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1

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

2

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....

3

Scanning electron microscope cathodoluminescence analysis of quartz reveals complex growth histories in veins from the Butte porphyry copper deposit, Montana  

Microsoft Academic Search

Scanning electron microscope cathodoluminescence (SEM-CL) analysis of quartz reveals textures that cannot be observed using optical microscopy or backscattered electrons. These cryptic textures yield insight into timing and physical conditions of quartz growth, especially in environments with multiple quartz-precipitation events. Hydrothermal quartz from quartz-sulfide veins in the porphyry copper deposit in Butte, Montana, was analyzed by SEM-CL, revealing the following

Brian Rusk; Mark Reed

2002-01-01

4

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

USGS Publications Warehouse

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

Ayuso, Robert A.; Shank, Stephen G.

1983-01-01

5

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

6

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

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

Investigating the strengthening of quartz ceramics by hydrothermal treatment  

Microsoft Academic Search

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

S. M. Itkin; V. V. Vikulin

1993-01-01

9

Titanium-in-quartz thermometry on synkinematic quartz veins in a retrograde crustal-scale normal fault zone  

NASA Astrophysics Data System (ADS)

Previous studies have suggested that estimation of deformation temperatures in quartz mylonites by titanium-in-quartz geothermometry is only possible at temperatures > 500 °C, above which efficient Ti-exchange is achieved via grain boundary migration recrystallization. Based on quartz mylonite samples collected across the Simplon Fault Zone (SFZ) we demonstrate that deformation temperatures of dynamic recrystallization can be obtained down to ~ 350 °C. A prerequisite for such temperature estimates at the low temperature end of ductile deformation of quartz is the formation of synkinematic quartz veins and their immediate overprint either by subgrain rotation (SGR) or bulging recrystallization (BLG). It is the slow growth of the synkinematically precipitating vein quartz that allows for equilibration of Ti in the vein quartz. This Ti-concentration may only slightly be modified during SGR; hence, Ti-in-qtz thermometry provides a close approach to the vein formation temperature. Ti-concentrations are partially reset during BLG, and resulting temperatures are thus maximum temperatures of quartz recrystallization. Importantly, undeformed vein quartz always yield vein formation temperatures. Investigation of the dynamic recrystallization processes overprinting synkinematic quartz veins thus allows for a critical, independent evaluation of the Ti-in-quartz temperatures obtained. For the SFZ, there is a decrease in recrystallized grain sizes towards the fault plane and a change in the dominant recrystallization process associated with a narrowing of the shear zone. As indicated by the Ti-in-quartz temperature estimates, this strain localization correlates with cooling from ~ 560 °C in the oldest microstructures at the periphery of the shear zone down to ~ 350 °C in the youngest microstructures of the footwall near the hanging wall contact. A great benefit of the approach presented here is that intermediate to low temperature plastic deformation in quartz can now also be assessed. Such novel temperature constraints on quartz crystallization are essential for better constraining deformation and rheology in the upper Earth's crust.

Haertel, Mike; Herwegh, Marco; Pettke, Thomas

2013-11-01

10

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

11

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

12

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

Microsoft Academic Search

The combination of scanning electron microscope–cathodoluminescence (CL), fluid inclusion analysis and high-resolution electron\\u000a probe microanalysis of Al, Ti, K and Fe in vein quartz has yielded results permitting a greater understanding of the complex\\u000a mineralisation of the Central Oyu Tolgoi and Zesen Uul porphyry-style deposits, southern Mongolia. These data demonstrate\\u000a the relationship between quartz precipitation, dissolution and ore deposition as

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

2010-01-01

13

Looking at Dauphiné twins in vein quartz as a potential paleostress indicator  

NASA Astrophysics Data System (ADS)

Paleostress studies commonly call upon (1) a fault slip data inversion technique, (2) a calcite twin stress inversion technique, (3) recrystallized grain size piezometry for quartz, or (4) direct measurements of residual lattice strain. Recent advances in orientation imaging microscopy (OIM) using electron backscatter diffraction (EBSD) on a scanning electron microscope (SEM) have revealed that Dauphiné twinning is very common in quartz in naturally deformed quartz-bearing rocks in a wide range of tectonometamorphic conditions. It has long been known that mechanical Dauphiné twinning in quartz can be stress-induced. Based on the results of an extensive EBSD-OIM analysis on vein quartz, taken from well-studied early to late-orogenic veins in the High-Ardenne slate belt (Germany, Belgium), we explore the potential use of mechanical Dauphiné twins as a paleostress indicator, possibly completing our toolbox for reconstructing paleostresses in the Earth's crust. The vein quartz studied precipitated in low-grade tectonometamorphic conditions (~200-400°C), typical for the brittle-plastic transition zone at the base of the seismogenic crust (~7-15km). Quartz has only been weakly affected by low to moderate temperature (200 to 400°C) crystal-plastic deformation. The samples show grains with a high concentration of Dauphiné twin boundaries and others free of twin boundaries, thus being untwinned or completely twinned. This pattern depends on the crystallographic orientation. Twin boundaries are arrested by grain or subgrain boundaries, suggesting that Dauphiné twinning occurred on a pre-existing fabric that resulted from crystal-plastic deformation. An analysis of the orientation distribution of the rhombs in the twinned variant domains of individual quartz (sub-)grains reveals a particular preferred orientation of the poles to rhombs. We will discuss the possible significance of these observations with respect to paleostresses that may have caused the mechanical Dauphiné twinning.

Sintubin, Manuel; Wenk, Hans-Rudolf

2013-04-01

14

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

15

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

NASA Astrophysics Data System (ADS)

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

Kerrich, R.; Feng, R.

1992-01-01

16

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

17

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

18

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

Microsoft Academic Search

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

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

2000-01-01

19

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

SciTech Connect

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

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

1996-12-31

20

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

21

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

Microsoft Academic Search

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

Masao Nakatani; Christopher H. Scholz

2004-01-01

22

Comparison of thermoluminescence (TL) and cathodoluminescence (ESEM-CL) properties between hydrothermal and metamorphic quartzes.  

PubMed

This paper reports on the Thermoluminescence (TL) and Cathodoluminescence (CL) emission of well-characterized hydrothermal milky quartz specimens from Hakkari in Turkey, labeled THQ, and Madrid in Spain, labeled SHQ, and metamorphic quartz from Madrid, in Spain, labeled SMQ. Both hydrothermal and metamorphic quartz samples display similar UV-IR CL spectra consisting of five groups of components centered at 330 nm and 380 nm linked to [AlO(4)]° centers, 420 nm due to intrinsic defects such as oxygen vacancies, lattice defects, and impurities which modify the crystal structure, 480 nm associated with [AlO(4)]° centers of substitutional Al(3+), and a red broad band related to the hydroxyl defects in the quartz lattice as precursors of non-bridging oxygen hole centers (NBOHC) and substitutional point defects. The Turkish quartz specimen exhibits higher CL intensity in the UV region (up to 330 nm) than the Spanish specimens probably linked to the presence of Ca (0.95% in THQ and less than 0.1% in SHQ and SMQ). At wavelengths greater than 330 nm, SMQ (formed at high pressure 6000 bars and temperatures over 500-600°C) shows higher intensity than the hydrothermal (growth at 2000 bars and temperatures 200-300°C) samples associated with the formation process. The natural blue TL glow curves of both THQ and SHQ display a weaker TL intensity than the SMQ, attributable to the Al (0.32%), Ti (0.14%), K (0.01%) and Zr (76 ppm) content. It is shown that mineralogical formation, crystallinity index and the content of the impurities seem to be the main parameters of influence in the shape intensity of the CL and TL glow curve emission. PMID:22476018

Topaksu, M; Correcher, V; Garcia-Guinea, J; Topak, Y; Göksu, H Y

2012-06-01

23

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

SciTech Connect

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

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

1997-05-01

24

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

25

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

NASA Astrophysics Data System (ADS)

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

Jiang, Z.

2011-12-01

26

Mineralogy and fluid inclusion studies of the Au-Cu quartz veins in the Hamash area, South-Eastern Desert, Egypt  

Microsoft Academic Search

Summary Field relations, petrographic observations and fluid inclusion data are used to characterize the mineralizing fluids of gold-copper bearing quartz veins, which are spatially associated with a granite-porphyry, metavolcanics and metagabbro in the Hamash area, South Eastern Desert of Egypt. Four generations of genetically related quartz veins occur in the Hamash mine area. Two types of alteration are developed in

H. M. Helmy; R. Kaindl

1999-01-01

27

Looking at Dauphiné twins in vein quartz from the High-Ardenne slate belt as a potential paleostress indicator  

NASA Astrophysics Data System (ADS)

Paleostress studies commonly call upon (1) a fault slip data inversion technique, (2) a calcite twin stress inversion technique, (3) recrystallized grain size piezometry for quartz, or (4) direct measurements of residual lattice strain. Recent advances in orientation imaging microscopy (OIM) using electron backscatter diffraction (EBSD) on a scanning electron microscope (SEM) have revealed that Dauphiné twinning is very common in quartz in naturally deformed quartz-bearing rocks, in particular in low-grade tectonometamorphic conditions (~250-450°C) typical for the brittle-plastic transition zone at the base of the seismogenic crust (~7-15km). It has long been known that mechanical Dauphiné twinning in quartz can be stress-induced and thus potentially could be used as a (paleo-)stress indicator. To address this question, we performed an extensive EBSD-OIM analysis on well-studied quartz veins in the High-Ardenne slate belt (Belgium, Germany), which precipitated and deformed in low-grade metamorphic conditions during different stages of the orogeny. The vein quartz studied has only been weakly affected by low to moderate temperature (200 to 400°C) crystal-plastic deformation. The samples show grains with a high concentration of Dauphiné twin boundaries and others free of twin boundaries, thus being untwinned or completely twinned. This pattern depends on the crystallographic orientation. Twin boundaries are arrested by grain or subgrain boundaries, suggesting that Dauphiné twinning occurred on a pre-existing fabric that resulted from crystal-plastic deformation. An analysis of the orientation distribution of the rhombs in the twinned variant domains of individual quartz (sub-)grains reveals a particular preferred orientation of the poles to rhombs. Based on these results we will discuss the potential use of Dauphiné twins in vein quartz as a paleostress indicator, possibly completing our toolbox for reconstructing paleostresses in the deep crust.

Sintubin, M.; Wenk, H.

2012-12-01

28

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

29

The ratio of dissolving surface area/growing surface area in the hydrothermal growth of quartz  

NASA Astrophysics Data System (ADS)

It was experimentally confirmed and theoretically proved that in the recrystallization of mineral substances through thermal gradient methods there exists a critical value of the ratio s = dissolving surface area/growing surface area. In the simplest case when the dissolution and growth can be treated as first order reactions, the critical value is determined by the ratio of the rate constants of the two processes, scr= k/k'. As long as the actual ratio of surface areas in an experiment is greater than scr, the growth rate of the seed does not depend on the surface areas, but when it becomes smaller than scr, the nutrient surface area becomes the rate determining step in crystal growth. In the hydrothermal recrystallization of quartz, a value of scr equal to or smaller than 2 was found, which is smaller and more reliable than the earlier proposed value of 5.

Christov, M.; Kirov, G. K.

1993-08-01

30

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

31

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

USGS Publications Warehouse

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

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

2003-01-01

32

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

33

Deformation Mechanics of Quartz at a Single Asperity under Hydrothermal Conditions  

NASA Astrophysics Data System (ADS)

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 asperities under load; diffusion along grain-to-grain contacts; and precipitation in the pore space. The kinetics of the process and the identity of the rate-limiting step in quartzose rocks are still a subject of debate and depend critically upon the structure of the intergranular boundary during deformation. To investigate the mechanisms and kinetics of pressure solution and the effects of changes in boundary morphology, we continuously monitored deformation and the evolution of boundary morphology at a Y-cut convex quartz lens that was pressed against a flat surface of Y-cut quartz under hydrothermal conditions in a see-through optical pressure vessel. Several different boundary morphologies were used, including polished flats, etched and roughened flats, and an island-channel structure fabricated by plasma etching. The island-channel structure had square pillars of quartz, either 4 or 8 ?m on a side, surrounded by an interconnected grid of open channels of comparable width. This geometry introduces stress concentrations within the overall intergranular contact region and dramatically reduces the diffusional path length within the solid-to-solid contact region from that present with polished, flat surfaces. The samples are loaded using quartz weights in an externally heated pressure vessel and relative motion between the quartz flat and lens is monitored using optical interferometry. Contact spot radius ranged from 25 ?m to 60 ?m and the mean effective normal stress at the contact ranged from 800 MPa to 150 MPa. The experiments were run, on an average, for 400 hours at 425°C and 150 MPa fluid pressure. The pore fluid was de-ionized water, which became saturated with quartz during the initial heat-up period. Deformation at the interface between the quartz flat and lens (i.e., intergranular convergence) was observed in only one case: the 4 ?m island-channel structure. In that instance, pillars within the contact region were eroded at a rate that decreased with time, and SEM photomicrographs after the experiment showed significant cataclasis within and adjacent to the pillars. The total transient convergence observed during the 420 hour period was less than the original pillar height. For all surface morphologies, the shapes of the surface structures in both the loaded and unloaded regions evolved, perhaps owing to capillarity forces. Although an interconnected island-channel structure was initially imposed upon some of the experiments, this open, fluid-filled boundary structure was seen to be a transient phenomenon that was largely destroyed during convergence. Thus, there was no evidence for a dynamically stable interface, as previously suggested.

Bakku, S.; Beeler, N. M.; Hickman, S.; Evans, B.

2009-12-01

34

Use of DTA to determine the effect of mineralizers on the cement-quartz hydrothermal reactions. Part 2. Clay addition  

Microsoft Academic Search

The effect of adding up to 40% by weight of kaolinite and metakaolinite to cement-quartz mortars hydrothermally cured (autoclaved) at 175°C was investigated by DTA. It is evident that aluminium substitution in the CSH-I lattice takes place with the clay additions in a manner similar to that observed for gibbsite addition, as reported in the previous paper (Part 1, Thermochim.

A. Ray; E. R. Cantrill; M. G. Stevens; L. Aldridge

1995-01-01

35

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

36

Nitrogen Partial Pressure in the Archean Atmosphere From Analysis of Hydrothermal Quartz  

NASA Astrophysics Data System (ADS)

Atmospheric nitrogen constitutes the main pool of one of the major biogenic elements, it may provide a record of the terrestrial magnetic field, and it might have been instrumental to maintain clement temperatures despite a lower energy provided by the ancient Sun. We have investigated the partial pressure of di-nitrogen in the Archean atmosphere by analyzing the ratio between N2 and argon-36 (a primordial, chemically inert noble gas for which there is no reason to suspect abundance variation in the atmosphere through time) in fluid inclusions (FI) trapped in two hydrothermal quartz from the 3.5 Ga-old Dresser formation, North Pole, Pilbara (NE Australia). These samples have different histories of fluid trapping and deposition, and their ages are constrained within 3.0-3.5 Ga from U-Xe, and Ar-Ar dating. FI nitrogen is a mixture between hydrothermal and air-saturated water (ASW) end-members, that can be identified through geochemical correlations between Cl/36Ar, 40Ar/36Ar and N2/36Ar ratios. The ASW component has a N2/36Ar ratio within 30 % of the modern value, implying a N2 partial pressure during the Archean was within 0.6-1 bar. The nitrogen isotopic composition of the ASW end-member is also found similar to the present-day one within 3 permil. Combined with the recent proposal from ancient raindrop imprints that the total atmospheric pressure was 0.5-1.14 bar, this leaves less than 0.7 bar for the pressure of other atmospheric gases including CO2. Thus nitrogen did not play a significant role in the thermal budget of the ancient Earth, and the terrestrial magnetic field was already strong enough at that time to shield the upper atmosphere from interaction with the solar wind, and therefore to prevent atmospheric escape that would have been recorded otherwise in the nitrogen composition. These results also imply that exchanges of nitrogen between the Earth's mantle and the surface were limited, or proceeded at similar rates in both ways from the Archean to Present.

Marty, B.; Zimmermann, L.; Burgess, R.; Pujol, M.; Philippot, P.

2012-12-01

37

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.

2014-06-01

38

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

39

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

Microsoft Academic Search

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

S. P. Kilias; J. Konnerup-Madsen

1997-01-01

40

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

41

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.

