in the hydrothermal system both inside and outside the caldera. We propose that a high-temperature hydrothermal system developed inside the caldera. In an early stage in the area surrounding the subvolcanic body, biotite isograd is reached and an alkali-metasomatism zone develops inside the body itself. This phase may also account for the development of a chlorite-albite-adularia zone extending to 400 m. A cooling phase (nearly 50 °C) followed, resulting in the substitution of biotite by mixed-layer biotite-vermiculite and by the crystallization of Fe-rich saponite instead of chlorite, within the currently active reservoir. A cooling phase has also been identified in the well outside the caldera.

Fulignati, Paolo; Malfitano, Giuseppe; Sbrana, Alessandro

1997-02-01

203

Quartz as a natural luminescence dosimeter  

NASA Astrophysics Data System (ADS)

Luminescence from quartz is commonly used in retrospective dosimetry, in particular for the dating of archaeological materials and sediments from the Quaternary period. The phenomenon of luminescence is related to the interaction of natural radiation with mineral grains, by the activation of and subsequent trapping of electrons at defects within the quartz lattice. The latent luminescence signal (i.e. the trapped electrons) is released when the grains are exposed to stimulation energy in the form of light or heat. Despite the fact that quartz is most nominally pure SiO 2, the mineral forms in several different geological settings, i.e. under different pressure and temperature conditions. The luminescence emitted from quartz is complex and shows a variety of different components with diverse physical properties. This complexity is explained by the variety of defects in quartz that are either intrinsic (e.g., Si and O vacancies) or related to impurity atoms (e.g., Al or Ti). The concentration of impurity-related defects is dependent on the conditions of mineral formation or subsequent alteration. Experimental data have shown that the luminescence properties of quartz are highly variable with geological source and vary even at a grain-to-grain level within a sediment. As a consequence, caution is needed when making any general statements about the luminescence properties of quartz. When using luminescence measurements as a dating technique, it is necessary to adjust the measurement procedures for each geological provenance. Furthermore, some quartz has luminescence properties that make it problematic, or even unsuitable, for certain applications. These problems can arise from low and changing luminescence sensitivity, thermal transfer of trapped electrons, thermal instability of the trapped electrons and low saturation dose. Reviewing the present knowledge reveals that insufficient information is available either to unambiguously link distinctive lattice defects with characteristic luminescence components, or even to explain problems observed in application studies by potential dynamics of the defects within the crystal. This paper gives some ideas on how future research could utilise innovative analytical tools to identify or map the distribution of lattice defects and how practitioners could relate lattice defects to measured luminescence properties of quartz.

Preusser, Frank; Chithambo, Makaiko L.; Götte, Thomas; Martini, Marco; Ramseyer, Karl; Sendezera, Emmanuel J.; Susino, George J.; Wintle, Ann G.

2009-12-01

204

Older Hydrothermal Activity along the Northern Yellowstone Caldera Margin at Sulphur Creek, Yellowstone Park, Wyoming  

NASA Astrophysics Data System (ADS)

The Tuff of Sulphur Creek (480 ka) is well exposed in the Seven Mile Hole area of the Grand Canyon of the Yellowstone River, Yellowstone National Park, Wyoming. The rhyolitic tuff erupted after the collapse of the Yellowstone Caldera (640 ka) and hosts more than 350 vertical meters of hydrothermal alteration. Two epithermal alteration assemblages with different mineral associations have been identified in the area: an illite-silica-pyrite phase and a kaolinite-alunite-silica-pyrite phase. Kaolinite and opal occur along the canyon rim, montmorillonite and other smectites are found at intermediate depths, and illite and sulfides (pyrite) are found deepest in the section. Our work on the north side of the Sevenmile Hole altered area has found a complex system of veining. The veins are concentrated in the eastern portion of the canyon and are less frequent to the west. Brecciated cross-cutting veins ranging from 2 to 30cm wide are found at the base of the canyon. Moving vertically up the canyons walls, the veining style becomes less complex. These veins are about 1 to 1.5cm wide and are not brecciated, occurring less frequently than the brecciated veins. The canyon walls and the canyon rim mainly contain millimeter-scale cross-cutting silica veinlets. These stockwork-like veinlets are the most abundant fracture filling that we find throughout the canyon walls. Veins at the base of the system, found in the stream bed, contain abundant sulfides (mainly pyrite). Sulfides are present in three forms: disseminated in a silica matrix, as massive pyrite in healed fractures, and encrusting clays and silica. The latter is the least common. Disseminated and massive sulfides are typically associated with the matrix in the brecciated veins. Breccias include angular clasts of altered tuff with argillized feldspar phenocrysts and fragments of earlier vein-filling opal. Sulfides are most abundant in the bottom of the canyon and in the western part of the field area. Hydrothermal silica, dominantly opal, is pervasive in the veins throughout the entire system. At the base of the system it is very dark grey and found in the matrix of the veins. The silica veins found on the canyon walls are most often white to cream in color. These veins rarely have cross-cutting relationship with other veins. The stockwork veinlets are found throughout the system. Though the veins are narrow, the wall rock surrounding them is pervasively silicified. The silica in these veins is usually bluish in color, or is rarely clear, and contains very minor sulfides. Wall rock alteration associated with all of the vein types does not vary significantly across the field area. The tuff deeper in the system is completely silicified, so much so that outcrops are well exposed and extensive. The canyon walls are mostly silicified though occasionally there are unsilicified pockets. The top of the system is not silicified though there is one section, on the ridge, that has been thoroughly altered such that the original lithology can not be determined in a hand sample.

Manion, J. L.; Larson, P.

2008-12-01

205

Familial central retinal vein occlusion  

Microsoft Academic Search

AimTo report four cases of central retinal vein occlusion (CRVO) in a French family.Patients and methodsOphthalmological examination and medical work-up of seven members of the family.ResultsThere were four cases of CRVO in two consecutive generations. Three of them had CRVO in both eyes. Arterial hypertension was present in two, associated to glaucoma in one. Medical work-up did not reveal additional

J-F Girmens; S Scheer; E Héron; J-A Sahel; E Tournier-Lasserve; M Paques

2008-01-01

206

Genesis and evolution of the upper oceanic crust (ODP-IODP site 1256, East Pacific Rise): inferences from structure and composition of late magmatic veins in a lava pond  

NASA Astrophysics Data System (ADS)

A complete intact "in situ" section of upper oceanic crust, from extrusive lavas, through dikes into gabbros has been recently drilled for the first time in a 15 Ma old crust that formed at the East Pacific Rise with a full spreading rate of >200 mm/yr. The study area is ODP-IODP Site 1256 (6°44.2N, 91°56.1W, Pacific Ocean). Holes 1256C and 1256D have been drilled into the basaltic basement during ODP Leg 206, IODP Expeditions 309 and 312. Hole 1256D has been deepened to a depth of ca. 1500 meters below seafloor (mbsf). The upper section of the igneous basement consists of thin (<3m) basaltic sheet flows separated by chilled margins, and massive basaltic flows (>3m). The massive flows include a ponded lava flow, located near the top of both Hole 1256C and 1256D, where it has a thickness of 32m and 74m, respectively. The lava pond is interpreted as a thick lava flow delivered either on-axis or off-axis and accumulated in a topographic depression. Although very close (ca. 30m), the two holes record different structural patterns of the lava pond, probably related to different steps of the lava flow emplacement. In the lava pond, both igneous (magmatic foliation, flow-related folds, late-magmatic veins) and post-magmatic (joints, veins, shear veins, and microfaults) structures were recognized. Late magmatic veins (LMVs), which were identified as primary features typical of the lava pond, are the main goal of this work. Mm-thick LMVs are mainly clustered in the middle (290-300 mbsf in hole 1256C and 282-297 mbsf in hole 1256D) and bottom (312-313 mbsf in hole 1256C and 311-328 mbsf in hole 1256D) parts of the lava pond. Structural measurements on cores suggest that they are mostly gently dipping structures, but we also observed sub-vertical LMVs. At the bottom of the lava pond in hole 1256C, late magmatic veins are often arranged in en echelon arrays and sigmoidal pull aparts, suggesting a syn/post-magmatic shear component. Thin-section observations show that basalt including LMVs consists of plagioclase, clinopyroxene, ilmenite, and spinel. LMVs cutting basalt are filled with quartz, quartz + plagioclase intergrowth showing a granophyric texture, clinopyroxene, ilmenite, spinel, and apatite. Rarely we observed pyrite crystals at the LMV core that cut plagioclase + quartz intergrowth. Quartz + plagioclase intergrowth (with apatite) are also present in the basalt as mm-size interstitial domains or rimming plagioclase (IDs = intergrowth domains). Rare samples display IDs with interstitial K-feldspar growing around plagioclase. LMVs often show sharp contacts with basalt. Plagioclase or pyroxene crystals of the basalt may be fragmented at the contact with LMVs (brittle rheology of basalt). Differently, IDs commonly corrode plagioclase crystals, without fragmentation (ductile rheology). The composition of basalt plagioclase ranges from Ab37 to Ab62, with a main concentration around Ab50. On the contrary, plagioclase in the LMVs intergrowth as well as that in the mm-sized IDs are Na-rich (Ab64-Ab98). Mineral analyses also highlight homogeneous clinopyroxene, spinel and ilmenite, without variations in the LMVs and IDs. Clinopyroxene usually shows a Ca-poor core (mainly augite or pigeonite) and a diopsidic rim. Opaque minerals often exhibit ilmenite-ulvospinel lamellae intergrowths. EDS mapping of IDs and LMVs cutting basalt supports the previous observations. LMVs and IDs have higher Si, Na and lower Al, Ca values than basalt. This distribution is only due to albitic plagioclase concentration in LMVs and IDs. K has low and homogeneous concentrations: rarely IDs are characterized by interstitial K enrichment (K-feldspar). Incompatible (Zr, Rb, Sr, Ba), hydrothermal elements (Cu, Cl), and F are undetectable or absent. We infer that LMVs and IDs likely crystallized from a pure Si-Al-Na-(Ca) melt. K, rarely noticed in the IDs, may be related to late magmatic fluids differentiation or to subsequent hydrothermal fluids. Core description, microstructural observations, mineral compositions and EDS mapping of the stud

Panseri, M.

2009-04-01

207

Central vein stenosis: a nephrologist's perspective.  

PubMed

Central vein stenosis is commonly associated with placement of central venous catheters and devices. Central vein stenosis can jeopardize the future of arteriovenous fistula and arteriovenous graft in the ipsilateral extremity. Occurrence of central vein stenosis in association with indwelling intravascular devices including short-term, small-diameter catheters such as peripherally inserted central catheters, long-term hemodialysis catheters, as well as pacemaker wires, has been recognized for over two decades. Placement of multiple catheters, longer duration, location in subclavian vein, and placement on the left-hand side of neck seem to predispose to the development of central vein stenosis. Endothelial injury with subsequent changes in the vessel wall results in development of microthrombi, smooth muscle proliferation, and central vein stenosis. Central vein stenosis is often asymptomatic in nondialysis patients, but can result in edema of ipsilateral extremity and breast when challenged by increased flow from an arteriovenous fistula or arteriovenous graft. Bilateral central vein stenosis or superior vena cava stenosis can produce a clinical picture of superior vena cava syndrome, associated with engorgement of face and neck. Endovascular interventions are the mainstay of management of central vein stenosis. Percutaneous angioplasty and stent placement for elastic and recurring lesions can restore the functionality of the vascular access, at least temporarily. Frequent or multiple interventions are usually required. In recalcitrant cases, surgical bypass of the obstruction is an option. In resistant cases with severe symptoms, occlusion of the functioning vascular access will usually provide relief of symptoms. Further study of mechanisms of development of central vein stenosis and search for a targeted therapy is likely to lead to better ways of managing central vein stenosis. Prevention of central vein stenosis is the key to avoid access failure and other complications from central vein stenosis and relies upon avoidance of central vein stenosis placement and timely placement of arteriovenous fistula in prospective dialysis patient. PMID:17244123

Agarwal, Anil K; Patel, Bhairavi M; Haddad, Nabil J

2007-01-01

208

Multi-Element Quartz Shock Gauge development  

NASA Astrophysics Data System (ADS)

A Multi-Element Quartz Shock Gauge (MEQSG) is being developed to characterize non-uniform spatial loading distributions, such as those encountered in pulsed electron, ion and x-ray irradiation environments. A unique MEQSG with 19 active sensing elements has been produced employing printed circuit board (PCB) technology meeting the essential one dimensional (1-D) requirements of the Sandia shunted quartz gauge. X-cut quartz mechanical and piezoelectric responses are anisotropic for non-uniform spatial loading on the MEQSG surface. Gas shock tube tests of the MEQSG have been conducted for both uniform and non-uniform spatial loading. The shock tube experimental results have been compared with theoretical calculations performed with a Sandia developed three-dimensional fully coupled (mechanical electrical) code that treats anisotropic materials. This paper presents experimental and theoretical results to date.

Lee, L. M.; Montgomery, S. T.; Jilbert, P. H.

2000-04-01

209

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

210

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

211

Cathodoluminescence characterization of quartz grains from the Upper Cretaceous of dinosaur fossil localities in the Gobi desert, Mongolia  

NASA Astrophysics Data System (ADS)

The Upper Cretaceous eolian sediments in Mongolia's Gobi desert are one of the most important occurrences of the dinosaurs in the world. Large numbers of confiscated dinosaur fossils illegally worked out by poachers has been stored in the Mongolian Paleontological Center at Ulaanbaatar. In most cases, their localities are unknown. The purpose of this study is to identify their localities by cathodoluminescence (CL) features of quartz grains attached to the dinosaur specimens by comparing to the quartz samples collected from the sediments of circumjacent resources in this area. This study focuses on the confiscated specimen which makes up the nest with the babies' Protoceratops. Most of all Protoceratops in every growth process, have been discovered from the Djadokhta Formation in the Gobi desert. This formation crops out at Tugrikin Shireh and Bayn Dzak in the central part of the Gobi desert, and is derived from medium- to fine-grained sand mainly composed of quartz grains, of which sedimentary environments should be obvious to be eolian. The formation age of the sand beds at Tugrikin Shireh and Bayn Dzak has been estimated to be Middle Campanian. CL spectra of quartz have been demonstrated to show different features between the quartz from hydrothermal, plutonic, volcanic and metamorphic origins, suggesting the spectra reflect the condition of the quartz formation and the local environment. Therefore, we have applied the CL characterization of quartz grains to the evaluation of the provenance of the desert sediments. The quartz grains after sieving (#60-80 mesh size) were embedded in the brass holders with non-luminescent epoxy resin, and their surfaces were polished with 1 ?m diamond abrasive. Color CL images obtained by the Luminoscope exhibit blue, violet and red emissions in the grains, suggesting various types of emission centers in the quartz. SEM-CL analysis was conducted using an SEM (JSM-5410) combined with a grating monochromator (Mono CL2) to measure CL spectra ranging from 300 to 800 nm in 1 nmsteps at accelerating voltage of 15 kV and beam current of 1.0 nA. Most of the quartz grains have double emission peaks at around 450nm in blue region and at around 620 nm in red region. The emission components of these spectral peaks have been assigned by deconvolution method using Gaussian curve fitting, and individual contributions were quantitatively evaluated by the integral intensities of the components.

Saneyoshi, M.; Nishido, H.; Masuda, R.; Tsogtbaatar, K.; Chinzorig, T.

2013-12-01

212

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

213

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

214

The fossil hydrothermal system of Saint Martin, Lesser Antilles: geology and lateral distribution of alterations  

NASA Astrophysics Data System (ADS)

The fossil geothermal system of Saint Martin, Lesser Antilles, was generated by an intrusion of quartz-diorite of Oligocene age into Eocene volcano-sedimentary host rocks. Adjacent to the pluton, the alteration pattern crops out continuously in the Fort Hill-Kool Bay area over a distance of 4 km. The lithology of the altered host rocks is the following: (1) alternating marls, limestones and minor hyaloclastite (Lower Eocene); (2) hyaloclastite and andesitic lava flows (Middle Eocene); (3) regularly bedded fine-grained hyaloclastite (Upper Eocene). On the basis of alteration petrography, chemistry and fluid-inclusion study, three alteration events have been distinguished: (1) High-temperature event (510 > T > 350°C) accompanied by fluids with salinity higher than 35 wt.% NaCl-eq), mainly represented by tourmaline, quartz, magnetite, orthoclase, apatite and sulfide veins, occurring at the periphery of the pluton and along distal regional faults. (2) Moderate temperature event occurring as veins and pervasive alteration. Veins containing quartz, phengite, pyrite and minor dickite or chlorite ( T = 300°C, very low salinity) are superimposed on the early high-temperature veins. Pervasive alteration affected large concentric zones: the inner zone (3 km width) shows an assemblage of epidote, quartz, actinolite ± magnetite at the periphery of the pluton and epidote, quartz and chlorite farther away. The outer zone (1 km width) shows calcite and mixed-layer illite/smectite (I/S) with ordering type R3 and chlorite/smectite (C/S). Fluid inclusions indicate that salinity and temperature decrease outward from the intrusion during the moderate-temperature pervasive alteration event (respectively from 320 to 140°C and from 30 to 5 wt.% NaCl-eq). (3) Low-temperature event ( T < 50°C) showing calcite, mixed-layer I/S (RO), chalcedonite or baryte in late disseminated veins. This lateral distribution of alteration is very similar to alteration zoning observed in porphyry ore environment or in active deep geothermal systems as Baca (Valles caldera). It shows contrast between zones of fracture permeability which controlled active flow in the system and large zones where pervasive alteration occurred in an inactive flow regime and can be included with metamorphic process. Phyllic alteration seems a good indicator of the active flow paths in the system of Saint Martin. The alteration pattern in Saint Martin is considered to represent the roots of a deep geothermal system (porphyry ore system?) of Oligocene age, actually eroded.

Beaufort, D.; Westercamp, D.; Legendre, O.; Meunier, A.

1990-04-01

215

Deformation mechanics of quartz at a single asperity under hydrothermal conditions  

E-print Network

Pressure solution is a naturally occurring deformation process in fluid-bearing rocks, with implications for sediment consolidation rates and deformation in the mid to upper crust. The process involves dissolution at ...

Bakku, Sudhish Kumar

2010-01-01

216

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

217

Bigeminal pulmonary vein ectopy suppressed by pulmonary vein isolation.  

PubMed

A 58-year-old man with atrial fibrillation underwent pulmonary vein (PV) isolation (PVI). Bigeminal atrial premature beats persisted from the beginning of the PVI. The cardiac recordings from a basket catheter (BC) revealed the PV ectopic origin in the distal right superior PV. Successful PVI with the guidance of BC was confirmed by the appearance of concealed ectopy. Surprisingly, the PV ectopy completely disappeared immediately after the successful PVI. The findings suggest that the generation of PV trigger is sometimes dependent on left atrial input and that the underlying mechanism of the PV trigger may have been triggered activity or reentry. PMID:18360071

Yamada, Takumi; Murakami, Yoshimasa; Toyama, Junji; Murohara, Toyoaki

2008-01-01

218

Pyrite-illite veins in basin-margin facies: evidence for detrital mineral control on pore-fluid evolution  

SciTech Connect

Diagenesis of the Upper Cambrian Lamotte Sandstone includes the formation of euhedral, predominantly cubic pyrite, and 1M and 2M illite as veins in association with extensive quartz dissolution. The illite in these veins is well crystallized and distinct from pore-filling illite found in the same deposit. The veins occur only in shallow marine-deposited quartzarenites that overlie or are adjacent to basin-margin alluvial fan deposits composed primarily of lithic arenite. Detrital K-feldspar (in volcanic rock fragments) and iron-bearing minerals, particularly biotite, are abundant in the lithic arenites. No apparent source for the sulfur can be identified within the Lamotte Sandstone. Therefore, the authors propose that sulfur-bearing compactional or thermobaric fluids from adjacent basinal facies provided the necessary sulfur for pyrite formation. The migration of these fluids through the lithic arenite, from which iron, potassium, aluminum, and silica were derived, resulted in pyrite and illite deposition in the adjacent quartzarenites. The increased alkalinity and elevated temperature of these fluids resulted in the extensive quartz dissolution. The absence of these pyrite-illite veins in similar quartzarenites basinward of the fan deposits suggests a detrital mineral control on the evolution of these fluids as they migrated through the Lamotte Sandstone. Further, the formation of illite as opposed to kaolinite indicates that these fluids were finally alkaline.

Bloch, J.D.; Bhattacharyya, D.P.

1986-05-01

219

Extensions of quartz-enhanced photoacoustic spectroscopy  

E-print Network

The goal of this thesis was to perform quartz-enhanced photoacoustic spectroscopy (QEPAS) on trace concentrations of NH3 in the 1.53 pm region with a DFB laser without the use of a resonating cavity. I analyzed the process ...

