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1

Quartz Vein in the Gunsight Formation  

USGS Multimedia Gallery

Quartz vein in biotite-rich rock in the Gunsight Formation of the Mesoproterozoic Lemhi Group. Bluish green copper-bearing minerals coat the quartz vein. Pale pinkish cobalt bloom and white caliche coat adjacent biotite-rich wallrock....

2

Contrasting paleofluid systems in the continental basement: a fluid inclusion and stable isotope study of hydrothermal vein mineralization, Schwarzwald district, Germany  

Microsoft Academic Search

An integrated fluid inclusion and stable isotope study was carried out on hydrothermal veins (Sb-bearing quartz veins, metal-bearing fluorite-barite-quartz veins) from the Schwarzwald district, Germany. A total number of 106 Variscan (quartz veins related to Variscan orogenic processes) and post-Variscan deposits were studied by micro- thermometry, Raman spectroscopy, and stable isotope analysis. The fluid inclusions in Variscan quartz veins are

B. BAATARTSOGT; G. SCHWINN; T. WAGNER; H. TAUBALD; T. BEITTER; G. MARKL

2007-01-01

3

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

4

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

SciTech Connect

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

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

1990-07-01

5

A discussion of 'Anomalous quartz from the Roter Kamm impact crater, Namibia - Evidence for post-impact hydrothermal activity?'  

NASA Technical Reports Server (NTRS)

This paper presents arguments against the statement made by Koeberl et al. (1989) to the effect that various differences between the quartz of the three quartz pebbles from the Roter Kamm impact crater (Namibia) and the quartz of the pegmatites present in the basement rocks of this crater can be best interpreted as evidence that the pebbles were formed (or 'recrystallized') by a post-impact hydrothermal system. Arguments are presented that suggest that the three quartz pebbles are, most likely, fragments of a preimpact vein quartz of hydrothermal origin.

Roedder, Edwin

1990-01-01

6

A fluid inclusion and light element stable isotope study of the gold-bearing quartz vein system, Falun, Sweden  

NASA Astrophysics Data System (ADS)

The Falun gold quartz vein mineralization is located ca 230 km NW of Stockholm, Sweden, within the Early Proterozoic volcano-sedimentary sequence of Bergslagen. The mineralization consists of a system with subparallel quartz veins that crosscut the alteration zone to the Falun massive sulphide deposit. Early barren and late gold-bearing quartz veins follow tectonic structures postdating the formation of the massive sulphide ore. Both generations of veins are epigenetic to the massive sulphide ore and were formed by hydrothermal processes. Fluid inclusion study of the gold-bearing quartz veins indicates a low-moderately saline fluid (0.3 to 17.4 equiv wt% NaCl). Heterogeneous trapping is indicated by coexisting inclusions showing a variable CO2 content from 100% CO2 ± CH4 to 100% aqueous fluid. Temperatures of total homogenization also show a wide spread from 116-350°C with a slightly bimodal distribution with peaks at ca 180°C and 280°C. Measured ?D values — 69 to — 63%0 (SMOW), of inclusion fluid and calculated ? 18O values of hydrothermal fluids — 7.5 to — 1.4%0 (SMOW), strongly suggest a meteoric origin for the fluids. The quite consistent ?D values and the range in ? 18O values indicate that major water-rock interaction led to the evolution in ?18O of the hydrothermal fluids.

Åberg, A.; Fallick, A. E.

1993-11-01

7

Porosity structures in synthetic quartz veins examined by micro X-ray CT  

NASA Astrophysics Data System (ADS)

Ubiquitous occurrences of quartz veins suggest that dissolution/precipitation of silica provides significant effects on the hydrological and mechanical properties within the crust. For example, a model has been proposed that fracture sealing processes control the change of pore fluid pressure and thus earthquake cycle. Previous studies on natural quartz veins have focused on estimates of P-T conditions, stress and strain fields and fluid compositions; however, details of dynamics of fluid flow and how fractures are sealed during vein formation are still unclear. In this study, we synthesized quartz veins by the hydrothermal experiments, and observed the aperture structures by using X-ray CT. The purpose of this study is to clarify how aperture structures evolve during vein formation especially focusing on effect of the state of water (vapor and supercritical region). We conducted the hydrothermal flow-through experiments for quartz precipitation from Si-supersaturated solutions under supercritical (430C, 30MPa) and vapor condition (370C, 20MPa). The experimental apparatus consists of two vessels for preparation of the Si-supersaturated solution and for precipitation, respectively. The precipitation vessel has double-structure: the main flow path was the inner alumina tube (diameter=4mm), and the outer SUS tube was filled with static solutions. Two situations were examined as the inner tubes; one is porous media composed of closed packed alumina balls(1mm in size), and the other one is fracture. The advantage of this system is that we can take out the non-destructive sample for the analyses by X-ray CT. Significant porosity reduction by silica precipitation at porous media. Under supercritical condition, amorphous silica was predominantly formed with covering the surfaces of the alumina balls and alumina tube, and discrete quartz crystal (50?m) within the amorphous silica layers. The porosity (?) gradually decreases with minimal porosity (? = 0.4) at ˜ 38mm from the inlet. However, under vapor condition, fine-grained quartz grains (0.1-1 ?m) were directly nucleated in solutions using surface of vapor, and immediately settled on the bottom. The porosity rapidly decreases from 18 mm (? = 0.8) to 25 mm (? < 0.1) from the inlet. These results suggest that a depressurization of crustal fluids related to fault dilation by earthquakes would cause a formation of fine-grained silica particles, and their mineralogy and transport/deposition properties strongly depend on properties water. We also discuss precipitation mechanism varied from nucreation to epitaxial over growth within rock fracture. The mineralogy and aperture structures changes systematically along the fluid flow path. From the inlet to 35 mm of fracture, nucleation predominantly occurred, regardless of vein wall minerals. From 35mm to outlet of fracture, silica precipitates occurred as epitaxial overgrowth from quartz crystal. The wavelength of aperture structures is controlled by distribution and grain size of quartz of the host granite. Accordingly, fractures are not sealed homogeneously, but complex 3D flow pathways are evolved during vein formation.

Yamada, R.; Okamoto, A.; Saishu, H.; Nakamura, M.; Okumura, S.; Sasaki, O.; Tsuchiya, N.

2013-12-01

8

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

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

9

Hydrothermal deformation of granular quartz sand  

Microsoft Academic Search

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

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

2008-01-01

10

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

USGS Publications Warehouse

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

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

1996-01-01

11

Structural evolution of a quartz–sillimanite vein and nodule complex in a late-to post-tectonic leucogranite, Western Adirondack Highlands, New York  

Microsoft Academic Search

Quartz–sillimanite veins and nodules within the carapace of a late- to post- tectonic leucogranite crosscut one another as well as calcsilicate schlieren. These relationships document a fracture-related and hydrothermal origin of the vein and nodule complex. Two dominant orientations (N50E, N20E) are observed with the former being the oldest and most deformed. Both of these sets have undergone deformation, including

James McLelland; Arthur Goldstein; Betsy Cunningham; Christopher Olson; Suzanne Orrell

2002-01-01

12

Origin and granite alteration effects of hydrothermal fluid: isotopic evidence from fluorite veins, Co. Galway, Ireland  

NASA Astrophysics Data System (ADS)

The Costelloe Murvey Granite is a chemically evolved, high heat production, leucocratic component of the 400 Ma old Galway Granite batholith and is host to hydrothermal fluorite-quartz-calcite veins. A previously reported clinopyroxene 40Ar-39Ar age of 231±4 Ma obtained from a pre-mineralization dolerite dyke is reinterpreted as dating this mineralization. The hydrothermal fluid extensively altered its granite wallrocks, leading to lower Sm and Nd and higher Rb concentrations in altered granite, disturbing both its Rb-Sr and Sm-Nd isotopic systems. The 87Sr/86Sr ratio of the hydrothermal fluid from which fluorite and calcite precipitated ranged from 0.7101 to 0.7139. These ratios are very much lower than in the Costelloe Murvey Granite at the time of mineralization, precluding the granite as a source for more than 2% of the hydrothermal Sr. The initial 143Nd/144Nd ratio varies between fluorite in different veins due to Nd derivation from local wallrocks, and between fluorite of petrographically distinct growth phases within a single hand specimen, highlighting the difficulty of Sm-Nd isochron dating of fluorite in cases where there are multiple sources of hydrothermal Nd. It is proposed that fluorite and calcite precipitated where hot, dilute fluids rising through the granite mixed with cooler, more saline fluids of basinal origin migrating through Lower Carboniferous limestone which then overlay the granite.

Menuge, J. F.; Feely, M.; O'Reilly, C.

1997-01-01

13

Investigating Alpine fissure rutilated quartz to constrain timing and conditions of post-metamorphic hydrothermal fluid flow  

NASA Astrophysics Data System (ADS)

Rutilated quartz, aka Venus' hair, is finely-acicular rutile intergrown with host quartz generated by fluid-mediated co-crystallization. It is commonly found in hydrothermal veins, including the renown cleft mineral locations of the Swiss Alps. Previous studies of Alpine cleft mineralizations used rare hydrothermal monazite [1] and titanite [2] to constrain vein formation to ~13.5-15.2 Ma, postdating peak metamorphism by ~2-4 Ma. Temperature (T) estimates of 150-450°C are based on fluid inclusions and bulk quartz-mineral oxygen isotope exchange equilibria, and formation pressures (P) are 0.5-2.5 kbar (for a geothermal gradient of 30°C/km) [2]. The potential of rutilated quartz as a thermochronometer, however, has not been harnessed previously. Here, we present the first results of age and P-T determinations for rutilated quartz from six locations in the Swiss Alps (San Gottardo; Feldbach, Binntal; Pi Aul, Vals; Faido, Leventina; Elm, Steinbach; Binntal). Samples were cut and mounted in epoxy discs to expose rutile (0.03 to 1 mm in diameter) and its host quartz which was also imaged in cathodoluminescence (CL). CL images for half of the samples' host quartz exhibited strong sector zoning, while others reveal only weak CL zonation. Isotopic and trace element analyses were carried out by SIMS using a CAMECA ims1270 for U-Pb, O-isotopes, and Ti-in-quartz, and a LA-ICP-MS system (213 nm New Wave laser coupled to an Agilent 7500a) for Zr-in-rutile. U-Pb rutile ages average 15.5×2.0 Ma (2?). T estimates are 352-575°C (rutile-quartz oxygen isotopes in touching domains), 470-530°C (Zr-in-rutile assuming P = 0.5 and equilibrium with host-rock zircon), and 251-391°C (Ti-in-quartz at assumed P = 0.5 kbar and aTiO2 = 1). CL zones are isotopically unzoned. Rutile-quartz oxygen isotopes are pressure insensitive, whereas Zr-in-rutile and Ti-in-quartz are minimum temperatures. These results demonstrate that rutilated quartz can constrain timing and conditions of post-metamorphic hydrothermal fluid flow and mineralization. Discrepancies in thermometers are attributed to differences between experimental calibrations of isotopic and trace element thermometers, and the conditions of post-metamorphic hydrothermal fluid flow. Only rutile-quartz oxygen isotope exchange [3] has been calibrated close to natural T conditions for rutilated quartz (500°C). This may help to extend the applicability of the Ti-in-quartz and Zr-in-rutile to T below experimental calibrations (>600°C; [4] and >700°C; [5], resp.). [1] Janots et al., 2012, Chem. Geol., 326-327, 61-71 [2] Mullis, 1996, Schweiz. Mineral. Petrogr. Mitt., 76, 159-164 [3] Matthews, 1994, J. Met. Geol., 12, 211-219 [4] Thomas et al., 2010, Contrib. Mineral. Petrol., 160, 743-759 [5] Ferry and Watson, 2007, Contrib. Mineral. Petrol., 154, 429-437

Shulaker, D. Z.; Schmitt, A. K.; Zack, T.; Bindeman, I. N.

2013-12-01

14

Vein quartz in lithic traditions: an analysis based on experimental archaeology  

Microsoft Academic Search

Worldwide, vein quartz was a commonly used raw material for stone tools but this material has proved difficult for archaeologists to analyse because many quartz assemblages appear to be comprised of amorphous pieces, not easily recognised as humanly modified or forming ‘tools’. This paper discusses the analysis of the debitage – focusing on the debitage fragmentation rate, the debitage, break,

Killian Driscoll

2011-01-01

15

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

NASA Astrophysics Data System (ADS)

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

Akawy, Ahmed

2007-02-01

16

Telescoped porphyry Cu-Mo-Au mineralisation, advanced argillic alteration and quartz-sulphide-gold-anhydrite veins in the Thames District, New Zealand  

NASA Astrophysics Data System (ADS)

Porphyry Cu-Mo-Au mineralisation with associated potassic and phyllic alteration, an advanced argillic alteration cap and epithermal quartz-sulphide-gold-anhydrite veins, are telescoped within a vertical interval of 400-800 m on the northeastern margin of the Thames district, New Zealand. The geological setting is Jurassic greywacke basement overlain by Late Miocene andesitic-dacitic rocks that are extensively altered to propylitic and argillic assemblages. The porphyry Cu-Mo-Au mineralisation is hosted in a dacite porphyry stock and surrounding intrusion breccia. Relicts of a core zone of potassic K-feldspar-magnetite±biotite alteration are overprinted by phyllic quartz-sericite-pyrite or intermediate argillic chlorite-sericite alteration assemblages. Some copper occurs in quartz-magnetite-chlorite-pyrite-chalcopyrite veinlets in the core zone, but the bulk of the copper and the molybdenum are associated with the phyllic alteration as disseminated chalcopyrite and as molybdenite-sericite-carbonate veinlets. The advanced argillic cap has a quartz-alunite-dickite core, which is enveloped by an extensive pyrophyllite-diaspore-dickite-kaolinite assemblage that overlaps with the upper part of the phyllic alteration zone. Later quartz-sphalerite-galena-pyrite-chalcopyrite-gold-anhydrite±carbonate veins occur within and around the margins of the porphyry intrusion, and are associated with widespread illite-carbonate (argillic) alteration. Multiphase fluid inclusions in quartz stockwork veins associated with the potassic alteration trapped a highly saline (50-84 wt% NaCl equiv.) magmatic fluid at high temperatures (450 to >600 °C). These hypersaline brines were probably trapped at a pressure of about 300 bar, corresponding to a depth of 1.2 km under lithostatic conditions. This shallow depth is consistent with textures of the host dacite porphyry and reconstruction of the volcanic stratigraphy. Liquid-rich fluid inclusions in the quartz stockwork veins and quartz phenocrysts trapped a lower salinity (3-20 wt% NaCl equiv.), moderate temperature (300-400 °C) fluid that may have caused the phyllic alteration. Fluid inclusions in the quartz-sphalerite-galena-pyrite-chalcopyrite-gold-anhydrite±carbonate veins trapped dilute (1-3 wt% NaCl equiv.) fluids at 250 to 320 °C, at a minimum depth of 1.0 km under hydrostatic conditions. Oxygen isotopic compositions of the fluids that deposited the quartz stockwork veins fall within the 6 to 10‰ range of magmatic waters, whereas the quartz-sulphide-gold-anhydrite veins have lower ?18Owater values (-0.6 to 0.5‰) , reflecting a local meteoric water (-6‰) influence. A ?18O versus ?D plot shows a trend from magmatic water in the quartz stockwork veins to a near meteoric water composition in kaolinite from the advanced argillic alteration. Data points for pyrophyllite and the quartz-sulphide-gold-anhydrite veins lie about midway between the magmatic and meteoric water end-member compositions. The spatial association between porphyry Cu-Mo-Au mineralisation, advanced argillic alteration and quartz-sulphide-gold-anhydrite veins suggests that they are all genetically part of the same hydrothermal system. This is consistent with K-Ar dates of 11.6-10.7 Ma for the intrusive porphyry, for alunite in the advanced argillic alteration, and for sericite selvages from quartz-gold veins in the Thames district.

Brathwaite, R.; Simpson, M.; Faure, K.; Skinner, D.

2001-10-01

17

Brittle-viscous deformation of vein quartz under fluid-rich low greenschist facies conditions  

NASA Astrophysics Data System (ADS)

A coarse grained, statically crystallized quartz vein, embedded in a phyllonitic matrix, was studied by EBSD and optical microscopy to gain insights into the processes of strain localization in quartz deformed under low-grade conditions, broadly coincident with the frictional-viscous transition. The vein is from a high strain zone at the front of the Porsa Imbricate Stack in the Paleoproterozoic Repparfjord Tectonic Window in northern Norway. The vein was deformed under lower greenschist facies conditions during deformation along a large out-of-sequence phyllonitic thrust of Caledonian age. The host phyllonite formed at the expense of metabasalt wherein feldspar broke down to form interconnected layers of fine, synkinematic phyllosilicates. In the mechanically weak framework of the phyllonite, the studied quartz vein acted as a relatively rigid body deforming mainly by coaxial strain. Viscous deformation was initially accommodated by basal ?a? slip of quartz during the development of a mesoscopic pervasive extensional crenulation cleavage. Under the prevailing boundary conditions, however, dislocation glide-accommodated deformation of quartz resulted inefficient and led to dislocation tangling and strain hardening of the vein. In response to hardening, to the progressive increase of fluid pressure and the increasing competence contrast between the vein and the weak foliated host phyllonite, quartz crystals began to deform frictionally along specific, optimally oriented lattice planes, creating microgouges along microfractures. These were, however, rapidly sealed by nucleation of new grains as transiently over pressured fluids penetrated the deforming system. The new nucleated grains grew initially by solution-precipitation and later by grain boundary migration. Due to the random initial orientation of the vein crystals, strain was accommodated differently in the individual crystals, leading to the development of remarkably different microstructures. Crystals oriented optimally for basal slip accommodated strain mainly viscously and experienced only minor fracturing. Instead, the crystals misoriented for basal slip hardened and deformed by pervasive domainal fracturing. This study indicates the importance of considering shear zones as dynamic systems wherein the activated deformation mechanisms vary transiently in response to the complex temporal and spatial evolution of the shear zone, often in a cyclic fashion.

Kjøll, H. J.; Viola, G.; Menegon, L.; Sørensen, B. E.

2015-01-01

18

Fluid immiscibility and gold deposition in the Birimian quartz veins of the Angovia deposit (Yaouré, Ivory Coast)  

NASA Astrophysics Data System (ADS)

The Paleoproterozoic terranes (Birimian) of West Africa are well known to host numerous economic gold mineralizations. The Angovia gold mineralization is located in a brecciated and mylonitic zone within the Birimian greenstones. The sulfide-gold mineralization is mainly represented by gold associated with pyrite and chalcopyrite. A fluid inclusion study undertaken on mineralized quartz veins revealed the presence of aqueous-carbonic (CO 2-H 2O) fluids, the association of carbonic (CO 2) and early aqueous fluids, followed by later aqueous (H 2O-salt) and finally nitrogen-rich fluids. Entrapment of the initial homogeneous aqueous-carbonic fluids prior to fluid immiscibility depicts the evolution of the P-T conditions during the exhumation of the terranes after the peak of green-schist metamorphism. The CO 2 rich-fluid occurs especially in gold-bearing quartz, and are considered as the main evidence of the ore-forming process in the gold-bearing quartz veins. It is considered as a product of immiscibility of the CO 2-H 2O parent. The volatile fraction of carbonic and aqueous-carbonic fluid inclusions is dominated by CO 2, containing minor amounts of N 2, even smaller amounts of CH 4 and sporadically, H 2S. The aqueous-carbonic fluids have moderate salinity (3-10 wt.% eq. NaCl). Late aqueous and N 2 - (CH 4-CO 2) fluids are considered as later, unrelated to the main ore stage, and were trapped during the cooling of the hydrothermal system from 300 to 200 °C. The immiscibility has been favored by a strong pressure drop, the main trapping P-T conditions being 320-370 °C and 105-135 MPa. The mineralizing process is likely related to the immiscibility event, which was probably favored by the release of the fluid pressure after fracturing along the main shear zones. The ore process is likely to have occurred along the main shear zones or related secondary structures affected by cycling of the fluid pressure and quartz sealing-fracturing processes. The superimposed process can also explain the relative complexity of the quartz textures and fluid inclusion microfractures, and the rather wide range in the density of both parent fluid and CO 2-dominated fluid.

Coulibaly, Y.; Boiron, M. C.; Cathelineau, M.; Kouamelan, A. N.

2008-02-01

19

Genesis of Syntectonic Hydrothermal Veins in the Igneous Rock of Teschenite Association (Outer Western Carpathians, Czech Republic): Growth Mechanism and Origin of Fluids  

NASA Astrophysics Data System (ADS)

Hydrothermal mineralization hosted by the Lower Cretaceous igneous rock of the teschenite association at Jasenice (Silesian Unit, Flysch Belt, Outer Western Carpathians) occurs in two morphological types - irregular vein filled by granular calcite and regular composite vein formed by both fibrous and granular calcite and minor chlorite, quartz, and pyrite. Crosscutting evidence indicates that the granular veins are younger than the composite vein. The composite vein was formed by two mechanisms at different times. The arrangement of solid inclusions in the marginal fibrous zone suggests an episodic growth by the crack-seal mechanism during syntectonic deformation which was at least partially driven by tectonic suction pump during some stages of the Alpine Orogeny. Both the central part of the composite vein and monomineral veins developed in a brittle regime. In these cases, the textures of vein suggest the flow of fluids along an open fracture. The parent fluids of both types of vein are characterized by low temperatures (Th=66-163 °C), low salinities (0.4 to 3.4 wt. % NaCl eq.), low content of strong REE-complexing ligands, and ?18O and ?13C ranges of + 0.2/+12.5 %. SMOW and -11.8/-14.1 %. PDB, respectively. The parent fluids are interpreted as the results of mixing of residual seawater and diagenetic waters produced by dewatering of clay minerals in the associ-ated flysch sediments. The flow of fluids was controlled by tectonic deformation of the host rock.

Urubek, Tomáš; Dolní?ek, Zden?k; Kropá?, Kamil

2015-01-01

20

Fluid inclusion studies of gold-bearing quartz veins from the Yirisen deposit, Sula Mountains greenstone belt, Masumbiri, Sierra Leone  

Microsoft Academic Search

The auriferous veins at Yirisen, Masumbiri, Sierra Leone, occurring mainly in the form of sericitic quartz-sulphide lodes and stringers, are hosted in metamorphosed volcano-sedimentary assemblages invaded by at least two generations of granitic intrusions. Detailed microthermometric studies of fluid inclusions from the veins coupled with laser Raman spectroscopic analysis show that the inclusions contain aqueous fluids of variable salinity (5

Ibrahim J. Barrie; Jacques L. R. Touret

1999-01-01

21

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

22

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

23

Hydrothermal breccias in vein-type ore deposits: A review of mechanisms, morphology and size distribution  

Microsoft Academic Search

Breccias are among the most widely distributed rock textures found in hydrothermal vein-type deposits. Previous studies have mainly been interested in developing qualitative descriptive approaches, leading to a confusing profusion of terms. Brecciation originates in numerous ways, resulting in highly complex classification systems and frequent misinterpretations of facies. Field observations are difficult to reconcile with physical theories of fragmentation, partly

Michel Jébrak

1997-01-01

24

Three sets of fine extinction bands in a tectonically deformed vein-quartz single crystal  

NASA Astrophysics Data System (ADS)

Intracrystalline fine extinction bands (FEBs) in quartz, are narrow (less than 5µm thick), planar microstructures with a misorientation up to 5° with respect to the host crystal, occurring in closely spaced sets (spacing of 4-5?m). FEBs have been commonly attributed to a large range of brittle and/or crystal-plastic mechanisms, revealing considerable disagreement on the responsible crystal-plastic slip systems and the ambient conditions. Another question that arises, is whether or not the FEBs rotate from a basal plane orientation to orientations ranging between the basal and prism planes. Usually only one set of FEBs occurs in a single crystal, though two sets are observed, in particular with increasing strain. Tentatively, a maximum of two sets of sub-basal FEBs has been postulated to develop in a single quartz crystal in a tectonic context. However, we identified several crystals in naturally deformed vein-quartz containing three sets of FEBs. The vein-quartz has been deformed under sub-greenschist metamorphic conditions, during the late Palaeozoic Variscan orogeny, in the High-Ardenne slate belt (Belgium). The vein-quartz has been subjected to bulging dynamic recrystallisation and shows a high degree of undulatory extinction, abundant subgrains and wide extinction bands sub-parallel to the c-axis. We attempted to characterise these three sets of FEBs by means of light microscopy, EBSD-OIM and universal stage microscopy. In both cases studied the c-axis is inclined less than 8° with respect to the thin-section plane. The different sets of FEBs show a consistent orientation with respect to the c-axis. One set of FEBs deviates maximum 10° from the basal plane. The other two sets deviate between 15 and 35° from a basal plane orientation. Corresponding FEBs, at the same angle with respect to the c-axis, have similar morphologies. In relative EBSD orientation maps FEBs show a maximum misorientation of 3°, and have a lower pattern quality than the host crystal. The FEB boundaries often coincide with Dauphiné twin boundaries. The misorientation inside FEBs gradually increases and can be asymmetrically distributed across the FEBs. Plotting the FEB orientations in the New Stereographic Projection Template (used for identifying the crystallographic orientation of planar deformation features), the FEBs appear to deviate from any particular crystallographic orientation. No trigonal symmetry is detected in the FEB orientation distribution. Firstly, the question arises whether the exceptional observation of three sets of FEBs is due to an observational bias caused by the particular orientation of the optical axis of the quartz crystals sub-parallel to the thin section plane, or whether the FEBs formed because of a specific crystallographic orientation with respect to the principal stresses during deformation. Secondly, we suggest that the development of FEBs is related to a range of possible slip systems, or to a combination of different slip systems. Dauphiné twinning seems to have taken place after FEB formation. Finally, we seriously question that FEBs could be formed solely by means of a single slip system, that FEBs rotate after their formation and that there could be a genetic relation between FEBs and primary growth banding.

Derez, Tine; Van der Donck, Tom; Pennock, Gill; Drury, Martyn; Sintubin, Manuel

2014-05-01

25

Hydrothermal calcium-carbonate veins reveal past ocean chemistry  

Microsoft Academic Search

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

Damon A. H. Teagle

2011-01-01

26

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

27

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

28

Dissolution-precipitation reactions in hydrothermal experiments with quartz-feldspar aggregates  

NASA Astrophysics Data System (ADS)

Batch and flow-through experiments were performed on quartz-feldspar granular aggregates at hydrothermal conditions (up to ?150 °C, up to 5 MPa effective pressure, and near-neutral pH) for up to 141 days. The effect of dissolution-precipitation reactions on the surface morphology of the mineral grains was investigated. The starting materials as well as the solids and fluids resulting from the experiments were characterized using BET, energy dispersive X-ray spectroscopy, electron microprobe analysis, inductively coupled plasma-optical emission spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, and X-ray fluorescence spectroscopy. The electrical conductivity of fluid samples was used as a proxy for the evolution of the fluid composition in the experiments. The chemical analyses of the fluids in combination with hydrogeochemical simulations with PHREEQC suggested the precipitation of Al-Si-bearing solid phases. Electron microscopy confirmed the formation of secondary amorphous Al-Si-bearing solid phases. The microscopic observations are consistent with a process of stoichiometric dissolution of the mineral grains, transport of dissolved ions in the fluid phase, and spatially coupled precipitation of sub-?m sized amorphous particles on mineral surfaces. These findings shed light onto early stages of diagenesis of quartz-feldspar sands and indicate that amorphous phases may be precursors for the formation of crystalline phases, for example, clay minerals.