42

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

43

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

44

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

45

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

NASA Astrophysics Data System (ADS)

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

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

2002-05-01

46

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

47

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

48

Direct measurement of asperity contact growth in quartz at hydrothermal conditions  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

49

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

50

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

NASA Astrophysics Data System (ADS)

Hydrothermal synthesis process of tobermorite (5CaO·6SiO 2·5H 2O) has been investigated by in-situ X-ray diffraction using high-energy X-rays from a synchrotron radiation source in combination with a purpose-build autoclave cell. Dissolution rates of quartz were largely affected by its particle size distribution in the starting mixtures. However, the composition (Ca/Si) of non-crystalline C-S-H at the start of tobermorite formation was identical regardless of the quartz dissolution rate. An effect of water-to-solid ratio (w/s) was investigated for samples using fine particle quartz. Tobermorite did not occur with w/s of 1.7 but occurred with w/s higher than 3.0. Surprisingly, however, the dissolution curves of quartz were nearly identical for all samples with w/s from 1.7 to 9, indicating that the dissolution rate is predominated by surface area. Possible reaction mechanism for tobermorite formation will be discussed in terms of Ca and/or silicate ion concentration in the liquid phase and distribution of Ca/Si in non-crystalline C-S-H.

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

2011-08-01

51

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

52

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

53

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

54

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

Microsoft Academic Search

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

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

2006-01-01

55

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

56

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

NASA Astrophysics Data System (ADS)

The phosphate-sulphate mineralization occurs in quartz veins in Lower Triassic metaquartzites of the Tribe? Mts., Central Western Carpathians, Slovakia. The mineralization comprises of lazulite, Ba, Sr, Ca, K-rich phosphates-sulphates and barite in an association with muscovite, hematite, locally rutile, zircon, chlorite and tourmaline. The most widespread lazulite forms up to 10 cm large pale to deep blue aggregates in massive quartz. Electron-microprobe analyses show a relatively uniform composition with Mg/(Mg + Fe) =0.85 to 0.93. The Mössbauer spectroscopy reveals 11-30% Fe 3+/Fe total. Possible primary goedkenite-bearthite binary s.s. shows the highest known Sr contents worldwide: Sr/(Sr + Ca) = 0.67-0.71; Mg, Ba and REE contents are negligible. The lazulite is replaced by a secondary association of Ba, Sr, Ca, K-rich phosphates-sulphates: gorceixite, rarely goyazite, crandallite, svanbergite, jarosite and a rare phase, close to (Ba,K,Sr)(Fe 3+,Al) 3[(OH,H 2O) 6(PO 4)(SO 4)] composition (Ba,Fe,S,P-phase). Gorceixite exhibits more restricted compositional variations between gorceixite-goyazite and gorceixite-crandallite s.s.: Ba/(Ba + Sr) = 0.73-0.99, Ba/(Ba + Ca) = 0.78-0.99 and (P - 1)/[(P - 1) + S] = 0.84-0.99. On the contrary, the secondary Sr, Ca-dominant phosphates-sulphates of the crandallite and beudantite groups show wide compositional variations and complex quarternary solid-solution series between goyazite-crandallite and svanbergite-woodhouseite with Sr/(Sr + Ca) = 0.16 to 0.99 and (P - 1)/[(P - 1) + S] = 0.07 to 0.97. The K, Ba-dominant phosphates-sulphates of the alunite and beudantite groups occur along jarosite-Ba,Fe,S,P-phase s.s. line with Ba/(Ba + K) = 0.07 to 0.56, Fe/(Fe + Al) = 0.55 to 0.99, P/(P + S) = 0.14 to 0.57 and elevated Sr and Ca (up to 0.24 and 0.12 apfu, respectively). The compositions indicate a close relationship and mutual substitutions between the crandallite, beudantite and alunite groups. Unlike to analogous phosphate-bearing assemblages in the Alps, investigated phosphate-sulphate association doesn't contains REE, Y and Sc minerals but it is rich in Ba-phases (barite, gorceixite). The peak metamorphic conditions of the host rocks estimated using the Kübler index of phyllosilicates point to anchizone/epizone boundary, i.e. ca. 270-350 °C. Fluid inclusions study constrained the minimum formation temperatures of the lazulite to 144-257 °C and of the superimposed sulphate-phosphate mineralization to 175-289 °C. Lazulite crystallized from brines of the system H 2O-Na-Mg-Cl-CO 2 with a salinity of 17.2 to 19.8 wt.% NaCl eq. We propose, that the studied mineralization originated from fluids enriched in elements from breakdown of feldspars, biotite, apatite and other phosphates in underlying Hercynian granites. The fluids passed upwards into the metaquartzites and precipitated discrete minerals, due to absence of any suitable sink for the elements among rock-forming minerals.

Uher, Pavel; Mikuš, Tomáš; Milovský, Rastislav; Biro?, Adrian; Spišiak, Ján; Lipka, Jozef; Jahn, Ján

2009-10-01

57

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

NASA Astrophysics Data System (ADS)

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

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

2004-02-01

58

Hydrothermal metamorphism and low-temperature alteration on the Mid-Atlantic ridge  

E-print Network

. 55 26 sulfides and/or penninite. The green copper chloride mineral atacamite is found within veins by itself or associated with quartz. Samples BA3 and 15-8 from the TAG area are also similar in mineral- ogy. They are both composed of plagioclase.... Subsequent oxidation of the greenschist facies rocks have altered Fe and Cu sulfides to geothite, hematite, amorphous Fe ? oxides and the green Cu chloride mineral, atacam? atacomite. Weathered basalts and basalts hydrothermally altered to zeolite facies...

Peron, Philippe Raymond

1978-01-01

59

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

60

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

61

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

E-print Network

not quartz seems to conuol the silica concentration in geothermal systems below 180'C (Fournier, 1973 and 1977; Arnorsson, 1979). The eventual removal of these phases resulted from dissolution enhanced by the introduction of distilled water during the pore...-511. Arnorsson S. (1979) Hydrochemistry in geothermal investigations in Iceland: Techniques and applications. Nordic Hydrology 10, 191-224. Beckwith R. S. and Reeve R. (1969) Dissolution and deposition of mono-silicic acid in suspensions of ground quartz...

Burns, Gregory Lee

2012-06-07

62

External micro-PIXE analysis of fluid inclusions: Test of the LABEC facility on samples of quartz veins from Apuan Alps (Italy)  

NASA Astrophysics Data System (ADS)

Fluid inclusions are small portions, usually smaller than 100 ?m, of fluid trapped within minerals during or after growth. Their characteristics provide therefore fundamental information on nature and evolution of fluids present in the past in different geological environments. At the LABEC laboratory in Firenze, high-salinity fluid inclusions in quartz crystals, coming from the Apuan Alps metamorphic complex, were analysed at the external scanning microbeam. Results, although still preliminary, have already provided us with hints on fluid-rock interaction processes during the metamorphism of the Apuan Alps.

Massi, M.; Calusi, S.; Giuntini, L.; Ruggieri, G.; Dini, A.

2008-05-01

63

The origin and significance of non-aqueous CO 2 fluid inclusions in the auriferous veins of Bin Yauri, northwestern Nigeria  

Microsoft Academic Search

Non-aqueous CO2 and CO2-rich fluid inclusions are found in the vein quartz hosting mesothermal gold-sulphide mineralization at Bin Yauri, northwestern\\u000a Nigeria. Although mineralizing fluids responsible for gold mineralization are thought to be CO2-rich, the occurrence of predominantly pure to nearly pure CO2 inclusions is nevertheless unusual for a hydrothermal fluid system. Many studies of similar CO2-rich fluid inclusions, mainly in

I. Garba; S. O. Akande

1992-01-01

64

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

65

Varicose Veins  

MedlinePLUS

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

66

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

67

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

68

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

69

Varicose Veins  

MedlinePLUS

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

70

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

71

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

72

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

73

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

74

Varicose Veins  

MedlinePLUS Videos and Cool Tools

... blood can reverse its flow. This causes increased pressure in the veins, and over time can cause ... swell and become bulging, varicose veins. The increased pressure can lead to significant symptoms such as: swelling ...

75

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

76

Hydrothermal alteration and evolution of the Ohakuri hydrothermal system, Taupo volcanic zone, New Zealand  

NASA Astrophysics Data System (ADS)

Erosion and excavations at Ohakuri in the Taupo Volcanic zone have exposed the upper portion (100-150 m) of a hydrothermal system that was active sometime between 700,000 and 160,000 years ago. Extensive hydrothermal alteration occurred within a host sequence of young, relatively undeformed, chemically and lithologically similar unwelded rhyolitic ignimbrite and air-fall tuffs. Mapping and petrologic work have identified six distinct alteration types. An early event formed a concentrically zoned suite of alteration through the pervasive movement of alkaline chloride type water. In the innermost zone, primary rock components were almost entirely converted to quartz + adularia ± illite ± hematite ± leucoxene. Mineralized veins and breccias of quartz ± pyrite ± adularia ± chlorite formed here in response to episodic hydraulic fracturing. This zone grades outward and upward into a zone of less intense, lower rank alteration with a mordenite + clinoptilolite + smectite + opal ± hematite assemblage, then a zone of weak clay alteration and into fresh rock. Calcite is conspicuously absent from the entire suite. Acid-sulphate type water, formed from steam-condensate, dominated the shallow activity in a second stage of alteration that followed local erosion. Widespread but discontinuous alteration converted the ignimbrite to kaolinite + opal ± hematite, with alunite occurring in the more intense zones. This alteration locally overprints the early alkali-chloride produced suite, but the focus of the second-stage activity was north of the focus of the older event. Scattered opaline sinters and silicified surficial deposits are products of either still later activity or the waning part of the second stage. Chemical analysis shows that the various alteration types have characteristic patterns of major element addition and removal; these reflect the key hydrothermal mineral reactions that formed the new assemblages. Quartz-adularia alteration involved mainly silicification, dehydration and cation exchange (K + for Na 2+, H +, Ca 2+, Mg 2+), whereas alteration in the mordenite zone was mostly a moderate hydration process. Kaolinite alteration involved strong hydration, hydrolysis and redistribution of silica. Trace elements show varying degrees of mobility and correlation with major elements. Alteration features identify the important upflow zones, zones of mixing between hydrothermal and shallow groundwater, and changes in alkali chloride water level. They also reflect a transition from diffuse to channel flow as sealing eliminated original rock porosity, and led to hydraulic fracturing which maintained fracture permeability in the system. Mineralogy and fluid inclusion studies indicate that the primary fluid at now-exposed levels was a high-pH (7-8), low-CO 2 and low-H 2S water cooler than 200°C, probably modified by boiling at depth.

Henneberger, R. C.; Browne, P. R. L.

1988-05-01

77

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

78

Dike intrusion controls on permeability and hydrothermal circulation of oceanic crust at IODP Hole 1256D  

NASA Astrophysics Data System (ADS)

We examine the hydrothermal structure of the lava-dike transition zone in oceanic crust of Integrated Ocean Drilling Program (IODP) Hole 1256D using detailed sample measurements of permeability, porosity, metamorphic minerals, and structures. The transition zone consists of basaltic sheet and massive flows, a cataclastic unit, and hyaloclastitic breccias. Structural investigations show that this transition occurs through a larger depth interval than that previously defined, extending 254 m upward from the top of the Sheeted Dike Complex (811.4 to 1065.7 meters below seafloor (mbsf)). Through the transition zone, models predict a general decrease in permeability, based on a corresponding decrease in porosity with depth. Laboratory measurements of physical properties show porosity decreases drastically, as does permeability. Thin sections reveal no open pore space, and all structures are filled: veins (mm- to cm-thick) or sets of parallel veins or vein networks, Riedel-deformation bands, cataclasites (quartz, chalcedony, and calcite are the main secondary minerals; hyaloclastic breccia hosts sulfides (mainly pyrite) and is cemented by chalcedony, quartz, calcite, anhydrite, and minor amphibole. The dip angle of planar structures (including cataclasites) show an average downdip increase, thus such sub-vertical structures may represent original cooling fractures and/or might be related to the regional tectonics (i.e., extensional tectonics of the rift zone) or to the local tensional stress field created at the top of the dikes as a direct consequence of dike intrusion. Since this transition zone is located near the boundary between the Low Temperature Alteration Zone (above) and the Hydrothermal Alteration Zone (below), we postulate that fracturing and hydrothermal alteration in the investigated crustal interval likely occurred during dike intrusion. Consequently, the lower part of the lavas (below 811.4 mbsf or 561 meters sub-basement) seems to mark a boundary layer between different stress fields, permeability regimes, and metamorphic imprints.

Gilbert, L. A.; Tartarotti, P.; Fontana, E.; Bona, M. L.; Gross, D.; LaPier, G.; Dempsey, C.

2012-12-01

79

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

NASA Astrophysics Data System (ADS)

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

Sonntag, Iris; Hagemann, Steffen

2010-05-01

80

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

PubMed

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

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

2011-01-01

81

What Causes Varicose Veins?  

MedlinePLUS

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

82

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

2014-12-01

83

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

84

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

NASA Astrophysics Data System (ADS)

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

Hulen, Jeffrey B.; Nielson, Dennis L.

1988-06-01

85

Sclerotherapy of Varicose Veins and Spider Veins  

MedlinePLUS

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

86

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

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

87

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

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

88

Varicose Veins and Spider Veins  

MedlinePLUS

... one-way flaps to prevent blood from flowing backwards as it moves up your legs. If the ... to heal. Sometimes they cannot heal until the backward blood flow in the vein is repaired. • Bleeding. ...

89

Varicose vein - noninvasive treatment  

MedlinePLUS

... Laser therapy - varicose veins; Radiofrequency vein ablation; Endovenous thermal ablation; Ambulatory phlebectomy; Transilluminated power phlebotomy; Endovenous laser ablation; Varicose vein therapy

90

Hydrothermal Processing  

SciTech Connect

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

Elliott, Douglas C.

2011-03-11

91

H2O CO2 CH4-BEARING FLUID INCLUSIONS IN QUARTZ: INSIGHTS INTO THE ORIGIN AND EVOLUTION OF TWO DIFFERENT HYDROTHERMAL AU DEPOSITS FROM THE EGYPTIAN EASTERN DESERT  

E-print Network

24061 Abstract Shear-related, mesothermal gold deposits of Um Egat and Dungash in the Egyptian Eastern. Both deposits are similar in alteration style, structural control, and mineralogy. Gold is related DIFFERENT HYDROTHERMAL AU DEPOSITS FROM THE EGYPTIAN EASTERN DESERT ZOHEIR, B.A.1, EL-SHAZLY, Aley K.2

El-Shazly, Aley

92

Hydrothermal fluid evolution and ore genesis in the Arghash epithermal gold prospect, northeastern Iran  

NASA Astrophysics Data System (ADS)

The Arghash epithermal gold prospect is located in the Sabzevar zone near the northern margin of the Central Iranian Microcontinent. The prospect includes six gold vein systems, hosted mostly by Lower-Middle Eocene intermediate to felsic volcanic and intrusive rocks with chemical compositions characteristic of continental arc magmas. Wall rocks are variably altered to clay minerals and subordinate carbonates, chlorite, and epidote, with intense alteration confined within 1-5 m of the veins. Mineralization consists of fracture fillings with local occurrences of hydrothermal breccias, and disseminations and veinlets in the immediate wall rocks. The veins consist of quartz, carbonates, minor sulfides, and gold. Pyrite is the main sulfide mineral in the hypogene ore in all vein systems except Au-VI where abundant stibnite occurs intergrown with quartz and minor pyrite; base metal sulfides are rare. Four generations of pyrite were identified: (1) disseminated euhedral to anhedral pyrite (Py-I), with up to 430 ppm Au; (2) framboidal pyrite (Py-II) with concentric As-poor and As-rich bands and up to 960 ppm Au; (3) arsenian pyrite overgrowths (Py-III) occurring on euhedral to anhedral Py-I grains, with up to 1980 ppm Au; and (4) fracture-filling, late-stage pyrite (Py-IV) that is anhedral and barren. Homogenization and ice-melting temperatures of fluid inclusions vary from 186 to 306 °C and -0.1 to -3.2 °C in quartz, and from 169 to 287 °C and 0.0 to 2.3 °C in calcite, respectively. Laser combustion analyses indicate a narrow range of ?34S values for Pyrites I-III, between -5.8‰ and +0.1‰, consistent with a magmatic source for sulfur. Pyrite IV is highly enriched in 34S (?34S = +8.9‰ to +23.7‰), and may reflect a contribution from a source enriched in 34S, such as evaporites. The ?34S values for two stibnite samples from the stibnite-rich vein (-18.8‰ and -14.4‰) sharply contrast with those of the pyrite, suggesting a different sulfur, and possibly metal source, or strong fractionation. The ?13C values for calcite are near 1‰, which is typical of marine carbonates. The calculated ?18O values for the hydrothermal fluid in equilibrium with quartz range from +5.5‰ to +7.1‰, and the calculated ?D values of the fluid in equilibrium with illite range from -48‰ to -57‰. The fluid inclusion and stable isotope data suggest that the fluids experienced a complex history of prolonged water/rock interaction, boiling, and mixing. Evidence for boiling is shown by quartz pseudomorphs after bladed calcite and coexisting vapor-rich and liquid-rich fluid inclusions. Water/rock interaction is supported by the occurrence of sulfides and anomalous concentrations of gold in the altered wall rocks adjacent to veins. The alteration and ore mineralogy, textures, fluid inclusion data, and calculated fluid isotopic composition are more consistent with the described characteristics of low-sulfidation epithermal deposits.