Masurkar, Amrita V

2009-01-01

220

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

221

Infrared absorption of defects in quartz  

Microsoft Academic Search

A number of sharp absorption bands in the infrared spectrum of ; crystalline alpha -quartz between 3200 and 3655 cm⁻¹ were assigned to ; defects in the lattice. Defects containing water may cause a broad absorption ; through this region of the spectrum in very imperfect parts of certain crystals, ; but it does not contribute to the sharp bands

D. Wood

1960-01-01

222

DC Plasma Anodization of Quartz Resonators.  

National Technical Information Service (NTIS)

A technique for final tuning AT-quartz resonators having aluminum electrodes by means of a low energy DC oxygen plasma is described. Compared to other techniques, this method is clean, dry, protective, selective, and does not significantly heat the crysta...

C. W. Shanley, L. N. Dworsky

1982-01-01

223

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

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 ? 13C 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 12C 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 ? 13C values of the kerogen in the silica dikes would have been heterogeneous (˜5‰) and at least some material had initial ? 13C values of ? -38‰. The inferred 13C-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

224

Shear Veins Under High Pore Pressure Condition Along Subduction Interface: Yokonami Mélange, Cretaceous Shimanto Belt, Shikoku, Southwest Japan  

NASA Astrophysics Data System (ADS)

Fluid pressure along subdcution interface is a key parameter to understand the fault strength, wedge geometry and seismogenic behavior. In this study, we focused on shear veins pervasively observed in exhumed accretionary complex, Yokonami mélange, Cretaceous Shiamanto Belt, Southwest Japan to examine paleo-stress, effective friction coefficient, fluid pressure ratio and fluid pressure along subduction interface. Lithology of the Yokonami mélange is mainly sandstones surrounded by foliated black shales with minor components of basalts, cherts, tuffs, and limestones, representing tectonic mélange textures. Shear veins cutting mélange foliations are pervasively observed. Shear veins are composed of quartz and calcite. Slicken lines and slicken steps are always observed on the surfaces of shear veins. Pressure-temperature conditions for shear veins are about 180MPa and about 200 degree C on the basis of fluid inclusion analysis. Since the distribution of shear veins are related to packages of ocean floor stratigraphy, formation of shear vein can be before underplating and after mélange formation along subduction interface. We conducted multiple inversion method using slip data of shear veins to examine paleo-stress. In the result, we obtained maximum shear stress horizontal to foliations with 0.3 of stress ratio that is defined as (sigma2-sigma3)/(sigma1-sigma3). Effective friction coefficient was estimated as about 0.10-0.22 by the lowest value of ratio of normal and shear stresses in the normalized Mohr's circle on each plane of shear vein. If we put friction coefficient under dry condition as 0.7 because shear veins cut lithified mélange through out, fluid pressure ratio is equivalent to 0.68-0.86. This is very high fluid pressure ratio along subduction plate interface. On the basis of this fluid pressure ratio and P-T conditions of shear veins from fluid inclusion analysis, 7-12km of depth and 20-30 degree C of geothermal gradient were estimated. The age of subducting plate in the Yokonami mélange was about 50-60Ma from the difference of depositional ages between chert and black shale. The geothermal gradient estimated from the slab age is consistent with from fluid pressure ratio and fluid inclusion analysis. This suggests that the low effective frictional coefficient and high fluid pressure ratio estimated from geological evidences are reasonable values for the formation of shear veins. Kitajima and Saffer (2012) revealed that very low frequency earthquakes (VLFs) occur in the high pore pressure area. Saito et al. (2013) found the quartz cemented fault rocks represent velocity weakening behavior and suggested that the quartz-rich shear veins in shallow accretionary complex might be a geological evidence of VLFs. Our result in this study can support this idea as a shear veins with high fluid pressure at the time of their formation.

Hashimoto, Y.; Eida, M.

2013-12-01

225

Mapping argillic and advanced argillic alteration in volcanic rocks, quartzites, and quartz arenites in the western Richfield 1° x 2 ° quadrangle, southwestern Utah, using ASTER satellite data  

USGS Publications Warehouse

The Richfield quadrangle in southwestern Utah is known to contain a variety of porphyry Mo, skarn, polymetallic replacement and vein, alunite, and kaolin resources associated with 27-32 Ma calc-alkaline or 12-23 Ma bimodal volcano-plutonic centers in Neoproterozoic to Mesozoic carbonate and siliciclastic rocks. Four scenes of visible to shortwave-infrared image data acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor were analyzed to generate maps of exposed clay, sulfate, mica, and carbonate minerals, and ASTER thermal infrared data were analyzed to identify quartz and carbonate minerals. Argillic and advanced argillic alteration minerals including alunite, pyrophyllite, dickite, and kaolinite were identified in both undocumented (U) and known (K) areas, including in the southern Paradise Mtns. (U); in calc-alkaline volcanic rocks in the Wah Wah Mtns. between Broken Ridge and the NG area (U/K); at Wah Wah Summit in a small zone adjacent to 33.1 Ma diorite and marble (U); in fractures cutting quartzites surrounding the 20-22 Ma Pine Grove Mo deposit (U); in volcanic rocks in the Shauntie Hills (U/K); in quartzites in the west-central San Francisco Mtns. (U); in volcanic rocks in the Black Mtns. (K); and in mainly 12-13 Ma rhyolitic rocks along a 20 km E-W belt that includes the Bible Spring fault zone west of Broken Ridge, with several small centers in the Escalante Desert to the south (U/K). Argillized Navajo Sandstone with kaolinite and (or) dickite ± alunite was mapped adjacent to calc-alkaline intrusions in the Star Range (U). Intense quartz-sericite alteration (K) with local kaolinite was identified in andesite adjacent to calc-alkaline intrusions in the Beaver Lake Mountains. Mo-bearing phyllic alteration was identified in 22.2 Ma rhyolite plugs at the center of the NG alunite area. Limestones, dolomites, and marbles were differentiated, and quartz and sericite were identified in most unaltered quartzites. Halos of argillically-altered rock ?12 km in diameter surround the Pine Grove deposit, the central rhyolites at NG, and the North Peaks just south of the Bible Spring fault zone. A southward shift from 22-23 Ma alunite at NG in the northeast to the 12-13 Ma alunite near Broken Ridge in the southwest mirrors a shift in the locus of bimodal magmatism and is similar to the southward shift of activity from the Antelope Range to Alunite Ridge (porphyry Mo potential) in the Marysvale volcanic field farther east. The poster provided in this report compares mineral maps generated from analysis of combined visible-near infrared (VNIR) and shortwave-infrared (SWIR) data and thermal infrared (TIR) ASTER data to a previously published regional geologic map. Such comparisons are used to identify and differentiate rock-forming and hydrothermal alteration-related minerals, which aids in lithologic mapping and alteration characterization over an 11,245 square kilometer area.

Rockwell, Barnaby W.; Hofstra, Albert H.

2012-01-01

226

Thermometry of quartz mylonites: Importance of dynamic recrystallization on Ti-in-quartz reequilibration  

Microsoft Academic Search

Grain boundary migration is crucial for the diffusive equilibration during deformationTitaniQ yields deformation temperature for quartz mylonites T > 540 deg CIn mylonites formed under 540 deg C the preexisting Ti concentrations were preserved

Djordje Grujic; Michael Stipp; Joseph L. Wooden

2011-01-01

227

U/Th geochronology of hydrothermal activity in Long Valley caldera: Little Hot Creek and the Blue Chert  

SciTech Connect

To better define the evolution of the Long Valley hydrothermal system, we have embarked on a program of U/Th age determinations of hydrothermal products from outcrops and drill cores within the caldera. The U/Th system is appropriate for determining ages less than about 350 Ka in suitable materials. Results presented are from dense chalcedonic silica veins, collected from base to top of the outcrop beginning 40 m N of hot spring LHC-1 in Little Hot Creek canyon, and from samples of the Blue Chert.

Sturchio, N.C.; Binz, C.M.; Sorey, M.L.

1986-01-01

228

Hydrothermal vents is Lake Tanganyika, East African Rift system  

SciTech Connect

Sublacustrine hydrothermal vents with associated massive sulfides were discovered during April 1987 at Pemba and Cape Banza on the Zaire side of the northern basin of Lake Tanganyika, East African Rift system. New investigations by a team of ten scuba divers during the multinational (France, Zaire, Germany, and Burundi) TANGANYDRO expedition (August-October 1991) found hydrothermal vents down to a depth of 46 m along north-trending active faults bounding the Tanganyika rift on the western side. Temperatures from 53 to 103 {degrees}C were measured in hydrothermal fluids and sediments. Veins of massive sulfides 1-10 cm thick (pyrite and marcasite banding) were found associated with vents at the Pemba site. At Cape Banza, active vents are characterized by 1-70-cm-high aragonite chimneys, and there are microcrystalline pyrite coatings on the walls of hydrothermal pipes. Hydrothermal fluid end members show distinctive compositions at the two sites. The Pemba end member is a NaHCO{sub 3}-enriched fluid similar to the NaHCO{sub 3} thermal fluids form lakes Magadi and Bogoria in the eastern branch of the rift. The Cape Banza end member is a solution enriched in NaCl. Such brines may have a deep-seated basement origin, as do the Uvinza NaCl brines on the eastern flank of the Tanganyika basin. Geothermometric calculations have yielded temperatures of fluid-rock interaction of 219 and 179 {degrees}C in the Pemba and Cape Banza systems, respectively. Abundant white or reddish-brown microbial colonies resembling Beggiatoa mats were found surrounding the active vents. Thermal fluid circulation is permitted by opening of cracks related to 130{degrees}N normal-dextral faults that intersect the north-south major rift trend. The sources of heat for such hydrothermal systems may relate to the existence of magmatic bodies under the rift, which is suggested by the isotopic composition of carbon dioxide released at Pemba and Cape Banza. 21 refs., 2 figs.

Tiercelin, J.J. [Universite de Bretagne Occidentale, Brest (France)] [Universite de Bretagne Occidentale, Brest (France); Pflumio, C.; Castrec, M. [Universite Paris VI, Paris (France)] [and others] [Universite Paris VI, Paris (France); and others

1993-06-01

229

The adrenal and renal veins of man and their connections with azygos and lumbar veins.  

PubMed Central

There exist many variations in the manner of formation, dimensions and place of termination of the central adrenal veins. In addition, some superficial adrenal veins may be substantial in size and may themselves drain directly into the renal veins and/or into other vessels which communicate with azygos and lumbar veins. This provides a route for venous adrenal blood to the heart via the azygos system and the superior vena cava rather than via the inferior vena cava. Variations in the formation and disposition of the renal veins are also described and the patterns of communication between somatic veins (including veins of the azygos and lumbar systems) and the left renal vein are illustrated and discussed in relation to the findings of others. Images Fig. 7 Fig. 8 Fig. 6 PMID:3693053

Monkhouse, W S; Khalique, A

1986-01-01

230

The Black Pearl mine, Arizona - Wolframite veins and stockscheider pegmatite related to an albitic stock  

NASA Technical Reports Server (NTRS)

Wolframite-bearing quartz veins flanked by greisen alteration occur at and near the Black Pearl mine, Yavapai County, Arizona. The veins are genetically related to a small albitite stock, and cut a series of Proterozoic metasedimentary and intrusive rocks. The largest vein, the only one mined, is located at the apex of the stock. Field relations imply that this stock is a late-stage differentiate of time 1.4-Ga anorogenic Lawler Peak batholith, which crops out about 3 km to the south. The albitites are of igneous origin and have suffered only minor deuteric alteration. A thin (1 to 2 m) pegmatite unit ('stockscheider') occurs at the contact of the Black Pearl Albitite stock with the country rocks. Directional indicators and other evidence suggest that the pegmatite was formed in the presence of a volatile-rich fluid phase close to the time of magma emplacement. The sudden change from coarse-grained microcline-rich pegmatite to fine-grained, albite-rich albitite suggests pressure quenching, possibly due to escape of fluids up the Black Pearl vein. Stockscheider-like textures typically occur near the apical contacts of productive plutons. The presence or absence of this texture is a useful guide in prospecting for lithophile metal deposits.

Schmitz, Christopher; Burt, Donald M.

1990-01-01

231

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

232

Isotope and fluid inclusion studies of geological and hydrothermal processes, northern Peru  

SciTech Connect

Mineralization in the Hualgayoc district of northern Peru occurs in altered Miocene felsic intrusions and in mid-Cretaceous platform sedimentary rocks of the Goyllarisquizga, Inca, and Chulec formations. The ores occur both as stratiform and stratabound pyritiferous base-metal deposits (mantos), and as steeply dipping, sedimentary and intrusive rock-hosted base-metal veins. Igneous rocks in the district are affected by propylytic, sericitic-argillic, sericitic, potassic, and acid-sulfate alteration. K-Ar and Rb-Sr dating and geological evidence indicate multiple stages of intrusive activity and hydrothermal alteration, including close spatial emplacement of two or more separate Miocene magmatic-hydrothermal systems. K-Ar dates on sericite, hydrothermal biotite, and alunite indicate that the most important hydrothermal episodes in the district took place {approx}13.24 and 12.4 Ma. Other K-Ar dates on altered rocks in the district may reflect various amounts of resetting by the emplacement of the 9.05 {+-} 0.2 Ma Hualgayoc rhyodacite. A five-point Rb-Sr isochron for the San Miguel intrusion at Cerro Coymolache yields an age of 45 {+-} 3.4 Ma, which indicates much earlier magmatic activity in this area than recognized previously. Fluid inclusion and paragenetic studies reveal a clear temporal evolution of fluid temperature and chemistry in the San Agustin area at Hualgayoc. Gradually, ore formation shifted to precipitation of vein minerals in the brittle fractures as the mantos became less permeable and were sealed off. Vein formation continued from progressively cooler and more diluted fluids (down to {approx}150{degrees}C and 4.3 wt% NaCl equivalent) as the system waned. No evidence for phase separation is observed in the fluids until the very last paragenetic stage, which contributed no economic mineralization. 53 refs., 15 figs., 7 tabs.

MacFarlane, A.W. [Florida International Univ., Miami, FL (United States); Prol-Ledesma, R.M. [Cd. Universitaria, Coyoacan (Mexico); Conrad, M.E. [Lawrence Berkeley Lab., CA (United States)

1994-07-01

233

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

234

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

235

Insights Into Peridotite-Hosted Hydrothermal Systems From Petrological and Geochemical Studies of the Lost City Hydrothermal System  

NASA Astrophysics Data System (ADS)

The Lost City hydrothermal field is a rare example of an active peridotite-hosted hydrothermal system, in which reactions between seawater and ultramafic rocks produce high pH (9 to 11) fluids that result in the formation of up to 60m tall carbonate-brucite structures. The 25 to 90° C fluids are enriched in hydrogen, methane and other hydrocarbons, and support dense microbial communities dominated by archaea [Kelley et al., 2005]. We present an overview of field, petrological, and geochemical studies of the basement rocks and hydrothermal precipitates, which provide important insights into the complex interplay between deformation, fluid flow, mass transfer and hydrothermal activity during a long-lived history of detachment faulting, uplift and seawater-peridotite interaction in the Atlantis Massif. Sampling by submersible of this fault-bounded, dome-like oceanic core complex recovered a heterogeneous suite of variably altered and deformed peridotites and gabbroic rocks, overlain by less abundant basalts, breccias and pelagic carbonates. The harzburgitic peridotites are 70-90% serpentinized and have variable mineral and bulk rock chemistries that reflect heterogeneous mantle compositions, varying degrees of melt impregnation, and multiple phases of serpentinization, metasomatism and veining. Talc-amphibole-chlorite metasomatism is a key element of the detachment fault zone at the top of the massif and reflects a deformation and metamorphic history that is distinct from the underlying serpentinites. Major and trace elements compositions of the metasomatic rocks indicate complex interaction between mafic and ultramafic rocks during detachment faulting and suggest localized circulation of oxidizing, Si-Al-Ca-rich fluids in high strain deformation zones. Extensive seawater-peridotite interaction under varying temperatures and high fluid-rock mass ratios in the basement at Lost City are evident by distinct enrichments in B and U contents in the serpentinites, by systematic changes in Sr- and Nd-isotope ratios towards seawater compositions, and by highly depleted bulk rock O-, H-, and B- isotopic compositions. These data together with C-, H-, O- and B-isotope compositions of end-member vent fluids and hydrothermal carbonates document mixing of seawater and deep, serpentinization-derived, CO2-poor, H2-rich hydrothermal fluids under a range of temperatures from ambient conditions to >200° C at depth. Our field observations indicate that outflow at the vent sites is controlled by fractures and faults in the basement, and that much of the subsurface flow is along subhorizontal surfaces producing carbonate deposits parallel to the basement foliation and subparallel to gently west-dipping faults. References: Kelley, D.S. et al., (2005) Science, 307(5714), 1428-1434.

Fruh-Green, G. L.; Boschi, C.; Kelley, D. S.; Delacour, A.; Bernasconi, S. M.; Karson, J. A.

2005-12-01

236

Serotonin (5HT) in Veins: Not All in Vain  

Microsoft Academic Search

The circulatory system consists of veins and arteries. Com- pared with arteries, veins have been neglected in cardiovascu- lar research. Although veins are significantly less muscular than similarly sized arteries, the contribution of veins to cardiovas- cular homeostasis cannot be left un-noted because veins ac- commodate 70% of the circulating blood. Circulating blood platelets contain the majority of systemic 5-HT

A. Elizabeth Linder; Wei Ni; Jessica L. Diaz; Theodora Szasz; Robert Burnett; Stephanie W. Watts

2007-01-01

237

Facial vein draining into external jugular vein in humans: its variations, phylogenetic retention and clinical relevance  

Microsoft Academic Search

The superficial veins, especially the external jugular vein (EJV), are increasingly being utilized for cannulation to conduct diagnostic procedures or intravenous therapies. Ultrasound-guided venipuncture is a viable possibility in cases of variations in the patterns of superficial veins, and their knowledge is also important for surgeons doing reconstructive surgery. This study was done on 89 dissected adult cadavers (178 sides)

V. Gupta; A. Tuli; R. Choudhry; S. Agarwal; A. Mangal

2003-01-01

238

Oxygen and carbon isotope ratios of hydrothermal minerals from Yellowstone drill cores  

USGS Publications Warehouse

Oxygen and carbon isotope ratios were measured for hydrothermal minerals (silica, clay and calcite) from fractures and vugs in altered rhyolite, located between 28 and 129 m below surface (in situ temperatures ranging from 81 to 199??C) in Yellowstone drill holes. The purpose of this study was to investigate the mechanism of formation of these minerals. The ??18O values of the thirty-two analyzed silica samples (quartz, chalcedony, ??-cristobalite, and ??-cristobalite) range from -7.5 to +2.8???. About one third of the silica 7samples have ??18O values that are consistent with isotopic equilibrium with present thermal waters; most of the other silica samples appear to have precipitated from water enriched in 18O (up to 4.7???) relative to present thermal water, assuming precipitation at present in situ temperatures. Available data on fluid-inclusion homogenization temperatures in hydrothermal quartz indicate that silica precipitation occurred mostly at temperatures above those measured during drilling and imply that 15O enrichments in water during silica precipitation were generally larger than those estimated from present conditions. Similarly, clay minerals (celadonite and smectite) have ??18O values higher (by 3.5 to 7.9???) than equilibrium values under present conditions. In contrast, all eight analyzed calcite samples are close to isotopic equilibrium with present thermal waters. The frequent incidence of apparent 18O enrichment in thermal water from which the hydrothermal minerals precipitated may indicate that a higher proportion of strongly 18O-enriched deep hydrothermal fluid once circulated through shallow portions of the Yellowstone system, or that a recurring transient 18O-enrichment effect occurs at shallow depths and is caused either by sudden decompressional boiling or by isotopic exchange at low water/rock ratios in new fractures. The mineralogy and apparent 18O enrichments of hydrothermal fracture-filling minerals are consistent with deposition during transient boiling or rock-water exchange (fracturing) events. ?? 1990.

Sturchio, N.C.; Keith, T.E.C.; Muehlenbachs, K.