Schepers, Ansgar; Milsch, Harald

2013-01-01

29

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

30

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

31

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

32

Ion microprobe analysis of oxygen isotope ratios in quartz from Skye granite: healed micro-cracks, fluid flow, and hydrothermal exchange  

Microsoft Academic Search

Quartz grains in hydrothermally altered granites from the Isle of Skye are highly heterogeneous and not equilibrated in oxygen isotope ratio at the 20 mum scale. Ion microprobe analysis of one grain shows a gradient of 130\\/00 over 400 mum and a greater range in delta 18O than all quartz previously analyzed on the Isle of Skye. Other crystals from

J. W. Valley; Colin M. Graham

1996-01-01

33

Structure, alteration, and geochemistry of the Charlotte quartz vein stockwork, Mt Charlotte gold mine, Kalgoorlie, Australia: time constraints, down-plunge zonation, and fluid source  

NASA Astrophysics Data System (ADS)

The Kalgoorlie district in the Archean Yilgarn Craton, Western Australia, comprises two world-class gold deposits: Mt Charlotte (144 t Au produced to 2013) in the northwest and the Golden Mile (1,670 t Au) in the southeast. Both occur in a folded greenschist-facies gabbro sill adjacent to the Golden Mile Fault (D2) in propylitic alteration associated with porphyry dikes. At Mt Charlotte, a shear array of fault-fill veins within the Golden Mile Fault indicates sinistral strike-slip during Golden Mile-type pyrite-telluride mineralization. The pipe-shaped Charlotte quartz vein stockwork, mined in bulk more than 1 km down plunge, is separated in time by barren D3 thrusts from Golden Mile mineralization and alteration, and occurs between two dextral strike-slip faults (D4). Movement on these faults generated an organized network of extension and shear fractures opened during the subsequent infiltration of high-pressure H2S-rich fluid at 2,655 ± 13 Ma (U-Pb xenotime). Gold was deposited during wall rock sulphidation in overlapping vein selvages zoned from deep albite-pyrrhotite (3 g/t Au) to upper muscovite-pyrite assemblages (5 g/t Au bulk grade). Chlorite and fluid inclusion thermometry indicate that this kilometre-scale zonation is due to fluid cooling from 410-440 °C at the base to 350-360 °C at the top of the orebody, while the greenstone terrane remained at 250 °C ambient temperature and at 300 MPa lithostatic pressure. The opened fractures filled with barren quartz and scheelite during the retrograde stage (300 °C) of the hydrothermal event. During fracture sealing, fluid flux was periodically restricted at the lower D3 thrust. Cycles of high and low up-flow, represented by juvenile H2O-CO2 and evolved H2O-CO2-CH4 fluid, respectively, are recorded by the REE and Sr isotope compositions of scheelite oscillatory zones. The temperature gradient measured in the vein stockwork points to a hot (>600 °C) fluid source 2-4 km below the mine workings, and several kilometres above the base of the greenstone belt. Mass balance calculations involving bulk ore indicate enrichment of both felsic (K, Rb, Cs, Li, Ba, W) and mafic elements (Ca, Sr, Mg, Ni, V, Cr, Te), a source signature compatible with the local high-Mg porphyry suite but not with the meta-gabbro host rock. The initial 87Sr/86Sr ratios of the vein scheelites (0.7014-0.7016) are higher than the mantle ratio of the meta-gabbro (0.7009-0.7011) and overlap those of high-Mg monzodiorite intrusions (0.7016-0.7018) emplaced along the Golden Mile Fault at 2,662 ± 6 Ma to 2,658 ± 3 Ma.

Mueller, Andreas G.

2015-02-01

34

Direct measurement of asperity contact growth in quartz at hydrothermal conditions  

USGS Publications Warehouse

Earthquake recurrence requires interseismic fault restrengthening which results from solid state deformation in room-temperature friction and indentation experiments. In contrast exhumed fault zones show solution-transport processes such as pressure solution and contact overgrowths influence fault zone properties . In the absence of fluid flow, overgrowths are driven by gradients in surface curvature where material is dissolved, diffuses, and precipitates at the contact without convergence normal to the contact. To determine the rate of overgrowth for quartz, we conducted single contact experiments in an externally heated pressure vessel. Convergence was continuously monitored using reflected-light interferometry through a long-working-distance microscope. Contact normal force was constant with an initial effective normal stress of 1.7 MPa, temperature was between 350 and 530{degree sign}C, and water pressure was constant at 150 MPa. Two control experiments were conducted: one dry at 425{degree sign}C and one bi-material (sapphire) at 425{degree sign}C and 150 MPa water pressure. No contact growth or convergence was observed in the controls. For wet single-phase contacts, growth was initially rapid and then decreased with time. No convergence was observed. Fluid inclusions indicate that the contact is not uniformly wetted. The contact is bounded by small regions of high aperture, reflecting local free-face dissolution as the source for the overgrowth. The apparent activation energy is ~125 kJ/mol. Extrapolation predicts rates of contact area increase orders of magnitude faster than in dry, room-temperature and hydrothermal friction experiments, suggesting that natural strength recovery near the base of the seismogenic zone could be dominated by contact overgrowth.

Beeler, Nicholas M.; Hickman, Stephen H.

2015-01-01

35

Kinetics of quartz dissolution in electrolyte solutions using a hydrothermal mixed flow reactor  

NASA Astrophysics Data System (ADS)

A hydrothermal mixed flow reactor has been developed to study the reaction kinetics of a wide variety of mineral/solution systems. The reactor is constructed of commercially pure titanium to minimize corrosion and operates at temperatures of 25 to 300°C and pressures up to 124 bars. This system is used to measure the dissolution rates of quartz at near-neutral pH in 0.0 to 0.15 m solutions of NaCl, KCl, LiCl, MgCl 2 over a temperature range of 100 to 300°C. In all cases, small concentrations of electrolytes increase the rate, some by as much as 1.5 orders of magnitude above the values measured for deionized water. The effect is greatest for solutions of NaCl and KCl where reaction rates increase with increasing electrolyte concentrations up to 0.05 molal and become constant at higher molalities. Smaller rate increases are observed for LiCl and MgCl 2 solutions. The first-order rate equation for quartz dissolution in pure water at temperatures of 100 to 300°C is given by r H 4sio 4 = k +(a sio2)(a H 2o ) 2(1 - Q/K) for a standard system of 1 m 2 of surface area and 1 kg of solution. The addition of electrolytes to reacting solutions at near-neutral pH accelerates the rate according to a Langmuir adsorption model and has the form r H 4sio 4 = (k + + k adK me +/1 + k me +)(a sio2)(a H 2o ) 2(1 - Q/K). m me + Analysis of the data indicates that the observed rate increases are controlled by the identity and concentration of the cation where alkali cations coordinate with the surface to increase the reactivity of siloxane groups by disrupting the structure of the mineral-solution interface. The rate-limiting step for the dissolution mechanism is described by (?Si - O - Si?) + H 2O = (Si - O - Si · OH 2)† ? 2(?Si - O - H) where the intermediate species is probably the same in deionized water and electrolyte solutions, but the reaction frequency is higher in electrolyte solutions due to increases in the accessibility of water to the mineral surface structures. Transition state calculations support this mechanism by showing that the rate increases are caused by an increase in the pre-exponential factor, A, where the activation entropy, ? s†, becomes more positive and/or the mole fraction of water at the reactive sites, X H 2o , increases. The activation enthalpy, ? H†, remains constant. Increased reactivity of the surface in the presence of adsorbed cations is also demonstrated by ab initio molecular orbital calculations of possible surface intermediate species, which show that the presence of certain cations increase the Si - O - Me angle. These results suggest that the mobility of quartz in geologic settings may be quite different from predictions made based on experiments conducted in pure water.

Dove, Patricia M.; Crerar, David A.

1990-04-01

36

Fracture-controlled paleohydrology in a map-scale detachment fold: Insights from the analysis of fluid inclusions in calcite and quartz veins  

Microsoft Academic Search

This study uses fluid inclusions in quartz and calcite veins to characterize the fracture-controlled paleohydrology of a map-scale, evaporite-cored detachment fold in the Sierra Madre Oriental of northeastern Mexico. Field observations indicate that the veins are tectonic in origin, and that they formed in a general sequence that corresponds to four broad stages of progressive folding. We collected samples from

Mark P. Fischer; I. Camilo Higuera-Díaz; Mark A. Evans; Eugene C. Perry; Liliana Lefticariu

2009-01-01

37

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

Microsoft Academic Search

In core samples from the deep geothermal well RWTH-1 we studied Variscan quartz-chlorite veins formed by crack-seal processes in siliciclastics at the brittle to ductile transition. These sheared veins are common in sections of the well, which are interpreted as Variscan thrust zones based on image logs and seismic data. Microstructures interpreted to reflect different stages in the evolution of

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

2011-01-01

38

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

Microsoft Academic Search

In core samples from the deep geothermal well RWTH-1 we studied Variscan quartz–chlorite veins formed by crack-seal processes in siliciclastics at the brittle to ductile transition. These sheared veins are common in sections of the well, which are interpreted as Variscan thrust zones based on image logs and seismic data. Microstructures interpreted to reflect different stages in the evolution of

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

2011-01-01

39

Ion microprobe analysis of oxygen isotope ratios in quartz from Skye granite: healed micro-cracks, fluid flow, and hydrothermal exchange  

Microsoft Academic Search

Quartz grains in hydrothermally altered granites from the Isle of Skye are highly heterogeneous and not equilibrated in oxygen\\u000a isotope ratio at the 20??m scale. Ion microprobe analysis of one grain shows a gradient of 13‰ over 400??m and a greater range\\u000a in ?\\u000a 18O than all quartz previously analyzed on the Isle of Skye. Other crystals from the same

John W. Valley; Colin M. Graham

1996-01-01

40

Mechanisms of hydrothermal crystallization of quartz at 250°C and 15 kbar  

NASA Astrophysics Data System (ADS)

Oxygen isotopic exchange between quartz and water, using a novel technique in which both 18O/ 16O and 17O/ 16O fractionations were measured, yielded an equilibrium fractionation ? 18 = 9.0 at 250°C and 15 kbar. The reaction proceeds predominantly by solution of fine grains and growth of larger grains. Exchange by solid-state diffusion is immeasurably slow at this temperature. Under the same experimental conditions, cristobalite behaves quite differently, becoming transformed to sub-micron quartz crystals in a few minutes. The phase transformation is accompanied by a kinetic isotope effect yielding quartz in isotopic disequilibrium with water. It is possible that such disequilibrium products are also formed in other experiments involving phase transitions or mineral syntheses.

Matsuhisa, Yukihiro; Goldsmith, Julian R.; Clayton, Robert N.

1978-02-01

41

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

42

Tracing the evolution of crustal-scale, transient permeability in a tectonically active, mid-crustal, low-permeability environment by means of quartz veins  

NASA Astrophysics Data System (ADS)

In mid-crustal, low-permeability environments pervasive fluid flow is primarily driven by the production of internally-derived metamorphic fluids, causing a near permanent state of near-lithostatic fluid-pressure conditions. In a tectonically active crust, these overpressured fluids will generate intermittently an enhanced permeability that will facilitate fluid flow through the crust. The High-Ardenne slate belt (Belgium, France, Germany) can be considered as a fossil (late Palaeozoic) analogue of such mid-crustal, low-permeability environment at the brittle-plastic transition (depth range from 7 to 15 km). Low-grade metamorphic (250°C-350°C), predominantly fine-grained, siliciclastic metasediments were affected by a contraction-dominated deformation, materialized by a pervasive slaty cleavage. Quartz veins, abundantly present in the slate belt, are used as a proxy for the enhanced permeability. Detailed structural, petrographical, mineralogical and geochemical studies of different quartz-vein occurrences has enabled to reconstruct the evolution of the crustal-scale permeability , as well as to constrain the coupled fluid-pressure and stress-state evolution throughout the orogenic history. Extensive veining on a regional scale seems confined to periods of tectonic stress inversion, both at the onset (compressional stress inversion) and in the final stages (extensional stress inversion) of orogeny. Firstly, compressional stress inversion is expressed by pre-orogenic bedding-normal extension veins, consistently arranged in parallel arrays, followed by early orogenic bedding-parallel hybrid veins. Fluid-inclusion studies demonstrate near-lithostatic to supralithostatic fluid pressures, respectively. Secondly, discordant veins, transecting the pre-existing cleavage fabric, are interpreted to be initiated shortly after the extensional stress inversion, reflecting the late-orogenic extensional destabilisation of the slate belt. Veining again occurred at high fluid pressures. Thus, periods of tectonic stress inversion, characterised by sustained near-lithostatic fluid pressures and low shear stresses, turn out to be key moments of enhanced permeability in mid-crustal, low-permeability environments, guaranteeing fluid-pressure driven flow of internally-derived metamorphic fluids. Syn-orogenic veining, on the other hand, is relatively uncommon in the slate belt. Quartz veins occupy deformation-controlled, low-displacement, structures (e.g. saddle reefs, dilational jogs, boudin necks). During the main stages of orogeny, rather locally enhanced permeability is thus primarily deformation-controlled. Throughout orogeny, intermittent, crustal-scale enhanced permeability is materialized by the different quartz-vein occurrences. Quartz veins occupy low-displacement structures, reflecting brittle (e.g. fault-fracture meshes) or ductile deformation (e.g. folds). Remarkably, the enhanced permeability is highly anisotropic, with primarily a horizontal connectivity, parallel to the intermediate principal stress or the structural grain. Mixed brittle-plastic deformation behaviour is furthermore responsible for maintaining long-lived permeability structures by a steady-state deformation of fluid-filled cavities, ensuring sustained, crustal-scale fluid flow.

Sintubin, M.

2013-12-01

43

Experimental transport of Si, Al and Mg in hydrothermal solutions: an application to vein mineralization during high-pressure, low-temperature metamorphism in the French Alps  

NASA Astrophysics Data System (ADS)

A study of hydrothermal vein mineralization in meta-argillites subjected to high-pressure, low-temperature metamorphism reveals that ferromagnesian (e.g., chlorite) and pure aluminosilicate (e.g., pyrophyllite) mineralization can be correlated with regimes of increasing and decreasing temperature, respectively. An experimental study of the transport of silica, aluminum and magnesium in hydrothermal solutions has been undertaken to simulate variations in the physical conditions during metamorphism and the accompanying mass transport in a closed system. Thermodynamic and kinetic analysis of the experimental results indicates that local equilibrium among aqueous and mineral phases controls the distribution and composition of hydrothermal vein mineralization and that vein mineralogy can be used to infer the sense of variation of pressure and temperature during metamorphism.

Goffé, Bruno; Murphy, William M.; Lagache, Martine

1987-12-01

44

Hydrothermal Alteration and Mineralization Zoning in Iron-Oxide(-Cu-Au) Vein Deposits, near Copiap, Chile  

E-print Network

as a function of structural levels. Two vein systems hosted in La Brea diorite phase of the Copiapó batholith vein formed near the upper contact of the host La Brea diorite. Few IOCG systems have well documented and Sollner, 2006; M.D. Barton et al., unpubl. data). The plutons are broadly dioritic in composition

Barton, Mark D.

45

Experimental transport of Si, Al and Mg in hydrothermal solutions: an application to vein mineralization during high-pressure, low-temperature metamorphism in the French Alps  

Microsoft Academic Search

A study of hydrothermal vein mineralization in meta-argillites subjected to high-pressure, low-temperature metamorphism reveals that ferromagnesian (e.g., chlorite) and pure aluminosilicate (e.g., pyrophyllite) mineralization can be correlated with regimes of increasing and decreasing temperature, respectively. An experimental study of the transport of silica, aluminum and magnesium in hydrothermal solutions has been undertaken to simulate variations in the physical conditions during

Bruno Goffé; William M. Murphy; Martine Lagache

1987-01-01

46

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

47

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

48

From evaporated seawater to uranium-mineralizing brines: Isotopic and trace element study of quartz-dolomite veins in the Athabasca system  

NASA Astrophysics Data System (ADS)

Stable isotope (O, H, C), radiogenic isotope (Sr, Nd) and trace element analyses have been applied to quartz-dolomite veins and their uranium(U)-bearing fluid inclusions associated with Proterozoic unconformity-related UO2 (uraninite) ores in the Athabasca Basin (Canada) in order to trace the evolution of pristine evaporated seawater towards U-mineralizing brines during their migration through sediments and basement rocks. Fluid inclusion data show that quartz and dolomite have precipitated from brines of comparable chemistry (excepted for relatively small amounts of CO2 found in dolomite-hosted fluid inclusions). However, ?18O values of quartz veins (?18O = 11‰ to 18‰) and dolomite veins (?18O = 13‰ to 24‰) clearly indicate isotopic disequilibrium between quartz and dolomite. Hence, it is inferred that this isotopic disequilibrium primarily reflects a decrease in temperature between the quartz stage (˜180 °C) and the dolomite stage (˜120 °C). The ?13C values of CO2 dissolved in dolomite-hosted fluid inclusions (?13C = -30‰ to -4‰) and the ?13C values of dolomite (?13C = -23.5‰ to -3.5‰) indicate that the CO2 dissolved in the mineralizing brines originated from brine-graphite interactions in the basement. The resulting slight increase in the fluid partial pressure of CO2 (pCO2) may have triggered dolomite precipitation instead of quartz. ?18O values of quartz veins and previously published ?18O values of the main alteration minerals around the U-ores (illite, chlorite and tourmaline) show that quartz and alteration minerals were isotopically equilibrated with the same fluid at ˜180 °C. The REE concentrations in dolomite produce PAAS-normalized patterns that show some similarities with that of UO2 and are clearly distinct from that of the other main REE-bearing minerals in these environments (monazite, zircon and aluminum phosphate-sulfate (APS) minerals). The radiogenic isotope compositions of dolomite (87Sr/86Sri = 0.7053 to 0.7161 and ?Nd(t) = -8.8 to -20.3) differ from one deposit to another, reflecting both heterogeneity in the basement geology and variable preservation of the original composition of brines. The previously published 87Sr/86Sri and ?Nd(t) values of UO2 compare with the most evolved dolomites, i.e. dolomites precipitated from brines that exchanged the most with the basement. This reinforces a close genetic link between dolomites and UO2 deposition and implies that UO2 deposition occurred in a cooling system during the transition from quartz to dolomite formation. The ?18O and ?D values of the mineralizing brines (?18O = -1‰ to 8‰ and ?D = -150‰ to -50‰) are considerably shifted from that of their theoretical original values acquired during evaporation of seawater (?18O = ˜-3‰ and ?D = ˜-40‰). The positive ?18O shift is explained by protracted fluid-rock interaction within the basin and basement rocks. The negative ?D shift is attributed to incomplete mixing between the U-mineralizing brines and low ?D water. This low ?D water was likely produced during the abiogenic synthesis of bitumen by Fisher-Tropsch-like reactions involving CO2 derived from brine-graphite interaction in the basement, and radiolytic H2. The resulting low ?D brines have been equilibrated with alteration minerals. This may explain why some alteration minerals yield anomalously low ?D values whose significance has long been debated.

Richard, Antonin; Boulvais, Philippe; Mercadier, Julien; Boiron, Marie-Christine; Cathelineau, Michel; Cuney, Michel; France-Lanord, Christian

2013-07-01

49

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

50

Slip velocity has major impact on the frictional strength and microstructure of quartz-muscovite gouges under hydrothermal conditions  

NASA Astrophysics Data System (ADS)

Previous friction experiments on rock analogue experiments of mixtures of salt and phyllosilicates, demonstrated the possibility of producing mylonitic fault rocks through the simultaneous operation of pressure solution and frictional sliding. This frictional-viscous flow process produces a strong velocity-dependence of friction, with friction values dropping from 0.8 to ~0.2-0.3 over just one order of magnitude decrease in sliding velocity. Here, we present the results of rotary shear experiments on simulated fault gouges of 80 wt% quartz and 20 wt% muscovite. Sliding experiments using a four orders of magnitude range of constant velocities (0.03 - 300 ?m/s) to a displacement of 30 mm were done at 500 °C, 120 MPa effective normal stress and 80 MPa fluid pressure to verify the mechanism at hydrothermal conditions and to link the produced microstructure to the observed strength. At the lowest sliding velocity tested, final friction reached a value of ~0.3, which is lower than that of pure muscovite under similar conditions. With increasing sliding velocity, friction increases, reaching a maximum of ~0.9 at 3 ?m/s after which it decreases mildly to ~0.8 at 300 ?m/s. The bulk microstructure of the sample sheared at 0.03 ?m/s shows an anastomosing foliation of muscovite grain intervened by asymmetrical quartz clasts, with an average grain size of about 20 ?m, slightly lower than the median starting size (~49 ?m). In contrast, the grains of the sample deformed at 300 ?m/s are very small, many of them smaller than distinguishable in the light microscope (i.e. < 1 ?m). In addition, the microstructure is characterized by clear bands of strong uniform extinction in P- and B-shear orientations, possibly indicating a Crystallographic Preferred Orientation. These zones of uniform extinction can be found in all samples and their thickness decreases monotonically with decreasing sliding velocity. The microstructure observed at low velocity, in the frictional-viscous regime, is similar to examples from natural fault rocks (e.g. the Zuccale Fault). The slowest sliding velocity employed here corresponds to a shear strain rate of ~3 * 10-5 s-1, still several orders of magnitude higher than tectonic plate rates. At natural, lower strain rates, the frictional-viscous flow regime, where friction is low, is predicted to be operative down to temperatures as low as 250 °C and possibly even lower for other minerals than quartz. In contrast to the low velocity regime, microstructures similar to those observed here at high velocity, have not been reported for natural fault rocks, implying that either these do not survive exhumation (possibly due to the very fine grain size), get overprinted by later, slow deformation, or are not formed in the first place. The strain rates here are still well below the values reached during seismic slip and are probably not common values in nature, nor will they be long-lived and thus not impose a large shear strain. Dynamic or static grain growth after a transient, faster slip pulse will most likely obliterate any evidence of slip rates fluctuating between aseismic and seismic. Clearly, more hydrothermal experiments aimed at understanding the link between the fault microstructure and its strength and the variation of these with sliding velocity, are needed.

Niemeijer, A. R.; Den Hartog, S.; Spiers, C. J.

2013-12-01

51

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

52

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

SciTech Connect

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

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

2011-08-15

53

The age of Au-Cu-Pb-bearing veins in the poly-orogenic Ubendian Belt (Tanzania): U-Th-total Pb dating of hydrothermally altered monazite  

NASA Astrophysics Data System (ADS)

The age of gold-copper-lead mineralization in the Katuma Block of the Ubendian Belt remains controversial because of the lack of radiometric ages that correlate with the age of tectonothermal events of this poly-orogenic belt. Previous studies reported whole rock and mineral Pb-Pb ages ranging between 1,660 and 720 Ma. In this study, we report U-Th-total Pb ages of monazite from hydrothermally altered metapelites that host the Au-Cu-Pb-bearing veins. Three types of chemically and texturally distinct types of monazite grains or zones of grains were identified: monazite cores, which yielded a metamorphic age of 1,938 ± 11 Ma ( n = 40), corresponding to known ages of a regional metamorphic event, deformation and granitic plutonism in the belt; metamorphic overgrowths that date a subsequent metamorphic event at 1,827 ± 10 Ma ( n = 44) that postdates known eclogite metamorphism (at ca. 1,880 Ma) in the belt; hydrothermally altered poikilitic monazite, formed by dissolution-precipitation processes, representing the third type of monazite, constrain the age of a hydrothermal alteration event at 1,171 ± 17 Ma ( n = 19). This Mesoproterozoic age of the hydrothermal alteration coincides with the first amphibolite grade metamorphism of metasediments in the Wakole Block, which adjoins with a tectonic contact the vein-bearing Katuma Block to the southwest. The obtained distinct monazite ages not only constrain the ages of metamorphic events in the Ubendian Belt, but also provide a link between the metamorphism of the Wakole metasediments and the generation of the hydrothermal fluids responsible for the formation of the gold-copper-lead veins in the Katuma Block.

Kazimoto, Emmanuel Owden; Schenk, Volker; Appel, Peter

2015-01-01

54

Zonation of primary haloes of Atud auriferous quartz vein deposit, Central Eastern Desert of Egypt: A potential exploration model targeting for hidden mesothermal gold deposits  

NASA Astrophysics Data System (ADS)

The Atud gold mine located in the Neoproterozoic diorite and metagabbro of the Central Eastern Desert of Egypt has been initially excavated during Pharaonic times. Between 1953 and 1969, the Egyptian Geological Survey and Mining Authority performed underground prospection in the auriferous quartz vein and metasomatic alteration zones in the main Atud area, estimating a principal gold lode of 19,000 tones (16.28 g/ton), and 1600 tons of damp (1.24 g/ton). Yet the potentiality of the deposit has not been exhausted. However, for exploration of hidden ore, quantitative characterization using trace elements zoning of mineralization haloes with 280 samples from surface and three underground mining levels is applied. This was through multivariate statistical analysis (Factor analysis) of 11 selected trace elements. Axial (vertical) extents of primary haloes above and beneath gently dipping orebody are also visualized to interpret the level of erosion, determine the direction of mineralizing solutions as well as to examine whether the hidden orebody is promising at the Atud mine. Axial zones of primary dispersion aureoles of trace elements are: Ag, As, S and U around the auriferous quartz veins; Cu, and Pb in the surface horizons; and Zn, Ni, Co, and U along the lower margin of mineralization zone. Gold contents in bedrock and quartz vein samples from level-42M are the highest (5.7 and 40.3 ppm, respectively). In the transverse (lateral) direction, the maximum relative accumulation of Au and Zn occurs at the Northern Shaft; Pb, Cu, As, and U at the Main Shaft; and Ag, S, Co, and Ni at the Southern Shaft. The estimated axial zonation sequence of indicator elements using the variability index is Pb ? Cu ? Ag ? Au ? As ? S ? Ni ? Co ? U ? Zn. According to this zonation, an index such as (Pb × Cu)D/(U × Zn)D can be a significant for predicting the Au potentiality at a particular depth. In addition, the Pb/U zonality index is an appropriate indicator for the degree of erosion at the Atud gold mine. The degree of surficial zonality of the mineralization as deduced from geochemical maps and the level of erosion of the geochemical anomalies as well as the decreasing of gold content with depth recorded throughout the different underground mine workings make it necessary for the prospection model to evaluate the drainage patterns dissecting the mineralized zone. The application of R-mode factor analysis estimated seven statistical factors, and factor score maps are portrayed. Factors 1 (Ag, Au, As, Co, S, U and Zn) and 2 (Zn, U, Co and S) significantly reflect the Au-mineralization (ore-controlled), and their score maps enable a more precise delineation of auriferous quartz veins and the area which may contain primary gold mineralization. The other factors reveal the distribution of Cu- and Pb-bearing minerals (supergene alteration factors), and Ba and Ni in the host diorite (lithologically-controlled). These are consistent with the calculated maximum relative accumulation of trace elements, proposing a potential model of exploration based on integrating underground geochemical data from old gold mine workings with spatial information from R-mode factor score maps.

Harraz, Hassan Z.; Hamdy, Mohamed M.

2015-01-01

55

Superdense CO2 inclusions in Cretaceous quartz stibnite veins hosted in low-grade Variscan basement of the Western Carpathians, Slovakia  

NASA Astrophysics Data System (ADS)

CO2 inclusions with density up to 1,197 kg m-3 occur in quartz stibnite veins hosted in the low-grade Palaeozoic basement of the Gemericum tectonic unit in the Western Carpathians. Raman microanalysis corroborated CO2 as dominant gas species accompanied by small amounts of nitrogen (<7.3 mol%) and methane (<2.5 mol%). The superdense CO2 phase exsolved from an aqueous bulk fluid at temperatures of 183 237°C and pressures between 1.6 and 3.5 kbar, possibly up to 4.5 kbar. Low thermal gradients (˜12 13°C km-1) and the CO2 CH4 N2 fluid composition rule out a genetic link with the subjacent Permian granites and indicate an external, either metamorphogenic (oxidation of siderite, dedolomitization) or lower crustal/mantle, source of the ore-forming fluids. According to microprobe U Pb Th dating of monazite, the stibnite-bearing veins formed during early Cretaceous thrusting of the Gemeric basement over the adjacent Veporic unit. The 15- to 18-km depth of burial estimated from the fluid inclusion trapping PT parameters indicates a 8- to 11-km-thick Upper Palaeozoic Jurassic accretionary complex overlying the Gemeric basement and its Permo-Triassic autochthonous cover.