Ashrafpour, Esmaeel; Ansdell, Kevin M.; Alirezaei, Saeed

2012-06-01

93

Origin of the color in cobalt-doped quartz  

Microsoft Academic Search

Synthetic Co-doped quartz was grown hydrothermally in steel autoclaves at the Technological Center of Minas Gerais (CETEC), Brazil. The quartz samples, originally yellow in the as-grown state acquired blue coloration after prolonged heat treatment times at 500°C near the alpha-beta transition temperature. UV-VIS-NIR absorption spectroscopy shows the characteristic spectra of Co3+ before heat treatment. After heat treatment, the optical absorption

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

2011-01-01

94

Origin of the color in cobalt-doped quartz  

Microsoft Academic Search

Synthetic Co-doped quartz was grown hydrothermally in steel autoclaves at the Technological Center of Minas Gerais (CETEC),\\u000a Brazil. The quartz samples, originally yellow in the as-grown state acquired blue coloration after prolonged heat treatment\\u000a times at 500°C near the alpha–beta transition temperature. UV–VIS–NIR absorption spectroscopy shows the characteristic spectra\\u000a of Co3+ before heat treatment. After heat treatment, the optical absorption

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

95

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

96

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

97

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

98

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

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

99

Oxygen isotope fractionation in quartz, albite, anorthite and calcite  

Microsoft Academic Search

Laboratory measurements of equilibrium oxygen isotope fractionation in quartz, albite, anorthite, and calcite have been carried out by anhydrous exchange between silicates and calcite at temperatures of 600°C and above. Exchange in these systems is as rapid as exchange between silicates and water. In this paper results are compared with published theoretical estimates as well as data derived from hydrothermal

Robert N. Clayton; Julian R. Goldsmith; Toshiko K. Mayeda

1989-01-01

100

Focus on Varicose Veins  

MedlinePLUS

... Varicose Veins How are varicose veins diagnosed? The diagnosis of varicose veins is made primarily by physical examination. The accuracy of physical examination is further improved with the aid of a hand-held Doppler ( ...

101

What Are Varicose Veins?  

MedlinePLUS

... Main Page The Pink Locker Society What Are Varicose Veins? KidsHealth > Kids > Health Problems of Grown-Ups > Q & ... why veins look purple or blue. What Causes Varicose Veins? It's a lot of work to move all ...

102

Deep Vein Thrombosis  

MedlinePLUS

... the NHLBI on Twitter. What Is Deep Vein Thrombosis? Español Deep vein thrombosis (throm-BO-sis), or DVT, is a blood ... This Content: Next >> October 28, 2011 Deep Vein Thrombosis Clinical Trials Clinical trials are research studies that ...

103

CHLORBARTONITE, K6Fe24S26(Cl,S), A NEW MINERAL SPECIES FROM A HYDROTHERMAL VEIN IN THE KHIBINA MASSIF, KOLA PENINSULA, RUSSIA: DESCRIPTION AND CRYSTAL STRUCTURE  

Microsoft Academic Search

Chlorbartonite, ideally K 6Fe24S26(Cl,S), is a new potassium iron sulfide chloride found as an accessory mineral in a microcline - pectolite - sodalite - aegirine vein within feldspathic urtite at Mount Koashva, Khibina massif, Kola Peninsula, Russia. The mineral occurs as roundish grains up to 2 cm across included in sodalite and natrolite crystals; it is associated with djerfish erite

VICTOR N. YAKOVENCHUK; YAKOV A. PAKHOMOVSKY; YURY P. MEN' SHIKOV; GREGORY Y. U. IVANYUK; SERGEY V. KRIVOVICHEV; PETER C. BURNS

2003-01-01

104

Composite synvolcanic intrusions associated with Precambrian VMS-related hydrothermal systems  

NASA Astrophysics Data System (ADS)

Large subvolcanic intrusions are recognized within most Precambrian VMS camps. Of these, 80% are quartz diorite-tonalite-trondhjemite composite intrusions. The VMS camps spatially associated with composite intrusions account for >90% of the aggregate sulfide tonnage of all the Precambrian, intrusion-related VMS camps. These low-alumina, low-K, and high-Na composite intrusions contain early phases of quartz diorite and tonalite, followed by more voluminous trondhjemite. They have a high proportion of high silica (>74% SiO2) trondhjemite which is compositionally similar to the VMS-hosting rhyolites within the volcanic host-rock successions. The quartz-diorite and possibly tonalite phases follow tholeiitic fractionation trends whereas the trondhjemites fall within the composition field for primitive crustal melts. These transitional M-I-type primitive intrusive suites are associated with extensional regimes within oceanic-arc environments. Subvolcanic composite intrusions related to the Archean Sturgeon Lake and Noranda, and Paleoproterozoic Snow Lake VMS camps range in volume from 300 to 1,000 km3. Three have a sill morphology with strike lengths between 15 and 22 km and an average thickness between 1,500 and 2,000 m. The fourth has a gross stock-like shape. The VMS deposits are principally restricted to the volcanic strata above the strike length of the intrusions, as are areally extensive, thin exhalite units. The composite intrusions contain numerous internal phases which are commonly clustered within certain parts of the composite intrusion. These clusters underlie eruptive centers surrounded by areas of hydrothermal alteration and which contain most of the VMS deposits. Early quartz-diorite and tonalite phases appear to have intruded in rapid succession. Evidence includes gradational contacts, magma mixing and disequilibrium textures. They appear to have been emplaced as sill-dike swarms. These early phases are present as pendants and xenoliths within later trondhjemite phases. The trondhjemite phases contain numerous internal contacts indicating emplacement as composite sills. Common structural features of the composite intrusions include early xenolith phases, abundant small comagmatic dikes, fractures and veins and, in places, columnar jointing. Internal phases may differ greatly in texture from fine- to coarse-grained, aphyric and granophyric through seriate to porphyritic. Mineralogical and isotopic evidence indicates that early phases of each composite intrusion are affected by pervasive to fracture-controlled high-temperature (350-450 °C) alteration reflecting seawater-rock interaction. Trondhjemite phases contain hydrothermal-magmatic alteration assemblages within miarolitic cavities, hydrothermal breccias and veins. This hydrothermal-magmatic alteration may, in part, be inherited from previously altered wall rocks. Two of the four intrusions are host to Cu-Mo-rich intrusive breccias and porphyry-type mineralization which formed as much as 14 Ma after the main subvolcanic magmatic activity. The recognition of these Precambrian, subvolcanic composite intrusions is important for greenfields VMS exploration, as they define the location of thermal corridors within extensional oceanic-arc regimes which have the greatest potential for significant VMS mineralization. The VMS mineralization may occur for 2,000 m above the intrusions. In some cases, VMS mineralization has been truncated or enveloped by late trondhjemite phases of the composite intrusions. Evidence that much of the trondhjemitic magmatism postdates the principal VMS activity is a critical factor when developing heat and fluid flow models for these subseafloor magmatic-hydrothermal systems.

Galley, Alan G.

2003-06-01

105

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

106

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

107

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

108

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

E-print Network

I have studied syntectonic veins from shales and coarse calcareous sands of the Ordovician Womble Shale, Benton uplift, Arkansas. All veins are composed of calcite with minor quartz and trace feldspar and dolomite or high-Mg calcite in the coarser...

Chung, Jae Won

2004-09-30

109

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

NASA Astrophysics Data System (ADS)

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

Kotula, Piotr

2013-09-01

110

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

111

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

112

Mineralogy and Geochemistry of the Nižná Boca Sb-Au Hydrothermal Ore Deposit (Western Carpathians, Slovakia)  

NASA Astrophysics Data System (ADS)

Samples from hydrothermal Sb-Au mineralization in the area SE of Nižná Boca village in the N&iAzke Tatry Mountains were investigated using a variety of geochemical and mineralogical methods. Ore minerals typically occur in N-S striking quartz-carbonate veins hosted by an I-type biotite granodiorite to tonalite of Variscan Age (the ?umbier Type). Paragenetic associations in the deposit are comparable to other mineralizations of the same type in the ?umbierske Nízke Tatry Mountains. A quartz-arsenopyrite, pyrite stage of mineralization is the oldest with a calculated temperature of formation of about 445°C. It is followed by a quartz-carbonate-stibnite, zinkenite stage and, in turn, a quartz-carbonate-sphalerite-galena, boulangerite-gold stage. The gold typically contains between 9-18 wt.% Ag regardless of mineral association. No evidence for further generations of gold was found although it is possible that some gold was remobilized from the structure of the auriferous arsenopyrite. The Au and Ag content of the bulk ore ranges from 0.53 g.t-1 to 20.2 g.t-1 and from 0.9 g.t-1 to 31.2 g.t-1, respectively. A tetrahedrite-chalcopyrite stage is followed by a barite-hematite stage - the youngest assemblage in the deposit. Fluid inclusions from the first mineralization stage are usually less than 3 ?m in size and contain less than 3.6 wt.% CO2; salinity, density and homogenization temperature range from 2.7-16.3 wt.% NaCl(eq), 0.85-1.03 g.cm-1 and 128-280°C, respectively.

Smirnov, Alexander; Pršek, Jaroslav; Chovan, Martin

2007-01-01

113

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

114

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

115

Thermoluminescence in Quartz  

Microsoft Academic Search

X-ray- and uv-excited thermoluminescence in natural quartz was ; investigated by studying the properties of synthetic samples. The results for a ; large number of natural samples, including singie crystals, outcrop specimens, ; and core-hole samples showed that most of them had four prominent glow peaks in ; common. One of these is due to the presence of Ti and

W. L. Medlin

1963-01-01

116

Galileo quartz clock  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

117

Microstructural evolution of syntaxial veins formed by advective flow  

NASA Astrophysics Data System (ADS)

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

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

2004-03-01

118

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

119

Inverted high-temperature quartz  

Microsoft Academic Search

Fifty-two samples of inverted high-temperature quartz from volcanic rocks were investigated by Guinier-Jago powder diffractometry\\u000a and differential scanning calorimetry (DSC). Quartz megacrysts from Clear Lake and Cinder Cone, California show a variability\\u000a of ?2.5 ° K in their ?-? transition temperature (T\\u000a ?-?). Quartz phenocrysts and quartz from crystalline rocks give a range of 0.5 ° K in T\\u000a ?-?.

M. S. Ghiorso; I. S. E. Carmichael; L. K. Moret

1979-01-01

120

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

NASA Astrophysics Data System (ADS)

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

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

2004-05-01

121

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

122

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

123

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

124

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

125

Plastic Deformation of Quartz: Unfinished business?  

NASA Astrophysics Data System (ADS)

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

Paterson, M. S.

2011-12-01

126

Force chain forming quartz in an ultramylonite  

NASA Astrophysics Data System (ADS)

Polymineralic ultramylonites often show microstructures indicative of grain size sensitive creep with dissolution precipitation or diffusion accommodated grain boundary sliding. Typically phases show an anticorrelated distribution, the grain size is small and a crystallographic preferred orientation is absent. The latter observation is usually thought to originate from rigid body rotation of grains because flow dominated by diffusion creep operates at differential stresses, which are too low to activate crystal-plastic mechanisms. Here, we present quartz texture measurements from a natural ultramylonite, deformed under upper amphibolite facies conditions from the Nordmannvik Nappe, Upper Allochton of the Norwegian Caledonides. The ultramylonite has a mean grain size < 10 ?m (eq. diameter) and shows a very homogeneous microstructure with an anticorrelated phase distribution with quartz (50 vol%), separated by a matrix of biotite, white mica, plagioclase and titanite while garnet forms porphyroclasts. Quartz occurs either as isolated grains or in 'one grain' thick, small clusters. Two types of clusters can be distinguished: foliation parallel clusters and oblique clusters with a long axis at a small angle to the inferred shortening direction, the latter being prominent in the most homogeneous ultramylonite. Quartz shows a weak but non-random texture. In the foliation parallel clusters a [c]-axis maximum is elongated around the y-direction towards the normal of the foliation, -axes form point maxima at a small angle to the lineation, very similar to textures found in high temperature quartz mylonites (e.g. Pennacchioni et al., 2010). In the foliation oblique clusters, the [c]-axes form a very broad maximum around the y-direction and axes show three distinct, close to orthogonal maxima close to x,y,z-directions, rotated about 10-15° antithetically around the y-direction. Isolated quartz grains also show a weak texture of this type. Quartz grains contain low angle boundaries, some of which can be interpreted as subgrain boundaries, mainly related to prism-a and rhomb-a slip, suggesting the activation of crystal-plastic processes. Alternative texture forming processes (e.g. growth textures) are also discussed. The texture in the foliation parallel clusters is thought to be an inherited texture from lower strain stages in the ultramylonite, as it is mostly present in the least deformed parts of the ultramylonite. However, we suggest that the texture formed in the foliation oblique clusters is related to a dynamic formation of force chains between quartz grains, where differential stresses become high enough for plastic yielding. The presence of force chains questions whether ultramylonites necessarily need to possess a linear viscous rheology, even if microstructures would indicate a diffusion creep mechanism. Pennacchioni G., Menegon L., Leiss B., Nestola F., Bromiley G., 2010: Development of crystallographic preferred orientation and microstructure during plastic deformation of natural coarse?grained quartz veins. Journal of Geophysical Research, Vol. 115, B12405

Kilian, Rüdiger; Morales, Luiz F. G.; Peters, Max

2014-05-01

127

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

128

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

129

Experimental dissolution of sanidine under hydrothermal conditions: Mechanism and rate  

Microsoft Academic Search

Dissolution rate measurements of sanidine at 100° to 300°C provide new insight into the rate limiting reactions governing feldspar dissolution behavior close to chemical equilibrium. The experiments were conducted under various condi- tions, but mainly at neutral pH and at saturation with respect to quartz, these conditions being assumed to be representative of diagenetic and hydrothermal environ- ments. Far from

GILLES BERGER; DANIEL BEAUFORT; JEAN-CLAUDE LACHARPAGNE

2002-01-01

130

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

131

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

132

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

NASA Astrophysics Data System (ADS)

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

Gillis, K. M.

2008-12-01

133

Recurrent varicose veins  

Microsoft Academic Search

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

John P. Royle

1986-01-01

134

Major peripheral veins injuries.  

PubMed

The injury was severe in wounded limb patients of this series who suffered from an associated major peripheral vein trauma. The presence of such an injury weighed heavily on the prognosis. Thirty eight patients with major peripheral veins injuries are reviewed. The injury had resulted from war wounds, work or road accidents. The superficial femoral vein was the most frequently injured vein. Associated injuries were frequently noted: soft tissues injuries in 35 patients, fractures in 33, arterial injuries in 32 and peripheral nerve injuries in 22 patients. Shock was more often present and more severe in patients who suffered also from a vein injury than in patients with an arterial injury only. The lacerated femoral vein was ligated in the majority of patients. Attempts were made to repair the lacerated popliteal veins. Repair of the vein was usually done by anastomosis of debrided ends. When an arterial injury was also present, it was repaired first. The postoperative complications were frequent and included infections, thrombophlebitis and pulmonary embolisations. Twenty four patients were discharged with a viable limb. Complete function was recovered in seven patients only. Partial neurological deficit remained in twelve patients and complete paralysis in five. Twelve patients underwent subsequent amputation of the injured limb. Indications for amputation were ischemia in eight, infection or extensive destruction of tissues in four. Two patients died. PMID:961040

Romanoff, H; Goldberger, S

1976-01-01

135

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

136

Vein graft failure.  