1990-01-01

239

Aligned carbon nanotubes on quartz substrate for liquid gated biosensing  

Microsoft Academic Search

A facile and high performance biosensing platform using aligned carbon nanotubes on quartz substrate is reported in this communication. Single walled carbon nanotubes are grown on quartz substrates by a chemical vapor deposition process and are characterized with field emission scanning electron microscopy and atomic force microscopy in order to verify the quality of the material. The quartz substrate is

Al. Palaniappan; W. H. Goh; J. N. Tey; I. P. M. Wijaya; S. M. Moochhala; B. Liedberg; S. G. Mhaisalkar

2010-01-01

240

Effects of glacial ice on subsurface temperatures of hydrothermal systems in Yellowstone National Park, Wyoming: Fluid-inclusion evidence  

Microsoft Academic Search

Hydrothermal quartz and fluorite crystals containing liquid-rich fluid inclusions (coexisting vapor-rich fluid inclusions were not observed) were found in drill cores from eight relatively shallow research holes drilled by the US Geological Survey in and near major geyser basins of Yellowstone National Park. Homogenization temperatures (T{sub h}) for mostly secondary fluid inclusions show variations in temperature that have occurred at

Keith E. Bargar; Robert O. Fournier

1988-01-01

241

Effects of glacial ice on subsurface temperatures of hydrothermal systems in Yellowstone National Park, Wyoming: Fluid-inclusion evidence  

Microsoft Academic Search

Hydrothermal quartz and fluorite crystals containing liquid-rich fluid inclusions (coexisting vapor-rich fluid inclusions were not observed) were found in drill cores from eight relatively shallow research holes drilled by the U.S. Geological Survey in and near major geyser basins of Yellowstone National Park. Homogenization temperatures (Th) for mostly secondary fluid inclusions show variations in temperature that have occurred at given

Keith E. Bargar; Robert O. Fournier

1988-01-01

242

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

243

Quartz Cherenkov counters for fast timing: QUARTIC  

NASA Astrophysics Data System (ADS)

We have developed particle detectors based on fused silica (quartz) Cherenkov radiators read out with microchannel plate photomultipliers (MCP-PMTs) or silicon photomultipliers (SiPMs) for high precision timing (?t ~ 10-15 ps). One application is to measure the times of small angle protons from exclusive reactions, p+p?p+X+p, at the Large Hadron Collider, LHC. They may also be used to measure directional particle fluxes close to external or stored beams. The detectors have small areas (cm2), but need to be active very close ( ~ 4 mm) to the intense LHC beam, and so must be radiation hard and nearly edgeless. We present results of tests of detectors with quartz bars inclined at the Cherenkov angle, and with bars in the form of an "L" (with a 90° corner). We also describe a possible design for a fast timing hodoscope with few mm2 elements.

Albrow, M. G.; Kim, Heejong; Los, S.; Mazzillo, M.; Ramberg, E.; Ronzhin, A.; Samoylenko, V.; Wenzel, H.; Zatserklyaniy, A.

2012-10-01

244

Emission polarization study on quartz and calcite.  

NASA Technical Reports Server (NTRS)

Calculation of the spectral emission polarization of quartz and calcite polished plates for observation angles of 20 and 70 deg by the substitution of complex index of refraction values for each mineral into Fresnel's equations. The emission polarization is shown to be quite wavelength-dependent, demonstrating that selected narrow or medium-width spectral bands exhibit a significantly higher percentage of polarization than a broad spectral band for these two minerals. Field measurements with a broadband infrared radiometer yield polarizations on the order of 2% for a coarse-grained granite rock and beach sand (both quartz-rich). This implies that a more sensitive detector with a selected medium-width filter may be capable of measuring emission polarization accurately enough to make this parameter useful as a remote sensing tool for discrimination among rocks on the basis of texture.

Vincent, R. K.

1972-01-01

245

Long-Lived Serpentinization and Carbonate Precipitation at the Lost City Hydrothermal Vent Field  

NASA Astrophysics Data System (ADS)

The discovery of spectacular, actively venting carbonate chimneys at the Lost City hydrothermal vent field (LCHF) on the Atlantis Massif (MAR 30oN) has stimulated great interest in the role of serpentinization in driving hydrothermal circulation in peridotite-hosted systems and in the biological communities that may be supported in these environments. The top of this fault-bounded, dome-like massif consists of variably deformed, talc-bearing serpentinites and gabbroic rocks ( ˜1.5 Ma), unconformably overlain by polymictic sedimentary breccias and bedded pelagic limestones or chalks that form a flat-lying carbonate cap. The limestones and matrix of the breccias consist of highly indurated foraminiferal sand with a well-preserved sub-tropical fauna, which were at least locally deposited before the last glacial maximum. Calcite and/or aragonite veins are abundant; fractures in the basement are filled by carbonate sediments and lithic fragments. Veining generally pre-dates sedimentary fracture-infilling. The youngest hydrothermal phases include the LCHF chimneys and carbonate precipitates on outcrop surfaces, in cavities, and as growths protruding from fissures that are locally venting fluids. Sr-, C- and O-isotope analyses and radiocarbon age-dating indicate that this system is the integrated effect of tectonic activity, serpentinization, and hydrothermal flow that has lasted at least 30,000 years. C- and O-isotope compositions indicate a range of precipitation temperatures from ambient conditions up to ˜ 250oC at depth and reflect mixing of seawater and serpentinization-derived hydrothermal fluids. Analyses of separated fractions of sedimentary and hydrothermal components define a sedimentary end-member composition of ? 13C = 1.3 +/- 0.3 and ? 18O = 1.5 +/- 0.5‰ (VPDB) and a hydrothermal end-member composition of ? 13C = 3.3 and ? 18O = 5‰ . Based on the present-day degree of serpentinization, the geophysical structure and age of the lithosphere at the Atlantis Massif, and the radiocarbon ages, we estimate a minimum rate of serpentinization of 1.2 ? 10-4}km{3/y. Our field observations together with available gravity and seismic data indicate that a considerable proportion of the massif is relatively unaltered peridotite. The access of seawater to relatively cool, fresh peridotite, coupled with faulting, volumetric expansion and mass wasting processes are crucial to sustain such systems. In addition, diffusely percolating, high pH fluids emanating from the underlying serpentinites promote rapid sediment lithification, which offers an efficient mechanism for slowing heat loss and maintaining higher temperatures in the basement. Collectively these processes have the potential to prolong hydrothermal activity for tens of thousands of years.

Frueh-Green, G. L.; Kelley, D. S.; Karson, J. A.; Bernasconi, S. M.; Proskurowski, G.; Ludwig, K. A.

2003-12-01

246

21 CFR 880.6980 - Vein stabilizer.  

Code of Federal Regulations, 2010 CFR

...prongs. The device is placed on the skin so that the prongs are on either side of a vein and hold it stable while a hypodermic needle is inserted into the vein. (b) Classification. Class I (general controls). The device is exempt from the...

2010-04-01

247

Duplex ultrasonography in portal vein thrombosis  

Microsoft Academic Search

Duplex ultrasonography (US) was performed in 23 patients with portal vein thrombosis. In 7 children and 16 adults, duplex US demonstrated intraluminal thrombi (4 cases), thrombus and periportal collaterals (2 cases), and cavernomatous transformation of the portal vein (17 cases). Real-time US is a suitable means of demonstrating the anatomy of the portal venous system; pulsed Doppler provided information on

Z. Harkányi; M. Temesi; G. Varga; V. Weszelits

1989-01-01

248

Running head: SEM-CL/optical microscopy of quartz PROVENANCE ANALYSIS BY SINGLE-QUARTZ-GRAIN SEM-CL / OPTICAL  

E-print Network

1 Running head: SEM-CL/optical microscopy of quartz PROVENANCE ANALYSIS BY SINGLE-QUARTZ-GRAIN SEM: quartz arenite, SEM-CL, optical microscopy, provenance, New Zealand ABSTRACT: The integration of panchromatic scanning electron microscopy- cathodoluminescence (SEM-CL) with optical microscopy analysis

Paris-Sud XI, Université de

249

Element transport in veins during serpentinization  

NASA Astrophysics Data System (ADS)

Serpentinization of ultramafic rocks has wide ranging implications for the petrology, rheology, and petrophysical properties of the oceanic lithosphere. During hydration of the peridotite, fluid-rock ratios and temperature control mineral formation in the veins. We studied a partly serpentinized peridotite from the Santa Elena ophiolite complex in Costa Rica and tracked element mobility during water-rock interaction. Serpentinization of the studied harzburgite is around 30 to 40%, with serpentinization of olivine being more advanced than serpentinization of orthopyroxene. Element mapping and point analyses show that the veins preserve characteristic element distributions within orthopyroxene and olivine, and with distance to orthopyroxene-hosted serpentine veins. With increasing distance from the orthopyroxene the following vein assemblages were observed in olivine: pure serpentine veins, serpentine + brucite veins, serpentine + brucite + magnetite veins. Veins are enriched in SiO2 in the proximity of orthopyroxene suggesting that a net transfer of SiO2 takes place from serpentinizing orthopyroxene to olivine. The magnetite-bearing serpentine veins mostly consist of Mg-rich serpentine (Mg# = 90 - 95) and Fe-rich brucite (Mg# = 70 - 75) finely intergrown. In contrast, the center of these veins contains a thin zone of high-Mg serpentine (Mg# 97), and high-Mg brucite (Mg# 92 - 94) next to magnetite. We infer from thermodynamic calculations that these mineral assemblages are controlled by H2O activity and low SiO2 activities. Within orthopyroxene, serpentine (Mg# = 84 - 89) with an elevated Al2O3 content (< 4.14wt.%) was detected, but talc was absent, indicating net loss of SiO2 from orthopyroxene during serpentinization. CaO and Al2O3 migrate from orthopyroxene, but occur only as trace components in serpentine at > 100 ?m and > 200 ?m, respectively, from the orthopyroxene. We infer that brucite is not stable in close proximity to orthopyroxene due to elevated SiO2 derived from orthopyroxene breakdown. Orthopyroxene serpentinization results in net transfer of Al2O3 into serpentine, but only in the immediate vicinity of the orthopyroxene. Overall, our study indicates that the extent of orthopyroxene serpentinization controls SiO2 and Al2O3 availability in the fluid and therefore the mineral assemblages present in the veins. The net transfer of SiO2 is manifested by the lack of talc in serpentine veins in orthopyroxene and the lack of brucite in serpentine veins proximal to orthopyroxene grain boundaries. Within veins, local transport of Si, Mg and Fe takes place during reaction of serpentine + brucite with H2O to form magnetite + Mg-rich serpentine + Mg-rich brucite.

Schwarzenbach, E. M.; Beard, J. S.; Caddick, M. J.

2013-12-01

250

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

251

21 CFR 880.6970 - Liquid crystal vein locator.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 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...

2012-04-01

252

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

253

21 CFR 880.6970 - Liquid crystal vein locator.  

...2014-04-01 2014-04-01 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...

2014-04-01

254

21 CFR 880.6970 - Liquid crystal vein locator.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 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...

2011-04-01

255

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

256

[News in the lower extremity veins morphology].  

PubMed

This comprehensive article notifies on the latest information concerning the morphology of the lower extremity veins, including their anatomical terminology. As a consequence of vehement development of the diagnostic and therapeutic techniques, the more detailed knowledge of anatomy, terminology, venous system variants and venous wall structure is necessary both for the phlebologists, sonographists and for the surgeons and cardiosurgeons. The histological part brings information about the content of collagen and elastin fibers in all layers of the superficial veins wall and about the arrangement of the vasa vasorum in both normal and varicose vena saphena magna. The anatomical-terminological part enlightens the variability of the superficial venous system of the lower extremity and the completion of the terminology of some superficial and deep veins, veins of the pelvis and perforating veins. The simple and clear anatomical terminology is the base for easy and non-problematic communication and discussion between inland and foreign specialists. PMID:19110951

Riedlová, J; Smrzová, T

2008-10-01

257

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

258

Conditions for veining in the Barrandian Basin (Lower Palaeozoic), Czech Republic: evidence from fluid inclusion and apatite fission track analysis  

NASA Astrophysics Data System (ADS)

The interplay between fracture propagation and fluid composition and circulation has been examined by deciphering vein sequences in Silurian and Devonian limestones and shales at Kosov quarry in the Barrandian Basin. Three successive vein generations were recognised that can be attributed to different stages of a basinal cycle. Almost all generations of fracture cements host abundant liquid hydrocarbon inclusions that indicate repeated episodes of petroleum migration through the strata during burial, tectonic compression and uplift. The earliest veins that propagated prior to folding were displacive fibrous "beef" calcite veins occurring parallel to the bedding of some shale beds. Hydrocarbon inclusions within calcite possess homogenisation temperatures between 58 and 68 °C and show that the "beef" calcites originated in the deeper burial environment, during early petroleum migration from overpressured shales. E-W-striking extension veins that postdate "beef" calcite formed in response to Variscan orogenic deformations. Based on apatite fission track analysis (AFTA) data and other geological evidence, the veins probably formed 380-315 Ma ago, roughly coinciding with peak burial heating of the strata, folding and the intrusion of Variscan synorogenic granites. The veins that crosscut diagenetic cements and low-amplitude stylolites in host limestones are oriented semi-vertically to the bedding plane and are filled with cloudy, twinned calcite, idiomorphic smoky quartz and residues of hardened bitumen. Calcite and quartz cements contain abundant blue and blue-green-fluorescing primary inclusions of liquid hydrocarbons that homogenise between 50 and 110 °C. Geochemical characteristics of the fluids as revealed by gas chromatography-mass spectrometry, particularly the presence of olefins and parent aromatic hydrocarbons (phenonthrene), suggest that the oil entrapped in the inclusions experienced intense but geologically fast heating that resulted in thermal pyrolysis of its hydrocarbons. This implies that the organic fluids in the fractures may have been partly influenced by heating associated with igneous intrusions that are hidden below the surface. Subvertical N-S-striking veins represent the most recent fracturing event(s). Some of these veins are only a few millimeters thick and sparsely mineralised with thin leaf-like quartz crystals that contain tiny blue and yellow-orange-fluorescing hydrocarbon inclusions. Most of the N-S veins, however, occur as thick calcite veins that generally crystallised at 70 °C or less from H 2O-NaCl solutions of variable salinity with admixture of petroleum. The origin of these fluids is interpreted in terms of deeply circulating meteoric waters that partially mixed with deep basinal fluids. Wider structural considerations combined with fission-track analysis of adjacent host sediments suggest that N-S veins formed during post-Mesozoic uplift of the area, probably in response to major Tertiary Alpine deformations transmitted far into the Bohemian Massif.

Suchy, V.; Dobes, P.; Filip, J.; Stejskal, M.; Zeman, A.

2002-04-01

259

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 ± 0.3wt% 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.

Nehlig, Pierre

1991-03-01

260

Hydrothermal synthesis of ammonium illite  

USGS Publications Warehouse

Synthetic gel and glass of illitic composition, natural kaolinite, and mixed-layer illite-smectite were used as starting materials for hydrothermal synthesis of ammonium illite. Ammonium illite was prepared from synthetic gel by hydrothermal treatment at 300??C. The onset of crystallization began within 3 h, and well-crystallized ammonium illite appeared at 24 h. Increasing reaction time (up to four weeks) led to many illite layers per crystal. In the presence of equivalent proportions of potassium and ammonium, the gel was transformed to illite with equimolar contents of K and NH4. In contrast, synthesis using glass under the same conditions resulted in a mixture of mixed-layer ammonium illite-smectite with large expandability and discrete illite. Hydrothermal treatments of the fine fractions of natural kaolinite and illite-smectite produced ammonium illite from kaolinite but the illite-smectite remained unchanged.

Sucha, V.; Elsass, F.; Eberl, D.D.; Kuchta, L'.; Madejova, J.; Gates, W.P.; Komadel, P.

1998-01-01

261

Exploration strategies for hydrothermal deposits.  

PubMed

With unlimited money the most certain strategy for finding most hydrothermal metal deposits would be by drilling to 5000 m at 50 m spacing. However, the cost would far outweigh the benefit of the discoveries. Geological knowledge and exploration techniques may be used to obtain the greatest benefit for minimum cost, and to concentrate human and material resources in the most economic way in areas with the highest probability of discovery. This paper reviews the economic theory of exploration based on expected value, and the application of geological concepts and exploration techniques to exploration for hydrothermal deposits. Exploration techniques for hydrothermal-systems on Mars would include geochemistry and particularly passive geophysical methods. PMID:9243019

Horn, R A

1996-01-01

262

[Causes of postoperative recurrent varicose veins of lower extremities].  

PubMed

We analysed venograms of recurrent varicose veins in 180 cases (206 lower limbs). Deep vein valvular insufficiency resulted in varicose veins in 52.9% cases, and post-thrombotic syndrome in 18.9%. The causes of postoperative recurrent varicose veins varied: blindly performed single superficial veins operation, low ligation of the long saphenous trunk, incomplete stripping of varicose veins, missing of the short varicose saphena or incomplete ligation of the perforating veins and failure of deep vein valvular repairs. Venography is of value in making correct diagnosis and choosing appropriate operations. PMID:7553147

Gu, X; Yang, Z; Chen, J

1995-06-01

263

Complex vein systems as a data source in tectonics: An example from the Ugab Valley, NW Namibia  

NASA Astrophysics Data System (ADS)

Neoproterozoic metaturbidites in the Lower Ugab Domain, Namibia, contain a complex network of four sets of quartz-calcite veins, overprinted by km-scale folds associated with four regional foliations. The veins formed by fluid overpressure predating the main deformation. Deformation structures developed at the junction of two mobile belts during the assembly of Gondwana, the NS Kaoko Belt, and the EW trending Damara Belt. Km-scale NS trending folds were initiated during EW constriction in the Kaoko Belt, while their further development and all subsequent events are related to constriction in the EW-Damara Belt, with coeval sinistral strike slip in the Kaoko Belt. Deformation of the veins, and development of four orthogonal foliations are due to gradual changes in the bulk tectonic framework rather than separate orogenic events. The veins are deformed in a complex manner allowing a full 3D reconstruction of regional sequence of events. The local complex tectonics could be reconstructed because of the perfect local exposure and the multitude of veins: it illustrates the potential complexity of tectonic events and structural evolution in apparently simple slate belts.

Maeder, Xavier; Passchier, Cees W.; Trouw, Rudolph A. J.

2014-05-01

264

A tectonic model for the spatial occurrence of porphyry copper and polymetallic vein deposits - applications to Central Europe  

USGS Publications Warehouse

A structural-tectonic model, which was developed to assess the occurrence of undiscovered porphyry copper deposits and associated polymetallic vein systems for the Matra Mountains, Hungary, has been expanded here and applied to other parts of central Europe. The model explains how granitoid stocks are emplaced and hydrothermal fluids flow within local strain features (duplexes) within strike-slip fault systems that develop in continental crust above subducting plates. Areas of extension that lack shear at the corners and along the edges of the fault duplexes are structural traps for the granitoid stocks associated with porphyry copper deposits. By contrast, polymetallic vein deposits are emplaced where shear and extension are prevalent in the interior of the duplexes. This model was applied to the Late Cretaceous-age porphyry copper and polymetallic vein deposits in the Banat-Timok-Srednogorie region of Romania-Serbia-Bulgaria and the middle Miocene-age deposits in Romania and Slovakia. In the first area, porphyry copper deposits are most commonly located at the corners, and occasionally along the edges, of strike-slip fault duplexes, and the few polymetallic vein deposits identified are located at interior sites of the duplexes. In the second area, the model accounts for the preferred sites of porphyry copper and polymetallic vein deposits in the Apuseni Mountains (Romania) and central Slovakian volcanic field (Slovakia).

Drew, Lawrence J.

2006-01-01

265

A Reappraisal of Saphenous Vein Grafting  

PubMed Central

Autologous saphenous vein grafting has been broadly used as a bypass conduit, interposition graft, and patch graft in a variety of operations in cardiac, thoracic, neurovascular, general vascular, vascular access, and urology surgeries, since they are superior to prosthetic veins. Modified saphenous vein grafts (SVG), including spiral and cylindrical grafts, and vein cuffs or patches, are employed in vascular revascularization to satisfy the large size of the receipt vessels or to obtain a better patency. A loop SVG helps flap survival in a muscle flap transfer in plastic and reconstructive surgery. For dialysis or transfusion purposes, a straight or loop arteriovenous fistula created in the forearm or the thigh with an SVG has acceptable patency. The saphenous vein has even been used as a stent cover to minimize the potential complications of standard angioplasty technique. However, the use of saphenous vein grafting is now largely diminished in treating cerebrovascular disorders, superior vena cava syndrome, and visceral revascularization due to the introduction of angioplasty and stenting techniques. The SVG remains the preferable biomaterial in coronary artery bypass, coronary ostioplasty, free flap transfer, and surgical treatment of Peyronie disease. Implications associated with saphenous vein grafting in vascular access surgery for the purpose of dialysis and chemotherapy are considerable. Vascular cuffs and patches have been developed as an important and effective means of enhancing the patency rates of the grafts by linking the synthetic material to the receipt vessel. In addition, saphenous veins can be a cell source for tissue engineering. We review the versatile roles that saphenous vein grafting has played as well as its current status in therapy. PMID:21245602

Yuan, Shi-Min; Jing, Hua

2011-01-01

266

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

NASA Astrophysics Data System (ADS)

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

Filimonova, L. G.; Trubkin, N. V.; Chugaev, A. V.