Urban, Márian; Thomas, Rainer; Hurai, Vratislav; Koneèný, Patrik; Chovan, Martin

2006-03-01

56

Features of ore formation in the gold-quartz Sovinoye deposit (Northern Chukotka)  

NASA Astrophysics Data System (ADS)

The results of studying fluid inclusions in the quartz of ore body no. 6 from the Sovinoye deposit developed by the underground mine workings at a depth of 80 m from the surface are considered. The investigations showed that the ore in the Sovinoye deposit was formed at average temperatures during several stages from weakly concentrated hydrotherms saturated with Na, Cl, Mg, and Fe ions. Such ore-forming conditions are typical of mezothermal gold-quartz veined deposits in the terrigeneous quartz-carbonate strata. The results of FI study by modern methods do not contradict the previously offered metamorphogenic-magmatogenic model of ore formation for the Sovinoye deposit.

Kolova, E. E.; Volkov, A. V.; Prokof'ev, V. Yu.; Sidorov, A. A.

2014-12-01

57

The Ixtacamaxtitlán kaolinite deposit and sinter (Puebla State, Mexico): a magmatic-hydrothermal system telescoped by a shallow paleoaquifer  

Microsoft Academic Search

The Ixtacamaxtitlan hydrothermal deposit is made up of a succession, from bottom to top, of: (1) a porphyritic subvolcanic body, crosscut by quartz veins, and a stockwork with subordinate sulfides (pyrite and chalcopyrite), showing propylitic alteration haloes overprinting a previous potassic alteration event (biotitization); (2) an overly- ing, kaolinized lithic-rich rhyolitic tuff; and (3) a layered opal deposit with preserved

J. Tritlla; A. Camprubí; J. M. Morales-Ramírez; A. Iriondo; R. Corona-Esquivel; E. González-Partida; G. Levresse; A. Carrillo-Chávez

2004-01-01

58

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

59

Controls to hydrothermal gold mineralization in the Witwatersberg Goldfield; situated in the floor to the south of the Bushveld Complex, South Africa  

Microsoft Academic Search

An exploration programme over the Blaauwbank group of gold deposits in the Witwatersberg Goldfield, which lies to the south and in the footwall of the Bushveld Complex, South Africa, has shown that these deposits possess many similarities and some differences to turbidite-hosted gold deposits.The dominant control to this hydrothermal mineralization is structural, with the associated quartz veins being localized along

A. M. Killick; R. Scheepers

2005-01-01

60

Time scales of porphyry Cu deposit formation: insights from titanium diffusion in quartz  

USGS Publications Warehouse

Porphyry dikes and hydrothermal veins from the porphyry Cu-Mo deposit at Butte, Montana, contain multiple generations of quartz that are distinct in scanning electron microscope-cathodoluminescence (SEM-CL) images and in Ti concentrations. A comparison of microprobe trace element profiles and maps to SEM-CL images shows that the concentration of Ti in quartz correlates positively with CL brightness but Al, K, and Fe do not. After calibrating CL brightness in relation to Ti concentration, we use the brightness gradient between different quartz generations as a proxy for Ti gradients that we model to determine time scales of quartz formation and cooling. Model results indicate that time scales of porphyry magma residence are ~1,000s of years and time scales from porphyry quartz phenocryst rim formation to porphyry dike injection and cooling are ~10s of years. Time scales for the formation and cooling of various generations of hydrothermal vein quartz range from 10s to 10,000s of years. These time scales are considerably shorter than the ~0.6 m.y. overall time frame for each porphyry-style mineralization pulse determined from isotopic studies at Butte, Montana. Simple heat conduction models provide a temporal reference point to compare chemical diffusion time scales, and we find that they support short dike and vein formation time scales. We interpret these relatively short time scales to indicate that the Butte porphyry deposit formed by short-lived episodes of hydrofracturing, dike injection, and vein formation, each with discrete thermal pulses, which repeated over the ~3 m.y. generation of the deposit.

Mercer, Celestine N.; Reed, Mark H.; Mercer, Cameron M.

2015-01-01

61

Rb-sr dating of epithermal vein mineralization stages in the eastern Harz Mountains (Germany) by paleomixing lines  

NASA Astrophysics Data System (ADS)

A method is evaluated that enables the dating of binary isotopic paleomixing in hydrothermal alteration assemblages by iterative reconstruction and regression of corresponding two-component mixing lines from conventional Rb-Sr data. The model has been applied to illite-bearing granulometric fractions of hydrothermally altered sedimentary rocks associated with epithermal vein mineralization in the eastern Harz Mountains, Germany. These veins are characterized by a principal quartz-sulfide stage containing quartz, base metal sulfides, and siderite and a subsequent dominant calcite-fluorite-quartz stage. Rb-Sr analyses were performed on untreated granulometric fractions, HCl-treated residues, corresponding HCl leachates, and cogenetic vein minerals obtained from two silicified rock samples related to the quartz-sulfide and the calcite-fluorite-quartz mineralization, respectively. Neither the untreated nor the HCl-leached fractions of these rock samples yield statistically robust and geochronologically meaningful isochrons. When applying the binary mixing model, however, two well-defined paleomixing lines can be reconstructed for the HCl-treated fractions of the rock samples and associated vein minerals at model ages of 226 ± 1 Ma (quartz-sulfide alteration) and 209 ± 2 Ma (calcite-fluorite-quartz alteration). We examine the significance and reliability of these model ages and the corresponding paleomixing lines by means of statistical and geological criteria and discuss the effects of leaching experiments performed on the granulometric fractions using 1 N HCl as well as the nature and origin of the components dissolved in the acid leachates. Our results suggest that the mixing model provides a successful dating concept for isotopic disequilibrium processes during low-temperature hydrothermal events that produce binary mixtures among newly formed alteration phases.

Schneider, Jens; Haack, Udo; Stedingk, Klaus

2003-05-01

62

Involvement of Overpressured Fluids in the Nucleation of High-Angle Reverse Ruptures: Evidence from Fault-Hosted Hydrothermal Vein Systems  

NASA Astrophysics Data System (ADS)

Dips of near-pure reverse-slip M>5.5 ruptures are bimodally distributed with a dominant peak at ? = 30±5°, a subordinate peak at ? = 50±5°, and no ruptures with ? > 60°. Assuming horizontal trajectories for maximum compressive stress (?1), the dominant peak corresponds to optimally oriented faults with Byerlee friction coefficients (?s = 0.6) for which frictional lock-up is expected at ? = 60°. In recent years, several compressional inversion earthquakes in the upper crust of Honshu, Japan (e.g. the 2003 Mw6.5 Northern Miyagi, the 2004 Mw6.6 Mid-Niigata Prefecture, and the 2007 Mw6.7 Noto-Hanto sequences) have involved high-angle reverse-slip with dips of 50-60° on inherited normal faults along the margins of Miocene extensional basins. Rupturing during these earthquakes thus took place on faults that were poorly oriented for frictional reactivation and close to lock-up. Frictional mechanics suggests that reshear of the steep reverse faults (in preference to the formation of new favorably oriented thrusts within intact crust) is allowable only under near- lithostatic fluid pressures with Pf approaching ?3, and that reshear of severely misoriented faults (? > c.60°) requires Pf > ?3 (the hydrofracture condition). Notably, the 2004 Mid-Niigata sequence involved a criss-crossing network of high-angle and low-angle reverse ruptures, suggesting competition between reshear of steep inherited faults and the formation of more favorably oriented thrusts. A range of geophysical evidence, including local bright S-wave reflectors, indicates strong fluid overpressuring in the focal regions of these earthquakes. Mesozonal Au-quartz vein systems hosted in reverse faults exhumed from depths corresponding to the lower half of the seismogenic zone (P ~ 2-4 kbar; T ~ 250-400°C) occur throughout the geological record and provide additional evidence for the involvement of strongly overpressured fluids in reverse fault rupturing. Incrementally deposited fault-infill veins up to meters in thickness may extend for 1-2 km down-dip with comparable dimensions along-strike. For steeper faults, especially, these fault-veins are commonly in mutual cross-cutting relationships with arrays of flat-lying extension veins that are the product of hydraulic extension fracturing. Individual extension veins extend laterally for tens to hundreds of metres, tapering away from the reverse faults, but flat vein arays may extend over greater distances. The fault-related vein systems have been interpreted as the product of cyclical fault-valve action whereby failure on severely misoriented reverse faults (oriented at > 55-60° to ?1) is triggered by the accumulation of overpressure to near-lithostatic values, the ensuing fault rupture then allowing postfailure discharge upwards along the fault. Fluid inclusion studies support the cycling of fluid-pressure between ~lithostatic prefailure and sublithostatic postfailure values. The flat-lying hydrofracture arrays provide an explanation for the bright-spot reflectors observed around the base of the seismogenic zone, while the fault-vein complex may represent rupture nucleation sites on steep reverse faults where failure is predominantly fluid-driven. Under such circumstances, near-total shear stress relief may accompany rupture. Net fluid volumes involved in the formation of these vein systems may be of the order of 1 km3 per kilometer strike-length, but the fluid volume involved in each fault-valve cycle is likely to be 2-4 orders of magnitude lower.

Sibson, R. H.

2007-12-01

63

Field occurrence and lithology of Archean hydrothermal systems in the 3.2Ga Dixon Island Formation, Western Australia  

NASA Astrophysics Data System (ADS)

Stratigraphic transition of black chert to iron-rich sedimentary rocks above volcanic sequences with hydrothermal systems is common and characteristic feature of Archean greenstone belts. The 3.2 Ga Dixon Island Formation, exposed along the northern coast of Dixon Island located in the coastal Pilbara terrane, Western Australia, is one of such units and the focus of our study. We introduce field occurrence and lithology of the Dixon Island Formation that preserves features of paleohydrohermal environment in the Mesoarchean ocean. The Dixon Island Formation is composed of the following three members (in ascending order): Komatiite-Rhyolite Tuff, Black Chert, and Varicolored Chert members (Kiyokawa and Taira, 1998). Here we focus on the Komatiite-Rholite Tuff member. It preserves two cycles of highly altered komatiite lavas and well-stratified rhyolite tuff. Komatiite lavas include dendritic crystals of chrome spinel and ghosts of spinifex, euhedral and sheet-like olivines and pyroxenes. These rocks are now composed of granular microcrystalline quartz with chromian muscovite, chrome spinel and chrorite that formed by intense silicification. Its upper part contains hydrothermal veining and alteration (i.e., many vein swarms composed of veins of quartz and organic carbon-rich black chert). Most black chert veins intrude vertically into overlying layers, and contain barite, pyrite, monazite and clay minerals which were least affected by silicificatio. Based on the cross-cutting relationship seen in the outcrops, we recognized two generations of black chert veins (type 1 and type 2 veins; Kiyokawa et al., 2006). Type 1 veins are mainly composed of carbonaceous peloids in a microcrystalline quartz matrix. Euhedral and xenocrystic tourmaline are found only in Type1 veins. Type 2 veins are organic carbon-poor and contain fragments of black chert and siliceous volcanic breccia (Kiyokawa et al., 2006). Intense silicification of komatiitic volcaniclastics and lava, enriched in Si and K and depleted in Mg, occurred earlier than the formation of black chert veins and probably during sedimentation of the overlying Black Chert member. Petrographycally, tourmaline in Type1 veins formed by hydrothermal processes and can be used to infer physicochemical conditions of the hydrothermal activity. Fragmentation of black chert and volcanic rocks within Type 2 veins was probably due to high pressure caused by hydrothermal activity.

Aihara, Y.; Kiyokawa, S.; Ito, T.; Ikehara, M.; Yamaguchi, K. E.; Horie, K.; Sakamoto, R.; Miki, T.

2013-12-01

64

Melt inclusions in veins: linking magmas and porphyry Cu deposits.  

PubMed

At a porphyry copper-gold deposit in Bajo de la Alumbrera, Argentina, silicate-melt inclusions coexist with hypersaline liquid- and vapor-rich inclusions in the earliest magmatic-hydrothermal quartz veins. Copper concentrations of the hypersaline liquid and vapor inclusions reached maxima of 10.0 weight % (wt %) and 4.5 wt %, respectively. These unusually copper-rich inclusions are considered to be the most primitive ore fluid found thus far. Their preservation with coexisting melt allows for the direct quantification of important oreforming processes, including determination of bulk partition coefficients of metals from magma into ore-forming magmatic volatile phases. PMID:14684818

Harris, Anthony C; Kamenetsky, Vadim S; White, Noel C; van Achterbergh, Esmé; Ryan, Chris G

2003-12-19

65

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

66

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

67

Recent experiments in a silver lined autoclave [quartz growth  

Microsoft Academic Search

A research program to develop hydrothermal quartz culturing equipment and processes capable of economically producing quartz is discussed. The initial phase covers the production of the highest quality quartz, given state-of-the-art sodium carbonate process equipment. The second phase seeks to establish definitive relationships between process variables and quartz quality. Given the results obtained in phase I and II, the third

R. Irvine; J. Foise; E. Leeson; G. Johnson

1988-01-01

68

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

USGS Publications Warehouse

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

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

2007-01-01

69

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

70

Impact-generated Hydrothermal Activity at the Chicxulub Crater  

NASA Astrophysics Data System (ADS)

Borehole samples recovered from PEMEX exploration boreholes and an ICDP scientific borehole indicate the Chicxulub impact event generated hydrothermal alteration throughout a large volume of the Maya Block beneath the crater floor and extending across the bulk of the ~180 km diameter crater. The first indications of hydrothermal alteration were observed in the crater discovery samples from the Yucatan-6 borehole and manifest itself in the form of anhydrite and quartz veins. Continuous core from the Yaxcopoil-1 borehole reveal a more complex and temporally extensive alteration sequence: following a brief period at high temperatures, impact- melt-bearing polymict breccias and a thin, underlying unit of impact melt were subjected to metasomatism, producing alkali feldspar, sphene, apatite, and magnetite. As the system continued to cool, smectite-series phyllosilicates appeared. A saline solution was involved. Stable isotopes suggest the fluid was dominated by a basinal brine created mostly from existing groundwater of the Yucatan Peninsula, although contributions from down-welling water also occurred in some parts of the system. Numerical modeling of the hydrothermal system suggests circulation occurred for 1.5 to 2.3 Myr, depending on the permeability of the system. Our understanding of the hydrothermal system, however, is still crude. Additional core recovery projects, particularly into the central melt sheet, are needed to better evaluate the extent and duration of hydrothermal alteration.

Kring, D. A.; Zurcher, L.; Abramov, O.

2007-05-01

71

The Benedikt hydrothermal system (north-eastern Slovenia)  

NASA Astrophysics Data System (ADS)

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

Kralj, Peter; Eichinger, Lorenz; Kralj, Polona

2009-10-01

72

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

73

Carbon isotope studies of auriferous quartz carbonate veins from two orogenic gold deposits from the Neoarchean Chitradurga schist belt, Dharwar craton, India: Evidence for mantle/magmatic source of auriferous fluid  

NASA Astrophysics Data System (ADS)

Carbon and oxygen isotopic compositions of carbonates from auriferous quartz carbonate veins (QCVs) of two orogenic gold deposits - Ajjanahalli and Guddadarangavvana Halli (G.R. Halli) - from the Neoarchean Chitradurga schist belt of the Dharwar craton, southern India are examined to understand the origin of the mineralizing fluids. The average carbonate carbon (?13Cpdb) and oxygen (?18Osmow) isotope compositions of QCVs of Ajjanahalli are -5.5 ± 1.3‰ and 14.1 ± 2.7‰, respectively. The same ratios for the QCVs of G.R. Halli are -6.2 ± 1.9‰ and 14.1 ± 0.5‰. The corresponding average fluid ?13C and ?18O compositions are -5.81 ± 1.14‰, 13.78 ± 5.1‰ for Ajjanahalli and -4.64 ± 0.7‰, -6.50 ± 0.6‰ for G.R. Halli. The ?13Cpdb of syn-sedimentary carbonates of BIF of Ajjanahalli (-1.8 ± 0.1‰), carbonated metabasalts of Ajjanahalli (-1.4‰) and G.R. Halli (-1.3‰) fall in the compositional range of marine carbonates (0 ± 2‰). As dissolution/decarbonation reactions during metamorphism of pre-existing carbonate/carbonated rocks produce CO2 with ?13C values similar to or more enriched than parent rock, the carbonate or fluid ?13C ratios of the QCVs (which fall in the compositional range of mantle/magmatic derived CO2 or carbonates) obtained in this work cannot be the result of metamorphism. It is proposed that gold mineralizing fluids were derived from juvenile magmatic melts and were channeled through crustal scale shear zones to give rise to the gold deposits.

Sarangi, S.; Sarkar, A.; Srinivasan, R.; Patel, S. C.

2012-06-01

74

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

75

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

76

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

77

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

78

Lithogeochemistry and fluid inclusions of an Au-Ag vein deposit in a granodiorite intrusive  

SciTech Connect

Forty-eight samples of altered and unaltered rocks and quartz veins from the Acme mine in northeast Washington, an Au-Ag vein deposit in a granodiorite intrusive, have been analyzed for SiO/sub 2/, Al/sub 2/O/sub 3/, Fe/sub 2/O/sub 3/, Feo, MgO, CaO, Na/sub 2/O, K/sub 2/O, TiO/sub 2/, MnO, P/sub 2/O/sub 5/, H/sub 2/O, CO/sub 2/, Ag, Au, Ba, Cu, Pb, Rb, Sr, Tl, and Zn. A comparison of major and trace elements shows that the altered granodiorite is enriched in SiO/sub 2/, Fe/sub 2/O/sub 3/, K/sub 2/O, Ag, Au, Ba, Cu, Pb, Rb, Tl, and Zn and depleted in Al/sub 2/O/sub 3/, FeO, MgO, CaO, Na/sub 2/O, TiO/sub 2/, MnO, P/sub 2/O/sub 5/, and Sr. The average contents of Au in unaltered and altered granodiorite and quartz veins are 9 ppb. 270 ppb and 1020 ppb respectively. The average Ba/Tl ratio in the altered samples decrease and average Rb/Sr and Tl/Sr ratios increase. K, Rb, and Tl are enriched in the altered granodiorite by factors of 1.5, 1.6, and 1.4 respectively. Tl is not enriched relative to Rb and K in the altered samples due to the high temperature of the deposit. The Ba/Tl, K/Tl and K/Rb ratios do not show complete separation of altered from unaltered samples. However, the Ba/Tl and K/Tl ratios in the quartz vein are significantly lower than the unaltered and altered granodiorite. This is due to the enrichment of Tl over K and Rb in the quartz veins. The Rb/Sr and Tl/Sr ratios are higher in the altered granodiorite and quartz veins compared to unaltered samples. The enrichment of Tl and presence of low Ba/Tl and high Rb/Sr and Tl/Sr ratios in a granodiorite indicate that the rocks are hydrothermally altered and represent a possible Au-Ag target.

Hahn, R.; Ikramuddin, M.

1985-01-01

79

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

80

Mineralogy and stable isotope geochemistry of hydrothermally altered oceanic rocks  

NASA Astrophysics Data System (ADS)

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

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

1982-02-01

81

Shock metamorphism of deformed quartz  

NASA Technical Reports Server (NTRS)

The effect produced by shock loading (to peak pressures of 12 and 24) on deformed synthetic quartz containing a dislocation and abundant bubbles and small inclusions was investigated, and the relationships between preexisting dislocation density shock lamellae in the target material were examined. The resultant material was found to be inhomogeneously deformed and extremely fractured. Results of TEM examinations indicate that no change in dislocation density was caused by shock loading except in regions containing shock lamellae, where the dislocation density was lowered. The shock-induced defects tend to nucleate on and be controlled by preexisting stress concentrators; shock lamellae, glassy veins, and most curviplanar defects form in tension, presumably during release. An extremely mobile silica fluid is formed and injected into fractures during release, which forcibly removes crystalline fragments from vein walls. It is concluded that shock deformation in quartz is dominated by fracture and melting.

Gratz, Andrew J.; Christie, John; Tyburczy, James; Ahrens, Thomas; Pongratz, Peter

1988-01-01

82

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

83

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

84

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

85

Timing of porphyry (Cu-Mo) and base metal (Zn-Pb-Ag-Cu) mineralisation in a magmatic-hydrothermal system—Morococha district, Peru  

NASA Astrophysics Data System (ADS)

The Morococha district in central Peru is characterised by economically important Cordilleran polymetallic (Zn-Pb-Ag-Cu) vein and replacement bodies and the large Toromocho porphyry Cu-Mo deposit in its centre. U-Pb, Re-Os, and 40Ar/39Ar geochronology data for various porphyry-related hydrothermal mineralisation styles record a 3.5-Ma multi-stage history of magmatic-hydrothermal activity in the district. In the late Miocene, three individual magmatic-hydrothermal centres were active: the Codiciada, Toromocho, and Ticlio centres, each separated in time and space. The Codiciada centre is the oldest magmatic-hydrothermal system in the district and consists of a composite porphyry stock associated with anhydrous skarn and quartz-molybdenite veins. The hydrothermal events are recorded by a titanite U-Pb age at 9.3 ± 0.2 Ma and a molybdenite Re-Os age at 9.26 ± 0.03 Ma. These ages are indistinguishable from zircon U-Pb ages for porphyry intrusions of the composite stock and indicate a time span of 0.2 Ma for magmatic-hydrothermal activity. The small Ticlio magmatic-hydrothermal centre in the west of the district has a maximum duration of 0.3 Ma, ranging from porphyry emplacement to porphyry mineralisation at 8.04 ± 0.14 Ma (40Ar/39Ar muscovite cooling age). The Toromocho magmatic-hydrothermal centre has a minimum of five recorded porphyry intrusions that span a total of 1.3 Ma and is responsible for the formation of the giant Toromocho Cu-Mo deposit. At least two hydrothermal pulses are identified. Post-dating a first pulse of molybdenite mineralisation, wide-spread hydrous skarn covers an area of over 6 km2 and is recorded by five 40Ar/39Ar cooling ages at 7.2-6.8 Ma. These ages mark the end of the slowly cooling and long-lived Toromocho magmatic-hydrothermal centre soon after last magmatic activity at 7.26 ± 0.02 Ma. District-wide (50 km2) Cordilleran base metal vein and replacement bodies post-date the youngest recorded porphyry mineralisation event at Toromocho by more than 0.5 Ma. Polymetallic veins (5.78 ± 0.10 and 5.72 ± 0.18 Ma; 40Ar/39Ar ages) and the Manto Italia polymetallic replacement bodies (6.23 ± 0.12 and 6.0 ± 0.2 Ma; 40Ar/39Ar ages) are interpreted to have been formed by a single hydrothermal pulse. Hydrothermal activity ceased after the formation of the base metal vein and replacement bodies. Overlapping monazite U-Pb (8.26 ± 0.18 Ma) and muscovite 40Ar/39Ar ages (8.1 ± 0.5 Ma) from the early base metal stage of one Cordilleran vein sample in the Sulfurosa area provide evidence that a discrete hydrothermal pulse was responsible for polymetallic vein formation 2.6 Ma prior to the district-wide polymetallic veins. These ages pre-date those of Toromocho porphyry Cu-Mo formation and show that Zn-Pb-Ag-Cu mineralisation formed during several discrete magmatic-hydrothermal pulses in the same district.

Catchpole, Honza; Kouzmanov, Kalin; Bendezú, Aldo; Ovtcharova, Maria; Spikings, Richard; Stein, Holly; Fontboté, Lluís

2015-02-01

86

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

SciTech Connect

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

Cummings, M.L.; Bull, M.K. (Portland State Univ., Oregon (USA)); Pollock, J.M. (Reed Coll., Portland, OR (USA)); Thompson, G.D. (Pioneer Metals Corp., Ruidoso, NM (USA))

1990-11-10

87

Vein Problems Related to Varicose Veins  

MedlinePLUS

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

88

Fluid inclusions from the Jinchang Cu-Au deposit, Heilongjiang Province, NE China: Genetic style and magmatic-hydrothermal evolution  

NASA Astrophysics Data System (ADS)

The Jinchang Cu-Au deposit is located in the easternmost part of the Central Asian Orogenic Belt (CAOB). The mineralization here is associated with Cretaceous porphyritic intrusions of ca. 120-110 Ma and is mainly hosted within intensely altered Mesozoic granites, breccia pipes, ringed and radial faults. The gold ores are disseminated in the wall rock, and also occur as massive auriferous quartz-sulfide veins in fractures and breccias. Fluid inclusion data from breccias, chalcopyrite-quartz vein, and pyrite-quartz vein display homogenization temperatures in the range of 200 to >550 °C and the fluids show variable salinity in the range of 0-58 wt.% (NaCl equiv.). The halite absent fluid inclusions shows a slight increase in salinity with a sharp decrease in temperature. We interpret that the high-salinity brine and low salinity vapor- or aqueous-rich fluids from ores represent fluid unmixing from magma. The fluid inclusion data from Jinchang demonstrate that the main mineralization took place at temperatures from 480 °C to 200 °C, and evolved from high to low salinities. Geology and fluid inclusion data suggest that the Jinchang deposit is an oxidized intrusion-related Cu-Au deposit. The voluminous hydrothermal magnetite formed during high temperature potassic alteration of wall rocks in this ore deposit can be used as a potential prospecting tool.

Zhang, Hua-Dong; Zhang, Hua-Feng; Santosh, M.; Li, Sheng-Rong

2014-03-01

89

The interplay of evolved seawater and magmatic-hydrothermal fluids in the 3.24 Ga panorama volcanic-hosted massive sulfide hydrothermal system, North Pilbara Craton, Western Australia  

USGS Publications Warehouse

The ~3240 Ma Panorama volcanic-hosted massive sulfide (VHMS) district is unusual for its high degree of exposure and low degree of postdepositional modification. In addition to typical seafloor VHMS deposits, this district contains greisen- and vein-hosted Mo-Cu-Zn-Sn mineral occurrences that are contemporaneous with VHMS orebodies and are hosted by the Strelley granite complex, which also drove VHMS circulation. Hence the Panorama district is a natural laboratory to investigate the role of magmatic-hydrothermal fluids in VHMS hydrothermal systems. Regional and proximal high-temperature alteration zones in volcanic rocks underlying the VHMS deposits are dominated by chlorite-quartz ± albite assemblages, with lesser low-temperature sericite-quartz ± K-feldspar assemblages. These assemblages are typical of VHMS hydrothermal systems. In contrast, the alteration assemblages associated with granite-hosted greisens and veins include quartz-topaz-muscovite-fluorite and quartz-muscovite (sericite)-chlorite-ankerite. These vein systems generally do not extend into the overlying volcanic pile. Fluid inclusion and stable isotope studies suggest that the greisens were produced by high-temperature (~590°C), high-salinity (38–56 wt % NaCl equiv) fluids with high densities (>1.3 g/cm3) and high ?18O (9.3 ± 0.6‰). These fluids are compatible with the measured characteristics of magmatic fluids evolved from the Strelley granite complex. In contrast, fluids in the volcanic pile (including the VHMS ore-forming fluids) were of lower temperature (90°–270°C), lower salinity (5.0–11.2 wt % NaCl equiv), with lower densities (0.88–1.01 g/cm3) and lower ?18O (?0.8 ± 2.6‰). These fluids are compatible with evolved Paleoarchean seawater. Fluids that formed the quartz-chalcopyrite-sphalerite-cassiterite veins, which are present within the granite complex near the contact with the volcanic pile, were intermediate in temperature and isotopic composition between the greisen and volcanic pile fluids (T = 240°–315°C; ?18O = 4.3 ± 1.5‰) and are interpreted to indicate mixing between the two end-member fluids. Evidence of mixing between evolved seawater and magmatic-hydrothermal fluid within the granite complex, together with the lack of evidence for a magmatic component in fluids from the volcanic pile, suggest partitioning of magmatic-hydrothermal from evolved seawater hydrothermal systems in the Panorama VHMS system. This separation is interpreted to result from either the swamping of a relatively small magmatic-hydro-thermal system by evolved seawater or density contrasts precluding movement of magmatic-hydrothermal fluids into the volcanic pile. Variability in the salinity of fluids in the volcanic pile, combined with evidence for mixing of low- and high-salinity fluids in the massive sulfide lens, is interpreted to indicate that phase separation occurred within the Panorama hydrothermal system. Although we consider this phase separation to have most likely occurred at depth within the system, as has been documented in modern VHMS systems, the data do not allow the location of the inferred phase separation to be determined.

