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1

Pre-biotic organic molecules in hydrothermal quartz veins from the Archaean Yilgarn province, Australia  

NASA Astrophysics Data System (ADS)

According to a model recently published by Schreiber et al. (OLEB 2012), pre-biotic organic molecules as earliest markers for a chemical evolution have been formed in tectonic faults of the first Archaean cratons. These faults are often documented by quartz- and other hydrothermal vein mineralization. During the growth of these quartzes, small portions of hydrothermal fluids are enclosed which conserve the chemical composition of the given fluid medium. According to our model, the preconditions for the geochemical formation of organic molecules are a suitable carbon source (e.g. carbon dioxide), varying P/T conditions, and catalysts. This given, rising hydrothermal fluids such as mineral-rich water and supercritical carbon dioxide in deep faults with contacts to the upper earth mantle offer conditions which allow for reactions similar to the Fischer-Tropsch synthesis. So far, the inclusions which possibly have conserved the products of these reactions have not been analyzed for possible organic constituents. First analytical results of a Mesozoic hydrothermal quartz vein from central Germany (Taunus) reveal that several organic compounds are found in fluid inclusions. However, the true origin of these compounds is unclear due to possible contamination by adjacent Corg-rich metasediments. Therefore, we have extended the study to hydrothermal quartz veins from the Archaean Yilgarn craton, to impact-generated quartz veins of the Shoemaker-Crater as well as to hydrothermal quartz boulders from a 2.7 to 3 billion years old conglomerate near Murchison (Western Australia). In one of the samples from the conglomerate, a wide spectrum of organic compounds such as bromomethane, butane, isoprene, benzene, and toluene have been detected. The time interval between the quartz formation, its erosion and its sedimentation is unknown. Possibly, the analyzed quartz sample was formed in a hydrothermal vein long before any living cells have existed on earth. In this case, the given result would be the first indication for pre-biotic organic chemistry. In contrast, almost no organic compounds have been detected inside fluid inclusions from impact-generated quartz veins of the Shoemaker-Crater (its geological age is estimated between 1.6 and 1.0 Ga), even though they partially have formed in stromatolite-bearing sedimentary rocks. Some of them occur in Precambrian gneisses. We interpret the absence of organic compounds as a consequence of the different genesis of the quartzes near the Shoemaker-crater: the impact-induced hydrothermal system had no connection to the Earth's mantle and hence, no contact to rising volcanic fluids. Our analytical results prove the presence of complex organic molecules in fluid inclusions trapped in quartz veins from the Archaean Yilgarn craton in Australia. They allow a more detailed understanding of the synthetic processes which have occurred in rising hydrothermal fluids in the upper crust of the earth and which may have led to the formation of early pre-biotic organic molecules. Based on the findings, laboratory experiments will be designed to reproduce these processes and to yield further understanding on their mechanism. Furthermore, they should yield a collection of possible products which may have formed the basis for the first biomolecules in Earth's history.

Mayer, Christian; Schreiber, Ulrich; Dyker, Gerald; Kirnbauer, Thomas; Mulder, Ines; Sattler, Tobias; Schöler, Heinfried; Tubbesing, Christoph

2013-04-01

2

Micro-Fourier Transform Infrared (FT-IR) and ?D value investigation of hydrothermal vein quartz: Interpretation of fluid inclusion ?D values in hydrothermal systems  

NASA Astrophysics Data System (ADS)

Some recent studies have suggested that the hydrogen isotopic composition ( ?D) of hydrothermal fluids, released in vacuo by thermal decrepitation of quartz, are not always accurately revealed. We report the results of a step-heating ?D value study of vein quartz, hosted by Lower Palaeozoic rocks in SW England, which was analyzed by micro-FT-IR for hydrogen speciation, before and after fluid extraction at temperatures between 750 and 1500 °C. The ?D values of individual aliquots of released water vary between -3‰ and -208‰, with the lowest values generally corresponding to the highest temperature fractions and samples of relatively low yield. The data show significant departures from geologically reasonable ?D. Micro-FT-IR analyses show that a variety of OH species are present within the vein quartz, with significant intra and inter sample variation. Typically a broad absorption due to molecular water, in the region 3400 cm -1 is observed, along with bands attributed to Li-OH and Al-OH. On heating, the broad absorption due to molecular water is reduced, accompanied by a measurable loss of Li-OH species. The latter becomes more pronounced in the higher temperature fractions (>750 °C). These data support earlier studies which indicated that contributions from the contrasting OH reservoirs in quartz can significantly influence the reported ?D values. These new data also suggest that the incorporation of OH released from Li-OH sites in the quartz may be the most important factor in the generation of the anomalous values for these samples.

Gleeson, S. A.; Roberts, S.; Fallick, A. E.; Boyce, A. J.

2008-09-01

3

Quantitative modeling of quartz vein sealing  

NASA Astrophysics Data System (ADS)

Mineral precipitation significantly effects many aspects of fluid-rock interaction across all length scales, as the dynamical change of permeability, of mechanical interaction and redistribution of dissolved material. The hydrothermal growth of quartz establishes one of the most important mineralization processes in fractures. Tectonically caused fracturing, deformation and fluid transport leaves clear detectable traces in the microstructure of the mineralized veins. As these patterns give hints on the deformation history and the fluid pathways through former fracture networks, accurate spatio-temporal modeling of vein mineralization is of special interest, and the objective of this study. Due to the intricate polycrystalline geometries involved, the underlying physical processes like diffusion, advection and crystal growth have to be captured at the grain scale. To this end, we adapt a thermodynamically consistent phase-field model (PFM), which combines a kinetic growth law and mass transport equations with irreversible thermodynamics of interfaces and bulk phases. Each grain in the simulation domain is captured by a phase field with individual orientation given by three Euler angles. The model evolves in discrete time steps using a finite difference algorithm on a regular grid, optimized for large grain assemblies. The underlying processes are highly nonlinear, and for geological samples, boundary conditions as well as many of the physical parameters are not precisely known. One motivation in this study is to validate the adequately parameterized model vs. hydrothermal experiments under defined (p,T,c) conditions. Different from former approaches in vein growth simulation, the PFM is configured using thermodynamic data from established geochemical models. Previously conducted batch flow experiments of hydrothermal quartz growth were analyzed with electron backscatter diffraction (EBSD) and used to calibrate the unknown kinetic anisotropy parameters. In the simulations, we study the sealing of syntaxial veins of 300 microns aperture by epitaxial overgrowth of preexisting grains from the rock surface. 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. The initial formation of quartz crystal bridges, especially pronounced in the regime of low supersaturation, is observed. The morphological evolution of micro-ensembles of grain neighbourhoods from the rock sample compares well to that of the simulations. To juxtapose larger polycrystal domains, the variation of grain number, texture and porosity as function of scaled distance from the initial wall is calculated. Velocity profiles from solutions of the isothermal incompressible Navier-Stokes equation are used to record permeability evolution and to evaluate deviations from the cubic law. Both, the geometry of the microstructure and the permeability of the flow pathway, are used as upscaling parameters for larger scale (fracture scale) simulations.

Wendler, Frank; Okamoto, Atsushi; Schwarz, Jens-Oliver; Enzmann, Frieder; Blum, Philipp

2014-05-01

4

Quartz-molybdenite veins in the Priestly Lake granodiorite, north-central Maine  

USGS Publications Warehouse

Quartz-molybdenite veins up to 15 cm in width occur in fine to medium-grained porphyritic biotite-hornblende granodiorite at Priestly Lake north-central Maine. An area of about 150 m x 150 m contains quartz-molybdenite veins; a larger area is characterized by barren quartz veins. Quartz-molybdenite veins are concentrated within the most felsic variants of the intrusion as suggested by lower mafic mineral contents. The pluton has a narrow range in SiO2 (67-70 wt.%), major oxides, and in trace-element compositions. Molybdenite occurs as coarse grained clusters in pockets within the quartz veins, and fills fractures in the quartz veins and host rocks. Disseminated molybdenite in the granodiorite is relatively rare and occurs only in the area characterized by a high density of quartz veins (up to 50 veins per square meter). Alteration envelopes along the quartz veins are very thin or absent, although in some areas the granodiorite appears to be selectively and pervasively altered. Sericite, chlorite, epidote, calcite, pyrite, and quartz are concentrated near the quartz-molybdenite veins. Many of the field and geochemical characteristics of the Priestly Lake pluton are unlike those of major molybdenum-producing areas (Climax, Henderson, Urad). For example, the area of alteration seems to be of limited extent, the host rock is not intensely altered hydrothermally at the surface, the density of fractures is rather low in the mineralized area, and the amount of disseminated molybdenite appears to be small. However, the Priestly Lake pluton may be a small fraction of a concealed batholith as suggested by geophysical data. It is conceivable that the type of mineralization at the surface might be the expression of more extensive molybdenite mineralization at depth. The quartz-molybdenite veins in the Priestly Lake pluton are significant because they indicate that potential molybdenum sources for producing mineralized granites were available at depth. Future studies should be aimed at delineating the area of quartz-molybdenite mineralization, documenting hydrothermal alteration and zonation, determining fracture density, and evaluating the sulfide assemblage.

Ayuso, Robert A.; Shank, Stephen G.

1983-01-01

5

Cathodoluminescence investigation and fluid inclusion analyses of hydrothermal quartz in the Erdenetiin Ovoo porphyry Cu-Mo deposit in Northern Mongolia  

NASA Astrophysics Data System (ADS)

Scanning electron microscope-cathodoluminescence (SEM-CL) reveals textures in quartz that are not apparent with other methods such as optical microscopy or backscattered electron images. Hydrothermal quartz from quartz-sulfide veins in the Erdenetiin Ovoo porphyry Cu-Mo deposit, Mongolia was analyzed by SEM-CL. They reveal euhedral growth zones with CL-bright and gray, wide CL-dull bands that cut across multiple quartz grains, CL-dark splatters of quartz connected by networks of cobweb-shaped CL-dark quartz with decreasing in luminescence along splatters and grain boundaries, and recrystallization of CL-bright quartz to CL-gray quartz. These cryptic textures indicate that a single vein of molybdenite-quartz vein has undergone at least 4 events: (1) precipitation of CL-bright and CL-gray quartz with euhedral quartz, (2) fracturing and following growth of CL-dull quartz, (3) dissolution along microfractures and following CL-dark precipitation with decreasing in luminescence intensity along microfractures and grain boundaries, and (4) precipitation of pyrite-quartz vein cutting the molybdenite-quartz vein. Fluid inclusions in molybdenite-quartz veins are presented by liquid type, liquid-vapor type (vapor occupies 20 volume %), and liquid-vapor type bearing a solid phase. The liquid-vapor type inclusions within CL-gray quartz of the first event show their homogenization temperatures ranging from 204 to 312°C. Typical homogenization temperatures of porphyry deposits range from 250 to 800°C. Molybdenite-quartz vein in the Erdenetiin Ovoo porphyry system formed through the low temperature hydrothermal processes. Keywords: Erdenetiin Ovoo, hydrothermal, quartz, veins, cathodoluminescence, fluid inclusions

Cha, B.; Lee, I.; Seo, J.; Moon, I.

2012-12-01

6

Genetic significance of the trace element content in metamorphic and hydrothermal quartz: a reconnaissance study  

NASA Astrophysics Data System (ADS)

A reconnaissance study on trace elements in metamorphic and hydrothermal quartz was carried out using quartz samples from the tin district Erzgebirge, Germany, the gold mineralization at Ka\\vsperské Hory, Czech Republic, and the gold-quartz vein deposits Muruntau and Myutenbai, Uzbekistan. A new method of sample preparation has been developed to prepare pure quartz samples by combining conventional hand-picking with microscopic and spectroscopic studies as well as acid wash/etch procedures. Preparation of monomineralic samples was followed by sample dissolution and measurement by ICP-MS. The metamorphic quartz has very low concentrations of Li (?0.4 ppm), Al (?30 ppm), K (?35 ppm), Rb (?50 ppb), Sr (?0.3 ppm), and Y (?15 ppb). Moreover, it is characterized by light rare earth element enriched lanthanide distribution patterns lacking Eu anomalies. The low element concentrations in metamorphic quartz are interpreted to result from recrystallization. Metamorphic quartz from alteration halos enveloping tin and gold deposits has distinctly different trace element signatures. These differences are related to the hydrothermal overprint of the pre-existing metamorphic quartz by the mineralizing fluids. Hydrothermally altered metamorphic quartz from tin deposits has elevated concentrations of Li (?0.9 ppm), Al (?50 ppm), K (?45 ppm), Rb (?250 ppb), and Y (?40 ppb) whereas altered metamorphic quartz from gold deposits is characterized by elevated concentrations of Sr (?0.5 ppm). The rare earth element distribution patterns of altered metamorphic quartz show variable enrichments of the heavy rare earth elements and frequently display positive Eu anomalies. Hydrothermal vein quartz from the gold deposits usually has elevated Al (?50 ppm) and Sr (?0.6 ppm) contents. The lanthanide distribution patterns exhibit variable enrichments of the heavy rare earth elements and commonly show positive Eu anomalies. The elevated Sr concentrations in the quartz from gold deposits are best explained by Sr release during feldspar alteration in the wall rocks. This mechanism may also account for the relative enrichment of Eu in the mineralizing fluids although other processes may not be unambiguously ruled out.

Monecke, T.; Kempe, U.; Götze, J.

2002-09-01

7

Al Impurity Purification in Quartz Grown by the Hydrothermal Method  

NASA Astrophysics Data System (ADS)

Al impurity purification in synthetic quartz grown by the hydrothermal method was studied by atomic absorption spectroscopy. The purification process can be expressed by the equation. Alsq{=}a{\\cdot}\\exp (b\\cdotAllasca), with Alsq and Allasca representing the respective Al contents in synthetic quartz and lascas used as the nutrient. a and b are constants which depend on the growth condition. Analytical data showed different Al content depending on growth region: it was highest in the S-region and lowest in the Z-region. Al content in the Z-region did not significantly differ (˜10 ppm), when the nutrient used for crystal growth had an Al content of between 29 ppm and 240 ppm. S-regions were not purified when the nutrient with Al content of less than 30 ppm was used. Influence of Al content on crystal morphology in the purification process was discussed.

Iwasaki, Fumiko; Iwasaki, Hideo; Suzuki, Carlos K.

1989-01-01

8

Geochemistry of cassiterite and wolframite from tin and tungsten quartz veins in Portugal  

Microsoft Academic Search

Cassiterite and wolframite compositions from Sn>W- and W>Sn-bearing quartz veins in Northern and Central Portugal are compared to provide evidence on fluid compositions. In Sn>W-bearing quartz veins, euhedral cassiterite shows sequences of alternating parallel darker and lighter zones. The darker zones are pleochroic, oscillatory zoned, exhibit exsolutions of columbite and ixiolite and are richer in Nb, Ta and Fe than

A. M. R. Neiva

2008-01-01

9

Development of crystallographic preferred orientation and microstructure during plastic deformation of natural coarse-grained quartz veins  

Microsoft Academic Search

The microstructure and crystallographic preferred orientation (CPO) of quartz were quantified in 17 samples of natural monomineralic tabular veins. The veins opened and were deformed, up to shear strain ? > 15, in a small temperature window (about 25°C) above 500°C, as established by Ti-in-quartz thermometry. The veins filled a set of fractures within the Adamello tonalite (southern Alps, Italy)

Giorgio Pennacchioni; Luca Menegon; Bernd Leiss; Fabrizio Nestola; Geoffrey Bromiley

2010-01-01

10

Conditions of Formation of Secondary Quartz in Hydrothermally Altered, Subsurface Dacite beneath the Deep-Sea PACMANUS Hydrothermal Field, Manus Basin, Papua New Guinea  

NASA Astrophysics Data System (ADS)

New fluid inclusion (FI) data from secondary quartz within the altered felsic rocks underlying the PACMANUS hydrothermal field provide additional constraints on the thermal conditions and fluid salinities accompanying hydrothermal alteration. PACMANUS, at a water depth of about 1650 to 1700 m on the summit of the neovolcanic Pual Ridge in the eastern part of the Manus backarc basin, is an active seafloor system situated in a felsic volcanic setting at a convergent plate boundary. Two sites of active venting - Roman Ruins, with high-temperature (220-276° C) sulfide chimneys, and Snowcap, which is an area of lower-temperature (6- 65° C) diffuse flow - were cored during Ocean Drilling Program Leg 193. Drilling reached sub-seafloor depths of 387 m at Snowcap and 206 m at Roman Ruins. At both Snowcap and Roman Ruins, fresh dacite/rhyodacite is underlain by highly to completely altered rocks with clays (illite, illite-smectite, chlorite, and mixed layer clays), disseminated pyrite, silica and late stage anhydrite. At shallow depths the silica is mostly cristobalite, whereas quartz is the polymorph at depth. Secondary quartz occurs in amygdules, alone or with accessory anhydrite and pyrite; in cm-scale granular nodules; and as tiny grains forming an open mosaic with interstitial clays and pore space. Scarce FI in secondary quartz are small (10-20?), irregular, and contain liquid (L) plus vapor. Only a few are arrayed along healed fractures, and most are interpreted as primary. FI from Snowcap homogenize to L between 290° C and 390° C. Ice melting temperatures vary between about -10° C and -0.4° C, with most ice melting near -2.0° C. Thus, while most FI have near-seawater salinities, a significant number are much more saline, while others are much less saline, approaching fresh water. FI from Roman Ruins homogenize between 257° C and 370° C, and ice melting temperatures vary from about -14° C to -1.2° C. These data are best explained if the hydrothermal solution periodically phase-separated and, in fact, many FI indicate temperatures essentially on the boiling curve for seawater at the appropriate hydrostatic pressure. FI data from quartz are nearly identical to data from anhydrite, indicating very little difference in the temperatures and fluid salinities. Although the anhydrite veining appears to be a late stage event, the FI data suggest a single event. FI trapping temperatures are broadly consistent with quartz oxygen isotopic temperatures calculated with the assumption that the fluid isotopic ratio was similar to or shifted slightly from SMOW.

Vanko, D. A.; Wicker, S. G.; Binns, R. A.

2006-05-01

11

Copper deposition during quartz dissolution by cooling magmatic hydrothermal fluids: The Bingham porphyry  

NASA Astrophysics Data System (ADS)

Scanning electron microscope cathodoluminescence imaging is used to map successive generations of fluid inclusions in texturally complex quartz veinlets representing the main stage of ore metal introduction into the porphyry Cu-Au-Mo deposit at Bingham, Utah. Following conventional fluid inclusion microthermometry, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICPMS) is applied to quantify copper and other major and trace-element concentrations in the evolving fluid, with the aim of identifying the ore-forming processes. Textures visible in cathodoluminescence consistently show that the bulk of vein quartz (Q1), characterized by bright luminescence, crystallized early in the vein history. Cu-Fe-sulfides are precipitated later in these veins, in a microfracture network finally filled with a second generation of dull-luminescing Q2 quartz. Mapping of brine and vapor inclusion assemblages in these successive quartz generations in combination with LA-ICPMS microanalysis shows that the fluids trapped before and after Cu-Fe-sulfide precipitation are very similar with respect to their major and minor-element composition, except for copper. Copper concentrations in inclusions associated with ore formation drop by two orders of magnitude, in a tight pressure-temperature interval between 21 and 14 MPa and 425-350 °C, several hundred degrees below the temperature of fluid exsolution from the magma. Copper deposition occurs within a limited P- T region, in which sulfide solubility shows strong normal temperature dependence while quartz solubility is retrograde. This permits copper sulfide deposition while secondary vein permeability is generated by quartz dissolution. The brittle-to-ductile transition of the quartz-feldspar-rich host rocks occurs in the same temperature range, which further enhances vein reactivation and promotes cooling and expansion of fluids ascending across the transition from lithostatic to hydrostatic conditions.

Landtwing, Marianne R.; Pettke, Thomas; Halter, Werner E.; Heinrich, Christoph A.; Redmond, Patrick B.; Einaudi, Marco T.; Kunze, Karsten

2005-06-01

12

Hydrothermal reaction of CA(OH){sub 2} with quartz in coal  

SciTech Connect

Quartz is generally most abundant as mineral matter in coal. In order to obtain fundamental information for chemical demineralization of coal with Ca(OH){sub 2}, the hydrothermal reaction of Ca(OH){sub 2} with reagent quartz has been studied in detail. The results showed that the quartz was converted to various silicates, depending on autoclaving conditions. At a CaO/SiO{sub 2} ratio of about 1, quartz was initially converted to Ca{sub 2}SiO{sub 4}. H{sub 2}O, then to tobermorite-like compounds, and finally to xonotlite, Higher temperature and longer reaction time are preferable to the complete conversion of quartz. The formed calcium silicates were susceptible to dissolution in acid.

Wang, J.; Tomita, A. [Tohoku Univ., Sendai (Japan); Taylor, G.H. [Australian National Univ., Canberra (Australia)

1996-12-31

13

Prospective Areas for Intrusion-Related Gold-Quartz Veins in Southern British Columbia  

Microsoft Academic Search

trusion-related gold-quartz vein occurrences (i.e. Valparaiso and Cam-Gloria) are located in southern Brit- ish Columbia associated with the mid-Cretaceous Bayonne Suite (Logan, 2000). In contrast with the metaluminous, subalkalic, reduced I-type Tombstone Suite, t he B ayonne s uite c onsists o f m ostly peraluminous, s ubalkalic h ornblende-bioti te granodiorite and highly fractionated 2-mica granites, aplites and pegmatites.

James M. Logan

14

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

15

Hydrothermal vein and deformation characteristics in the Nojima fault zone, Japan  

NASA Astrophysics Data System (ADS)

The hydrothermal vein formation and deformation in the Nojima fault zone were examined in the core recovered from a borehole drilled by the Geological Survey of Japan (GSJ) twelve months after the 1995 Hyogo-ken Nanbu (Kobe) earthquake (MJMA=7.2), southwest Japan. The borehole was drilled across a slipped portion of the fault to a depth of 747 m. The fault zone was intersected at 426 m and is characterized by a greater intensity of brittle deformation and/or hydrothermal alteration than typical host granodiorite. The fault core consists of three types of fault gouge, and occurs at the depth range of 623 m to 625 m. The fluid circulation and deformation have occurred along the fault and the fault rocks from this borehole enable to understand the hydrothermal vein formation and deformation in the fault zone. The hydrothermal veins are developed along the entire depth of the core (152 to 767 m depth). Vein materials are zeolite (laumontite and stilbite) and carbonate (calcite, siderite, ankerite and dolomite). Zeolite veins are well developed and exhibit network-like structure and opening of host rocks. These indicate the fault rocks were dilated during the zeolite vein formation. Euhedral zeolites are often included in veins. This also supports dilatation of the fault zone. Carbonate often constitutes complex veins of siderite and calcite. Most zeolite mineralization preceded carbonate mineralization. The characteristic feature in the fault zone is minor fault zones. Some of them contain zeolite and/or carbonate. Biotite is partly preserved and elongated in minor fault zones. Host rocks often suffered strong zeolitization in the fault zone. These suggest a wide variety of the hydrothermal vein formation and deformation in the fault zone. The range of 625 to 635 m depth just below the fault core contains unconsolidated low-angle minor fault zones with small carbonates. These might be products of recent fluid circulation and deformation.

Ohtani, T.; Fujimoto, K.; Boullier, A.-M.; Tanaka, H.; Ito, H.

2003-04-01

16

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

17

Dynamic analysis and two types of kink bands in quartz veins deformed under subgreenschist conditions  

NASA Astrophysics Data System (ADS)

In order to clarify deformation mechanisms and behaviours of quartz in a low-temperature regime in the earth's crust, microstructural analyses, particularly on kink bands have been carried out for quartz veins moderately deformed under subgreenschist conditions. Both the dominance of subbasal deformation lamellae and geometry of kink bands suggest that basal (0001) slip was the sole active slip system in the deformed quartz. On a morphological basis, kink bands in the quartz were classified into two types: type I is characterized by conjugate and narrow bands with angular hinge zones, and type II by a wide monoclinal band. Dynamic analyses using deformation lamellae and kink bands have revealed that type I kink bands were formed in grains with basal plane (sub-)parallel to the compression axis, whereas type II kink bands were formed in grains with basal planes inclined to it. Using a numerical model of kinking of elastic multilayers modified after Honea and Johnson (Tectonophysics 30, 197-239, 1976), changes of the level of yielding stress for kinking and the width of kink bands as a function of the angle ? between the slip plane and the compression axis have been examined. The theory predicts that type I kink bands were formed at a higher stress level than type II kink bands, and hence occurrence of type I kink bands suggests that a significant strain hardening occurred in the deformed quartz veins. The theory also well explains the fact that the width of type I kink bands ( ?=0 to 10°) is narrower by an order of magnitude than type II kink bands ( ?=10 to 80°).

Nishikawa, Osamu; Takeshita, Toru

1999-01-01

18

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

Microsoft Academic Search

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

Masao Nakatani; Christopher H. Scholz

2004-01-01

19

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

NASA Astrophysics Data System (ADS)

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

Sharifi, R.

2009-04-01

20

Hydrothermal reaction of Ca(OH){sub 2} with quartz in connection with coal demineralization  

SciTech Connect

The hydrothermal reaction of Ca(OH){sub 2} with reagent quartz at temperatures between 175 and 340 C has been studied to obtain fundamental information on coal demineralization with Ca-(OH){sub 2}. X-ray diffraction analysis was used to measure the conversion of quartz and to identify reaction products. The reaction sequence strongly depended on Ca/Si atomic ratio and on autoclaving conditions. At a Ca/Si atomic ratio of about 1, quartz was first converted to Ca{sub 2}-Si{sub 7}O{sub 4}{center_dot}H{sub 2}O, which then reacted with residual quartz or residual Ca(OH){sub 2}, forming a silica-rich phase or a calcium-rich phase, and finally all these intermediate compounds were transformed to xonotlite upon a prolonged high-temperature treatment. At higher Ca/Si ratios, a fraction of quartz remained unreacted even after severe treatments, and the final products were jaffeite (Ca/Si = 3) and tobermorite-like compounds (Ca/Si = {approximately}1) instead of xonotlite. On the basis of the above investigations on model reaction, demineralization reactions to remove quartz from coal through Ca(OH){sub 2}/HCl leaching were interpreted and a suitable acid-washing method was proposed.

Wang, J.; Tomita, Akira [Tohoku Univ., Sendai (Japan). Inst. for Chemical Reaction Science] [Tohoku Univ., Sendai (Japan). Inst. for Chemical Reaction Science

1997-05-01

21

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

USGS Publications Warehouse

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

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

2006-01-01

22

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

23

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

NASA Astrophysics Data System (ADS)

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

Jiang, Z.

2011-12-01

24

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

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

25

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

26

Vein quartz microfabrics indicating progressive evolution of fractures into cavities during postseismic creep in the middle crust  

NASA Astrophysics Data System (ADS)

Discordant quartz veins in metamorphic rocks formed at temperatures similar to 300 °C in an extensional tectonic regime. The vein shape is characterized by an aperture to length ratio exceeding the maximum value feasible for purely elastic deformation by orders of magnitude. Non-elastic ductile deformation of the host rock must have controlled widening of the arrested cracks. Fracture parallel shortening is low. Due to the low accumulated strain, the microstructural record of this stage of deformation cannot be isolated in the polyphase host rock. Information is exclusively obtained from the microfabrics of the vein sealing quartz. There, the density of geometrically necessary dislocations, derived from orientation maps created by electron backscatter diffractometry (EBSD), decreases markedly from the vein wall to the centre. The gradient is attributed to progressive cavity formation and buckling of the vein walls during sealing. Early grown crystals at the vein margins record a prolonged deformation history compared to lately grown grains in the centre of the vein. The gradient and the lack of significant crystal plastic deformation of the crystals in the vein centre show that deformation of the completed vein is insignificant compared to deformation during progressive opening and sealing. In view of the precursory brittle deformation and the intense crystal plastic deformation at the vein margins, the monogenetic veins are interpreted to record a single mid-crustal stress transient, related to the earthquake cycle. Fracturing is proposed to be a consequence of coseismic loading, while progressive opening and sealing record the deformation during postseismic stress relaxation by creep.

Nüchter, Jens-Alexander; Stöckhert, Bernhard

2007-09-01

27

Development of crystallographic preferred orientation and microstructure during plastic deformation of natural coarse-grained quartz veins  

NASA Astrophysics Data System (ADS)

The microstructure and crystallographic preferred orientation (CPO) of quartz were quantified in 17 samples of natural monomineralic tabular veins. The veins opened and were deformed, up to shear strain ? > 15, in a small temperature window (about 25°C) above 500°C, as established by Ti-in-quartz thermometry. The veins filled a set of fractures within the Adamello tonalite (southern Alps, Italy) and localized homogeneous simple shear during postmagmatic cooling. The local (square millimeter scale) and bulk (square centimeter) CPO were investigated by computer-integrated polarization microscopy (CIP) and X-ray texture goniometry. Weakly deformed veins (WDV: ? < 1) consist of millimeter- to centimeter-sized crystals with a strong CPO showing a c-axis girdle slightly inclined, mostly with the shear sense, to the foliation (XY) plane and a strong maximum close to the lineation (X). Moderately deformed veins (MDV: 2 < ? < 3) consist of elongated nonrecrystallized ribbon grains and most have a CPO showing a strong Y maximum of c axes some with weak extension into a YZ girdle. Strongly deformed veins (SDV: ? = 4 to 15) are pervasively to completely recrystallized to fine (34-40 ?m grain size) aggregates with a strong CPO similar to that of MDV. The slip systems during plastic deformation were dominantly prism with subordinate rhomb and basal slip. Recrystallization occurred rather abruptly for 3 < ? < 4. In contrast to dislocation creep experiments in quartz (and other minerals), a steady-state recrystallized fabric is achieved at early stages of deformation (? ? 4) as there is no evidence, with increasing strain, of strengthening of the CPO, of rotation of the fabric skeleton, or of change in grain size. WDV represent weakly deformed relicts of veins with an initial CPO believed to have developed during crystal growth but unsuitably oriented for prism slip during subsequent shear. MDV and SDV appear to derive from veins different from WDV, where the vein crystals grew with orientation favorable for prism slip. The relationship between the initial growth CPO and the kinematic framework suggests that veins opened at a temperature close to that at which there is a switch between the activity of prism and prism slip, with the temperature of growth causing growth of crystals well oriented for slip. The initial CPO of veins, from which quartz mylonites are commonly derived, plays a critical role in the fabric evolution. The strong growth- and strain-induced CPOs of these sheared veins inhibited significant reworking during lower temperature stages of pluton cooling when basal slip would have been dominant.

Pennacchioni, Giorgio; Menegon, Luca; Leiss, Bernd; Nestola, Fabrizio; Bromiley, Geoffrey

2010-12-01

28

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

SciTech Connect

Mass transfer and fluid-rock interaction have been evaluated along two sample traverses in low-sillimanite grade quartz-mica schist adjacent to a synmetamorphic quartz-graphite vein in the southern Black Hills, South Dakota. In an {approximately}17 cm halo between apparently unaltered schist and the vein contact is an outer zone of cryptic alteration and three inner zones of visible alteration. The cryptic zone consists of the original prograde metamorphic mineral assemblage plus anomalously high amounts of tourmaline. The outermost visible zone contains abundant graphite. The second visible zone is defined by intensive bleaching of the schist. The innermost visible zone, immediately adjacent to the vein, is tourmaline + quartz + plagioclase + limonite + graphite. The vein is composed almost entirely of quartz, but also contains trace amounts of graphite. Mass balance calculations indicate that Al was essentially inert. The predominant chemical changes during wall-rock alteration were addition of B and C from the vein-forming fluid along with loss of K from the wall rocks, corresponding to precipitation of tourmaline and graphite, and the progressive destruction of microcline, biotite, and muscovite toward the vein. In addition, the elements V, Cr, Cu, Zn, Pb, As, Sb, W, and Au were introduced into the country rock, whereas Si, Rb, Ba, and Cs were removed. Fluid-rock interaction modeling suggests that between one and four equivalent masses of fluid interacted chemically with the most altered mineral assemblages. In addition, greater than one equivalent mass of reactive fluid penetrated to distances of at least 5 cm from the vein contact.

Galbreath, K.C.; Duke, E.F.; Papike, J.J. (South Dakota School of Mines and Technology, Rapid City, SD (USA)); Laul, J.C. (Pacific Northwest Laboratories, Richland, WA (USA))

1988-07-01

29

Compaction of granular quartz under hydrothermal conditions: Controlling mechanisms and grain boundary processes  

NASA Astrophysics Data System (ADS)

We report isostatic compaction experiments performed on granular quartz under hydrothermal conditions (3-129 ?m of initial grain size, 300-600°C, 200 MPa of fluid pressure, and 25-100 MPa of effective pressure). From microstructural evidence, it was determined that, whereas microcracking controlled precompaction at room temperature, pressure solution was the main mechanism during hydrothermal compaction, although a role of microcracking could not be excluded entirely. Our mechanical data, together with theoretical pressure solution rate models, further indicated that pressure solution was controlled by interface kinetics, dissolution being the most likely rate-controlling mechanism. An empirical relation of the form ? = 10-7.8 (?/?0)10.0?3.4d-1 exp (-105,000/RT) was fitted to our data to describe experimental compaction rates. Electron backscatter diffraction (EBSD) analysis performed on one sample showed limited evidence for plastic deformation (Dauphiné twinning and lattice bending) at grain contact points under high stress. Contact microstructures formed during compaction were studied using quartz single crystal discs or a mica plate as reference surfaces. This showed that, in all contacts, microstructures were rough, with a micrometer scale roughness. Many contacts also showed internal microcracking, and it is inferred that microcracking is likely an important mechanism for creating and maintaining rough contacts during quartz pressure solution, at least under the present experimental conditions. Extrapolation of our empirical equation for compaction rates to natural conditions is consistent with previous observations that, during burial and diagenesis of a sandstone, pressure solution starts to operate at depths of about ˜1.5-2 km, becoming the dominant compaction mechanism at depths greater than ˜2.5-3 km. The extrapolation gives good agreement with porosity-depth trends reported for natural, arenitic sandstones.

van Noort, Reinier; Spiers, Christopher J.; Pennock, Gill M.