2014-05-01

267

An Experimental Study of Lithium Isotope Partitioning Among Quartz, Muscovite, and Fluid  

NASA Astrophysics Data System (ADS)

Preliminary results from an experimental study suggest that lithium isotopes may serve as an indicator of magmatic hydrothermal processes in felsic environments, such as granitic pegmatites and porphyry-type ore deposits. The experiments were carried out with natural (pegmatitic) specimens of quartz and muscovite and with a chloride-bearing aqueous fluid at 400-500° C and 50-100 MPa. Lithium was introduced into the experimental charges through the fluid, which also contains KCl and HCl (K/Li/H = 100/10/1) and is 1M in total chloride. Two other phases (K-feldspar and phlogopite) were included in the charges to permit coupled substitutions by Li + Al and by Li + Mg into Qz and Ms. In contrast with experiments in other isotope systems (eg., O), Li partitioning experiments require allowance for coupled substitutions because some crystallographic sites only become available to Li through coupled substitutions and because the chemical potentials of components necessary for coupled substitutions must be fixed to define fully the thermodynamic conditions of Li partitioning. In two of the experiments a 6Li spike was used to prepare the fluid to magnify the shifts in Li isotopic compositions among run products. The experiments were conducted for 15-60 days under argon pressure with Pt capsules, which were loaded into Inconel 625 cold seal vessels. The experimental design permits simultaneous determination of isotopic fractionation and elemental partitioning by Li among quartz, muscovite and the fluid. Lithium isotopic compositions were determined by thermal ionization mass spectrometry with a triple-filament technique, in which samples are evaporated from side filaments as a phosphate and Li ions are measured directly by the peak-jumping method. Replicate analyses and duplicate experiments indicate reproduceability within approximately +/-1-2‰ . Li concentrations were determined by isotope dilution. For the 500° C runs, the preliminary results provide some indications that equilibrium was approached, such as lack of variance with run duration or with approach from higher as compared with lower temperature. The preliminary results, particularly those from the spiked runs, suggest that quartz and muscovite are susceptible to appreciable changes in Li isotopic composition within short times through diffusion by interaction with a Li-bearing fluid at 500° C. At that temperature, the quartz run products were enriched in 7Li by approximately 9‰ compared with the fluid run products but were depleted in 7Li by approximately 10‰ compared with the muscovite run products. The results also suggest that the Li isotopic composition of the two minerals is likely influenced by temperature, though not measurably by pressure. The results may provide a way to model the Li isotopic composition of hydrothermal fluids that have interacted with felsic rocks. For example, if the quartz starting specimen used in the experiments were assumed hypothetically to have crystallized in a pegmatite body that interacted with a Li-bearing fluid at 500° C, the Li isotopic composition of the starting specimen (? 7Li = +28) would imply a model ? 7Li value of +19 for the fluid (? Quartz-Fluid = 9).

Lynton, S. J.; Walker, R. J.; Candela, P. A.

2002-05-01

268

Hydrothermal alteration of a rhyolitic hyaloclastite from Ponza Island, Italy  

NASA Astrophysics Data System (ADS)

A rhyolitic hyaloclastite from Ponza island, Italy, has been hydrothermally altered producing four distinct alteration zones based on XRD and field textures: (1) non-pervasive argillic zone; (2) propylitic zone; (3) silicic zone; and (4) sericitic zone. The unaltered hyaloclastite is a volcanic breccia with clasts of vesiculated obsidian in a matrix of predominantly pumice lapilli. Incomplete alteration of the hyaloclastite resulted in the non pervasive argillic zone, characterized by smectite and disordered opal-CT. Obsidian clasts, some pumice lapilli, and pyrogenic plagioclase and biotite are unaltered. Smectite has an irregular flakey morphology, although euhedral particles are occasionally observed. The propylitic zone is characterized by mixed-layer illite/smectite (I/S) with 10 to 85% illite (I), mordenite, opal-C and authigenic K-feldspar (akspar). The matrix of the hyaloclastite is completely altered and obsidian clasts are silicified; however, plagioclase and biotite phenocrysts remain unaltered. Flakey I/S replaces pumice, and mordenite, akspar and silica line and fill pores. I/S particles are composed predominantly of subequant plates and euhedral laths. The silicic zone is characterized by highly illitic I/S with ? 90% I, quartz, akspar and occasional albite. In this zone the matrix and clasts are completely altered, and pyrogenic plagioclase shows significant alteration. Illitic I/S has a euhedral lath-like morphology. In the sericitic zone the hyaloclastite altered primarily to illitic I/S with ? 66% I, quartz, and minor akspar and pyrite. Clay minerals completely replace pyrogenic feldspars and little evidence remains of the original hyaloclastite texture. Unlike other zones, illitic I/S is fibrous and pure illite samples are composed of euhedral laths and hexagonal plates. The temperatures of hydrothermal alteration likely ranged from 30 to 90 °C for the argillic zone, from 110 to 160 °C for the propylitic zone, from 160 to 270 °C for the silicic zone, and were possibly as high as 300 °C for the sericitic zone. The four zones occur as linear bands that increase in intensity north of the bentonite mine at Cala dell'Acqua. The alteration zones have two orientations and may be structurally controlled by E-W- and NE-SW-trending faulting which is consistent with the dominant structural trends of the Pontine archipelago. Finally, hydrothermal alteration most likely involved seawater based on the geologic evolution of Ponza.

Ylagan, Robert F.; Altaner, Stephen P.; Pozzuoli, Antonio

1996-12-01

269

gr veins gr + x Boom House Group  

E-print Network

outcrop (darkened) gravel road Fault Strike and Dip16 RipogenusFm Ordovician and Older Silurian - Early Devonian Early Devonian Conodont fossil locality Line of section quartz diorite dike Photo site Katahdin

Kidd, William S. F.

270

Calorimetric thermobarometry of experimentally shocked quartz  

NASA Technical Reports Server (NTRS)

Structural damage in experimentally shock-metamorphosed, granular quartz is quantitatively measurable by differential scanning calorimetry (DSC). Shock-induced loss of crystallinity is witnessed by disappearance of the alpha/beta phase transformation and evolution of a broad endoenthalpic strain peak at 650-900 K. The strain-energy peak grows rapidly at less than 10 GPa but declines with increasing shock pressure; it approaches zero at 32 GPa where vitrification is extensive. Effects of grain size and post-shock thermal history must be better understood before calorimetric thermobarometry of naturally shocked samples becomes possible.

Ocker, Katherine D.; Gooding, James L.; Hoerz, Friedrich

1994-01-01

271

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

272

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

273

Investigation of gold-bearing veins using magnetics and TEM  

NASA Astrophysics Data System (ADS)

Gold-bearing fractures have been mined at Charters Towers, Queensland for a century. The ore occurs in quartz-sulfide veins hosted in granitoids. The gold is found in lenses within the veins. The purpose of our work was to determine if geophysical methods could be used to identify and delineate known lode-bearing veins. The study site is around the Warrior Mine immediately south of the town. Two structures are being mined at 100-300 m depth: Warrior and Sons of Freedom. While IP is typically used to locate disseminated sulfides, we used a different approach: we integrated airborne magnetic data with ground TEM data to map the geometries of the gold-bearing fracture zones. TEM is advantageous because it does not involve injection of current into the ground with the uncertainty of current flow patterns in such resistive, fractured rocks. Fixed loop TEM surveying was utilized as this approach is much faster to perform than moving loop surveys. Although TEM is commonly used for mapping layered structures and strong conductors, it is much less used for detecting weak conductors, such as those found in gold exploration, contaminant plumes, or geotechnical applications. Here the fracture zones are highly weathered and wet thus producing weak conductors. Upon mapping the vertical derivative of the RTP magnetic data, many linear anomalies were noted, including over both mined structures. These anomalies all indicate negative susceptibility, as would be expected because the structures are depleted in magnetite with respect to the granitoids. Modeling of the RTP total field and derivatives confirms a negative susceptibility. The RTP data indicate the approximate dip, which agrees with known information. Depth resolution is limited in standard 3D inversions, which utilize orthogonal grids with the normal axis in the vertical direction. In this study, we use a dipping grid which strikes and dips according to known information, and have obtained good results. TEM surveying at the Warrior site presents challenges as there is an operating mine and many other man-made features. The TEM surveys were carefully planned to minimize their impact on the response. Modeling of the TEM data indicates that the structures which include the mineralized veins are weakly conductive and are actually composed of multiple structures in close proximity. There is a strong correlation between the TEM structural interpretation and the magnetic highs, not only at the mined structures, but also over the three new structures, which are to be studied in future exploration plans including borehole TEM. The EM models were converted to magnetic models with thicknesses of 5 m and susceptibilities between -0.1 and -0.05 (SI), and the simulated magnetic response was in good agreement with the measured data. Interestingly, the rather large negative susceptibilities indicate a greater volume than can be explained by the veins alone. It is expected that this approach will be used to find potential lode-bearing structures in the Charters Towers goldfield. Areas of interest can be first identified in the magnetic data based on the RTP vertical derivative, and then TEM will be performed at these sites. We have demonstrated that, through careful modeling, TEM can be used to understand the geometry of weak conductors.

Davis, L.; Groom, R.

2012-12-01

274

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

275

MAPping Out Arteries and Veins  

NSDL National Science Digital Library

Growing evidence suggests that a genetic program specifies the identity of arteries and veins before the onset of circulation. A signaling cascade involving sonic hedgehog (Shh), vascular endothelial growth factor (VEGF), the VEGF receptor 2 (VEGFR2), homeobox proteins Foxc1 and Foxc2, the Notch receptor, and the downstream transcription factor gridlock is required for expression of arterial markers, whereas only a single transcription factor, COUP-TFII (chicken ovalbumin upstream promoter–transcription factor II), has previously been implicated in maintaining venous fate. Recent work has now implicated two competing pathways downstream of VEGFR2 in arterial versus venous specification: Activation of the phospholipase C–γ (PLC-γ)–mitogen-activated protein kinase (MAPK) pathway acts in arterial specification, whereas the phosphoinositide 3-kinase (PI3K)–Akt pathway acts to allow a venous fate by inhibition of the PLC-γ–MAPK pathway. Here, we review this work and discuss how activation of the MAPK signaling cascade could stimulate an arterial fate.

Ryan E. Lamont (Canada;University of Calgary, Calgary AB REV); Sarah Childs (Canada;University of Calgary, Calgary AB REV)

2006-10-03

276

ESR dating of submarine hydrothermal activities using barite in sulfide deposition  

NASA Astrophysics Data System (ADS)

The temporal change of submarine hydrothermal activities has been an important issue in the aspect of the evolution of hydrothermal systems which is related with ore formation (Urabe, 1995) and biological systems sustained by the chemical species arising from hydrothermal activities (Macdonald et al., 1980). Determining the ages of the hydrothermal deposit will provide essential information on such studies. Dating methods using disequilibrium between radioisotopes such as U-Th method (e.g. You and Bickle, 1998), 226}Ra-{210Pb and 228}Ra-{228Th method (e.g. Noguchi et al., 2011) have been applied to date submarine hydrothermal deposits. ESR (electron spin resonance) dating method is commonly applied to fossil teeth, shells, and quartz of Quaternay period where the natural accumulated dose is obtained from the intensities of the ESR signals which are created by natural radiation. The natural dose is divided by the dose rate to the mineral/sample to deduce the age. Okumura et al., (2010) made the first practical application of ESR (electron spin resonance) dating technique to a sample of submarine hydrothermal barite (BaSO4) to obtain preliminary ages, where Kasuya et al. (1991) first pointed out that barite can be used for ESR dating. Knowing that ESR dating of barite is promising, in this paper, we will present how we have investigated each factor that contributes ESR dating of barite in submarine hydrothermal sulfide deposition. (1) The best ESR condition for measuring the SO3- signal in barite is with the microwave power of 1mW and modulation amplitude of 0.1mT. (2) As results of heating experiments, the signal was found to be stable for the dating age range of several thousands. (3) 226Ra replacing Ba in barite is the source of the radiation. The amount of radioactive elements in sulfide mineral surrounding barite is negligible. (4) The external radiation from the sea water is negligible even in the submarine hydrothermal area where the radiation level is much higher than usual sea water. (5) The decay of 226Ra has to be considered. (6) Major terms of dose rate are the internal alpha dose rate and the external beta and gamma dose rates. (7) The alpha effectiveness, the ratio of forming the radical by internal alpha particles to by beta and gamma rays, was obtained to be 0.043±0.018. (8) The shape of the chimney sample should be considered for gamma ray dose. Examples of dating results for submarine hydrothermal deposits from South Mariana and Okinawa Trough will be presented.

Toyoda, S.; Fujiwara, T.; Ishibashi, J.; Isono, Y.; Uchida, A.; Takamasa, A.; Nakai, S.

2012-12-01

277

Hydrogen movement into and out of fluid inclusions in quartz: Experimental evidence and geologic implications  

NASA Astrophysics Data System (ADS)

Natural chalcopyrite-bearing fluid inclusions from the Red Mountain, Arizona, porphyry copper prospect have been used to experimentally document the movement of hydrogen into and out of fluid inclusions in quartz. Chalcopyrite daughter minerals in inclusions do not dissolve during heating studies of "as collected" quartz vein material. However, after the samples were held at an elevated (but unknown) hydrogen pressure in a cold-seal-type pressure vessel at 600°C and 2.5 kbar for seven days, chalcopyrite daughter crystals in fluid inclusions dissolve easily and completely during subsequent heating. The presence of hydrogen in the re-equilibrated inclusions was confirmed by both Raman microprobe and quadrupole mass spectrometric analyses of the inclusions. Repeated heating of re-equilibrated inclusions to measure the dissolution temperature of chalcopyrite (Tm Cpy) results in a considerably higher Tm Cpy during each successive run until, eventually, the chalcopyrite no longer dissolves when heated to the upper limit of the heating stage. This behavior is interpreted to indicate that hydrogen which had diffused into inclusions during re-equilibration experiments diffused out of the inclusions during microthermometric analyses. The dissolution of chalcopyrite following re-equilibration and its failure to dissolve before re-equilibration are consistent with proposed solubility models for chalcopyrite in aqueous solutions. The rapid movement of hydrogen into inclusions is also consistent with experimentally determined diffusion rates for hydrogen through quartz. These results reinforce conclusions reached by earlier workers who suggested that the failure of some fluid inclusion daughter minerals to dissolve during heating is a result of hydrogen loss. These results also support earlier workers who have suggested that unexpectedly low ?D values obtained from inclusion fluids were produced by the preferential movement of hydrogen (relative to deuterium) into fluid inclusions. Finally, these results suggest that ƒ o 2 conditions inferred from Raman or other microanalytical data obtained from fluid inclusions may not represent ƒ O 2 conditions present at the time of trapping.

Mavrogenes, J. A.; Bodnar, R. J.

1994-01-01

278

A cervelleite-like mineral and other Ag-Cu-Te-S minerals [Ag 2 CuTeS and (Ag,Cu) 2 TeS] in gold-bearing veins in metamorphic rocks of the Cycladic Blueschist Unit, Kallianou, Evia Island, Greece  

Microsoft Academic Search

A cervelleite-like mineral, two unnamed silver sulfotellurides in the system Ag-Cu-Te-S [Ag2CuTeS, (Ag,Cu)2TeS], Te-rich polybasite and cadmian tetrahedrite occur in gold-bearing quartz veins in metapelites and faults within brecciated\\u000a marbles of the Cycladic Blueschist Unit in the Kallianou area (southern Evia Island, Greece). The quartz veins and faults\\u000a are discordant to syn-metamorphic structures and formed during ductile to brittle deformation

Panagiotis Christos Voudouris; Paul G. Spry; Gregory Aarne Sakellaris; Constantinos Mavrogonatos

2011-01-01

279

Exploiting Quartz to Constrain Pressure-Temperature-time-Deformation Histories in Metamorphic Rocks Through Recent Innovations in Thermobarometry and Geospeedometry  

NASA Astrophysics Data System (ADS)

Despite the abundance of quartz in continental crust, it has only recently been exploited for thermobarometric purposes. We are using trace element content, cathodoluminescence (CL) characteristics, fabric properties, extent of recrystallization, elastic properties and chemical diffusivities of quartz to better understand the pressure-temperature-time-deformation (P - T - t - D) histories of metamorphic rocks. The Ti-in-quartz thermobarometer has significant potential for unveiling important information on the metamorphic history of rocks, since quartz is commonly present in multiple microstructural settings (e.g. matrix, veins, inclusions) and zoning may be present in single crystals that reveal information about the reequilibration, recrystallization and growth histories of quartz. CL imaging provides a qualitative way to obtain such information, and provides a domainal framework for targeted quantitative analyses. We illustrate such analyses with examples from Vermont, India and Greece. A recent study in metapelites from central-eastern Vermont revealed crystals that have low Ti cores (interpreted to be preserved early prograde growth), with mantles that grade to higher Ti, attributed to temperature increase during fabric development and liberation of Si during crenulation cleavage development in the micaceous matrix. Low-Ti overgrowth rims that form sharp boundaries with these graded mantles may be later retrograde overgrowths. Forward modeling the expected volume of quartz present in the rock in P - T space may be implemented to confirm periods of quartz production/precipitation and dissolution. Rocks from the Sutlej Valley (north-west India) have matrix quartz grains with triple junction grain boundaries indicating extensive recovery. CL imaging, however, reveals high Ti ribbons that may be indicative of chemically-preserved paleo-microstructures. At the temperatures and metamorphic rates experienced by these samples, grain boundaries during recovery may not redistribute impurities, but rather behave passively. A recent advance in implementing Raman spectroscopy on quartz inclusions in porphyroblasts facilitates accurate geobarometry for the time of porphyroblast growth. The method requires that elastic parameters of the host and inclusion are determined, but is independent of the composition of these phases. A recent application of this technique to garnets from blueschists in Sifnos, Greece, resulted in P - T paths for garnet growth from 19.5 kbar at 460 ° C to 21.5 kbar at 550 ° C. These results are in good agreement with recent studies attempting to constrain peak metamorphic histories for these rocks through equilibrium assemblage diagrams and trace element thermobarometry. Preliminary Raman work from the Sutlej Valley samples suggests peak pressures of c. 6.3 kbar approaching the Main Central Thrust. It may be advantageous to couple this geobarometer with Ti-in-quartz on inclusions in garnet to elucidate thermobarometric information relative to microstructural context and deformation history. An additional benefit to this technique is that pressure constraints needed for Ti-in-quartz thermobarometry may now be independently constrained and requires no knowledge of stable mineral assemblages, component activities or mixing parameters. Titanium diffusion from host (garnet) to included quartz may also be implemented to obtain geospeedometry information to estimate the duration of metamorphism. The integration of microstructural analysis with these various techniques may allow for a better understanding of the P - T - t - D histories of rocks than previously obtained using conventional techniques.

Ashley, Kyle; Law, Richard; Thomas, Jay; Caddick, Mark; Stahr, Donald, III

2013-04-01

280

Adsorption of B. Subtilis and P. Mendocina Onto Fe-Oxide Coated Quartz and Pure Quartz  

NASA Astrophysics Data System (ADS)

Understanding the controls on bacterial adsorption onto mineral surfaces is crucial in order to model a range of processes, such as contaminant transport, mineral dissolution behavior, and bioremediation techniques. At present, little is known concerning the adsorption behavior of bacteria, even onto some of the most common mineral surfaces present in near-surface environments. In this study, we measured the adsorption of a Gram positive bacterial species (B. subtilis) and a Gram negative species (P. mendocina) onto a quartz sand, and onto an Fe-oxide coated quartz sand, both as functions of time, pH and bacteria:mineral mass ratio. The extent of adsorption was determined by measuring the concentration of free bacteria in the mineral-bacteria systems both before, and after, reaction, using a uv-vis spectrophotometric approach. pH and bacteria:mineral ratio exert strong controls on the extent of bacterial adsorption of both species onto Fe-coated quartz. The extent of adsorption of B. subtilis onto the Fe-coated quartz increases with decreasing pH from close to 0% at pH 10 to a plateau of approximately 80% adsorption between pH 6 and 4. Below pH 4, adsorption of B. subtilis decreases to 50% at pH 2. Adsorption of P. mendocina is similar to that observed for B. subtilis, only it is significantly less extensive under otherwise identical conditions. These adsorption behaviors are in marked contrast to that observed for both species onto the uncoated quartz. There is little to no adsorption of either species onto the uncoated quartz sand over most of the pH range studied. We use a thermodynamic approach to model the adsorption behavior of each species onto the Fe-coated quartz sand, determining equilibrium constants for the dominant adsorption reactions. Our results demonstrate that bacterial adsorption within geologic systems can be strongly dependent on mineralogy, fluid composition, and on the bacterial species present. However, our modeling approach enables the prediction of the extent of adsorption of each bacterial species under a wide range of geologic conditions.

Ams, D.; Fein, J. B.