Drieberg, Susan L.; Hagemann, Steffen G.; Huston, David L.; Landis, Gary; Ryan, Chris G.; Van Achterbergh, Esmé; Vennemann, Torsten

2013-01-01

90

Fluid-inclusion microthermometry and the Zr-in-rutile thermometer for hydrothermal rutile  

NASA Astrophysics Data System (ADS)

The Zr-in-rutile thermometer is well established for the determination of metamorphic temperatures, particularly in high-grade metamorphic terrains, and for sedimentary provenance studies. The robustness of the rutile thermometry has not been tested on hydrothermal systems. Unlike quartz, a common hydrothermal mineral with abundant fluid inclusions, it is difficult to find fluid inclusions in rutile that are suitable for fluid-inclusion microthermometry. Here, we report fluid-inclusion microthermometric measurements in rutile from the auriferous quartz-kaolinite-hematite vein that typifies the gold deposit of Mil Oitavas in the southern Serra do Espinhaço, Minas Gerais, Brazil. Primary fluid inclusions in the rutile record moderately saline (10-12 wt% NaCl equivalent), aqueous-carbonic fluids with a total homogenization temperature of ~250 °C, which were likely trapped at about 300 °C and 2.0 kbar. This temperature is approximately 200 °C lower than that predicted by the Zr-in-rutile thermometer. For hydrothermal conditions of relatively low temperature, direct measurements of homogenization temperatures in rutile-hosted fluid inclusions should be preferred to the Zr-in-rutile thermometer.

Cabral, Alexandre Raphael; Rios, Francisco Javier; de Oliveira, Lucilia Aparecida Ramos; de Abreu, Francisco Robério; Lehmann, Bernd; Zack, Thomas; Laufek, František

2015-03-01

91

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

92

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

93

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

Microsoft Academic Search

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

H. Lowers; B. Rusk; A. Koenig

2007-01-01

94

Varicose vein stripping  

MedlinePLUS

Vein stripping with ligation, avulsion, or ablation; vein ligation and stripping; vein surgery ... Surgical vein stripping reduces pain and improves the appearance of your leg. Rarely, vein stripping causes scars. Mild leg ...

95

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

96

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

USGS Publications Warehouse

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

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

2002-01-01

97

Sequence of Late Jurassic-Early Cretaceous magmatic-hydrothermal events in the Xiong'ershan region, Central China: An overview with new zircon U-Pb geochronology data on quartz porphyries  

NASA Astrophysics Data System (ADS)

Recent investigations have revealed several large Au and Mo deposits in the Xiong'ershan region, Central China. Most quartz porphyries associated with the mineralization occur as dikes and apophyses, or as rubbles cemented in mineralized breccia pipes. Three types of quartz porphyries were sampled from the Leimengou Mo deposit, the Qiyugou Au deposit, and the Niutougou Au deposit. LA-ICP-MS zircon U-Pb analysis was performed in zircons from two quartz porphyries; the results yielded ages of 125.4 ± 0.77 Ma for Leimengou Mo deposit and 150.1 ± 1.1 Ma for Qiyugou Au deposit. The magma source of Leimengou quartz porphyry is similar to that of the mineralized cementing material in breccia pipes of the Qiyugou Au deposit, whereas the magma source of Qiyugou quartz porphyry is the same as that of quartz porphyries in Niutougou Au deposit. Based on the new U-Pb isotopic ages of granitic plutons reported in this study, together with the age data in the literature, we identify distinct magmatic pulses in the Xiong'ershan region at ca.160, 150, 143, 133, 125, and 115 Ma during the Late Jurassic-Early Cretaceous. The ages of Au and Mo mineralization coincide with the thermal events at about 115, 125, 133, and 143 Ma are considered to be co-eval with granitic magmatism. No mineralization ages of 150 and 160 Ma thermal events have been previously reported. Our study demonstrates Late Jurassic-Early Cretaceous multiple magmatic pulses and mineralization in the Xiong'ershan region.

Deng, Jun; Gong, Qingjie; Wang, Changming; Carranza, Emmanuel John M.; Santosh, M.

2014-01-01

98

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

USGS Publications Warehouse

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

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

1991-01-01

99

Varicose Veins and Other Vein Disorders  

MedlinePLUS

... the skin’s surface. Varicose veins are usually dark purple or blue in color, and may look “ropey” or twisted. Smaller varicose veins may be thinner and red rather than purple and swollen; these are called “spider veins.” Other ...

100

Deep Vein Thrombosis  

MedlinePLUS

MENU Return to Web version Deep Vein Thrombosis Overview What is deep vein thrombosis? Deep vein thrombosis (also called DVT) is a blood clot in a vein deep inside your body. These clots usually occur in ...

101

Quartz pseudomorphs after coesite  

Microsoft Academic Search

Coesite has recently been described as a primary phase in a mantle-derived kyanite eclogite from the Roberts-Victor kimberlite, South Africa. An additional specimen from the same locality contains large polycrystalline aggregates of quartz, resembling the quartz rims on the coesite grains in the first specimen. The characteristic textures of these quartz pseudomorphs after coesite are described to aid in the

1977-01-01

102

Quartz pseudomorphs after coesite  

Microsoft Academic Search

Coesite has recently been described as a primary phase in a mantle-derived kyanite eclogite from the Roberts-Victor kimberlite, South Africa. An additional specimen from the same locality contains large polycrystalline aggregates of quartz, resembling the quartz rims on the coesite grains in the first specimen. The characteristic textures of these quartz pseudomorphs after coesite are described to aid in the

JosspH R. Srrlyrs

103

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

104

The anatomy of a hydrothermal (explosion ) breccia, Abbot Village, central Maine  

SciTech Connect

An apparently intrusive hydrothermal breccia is exposed in a large outcrop along Kingsbury Stream downstream from the Route 6 bridge in Abbot Village. The breccia intrudes the Siluro-Devonian Madrid Formation which is comprised of thick-bedded metasandstone interbedded with less fine-grained schist and phyllite at regional biotite grade. In the vicinity of the breccia, the bedding attitude in the Madrid is N60E 70SE and the section faces SE. The breccia is a concordant body with respect to bedding and the exposure shows what appears to the SW terminus of the intrusion which extends an unknown distance NE. The main phase of the breccia consists of randomly oriented and angular clasts'' of Madrid metasandstone and schist that are cemented by a quartz-dominated matrix. The random orientation of the clasts is present this phase were it is in contact with the country rock. The matrix comprises about 15% of the volume of the breccia and, in addition to quartz, contains biotite, galena, chalcopyrite ( ), pyrite, and an iron-carbonate. In some interstitial matrix, apparently late iron-carbonate fills post-quartz vugs that contain quartz-crystal terminations. The wall phase contains a higher proportion of biotite schist clasts that in places are bent around each other and metasandstone clasts. Quartz veins extending into the country rock near the breccia follow prominent regional joint directions and suggest hydrofracturing of the Madrid was the principal mechanism for breccia formation. The breccia is interpreted to be of explosive origin with the main phase of the body representing clasts that fell down within the vent'' following upward transport. The wall phase is taken to have formed due to adhesion to the wall of breccia clasts during the eruptive stage.

Roy, D.C. (Boston Coll., Chestnut Hill, MA (United States). Dept. of Geology and Geophysics)

1993-03-01

105

Revelation of stepped dislocations in amethyst crystals by hydrothermal etching  

Microsoft Academic Search

Triangular etch pits on rhombohedral surfaces due to hydrothermal etching are reported. Our experiments show that the hydrothermal etch pits on rhombohedral surfaces of amethyst have the same dislocation origin they have for quartz. We demonstrate that for a good number of cases successive etching results in the development of another pit away from the geometrical center of the original

M. S. Josut; M. A. IrryncHrN

106

Controls to hydrothermal gold mineralization in the Witwatersberg Goldfield; situated in the floor to the south of the Bushveld Complex, South Africa  

NASA Astrophysics Data System (ADS)

An exploration programme over the Blaauwbank group of gold deposits in the Witwatersberg Goldfield, which lies to the south and in the footwall of the Bushveld Complex, South Africa, has shown that these deposits possess many similarities and some differences to turbidite-hosted gold deposits. The dominant control to this hydrothermal mineralization is structural, with the associated quartz veins being localized along bedding planes, fold axes and a variety of semi-ductile to brittle faults. The deposits of the Witwatersberg Goldfield are also preferentially located in the Klapperkop Quartzite Member and overlying shales of the Timeball Hill Formation, Transvaal Supergroup. The rocks do not appear to form a particularly favourable protore but rather represent a favourable depositional site. The competency contrast of the shales, siltstones and sandstones in this stratigraphic interval is regarded as being important in facilitating vein formation, and the zone is also characterized by a high Fe 2+/Fe 3+ ratio and high C content, which may have reduced the mineralizing fluids and caused gold to precipitate. Fluid inclusion data show the quartz veins formed at 250-330 °C and pressures of 1.3-1.75 kb, from CaCl 2-rich brines. Comparison with structural studies to the north and with the Sabie-Pilgrim's Rest Goldfield to the east suggest that the mineralization probably predates the peak of metamorphism related to the intrusion of the Bushveld Complex.

Killick, A. M.; Scheepers, R.

2005-02-01

107

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 clots occur in the lower leg or ... vein swells, the condition is called thrombophlebitis. A deep vein thrombosis can break loose and cause a ...

108

Riedel-shear control on the development of pennant veins: Field example and analogue modelling  

NASA Astrophysics Data System (ADS)

The wall rocks of a crustal scale sinistral ductile shear zone in Namibia, the Purros Mylonite Zone, contain two types of asymmetric quartz veins. Bedding surfaces contain sigmoidal quartz veins with limited thickness along their symmetry axes that can be classified as tension gashes. A second type of veins consists of a striated central fault vein separating pennant-type quartz filled terminations. The tips of these "pennant veins" have a different orientation to those of the tension gashes. Analogue experiments were carried out using a sheet of silicone powder suspended on a slab of poly-dimethyl-siloxane (PDMS), both deformed in simple shear. These experiments produced open fractures very similar to the pennant veins that form by intersection of R and R' Riedel shear fractures. These fractures rotate and slip during progressive deformation, opening pennant shaped gaps. We interpret the natural pennant veins to form by the same mechanism of R and R' shear fracture initiation, and subsequent rotation and opening. Since this mechanism differs from that of previously described vein types such as wing cracks, tension gashes and swordtail or fishmouth termination veins, which mainly open as tension veins, we consider pennant veins as in new independent class of asymmetric mineral-filled veins.

Coelho, Sara; Passchier, Cees; Marques, Fernando

2006-09-01

109

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 ... of Obstetricians and Gynecologists f AQ • What is deep vein thrombosis (DVT)? • How does a clot form ...

110

Deep Vein Thrombosis  

MedlinePLUS

... page from the NHLBI on Twitter. What Is Deep Vein Thrombosis? Español Deep vein thrombosis (throm-BO-sis), or DVT, is a blood clot that forms in a vein deep in the body. Blood clots occur when blood ...

111

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

112

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

113

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

114

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

115

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

NASA Astrophysics Data System (ADS)

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

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

2006-07-01

116

Br\\/Cl geochemistry of hydrothermal brines associated with Proterozoic metasediment-hosted copper mineralization at Mount Isa, northern Australia  

Microsoft Academic Search

Instrumental neutron activation analyses (INAA) of small bulk samples of vein quartz are used to estimate the Br\\/Cl ratio of saline fluid inclusions associated with late-metamorphic copper mineralization in quartz-dolomite breccias at Mount Isa. The results are compared with similar data from veins associated with district-scale metasomatism in potential copper source rocks near Mount Isa and with quartz samples from

C. A. Heinrich; J. H. C. Bain; J. J. Fardy; C. L. Waring

1993-01-01

117

Miniature crystalline quartz electronical structure  

Microsoft Academic Search

The photolithographic and chemical milling techniques used in fabricating a variety of three-dimensional monocrystalline quartz microstructures are presented. The piezoelectric effect, which is the electromechanical phenomenon utilized in the various applications of quartz technology, is described. Examples of quartz resonators used in sensing applications are presented. These miniature quartz sensors are incorporated into transducer systems which measure pressure, temperature, force,

L. D. Clayton; E. P. EerNisse; R. W. Ward; R. B. Wiggins

1989-01-01

118

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

Microsoft Academic Search

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

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

1993-01-01

119

Portal vein thrombosis.  

PubMed

Portal vein thrombosis (PVT) is the blockage or narrowing of the portal vein by a thrombus. It is relatively rare and has been linked with the presence of an underlying liver disease or prothrombotic disorders. We present a case of a young male who presented with vague abdominal symptoms for approximately one week. Imaging revealed the presence of multiple nonocclusive thrombi involving the right portal vein, the splenic vein, and the left renal vein, as well as complete occlusion of the left portal vein and the superior mesenteric vein. We discuss pathogenesis, clinical presentation, and management of both acute and chronic thrombosis. The presence of PVT should be considered as a clue for prothrombotic disorders, liver disease, and other local and general factors that must be carefully investigated. It is hoped that this case report will help increase awareness of the complexity associated with portal vein thrombosis among the medical community. PMID:25802795

Cohen, Ronny; Mallet, Thierry; Gale, Michael; Soltys, Remigiusz; Loarte, Pablo

2015-01-01

120

Varicose vein - noninvasive treatment  

MedlinePLUS

... The vein will harden and then disappear. Laser treatment can be used on the surface of the skin. Small bursts of light make small varicose veins disappear. Phlebectomy treats surface ... guide treatment. This may be done along with other procedures, ...

121

Portal Vein Thrombosis  

PubMed Central

Portal vein thrombosis (PVT) is the blockage or narrowing of the portal vein by a thrombus. It is relatively rare and has been linked with the presence of an underlying liver disease or prothrombotic disorders. We present a case of a young male who presented with vague abdominal symptoms for approximately one week. Imaging revealed the presence of multiple nonocclusive thrombi involving the right portal vein, the splenic vein, and the left renal vein, as well as complete occlusion of the left portal vein and the superior mesenteric vein. We discuss pathogenesis, clinical presentation, and management of both acute and chronic thrombosis. The presence of PVT should be considered as a clue for prothrombotic disorders, liver disease, and other local and general factors that must be carefully investigated. It is hoped that this case report will help increase awareness of the complexity associated with portal vein thrombosis among the medical community.

Mallet, Thierry; Soltys, Remigiusz; Loarte, Pablo

2015-01-01

122

Optical contacting of quartz  

NASA Technical Reports Server (NTRS)

The strength of the bond between optically contacted quartz surfaces was investigated. The Gravity Probe-B (GP-B) experiment to test the theories of general relativity requires extremely precise measurements. The quartz components of the instruments to make these measurements must be held together in a very stable unit. Optical contacting is suggested as a possible method of joining these components. The fundamental forces involved in optical contacting are reviewed and relates calculations of these forces to the results obtained in experiments.

Payne, L. L.

1982-01-01

123

The Investigation on Fibrous Veins and Their Host from Mt. Ida, Ouachita Mountains, Arkansas  

E-print Network

increases from the coarse-grained layer toward the fine-grained layer. f) Saw-tooth (serrated) texture is shown in grain boundaries. g) N7E veins consist of fibrous or blocky calcite near the vein wall and blocky quartz grains in center which are wider... than calcite grains. h) Calcareous sandstone containing N7E veins is grouped into two layers: fine grained calcite-poor layer (CPL) and coarse-grained calcite-rich layer (CRL). Cc:calcite, Qtz: quartz, S: stylolites, and St: saw-tooth (serrated...

Chung, Jae Won

2004-09-30

124

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

USGS Publications Warehouse

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

Böhlke, J.K.

1989-01-01

125

Mechanical deformation of quartz  

Microsoft Academic Search

Studies of stress relaxation in plastically deformed synthetic quartz crystals are reported. The calculated activation volumes range between b and 10b , where b is the modulus of the Burgers vector of the slip dislocations. For the same conditions of testing, the measured activation volumes for slip involving either of the Burgers vectors a or c are identical; relatively smaller

R. D. Baéta; K. H. G. Ashbee

1970-01-01

126

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

127

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

128

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

SciTech Connect

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

WoldeGabriel, G.

1989-03-01

129

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

SciTech Connect

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

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

1989-11-01

130

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

131

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

SciTech Connect

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

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

1981-05-01

132

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

133

Nanofabricated quartz cylinders for angular  

E-print Network

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

Wang, Michelle

134

Extensional failure and hydraulic valving at Minas da Panasqueira, Portugal: evidence from vein spatial distributions, displacements and geometries  

NASA Astrophysics Data System (ADS)

At Panasqueira, Portugal, exceptional exposure and demonstrable vein connectivity allow robust characterisation of brittle/elastic failure mechanisms in intrusive-related environments. Extensional failure was driven by cycles of fluid injection (hydraulic valving) and vein growth under conditions with ?v?1 and differential stress <4 T. Failure was episodic and produced a swarm of W-Sn-bearing quartz veins characterised by positive volumetric strain. Worked veins consist of families of co-planar vein-lobes linked at branch-points. Geometrically coherent vein displacements constrain an elliptical anomaly (the damage zone) in which values of extensional strain are symmetrically distributed, decreasing systematically away from a centrally located maxima to zero at a tip-line loop. Vein textures indicate rapid, episodic, vein opening, ?m- to dm-scale vein apertures, spatially and temporally variable rates of vein filling and periodic baffling of fluid migration pathways. Although the vein swarm represents a single vein cluster, vein thickness and spacing populations are typically non-power law and define anomaly-scale heterogeneous strain with inhomogeneously deformed marginal zones surrounding a homogeneously deformed high-strain core. Deviations from power-law behaviour were promoted by competitive vein growth that provided mechanisms for (i) inhibiting vein nucleation and (ii) localising deformation onto a few evenly spaced veins.

Foxford, K. A.; Nicholson, R.; Polya, D. A.; Hebblethwaite, R. P. B.

2000-08-01

135

Fluid evolution in the W–Cu–Zn–Pb San Cristobal vein, Peru: fluid inclusion and stable isotope evidence  

Microsoft Academic Search

The Zn–Pb±Ag±Cu San Cristobal district is located 100 km east of Lima in the western cordillera of Peru. It is centred around the Chumpe intrusion and is composed of vein and carbonate replacement ore types. The main San Cristobal vein presents a paragenesis that can be divided into three stages: (a) an early wolframite–quartz–pyrite stage, (b) a quartz–base metal stage,

S. Beuchat; R. Moritz; T. Pettke

2004-01-01

136

Hydrothermal Processes  

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

137

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

138

The compression pathway of quartz  

SciTech Connect

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

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

2011-11-07

139

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

140

Role of Sulfur in the Formation of Magmatic-Hydrothermal Copper-Gold Deposits  

NASA Astrophysics Data System (ADS)

Sulfur plays essential roles in hydrothermal ore-forming processes [1], which calls for precise and accurate quantitative sulfur determination in fluid inclusions. Feasibility tests for sulfur quantification by comparing data from both LA-Quadrupole (Q) - ICP-MS and LA-High Resolution (HR) - ICP-MS show that reliable sulfur quantification in fluid inclusions is possible [2], provided that a very careful baseline correction is applied. We investigate the metal transporting capabilities of sulfur by measuring sulfur together with copper and other elements in cogenetic brine and vapor inclusions ('boiling assemblages') in single healed crack hosted by quartz veins. Samples are from high-temperature magmatic-hydrothermal ore deposits and miarolitic cavities of barren granitoid. Clear compositional correlations of sulfur with copper and gold were found. A molar S/Cu ratio commonly close to 2 but never above 2, indicates sulfur-complexed metal transportation in the high-temperature hydrothermal vapor, and probably also in the Na-Fe-K-Cl-enriched brines. Vapor/brine partitioning trends of the S and Cu are shown to be related with the chemistry of the fluids (possibly by various sulfur speciations in varying pH, fO2) and causative magma source. In the boiling hydrothermal environments, higher vapor partitioning of Cu and S is observed at reduced and peraluminous Sn-W granite, whereas oxidized and perakaline porphyry-style deposits have a lower partitioning to the vapor although the total concentration of S, Cu, Au in both fluid phase is higher than in the Sn-W granite [3]. Vapor inclusion in the boiling assemblages from magmatic-hydrothermal ore deposits and granitic intrusions generally contain an excess of sulfur over ore metals such as Cu, Fe, and Mo. This allows efficient sulfide ore precipitation in high-temperature porphyry-type deposits, and complexation of gold by the remaining sulfide down to lower temperatures. The results confirm earlier interpretations [1] and recent laboratory experiments [4], indicating that sulfur is the key component determining the efficiency of ore formation in porphyry-style and epithermal systems. [1] Heinrich et al. (1999) Geology [2] Guillong et al. (2008) J.Anal. At. Spectrom. [3] Seo et al. (2009) Earth Planet. Sci. Lett. in review. [4] Pokrovski et al. (2008) Earth Planet. Sci. Lett.

Seo, J.; Guillong, M.; Heinrich, C.

2009-05-01

141

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

142

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

143

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

144

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

NASA Astrophysics Data System (ADS)

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

Cervantes, P.; Wiltschko, D. V.

2005-12-01

145

Quartz and Cholesterol  

NSDL National Science Digital Library

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

146

Hydrothermal calderas  

NASA Astrophysics Data System (ADS)

The standard model of caldera formation is related to the emptying of a magma chamber and ensuing roof collapse during large eruptions or subsurface withdrawal. Although this model works well for numerous volcanoes, it is inappropriate for many basaltic volcanoes (with the notable exception of Hawaii), as these have eruptions that involve volumes of magma that are small compared to the collapse. Many arc volcanoes also have similar oversized depressions, such as Poas (Costa Rica) and Aoba (Vanuatu). In this article, we propose an alternative caldera model based on deep hydrothermal alteration of volcanic rocks in the central part of the edifice. Under certain conditions, the clay-rich altered and pressurized core may flow under its own weight, spread laterally, and trigger very large caldera-like collapse. Several specific mechanisms can generate the formation of such hydrothermal calderas. Among them, we identify two principal modes: mode 1: ripening with summit loading and flank spreading and mode II: unbuttressing with flank subsidence and flank sliding. Processes such as summit loading or flank subsidence may act simultaneously in hybrid mechanisms. Natural examples are shown to illustrate the different modes of formation. For ripening, we give Aoba (Vanuatu) as an example of probable summit loading, while Casita (Nicaragua) is the type example of flank spreading. For unbuttressing, Nuku Hiva Island (Marquesas) is our example for flank subsidence and Piton de la Fournaise (La Réunion) is our example of flank sliding. The whole process is slow and probably needs (a) at least a few tens of thousands of years to deeply alter the edifice and reach conditions suitable for ductile flow and (b) a few hundred years to achieve the caldera collapse. The size and the shape of the caldera strictly mimic that of the underlying weak core. Thus, the size of the caldera is not controlled by the dimensions of the underlying magma reservoir. A collapsing hydrothermal caldera could generate significant phreatic activity and trigger major eruptions from a coexisting magmatic complex. As the buildup to collapse is slow, such caldera-forming events could be detected long before their onset.

Merle, Olivier; Barde-Cabusson, Stéphanie; van Wyk de Vries, Benjamin

2010-03-01

147

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

148

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

149

How Are Varicose Veins Treated?  

MedlinePLUS

... a vein using a very fine needle. The chemical scars the inner lining of the vein, causing it to close off. Laser Surgery This procedure applies light energy from a laser onto a varicose vein. The ...

150

Quartz Crystal Microbalance Data  

SciTech Connect

We are using a Qpod quartz crystal microbalance (manufactured by Inficon) for use as a low-volume non-volatile residue analysis tool. Inficon has agreed to help troubleshoot some of our measurements and are requesting to view some sample data, which are attached. The basic principle of an NVR analysis is to evaporate a known volume of solvent, and weigh the remaining residue to determine the purity of the solvent. A typical NVR analysis uses 60 g of solvent and can measure residue with an accuracy of +/- 0.01 mg. The detection limit is thus (0.01 mg)/(60 g) = 0.17 ppm. We are attempting to use a quartz crystal microbalance (QCM) to make a similar measurement. The attached data show the response of the QCM as a 5-20 mg drop of solvent evaporates on its surface. The change in mass registered by the QCM after the drop evaporates is the residue that deposits on the crystal. On some measurements, the change in mass in less than zero, which is aphysical since the drop will leave behind {>=}0 mass of residue. The vendor, Inficon, has agreed to look at these data as a means to help troubleshoot the cause.

Baxamusa, S H

2011-11-16

151

Geology, alteration, and magmatic-hydrothermal history of The Geysers felsite -- potential applications for exploration and development  

SciTech Connect

The [open quotes]felsite[close quotes] is a shallow, young, granitic intrusive body centrally located within and beneath. The Geysers steam field. The field and the felsite are coaxial, and hydrothermal alteration effected by hot-water dominated geothermal systems antedating the modern steam reservoir shows systematic vertical zonation with respect to the pluton. The research summarized in this communication was undertaken both to clarify the role of the pluton in reservoir evolution, and to characterize critical felsite-specific controls on the fields's deep porosity and permeability. The felsite comprises at least three major intrusive phases. Two are high-silica granites probably older than 1.3 Ma. The third is granodiorite (1 Ma), temporally and chemically equivalent to overlying extrusive dacites of the Clear Lake volcanic field. All three intrusive phases are too old to be heat sources for the modern steam field, but probably were the heat engines for the prior liquid-dominant systems. Younger, deeper magmatic heat sources are strongly implied for the current vapor-dominated regime. Porosity in the felsite is provided by: (1) Extensively mineralized fractures and breccias, probably of both tectonic and high-temperature hydrothermal origin; and (2) miarolitic cavities in the upper levels of the pluton. The latter could be analogous to calcite-dissolution cavities in overlying metagraywacke -- they could serve as storage sites for the fields's liquid water reserves. Porosity in these fractures, breccias, and vugs in partially occluded by hydrothermal vein minerals deposited in prior hotwater-dominated systems --tourmaline, ferroaxinite, quartz, potassium feldspar, epidote, actinolite, prehnite, and many others. Such secondary mineralization conceptually could serve as an excellent exploration guide to potentially productive portions of the felsite beyond the field's present boundaries.

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

1993-01-01

152

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

153

Deep vein thrombosis - discharge  

MedlinePLUS

You were treated for deep venous thrombosis (DVT). This is a condition in which a blood clot forms in a vein that is not on ... especially if it gets worse upon taking a deep breath in You cough up blood

154

Focus on Varicose Veins  

MedlinePLUS

... procedure can be performed in the outpatient setting. Recovery time is usually fast with positive short and mid-term results. • RF treatment involves controlled delivery of radio- frequency (RF) energy directly to a vein wall by a thin ...

155

Electrical resistivity surveys for gold-bearing veins in the Yongjang mine, Korea  

NASA Astrophysics Data System (ADS)

The Yongjang mine is an Au-Ag deposit near Masan, located at the southernmost tip of the Korean Peninsula. The deposit lies within Cretaceous sedimentary rocks and contains many quartz veins which contain elements such as gold and silver, and sulfides. In the mine, the Yongjang, En and Ansan quartz veins have been found to be gold bearing. These veins have thicknesses of 2-40 cm and extents of 100-260 m. Electrical resistivity surveys were conducted to clarify the location of gold deposits at both prospect and detailed scales. Apparent resistivity data were collected with a dipole-dipole array on the ground surface and in boreholes, and with a pole-dipole array for surface-to-borehole surveys. The datasets derived from three-dimensional inversion of apparent resistivities are quite effective at delineating the geological structures related to gold-bearing quartz veins. These appear as a low-resistivity anomaly because almost all of the gold mineralization occurs in fractured areas associated with faults or shear zones. The surface-to-borehole survey had better resolution than the surface dipole-dipole survey when imaging gold-bearing quartz veins. The low-resistivity anomalies indicating the Yongjang and Ansan veins extend nearly vertically to sea level and dip steeply below sea level. They run NW-SE parallel to each other at a distance of about 70 m. The En vein is imaged near the Yonjang vein with a strike direction of N60°-70° W and a dip angle of about 45°.