PubMed

After the creation of an autogenous lower extremity bypass graft, the vein must undergo a series of dynamic structural changes to stabilize the arterial hemodynamic forces. These changes, which are commonly referred to as remodeling, include an inflammatory response, the development of a neointima, matrix turnover, and cellular proliferation and apoptosis. The sum total of these processes results in dramatic alterations in the physical and biomechanical attributes of the arterialized vein. The most clinically obvious and easily measured of these is lumen remodeling of the graft. However, although somewhat less precise, wall thickness, matrix composition, and endothelial changes can be measured in vivo within the healing vein graft. Recent translational work has demonstrated the clinical relevance of remodeling as it relates to vein graft patency and the systemic factors influencing it. By correlating histologic and molecular changes in the vein, insights into potential therapeutic strategies to prevent bypass failure and areas for future investigation are explored. PMID:24095042

Owens, Christopher D; Gasper, Warren J; Rahman, Amreen S; Conte, Michael S

2015-01-01

137

Petrochemical Characteristics of the Felsic Veins within the Kaman Metamorphic Rocks: Central Anatolia, Turkiye  

NASA Astrophysics Data System (ADS)

The basement metamorphic rocks which outcrops in the vicinity of Kaman-Kirsehir, in Central Anatolia are composed of gneiss, biotite schist, amphibole schist, quartzite intercalated with amphibolite lenses in the región. This metamorphic rocks are cut by felsic veins. Felsic vein rocks are mainly composed of orthoclase, quartz, plagioclase, biotite and pyroxene minerals with accessory titanite and opaque minerals. Felsic vein rocks have holocrystalline texture in general and composed of mega crystalline orthoclase, quartz and mostly euhedral mafic minerals. The felsic veins are quartz syenite in composition. They are characterised by the lack of mafic magmatic enclaves. Clay formation, chloritization and opasitization with minor amount of uralitization are the main alteration part of the unit. The felsic veins which cut the Kaman Metamorphic rocks have SiO2 % concentration vary between 57.22-70.9 %, Na2O% concentration between 1.9-2.63% and K2O% concentration between 6.34 - 9.01%. Felsic veins are enriched in LIL (large ion lithophile) elements compared to HFS (high field strength) elements. Obtained geochemical and petrographical datas suggest that the felsic veins are genetically related with Central Anatolia alkalen magmatic rocks and they may belong to the alkalen magmatic rocks which have excess crustal contamination.

Kilic, C. O.; Kadioglu, Y. K.

2012-04-01

138

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.

139

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

PubMed

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

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

2013-05-01

140

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

141

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

142

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

SciTech Connect

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

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

1985-01-01

143

Deep Vein Thrombosis  

MedlinePLUS

... also called blood thinners) such as warfarin or heparin. Anticoagulants thin your blood so that clots won' ... form. Warfarin is taken as a pill and heparin is given intravenously (in your veins). If you ...

144

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

145

A comparative mineralogical study of Te-rich magmatic-hydrothermal systems in northeastern Greece  

NASA Astrophysics Data System (ADS)

Several magmatic-hydrothermal systems in northeastern Greece (western Thrace and Limnos Island) are highly enriched in tellurides which, in addition to native gold and electrum, represent major carriers of precious metals in the ore. Deposition near the porphyry-epithermal transition for several systems is indicated by field relations and by the presence of key minerals (Pb- and Ag-rich tellurides, Bi-sulfosalts and Bi-tellurides/tellurosulfides). Hessite, stützite, sylvanite, petzite, coloradoite, altaite, unnamed Ag-sulfotelluride, native tellurium and electrum are abundant in intermediate sulfidation quartz-carbonate veins together with zincian tetrahedrite-group minerals, chalcopyrite and galena. The presence of hessite, goldfieldite, native gold and enargite or famatinite suggests deposition at a high sulfidation state. The main stage of telluride deposition took place at ˜275 °C at log fTe2 values of -8.5 to -7.1 and log fS2 values of -10.8 to -9.0, based on the Fe-content in sphalerite and the sulfide-telluride mineralogy. The close spatial association of telluride mineralization with intrusive centers of intermediate composition, the base metal enrichment and the trace element signature involving Au, Ag, Te, Bi, Sn and Mo suggest that ore-forming components were introduced at the porphyry-epithermal transition. Potential sources of tellurium are the high-K calc-alkaline (western Thrace) to shoshonitic (Limnos) intrusive rocks.

Voudouris, P.

2006-07-01

146

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

147

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

148

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

149

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

USGS Publications Warehouse

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

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

1994-01-01

150

Thermal Effects in the Hydrothermal Regime of Magmatic-Hydrothermal Systems  

NASA Astrophysics Data System (ADS)

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

Candela, P. A.

2002-05-01

151

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

152

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

USGS Publications Warehouse

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

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

1979-01-01

153

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

154

Thermoelectrically-cooled quartz microbalance  

NASA Technical Reports Server (NTRS)

Temperature of microbalance can be maintained at ambient temperature or held at some other desired temperature. Microbalance has tow-stage thermoelectric device that controls temperature of quartz crystal. Heat can be pumped to or from balance by Peltier effect.

Mckeown, D.

1975-01-01

155

Epidemiology of varicose veins  

Microsoft Academic Search

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

Robert Beaglehole

1986-01-01

156

Influence of tobermorite formation on mechanical properties of hydrothermally solidified blast furnace slag  

Microsoft Academic Search

A hydrothermal processing method has been used to solidify blast furnace water-cooled slag (BFWS), in which the BFWS could\\u000a be solidified in an autoclave under saturated steam pressure (1.56 MPa) at 200 °C for 12 h by the additions of quartz or coal\\u000a fly ash. The experimental results showed that the addition of the quartz or fly ash was favorable to the formation

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

2008-01-01

157

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

158

Hydrothermal solidification of blast furnace slag by formation of tobermorite  

Microsoft Academic Search

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

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

2007-01-01

159

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

160

ORIGIN OF MAGNESITE VEINS IN SERPENTINITES FROM MOUNT EL-RUBSHI AND MOUNT EL-MAIYIT, EASTERN DESERT, EGYPT  

Microsoft Academic Search

Serpentinite-hosted magnesite veins have been studied in Mt. El-Rubshi and Mt. El- Maiyit, Eastern Desert, Egypt, in order to elucidate the origin of this type of ore. The studied cryptocrystalline magnesite veins were formed as the fracture fillings from ascending CO2-rich hydrothermal solutions. These solutions were brought from deeper- seated horizons upwards to a shallower zone, where due to the

MOHAMED F. GHONEIM; IBRAHIM A. SALEM; MOHAMED M. HAMDY

161

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

162

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

163

Hydrothermal Liquefaction of Biomass  

Microsoft Academic Search

Hydrothermal liquefaction technology is describes in its relationship to fast pyrolysis of biomass. The scope of work at PNNL is discussed and some intial results are presented. HydroThermal Liquefaction (HTL), called high-pressure liquefaction in earlier years, is an alternative process for conversion of biomass into liquid products. Some experts consider it to be pyrolysis in solvent phase. It is typically

Douglas C

2010-01-01

164

Hydrothermal Mineralization Along the Volcanically Active Mariana Arc  

NASA Astrophysics Data System (ADS)

In March and April, 2004, ROPOS ROV dives took place from the R/V T.G. Thompson along the volcanically active Mariana arc to ground truth CTD data collected a year earlier that indicated hydrothermal activity. Dives took place on seven volcanoes, six of which showed hydrothermal activity. We present data on samples collected from NW Rota-1 (14° , 36'N, 144° , 46'E), E. Diamante (15° , 56'N, 145° , 41'E), and NW Eifuku (21° , 29'N, 144° , 03'E), the three sites most studied. All the hydrothermal systems found are associated with volcano summits, or with resurgent domes inside a caldera. Brimstone vent at NW Rota-1 provided a dramatic display of thick, bellowing, yellow plumes that contained ash and molten sulfur. This site occurs at 500 m water depth and clearly shows closely associated magmatic-hydrothermal discharge. Sulfur was the dominant hydrothermal mineral deposited around the vent and occurs as spheres in the surrounding volcaniclastic sediment, fracture fill and veins, and massive deposits. The Black Forest vent field at E Diamante consists of a sulfide-sulfate chimney system developed at about 650 m water depth. This is the only mature system discovered and consists of numerous tall (up to 9 m) chimneys. The measured fluid temperature of 240° C produces boiling at the depth of the vents. The chimneys and mounds are composed of varying amounts of pyrite, sphalerite, chalcopyrite, barite, and anhydrite. Hydrothermal Mn oxides occur on the surface of inactive chimneys. This mineralogy contrasts with the other two systems, which deposit sulfur as the dominant hydrothermal product. The Cu-Zn-Fe-Ba mineralization is perhaps largely controlled by water/rock interaction. A unique hydrothermal field (Champagne field) was found at NW Eifuku where liquid CO2 is discharging from focused- and diffuse-flow vents at 1600 m water depth. The focused-flow vents consist of small chimneys and mounds up to a meter high that are composed of sulfur and yet to be identified minerals. Sulfides were not recovered from this site. At Champagne, sulfur also occurs as crusts on the surface of sediment in areas of diffuse-flow venting, as fracture fill and veins, and as massive deposits. The dominant characteristics of the hydrothermal mineralization along the Mariana arc are shallow-water systems, highly permeable rocks, gas (SO2, H2S, CO2)-rich discharge, and magmatic-hydrothermal systems controlled by the depth-to-boiling-point curve. These characteristics result predominantly in the subsurface deposition of sulfide mineralization, with E Diamante being the exception.

de Ronde, C. E.; Hein, J. R.; Embley, R. W.; Stern, R. J.

2004-12-01

165

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

166

Structure and properties of loaded silica contacts during pressure solution: impedance spectroscopy measurements under hydrothermal conditions  

Microsoft Academic Search

In order to investigate directly the structure and properties of grain boundaries in silicate materials undergoing pressure solution, in situ measurements of these properties are required. We report electrical impedance spectroscopy measurements, performed, under hydrothermal conditions, on individual glass-glass and glass-quartz contacts undergoing pressure solution. Resulting estimates of the average grain boundary diffusivity product ( Z = Ddelta_{{av}} C^{*} )

R. van Noort; C. J. Spiers; C. J. Peach

2011-01-01

167

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

168

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

169

About Quartz Crystal Resonator Noise: Recent Study  

E-print Network

to the drive level, the temperature operating point and the tuning capacitor. Keywords: Flicker Noise, Quartz of a quartz crystal resonator is now clearly identified as 1/f noise and it is the main limitation of ultra

Paris-Sud XI, Université de

170

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

171

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

172

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

173

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

Microsoft Academic Search

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

Y. Tong; J. Royle

1995-01-01

174

The Quartz–Coesite Transition  

Microsoft Academic Search

The quartz-coesite transition curve has been determined over the temperature range 700 ø to 1700øC in the pressure range 20 to 40 kb. The equation for the curve is P ---- 19.5 - 0.0112T, where P is in kilobars and T is in degrees centigrade. The determination was made with an internally heated tungsten carbide pressure vessel utilizing talc for

F. R. Boyd; J. L. England

1960-01-01

175

Redistribution of Water During Deformation of Milky Quartz  

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

176

Infrared imaging of varicose veins  

NASA Astrophysics Data System (ADS)

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

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

2004-06-01

177

Recent Hydrothermal Systems  

NASA Astrophysics Data System (ADS)

The investigation of recent hydrothermal systems, especially the understanding of their development and structure, is one of the main fields of application of reactive transport simulation models. The aim of numerical studies of recent hydrothermal systems is to set-up or evaluate conceptual models of geothermal areas which are able to describe the processes of fluid flow and heat transfer as well as to explain the formation of observed alteration products. This is the preliminary stage to the application of reactive transport simulation for reservoir management (compare Chap. 7) where evaluated models are used for parameter estimation in response to the exploitation of a hydrothermal system. Within the first part of this chapter typical, currently published numerical studies of recent hydrothermal systems are summarized. The published case studies describe sophisticated numerical simulations contributing new insights to the understanding of the structure and development of hydrothermal systems. The following second part is a detailed case study of the shallow hydrothermal system of Waiwera (New Zealand). The case study evaluates the proposed conceptual model of the geothermal field and the derived natural state is used for history matching of the exploitation since 1863. Under consideration of the current conditions reservoir development is estimated until the year 2018.

Kühn, Michael

178

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

179

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

180

Weathering and hydrothermal alteration of basalts in Iceland: mineralogy from VNIR, TIR, XRD, and implications for Mars  

NASA Astrophysics Data System (ADS)

Recent orbital investigations have revealed that aqueous alteration on early Mars took place in diverse alteration environments indicated by distinctive assemblages of minerals (Murchie et al., 2009, JGR). There is growing evidence for past diagenetic or low-temperature/pressure hydrothermal activity on Mars at neutral to alkaline pH, indicated by the presence of Fe/Mg smectites, chlorite, prehnite, serpentine, opaline silica, and zeolites such as analcime in Noachian terrains (Ehlmann et al., 2009, JGR). In recent investigations of terrestrial Mars analog sites, neutral to alkaline pH alteration of basalt, both pedogenic and hydrothermal, has been understudied in favor of sulfur-rich, acidic systems including those at the Hawaiian volcanoes and Rio Tinto, Spain. We began study of the alteration of basalt lava flows in Iceland as a geochemical analog for Noachian Mars. Because the basaltic bedrock is recently formed (<16Ma) with few localities of more highly evolved composition and has poorly formed soils and spare vegetation, the ground and surface waters are broadly similar to those which might have existed on Noachian Mars. Iceland has a variety of geothermal spring systems--low T, low S; low T, high S; and high T, high S--each of which creates distinctive mineralogic assemblages. Here we examine rocks of the Hvalfjordur peninsula, collected from basalt flows that were in some places altered at the surface by pedogenesis and in other locations were hydrothermally altered by non-sulfurous groundwater circulation (low T, low S) following the emplacement of a later hot basalt flow. Rock samples were surveyed in the field using a portable VNIR spectrometer. Altered and unaltered rocks that were typical for the locality were collected as were altered rocks whose spectra were most similar to those measured by CRISM from Mars orbit. Ten rocks were ultimately selected for detailed laboratory analyses: zeolitized basaltic rocks bearing minerals including analcime and thomsonite, basalts with silica/quartz-bearing veins, basalts bearing celadonite, and basalts partially altered to montmorillonite, Fe/Mg smectite, or mixed smectite-chlorite. Analyses included: (1) measurement of reflectance spectra of the whole rock by the ASD; (2) measurement of VNIR and TIR spectra in RELAB of particle-size separates (<25um and <125um) derived from the bulk rock and from precipitated minerals extracted from the vesicles; (3) measurement of X-ray diffraction (XRD) patterns, including quantitative XRD; and (4) electron microprobe chemical analyses. These data emulate orbital data from CRISM, OMEGA, and TES, which detect the infrared active components, linked to in-situ data on whole rock modal mineralogy such as will be measured by the ChemMin instrument on the MSL rover.

Ehlmann, B. L.; Mustard, J. F.; Bish, D. L.

2009-12-01

181

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

NASA Astrophysics Data System (ADS)

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

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

2002-03-01

182

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

183

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

184

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

185

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

186

Geometry and petrography of stockwork vein swarms, Macraes mine, Otago Schist, New Zealand  

Microsoft Academic Search

The Macraes gold deposit is located in a low?angle northeast?dipping (c. 15°) shear zone, the Hyde?Macraes Shear Zone (HMSZ) cutting greenschist facies metasediments of the Otago Schist. The shear zone is host to large volumes of mineralised schist and relatively sparse quartz veins. During the development of this through?going shear, the schist underwent episodes of hydrofracturing and fluid redistribution. As

M. J. Begbie; D. Craw

2006-01-01

187

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

188

Surface and interfacial free energies of quartz  

Microsoft Academic Search

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

George A. Parks

1984-01-01

189

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

NASA Astrophysics Data System (ADS)

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

Rozendaal, A.; Moyen, J.

2009-05-01

190

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

NASA Astrophysics Data System (ADS)

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

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

1983-06-01

191

Precipitation mechanism of Al-substituted tobermorite using hydrothermal reaction  

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

192

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

193

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

194

Fault and vein relationships in a reverse fault system at the Centenary orebody (Darlot gold deposit), Western Australia: Implications for gold mineralisation  

NASA Astrophysics Data System (ADS)

The Centenary orebody within the Darlot gold deposit is located in the Yandal greenstone belt in the Yilgarn Craton, Western Australia. At Centenary, moderately (˜45°) west dipping reverse faults and steeply dipping (>70°) faults of variable strike failed during gold mineralisation in response to sub-horizontal east-west shortening and sub-vertical extension. Gently dipping veins are temporally, genetically and spatially related subsidiary structures to west dipping reverse and steeply dipping faults. Line analyses of subsidiary vein distributions in 23 drill cores around Centenary suggest that the gold-related subsidiary veins are localised within a 200-300 m wide tabular linking damage zone between three west dipping faults (Thompson, Lords and Walters). The damage zone is a laterally stepping relay zone between the Thompson and Lords-Walters faults and has a pull-apart geometry. Anomalous vein-related extensional strain (>0.005), vein density (>0.20) and power-law vein thickness population characteristics ( D t 0.58-1.84) distinguish this zone from the surrounding rock. Within the linking damage zone the highest number and volume of veins are observed at the tip of the Walters fault. At the fault tip, the exponent of the power-law distribution of vein thickness is highest ( D t 1.84) indicating that vein-related extensional strain is distributed on a high number of relatively small thickness veins. At approximately 300 m distance from the fault tip the densities of veins and the measured exponents of power-law vein thickness distributions are lower (<0.80 and D t <1.3, respectively). However, bulk vertical extensional strain remains high (>0.005), indicating that subsidiary vein material is concentrated on a greater number of anomalously thick veins. These systematic variations suggest that the fault tip imparted a strong control on vein localisation. Strain localisation within the linking damage zone is complex with coefficients of variation of vein spacing greater than one implying vein clustering. Gently dipping veins occur as wing crack arrays to the reverse faults and also in arrays comprising curviplanar, intersecting networks of subsidiary veins. The linking damage zone corresponds closely with the Centenary gold resource indicating that it has been an important locus for the focussed flux of gold-bearing hydrothermal fluids. However, within the damage zone, individual veins and vein arrays on the tens of metre scale do not always correlate with high gold grade indicating additional complexity within the system.