2002-12-01

281

Shock characterization of quartz phenolic composite  

SciTech Connect

Goal was to obtain dynamic mechanical property data on a quartz phenolic (abbreviated QP) composite. Shock loading and shock release measurements have been conducted using impact techniques utilizing both a light-gas gun and a powder gun at impact pressures up to 20 GPa. The primary diagnostic tool used was a velocity interferometer. The data analysis includes Hugoniot measurements to give both pressure-particle velocity and shock velocity-particle velocity relationships; spall measurements to determine the fracture stress at which the material spells; and attenuation measurements to determine the shock attenuation with material thickness. The QP Hugoniot relationship was found to be significantly different than that of a phenolic without a filler material indicating that the impedance of the QP used in this investigation was higher. The spall strength was measured to be {approximately}0.075 GPa, similar to nonfilled phenolic, which indicated that the presence of quartz fibers was not contributing to the fracture strength. The material was found to attenuate an imposed shock of approximately 6.3 GPa pressure and 0.18 {mu}s to 50% of the initial impact value after a propagation distance of 7mm.

Weirick, L.J.; Chhabildas, L.C.

1994-03-01

282

Insitu Calibration of Quartz Crystal Microbalances  

NASA Technical Reports Server (NTRS)

Computer models that predict the rate at which molecular contamination will deposit on optical surfaces typically use outgassing source terms, measured with quartz crystal microbalances, as a basis for the prediction. The American Society of Testing and Materials, Standard Test Method for Contamination Outgassing Characteristics of Spacecraft Materials (Method E-1559), is probably the best know technique used by the aerospace community to measure the outgassing rates or source terms of materials. A simple method for the insitu calibration of quartz crystal microbalances, based on the heat of enthalphy of Adipic Acid, has been developed and demonstrated by the Marshall Space Flight Center, Environmental Effects Group. The calibration has been demonstrated over a sample temperature range of 25 to 66 degrees Celsius and deposition rates of 7 x 10 (exp -11) grams/cm(sup 2)-s and greater, for several measurement system configurations. This calibration technique is fully compatible with the American Society for Testing and Materials, Method E-1559, as well as other methodology. The calibration requires no modification of outgassing facilities employing an effusion cell and does not degrade the performance or function of typical vacuum systems.

Albyn, Keith; Burns, Dewit

2006-01-01

283

Epithelioid hemangioendothelioma encasing the left brachiocephalic vein  

PubMed Central

Epithelioid hemangioendotheliomas are rare vascular tumors, often arising from medium to large veins in the extremities. Symptoms of these tumors vary depending upon location. Rarely, tumors may arise in chest and involve large vessels in the mediastinum. We present a case of a 17-year-old male presenting with compressive symptoms of the left upper extremity who was found to have a large epithelioid hemangioendothelioma encasing the left brachiocephalic vein. PMID:24898409

Long, Kristin; Skinner, Sean; Martin, Jeremiah

2014-01-01

284

Gross anatomy of primary varicose veins observed in endoscopic surgery.  

PubMed

The gross anatomy of varicose veins is one of the most important factors in the study of varicosity. Because of wide variations in the extent of involvement and degree of severity of varicose veins, it is difficult to obtain live and intact specimens of varicose veins. With good illumination and magnified monitor viewing, the varicositic main channel, its tributaries, and the incompetent perforating veins can be dissected and visualized clearly during endoscopic surgery. Thus, the whole range of varicosities can be observed directly in situ. Characteristic features of the varicosities of 350 limbs have been recorded by video and photographs for study and classification. These features include: 1) poor contractility of varicose veins; 2) dilated and tortuous changes of varicose veins; 3) saccular or lateral bulging deformities of vein walls, or both; 4) uniformly dilated and tortuous deformities of a long vein; 5) varicositic changes of the accessory vein; 6) anatomic abnormalities of varicose veins, such as supernumerary tributaries, varicositic clusters, and a crowded relationship among the long saphenous vein, perforating vein and tributaries; 7) various conditions of the perforating veins; and 8) the close relationship among the long saphenous vein, perforating veins, and the saphenous nerve. These data provide valuable information for the study and management of primary varicose veins. PMID:12461435

Lin, Sin-Daw; Chang, Kao-Ping; Yang, Yu-Li; Lee, Su-Shin; Lin, Tsai-Ming; Tsai, Chih-Cheng; Lai, Chung-Sheng

2002-12-01

285

Valences and site characteristics of iron in radioactive magmatic veins (Egypt): A Mössbauer and chemical study  

NASA Astrophysics Data System (ADS)

Radioactive veins in shear zones of the El-Seboah granite in Egypt with anomalous concentrations of Nd, Ce, Zr, Y, Nb, Sm, Th and U were studied by petrographic microscopy, x-ray diffraction, 57Fe Mössbauer and wet chemical methods. The veins are composed essentially of quartz, aegirine-augite and minor K-feldspar ± ?-iron oxide (hematite) ± ?-iron oxide hydroxide (goethite). They likely represent late-stage felsic melt that was quenched and devitrified at high temperature to yield crystals and crystallites, and then subjected to low temperature alteration during which most of the K feldspar transformed to kaolinite and opal. Mössbauer parameters of the samples indicate that the existing Fe-bearing minerals are primary, with appreciable ordering in the Fe sites. The bulk-sample iron (?Fe) contents are extremely high (12.3-22.4%). The extent of oxidation of the Fe has been found to be 100% by Mössbauer spectroscopy and 95.36-99.69% by a chemical method. These conditions of Fe enrichment and strong oxidation suggest that the veins are extreme differentiates of granite magmas where high states of oxygen fugacity prevailed.

Hassan, Kamaledin M.

2010-01-01

286

Water transport during metamorphic vein formation: the role of reaction-induced pressure buildup during serpentinization  

NASA Astrophysics Data System (ADS)

At slow-spreading ridges, the extension is accommodated both by an exhumation of mantle rocks and a magmatic input. The heat released during the crystallization of the magmas is evacuated through the hydrothermal circulation transporting high-temperature fluids up to mantle rocks which can be hydrated through a serpentinization reaction. At the millimetre scale, water transport is also accommodated by advection in the highly permeable fracture network typically found in serpentinized peridotites. This high permeability is the consequence of fracturing processes related to lithospheric scale deformation, thermal contraction or a pressure build-up associated with the positive volume increase occurring during the reaction. If the relationship between pressure increase and fracturing has been studied in details, the impact of this pressure increases on the fluid flow is still unclear. Therefore, we used existing data on the texture and composition of serpentine veins (mm to µm scale) found in peridotites to identify the physical processes involved in the transport of water during the reaction. A finite difference model was then developed to investigate the couplings between pressure increase and fluid flow at the scale of the vein. This model will allow us to probe the influence on the reaction of parameters such as the kinetics of the reaction, the geometry and the texture of the veins, the amount of the volume increase, or the external forces.

Malvoisin, Benjamin; Podladchikov, Yuri

2014-05-01

287

Composition and timing of carbonate vein precipitation within the igneous basement of the Early Cretaceous Shatsky Rise, NW Pacific  

NASA Astrophysics Data System (ADS)

Shatsky Rise is an Early Cretaceous large igneous province located in the NW Pacific ca. 1500 km east of Japan and is the third-largest oceanic plateau on Earth (after Ontong Java and Kerguelen). Numerous calcium carbonate veins were recovered from the igneous basement of Shatsky Rise during Integrated Ocean Drilling Program Expedition 324 (Sager et al., 2010). The chemical (Sr/Ca, Mg/Ca) and isotopic (87Sr/86Sr, 143Nd/144Nd, ?18O, ?13C) compositions of these veins were determined to constrain the timing of vein formation and to provide valuable data for the reconstruction of past seawater composition. A dominant control of seawater chemistry on calcite composition is evident for most investigated vein samples with varying compositional contribution from the basaltic basement. The Sr/Ca ratio of the vein calcite is positively correlated with Mg/Ca and with ?18O, indicating warmer/colder precipitation temperatures with decreasing/increasing Sr/Ca (and Mg/Ca) ratios, respectively. Distinctly higher formation temperatures (as inferred from oxygen isotope ratios) indicative of hydrothermal vein formation are only observed at one site (Site U1350, drilled into the central part of Shatsky Rise). The highest 87Sr/86Sr ratios (least basement influence) of vein samples at each drill site range form 0.707264 to 0.707550 and are believed to best reflect contemporaneous Early Cretaceous seawater composition. In principle, age information can be deduced by correlating these ratios with the global seawater Sr isotope evolution. Since the Sr isotopic composition of seawater has fluctuated three times between the early and mid Cretaceous (McArthur et al., 2001) no unambiguous precipitation ages can be constrained by this method and vein precipitation could have occurred at any time between ˜80 and 140 Ma. However, based on combined chemical and isotopic data and correlations of vein composition with formation depth and inferred temperature, we argue for a rather early precipitation of the veins shortly after basement formation at each respective drill site. References: Sager, W.W., Sano, T., Geldmacher, J. and the IODP Expedition 324 Scientists (2010) Testing plume and plate models of ocean plateau formation at Shatsky Rise, northwest Pacific Ocean. Proceedings IODP, 324, Tokyo, doi:10.2204/iodp.pr.324.2010. McArthur, J.M., Howarth, R.J., Bailey, T.R. (2001) Strontium isotope stratigraphy: LOWESS Version 3. Best-fit line to the marine Sr-isotope curve for 0 to 509 Ma and accompanying look-up table for deriving numerical age. Journal of Geology 109, 155-169.

Geldmacher, J.; Li, S.; Hauff, F. F.; Garbe-Schoenberg, C.; Yu, S.; Zhao, S.; Rausch, S.

2013-12-01

288

Transport and Distribution of Water in Quartz Aggregates  

Microsoft Academic Search

Water is known to play a critical role in the deformation of silicates, especially quartz aggregates. This study was conducted to investigate the distribution and transport rates of water and water-related species in natural quartz aggregates at temperatures that span the brittle-ductile transition. Starting materials included a fine-grained (1.2 micron) novaculite and a naturally deformed quartz arenite (Tuscarora Sandstone). Samples

J. R. Farver

2006-01-01

289

Mineral resource of the month: cultured quartz crystal  

USGS Publications Warehouse

The article presents information on cultured quartz crystals, a mineral used in mobile phones, computers, clocks and other devices controlled by digital circuits. Cultured quartz, which is synthetically produced in large pressurized vessels known as autoclaves, is useful in electronic circuits for precise filtration, frequency control and timing for consumer and military use. Several ingredients are used in producing cultured quartz, including seed crystals, lascas, a solution of sodium hydroxide or sodium carbonate, lithium salts and deionized water.

2008-01-01

290

Veins improve fracture toughness of insect wings.  

PubMed

During the lifetime of a flying insect, its wings are subjected to mechanical forces and deformations for millions of cycles. Defects in the micrometre thin membranes or veins may reduce the insect's flight performance. How do insects prevent crack related material failure in their wings and what role does the characteristic vein pattern play? Fracture toughness is a parameter, which characterises a material's resistance to crack propagation. Our results show that, compared to other body parts, the hind wing membrane of the migratory locust S. gregaria itself is not exceptionally tough (1.04±0.25 MPa?m). However, the cross veins increase the wing's toughness by 50% by acting as barriers to crack propagation. Using fracture mechanics, we show that the morphological spacing of most wing veins matches the critical crack length of the material (1132 µm). This finding directly demonstrates how the biomechanical properties and the morphology of locust wings are functionally correlated in locusts, providing a mechanically 'optimal' solution with high toughness and low weight. The vein pattern found in insect wings thus might inspire the design of more durable and lightweight artificial 'venous' wings for micro-air-vehicles. Using the vein spacing as indicator, our approach might also provide a basis to estimate the wing properties of endangered or extinct insect species. PMID:22927966

Dirks, Jan-Henning; Taylor, David

2012-01-01

291

Note: Sensitivity multiplication module for quartz crystal microbalance applications  

NASA Astrophysics Data System (ADS)

In this Note, a novel sensitivity multiplication module was added to classical quartz crystal microbalance (QCM). The purpose is to increase QCM frequency shift without changing nominal frequency of the quartz crystal resonator or nominal frequency value delivered to the frequency counter. Allan deviance measurement confirms that the multiplication of the frequency shift is limited by the quartz crystal loads with direct effect in quartz crystal quality factor and oscillator stability. An experimental implementation of this new sensitivity multiplication module that can increase up to six times the frequency shift of the QCM was experimentally investigated using different load conditions.

Burda, Ioan; Silaghi, Andreea; Tunyagi, Arthur; Simon, Simion; Popescu, Octavian

2014-02-01

292

Scattering Removal for Finger-Vein Image Restoration  

PubMed Central

Finger-vein recognition has received increased attention recently. However, the finger-vein images are always captured in poor quality. This certainly makes finger-vein feature representation unreliable, and further impairs the accuracy of finger-vein recognition. In this paper, we first give an analysis of the intrinsic factors causing finger-vein image degradation, and then propose a simple but effective image restoration method based on scattering removal. To give a proper description of finger-vein image degradation, a biological optical model (BOM) specific to finger-vein imaging is proposed according to the principle of light propagation in biological tissues. Based on BOM, the light scattering component is sensibly estimated and properly removed for finger-vein image restoration. Finally, experimental results demonstrate that the proposed method is powerful in enhancing the finger-vein image contrast and in improving the finger-vein image matching accuracy. PMID:22737028

Yang, Jinfeng; Zhang, Ben; Shi, Yihua

2012-01-01

293

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

2008-09-01

294

Characteristics, extent and origin of hydrothermal alteration at Mount Rainier Volcano, Cascades Arc, USA: Implications for debris-flow hazards and mineral deposits  

USGS Publications Warehouse

Hydrothermal alteration at Mount Rainier waxed and waned over the 500,000-year episodic growth of the edifice. Hydrothermal minerals and their stable-isotope compositions in samples collected from outcrop and as clasts from Holocene debris-flow deposits identify three distinct hypogene argillic/advanced argillic hydrothermal environments: magmatic-hydrothermal, steam-heated, and magmatic steam (fumarolic), with minor superimposed supergene alteration. The 3.8??km3 Osceola Mudflow (5600??y BP) and coeval phreatomagmatic F tephra contain the highest temperature and most deeply formed hydrothermal minerals. Relatively deeply formed magmatic-hydrothermal alteration minerals and associations in clasts include quartz (residual silica), quartz-alunite, quartz-topaz, quartz-pyrophyllite, quartz-dickite/kaolinite, and quartz-illite (all with pyrite). Clasts of smectite-pyrite and steam-heated opal-alunite-kaolinite are also common in the Osceola Mudflow. In contrast, the Paradise lahar, formed by collapse of the summit or near-summit of the edifice at about the same time, contains only smectite-pyrite and near-surface steam-heated and fumarolic alteration minerals. Younger debris-flow deposits on the west side of the volcano (Round Pass and distal Electron Mudflows) contain only low-temperature smectite-pyrite assemblages, whereas the proximal Electron Mudflow and a < 100??y BP rock avalanche on Tahoma Glacier also contain magmatic-hydrothermal alteration minerals that are exposed in the avalanche headwall of Sunset Amphitheater, reflecting progressive incision into deeper near-conduit alteration products that formed at higher temperatures. The pre-Osceola Mudflow alteration geometry is inferred to have consisted of a narrow feeder zone of intense magmatic-hydrothermal alteration limited to near the conduit of the volcano, which graded outward to more widely distributed, but weak, smectite-pyrite alteration within 1??km of the edifice axis, developed chiefly in porous breccias. The edifice was capped by a steam-heated alteration zone, most of which resulted from condensation of fumarolic vapor and oxidation of H2S in the unsaturated zone above the water table. Weakly developed smectite-pyrite alteration extended into the west and east flanks of the edifice, spatially associated with dikes that are localized in those sectors; other edifice flanks lack dikes and associated alteration. The Osceola collapse removed most of the altered core and upper east flank of the volcano, but intensely altered rocks remain on the uppermost west flank. Major conclusions of this study are that: (1) Hydrothermal-mineral assemblages and distributions at Mount Rainier can be understood in the framework of hydrothermal processes and environments developed from studies of ore deposits formed in analogous settings. (2) Frequent eruptions supplied sufficient hot magmatic fluid to alter the upper interior of the volcano hydrothermally, despite the consistently deep (??? 8??km) magma reservoir which may have precluded formation of economic mineral deposits within or at shallow depths beneath Mount Rainier. The absence of indicator equilibrium alteration-mineral assemblages in the debris flows that effectively expose the volcano to a depth of 1-1.5??km also suggests a low potential for significant high-sulfidation epithermal or porphyry-type mineral deposits at depth. (3) Despite the long and complex history of the volcano, intensely altered collapse-prone rocks were spatially restricted to near the volcano's conduit system and summit, and short distances onto the upper east and west flanks, due to the necessary supply of reactive components carried by ascending magmatic fluids. (4) Intensely altered rocks were removed from the summit, east flank, and edifice interior by the Osceola collapse, but remain on the upper west flank in the Sunset Amphitheater area and present a continuing collapse hazard. (5) Visually conspicuous rocks on the lower east and mid-to-lower

John, D.A.; Sisson, T.W.; Breit, G.N.; Rye, R.O.; Vallance, J.W.

2008-01-01

295

Characteristics, extent and origin of hydrothermal alteration at Mount Rainier Volcano, Cascades Arc, USA: Implications for debris-flow hazards and mineral deposits  

NASA Astrophysics Data System (ADS)

Hydrothermal alteration at Mount Rainier waxed and waned over the 500,000-year episodic growth of the edifice. Hydrothermal minerals and their stable-isotope compositions in samples collected from outcrop and as clasts from Holocene debris-flow deposits identify three distinct hypogene argillic/advanced argillic hydrothermal environments: magmatic-hydrothermal, steam-heated, and magmatic steam (fumarolic), with minor superimposed supergene alteration. The 3.8 km 3 Osceola Mudflow (5600 y BP) and coeval phreatomagmatic F tephra contain the highest temperature and most deeply formed hydrothermal minerals. Relatively deeply formed magmatic-hydrothermal alteration minerals and associations in clasts include quartz (residual silica), quartz-alunite, quartz-topaz, quartz-pyrophyllite, quartz-dickite/kaolinite, and quartz-illite (all with pyrite). Clasts of smectite-pyrite and steam-heated opal-alunite-kaolinite are also common in the Osceola Mudflow. In contrast, the Paradise lahar, formed by collapse of the summit or near-summit of the edifice at about the same time, contains only smectite-pyrite and near-surface steam-heated and fumarolic alteration minerals. Younger debris-flow deposits on the west side of the volcano (Round Pass and distal Electron Mudflows) contain only low-temperature smectite-pyrite assemblages, whereas the proximal Electron Mudflow and a < 100 y BP rock avalanche on Tahoma Glacier also contain magmatic-hydrothermal alteration minerals that are exposed in the avalanche headwall of Sunset Amphitheater, reflecting progressive incision into deeper near-conduit alteration products that formed at higher temperatures. The pre-Osceola Mudflow alteration geometry is inferred to have consisted of a narrow feeder zone of intense magmatic-hydrothermal alteration limited to near the conduit of the volcano, which graded outward to more widely distributed, but weak, smectite-pyrite alteration within 1 km of the edifice axis, developed chiefly in porous breccias. The edifice was capped by a steam-heated alteration zone, most of which resulted from condensation of fumarolic vapor and oxidation of H 2S in the unsaturated zone above the water table. Weakly developed smectite-pyrite alteration extended into the west and east flanks of the edifice, spatially associated with dikes that are localized in those sectors; other edifice flanks lack dikes and associated alteration. The Osceola collapse removed most of the altered core and upper east flank of the volcano, but intensely altered rocks remain on the uppermost west flank. Major conclusions of this study are that: (1) Hydrothermal-mineral assemblages and distributions at Mount Rainier can be understood in the framework of hydrothermal processes and environments developed from studies of ore deposits formed in analogous settings. (2) Frequent eruptions supplied sufficient hot magmatic fluid to alter the upper interior of the volcano hydrothermally, despite the consistently deep (? 8 km) magma reservoir which may have precluded formation of economic mineral deposits within or at shallow depths beneath Mount Rainier. The absence of indicator equilibrium alteration-mineral assemblages in the debris flows that effectively expose the volcano to a depth of 1-1.5 km also suggests a low potential for significant high-sulfidation epithermal or porphyry-type mineral deposits at depth. (3) Despite the long and complex history of the volcano, intensely altered collapse-prone rocks were spatially restricted to near the volcano's conduit system and summit, and short distances onto the upper east and west flanks, due to the necessary supply of reactive components carried by ascending magmatic fluids. (4) Intensely altered rocks were removed from the summit, east flank, and edifice interior by the Osceola collapse, but remain on the upper west flank in the Sunset Amphitheater area and present a continuing collapse hazard. (5) Visually conspicuous rocks on the lower east and mid-to-lower west flanks are not intensely altered and probably have not significantly weakened the rock, an

John, David A.; Sisson, Thomas W.; Breit, George N.; Rye, Robert O.; Vallance, James W.