Park, Jong-Oh; You, Young-June; Kim, Hee Joon

2009-03-01

156

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

157

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

158

Temperature, pressure, and composition of hydrothermal fluids, with their bearing on the magnitude of tectonic uplift at mid-ocean ridges, inferred from fluid inclusions in oceanic layer 3 rocks  

NASA Astrophysics Data System (ADS)

Quartz-bearing veins in metagabbroic rocks dredged from the Mathematician Ridge, east Pacific, contain abundant fluid inclusions. Heating and freezing data on nearly 400 inclusions from seven samples allow determination of the temperatures, pressures, and fluid compositions in the subseafloor hydrothermal system at the time of quartz growth. Coexisting dense halite-saturated inclusions and low-density, low-salinity vapor-rich inclusions (average 45 and 2 wt % NaCl equivalent, respectively) attest to an episode of phase separation in some samples. The phase separation occurred at temperatures of about 600°-700°C and pressures of 60-100 MPa (600-1000 bars). The fact that samples that formed at 60-100 MPa are now exposed on the seafloor, where ambient hydrostatic pressure is only 30-35 MPa, suggests that the samples have been tectonically uplifted of the order of 3 km. The fluids could originally have been part of a deep axial hydrothermal circulation cell, or alternatively, they could have been formed in a deep convection cell underlying the off-axis edges of a magma chamber. Fluids are NaCl-CaCl2 brines with molar Na: Ca of 4-8. This range of molar Na: Ca is very close to that of the inferred hydrothermal end-member from various active black smokers, to the measured ratios from basalt-seawater interaction experiments, and to the ratio calculated during numerical basalt-seawater interaction calculations. Crushing experiments indicate little or no compressible gas within the fluids. Fluid inclusions in albite suggest trapping temperatures of around 410°-500°C. Those in epidote may have been trapped at around 500°C and 110 MPa (1.1 kbar) pressure, or around 3 km beneath the Mathematician Ridge seafloor.

Vanko, David A.

1988-05-01

159

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

160

Quartz crystal fabrication facility  

NASA Astrophysics Data System (ADS)

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

Ney, R. J.

1980-05-01

161

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

162

Uranium-series age determination of calcite veins, VC-1 drill core, Valles Caldera, New Mexico  

NASA Astrophysics Data System (ADS)

Uranium-series analysis (238U-234U-230Th) of 13 calcite veins from the hydrothermally altered Madera Limestone in the VC-1 drill core was performed to determine the ages of the veins and their relation to the Valles hydrothermal system. Thermal water from VC-1 and two hot springs in San Diego Canyon was analyzed for U and (234U/238U) to help evaluate the constancy of initial (234U/238U). The (230Th/234U) age of one of the veins is ˜95 kyr, and those of two other veins are ˜230 and ˜250 kyr. Five of the veins have near equilibrium (230Th/234U) and are probably older than ˜0.3 m.y. Uranium concentrations in the remaining veins are too low for analysis by the ?-spectrometry techniques employed in this study. Of the five veins near (230Th/234U) equilibrium, four are also near (234U/238U) equilibrium, suggesting ages greater than ˜1.0 m.y., but one has (234U/238U) = 1.15, suggesting an age between ˜0.3 and ˜1.0 m.y. Calculated initial (234U/238U) of the veins yielding relatively young ages are neither equal to each other nor to (234U/238U) in thermal water from VC-1, indicating inconstancy of initial (234U/238U) that may be related to variations in groundwater mixing proportions. Three of the four veins that yield relatively young ages consist of coarse, sparry, vuggy calcite, suggesting that this may be the type of calcite vein which forms under conditions resembling those encountered presently in VC-1. The analytical data are consistent with closed-system behavior of U and Th in the VC-1 calcite veins.

Sturchio, Neil C.; Binz, Carl M.

1988-06-01

163

Empirical calibration of the oxygen isotope fractionation between quartz and Fe-Mg-chlorite  

NASA Astrophysics Data System (ADS)

An empirical calibration has been made of the oxygen isotope fractionation between chlorite and quartz, using samples from localities in metamorphic terrains where the formation temperature has been constrained by independent methods (e.g., fluid inclusion homogenization temperatures, mineral assemblages and petrology of the host rocks to the veins, thermodynamic modeling, and Raman spectrometry). Textural equilibrium of chlorite and quartz was a pre-requisite and the chemical composition of chlorite was determined. The chlorite analyzed had a range in Fe/Mg varying between 0.35 and 0.7. Except for pure Mg-chlorite, Fe-Mg substitution within the range measured does not change the oxygen isotope fractionation between quartz and chlorite measurably. The results support a linear correlation for chlorite-quartz fractionation over the temperature range given by this study (240-550 °C):

Lacroix, Brice; Vennemann, Torsten

2015-01-01

164

Late Hercynian polymetallic vein-type base-metal mineralization in the Iberian Pyrite Belt: fluid-inclusion and stable-isotope  

E-print Network

ARTICLE Late Hercynian polymetallic vein-type base-metal mineralization in the Iberian Pyrite Belt-type mineralization in the Iberian Pyrite Belt, related to the rejuvenation of pre- existing fractures during late Variscan extensional tecto- nism, comprises pyrite­chalcopyrite, quartz­galena­ sphalerite, quartz

Banks, David

165

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

166

Luminescence sensitivity changes in quartz  

Microsoft Academic Search

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

A. G. Wintle; A. S. Murray

1999-01-01

167

Portal vein thrombosis.  

PubMed

Portal vein thrombosis (PVT) is a rare event in the general medical setting that commonly complicates cirrhosis with portal hypertension, and can also occur with liver tumors. The diagnosis is often incidental when a thrombus is found in the portal vein on imaging tests. However, PVT may also present with clinical symptoms and can progress to life-threatening complications of ischemic hepatitis, liver failure, and/or small intestinal infarction. This article reviews the pathophysiology of this disorder, with a major focus on PVT in patients with cirrhosis, and presents detailed guidelines on optimal diagnostic and therapeutic strategies. PMID:25454305

Basit, Syed Abdul; Stone, Christian D; Gish, Robert

2015-02-01

168

Melt inclusions in quartz from an evolved peraluminous pegmatite: Geochemical evidence for strong tin enrichment in fluorine-rich and phosphorus-rich residual liquids  

NASA Astrophysics Data System (ADS)

We have investigated the magmatic evolution of a late-stage, F- and P-rich, pegmatite-forming aluminosilicate liquid and the geochemical controls on magmatic mineralizing processes by remelting totally-crystallized melt inclusions in quartz and analyzing the quenched glass by EPMA and SIMS. The quartz phenocrysts were sampled from a pegmatite that occurs in a Variscan granite genetically associated with cassiterite- and wolframite-mineralized greisen veins at the Ehrenfriedersdorf Sn?W deposit, central Erzgebirge, SE Germany. The melt inclusion compositions imply that the pegmatite-forming liquid achieved extreme levels of chemical differentiation. It contained high abundances of Sn, F, P, Li, Rb, Cs, Nb, Ta, and Be and abnormally low concentrations of Ca, Y, Sr, and REE for a granite, and it was strongly peraluminous (the molar [Al 2O 3/CaO + Na 2O + K 2O] ranged from 1.3 to 2.0). Fractions of the pegmatite-forming liquid were extremely enriched in P 2O 5 + F + Al 2O 3, and the molar abundances of (F + P) in the glasses correlate strongly with moles of network-modifying Al ions implying that the bulk liquid included F-, P-, and Al-bearing complexes. Formation of these complexes reduced the activities of F, P, and Al in bulk liquid, suppressed the crystallization of magmatic topaz and P-rich minerals, and allowed the liquid to become enriched in these constituents. Some fractions of the Ehrenfriedersdorf aluminosilicate liquid contained 1000-2000 ppm Sn. These levels of Sn enrichment were up to 2 orders of magnitude greater than that ever reported for nonmineralized, metaluminous and peraluminous igneous materials and are consistent with some experimentally-derived Sn solubilities in cassiterite-saturated granitic liquids at geologically relevant pressures and temperatures. This concordance implies that cassiterite could have crystallized directly from this highly evolved, P- and F-rich peraluminous granitic liquid without the involvement of hydrothermal fluids.

Webster, James D.; Thomas, Rainer; Rhede, Dieter; Förster, Hans-Jürgen; Seltmann, Reimar

1997-07-01

169

Living with Deep Vein Thrombosis  

MedlinePLUS

... page from the NHLBI on Twitter. Living With Deep Vein Thrombosis NHLBI Resources Pulmonary Embolism (Health Topics) Non-NHLBI Resources Deep Vein Thrombosis (MedlinePlus) Pulmonary Embolism (MedlinePlus) Clinical Trials ...

170

Treatment of varicose veins.  

PubMed

Varicose veins (VVs) are the most common manifestation of chronic venous insufficiency, affecting 25% of women and 15% of men. Reticular veins and telangiectasias (spider veins) are found in more than 80% of the general population. VVs produce symptoms of pain, swelling, heaviness, fatigue, and pruritus and predispose patients to complications including bleeding, superficial thrombophlebitis, and ulcerations that interfere with activities of daily living and result in lost time from work. Current treatments for VVs include conservative measures, and when these are unsuccessful, more invasive surgical and endovenous interventions primarily aimed at reducing venous hypertension and preventing progression to chronic inflammation and ulcerations. Surgical procedures including saphenous vein stripping, ligation of the saphenofemoral junction, and ambulatory phlebectomy are effective in the treatment of VVs but are associated with a high complication rate and recovery time. Emerging endovenous therapies, including endovenous laser therapy, radiofrequency ablation, and endovenous foam sclerotherapy, have shown similar efficacy in the treatment of VVs compared with more invasive surgical procedures, with lower complication rates and less time lost from work. PMID:19289022

Nael, Raha; Rathbun, Suman

2009-04-01

171

Postpartum Ovarian Vein Thrombosis  

PubMed Central

Background: Ovarian vein thrombosis (OVT) is a rare but potentially serious postpartum complication, which occurs in 0.05% to 0.18% of pregnancies and is diagnosed on the right side in 80% to 90% of the cases. Case Report: A 32-year-old woman presented at 15 days postpartum to our emergency department with severe abdominal pain, fever, and abdominal distension. Abdominal examination revealed right lower quadrant pain with rebound tenderness. The plain abdominal radiography evidenced a diffuse fecal stasis; abdominal ultrasound showed the presence of free fluid in the Douglas’ pouch and between small bowel loops. Diagnosis of acute appendicitis was made. The patient immediately underwent explorative laparoscopy; at surgery, a woody tumoration consistent with right ovarian vein thrombosis was found. Laparoscopic ultrasound confirmed the diagnosis. Anticoagulation therapy and antibiotics were instituted. CT-scan confirmed the presence of thrombosis up to the vena cava. The patient was discharged on postoperative day 4. At 1-month follow-up, she remained stable and symptom free. Discussion: Even though postpartum ovarian vein thrombosis is rare, recognition and treatment is needed to institute adequate therapy and avoid potential serious sequelae. The diagnosis can be established by ultrasound, CT scan, and MRI examinations, although, as in the case described, the limitation of ultrasound includes obscuration of the gonadic vein by overlying bowel gas. Conclusion: OVT should be considered in any woman in the postpartum period with lower abdominal pain, fever, and leucocytosis. PMID:21902992

Romano, Nicola; Bimbi, Marco; Lorenzetti, Luca; Pietrasanta, Dario; Goletti, Orlando

2011-01-01

172

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

173

Hydrothermal organic synthesis experiments  

NASA Technical Reports Server (NTRS)

Ways in which heat is useful in organic synthesis experiments are described, and experiments on the hydrothermal destruction and synthesis of organic compounds are discussed. It is pointed out that, if heat can overcome kinetic barriers to the formation of metastable states from reduced or oxidized starting materials, abiotic synthesis under hydrothermal conditions is a distinct possibility. However, carefully controlled experiments which replicate the descriptive variables of natural hydrothermal systems have not yet been conducted with the aim of testing the hypothesis of hydrothermal organic systems.

Shock, Everett L.

1992-01-01

174

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

175

Mixed-layer illite\\/smectite as a paleotemperature indicator in the Amethyst vein system, Creede district, Colorado, USA  

Microsoft Academic Search

Ordered illite\\/smectite is the most abundant and widespread product of argillic alteration associated with the Oligocene, epithermal, Ag-Pb-Zn-Cu-Au Amethyst vein system, southwest Colorado. Hydrothermal illite\\/smectites exhibit all Reichweite from 1 to ?3 and span the composition range from about 25% to about 3% illite.— The composition and Reichweite of illite\\/smectite vary smoothly with distance from the Amethyst vein. With increasing

Duane G. Horton

1985-01-01

176

Laser welding of fused quartz  

DOEpatents

Refractory materials, such as fused quartz plates and rods are welded using a heat source, such as a high power continuous wave carbon dioxide laser. The radiation is optimized through a process of varying the power, the focus, and the feed rates of the laser such that full penetration welds may be accomplished. The process of optimization varies the characteristic wavelengths of the laser until the radiation is almost completely absorbed by the refractory material, thereby leading to a very rapid heating of the material to the melting point. This optimization naturally occurs when a carbon dioxide laser is used to weld quartz. As such this method of quartz welding creates a minimum sized heat-affected zone. Furthermore, the welding apparatus and process requires a ventilation system to carry away the silicon oxides that are produced during the welding process to avoid the deposition of the silicon oxides on the surface of the quartz plates or the contamination of the welds with the silicon oxides.

Piltch, Martin S.; Carpenter, Robert W.; Archer III, McIlwaine

2003-06-10

177

Color Center in Amethyst Quartz  

Microsoft Academic Search

Treatment with x-rays increased the intensity of color of natural amethyst up to fivefold, and an electron paramagnetic resonance spectrum was detected. The intensity of the spectrum was proportional to the intensity of the optical absorption near 545 mmu. The EPR spectrum of the color center corresponded to a positive hole trapped on a substitutional Fe3+ ion in the quartz

Gerhard Lehmann; Walter J. Moore

1966-01-01

178

Patterns in Global Hydrothermal  

E-print Network

) High-T vents High = hydrothermal discharge Low = active or inactive discharge sites B. Davy, GNS NZ #12Patterns in Global Hydrothermal Activity noaa ocean exploration Presenter: Edward T. Baker #12;First vents discovered in the S Atl. First hi-T vents discovered on ultra-slow ridge Eruption discovered

179

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

180

Amorphization of ?-Quartz under Irradiation  

NASA Astrophysics Data System (ADS)

The course of radiation induced damage produced in ?-quartz by neutrons, ions, electrons or photons — commonly known as metamictization — has been re-analyzed by careful comparison of available experimental data. Specific interest was devoted to confront experimental metamict state features with current structural models. It comes out that the metamict state of irradiated quartz should exhibit some structural characteristics of the modulated structure proposed for vitreous silica. The metamictization process is consistent with a structural relaxation process of a highly defective quartz matrix. According to this new point defect analysis, structural relaxation should be triggered by a critical concentration of oxygen vacancy point defects likely to significantly lower the connectivity of the SiO{2} network. Various experimental results are interpreted by incorporating the influence of the SiO{2} crystalline polymorph and the influence of the nature of the irradiating particle to the point defect model. Nous avons étudié les modifications de propriétés et de structures de monocristaux de quartz ?, consécutives à une irradiation sévère par des neutrons, des ions, des électrons ou des photons. Ce phénomène d'altération du quartz sous irradiation porte le nom de métamictisation. Notre travail exploite les recoupements de travaux antérieurs. Une attention particulière a été portée à la confrontation entre les données structurales expérimentales disponibles sur l'état métamicte du quartz et les modèles structuraux proposés. L'état métamicte du quartz présente ainsi les caractéristiques structurales du modèle de structure modulée, avancé pour décrire la structure de la silice thermique. Le mécanisme de métamictisation procéderait par relaxation de la matrice cristalline fortement endommagée. Ce phénomène de relaxation serait initié par l'apparition de concentration critique de défauts ponctuels de type lacunes d'oxygène responsables d'une forte augmentation des degrés de liberté des tétraèdres élémentaires SiO{4} au sein du crystal. Ce modèle de défaut ponctuel permet, par la prise en compte de la nature de la forme cristalline du dioxyde de silicium et la nature du projectile utilisé, de rendre compte de l'essentiel des donnés expérimentales.

Douillard, L.; Duraud, J. P.

1996-12-01

181

The Widespread Distribution of a Novel Silica Polymorph in Microcrystalline Quartz Varieties  

NASA Astrophysics Data System (ADS)

An x-ray examination of more than 150 specimens of fine-grained quartz varieties from around the world has revealed that more than 10% and as much as 80% of the silica in many samples is actually moganite, a little-known silica polymorph. Rietveld refinements of 50 powder x-ray diffraction patterns produced by fibrous quartz (agate, chalcedony) and nonfibrous quartz (chert, flint) indicate that the concentrations of moganite within each subgroup are widely distributed. The large amount of moganite (>30%) found in cherts from arid, alkaline environments may resurrect length-slow silica as an indicator of evaporitic regimes, and the absence of moganite in weathered and hydrothermally altered silica samples may be a useful measure of fluid-rock interaction.

Heaney, Peter J.; Post, Jeffrey E.

1992-01-01

182

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

PubMed

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

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

2010-01-01

183

Hydrothermal alteration of Tertiary igneous rocks from the Isle of Skye, northwest Scotland  

Microsoft Academic Search

Hydrothermal alteration of Tertiary gabbros from Skye involved the reaction of igneous olivine, augite, hypersthene, plagioclase, magnetite, and ilmenite with aqueous fluid primarily to combinations of talc, chlorite, montmorillonite, calcic amphibole, biotite, and secondary magnetite. Lesser amounts of calcite, epidote, quartz, sphene, prehnite, and garnet also developed. During mineralogical alteration of gabbro there was a net addition to rock of

John M. Ferry

1985-01-01

184

Fluid inclusions in quartz-pebbles of the gold-bearing Tarkwaian conglomerates of Ghana as guides to their provenance area  

Microsoft Academic Search

Quartz-pebbles of the early Proterozoic Au-bearing Tarkwaian conglomerates in Ghana reveal several original (inherited) pre-sedimentary\\u000a fluid inclusions. These inclusions are CO2-N2 rich and display a distinct high density (up to 1.15 g\\/cm3). The unusual high density and composition compare well with CO2-N2-rich inclusions in quartz-vein type gold deposits of the Birimian Supergroup in Ghana and Burkina Faso. This type of

R. Klemd; W. Hirdes; M. Olesch; T. Oberthür

1993-01-01

185

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

SciTech Connect

The Galapagos Fossil Hydrothermal Field is composed of altered oceanic crust and extinct hydrothermal vents within the eastern Galapagos Rift between 85{degree}49 feet W and 85{degree} 55 feet 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. 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. 50 refs., 10 figs., 4 tabs.

Ridley, W.I. [Denver Federal Center, CO (United States)] [Denver Federal Center, CO (United States); Perfit, M.R.; Smith, M.F. [Univ. of Florida, Gainesville, FL (United States)] [Univ. of Florida, Gainesville, FL (United States); Jonasson, I.R. [Geological Survey of Canada, Ontario (Canada)] [Geological Survey of Canada, Ontario (Canada)

1994-06-01

186

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

USGS Publications Warehouse

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

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

2005-01-01

187

Hydrothermal synthesis of hydroxyapatite  

Microsoft Academic Search

A hydrothermal method of synthesizing hydroxyapatite by heating a precipitate, formed by mixing Ca(NO3)2?4H2O 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

J S Earl; D J Wood; S J Milne

2006-01-01

188

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

NASA Astrophysics Data System (ADS)

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

Wohlers, A.; Manning, C. E.

2012-04-01

189

How Is Deep Vein Thrombosis Treated?  

MedlinePLUS

... page from the NHLBI on Twitter. How Is Deep Vein Thrombosis Treated? Doctors treat deep vein thrombosis (DVT) with medicines and other devices ... stockings. Rate This Content: Next >> October 28, 2011 Deep Vein Thrombosis Clinical Trials Clinical trials are research ...

190

Who Is at Risk for Varicose Veins?  

MedlinePLUS

... for varicose veins. This is because staying in one position for a long time may force your veins to work harder to ... Veins Clinical Trials Clinical trials are research studies that explore whether ...

191

The economics of vein disease.  

PubMed

The management of cosmetic vein problems requires a very different approach than that for the majority of most other vascular disorders that occur in a vascular surgery practice. This article focuses on the business aspects of a cosmetic vein practice, with particular attention to the uniqueness of these issues. Managing patient expectations is critical to the success of a cosmetic vein practice. Maneuvering within the insurance can be difficult and frustrating for both the patient and the practice. Practices should use cost accounting principles to evaluate the success of their vein work. Vein surgery--especially if performed within the office--can undergo an accurate break-even analysis to determine its profitability. PMID:17911565

Sales, Clifford M; Podnos, Joan; Levison, Jonathan

2007-09-01

192

Varicose Veins - Sclerotherapy  

NSDL National Science Digital Library

This patient education program explains the benefits and risks of sclerotherapy for varicose veins. It also reviews the anatomy of the cardiovascular system, symptoms, causes, preventive measures, what the procedure involves, and possible complications. This resource is a MedlinePlus Interactive Health Tutorial from the National Library of Medicine, designed and developed by the Patient Education Institute. NOTE: This tutorial requires a special Flash plug-in, version 4 or above. If you do not have Flash, you will be prompted to obtain a free download of the software before you start the tutorial. You will also need an Acrobat Reader, available as a free download, in order to view the Reference Summary.

Patient Education Institute

193

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

194

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

195

Sagittal vein thrombosis caused by central vein catheter.  

PubMed

Cerebral venous thrombosis, including thrombosis of cerebral veins and major dural sinuses, is an uncommon disorder in the general population. However, it has a higher frequency among patients younger than 40 years of age, patients with thrombophilia, pregnant patients or those receiving hormonal contraceptive therapy or has foreign body such as catheter in their veins or arterial system. In this case report, we described clinical and radiological findings in a patient with protein C-S deficiency and malposition of central vein catheter. PMID:25796028

Sabzi, Feridoun; Karim, Hosein; Heydar Pour, Behzad; Faraji, Reza

2015-03-01

196

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

197

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

198

Learning from the pulmonary veins.  

PubMed

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

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

2013-01-01

199

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

200

Vein matching using artificial neural network in vein authentication systems  

NASA Astrophysics Data System (ADS)

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

Noori Hoshyar, Azadeh; Sulaiman, Riza

2011-10-01

201

NMR characterization of shocked quartz  

SciTech Connect

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

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

1994-03-01

202

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.

203

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, W.W., Jr.; Marsh, T.; Iriondo, A.

2009-01-01

204

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

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

205

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

206

COMBUSTION OF HYDROTHERMALLY TREATED COALS  

EPA Science Inventory

The report gives results of an evaluation of: (1) the relationship of the combustion characteristics of hydrothermally treated (HTT) coals to environmental emissions, boiler design, and interchangeability of solid fuels produced by the Hydrothermal Coal Process (HCP) with raw coa...

207

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 ...

208

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

209

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

210

Preliminary study of the importance of hydrothermal reactions on the temperature history of a hot, dry rock geothermal reservoir  

Microsoft Academic Search

A theoretical computer model, based upon the finite element method, of a two-dimensional fracture in a hot, dry rock geothermal reservoir was developed and tested. Hydrothermal reactions occurring between water and a granitic source rock were subdivided into two categories: dissolving reactions and alteration reactions. It was found that the quartz dissolving reaction had little or no direct effect on

J. R. Morris

1975-01-01

211

Hydrothermal carbonization of microalgae  

Microsoft Academic Search

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

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

2010-01-01

212

Bacteria at Hydrothermal Vents  

NSDL National Science Digital Library

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

Expeditions to the Sea Floor Dive and Discover

213

Tectonic-hydrothermal pegmatites  

Microsoft Academic Search

The proposed model for the genesis of complex zoned pegmatites depends on two basis conditions: (1) an alkali chloride intergranular fluid phase (of either magmatic or metamorphic origin) is in equilibrium with the solid phases in the host rock, and (2) deformation produces low pressure zones in the host rock. The phase relations of quartz-mica-feldspar in alkali chloride solutions predict

Randall L. Gresens

1967-01-01

214

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

Microsoft Academic Search

The cathodoluminescence (CL) of quartz from ore, stockwork, veins, and interstitial fillings between lava pillows from the ?2.7 Ga Noranda, Ben Nevis and Matagami volcanogenic massive sulfide (VMS) districts, Abitibi greenstone belt, has been investigated using the “hot cathode” technique (HC1-LM system) to assess the potential of these various sample types to host primary, seafloor VMS-related fluids trapped as inclusions

S. E. Ioannou; J. Götze; L. Weiershäuser; S. M. Zubowski; E. T. C. Spooner

2004-01-01

215

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

216

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 L.

2013-01-01

217

High-grade iron ore at Windarling, Yilgarn Craton: a product of syn-orogenic deformation, hypogene hydrothermal alteration and supergene modification in an Archean BIF-basalt lithostratigraphy  

NASA Astrophysics Data System (ADS)

Banded iron formation (BIF)-hosted iron ore deposits in the Windarling Range are located in the lower greenstone succession of the Marda-Diemals greenstone belt, Southern Cross domain, Yilgarn Craton and constitute a total hematite-martite-goethite ore resource of minimum 52 Mt at 60 wt.% Fe (0.07 P). Banded iron formation is interlayered with high-Mg basalts at Windarling and precipitated during episodes of volcanic quiescence. Trace element content and the rare earth element (REE) ratios Y/Ho (42 to 45), Sm/Yb (1.5), together with positive La and Gd anomalies in `least-altered' hematite-magnetite-metachert-BIF indicate the precipitation from Archean seawater that was fertilised by hydrothermal vent fluids with a basaltic HREE-Y signature. Hypogene iron ore in sub-greenschist facies metamorphosed BIF formed during three distinct stages: ore stage 1 was a syn- to post-metamorphic, syn-D1, Fe-Ca-Mg-Ni-Co-P-REE metasomatism that produced local Ni-REE-rich Fe-dolomite-magnetite alteration in BIF. Hydrothermal alteration was induced by hot fluid flow controlled by brittle-ductile reactivation of BIF-basalt margins and crosscutting D1 faults. The Ni-Co-rich content of dolomite and a shift in REE ratios in carbonate-altered BIF towards Archean mafic rock signature (Y/Ho to 31 to 40, Sm/Yb to 1 to 2 and Gd/Gd* to 1.2 to 1.4) suggest that high-Mg basalts in the Windarling Range were the primary source of introduced metals. During ore stage 2, a syn-deformational and likely acidic and oxidised fluid flow along BIF-basalt margins and within D1 faults leached carbonate and precipitated lepidoblastic and anhedral/granoblastic hematite. High-grade magnetite-hematite ore is formed during this stage. Ore stage 3 hydrothermal specular hematite (spcH)-Fe-dolomite-quartz alteration was controlled by a late-orogenic, brittle, compressional/transpressional stage (D4; the regional-scale shear-zone-related D3 is not preserved in Windarling). This minor event remobilised iron oxides, carbonate and quartz to form veins and breccia but did not generate significant volumes of iron ore. Ore stage 4 involved Mesozoic(?) to recent supergene oxidation and hydration in a weathering environment reaching down to depths of ˜100 to maximum 200 m below surface. Supergene ore formation involved goethite replacement of dolomite and quartz as well as martitisation. Important `ground preparation' for supergene modification and upgrade were mainly the formation of steep D1 to D4 structures, steep BIF/basalt margins and particularly the syn-D1 to syn-D2 carbonate alteration of BIF that is most susceptible to supergene dissolution. The Windarling deposits are structurally controlled, supergene-modified hydrothermal iron ore systems that share comparable physical, chemical and ore-forming characteristics to other iron ore deposits in the Yilgarn Craton (e.g. Koolyanobbing, Beebyn in the Weld Range, Mt. Gibson). However, the remarkable variety in pre-, syn- and post-deformational ore textures (relative to D1 and D2) has not been described elsewhere in the Yilgarn and are similar to the ore deposits in high-strain zones, such as of Brazil (Quadrilátero Ferrífero or Iron Quadrangle) and Nigeria. The overall similarity of alteration stages, i.e. the sequence of hydrothermal carbonate introduction and hypogene leaching, with other greenstone belt-hosted iron ore deposits supports the interpretation that syn-orogenic BIF alteration and upgrade was crucial in the formation of hypogene-supergene iron ore deposits in the Yilgarn Craton and possibly in other Archean/Paleoproterozoic greenstone belt settings worldwide.

Angerer, Thomas; Hagemann, Steffen G.; Danyushevsky, Leonid

2013-08-01

218

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

PubMed

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. PMID:24987551

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

2014-06-01

219

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

220

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

PubMed Central

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

2011-01-01

221

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

E-print Network

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

Soja, Constance M.