2008-12-01

30

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

31

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

NASA Astrophysics Data System (ADS)

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

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

1996-05-01

32

Deformation assisted by fluids in quartz veins of shear zones: an example from Iron Formations of Quadrilátero Ferrífero, Brazil.  

NASA Astrophysics Data System (ADS)

The evidences of fluid activity in rocks are well recognized. In many cases, the fluid is responsible to remobilize many elements (e.g. Au, Mn, Si) that may be transported over a long distance and precipitated as new minerals in regions of low stress of the rock. In many deformed rocks, the origin of a large number of structures (veins, pressure shadows, dissolved grain boundaries, etc) may be correlated to the fluid activity. However, the fluids are important not only during the crack-and-seal process but also after the sealing ceases. As an example of how the fluids are responsible to rearrange the structure of the rock, we studied many quartz veins of one iron-formation from Brazil. The rocks were collected in Quadrilátero Ferrífero (QF), Brazil, that is one of the most important metalogenetic provinces in the world. It is assumed the existence of a deformational and metamorphic gradient in the rocks of QF, increasing the occurrence of penetrative structures from southwest to northeast. However, the effects of the local shear zones in the deformation pattern of QF may not be neglected. Shear zones are generally recognized as structures that accommodate deformation, eventually with intense fluid percolation. It is indubitable that there is a relationship between the fluid activity and the deformation accommodation in shear zones. So, to investigate how the fluid activity can affect the mechanisms of accommodation of deformation in rocks of shear zones from QF, we characterized the crystallographic preferred orientation (CPO) of some quartz vein by EBSD (electron backscattering diffraction). All the samples came from the same outcrop and from the same dextral shear zone, localized in the low-deformation region of QF, under greenschist metamorphic conditions. The samples were oriented according to the XYZ reference system, with X parallel to the foliation and Z normal to the XY plane. The veins are quartz-rich layers parallel to the rock foliation. They do not exhibit any kind of fibrous structures that can indicate a sense of growth of the quartz crystals inside the vein. The less deformed veins are composed of tabular crystals of quartz, with the optical axes oriented sub-parallel to the foliation. Mechanical Dauphiné twinning of quartz may also be observed in the single crystals. On the other hand, the deformed veins are represented by polycrystalline layers of quartz, with two distinct CPOs of c-axes: 1) oblique to the foliation and 2) parallel to the Y axis. We suppose that the veins are the result of a concurrence between transformation, recrystallization and recovery of quartz assisted by fluid activity at low temperature and confining pressure. In the related deformation conditions, slip on basal planes and mechanical twinning are consistent with a strong c-axis CPO of quartz sub-parallel to the foliation, but it is not acceptable to the c-axis CPO around Y. To achieve this distinct crystallographic orientation, it is necessary a slip system on prismatic planes followed by grain boundary migration. At low temperatures, one possible situation to explain the CPO under theses conditions is the progressive deformation assisted by fluid activity. A posterior static recrystallization by discontinuous grain growth of quartz may be responsible for the concentration of the c-axis around the Y, intensifying the CPO.

Barbosa, Paola; Lagoeiro, Leonardo

2013-04-01

33

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

34

Deep penetration of sedimentary fluids in basement rocks from southern Norway: Evidence from hydrocarbon and brine inclusions in quartz veins  

NASA Astrophysics Data System (ADS)

This paper presents evidence for fluid flow and fluid-rock interaction at upper crustal levels within the crystalline basement of southern Norway. In the high-grade Modum Complex postmetamorphic veins of quartz occur in association with albitisation of metagabbros and metasediments. Pressure-temperature conditions for the formation of these veins are in the range 250-300°C and ca. 1-2 kbar. Primary and pseudosecondary fluid inclusions in the quartz veins show two fluids: (1) hydrocarbon ± C0 2 inclusions and (2) aqueous inclusions with variable salinities. Dark carbonaceous solid inclusions are also present. The hydrocarbon inclusions are methane dominated (ca. 80-100 mot%), and the presence of higher, complex hydrocarbons is demonstrated. The aqueous inclusions in the metagabbro-hosted veins show more saline compositions than the metasediment-hosted veins. A salinity range of ca. 23-0 wt% NaCl eq is found. Some of the aqueous inclusions may contain NaHCO 3. Crush-leach analyses of inclusion fluids show Na-Ca-K-CI dominated compositions, with Na?Ca>K. Hydrocarbon-poor concentrates yield Br/Cl ratios close to seawater, while hydrocarbon-rich concentrates show higher values. The types and chemistry of the hydrocarbons in these veins indicate a biogenic origin of the hydrocarbon fluids. The inclusion fluids are interpreted as derived from an overlying sedimentary basin in late Precambrian or Permian times. The veining is interpreted as the deep expression of the percolation of basinal fluids into the metamorphic basement during crustal extension.

Munz, I. A.; Yardley, B. W. D.; Banks, D. A.; Wayne, D.

1995-01-01

35

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

36

Fluid inclusion study of metamorphic gold-quartz veins in northwestern Nevada, U.S.A.: Characteristics of tectonically induced fluid  

Microsoft Academic Search

The study shows the nature of the fluid inclusions analyses in tectonically induced gold-quartz veins in northwestern Nevada,\\u000a U.S.A. and compares the results of fluid inclusions with those of other gold deposits of similar environments in the world.\\u000a The quartz veins are present in low-grade regionally metamorphosed rocks, and form clusters of prospects along a north-trending\\u000a regional shear zone. These

Sangwon Cheong

2002-01-01

37

Using vein fabric and fluid inclusion characteristics as an integrated proxy to constrain the relative timing of non cross-cutting, syn- to late-orogenic quartz vein generations  

NASA Astrophysics Data System (ADS)

Research on ancient fluid systems mainly focuses on veins, because they offer the opportunity to combine macro- and microstructural data with geochemical data to gain insight into the P-T-X conditions present during veining. By applying such an integrated petrographic and microthermometric methodology to syn- to late-orogenic quartz veins in the Palaeozoic High-Ardenne slate belt (Belgium), we were able to define the relative timing and related P-T-X conditions of different quartz vein generations, despite of the absence of any mutual cross-cutting relationships in the field (Jacques et al., 2014). The different quartz vein generations represent the meso-scale brittle accommodation during fold initiation, amplification and locking. The presence of free polycrystal growth in cavities at a midcrustal depth, and fluid-assisted brecciation indicate that veining occurred under overpressured fluid conditions during the orogeny. Significant differences in crystal-plastic deformation microstructures and P-T trapping conditions indicate that the different processes accommodating folding occurred in a progressive manner along a retrograde deformation path. While vein quartz in an extrados vein and in the peripheral part of a lenticular, fault-accommodating vein shows moderate crystal-plastic deformation (e.g. bulging recrystallisation, deformation lamellae, shear bands), crystal-plastic deformation is relatively absent in the vein quartz of a saddle reef and the core of the lenticular vein (i.e. no to minor undulose extinction). Successive veining occurred from peak metamorphic conditions (ca. 300 ° C and 190 MPa), measured in the extrados vein, to lower P-T conditions in the periphery of the lenticular vein (ca. 275 ° C and 180 MPa), the late-orogenic saddle reef (ca. 245 ° C and 160 MPa) and the core of the lenticular vein (ca. 220 ° C and 150 MPa). The relative timing and accompanying decrease in P-T conditions of the different quartz vein generations reflect the gradual exhumation of the slate belt from ca. 7.5 to 6 km depth along a retrograde deformation path. A comparison of these results with a former study of syn- to late-orogenic calcite veins at the Variscan front zone (Kenis et al., 2000), indicates that exhumation processes throughout the Rhenohercynian fold-and-thrust belt were diachronous. While exhumation and related quartz veining in the High-Ardenne slate belt occurred during the Sudetic stage of the Variscan orogeny (ca. 325-310 Ma), the exhumation and related calcite veining at the Variscan front zone occurred during the Asturian stage of the Variscan orogeny (ca. 300 Ma). With this study we demonstrate that a relative timing for different vein generations, lacking any cross-cutting relationship, can still be attained through an integration of petrographic and microthermometric arguments. Moreover, this particular approach, enables to further delineate the P-T history of an orogenic system from its pre-, to its syn-, late- and finally postkinematic stages. References Jacques, D., Derez, T., Muchez, P., Sintubin, M., 2014. Syn- to late-orogenic quartz veins marking a retrograde deformation path in a slate belt: Examples from the High-Ardenne slate belt (Belgium). Journal of Structural Geology, 58, 43-58. Kenis, I., Muchez, P., Sintubin, M., Mansy, J.-L., Lacquement, F., 2000. The use of a combined structural, stable isotope and fluid inclusion study to constrain the kinematic history at the northern Variscan front zone (Bettrechies, northern France). Journal of Structural Geology, 22, 589-602.

Jacques, Dominique; Muchez, Philippe; Sintubin, Manuel

2014-05-01

38

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

39

Fluid inclusion and stable isotope evidence for the genesis of quartz-scheelite veins, Metaggitsi area, central Chalkidiki Peninsula, N. Greece  

Microsoft Academic Search

Scheelite mineralization accompanied by muscovite and albite, and traces of Mo-stolzite and stolzite occurs in epigenetic\\u000a quartz vein systems hosted by two-mica gneissic schists, and locally amphibolites, of the Paleozoic or older Vertiskos Formation,\\u000a in the Metaggitsi area, central Chalkidiki, N Greece. Three types of primary fluid inclusions coexist in quartz and scheelite:\\u000a type 1, the most abundant, consists of

S. P. Kilias; J. Konnerup-Madsen

1997-01-01

40

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

41

Epidote-group mineral+quartz veins in metatuff: Petrography, chemistry, timing, style and redox implications of fluid-derived minerals in altered arc crust  

NASA Astrophysics Data System (ADS)

In volcanoplutonic arc crust, alteration is fluid-controlled during long histories, yet little understood compared to other fluid-rock settings. The Ritter Range pendant, Sierra Nevada, CA, contains subarial to submarine tuffs erupted and altered in the Jurassic, then metamorphosed and altered by Cretaceous plutonism. Some metatuffs display veining systems dominated by epidote-group minerals [EGM: clinozoisite (Ca2Al3Si3O11(OH2)), pistacite (Ca2Fe3+Al2Si3O11(OH2)), piemontite (Ca2(Mn3+ Fe3+ Al2)AlSi3O11(OH2)) and Mn-rich epidote (pale pink-to-pale green pleochroic); a solid solution of the other end-members). Field relations and petrography track the effects of syn- to slightly post-eruption fluids, and later, pluton-related veining and alteration. Many EGM grains show micro-scale disequilibrium features, for example, oscillatory zoning, resorption, overgrowths, composition changes along former cracks and patchy zoning. Many quartz veins contain EGM in margins, cores, selvages and host rocks, EGM compositions in any of these settings may differ within a few 10s of meters. Early, highly transposed braunite (Mn7SiO12)+/-quartz veins and late, crosscutting, quartz-dominant, EGM-bearing veins reflect distinct fluid-rock processes. A likely protolith for braunite+/-piemontite veins is Mn-nodules (or crusts) inherited from a syn-depositional, low-T submarine alteration system. In contrast, fluid influx during late-stage veining produced both "watermelon" (piemontite cores, pistacite rims) and "reverse watermelon" EGM grains. Other outcrops show disequilibrium between EGM in veins versus host rocks, yielding "green" host rocks with "pink" veins. Additional small-scale veins include: 1) quartz+piemontite fibre veins in piemontite-bearing host rocks; and 2) pistacite-rich, pervasively epidotized or pink- and green-zoned, "brown epidote"-bearing host rocks, cut by quartz veins that contain pink-green epidote +/- piemontite-rich cores or rims. At larger scales, some outcrops show quartz+piemontite veins in piemontite-bearing host rocks, overlain within meters by quartz+pistacite veins in pistacite-bearing host rocks; some EGM alteration is layer-bound. Both SEM and LA-ICP-MS data show that fluids transported minor and trace elements on m-scales: this scale and style of major element mobility yielded assemblages with brilliant colors and complex microstructures within several units of Ritter Range metatuff. Experiments show that at 600oC (a plausible metamorphic T), pistacite forms at fO2 conditions between the HM and NNO buffers, whereas piemontite requires the extreme fO2 conditions of the CuCuO buffer (Liou, 1973; Keskinen and Liou, 1987). Veining of these metatuffs testifies to: 1) unusual protoliths; 2) short-length scale excursions from "fluid-" to "rock-buffered" alteration styles; 3) seafloor-based, syn- to slightly post-eruptive alteration, followed much later by pluton-related, fluid-buffered alteration; and 4) a possible influence of fluid-mediated redox excursions upon mineral stabilities.

Sorensen, S. S.

2012-12-01

42

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

43

Origin of quartz-free gold nuggets and supergene gold found in laterites and soils - a review and some new observations  

Microsoft Academic Search

Although most quartz-bearing gold nuggets have been shed from quartz veins, supergene processes commonly upgrade the quality (fineness) of their gold. Similarly, some quartz-free nuggets can be shown to have been shed from ultramafic schists or carbonates where they were precipitated from hydrothermal fluids. On the other hand, other quartz-free nuggets of superior fineness (e.g. Au 96.5, Ag 3.5, wt.%)

Allan F. Wilson

1984-01-01

44

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

45

Fluid evolution in quartz vein-hosted tungsten mineralization in Chhendapathar, Bankura District, West Bengal: Evidence from fluid inclusion study  

NASA Astrophysics Data System (ADS)

Tungsten mineralization in Chhendapathar area is hosted by quartz veins that traverse mostly the metasediments in and around Jikhu Nala. Fluid inclusion microthermometric experiments reveal the presence of four distinct types of inclusions. These are: aqueous biphase, monophase carbonic, aqueouscarbonic and halite-bearing polyphase inclusions. Salinity-temperature variation points towards the presence of two fluids of contrasting salinities and both independently followed simple cooling paths without any indication of fluid mixing. The P-T of mineralization was calculated from the intersection of coexisting and coeval aqueous biphase, carbonic and halite-bearing inclusions. The deduced values range from 1.63kb/361°C to 2.30kb/385°C. However, the initial temperature must have been much higher as indicated from the high dissolution temperature (> 450°C) of halite. Transportation of tungsten in the high saline fluid was facilitated by cation-tungstate ion pairing, i.e., with the help of Na2WO4 and/or NaHWO4 complexes. A rapid fall in solubility in such fluid with falling temperature (in the range of 300-400°C), and by occasional fluid-rock interaction triggered precipitation of wolframite.

Mishra, B.; Pal, D. C.; Panigrahi, M. K.

1999-03-01

46

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

47

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

Microsoft Academic Search

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

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

2001-01-01

48

Combined gas and ion chromatographic analysis of fluid inclusions: Applications to Archean granite pegmatite and gold-quartz vein fluids  

NASA Astrophysics Data System (ADS)

The first stage in the interpretation of bulk fluid inclusion analytical data involves consideration of the relative amounts and types of fluid inclusions in a sample, in order to determine which inclusion type dominates the volatile and/or ion bulk analytical data. This then permits discussion of processes affecting fluid chemistry such as fluid-mineral equilibria, metasomatism, and phase separation, and leads to constraints on primary source region fluid composition. This interpretive procedure has been applied to data obtained by combined gas and ion Chromatographic analysis of well characterized samples from the Archean Tanco granitic pegmatite, southeastern Manitoba and the Hollinger-McIntyre and Kerr Addison Archean Au-quartz vein systems, northern Ontario. The bulk composition of an homogeneous late stage magmatic fluid in Lower Intermediate Zone vug quartz from the Tanco pegmatite is 90.6 mol% H 2O, 3.35 mol% CO 2, 2.45 mol% Li + , 2.40 mol% Cl -, 1.01 mol% Na +, and other trace species < 1 mol%. The Li +/(Li + + Na +) ratio of 0.69 ± 0.008 for this fluid is greater than a published experimental determination of 0.45 ± 0.02 for a comparable system, probably owing to the CO 2-rich nature of the vug quartz fluids. The halogen (Cl -, Br -, I -) and alkali metal enriched nature of this fluid is consistent with the advanced degree of igneous fractionation of the pegmatite. Compared to estimated bulk earth values, the Br -/Cl - ratio of 12.9 × 10 -3 (molar) is high and may be the result of igneous fractionation while the I -/Cl - ratio (140 × 10 -6molar) is low, suggesting that another process governs I - behaviour. Tanco quartz zone samples show trace gas depletion trends comparable to those obtained from samples trapping phase separated fluids in low pressure geothermal systems. Trends in the Tanco cation/anion data reflect both fluid-mineral equilibria and phase separation effects. Li + and Cl - show a closely correlated decrease with increasing CO 2/CH 4 ratio while Na + shows no change, consistent with partitioning of Li + and Cl - in favour of the CO 2-rich phase, which could have contributed to the calcite and holmquistite-bearing propylitic alteration zone around the pegmatite. Average bulk compositions for Hollinger-McIntyre and Kerr Addison fluids are similar and consist of 80-90 mol% H 2, 2-15 mol% CO 2, 1-3 mol% Cl -, 2-4 mol% Na +, and trace species < 1 mol%. Hollinger-McIntyre volatiles show clear wall rock reaction effects while Kerr Addison fluids show strong phase separation trends. Br -/Cl - ratios of ˜5.5 to 10 × 10 -3 for Hollinger-McIntyre and Kerr Addison fluids are greater than bulk earth while I -/Cl - × 10 6 ratios are low, with a range from ˜20-105. Hollinger-McIntyre and Tanco samples dominated by secondary brine inclusions have Br -/Cl - × 10 3 ratios of ˜13 and ˜ 15, respectively, showing that these secondary fluids are distinct from shield brines ( Br -/Cl - ˜ 3 to 5.5 × 10 -3). Both of these samples have distinctive trace hydrocarbon signatures.

DeR Channer, D. M.; Spooner, E. T. C.

1994-02-01

49

Colloidal gold and silica in mesothermal vein systems  

Microsoft Academic Search

Some of the textural features of mesothermal gold-quartz veins may be best explained by the initial precipitation of amorphous silica gel (colloid), which subsequently crystallizes to quartz. This can occur in brittle-ductile shear zones where a significant fluid-pressure drop occurs during stick-slip failure. Such a process rapidly supersaturates the hydrothermal fluid with respect to amorphous silica, which precipitates instead of

R. J. Herrington; J. J. Wilkinson

1993-01-01

50

Permeability and Porosity Evolution of Quartz Fault Gouges During Hot Pressing Under Hydrothermal Conditions  

NASA Astrophysics Data System (ADS)

We present experimental results designed to explore the evolution of fluid transport properties of fault zones during the interseismic period. Permeability (k) was measured in situ during hot pressing (HIPing) experiments at temperatures between 700-850°C, with confining and pore water pressures of 250 MPa and 150 MPa, respectively. To test the effects of grain size and differential stress on the compaction process, we used two different quartz powders and varied the applied axial load in one experiment. Over the range of temperatures tested, significant permeability reduction was observed. Permeability change was fastest at the highest temperature (850°C), decreasing more than one order of magnitude per hour. Permeability decreased exponentially with time, with the permeability reduction rate increasing with increasing temperature, increasing differential stress, and decreasing grain size. Total porosity (?) and accessible porosity of hot-pressed samples were analysed using four different methods. Analysis of the obtained k- ? relationship indicates that fluid flow in the simulated gouge analogue shuts off at a critical porosity of 0.045±0.04. The microstructure of deformed specimens is dominated by dissolution and precipitation features as indicated by grain interpenetration, grain-shape truncation, arrays of fluid inclusions and development of quartz overgrowths. The apparent activation energy between 700-800°C was determined as 73±14kJ/mol, which is in good agreement with previous studies at much lower temperatures in which solution-precipitation creep was inferred the dominant deformation mechanism. Using the determined apparent activation energy, the permeability reduction rates of this study are extrapolated to temperatures typical of the continental seismogenic regime (i.e. ? 300-450°C) to constrain how permeability evolves during the interseismic period. For example, at 200°C, the permeability of a quartz fault gouge with a grain size ? 37?m decreases about one order of magnitude every 16 years. At this rate, permeability could decrease orders of magnitude in fault wear products within the recurrence time of major earthquakes. Our results have significant implications for understanding how fluid flow rates and fluid pressures might evolve during interseismic periods in fault zones, and thereby impact on rupture nucleation and recurrence in the continental seismic regime.

Giger, S. B.; Tenthorey, E.; Cox, S. F.; Fitz Gerald, J.

2006-12-01

51

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

52

Huebnerite veins near Round Mountain, Nye County, Nevada  

SciTech Connect

Small huebnerite-bearing quartz veins occur in and near Cretaceous (about 95 m.y. old) granite east and south of Round Mountain. The veins are short, lenticular, and strike mostly northeast and northwest in several narrow east-trending belts. The quartz veins were formed about 80 m.y. ago near the end of an episode of doming and metamorphism of the granite and emplacement of aplite and pegmatite dikes in and near the granite. An initial hydrothermal stage involved deposition of muscovite, quartz, huebnerite, fluorite, and barite in the veins. Veins were then sheared, broken, and recrystallized. A second hydrothermal stage, possibly associated with emplacement of a rhyolite dike swarm and granodiorite stock about 35 m.y. ago, saw deposition of more muscovite, quartz, fluorite, and barite, and addition of scheelite, tetrahedrite-tennantite, several sulfide minerals, and chalcedony. Finally, as a result of near-surface weathering, secondary sulfide and numerous oxide, tungstate, carbonate, sulfate, phosphate, and silicate minerals formed in the veins. Depth of burial at the time of formation of the veins, based on geologic reconstruction, was about 3-3.5 km. The initial hydrothermal stage ended with deposition of quartz at a temperature of about 210/sup 0/C and pressures of about 240 to 280 bars from fluids with salinity of about 5 wt % sodium chloride. Fluorite then was deposited at about 250/sup 0/ to 280/sup 0/C from solutions of similar salinity and containing a small amount of carbon dioxide. During shearing that followed initial mineralization, quartz was recrystallized at a temperature of 270/sup 0/ to 290/sup 0/C and in association with fluids of about 5 wt % sodium chloride equivalent and containing carbon dioxide. Late-stage fluorite was deposited from fluids with similar salinity but devoid of carbon dioxide at a temperature of about 210/sup 0/C. 76 refs., 38 figs., 8 tabs.

Shawe, D.R.; Foord, E.E.; Conklin, N.M.

1984-01-01

53

Extreme chemical heterogeneity of granite-derived hydrothermal fluids: An example from inclusions in a single crystal of miarolitic quartz  

NASA Astrophysics Data System (ADS)

Magma-derived fluids are important in geologic processes (e.g., metal sequestration and ore deposition) but are intrinsically transient. Samples of magmatic fluids represented by fluid inclusions in a single zoned quartz crystal from a miarolitic cavity within a porphyritic leucogranite hosting the Industrialnoe tin deposit, northeastern Russia, were studied by using modern in situ analytical methods (laser Raman spectroscopy, proton-induced X-ray emission). The fluid inclusions are either dominated by vapor or by complex multiphase brines. The inclusions within a given trapping plane have similar phase relationships; however, there are significant variations between inclusions in different healed fractures. Phase and chemical compositions of individual brine inclusions demonstrate significant compositional heterogeneity (in terms of absolute element concentrations and ratios) of high-temperature magmatic fluids accumulated in the miarolitic cavity. This finding suggests that fluids leaving a crystallizing magma may have variable initial compositions that are subsequently modified by reactions with the rocks while the fluid is in transit to a miarolitic cavity, as well as by processes in the cavity, such as mixing, crystallization, and boiling. The inferred chemical diversity and fractionation of granite-derived fluids at near-magmatic conditions imply that fluids entering a cooler hydrothermal system are extremely complex and their metallogenic signature may differ from that of related ore deposits.

Kamenetsky, Vadim S.; van Achterbergh, Esme; Ryan, Chris G.; Naumov, Vladimir B.; Mernagh, Terrence P.; Davidson, Paul

2002-05-01

54

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

55

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

56

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

NASA Astrophysics Data System (ADS)

Ocean Drilling Program Leg 193 drilled into areas of focused and diffuse venting from the PACMANUS hydrothermal field along Pual Ridge, eastern Manus Basin. Pual Ridge is primarily composed of fresh dacite that is pervasively altered to argillaceous (illite-chlorite) and overprinting acid-sulfate (pyrophyllite-anhydrite) and siliceous secondary mineral assemblages. Anhydrite is an abundant precipitate in all cores recovered beneath the active vent field. Isotopic (Sr, S), elemental (Mg, Sr, REE) and fluid inclusion analyses on anhydrite mineral separates demonstrate that pathways of fluid evolution (magmatic input, variable fluid composition, seawater entrainment) differ on the meter scale within this system. In addition, large variations in REE content, S (? 34S > 5‰ ) and Sr (87Sr/86Sr > 1000 ppm) isotope composition are observed within individual anhydrite veins. Using microbeam techniques, we have analyzed this small scale chemical and isotopic heterogeneity in order to unravel the record of hydrothermal processes occurring at PACMANUS. Cathodoluminescence microscopy is used to distinguish between different crystal growth textures (e.g., oscillatory versus sector zoning). A Finnigan Neptune laser-ablation MC-ICP-MS is used to measure 87Sr/86Sr, and a Cameca 3f ion microprobe and a Finnigan Element2 laser-ablation MC-ICP-MS to measure REE and minor element concentrations in these zones. Initial microbeam measurements of sector-zoned crystals reveal REE patterns trending from mid-REE enriched to MREE depleted with distance from crystal center and with a uniform 87Sr/86Sr (0.7087). Analyses for oscillatory zoned crystals reveal variable and increasing 87Sr/86Sr (0.7043 to 0.7089) and REE patterns trending from light-REE enriched to LREE depleted with both negative and positive Eu anomalies during crystal growth. 87Sr/86Sr reproducibility for an isotopically homogenous anhydrite is better than 40 ppm. The Sr isotopic composition range for heterogenous crystals (> 4000 ppm) is hence greater than 100 times the analytical uncertainty of our LA-MC-ICP-MS method. The general trend of these data can be modeled by Rayleigh-type fractional crystallization of anhydrite, with sector zoned anhydrite precipitating from a seawater dominated fluid and oscillatory zoned anhydrite forming from a hydrothermally dominated fluid following introduction of seawater into the basement. Future microbeam REE, Sr and S-isotope analyses are planned to provide a more comprehensive view of fluid evolution and mineral formation within this backarc hydrothermal system.

Craddock, P. R.; Bach, W.

2004-12-01

57

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

58

Thermodynamics of hydrothermal systems with oxalate ion  

Microsoft Academic Search

The geochemical and industrial significance of oxalates have led to great interest in the behavior of oxalate ion in hydrothermal systems. On the basis of a study by G.B. Naumov et al (1971) of gaseous-liquid inclusions it is shown that whewellite (CaC2O4•H2O) which was found in quartz-calcite-fluorite veins in the uranium ore deposit of the Eastern Transbaikal region was formed

I. L. Khodakovsky; O. A. Devina

2009-01-01

59

Mesothermal gold vein mineralization of the Samdong mine, Youngdong mining district, Republic of Korea  

Microsoft Academic Search

Mesothermal gold mineralization at the Samdong mine (5.5–13.5 g\\/ton Au), Youngdong mining district, is situated in massive quartz veins up to 1.2 m wide which fill fault fractures within upper amphibolite to epidote-amphibolite facies, Precambrian-banded biotite gneiss. The veins are mineralogically simple, consisting of iron- and base-metal sulfides and electrum, and are associated with weak hydrothermal alteration zones (2 and

Chil-Sup So; Seong-Taek Yun; K. L. Shelton

1995-01-01

60

Quantitative trace element analysis of single fluid inclusions by proton-induced X-ray emission (PIXE): application to fluid inclusions in hydrothermal quartz  

NASA Astrophysics Data System (ADS)

Single fluid inclusion analogues with known elemental composition and regular shape were analyzed for trace element contents by particle-induced X-ray emission (PIXE)—a nondestructive method for the analysis of single fluid inclusions—to evaluate the accuracy and detection limits of this type of analysis. Elements with concentrations of 10 to 1000 ppm were measured with average estimated relative error of ±7%. For natural fluid inclusions with 30 ?m radius and 20 ?m depth in quartz, the total analytical errors were estimated to be ±40% relative for Ca, ±16% for Fe, ±13% for Zn, ±12% for Sr, and ±11% for Br and Rb, by considering uncertainties in microscopic measurements of inclusion depths. Detection limits of 4 to 46 ppm for elements of mass numbers 25-50 were achieved for analyses of a spherical fluid inclusion with 30 ?m radius and 20 ?m depth in quartz, at an integrated charge of 1.0 ?C. The trace element compositions of single fluid inclusions in a hydrothermal quartz crystal were also determined. The elemental concentrations in the inclusions varied widely: 0.2-9 wt.% for Ca and Fe, 300-8000 ppm for Mn and Zn, 40-3000 ppm for Cu, 100-4000 ppm for Br, Rb, Sr, and Pb, and less than 100 ppm for Ge. Elemental concentrations of secondary fluid inclusions on the same trail varied over an order of magnitude, even though all these inclusions were formed from the same fluid. Elemental concentrations in inclusions on the same trail are positively correlated with each other, except for Cu and Rb. Ratios of almost all elements in the inclusions on the trail were essentially unchanged; thus, the elemental ratios can provide original information on trace element compositions of a hydrothermal fluid.

Kurosawa, Masanori; Shimano, Sadayoshi; Ishii, Satoshi; Shima, Kunihiro; Kato, Takumi

2003-11-01

61

Quartz diorite veins in a peridotite xenolith from Tallante, Spain: implications for reaction and survival of slab-derived SiO2-oversaturated melt in the upper mantle  

NASA Astrophysics Data System (ADS)

We found quartz diorite veins (up to 5 mm thick), composed mainly of plagioclase and quartz, in a plagioclase-bearing spinel lherzolite xenolith in alkali basalt from Tallante, Southern Spain. The quartz diorite veins are coarse-grained, the average grain size being 0.5 mm, and have thin orthopyroxenite rim along olivine wall. Thinner veins free of quartz and composed solely of plagioclase with orthopyroxene selvage are much more common in other xenoliths from Tallante. The involved melt was strongly reactive with olivine to form orthopyroxene, which can protect against further reaction. This suggests how the silica-oversaturated melts, after supplied from downgoing slabs, can move through peridotite and reach the shallow mantle with preserving the silica-oversaturated character. The armor of orthopyroxenite is of vital importance for the melt to keep its silica-oversaturated character within peridotite. Precipitation of orthopyroxene combined with olivine consumption somewhat controls the general chemical trend of adakite. Orthopyroxenite vein network at the expense of olivine is expected to be common as fossil conduits within the mantle wedge. This kind of orthopyroxenite has contributed to Si-enrichment of the mantle wedge.

Arai, S.; Shimizu, Y.; Gervilla, F.

62

Molybdenite Re-Os and muscovite 40Ar/39Ar dating of quartz vein-type W-Sn polymetallic deposits in Northern Guangdong, South China  

NASA Astrophysics Data System (ADS)

Northern Guangdong is an important part of Nanling tungsten-tin metallogenic belt, South China. The tungsten mineralization in this area consists of mainly quartz-wolframite vein-type mineralization, with W-Sn polymetallic deposits mostly distributed at the outer contact zone between concealed Late Jurassic granitic stocks and Cambrian-Ordovician low-metamorphosed sandstones and shales. Molybdenite Re-Os and muscovite 40Ar/39Ar isotopic dating of three typical tungsten vein-type deposits (Yaoling, Meiziwo, and Jubankeng) in northern Guangdong, show that two episodes of Late Jurassic W-Sn polymetallic mineralization occurred in this area: an early episode during the Late Jurassic (158-159 Ma) represented by the Yaoling, Hongling, and Meiziwo tungsten deposits, and a younger event during the Early Cretaceous (138 Ma) represented by the Jubankeng deposit. Analysis of available radiometric ages of several W-Sn deposits in the Nanling region indicate that these deposits formed at several intervals during the Mesozoic at 90-100, 134-140, 144-162, and 210-235 Ma, and that large-scale W-Sn mineralization in this region occurred mainly between 150 and 160 Ma.

Qi, Hua-Wen; Hu, Rui-Zhong; Wang, Xiao-Fei; Qu, Wen-Jun; Bi, Xian-Wu; Peng, Jian-Tang

2012-08-01

63

Tectono-metamorphic evolution of the siliciclastic units in the Middle Tuscan Range (inner Northern Apennines): Mg-carpholite bearing quartz veins related to syn-metamorphic syn-orogenic foliation  

NASA Astrophysics Data System (ADS)

This paper accounts for a new finding of High Pressure-Low Temperature (HP-LT) metamorphism documented in continental-derived rocks exposed in the central part of the Middle Tuscan Range, representing the easternmost location, in the Tyrrhenian Region, where blueschist facies metamorphism has been documented. It describes the development mechanism of Mg-carpholite bearing quartz veins in the framework of the deformational events described for the inner Northern Apennines. The HP-LT peak metamorphism can be estimated in P ? 1.1 GPa and T = 370°-420 °C as supported by the mineralogical assemblage consisting of quartz-muscovite-chloritoid-pyrophylite-hematite ± chlorite ± paragonite ± Ti-oxides, documented in the aluminous metasediments (pelites and quartzose sandstones) of the Triassic Verrucano succession. This paragenesis defines the S1 schistosity, an axial planar tectonic foliation associated to map- and mesoscale isoclinals folds (F1); S1 schistosity is a composite foliation resulted from a non-coaxial progressive deformation associated to the DE1 collisional event (Late Oligocene-Early Miocene). Mg-carpholite bearing quartz veins developed as tension gashes in en-échelon arrays within brittle/ductile shear zones. The development of quartz veins was guaranteed by the high volumes of Si-rich fluids produced by the dynamic recrystallization process on the siliciclastic rocks.