2008-08-01

296

Outcome of patients with pre-existing portal vein thrombosis undergoing arterialization of the portal vein during liver transplantation  

Microsoft Academic Search

Arterialization of the portal vein is being propagated as a technical possibility in liver transplant recipients with pre-existing portal vein thrombosis. In our own small series, portal vein arterialization (PVA) was carried out in four patients undergoing orthotopic liver transplantation. In three of these cases, the portal vein was anastomosed to the aorta via an interposed iliac artery, and in

Rudolf Ott; Cathrin Böhner; Susanna Müller; Thomas Aigner; Michaela Bussenius-Kammerer; Suleyman Yedibela; Hermann Kissler; Werner Hohenberger; Thomas Reck; Volker Müller

2003-01-01

297

Minor vein structure and sugar transport in Arabidopsis thaliana  

Microsoft Academic Search

.   Leaf and minor vein structure were studied in Arabidopsis thaliana (L.) Heynh. to gain insight into the mechanism(s) of phloem loading. Vein density (length of veins per unit leaf area) is\\u000a extremely low. Almost all veins are intimately associated with the mesophyll and are probably involved in loading. In transverse\\u000a sections of veins there are, on average, two companion

Edith Haritatos; Richard Medville; Robert Turgeon

2000-01-01

298

Cephalic Vein Transposition versus Vein Grafts for Venous Outflow in Free-flap Breast Reconstruction  

PubMed Central

Introduction: When recipient veins for free-flap breast reconstruction are unavailable or inadequate, vein grafts or cephalic vein transposition (CVT) an option to provide alternate venous outflow. There are no comparative data to elucidate the indications and outcomes for each. We hypothesize that the CVT is as reliable as vein grafts when indicated. Methods: All consecutive cases where a CVT or venous vein grafts were used for free-flap breast reconstruction between 2000 and 2012 were reviewed. Patient demographics, operative notes, indications, and flap survival were compared between the 2 groups. Results: Ten patients underwent a CVT and 38 patients received a vein graft for insufficient venous outflow. There were no differences in average age, body mass index, or comorbid conditions between the groups. Similarly, there was no difference in previous radiotherapy, timing of reconstruction, or side of reconstruction. A CVT was used for salvage following venous thrombosis in 7 patients (70.0%) and for primary venous outflow in the remaining patients due to inability to use the internal mammary vein. Vein grafts were performed primarily in 31 patients, 22 for augmenting venous drainage (supercharge), 9 for the dominant venous outflow, and 7 for salvage of a thrombosis. One patient in each group suffered a complete loss of the free flap (cephalic: 10.0% vs vein graft: 14.3%, P = 0.36). Conclusions: The CVT is a reliable alternate venous outflow that can be used as a primary recipient vein or as a salvage option following venous thrombosis. Surgeons should consider a CVT when primary recipient veins are compromised or unavailable. PMID:25289334

Chang, Edward I.; Fearmonti, Regina M.; Chang, David W.

2014-01-01

299

Distribution, microfabric, and geochemical characteristics of siliceous rocks in central orogenic belt, China: implications for a hydrothermal sedimentation model.  

PubMed

Marine siliceous rocks are widely distributed in the central orogenic belt (COB) of China and have a close connection to the geological evolution and metallogenesis. They display periodic distributions from Mesoproterozoic to Jurassic with positive peaks in the Mesoproterozoic, Cambrian--Ordovician, and Carboniferous--Permian and their deposition is enhanced by the tensional geological settings. The compressional regimes during the Jinning, Caledonian, Hercynian, Indosinian, and Yanshanian orogenies resulted in sudden descent in their distribution. The siliceous rocks of the Bafangshan-Erlihe ore deposit include authigenic quartz, syn-depositional metal sulphides, and scattered carbonate minerals. Their SiO2 content (71.08-95.30%), Ba (42.45-503.0 ppm), and ?REE (3.28-19.75 ppm) suggest a hydrothermal sedimentation origin. As evidenced by the Al/(Al + Fe + Mn), Sc/Th, (La/Yb) N, and (La/Ce) N ratios and ?Ce values, the studied siliceous rocks were deposited in a marginal sea basin of a limited ocean. We suggest that the Bafangshan-Erlihe area experienced high- and low-temperature stages of hydrothermal activities. The hydrothermal sediments of the former stage include metal sulphides and silica, while the latter was mainly composed of silica. Despite the hydrothermal sedimentation of the siliceous rocks, minor terrigenous input, magmatism, and biological activity partly contributed to geochemical features deviating from the typical hydrothermal characteristics. PMID:25140349

Li, Hongzhong; Zhai, Mingguo; Zhang, Lianchang; Gao, Le; Yang, Zhijun; Zhou, Yongzhang; He, Junguo; Liang, Jin; Zhou, Liuyu; Voudouris, Panagiotis Ch

2014-01-01

300

Terahertz quartz enhanced photo-acoustic sensor  

NASA Astrophysics Data System (ADS)

A quartz enhanced photo-acoustic sensor employing a single-mode quantum cascade laser emitting at 3.93 Terahertz (THz) is reported. A custom tuning fork with a 1 mm spatial separation between the prongs allows the focusing of the THz laser beam between them, while preventing the prongs illumination. A methanol transition with line-strength of 4.28 × 10-21 cm has been selected as target spectroscopic line. At a laser optical power of ˜ 40 ?W, we reach a sensitivity of 7 parts per million in 4s integration time, corresponding to a 1? normalized noise-equivalent absorption of 2 × 10-10 cm-1W/Hz½.

Borri, S.; Patimisco, P.; Sampaolo, A.; Beere, H. E.; Ritchie, D. A.; Vitiello, M. S.; Scamarcio, G.; Spagnolo, V.

2013-07-01

301

Deep vein thrombosis: a clinical review  

PubMed Central

Background: Deep vein thrombosis (DVT) is the formation of blood clots (thrombi) in the deep veins. It commonly affects the deep leg veins (such as the calf veins, femoral vein, or popliteal vein) or the deep veins of the pelvis. It is a potentially dangerous condition that can lead to preventable morbidity and mortality. Aim: To present an update on the causes and management of DVT. Methods: A review of publications obtained from Medline search, medical libraries, and Google. Results: DVT affects 0.1% of persons per year. It is predominantly a disease of the elderly and has a slight male preponderance. The approach to making a diagnosis currently involves an algorithm combining pretest probability, D-dimer testing, and compression ultrasonography. This will guide further investigations if necessary. Prophylaxis is both mechanical and pharmacological. The goals of treatment are to prevent extension of thrombi, pulmonary embolism, recurrence of thrombi, and the development of complications such as pulmonary hypertension and post-thrombotic syndrome. Conclusion: DVT is a potentially dangerous condition with a myriad of risk factors. Prophylaxis is very important and can be mechanical and pharmacological. The mainstay of treatment is anticoagulant therapy. Low-molecular-weight heparin, unfractionated heparin, and vitamin K antagonists have been the treatment of choice. Currently anticoagulants specifically targeting components of the common pathway have been recommended for prophylaxis. These include fondaparinux, a selective indirect factor Xa inhibitor and the new oral selective direct thrombin inhibitors (dabigatran) and selective factor Xa inhibitors (rivaroxaban and apixaban). Others are currently undergoing trials. Thrombolytics and vena caval filters are very rarely indicated in special circumstances. PMID:22287864

Kesieme, Emeka; Kesieme, Chinenye; Jebbin, Nze; Irekpita, Eshiobo; Dongo, Andrew

2011-01-01

302

Fluid inclusion analysis of chert veins from the Mendon Formation, Barberton Greenstone Belt, South Africa  

NASA Astrophysics Data System (ADS)

Strongly silicified volcanic rocks and overlying sediments are a common feature in the Mesoarchean Barberton Greenstone Belt, South Africa. The silification predominantly occurs at the top of mafic to ultramafic lava flows at the contact to sedimentary chert horizons, and has been interpreted as a result of fluid circulation in shallow subseafloor convection cells (Hofmann & Harris, 2008). Six samples of silicified rocks of the Mendon Formation were used for a fluid inclusion study to better constrain the conditions of formation and the source and physico-chemical evolution of the fluid that might have been responsible for the alteration. The studied samples consist of silicified ultramafic rock and chemical precipitates with abundant chert and/or quartz veins. The silicified ultramafic rocks are mainly made up of quartz, Cr-muscovite and Cr-Spinell. Tourmaline and chlorite are locally present. Sedimentary cherts are nearly pure quartz with minor accessory minerals such as rutile and Fe-(hydr)oxides. Fluid inclusions are present in coarse-grained quartz in mainly bedding parallel syntaxial veins. Primary fluid inclusions occur as clusters in the crystal's core with an average size of 5-10 µm. They occur as two phase aqueous (liquid-vapour) inclusions at room temperature with a relatively constant vapour fraction (c.15-20 vol.%). Most fluid inclusions from veins crosscutting the silicified ultramafic rocks have a salinity between 0.5 and 11.0. wt.% NaCl equiv., one sample additionally contains inclusions with distinctly higher salinities (18 - 30 wt.% NaCl equiv.). Homogenization into the liquid phase occurs from 110°C to 210°C; with most values ranging between 150 and 180°C. The sample showing two distinct groups in salinity shows the lowest Th ranging from 110°C to 150°C. The sedimentary cherts show substantial differences i.e. the presence of a phase that prohibits freezing with a N-cooled freezing stage; probably CH4 or N2. Independent temperature estimates were derived from chlorite thermometry and illite cristallinity. Chlorite thermometry yielded temperatures of 250-350°C, whereas a Kübler index of < 0.25 ?°2? means the samples belong to the Epi-zone. Excluding the high salinity and sedimentary samples, the pressure during fluid inclusion entrapment is calculated at 1.6 - 2.4 kbar, corresponding to a depth of 5 - 8 km. These values argue against a shallow water deposition, yet could mean that the crystalline parts of the veins formed after burial during a later deformation or a late stage fluid infiltration event. However, if the veins formed at ca. 150 - 180°C during early seafloor alteration, the primary fluid inclusions may have also survived any subsequent thermal event.

Farber, Katja; Dziggel, Annika; Meyer, Franz M.

2013-04-01

303

Boron isotope systematics of hydrothermal fluids from submarine hydrothermal systems  

NASA Astrophysics Data System (ADS)

Boron is highly mobile in submarine hydrothermal systems and useful to trace the process of water-rock reaction. In this study, we measured the boron content and isotopic composition of vent fluids collected from arc-backarc hydrothermal systems in the western Pacific. In sediment-starved hydrothermal systems (Manus Basin, Suiyo Seamount, and Mariana Trough), the boron content and isotopic composition of vent fluids are dependent on type of host rock. The end member fluids from MORB-like basalt-hosted Vienna Woods in the Manus Basin showed low boron content and high ?11B value (0.53 mM, 29.8‰), while dacite-hosted PACMANUS and the Suiyo Seamount showed high boron contents and low ?11B values (1.45 and 1.52 mM, 13.6 and 18.5‰, respectively). The Alice Springs and Forecast Vent field in the Mariana Trough showed values intermediate between them (0.72 and 0.63 mM, 19.9 and 24.0‰, respectively), reflecting reaction of seawater and basalt influenced by slab material. In phase separated hydrothermal systems (North Fiji Basin), boron content and isotopic composition of vent fluids (0.44-0.56 mM, 34.5-35.9‰) were similar to those in the Vienna Woods. Considering little fractionation of boron and boron isotope during phase separation demonstrated by the previous experimental studies, it is suggested that the host rock in the North Fiji Basin is MORB-like basalt. In sediment-hosted hydrothermal system (Okinawa Trough), the reaction with boron-enriched sediment following seawater-rock reaction resulted in significantly high boron contents and low ?11B values of vent fluids (4.4-5.9 mM, 1.5-2.6‰). The water-sediment ratio was estimated to be ~2. In spite of the different geological settings, the end member fuids from all vent fields are enriched in B relative to seawater (0.41 mM, 39.6‰) and the ?11B values are inversely propotional to the boron concentrations. It suggests that boron isotopic composition of vent fluid predominantly depends on the amount of boron originated from solid-phase.

Yamaoka, K.; Hong, E.; Ishikawa, T.; Gamo, T.; Kawahata, H.

2013-12-01

304

Varicose Veins, Deep Vein Thrombosis, and Haemorrhoids: Epidemiology and Suggested Aetiology  

PubMed Central

Current concepts on the aetiology of varicose veins, deep vein thrombosis, and haemorrhoids have been examined and, in the light of epidemiological evidence, found wanting. It is suggested that the fundamental cause of these disorders is faecal arrest which is the result of a low-residue diet. PMID:5032782

Burkitt, Denis P.

1972-01-01

305

Contrasting D/H ratios in hydrothermally altered thrust and strike-slip faults, western Chugach Mountains, AK  

SciTech Connect

In the western Chugach Mountains of southern Alaska, the Cretaceous Knik River Terrane, a complex of regionally metamorphosed amphibolites and schists, tonalite and trondhjemites intrusives and ultramafic rocks, is thrust over the Jurassic-Cretaceous Flysch of the Chugach terrane by the Border Ranges Fault System (BRFS). Parts of the BRFS were reactivated in the Tertiary by brittle strike-slip faulting along the dextral Carpenter Creek Fault (CCF) and related faults. Lithologies in the Knik River Terrane commonly show strong hydrothermal alteration along the Carpenter Creek Fault. In order to determine the origin and circulation patterns of hydrothermal fluids responsible for the alteration of samples in the BRFS and CCF, the authors have analyzed D/H ratios of minerals, whole rocks and veins from unfaulted metamorphic and intrusive rocks and from within and adjacent to hydrothermally altered cretaceous thrust faults and Tertiary strike-slip faults. The fluids responsible for hydrothermal alteration in the BRFS were apparently in D/H exchange equilibrium with the unfaulted lithologies presently exposed in the Western Chugach. These fluids may have been derived from devolatilization of the footwall during prograde metamorphism contemporaneous with thrust faulting. The fluids responsible for hydrothermal alteration of the CCF were apparently local meteoric waters confined in a channelized fracture flow system where isotopic equilibration with the wall rocks was strongly inhibited.

Barnett, D.E.; Bowman, J.R. (Univ. of Utah, UT (United States). Geology and Geophysics); Pavlis, T. (Univ. of New Orleans, LA (United States)); Rubenstone, J. (LDGO, Palisades, NY (United States))

1992-01-01

306

Animal Model of Acute Deep Vein Thrombosis  

SciTech Connect

Purpose: To develop an animal model of acute deep vein thrombosis (DVT). Methods: In part I of the study nine juvenile domestic pigs were used. Each external iliac vein was transluminally occluded with a balloon catheter. Thrombin was infused through a microcatheter in one leg according to one of the following protocols: (1) intraarterial (IA): 1250 U at 25 U/min in the common femoral artery (n= 3); (2) intravenous (IV): 5000 U in the popliteal vein at 500 U/min (n= 3), or at 100 U/min (n= 3). Saline was administered in the opposite leg. After the animals were killed, the mass of thrombus in the iliofemoral veins was measured. The pudendoepiploic (PEV), profunda femoris (PF), and popliteal veins (PV) were examined. Thrombosis in the tributaries of the superficial femoral vein (SFVt) was graded according to a three-point scale (0, +, ++). In part II of the study IV administration was further investigated in nine pigs using the following three regimens with 1000 U at 25 U/min serving as the control: (1) 1000 U at 100 U/min, (2) 250 U at 25 U/min, (3) 250 U at 6.25 U/min. Results: All animals survived. In part I median thrombus mass in the test limbs was 1.40 g as compared with 0.25 g in the controls (p= 0.01). PEV, PFV and PV were thrombosed in all limbs infused with thrombin. IV infusion was more effective in inducing thrombosis in both the parent veins (mass 1.32-1.78 g) and SVFt (++ in 4 of 6 legs), as compared with IA infusion (mass 0.0-1.16 g; SFVt ++ in 1 of 3 legs). In part II thrombus mass in axial veins ranged from 1.23 to 2.86 g, and showed no relationship with the dose of thrombin or the rate of infusion. Tributary thrombosis was less extensive with 250 U at 25 U/min than with the other regimens. Conclusion: Slow distal intravenous thrombin infusion in the hind legs of pigs combined with proximal venous occlusion induces thrombosis in the leg veins that closely resembles clinical DVT in distribution.

Roy, Sumit; Laerum, Frode [Institute for Surgical Research, National Hospital, N-0027 Oslo (Norway); Brosstad, Frank [Research Institute for Internal Medicine, National Hospital, N-0027 Oslo (Norway); Kvernebo, Knut [Department of Surgery, Ulleval Hospital, Kirkevien 166, N-0407 Oslo (Norway); Sakariassen, Kjell S. [Nycomed Bioreg A/S, Forskningsparken, Gaustadalleen 21, N-0371 Oslo (Norway)

1998-07-15

307

Excitation and Attenuation of Hypersonic Waves in Quartz  

Microsoft Academic Search

A method for the generation and detection of hypersonic waves, which has only been briefly described earlier, together with some absorption measurements in quartz, is discussed in some detail. Further measurements of the hypersonic absorption in quartz at different crystal orientations and after neutron irradiation are reported. The results are in qualitative agreement with a phonon-phonon relaxation process.

H. E. Bömmel; K. Dransfeld

1960-01-01

308

Passivation of quartz for halogen-containing light sources  

DOEpatents

Lifetime of halogen containing VUV, UV, visible or IR light sources can be extended by passivating the quartz or glass gas containers with halogens prior to filling the quartz with the halogen and rare gas mixtures used to produce the light.

Falkenstein, Zoran (Los Alamos, NM)

1999-01-01

309

Femtosecond laser assisted etching of quartz: microstructuring from inside  

Microsoft Academic Search

In quartz crystal substrates, microchannels were made by femtosecond laser assisted etching, i.e., irradiation of focused femtosecond laser pulses followed by wet etching. By the use of wet etching, the laser irradiated region was selectively etched out, and a microchannel was formed inside the quartz substrate. The laser irradiated region was found to be amorphous by transmission electron microscopy. Anisotropy

S. Matsuo; Y. Tabuchi; T. Okada; S. Juodkazis; H. Misawa

2006-01-01

310

Luminescence sensitivity changes in quartz as a result of annealing  

Microsoft Academic Search

Retrospective dosimetry using optically stimulated luminescence (OSL) on quartz extracted from (for example) bricks needs to account for strong OSL sensitivity changes that are known to occur depending on the previous thermal treatment of the sample. Non-heated quartz exhibits OSL orders of magnitude less per unit radiation than that for heated material. The reason these temperature-induced sensitivity changes occur in

L. Bøtter-Jensen; N. Agersnap Larsen; V. Mejdahl; N. R. J. Poolton; M. F. Morris; S. W. S. McKeever

1995-01-01

311

Optimization of subcutaneous vein contrast enhancement  

NASA Astrophysics Data System (ADS)

A technique for enhancing the contrast of subcutaneous veins has been demonstrated. This techniques uses a near IR light source and one or more IR 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 a n LCD video projector. The use of an IR 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 and children, both Caucasian and African-American, and it enhances veins quite well in all cases. The most difficult cases are those where significant deposits of subcutaneous fat are present which make the veins invisible under normal room illumination. Recent attempts to see through fat using different IR wavelength bands and both linearly and circularly polarized light were unsuccessful. The key to seeing through fat turns out to be a very diffuse source of RI light. Results on adult and pediatric subjects are shown with this new IR light source.

Zeman, Herbert D.; Lovhoiden, Gunnar; Deshmukh, Harshal

2000-05-01

312

A new approach for sclera vein recognition  

NASA Astrophysics Data System (ADS)

The vein structure in the sclera is stable over time, unique to each person, and well suited for human identification. A few researchers have performed sclera vein pattern recognition and reported promising initial results. Sclera recognition poses several challenges: the vein structure moves and deforms with the movement of the eye; images of sclera patterns are often defocused and/or saturated; and, most importantly, the vein structure in the sclera is multi-layered and has complex non-linear deformation. In this paper, we proposed a new method for sclera recognition: First, we developed a color-based sclera region estimation scheme for sclera segmentation. Second, we designed a Gabor wavelet-based sclera pattern enhancement method, and an adaptive thresholding method to emphasize and binarize the sclera vein patterns. Third, we proposed a line descriptor-based feature extraction, registration, and matching method that is illumination-, scale-, orientation-, and deformation-invariant, and can mitigate the multi-layered deformation effects exhibited in the sclera and tolerate segmentation error. It is empirically verified using the UBIRIS database that the proposed method can perform accurate sclera recognition.

Thomas, N. L.; Du, Yingzi; Zhou, Zhi

2010-04-01

313

Sulfur and oxygen isotope insights into sulfur cycling in shallow-sea hydrothermal vents, Milos, Greece.  