222

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

USGS Publications Warehouse

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

Worl, Ronald G.; Lewis, Reed S.

2001-01-01

223

U-Pb isochron age and Pb isotope systematics of the Golden Fleece vein - implications for the relationship of mineralization to the Lake City caldera, western San Juan Mountains, Colorado.  

USGS Publications Warehouse

A U/Pb isochron age of 27.5 + or - 0.5 m.y. is determined for the Golden Fleece vein, an age which is identical with the age of the quartz latite lavas that the vein cuts. Within the Lake City area, only the Golden Fleece vein contains pitchblende and Au-Ag tellurides and has Pb isotope ratios that together define it as unique within the area. The 27.5 m.y. age relates this vein to the waning stages of the Uncompahgre caldera (27-29) rather than to the Lake City caldera (23.1 m.y.). -G.J.N.

Hon, K.; Ludwig, K. R.; Simmons, K.R.; Slack, J.F.; Grauch, R.I.

1985-01-01

224

Central and west african rare-Metal granitic pegmatites, related aplites, quartz veins and mineral deposits  

Microsoft Academic Search

The author summarises the results of his studies of Central and West African rare-metal pegmatites and supplements them by the newest datas obtained by H. Adam in Ivory Coast. He compares then the classification of African rare-metal pegmatites with the classifications obtained in U.S.S.R., in U.S.A. and in Canada for the same kind of pegmatites. The author's conclusions may be

N. Varlamoff

1972-01-01

225

Low angle boundaries in dry quartz  

NASA Astrophysics Data System (ADS)

The Truzzo Granite in the Central Alps (Italy), is heterogeneously deformed under amphibolite facies conditions. Quartz grains in polycrystalline aggregates are dynamically recrystallized and the microstructure is indicative of grain boundary migration recrystallization. Fourier transform infrared spectroscopy (FTIR) reveals that quartz has a very low intracrystalline water content (< 100 H/10^6Si), which is comparable to that of Brazil quartz. Additionally, it is demonstrated that intragranular water (e.g. in fluid inclusions) is removed during grain boundary migration recrystallization. There is clear evidence (CPO, SPO, grain size) that quartz deformed by dislocation creep at relatively low differential stresses. This is not to be expected in the light of the experimentally obtained knowledge about the mechanical behavior of dry quartz, which should be very strong and dislocation related processes should be difficult (e.g. Griggs & Blacic, 1964/5; Paterson, 1989). Quartz grains show substructures, which are planar elements across which the crystal lattice changes its orientation. Some of planar elements are decorated with (partly solid) inclusions. Using a combination of EBSD-derived orientation data and light microscopy some of these planar elements can be identified as subgrain boundaries while in other cases a fracture origin cannot be ruled out. The planar defects indicate that under natural conditions a) dislocation climb is possible even in quartz with very low H-contents, and b) fracturing might also occur under low differential stress, high temperature conditions and result in substructures which very much resemble subgrain boundaries caused by dislocation processes.

Kilian, R.; Heilbronner, R.; Stünitz, H.

2012-04-01

226

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

NASA Astrophysics Data System (ADS)

Southwest Turkey is seismically active as a result of the Hellenic subduction process in the Eastern Mediterranean. We conducted high-resolution micro-sampling, high-precision U-series dating and microchemical analysis on an extensional vein system in a tectonically active but non-hydrothermal area. U/Th age data and microscopic observations provide evidence of repeated fracturing of a previously sealed crack system followed by a new increment of veining. Repeated injection of veinlets suggests that the vein system was formed by the crack-seal mechanism. Four major U/Th age groups for the emplacement of the vein system fall between 23.9 ± 0.2 ka and 23.2 ± 0.4 ka, 21.7 ± 0.4 ka and 19.2 ± 0.2 ka, 17.3 ± 0.1 ka and 16.2 ± 0.3 ka, and at 11.8 ± 0.2 ka. Stable and Sr isotope geochemistry of the calcite vein samples indicates that surface water interacting with the soil cover was the major component of the groundwater system from which the extensional veins precipitated. Trace element and O isotope data of the vein system are interpreted to reflect carbonate precipitation associated with seismic cycles involving fluids with different trace element compositions and CO 2 contents. Initial carbonate precipitation during a single seismic cycle occurred from CO 2-dominated fluids that were degassed from the original CO 2-water mixture. This was followed consecutively by carbonate precipitation from the remaining water, which was relatively impure with higher trace element contents. Millimetre to submillimetre-scale U-series dating in conjunction with geochemistry of carbonate veins related to active tectonism offers an innovative means of constraining the absolute timing of late Quaternary seismic and inter-seismic events.

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

2011-02-01

227

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

NASA Astrophysics Data System (ADS)

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

Fukuchi, Tatsuro; Imai, Noboru; Shimokawa, Koichi

1986-05-01

228

Portal Vein Thrombosis in Cirrhosis  

PubMed Central

Portal vein thrombosis (PVT) is being increasingly recognized in patients with advanced cirrhosis and in those undergoing liver transplantation. Reduced flow in the portal vein is probably responsible for clotting in the spleno-porto-mesenteric venous system. There is also increasing evidence that hypercoagulability occurs in advanced liver disease and contributes to the risk of PVT. Ultrasound based studies have reported a prevalence of PVT in 10–25% of cirrhotic patients without hepatocellular carcinoma. Partial thrombosis of the portal vein is more common and may not have pathophysiological consequences. However, there is high risk of progression of partial PVT to complete PVT that may cause exacerbation of portal hypertension and progression of liver insufficiency. It is thus, essential to accurately diagnose and stage PVT in patients waiting for transplantation and consider anticoagulation therapy. Therapy with low molecular weight heparin and vitamin K antagonists has been shown to achieve complete and partial recanalization in 33–45% and 15–35% of cases respectively. There are however, no guidelines to help determine the dose and therapeutic efficacy of anticoagulation in patients with cirrhosis. Anticoagulation therapy related bleeding is the most feared complication but it appears that the risk of variceal bleeding is more likely to be dependent on portal pressure rather than solely related to coagulation status. TIPS has also been reported to restore patency of the portal vein. Patients with complete PVT currently do not form an absolute contraindication for liver transplantation. Thrombectomy or thromboendovenectomy is possible in more than 75% of patients followed by anatomical end-to-end portal anastomosis. When patency of the portal vein and/or superior mesenteric vein is not achieved, only non-anatomical techniques (reno-portal anastomosis or cavo-portal hemitransposition) can be performed. These techniques, which do not fully reverse portal hypertension, are associated with higher morbidity and mortality risks in the short term. PMID:25755579

Raja, Kaiser; Jacob, Mathew; Asthana, Sonal

2013-01-01

229

Portal vein thrombosis in cirrhosis.  

PubMed

Portal vein thrombosis (PVT) is being increasingly recognized in patients with advanced cirrhosis and in those undergoing liver transplantation. Reduced flow in the portal vein is probably responsible for clotting in the spleno-porto-mesenteric venous system. There is also increasing evidence that hypercoagulability occurs in advanced liver disease and contributes to the risk of PVT. Ultrasound based studies have reported a prevalence of PVT in 10-25% of cirrhotic patients without hepatocellular carcinoma. Partial thrombosis of the portal vein is more common and may not have pathophysiological consequences. However, there is high risk of progression of partial PVT to complete PVT that may cause exacerbation of portal hypertension and progression of liver insufficiency. It is thus, essential to accurately diagnose and stage PVT in patients waiting for transplantation and consider anticoagulation therapy. Therapy with low molecular weight heparin and vitamin K antagonists has been shown to achieve complete and partial recanalization in 33-45% and 15-35% of cases respectively. There are however, no guidelines to help determine the dose and therapeutic efficacy of anticoagulation in patients with cirrhosis. Anticoagulation therapy related bleeding is the most feared complication but it appears that the risk of variceal bleeding is more likely to be dependent on portal pressure rather than solely related to coagulation status. TIPS has also been reported to restore patency of the portal vein. Patients with complete PVT currently do not form an absolute contraindication for liver transplantation. Thrombectomy or thromboendovenectomy is possible in more than 75% of patients followed by anatomical end-to-end portal anastomosis. When patency of the portal vein and/or superior mesenteric vein is not achieved, only non-anatomical techniques (reno-portal anastomosis or cavo-portal hemitransposition) can be performed. These techniques, which do not fully reverse portal hypertension, are associated with higher morbidity and mortality risks in the short term. PMID:25755579

Raja, Kaiser; Jacob, Mathew; Asthana, Sonal

2014-12-01

230

Evidence of porphyry copper-type hydrothermal activity from a submerged remnant back-arc volcano of the Izu-Bonin arc  

Microsoft Academic Search

The first example of a porphyry copper-type hydrothermal activity associated with the back-arc volcanism in the Izu-Bonin arc is presented. Hydrothermally-altered rocks exposed at the flat summit of the Manji Seamount show strong similarities to those associated with porphyry copper-type deposits, i.e. (1) alteration mineral assemblages corresponding to potassic and propylitic alteration zone, (2) occurrence of stockwork of quartz–magnetite veinlets,

Osamu Ishizuka; Makoto Yuasa; Kozo Uto

2002-01-01

231

Magnetic fabrics and fluid flow directions in hydrothermal systems. A case study in the Chaillac Ba-F-Fe deposits (France)  

NASA Astrophysics Data System (ADS)

This study presents a possible use of anisotropy of magnetic susceptibility (AMS) to describe the mineralizing process in hydrothermal systems. Ba-F-Fe-rich deposits within the Chaillac Basin are on the southern border of the Paris Basin. In these deposits hydrothermal textures and tectonic structures have been described in veins, sinters, and sandstone cemented by hydrothermal goethite. 278 oriented cores from 24 sites have been collected in these formations. In addition, a lateritic duricrust superimposed on the hydrothermal formation has been sampled. Rock magnetic investigations show that the principal magnetic carrier is goethite for the hydrothermal mineralization and for the laterite level. The AMS measurements show distinguishable behaviors in the different mineralogical and geological contexts. The K1 magnetic lineation (maximum axis) is strongly inclined for the vertical veins. For the horizontally mineralized sinters, the magnetic lineation is almost horizontal with an azimuth similar to the sedimentary flow direction. The AMS of goethite-rich sandstone close to the veins shows strongly inclined K1 as they are probably influenced by the vertical veins; however, when the distance from the vein is larger than 1 m, the AMS presents rather horizontal K1 directions, parallel to the sedimentary flow. The laterite has a foliation dominance of AMS with vertically well-grouped K3 axes and scattered K1 and K2 axes. Field structural observations suggest that the ore deposit is mainly controlled by EW extension tectonics associated with NS trending normal faults. Combining the AMS results on the deposit with vein textures and field data a model is proposed in which AMS results are interpreted in terms of hydrothermal fluid flow. This work opens a new investigation field to constrain hydrodynamic models using the AMS method. Textural study combined with efficient AMS fabric measurements should be used for systematic investigation to trace flow direction in fissures and in sand porosity.

Sizaret, Stanislas; Chen, Yan; Chauvet, Alain; Marcoux, Eric; Touray, Jean Claude

2003-02-01

232

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

233

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

234

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

235

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

236

Fabrication of a novel quartz micromachined gyroscope  

NASA Astrophysics Data System (ADS)

A novel quartz micromachined gyroscope is proposed in this paper. The novel gyroscope is realized by quartz anisotropic wet etching and 3-dimensional electrodes deposition. In the quartz wet etching process, the quality of Cr/Au mask films affecting the process are studied by experiment. An excellent mask film with 100 Å Cr and 2000 Å Au is achieved by optimization of experimental parameters. Crystal facets after etching seriously affect the following sidewall electrodes deposition process and the structure's mechanical behaviours. Removal of crystal facets is successfully implemented by increasing etching time based on etching rate ratios between facets and crystal planes. In the electrodes deposition process, an aperture mask evaporation method is employed to prepare electrodes on 3-dimensional surfaces of the gyroscope structure. The alignments among the aperture masks are realized by the ABM™ Mask Aligner System. Based on the processes described above, a z-axis quartz gyroscope is fabricated successfully.

Xie, Liqiang; Xing, Jianchun; Wang, Haoxu; Wu, Xuezhong

2015-04-01

237

Quartz-Enhanced Photoacoustic Spectroscopy: A Review  

PubMed Central

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

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

2014-01-01

238

Quartz-enhanced photoacoustic spectroscopy: a review.  

PubMed

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

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

2014-01-01

239

Fluid evolution in submarine magna-hydrothermal systems at the Mid-Atlantic Ridge  

Microsoft Academic Search

Fluid inclusion in a suite of gabbro, quartz-breccia, and metabasalt samples recovered from the Mid-Atlantic Ridge Kane Fracture Zone (MARK) area on the Mid-Atlanitc Ridge are the product of a complex hydrothermal history involving late stage magmatic fluids at temperatures greater than 700 C and penetration by modified seawater at 300-400 C. The evolution of volatiles during the early stage

Deborah S. Kelley; Kathryn M. Gillis; Geoff Thompson

1993-01-01

240

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

241

Deep Vein Thrombosis (DVT) (Beyond the Basics)  

MedlinePLUS

... Find synonyms Find synonyms Find exact match Print DEEP VEIN THROMBOSIS OVERVIEW Venous thrombosis is a condition ... pain. Most commonly, venous thrombosis occurs in the "deep veins" in the legs, thighs, or pelvis ( figure ...

242

If I Had - Deep Vein Thrombosis  

MedlinePLUS

... with Dr. Kenneth Saag, MD) If I Had - Deep Vein Thrombosis - Dr. David Lee, MD In the Spotlight - Dr. ... Researcher Back to Home Page If I Had - Deep Vein Thrombosis - Dr. David Lee, MD (November 15, 2007 - Insidermedicine) ...

243

The optical properties of amethyst quartz  

Microsoft Academic Search

Circularly-polarized waves of light, in passing through a section-plate of amethyst quartz, would obviously be retarded unequally in the alternate laminae having right- and left-handed optical activities. Diffraction effects must therefore arise, and these can actually be observed even in almost colourless varieties of the quartz. The section-plate behaves in effect as a phase-change diffraction grating, and the question of

C. V. Raman; K. Banerji

1925-01-01

244

The Treatment of Varicose Veins  

PubMed Central

INTRODUCTION Over the past few years, there has been a move to less invasive endoluminal methods in the treatment of lower limb varicose veins combined with a renewed interest in sclerotherapy, with the recent addition of foam sclerotherapy. The development of these new techniques has led many to question some of the more conventional teaching on the treatment of varicose veins. This review examines these new treatments for lower limb varicose veins and the current evidence for their use. MATERIALS AND METHODS An extensive search of available electronic and paper-based databases was performed to identify studies relevant to the treatment of varicose veins with particular emphasis on those published within the last 10 years. These were analysed by both reviewers independently. RESULTS There is no single method of treatment appropriate for all cases. Conventional surgery is safe and effective and is still widely practised. Whilst the new treatments may be popular with both surgeons and patients, it is important that they are carefully evaluated not only for their clinical benefits and complications when compared to existing treatments but also for their cost prior to their wider acceptance into clinical practice. PMID:17346396

Subramonia, S; Lees, TA

2007-01-01

245

Blackberry Yellow Vein Disease Complex  

Technology Transfer Automated Retrieval System (TEKTRAN)

A new virus disease has emerged in the Midsouth and Southeastern United States and was named blackberry yellow vein disease (BYVD). Originally, it was thought the disease was caused by Tobacco ringspot virus (TRSV) as the virus was found in many diseased plants and symptoms were very similar to thos...

246

Vaginal vein thrombosis in pregnancy.  

PubMed Central

Vaginal vein thrombosis in a pregnant woman is reported. This entity should be differentiated from vaginal arteriovenous fistula which may cause severe antepartum, intrapartum and post-partum haemorrhage. The humoral and mechanical factors which favour the occurrence of varicosities and thrombosis are briefly described. Surgical management is suggested as being both simple and effective. Images Fig. 1 PMID:6634550

Gitstein, S.; Ballas, S.; Peyser, M. R.

1983-01-01

247

ESR studies on bleached sedimentary quartz  

NASA Astrophysics Data System (ADS)

Some ESR signals in quartz are reported to be bleachable by sunlight and so they promise to be useful for dating sediments (Grün, 1989). The Ge signal in quartz is the only one that shows bleaching effects with UV light in short time scales (hours). Therefore we used quartz samples from the sites of Mauer ( 'Homo erectus heidelbergensis'), samples from a borehole in the Neckar valley ('Entensee', Ladenburg near Heidelberg) and samples from a pegmatite for basic studies on the Ge signal. The results show that with our standard sample preparation procedure for quartz separation (using red light as for TL samples), the natural Ge signal is not detectable, but rises clearly with gamma irradiation. Several experiments for examination of the stability and sensitivity of the Ge centre in quartz were carried out. For comparison with the behaviour of the Ge signal we measured the Al signal as well. Our experiments show that the Al signal is bleachable in long time scales (weeks). The behaviour on bleaching, irradiation and thermal annealing is very complicated, as the Al centre is a hole centre (it possibly interacts with several electron centres in the quartz and so the processes are of higher order).

Walther, R.; Zilles, D.

248

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

249

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

NASA Astrophysics Data System (ADS)

The complex vein associations hosted in southern Sulu ultrahigh-pressure (UHP) eclogites contain quartz ± omphacite (or jadeite) ± kyanite ± allanite ± zoisite ± rutile ± garnet. These minerals have chemical compositions similar to those of host eclogites. Inclusions of polycrystalline quartz pseudomorphs after coesite were identified in vein allanite and garnet, and coesite inclusions were found in vein zircon. These facts suggest that the veins together with host eclogites have been subjected to synchronous UHP metamorphism. The vein minerals contain relatively high concentrations of rare earth elements (REE), high-field-strength elements (HFSE) and transition metal elements (TME). A kyanite-quartz vein has a whole-rock composition similar to adjacent UHP metamorphic granitic gneisses. Abundant primary multi-solid fluid inclusions trapped within UHP vein minerals contain complex daughter minerals of muscovite, calcite, anhydrite, magnetite, pyrite, apatite, celestite and liquid and gas phase of H 2O with solids up to 30-70% of the inclusion volume. The presence of daughter minerals anhydrite and magnetite indicates the subduction fluids were oxidizing, and provides a possible interpretation for the high oxygen fugacity of subduction zone magmas. These characteristics imply that the UHP vein minerals were crystallized from supercritical silicate-rich aqueous fluids that were in equilibrium with peak-UHP minerals, and that the fluids in deeply subducted continental crust may contain very high concentrations of silicate as well as HREE, HFSE and TME. Such fluids might have resulted in major fractionation between Nb and Ta, i.e. the UHP fluids have subchondritic Nb/Ta values, whereas the host eclogites after extraction of the fluids have suprachondritic Nb/Ta values. Therefore, voluminous residual eclogites with high Nb/Ta ratios may be the complementary suprachondritic reservoir capable of balancing the subchondritic depleted mantle and continental crust reservoirs.

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

2008-07-01

250

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

251

A Model of Vein Graft Intimal Hyperplasia  

Microsoft Academic Search

When vein graft is implanted in the arterial system, the vein graft wall becomes thicker as an adaptive process. We have developed a model of early adaptive vein graft intimal thickening induced by shear stress. Intimal thickness and the rate of intimal thickening are expressed as functions of shear stress and time based on experimental data. The model describes the

Roger Tran-Son-Tay; Minki Hwang; Scott A. Berceli; C. Keith Ozaki; Marc Garbey

2007-01-01

252

Remote sensing using quartz sensors  

NASA Astrophysics Data System (ADS)

Sensors based on quartz material can be used for measurement of mechanical strain. There exist two different structures due to propagation mode of the mechanical waves: bulk acoustic wave (BAW) and surface acoustic wave devices (SAW). Another way to classify the sensors is to divide them into resonators or delay-lines (latter only SAW). The sensors are passive elements so that no additional energy supply is needed. The interrogation signal is both information and energy-carrier. Furthermore the measurement system works in the MHz range. With these properties it is possible to operate the system using wireless transmission. In this way a sensor is obtained that is well suited for applications which are not easy or impossible to realize using wired systems: e.g. torque on rotating shafts can be measured at high rates (using DSP up to 10,000 measurements/second). The principle of signal processing works as follows: several periods of a rf sine-wave are received by the sensor antenna every 10 - 50 microseconds for a duration of some 100 ns. They are coupled into the sensor via the piezoelectric effect. Depending on the sensor type a damped oscillation (resonator) or a number of reflected sine-waves (delay line) can be received. In case of the resonator the resonant frequency changes with mechanical strain applied to the sensor and can be measured via radio echo transmission. The principle of signal processing for the SAW delay line is the same as that used for coherent pulse radar: a stressed sensor causes a phase shift of the received signal which is proportional to the elongation. With a maximum elongation of about 1000 ppm of the device used and a resolution of about 5 ppm provided by the signal processing, an accuracy of 0.5% is achieved. Fluctuations of temperature can be eliminated by summing the received signals of two sensors, one of which is stressed and the other compressed. By subtracting the two received and processed signals from each other the temperature can also be measured.

Sachs, Thomas; Grossmann, Rainer; Michel, Juergen; Schruefer, Elmar

1996-05-01

253

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

Microsoft Academic Search

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

Rolf S Wernicke; Hans J Lippolt

1997-01-01

254

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

255

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

NASA Astrophysics Data System (ADS)

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

Omer, Muhamed F.; Friis, Henrik

2014-03-01

256

Geochemistry of the quartz dioritegranite association, Roded area, southern Israel  

E-print Network

Geochemistry of the quartz diorite­­granite association, Roded area, southern Israel Ron Bogoch a Accepted 20 May 2002 Abstract The Roded quartz diorite of southern Israel formed by fractional contained within the quartz diorite, formed in irregularly spaced ``pockets'' near the end of quartz diorite

Dov, Avigad

257

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

258

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

259

Life at Hydrothermal Vents  

NSDL National Science Digital Library

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

Sohmer, Rachel.

2002-01-01

260

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

SciTech Connect

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

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

1981-01-01

261

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

262

Biocatalytic transformations of hydrothermal fluids  

NASA Astrophysics Data System (ADS)

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

Jannasch, H. W.

263

Abnormal patterns of the renal veins  

PubMed Central

Knowledge of the renal vascular anatomy may greatly contribute to the success of surgical, invasive and radiological procedures of the retroperitoneal region. Here, morphometric and histological studies of a human cadaveric specimen presented a complex, anomalous pattern of renal veins. The left renal vein had an oblique retro-aortic course and received two lumbar veins. It bifurcated near its drainage point into the inferior vena cava. The right renal vein received the right testicular vein. In addition, the left kidney was located at a low position. The spleen was enlarged. The present case is unique and provides information that may help surgeons or angiologists to apply safer interventions. PMID:22536553

Azari, Hassan; Abedinzadeh, Mehdi

2012-01-01

264

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

265

Assessing the origin of old apparent ages derived by Pb stepwise leaching of vein-hosted epidote from Mount Isa, northwest Queensland, Australia  

NASA Astrophysics Data System (ADS)

Epidote metasomatism affected large areas of tholeiitic metabasalts of the ~1,780 Ma Eastern Creek Volcanics in the Western Fold Belt of the Proterozoic Mount Isa inlier. Hydrothermal epidote generally occurs in quartz veins parallel to or boudinaged within the dominant S2 fabrics which formed during the regional metamorphic peak at ~1,570 Ma associated with the Isan orogeny. Previously published stable isotopic and halogen data suggest that the fluids responsible for epidote formation are metamorphic in origin (with an evaporitic component). Application of the Pb stepwise leaching technique to the epidote does not separate radiogenic Pb4+ and common Pb2+, generating little spread in 206Pb/204Pb (between 16.0 and 30.5). The causes for this relatively low range are twofold: There is little radiogenic Pb in the epidotes (the most radiogenic steps account for <1 % of Pb released) and both Pb2+ and uranogenic Pb4+ substitute into the same site in the epidote crystal lattice. Consequently, age regressions using the Pb stepwise leaching data give ages between 150 and 1,500 myrs older than the host rocks and over 450 myrs older than the thermal metamorphic peak. These old ages are attributed to chemical inheritance from the host metabasalts, via radiogenic Pb release by breakdown of phases such as zircon, monazite, titanomagnetite, and ilmenite during metamorphism. This idea is supported by trace element data and chrondrite-normalized rare earth element patterns that are similar to both the metabasalts and epidotes (except for a variable Eu anomaly in the latter). Relatively high fO2 during vein formation (Fe3+ dominates in the epidote crystal lattice) would allow the incorporation of Th4+ and exclusion of U6+ and would explain elevated Th/U ratios (up to 12) in epidote compared with the host metabasalts. Non-incorporation of U would explain the relatively low U/Pb ratios and non-radiogenic character of the epidote. This process may provide a source of metal for the small U deposits around Mount Isa and may also suggest a relationship between U mineralization and regional Cu mobilization during the Isan orogeny. Our work suggests that non-conventional geochronometers should be used only if additional geological information and geochemical data (e.g., mineral chemistry, trace elements) are available to evaluate any resulting age calculations.

Duncan, Robert J.; Maas, Roland

2014-12-01

266

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

267

JEDNOTNÉ REGIONÁLNÍ PROJEVY POIMPAKTOVÉ HYDROTERMÁLNÍ FÁZE ?ESKÉHO KRÁTERU Uniform regional manifestations of the post-impact hydrothermal activity in the Czech crater  

Microsoft Academic Search

The occurrence of ilmenite coatings, kyanite + silli- manite mineral lineations and andalusite on shocked quartz pods, together with the anthophyllite reaction rims on the numerous serpentinite fragments and silicious geyzirites in the former crater fill in the Bohemian Massif astrobleme points to an important hydrothermal activity. It postdated the probable Lower Protero- zoic impact (2000 Ma) and occurred in

PETR RAJLICH

268

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

269

Frictional slip of granite at hydrothermal conditions  

USGS Publications Warehouse

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

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

1995-01-01

270

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

271

Historical overview of varicose vein surgery.  

PubMed

Varicose veins are as old as Hippocrates. Varicose vein treatments come and go. Surgery for varicose vein disease is one of the commonest elective general surgical procedures. The history of varicose vein surgery has been traced. We note the first descriptions of varicose veins, and we particularly focus on the ligation of the saphenofemoral junction, stripping of the great saphenous veins, phlebectomy, and perforant vein surgery. We end with the rapid rise of minimally invasive procedures, such as foam sclerotherapy, radiofrequency ablation, and endovenous lasertherapy. Within 10 years, the advantages of minimal invasiveness for these procedures, combined with claims of equivalent short-term outcomes and even better long-term results, have already influenced our everyday practice. At present, the gold standard treatment of varicose veins still is surgical ligation and stripping of the insufficient vein. Concomitantly or sequentially with the treatment of truncal insufficiency, residual varicosities can be treated by phlebectomy. New minimally invasive techniques, however, have changed the clinical landscape for varicose vein surgery tremendously. The dramatic changes of the last decade are probably the precursors of the next generation. PMID:20144527

van den Bremer, Jephta; Moll, Frans L

2010-04-01

272

nanotubes via hydrothermal method  

NASA Astrophysics Data System (ADS)

Red long-lasting phosphor Y2O2S:Eu3+, Zn2+, Ti4+ nanotubes were prepared by hydrothermal method. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence and thermoluminescence spectra (TL) were used to characterize the long-lasting phosphor. XRD investigation revealed that the product synthesised under 750 °C for 6 h was a pure phase of Y2O2S. SEM observation showed that the sulfuretted phosphor inherited the tube-like shape from the precursor. Under 325 nm UV excitation, the result indicated the strongest red-emission lines at 627 nm, corresponded to the transition from 5D0 to 7F2 level of Eu3+ ion. Both the afterglow decay curves and TL curves revealed that the phosphor had efficient luminescent and excellent long-lasting properties.

Huang, Ping; Liu, Dan; Cui, Cai E.; Wang, Lei; Jiang, Guowei

2014-08-01

273

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

274

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

275

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

NASA Astrophysics Data System (ADS)

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

Hashimoto, Y.; Eida, M.

2013-12-01

276

Deformation mechanics of quartz at a single asperity under hydrothermal conditions  

E-print Network

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

Bakku, Sudhish Kumar

2010-01-01

277

Endovenous laser treatment for primary varicose veins.  