Brogi, Andrea; Giorgetti, Giovanna

2012-03-01

64

Hydrothermal alteration of oxygen isotope ratios in quartz phenocrysts, Kidd Creek mine, Ontario: Magmatic values are preserved in zircon  

Microsoft Academic Search

Zircons from rhyolites hosting the Kidd Creek volcanogenic massive sulfide deposit preserve magmatic oxygen isotope ratios (delta18O = 5.40\\/00 ± 0.30\\/00, n = 11) that are indistinguishable from average values of other plutonic and volcanic rocks of the Superior Province. Oxygen isotope ratios of petrographically pristine, primary quartz phenocrysts, however, are greatly elevated in delta18O and heterogeneous (delta18O = 14.20\\/00

Elizabeth M. King; C. Tucker Barrie; John W. Valley

1997-01-01

65

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

66

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

67

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

USGS Publications Warehouse

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

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

2005-01-01

68

40 Ar\\/ 39 Ar and K–Ar geochronology of magmatic and hydrothermal events in a classic low-suphidation epithermal bonanza deposit: El Peñon, northern Chile  

Microsoft Academic Search

The epithermal El Peñon gold–silver deposit consists of quartz–adularia veins emplaced within a late Upper Paleocene rhyolitic dome complex, located in the Paleocene–Lower Eocene Au–Ag belt of northern Chile. Detailed K–Ar and 40Ar\\/39Ar geochronology on volcano–plutonic rocks and hydrothermal minerals were carried out to constrain magmatic and hydrothermal events. The Paleocene to Lower Eocene magmatism in the El Peñon area

Gloria Arancibia; Stephen J. Matthews; Paula Cornejo; Carlos Pérez de Arce; José I. Zuluaga; Stabro Kasaneva

2006-01-01

69

Porphyry-Cu-Mo Stockwork Formation by Dynamic, Transient Hydrothermal Pulses: Mineralogic Insights From the Deposit at Butte, Montana  

NASA Astrophysics Data System (ADS)

The temperature profile in magmatic-hydrothermal systems directly affects the chemical behavior and pressure regime of hydrothermal fluids and the resulting diversity of mineralization. We combine textural observations of igneous and hydrothermal minerals using SEM-CL and -BSE images with three independent mineral thermobarometers to better understand the thermal profile at the porphyry-Cu-Mo deposit in Butte, Montana. We apply the two most recent (and controversial) forms of the Ti-in-quartz thermobarometer from Thomas et al. (2010) and Huang and Audétat (2011), the Zr-in-rutile thermobarometer of Tomkins et al. (2007), and the XMg-Ti-in-biotite thermometer of Henry et al. (2005) to estimate the formation temperatures of these magmatic and hydrothermal minerals. In a comparison of isobaric temperature distributions from Ti-in-quartz (Thomas et al., 2010) and Zr-in-rutile we find that the Thomas et al. calibration consistently yields temperatures that are 50 to 200°C lower than those from Zr-in-rutile. These quartz temperatures are unreasonably low for quartz phenocrysts and are considerably lower than previous estimates for vein quartz. Temperature estimates from the Zr-in-rutile and XMg-Ti-in-biotite thermobarometers agree well with each other and with previous temperature estimates. We conclude that application of the Ti-in-quartz thermobarometer of Thomas et al. is not appropriate for this natural system. Quartz temperatures calculated using the calibration of Huang and Audétat (2011) are closer to those from rutile and biotite. Application of the Ti-in-quartz thermobarometer of Huang and Audétat to hydrothermal samples yields maximum temperature estimates, however, and requires evaluation of trace element abundances (e.g., Ti, Al) and other crystal lattice impurities (e.g., fluid inclusions) in growth zones as a means to determine whether growth zones represent slow or fast-growing quartz. Using thermobarometry from rutile, biotite, and quartz (Huang and Audétat, 2011), we estimate that the final dike injection temperature, and hence the initial magmatic-hydrothermal fluid temperature, was ~700°C while the ambient host rock temperature was ?500°C. There is a magmatic-hydrothermal continuum represented in hydrothermal veins, ranging from ~710 to <440°C. Distinct mineral generations within veins consistently display large temperature ranges, spanning 50 to 250°C, likely recording mineralization from thermally unequilibrated fluids. Mineral precipitation temperatures within veins are indistinguishable from those in accompanying envelopes, indicating contemporaneous formation of veins and envelopes. Magmatic and hydrothermal samples show no systematic relationship between temperature and depth within the deposit, and we observe anomalous cross-cutting relationships indicating that vein formation temperatures fluctuated significantly within a single cm3 parcel of rock. We suggest that the thermal profile does not mimic domical isograds at any given time, but rather evolves dynamically by discrete cycles of transitory, high-temperature hydrofracturing, fluid release, and vein formation that overprints the cooler host rock thermal gradient.

Mercer, C. N.; Reed, M. H.

2011-12-01

70

Organic inclusions within hydrothermal minerals from S.W. Africa and elsewhere.  

NASA Technical Reports Server (NTRS)

It was observed that quartz crystals from veins within a diabase dike of precambrian age from S.W. Africa contain organic particles which closely resemble, in detailed morphology, coacervates, proteinoid microspheres or fossil and recent microorganisms. The microphotospectrographs in visible and near-ultraviolet light of these minute particles revealed a strong absorption peak at the vicinity of 4000 A, which is indicative of lipids. Hydrothermal mineral from veins from a number of other localities proved to contain the biomorphic organic particles. The theoretical significance of these organic particles is discussed with reference to problems of origin of life.

Mueller, G.

1972-01-01

71

Comparative study of ore-forming fluids of hydrothermal copper–gold deposits in the lower Yangtze River Valley, China  

Microsoft Academic Search

Fluid-inclusion and stable isotope studies were carried out on five types of Mesozoic (Yanshanian) hydrothermal copper–gold deposits in the lower Yangtze River Valley. Deposits include (1) copper in cryptoexplosive breccia pipes, (2) skarn copper, (3) porphyry copper, (4) high-temperature quartz vein-type copper and gold, and (5) medium–lower temperature fracture zone gold. This research has allowed a comparison between various types

Lianxing Gu; Changzhi Wu; Zunzhong Zhang; Franco Pirajno; Pei Ni; Peirong Chen; Xinjian Xiao

2011-01-01

72

Cl\\/Br ratios and stable chlorine isotope analysis of magmatic-hydrothermal fluid inclusions from Butte, Montana and Bingham Canyon, Utah  

Microsoft Academic Search

A bulk geochemical study has been carried out on fluid inclusion leachates extracted from quartz veins from porphyry Cu deposits in Butte, Montana, USA and Bingham Canyon, Utah, USA. The leachates mostly represent low-salinity magmatic-hydrothermal fluid inclusions. Their halogen ratios (Br\\/Cl) of fluid inclusion leachates were determined by ion chromatography, and delta Cl-37 values of the leachates were measured by

Taras Nahnybida; Sarah A. Gleeson; Brian G. Rusk; Len I. Wassenaar

2009-01-01

73

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

NASA Astrophysics Data System (ADS)

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

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

1996-01-01

74

A structural analysis of the Minas da Panasqueira vein network and related fracture generations  

NASA Astrophysics Data System (ADS)

The Minas da Panasqueira is a world-class W-Cu-Sn vein-type deposit, situated within the Central Iberian Zone of the Palaeozoic Iberian Massif (Portugal). The deposit consists of a network of subhorizontal, sill-like massive quartz veins situated above the southwestern extremity of a greisen cupola, within regionally metamorphosed, isoclinally folded, lower-greenschist slates and greywackes. The greisen cupola is part of a larger intrusive complex, emplaced during the late- to post-tectonic stage of the Variscan orogeny. The late-Variscan granitoid(s) underlying the Panasqueira deposit is considered to have served as a major metal source. The structure of the network of subhorizontal extension veins, consists of numerous planar vein lobes that are separated by host-rock bridges and merge at branch-points. A structural analysis demonstrates that not only within the Panasqueira mine, but also on a more regional scale, one or more generations of flat-lying fractures are present. The veins clearly exploited these pre-existing discontinuities, as confirmed by (1) the vein geometry being directly influenced by variations in the orientation of the initial fracture sets and (2) the geometry of the rock bridges and overlapping vein morphologies, consistently showing straight-line propagating crack tips. If veining is governed by a preferential, strongly developed anisotropy in the host rock, the hypothesis of vein lobes and rock bridges forming during propagation of the parent crack by tip-line bifurcation and confinement processes (Foxford et al., 2000) does not seem plausible. Instead, we propose that the rock bridges formed from several, initially separate and small veinlets that eventually overlapped in an en echelon arrangement during progressive propagation and inflation. Bending of the rock bridges and incipient vein rotation indicate that veining occurred near the brittle-ductile transition. Using a quantitative analysis of bridge orientations, vein aspect ratios and tip lines, we try to sort out if a dominant ?2 propagation direction, typical for hydrofractures, exists within the vein network. By doing so, we can evaluate whether the subhorizontal vein network formed under a compressive stress regime, or was mainly dictated by the strength anisotropy of the rocks under near-isotropic stress conditions of ?hmax ? ?hmin. The regional dominance of subhorizontal aplites, pegmatites and hydrothermal veins, exploiting subhorizontal fracture networks, occurs over a wide area of more than 100 km2 along the Serra de Estrela granitic massif (Derré et al., 1986). This orientation contrasts with the more common vertical attitude of granite-related hydrothermal veins, observed throughout the Iberian massif. A detailed orientation analysis of the fracture sets should allow to explore the possible causes of this particular late orogenic, flat-lying fracture network related to the granitic intrusion. References Derré, C., Lecolle, M., Roger, G., Tavares de Freitas Carvalho, J., 1986. Tectonics, magmatism, hydrothermalism and sets of flat joints locally filled by Sn-W, aplite-pegmatite and quartz veins, southeastern border of the Serra de Estrela granitic massif (Beira Baixa, Portugal). Ore Geology Reviews 1, 43-56. Foxford, K. A., Nicholson, R., Polya, D. A., and Hebblethwaite, R. P. B., 2000. Extensional failure and hydraulic valving at Minas da Panasqueira, Portugal; evidence from vein spatial distributions, displacements and geometries. Journal of Structural Geology 22, 1065-1086.

Jacques, Dominique; Vieira, Romeu; Muchez, Philippe; Sintubin, Manuel

2014-05-01

75

Varicose Veins  

MedlinePLUS

Varicose veins are swollen, twisted veins that you can see just under the skin. They usually occur in ... of the body. Hemorrhoids are a type of varicose vein. Your veins have one-way valves that help ...

76

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

77

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

78

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

79

Middle Archean island arc volcano-hydrothermal sequence: 3.2-Ga Dixon Island Formation, coastal Pilbara terrane, Australia  

NASA Astrophysics Data System (ADS)

The 3.2-Ga Dixon Island Formation in the Cleaverville Group of the coastal Pilbara terrane, Australia, is one of the most complete and best-preserved examples of middle Archean oceanic stratigraphy. Field observations and geochemical evidence suggest that this formation contains a low-temperature hydrothermal-vent system with a biogenic microbial colony from the Archean ocean. The Dixon Island Formation is approximately 350 m thick and consists of the Rhyolite Tuff, Black Chert and Varicolored Chert members, in ascending order. The Rhyolite Tuff Member contains many vein swarms, such as fine quartz vein and two black-chert veins with in highly altered rhyolite tuff layers. This vein rich and highly altered vein zones are identified as an underground bypass zone for circulating hydrothermal fluid. The Black Chert Member, which is 10 - 15 m thick, is composed of massive black chert, laminated black chert, dark greenish siliceous shale, stromatolite-like biomat bed and tuffaceous laminated chert. The absence of detrital sediment of continental origin and the many vein injections imply that this sedimentary facies represents a pelagic hydrothermal environment at about 500 - 2000 m in paleodepth, and may have been on the slope of an immature island arc. More then 500 samples of detail chemical anarysis from black chert veins and black chert bed suggest that the total organic carbon (TOC) value of massive black chert in the lower part of the Black Chert Member is higher (TOC=0.15-0.45%) than that of the overlying laminated chert section (TOC=0.02-0.15%) and the black chert vein (TOC=0.1-0.13). The carbon isotope (delta13C) values of this lithology (-33 - -27 per mil) are also lighter than for the black-chert veins (-29--26 per mill) and the laminated black chert in the upper part of the Black Chert Member and the Vari-colored Chert Member (-27 - -13 per mil). Especially, -40 per mill carbon isotope identified near the biomat beds. These evidences suggest that the carbonaceous grains bearing massive black chert in the lower part of the Black Chert Member is identified as directory from the black chert vein. On the other hand, biogenic materials, biomat bed and very low carbon isotope suggest the biogenic activity formed above a low-temperature hydrothermal vent. The microbial colony may have been rapidly fossilized by silicification related to hydrothermal activity. Laminated black chert in the upper part of the Black Chert and the Varicolored Chert members may have formed by cyanobacterial sedimentation from the ocean surface.

Kiyokawa, S.; Katagami, A.; Ito, T.; Ikehara, M.; Kitajima, F.

2005-12-01

80

Varicose Veins  

MedlinePLUS

... page from the NHLBI on Twitter. What Are Varicose Veins? Varicose (VAR-i-kos) veins are swollen, twisted ... can form in other parts of the body. Varicose veins are a common condition. They usually cause few ...

81

Quartz Crystal.  

National Technical Information Service (NTIS)

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

J. E. Ferrell

1985-01-01

82

Age and origin of base and precious metal veins of the Coeur d'Alene mining district, Idaho  

USGS Publications Warehouse

Ore-bearing quartz-carbonate veins of the Coeur d'Alene mining district yield 87Sr/86Sr ratios of 0.74 to >1.60 for low Rb/Sr, carbonate gangue minerals, similar to current ranges measured in Middle Proterozoic, high Rb/Sr rocks of the Belt Supergroup. Stable isotope and fluid inclusion studies establish a genetic relationship between vein formation and metamorphic-hydrothermal systems of the region. These extraordinary 87Sr/86Sr ratios require accumulation of radiogenic 87Sr in a high Rb/Sr system over an extended period prior to incorporation of Sr into the hydrothermal veins. Evaluation of the age and composition of potential sources of highly radiogenic Sr indicates that the ore-bearing veins of the Coeur d'Alene district formed during the Cretaceous from components scavenged from rocks of the Belt Supergroup, the primary host rocks of the district. Proterozoic Pb isotope ratios observed in galena from many Coeur d'Alene veins were established when Pb separated from uranium during deposition or diagenesis of the Belt Supergroup at 1400 to 1500 Ma, possibly as disseminated syngenetic deposits. K-Ar and Rb-Sr apparent ages and ??18O values of Belt Supergroup rocks decrease from the Coeur d'Alene district toward the Idaho and Kaniksu batholiths, approximately normal to the trends of metamorphic isograds, fold axes, foliation, and the major reverse faults of the district. Isoclinal folding, thrust faulting, high-temperature metamorphism, granitic plutonism, and regional-scale metamorphic-hydrothermal activity is documented in the region between 140 and 45 Ma, representing the only such combination of events in the Coeur d'Alene region subsequent to about 1300 Ma. The Sr and oxygen results and geologic evidence favor formation of the ore-bearing carbonate veins by fluids related to a complex metamorphic-hydrothermal system during the Cretaceous. Pb with Proterozoic isotopic compositions was probably mobilized and incorporated like other metals into the hydrothermal veins during this event. The ore-bearing veins were sheared and displaced during early Tertiary northwest-trending dextral strike-slip faulting along the Osburn fault and related structures of the Lewis and Clark line.

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

2002-01-01

83

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

84

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

85

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

86

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

SciTech Connect

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

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

2000-11-07

87

Mineral distribution within polymineralic veins in the Sanbagawa belt, Japan: implications for mass transfer during vein formation  

Microsoft Academic Search

Pelitic schists of the Sanbagawa metamorphic belt contain several types of polymineralic veins that formed during the late\\u000a stages of exhumation. The vein mineral assemblages are quartz + albite + K-feldspar + chlorite ± calcite (Type I, II) and\\u000a quartz + albite + calcite (Type III). Type I and II veins contain quartz and albite with stretched-crystal and elongate-blocky\\u000a textures, respectively. The mineral species within Type I veins vary with compositional bands

Atsushi Okamoto; Taketo Kikuchi; Noriyoshi Tsuchiya

2008-01-01

88

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

NASA Astrophysics Data System (ADS)

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

Wise, Michael A.

2009-07-01

89

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

90

Leadville, Colorado district: oxygen isotopic evidence for a magmatic-hydrothermal origin  

SciTech Connect

A magmatic-hydrothermal origin for much of the manto and vein complex at Leadville, Colorado, is indicated by 60 /sup 18/O//sup 16/O and D/H analyses of rocks and minerals. The ore-related samples around Breece Hill all interacted with a high-/sup 18/O and high-D fluid. Phyllically altered Tertiary porphyries equilibrated with fluids of delta/sup 18/O = +4.5 to +7.5 and deltaD = -53 to -70 permil (SMOW). Metal-rich quartz veins above, and vug quartz within manto ore, were deposited by fluids with delta/sup 18/O = +3.4 to +11.3. The host Leadville Dolomite shows high-/sup 18/O alteration adjacent to ore. Finally, silica-dolomite tubes surrounding mantos, possible conduits for spent ore fluids, transmitted fluids of delta/sup 18/O = +6.4 to +8.7. By contrast, early jasperoid and late golden barite formed from meteoric waters. Early white barite formed from a fluid of indeterminate origin. These data clearly show that a local meteoric-hydrothermal system was interrupted by a massive flux of high-/sup 18/O high-D fluid with the isotopic character of magmatic water.

Beaty, D.W.; Thompson, T.B.; Solomon, G.C.

1985-01-01

91

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

92

A Hydrothermal System Associated with the Siljan Impact Structure, Sweden-Implications for the Search for Fossil Life on Mars  

NASA Astrophysics Data System (ADS)

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

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

2003-06-01

93

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

PubMed

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

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

2003-01-01

94

Varicose Veins and Spider Veins  

MedlinePLUS

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95

Vein Problems Related to Varicose Veins  

MedlinePLUS

... this page from the NHLBI on Twitter. Vein Problems Related to Varicose Veins Many vein problems are ... have varicoceles, see your doctor. Other Related Vein Problems Other types of varicose veins include venous lakes, ...

96

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

NASA Astrophysics Data System (ADS)

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

Hulen, Jeffrey B.; Nielson, Dennis L.

1988-06-01

97

Focus on Varicose Veins  

MedlinePLUS

What are varicose veins? Varicose veins are the visible and large, bulging, surface veins, felt under the skin. They generally are larger ... and treatment Focus on Varicose Veins How are varicose veins diagnosed? The diagnosis of varicose veins is made ...

98

What Causes Varicose Veins?  

MedlinePLUS

... page from the NHLBI on Twitter. What Causes Varicose Veins? Weak or damaged valves in the veins can ... space. These are varicose veins. Normal Vein and Varicose Vein Figure A shows a normal vein with a ...

99

Timing of mineralization and source of fluids in a slate-belt auriferous vein system, Hill End goldfield, NSW, Australia: Evidence from {40Ar }/{39Ar } dating and O- and H-isotopes  

NASA Astrophysics Data System (ADS)

{40Ar }/{39Ar } dating of metamorphic biotite and alteration muscovite from the auriferous veins and host rocks at the Hill End goldfield, N.S.W., Australia, has distinguished four major geological events, including the timing of gold mineralization. The earliest hydrothermal event occurred during the Middle Devonian Tabberabberan Orogeny (370-380 Ma) and resulted in the formation of quartz veins barren of Au. A second and major episode of vein emplacement occurred in the Early Carboniferous during the principal phase of metamorphism and deformation at 359-363 Ma. This was followed by Au accumulation in two stages: (1) after the major phases of quartz deposition, and (2) during and after the development of conspicuous internal vein laminations ( 357 Ma and 343 Ma, respectively). Two sources of fluid are proposed for vein and ore formation. The first is a local metamorphic fluid characterized by ? 18O H 2O values of 8.9 to 12.5 per mil and ?D H 2O values of -87 to -90 per mil. The second is a mixed ore fluid with ? 18O and ?D values in the range of ? 18O H 2O 8.4 to 11 per mil and ?D H 2O of -49 to -36 per mil. Progressive entry of this second fluid, sourced from trough-fill or deeper crustal rocks, is linked closely to cycles of gold precipitation at Hill End.

Lu, J.; Seccombe, P. K.; Foster, D.; Andrew, A. S.

1996-09-01

100

Fluid-Dacite Interaction in the PACMANUS Subseafloor Hydrothermal System - Preliminary Results From Secondary Mineral Chemistry and Geochemical Modeling  

NASA Astrophysics Data System (ADS)

During Ocean Drilling Program Leg 193, several holes (as deep as 386 meters below sea floor) intersected variably altered and veined dacites on Pual Ridge in the eastern Manus back-arc basin. The hydothermal alteration is complex and multi-stage, and includes pervasive alteration and alteration halos along anhydrite±pyrite±quartz veins. Our preliminary interpretation is that an early pervasive "chloritic" alteration (chlorite, chlorite/smectite, quartz, +/-albite, +/-magnetite) is overprinted locally by illite-pyrophyllite-anhydrite+/-diaspore alteration followed by silica (quartz and cristobalite) flooding. Two drill holes at Snowcap, a site of diffuse venting, reveal alteration profiles of strongly illite-pyrophyllite-anhydrite altered rocks in the shallow parts grading downwards into rocks that show dominant chloritic alteration. At Roman Ruins, a site of discrete venting, K-feldspar and illite-smectite mixed layer phases are abundant and magnetite is rare. K-feldspar appears to be part of the "chloritic" alteration assemblage. Anhydrite is locally abundant but generally less common than at Snowcap. There is a strong lateral heterogeneity in basement alteration as revealed by the differences between sites in the depths of cristobalite-quartz transition and the zones of prevailing alteration styles. Geochemical modeling suggests that the rocks have been altered at temperatures of about 250 to 300° C under variable fluid-to-rock ratios. While all the mineral assemblages are consistent with quartz/cristobalite saturation of the fluids, the formation of diaspore must be related to episodic interaction of the rocks with fluids highly undersaturated in quartz. The early stage of chloritic alteration represents interaction of the dacites with fluids of a fairly high pH ({>}4). In contrast, the occurrence of pyrophyllite and local diaspore suggests lower pH fluid ({<}3) during later hydrothermal stages. A zone of abundant alunite at 350 m deep in the basement at Snowcap may represent local ingress of very acidic fluids (pH{<}2). Our working hypothesis is that these low-pH fluids indicate significant contributions of a magmatic fluid component that is rich in H2SO4 and HF. Furthermore, the late-stage acidic alteration seems to be more common at Snowcap. Rare-earth element (REE) data from anhydrite veins are consistent with this interpretation. The majority of the anhydrite veins from the Snowcap site display REE patterns that suggest formation of aqueous fluoride and sulfate complexes was important. High F- activities can also be inferred from the presence of minor F-apatite in some anhydrite veins from Snowcap. In contrast, anhydrite from the Roman Ruins site, where evidence for acidic rock alteration style is scarse, shows uniformly light REE enriched patterns.

Yeats, C. J.; Bach, W.; Vanko, D. A.; Roberts, S.; Lackschewitz, K.; Paulick, H.

2001-12-01

101

Sclerotherapy of Varicose Veins and Spider Veins  

MedlinePLUS

Sclerotherapy of Varicose Veins and Spider Veins • Overview Sclerotherapy is a minimally invasive treatment used to treat varicose and spider veins. The ... cramps. It is the primary treatment for small varicose veins in the legs. top of page • Preparation You ...

102

Hydrothermal Processing  

SciTech Connect

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

Elliott, Douglas C.

2011-03-11

103

The Subsurface Structure of a Submarine Hydrothermal System, ODP/IODP Hole 1256D  

NASA Astrophysics Data System (ADS)

Hole 1256D penetrates a full upper oceanic crustal section through lavas, sheeted dikes, and ~100 m into upper plutonic rocks that formed at a superfast spreading rate at the East Pacific Rise 15 m.y. ago. Electron microprobe analyses of secondary minerals plus oxygen isotope analyses of vein minerals document the thermal structure of the hydrothermal system. The ~800 m volcanic section consists of mainly sheet and massive flows, partly altered to saponite and celadonite, typical of altered submarine basalts but with little oxidation effects. Saponite and Celadonite (n=9) have ?18O values of 13.2-17.8‰, and quartz/chalcedony (n=12) has values of 20.1-30.9‰. These indicate temperatures of 50-110°C in the volcanic section, generally increasing downward. There is a stepwise increase in alteration grade downward across the 60 m lithologic transition from lavas to dikes, which are variably altered to chlorite and other greenschist minerals at temperatures ~250-350°C. Alteration intensity and grade increase downward in the 350 m sheeted dikes, with more amphibole than chlorite below 1300 mbsf, and common retrograde effects. The lower 60 m of sheeted dikes are variably recrystallized to granoblastic textures (Ca-plagioclase, clinopyroxene, orthopyroxene, ilmenite, magnetite). Plagioclase-amphibole and two-pyroxene thermometry indicate temperatures of up to >800°C for this contact metamorphism. Oxygen isotope data indicate formation of quartz veins in the dikes at temperatures of 300°C up to 400-500°C, depending on fluid compositions. Two fractionated gabbro units intrude into granoblastic sheeted dikes beginning at 1407 mbsf. The gabbroic rocks are moderately to highly altered to amphibole, secondary plagioclase, epidote, chlorite, prehnite and laumontite. Plagioclase-amphibole thermometry indicates maximum temperatures of 400- >800°C in the plutonic section, whereas oxygen isotope analyses of quartz veins in these rocks indicate temperatures of 260°C up to 400-500°C, depending on fluid compositions. The stepped thermal gradient in the upper section is similar to that in Hole 504B, but the thermal gradient in the thin sheeted dike complex at Site 1256 was steep. The transition to the plutonic section reveals a complex history of repeated cycles of magmatism and hydrothermal alteration, with contact metamorphism influenced by prior hydrothermal effects.

Alt, J.; Coggon, R.; Teagle, D.; Laverne, C.; Banerjee, N.

2007-12-01

104

Molecular Structure of Quartz  

NSDL National Science Digital Library

Quartz has been known since ancient times. It was referred to as krystallos by the Greeks, but this later became the generic term for crystal. The name quartz is derived from the German quarz (c. 1530 A.D.). Although quartz occurs in almost every geological environment including the United States, the U.S. is 100% import reliant on industrial quartz. The major import sources for 1997-2000 were Brazil, Germany, and Madagascar. Many varieties of gemstones are quartz, including amethyst, smoky quartz, and rose quartz. One of the uses for electronic-grade quartz crystal is frequency control in radios, televisions, and other electronic communications. Quartz sandstone is used for building and quartz sand is used to make sandpaper.

2002-08-26

105

Nitrogen 15-enriched Precambrian kerogen and hydrothermal systems  

NASA Astrophysics Data System (ADS)

Nitrogen isotope data are reported for kerogen from Precambrian black shales at prehnite-pumpellyite to greenschist facies and for micas from postmetamorphic hydrothermal quartz vein systems. Nitrogen in micas was acquired from N-bearing aqueous metamorphic hydrothermal fluids generated, from breakdown of sedimentary kerogen and dehydration of K-silicates, at deeper crustal levels. The 2.7 Ga kerogens and hydrothermal K-micas yield ?15N values of 15-24‰, compared to existing data of 2-6‰ in Phanerozoic counterparts. Paleoproterozoic equivalents have intermediate ?15N of 7-12‰, implying a secular decrease in ?15N of shale kerogen. The 15N-enriched nitrogen in Archean shales and hydrothermal vein systems cannot be caused either by N isotopic shifts accompanying metamorphism or Rayleigh fractionation because premetamorphic and postmetamorphic samples from the same terrane are both enriched and lack covariation of ?15N with N, C/N ratios, or metamorphic grade. The magnitude of shifts during progressive metamorphism of sedimentary rocks in previous studies is constrained at <1‰ to greenschist and about 3‰ to amphibolite facies. Furthermore, 15N-enriched values cannot stem from long-term preferential diffusional loss of 14N as samples were selected from terranes where 40Ar/39Ar ages are within a few million years of concordant U-Pb ages; nitrogen is structurally bound in micas, whereas Ar is not. It is possible that the 15N-enriched values stem from a different N cycle in the Archean, with large biologically mediated fractionations, yet the magnitude of the fractionations observed exceeds any presently known, and chemoautotrophic communities tend to depleted values. Earlier results on Archean cherts show a range from -6 to 30‰. Given the temporal association of chert-banded iron formation with mantle plumes, the range is consistent with mixing between mantle N2 of -5‰ and the enriched marine reservoir identified in this study. We attribute the secular trend from Archean kerogen of 15-24‰ to Phanerozoic kerogen averaging 3-4‰ to a secondary atmosphere derived from CI-chondrite-like material and comets with ?15N of 30-42‰. Shifts of ?15N to its present values of 0‰ can be accounted for by a combination of sequestration of atmospheric N2 into sedimentary rocks and mantle degassing of -5‰ mantle N2.

Jia, Yiefei; Kerrich, Robert

2004-07-01

106

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

107

Nickel Electrobonded Quartz Blanks.  

National Technical Information Service (NTIS)

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

J. M. Stanley

1971-01-01

108

Thermodynamics of hydrothermal systems with oxalate ion  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

109

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

Microsoft Academic Search

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

Christopher Schmitz; Donald M. Burt

1990-01-01

110

Deep Vein Thrombosis  

MedlinePLUS

Deep vein thrombosis, or DVT, is a blood clot that forms in a vein deep in the body. Most deep vein ... the condition is called thrombophlebitis. A deep vein thrombosis can break loose and cause a serious problem ...

111

Hydrothermal processes above the Yellowstone magma chamber: Large hydrothermal systems and large hydrothermal explosions  

USGS Publications Warehouse

Hydrothermal explosions are violent and dramatic events resulting in the rapid ejection of boiling water, steam, mud, and rock fragments from source craters that range from a few meters up to more than 2 km in diameter; associated breccia can be emplaced as much as 3 to 4 km from the largest craters. Hydrothermal explosions occur where shallow interconnected reservoirs of steam- and liquid-saturated fluids with temperatures at or near the boiling curve underlie thermal fields. Sudden reduction in confi ning pressure causes fluids to fl ash to steam, resulting in signifi cant expansion, rock fragmentation, and debris ejection. In Yellowstone, hydrothermal explosions are a potentially signifi cant hazard for visitors and facilities and can damage or even destroy thermal features. The breccia deposits and associated craters formed from hydrothermal explosions are mapped as mostly Holocene (the Mary Bay deposit is older) units throughout Yellowstone National Park (YNP) and are spatially related to within the 0.64-Ma Yellowstone caldera and along the active Norris-Mammoth tectonic corridor. In Yellowstone, at least 20 large (>100 m in diameter) hydrothermal explosion craters have been identifi ed; the scale of the individual associated events dwarfs similar features in geothermal areas elsewhere in the world. Large hydrothermal explosions in Yellowstone have occurred over the past 16 ka averaging ??1 every 700 yr; similar events are likely in the future. Our studies of large hydrothermal explosion events indicate: (1) none are directly associated with eruptive volcanic or shallow intrusive events; (2) several historical explosions have been triggered by seismic events; (3) lithic clasts and comingled matrix material that form hydrothermal explosion deposits are extensively altered, indicating that explosions occur in areas subjected to intense hydrothermal processes; (4) many lithic clasts contained in explosion breccia deposits preserve evidence of repeated fracturing and vein-fi lling; and (5) areal dimensions of many large hydrothermal explosion craters in Yellowstone are similar to those of its active geyser basins and thermal areas. For Yellowstone, our knowledge of hydrothermal craters and ejecta is generally limited to after the Yellowstone Plateau emerged from beneath a late Pleistocene icecap that was roughly a kilometer thick. Large hydrothermal explosions may have occurred earlier as indicated by multiple episodes of cementation and brecciation commonly observed in hydrothermal ejecta clasts. Critical components for large, explosive hydrothermal systems include a watersaturated system at or near boiling temperatures and an interconnected system of well-developed joints and fractures along which hydrothermal fluids flow. Active deformation of the Yellowstone caldera, active faulting and moderate local seismicity, high heat flow, rapid changes in climate, and regional stresses are factors that have strong infl uences on the type of hydrothermal system developed. Ascending hydrothermal fluids flow along fractures that have developed in response to active caldera deformation and along edges of low-permeability rhyolitic lava flows. Alteration of the area affected, self-sealing leading to development of a caprock for the hydrothermal system, and dissolution of silica-rich rocks are additional factors that may constrain the distribution and development of hydrothermal fields. A partial lowpermeability layer that acts as a cap to the hydrothermal system may produce some over-pressurization, thought to be small in most systems. Any abrupt drop in pressure initiates steam fl ashing and is rapidly transmitted through interconnected fractures that result in a series of multiple large-scale explosions contributing to the excavation of a larger explosion crater. Similarities between the size and dimensions of large hydrothermal explosion craters and thermal fields in Yellowstone may indicate that catastrophic events which result in l

Morgan, L. A.; Pat, Shanks, III, W. C.; Pierce, K. L.

2009-01-01

112

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

113

The Thermal Structure of a Submarine Hydrothermal System, ODP/IODP Hole 1256D  

NASA Astrophysics Data System (ADS)

Secondary mineralogy plus oxygen isotope analyses of vein minerals document the thermal structure of the fossil hydrothermal system penetrated by Hole 1256D. This hole provides an upper crustal section of lavas, sheeted dikes, and ~100 m into upper plutonic rocks that formed at a superfast spreading rate at the East Pacific Rise 15 m.y. ago. The ~800 m volcanic section is partly altered to saponite and celadonite, typical of altered submarine basalts but with little oxidation effects. Oxygen isotope analyses of saponite and celadonite (?18O =13.2-17.8 per mil), quartz/chalcedony (20.1-30.9 per mil), and anhydrite (13.1-17.1 per mil) indicate temperatures of 50-150° C in the volcanic section, generally increasing downward. There is a stepwise increase in alteration grade downward across the 60 m transition from lavas to dikes, which are variably altered to chlorite and other greenschist minerals at temperatures ~250- 350° C. Alteration intensity and grade increase downward in the 350 m sheeted dikes, although retrograde effects are common. The lower 60 m of sheeted dikes are variably contact metamorphosed to granoblastic textures, with pyroxene thermometry indicating equilibration at 850-950° C. Two gabbro units intrude granoblastic dikes beginning at 1407 mbsf. The gabbroic rocks are moderately to highly altered to amphibole, plagioclase, epidote, chlorite, prehnite and laumontite, with maximum alteration temperatures of 400->800° C indicated by plagioclase-amphibole thermometry. Fluid inclusion filling temperatures indicate formation of quartz veins in the dikes and gabbros at temperatures of 360-426° C, and combined with oxygen isotope analyses of quartz (5.5-10.8 per mil) imply evolved fluids having ?18O = 0.6-5.5 per mil. Anhydrites in the dikes have ?18O of 2.2-28.7 per mil, reflecting widely varying formation conditions. The stepped thermal gradient in the upper section of Hole 1256D is generally similar to that in Hole 504B, but the thermal gradient in the thin sheeted dike complex at Site 1256 was steep. The transition to the plutonic section reveals a complex history of repeated cycles of magmatism and hydrothermal alteration, with contact metamorphism influenced by prior hydrothermal effects.