PubMed

Shallow-sea (5 m depth) hydrothermal venting off Milos Island provides an ideal opportunity to target transitions between igneous abiogenic sulfide inputs and biogenic sulfide production during microbial sulfate reduction. Seafloor vent features include large (>1 m(2)) white patches containing hydrothermal minerals (elemental sulfur and orange/yellow patches of arsenic-sulfides) and cells of sulfur oxidizing and reducing microorganisms. Sulfide-sensitive film deployed in the vent and non-vent sediments captured strong geochemical spatial patterns that varied from advective to diffusive sulfide transport from the subsurface. Despite clear visual evidence for the close association of vent organisms and hydrothermalism, the sulfur and oxygen isotope composition of pore fluids did not permit delineation of a biotic signal separate from an abiotic signal. Hydrogen sulfide (H2S) in the free gas had uniform ?(34)S values (2.5?±?0.28‰, n?=?4) that were nearly identical to pore water H2S (2.7?±?0.36‰, n?=?21). In pore water sulfate, there were no paired increases in ?(34)SSO4 and ?(18)OSO4 as expected of microbial sulfate reduction. Instead, pore water ?(34)SSO4 values decreased (from approximately 21‰ to 17‰) as temperature increased (up to 97.4°C) across each hydrothermal feature. We interpret the inverse relationship between temperature and ?(34)SSO4 as a mixing process between oxic seawater and (34)S-depleted hydrothermal inputs that are oxidized during seawater entrainment. An isotope mass balance model suggests secondary sulfate from sulfide oxidation provides at least 15% of the bulk sulfate pool. Coincident with this trend in ?(34)SSO4, the oxygen isotope composition of sulfate tended to be (18)O-enriched in low pH (<5), high temperature (>75°C) pore waters. The shift toward high ?(18)OSO4 is consistent with equilibrium isotope exchange under acidic and high temperature conditions. The source of H2S contained in hydrothermal fluids could not be determined with the present dataset; however, the end-member ?(34)S value of H2S discharged to the seafloor is consistent with equilibrium isotope exchange with subsurface anhydrite veins at a temperature of ~300°C. Any biological sulfur cycling within these hydrothermal systems is masked by abiotic chemical reactions driven by mixing between low-sulfate, H2S-rich hydrothermal fluids and oxic, sulfate-rich seawater. PMID:25183951

Gilhooly, William P; Fike, David A; Druschel, Gregory K; Kafantaris, Fotios-Christos A; Price, Roy E; Amend, Jan P

2014-01-01

314

Exploding Quartz From the Huckleberry Tuff, Idaho  

NASA Astrophysics Data System (ADS)

Sand size quartz grains from the 2.1 my old Huckleberry Ridge Tuff from near Idaho Falls, ID, display distinctive surface features that indicate explosion of internal fluid-filled inclusions. This was a mega-eruption of the Yellowstone Hotspot that blanketed much of the present United States. In the simplest case a lens- shaped fragment has been ejected along a fresh conchoidal fracture, leaving a shallow crater with a small, steep-walled empty cavity at the bottom center. Most grains are clearly crystals of the high-temperature beta form; others probably are but lack crystal faces. It is assumed that decompression during this mega-eruption was so rapid and intense that gas and liquid-filled inclusions experienced increases in pressure sufficient to exceed the tensional limit of the quartz. The shape of the surface fracture clearly indicates that the force came from inside and is not the result of surface impact. The simple form is commonly modified into a complex crater and cavity by a number of factors: multiple fluid-filled inclusions, solid mineral inclusions of other minerals, pre-existing fractures, open embayments, and junctions of composite beta forms. It is important to note that these explosion craters were discovered by examination of loose grains, which could be examined from all orientations: almost certainly they would not be detected in thin sections. Over several decades I have examined loose sand- sized grains from a great many volcanic ashes (not mega-eruptions) without noting such features: perhaps they were overlooked. . Somewhat similar features occur in several sandstones but are questionable because abrasion significantly modifies shape and surface texture. No effort has yet been made to observe other minerals with inclusions but one much smaller euhedral zircon contained a very similar feature except the central cavity is not clear. At present the frequency, distribution, origin and significance of explosion craters are not known; they await the accumulation of many more observations to relate them to the multiple variables of volcanic eruptions.

Triplehorn, D. M.

2008-12-01

315

Atrioesophageal fistula after cryoballoon pulmonary vein isolation.  

PubMed

The risk of atrioesophageal fistula after cryoballoon pulmonary vein isolation is thought to be much lower than after radiofrequency ablation, seeing that no data exist on this complication so far. We report for the first time on the occurrence of an atrioesophageal fistula 4 weeks after cryoballoon ablation at the site of the left inferior pulmonary vein. We suggest that even when using cryothermal ablation technique, an imaging modality to assess the proximity of esophagus and left atrium should be routinely performed to avoid this fatal complication. PMID:22486804

Stöckigt, Florian; Schrickel, Jan W; Andrié, René; Lickfett, Lars

2012-11-01

316

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

317

75 FR 12468 - Airworthiness Directives; Quartz Mountain Aerospace, Inc. Model 11E Airplanes  

Federal Register 2010, 2011, 2012, 2013

...2120-AA64 Airworthiness Directives; Quartz Mountain Aerospace, Inc. Model 11E Airplanes...airworthiness directive (AD) for all Quartz Mountain Aerospace, Inc. Model 11E airplanes...Friday, except Federal holidays. Quartz Mountain Aerospace, Inc. is in...

2010-03-16

318

75 FR 30282 - Airworthiness Directives; Quartz Mountain Aerospace, Inc. Model 11E Airplanes  

Federal Register 2010, 2011, 2012, 2013

...2120-AA64 Airworthiness Directives; Quartz Mountain Aerospace, Inc. Model 11E Airplanes...airworthiness directive (AD) for all Quartz Mountain Aerospace, Inc. Model 11E airplanes...listed in this AD. ADDRESSES: Quartz Mountain Aerospace, Inc. is in...

2010-06-01

319

Magmatic intrusions and hydrothermal systems  

NASA Astrophysics Data System (ADS)

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 history and the most Earth-like stream valleys on Mars formed well after the decline of the early putative Earth-like climate, it may be unnecessary to invoke drastically different climatic conditions for the formation of the earliest stream valleys. The morphology of most Martian fluvial valleys indicates formation by ground-water sapping which is consistent with a subsurface origin. Additionally, many Martian fluvial valleys formed on volcanoes, impact craters, near fractures, or adjacent to terrains interpreted as igneous intrusions; all are possible locales of vigorous, geologically long-lived hydrothermal circulation. Comparison of Martian valley morphology to similar features on Earth constrains valley genesis scenarios. Volumes of measured Martian fluvial valleys range from 1010 to 1013 m3. Based on terrestrial analogs, total water volumes required to erode these valleys range from approximately 1010 to 1015 m3. The clustered distribution of Martian valleys within a given terrain type, the sapping dominated morphology, and the general lack of associated runoff valleys all indicate the importance of localized ground-water outflow in the formation of these fluvial systems. An analytic model of a conductively cooling cylindrical intrusion is coupled with the U.S. Geological Survey's numerical ground-water computer code SUTRA to evaluate the magnitude of ground-water outflow expected from magmatically-driven hydrothermal systems on Mars. Results indicate that magmatic intrusions of several 102 km3 or larger can provide sufficient ground-water outflow over periods (several 105 years) required to form Martian fluvial valleys. Therefore, a vastly different climate on early Mars may not be necessary to explain the formation of the observed valleys. Martian hydrothermal systems would have also produced long-lived sources of near-surface water; these localized regions may have provided oases for any microbial life that may have evolved on the planet.

Gulick, Virginia Claire

1993-01-01

320

Hydrothermal vents and the origin of life  

Microsoft Academic Search

Submarine hydrothermal vents are geochemically reactive habitats that harbour rich microbial communities. There are striking parallels between the chemistry of the H2–CO2 redox couple that is present in hydrothermal systems and the core energy metabolic reactions of some modern prokaryotic autotrophs. The biochemistry of these autotrophs might, in turn, harbour clues about the kinds of reactions that initiated the chemistry

John Baross; Deborah Kelley; Michael J. Russell; William Martin

2008-01-01

321

Whole Algae Hydrothermal Liquefaction Technology Pathway  

SciTech Connect

This technology pathway case investigates the feasibility of using whole wet microalgae as a feedstock for conversion via hydrothermal liquefaction. Technical barriers and key research needs have been assessed in order for the hydrothermal liquefaction of microalgae to be competitive with petroleum-derived gasoline-, diesel-, and jet-range hydrocarbon blendstocks.

Biddy, M.; Davis, R.; Jones, S.

2013-03-01

322

Hydrothermal Scheduling Using Benders Decomposition: Accelerating Techniques  

Microsoft Academic Search

A new decomposition method is presented that includes the network through ac modeling within the hydrothermal scheduling optimization process including the losses. In short-term hydrothermal scheduling, the transmission network is typically modeled with dc power flow techniques. Such modeling, however, can lead to impractical solutions when it is verified with ac power flow. Another proposal considers in thermal systems the

Wilfredo S. Sifuentes; Alberto Vargas

2007-01-01

323

Dispatch from the Deep: Hydrothermal Vent Formation  

NSDL National Science Digital Library

This dispatch from the research vessel Atlantis discusses how hydrothermal vents are formed and why scientists monitor minute temperature changes around them. It includes an account of preparing temperature probes to be deployed for a year-long study, an explanation of deep sea vents and their hydrothermal nature and an explanation of why deep sea vents seem to spew black smoke.

324

Hydrothermal studies in the Aegean Sea  

Microsoft Academic Search

The aims of the Aegean Hydrothermal Fluxes and Biological Production project were to estimate the fluxes of fluids, chemicals, heat and bacteria, from hydrothermal vents, establish the controls on venting dynamics, measure the productivity in the region of the vents and establish the effect of the vents on biodiversity of both prokaryotes and eukaryotes. This paper presents an initial synthesis

P. R. Dando; S. Aliani; H. Arab; C. N. Bianchi; M. Brehmer; S. Cocito; J GUNDERSEN; L HOOPER; R KOLBH

2000-01-01

325

New multiphase equation of state for polycrystalline quartz  

SciTech Connect

We have generated separate equations of state (EOS's) for the alpha quartz, coesite, and stishovite phases of polycrystalline quartz (SiO{sub 2}) using the computer program GRIZZLY. We also modified the program GRIZZLY to combine two single-phase EOS's for a given material into a single two-phase EOS via minimization of the Gibbs free energy. This new version of GRIZZLY has been used to generate a three-phase SESAME type EOS for polycrystalline quartz using the three EOS's mentioned above. All four of the EOS's produced for SiO{sub 2} are now available on request. 17 refs., 4 figs., 1 tab.

Boettger, J.C.; Lyon, S.P.

1990-10-01

326

varicose veins smoking obesity swine flu high blood pressure  

E-print Network

varicose veins smoking obesity swine flu high blood pressure parkinson's stress depression muscle smoking obesity swine flu high blood pressure parkinson's stress depression muscle stiffness heart attack arthritis prostate disease bladder infection incontinence cancer varicose veins smoking obesity swine flu

Diggle, Peter J.

327

Why Do Some Pregnant Women Get Varicose Veins?  

MedlinePLUS

... Social Media: Connect With Us Why Do Some Pregnant Women Get Varicose Veins? KidsHealth > Parents > Q&A > Pregnancy and Infants > Why Do Some Pregnant Women Get Varicose Veins? Print A A A Text ...

328

Tectonic fibrous veins: initiation and evolution. Ouachita Orogen, Arkansas  

E-print Network

these fractures initiate where they do and how the vein evolves once started. We studied veins from the Lower Ordovician Mazarn Formation in the Arkansas’ Ouachitas combining textural observations, stable isotopes, fluid inclusions, SEM-based cathodoluminescence...

Cervantes, Pablo

2009-05-15

329

Portal vein embolization before major hepatectomy  

Microsoft Academic Search

Abstract Abstract Abstract Abstract To discuss the rationale, techniques and the unsolved issues regarding preoperative portal vein embolization (PVE) before major hepatectomy. After a systematic search of Pubmed, we reviewed and retrieved literature related to PVE. Preoperative PVE is an approach that is gaining increasing acceptance in the preoperative treatment of selected patients prior to major hepatic resection. Induction of

Hai Liu; Yong Fu

330

Deep vein thrombosis: related to anemophilous pollen?  

PubMed

The etiology of deep vein thrombosis (DVT) is still not elucidated nowadays. Based on the accordance between DVT incidence and the anemophilous pollen concentration in the air, we proposed the hypothesis that allergic reaction induced by anemophilous pollen may cause "idiopathic" DVT, and proinflammatory factors may play an important role in the thrombosis process. PMID:21823027

Zhou, Bin; Li, Yiqing; Shang, Dan; Dang, Yiping; Wang, Weici; Sheng, Shi; Kong, Xianghai; Jin, Bi

2011-08-01

331

Thoracic Outlet Decompression for Subclavian Vein Thrombosis  

Microsoft Academic Search

Hypothesis:Thereisadifferenceinoutcomeswhenpa- tients have neurogenic thoracic outlet syndrome in ad- dition to subclavian vein thrombosis. Methods: Analysis of a prospectively developed data- base, medical record review, and a patient question- naire were used to summarize clinical experience from December 1990 to December 2001 on the basis of the patient's original evaluation. Patients were stratified on the presence (group 1) or absence

Vasu Divi; Mary C. Proctor; David A. Axelrod; Lazar J. Greenfield

2005-01-01

332

Endoscopic vein harvesting: technique, outcomes, concerns & controversies  

PubMed Central

The choice of the graft conduit for coronary artery bypass grafting (CABG) has significant implications both in the short- and long-term. The patency of a coronary conduit is closely associated with an uneventful postoperative course, better long-term patient survival and superior freedom from re-intervention. The internal mammary artery is regarded as the primary conduit for CABG patients, given its association with long-term patency and survival. However, long saphenous vein (LSV) continues to be utilized universally as patients presenting for CABG often have multiple coronary territories requiring revascularization. Traditionally, the LSV has been harvested by creating incisions from the ankle up to the groin termed open vein harvesting (OVH). However, such harvesting methods are associated with incisional pain and leg wound infections. In addition, patients find such large incisions to be cosmetically unappealing. These concerns regarding wound morbidity and patient satisfaction led to the emergence of endoscopic vein harvesting (EVH). Published experience comparing OVH with EVH suggests decreased wound related complications, improved patient satisfaction, shorter hospital stay, and reduced postoperative pain at the harvest site following EVH. Despite these reported advantages concerns regarding risk of injury at the time of harvest with its potential detrimental effect on vein graft patency and clinical outcomes have prevented universal adoption of EVH. This review article provides a detailed insight into the technical aspects, outcomes, concerns, and controversies associated with EVH. PMID:24251019

Sarang, Zubair

2013-01-01

333

Central retinal vein occlusion in young people  

Microsoft Academic Search

In a study performed on 20 subjects with central retinal vein occlusion (CRVO) aged 40 years or less we found the ischemic form in 20%. Disc edema was a common finding at the onset, while macular edema was less frequently seen. Systemic or ocular disorders that could be related with the development of the CRVO were often found; a patient

Giuseppe Giuffré; Gaetano Randazzo-Papa; Carlo Palumbo

1992-01-01

334

Management of Central Retinal Vein Occlusion  

Microsoft Academic Search

The management of central retinal vein occlusion (CRVO) is discussed briefly. Since the prognosis, complications, visual outcome and management of nonischemic and ischemic CRVO are very different, the first essential step in the management of CRVO is to determine which type of CRVO one is dealing with. The various parameters which help to differentiate the two types reliably are described

Sohan Singh Hayreh

2003-01-01

335

Progression of Nonischemic Central Retinal Vein Occlusion  

Microsoft Academic Search

Progression of nonischemic central retinal vein occlusion (CRVO) to ischemic CRVO occurs in up to 5–20 % of patients with nonischemic CRVO. Eyes presenting with nonischemic CRVO and exhibiting an increase in intraretinal hemorrhages together with angiographic findings of aggravation of venule wall staining were assumed to be showing early signs of progression. Eight eyes of 7 patients were followed

A. Pollack; H. Leiba; M. Oliver

1997-01-01

336

Central retinal vein occlusion and thrombophilia  

Microsoft Academic Search

Central retinal vein occlusion is one of the commonest vascular diseases of the eye. The pathogenesis is multifactorial with both local factors and systemic diseases being aetiologically important. Many thrombophilic conditions have recently been identified and studies looking at their potential role in CRVO have been undertaken. The aim of this review is to critically appraise these studies as to

C D Fegan

2002-01-01

337

Preoperative portal vein embolization for hepatocellular carcinoma  

Microsoft Academic Search

As a countermeasure to portal tumor thrombi, which are a serious danger in liver cancer, we did portal vein embolization (PVE) during percutaneous transhepatic portography. Our 21 patients later underwent hepatic resection. After PVE, portal pressure increased and there was slight liver function damage, but this procedure was safer than transarterial embolization (TAE). We examined the pathologic specimens to view

Hiroaki Kinoshita; Katsuji Sakai; Kazuhiro Hirohashi; Sumito Igawa; Osamu Yamasaki; Shoji Kubo

1986-01-01

338

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

339

Omental vein catheter thrombolysis for acute porto-mesenteric vein thrombosis.  

PubMed

Mesenteric venous thrombosis (MVT) is an uncommon clinical condition with potential high morbidity. We report here a patient who presented with acute-onset MVT and bowel infarction, which was successfully ameliorated with intramesenteric vein thrombolytic therapy. PMID:23566871

Fonseca, Annabelle L; Cleary, Muriel A; Cholewczynski, Walter; Sumpio, Bauer E; Atweh, Nabil A

2013-05-01

340

Hepatopetal collaterals after portal vein thrombosis following liver transplantation  

Microsoft Academic Search

Two liver transplant patients with hepatopetal collaterals after portal vein thrombosis are described. Angiographically, the\\u000a appearance is similar to cavernous transformation of the portal vein. The demonstration of hepatopetal collaterals is diagnosic\\u000a of portal vein occlusion from whatever cause. After portal vein occlusion, collaterals develop from preexisting periportal\\u000a vessels which undergo compensatory enlargement and reconstitute the intraheptic portal vessels. In

Albert B. Zajko; Klaus M. Bron

1986-01-01

341

Distribution of Hydrothermal Mineral Assemblages in the Sevenmile Hole Area, Grand Canyon of the Yellowstone River, Yellowstone National Park, Wyoming  

NASA Astrophysics Data System (ADS)

Incision of the Grand Canyon of the Yellowstone River in Yellowstone National Park has exposed approximately 350 vertical meters of hydrothermally altered rhyolites. This older alteration formed in the shallow portion of a hydrothermal system that was most likely similar to the modern Yellowstone hydrothermal environment. Hydrothermal fluid circulation is related to the ongoing rhyolitic magmatism that produced the Yellowstone caldera at 640 ka. The rhyolitic magmatism and hydrothermal system are shallow expressions of deeper mantle- derived basalts. The older alteration is well exposed in the Sevenmile Hole area, near the northeastern margin of the caldera. Here, the alteration protolith is the high silica, low-18O, rhyolitic Tuff of Sulfur Creek. The tuff erupted at about 480 ka after resurgent doming associated with the third cycle collapse of the Yellowstone caldera. The tuff is a rheomorphically deformed densely welded agglutinate fallout ash that was deposited along the caldera wall. It contains phenocrysts of quartz, sodic plagioclase, and potassium feldspar. The tuff is exposed from the rim of the canyon, which is very close to the pre-alteration paleosurface, to the river bottom where it is covered by detrital sediments and actively forming hot spring deposits. Rocks exposed within the field area are pervasively hydrothermally altered. Mineral phases in approximately 90 samples were determined in the field using a Portable Infrared Mineral Analyser (PIMA). Subsequently, more precise mineral determinations were made using standard petrographic and powder XRD techniques. The alteration mineralogy consists of variable assemblages that include zones of kaolinite + opal; kaolinite + alunite with local dickite and typically high opal and/or quartz concentrations; highly silicified zones containing illite with or without smectite; and weakly silicified zones containing mostly illite. Minor (less than 1 percent) fine-grained disseminated pyrite is ubiquitous. The alteration is predominantly an advanced argillic, acid sulfate assemblage. Distribution of clay minerals may indicate a vertical temperature gradient related to depth below the paleosurface. Kaolinite and opal tend to occur along and just below the canyon rim. Montmorillonite (smectite) is the dominant clay mineral at intermediate depths or in areas suspected to be near zones of higher heat flow. Illite is the most common clay in the deepest exposures, and also at intermediate depths along a strongly silicified ridge that locally contains vuggy quartz alteration and hydrothermal breccias. The ridge is believed to be a local center of higher temperature fluid upwelling. This hydrothermal environment was most likely produced by deeper seated vapors that rose and mixed with shallow surface meteoric waters. A single sample of alunite yielded an 40Ar/39Ar age of 150 ka for the Sevenmile Hole altered area. It is unknown if the hydrothermal system in this area has been continuously or intermittently active since caldera collapse. The distribution of clay and other hydrothermal minerals preserved in the Grand Canyon walls suggest patterns in temperature and zonation that can be applied to the interpretation of the temporal evolution of the active hot spring systems in Yellowstone National Park.