Kenworthy, Shane; Hagemann, Steffen G.

2007-04-01

195

Geochemistry of hydrothermal fluids at the Hatoma Knoll in Okinawa Trough  

NASA Astrophysics Data System (ADS)

Hatoma knoll is a caldera volcano which exists in the southern part of Okinawa Trough, and the hydrothermal field was discovered in the caldera in 1999. A lava dome exists in the center part of the caldera, and clear smokers up to 324.5°C, benthic organism colony and liquid CO2, and CO2 hydrate have been observed around the dome. Since 2000, the investigation cruise (NT00-06, YK07-04, NT07-12, NT08-13, and NT09-10) by "Shinkai2000", "Shinkai6500" and the "HYPER-DOLPHIN 3K" has been carried out. Hydrothermal fluid samples were taken from the hydrothermal system, and chemical and isotopic compositions of the hydrothermal fluid samples were investigated. The chemical composition of hydrothermal fluid has high pH compared with the hydrothermal fluid in the mid-ocean ridge, and ammonium concentration is high, suggesting that the sediments covered the Okinawa Trough contribute to the chemical composition of hydrothermal fluid. The end-members of hydrothermal fluid show a variation, but the ratios of the end-members are consistent with each other, suggesting that the hydrothermal system has a single source and subcritical phase separation occurs below the seafloor. The equilibrium temperature with the quartz based on Si concentration was 350-400°C at 1-2 km below the seafloor. CO2 concentration in hydrothermal fluid showed the high-level value in the hydrothermal system in the world. The origin of the abundant CO2 is the carbonate on the subducting plate and the sediment in the Okinawa Trough based on the carbon isotope and the helium isotope. Methane is also the high-level concentration in the hydrothermal system in the world. Most of methane is generated through methanogenesis based on the carbon isotope ratio. Sr isotopic ratio in the hydrothermal fluid suggests the influence of sediment. However, the knoll surface was covered by rhyolite, the influence of sediment would occur in the recharge zone of the hydrothermal system. The methane would be microbially produced in the sediment of the recharge zone, and entrained by the hydrothermal fluid.

Toki, T.; Shinjo, R.; Ishibashi, J.; Tsunogai, U.; Sano, Y.; Takahata, N.; Yamanaka, T.; Kawagucci, S.; Ueno, Y.; Nunoura, T.; Takai, K.

2012-12-01

196

Electron irradiation damage in quartz, SiO2  

NASA Astrophysics Data System (ADS)

Crystallographically orientated samples of synthetic optical-grade colourless quartz with high chemical purity and low dislocation density together with synthetic gem-grade amethyst with high Fe-concentration and ca. 250 H/106 Si (“dry”) or 600 H/106 Si (“wet”) and with very high dislocation densities were irradiated using TEM. Samples of cuts perpendicular (-cuts) and parallel (-cuts) to the c-axis, that were as-grown or pretreated for 5 days at 820 K on air or under p(H2O)=108 Pa were prepared. Characterization methods used include AAS, FTIR, Raman-spectroscopy, X-ray-topography, REM, TEM in SAED and bright-field mode and polarized light microscopy. Radiolysis was carried out in TEM from 10 to 300 K with 100 kV and from 70 850 K (low-high-transition temperature of quartz) with 200 kV. Irradiation damage was investigated by decay of Kikuchi-lines or of Bragg reflections in SAED and in bright-field mode by development of strain contrast centres and of noncrystalline volume areas. Special preparates where the irradiation damage was of microscopic dimensions were investigated using Raman-spectroscopy. Radiolysis of quartz is able to proceed at 10 K with measurable velocity. The required electron dose for a standardized irradiation damage decreases with increasing temperature. At ca. 500 K it goes through a minimum and then increases steadily up to ca. 700 K. From there the increase is steep until ca. 820 K where it culminates sharply, showing strong fluctuations until 850 K. The -cuts in the as-grown state show significantly higher irradiation damage sensitivity than -cuts. Dry or hydrothermal preheating increases the overall sensitivity of irradiation damage and levels out the orientation differences. The high Fe-concentrations in amethyst in comparison with very pure quartz have no detectable influence on the damage sensitivity. This is also true for different water concentrations independently from the ratio of silanole-group to molecular water. Sample thinning by ion etching with different gun currents produces differences in irradiation sensitivity. Thinning by crushing produces samples with sensitivities comparable with ion-etching at low gun current.

Martin, B.; Flörke, O. W.; Kainka, E.; Wirth, R.

1996-10-01

197

Sampling methane in hydrothermal minerals on Earth and Mars  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

198

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

199

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

PubMed Central

Veins of the head and neck exhibiting anatomical variations or malformations are clinically significant. Anatomical variation in the external jugular vein is very common. However, anatomical variation in the retromandibular vein is rare. In this paper, we report a rare case of complete absence of the retromandibular vein. In the absence of the retromandibular vein, the maxillary vein divided into anterior and posterior divisions. The posterior division joined the superficial temporal vein to form an atypical external jugular vein, and the anterior division joined the facial vein to form an anonymous vein. In clinical practice, radiologists and surgeons use the retromandibular vein as a guide to expose the branches of the facial nerve during superficial parotidectomy. Therefore, absence of the retromandibular vein is a hurdle during this procedure and may affect the venous drainage pattern from the head and neck. PMID:24987551

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

2014-01-01

200

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

201

Thermal conductivities of fused and crystalline quartz  

Microsoft Academic Search

The thermal conductivities of fused quartz and of crystalline quartz (heat-flow at 90° to the optic axis) have been measured by steady-state plate methods; the former over the range -150 to 50° C, and the latter at 28° C. The most probable thermal conductivity values of these two materials have been formulated as functions of temperature, having in mind their

E H Ratcliffe

1959-01-01

202

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

PubMed

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

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

2011-01-01

203

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

204

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

SciTech Connect

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

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

1990-09-01

205

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

NASA Astrophysics Data System (ADS)

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

Palazzin, Giulia; Raimbourg, Hugues; Famin, Vincent

2014-05-01

206

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

207

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

208

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

209

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

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

210

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

211

Quartz cement in sandstones: a review  

NASA Astrophysics Data System (ADS)

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

McBride, Earle F.

212

Structure and properties of loaded silica contacts during pressure solution: impedance spectroscopy measurements under hydrothermal conditions  

Microsoft Academic Search

In order to investigate directly the structure and properties of grain boundaries in silicate materials undergoing pressure\\u000a solution, in situ measurements of these properties are required. We report electrical impedance spectroscopy measurements,\\u000a performed, under hydrothermal conditions, on individual glass–glass and glass-quartz contacts undergoing pressure solution.\\u000a Resulting estimates of the average grain boundary diffusivity product ($$ Z = D\\\\delta_{\\\\text{av}} C^{*} $$)

R. van Noort; C. J. Spiers; C. J. Peach

2011-01-01

213

Substrate effect of hydrothermally grown ZnO nanorods and its luminescence properties  

Microsoft Academic Search

We report the hexagonal wurtzite crystalline structure of ZnO nanorod growth by hydrothermal chemical wet synthesis at low temperature (90°C). We have used p-Si (100), n-Si (100), ?-quartz (0001), MgO (0001) and ITO (polycrystalline) substrates to understand the growth mechanism of ZnO nanorods with a low pressure environment. X-ray diffraction study confirms the hexagonal structure of the ZnO nanorod. Scanning

Siddhant K. Das; Surya N. Sahoo; S. N. Sarangi; P. K. Sahoo

2012-01-01

214

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

215

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

NASA Astrophysics Data System (ADS)

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

Lin, Aiming; Yamashita, Katsuhiko; Tanaka, Makoto

2013-03-01

216

Vascular Remodeling in Varicose Veins  

Microsoft Academic Search

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

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

1998-01-01

217

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

218

What Are the Signs and Symptoms of Varicose Veins?  

MedlinePLUS

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

219

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

220

Quartz crystal microbalance use in biological studies  

NASA Technical Reports Server (NTRS)

Design, development, and applications of quartz crystal microbalance are discussed. Two types of crystals are used. One serves as reference and other senses changes in mass. Specific application to study of bacterial spores is described.

Green, R. H.; Godfrey, J. F.; Laue, E. G.; Laue, T. M.; Paik, W. W.; Wardle, M. D.

1972-01-01

221

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

222

(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

223

Quartz resonator fluid monitors for vehicle applications  

SciTech Connect

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

Cernosek, R.W.; Martin, S.J.; Wessendorf, K.O.; Terry, M.D. [Sandia National Labs., Albuquerque, NM (United States); Rumpf, A.N. [Ktech Corp., Albuquerque, NM (United States)

1994-09-01

224

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

225

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

226

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

227

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

NASA Astrophysics Data System (ADS)

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

Asadi, Sina; Rajabzadeh, Mohammad Ali

2010-05-01

228

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

229

Microstructures and Chemistry of Serpentine Minerals in Veins: Constraints on the Hydration Processes of Oceanic Peridotites  

NASA Astrophysics Data System (ADS)

Serpentine minerals are hydrous sheet silicates forming in various geological settings (oceanic extension, subduction, transform faulting) by hydrothermal alteration of magnesian silicates, major components of mantle rocks. They are known to display a large variety of structural types (chrysotile, polygonal serpentine, lizardite, antigorite) whose relative stabilities are poorly constrained by P, T and chemistry. Recent experimental studies suggest that other parameters such as the water-rock ratio, crystallization kinetics, and deformation may affect formation of serpentine types. This study investigates the role of these parameters in natural settings to test if the wide range of serpentine microstructures can record environmental conditions of crystallization. Oceanic serpentinization is accompanied by abundant veining showing different generations of veins with various morphologies and internal textures corresponding to different opening and crystallization conditions. We have selected a representative and extensive set of veins from oceanic serpentinites. We present a detailed chemical, micro- and nano-structural study of the vein-filling serpentine minerals. Vein formation mechanisms are deduced from morphology and texture which then provide constraints on serpentine crystallization conditions. In addition to petrological observations, genetic relationships among the different serpentine types in veins have been identified at different scales using a wide variety of techniques (RAMAN spectroscopy, SEM, TEM, and chemical analyses). The relative importance of parameters that control microstructure stability of serpentines is compared with those obtained from laboratory experiments. These results show how the suite of serpentine microstructures observed in veins is linked to the evolution of environmental conditions (T, chemistry, W/R, mass transfer process-deformation, kinetic) during serpentinization.

Andreani, M.; Mevel, C.; Boullier, A.; Baronnet, A.

2005-12-01

230

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

231

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

232

Hydrothermal Liquefaction of Biomass  

SciTech Connect

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

Elliott, Douglas C.

2010-12-10

233

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

234

The Pantelleria caldera geothermal system: Data from the hydrothermal minerals  

NASA Astrophysics Data System (ADS)

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

Fulignati, Paolo; Malfitano, Giuseppe; Sbrana, Alessandro

1997-02-01

235

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

236

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

237

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

238

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

NASA Astrophysics Data System (ADS)

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

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

1990-04-01

239

Hydrothermal processes at seafloor spreading centers,  

SciTech Connect

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

Sleep, N.H.

1983-01-01

240

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

241

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

242

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

243

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

244

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

245

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

246

Preduodenal portal vein: its surgical significance.  

PubMed

Preduodenal portal vein is a rare anatomical variant which may be one of many anomalies in the neonate with duodenal "atresia." Preduodenal portal vein also may be an occasional finding in an adult undergoing biliary, gastric, or pancreatic surgery. Awareness and recognition of the anomaly are essential for the avoidance of injury during such operations. We report here a symptomless patient whose preduodenal portal vein was discovered at cholecystectomy. PMID:715684

Makey, D A; Bowen, J C

1978-11-01

247

Jugular vein thrombosis associated with distant malignancy.  

PubMed Central

We describe two patients who developed internal jugular vein thrombosis associated with primary malignant disease arising outside the neck, and in one patient it was the presenting feature. Computed tomography was performed and the findings characteristic of internal jugular vein thrombosis are illustrated. We conclude that malignant disease should be considered in patients presenting with spontaneous internal jugular vein thrombosis with no other predisposing factors and that computed tomography is of value in confirming the diagnosis. Images Figure 1 Figure 2 PMID:3211826

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

1988-01-01

248

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

249

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

PubMed Central

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

Monkhouse, W S; Khalique, A

1986-01-01

250

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

251

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

252

Idiopathic rupture of the iliac vein.  

PubMed

Idiopathic rupture of large veins is very rare. There has been one report in the Portugese literature of such an instance involving the iliac vein. Our patient was an elderly woman in whom evidence of intra-abdominal hemorrhage developed. There was no clinical evidence of trauma. At laparotomy a large retroperitoneal hematoma secondary to an 8-mm tear in the left common iliac vein was found. The tear occurred adjacent to where the right common iliac artery passes over the vein. Repair was followed by uneventful recovery. Results of the pathological examination showed nonspecific information. PMID:831681

Brown, L; Sanchez, F; Mannix, H

1977-01-01

253

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

254

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

255

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

256

Fused quartz substrates for microchip electrophoresis  

SciTech Connect

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

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

1995-07-01

257

Quartz rate gyro sensor for automotive control  

Microsoft Academic Search

A new quartz rate gyro sensor has been developed for automotive controls. The principle of the sensor is detection of the Coriolis force with a vibrator. An H shape vibrator supported with a stem at its center was used. The vibrator supported at the center was good for the isolation of a small detection motion from a large excitation motion.

Y. Nonomura; M. Fujiyoshi; Y. Omura; K. Tsukada; M. Okuwa; T. Morikawa; N. Sugitani; S. Satou; N. Kurata; S. Matsushige

2004-01-01

258

Quartz angular rate sensor for automotive control  

Microsoft Academic Search

A new quartz angular rate sensor has been developed for automotive controls. The principle of the sensor is detection of the Coriolis force with a vibrator An H shape vibrator supported with a stein at the center was used The vibrator supported at the center was good for the isolation of a small motion detecting angular rate from an extremely

Y. Nonomura; M. Fujiyoshi; Y. Omura; K. Tsukada; M. Okuwa; T. Morikawa; N. Sugitani; S. Satou; N. Kurata; S. Matsushige

2001-01-01

259

Extensions of quartz-enhanced photoacoustic spectroscopy  

E-print Network

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

Masurkar, Amrita V

2009-01-01

260

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

261

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

262

Crack Healing in Quartz: Influence of Crack Morphology and pOH-  

NASA Astrophysics Data System (ADS)

Crack healing in quartz has been investigated by optical microscopy and interferometry of rhombohedral r-cleavage cracks in polished Brazilian quartz prisms that were hydrothermally annealed. Quartz prisms were pre-cracked at room temperature and then annealed at temperatures T of 250° and 400° C for 2.4 to 240 hours, fluid pressure Pf = 41 MPa (equal to confining pressure Pc), and varying pOH- (from 5.4 to 1.2 at 250° C for fluids consisting of distilled water and NaOH solutions). Crack morphologies before and after annealing were recorded for each sample in plane light digital images and apertures were determined from interference fringes recorded using transmitted monochromatic light (? = 598 nm). As documented in previous studies (Smith and Evans, 1984; Brantley et al., 1990; Beeler and Hickman, 1996), crack healing of quartz is driven by reductions in surface energy and healing rates appear to be limited by diffusional solute transport; sharply defined crack tips become blunted and break up into fluid-filled tubes and inclusions. However, fluid inclusion geometries are also observed with nonequilibrium shapes that depend on initial surface roughness. Crack healing is significant at 400° C after short run durations (24 hr) with healing rates reaching 10-5 mm/s. Crack healing is also observed at T=250° C, but only for smooth cracks with apertures < 0.6 ? m or for cracks subject to low pOH-. The extent of crack healing is sensitive to crack aperture and to hackles formed by fine-scale crack branching during crack growth. Initial crack apertures appear to be governed by the presence of fine particles, often found in the vicinity of hackles, which maintain the separation of crack surfaces. Where rough cracks exhibit healing, hackles are sites of either enhanced or reduced loss of fluid-solid interface depending on slight mismatches and sense of twist of opposing crack surfaces. Hackles of open r-cleavage cracks are replaced either by (1) healed curvilinear quartz bridges and river patterns surrounded by open fluid-filled crack, or by (2) fluid-filled tubes surrounded by regions of fully healed quartz. For a given temperature, aperture, and anneal time, crack healing is enhanced for samples annealed in NaOH solutions compared with healing for samples annealed in water. Accelerated crack healing rates at low pOH- are interpreted to result from increased rates of diffusive mass transport that depend, in turn, on higher silica concentrations of the fluid.