PubMed

Venous insufficiency of the lower extremities is a highly prevalent condition. Successful treatment of superficial venous insufficiency will most often necessitate treatment of the saphenofemoral junction incompetence with correction of saphenous vein reflux. In the majority of patients it concerns a reflux of the greater saphenous vein. The standard procedure consists of ligation and stripping of the greater saphenous vein combined with with additional phlebectomies or ligation of insufficient perforant veins if necessary. Although the standard procedure is widely known and accepted, the postoperative morbidity and postoperative limitations of activity are high. In this context minimally invasive percutaneous endovenous techniques were developed to improve the patients comfort and faster resumption of work. Among these, endovenous laser ablation of the greater saphenous vein is a relatively new procedure. Percutaneous introduction of a laser fiber into the incompetent vein and ablation with pulsed laser energy is far less invasive than stripping. PMID:16612909

Van den Bussche, D; Moreels, N; De Letter, J; Lanckneus, M

2006-01-01

278

Fluorous-based carbohydrate Quartz Crystal Microbalance.  

PubMed

Fluorous chemistry has brought many applications from catalysis to separation science, from supramolecular materials to analytical chemistry. However, fluorous-based Quartz Crystal Microbalance (QCM) has not been reported so far. In the current paper, fluorous interaction has been firstly utilized in QCM, and carbohydrate-protein interaction and carbohydrate-carbohydrate interaction have been detected afterward. PMID:25541017

Chen, Lei; Sun, Pengfei; Chen, Guosong

2015-03-20

279

Damage threshold measurement of quartz windows  

NASA Astrophysics Data System (ADS)

The damage threshold of five different types of quartz glass obtained from NSG Precision Cells, Inc. was determined using nanosecond pulses at 532 nm. It was found that the damage threshold of one of the glasses is more than twice that of others.

Said, Ali A.; Xia, Tie J.; Dogariu, Aristide C.; Hagan, David J.; Soileau, M. J.; Van Stryland, Eric W.; Mohebi, Mehrdad

1995-07-01

280

From hertz to gigahertz - Quartz oscillators  

Microsoft Academic Search

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

J. J. Gagnepain; J. Uebersfeld

1976-01-01

281

Deep Vein Thrombosis (DVT) / Pulmonary Embolism (PE) - Blood Clot Forming in a Vein  

MedlinePLUS

... Form Controls NCBDDD Cancel Submit Search The CDC Deep Vein Thrombosis (DVT) / Pulmonary Embolism (PE) â?? Blood ... Español (Spanish) Recommend on Facebook Tweet Share Compartir Deep Vein Thrombosis and Pulmonary Embolism (DVT/PE) are ...

282

MR Venography for the Assessment of Deep Vein Thrombosis in Lower Extremities with Varicose Veins  

PubMed Central

Objective: To assess the performance of magnetic resonance venography (MRV) for pelvis and deep vein thrombosis in the lower extremities before surgical interventions for varicose veins. Materials and Methods: We enrolled 72 patients who underwent MRV and ultrasonography before stripping for varicose veins of lower extremities. All images of the deep venous systems were evaluated by time-of-flight MRV. Results: Forty-six patients (63.9%) of all were female. Mean age was 65.2 ± 10.2 years (37–81 years). There were forty patients (55.6%) with varicose veins in both legs. Two deep vein thrombosis (2.8%) and three iliac vein thrombosis (4.2%) were diagnosed. All patients without deep vein thrombosis underwent the stripping of saphenous veins, and post-thrombotic change was avoided in all cases. Conclusion: MRV, without contrast medium, is considered clinically useful for the lower extremity venous system. PMID:25593625

Nakahara, Hideki

2014-01-01

283

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

284

Microbial ecology of hydrothermal biotypes  

NASA Astrophysics Data System (ADS)

Hydrothermal environments, whether terrestrial or marine, provide a window into potentially thriving ecosystems on other solar bodies. If such extraterrestrial biotopes do exist, they might be inhabited by extremophilic microorganisms, perhaps related to hyperthermophiles (optimal growth temperature > 80°C) previously characterized from geothermal sites on this planet. Study of the physiological and metabolic patterns in hyperthermophiles will shed light on microbial lifestyles consistent with putative hydrothermal niches on other planets and moons.

Montero, Clemente I.; Conners, Shannon B.; Johnson, Matthew R.; Pysz, Marybeth A.; Shockley, Keith R.; Kelly, Robert M.

2004-02-01

285

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

286

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

287

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

USGS Publications Warehouse

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

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

1988-01-01

288

Granite-hosted molybdenite mineralization from Archean Bundelkhand craton-molybdenite characterization, host rock mineralogy, petrology, and fluid inclusion characteristics of Mo-bearing quartz  

NASA Astrophysics Data System (ADS)

The dominantly high-K, moderate to high SiO2 containing, variably fractionated, volcanic-arc granitoids (± sheared) from parts of Bundelkhand craton, northcentral India are observed to contain molybdenite (Mo) in widely separated 23 locations in the form of specks, pockets, clots and stringers along with quartz ± pyrite ± arsenopyrite ± chalcopyrite ± bornite ± covellite ± galena ± sphalerite and in invisible form as well. The molybdenite mineralization is predominantly associated with Bundelkhand Tectonic Zone, Raksa Shear Zone, and localized shear zones. The incidence of molybdenite is also observed within sheared quartz and tonalite-trondhjemite-granodiorite (TTG) gneisses. The fluid inclusion data show the presence of bi-phase (H2O-CO2), hypersaline and moderate temperature (100°-300°C) primary stretched fluid inclusions suggesting a possible hydrothermal origin for the Mo-bearing quartz occurring within variably deformed different granitoids variants of Archean Bundelkhand craton.

Pati, J. K.; Panigrahi, M. K.; Chakarborty, M.

2014-06-01

289

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

Microsoft Academic Search

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

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

2007-01-01

290

Hydrothermal fluids responsible for the formation of precious minerals in the Nigerian Younger Granite Province  

NASA Astrophysics Data System (ADS)

Preliminary investigations in the Younger Granite Province of Nigeria have revealed that precious and semi-precious minerals like rubies, sapphires, emeralds, aquamarine, zircon and fluorite can be found in the region. The gem minerals are shown to have been produced either by direct deposition along fissures, veins and greisens by hydrothermal fluids or as a result of hydrothermal fluids reacting with wall-rocks. These wall rocks are either biotite granites from which the hydrothermal fluids originated or basement rocks or any other rocks which the biotite granites intrude and their residual hydrothermal fluids have invaded. The hydrothermal fluids appear to have been rich in alkalis (Na+, K+, etc.), rare elements (Be, Zr, F, REE, etc.) and siliceous. As these fluids rose through fractures and channel ways through the rocks, they either deposited the gem minerals in the fractures at the appropriate stability conditions or reacted with the wall-rocks producing the gem minerals at the expense of elements like Ca and A1 in the minerals of these rocks.

Abaa, S. I.

1991-04-01

291

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

USGS Publications Warehouse

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

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

1990-01-01

292

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

293

Field-assisted bonding of single crystal quartz  

Microsoft Academic Search

A technique to produce strong, hermetic bonds between plates of single crystal quartz using a modified field-assisted bonding process is presented. Field-assisted bonding is a technique traditionally used to join glass to metals at temperatures well below normal glass softening temperatures. To promote reactivity between quartz within an electrical field at temperatures well below quartz transformation temperatures, thin films of

Randall D. Watkins; Clinton D. Tuthill; Richard M. Curlee; Dale R. Koehler; Charles F. Joerg

1989-01-01

294

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

295

Probing Hydrothermal Organic Reaction Mechanisms with Hydrothermal Photochemistry  

NASA Astrophysics Data System (ADS)

In most hydrothermal organic experiments the emphasis is on reaction product distributions and kinetic measurements, with mechanistic information or the direct evidence of proposed reaction intermediates rare or lacking. We believe that greater mechanistic insight will yield greater predictive power. Previously, we studied the reactions of a model ketone, dibenzylketone (DBK) in aqueous media at 300°C and 700 bars for durations up to several days [1], and found that many of the reaction products arise from coupling of benzyl and related radicals generated through homolytic bond cleavage of DBK. In the present work, we find that in situ photochemical generation of the radicals can provide independent evidence for radical intermediates in the hydrothermal reaction of DBK, yielding valuable insights into the thermal reactions. Hydrothermal photochemical experiments of DBK were conducted in water in sealed fused silica glass tubes at 300°C and 86 bars under UV irradiation for minutes. The short timescale of the experiments allows the primary radical coupling products of DBK to be generated and identified, and their follow-up reactions to be monitored directly. The primary hydrothermal photolysis products include toluene, bibenzyl, a three-benzene-ring product (with isomers), and two four-benzene-ring products (with isomers), which represent a much simpler version of the products obtained through thermal reactions under similar conversions. Most of the observed photolysis products were identical to the ones in the thermal reactions, and those not observed in thermal reactions were found to be the short-lived precursors of the thermal products. As an example, the transformation of one four-ring product to the other was attained and monitored by experiments in which hydrothermal photolysis of DBK was followed by thermolysis at 300°C for a further few hours. The transformation steps included dehydration and isomerization, which were known to be thermodynamically favorable and rapid at hydrothermal conditions [1]. These results show that several relatively stable hydrothermal products from DBK are derived from the radical-coupled intermediates, and that these intermediates can be successfully captured using the tool of hydrothermal photolysis. Analysis of the product distributions and the quantum yields for the hydrothermal photolysis also provides convincing evidence for the previously proposed radical cleavage mechanism for the thermal reactions of DBK. [1] Yang et al. (2012) Geochim. Cosmochim. Acta 98, 48-65.

Yang, Z.; Gould, I.; Shock, E.

2013-12-01

296

Nitroxidergic nerve stimulation relaxes human uterine vein  

Microsoft Academic Search

The predominant action of nitroglycerin, a nitric oxide (NO) donor, on veins over arterioles is well recognized. This study was carried out to determine whether endogenous NO derived from vasodilator nerve regulates the tone of human uterine venous strips. The isolated vein partially contracted with prostaglandin F2? responded to nicotine with a contraction or a relaxation; the contraction was reversed

Noboru Toda; Toshio Kimura; Tomio Okamura

1995-01-01

297

Biometric Identification through Hand Vein Patterns  

Microsoft Academic Search

Vein pattern is the vast network of blood vessels underneath a person's skin. These patterns in the hands are assumed to be unique to each individual and they do not change over time except in size. The properties of uniqueness, stability and strong immunity to forgery of the vein patterns make it a potentially good biometric trait. In this study,

A. Yu?ksel; L. Akarun; B. Sankur

2010-01-01

298

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

299

JAMA Patient Page: Treatment of Varicose Veins  

MedlinePLUS

... socks that fit tightly over the legs and ankle can be used for symptom relief. For patients with varicose veins resulting from clots in the large, deep veins ( postthrombotic syndrome ) or patients with skin ulcers, stockings applying 30 to 40 mm Hg of ...

300

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

301

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

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

302

Element transport in veins during serpentinization  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

303

21 CFR 880.6970 - Liquid crystal vein locator.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Liquid crystal vein locator. 880.6970 Section 880...Miscellaneous Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a device used to...

2010-04-01

304

21 CFR 880.6970 - Liquid crystal vein locator.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Liquid crystal vein locator. 880.6970 Section 880...Miscellaneous Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a device used to...

2011-04-01

305

21 CFR 870.4885 - External vein stripper.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false External vein stripper. 870.4885 Section...Cardiovascular Surgical Devices § 870.4885 External vein stripper. (a) Identification. An external vein stripper is an extravascular...

2010-04-01

306

21 CFR 870.4885 - External vein stripper.  

Code of Federal Regulations, 2011 CFR

... 2011-04-01 false External vein stripper. 870.4885 Section 870.4885 Food...Devices § 870.4885 External vein stripper. (a) Identification. An external vein stripper is an extravascular device used to...

2011-04-01

307

Quartz Channel Fabrication for Electrokinetically Driven Separations  

SciTech Connect

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

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

1998-12-01

308

Abbreviated method of determining vein volume in balloon-controlled vein ablation.  

PubMed

Traditional surgical ligation and stripping for the treatment of saphenous vein incompetence has been replaced by minimally invasive alternative treatments during the last five years. Endovenous ablation with radiofrequency (RP) and laser (EVL) have proven to be safe, durable, and widely accepted by patients. Catheter-delivered sclerotherapy (CDS) with foam and liquid for ablation of the great saphenous vein is also under investigation. In this technique, vein volume must be measured accurately by ultrasound just prior to the procedure and can require up to 11 diameter measurements. The purpose of this study was to identify an abbreviated method of determining vein volume to expedite associated endovenous procedures. Seventy-five veins were treated in 55 subjects with catheter-directed sclerotherapy in a three-center clinical study using a standardized protocol. Vein volume was carefully calculated by determining vein diameter over the Treatment Length in 4 cm intervals. These measurements were compared to vein volume calculations where only three measurements were taken. Our results suggest that the abbreviated method is capable of significantly reducing the number of diameter measurements without sacrificing accuracy. We found the method produced a vein volume that fell within 1 mL or 15% of the actual vein volume in 80% of cases. The abbreviated method cannot be used with accuracy in veins that are Erratic. PMID:18265553

Raines, J K; Garcia de Quevedo, W; Jahrmarkt, S; Mackay, E; Morrison, N; Almeida, J I

2007-01-01

309

Quartz analog watch with perpetual calendar  

NASA Astrophysics Data System (ADS)

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

Favre, Eric; Schmidli, Pierre; Erni, Bruno

310

MAPping Out Arteries and Veins  

NSDL National Science Digital Library

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

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

2006-10-03

311

Retinal vein occlusion: current treatment.  

PubMed

Retinal vein occlusion (RVO) is a pathology noted for more than 150 years. Although a lot has been written on the matter, it is still a frequent condition with multifactorial etiopathogenesis with many unclear aspects. The RVO pathogenesis has varied systemic and local implications that make it difficult to elaborate treatment guidelines. The management of the patient with RVO is very complex and a multidisciplinary approach is required in order to identify and correct the associated risk factors. Laser therapy remains the gold standard in RVO, but only modest functional improvement has been shown in branch retinal occlusion forms. Multicenter studies of intravitreal drugs present them as an option to combine with laser. Anti-vascular endothelial growth factor, corticosteroids and sustained-release implants are the future weapons to stop disease progression and get a better visual outcome. Consequently, it is useful to clarify some aspects of the pathology that allow a better patient management. PMID:20938213

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

2011-01-01

312

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

USGS Publications Warehouse

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

Drew, Lawrence J.

2006-01-01

313

Hydrothermal pretreatment of coal  

SciTech Connect

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

Ross, D.S.

1989-12-21

314

Temperature record of quartz mylonite during exhumation  

NASA Astrophysics Data System (ADS)

We present a study in which quartz microstructure, texture, geothermometry (Ti-in-quartz) and conventional thermobarometry are used to constrain the temperature of deformation in a granulite grade shear zone during exhumation and cooling. The samples are from a major crustal detachment in central-south Madagascar. The 1 to 25 km thick Betsileo shear zone separates two contrasting major geological units: (1) the Antananarivo Block in the footwall and (2) in the hanging wall the Southwest Madagascar Block comprising several lithotectonic domains. Due to the complex deformation history of both blocks and of the shear zone there is no consensus on its kinematics and age but the shear zone was most likely playing major role in both crustal thickening and crustal thinning during the Late Neo-Proterozoic to Ordovician. Quartz optical microstructure is characterized by the grain boundary migration recrystallisation as the dominant dynamic deformation mechanism, which together with chessboard extinction suggests peak deformation temperatures in excess of 650 °C. This microstructure is overprinted to different degree by the subgrain rotation recrystallisation. Because of the large grain size any standard crystallographic preferred orientation measurement would show single-grain texture and thus be statistically irrelevant. For this reason we performed texture measurements on a neutron texture goniometer which analyses rock cylinders 28 mm in diameter and 28 mm high. The obtained texture is consistent with high temperature of deformation inferred from the microstructure and thermobarometry. The kinematics of the shear zone is consistent with a dominant flattening rather than a plane-strain simple shear, which may be an additional reason why researchers disagree on the kinematics of the shear zone. The analyses for the Ti-in-quartz thermometry were all done on the SHRIMP RG (Sensitive High Resolution Ion MicroProbe, Reverse Geometry), which allows for a high spatial resolution and high sensitivity of measurements. To link the temperature measurements to the microstructure and texture the samples were imaged by cathodoluminescence and electron backscatter diffraction before and after the SHRIMP measurements respectively. The range of within-sample temperature variation is consistent with the relative degree of the retrograde overprint. However there temperature distribution is more consistent with the CL pattern than with the microstructure and texture. Together with relatively low temperatures (500-550 °C) this suggest that the cooling and related volume diffusion of trace elements (i.e. Ti) in quartz outlasted the deformation.

Grujic, Djordje; Heidelbach, Florian; Mrkwiczka, Sanna; Ullemeyer, Klaus

2013-04-01

315

Varicose vein surgery and endovenous laser therapy.  

PubMed

Varicose veins are a widespread problem, and are encountered by various medical specialists. Symptoms can appear from mild, such as tiredness of the legs, to severe chronic ulcers. Varicose veins are generally caused by the reflux of an incompetent saphenofemoral junction and long saphenous vein. In the presence of reflux, the treatment should be directed at the ablation of the hydrostatic forces of the reflux. Conventional surgical treatment consists of a high ligation of the saphenofemoral junction and stripping of the saphenous vein. In the era of minimally invasive surgery, various endovenous techniques have been developed, including endovenous laser therapy. This technique is relatively cheap and can be performed under only local anesthesia. During endovenous laser therapy, energy is delivered to the vein wall, causing it to shrink and eventually occlude. Currently, the mechanisms of action involved in laser treatment are not fully understood. Clinical studies have shown occlusion rates to be very competitive to conventional high ligation and stripping and superior cosmetics. Complications may include mild to moderate pain, ecchymosis, induration, hematoma, and phlebitis. All of these are generally self-limiting. In the challenge of finding the correct balance between a low incidence of varicose vein recurrence and complications and optimal cosmetic results, endovenous laser therapy is a promising modality. However, controlled studies that assess the effectiveness of endovenous laser therapy in comparison to saphenofemoral ligation with saphenous vein stripping are crucial before considering endovenous laser therapy as the new standard treatment. PMID:17429785

Reijnen, Michel M P J; Disselhoff, Ben C V M; Zeebregts, Clark J

2007-01-01

316

Personal authentication through dorsal hand vein patterns  

NASA Astrophysics Data System (ADS)

Biometric identification is an emerging technology that can solve security problems in our networked society. A reliable and robust personal verification approach using dorsal hand vein patterns is proposed in this paper. The characteristic of the approach needs less computational and memory requirements and has a higher recognition accuracy. In our work, the near-infrared charge-coupled device (CCD) camera is adopted as an input device for capturing dorsal hand vein images, it has the advantages of the low-cost and noncontact imaging. In the proposed approach, two finger-peaks are automatically selected as the datum points to define the region of interest (ROI) in the dorsal hand vein images. The modified two-directional two-dimensional principal component analysis, which performs an alternate two-dimensional PCA (2DPCA) in the column direction of images in the 2DPCA subspace, is proposed to exploit the correlation of vein features inside the ROI between images. The major advantage of the proposed method is that it requires fewer coefficients for efficient dorsal hand vein image representation and recognition. The experimental results on our large dorsal hand vein database show that the presented schema achieves promising performance (false reject rate: 0.97% and false acceptance rate: 0.05%) and is feasible for dorsal hand vein recognition.

Hsu, Chih-Bin; Hao, Shu-Sheng; Lee, Jen-Chun

2011-08-01

317

Hydrothermal Systems Associated with Martian Impact Craters  

Microsoft Academic Search

With widespread evidence of both heat sources and water (either liquid or solid), hydrothermal systems are likely to have existed on Mars. We model hydrothermal systems in two sizes of fresh impact craters, one simple and one complex, and find that a hydrothermal system forms on the crater floor. In the larger complex craters with a substantial melt sheet, a

Julie A. Rathbun; Steven W. Squyres

2002-01-01

318

Systematic review of treatments for varicose veins.  

PubMed

This systematic review compares the safety and efficacy of varicose vein treatments, including conservative therapy, sclerotherapy, phlebectomy, endovenous laser therapy, radiofrequency ablation, and surgery involving saphenous ligation and stripping. Systematic searches of medical bibliographic databases were conducted in February 2008 to identify suitable studies published from January 1988 onward. Articles were considered eligible for inclusion through the application of a predetermined protocol. Safety and effectiveness data from the comparison of two or more varicose vein procedures were extracted and analyzed. Seventeen studies, published between 2003 and 2007, were included in this review. Serious adverse events were rare. Minor adverse events were more common but generally self-limiting. All treatments displayed levels of effectiveness depending on the extent of the vein in question. Short-term advantages appeared to be associated with sclerotherapy and endovenous treatments, and long-term effectiveness was more apparent following surgical intervention. Evidence suggests conservative therapy is less effective than sclerotherapy and surgery for the treatment of varicose veins. Ligation with stripping plus phlebectomy is generally regarded as the "gold standard" for treating primary long saphenous veins. Sclerotherapy and surgery both appear to have a place in the management of varicose veins. Sclerotherapy and phlebectomy may also be more appropriate in patients with minor superficial varicose veins not related to reflux of the saphenous system or as a post- or adjunctive treatment to other procedures, such as surgery. Current evidence suggests endovenous laser therapy and radiofrequency ablation are as safe and effective as surgery, particularly in the treatment of saphenous veins. Most importantly, the type of varicose vein should govern the intervention of choice, with no single treatment universally employed. PMID:19059756

Leopardi, Deanne; Hoggan, Ben L; Fitridge, Robert A; Woodruff, Peter W H; Maddern, Guy J

2009-03-01

319

A Reappraisal of Saphenous Vein Grafting  

PubMed Central

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

Yuan, Shi-Min; Jing, Hua

2011-01-01

320

Hydrothermal Vents: Thar She Blows!  

NSDL National Science Digital Library

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

321

Hand vein recognition based on orientation of LBP  

NASA Astrophysics Data System (ADS)

Vein recognition is becoming an effective method for personal recognition. Vein patterns lie under the skin surface of human body, and hence provide higher reliability than other biometric traits and hard to be damaged or faked. This paper proposes a novel vein feature representation method call orientation of local binary pattern (OLBP) which is an extension of local binary pattern (LBP). OLBP can represent the orientation information of the vein pixel which is an important characteristic of vein patterns. Moreover, the OLBP can also indicate on which side of the vein centerline the pixel locates. The OLBP feature maps are encoded by 4-bit binary values and an orientation distance is developed for efficient feature matching. Based on OLBP feature representation, we construct a hand vein recognition system employing multiple hand vein patterns include palm vein, dorsal vein, and three finger veins (index, middle, and ring finger). The experimental results on a large database demonstrate the effectiveness of the proposed approach.

Bu, Wei; Wu, Xiangqian; Gao, Enying

2012-06-01

322

Plantar vein thrombosis and pulmonary embolism.  

PubMed

Plantar vein thrombosis is an unusual and under-diagnosed condition that affects the plantar deep venous system. Current ultrasound investigation protocols for deep venous thrombosis neglect this entity. To our knowledge, there are only seven reports in the literature of 20 patients with plantar vein thrombosis detected with sonography without an associated pulmonary embolism. We present a case report of a patient with a plantar vein thrombosis associated with pulmonary embolism. Patients who present with pain and/or swelling of the foot should undergo ultrasound examination and careful evaluation for respiratory symptoms. PMID:24429378

Barros, Mvl; Nascimento, Is; Barros, Tls; Labropoulos, N

2015-02-01

323

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

324

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

NASA Astrophysics Data System (ADS)

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

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

2002-05-01

325

OH-defect content in detrital quartz grains as an archive for crystallisation conditions  

NASA Astrophysics Data System (ADS)

Infrared spectra of 433 oriented detrital quartz grains from different large sedimentary reservoirs worldwide are evaluated with respect to their OH-defect concentration (expressed as wt ppm water), which varies between 0 and 160 wt ppm for individual grains. OH-defect contents, averaged over each individual sample, range between 5 and 20 wt ppm defect water, with a mean value around 10 wt ppm. Sand samples tend to have lower average OH-defect contents than older sandstones deposited earlier from a similar source region. Three of the most OH-defect rich grains from our data set were observed in the oldest and the most strongly cemented sandstone investigated (1400 Ma old Dala sandstone from Dalarna/Sweden), suggesting that OH-defects are barely affected during diagenetic conditions even over geological time scales. Furthermore, the average OH-defect content of each sample is well correlated to its maturity. Combined with results from high-pressure experiments in different model systems, the new results may provide an indirect method to estimate the source rock inventory of the upper crust (igneous, hydrothermal or metamorphic) and depth of the sampled crustal section. Results further suggest that provenance analyses of mature sediments and sedimentary rocks could benefit from the analysis of OH-defect content in quartz.

Stalder, Roland

2014-06-01

326

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

327

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

NASA Astrophysics Data System (ADS)

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

Taghipour, Sedigheh; Taghipour, Batoul

2010-05-01

328

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

329

Portal vein stenting to treat portal vein tumor thrombus in hepatocellular carcinoma.  

PubMed

Tumor thrombus in the portal vein is refractory to therapy and a serious negative prognostic factor in hepatocellular carcinoma. We describe herein the case of a patient in whom an expandable metallic stent was successfully employed to treat portal vein tumor thrombus by restoring blood flow. An expandable metallic stent was implanted in a patient with severe main portal vein stenosis caused by tumor thrombus protruding from the left portal vein branch. Immediately after stent placement, the stenotic lesion was effectively dilated, the portal blood flow restored, and portal hypertension relieved. Angiography, computed tomography, and doppler ultrasonography done 2 months after the stent placement revealed continued patency of the portal vein. Thus, intraportal placement of an expandable metallic stent appears to be an effective treatment for major portal vein tumor PMID:11252736

Higaki, I; Hirohashi, K; Kubo, S; Tanaka, H; Tsukamoto, T; Omura, T; Kinoshita, H

2000-12-01

330

Geology and uranium evaluation of the precambrian quartz-pebble conglomerates of the Needle Mountains, Southwest Colorado. Final report  

SciTech Connect

Precambrian quartz-pebble conglomerates of the Needle Mountains of southwest Colorado are present in the Vallecito Conglomerate and the basal conglomerate of Uncompahgre Formation. Three conglomerates have lithologic, sedimentologic and mineralogic characteristics that are similar to those of the Precambrian uranium-bearing fossil placer deposits of the Witwatersrand in South Africa and the Blind River Elliot Lake district in Ontario, Canada. However, the Precambrian quartz-pebble conglomerates of Colorado do not contain the key indicator minerals of primary detrital pyrite, uraninite, and other uranium mineral species. The absence of these minerals and the structural and stratigraphic relations of these two formations suggest that they were deposited between 1780 and 1460 million years ago. These formations are, therefore, not old enough to have been deposited under the reducing atmospheric conditions thought to be necessary for the formation of placer uranium deposits. The average uranium content of the Precambrian quartz-pebble conglomerates sampled is 2.9 ppM based on analyses of 502 rock samples. Maximum values for uranium (total by neutron activation are 11 ppM for the Vallecito Conglomerate and 5.0 ppM for the basal part of the Uncompahgre Formation. The Vallecito Conglomerate contains on the average 1.2 ppM total uranium and the Uncompahgre Formation contains 1.2 ppM total uranium. These low values further indicate the low potential of these quartz-pebble conglomerates as fossil-placer uranium deposit. Uranium contents of up to 330 ppM were found in dark slates of the Uncompahgre Formation; however, these units were not closely associated with the pebble conglomerates. Some potential uranium targets of vein type and in black pelitic units are found in the Uncompahgre Formation, but these are not the fossil-placer quartz-pebble conglomerate type of deposits.

Burns, L.K.; Ethridge, F.G.; Tyler, N.; Gross, A.S.; Campo, A.M.

1980-05-01

331

Orientation of doubly rotated quartz plates.  