Alt, J. C.; Coggon, R.; Laverne, C.; Smith-Duque, C.; Teagle, D. A.; Morgan, S.

2008-12-01

114

Low Sulphide Mineralisation of the Sudbury Igneous Complex, Canada: Examples of Fractionated Magmatic or Hydrothermal Systems?  

NASA Astrophysics Data System (ADS)

Low Sulphide mineralisation occurs within the footwall of the Sudbury Igneous Complex. Samples of mineralised material have been collected from five properties and analysed using petrographic, microthermometric, point and bulk geochemical techniques. Two distinct mineralisation types have been identified for the North range (NR), a magmatic chalcopyrite (ccp) + millerite (mi) + pentlandite (pn) ± pyrrhotite (po) assemblage displaying epidote + chamosite + actinolite rich margins and haloes; and a hydrothermal ccp + mi + pyrite (py) + quartz + carbonate assemblage. South range (SR) mineralisation displays the same pattern with a po + pn + ccp ± cubanite magmatic assemblage and a hydrothermal ccp + po + pn + quartz + carbonate assemblage. Both types display a preference for exploiting lithological contacts, structures, fabrics, granophyric veins and Sudbury breccia matrix - clast contacts; and occur as cm and mm scale veins, blebs and disseminations. Analysis of mineralised material has revealed elevated precious and semi-metal concentrations dissolved within sulphides and as discrete crystals, intergrowths or aggregates of Pt, Pd, Au and Ag bismuthinides, tellurides, arsenides, antimonides, selenides and combinations thereof. Sizes range from 1-75?m, occurring interstitially or fully enclosed in sulphides and silicates. Magmatic material displays elevated concentrations of Pd in pn, Ag in ccp and Se in all sulphides when compared to contact and ''traditional" footwall mineralisation, suggesting precipitation from a strongly fractionated sulphide liquid down to temperatures of 379 to <282oC, inferred from the presence of interstitial millerite and polydymite. Hydrothermal mineralisation displays the same elevations suggesting a link to the magmatic material, with primary fluid inclusions in associated quartz giving Th (NR) of between 350-407oC and salinities of 30-35% NaCl and 18-24% NaCl-CaCl2 and tentative Th (SR) of 350-388oC and salinities of 15-28% NaCl-CaCl2 for mineralised material . The data above will be combined with thermodynamic modelling, bulk and mineral halogen analysis, outcrop mapping, acid etching, geothermometry and geobarometry to produce a genesis and exploration model for this challenging new deposit type.

White, C.; Mungall, J.; Spooner, E.

2009-05-01

115

The solubility of gallium oxide in vapor and two-phase fluid filtration in hydrothermal systems  

NASA Astrophysics Data System (ADS)

The solubility of gallium and aluminum oxides in gas phase in the system Ga2O3 (Al2O3)-HCl-H2O was studied at 150-350°C and pressure up to saturated vapor. The concentration of gallium increases with the increasing of HCl pressure. The formulae of gallium gaseous specie was determined as GaOHCl2. The constant of gallium oxide solubility reaction was calculated at 150, 200, 250, 300 and 350°C. The concentration of aluminum in gas phase is insignificant in the same conditions. The possibility of gallium transportation in gas phase with small quantity of Al allow to divide this elements in hydrothermal processes with gas phase. The Ga/Al ratio in muscovite can be used as the indicator of gas phase separation and condensation. This indicator was not considered in the geochemical literature earlier. The separation of gas and liquid phases was determined in Akchatau (Kazahstan) and Spokoinoe (Russia) greisen W deposit by carbon isotope fractionation of carbon dioxide in fluid inclusion. The important feature of both ore mains is heterogenization and boiling of ore-forming fluids. Greisen ore bodies are formed as a result of strongly focused solution flow in the T-P gradient fields. It is possible to divide ore bodies of Akchatau in two types: muscovite and quartz. Muscovite type veins are thin and have small metasyntactic zone. Quartz type veins are localized in fault with large vertical extent (500 m) and content the large quantity of wolframite. These veins formed in condition of significant pressure decreasing from 2.5 to 0.5 kbar with fluid boiling. Gas and liquid phase separation specifies the vertical zonality of quartz type veins. The gas phase with the high gallium concentration is separated from a flow of liquid phase. Liquid phase react with the granites forming greisen metasomatites. Condensation of the gas phase in upper parts of massive produces the increasing of Ga/Al ratio in muscovite 3-5 times more, then in granites and bottom part of vein (from 2×10-4 to 8×10-4 mass ratio). The muscovite type veins has no separation between gas and liquid due to there thickness and small pressure gradient. There is no difference in Ga/Al ratio in muscovite from this veins. The Spokoinoe deposit is classified by mineralized dome type. The heterogenization of fluid occurs in H2O-CO2 system for water phase and carbon dioxide with temperature decreasing. Two-phase flow is separated in granite, forming greisen metosomatites. The Ga/Al ratio in rock increase up to 3 times to the upper part of metasomatitic zone. The Ga/Al ratio in muscovite can be applied for other hydrothermal systems for geochemical indicator of gas phase separation and condensation zone determination. This work is supported by RFBR project 10-05-00670 and 10-05-00320.

Bychkov, Andrew; Matveeva, Svetlana; Nekrasov, Stanislav

2010-05-01

116

Structural setting, style and timing of vein-hosted gold mineralization at the Pogo deposit, east central Alaska  

Microsoft Academic Search

Gold-bearing veins within the Liese zone of the Pogo deposit display a two-stage evolutionary history that records temporal variation in kinematics, fluid chemistry and temperature. Several stacked shallow northwest-dipping shear veins are developed at Pogo, and collectively comprise the Liese Zone. Veins consist of: (1) early, narrow biotite-bearing shear veins; (2) white quartz veins with pyrite-arsenopyrite bands, referred to as

David Rhys; Jack Dimarchi; Moira Smith; Robert Friesen; Cameron Rombach

2003-01-01

117

Numerical Modelling of Vein Microstructures  

NASA Astrophysics Data System (ADS)

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

Bons, P. D.

2005-12-01

118

Why calcite can be stronger than quartz  

NASA Astrophysics Data System (ADS)

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

Mancktelow, N. S.; Pennacchioni, G.

2009-04-01

119

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

Microsoft Academic Search

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

Andreas Lüttge; Paul Metz

1993-01-01

120

Deep Vein Thrombosis  

MedlinePLUS

... veins include: Age Previous history of DVT or PE Metastatic malignancy Vein disease (such as varicose veins) ... lungs, where it is called a pulmonary embolism (PE). A pulmonary embolism is a potentially fatal condition ...

121

Renal vein thrombosis  

MedlinePLUS

Renal vein thrombosis is a blood clot that develops in the vein that drains blood from the kidney. ... Renal vein thrombosis is an uncommon disorder that may be caused by: Abdominal aortic aneurysm Clotting disorders Dehydration (mostly in infants) ...

122

Retinal vein occlusion  

MedlinePLUS

... small veins that carry blood away from the retina. The retina is the layer of tissue at the back ... smaller veins (branch veins or BRVO) in the retina often occurs when retinal arteries that have been ...

123

Shallow to near-surface, vein-type epithermal gold mineralization at Lalab in the Sibutad gold deposit, Zamboanga del Norte, Mindanao, Philippines  

NASA Astrophysics Data System (ADS)

The Sibutad vein-type epithermal gold deposit is the most promising economically feasible gold mineralization found in recent years in Zamboanga del Norte province in Zamboanga Peninsula, Mindanao island. The Sibutad gold deposit occurs in Pliocene to Pleistocene volcanic rocks, resting on a deformed island arc block to the east of the tectonically active Sindangan-Cotabato-Daguma Lineament. The host rocks are the Malindang Volcanics, composed of lower and upper members, which are both intruded by andesite porphyry. The lower member is made up of andesite flows, dacite tuff and tuffite, whereas volcanic breccia and tuff breccia characterize the upper member. The Sibutad gold deposit is subdivided into the Larayan and Lalab prospects. In Lalab, which is the prospect studied, hydrothermal activity and gold mineralization occur in the andesite flows. The geology, alteration and mineralization of the Lalab orebody are of adularia-sericite type that suggests the gold was precipitated from reduced, near-neutral pH solutions within a shallow to near-surface environment. The following events produced the Lalab orebody: (1) pre-breccia wallrock alteration, (2) hydrothermal brecciation, (3) post-breccia wallrock alteration, and (4) gold mineralization. Gold precipitated in quartz veins was a response to boiling, followed by fluid mixing. Prolific gold zones occur between 30 m below sea level and 200 m above sea level.

Jimenez, F. A.; Yumul, G. P.; Maglambayan, V. B.; Tamayo, R. A.

2002-12-01

124

New approach for the quantification of paleostress magnitudes: application to the Soultz vein system (Rhine graben, France)  

Microsoft Academic Search

Quartz veins often appear in pre-existing cracks and are the witnesses of paleofluid flows. A new method of paleostress magnitude quantification is proposed in this paper based on the knowledge of: (i) the geometrical distribution of vein poles, (ii) empirical considerations of rupture criteria and (iii) the fluid pressure. Stress axis orientations, deduced from the geometrical distribution of the vein

Anne-Sylvie André; Judith Sausse; Marc Lespinasse

2001-01-01

125

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

126

Quartz Crystal Clocks  

NASA Technical Reports Server (NTRS)

General Time Corporation, under contract to NASA, developed a quartz crystal for obtaining a stable time base from which all mission times could be derived. This later became basis of consumer clocks and watches with accuracy of one minute a year, watches useful in timing sports events as well as general use. When quartz is electrically stimulated it can vibrate millions of times a second. Since timepieces use a vibrating body to keep up time, incredibly fast vibration of a quartz crystal--up to 4,194,304 beats a second opened a new horizon in accuracy.

1976-01-01

127

Preventing Deep Vein Thrombosis  

MedlinePLUS

What is deep vein thrombosis (DVT)? Deep vein thrombosis is a condition in which blood clots (or thrombi) form in deep veins in the legs ... and Gynecologists f AQ • What is deep vein thrombosis (DVT)? • How does a clot form in a ...

128

Thermoelasticity in Quartz.  

National Technical Information Service (NTIS)

A critical analysis of experimental measurements of alpha quartz thermal expansion reported in the literature is presented. A recommended set of best measured values over the temperature range -50 to +150C was determined, as were values for the coefficien...

J. A. Kosinski J. G. Gualtieri A. Ballato

1992-01-01

129

Tip to midpoint observations on syntectonic veins, Ouachita orogen, Arkansas: Trading space for time  

NASA Astrophysics Data System (ADS)

By examining a vein from its tip to center, we have established the transition from a single filled fracture at the vein tip to typical 'crack-seal' textures observed in fibered, laminated veins. The vein is contained in the boudin neck of a sandstone layer within the Lower Ordovician Mazarn Formation, Benton Uplift, Ouachita orogen. The tip of the vein is composed of one or more isolated veinlets, defined as quartz-filled narrow (5-25 ?m) fractures parallel to the larger vein's long dimension. Scanned SEM-based cathodoluminescence shows that quartz laminae of the same orientation and thickness are found throughout the vein. Wall-normal fibers first appear in the vein where detrital grains are cut by multiple veinlets, each veinlet mimicking the crystallographic orientation of the detrital grain, whereas later veinlets reflect the established crystallographic orientation of the fiber. Fibers throughout the vein retain evidence of having been formed by repeated fracturing and filling of a pre-existing grain (at the vein walls) or fiber. However, recrystallization later modified the fibers by obliterating some evidence of the veinlets and moving fiber walls. Boudin formation provided the extension site that localized fracturing and vein filling. The vein grows by the repeated addition of veinlets in the neck region. Recrystallization altered the shape of previously formed fibers.

Cervantes, Pablo; Wiltschko, David V.

2010-08-01

130

Archean hydrothermal sea-floor surface environment: Australia VS South Africa  

NASA Astrophysics Data System (ADS)

Archean greenstone belt typically contains chemical sedimentary sequences such as cherts and BIFs and underlying thick volcanics. These sequences may be used to extract information on hydrothermal activity and potential biological activity on early Earth. We compare the geological and geochemical characteristics of such chemical sediments in the 3.2 Ga Cleaverville Group and 3.4 Ga Warrawoona Group (Marble Bar Chert) in the Pilbara district and coeval Onverwacht Group (Masauri River Chert) and Komati River Formation in the Barberton Greenstone Belt. The Cleaverville Group formed by bimodal volcanism in an immature island arc. The Dixon Island Formation of the Cleaverville Group is one of the best-preserved sequences of Archean hydrothermal activity. The Dixon Island Formation is composed of Komatiite-Rhyolite Tuff, Black Chert, and Varicolored Chert Members to the top. The Komatiite-Rhyolite Tuff Member contains highly altered volcanic rocks with black chert veins. The thick Black Chert Member is characterized by low organic carbon contents (<0.5 percent) and low carbon isotope compositions (- 28 to -40 per mil). It contains fossil-like carbonaceous materials. The Masauri River Chert is also a hydrothermal sequence that is quite similar to the Dixon Island Formation. It contains highly altered volcanic rocks with numerous quartz swarms and black chert dikes, which are covered by volcanic tuff and well-stratified black/white cherts. Its upper sequence contains Fe- rich black/white cherts. Black chert of the Masauri River Chert is also characterized by low organic carbon content (<0.5 percent) and relatively high carbon isotope compositions (-20 to -30 per mil). Similarity in the petrographical and geochemical characteristics of black chert veins and massive black chert beds in the Australian and South African sections suggest that the depositional environments for those rocks were also similar. These evidences strong suggest that Archean hydrothermal system contains organic matter which is blowout from the see-floor surface. Early life exuberate (such as bacteria) on these organic rich see-floor along the vent system.

Kiyokawa, S.; Ito, T.; Koge, S.; Inamoto, Y.; Ikehara, M.; Kitajima, F.; Yamaguchi, K.

2007-12-01

131

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

132

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

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

133

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

134

Long-term behaviour of continental hydrothermal systems  

Microsoft Academic Search

U-series dating of hydrothermal carbonates, deposited by CO2-rich thermo-mineral waters of the French Massif Central, provides new insights on the long-term behaviour of a continental hydrothermal system. Dating of aragonite veins and travertines impregnating old terrace levels of the Allier river allowed identification of the main episodes of surface deposition, and thus factors likely to influence these circulations. Fifteen layers

Sophie Rihs; Michel Condomines; Jean-Louis Poidevin

2000-01-01

135

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

Bohlke, J. K.

1989-01-01

136

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

137

Evidence of Nb-Ta mobility in high temperature F-rich fluids evidenced by the La Bosse quartz-Nb-ferberite stockwork (Echassières, French Massif Central).  

NASA Astrophysics Data System (ADS)

In the Echassières district (northern French Massif Central), the 310 Ma Beauvoir granite (a P-rich peraluminous RMG) overprints a quartz-ferberite stockwork. The 900 m-deep GPF1 scientific hole shows that the stockwork is split into two parts by the gently dipping Beauvoir intrusion: the upper section (~ 100m thick) occurs in the La Bosse quarry, , and the lower section (? 60 m thick) below the granite floor. The root of the stockwork (hypothetic La Bosse granite) has not been reached. The stockwork comprises flat-lying quartz veins (? 0.6 m thick) concordant to the regional schistosity of surrounding micaschists, and steep N10-N50°E quartz veins (? 0.2 m thick). The two sets result from hydraulic fracturing, and consistently display crack seal features. A family of aplites and aplo-pegmatites dikes follow the same set of fractures, being either later (with partial dissolution of pre-existing quartz veins) or earlier, than the quartz veins. There is no alteration, nor associated mineral other than ferberite, at the La Bosse quarry, whereas micaceous selvages are observed in the lower section. Ferberite display a trend of ferberite enrichment with increasing depth (0.71 to 0.95 Fb mole%). In the La Bosse quarry, three ferberite habitus are present: acicular, lanceolate and prismatic. Acicular crystals are typically nicely zoned, with alternating Nb-rich (4.95±0.94 % Nb2O5) and Nb-poor (1.57±0.38 % Nb2O5) growth bands. Ta (up to 0.30 Ta2O5), Ti and Sn are also enriched in the Nb-rich bands. Nb and Ta incorporation into the ferberite is in the form of columbite, as either true solid solution or nanoinclusions. Lanceolate crystals have a similarly zoned acicular core and a Nb-poor rim (1.08±0.66 % Nb2O5). Prismatic crystals are unzoned and Nb-poor (0.67±0.20 % Nb2O5). In the lower part of the stockwork, the Nb contents are lower (2.17 % Nb2O5 in the Nb-rich bands, 1.36 % in the Nb-poor bands, 0.08 % in the unzoned cortex, 0.15 % in the unzoned prisms). Thus the unusual Nb content of the La Bosse ferberites is correlated to the apparently very distal setting of this quartz system relatively to the parent granite, in contrast with most quartz-W systems in the French Massif Central (Aïssa et al. 1987). When invaded by aplites or aplopegmatites, the ferberite-bearing quartz veins are dissolved, but the ferberites remain apparently unaffected - they are not dissolved by the granite melt. Yet, the acicular and lanceolate crystals have lost their Nb-zoning and display uniform homogenised Nb content. The emplacement of the Beauvoir granite was associated with late magmatic exsolution of an Al- and F-rich, silica undersaturated, hydrothermal fluid that percolated upwards in the surrounding schists (Cuney et al. 1992). When interacting with the quartz veins of the La Bosse stockwork, this fluid precipitated topazites. Again, included ferberites remain apparently unaffected. However, they display microscopic vuggy cavities, successively filled by a Nb-rich ferberite (up to 8.91% Nb2O5) with significant Ta content (up to 0.35 % Ta2O5), a wolframo-ixiolite and a Ta-rich columbite. Later Li-phengite was precipitated from the same magmatic fluid, and was associated with hubnerite enrichment of pre-existing ferberites along Li-phengite-bearing microcracks (down to 0.20 mole % Fb). Ta and Nb are known for their poor solubility in hydrothermal fluids, but the Nb and Ta enrichments observed in the wolframite of La Bosse stockwork show that they can be transported to some extent by F-rich fluids. Aïssa, M., Marignac, C., Weisbrod, A. (1987). Le stockwerk à ferbérite d'Echassières : évolution spatiale et temporelle; cristallochimie des ferbérites. In : Cuney, M., Autran, A. (eds), Echassières : le forage scientifique d'Echassières (Allier). Une clé pour la compréhension des mécanismes magmatiques et hydrothermaux associés aux granites à métaux rares. Mém. GPF, tome 1, 311-334. M Cuney, C Marignac, A Weisbrod (1992). The Beauvoir topaz-lepidolite albitic granite (Massif Central, France). A highly specialized granite w

Marignac, C.; Cuney, M.

2012-04-01

138

Varicose Veins and Venous Insufficiency  

MedlinePLUS

... venous system. Varicose Vein Treatments Minimally Invasive Vein Ablation Treatment Endovenous (or vein) ablation is a minimally ... leg, re-establishing normal flow. Benefits of Vein Ablation Treatment The treatment takes less than an hour ...

139

Structural control and history of origin of hydrothermal metallogeny in western Cuba  

Microsoft Academic Search

The main structural-lithological factors responsible for the localization of hydrothermal mineralization on a regional, as well as on a local scale in the metallogenic province of western Cuba are summarized. The supply function of regional fault structures extending towards depth is emphasized and light is thrown on the localization of hydrothermal veins in fissures of the folded San Cayetano Formation.

Karel Benes; Václav Hanus

1967-01-01

140

Endoscopic Saphenous Vein Harvesting  

Microsoft Academic Search

Although the use of arterial conduit has decreased the amount of saphenous vein required for routine coronary artery bypass grafting, the saphenous vein as a bypass conduit remains an essential component of most practices. We describe the technique of endoscopic vein harvest that, in our initial experience with 30 patients, has improved patient satisfaction and decreased the complications associated with

Keith B Allen; Carl J Shaar

1997-01-01

141

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

142

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

143

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

144

Granulite-Facies High-sulfidation VHMS-like Hydrothermal System in the La Romaine Area, Eastern Grenville Province, Quebec: a Metamorphic and Geochemical Overview  

NASA Astrophysics Data System (ADS)

An extensive Cu-mineralized hydrothermal system has been recognized among the 1.5 Ga La Romaine volcano-sedimentary belt, in the eastern Grenville Province. This high-grade metamorphosed supracrustal belt occurs as a narrow basin within coeval granitoids. Granulite-facies alteration halos, encompassing rocks diagnostic of advanced argillic alteration (sillimanite-garnet-cordierite gneiss), silicification (quartz-cordierite gneiss) and sericite alteration (quartz-muscovite-sillimanite-iron oxide nodules or veins), are mapped among rhyolitic to dacitic tuffs and lapillistones. Some of these altered rocks have preserved primary lapilli textures. Amphibolite units of uncertain volcanic or intrusive origin overly the felsic pyroclastics and form a structurally coherent, east-west oriented unit. A narrow zone of ironstones (magnetite-rich amphibolite and biotite gneiss), carbonated zones (epidote-, diopside-, anorthite-, Ca garnet-, and/or calcite-rich calc-silicate rocks) and disseminated Cu sulphides, is found across its trend and testify of focused fluid discharge and mineralization. Structural and petrographic data suggest that mineralization and alteration are controlled by synvolcanic faults, with the amphibolite unit serving as a cap rock. Despite high-grade metamorphism, the volcanic and granitic rocks preserve a reproducible signature of calc-alkaline affinity. Element ratios analysis indicates that these rocks have not experienced significant LILE depletion and that metamorphism was, for the most part, isochemical. Element mobility of altered rocks is thus interpreted as produced by hydrothermal activity. AFM, ACF and AKF ternary plots of altered rocks and their protolith, define diagnostic alteration vectors, which reflect major elements mobility for the various alteration facies. Strong silica mobility is revealed by mass-balance calculations for altered pyroclastics. REE patterns of these rocks also show the mobility of heavy REE, in particular Tb, Dy and Ho. Such unusual pattern has been described for rocks altered by acid hydrothermal fluids in volcanic arc environments.

Bonnet, A.; Corriveau, L.; Laflèche, M. R.

2004-05-01

145

Quartz Rheology - A Multidisciplinary Analysis of a Fossil Brittle-ductile Shear Array in the Central Southern Alps, New Zealand  

NASA Astrophysics Data System (ADS)

An exhumed fossil brittle-ductile shear array in the central Southern Alps, New Zealand, provides a natural laboratory for the investigation of the rheological behaviour of natural quartz under mid-lower crustal levels during transiently high stresses that are related to the upramping of the Pacific plate onto the Alpine Fault and followed by a stress drop. At depths >20 km, temperatures of 450-500° C, fluctuating fluid pressures of 310 MPa to 560 MPa (near lithostatic) and minimum strain rates of ~10^{-13 s-1, quartzofeldspathic wall rocks were faulted brittlely, presumably by aseismic stable sliding. Where brittle fault tips encounter older quartz veins embedded in the wall rocks, they terminate into shear zones in the quartz veins, deforming them brittlely and/or ductilely. Some embedded quartz veins deformed entirely ductilely to finite shear strains of 5-15. Despite these high strains and despite the smooth, coherent and ductile nature of the shearing of the veins, most of the ductilely sheared quartz veins show randomised or poorly developed CPO patterns. Most of the brittle faults are infilled by quartz-calcite veins indicating their role as conduits of fluids during deformation. We evaluate geological field observations such as deformed vein shape, scaling relationships between vein thickness and ductility and vein thickness distribution density and spacing of the brittle faults. Using finite element modelling, we simulate the observed vein structures in order to derive one or more flow laws that can explain the observed deformation for these naturally deformed quartz veins within the available time constraints and within the constraints of the known physical conditions. Two-dimensional models were set up and initially deformed to small finite strains in order to gain insight into the observed scaling relationship between the vein thickness and the proportional fraction of ductile creep strain (i. e. ductility of the quartz veins). The results show that the fraction of ductile flow in the veins increases as a function of decreasing strain rate in the shear zones and as a function of increasing thickness of the veins. Assuming the quartz flow law from Paterson & Luan (1990) for the deformed veins at a temperature of 500° C and a yield stress of 100 MPa, we can explain the observations if the quartz veins were deformed at maximum strain rates of ca. 10^{-8} to 10-7 s-1. The lack of a CPO in most of the sheared quartz veins and the fluid-rich deformation conditions during the deformation suggest that more complex flow laws may have been applicable. Wightman et al. (2006) suggest a deformation mechanism change from dislocation creep to a late increment of diffusion creep-accommodated grain boundary sliding and hence CPO weakening. Such a change in deformation mechanism was probably facilitated by the presence of fluids enhancing diffusive processes between the grain boundaries. Preliminary results from earlier computer models show that a combination of existing flow laws for dislocation and diffusion creep could account for the observed shear strains. This model for randomisation of the CPOs implies non- steady state flow and a change in flow laws that may have been facilitated not only by fluids but also by a large stress drop once the rocks had been upramped onto the Alpine Fault.

Grigull, S.; Little, T. A.; Ellis, S.

2006-12-01

146

Minerals Yearbook 1991: Quartz Crystal.  

National Technical Information Service (NTIS)

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

J. A. Ober

1992-01-01

147

Minerals Yearbook, 1990: Quartz Crystal.  

National Technical Information Service (NTIS)

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

J. A. Ober

1991-01-01

148

Hydrothermal alteration minerals in Aluto Langano geothermal wells, Ethiopia  

SciTech Connect

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

Gebregzabher, Z.

1986-01-01

149

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

150

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

151

Field guide to hydrothermal alteration in the White River altered area and in the Osceola Mudflow, Washington  

USGS Publications Warehouse

The Cenozoic Cascades arcs of southwestern Washington are the product of long-lived, but discontinuous, magmatism beginning in the Eocene and continuing to the present (for example, Christiansen and Yeats, 1992). This magmatism is the result of subduction of oceanic crust beneath the North American continent. The magmatic rocks are divided into two subparallel, north-trending continental-margin arcs, the Eocene to Pliocene Western Cascades, and the Quaternary High Cascades, which overlies, and is east of, the Western Cascades. Both arcs are calc-alkaline and are characterized by voluminous mafic lava flows (mostly basalt to basaltic andesite compositions) and scattered large stratovolcanoes of mafic andesite to dacite compositions. Silicic volcanism is relatively uncommon. Quartz diorite to granite plutons are exposed in more deeply eroded parts of the Western Cascades Arc (for example, Mount Rainier area and just north of Mt. St. Helens). Hydrothermal alteration is widespread in both Tertiary and Quaternary igneous rocks of the Cascades arcs. Most alteration in the Tertiary Western Cascades Arc resulted from hydrothermal systems associated with small plutons, some of which formed porphyry copper and related deposits, including copper-rich breccia pipes, polymetallic veins, and epithermal gold-silver deposits. Hydrothermal alteration also is present on many Quaternary stratovolcanoes of the High Cascades Arc. On some High Cascades volcanoes, this alteration resulted in severely weakened volcanic edifices that were susceptible to failure and catastrophic landslides. Most notable is the sector collapse of the northeast side of Mount Rainier that occurred about 5,600 yr. B.P. This collapse resulted in formation of the clay-rich Osceola Mudflow that traveled 120 km down valley from Mount Rainier to Puget Sound covering more than 200 km2. This field trip examines several styles and features of hydrothermal alteration related to Cenozoic magmatism in the Cascades arcs. The morning of the trip will examine the White River altered area, which includes high-level alteration related to a large, early Miocene magmatic-hydrothermal system exposed about 10 km east of Enumclaw, Washington. Here, vuggy silica alteration is being quarried for silica and advanced argillic alteration has been prospected for alunite. Clay-filled fractures and sulfide-rich, fine-grained sedimentary rocks of hydrothermal origin locally are enriched in precious metals. Many hydrothermal features common in high-sulfidation gold-silver deposits and in advanced argillic alteration zones overlying porphyry copper deposits (for example, Gustafson and Hunt, 1975; Hedenquist and others, 2000; Sillitoe, 2000) are exposed, although no economic base or precious metal mineralized rock has been discovered to date. The afternoon will be spent examining two exposures of the Osceola Mudflow along the White River. The Osceola Mudflow contains abundant clasts of altered Quaternary rocks from Mount Rainier that show various types of hydrothermal alteration and hydrothermal features. The mudflow matrix contains abundant hydrothermal clay minerals that added cohesiveness to the debris flow and helped allow it to travel much farther down valley than other, noncohesive debris flows from Mount Rainier (Crandell, 1971; Vallance and Scott, 1997). The White River altered area is the subject of ongoing studies by geoscientists from Weyerhaeuser Company and the U.S. Geological Survey (USGS). The generalized descriptions of the geology, geophysics, alteration, and mineralization presented here represent the preliminary results of this study (Ashley and others, 2003). Additional field, geochemical, geochronologic, and geophysical studies are underway. The Osceola Mudflow and other Holocene debris flows from Mount Rainier also are the subject of ongoing studies by the USGS (for example, Breit and others, 2003; John and others, 2003; Plumlee and others, 2003, Sisson and others, 2003; Vallance and others, 2003). Studies of hydrothermal alteration in the Osceola Mudflow are being used to bett

John, David A.; Rytuba, James J.; Ashley, Roger P.; Blakely, Richard J.; Vallance, James W.; Newport, Grant R.; Heinemeyer, Gary R.

2003-01-01

152

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

NASA Astrophysics Data System (ADS)

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

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

1991-11-01

153

Microstructural evolution of syntaxial veins formed by advective flow  

NASA Astrophysics Data System (ADS)

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

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

2004-03-01

154

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

155

The N story of a hydrothermal Acheaen BIF-bearing chert  

NASA Astrophysics Data System (ADS)

N isotopes in rocks can trace past biological activity, but it implies a deep knowledge of the N trapping sites and of the associated geo-biochemical N fractionation processes. The studied chert (PB 458) belongs to the 3.2 Ga Marble Bar complex, Pilbara, Western Australia. Isotopic analyses showed two N components with d15N of 6.7±1.6% and 10.0±1.6%, respectively. New mineralogical and REE analyses distinguished three microenvironments: 1) a silicified basalt having preserved its porphyric texture, with euhedral hydrothermal Fe-sulfides precipitated in the protomafic minerals; (2) Fe-Mn oxyhydroxide (BIFs) laminae and associated Ni-Cu-Mn-Au-Pd alloys and HREE-Y phosphates alternate with cryptocrystalline quartz, hosting magnetite inclusions. BIFs are initially composed of magnetite and carbonates, segregated from a Fe-Ca-Mg-enriched fluid, resulting from water-basalt interaction; (3) massive cryptocrystalline quartz with interstitial K-feldspar, Ba-K-mica and Fe-sulfides representing the residual fluids. K-Al-silicates incorporated 130 to 2540 ppm of N, probably NH4+ and 2990 to 6970 ppm of C from hydrothermal fluids. Oxidizing and slightly acid fluids later infiltrated the chert, and quartz veins were formed during diagenesis. Goethite and hydrous Mn-Fe minerals replaced carbonates, sulfides and magnetite, incorporating 500 to 4550 ppm of N and 3440 to 6000 ppm of C. N might occur as NH4+, replacing K+ in the Fe-Mn oxyhyroxide structure. The oxyhydroxide texture is vermicular and filamentous Their heterogeneous chemical composition is caused possibly by microbial activity. This is in agreement with measured N/C ratios of 0.06-0.6, similar to those known for marine bacteria. The d15N signatures of N are similar to those measured in marine sediments and derived from metabolic activity of bacteria (d15N=7.6%). The higher measured d15N values of 10% could be due to post-emplacement devolatilization of the sample or alternatively to different redox conditions during N fixation into sediments by organisms.

Wagner, C.; Orberger, B.; Pinti, D. L.; Gallien, J.; Fialin, M.; Daudin, L.; Hashizume, K.

2004-05-01

156

Spatial variability in hydrothermal systems in fast-spreading crust: evidence from tectonic windows exposed at Pito and Hess Deeps  

NASA Astrophysics Data System (ADS)

Tectonic windows of the oceanic crust provide views of the internal structure of mid-ocean ridge hydrothermal systems. Targeted exploration of escarpments that formed at the fast- to very fast-spreading East Pacific Rise exposed at Pito and Hess Deeps have allowed us to address questions that 1-D "pinpricks" afforded by ocean drilling cannot. Outcrop imaging along closely spaced submersible and ROV tracks document the geological context of hydrothermal alteration in 3-dimensions. These broad views reveal how and why the conditions and products of fluid-rock reaction were spatially and temporally variable. Alteration characteristics in the sheeted dike complexes at Pito and Hess Deeps are similar. The dikes are relatively fresh (average extent of alteration is 27%, ranging from 0 to >80%) and the background alteration is amphibole- dominated. At Hess Deep chlorite dominates within a few hundred metre wide zones, whereas at Pito Deep chlorite-rich dikes are sporadically distributed throughout. Mineral assemblages and compositions, and distributed Cu and Zn depletion, indicate that peak temperatures ranged from <300 to >400° C and did not vary systematically with depth. Vein systems are rare at Hess Deep, whereas amphibole and chlorite veins are ubiquitous and quartz-filled fractures are only locally present at Pito Deep. Regional variability in alteration characteristics is found on a scale of <1 to 2 km, illustrating the diversity of fluid-rock interaction that can be expected at fast-spreading ridges. Migration of circulating cells along ridges and local evolution of fluid compositions produce sections of the upper crust with a distinctive character of alteration, on time scales of <5-20 kyr. It is interesting to note that the time-integrated fluid fluxes, calculated from Sr-isotopic mass balance, are comparable between areas, despite the distinctive character of alteration.