Fallon, J. A.; Kronenberg, A. K.; Popp, R. K.; Lamb, W. M.

2004-12-01

263

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

264

Endovenous management of saphenous vein reflux  

Microsoft Academic Search

Purpose: This study assessed clinical outcomes of two catheter-based endovenous procedures to eliminate or greatly mitigate saphenous vein reflux. Materials and Methods: A computer-controlled, dedicated generator and two catheter designs were used to treat 210 patients at 16 private clinic and university centers in Europe. The Closure catheter applied resistive heating over long vein lengths to cause maximum wall contraction

Stefano Manfrini; Vincenzo Gasbarro; Gudmundur Danielsson; Lars Norgren; James G. Chandler; Andrew F. Lennox; Zaki A. Zarka; Andrew N. Nicolaides

2000-01-01

265

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

NASA Astrophysics Data System (ADS)

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

Bose, Narayan; Bhattacharya, Gourab; Mukherjee, Soumyajit

2013-04-01

266

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

NASA Astrophysics Data System (ADS)

Quartz-pebbles of the early Proterozoic Au-bearing Tarkwaian conglomerates in Ghana reveal several original (inherited) pre-sedimentary 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 fluid inclusions has not been reported from any other lode-gold deposit of greenstone affiliation and is thus a specific characteristic for Birimian-hosted gold deposits. Therefore, it can be used as an unequivocal pathfinder for epigenetic as well as for syn-sedimentary gold mineralization of the early Proterozoic of West Africa. The inherited fluid inclusions with the unique physicochemical characteristics suggest that the Tarkwaian quartz-pebbles and possibly some gold were derived from Au-quartz vein deposits comparable in mineralogy, petrography and genesis to those along the NW-margin of the Ashanti belt (e.g. Ashanti Mine, Prestea Mine).

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

1993-11-01

267

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

268

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

NASA Astrophysics Data System (ADS)

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

Asadi, S.; Rajabzadeh, M. A.

2009-04-01

269

Hydrothermally prepared inorganic siliceous wastes: Hydrothermal reaction of calcareous and steatite ceramic tile wastes  

SciTech Connect

Possibility of solidification of various ceramic wastes by hydrothermal processing was investigated. The starting materials were feldspathic porcelain tile waste, steatite ceramic tile waste, and calcareous ceramic tile waste. These were mixed with CaO so as to obtain a Ca/Si molar ratio of 0.5. After forming, they were cured for 2 to 20 h under the saturated steam pressure at 200{degrees}C. Although the SiO{sub 2} content of these ceramic wastes was about 70 mass% and they contain various alkaline ions and alkaline earth ions, solidified specimens with flexural strength up to 35MPa were obtained. This is within the range of strengths when quartz or fused silica is used as pure SiO{sub 2} sources. Formation of tobermorite, which was detected in all systems after 2 h of curing, was considered to affect the increase of the strength. It was found that there is a possibility of aluminum and alkali ions being included in the structure of the formed tobermorite. In the case of using steatite ceramic tile waste containing Mg, magnesium silicate hydrates were also formed. The modal pore diameter shifted to 0.01 {mu} m with the formation of these hydrates and there was correlation between the flexural strength and the pore size distribution.

Maenami, Hiroki; Yamamoto, Takeyuki; Ishida, Hideki [INAX Corp., Aichi (Japan)] [and others

1996-12-31

270

Improved thermoelectrically cooled quartz crystal microbalance  

NASA Technical Reports Server (NTRS)

Design changes in the thermoelectrically-cooled quartz microbalance, which is used to monitor surface contamination in space simulation chambers, is described in terms of its extended temperature range, increased temperature control, mass sensitivity, and cooling power. The mass sensor uses 20 MHz quartz crystals having a sensitivity of 8.8 x 10 to the minus tenth power g/sq cm - Hz. The crystals are optically polished, metal plated, and overplated with magnesium fluoride to simulate an optical surface. The microbalance temperature circuitry is designed to readout and control surface temperature between 100 C and minus 59 C to plus or minus 0.5 C, and readout only temperature between minus 60 C and minus 199 C using auxiliary liquid nitrogen cooling. Data is included on the measurement of oil contamination of surfaces as a function of temperature in space simulation chambers.

Mckeown, W. E.; Corbin, W. E., Jr.; Fox, M. G.

1974-01-01

271

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

272

Error analysis of quartz crystal resonator applications  

SciTech Connect

Quartz crystal resonators in chemical sensing applications are usually configured as the frequency determining element of an electrical oscillator. By contrast, the shear modulus determination of a polymer coating needs a complete impedance analysis. The first part of this contribution reports the error made if common approximations are used to relate the frequency shift to the sorbed mass. In the second part the authors discuss different error sources in the procedure to determine shear parameters.

Lucklum, R.; Behling, C.; Hauptmann, P. [Otto-von-Guericke-Univ., Magdeburg (Germany); Cernosek, R.W.; Martin, S.J. [Sandia National Labs., Albuquerque, NM (United States)

1996-12-31

273

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

274

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.

275

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

276

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

277

Brain vein disorders in newborn infants.  

PubMed

The brain veins of infants are in a complex phase of remodelling in the perinatal period. Magnetic resonance venography and susceptibility-weighted imaging, together with high-resolution Doppler ultrasound, have provided new tools to aid study of venous developmental anatomy and disease. This review aims to provide a comprehensive background of vein development and perinatal venous lesions in preterm and term-born infants, and to encourage further research in both the fetus and the newborn infant, with the aim of preventing or mitigating parenchymal injury related to diseases involving veins. PMID:25212961

Raets, Marlou; Dudink, Jeroen; Raybaud, Charles; Ramenghi, Luca; Lequin, Maarten; Govaert, Paul

2015-03-01

278

Abernethy malformation with portal vein aneurysm.  

PubMed

We present the case of a 24-year-old man who was incidentally diagnosed with congenital extrahepatic portosystemic shunt with portal vein aneurysm during an investigation for non-specific abdominal pain. These are rare anomalies, and to the best of our knowledge, this is the first case reported with both anomalies associated together. Ultrasound, including color Doppler, computed tomography, and magnetic resonance imaging were performed which revealed a side-to-side shunt between the extrahepatic portal vein and the inferior vena cava, with aneurysmal fusiform dilatation of the proximal intrahepatic portal vein which ended abruptly. Etiology, clinical significance, and management strategies with regard to these abnormalities are discussed. PMID:18814137

Kumar, Atin; Kumar, Jyoti; Aggarwal, Rakesh; Srivastava, Siddharth

2008-09-01

279

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

280

Detailed anatomy of the internal spermatic vein and the ovarian vein. Human cadaver study and operative spermatic venography: clinical aspects.  

PubMed

The exact anatomical course of the spermatic vein and the ovarian vein (gonadal) has not been described in detail previously. To determine the precise anatomy of the gonadal veins an autopsy study of 70 fresh human cadavers (40 men, 10 women, 10 male stillborns and 10 female stillborns) was performed by making a resin cast of both gonadal veins which then was carefully dissected. The study showed absence of valves in the spermatic vein, cross-communications between the right and left spermatic veins, and communication between the spermatic and renal capsular veins, spermatic and ipsilateral ureteral veins, and spermatic ipsilateral colonic veins. For clarification of the presence of valves intraoperative antegrade spermatic venography was done in 6 men with and 5 without varicocele. In both groups valves were not detected. These observations regarding the anatomy of the spermatic vein and the ovarian vein may help to explain related clinical conditions. PMID:2005700

Wishahi, M M

1991-04-01

281

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

282

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

283

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

284

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

285

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

286

Who Is at Risk for Varicose Veins?  

MedlinePLUS

... Division of Intramural Research Research Resources Scientific Reports Technology Transfer Clinical Trials What Are Clinical Trials? Children & ... factors may raise your risk for varicose veins, including family history, older age, gender, pregnancy, overweight or ...

287

How Is Deep Vein Thrombosis Treated?  

MedlinePLUS

... vein (called intravenous, or IV, injection). Warfarin and heparin are two blood thinners used to treat DVT. ... Coumadin® is a common brand name for warfarin.) Heparin is given as an injection or through an ...

288

How Can Varicose Veins Be Prevented?  

MedlinePLUS

... Toned muscles help blood move through the veins. Wear compression stockings if your doctor recommends them. These ... trials are research studies that explore whether a medical strategy, treatment, or ...

289

Recrystallized ultrafine-grained quartz associated with pseudotachylyte-bearing faults  

NASA Astrophysics Data System (ADS)

Tectonic pseudotachylytes (pst), solidified friction-induced silicate melts, record coseismic slip and are mainly reported from the brittle crust and in association with cataclastic deformation. In this study, we report the close spatial association between crystal-plastic deformation of quartz, recorded by ultrafine-grained (grain size 1-2 µm) microshear zones, and pst and speculate about the possible origin of this association. This association appears to be frequent in nature and we present data from two different localities, namely: (1) Schneeberger Zug (Eastern Alps, Southern Tyrol, Italy) where the pst occur within amphibolite facies, impure quartzite, and (2) the Adamello (Southern Alps, Italy) where pst occur within tonalitie. In both cases, localized microshear zones (50-150 µm thick) of ultrafine recrystallized quartz occur adjacent, or within a few millimetres distance, to pst fault veins and are absent in the rest of host rock. The kinematics of the microshear zones is consistent with the sense of slip along the fault. We have investigated the microstructure and the crystallographic preferred orientation (CPO) of the microshear zones by EBSD and TEM. The host rock quartz deformed along the microshear zones shows patchy undulatory extinction, deformation lamellae and lattice deflection around rational crystallographic axes coincident with the bulk vorticity axis. At the microshear zone margins subgrains make transition to a recrystallized aggregates of polygonal small (<2µm) new grains delineating the microshear zone. The CPO of the aggregates is random and the new recrystallized grains are almost dislocations free. We refer the plastic deformation of quartz accompanied by dramatic grain size refinement to the coseismic stages of fault slip consistently with the observation of Ree et al. (2009) in Carrara calcite marble during high-speed torsion experiments. The development of quartz microstructure could have occurred during the accelerating stages of the seismic faulting and/or by strain rate partitioning during the coseismic slip along the principal pst-bearing plane. Ree, J.-H., Ando, J.-I., Han, R., Kim. J.-W., Shimamoto, T., 2009. Coseismic microstructures of simulated fault zones in Carrara marble and halite revealed by electron microscopy. Abstract volume, Micro-Analysis, Processes, Time (MAPT) international meeting, 30th August - 4th September 2009, Edinburgh, 65.

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

2010-05-01

290

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

291

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

292

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

293

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

294

Suspended polymer nanobridge on a quartz resonator  

NASA Astrophysics Data System (ADS)

A chemical vapor sensor based on a free-standing polystyrene (PS) nanofilm suspended between the tines of a quartz tuning fork (QTF) is demonstrated. Exposure to ethanol vapor decreased the modulus of the PS membrane, which resulted in a decrease in the resonance frequency of the QTF as a function of ethanol concentration. The suspended PS membrane structure on the QTF allowed gas molecules to diffuse into the membrane from both the top and bottom allowing faster response. The QTF response time was found to be 6.5 times faster than the response time of a conventional PS film-coated resonator sensor.

Yun, Minhyuk; Lee, Seongjae; Yim, Changyong; Jung, Namchul; Thundat, Thomas; Jeon, Sangmin

2013-07-01

295

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

296

Scattering Removal for Finger-Vein Image Restoration  

PubMed Central

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

Yang, Jinfeng; Zhang, Ben; Shi, Yihua

2012-01-01

297

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

298

Gonadal vein tumor thrombosis due to renal cell carcinoma  

PubMed Central

Renal cell carcinoma (RCC) had a tendency to extend into the renal vein and inferior vena cava, while extension into the gonadal vein has been rarely reported. Gonadal vein tumor thrombosis appears as an enhancing filling defect within the dilated gonadal vein anterior to the psoas muscle and shows an enhancement pattern identical to that of the original tumor. The possibility of gonadal vein thrombosis should be kept in mind when looking at an imaging study of patients with RCC

Haghighatkhah, Hamidreza; Karimi, Mohammad Ali; Taheri, Morteza Sanei

2015-01-01

299

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

300

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

301

Substance-to-substance joining of quartz glass  

Microsoft Academic Search

A pioneering procedure for substance-to-substance joining of quartz glass is described. Diffusion welding was examined as a possible joining method. Welded components made of quartz glass are applied in high-temperature engineerin g for laser and optics applications. Quartz glass was joined without interlayers in order to mainta in optical characteristics of the joining partners. Based on the principles of joint

Steffen Dahms; Priit Kulu; Renno Veinthalb; Ursula Basler; Sabine Sändiga

2009-01-01

302

The sliding characteristics of sandstone on quartz fault-gouge  

Microsoft Academic Search

Summary Three types of triaxial compression experiments are used to characterize the frictional processes during sliding on quartz gouge. They are: 1) pre-cut Tennessee Sandstone sliding on an artificial layer of quartz gouge; 2) fractured Coconino Sandstone sliding along experimentally produced shear fractures; and 3) a fine-grained quartz aggregate deformed in compression. The specimens were deformed to 2.0 kb confining

JAMES T. ENGELDERZ; John M. Logan; John Handin

1975-01-01

303

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

304

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

305

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

306

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

307

Penile vein ligation for venogenic impotence.  

PubMed

We have performed penile vein ligation on 35 patients with venogenic impotence from July 1989 to December 1991. The criteria for surgery were (1) age less than 60 years; (2) negative vasoactive agent intracavernous injection but normal penile arterial function, and (3) abnormal venous leakage documented by dynamic infusion cavernosometry and cavernosography. The procedure in venous ligation is excision of the deep dorsal vein from coronary sulcus to pubic arch, and ligation of cavernous veins after identification. The average follow-up was 27.5 months (range 12-37 months) for 30 patients. The 2 patients who revealed no erection at all immediately after operation had dense adhesion of penile hilar region caused in one case by severe pelvic trauma and in the other by pubic bone fracture. Twenty-eight (93.3%) patients were found to sustain excellent erection within 3 months postoperatively. However, only 12 (40.0%) patients sustained spontaneous erection at long-term follow-up, while another 7 (23.3%) responded to intracavernous injection. It is worth mentioning that tortuous and marked dilation of the deep dorsal vein and/or cavernous veins were found intraoperatively in 6 patients who were observed to have excellent erections postoperatively. Inadequate elimination of the leakage veins, especially crural veins, is the most likely factor in those who had a recurrence of erectile dysfunction. However, the corpus cavernosum, particularly a myopathic condition or inadequate neurotransmitters, also plays an important role. Complications included shortness of penis (3 patients), penile deviation (3), numbness of glans penis (4) and wound infection (1).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7925529

Hwang, T I; Yang, C R

1994-01-01

308

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

Microsoft Academic Search

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

Denis P. Burkitt

1972-01-01

309

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

310

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

311

Note: Sensitivity multiplication module for quartz crystal microbalance applications  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

312

Endovascular Radiofrequency Ablation for Varicose Veins  

PubMed Central

Executive Summary Objective The objective of the MAS evidence review was to conduct a systematic review of the available evidence on the safety, effectiveness, durability and cost–effectiveness of endovascular radiofrequency ablation (RFA) for the treatment of primary symptomatic varicose veins. Background The Ontario Health Technology Advisory Committee (OHTAC) met on August 26th, 2010 to review the safety, effectiveness, durability, and cost-effectiveness of RFA for the treatment of primary symptomatic varicose veins based on an evidence-based review by the Medical Advisory Secretariat (MAS). Clinical Condition Varicose veins (VV) are tortuous, twisted, or elongated veins. This can be due to existing (inherited) valve dysfunction or decreased vein elasticity (primary venous reflux) or valve damage from prior thrombotic events (secondary venous reflux). The end result is pooling of blood in the veins, increased venous pressure and subsequent vein enlargement. As a result of high venous pressure, branch vessels balloon out leading to varicosities (varicose veins). Symptoms typically affect the lower extremities and include (but are not limited to): aching, swelling, throbbing, night cramps, restless legs, leg fatigue, itching and burning. Left untreated, venous reflux tends to be progressive, often leading to chronic venous insufficiency (CVI). A number of complications are associated with untreated venous reflux: including superficial thrombophlebitis as well as variceal rupture and haemorrhage. CVI often results in chronic skin changes referred to as stasis dermatitis. Stasis dermatitis is comprised of a spectrum of cutaneous abnormalities including edema, hyperpigmentation, eczema, lipodermatosclerosis and stasis ulceration. Ulceration represents the disease end point for severe CVI. CVI is associated with a reduced quality of life particularly in relation to pain, physical function and mobility. In severe cases, VV with ulcers, QOL has been rated to be as bad or worse as other chronic diseases such as back pain and arthritis. Lower limb VV is a very common disease affecting adults – estimated to be the 7th most common reason for physician referral in the US. There is a very strong familial predisposition to VV. The risk in offspring is 90% if both parents affected, 20% when neither affected and 45% (25% boys, 62% girls) if one parent affected. The prevalence of VV worldwide ranges from 5% to 15% among men and 3% to 29% among women varying by the age, gender and ethnicity of the study population, survey methods and disease definition and measurement. The annual incidence of VV estimated from the Framingham Study was reported to be 2.6% among women and 1.9% among men and did not vary within the age range (40-89 years) studied. Approximately 1% of the adult population has a stasis ulcer of venous origin at any one time with 4% at risk. The majority of leg ulcer patients are elderly with simple superficial vein reflux. Stasis ulcers are often lengthy medical problems and can last for several years and, despite effective compression therapy and multilayer bandaging are associated with high recurrence rates. Recent trials involving surgical treatment of superficial vein reflux have resulted in healing and significantly reduced recurrence rates. Endovascular Radiofrequency Ablation for Varicose Veins RFA is an image-guided minimally invasive treatment alternative to surgical stripping of superficial venous reflux. RFA does not require an operating room or general anaesthesia and has been performed in an outpatient setting by a variety of medical specialties including surgeons and interventional radiologists. Rather than surgically removing the vein, RFA works by destroying or ablating the refluxing vein segment using thermal energy delivered through a radiofrequency catheter. Prior to performing RFA, color-flow Doppler ultrasonography is used to confirm and map all areas of venous reflux to devise a safe and effective treatment plan. The RFA procedure involves the introduction of a guide wire into the target v