PubMed

A derivation from classical spherical trigonometry of equations to compute the orientation of doubly-rotated quartz blanks from Bragg X-ray data is discussed. These are usually derived by compact and efficient vector methods, which are reviewed briefly. They are solved by generating a quadratic equation with numerical coefficients. Two methods exist for performing the computation from measurements against two planes: a direct solution by a quadratic equation and a process of convergent iteration. Both have a spurious solution. Measurement against three lattice planes yields a set of three linear equations the solution of which is an unambiguous result. PMID:18284990

Sherman, J R

1989-01-01

332

Calorimetric thermobarometry of experimentally shocked quartz  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

333

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

334

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

SciTech Connect

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

Harris, M.

1985-01-01

335

MRI diagnosis of bilateral adrenal vein thrombosis.  

PubMed

We report a case of bilateral adrenal vein thrombosis in an adult female who had a history of breast cancer. The patient does not have clinical, serological or imaging evidence of metastatic disease 14 months from the initial diagnosis. Adrenal vein thrombosis is a rare entity. There have been no previous reports specifically stating an association between adrenal vein thrombosis and hypercoaguability, but there are many cases in the literature documenting venous thrombosis elsewhere within the body in patients with hypercoaguable states. Laboratory testing performed to exclude a hypercoaguable state, revealed heterozygosity for the Factor V Leiden mutation/activated protein C resistance and elevated factor VIII levels [3660 IU l(-1) (<1500)]. This is the first reported case of bilateral metachronous adrenal vein thrombosis in which MRI established the diagnosis. PMID:12893701

Ryan, M F; Murphy, J P; Jay, R; Callum, J; MacDonald, D

2003-08-01

336

Hydrothermal processes at seafloor spreading centers,  

SciTech Connect

This book examines research on the description and interpretation of hydrothermal and associated phenomena at seafloor spreading centers. An interdisciplinary overview of the subject is presented, including geological, geophysical, geochemical, and biological discoveries. The implications of the discoveries for understanding the earth's heat transfer, geochemical mass balances and cycles, mineralization, and biological adaptation are discussed. Topics considered include geologic setting (e.g., the four dimensions of the spreading axis, geological processes of the mid-ocean ridge), hydrothermal convection (e.g., oxygen and hydrogen isotope studies, the basic physics of water penetration into hot rock), Iceland and oceanic ridges (e.g., chemical evidence from Icelandic geothermal systems, the physical environment of hydrothermal systems), mass balances and cycles (e.g., reduced gases and bacteria in hydrothermal fluids, the effects of hydrothermal activity on sedimentary organic matter), ferromanganese deposits, hydrothermal mineralization, and the biology of hydrothermal vents.

Rona, P.A.; Bostrom, K.; Laubier, L.; Smith, K.L.

1983-01-01

337

Isolated inferior mesenteric portal hypertension with giant inferior mesenteric vein and anomalous inferior mesenteric vein insertion.  

PubMed

Extrahepatic portal hypertension is not an uncommon disease in childhood, but isolated inferior mesenteric portal varices and lower gastrointestinal (GI) bleed have not been reported till date. A 4-year-old girl presented with lower GI bleed. Surgical exploration revealed extrahepatic portal vein obstruction with giant inferior mesenteric vein and colonic varices. Inferior mesenteric vein was joining the superior mesenteric vein. The child was treated successfully with inferior mesenteric - inferior vena caval anastomosis. The child was relieved of GI bleed during the follow-up. PMID:23798814

Prasad, G Raghavendra; Billa, Srikar; Bhandari, Pavaneel; Hussain, Aijaz

2013-04-01

338

Fatal bilateral pneumothoraces complicating subclavian vein catheterization.  

PubMed

Bilateral pneumothoraces complicating attempted bilateral subclavian vein catheterization culminated in the iatrogenic death of the patient. Complications of subclavian vein catheterization are reviewed briefly. This procedure should be limited to patients in whom its use is clearly indicated and should be performed only by individuals who are experienced in the anatomy of the region, who are trained in the technique of subclavian puncture, and who have the means and ability to perform immediate tube thoracostomy should pneumothorax occur. PMID:404118

Maggs, P R; Schwaber, J R

1977-04-01

339

[Portal vein embolization prior to liver surgery].  

PubMed

Portal vein embolization is performed with the intention to occlude the portal veins to liver segments with malignancies and direct the portal flow to the healthy part (usually the left lobe) of the liver. Thus, hyperperfusion through the non-embolized part of the liver will create hyperplasia and hyperfunction, which allow extensive liverresection at a later stage in patients where it otherwise would have been contradictory to operate because of too small volume of the residual liver. PMID:23331942

Andersen, Poul Erik; Mahdi, Bassam; Nielsen, Henning Overgaard

2013-01-14

340

Primary leiomyosarcoma of the innominate vein.  

PubMed

Primary venous leiomyosarcoma is rare. We report the case of a primary leiomyosarcoma of the left innominate vein, with neoplastic thrombus extending into the left jugular and subclavian veins. The tumor was curatively resected en bloc with anterior mediastinal and laterocervical lymphatics, through a median sternotomy prolonged into left cervicotomy. Primary venous sarcomas may be associated with prolonged survival in individual cases, with curative resection recommended as the standard treatment, in the absence of distant spread. PMID:17349340

Illuminati, Giulio; Miraldi, Fabio; Mazzesi, Giuseppe; D'urso, Antonio; Ceccanei, Gianluca; Bezzi, Marcello

2007-01-01

341

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

342

Current evaluation and treatment of lower extremity varicose veins.  

PubMed

Historically, treatment for symptomatic lower extremity varicose veins has consisted primarily of surgical stripping of pathologic veins. Over the past 2 decades, therapeutic options for lower extremity varicose veins has greatly expanded and now includes several percutaneous and endovascular techniques. This article will discuss the pathophysiology, clinical significance and current therapy for varicose veins. PMID:19486710

Kouri, Brian

2009-06-01

343

Biometric identification through palm and dorsal hand vein patterns  

Microsoft Academic Search

Hand vein patterns are among the biometric traits being investigated today for identification purposes, attracting interest from both the research community and industry. This paper presents a multimodal system that combines hand-palm vein and hand-dorsal vein biometrics information at the score level. The palm and dorsal veins are considered as texture samples being automatically extracted from the user's hand image.

Sanchit; Mauricio Ramalho; Paulo Lobato Correia; Luis Ducla Soares

2011-01-01

344

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

345

Inferred role of natural fractures, veins, and breccias in development of the artificial geothermal reservoir at the Ogachi Hot Dry Rock site, Japan  

NASA Astrophysics Data System (ADS)

At the Ogachi Hot Dry Rock (HDR) test site, located in a Neogene caldera, northeast Japan, two artificial reservoirs, the upper one at 700 m depth and the lower one at 1000 m depth, were created in granitic basement by hydraulic stimulation. The new fracture sets, forming the reservoirs, propagated in different directions, the upper one to the east and the lower one to the NNE. Water recovery rate from a production well penetrating the two reservoirs was at best 25%, which is very low compared to other HDR test sites such as Fenton Hill, United States, and Soultz, France. In order to understand these phenomena, natural fractures were investigated using mainly core samples from the production well. It was found that natural fractures in the upper and lower reservoirs are remarkably different: the upper reservoir, at depths less than 900 m, is more densely fractured and contains far fewer thick hydrothermal veins than in the lower reservoir. It is believed that these features are due to hydrothermal brecciation associated with Neogene caldera formation and that they could greatly affect the HDR reservoir system. Thick hydrothermal veins and andesite dykes are expected to loci for reservoir fracture propagation and major flow paths because the veins and dykes occupy a prominent fracture system whose orientation coincides well with that of the reservoir propagation. On the other hand, the intensely brecciated zone is not associated with any major flow paths.

Ito, Hisatoshi

2003-09-01

346

Fracture and vein characterization of a crystalline basement reservoir, central Yemen  

NASA Astrophysics Data System (ADS)

The country of Yemen is located in the south-western part of the Arabian plate. The Pan-African basement found in western and central Yemen is highly deformed during the Proterozoic eon and is part of the Arabian-Nubian shield ANS (670-540Ma). This ANS is a result of the amalgamation of high-grade gneiss terranes and low-grade island arcs. The development of an extensive horst-and-graben system related to the breakup of Gondwana in the Mesozoic, has reactivated the Pan-African basement along NW-SE trending normal faults. As a result, younger Meosozoic marls, sandstones, clastics and limestones are unconformably overlying the basement. Some of these formations act as a source and/or reservoir for hydrocarbons. Due to fracturing of the basement, hydrocarbons have migrated horizontally into the basement, causing the crystalline basement to be a potential hydrocarbon reservoir. Unfortunately, little is known about the Pan-African basement in Central Yemen and due its potential as a reservoir, the deformation and oil migration history (with a main focus on the fracturing and veining history) of the basement is investigated in high detail. Representative samples are taken from 2 different wells from the Habban Field reservoir, located approximately 320 ESE of Sana'a. These samples are analysed using e.g. the Optical Microscope, SEM, EDX and CL, but also by doing Rb-Sr age dating, isotope analysis and fluid inclusion analysis. In well 1, the only lithology present is an altered gneiss with relative large (<5 cm diameter) multi-mineralic veins. In well 3, quartzite (top), gneiss (middle) and quartz porphyry's (middle) are intruded by a so called "younger" granitoid body (592.6±4.1Ma). All lithologies record polyphase systems of mineral veins. Pyrite and saddle dolomite in these veins have euhedral shapes, which means that they have grown in open cavities. Calcite is the youngest mineral in these veins, closing the vein and aborting the fluid flow. Fluid inclusions inside the calcite record homogenization temperatures (Th) of approximately 120°C with a maximum of 140°C. This is thought to be approximately equal to the calcite formation temperature. Also the euhedral saddle dolomite is thought to be formed at approximately these temperatures. Migration and precipitation of the vein systems represents an important process in the formation of the crystalline basement hydrocarbon reservoir.

Veeningen, R.; Grasemann, B.; Decker, K.; Bischoff, R.; Rice, A. H. N.

2012-04-01

347

Subclavian vein thrombosis: A continuing challenge  

SciTech Connect

Subclavian vein thrombosis is a relatively uncommon but potentially morbid disease entity. To determine the frequency, cause, and best mode of treatment of this problem, we performed a chart review of all patients with a diagnosis of subclavian vein thrombosis at two major metropolitan hospitals during a 6-year period. A total of 40 patients were identified with subclavian vein thrombosis, which represented 3.5% of all venous thromboses detected during the 6-year period. No side or sex predilection was noted and the majority of patients were outpatients. The cause was fairly evenly divided among intravenous catheters (32%), anatomic abnormalities (45%), and carcinoma with postoperative radiation (22.5%). Despite the increasing use of the subclavian veins for pacemaker leads, hyperalimentation, and permanent intravenous access for chemotherapy, there has not been an increase in diagnosed subclavian vein thrombosis. Anatomic abnormalities with compression of the vein respond well to either heparinization or lytic therapy but require surgery if the venous abnormality persists. Treatment consisted of lytic therapy in 20%, heparinization in 55%, and elevation with removal of the central line in 25% of patients. All patients responded well to treatment, with a decrease in swelling and symptoms; no patient progressed to venous gangrene and only one (2.5%) had a documented pulmonary embolus. Medical treatment provides excellent long-term benefit in most cases unless complicated by an anatomic abnormality.

Hill, S.L.; Berry, R.E. (Community Hospital of Roanoke Valley, Roanoke Memorial Hospital, VA (USA))

1990-07-01

348

Veins Improve Fracture Toughness of Insect Wings  

PubMed Central

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

Dirks, Jan-Henning; Taylor, David

2012-01-01

349

Pharmacology of the human saphenous vein.  

PubMed

Nowadays, the great saphenous vein is the vascular conduit that is most frequently employed in coronary and peripheral revascularization surgery. It is known that saphenous vein bypass grafts have shorter patency than arterial ones, partly because the wall of the normal saphenous vein has different structural and functional characteristics. The features of this vein can be affected by the large distention pressures it is submitted to during its preparation and insertion into the arterial system. Indeed, a vein graft is subjected to considerable changes in hemodynamic forces upon implantation into the arterial circulation, since it is transplanted from a non-pulsatile, low-pressure, low-flow environment with minimal shear stress to a highpressure system with pulsatile flow, where it undergoes cyclic strain and elevated shear. These changes can be responsible for functional and morphological alterations in the vessel wall, culminating in intima hyperproliferation and atherosclerotic degeneration, which contribute to early graft thrombosis. This review has followed a predetermined strategy for updating information on the human saphenous vein (HSV). Besides presenting the aspects relative to the basic pharmacology, this text also includes surgical aspects concerning HSV harvesting, the possible effects of the major groups of cardiovascular drugs on the HSV, and finally the interference of major cardiovascular diseases in the vascular reactivity of the HSV. PMID:21143161

Joviliano, Edwaldo E; Dellalibera-Joviliano, Renata; Celotto, Andrea Carla; Capellini, Verena K; Dalio, Marcelo B; Picconato, Carlos E; Evora, Paulo Roberto B

2011-07-01

350

Cathodoluminescence microanalysis of silica and amorphized quartz  

NASA Astrophysics Data System (ADS)

Cathodoluminescence (CL) techniques are used to investigate the defect structures of pure synthetic silicon dioxide (SiO2) polymorphs. Pure, synthetic Types I, II, III and IV amorphous SiO2 polymorphs, pure, synthetic crystal ?-SiO2 and pure, synthetic amorphized crystal ?-SiO2 have been investigated and their characteristic defects have been determined and compared. The CL emission from pure SiO2 polymorphs is generally related to local point defects in the tetrahedrally coordinated SiO2 host lattice. A range of CL emissions associated with non bridging oxygen defects, oxygen deficient defects and the radiative recombination of self trapped excitons are observed from both the pure synthetic crystal and amorphous SiO2 polymorphs. In addition CL emissions associated with residual concentrations of Aluminium impurities are also observed from ?-SiO2 (quartz) and Type I and II a-SiO2 (fused quartz). Localised amorphous micro-volumes may exist within natural ?-SiO2 due to the presence of a high concentration of pre-existing or induced defects. Amorphization of ?-SiO2 diminishes the difference between the defect structures and associated CL from ?-SiO2 and a-SiO2. Thus CL investigation of the defect structure of a-SiO2 polymorphs provides useful insight into the microstructure of amorphized ?-SiO2.

Stevens-Kalceff, Marion A.

2013-06-01

351

Plasma technology for advanced quartz mask etching  

NASA Astrophysics Data System (ADS)

We review the state-of-art and issues of dry etching of masks for nano-device photo lithography. After introducing the basics of photo-mask structures and their plasma etching, we discuss the specifics of mask etching as compared to the etching of silicon wafers, focusing on processes for the two most-challenging cases: phase-shift masks and NGL where it is achieved by etching the quartz exactly to the prescribed depth. State-of the art solutions for the etching of such masks must provide stringent etching uniformity and accurate end-point monitoring. This can be addressed by either reducing the lithography fields to half or even quarter of their present area, with two to four times worse productivity, or working with larger masks of 9 and later 12 inch. The pressure for such development is becoming stronger with the wider adoption of 450 mm wafers. The new masks may need to be thicker to prevent unwanted deformations. Etching uniformity will have to be sustained over much wider areas. Furthermore, RF bias control for thicker substrates is not straightforward due to the quartz impedance preventing effective RF coupling. Our etching experiments in Ar and Cl2 showed that well established mask etching conditions can be reproduced for moderately thicker substrates, while further increase of substrate thickness may require essentially different approach, such as a series resonance of the inductive plasma bulk and the capacitive sheath.

Iwami, Munenori; Ita, Hirotsugu; Kase, Yoshihisa; Azumano, Hidehito; Nakazawa, Kazuki; Okamoto, Yoshie; Shirahama, Hiroki; Yoshimori, Tomoaki; Muto, Makoto; Ganachev, Ivan

2014-10-01

352

Insitu Calibration of Quartz Crystal Microbalances  

NASA Technical Reports Server (NTRS)

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

Albyn, Keith; Burns, Dewit

2006-01-01

353

Quartz CPO in a polymineralic ultramylonite  

NASA Astrophysics Data System (ADS)

Polymineralic ultramylonites often show microstructures indicative of diffusion creep. Disintegration of monomineralic aggregates and phase mixing inhibits dislocation creep of single phases. Grain boundary sliding can lead to rigid body rotation of individual grains and low differential stresses prevent dislocation glide to occur at a significant rate. Thus, grain boundary sliding and low differential stresses usually preclude the presence of a strong crystallographic preferred orientation (CPO). The Truzzo granite in the Central Alps (Italy) hosts ultramylonitic shear zones which formed under amphibolite facies conditions. At high strain quartz aggregates with a preexisting CPO disintegrate and form a grain-scale phase mixture together with oligoclase, biotite and K-feldspar. Within the ultramylonite quartz CPOs are very weak but distinct from random. Shape and size dependent CPOs and CPO-dependent shapes have been analyzed by means of computer integrated polarization microscopy, EBSD and image analysis techniques. In partially mixed layers, larger grains (> 50 µm), which are more elongated (axial ratio > 0.5) and have a small angle between the grain long axis and the lineation, show a preferred c-axis orientation close to the lineation. This is usually interpreted to result from prism [c] slip. Smaller grains (< 50 µm) with more equant shapes show a peripheral c-axis orientation at a high angle to the lineation, inclined against the sense of shear. At the highest degree of phase mixing, only a peripheral c-axis maximum is observed, which is inclined against the sense of shear. This CPO type is different from what would typically occur in monomineralic quartz aggregates, which are deformed by dominant simple shear. Larger grains (> 50 µm) contain abundant low angle boundaries. Analysis of the intragranular crystallographic misorientation indicates that at least some low angle boundaries can be attributed to subgrain boundaries related to the basal or prism [c] slip system with edge dislocations forming tilt walls. The presented data indicates that certain phases can still undergo dislocation glide during diffusion creep of a polymineralic rock within a grain-scale phase mixture. The data is incompatible with dissolution-precipitation creep of quartz as suggested in the literature for low grade conditions (e.g. Hippert 1994). The activity of prism [c] slip is probably related to the earliest high temperature initiation of shear zones. However, the metamorphic assemblage does not record a temperature drop or earlier high temperature relics. We propose that the development of the dominant but weak CPO type forms by a combination of basal slip and grain-scale strain partitioning. Quartz grains behave as higher viscous particles and therefore some grains experience internal back-rotation of the c-axis into the shortening field as expected for pure shear flow.

Kilian, R.; Heilbronner, R.; Stünitz, H.

2012-04-01

354

Mineral resource of the month: cultured quartz crystal  

USGS Publications Warehouse

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

U.S. Geological Survey

2008-01-01

355

Cathodoluminescence of shocked quartz at the Cretaceous-Tertiary boundary  

NASA Technical Reports Server (NTRS)

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 rocks generally luminesces darker purple-blue, whereas quartz recrystallized under low-grade metamorphic conditions luminesces reddish-brown. Quartz grains in most sandstones luminesce a heterogeneous mixture of these colors because the grains were derived from a variety of ultimate source rocks. If shocked quartz found at the Cretaceous-Tertiary (K-T) boundary is volcanic in origin, its cathodoluminescence should be predominantly pale blue. Alternatively, quartz grains derived from bolide impact upon, and ejection of, mixed igneous, metamorphic, and sedimentary rocks should luminesce a variety of colors. Grain mounts of sand collected at the K-T boundary horizon from the Clear Creek North site in the Raton Basin, Colorado were examined. Shocked quartz luminesced a variety of colors and very few grains luminesced the pale blue color that is typical of volcanic quartz. It was concluded that the shocked quartz was derived from a petrologically diverse source region without substantial volcanic contribution. Most shocked grains apparently were derived from low-grade metamorphic rocks, with a slightly smaller contribution from high-grade metamorphic and intrusive igneous rocks. Rare quartz grains with brown-luminescing rims reflect a minor addition from detrital sedimentary sources. The apparent relative abundances of intrusive (and rare extrusive) igneous, metamorphic, and sedimentary ultimate source rocks suggested by CL colors of shock-deformed quartz at the K-T boundary is consistent with a crustal/supracrustal origin for the grains.

Owen, Michael R.; Anders, Mark H.

1988-01-01

356

The Iceland Deep Drilling Project (IDDP): (4) A Quartz Fluid Inclusion Tool for Sampling Supercritical Geothermal Fluids Downhole  

NASA Astrophysics Data System (ADS)

Chemical analyses of in situ samples of supercritical geothermal fluids would provide a uniquely good measure of fluid composition at depth relative to compositions reconstructed from analyses of gas and liquid sampled at wellheads. Fluids sampled at the wellhead are commonly a mixture from multiple aquifers and, in many circumstances, they lack components such as sulfate, sulfide, Ca, Cu, Zn, and Fe that precipitated in scale minerals where the fluids boiled or cooled during their ascent. To circumvent the above problems and the failings of downhole mechanical samplers at temperatures exceeding 300°C and to obtain total fluid samples at supercritical conditions in the IDDP wells, we plan to trap fluids in fluid inclusions formed in fractured quartz that we suspend in a geothermal well on a wireline. In a series of hydrothermal laboratory experiments at 450°C and 600 bar and spanning 6 hr to 5 days in length, thermal shock fractures in natural and synthetic quartz crystals heal, forming ragged fluid inclusions in one day and many well formed inclusions in three days. Amorphous silica is added to the experimental charge, without which, fractures heal little and only 1-2 micron inclusions form. Microthermometry measurements on the inclusions produced in experiments return the run temperature within 20°C at the experimental pressure, indicating that inclusions formed and sealed at the run conditions. The fluid inclusion tool (FIT) consists of a perforated stainless steel pipe containing multiple stainless steel mesh canisters with non-mesh ends to minimize vertical fluid flow. The canisters contain 10mm-scale chunks of fractured quartz surrounded by ground quartz glass. The perforated pipe will be fixed within a one-meter outer perforated stainless steel housing that is suspended on a stainless steel slick line. The FIT is weighed by one or more 10kg lead sinker bars. The entire assembly is lowered into the well from a lubricator fitted on the wellhead, thus enabling sampling under high temperatures and pressures. In the initial field testing runs, the contents of the mesh canisters will be varied to examine the effects of ground glass grain size, and the suitability of clear natural quartz vs synthetic quartz, both with respect to fluid inclusion development and chemical analyses of inclusions. Inclusions will be analyzed by various bulk methods and by LA-ICP-MS on individual inclusions. Once we optimize the fluid inclusion tool configuration in field tests and by analytical results, the volume of sampling quartz can be scaled up as needed to provide for optimum sampling and analyses.

Reed, M. H.; Grist, H.; Fridriksson, T.; Danielsen, P.; Senkovich, D.; Johnston, A.; Elders, W. A.; Fridleifsson, G. O.

2009-12-01

357

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

USGS Publications Warehouse

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

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

2008-01-01

358

Corrosion cast study of the canine hepatic veins.  

PubMed

This study presents a detailed description of the distribution, diameters and drainage patterns of hepatic veins on the basis of the corrosion cast analysis in 18 dogs. We classified the hepatic veins in three main groups: the right hepatic veins of the caudate process and right lateral liver lobe, the middle hepatic veins of the right medial and quadrate lobes and the left hepatic veins of both left liver lobes and the papillary process. The corrosion cast study showed that the number of the veins in the Nomina Anatomica Veterinaria and most anatomical textbooks is underestimated. The number of various-sized hepatic veins of the right liver division ranged from 3 to 5 and included 1 to 4 veins from the caudate process and 2 to 4 veins from the right lateral liver lobe. Generally, in all corrosion casts, one middle-sized vein from the right part of the right medial lobe, which emptied separately in the caudal vena cava, was established. The other vein was a large-sized vein from the remainder of the central division, which frequently joined the common left hepatic vein from the left liver lobes. The common left hepatic vein was the largest of all the aforementioned hepatic veins. PMID:25448906

Urši?, M; Vrecl, M; Fazarinc, G

2014-11-01

359

Hydrothermal phonolite alteration in the Kaiserstuhl Volcanic Complex, Germany  

NASA Astrophysics Data System (ADS)

The subvolcanic Fohberg and Endhale phonolitic intrusions in the Kaiserstuhl volcanic complex in SW Germany are economic zeolite deposits, formed by hydrothermal alteration of primary magmatic minerals. Due to the high (>40 wt%) zeolite content, which accounts for the remarkable zeolitic physicochemical properties of the ground rock, the zeolitized phonolites are in economic interest. New mineralogical and geochemical studies are carried out a) to evaluate the manifestation of hydrothermal alteration of the Fohberg and Endhale phonolitic intrusions, and b) to constrain the physical and chemical properties of the fluids, which promoted hydrothermal replacement of primary igneous minerals. The alkaline intrusive bodies are characterized by the primary mineralogy: feldspathoid mineral, K-feldspar, aegirine-augite, wollastonite, and andradite. The REE-phase götzenite is formed during late stage magmatic crystallization. Fluid-induced re-equilibration of feldspathoid minerals and wollastonite caused breakdown to a set of secondary phases. Feldspathoid minerals are totally replaced by secondary phases including various zeolite species, calcite, and barite. Wollastonite breakdown results in the formation of various zeolites, calcite, pectolite, sepiolite, and quartz. The large variability of secondary minerals indicates a heterogenic fluid composition throughout the phonolitic intrusions and through time. Zeolites formed during sub-solidus hydrothermal alteration under alkaline conditions and completely replacefeldspathoid minerals in the matrix of the rock. A sequence of Ca-Na dominated zeolite species (gonnardite, thomsonite, mesolite) is followed by pure sodium endmember species. The sequence reflects an increase in log[aNa+)/(aH+)] of the precipitating fluid. Low radiogenic 87Sr/86Sr values of secondary calcite indicate a local origin of Ca and elements necessary for secondary mineral formation most probably derived from primary igneous phases. The Fohberg phonolite is cut by fractures, which are totally or partially sealed with secondary minerals. Secondary minerals contain zeolites, followed by calcite and a variety of other silicates, carbonates and sulphates as younger generations. Stable isotope analyses of late fracture calcite indicate the late circulation of meteoric fluids and mobilization of organic matter from surrounding sedimentary units.

Weisenberger, T. B.; Spürgin, S.

2013-12-01

360

Deep vein thrombosis: a clinical review  

PubMed Central

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

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

2011-01-01

361

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

PubMed

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

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

2014-01-01

362

Distribution, Microfabric, and Geochemical Characteristics of Siliceous Rocks in Central Orogenic Belt, China: Implications for a Hydrothermal Sedimentation Model  

PubMed Central

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

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

2014-01-01

363

Chemical equilibrium and mass balance relationships associated with the Long Valley hydrothermal system, California, U.S.A.  

USGS Publications Warehouse

Recent drilling and sampling of hydrothermal fluids from Long Valley permit an accurate characterization of chemical concentrations and equilibrium conditions in the hydrothermal reservoir. Hydrothermal fluids are thermodynamically saturated with secondary quartz, calcite, and pyrite but are in disequilibrium with respect to aqueous sulfide-sulfate speciation. Hydrothermal fluids are enriched in 18O by approximately 1??? relative to recharge waters. 18O and Cl concentrations in well cuttings and core from high-temperature zones of the reservoir are extensively depleted relative to fresh rhyolitic tuff compositions. Approximately 80% of the Li and 50% of the B are retained in the altered reservoir rock. Cl mass balance and open-system 18O fractionation models produce similar water-rock ratios of between 1.0 and 2.5 kg kg-1. These water-rock ratios coupled with estimates of reservoir porosity and density produce a minimum fluid residence time of 1.3 ka. The low fluid Cl concentrations in Long Valley correlate with corresponding low rock concentrations. Mass balance calculations indicate that leaching of these reservoir rocks accounts for Cl losses during hydrothermal activity over the last 40 ka. ?? 1991.

White, A.F.; Peterson, M.L.

1991-01-01

364

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

NASA Astrophysics Data System (ADS)

Strongly silicified volcanic rocks and overlying sediments are a common feature in the Mesoarchean Barberton Greenstone Belt, South Africa. The silification predominantly occurs at the top of mafic to ultramafic lava flows at the contact to sedimentary chert horizons, and has been interpreted as a result of fluid circulation in shallow subseafloor convection cells (Hofmann & Harris, 2008). Six samples of silicified rocks of the Mendon Formation were used for a fluid inclusion study to better constrain the conditions of formation and the source and physico-chemical evolution of the fluid that might have been resp