Gillis, K. M.

2008-12-01

157

Hydrothermal macroscopic Fe-sepiolite from Oujda Mounts (Middle Atlas, Eastern Morocco)  

NASA Astrophysics Data System (ADS)

The Triassic-Jurassic series in the Oujda Mounts (Middle Atlas, NE Morocco) includes two basaltic units. The whole sequence is crosscut by veins filled with Fe-sepiolite + chalcedony + calcite + smectite and mixed layer talc-saponite. Fe-sepiolite occurs as macroscopic fibres and is one of the latest mineral phases in the filling sequence of the veins. The compositional relationships and crystallographic parameters obtained on carefully selected samples of sepiolite are compared with previous data, and support the actual development of Mg-Fe substitution in this clay mineral, given the adequate hydrothermal conditions. Genesis of this uncommon variety of sepiolite in veins is interpreted as the result of regional low temperature hydrothermalism that affected the Middle Atlas during the Jurassic. The Mg-rich hydrothermal solutions interacted with the basaltic sequences, previously affected by alteration processes, producing the mobilization of Fe and allowing for the precipitation of Fe-sepiolite as a late mineral in the veins.

Arranz, Enrique; Lago, Marceliano; Bastida, Joaquín; Galé, Carlos; Soriano, Jesús; Ubide, Teresa

2008-10-01

158

[The iliac vein occlusion].  

PubMed

Basing on roentgenological and morphological investigations the causes of the iliac veins passability disorder were studied up. In 45.1% of observations the stenosis was revealed of the left and in 1.2% of the right common iliac vein. Among the stenosis causes were osteal or cartilagenous prominences of vertebral column, intravascular structures (webs, membranes) in the left common iliac vein, the external iliac vein squeeze by internal iliac artery, retroperitoneal fibrosis, the right common iliac artery aneurysm, anomalous branching of parietal pelvic artery. PMID:10370311

Baeshko, A A; Rogov, Iu I; Kriukov, A G; Sysoev, A V; Puchkov, A F; Berlov, G A

1999-01-01

159

Faults and damage zones in fast-spread crust exposed on the north wall of the Hess Deep Rift: Conduits and seals in seafloor hydrothermal systems  

NASA Astrophysics Data System (ADS)

The northern escarpments of the Hess Deep Rift provide cross-sectional views of in situ, ˜1-Ma-old, upper oceanic crust that underwent extensive, spreading-related brittle deformation. Most of the deformation and associated alteration occurred within the locus of magmatic construction of the East Pacific Rise, in the presence of high-temperature hydrothermal fluids. Passing laterally from undeformed host rocks, brittle deformation zones are classified as (1) damage zones where densely spaced fractures overprint the primary structure of dikes and lavas, (2) cataclastic zones where interconnected fractures, comminuted grains, and matrix minerals define deformational fabrics, and (3) very fine-grained, gouge-filled fault cores. Relative to the host rock, damage and cataclastic zones are rich in veins of chlorite and/or actinolite, and lesser amounts of titanite, epidote, and quartz. These phases mark relict hydrothermal fluid pathways. Trace and major element compositions of representative samples also indicate fault-localized hydrothermal alteration, including an increase in MgO by several weight percent within cataclastic and damage zones. In contrast, the fault cores are composed of very finely comminuted basaltic material and have MgO concentrations similar to the damage zones. Integrated compositional, textural, and outcrop-scale structural data inform an evolutionary model for fault growth from the early, widespread dilational phases of damage-zone development to more restricted noncoaxial strain in the cataclastic zones. With continued fault development, gouge develops and seals the fault cores. While the fault cores are sealed by gouge, surrounding zones remain conduits to hydrothermal fluid flow, except where sealed by secondary minerals. Sealed faults can later be reactivated as conduits with additional increments of fault slip. The dual behavior of faults as conduits and seals inevitably leads to compartmentalization of the flow regime in subaxial and ridge-flank areas.

Hayman, Nicholas W.; Karson, Jeffrey A.

2007-10-01

160

Reconstruction of Ancestral Hydrothermal Systems on Mount Rainier Using Hydrothermally Altered Rocks in Holocene Debris Flows and Tephras  

NASA Astrophysics Data System (ADS)

Mount Rainier is the result of episodic stages of edifice growth during periods of high eruptive activity and edifice destruction during periods of relative magmatic quiescence over the past 500 kyr. Edifice destruction occurred both by slow erosion and by catastrophic collapses, some of which were strongly influenced by hydrothermal alteration. Several large-volume Holocene debris-flow deposits contain abundant clasts of hydrothermally altered rocks, most notably the 4-km3 clay-rich Osceola Mudflow which formed by collapse of the northeast side and upper 1000+ m of the edifice about 5600 ya and flowed >120 km downstream into Puget Sound. Mineral assemblages and stable isotope data of hydrothermal alteration products in Holocene debris-flow deposits indicate formation in distinct hydrothermal environments, including magmatic-hydrothermal, steam-heated (including a large fumarolic component), magmatic steam (including a possible fumarolic component), and supergene. The Osceola Mudflow and phreatic components of coeval tephras contain the highest-temperature and inferred most deeply formed alteration minerals; assemblages include magmatic-hydrothermal quartz-alunite, quartz-topaz, quartz-pyrophyllite and quartz-illite (all +pyrite), in addition to steam-heated opal-alunite-kaolinite and abundant smectite-pyrite. In contrast, the Paradise lahar, which formed by a collapse of the surficial upper south side of the edifice, contains only steam-heated assemblages including those formed largely above the water table from condensation of fumarolic vapor (opal-alunite-jarosite). Younger debris-flow deposits on the west side of the volcano (Round Pass lahar and Electron Mudflow) contain only smectite-pyrite alteration, whereas an early 20th century rock avalanche on Tahoma Glacier also contains magmatic-hydrothermal alteration that is exposed in the avalanche headwall of Sunset Amphitheater. Mineralogy and isotopic composition of the alteration phases, geologic and geophysical data, as well as analog fossil hydrothermal systems in volcanoes elsewhere, constrain hydrothermal alteration geometry on the pre-Osceola-collapse edifice of Mount Rainier. Relatively narrow zones of acid magmatic-hydrothermal alteration in the central core of the volcano grade to more widely distributed smectite-pyrite alteration farther out on the upper flanks, capped by steam-heated alteration with a large component of alteration resulting from condensation of fumarolic vapor above the water table. Alteration was polygenetic in zones formed episodically, and was strongly controlled by fluxes of heat and magmatic fluid and by local permeability.

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

2005-12-01

161

Quantitative constraints on the interplay of fluid properties and rock mechanics in the formation of magmatic-hydrothermal ore deposits  

NASA Astrophysics Data System (ADS)

Porphyry copper and epithermal gold are among the most abundant types of ore deposits worldwide. There is evidence that both might form in a common type of magmatic-hydrothermal system related to the crystallization of subduction-related hydrous magmas in the upper crust. Our recent numerical modelling quantitatively shows that the implementation of real non-linear fluid properties and transient feedbacks with rock mechanics are key to explain some first-order controls on their formation. The salinity of the volatiles released from the solidifying magma extends the pressure-temperature range of two- or three-phase coexistence of vapour, liquid and solid halite to significantly higher pressures and temperatures as compared to pure water, and fluid inclusion analyses and theoretical models show the importance of these phase relations for metal transport and ore precipitation. Many magmatic-hydrothermal systems like porphyry-type ore deposits have dense quartz-vein networks that were formed by hydrofracturing of the rock and that are clearly associated with ore formation. In order to quantitatively constrain the hydrology of these systems in a physically rigorous way, we developed a numerical magmatic-hydrothermal simulator that can combine an accurate model of saltwater and a transient pressure- and temperature-dependent permeability model with a transport scheme that can handle the expulsion of magmatic fluids. Generic simulations demonstrate the role of fluid and rock properties in self-organizing and stabilizing fluid flow at conditions favourable for metal enrichment to economic grades in the porphyry and epithermal environments.

Weis, P.; Driesner, T.; Heinrich, C. A.

2012-12-01

162

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

NASA Astrophysics Data System (ADS)

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

Rajabzadeh, M. A.; Asadi, S.

2009-04-01

163

[Spectral characteristics and implications of quartz from Heliao lead-zinc polymetallic ore district in the south of Qinzhou-Hangzhou joint belt].  

PubMed

The XRD, FTIR and Raman spectrum were employed to study the characters of quartz from three types of rock samples, which are mineralized rock sample, near ore body rock sample and far away from ore body rock sample in Heliao lead-zinc polymetallic ore district. The research shows that the quartz in the mineralized rock and far away from ore body rock is pure, while the quartz in near ore body rock contains a small amount of impurities. But such small amounts of impurities did not cause apparent change in the quartz lattice parameters. From far away from ore body rock-->near ore body rock-->mineralized rock, the crystallinity and order degree of quartz are higher and higher. And the quartz in the mineralized rock has a trend to change into low symmetry quartz. It's a unique to mineralized rock that the quartz's absorption peak at 1 050 cm(-1) was split into two strongest ones. It can be used as the signs of whether exists mineralization. The cause for the quartz microstructure changes may be related to the activities of late mineralized hydrothermal fluids. Late hydrothermal influence was very weak to the quartz far away from ore body rock. And through the impact of the multi-stage hydrothermal effect, the quartz in mineralized rock may be purified by recrystallization and structural adjustment. However the quartz in near ore body rock didn't have enough hydrothermal influence, so it's not pure. Genealogy research technology is a useful technique for in-depth exploration of study area mineralization process and metallogenic regularity. PMID:23905355

Lü, Wen-Chao; Yang, Zhi-Jun; Zhou, Yong-Zhang; Li, Hong-Zhong; Zeng, Xiang-Qing; Chen, Qing; Liang, Jin; Zeng, Chang-Yu

2013-05-01

164

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.

165

Local origin of high pressure vein material in eclogite facies rocks of the Zermatt-Saas-Zone, Switzerland  

Microsoft Academic Search

Prograde dehydration reactions within metabasalts at the blueschist- eclogite facies transition produce kyanite veins, usually with quartz, sometimes with omphacite or chloritoid, of up to several meters length and 20 cm width. Bulk rock analyses show clear depletion haloes for Al2O3 and SiO2 near the veins. Mass balance calculations support the suggestion that the vein material must have been derived

TIMO WIDMER; ALAN BRUCE THOMPSON

2001-01-01

166

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

167

Deep vein thrombosis.  

PubMed

Deep vein thrombosis (DVT) is a thrombus or blood clot that can occur in any of the deep veins in the body. DVTs occur most commonly in the leg or pelvis but also travel to the lungs, causing pulmonary embolism. PMID:24938985

Jackson, Mike

2014-06-18

168

Recurrent varicose veins  

Microsoft Academic Search

When Doppler ultrasound was introduced for the assessment of patients with varicose veins, a more accurate clinical appraisal of the pathophysiology of this condition became possible. In particular, it enabled identification of those patients with recurrent varicose veins who had had inappropriate or inadequate initial treatment. It facilitated planning of appropriate further treatment.

John P. Royle

1986-01-01

169

ORIGIN OF QUARTZ IN COAL.  

USGS Publications Warehouse

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

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

1984-01-01

170

How Are Varicose Veins Treated?  

MedlinePLUS

... page from the NHLBI on Twitter. How Are Varicose Veins Treated? Varicose veins are treated with lifestyle changes and medical procedures. ... relieve symptoms, prevent complications, and improve appearance. If varicose veins cause few symptoms, your doctor may simply suggest ...

171

Quartz resonator processing system  

DOEpatents

Disclosed is a single chamber ultra-high vacuum processing system for the oduction of hermetically sealed quartz resonators wherein electrode metallization and sealing are carried out along with cleaning and bake-out without any air exposure between the processing steps. The system includes a common vacuum chamber in which is located a rotatable wheel-like member which is adapted to move a plurality of individual component sets of a flat pack resonator unit past discretely located processing stations in said chamber whereupon electrode deposition takes place followed by the placement of ceramic covers over a frame containing a resonator element and then to a sealing stage where a pair of hydraulic rams including heating elements effect a metallized bonding of the covers to the frame.

Peters, Roswell D. M. (Rustburg, VA)

1983-01-01

172

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

173

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

174

Deep vein thrombosis - discharge  

MedlinePLUS

Deep venous thrombosis (DVT) is when a blood clot forms in a vein that is not on the surface of the ... al. Executive Summary: Antithrombotic Therapy and Prevention of Thrombosis. 9th ed. American College of Chest Physicians Evidence- ...

175

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

USGS Publications Warehouse

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

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

1996-01-01

176

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

NASA Astrophysics Data System (ADS)

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

Gratz, Andrew J.; Fisler, Diana K.; Bohor, Bruce F.

1996-08-01

177

The chemistry of hydrothermal magnetite: a review  

USGS Publications Warehouse

Magnetite (Fe3O4) is a well-recognized petrogenetic indicator and is a common accessory mineral in many ore deposits and their host rocks. Recent years have seen an increased interest in the use of hydrothermal magnetite for provenance studies and as a pathfinder for mineral exploration. A number of studies have investigated how specific formation conditions are reflected in the composition of the respective magnetite. Two fundamental questions underlie these efforts — (i) How can the composition of igneous and, more importantly, hydrothermal magnetite be used to discriminate mineralized areas from barren host rocks, and (ii) how can this assist exploration geologists to target ore deposits at greater and greater distances from the main mineralization? Similar to igneous magnetite, the most important factors that govern compositional variations in hydrothermal magnetite are (A) temperature, (B) fluid composition — element availability, (C) oxygen and sulfur fugacity, (D) silicate and sulfide activity, (E) host rock buffering, (F) re-equilibration processes, and (G) intrinsic crystallographic controls such as ionic radius and charge balance. We discuss how specific formation conditions are reflected in the composition of magnetite and review studies that investigate the chemistry of hydrothermal and igneous magnetite from various mineral deposits and their host rocks. Furthermore, we discuss the redox-related alteration of magnetite (martitization and mushketovitization) and mineral inclusions in magnetite and their effect on chemical analyses. Our database includes published and previously unpublished magnetite minor and trace element data for magnetite from (1) banded iron formations (BIF) and related high-grade iron ore deposits in Western Australia, India, and Brazil, (2) Ag–Pb–Zn veins of the Coeur d'Alene district, United States, (3) porphyry Cu–(Au)–(Mo) deposits and associated (4) calcic and magnesian skarn deposits in the southwestern United States and Indonesia, and (5) plutonic igneous rocks from the Henderson Climax-type Mo deposit, United States, and the un-mineralized Inner Zone Batholith granodiorite, Japan. These five settings represent a diverse suite of geological settings and cover a wide range of formation conditions. The main discriminator elements for magnetite are Mg, Al, Ti, V, Cr, Mn, Co, Ni, Zn, and Ga. These elements are commonly present at detectable levels (10 to > 1000 ppm) and display systematic variations. We propose a combination of Ni/(Cr + Mn) vs. Ti + V, Al + Mn vs. Ti + V, Ti/V and Sn/Ga discriminant plots and upper threshold concentrations to discriminate hydrothermal from igneous magnetite and to fingerprint different hydrothermal ore deposits. The overall trends in upper threshold values for the different settings can be summarized as follows: (I) BIF (hydrothermal) — low Al, Ti, V, Cr, Mn, Co, Ni, Zn, Ga and Sn; (II) Ag–Pb–Zn veins (hydrothermal) — high Mn and low Ga and Sn; (III) Mg-skarn (hydrothermal) — high Mg and Mn and low Al, Ti, Cr, Co, Ni and Ga; (IV) skarn (hydrothermal) — high Mg, Al, Cr, Mn, Co, Ni and Zn and low Sn; (V) porphyry (hydrothermal) — high Ti and V and low Sn; (VI) porphyry (igneous) — high Ti, V and Cr and low Mg; and (VII) Climax-Mo (igneous) — high Al, Ga and Sn and low Mg and Cr.

Nadoll, Patrick; Angerer, Thomas; Mauk, Jeffrey L.; French, David; Walshe, John

2014-01-01

178

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

179

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

180

Lead isotope compositions as guides to early gold mineralization: the North Amethyst vein system, Creede district, Colorado  

USGS Publications Warehouse

The North Amethyst vein system, which is hosted by ~27 Ma Carpenter Ridge Tuff and ~26 Ma Nelson Mountain Tuff, has two mineral associations separated by brecciation and sedimentation in the veins. The early association consists of quartz, rhodonite, hematite, magnetite, electrum, Mn carbonate, Au-Ag sulfide, Ag sulfosalt, and base metal sulfide minerals. The later mineral association cuts the Mn- and Au-bearing assemblages and consists of quartz, calcite, sericite, chlorite, hematite, adularia, fluorite, base metal sulfides, and Ag-bearing tetrahedrite. Detailed studies of the Pb isotope compositions of minerals of the vein system are described. Paragenetically early sulfide-rich vein assemblages have the least radiogenic galenas and generally also have the highest Au contents. Thus, identification of paragenetically early vein assemblages with relatively unradiogenic Pb isotope compositions similar to those of the North Amethyst area provides an additional exploration tool for Au in the central San Juan Mountains area. -from Authors

Foley, N. K.; Ayuso, R. A.

1994-01-01

181

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

182

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

183

Hydrogen speciation in synthetic quartz  

Microsoft Academic Search

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

Roger D. Aines; Stephen H. Kirby; George R. Rossman

1984-01-01

184

Hydrothermal solidification of blast furnace slag by formation of tobermorite  

Microsoft Academic Search

Blast furnace water-cooled slag (BFWS) has been solidified using a hydrothermal processing method, in which the BFWS could\\u000a be solidified in an autoclave under saturated steam pressure (1.56 MPa) at 200 ?C for 12 h by the additions of quartz or coal\\u000a flyash. The tensile strength development was shown to depend on the formation of tobermorite and the packing state of the\\u000a formed

Zhenzi Jing; F. Jin; T. Hashida; N. Yamasaki; H. Ishida

2007-01-01

185

General characteristics and structural evolution of metamorphic goldquartz veins in northwestern Nevada, U.S.A  

Microsoft Academic Search

Metamorphic gold-quartz veins in northwestern Nevada, U.S.A. formed during both brittle and brittle-ductile shear deformations\\u000a in three tectono-stratigraphic terranes. The veins are concentrated in a 60- to 100-km-wide, 200-km-long, linear, northtrending\\u000a corridor. The veins show a consistent northeast strike in the central parts of the corridor and several kinematic indicators\\u000a strongly suggest that the broad corridor acted as a regional-scale

Sangwon Cheong

2000-01-01

186

Pseudotachylyte in muscovite-bearing quartzite: Coseismic friction-induced melting and plastic deformation of quartz  

NASA Astrophysics Data System (ADS)

Thin (0.5-2 mm thick) pseudotachylyte veins occur within muscovite-bearing (˜10% volume), amphibolite-facies quartzites of the Schneeberg Normal Fault Zone (Austroalpine, Southern Tyrol, Italy). Pseudotachylytes are associated with precursor localized plastic microshear zones (50-150 ?m thick) developed sub-parallel to the host-rock foliation and with conjugate sets oriented at a high angle to the foliation. Such microshear zones are characterized by recrystallization to ultrafine-grained (1-2 ?m grain size) mosaic aggregates of quartz showing a transition from a host-controlled to a random crystallographic preferred orientation towards the shear zone interior. Subsequent coseismic slip mainly exploited these microshear zones. Microstructural analysis provides evidence of extensive friction-induced melting of the muscovite-bearing quartzite, producing a bimodal melt composition. First, the host-rock muscovite was completely melted and subsequently crystallized, mainly as K-feldspar. Then, about 60% volume of the ultrafine-grained quartz underwent melting and crystallized as spherulitic rims (mostly consisting of quartz ± Ti ± Fe) around melt-corroded quartz clasts. The two melts show immiscibility structures in the major injection veins exploiting microshear zones at high angles to the quartzite foliation. In contrast, they were mechanically mixed during flow along the main fault veins.

Bestmann, Michel; Pennacchioni, Giorgio; Frank, Gerhard; Göken, Mathias; de Wall, Helga

2011-02-01

187

Hydrothermal dolomitization and recrystallization of dolomite breccias from the Miocene Monterey Formation, Tepusquet area, California  

SciTech Connect

Despite the intensity of brecciation and its potential importance as an analog to Monterey fractured hydrocarbon reservoirs, no detailed petrographic, crystallographic, or geochemical analyses have been performed on the breccias from the Tepusquet area. In the present study, petrographic, crystallographic, and geochemical analyses show that the vein-filling dolomites were precipitated from hydrothermal fluids that were associated with hydrocarbon migration, and that the early diagenetic matrix dolomites have been recrystallized, resetting their geochemical and crystallographic properties. The close chemical similarity of the vein dolomites and the most recrystallized matrix dolomites, the episodic association between hydrocarbons and the vein dolomites, and the recrystallization trends in the matrix dolomites, all indicate that evolved formation waters were the source of the hydrothermal fluids that precipitated the vein dolomites.

Malone, J.J.; Baker, P.A. [Duke Univ., Durham, NC (United States). Dept. of Geology; Burns, S.J. [Univ. Bern (Switzerland). Geologisches Inst.

1996-09-01

188

Pelvic Vein Embolisation in the Management of Varicose Veins  

SciTech Connect

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

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

2008-11-15

189

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

190

Ore-bearing hydrothermal metasomatic processes in the Elbrus volcanic center, the northern Caucasus, Russia  

NASA Astrophysics Data System (ADS)

Precaldera, caldera, and postcaldera cycles are recognized in the geological evolution of the Pleistocene-Holocene Elbrus volcanic center (EVC). During the caldera cycle, the magmatic activity was not intense, whereas hydrothermal metasomatic alteration of rocks was vigorous and extensive. The Kyukyurtli and Irik ore-magmatic systems have been revealed in the EVC, with the former being regarded as the more promising one. The ore mineralization in rocks of the caldera cycle comprises occurrences of magnetite, ilmenite, pyrite and pyrrhotite (including Ni-Co varieties), arsenopyrite, chalcopyrite, millerite, galena, and finely dispersed particles of native copper. Pyrite and pyrrhotite from volcanics of the caldera cycle and dacite of the Kyukyurtli extrusion are similar in composition and differ from these minerals of the postcaldera cycle, where pyrite and pyrrhotite are often enriched in Cu, Co, and Ni and millerite is noted as well. The composition of ore minerals indicates that the hydrothermal metasomatic alteration related to the evolution of the Kyukyurtli hydrothermal system was superimposed on rocks of the caldera cycle, whereas the late mineralization in rocks of the postcaldera cycle developed autonomously. The homogenization temperature of fluid inclusions in quartz and carbonate from crosscutting veinlets in the apical portion of the Kyukyurtli extrusion is 140-170°C and in quartz from geyserite, 120-150°C. The temperature of formation of the chalcopyrite-pyrite-pyrrhotite assemblage calculated using mineral geothermometers is 156 and 275°C in dacite from the middle and lower portions of the Malka lava flow and 190°C in dacite of the Kyukyurtli extrusion. The hydrothermal solutions that participated in metasomatic alteration of rocks pertaining to the Kyukyurtli ore-magmatic system (KOMS) and formed both secondary quartzite and geyserite were enriched in fluorine, as evidenced from the occurrence of F-bearing minerals-zharchikhite, ralstonite, ?-ralstonite, and fluorite-identified in these metasomatic rocks for the first time. By analogy with porphyry Cu-Mo deposits in Chile and the United States, the ore mineralization of the KOMS may be classified by composition and textural and structural attributes as a supraore level of porphyry copper genetic type. The volcanic rocks of the KOMS and the EVC as a whole are enriched in Ag, Mo, Zn, As, Sb, Se, and Ba. Judging from the scale of argillic alteration and taking into account the data on porphyry Cu-Mo ore-magmatic systems of the Greater Caucasus, veined Pb-Zn ore mineralization may be expected in the propylitic zone at a depth down to 1000 m from the present-day erosion level of the KOMS. Stringer-disseminated Au-Ag, Cu, and Cu-Mo ore mineralization of the upper part of the porphyry ore-magmatic system related to subvolcanic dacitic intrusions may be localized somewhat deeper.

Gurbanov, A. G.; Bogatikov, O. A.; Dokuchaev, A. Ya.; Gazeev, V. M.; Abramov, S. S.; Groznova, E. O.; Shevchenko, A. V.

2008-06-01

191

Geochemical environment of mineralization and alteration in the southern Ohio vein, Creede, Colorado  

SciTech Connect

Detailed mineralogical, paragenetic, and geochemical studies in the southern Ohio vein at Creede, Colorado, a Tertiary volcanic hosted Pb-Zn-Ag epithermal deposit, indicate that two hypogene vein fluids with distinct redox characteristics alternately precipitated oxidized and reduced assemblages. Oxidized assemblages are characterized by barite and hematite, whereas the reduced fluids appear responsible for the base and precious metal, as well as gangue deposition. The oxidizing fluid was generated either through shallow level boiling or volatile exsolution (CO/sub 2/, H/sub 2/S) of an initially reduced primary hydrothermal fluid or through mixing with an oxidized groundwater. Hypogene events in the wallrock, contemporaneous with vein mineralization, have the following paragenesis: 1) pervasive bleaching of the wallrock via pyritization of groundmass hematite with introduction of reduced hydrothermal vein fluids, 2) argillization (illite with 3-15 +/- 2% interlayered smectite) of the wallrock and disseminated sulfide mineralization, and 3) vein related silicification overprinting earlier events. These reactions result from the introduction of low pH (approx. 5.0), sulfur poor (10/sup -3/ - 10/sup -3.5/ m), reduced (H/sub 2/S) hydrothermal fluids into the wallrock. Mineralization occurred over a decreasing temperature regime (approx. 250 to 180/sup 0/C) possibly coupled with a pH increase related to argillization. The nature and distribution of wallrock alteration is controlled by permeability, fluid composition, and temperature.

Gorman, J.

1985-01-01

192

Role of Substrate on Quartz Cementation in Quartz Aggregates  

NASA Astrophysics Data System (ADS)

Quartz cementation in quartz aggregates has been experimentally investigated. The starting material was disaggregated detrital quartz grains from the well-sorted, mature St. Peter Sandstone. The ‘as-is’ grains have patches of iron oxide coatings and some have euhedral overgrowths that contain iron oxide dust rims. In addition a set of experiments was run using grains that were cleaned by soaking in sodium hydrosulfite and sodium bisulfate solutions to remove exposed iron oxide coatings. Experimental charges consisted of amorphous silica powder (?30 mg) to provide a source of silica for the quartz cement, AlCl3 powder (?3 mg) to provide a tracer for Cathodoluminescence (CL) identification of cement formed during the experiment, 25 wt% NaCl brine solution (?25 mg) to increase the silica solubility and to better mimic oil field brines, and the natural quartz grains (100-130 mg). The charges were weld-sealed in Au capsules and run in cold-seal pressure vessels at 250°C to 450°C at 150 MPa confining pressure for up to 8 weeks. After the experiments, the samples were vacuum impregnated with a low viscosity epoxy containing a blue dye. After curing, the sample charge was sawn in half along its long axis and one half was polished (to 1 micron diamond paste) for analysis. The nature and amount of quartz cement in the samples were determined by a combination of CL, light microscopy, and scanning electron microscopy. Photomosaics of the samples were created and the amount of cement, porosity, and average grain sizes were determined by point-counting. The cement formed during the experiment was easily recognized from the quartz grains (and previous overgrowths) by the difference in luminescence. The results indicate the amorphous silica powder provides a ready source for silica for quartz cementation due to its greater solubility than the quartz. The cementation rates are rapid (>14% cement formed in 2 weeks at 450°C and >7% in 8 weeks at 250°C). Compared to experiments using crushed fragments of synthetic quartz (Pepple, 2007), the amount of cement in these natural samples was greater. Cementation followed a common pattern in all samples. Microfractures, which formed during pressurization of the charges, healed very rapidly followed by overgrowths on the quartz grains. Cementation began closest to the amorphous silica, then progressed away. There was no measurable difference in the amount of quartz cement formed in samples of the as-is and cleaned St. Peter Sandstone indicating that iron played no role in the rate of cementation. Although the amount of cement formed increased with increasing temperature and duration of the experiments, the rate of cementation decreased dramatically in longer duration (8 weeks) experiments suggesting a change in the precipitation mechanism/rate. This apparent change in precipitation rate may reflect a decrease in available surfaces for nucleation and/or a decrease in growth rate as euhedral faces develop as proposed by Lander et al (2008).

Farver, J. R.; Winslow, D.; Onasch, C.

2010-12-01

193

Epidemiology of varicose veins  

Microsoft Academic Search

The prevalence rate of varicose veins in adults varies from less than 1% in lowland New Guinea women to over 50% in women in south Wales. Within populations the prevalence increases with age, is generally greater in women, is directly related to body mass, has an inconsistent relationship with occupation, and usually increases with increasing parity. None of these factors

Robert Beaglehole

1986-01-01

194

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

195

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

Microsoft Academic Search

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

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

2002-01-01

196

Numerical Modelling of Vein Microstructures  

Microsoft Academic Search

Mineral veins occur in a variety of forms (syntaxial, antitaxial, etc.), and with various microstructures (fibrous, stretched crystals, vuggy, etc.). These structures can, if correctly interpreted, provide useful insight into the geological and tectonic conditions at which the veins formed (Oliver and Bons 2001). Durney and Ramsay (1973) defined the base for the modern classification and interpretation of vein (micro-)

P. D. Bons

2005-01-01

197

Virus Necrosis of Tobacco Veins.  

National Technical Information Service (NTIS)

Virus necrosis of tobacco veins (browning of tobacco veins) occurs all over Poland and causes major economic losses. Studies of a number of orders show that the necrosis of tobacco veins is caused by a virus, which belongs to the group of potato virus Y (...

J. Berbec

1964-01-01

198

Pineal veins in vertebral angiography.  

PubMed

Angiographic patterns of pineal veins in normal and pathological conditions are examined. The diagnostic value of these veins for midline growths is limited owing to their inconstant visualization, multifarious angiographic patterns and minute size. With this in mind, greater significance of classical displacements of the internal and basal veins is outlined. PMID:1196485

Turtas, S

1975-11-21

199

The fossil hydrothermal rootzone from the Northern Apennine ophiolites (Italy)  

NASA Astrophysics Data System (ADS)

The Northern Apennine ophiolites are lithosphere remnants of the Late Jurassic -- Early Cretaceous Ligurian Tethys, which is considered to have developed in conjunction with the opening of the Central Atlantic Ocean. In the Bonassola area, a km-scale gabbroic body permits the study of the magmatic-hydrothermal transition. The body mostly consists of coarse-grained gabbros of cumulus origin that exhibit granulite-facies recrystallization along ductile shear zones, which most likely occurred in the absence of seawater-derived fluids. These shear zones are crosscut at high angle by parallel swarms of hornblende (± plagioclase) veins. The development of these veins is correlated with coronal hornblende growth at the expenses of igneous clinopyroxene in the host gabbro. Scattered, elongated bodies of hornblende-bearing albitites also crop out. In particular, two different generations of albitite bodies have been recognized. The albitite (1) bodies show irregular contacts against the host gabbro, which are characterized by hornblende-rich reaction zones. These albitites are inferred to have developed when the gabbro was not completely solidified. The albitite (2) bodies has sharp contacts, post-date the granulite-facies foliation in the host gabbros, and show the same elongation direction of hornblende veins. The albitite (2) bodies are therefore related to the same brittle deformation event that gave rise to the hornblende veins. Major, trace, halogen and oxygen isotope analyses of hornblende from both veins and albitite bodies have been carried out. The geochemical signature of hornblende from albitite (1) bodies and related contact reaction zones is similar to that of accessory titanian pargasite of igneous origin in the host gabbro, thus indicating that these albitites were derived by extreme differentiation of basaltic liquid. Two different chemical fingerprints have been recognized for the vein hornblendes. The first type indicates a formation by local reaction between migrating seawater-derived fluids and the gabbros. The development of these veins can be ascribed to a high-temperature, amphibolite-facies hydrothermal event. On the other hand, the hornblende from the less diffuse, thickest and fibrous veins has intermediate geochemical features, similar to the hornblende from albitite (2) bodies. These hornblendes provide evidence for interaction between magmatic and hydrothermal systems.

Tribuzio, R.; Zanetti, A.; Dallai, L.

2003-04-01

200

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

201

Visualizing trace element distribution in quartz using cathodoluminescence, electron microprobe, and laser ablation-inductively coupled plasma-mass spectrometry  

USGS Publications Warehouse

Cathodoluminescent (CL) textures in quartz reveal successive histories of the physical and chemical fluctuations that accompany crystal growth. Such CL textures reflect trace element concentration variations that can be mapped by electron microprobe or laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Trace element maps in hydrothermal quartz from four different ore deposit types (Carlin-type Au, epithermal Ag, porphyry-Cu, and MVT Pb-Zn) reveal correlations among trace elements and between trace element concentrations and CL textures. The distributions of trace elements reflect variations in the physical and chemical conditions of quartz precipitation. These maps show that Al is the most abundant trace element in hydrothermal quartz. In crystals grown at temperatures below 300 °C, Al concentrations may vary by up to two orders of magnitude between adjacent growth zones, with no evidence for diffusion. The monovalent cations Li, Na, and K, where detectable, always correlate with Al, with Li being the most abundant of the three. In most samples, Al is more abundant than the combined total of the monovalent cations; however, in the MVT sample, molar Al/Li ratios are ~0.8. Antimony is present in concentrations up to ~120 ppm in epithermal quartz (~200–300 °C), but is not detectable in MVT, Carlin, or porphyry-Cu quartz. Concentrations of Sb do not correlate consistently with those of other trace elements or with CL textures. Titanium is only abundant enough to be mapped in quartz from porphyry-type ore deposits that precipitate at temperatures above ~400 °C. In such quartz, Ti concentration correlates positively with CL intensity, suggesting a causative relationship. In contrast, in quartz from other deposit types, there is no consistent correlation between concentrations of any trace element and CL intensity fluctuations.