2011-01-01

313

Ligation of superior mesenteric vein and portal to splenic vein anastomosis after superior mesenteric-portal vein confluence resection during pancreaticoduodenectomy – Case report  

PubMed Central

62 year old Caucasian female with pancreatic head mass abutting the superior mesenteric vein (SMV) presented with fine needle aspiration biopsy confirmed diagnosis of ductal adenocarcinoma. CT scan showed near complete obstruction of portal vein and large SMV collateral development. After 3 months of neoadjuvant therapy, her portal vein flow improved significantly, SMV collateral circulation was diminished. Pancreaticoduodenectomy (PD) and superior mesenteric portal vein (SMPV) confluence resection were performed; A saphenous vein interposition graft thrombosed immediately. The splenic vein remnant was distended and adjacent to the stump of the portal vein. Harvesting an internal jugular vein graft required extra time and using a synthetic graft posed a risk of graft thrombosis or infection. As a result, we chose to perform a direct anastomosis of the portal and splenic vein in a desperate situation. The anastomosis decompressed the mesenteric venous system, so we then ligated the SMV. The patient had an uneventful postoperative course, except transient ascites. She redeveloped ascites more than one year later. At that time a PET scan showed bilateral lung and right femur metastatic disease. She expired 15 months after PD. Conclusion The lessons we learned are (1) Before SMPV confluence resection, internal jugular vein graft should be ready for reconstruction. (2) Synthetic graft is an alternative for internal jugular vein graft. (3) Direct portal vein to SMV anastomosis can be achieved by mobilizing liver. (4) It is possible that venous collaterals secondary to SMV tumor obstruction may have allowed this patient's post-operative survival.

Tang, Jianlin; Abbas, Jihad; Hoetzl, Katherine; Allison, David; Osman, Mahamed; Williams, Mallory; Zelenock, Gerald B.

2014-01-01

314

Biomolecular mechanisms in varicose veins development.  

PubMed

Varicose veins can be described as tortuous and dilated palpable veins, which are more than 3 mm in diameter. They are one of the clinical presentations of chronic venous disorders, which are a significant cause of morbidity. The prevalence of varicose veins has been estimated at 25% to 33% in women and 10% to 20% in men and is still increasing at an alarming rate. Family history, older age, female, pregnancy, obesity, standing occupations and a history of previous deep venous thrombosis are the predominant risk factors. A great amount of factors are implicated in the pathogenesis of varicose veins, including changes in hydrostatic pressure, valvular incompetence, deep venous obstruction, ineffective function of calf muscle pump, biochemical and structural alterations of the vessel wall, extracellular matrix abnormalities, impaired balance between growth factors or cytokines, genetic alterations and several other mechanisms. Nevertheless, the issue of pathogenesis in varicose veins is still not completely known, even if a great progress has been made in understanding their molecular basis. This kind of studies appears promising and should be encouraged, and perhaps the new insight in this matter may result in targeted therapy or possibly prevention. PMID:25449990

Segiet, Oliwia Anna; Brzozowa, Marlena; Piecuch, Adam; Dudek, Damian; Reichman-Warmusz, Edyta; Wojnicz, Romuald

2014-10-30

315

Retinal vein occlusion in high altitude.  

PubMed

Staying at high altitude has been reported to be associated with thrombosis in lowlanders. We report 3 cases of retinal vein occlusion in high altitude. Two were males 31 and 37 years of age, who developed nonischemic central retinal vein occlusion while staying at high altitude. The former developed central retinal vein occlusion after 90 days at 6309 m, while the latter was affected at an altitude of 3353 m where he had been for the past 1 year and had recurrence of central retinal vein occlusion in the other eye on re-entry to the same altitude. The third case is that of a 40-year-old female who developed inferotemporal branch retinal vein occlusion on the second day after entry into high altitude (3353 m) by air, while ascending further in a vehicle at an altitude of approximately 4572 m. All three did not have any systemic disease and showed complete recovery on descent to a lower altitude. PMID:22206565

Gupta, Atul; Singh, Surinderpal; Ahluwalia, Tejinder Singh; Khanna, Anurag

2011-01-01

316

OH zoning in alpine quartz from Austria  

NASA Astrophysics Data System (ADS)

Rock crystals from various alpine clefts in Austria were investigated in terms of morphology, domain structure, and OH defects. Since the formation of alpine clefts is a long lasting and multiphase process, the crystal growth of alpine quartz is dominated by different morphologies and various OH defects. 140 samples were investigated by FTIR spectroscopy and optical methods to reveal complementary information on morphology, twining, hydrogen incorporation, and zoning of the OH defects. IR spectroscopic measurements of colourless and smoky quartz samples revealed six characteristic absorption bands in the range of the OH stretching frequencies at 3315, 3380, 3430, 3480, 3510 and 3595 cm-1. The quantitative analysis of the water content revealed an amount of 0.5-20 ppm H_2O. With a maximum of frequency in the 1-2 ppm range the amount of water incorporation is comparably lower than known from non-alpine deposits. The spectra can be divided in four types characterised by the number and/or the relative band intensities. Among the Austrian samples one type, showing clearly all the six bands, is abundant and has not been found in the spectra from non-alpine sites. A significant relation between spectra type, crystal morphology, mineral deposit (within Austria), and OH content cannot be deduced. Microspectroscopic measurements of profiles through crystals cut perpendicular to the c-axis revealed that the spectra types rarely change within one sample. However, a variation of the water content is commonly related to a change of the relative intensity of the 3480 cm-1 absorption band. Regarding the hydrogen incorporation all samples show a distinct zoning. In addition, the OH zoning as well as the crystal growth appear regularly, leading to different hydrogen amounts in core and mantle zone of the crystals. The average zoning is given by factor 1.2, whereas strong variations were measured up to factor 2.5. The formation of Brazil twin domains often coincides with a distinct change of the water content within one crystal. Such coincidences were not measured with other structural phenomena such as lamellar structure or colour zoning in smoky quartz. A dependency of the hydrogen incorporation from regional metamorphic grades of the host rocks, as known from the Swiss Alps (Bambauer et al., 1962), cannot be derived. Bambauer, H.U., Brunner, G.O. &Laves, F. (1962). Wasserstoff-Gehalte in Quarzen aus Zerrklüften der Schweizer Alpen und die Deutung ihrer regionalen Abhängigkeit. Schweiz. Min. Petr. Mitt. 42, 221-236.

Hertweck, B.; Niedermayr, G.; Beran, A.

2003-04-01

317

[Experimental silicosis. II. Effects of high temperature of fibrogenic effect of quartz and quartz sands used in ceramics].  

PubMed

Fibrogenic effects of siliceous ceramic raw materials (quartz and quartz sand), heated at 1200 degrees C for 72 hours (conditions of ceramic products burning) have been investigated. The evaluation of fibrogenic effects has been based on wet lungs weight and hydroxyproline content in rats' lungs after an intratracheal administration of 50 mg of the test dust, during 3 and 6 months' experiment. The obtained results indicate that high temperature affects the polymorphous transformation of silica. The transformation varies, e.g. crystabillite has been found in quartz, whereas in quartz sands, quartz has been found apart from crystaballite. In the Isere quartz from Nowosolna crystalline silica content has been decreased, as compared to unheated samples. Heating does not reduce fibrogenic effects of some samples e.g. quartz sand from Bia?a Góra), or the activity may be increased (e.g. quartz sand from Winiary), or is not changed (quartz from Austria). The tendency of changes in biological aggressiveness of siliceous dusts subjected to high temperature cannot be foreseen, as those changes depend on different factos, among others on the content of various impurities. PMID:6273685

Go?cicki, J; Wo?niak, H; Wiecek, E; Wojtczak, J

1981-01-01

318

Oversized vein grafts develop advanced atherosclerosis in hypercholesterolemic minipigs  

PubMed Central

Background Accelerated atherosclerosis is the main cause of late aortocoronary vein graft failure. We aimed to develop a large animal model for the study of pathogenesis and treatment of vein graft atherosclerosis. Methods An autologous reversed jugular vein graft was inserted end-to-end into the transected common carotid artery of ten hypercholesteroemic minipigs. The vein grafts were investigated 12-14 weeks later with ultrasound and angiograpy in vivo and microscopy post mortem. Results One minipig died during follow up (patent vein graft at autopsy), and one vein graft thrombosed early. In the remaining eight patent vein grafts, the mean (standard deviation) intima-media thickness was 712 ?m (276 ?m) versus 204 ?m (74 ?m) in the contralateral control internal jugular veins (P < .01). Advanced atherosclerotic plaques were found in three of four oversized vein grafts (diameter of graft > diameter of artery). No plaques were found in four non-oversized vein grafts (P < .05). Conclusions Our model of jugular vein graft in the common carotid artery of hypercholesterolemic minipigs displayed the components of human vein graft disease, i.e. thrombosis, intimal hyperplasia, and atherosclerosis. Advanced atherosclerosis, the main cause of late failure of human aortocoronary vein grafts was only seen in oversized grafts. This finding suggests that oversized vein grafts may have detrimental effects on patient outcome. PMID:22463679

2012-01-01

319

Origin of the Düvertepe kaolin-alunite deposits in Simav Graben, Turkey: Timing and styles of hydrothermal mineralization  

NASA Astrophysics Data System (ADS)

The Düvertepe district located on the western end of the Simav Graben is the largest known fossil hydrothermal kaolin deposit in Turkey. Active hot springs occur to the north of Simav city (Eynal, Çitgöl, Na?a) and geothermal fields occur to the west of the graben (Hisaralan). Kaolin in the Düvertepe district formed at the expense of Miocene rhyolites-rhyodacites and tuffs emplaced in a tectonically active system undergoing N-S extension. Upward fan-shaped deposits of silicification and kaolin are found along fault zones and define areas of enhanced kaolinization. Silica sinters located above the kaolin zones suggest that hydrothermal fluids followed the fracture systems and mark outflow of geothermal waters. Fractured volcanic rocks rich in glass shards bear sufficient porosity and permeability for hydrothermal circulation. Two mineral facies, "kaolinite and alunite" dominate the deposits, which respectively include: (1) kaolinite-alunite-quartz and (2) alunite-opal-CT-quartz-halloysite. Kaolinite crystals are well-formed hexagonal vermiform habits and alunite crystals are idiomorphic rhombohedral forms. Needle- and tubular-shaped halloysites are common in the alunite facies. The ?34S values for alunite range from - 1.55 to + 6.18‰. Kaolinites have ?D ranging from - 49.0 to - 94.3‰ and the ?18O values range from + 5.8 to + 14.8‰. Calculated formation temperatures of kaolin mineralization (using ?18O values) suggest that hydrothermal alteration occurred in the range of 38° to 129 °C. Independent K/Ar and 40Ar/39Ar ages of alunite are concordant and indicate that alteration occurred from 20.1 to 20.6 Ma in the southern part of the graben and 17.3 to 19.2 Ma in the northern part. These results suggest that metasomatism by steam-heated hydrothermal fluids sourced by rhyolitic magma is responsible for the Düvertepe kaolin and alunite deposit origins.

Ece, Ömer I.; Ekinci, Bala; Schroeder, Paul A.; Crowe, Douglas; Esenli, Fahri

2013-04-01

320

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

PubMed

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

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

2014-01-01

321

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

PubMed Central

Shallow-sea (5 m depth) hydrothermal venting off Milos Island provides an ideal opportunity to target transitions between igneous abiogenic sulfide inputs and biogenic sulfide production during microbial sulfate reduction. Seafloor vent features include large (>1 m2) white patches containing hydrothermal minerals (elemental sulfur and orange/yellow patches of arsenic-sulfides) and cells of sulfur oxidizing and reducing microorganisms. Sulfide-sensitive film deployed in the vent and non-vent sediments captured strong geochemical spatial patterns that varied from advective to diffusive sulfide transport from the subsurface. Despite clear visual evidence for the close association of vent organisms and hydrothermalism, the sulfur and oxygen isotope composition of pore fluids did not permit delineation of a biotic signal separate from an abiotic signal. Hydrogen sulfide (H2S) in the free gas had uniform ?34S values (2.5?±?0.28‰, n?=?4) that were nearly identical to pore water H2S (2.7?±?0.36‰, n?=?21). In pore water sulfate, there were no paired increases in ?34SSO4 and ?18OSO4 as expected of microbial sulfate reduction. Instead, pore water ?34SSO4 values decreased (from approximately 21‰ to 17‰) as temperature increased (up to 97.4°C) across each hydrothermal feature. We interpret the inverse relationship between temperature and ?34SSO4 as a mixing process between oxic seawater and 34S-depleted hydrothermal inputs that are oxidized during seawater entrainment. An isotope mass balance model suggests secondary sulfate from sulfide oxidation provides at least 15% of the bulk sulfate pool. Coincident with this trend in ?34SSO4, the oxygen isotope composition of sulfate tended to be 18O-enriched in low pH (<5), high temperature (>75°C) pore waters. The shift toward high ?18OSO4 is consistent with equilibrium isotope exchange under acidic and high temperature conditions. The source of H2S contained in hydrothermal fluids could not be determined with the present dataset; however, the end-member ?34S value of H2S discharged to the seafloor is consistent with equilibrium isotope exchange with subsurface anhydrite veins at a temperature of ~300°C. Any biological sulfur cycling within these hydrothermal systems is masked by abiotic chemical reactions driven by mixing between low-sulfate, H2S-rich hydrothermal fluids and oxic, sulfate-rich seawater. PMID:25183951

2014-01-01

322

Mystery of the Megaplume: Hydrothermal Vent Chemistry  

NSDL National Science Digital Library

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

323

Intracavity quartz-enhanced photoacoustic sensor  

SciTech Connect

We report on a spectroscopic technique named intracavity quartz-enhanced photoacoustic spectroscopy (I-QEPAS) employed for sensitive trace-gas detection in the mid-infrared spectral region. It is based on a combination of QEPAS with a buildup optical cavity. The sensor includes a distributed feedback quantum cascade laser emitting at 4.33??m. We achieved a laser optical power buildup factor of ?500, which corresponds to an intracavity laser power of ?0.75?W. CO{sub 2} has been selected as the target molecule for the I-QEPAS demonstration. We achieved a detection sensitivity of 300 parts per trillion for 4?s integration time, corresponding to a noise equivalent absorption coefficient of 1.4?×?10{sup ?8}?cm{sup ?1} and a normalized noise-equivalent absorption of 3.2?×?10{sup ?10} W cm{sup ?1}?Hz{sup ?1/2}.