Phillips, A.; Larson, P.; John, D.; Cosca, M.; Pauley, B.; Manion, J.; Pritchard, C.; Andersen, A.

2007-12-01

342

Host range comparison of the causal agents of pepper yellow vein and lettuce big vein  

Microsoft Academic Search

A number of solanaceous and composite plant species were tested as hosts for the causal agents of pepper yellow vein (PYVA) and lettuce big vein (LBVA), transmitted by a pepper and a lettuce isolate ofOlpidium brassicae, respectively. The agents had the following artificial hosts in common:Lycopersicon esculentum, Solanum melongena, Physalis floridana, Nicandra physaloides, Lactuca sativa, Sonchus oleraceus andL. virosa. Capsicum

A. Th. B. Rast

1992-01-01

343

Portal vein absence and nodular regenerative hyperplasiaof the liver with giant inferior mesenteric vein  

Microsoft Academic Search

.   We present a patient with nodular regenerative hyperplasia of the liver (NRH) and portal vein absence studied with CT, MR\\u000a imaging, and MR angiography. The most striking feature was exuberant hemorrhoids due to a giant hepatofugal inferior mesenteric\\u000a vein. A relationship between unbalanced portal blood flow and nodular regenerative transformation of the liver is suggested\\u000a in this patient.

E. Arana; L. Martí-Bonmatí; V. Martínez; M. Hoyos; H. Montes

1997-01-01

344

Pulsed Doppler duplex sonography and CT of portal vein thrombosis  

Microsoft Academic Search

Five patients with partial or complete portal vein thrombosis were examined by both computed tomography (CT) and pulsed Doppler duplex scanning. Duplex scanning correctly identified portal vein thrombosis in all five. Duplex sonography may be the preferred technique to detect and follow portal vein thrombosis because of lower cost, lack of need for intravenous contrast material, and easier availability for

Valerie E. Miller; Lincoln L. Berland

1985-01-01

345

Long-term assessment of cryopreserved vein bypass grafting success  

Microsoft Academic Search

Purpose: When autogenous vein is unavailable, cryopreserved veins have been used in patients as a means of attempted limb salvage. We evaluated the long-term patency and limb salvage rates for patients undergoing bypass grafting with cryopreserved veins. Methods: Medical records were reviewed for patients undergoing cryovein bypass grafting at two hospitals from 1992 to 1997. Follow-up data were obtained from

Linda Harris; Monica O'Brien-Irr; John J. Ricotta

2001-01-01

346

Axial Length and Refraction in Retinal Vein Occlusions  

Microsoft Academic Search

To assess whether axial length and refraction are risk factors for retinal vein occlusion, we measured these parameters in 88 consecutive patients with unilateral branch retinal vein occlusion (BRVO), in 58 consecutive patients with unilateral central retinal vein occlusion (CRVO) and in 50 patients selected as a control group. Patients and controls were free or affected by systemic or local

Francesco Bandello; Alessandra Tavola; Luisa Pierro; Giulio Modorati; Claudio Azzolini; Rosario Brancato

1998-01-01

347

Systemic diseases associated with various types of retinal vein occlusion  

Microsoft Academic Search

PURPOSE: To investigate systemic diseases associated with various types of retinal vein occlusion.METHODS: We investigated prospectively in 1090 consecutive patients with retinal vein occlusion, almost all Caucasian (consistent with the racial pattern here), the prevalence of associated systemic disorders before or at the onset of various types of retinal vein occlusion. The patients were categorized into six types of retinal

Sohan Singh Hayreh; Bridget Zimmerman; Mark J. McCarthy; Patricia Podhajsky

2001-01-01

348

Quartz deposition and its influence on the deformation process of megathrusts in subduction zones  

NASA Astrophysics Data System (ADS)

We present a quantitative examination of the liberation and subsequent deposition of silica at the subduction zone plate interface in the Mugi mélange, an exhumed accretionary complex in the Shimanto Belt of southwest Japan. Frequency and thickness measurements indicate that mineralized veins hosted in deformed shales make up approximately 0.4% of the volume of this exposure. In addition, whole-rock geochemical evidence suggests that the net volume of SiO2 liberated from the mélange at temperatures of < 200°C was as much as 35%, with up to 40% of the SiO2 loss related to the smectite-illite (S-I) conversion reaction, and the rest attributable to the pressure solution of detrital quartz and feldspar. Kinetic modeling of the S-I reaction indicates active liberation of SiO2 at approximately 70°C to 200°C, with peak SiO2 loss at around 100°C, although these estimates should be slightly shifted toward lower temperature conditions based on X-ray diffraction (XRD) analyses of mixed-layer S-I in the Mugi mélange. The onset of pressure solution was not fully constrained, but has been documented to occur at around 150°C in the study area. The deposition in deformed shales of quartz liberated by pressure solution and the S-I reaction is probably linked to seismogenic behavior along the plate interface by (1) progressively enhanced velocity-weakening properties, which are favorable for unstable seismogenic faulting, including very-low-frequency earthquakes and (2) increasing intrinsic frictional strength, which leads to a step-down of the plate boundary décollement into oceanic basalt.

Kameda, Jun; Kawabata, Kuniyo; Hamada, Yohei; Yamaguchi, Asuka; Kimura, Gaku

2014-12-01

349

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

NASA Astrophysics Data System (ADS)

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 non-chondritic Y/Ho ratios of up to 200. This suggests that Y and Ho, although similar in charge and size, may be fractionated in fluorine-rich medium-temperature aqueous fluids. In such solutions Y acts as a pseudolanthanide heavier than Lu. Y/Ho ratios of hydrothermal siderites are slightly below those of chondrites, suggesting that in (bi)carbonate-rich siderite-precipitating solutions Y may act as a Sm-like light pseudolanthanide. This indicates that Y-Ho fractionation is not a source-related phenomenon but depends on fluid composition. Based on these results it is strongly recommended that discussions of normalized REE patterns in general should be extended to normalized Rare-Earth-and-Yttrium (REY) patterns (Y inserted between Dy and Ho), because the slightly variable behaviour of the pseudolanthanide yttrium with respect to the REE may provide additional geochemical information. Available thermodynamic data suggest a negative correlation between Y/Ho and La/Ho during migration of a fluorite-precipitating hydrothermal solution. Cogenetic fluorites, therefore, should display either similar Y/Ho and similar La/Ho ratios, or a negative correlation between these ratios. This criterion may help to choose samples suitable for Sm-Nd isotopic studies prior to isotope analysis. However, in cogenetic hydrothermal vein fluorites the range of Y/Ho ratios is often almost negligible compared to the range of La/Ho ratios. This may be explained by modification of REE distributions by post-precipitation processes involving (partial) loss of a separate LREE-enriched phase. The presence of variable amounts of such an accessory phase in most fluorite samples is revealed by experiments employing stepwise incomplete fluorite decomposition. Fluorites derived from and deposited near to igneous rocks apparently display chondritic Y/Ho ratios close to those of their igneous source-rocks. However, a positive YSN anomaly is likely to develop as the distance between sites of REY mobilization and deposition increases.

Bau, Michael; Dulski, Peter

1995-03-01

350

Magmatic and tectonic processes related to the formation of hydrothermal mineral deposits in the Rocky Mountains  

SciTech Connect

Hydrothermal mineral deposits along the Rocky Mountain trend from Montana to New Mexico occur along distinct northeasterly linear trends, reflecting first order structural control on localization of the deposits. The Great Falls Tectonic Zone, Colorado Mineral Belt, and Jemez Zones have localized hydrothermal mineral deposits from Late Cretaceous to the late Tertiary. The deposits range from porphyry-related Climax-and Leadville-types of deposits to epithermal vein and breccia system that have some magmatic component. Local skarn development is important in some districts, typically exhibiting retrograde effects. Less common north and northwest trends localized mineral deposits. Notably, the Wyoming Archean terrane was less favorable than the Proterozoic basement terrane elsewhere along the Rocky Mountains. Magmas associated with the hydrothermal mineral deposits range from subduction-related calc-alkaline systems to back-arc alkaline systems. The two magma types are temporally-separated but spatially associated. The alkaline systems developed with the inception of extensional tectonics. Areas with thin (<40 km) continental crust were important in localizing the alkaline magmas and associated mineral deposits. The limited Nd- and Sr-isotopic data indicate that Late Cretaceous to Tertiary intrusive-volcanic systems exhibit increased [epsilon][sub Nd] and initial Sr values with decreasing age, interpreted to reflect increasing crustal contamination. S, O, H, and Pb isotopic- and fluid inclusion-data from many of the Rocky Mountain ore systems exhibit a wide range of sources, but reflect the importance of igneous activity in the ore-forming process.

Thompson, T.B. (Colorado State Univ., Fort Collins, CO (United States). Dept. of Earth Resources)

1993-04-01

351

APPLICATIONS OF CATHODOLUMINESCENCE OF QUARTZ AND FELDSPAR TO SEDIMENTARY PETROLOGY.  

USGS Publications Warehouse

Cathodoluminescence (CL), the emission of visible light during electron bombardment, was first used in sandstone petrology in the mid-1960's. CL techniques are especially useful for determining the origin and source of quartz and feldspar, two of the most common constituents in clastic rocks. CL properties of both minerals are dependent on their temperature of crystallization, duration of cooling, and/or history of deformation. Detrital quartz and feldspar are typically derived from igneous and metamorphic sources and luminesce in the visible range whereas authigenic quartz and feldspar form at low temperatures and do not luminesce. Quantification of luminescent and non-luminescent quartz and feldspar with the scanning electron microscope, electron microprobe, or a commercial CL device can allow for the determination of origin, diagenesis, and source of clastic rocks when used in conjunction with field and other petrographic analyses.

Ruppert, Leslie F.

1987-01-01

352

Appendix A. Fluorinated Silane Coating Procedure for Pyrex and Quartz  

E-print Network

or quartz surface: a. Wash with a basic lab soap (Micro® brand) or treat with NaOH solution. b. Rinse Nitrate (PAN) PAN formation proceeds during the oxidation of biogenic and anthropogenic hydrocarbons

353

Structure optimization and simulation analysis of the quartz micromachined gyroscope  

NASA Astrophysics Data System (ADS)

Structure optimization and simulation analysis of the quartz micromachined gyroscope are reported in this paper. The relationships between the structure parameters and the frequencies of work mode were analysed by finite element analysis. The structure parameters of the quartz micromachined gyroscope were optimized to reduce the difference between the frequencies of the drive mode and the sense mode. The simulation results were proved by testing the prototype gyroscope, which was fabricated by micro-electromechanical systems (MEMS) technology. Therefore, the frequencies of the drive mode and the sense mode can match each other by the structure optimization and simulation analysis of the quartz micromachined gyroscope, which is helpful in the design of the high sensitivity quartz micromachined gyroscope.

Wu, Xuezhong; Wang, Haoxu; Xie, Liqiang; Dong, Peitao

2014-03-01

354

Selective copper diffusion into quartz-hosted vapor inclusions: Evidence from other host minerals, driving forces, and consequences for Cu-Au ore formation  

NASA Astrophysics Data System (ADS)

Recent experimental studies have raised concerns that Cu concentrations in quartz-hosted fluid inclusions from magmatic-hydrothermal ore deposits do not represent pristine concentrations in the trapped fluids, but are modified by post-entrapment diffusional exchange through the host quartz. New microanalyses of fluid inclusions hosted in topaz show significantly lower Cu concentrations in vapor inclusions, compared to otherwise identical inclusions hosted by coexisting quartz, whereas coeval brine (hypersaline liquid) inclusions are very similar independent of host mineral in one sample. Sulfur is present as a major component in all vapor inclusions, as in most porphyry-related vapor inclusions, and Cu never exceeds S, but commonly matches the S content at a molar ratio of Cu:S ? 2 in vapor inclusions hosted by quartz. Univalent ions with a radius smaller than ˜1 Å are known to diffuse rapidly through the channels of the quartz structure, parallel to its crystallographic c axis. Since only Cu concentrations differ between topaz- and quartz-hosted inclusions, we hypothesize that Cu+ and H+ re-equilibrate by diffusional ion exchange through these channels, while all other element concentrations remain essentially unchanged. A thermodynamic model considering charge-balanced Cu+H+ exchange and diffusive H2 re-equilibration of an initially Cu-poor but S-rich vapor inclusion with a typical rock-buffered fluid environment outside the host crystal demonstrates a strong chemical driving force for Cu+ to migrate from the surrounding rock into the fluid inclusion during cooling of the system. The driving force for Cu diffusion, against the gradient in total Cu concentration, is the abundant H+ liberated inside the inclusion by dissociation of HCl and particularly by the precipitation of CuFeS2 by reaction with the initially trapped H2S and/or SO2. Gold is not only a much larger ion, but is subject to an opposing driving force, suggesting that high concentrations of this larger ion analyzed in vapor inclusions probably represent true gold concentrations in magmatic-hydrothermal vapor. These findings imply that brine-vapor separation in porphyry deposits does not cause selective Cu transfer to the vapor, but is more likely to destabilize Cu complexes and promote copper ore deposition during decompression and unmixing of the two fluid phases. By contrast, Au may be selectively transferred into the vapor phase, allowing its transport through the deeper porphyry copper deposits to form epithermal gold deposits closer to the earth's surface.

Seo, Jung Hun; Heinrich, Christoph A.

2013-07-01

355

Isolated Left-sided Scimitar Vein Connecting All Left Pulmonary Veins to the Right Inferior Vena Cava  

Microsoft Academic Search

When the common pulmonary vein fails to develop, the embryonic connections of the pulmonary veins to one or more of the systemic\\u000a veins almost always persist. Anomalous pulmonary venous connections to the inferior vena cava (IVC) are typically characterized\\u000a by hypoplasia of the involved pulmonary veins and pulmonary artery, as well as abnormal parenchyma of the involved lung. Such\\u000a cases

A. L. Juraszek; H. Cohn; R. Van Praagh; S. Van Praagh

2005-01-01

356

Ophthalmodynamometric assessment of the central retinal vein collapse pressure in eyes with retinal vein stasis or occlusion  

Microsoft Academic Search

Purpose. Using a new Goldmann contact lens associated ophthalmodynamometric device, it was the purpose of the present study to determine the central retinal vein collapse pressure in eyes with retinal vein occlusions or retinal venous stasis.Methods. The prospective clinical non-interventional comparative study included 19 patients with central retinal vein occlusion (n=8), branch retinal vein occlusion (n=4), or retinal venous stasis

Jost B. Jonas

2003-01-01

357

A study of optically contacted quartz at cryogenic temperatures  

NASA Technical Reports Server (NTRS)

Optical contacting as a method of joining the quartz components of the instruments for the Gravity Probe-B experiment is evaluated. The strength of the bond between optically contacted fused quartz surfaces at liquid helium temperature was investigated. A test apparatus which can be used for making measurements of the tensile strength of these bonds was designed. Results of the tensile pull tests are given and the reliability of such bonds analyzed.

Payne, L. L.

1982-01-01

358

New multiphase equation of state for polycrystalline quartz  

Microsoft Academic Search

We have generated separate equations of state (EOS's) for the alpha quartz, coesite, and stishovite phases of polycrystalline quartz (SiOâ) using the computer program GRIZZLY. We also modified the program GRIZZLY to combine two single-phase EOS's for a given material into a single two-phase EOS via minimization of the Gibbs free energy. This new version of GRIZZLY has been used

J. C. Boettger; S. P. Lyon

1990-01-01

359

Annealing Effect on Photovoltages of Quartz Single Crystals  

Microsoft Academic Search

We investigate the photovoltaic effects of quartz single crystals annealed at high temperatures in ambient atmosphere. The open-circuit photovoltages and surface morphologies strongly depend on the heating treatments. When the annealing temperature increases from room temperature to 900°C, the rms roughness of quartz single crystal wafers increases from 0.207 to 1.011 nm. In addition, the photovoltages decrease from 1.994muV at

Lu Tian; Song-Qing Zhao; Kun Zhao

2010-01-01

360

Effects of fluvial abrasion on shapes of quartz sand grains  

SciTech Connect

The effects of abrasion on the shapes of medium and fine quartz sand grains that are transported through a 300-mi (500-km) stretch of the Mississippi River were determined by Fourier grain-shape measurement and scanning electron microscopy. The results indicate that the abrasion of medium and fine quartz sand grains in the low-gradient stream does not significantly affect their source-inherited shapes.

Peterson, M.; Mazzullo, J.

1987-09-01

361

Surface adsorption of Cs137 ions on quartz crystals  

USGS Publications Warehouse

Adsorption tests were made on four large synthetic and three natural quartz crystals to see if surface defects might be detected by subsequent autoradiography techniques. The adsorbent used was radioactive Cs137 in a solution of Cs 137Cl. Natural quartz crystals adsorbed more cesium than the synthetic crystals. Certain surface defects were made evident by this method, but twinning features could not be detected.

Antkiw, Stephen; Waesche, H.; Senftle, F.

1954-01-01

362

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

363

MDCT Venography Evaluation of a Rare Collateral Vein Draining from the Left Subclavian Vein to the Great Cardiac Vein  

PubMed Central

Congenital vascular anomalies of the venous drainage in the chest affect both cardiac and non-cardiac structures. Collateral venous drainage from the left subclavian vein to the great cardiac vein is a rare venous drainage pattern. These anomalies present a diagnostic challenge. Multi-detector computed tomography (MDCT) is useful in the diagnosis and treatment planning of these clinically complex disorders. We present a case report of an 18-year-old Caucasian male who came to our institute for evaluation of venous drainage patterns to the heart. We describe the contrast technique of bilateral dual injection MDCT venography and the imaging features of the venous drainage patterns to the heart. PMID:25379351

Abchee, Antoine; Saade, Charbel; Al-Mohiy, Hussain; El-Merhi, Fadi

2014-01-01

364

Contact zones and hydrothermal systems as analogues to repository conditions  

SciTech Connect

Radioactive waste isolation efforts in the US are currently focused on examining basalt, tuff, salt, and crystalline rock as candidate rock types to encompass waste repositories. As analogues to near-field conditions, the distributions of radio- and trace-elements have been examined across contacts between these rocks and dikes and stocks that have intruded them. The intensive study of the Stripa quartz monzonite has also offered the opportunity to observe the distribution of uranium and its daughters in groundwater and its relationship to U associated with fracture-filling and alteration minerals. Investigations of intrusive contact zones to date have included (1) a tertiary stock into Precambrian gneiss, (2) a stock into ash flow tuff, (3) a rhyodacite dike into Columbia River basalt, and (4) a kimberlite dike into salt. With respect to temperature and pressure, these contact zones may be considered "worst-case scenario" analogues. Results indicate that there has been no appreciable migration of radioelements from the more radioactive intrusives into the less radioactive country rocks, either in response to the intrusions or in the fracture-controlled hydrological systems that developed following emplacement. In many cases, the radioelements are locked up in accessory minerals, suggesting that artificial analogues to these would make ideal waste forms. Emphasis should now shift to examination of active hydrothermal systems, studying the distribution of key elements in water, fractures, and alteration minerals under pressure and temperature conditions most similar to those expected in the near-field environment of a repository. 14 refs.

Wollenberg, H.A.; Flexser, S.

1984-10-01

365

Mechanism and kinetics of the reaction: 1 dolomite + 2 quartz = 1 diopside + 2 CO2: a comparison of rock-sample and of powder experiments  

NASA Astrophysics Data System (ADS)

Two experiments using cylindrical samples of a dolomite-quartz rock were carried out in a conventional hydrothermal apparatus for the forward reaction: 1 dolomite + 2 quartz = 1 diopside + 2 CO2, in order to compare the mechanism and the kinetics with results from experiments using mineral powders of dolomite and quartz at the same P-T-X conditions. Experimental conditions were as follows: total pressure 500 MPa; temperature 680° C (overstepping 65° C); CO2 content of the fluid phase, consisting of carbon dioxide and water, was nearly 90 mol%; the fluid/rock ratio was 1:37, and the H2O/rock ratio was about 1:740; run duration was 92 days. Scanning electron microscope (SEM) examination of a polished axial section of the rock cylinders after the run, using back-scattered electrons (BSE), shows that the reaction produced corona textures. The diopside crystals nucleate and grow exclusively on dolomite surfaces adjacent to quartz grains, i.e. in regions where there is intimate contact between the reactants. The dolomite matrix, in contrast, is diopside free. A concept of microsystems is used to compare directly the rock cylinder results with those from runs done with mineral powders. The microsystems, which consist of quartz, dolomite and diopside, are connected by the intergranular space which is filled by the fluid phase. The SEM analysis of the rock cylinders indicates a dissolution-crystallization mechanism operating in the microsystems; this is consistent with the resu