Rusk, Brian; Koenig, Alan; Lowers, Heather

2011-01-01

202

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

203

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

NASA Astrophysics Data System (ADS)

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

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

1994-06-01

204

Leg wound infections following greater saphenous vein harvesting: minimally invasive vein harvesting versus conventional vein harvesting.  

PubMed

Wound complications associated with long incisions used to harvest the greater saphenous vein are common and well documented. We compared leg wound infection rates, wound healing disturbances (WHDs), length of vein harvested, vein harvest time, and total surgical time between minimally invasive saphenous vein harvesting (MIVH) and conventional vein harvesting (CVH) techniques. This meta-analysis showed a significant reduction in wound infections in favor of the MIVH group (odds ratio = 0.19; 95% confidence interval = 0.14-0.25) and a significant reduction in WHDs in favor of the MIVH group (odds ratio = 0.26; 95% confidence interval = 0.20-0.34). The MIVH and CVH techniques are equivalent with respect to saphenous vein harvest time, saphenous vein harvest length, and total surgical time. A visual inspection of "funnel" plots suggests a mild to moderate publication bias. This meta-analysis suggests that leg wound infections and wound healing disturbances are reduced using MIVH techniques. PMID:18815201

Reed, James F

2008-12-01

205

Quartz microfabrics in ultrahigh-pressure metamorphic rocks as indicators of low stress during uplift  

NASA Astrophysics Data System (ADS)

Ultrahigh-pressure (UHP) metamorphic rocks form in convergent tectonic settings at depths > 90 km. In general, UHP conditions are defined by the stability of coesite. Coesite inclusions in various host minerals are a common feature in UHP rocks. We present data of typical quartz microfabrics, which resulted from the transformation of coesite to quartz in inclusions and intergranular regions, and evidence of high temperature quartz microfabrics. Jadeite-quartzites and eclogites from the Dabie Shan - Sulu orogenic belt (central China) were investigated, both of which experienced peak UHP conditions of ~ 660°C / > 2.6 GPa (Liou et al., 1997) and 700-800°C / 3.1-4.1 GPa (Yoshida et al., 2004), respectively, at c. 220-230 Ma due to a N-subduction of the Yangtze craton beneath the Sino-Korean craton, followed by a nearly isothermal decompression to ~ 1 GPa. Both rocks contain coesite and/or quartz inclusions (up to 350 ?m in diameter) in clinopyroxene and garnet and in their symplectitic rims with various microstructures: (i) rims of palisade quartz commonly in contact to coesite, (ii) quartz aggregates with sutured grain boundaries and central remnants of coesite, (iii) larger central quartz grains with subgrains, (iv) foam quartz (c. 50 ?m sized), and (v) apparently strain-free single quartz crystals. The foam quartz shows a random c-axis distribution but preferred crystallographic orientations of grain boundaries. Intergranular foam quartz is found in quartz-eclogites from the Sulu region, most probably indicating quartz-coesite transformation and, therefore, former UHP conditions. The preservation of foam quartz in intergranular regions and inclusions (especially in symplectites) indicates low stress and nearly no deformation during uplift in the stability field of quartz. This points to strain localization in shear zones (Zhao et al., 2003). In veins in the jadeite-quartzites and quartz-eclogites quartz occurs in larger aggregates with sutured grain boundaries. Fractal analysis of the grain boundaries indicates deformation-T > 700°C for jadeite-quartzite and quartz-eclogite. Furthermore, quartz grains of the Dabie Shan jadeite-quartzites show prism-, basal-, and rhombohedral-parallel subgrain boundaries, evidencing high temperature during formation and nearly no deformation after peak metamorphic conditions. The qualitative and quantitative analyses of quartz microfabrics of UHP rocks give insight into the grade of preservation of peak conditions, potential deformation and/or low-grade overprint, and help to understand uplift processes of deeply subducted crustal slices. Liou, J.G., Zhang, R.Y. and Jahn, B.-m., 1997. Petrology, geochemistry and isotope data on a ultrahigh-pressure jadeite quartzite from Shuanghe, Dabie Mountains, East-central China. Lithos 41, 59-78. Yoshida, D., Hirajima, T. and Ishiwatari, A., 2004. Pressure-temperature path recorded in the Yangkou garnet peridotite, in Su-Lu ultrahigh-pressure metamorphic belt, eastern China. J. Petrol. 45, 1125-1145. Zhao, Z.Y., Fang, A.M. and Yu, L.J., 2003. High- to ultrahigh-pressure (UHP) ductile shear zones in the Sulu UHP metamorphic belt, China: implications for continental subduction and exhumation. Terra Nova 15, 322-329.

Stäb, C.; Kruhl, J. H.; Trepmann, C.; Wang, L.

2012-12-01

206

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

207

The origin of massive hydrothermal alterations: what drives fluid flow?  

NASA Astrophysics Data System (ADS)

Hydrothermal alterations form when fluids warmer than the host rocks flow through them dissolving and precipitating minerals. These fluids typically flow upwards from deeper geologic units using faults as major conduits. In some cases, hydrothermal alterations affect large (km-scale) rock volumes. One example of such process is the massive high-temperature dolostones that crop out at the Benicàssim outcrop analogue (Maestrat Basin, E Spain). In this area, seismic-scale fault-controlled stratabound dolostone bodies extend over several kilometres away from large-scale faults, replacing Lower Cretaceous limestones. The fluid responsible for such alteration is a seawater-derived brine that interacted with underlying Permian-Triassic and Paleozoic basement rocks. The estimated volume of fluid required to produce the Benicàssim dolomitization is huge, with fluid-rock ratios in the order of several tens to a few hundreds, depending on composition and reaction temperature (Gomez-Rivas et al., 2014). An open key question is what brought this warm fluid (80 - 150 ºC) upwards to a depth of less than 1 km, where the dolomitization reaction took place. The driving forces should have been able not only to provide sufficient fluid volumes at shallow depths but also to heat up the whole host rock, including the non-replaced limestones. There are two hyphoteses for driving a warm fluid upwards in the Maestrat Basin: (a) rapid release through faults of overpressured solutions in recurrent pulses and (b) thermal convection. We present a series of heat and fluid flow numerical simulations to constrain the dolomitization conditions under these two end-member cases. The results indicate that in a pulsating model the fluid must flow upwards at velocities higher than cm/s to keep their elevated temperature. Otherwise they cool down quickly, and the host rocks cannot be heated. Such velocities can be reached if the fluid flow velocity equals that of fracture propagation, as in mobile hydrofractures (Bons, 2001). The main question is whether fast flow leaves recognizable signs, like hydrofractures of different scales and hydraulic breccias. We estimate fluid pressures reached at the reaction site, and discuss whether they are high enough to break the host rock, according to its petrophysical properties. Thermal convection could have driven pervasive fluid flow at lower flow rates, keeping the fluid warm and allowing time for the rock to react. But this mechanism would have required a shallow and very large intrusion or an anomalous geothermal gradient in order to activate flow by convection. This contribution presents a quantitative analysis of these hypotheses, and discusses their plausibility. Bons, P.D., 2001. The formation of large quartz veins by rapid ascent of fluids in mobile hydrofractures. Tectonophysics 336, 1-17. Gomez-Rivas, E., Corbella, M., Martín-Martín, J.D., Stafford, S.L., Teixell, A., Bons, P.D., Griera, A. and Cardellach, E. 2014. Reactivity of dolomitizing fluids and Mg source evaluation of fault-controlled dolomitization at the Benicàssim outcrop analogue (Maestrat Basin, E Spain). Marine and Petroleum Geology, in press.

Gomez-Rivas, Enrique; Bons, Paul D.; Martín-Martín, Juan-Diego; Corbella, Mercè; Stafford, Sherry L.; Griera, Albert; Teixell, Antonio; Salas, Ramón; Travé, Anna

2014-05-01

208

Multiple vortex vein ampulla varicosities  

PubMed Central

Vortex vein ampulla varicosities are asymptomatic, harmless, findings in the retina. They are incidentally picked up on routine eye examination or when presenting for unrelated ocular symptoms. Clinicians and other eye care professionals unaware of this condition may be alarmed and may subject patients to unnecessary anxiety and expensive investigations. We present a rare case of varicosity of two vortex veins involving one quadrant of the retina. We have also shown simple clinical methods of establishing the diagnosis of vortex vein varicosity.

Vahdani, K; Kapoor, B; Raman, V S

2010-01-01

209

Popliteal vein aneurysm.  

PubMed

Although popliteal venous aneurysms are uncommon, they are also potentially fatal because they can cause a pulmonary embolism. The authors report a case of a popliteal vein aneurysm in a healthy, asymptomatic 32-year-old patient as well as a review of the literature. Popliteal venous aneurysms are a rare but treatable cause of recurrent pulmonary embolism, with their true incidence probably being underestimated. Whenever possible, we recommend early surgical repair of both symptomatic and asymptomatic popliteal venous aneurysms because they are associated with an ill-defined risk of pulmonary embolism and death if left untreated. PMID:20103062

Roche-Nagle, Graham; Wooster, Douglas; Oreopoulos, George

2010-01-01

210

Symptomatic popliteal vein aneurysm.  

PubMed

Popliteal vein aneurysms (PVAs) can have serious consequences, including pulmonary embolism and death. We report a case of PVA in a previously healthy 58-year-old female with a history of pain in her right popliteal fossa for the past 3 years. Patient had no history of trauma or claudication of the right leg. Following a preoperative venogram to confirm the diagnosis, the PVA was dissected circumferentially through a posterior incision. The aneurysm was resected and repaired with lateral venorrhaphy. Patient had an uneventful recovery. Due to the possibility of severe consequences, if left untreated, early surgical repair is highly recommended whether the patient has symptoms or not. PMID:24420057

Premaratne, Shyamal; Tan, Tze-Woei; Coulter, Amy H; Doumite, Darin; Zhang, Wayne W

2014-04-01

211

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

212

Doubly rotated contoured quartz resonators  

Microsoft Academic Search

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

Bikash K. Sinha

2001-01-01

213

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

214

Submarine hydrothermal fossils confirmed  

NASA Astrophysics Data System (ADS)

Researchers from Princeton University (D. Crerrar et al, Econ. Geol., May 1982) have documented, in considerable detail, evidence for the formation of some of the 800 or more manganiferous chert deposits occurring in the central belt of the Fransiscan formation in northwestern California. They confirm the surprisingly old conclusion o f Tiaferro and Hudson (Cal. Div. Mines Bull., 125, 217-276, 1943) that the Fransiscan chert deposits probably represent the fossil remains of submarine hydrothermal vents.The deposits resemble recently discovered hydrothermal mounds near the Galapagos rift, the Gulf of Aden, and the Mid-Atlantic Ridge. As the Princeton investigators point out, there are important implications of the existence of deep hydrothermal circulation systems at oceanic spreading centers throughout geologic time. They note that the calculated annual flow of hydrothermal fluids in such processes is about 1017 g, which implies that the entire volume of the oceans could circulate completely every 10 million years. With such circulation, the hydrothermal processes along midocean ridges could control the composition of seawater and strongly influence the geochemical flux of elements in the marine environment.

Bell, Peter M.

215

Positronium physisorption at quartz surfaces  

NASA Astrophysics Data System (ADS)

The possibility of having positronium (Ps) physisorbed at a material surface is of great fundamental interest, since it can lead to new insight regarding quantum sticking and is a necessary first step to try to obtain a Ps2 molecule on a material host. Experimental evidence for physisorbed Ps at the surface of quartz was reported some years ago, but firm theoretical support for such a conclusion was lacking. With the FLAPW method we calculated the electronic structure and dielectric function of ?-quartz and obtained the interaction potential with a Ps atom on its surface. We show that there is indeed a bound state with an energy of ˜0.19 eV, which is reasonably close to the experimental estimates of 0.14 - 0.17 eV. A brief energy analysis in terms of the Langmuir-Hinshelwood mechanism further shows that the formation of a Ps2 molecule at quartz surface would be possible. Sferlazzo, Berko, Canter, Phys. Rev. B 3, 6067 (1985). Wimmer, Krakauer, Weinert, Freeman, Phys. Rev. B 24, 864 (1981).

Saniz, Rolando; Freeman, Arthur; Barbiellini, Bernardo; Platzman, Phil

2007-03-01

216

Fluid circulation in the upper brittle crust: Thickness distribution, hydraulic transmissivity fluid inclusion and isotopic data of veins hosted in the Oligocene sandstones of the Macigno Formation in southern Tuscany, Italy  

Microsoft Academic Search

We present structural analysis, fluid inclusion data on calcite and quartz, and isotopic composition of calcite forming veins occurring in the upper crustal level and hosted in Oligocene sandstone in southern Tuscany (Italy). The veins have been analysed in two sites few kilometres apart, along well-exposed coastal cliffs and in an abandoned quarry. These two sites were at a different

Francesco Mazzarini; Ilaria Isola; Giovanni Ruggieri; Chiara Boschi

2010-01-01

217

Hydrothermal Synthesis of Ceramic Powders.  

National Technical Information Service (NTIS)

The history of the hydrothermal synthesis is summarized and an appropriate definition of hydrothermal processing and its associated conditions is described. The chronological development of the present large scale process as it is now in operation in the ...

P. Krijgsman

1992-01-01

218

Pattern compensation in Drosophila wing vein development  

Microsoft Academic Search

Much interest in developmental genetics has focused on the formation of patterns. Using the wing vein pattern of Drosophila melanogasler as our model system, we show that vein placement is essentially independent of cell lineage. In studying vein placement in a variety of wing vein mutants, we observed that the position of a vein can move to compensate for the

James N Thompson; Joe V Toney; G Bradley Schaefer

1980-01-01

219

Experimental and theoretical investigation of the production of HCl and some metal chlorides in magmatic/hydrothermal systems  

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

1992-01-01

220

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

SciTech Connect

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

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

1993-08-01

221

Exsolved magmatic fluid and its role in the formation of comb-layered quartz at the Cretaceous Logtung W-Mo deposit, Yukon Territory, Canada  

USGS Publications Warehouse

Comb-layered quartz is a type of unidirectional solidification texture found at the roofs of shallow silicic intrusions that are often associated spatially with Mo and W mineralisation. The texture consists of multiple layers of euhedral, prismatic quartz crystals (Type I) that have grown on subplanar aplite substrates. The layers are separated by porphyritic aplite containing equant phenocrysts of quartz (Type II), which resemble quartz typical of volcanic rocks and porphyry intrusions. At Logtung, Type I quartz within comb layers is zoned with respect to a number of trace elements, including Al and K. Concentrations of these elements as well as Mn, Ti, Ge, Rb and H are anomalous and much higher than found in Type II quartz from Logtung or in igneous quartz reported elsewhere. The two populations appear to have formed under different conditions. The Type II quartz phenocrysts almost certainly grew from a high-silica melt between 600 and 800??C (as ??-quartz); in contrast, the morphology of Type I quartz is consistent with precipitation from a hydrothermal solution, possibly as ??-quartz grown below 600??C. The bulk compositions of comb-layered rocks, as well as the aplite interlayers, are consistent with the hypothesis that these textures did not precipitate solely from a crystallising silicate melt. Instead, Type I quartz may have grown from pockets of exsolved magmatic fluid located between the magma and its crystallised border. The Type II quartz represents pre-existing phenocrysts in the underlying magma; this magma was quenched to aplite during fracturing/degassing events. Renewed and repeated formation and disruption of the pockets of exsolved aqueous fluid accounts for the rhythmic banding of the rocks.

Lowenstern, J. B.; Sinclair, W. D.

1996-01-01

222

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

USGS Publications Warehouse

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

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

2009-01-01

223

Recurrent varicose veins following high ligation of long saphenous vein: a duplex ultrasound study  

Microsoft Academic Search

Duplex scanning was used to study recurrent varicose veins in 244 limbs with previous high ligation of the long saphenous vein. The recurrent varicose veins were classified into two types according to the presence or absence of a residual long saphenous vein. Varicose veins with a residual long saphenous vein (type I) occurred in 168 limbs (68.9%). A residual long

Y. Tong; J. Royle

1995-01-01

224

Age and Origin of Base and Precious-Metal Veins of the Coeur D'Alene Mining District, Idaho.  

National Technical Information Service (NTIS)

Ore-bearing quartz-carbonate veins of the Coeur d'Alene mining district yield(sup 87)Sr/(sup 86)Sr ratios of 0.74 to >1.60 for low-Rb/Sr, carbonate gangue minerals, similar to current ranges measured in Middle Proterozoic, high-Rb/Sr rocks of the Belt Sup...

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

2000-01-01

225

Infrared imaging of varicose veins  

NASA Astrophysics Data System (ADS)

It has been established that varicose veins are better visualized with infrared photography. As near-infrared films are nowadays hard to get and to develop in the digital world, we investigated the use of digital photography of varicose veins. Topics that are discussed are illumination setup, photography and digital image enhancement and analysis.

Noordmans, Herke Jan; de Zeeuw, Raymond; Verdaasdonk, Ruud M.; Wittens, Cees H. A.

2004-06-01

226

Infrared imaging of varicose veins  

Microsoft Academic Search

It has been established that varicose veins are better visualized with infrared photography. As near-infrared films are nowadays hard to get and to develop in the digital world, we investigated the use of digital photography of varicose veins. Topics that are discussed are illumination setup, photography and digital image enhancement and analysis.

Herke Jan Noordmans; Raymond de Zeeuw; Ruud M. Verdaasdonk; Cees H. A. Wittens

2004-01-01

227

Isotopic and fluid-inclusion constraints on the formation of polymetallic vein deposits in the central Argentinian Patagonia  

NASA Astrophysics Data System (ADS)

The lead isotope compositions of galena and the fluid-inclusion systematics of nine barite-bearing polymetallic (Au, Ag, Pb, Zn) deposits of the central Argentinian Patagonia (Chubut and Rio Negro provinces) have been investigated to constrain the compositions and sources of the mineralizing fluids. Most of the deposits occur as veins, with less common wall-rock disseminations and/or stockworks, and are low-sulfidation epithermal deposits hosted in Jurassic volcanic rocks. Fluid-inclusion homogenization temperatures (Th) from quartz and sphalerite from the deposits fall within the range of 100-300 °C, with the highest measured average temperatures for the most eastern deposits (Mina Angela - 298 °C; Cañadón Bagual - 343 °C). The salinities of the hydrothermal fluids at all deposits were low to moderate (?10.4 equiv. wt% NaCl). Three groups of ore deposits can be defined on the basis of 206Pb/204Pb ratios for galena and these show a general decrease from west to east (from 18.506 to 18.000). The central Argentinian Patagonia deposits have distinctly less radiogenic lead isotope compositions than similar deposits from Peru and Chile, except for the porphyry copper deposits of central and southern Peru. Galena from the Mina Angela deposit is characterized by very low radiogenic lead isotope compositions (18.000<206Pb/204Pb<18.037 and 38.03<208Pb/204Pb<38.09) and reflects interaction with Precambrian basement. The geographic trend in lead isotope compositions of both galena and whole rocks indicates a crustal contribution which increases eastwards, also reflected in the strontium-neodymium isotope systematics of the host lavas. Finally, due to the lack of precise age determinations for the central Patagonian polymetallic deposits, a potential link with Andean porphyry copper systems remains an open question.

Dejonghe, Léon; Darras, Benoît; Hughes, Guillermo; Muchez, Philippe; Scoates, James S.; Weis, Dominique

2002-03-01

228

Hepatic vein obstruction (Budd-Chiari)  

MedlinePLUS

Hepatic vein obstruction is a blockage of the hepatic vein, which carries blood away from the liver. ... Hepatic vein obstruction prevents blood from flowing out of the liver and back to the heart. This blockage can ...

229

How Is Deep Vein Thrombosis Treated?  

MedlinePLUS

... the NHLBI on Twitter. How Is Deep Vein Thrombosis Treated? Doctors treat deep vein thrombosis (DVT) with medicines and other devices and therapies. ... wear compression stockings. Rate This Content: Deep Vein Thrombosis Clinical Trials Clinical trials are research studies that ...

230

Quartz-tourmaline orbicules: Record of magmatic melt immiscibility in the Land's End granite, SW England  

NASA Astrophysics Data System (ADS)

Spherical quartz-tourmaline aggregations are a common sight throughout the Cornubian batholith in SW England. In the outer parts of the Land's End granite smaller rounded orbicules occur in a coarse-grained megacrystic biotite granite. The interior parts of the orbicules show poikilittic textures with fine-grained euhedral quartz chadacrysts enclosed by skeletal tourmaline oikocrysts, with outer zones showing typical replacement textures. Cathodoluminescence of quartz show at least two growth stages after the megacrystic stage. The quartz phenocrysts show an even, concentric zoning pattern, sometimes with a darker core indicating growth during stable physiochemical conditions. The orbicular quartz is strongly zoned with bright cores and darker rims, similar to the fine-grained quartz in the granite matrix. Ti content of quartz corresponds to the CL zoning, with 125 - 180 µg/g in the bright cores and 60 - 80 in the darker main stage orbicular quartz. Tourmaline in the orbicules is weakly zoned form dark to pale brown, but the zoning is more pronounced compared to tourmaline in the granite matrix. Chemically, both are well within the schorl field, and cannot be differentiated based on major elements. The B-isotope signature is also overlapping. Matrix tourmaline has higher Sc and V content, but lower Nb, Ta and Sn, and matrix and orbicule tourmaline can be distinguished using trace elements. The geometry and composition of the orbicules is difficult to explain by fractional crystallization alone, since the total FeO content of the granite is low, and Fe is bound primarily to magmatic phases such as ilmenite and biotite. A prolonged fractional crystallization sequence would have depleted the magma in respect to Fe, and Fe derived from breakdown of nearby biotite is not sufficient to stabilize orbicule tourmaline. Orbicular tourmaline is conspicuously different, both chemically and texturally, from the typical hydrothermal tourmaline in the area, and replacement by an extrinsic hydrothermal fluid is unlikely. We propose that the orbicules formed from an immiscible hydrous B-Fe rich melt that coalesced to the orbicules, and crystallized in a eutectic manner during the last stages of crystallization.

Drivenes, Kristian; Larsen, Rune; Müller, Axel; Sorensen, Bjorn; Wiedenbeck, Michael; Raanes, Morten

2014-05-01

231

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

232

Hydrothermal pretreatment of coal  

SciTech Connect

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

Loo, Bock; Ross, D.S.

1990-08-14

233

Hydrothermal Reactivity of Amines  

NASA Astrophysics Data System (ADS)

The reactivity of aqueous amines depends on temperature, pH, and redox state [1], all of which are highly variable in hydrothermal systems. Temperature and pH affect the ratio of protonated to unprotonated amines (R-NH2 + H+ = R-NH3+), which act as nucleophiles and electrophiles, respectively. We hypothesize that this dual nature can explain the pH dependence of reaction rates, and predict that rates will approach a maximum at pH = pKa where the ratio of protonated and unprotonated amines approaches one and the two compounds are poised to react with one another. Higher temperatures in hydrothermal systems allow for more rapid reaction rates, readily reversible reactions, and unique carbon-nitrogen chemistry in which water acts as a reagent in addition to being the solvent. In this study, aqueous benzylamine was used as a model compound to explore the reaction mechanisms, kinetics, and equilibria of amines under hydrothermal conditions. Experiments were carried out in anoxic silica glass tubes at 250°C (Psat) using phosphate-buffered solutions to observe changes in reaction rates and product distributions as a function of pH. The rate of decomposition of benzylamine was much faster at pH 4 than at pH 9, consistent with the prediction that benzylamine acts as both nucleophile and an electrophile, and our estimate that the pKa of benzylamine is ~5 at 250°C and Psat. Accordingly, dibenzylamine is the primary product of the reaction of two benzylamine molecules, and this reaction is readily reversible under hydrothermal conditions. Extremely acidic or basic pH can be used to suppress dibenzylamine production, which also suppresses the formation of all other major products, including toluene, benzyl alcohol, dibenzylimine, and tribenzylamine. This suggests that dibenzylamine is the lone primary product that then itself reacts as a precursor to produce the above compounds. Analog experiments performed with ring-substituted benzylamine derivatives and chiral methylbenzylamine suggest an SN2 mechanism for the formation of dibenzylamine. These results show the interdependence of pH and speciation with amine reaction rates. We predict the distribution of primary, secondary, tertiary, and quaternary amines in hydrothermal solutions can be used to solve for the pH of subsurface reaction zones in hydrothermal systems. [1] McCollom, T.M. (2013) The influence of minerals on decomposition of the n-alkyl-?-amino acid norvaline under hydrothermal conditions. Geochim. Cosmochim. Acta, 104, 330-357.

Robinson, K.; Shock, E.; Hartnett, H. E.; Williams, L. B.; Gould, I.

2013-12-01

234

Varicose Veins - Multiple Languages: MedlinePlus  

MedlinePLUS

... sharing features on this page, please enable JavaScript. Varicose Veins - Multiple Languages Russian (???????) Spanish (español) Russian (???????) Concerns and Discomforts of Pregnancy (Varicose Veins) English ???????? ? ?????????? ??? ???????????? - ?????????? ???? - ...

235

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

236

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

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

237

Hydrothermal vents in Lake Tanganyika, East African, Rift system  

NASA Astrophysics Data System (ADS)

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 °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 NaHCO3-enriched fluid similar to the NaHCO3 thermal fluids from lakes Magadi and Bogoria in the eastern branch off 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 off 219 and 179 °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 °N normal-dextral faults that intersect the north- south major rift trend. The source 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.

Tiercelin, Jean-Jacques; Pflumio, Catherine; Castrec, Maryse; Boulégue, Jacques; Gente, Pascal; Rolet, Joël; Coussement, Christophe; Stetter, Karl O.; Huber, Robert; Buku, Sony; Mifundu, Wafula

1993-06-01

238

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

239

Impact polymorphs of quartz: experiments and modelling  

NASA Astrophysics Data System (ADS)

We have used the light gas gun at the University of Kent to perform a series of impact experiments firing quartz projectiles onto metal, quartz and sapphire targets. The aim is to quantify the amount of any high pressure quartz polymorphs produced, and use these data to develop our hydrocode modelling to enable the predict ion of the quantity of polymorphs produced during a planetary scale impact.

Price, M. C.; Dutta, R.; Burchell, M. J.; Cole, M. J.

2013-09-01

240

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

Microsoft Academic Search

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

RONALD J. BAKKER; J. BEN H. JANSEN

1991-01-01

241

Method of chemically polishing quartz crystal blanks  

NASA Astrophysics Data System (ADS)

The general object of this invention is to provide a method of chemically polishing quartz crystal blanks. A more specific object is to provide such a method wherein the resulting chemically polished blanks will be suitable for use in resonators and oscillators. Quartz crystal blanks are chemically polished by thoroughly cleaning the blanks, treating the quartz crystal blanks with an etching solution at high pressures in a high pressure vessel while agitating to circulate the etchant and maintaining a uniform temperature throughout the etching solution, cooling the vessel, removing the quartz crystal blanks, rinsing thoroughly with water and spinning dry.

Brandmayr, R. J.

1985-09-01

242

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

NASA Astrophysics Data System (ADS)

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

Stalder, Roland; Neuser, Rolf Dieter

2013-08-01

243

Leiomyosarcoma of the Cephalic Vein  

PubMed Central

A 78-year-old man presented with a mass on his right forearm. A 5 x 4 x 3 cm3 mass was excised en bloc with extensions along the course of the cephalic vein and its tributaries. Histological analysis revealed the mass to be a high-grade leiomyosarcoma arising within the cephalic vein. The tumour was controlled locally and distally until the patient died 10 months later, from an unrelated illness. This is the first reported case of a venous leiomyosarcoma of the cephalic vein.

Dixon, John H.

2001-01-01

244

Semial ophiolite veins of United Arab Emirates—A fluid inclusions study  

Microsoft Academic Search

Calcite and quartz veins in the gabbroic and dunite rocks of the Semial ophiolite (UAE) were selected for fluid inclusion\\u000a analysis. The inclusions contain both aqueous low-salinity and hydrocarbon-dominated fluids. Microthermometry data indicate\\u000a that the aqueous fluids contain 0.22 to 1.45 equivalent wt% NaCl and occasionally contain traces of hydrocarbons. Homogenization\\u000a to liquid occurred between 91 and 152°C. Modeling based

Mohamed El Tokhi; Abdulla Musallam

2011-01-01

245

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.

2011-01-01

246

Plasma-assisted quartz-to-quartz direct bonding for the fabrication of a multilayered quartz template for nanoimprint lithography  

NASA Astrophysics Data System (ADS)

In this paper, a low-temperature plasma-assisted process is developed to realize a uniform, ultraviolet (UV) transparent and chemically inert quartz-to-quartz direct bonding. Two sets of pretests are performed in order to understand how the bond surface energy changes with the plasma exposure time and the wet etching of quartz, respectively. The developed technique is used to fabricate a multilayered quartz template for UV nanoimprint lithography (UV-NIL). The multilayered quartz template is fabricated by bonding a square piece of a standard quartz wafer, which is about 625 µm in thickness, to a wet-etched 6.35 mm thick quartz photomask plate. A fabricated multilayered template is loaded to the commercial UV-NIL tool Imprio™ 100, and NIL was performed successfully. The developed direct bonding technique makes it possible for standard quartz wafers, which are compatible with high-resolution semiconductor fabrication processes, to be utilized as the templates in commercial UV-NIL machines with enhanced mechanical stability.

Lee, Jihye; Ali, Altun; Kim, Ki-don; Kim, Jae-Hyun; Choi, Dae-guen; Choi, Jun-Hyuk; Jeong, Jun-ho

2010-04-01

247

How Are Varicose Veins Diagnosed?  

MedlinePLUS

... pain you're having. Diagnostic Tests and Procedures Duplex Ultrasound Your doctor may recommend duplex ultrasound to check blood flow in your veins and to look for blood clots. Duplex ultrasound combines traditional with Doppler ultrasound. Traditional ultrasound ...

248

Diagnosis of Deep Vein Thrombosis.  

National Technical Information Service (NTIS)

Clinical and laboratory diagnostic methods were studied in 301 consecutive patients with suspected deep vein thrombosis (DVT). Unexpectedly, phlebography (the reference method) was found to cause DVT in estimated 48 % of patients without initial DVT. Usin...

C. G. Olsson

1979-01-01

249

Hydrothermal synthesis of hydroxyapatite  

NASA Astrophysics Data System (ADS)

A hydrothermal method of synthesizing hydroxyapatite by heating a precipitate, formed by mixing Ca(NO3)2bold dot4H2O and (NH4)2HPO4 with distilled water, in a hydrothermal reactor at 200 °C for 24-72 hrs is described. A treatment time of 24 hrs produced single phase (as shown by XRD) hydroxyapatite powder, however for longer treatment times XRD patterns were indicative of the presence of a secondary phase, monetite (CaHPO4). SEM examination of the treated powders displayed particles of rod-like morphology with dimensions 100-500 nm in length and 10-60 nm in diameter. Preliminary results on the use of the particles for the infiltration of dentine tubules are presented.

Earl, J. S.; Wood, D. J.; Milne, S. J.

2006-02-01

250

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

SciTech Connect

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

Wilson, P.N.; Parry, W.T. (Univ. of Utah, Salt Lake City (USA))

1990-09-01

251

Enhancing the contrast of subcutaneous veins  

Microsoft Academic Search

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

Herbert D. Zeman; Gunnar Lovhoiden

1999-01-01

252

Palm vein authentication technology and its applications  

Microsoft Academic Search

This paper discusses the contactless palm vein authentication device that uses blood vessel patterns as a personal identifying factor. The vein information is hard to duplicate since veins are internal to the human body. The palm vein authentication technology offers a high level of accuracy, and delivers the following results: a false rejection rate (FRR) of 0.01%, and a false

Masaki Watanabe; Toshio Endoh; Morito Shiohara; Shigeru Sasaki

2005-01-01

253

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

254

Hydrothermal reactivity of saponite.  

USGS Publications Warehouse

The nature and extent of the reactions of synthetic Fe-free saponite have been investigated under experimental hydrothermal conditions as a first step towards understanding saponite reactivity under relatively simple conditions. Saponite crystallizes from amorphous gel of ideal saponite composition within 7 days at 300o-550oC under P = 1 kbar. Reactions subsequent to this initial crystallization depend on reaction T and interlayer cations. Saponite is found to react hydrothermally, over a period of 200 days, at T down to 400oC, at least 150oC lower than previously reported, but showed no signs of reaction below 400oC. At 450oC, a mixture of talc/saponite and saponite/phlogopite clays forms from K-saponite via intracrystalline layer transformations, while above 450oC the initial K-saponite dissolves, with talc and phlogopite forming as discrete phases. After 200 days reactions at 400-450oC were not complete, so that given sufficient time to reach equilibrium, a lower hydrothermal stability limit for saponite is possible. Further study of the Fe-bearing saponite system will be required before experimental results can be applied to natural systems.-D.F.B.

Whitney, G.

1983-01-01

255

The mineral chemistry of hydrothermally altered and metamorphosed wall-rocks at the Stollberg Fe-Pb-Zn-Mn(Ag) deposit, Bergslagen, Sweden  

Microsoft Academic Search

The c. 1.9 Ga old Stollberg sulphide and Mnrich skarn iron ores and sulphide ores in Bergslagen, south-central Sweden are hosted by hydrothermally altered and metamorphosed felsic volcanic and volcaniclastic rocks. The ores are underlain by comformable alteration zones characterized by albite-gedrite-quartz and biotite-muscovite-plagioclase-K-feldspar-quartz +\\/- garnet assemblages. The present mineralogies are interpreted as medium-grade metamorphic equivalents to the original alteration

M. Ripa

1994-01-01

256

Polishing and etching langasite and quartz crystals  

Microsoft Academic Search

Langasite is a promising new piezoelectric material which is similar to quartz in its acoustic behavior. Little was known until recently about the methods needed to mechanically polish and chemically polish\\/etch this material. The results of polishing and etching experiments are described. Conventional quartz polishing methods, with polishing agents such as a rare earth slurry or ruby powder, did not

Sally Laffey; Mary Hendrickson; John R. Vig

1994-01-01

257

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

258

Design of quartz accelerometer signal acquisition system  

Microsoft Academic Search

This paper presents a new quartz accelerometer signal acquisition system in order to collect quartz accelerometers' current signal. In the system, we could transform current signal to voltage signal through precision sampling resistor. Then the analog voltage signal will be converted into digital signal by the high precision A\\/D chip AD 7732. In the case of small current, the system

Chunfeng Yue; Huadong Yu; Jinkai Xu

2011-01-01

259

Open versus endoscopic saphenous vein harvesting: wound complications and vein quality  

Microsoft Academic Search

Background. The saphenous vein is an important conduit for coronary artery bypass grafting. Wound complications from traditional open vein harvesting occur often. Minimally invasive endoscopic saphenous vein harvesting may decrease wound complications. Vein quality may be an issue with endoscopic harvesting.Methods. We reviewed 568 patients who had bypass grafting and saphenous vein harvesting either endoscopic (group A, n = 180)

John D Crouch; Daniel P O’Hair; James P Keuler; Thomas P Barragry; Paul H Werner; Leonard H Kleinman

1999-01-01

260

Open Versus Endoscopic Saphenous Vein Harvesting: Wound Complications and Vein Quality  

Microsoft Academic Search

Background. The saphenous vein is an important con- duit for coronary artery bypass grafting. Wound compli- cations from traditional open vein harvesting occur often. Minimally invasive endoscopic saphenous vein harvest- ing may decrease wound complications. Vein quality may be an issue with endoscopic harvesting. Methods. We reviewed 568 patients who had bypass grafting and saphenous vein harvesting either endo- scopic

John D. Crouch; Daniel P. O'Hair; James P. Keuler; Thomas P. Barragry; Paul H. Werner; Leonard H. Kleinman

2010-01-01

261

Quartz gauge response in ion radiation  

SciTech Connect

This paper describes recent work to make high quality quartz gauge (temporal and spatial) shock wave measurements in a pulsed ion beam environment. Intense ion beam radiation, nominally 1 MeV protons, was deposited into material samples instrumented with shunted quartz gauges adjacent to the ion deposition zone. Fluence levels were chosen to excite three fundamentally different material response modes (1) strong vapor, (2) combined vapor and melt phase and (3) thermoelastic material response. A unique quartz gauge design was utilized that employed printed circuit board (PCB) technology to facilitate electrical shielding, ruggedness, and fabrication @e meeting the essential one dimensional requirements of the characterized Sandia shunted quartz gauge. Shock loading and unloading experiments were conducted to evaluate the piezoelectric response of the coupled quartz gauge/PCB transducer. High fidelity shock wave profiles were recorded at the three ion fluence levels providing dynamic material response data for vapor, melt and solid material phases.

Taylor, P.E.; Gilbert, P.H.; Kernthaler, C. [Ministry of Defense, Aldermaston (United Kingdom). Atomic Weapons Establishment; Lee, L.M.; Smith, E.A.; Reeder, S.T. [Ktech Corp., Albuquerque, NM (United States); Anderson, M.U. [Sandia National Labs., Albuquerque, NM (United States)

1995-12-31

262

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

263

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

NASA Astrophysics Data System (ADS)

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

Moore, Joseph N.; Gunderson, Richard P.

1995-10-01

264

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

265

Cathodoluminescence of Shocked Quartz at the Cretaceous-Tertiary Boundary.  

National Technical Information Service (NTIS)

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

M. R. Owen M. H. Anders

1988-01-01

266

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

267

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

268

Absence of retromandibular vein associated with atypical formation of external jugular vein in the parotid region  

PubMed Central

Veins of the head and neck exhibiting anatomical variations or malformations are clinically significant. Anatomical variation in the external jugular vein is very common. However, anatomical variation in the retromandibular vein is rare. In this paper, we report a rare case of complete absence of the retromandibular vein. In the absence of the retromandibular vein, the maxillary vein divided into anterior and posterior divisions. The posterior division joined the superficial temporal vein to form an atypical external jugular vein, and the anterior division joined the facial vein to form an anonymous vein. In clinical practice, radiologists and surgeons use the retromandibular vein as a guide to expose the branches of the facial nerve during superficial parotidectomy. Therefore, absence of the retromandibular vein is a hurdle during this procedure and may affect the venous drainage pattern from the head and neck.

Patil, Jyothsna; Swamy, Ravindra S.; D'Souza, Melanie R.; Guru, Anitha; Nayak, Satheesha B.

2014-01-01

269

Why calcite can be stronger than quartz  

NASA Astrophysics Data System (ADS)

In the Neves area (Eastern Alps), calcite forms asymmetric centimeter-scale single-crystal porphyroclasts in quartz mylonites developed during hydrous amphibolite facies metamorphism at ˜550°C. Under these conditions, coarse calcite was clearly stronger than the surrounding polycrystalline, dynamically recrystallized, quartz matrix. Experimental results indicate that coarse calcite is less strain rate sensitive than wet quartzite, consistent with an inversion in strength on extrapolation to natural strain rates. For this to occur, wet quartzite must be weak, flowing at differential stress of <10 MPa. The lack of high-temperature twins (showing bulging or recrystallization) in calcite clasts is consistent with such low stresses during shear zone development under near peak metamorphic conditions. The maximum effective viscosity ratio of coarse calcite to quartzite for these conditions is probably not large (<10). However, numerical modeling shows that ratios of around 2 are sufficient to maintain near rigid calcite clast behavior for power law rheology with stress exponents appropriate to quartz (n ˜ 3-4) and coarse calcite (n ? 6). The inversion in relative strength reflects the difference in influence of water on the crystal plastic flow of calcite and quartz: water has a dramatic effect for quartz but little or no effect for calcite. Quartz-rich rocks under hydrous amphibolite facies conditions in the middle to lower crust are therefore relatively weak (in fact, weaker than coarse calcite) and flow at much lower stresses than dry quartz-rich rocks at similar crustal levels.

Mancktelow, Neil S.; Pennacchioni, Giorgio

2010-01-01

270

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

271

Environment of ore deposition in the creede mining district, San Juan Mountains, Colorado: Part V. Epithermal mineralization from fluid mixing in the OH vein  

USGS Publications Warehouse

Detailed fluid inclusion studies on coarse-grained sphalerite from the OH vein, Creede, Colorado, have shown that the abrupt color changes between growth zones correspond to abrupt changes in the nature of the ore fluids. Within each growth zone, however, the composition of the fluids remained constant. The base of a distinctive orange-brown growth zone marks a sharp increase in both temperature and salinity relative to the preceding yellow-white zone. The orange-brown growth zone can be correlated along much of the vein and is believed to represent a time-stratigraphic interval. Along the vein, temperatures and salinities of fluid inclusions within this interval show a systematic decrease from about 285??C and 11.5 wt percent NaCl equiv near the base of the vein to about 250??C and 8 wt percent NaCl equiv, respectively, near the top of the vein. The iron concentration of this sphalerite growth zone shows a similar pattern, decreasing from about 2.8 to 1.2 mole percent FeS. When plotted on an enthalpy-salinity diagram, the fluid inclusion data define a spatial trend indicating the progressive mixing of deeply circulating hydrothermal brines with overlying, dilute ground waters. The hydrothermal brines entered the OH vein from below at a temperature, salinity, and density of approximately 285??C, 11.5 wt percent NaCl equiv, and 860 kg/m3, respectively, whereas the overlying ground waters appear to have been preheated to roughly 150??C and had an assumed salinity of 0 wt percent and a density of 920 kg/m3. The greater density of the heated ground water promoted mixing with the hydrothermal brine within the open fractures, causing sphalerite deposition. Although there were also episodes of boiling during vein mineralization, boiling appears unimportant for this sphalerite. Isotopic evidence and geochemical modeling studies also indicate that mixing was the depositional mechanism for sphalerite. An important aspect of the mixing hydrology of the Creede system involves an aquitard overlying the OH vein. This low permeability zone restricted the flow of ground water into the vein from above and forced the upwelling hydrothermal fluids to flow laterally along the vein. The mixing environment thus occurred along the interface between a deeply circulating hydrothermal convection cell and a topographically driven shallow ground-water system.

Hayba, D. O.

1997-01-01

272

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

273

Cody hydrothermal system  

SciTech Connect

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

Heasler, H.P.

1982-01-01

274

Mechanisms of OH defect incorporation in naturally occurring, hydrothermally formed diopside and jadeite  

Microsoft Academic Search

The IR spectrum of an alpine, hydrothermally formed diopside containing 17 wt ppm H2O consists of three main OH absorption bands centred at 3647, 3464 and 3359 cm?1. Jadeite from a Californian vein occurrence is characterised by bands at 3616 and 3557 cm?1 and contains about 197 wt ppm H2O. Based on the pleochroic scheme of the OH absorption bands in diopside, OH defect

M. Andrut; M. Wildner; J. Ingrin; A. Beran

2007-01-01

275

Hydrothermal REE and Zr mobilization in the Strange Lake peralkaline granitic system: a reaction path model linked to petrological and geochemical observations  

NASA Astrophysics Data System (ADS)

Extreme enrichment and hydrothermal mobilization of rare earth elements (REE) and other high-field strength elements (HFSE; i.e., Zr, Nb, Ta and Ti) is a feature of anorogenic alkaline and peralkaline igneous systems. Strange Lake in Quebec, Canada, is a mid-Proterozoic peralkaline granitic intrusion that is host to a world-class REE and HFSE deposit with >50 Mt of ore (>1.5 wt.% REE and >3 wt.% Zr). We have used Strange Lake as a natural laboratory and linked petrographic observations of the deposit and geochemical data with numerical simulations to constraint physicochemical conditions of hydrothermal REE and Zr mobilization and mineralization. The B-zone, in the NW of Strange Lake, contains a lens-shaped pegmatite-rich zone hosted in subsolvus granite. Three alteration styles were distinguished: i) an acid alteration caused by HCl-HF-bearing fluids from the pegmatites, ii) Na-metasomatism related to aegirinization/hematization of arfvedsonite, and iii) Ca-F-metasomatism involving late interaction of the rocks with a mixture of acidic F-rich and Ca-rich fluids. The acid alteration accounts for most of the hydrothermal mobilization of Zr and REE within and from the pegmatites, whereas the Ca-F-metasomatism is evident as late stage pore space fillings and veins of hydrothermal fluorite and quartz and a fluorite breccia. These different alteration styles are reflected in the bulk rock chemistry by variable mobility of Na, Fe, Al, Ca, F, HFSE and REE distinguishable on isocon diagrams. Elemental X-ray maps of REE- and Zr-minerals show evidence for a decoupled mobilization of LREE, HREE and Zr at different stages of fluid-rock interaction. Numerical simulations of the reaction of pegmatite with saline HF- and HCl-HF-bearing fluids at 400 °C to 250 °C predict the observed trends reasonably well. Fluids with pH <2 led to the formation of quartz and fluorite in the core of the pegmatites, and fluids with pH >4 to the formation of phyllosilicates and continued stability of K-feldspar in the pegmatite borders. Low fluid-rock ratios in the pegmatite borders ensured rock-buffering of pH, whereas higher fluid-rock ratios in the cores caused fluid-buffering of pH. As a result, pathways for mobilization of REE and Zr were created in the pegmatites cores by acidic fluids, which produced considerable porosity upon cooling. This was accompanied by aegirinization/hematization in the surrounding granites, where fluid-rock ratios were low and pH was rock-buffered to values >6. Owing to this rock-buffering of pH, there was also a corresponding decrease in the mobility of the REE/HFSE.

Gysi, A. P.; Williams-Jones, A. E.

2013-12-01

276

Quartz cement in sandstones: a review  

NASA Astrophysics Data System (ADS)

Quartz cement as syntaxial overgrowths is one of the two most abundant cements in sandstones. The main factors that control the amount of quartz cement in sandstones are: framework composition; residence time in the "silica mobility window"; and fluid composition, flow volume and pathways. Thus, the type of sedimentary basin in which a sand was deposited strongly controls the cementation process. Sandstones of rift basins (arkoses) and collision-margin basins (litharenites) generally have only a few percent quartz cement; quartzarenites and other quartzose sandstones of intracratonic, foreland and passive-margin basins have the most quartz cement. Clay and other mineral coatings on detrital quartz grains and entrapment of hydrocarbons in pores retard or prevent cementation by quartz, whereas extremely permeable sands that serve as major fluid conduits tend to sequester the greatest amounts of quartz cement. In rapidly subsiding basins, like the Gulf Coast and North Sea basins, most quartz cement is precipitated by cooling, ascending formation water at burial depths of several kilometers where temperatures range from 60° to 100° C. Cementation proceeds over millions of years, often under changing fluid compositions and temperatures. Sandstones with more than 10% imported quartz cement pose special problems of fluid flux and silica transport. If silica is transported entirely as H 4SiO 4, convective recycling of formation water seems to be essential to explain the volume of cement present in most sandstones. Precipitation from single-cycle, upward-migrating formation water is adequate to provide the volume of cement only if significant volumes of silica are transported in unidentified complexes. Modeling suggests that quartz cementation of sandstones in intracratonic basins is effected by advecting meteoric water, although independent petrographic, isotopic or fluid inclusion data are lacking. Silica for quartz cement comes from both shale and sandstone beds within the depositional basin, including possibly deeply buried rocks undergoing low-grade metamorphism, but the relative importance of potential sources remains controversial and likely differs for different formations. The most likely important silica sources within unmetamorphosed shales include clay transformation (chiefly illitization of smectite), dissolution/pressure solution of detrital grains, and dissolution of opal skeletal grains; the most likely important sources of silica within unmetamorphosed sandstones include pressure solution of detrital quartz grains at grain contacts and at stylolites, feldspar alteration/dissolution, and perhaps carbonate replacement of silicate minerals and the margins of some quartz grains. Silica released by pressure solution in many sandstones post-dates the episode of cementation by quartz; thus, this silica must migrate and cement shallower sandstones in the basin or escape altogether. Some quartz-cemented sandstones are separated vertically from potential silica source beds by a kilometer or more, requiring silica transport over long distances. The similarity of diagenetic sequences in sandstones of different composition and ages apparently is the result of the normal temperature and time-dependent maturation of sediments, organic matter and pore fluids during burial in sedimentary basins. Silica that forms overgrowths is released by one or more diagenetic processes that apparently are controlled by temperature and time. Most cementation by quartz takes place when sandstone beds were in the silica mobility window specific to a particular sedimentary basin. Important secondary controls are introduced by compartmentalized domains produced by faults (e.g., North Sea) or overpressure boundaries (e.g., Gulf Coast Tertiary). Shallow meteoric water precipitates only small amounts of silica cement (generally less than 5% in most fluvial and colian sandstones), except in certain soils and at water tables in high-flux sand aquifers. Soil silcretes are chiefly cemented by opal and microcrystalline quartz, whereas water-tab

McBride, Earle F.

277

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

278

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

279

A reinterpretation of the ??DH2O of inclusion fluids in contemporaneous quartz and sphalerite, Creede mining district, Colorodo: a generic problem for shallow orebodies?  

USGS Publications Warehouse

Water extracted from fluid inclusions in quartz from shallow epithermal ore deposits often has a hydrogen isotope compositon (??D) different from that of water extracted from inclusions in associated minerals. This difference is usually attributed to the involvement of primary fluids from multiple sources. Isotopic and homogenization and freezing temperature determinations on fluid inclusions from contemporaneous quartz and sphalerite from the epithermal, silver and base metal orebodies of the OH vein, Creede district, Colorado, suggest an alternatic explanation. In near-surface deposits, differences between ??DH2O of inclusion fluids in ore minerals and quartz may result, instead, from contamination during extraction of the fluids contained in primary inclusions by shallow groundwater trapped in pseudosecondary inclusions in quartz. -from Authors

Foley, N. K.; Bethke, P. M.; Rye, R. O.

1989-01-01

280

Quartz Mountain/Oklahoma Summer Arts Institute.  

ERIC Educational Resources Information Center

Describes the Quartz Mountain Oklahoma Summer Arts Institute program. It is designed to nurture artistic talent and to provide intensive arts experiences in music, dance, theater, and the visual arts for talented students aged 14-18. (AM)

Frates, Mary Y.; Madeja, Stanley S.

1982-01-01

281

Examination of Bragg backscattering from crystalline quartz  

NASA Astrophysics Data System (ADS)

The backscattering silicon single crystals normally used for hard X-ray inelastic scattering experiments suffer from parasitic reflections and gaps in photon energy where no backscattering reflection exists. Sapphire has been proposed as a possible alternative, but quartz may have advantages over sapphire at low photon energies (5 12.5 keV). Calculations of energy widths of backscattering reflections up to 30 keV for silicon, sapphire, and quartz are compared. The quartz (11 6 0) reflection is examined at 0.03° from backscattering with 0.8 meV bandwidth beam, and its energy width is measured. Finally, the thermal expansions of quartz and silicon are compared.

Sutter, John P.; Baron, Alfred Q. R.; Ishikawa, Tetsuya; Yamazaki, Hiroshi

2005-12-01

282

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.

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

2014-01-01

283

Abnormal continuation of umbilical vein into extra-hepatic portal vein: Report of three cases.  

PubMed

Anomalies of the umbilical venous system are perplexing essentially due to dissection errors and vascular connection delineation failure. Continuation of umbilical vein into the extra-hepatic portal vein is classified as group IV umbilical vein anomaly and involves the vitelline vein or its remnants. Despite this categorization most examiners ascribe fetal extra hepatic abdominal vascular abnormality as an umbilical vein anomaly. Since these anomalies involve vitelline vein, the term "umbilical vein anomaly" is inappropriate and should be referred to as "vitelline vein abnormalities". Vitelline vein abnormalities are exceedingly rare and to the best of our knowledge only three cases have been reported prenatally. We report three cases presenting with intrauterine fetal demise and on perinatal autopsy demonstrating aneurysmally dilated group IV umbilical vein anomaly. Review of the literature, embryological basis and clinical implications of persistent vitelline vein and its varix are discussed. PMID:24712478

Jaiman, Sunil; Nalluri, Hima Bindu

2013-12-01

284

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

NASA Astrophysics Data System (ADS)

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

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

2008-11-01

285

Method of making a quartz resonator  

DOEpatents

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

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

1981-01-01

286

Quartz resonator fluid monitors for vehicle applications  

NASA Astrophysics Data System (ADS)

Thickness shear mode (TSM) quartz resonators operating in a new 'Lever oscillator' circuit are used as monitors for critical automotive fluids. These monitors respond to the density and viscosity of liquids contacting the quartz surface. Sensors have been developed for determining the viscosity characteristics of engine lubricating oil, the state-of-charge of lead-acid storage batteries, and the concentration variations in engine coolant.

Cernosek, R. W.; Martin, S. J.; Wessendorf, K. O.; Terry, M. D.; Rumpf, A. N.

287

Why calcite can be stronger than quartz  

Microsoft Academic Search

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

Neil S. Mancktelow; Giorgio Pennacchioni

2010-01-01

288

Significance of geometrical relationships between low-temperature intracrystalline deformation microstructures in naturally deformed quartz  

NASA Astrophysics Data System (ADS)

Although quartz is one of the most studied minerals in the Earth's crust when it comes to its rheology, the interpretation of intracrystalline deformation microstructures with respect to deformation conditions and mechanisms, remains highly contentious. Moreover, inconsistent use of terminology for both deformation microstructures and mechanisms makes a correct assessment of observations and interpretations in published material very difficult. With respect to low-temperature intracrystalline deformation microstructures in quartz, different conflicting genetic models have been proposed. Most probably, the lack of consensus means that there is no unique interpretation for these microstructures, primarily because their initiation and development depend on many ambient conditions. We extensively studied these intracrystalline deformation microstructures by means of optical microscopy, Hot-Cathodoluminescence, SEM-Cathodoluminescence and Electron Backscatter Diffraction Orientation Imaging, in vein quartz of the High-Ardenne slate belt (Belgium, France, Luxemburg, Germany), (de)formed in a low-temperature regime. Firstly, we propose a new, purely descriptive terminology for the low-temperature intracrystalline deformation microstructures in naturally deformed quartz: fine extinction bands (FEB), wide extinction bands (WEB) and strings. The strings can be further subdivided into blocky (BS), straight (SS) and recrystallised (RS) morphological types. FEBs have consistently been called deformation lamellae in quartz and planar slip bands in metals. WEBs have been called deformation bands, prismatic kink bands or type II kink bands. Strings have formerly been called shear bands, deformation bands or type I kink bands. No distinction between blocky and straight morphological string types had ever been made. Secondly, a survey of the pre-recrystallisation stages in the history of the intracrystalline deformation microstructures reveals that the different types of low-temperature intracrystalline deformation microstructures in naturally deformed vein quartz show particular geometrical relationships, in our opinion a to date underexposed aspect of these microstructures. Several of these geometrical relationships will be presented and their potential implications with respect to deformation mechanisms and conditions will be discussed. The geometrical relationships observed may suggest a similar formation mechanism for the different microstructures, a weakening effect for successive microstructure formation and a strong dependency on the crystallographic orientation.

Derez, T.; Pennock, G.; Drury, M. R.; Sintubin, M.

2013-12-01

289

Biventricular Pacemaker Implantation via the Femoral Vein  

PubMed Central

We report the case of biventricular pacemaker implantation via the femoral vein, in a patient with impossibility of using standard superior vein approach and a contraindication to epicardial lead placement.

Agosti, Sergio; Brunelli, Claudio; Bertero, Giovanni

2012-01-01

290

Minimally invasive saphenous vein harvesting  

Microsoft Academic Search

Background. Minimally invasive techniques to harvest the saphenous vein for coronary artery bypass grafting continue to improve and evolve. Smaller cutaneous incisions have been shown to decrease postoperative discomfort and improve healing. We describe a technique involving carbon dioxide insufflation and endoscopic dissection to allow easier and atraumatic dissection.Methods. The VasoView endoscope system (Origin Medsystems, Inc) was used to harvest

Rohinton J Morris; Michael T Butler; Louis E Samuels

1998-01-01

291

Vascular Remodeling in Varicose Veins  

Microsoft Academic Search

The present study describes the histopathologic aspects of varicose (n=29; mean age, 52 ± 12 years) and normal saphenous veins (n=17; mean age, 51 ± 12 years) of patients from a similar age group. We focused on the changes that occur in the circular layer of the venous wall. We examined the venous walls by light microscopy and transmission electronmicroscopy.

Mark M. Kockx; Michiel W. M. Knaapen; Hilde E. Bortier; Kristel M. Cromheeke; Odile Boutherin-Falson; Michel Finet

1998-01-01

292

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

293

What Are the Signs and Symptoms of Varicose Veins?  

MedlinePLUS

... Twitter. What Are the Signs and Symptoms of Varicose Veins? The signs and symptoms of varicose veins include: ... signs of other, more serious conditions. Complications of Varicose Veins Varicose veins can lead to dermatitis (der-ma- ...

294

En Echelon Hydrothermal Systems  

NASA Astrophysics Data System (ADS)

En echelon hydrothermal systems develop within the porous rocks that surround, in three-dimensions, their distinctive plan-form and cross-sectional basaltic intrusion geometry. Examples that span several (self-similar) spatial scales include the en echelon off-set area of the East Rift Zone of Kilauea Volcano, Hawaii; the Northeast Rift Zone of Mauna Loa Volcano; the intrusive-eruptive fissures of the Krafla Central Volcano, Northeast Iceland; the ensemble of the three Icelandic central volcanoes Theistarekir-Krafla-Fremrinamur; major segments of the East Pacific Rise and the Mid-Atlantic Ridge; and several paleo-hydrothermal systems of the Mesozoic basins of eastern North America, including the Culpeper Basin. An en echelon hydrothermal system comprises two or more en echelon--arranged magma-filled fractures enclosed in a fluid-saturated porous matrix. Blocks of country rock between individual offset fracture segments are similarly porous and fluid-saturated. In 3-D, the system resembles the fan blades of a turbine rotor, with blades (dikes) emanating from a deep "master" fracture and turning smoothly in response to the local variations in the least compressive regional stress component. The primary geometric, hydrologic and thermal attributes of the system (on a horizontal plane) include dike thickness, dike-to-dike offset and overlap, the (initial) intrusion temperature, duration of magma flow, dike widths and lengths, the mean seepage velocity of regional subsurface aqueous fluid flow, and the mean flow azimuth in relationship to the plan-form geometry of the en echelon array. Finite element single phase models in horizontal cross-section have been developed for dike widths of 100 m, dike lengths of 1,500 m, overlaps of 500 m, dike-to-dike offsets of 500 m, intrusion temperatures of 1,200 C, horizontal seepage fluxes imposed at the sides of ~ 1,000 g cm-2 yr-1, and a matrix permeability of 10-14 m2. The regional flow field has been parameterized in dike-orthogonal, dike-parallel, and 45 degree angles of attack with respect to the major axes of the individual dikes within the en echelon array. Depending on the magnitudes and geometric arrangement of key system attributes, an en echelon hydrothermal system may either act as an efficient thermal radiator, effectively shedding heat to the surroundings, or may it act as an effective heater, thermally enhancing the environment between neighboring dikes in 3-D. Conditions that promote the efficient loss of heat include thin dikes of short length, large dike-to-dike offset, high matrix fluid velocities, and regional flow azimuths that are orthogonal to the individual dikes. Conditions that promote differential heating between the dikes include wide dikes with maximal overlap and minimal offset, low regional flow velocities and "angles of attack" of the regional flow field that provide for maximum hydrodynamic "shelter" for individual dikes within the interior of the en echelon array.

Ryan, M. P.; Carr, P. M.; Daniels, D. L.; Sutphin, D. M.

2005-12-01

295

Carbon dioxide embolism during endoscopic vein harvesting.  

PubMed

Endoscopic vein harvesting (EVH) is becoming common for the patients undergoing coronary artery bypass grafting. Using carbon dioxide insufflations during the vein harvest can produce rare but catastrophic CO(2) embolism. We report a case of massive right atrial CO(2) embolism due to femoral vein injury which occurred during the performance of a routine EVH procedure. PMID:18381362

Tamim, Muhammed; Omrani, Maher; Tash, Adel; El Watidy, Ahmed

2008-08-01

296

Prospective analysis of endoscopic vein harvesting  

Microsoft Academic Search

Background: Utilization of bridging vein harvesting (BVH) of saphenous vein grafts (SVG) for coronary artery bypass grafting (CABG) results in large wounds with great potential for pain and infection. Endoscopic vein harvesting (EVH) may significantly reduce the morbidity associated with SVG harvesting.Methods: A prospective database of 200 matched patients receiving EVH and BVH was compared. The patients all underwent CABG

Amit N Patel; Robert F Hebeler; Baron L Hamman; Carol Hunnicutt; Melody Williams; Lu Liu; Richard E Wood

2001-01-01

297

Endoscopic vein harvest: advantages and limitations  

Microsoft Academic Search

BackgroundAlthough long saphenous vein remains the most commonly used conduit in coronary revascularization, traditional open vein harvest (OVH) may lead to significantly impaired wound healing and postoperative pain. Endoscopic vein harvest (EVH) attempts to reduce this morbidity and improve patient satisfaction with no compromise in outcome.

Pramod Bonde; Alastair N. J Graham; Simon W MacGowan

2004-01-01

298

How Can Varicose Veins Be Prevented?  

MedlinePLUS

... from the NHLBI on Twitter. How Can Varicose Veins Be Prevented? You can't prevent varicose veins from forming. However, you can prevent the ones ... also can take steps to delay other varicose veins from forming. Avoid standing or sitting for long ...

299

Cephalic veins in coronary artery bypass surgery  

Microsoft Academic Search

Various alternative conduits for aortocoronary bypass grafting have been suggested when the saphenous vein quality is inadequate. During a 10-year period we have used the cephalic vein in 39 patients. Eighteen entered an angiographic follow-up study. A total of 31 arm vein grafts were used with 43 distal anastomoses. When calculating patency by number of patent distal anastomoses, this was

P. E. Andersen; E. Jacobsen; G. Lerbjerg

1996-01-01

300

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

301

Optimization of subcutaneous vein contrast enhancement  

Microsoft Academic Search

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

Herbert D. Zeman; Gunnar Lovhoiden; Harshal Deshmukh

2000-01-01

302

Gradient Based Image Segmentation for Vein Pattern  

Microsoft Academic Search

The biometrics identification technology based on vein pattern has being developed rapidly in recent years. However, the vein image acquired by near-infrared (NIR) imaging device has low contrast and usually has a mount of noise which make an effective image segmentation be a great challenge. Thresholding is a popular vein image segmentation method, which is easy to calculate and can

Yiding Wang; Hai Wang

2009-01-01

303

A new approach for sclera vein recognition  

Microsoft Academic Search

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;

N. L. Thomas; Yingzi Du; Zhi Zhou

2010-01-01

304

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

305

Long-term behaviour of continental hydrothermal systems: - U-series study of hydrothermal carbonates from the French Massif Central (Allier Valley)  

NASA Astrophysics Data System (ADS)

U-series dating of hydrothermal carbonates, deposited by CO 2-rich thermo-mineral waters of the French Massif Central, provides new insights on the long-term behaviour of a continental hydrothermal system. Dating of aragonite veins and travertines impregnating old terrace levels of the Allier river allowed identification of the main episodes of surface deposition, and thus factors likely to influence these circulations. Fifteen layers from three veins and four travertines from two separate areas were analysed. Sr isotope compositions were also measured on vein samples. The results show that this region was subjected to at least 3 main episodes of surface or near surface hydrothermal deposition: 253 to 208 ky, 135 to 100 ky and less than 8 ky. Comparison of these ages with a global climatic curve indicates that preferential deposition of carbonates occurs during warm periods, suggesting a strong influence of climatic conditions on the hydrothermal system. It is suggested that this climatic influence does not necessarily imply the absence of carbonate deposition during cold and dry periods, but rather that carbonate precipitation might occur at depth before the geothermal fluids reach the surface. In addition, the isotope compositions of fluids recorded by the 87Sr/ 86Sr and ( 234U/ 238U) initial ratios in the aragonite veins from Coudes remained remarkably constant over 250 ky, ranging from 0.71360 to 0.71371 and from 3.10 to 3.39 respectively. The two samples coming from Saladis show a slightly higher ( 234U/ 238U) initial ratio around 3.95. The constancy of these ratios over such a long period suggests a hydrothermal system in a near steady state with respect to water-rock interaction. We thus propose a possible model allowing a conservative steady state despite variations in the water recharge rates, in response to the climatic variations. The difference between ( 234U/ 238U) initial ratios measured in the Coudes and Saladis systems suggests the existence of two separate reservoirs and constrains their lateral extension to a few km at most.

Rihs, Sophie; Condomines, Michel; Poidevin, Jean-Louis

2000-09-01

306

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

307

3-D Mohr circle construction using vein orientation data from Gadag (southern India) - Implications to recognize fluid pressure fluctuation  

NASA Astrophysics Data System (ADS)

In this paper orientations of quartz veins from the Archaean age lode-gold bearing region of Gadag (southern India) are used to determine the relative stress and fluid pressure (Pf) conditions by constructing 3-D Mohr circle. Anisotropy of magnetic susceptibility (AMS) analysis of the host massive metabasalt reveals that the magnetic foliation is NW-SE striking, which is related to early NE-SW compression (D1/D2 deformation) that affected the region. The quartz veins have a wide range of orientations, with NW-SE striking veins (steep northeasterly dips) being the most prominent. Vein emplacement is inferred to have taken place under NW-SE compression that is known to have caused late deformation (D3) in the region. It is argued that the NW-SE fabric defined the pre-existing anisotropy and channelized fluid flow during D3. The permeability was initially low, which resulted in high Pf (>?2). 3-D Mohr circle analysis indicates that the driving pressure ratio (R?) was 0.94, a condition that favoured fracturing and reactivation of fabric elements (foliations and fractures) having a wide range of orientations. This led to an increase in permeability and fluid flowed (burped) into the fractures. Resulting vein emplacement and sealing of fractures led to a reduction of Pf (vein emplacement, while fractures of all other orientations were inactive and remained sealed. As a consequence, the study area has a cluster of NW-SE oriented veins. R? is calculated to be 0.07 from 3-D Mohr circle analysis at low Pf, when fractures with NW-SE orientation only were susceptible to dilation. However, it is envisaged that any emplacement of veins in these fractures would have sealed them, thus reducing the permeability and initiating the next cycle of rise in Pf (>?2). Thus, it is concluded that the quartz veins in the Gadag region are a consequence of an interplay between conditions that fluctuated from Pf > ?2 to Pf < ?2.

Mondal, Tridib Kumar; Mamtani, Manish A.

2013-11-01

308

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.

2014-01-01

309

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

310

Ever heard of the obturator vein?  

PubMed

We report a complication related to advancement of a large diameter long sheath in the obturator vein. In an adult with a previously thrombosed femoral vein, the obturator vein was inadvertently cannulated. During percutaneous pulmonary valve implantation, the Ensemble(R) delivery system could not be advanced after repositioning attempt. The obturator vein had been perforated and sheath was coiled up in the pelvis leading to a retroperitoneal pelvic hematoma. Continuity of the vein was established using two self-expanding covered stents. The obturator vein runs dorsally and joins the inferior caval vein at a very acute angle posterior in the pelvis, creating a corner in which stiff catheters or sheaths may get entrapped. PMID:19882714

Brown, Stephen C; Gewillig, Marc

2010-02-15

311

Leiomyosarcoma of the renal vein.  

PubMed

A 43-year-old woman was referred to our clinic for evaluation of a left retroperitoneal mass. She presented to our internal medicine department complaining of back pain. Computed tomography (CT) scan revealed a left retroperitoneal mass 55 mm in size in the hilum of the left kidney. Enhanced CT scan and magnetic resonance imaging (MRI) disclosed a poorly staining mass. Metaiodobenzylguanidine scintigraphy demonstrated no accumulation in the mass; moreover, endocrinologic examination was normal. Laparoscopic resection of the left retroperitoneal tumor was attempted; however, strong adhesion between the tumor and the left renal vein was encountered. Thus, left nephrectomy after open conversion was performed. Histological findings indicated leiomyosarcoma originating from the left renal vein. The postoperative course has been uneventful; neither recurrence nor metastasis is evident 2 years postsurgery. PMID:20694494

Imao, Tetsuya; Amano, Toshiyasu; Takemae, Katsurou

2011-02-01

312

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

313

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

314

Hydrothermal Input into Volcaniclastic Sediments of the SuSu Knolls Hydrothermal Field, Eastern Manus Basin, Bismarck Sea, Papua New Guinea  

NASA Astrophysics Data System (ADS)

Short sediment cores were examined from the active SuSu Knolls hydrothermal field in the eastern Manus back-arc basin in order to understand the origin of the hydrothermal component in sediments surrounding volcanogenic massive sulfide deposits. Their mineralogical and geochemical composition displays various inputs of intra-basin volcaniclastic, hydrothermal, terrigenous and biogenic components. A 40 cm-thick sediment recovered from the base of a core proximal to the Suzette chimney site consists of blocky nonvesicular to elongate vesicular volcanic glass fragments at different stages of alteration intermixed with pyrite, chalcopyrite, barite, gypsum, atacamite, illite, Fe oxyhydroxide, quartz, cristobalite, plagioclase and alunite. The composition indicates that the sediment was derived from erosion of volcanic edifices and old oxidized chimneys. Geochemical indicators for the mass wasting event are the extremely high concentrations of Cu (up to 2.3%) and Au (up to 3.5 ppm), elevated concentrations of As, Ba, Zn and Fe, as well as a positive Eu anomaly. The strong Cu-Au positive correlation suggests that chalcopyrite and gold-rich chimneys of the Suzette site are the source of hydrothermal detritus. 14C dating of foraminifera points to an approximate age of the beginning of the strongest mass wasting event at about 2050 ybp. This event was interrupted by deposition of a widespread apron of volcaniclastic sediment overlying the SuSu Knolls volcanic rocks. The volcaniclastic sediment consists of dacite fragments with plagioclase and pyroxene microlites, angular grains of Ca-rich plagioclase and clino- and orthopyroxenes, glass shards, cristobalite, aggregates of Si-dominated amorphous material and illite, alunite, pyrite, magnetite and barite. Based on the compositional similarity between the components of the volcaniclastic sediment and plagioclase-pyroxene porphyric dacite lavas building the SuSu Knolls together with the products of their hydrothermal alteration and mineralization, it is suggested that the volcaniclastic sediment originated from violent hydrothermal eruptions at the SuSu Knolls field. The incorporation of a hydrothermal component representing altered volcanics creates elevated concentrations of Au, Cu and Ba. On the other hand, the fast sedimentation of volcaniclastic material could obscure the geochemical signal, and in particular REE patterns, resulting from fallout of particles from a hydrothermal plume in the overlying water column. Deposition of plume derived hydrothermal material proximal to the venting source is inferred for the surface sediments of the cores adjacent to the Suzette site. Indicators are barite aggregates and Cu-containing particles of probable bacterial origin, which account for elevated concentrations of Ba and Cu. The Mn enrichment in the cores far from SuSu Knolls is considered to represent more distant deposition of the particulate fallout.

Hrischeva, E. H.; Scott, S. D.

2005-05-01

315

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

316

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

USGS Publications Warehouse

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

Drew, L. J.

2003-01-01

317

Everted cervical vein for carotid patch angioplasty.  

PubMed

Because of the theoretic benefits of autologous vein we undertook an investigation to evaluate cervical veins (facial, external jugular) as patch material after carotid endarterectomy. A device that stimulated both circumferential fixation by sutures and radial tension exerted on in vivo patches was constructed to measure burst strength of tissue. Mean bursting pressure for groin saphenous vein (n = 10) was 94.5 +/- 15.1 pounds per square inch (psi), 75.5 +/- 8.9 psi for ankle saphenous vein (n = 10), 83.3 +/- 14.5 psi for everted (double layer) cervical vein (n = 5) and 10 +/- 3.3 psi for single layer cervical vein (n = 5). No significant differences between saphenous vein at any level and everted (double layer) cervical vein, but all were significantly different from single layer cervical vein (p less than 0.05). From June 1987 through November 1989, 19 patients underwent 21 carotid endarterectomies complemented with adjunctive everted cervical vein patch angioplasty. Indications for surgery were asymptomatic stenosis (53%), transient ischemic attack (29%), and cerebrovascular accident with recovery (18%). All patients were studied after surgery with duplex scanning. Asymptomatic recurrent stenosis was observed in one patient. Transient hypoglossal nerve dysfunction occurred in one other patient. One postoperative death occurred as a result of massive aspiration. These results indicate that everted cervical vein is comparable to the saphenous vein in resistance to bursting and can yield similar results as patch material after carotid endarterectomy. Accordingly, saphenous vein can be spared and lower extremity incisions avoided.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2231962

Yu, A; Dardik, H; Wolodiger, F; Raccuia, J; Kapadia, I; Sussman, B; Kahn, M; Pecoraro, J P; Ibrahim, I M

1990-11-01

318

More great saphenous vein valves - less varicose veins?  

PubMed

Background: In patients with chronic venous disease (CVD) the number of venous valves and the degree of valve deterioration have not been extensively investigated and are poorly understood. The aim of this prospective study was to quantitatively and qualitatively investigate the venous valves in CVD patients in view of their clinical classification. Patients and methods: Within two years a consecutive series of 152 patients (223 limbs) undergoing primary surgery for great saphenous vein varicose veins was investigated. In all patients the ?C? class according to the basic CEAP-classification was registered preoperatively (C2 to C6) for each limb. Both the quantity and quality of venous valves were assessed in the GSV?s after removal. Qualitative evaluation of the valves was based on macroscopic appearance using a classification from 0 to 5 and described as ?valve disease class?. Results: A negative correlation between age and the number of valves was detected (p = 0.0035). There was an increase of C-class with increasing age. No significant correlation between the average number of valves per meter and the C-class was detected. For all C-classes an average of between four and five valves per meter was counted. Valve disease class was positively correlated with the C-class although the valve disease class was never higher than the C-class (p < 0.05). Conclusions: The valve disease class of the great saphenous vein correlates with the C-class of the CEAP-classification. The number of valves did not correlate with the ?C?-class. With each increase in the CEAP class the age increased as well. PMID:25007904

Gräub, Anna-Barbara; Naef, Markus; Wagner, Hans E; Mouton, Wolfgang G

2014-07-01

319

UNDERGROUND DEFORMATION MEASUREMENT USING NEW QUARTZ  

Microsoft Academic Search

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

INSTRUMENTS Bassam Saleh

320

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

321

Quartz resonator hydrogen sensor using platinum black  

Microsoft Academic Search

To achieve accurate detection of hydrogen concentration at the range of under 0.1% to 4% in air, we are developing the quartz resonator hydrogen sensor using platinum catalysts. The platinum electrodes of previous model were fabricated by sputtering. To improve its sensitivity, we focused on the platinum black of which structure has the three-dimensional porous. The electrodes of new model

Hiroshi Oigawa; Yu Kirino; Daisuke Yamazaki; Toshitsugu Ueda

2011-01-01

322

Release-Adiabat Measurements in Crystalline Quartz.  

National Technical Information Service (NTIS)

Results of release-adiabat measurements are reported for x-cut quartz shocked initially over the stress range of 15 GPa to 110 GPa. Release paths determined from a shock stress of 15 GPa indicate a return to the original density, while measurements of rel...

L. C. Chhabildas J. M. Miller

1985-01-01

323

Method of Chemically Polishing Quartz Crystal Blanks.  

National Technical Information Service (NTIS)

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

R. J. Brandmayr

1985-01-01

324

Microfabricated spherical biconvex quartz crystal microbalance array  

Microsoft Academic Search

A miniaturized spherical bi-convex quartz crystal microbalance (QCM) array was fabricated by reactive ion etching (RIE) and photoresist reflow with solvent vapor technology. The spherical convex shape is necessary to suppress a spurious mode and obtain a high Q factor. Not only can the large-radius spherical convex shape be achieved by this technology, but also miniaturization and batch fabrication. The

Li Li; Takashi Abe; Masayoshi Esashi

2005-01-01

325

Distinguishing the Asian dust sources based on cathodoluminescence analysis of single quartz grain  

NASA Astrophysics Data System (ADS)

Numerous tracers, such as mineralogical component, strontium (87Sr/86Sr) and neodymium (eNd(0)) isotopes (Liu et al., 1994; Biscaye et al.,1997; Bory et al., 2002, 2003; Kanayama et al., 2002, 2005), rare earth element composition (e.g., Svensson et al., 2000), oxygen isotope (Mizota et al., 1992; Hou et al., 2003) and ESR intensity of quartz (Ono et al., 1998; Sun et al., 2007), have been investigated to discriminate source areas of Asian dust. However, these analyses need large volume of samples (mostly more than 10 mg) and the applications to the dust samples are limited. Then, here we developed a provenance-tracing method by using a cathodoluminescence (CL) spectral of “single” quartz grain for applying it to small volume of aeolian dust samples, such as aeolian dust in the ice cores and marine sediments with the location of long distance from the Asian deserts. CL is the emission from a material which is excited by electron beam. Since CL spectroscopy and microscopy provide information on the existence and distribution of defects and trace elements in minerals, CL analyses have potential to characterize dust-source areas. CL spectra of quartz have been demonstrated to show different patterns between the quartz from hydrothermal, plutonic, volcanic and metamorphic origins (e.g., Zinkernagel, 1978; Götze et al., 2001), suggesting the spectra reflect the condition of the quartz formation and the local environment. Then, here we conducted CL spectral analysis of silt size quartz in the surface samples from the major Asian deserts, such as the Taklimakan Desert and Gobi Desert in southern Mongolia (hereafter Mongolian Gobi). CL spectra were measured in the areas of approximately 4 micron square for each quartz grain by a Scanning Electron Microscope-Cathodoluminescence (SEM-CL) at the Okayama University of Science, a SEM (Jeol: JSM-5410) attached with a grating monochromator (Oxford Instruments: Mono CL2), where EDS system can be used in combination with SEM-CL. The CL signals were collected by photon counting method using a PMT (Hamamatsu R2228) in the range from 300 to 800 nm. Most of the silt size quartz in the samples from the Taklimakan Desert and the Mongolian Gobi exhibit double peaks in blue region at around 450 nm (2.75 eV) and red region at around 620 nm (2.00 eV). The wavelengths (energy) of the red peak show slight but significant differences between the samples from the two deserts, although CL intensities of the two peaks show no distinct differences. This result implies that the red peaks of CL spectra of the quartz samples from the two deserts originate from different defects of quartz, and the characteristics of the red peaks have potential to distinguish the source areas of Asian dust.

Nagashima, K.; Nishido, H.; Kayama, M.; Tada, R.; Isozaki, Y.; Sun, Y.; Igarashi, Y.

2009-12-01

326

Hydrothermal Industrialization: Direct Heat Development. Final Report.  

National Technical Information Service (NTIS)

A description of hydrothermal resources suitable for direct applications, their associated temperatures, geographic distribution and developable capacity are given. An overview of the hydrothermal direct-heat development infrastructure is presented. Devel...

1982-01-01

327

Pervasive, high temperature hydrothermal alteration in the RN-17B drill core, Reykjanes Geothermal System-Iceland Deep Drilling Project  

NASA Astrophysics Data System (ADS)

In November 2008, 9.5 m of core were recovered from Reykjanes production well RN-17B at a depth of 2800m. The core consists mainly of hyaloclastite breccias, hetrolithic breccias with clasts of crystalline basalt, and volcaniclastic sandstones/siltstones. Much of the material appears to have been transported and redeposited, but homolithic breccias and hyaloclastites, some with upright flow lobes of basalt with quenched rims, are interpreted to have erupted in situ. Fine-scale features (glass rims, quench crystals, vesicles, phenocrysts) are well preserved, but all lithologies are pervasively hydrothermally altered such that primary clinopyroxene is ubiquitously uralitized and primary plagioclase (An42-80) is replaced by albite and/or more calcic plagioclase. In contrast, cuttings of similar lithologies, recovered by rotary drilling in intervals immediately above and below the core, exhibit much lesser degrees of hydrothermal alteration and commonly contain igneous plagioclase and clinopyroxene. Vitric clasts in the core are recrystallized into aggregates of chlorite and actinolite. In some breccias, cm-scale metadomains are composed of patchy albite or actinolite/magnesiohornblende giving the core a green and white spotted appearance. Minor amounts (<1%) of disseminated pyrite occur throughout the core, but two intervals with more abundant sulfide contain chalcopyrite and sphalerite in addition to pyrite. Amygdales and vugs in the breccias, initially filled with chlorite, actinolite, epidote, and/or albite, have been partly overprinted with hornblende and anorthite. The core is cut in places by < 1 cm- wide veins composed of early epidote + actinolite + titanite and later anorthite + magnesiohornblende/pargasite. Quartz is not present in any alteration domains observed in the core, although it is reported from virtually all of the cutting intervals above and below the cored section. Seawater-basalt reaction calculations suggest that albite formed during early burial at T<300 is replaced by more calcic plagioclase at higher temperature. Texturally, hydrothermal anorthite (An90-98) and pargasite (up to 13.5 wt % Al2O3) appear to have grown at the expense of earlier formed epidote + chlorite + actinolite. Measured downhole temperature at 2800m in RN-17B following reequilibration was 320°C, although amphibole-plagioclase geothermometry imply that anorthite + pargasite, if in equilibrium, should have formed at much higher temperatures. The differences in extent and intensity of alteration inferred from examination of cuttings compared to drill core indicate that selective recovery and mixing of cuttings from multiple depths may be a larger problem than presently appreciated. Previous work has shown that the Reykjanes geothermal system has evolved from a meteoric water-dominated system to higher salinity system dominated by seawater-recharge. The paragenetic relationships that are discernible in the core hopefully will allow us to quantify the alteration processes related to the change in salinity.

Zierenberg, R. A.; Schiffman, P.; Marks, N. E.; Reed, M. H.; Elders, W. A.; Fridleifsson, G. O.

2010-12-01

328

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

329

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

330

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

331

Minimally invasive vein surgery: ambulatory phlebectomy.  

PubMed

Ambulatory phlebectomy has proven to be an effective treatment for varicose veins. Alone or complementing the treatment of incompetent long or short saphenous vein by high ligation, saphenectomy, or transcatheter occlusion, ambulatory phlebectomy not only adequately and satisfactorily removes the diseased veins but also results in a series of extremely small micro-incisions, which are cosmetically pleasing to the patient and the surgeon. Furthermore, the entire procedure can be performed under local anesthesia on an ambulatory basis. PMID:14614696

Olivencia, Jose Antonio

2003-09-01

332

Portal vein aneurysm in a dog.  

PubMed

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

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

2012-09-01

333

Hemodialysis-associated subclavian vein stenosis  

Microsoft Academic Search

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

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

1988-01-01

334

Jugular vein thrombosis associated with distant malignancy.  

PubMed Central

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

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

1988-01-01

335

Thermal conductivity of fused quartz and quartz ceramic at high temperatures and high pressures  

Microsoft Academic Search

The thermal conductivity of fused quartz and quartz ceramic has been measured over the temperature range of 273–423K and at pressures up to 400MPa using a steady-state parallel-plate apparatus. It is an absolute, steady-state measurement device with an operational temperature a range of 273–1273K and pressure range up to 1500MPa. High-pressure measurements are made in an atmosphere of argon. The

I. M Abdulagatov; S. N Emirov; T. A Tsomaeva; Kh. A Gairbekov; S. Ya Askerov; N. A Magomedova

2000-01-01

336

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

SciTech Connect

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

Genter, A.; Traineau, H.

1992-01-01

337

Polarization State Transformation of Laser Beam Passing Through Quartz Crystals.  

National Technical Information Service (NTIS)

Periodical changing of laser beam polarization with initial polarization of 45 deg to the optical axis of quartz after its passing through quartz cube depends on crystallographic direction and turn angle of the cube. The resulting polarization is differen...

I. T. Bodnar M. P. Anatska

2000-01-01

338

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

MedlinePLUS

... Psoriasis Skin cancer Prevention and care Cosmetic treatments Gold Triangle Awards Home Media resources Stats and facts ... not prevent spider veins. Sclerotherapy is considered the gold standard in treating people with spider veins. This ...

339

Small hepatic veins Budd-Chiari syndrome.  

PubMed

Budd-Chiari syndrome is a rare disorder characterized by hepatic venous outflow obstruction at any level from the small hepatic veins to the atrio-caval junction, in the absence of heart failure or constrictive pericarditis. Various imaging modalities are available for investigating the gross hepatic vascular anatomy but there are rare forms of this disease where the obstruction is limited to the small intrahepatic veins, with normal appearance of the large hepatic veins at imaging. In this cases only a liver biopsy can demonstrate the presence of a small vessels outflow block. We report two cases of small hepatic veins Budd-Chiari syndrome. PMID:23813023

Riggio, Oliviero; Marzano, Chiara; Papa, Alessia; Pasquale, Chiara; Gasperini, Maria Ludovica; Gigante, Antonietta; Valla, Dominique Charles; Plessier, Aurélie; Amoroso, Antonio

2014-05-01

340

Pressure balance under hydrothermal conditions  

NASA Astrophysics Data System (ADS)

Low pressure, low temperature growth of potassium titanyl phosphate (KTP) crystals, the material of choice for certain kinds of laser eye surgery apparatus and other applications, requires hydrothermal growth in pressure balance noble metal cans. This paper discusses the problem of pressure balancing the Au cans used for hydrothermal KTP growth. The P-V-T behavior of the pressure balance medium (H2O) and the growth medium (KTP saturated K2HPO4) are described and the source of the 'dimples' in growth cans is explained and remediation strategies are suggested.

Laudise, R. A.; Bridenbaugh, P. M.; Iradi, T.

1994-06-01

341

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

SciTech Connect

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

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

2004-08-15

342

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

343

Millimeter And Submillimeter-Wave Integrated Circuits On Quartz  

NASA Technical Reports Server (NTRS)

Proposed Quartz substrate Upside-down Integrated Device (QUID) relies on UV-curable adhesive to bond semiconductor with quartz. Integrated circuits including planar GaAs Schottky diodes and passive circuit elements (such as bandpass filters) fabricated on quartz substrates. Circuits designed to operate as mixers in waveguide circuit at millimeter and submillimeter wavelengths. Integrated circuits mechanically more robust, larger, and easier to handle than planar Schottky diode chips. Quartz substrate more suitable for waveguide circuits than GaAs substrate.

Mehdi, Imran; Mazed, Mohammad; Siegel, Peter; Smith, R. Peter

1995-01-01

344

Hydrothermal scheduling based Lagrangian relaxation approach to hydrothermal coordination  

Microsoft Academic Search

This paper presents an improved Lagrangian relaxation based hydrothermal coordination algorithm. By using Lagrangian multipliers to relax system-wide demand and reserve requirements, the problem is decomposed into thermal and hydro subproblems. The thermal subproblem is solved by using dynamic programming without discretizing generation levels. Instead of solving the hydro subproblems independently as done in the standard Lagrangian relaxation formulation, the

M. S. Salam; K. M. Nor; A. R. Hamdam

1998-01-01

345

Temperature predicted from quartz microstructures from the Main Boundary Thrust Zone, Dehradun-Mussourie region, western Himalaya  

NASA Astrophysics Data System (ADS)

The Main Boundary Thrust (MBT) zone near Sahansahi Ashram (Dehradun-Mussourie area) is a top-to-SW brittle shear zone along with prominent oversteps developed inside the black schistose very fine-grained low-grade metamorphosed rock. Sigmoid quartz veins defining the P-planes under an optical microscope reveal fracturing, deformation bands, sutured and serrated boundaries, zones of small new grains (nucleations) etc. These indicate a temperature of 280±30 0C. Some ductile deformations are evident from bulging, smaller recrystallized quartz grains along grain boundaries etc. Large quartz porphyroclasts show undulose extinction along with deformation bands and -lamellae, small bulges preferably at triple junctions and along old grain boundaries, inter-granular micro-cracks, sutured grain boundaries, and the top-to-S/SW shear. Bulging recrystallization indicates a temperature between ~ 280-400 0C. In the same field of microscopic view, both the textures of higher- and lower temperatures are found in quartz aggregates. Very poorly developed rare 'core and mantle' like structures indicate peak deformation temperature approached the transition temperature (~ 400 0C) between 'bulging recrystallisation' and 'sub-grain rotation'. Thus, the MBT experienced a temperature up to 350-400 0C. Available data from the Western Lesser Himalaya indicates its temperature within 330-350 0C (e.g. Célérier et al., 2009a,b). We predict a higher probable range of temperatures from its sheared southern boundary (i.e. the MBT-zone).

Bose, Narayan; Bhattacharya, Gourab; Mukherjee, Soumyajit

2013-04-01

346

The use of spliced vein bypasses for infrainguinal arterial reconstruction  

Microsoft Academic Search

Purpose: The use of autogenous vein, whether in situ or excised, for arterial bypass procedures is well accepted. However, this usually requires the presence of a length of good-quality vein of adequate diameter. In patients lacking sufficient length of vein, two or more pieces of vein may be spliced together to complete the reconstruction. The effect of vein splicing on

Benjamin B. Chang; R. Clement Darling; Devon E. M. Bock; Dhiraj M. Shah; Robert P. Leather

1995-01-01

347

Quartz cementation mechanisms and porosity variation in Baltic Cambrian sandstones  

Microsoft Academic Search

Quartz is an import cementing material in siliciclastic sandstones that can reduce porosity and permeability severely. For efficiently predicting and extrapolating petrophysical properties such as porosity and permeability, the controls on the occurrence and the degree of quartz cementation need to be better understood. Toward this end, a succession of Cambrian marine quartz arenites in Lithuania, at a present burial

Nicolaas Molenaar; Jolanta Cyziene; Saulius Sliaupa

2007-01-01

348

Optical processing furnace with quartz muffle and diffuser plate  

DOEpatents

An optical furnace for annealing a process wafer comprising a source of optical energy, a quartz muffle having a door to hold the wafer for processing, and a quartz diffuser plate to diffuse the light impinging on the quartz muffle; a feedback system with a light sensor located in the wall of the muffle is also provided for controlling the source of optical energy.

Sopori, Bhushan L. (Denver, CO)

1996-01-01

349

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

350

Hydrothermal synthesis of perovskite nanotubes.  

PubMed

A low-temperature hydrothermal reaction has been utilized to generate crystalline barium titanate and strontium titanate nanotubes, which have been characterized by means of X-ray diffraction and transmission electron microscopy, coupled with energy dispersive X-ray analysis. PMID:12613636

Mao, Yuanbing; Banerjee, Sarbajit; Wong, Stanislaus S

2003-02-01

351

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

352

Radiation effects in natural quartz crystals  

Microsoft Academic Search

Optically clear, as visually observed, natural quartz crystals of Brazilian and Arkansas origins, which exhibit Al–OH?-centers in their as-received conditions, have been measured for their low temperature ESR spectra to see the presence of\\u000a Al-hole centers. The ESR spectra revealed the presence of Al-hole centers in their as-received conditions. These centers showed\\u000a an increase in their strength upon irradiation with

Harish Bahadur; Hélène Tissoux; Teruo Usami; Shin Toyoda

2008-01-01

353

Cut angles for quartz crystal resonators  

Microsoft Academic Search

The present invention concerns itself with crystallographically doubly rotated quartz orientations vibrating in the transverse c-mode with turnover temperatures which are considerably less sensitive to angular misorientation than the comparable well known AT- or BT-cuts. These crystals are arbitrarily designated as AK-cut crystals and are defined by phi-angle variations between 30 deg.-60 deg, and theta-angle variations between 12 deg.-32 deg.

A. Kahan

1985-01-01

354

Syntectonic Recrystallization and Texture Development in Quartz  

Microsoft Academic Search

I HAVE been carrying out an electron microscopy study of quartz which has undergone partial or complete recrystallization during natural deformation. This study has shown that syntectonic recrystallization and texture (fabric) development can be interpreted by dislocation processes similar to those observed in deforming metals and ceramics rather than by the crystal growth under non-hydrostatic stress proposed in the literature1-3.

S. White

1973-01-01

355

Hydrothermal alteration in the Reykjanes geothermal system: Insights from Iceland deep drilling program well RN-17  

NASA Astrophysics Data System (ADS)

The Reykjanes geothermal system is a seawater-recharged hydrothermal system that appears to be analogous to seafloor hydrothermal systems in terms of host rock type and low water/rock alteration. The similarities make the Reykjanes system a useful proxy for seafloor vents. At some time during the Pleistocene, the system was dominated by meteoric water recharge, and fluid composition at Reykjanes has evolved through time as a result of changing proportions of meteoric water influx as well as differing pressure and temperature conditions. The purpose of this study is to characterize secondary mineralization, degree of metasomatic alteration, and bulk composition of cuttings from well RN-17 from the Reykjanes geothermal system. The basaltic host rock includes hyaloclastite, breccia, tuff, extrusive basalt, diabase, as well as a marine sedimentary sequence. The progressive hydrothermal alteration sequence observed with increasing depth results from reaction of geothermal fluids with the basaltic host rock. An assemblage of greenschist facies alteration minerals, including actinolite, prehnite, epidote and garnet, occurs at depths as shallow as 350 m; these minerals are commonly found in Icelandic geothermal systems at temperatures above 250 °C (Bird and Spieler, 2004). This requires hydrostatic pressures that exceed the present-day depth to boiling point curve, and therefore must record alteration at higher fluid pressures, perhaps as a result of Pleistocene glaciation. Major, minor, and trace element profiles of the cuttings indicate transitional MORB to OIB composition with limited metasomatic shifts in easily mobilized elements. Changes in MgO, K 2O and loss on ignition indicate that metasomatism is strongly correlated with protolith properties. The textures of alteration minerals reveal alteration style to be strongly dependent on protolith as well. Hyaloclastites are intensely altered with calc-silicate alteration assemblages comprising calcic hydrothermal plagioclase, grandite garnet, prehnite, epidote, hydrothermal clinopyroxene, and titanite. In contrast, crystalline basalts and intrusive rocks display a range in alteration intensity from essentially unaltered to pervasive and nearly complete albitization of igneous feldspar and uralitization of clinopyroxene. Hydrothermal anorthite (An92-An98) occurs in veins in the most altered basalt cuttings and is significantly more calcic than igneous feldspar (An48-An79). Amphibole compositions change from actinolite to hornblende at depth. Hydrothermal clinopyroxene, which occurs in veins, has greater variation in Fe content and is systematically more calcic than igneous pyroxene and also lacks uralitic textures. Solid solutions of prehnite, epidote, and garnet indicate evolving equilibria with respect to aluminum and ferric iron.

Marks, Naomi; Schiffman, Peter; Zierenberg, Robert A.; Franzson, Hjalti; Fridleifsson, Gudmundur Ó.

2010-01-01

356

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

357

[Arteriovenous dissection for branch retinal vein occlusion].  

PubMed

Arteriovenous dissection (AVD) is a surgical maneuver to separate the retinal artery and vein at the crossing site in patients with branch retinal vein occlusion (BRVO). The published studies showed an evidence level 3. AVD seems to be maintainable in patients with recent onset of BRVO and decimal visual acuity < or =0.4. PMID:18317778

Feltgen, N; Hattenbach, L-O; Mirshahi, A; Hansen, L

2008-04-01

358

Arteries and veins of the zebra fish  

NSDL National Science Digital Library

Arteries and veins are blood vessels and are part of the circulatory system. Arteries take oxygenated blood away from the heart and veins bring blood back to the heart after it has circulated through the body. The circulatory system distributes oxygen to the body and also moves around nutrients.

Katie Hale (CSUF;Biological Sciences)

2007-06-19

359

Improving the management of varicose veins.  

PubMed

Up to 30% of the UK population are affected by varicose veins. They are a manifestation of increased venous pressure in the lower limb caused by impaired venous return. Primary varicosities result from poor drainage from the superficial to the deep venous system. Secondary varicosities arise as a result of underlying pathology impeding venous drainage, such as deep venous thrombosis or increased intra-abdominal pressure caused by a mass, pregnancy or obesity. Patients with bleeding varicose veins should be referred to a vascular service immediately. Referral is also indicated in the following cases: symptomatic primary or recurrent varicose veins; lower limb skin changes thought to be caused by chronic venous insufficiency; superficial vein thrombosis and suspected venous incompetence; a venous leg ulcer or healed venous leg ulcer. Imaging is crucial in the assessment of the superficial and deep venous system to enable assessment of venous competence. The gold standard imaging technique is colour duplex ultrasonography. Duplex ultrasound should be used to confirm the diagnosis of varicose veins and the extent of truncal reflux, and to plan treatment for patients with suspected primary or recurrent varicose veins. Superficial vein ligation, phlebectomy and stripping have been the mainstay of treatment. In recent years, new techniques have been developed that are minimally invasive, enabling treatment of superficial venous incompetence with reduced morbidity. NICE recommends that endothermal ablation, in the form of radiofrequency or laser treatment, should be offered as treatment for patients with confirmed varicose veins and truncal reflux. PMID:24555256

Onida, Sarah; Lane, Tristan R A; Davies, Alun H

2013-01-01

360

The Superior Ophthalmic Vein in Carotid Angiograms  

Microsoft Academic Search

Examination of routine carotid angiograms from 1,000 patients gave 52 definite and 80 possible cases in which the superior ophthalmic vein was filled with contrast medium. Only one of these cases suffered from sinus thrombosis. In the other cases no certain correlation could be found between the angiographic or clinical diagnosis and the filling of the orbital vein. However, the

M. Brüderlin; R. Wüthrich

1973-01-01

361

Who Is at Risk for Varicose Veins?  

MedlinePLUS

... the heart, increasing the risk for varicose veins. Rate This Content: Varicose Veins Clinical Trials Clinical trials are research studies that explore whether a medical strategy, treatment, or device is safe and effective for humans. To find clinical trials that are currently underway ...

362

Recognizing and managing retinal vein occlusion.  

PubMed

Retinal vein occlusion is the second most common retinal vascular disease after diabetic retinopathy and represents a significant cause of irreversible sight loss and disability in persons over the age of 50 years (The Branch Vein Occlusion Study Group, 1984). PMID:24402030

Arunakirinathan, Meena; Aj Ting, Michelle; Crawley, Laura

2014-01-01

363

Treating Varicose Veins with Transilluminated Powered Phlebectomy  

Microsoft Academic Search

In the past, patients endured hours of surgery, many incisions, and multiple scars to manually remove painful, unsightly, swollen varicose veins. Patients now have a new treatment option. Endoscopic resection and ablation of superficial varicosities is possible using a powered vein resector, irrigated illuminator, and tumescent anesthesia. This article describes this new technique, called transilluminated powered phlebectomy, and explains how

Lisa M. Zotto

2002-01-01

364

Basilic vein transposition: review of different techniques.  

PubMed

This is a review of the basilic vein procedure and changes that have evolved to improve outcomes. This includes reviewing data on the one-stage vs. two-stage technique as well as elevation for the basilic vein. The review discusses data that help the surgeon decide which technique he should evaluate. PMID:24817461

Glickman, Marc

2014-01-01

365

Optical processing furnace with quartz muffle and diffuser plate  

DOEpatents

An optical furnace for annealing a process wafer comprising a source of optical energy, a quartz muffle having a door to hold the wafer for processing, and a quartz diffuser plate to diffuse the light impinging on the quartz muffle; a feedback system with a light sensor located in the door or wall of the muffle is also provided for controlling the source of optical energy. The quartz for the diffuser plate is surface etched (to give the quartz diffusive qualities) in the furnace during a high intensity burn-in process.

Sopori, Bhushan L. (Denver, CO)

1995-01-01

366

Insights to magmatic-hydrothermal processes in the Manus back-arc basin as recorded by anhydrite  

NASA Astrophysics Data System (ADS)

Microchemical analyses of rare earth element (REE) concentrations and Sr and S isotope ratios of anhydrite are used to identify sub-seafloor processes governing the formation of hydrothermal fluids in the convergent margin Manus Basin, Papua New Guinea. Samples comprise drill-core vein anhydrite and seafloor massive anhydrite from the PACMANUS (Roman Ruins, Snowcap and Fenway) and SuSu Knolls (North Su) active hydrothermal fields. Chondrite-normalized REE patterns in anhydrite show remarkable heterogeneity on the scale of individual grains, different from the near uniform REE N patterns measured in anhydrite from mid-ocean ridge deposits. The REE N patterns in anhydrite are correlated with REE distributions measured in hydrothermal fluids venting at the seafloor at these vent fields and are interpreted to record episodes of hydrothermal fluid formation affected by magmatic volatile degassing. 87Sr/ 86Sr ratios vary dramatically within individual grains between that of contemporary seawater and that of endmember hydrothermal fluid. Anhydrite was precipitated from a highly variable mixture of the two. The intra-grain heterogeneity implies that anhydrite preserves periods of contrasting hydrothermal versus seawater dominant near-seafloor fluid circulation. Most sulfate ? 34S values of anhydrite cluster around that of contemporary seawater, consistent with anhydrite precipitating from hydrothermal fluid mixed with locally entrained seawater. Sulfate ? 34S isotope ratios in some anhydrites are, however, lighter than that of seawater, which are interpreted as recording a source of sulfate derived from magmatic SO 2 degassed from underlying felsic magmas in the Manus Basin. The range of elemental and isotopic signatures observed in anhydrite records a range of sub-seafloor processes including high-temperature hydrothermal fluid circulation, varying extents of magmatic volatile degassing, seawater entrainment and fluid mixing. The chemical and isotopic heterogeneity recorded in anhydrite at the inter- and intra-grain scale captures the dynamics of hydrothermal fluid formation and sub-seafloor circulation that is highly variable both spatially and temporally on timescales over which hydrothermal deposits are formed. Microchemical analysis of hydrothermal minerals can provide information about the temporal history of submarine hydrothermal systems that are variable over time and cannot necessarily be inferred only from the study of vent fluids.

Craddock, Paul R.; Bach, Wolfgang

2010-10-01

367

What Are the Signs and Symptoms of Deep Vein Thrombosis?  

MedlinePLUS

... Are the Signs and Symptoms of Deep Vein Thrombosis? The signs and symptoms of deep vein thrombosis ( ... life-threatening problems if not treated. Deep Vein Thrombosis Only about half of the people who have ...

368

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

369

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.