Borri, S., E-mail: simone.borri@ino.it; Galli, I.; Mazzotti, D.; Giusfredi, G.; De Natale, P. [CNR-INO UOS Sesto Fiorentino and LENS, via Carrara 1, 50019 Sesto Fiorentino FI (Italy); Patimisco, P.; Scamarcio, G.; Spagnolo, V. [CNR-IFN UOS Bari and Dipartimento Interateneo di Fisica, Università degli Studi di Bari e Politecnico di Bari, via Amendola 173, 70126 Bari BA (Italy); Akikusa, N. [Development Bureau Laser Device R and D Group, Hamamatsu Photonics KK, Shizuoka 434-8601 (Japan); Yamanishi, M. [Central Research Laboratories, Hamamatsu Photonics KK, Shizuoka 434-8601 (Japan)

2014-03-03

324

Hydrothermal vent complexes associated with sill intrusionsin sedimentarybasins  

E-print Network

Hydrothermal vent complexes associated with sill intrusionsin sedimentarybasins BJIbRNJAMTVEIT1 sedimentarybasinscause strongthermal perturbations and frequentlycause extensivehydrothermalactivity.Hydrothermal vent strata surrounding a central vent complex. comprisingmultiplesandstone dykes, pipes, and hydrothermal

Podladchikov, Yuri

325

Meta-igneous (non-gneissic) tonalites and quartz-diorites from an extensive ca. 3800 Ma terrain south of the Isua supracrustal belt, southern West Greenland: constraints on early crust formation  

Microsoft Academic Search

In the Itsaq Gneiss Complex south of the Isua supracrustal belt (West Greenland) some areas of early Archaean tonalite and\\u000a quartz-diorite are non-gneissic, free of pegmatite veins, and in rarer cases are undeformed with relict igneous textures and\\u000a hence were little modified by heterogeneous ductile deformation under amphibolite facies conditions in several Archaean events.\\u000a Such well-preserved early Archaean rocks are

Allen P. Nutman; Vickie C. Bennett; Clark R. L. Friend; Marc D. Norman

1999-01-01

326

Quartz dissolution in organic-rich aqueous systems  

Microsoft Academic Search

Organic electrolytes are a common component of natural waters and are known to be important in many rock-water interactions. The influence of organic electrolytes on silica mobility, quartz solubility, and quartz dissolution kinetics, however, is less well understood, While there is mounting evidence supporting the presence of an aqueous organic-silica complex in natural waters, the significance of this species is

P BENNETT

1991-01-01

327

U. Akgun, ECLIPSE06, Antalya, Quartz Plate Calorimeter Prototype  

E-print Network

U. Akgun, ECLIPSE06, Antalya, Turkey Quartz Plate Calorimeter Prototype "First Generation" U. Akgun. Onel The University of Iowa #12;U. Akgun, ECLIPSE06, Antalya, Turkey Introduction · While working for the first time this summer at CERN. #12;U. Akgun, ECLIPSE06, Antalya, Turkey Model Quartz Plate Prototype

Akgun, Ugur

328

Passivation of quartz for halogen-containing light sources  

DOEpatents

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

Falkenstein, Zoran (Los Alamos, NM)

1999-01-01

329

Light scattering coefficient by quartz particles suspended in seawater  

Microsoft Academic Search

A fast algorithm to compute scattering coefficient of quartz particles is presented. The algorithm is based on a regression between scattering efficiency and size parameter. This regression relationship was obtained by analyzing results of extensive Mie calculations in the range of size parameters between 48 to 40,000. A FORTRAN subroutine to compute scattering and backscattering coefficients of quartz suspensions is

Vladimir I. Haltrin; Eugeny B. Shybanov; Robert H. Stavn; Alan D. Weidemann

1999-01-01

330

The mechanism of thermoluminescence in an Australian sedimentary quartz  

Microsoft Academic Search

The thermoluminescence and related properties of a specific Australian quartz are considered, using both original experiments and data from the literature on comparable systems. It is concluded that the rapidly-bleaching peak at about 305 °C in the glow curve and the peaks at 220,180 and 100 °C, which all emit at wavelengths below about 430 nm in this quartz, form

A. D. Franklin; J. R. Prescott; R. B. Scholefield

1995-01-01

331

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

USGS Publications Warehouse

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

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

1993-01-01

332

The behaviour of boron in a peraluminous granite-pegmatite system and associated hydrothermal solutions: a melt and fluid-inclusion study  

NASA Astrophysics Data System (ADS)

Detailed analyses of melt and fluid inclusions combined with an electron-microprobe survey of boron-bearing minerals reveal the evolution of boron in a highly evolved peraluminous granite-pegmatite complex and the associated high- and medium-temperature ore-forming hydrothermal fluids (Ehrenfriedersdorf, Erzgebirge, Germany). Melt inclusions in granite represent embryonic pegmatite-forming melts containing about 10 wt% H2O and 1.8 wt% B2O3. These melts are also enriched in F, P, and other incompatible elements such as Be, Sn, Rb, and Cs. Ongoing differentiation and volatile enrichment drove the system into a solvus, where two pegmatite-forming melts coexisted. The critical point is at about 712 °C, 100 MPa, 20 wt% H2O and 4.1 wt% B2O3. Cooling and concomitant fractional crystallisation from 700 to 500 °C induced development of two conjugate melts, an H2O-poor (A-melt) and an H2O-rich melt (B-melt) along the opening solvus. Boron is a major element in both melts and is preferentially partitioned into the H2O-rich melt. Temperature-dependent distribution coefficients $ D{boron}{{B - melt/A - melt}} $ are 1.3 at 650 °C, 1.5 at 600 °C, and 1.8 at 500 °C. In both melts, boron concentrations decreased during cooling because of exsolution of a boron-rich hypersaline brine throughout the pegmatitic stage. Boromuscovite containing up to 8.5 wt% was another sink for boron at this stage. The end of the melt-dominated pegmatitic stage was attained at a solidus temperature of around 490 °C. Fluid inclusions of the hydrothermal stage reveal trapping temperatures of 480 to 370 °C, along with varying densities and highly variable B2O3 contents ranging from 0.20 to 2.94 wt%. A boiling system evolved, indicating a complex interplay between closed- and open-system behaviour. Pressure switched from lithostatic to hydrostatic and back, generating hydrothermal convection cells where meteoric waters were introduced and mixed with magmatic fluids. Boron-rich solutions originated from magmatic fluids, whereas boron-depleted fluids were mainly of meteoric origin. This highlights the potential of boron for discriminating fluids of different origin. Tin is continuously enriched during the evolution because tin and boron are cross-linked by formation of boron-, fluorine- and tin-fluorine-bearing complexes and is finally deposited within quartz-cassiterite veins during the transition from closed- to open-system behaviour. Boron does not only trace the complex evolution of the Ehrenfriedersdorf complex but exerts, together with H2O, F and P, an important control on the physical and chemical properties of pegmatite-forming melts, and particularly on the formation of a two-melt solvus at low pressure. We discuss this with respect to experimental results on H2O solubility and the critical behaviour of the haplogranite-water system which contained variable concentrations of volatiles.

Thomas, Rainer; Förster, Hans-Jürgen; Heinrich, Wilhelm

2002-09-01

333

The behaviour of boron in a peraluminous granite-pegmatite system and associated hydrothermal solutions: a melt and fluid-inclusion study  

NASA Astrophysics Data System (ADS)

Detailed analyses of melt and fluid inclusions combined with an electron-microprobe survey of boron-bearing minerals reveal the evolution of boron in a highly evolved peraluminous granite-pegmatite complex and the associated high- and medium-temperature ore-forming hydrothermal fluids (Ehrenfriedersdorf, Erzgebirge, Germany). Melt inclusions in granite represent embryonic pegmatite-forming melts containing about 10 wt% H2O and 1.8 wt% B2O3. These melts are also enriched in F, P, and other incompatible elements such as Be, Sn, Rb, and Cs. Ongoing differentiation and volatile enrichment drove the system into a solvus, where two pegmatite-forming melts coexisted. The critical point is at about 712 °C, 100 MPa, 20 wt% H2O and 4.1 wt% B2O3. Cooling and concomitant fractional crystallisation from 700 to 500 °C induced development of two conjugate melts, an H2O-poor (A-melt) and an H2O-rich melt (B-melt) along the opening solvus. Boron is a major element in both melts and is preferentially partitioned into the H2O-rich melt. Temperature-dependent distribution coefficients $ D{boron}{{B - melt/A - melt}} $ are 1.3 at 650 °C, 1.5 at 600 °C, and 1.8 at 500 °C. In both melts, boron concentrations decreased during cooling because of exsolution of a boron-rich hypersaline brine throughout the pegmatitic stage. Boromuscovite containing up to 8.5 wt% was another sink for boron at this stage. The end of the melt-dominated pegmatitic stage was attained at a solidus temperature of around 490 °C. Fluid inclusions of the hydrothermal stage reveal trapping temperatures of 480 to 370 °C, along with varying densities and highly variable B2O3 contents ranging from 0.20 to 2.94 wt%. A boiling system evolved, indicating a complex interplay between closed- and open-system behaviour. Pressure switched from lithostatic to hydrostatic and back, generating hydrothermal convection cells where meteoric waters were introduced and mixed with magmatic fluids. Boron-rich solutions originated from magmatic fluids, whereas boron-depleted fluids were mainly of meteoric origin. This highlights the potential of boron for discriminating fluids of different origin. Tin is continuously enriched during the evolution because tin and boron are cross-linked by formation of boron-, fluorine- and tin-fluorine-bearing complexes and is finally deposited within quartz-cassiterite veins during the transition from closed- to open-system behaviour. Boron does not only trace the complex evolution of the Ehrenfriedersdorf complex but exerts, together with H2O, F and P, an important control on the physical and chemical properties of pegmatite-forming melts, and particularly on the formation of a two-melt solvus at low pressure. We discuss this with respect to experimental results on H2O solubility and the critical behaviour of the haplogranite-water system which contained variable concentrations of volatiles.

Thomas, Rainer; Förster, Hans-Jürgen; Heinrich, Wilhelm

334

Hydrothermal alteration, fluid inclusions and stable isotope systematics of the Alvo 118 iron oxide-copper-gold deposit, Carajás Mineral Province (Brazil): Implications for ore genesis  

NASA Astrophysics Data System (ADS)

The Alvo 118 iron oxide-copper-gold (IOCG) deposit (170 Mt at 1.0 wt.% Cu, 0.3 g/t Au) lies in the southern sector of the Itacaúnas Shear Belt, Carajás Mineral Province, along a WNW-ESE-striking, 60-km-long shear zone, close to the contact of the ~2.76-Ga metavolcano-sedimentary Itacaiúnas Supergroup and the basement (~3.0 Ga Xingu Complex). The Alvo 118 deposit is hosted by mafic and felsic metavolcanic rocks and crosscutting granitoid and gabbro intrusions that have been subjected to the following hydrothermal alteration sequence towards the ore zones: (1) poorly developed sodic alteration (albite and scapolite); (2) potassic alteration (biotite or K-feldspar) accompanied by magnetite formation and silicification; (3) widespread, pervasive chlorite alteration spatially associated with quartz-carbonate-sulphide infill ore breccia and vein stockworks; and (4) local post-ore quartz-sericite alteration. The ore assemblage is dominated by chalcopyrite (~60%), bornite (~10%), hematite (~20%), magnetite (10%) and subordinate chalcocite, native gold, Au-Ag tellurides, galena, cassiterite, F-rich apatite, xenotime, monazite, britholite-(Y) and a gadolinite-group mineral. Fluid inclusion studies in quartz point to a fluid regime composed of two distinct fluid types that may have probably coexisted within the timeframe of the Cu-Au mineralizing episode: a hot (>200°C) saline (32.8‰ to 40.6 wt.% NaCl eq.) solution, represented by salt-bearing aqueous inclusions, and a lower temperature (<200°C), low to intermediate salinity (<15 wt.% NaCl eq.) aqueous fluid defined by two-phase (LH2O + VH2O) fluid inclusions. This trend is very similar to those defined for other IOCG systems of the Carajás Mineral Province. ? 18OH2O values in equilibrium with calcite (-1.0‰ to 7.5‰ at 277°C to 344°C) overlap the lower range for primary magmatic waters, but the more 18O-depleted values also point to the involvement of externally derived fluids, possibly of meteoric origin. Furthermore, sulphide ? 34S values (5.1‰ to 6.3‰), together with available boron isotope and Cl/Br-Na/Cl data provide evidence for a significant component of residual evaporative fluids (e.g., bittern fluids generated by seawater evaporation) in this scenario that, together with magma-derived brines, would be the main sources of the highly saline fluids involved in the formation Alvo 118 IOCG deposit. The restricted high temperature sodic alteration, the pervasive overprinting of the potassic alteration minerals by chlorite proximal to the ore zones, ore breccias with open-space filling textures in brittle structures, microthermometric and stable isotope data indicate, collectively, that the Alvo 118 IOCG system developed at structurally high levels and may be considered the shallower representative of the IOCG systems of the CMP.

Torresi, Ignacio; Xavier, Roberto Perez; Bortholoto, Diego F. A.; Monteiro, Lena V. S.

2012-03-01

335

Morphological ripening of fluid inclusions and coupled zone-refining in quartz crystals revealed by cathodoluminescence imaging: Implications for CL-petrography, fluid inclusion analysis and trace-element geothermometry  

NASA Astrophysics Data System (ADS)

Cathodoluminescence (CL) studies have previously shown that some secondary fluid inclusions in luminescent quartz are surrounded by dark, non-luminescent patches, resulting from fracture-sealing by late, trace-element-poor quartz. This finding has led to the tacit generalization that all dark CL patches indicate influx of low temperature, late-stage fluids. In this study we have examined natural and synthetic hydrothermal quartz crystals using CL imaging supplemented by in-situ elemental analysis. The results lead us to propose that all natural, liquid-water-bearing inclusions in quartz, whether trapped on former crystal growth surfaces (i.e., of primary origin) or in healed fractures (i.e., of pseudosecondary or secondary origin), are surrounded by three-dimensional, non-luminescent patches. Cross-cutting relations show that the patches form after entrapment of the fluid inclusions and therefore they are not diagnostic of the timing of fluid entrapment. Instead, the dark patches reveal the mechanism by which fluid inclusions spontaneously approach morphological equilibrium and purify their host quartz over geological time. Fluid inclusions that contain solvent water perpetually dissolve and reprecipitate their walls, gradually adopting low-energy euhedral and equant shapes. Defects in the host quartz constitute solubility gradients that drive physical migration of the inclusions over distances of tens of ?m (commonly) up to several mm (rarely). Inclusions thus sequester from their walls any trace elements (e.g., Li, Al, Na, Ti) present in excess of equilibrium concentrations, thereby chemically purifying their host crystals in a process analogous to industrial zone refining. Non-luminescent patches of quartz are left in their wake. Fluid inclusions that contain no liquid water as solvent (e.g., inclusions of low-density H2O vapor or other non-aqueous volatiles) do not undergo this process and therefore do not migrate, do not modify their shapes with time, and are not associated with dark-CL zone-refined patches. This new understanding has implications for the interpretation of solids within fluid inclusions (e.g., Ti- and Al-minerals) and for the elemental analysis of hydrothermal and metamorphic quartz and its fluid inclusions by microbeam methods such as LA-ICPMS and SIMS. As Ti is a common trace element in quartz, its sequestration by fluid inclusions and its depletion in zone-refined patches impacts on applications of the Ti-in-quartz geothermometer.

Lambrecht, Glenn; Diamond, Larryn William

2014-09-01

336

Microwave GaAs Integrated Circuits On Quartz Substrates  

NASA Technical Reports Server (NTRS)

Integrated circuits for use in detecting electromagnetic radiation at millimeter and submillimeter wavelengths constructed by bonding GaAs-based integrated circuits onto quartz-substrate-based stripline circuits. Approach offers combined advantages of high-speed semiconductor active devices made only on epitaxially deposited GaAs substrates with low-dielectric-loss, mechanically rugged quartz substrates. Other potential applications include integration of antenna elements with active devices, using carrier substrates other than quartz to meet particular requirements using lifted-off GaAs layer in membrane configuration with quartz substrate supporting edges only, and using lift-off technique to fabricate ultrathin discrete devices diced separately and inserted into predefined larger circuits. In different device concept, quartz substrate utilized as transparent support for GaAs devices excited from back side by optical radiation.

Siegel, Peter H.; Mehdi, Imran; Wilson, Barbara

1994-01-01

337

Huge Trombus including Left Renal Vein, Ovarian Vein, and Inferior Vena Cava Mimicking Renal Colic  

PubMed Central

A 31-year-old female presented with acute left flank pain; she had a C/S at the postpartum day 24. Ureteral stone was suspected but ultrasound examination was normal. Then Doppler ultrasound revealed a trombus in left renal vein and inferior vena cava. Contrast enhanced MDCT scan showed swelled and nonfunctional left kidney, a trombus including distal part of left ovarian vein, left renal vein, and inferior vena cava. We started anticoagulation treatment. Further examination revealed diagnosis of chronic myeloproliferative disease. The trombus was completely recanalized at 3-month followup. PMID:25140270

Coban, Sermin; Katgi, Abdullah; Obuz, Funda; Kefi, Aykut

2014-01-01

338

Endovascular Laser Therapy for Varicose Veins  

PubMed Central

Executive Summary Objective The objective of the MAS evidence review was to conduct a systematic review of the available evidence on the safety, effectiveness, durability and cost–effectiveness of endovascular laser therapy (ELT) for the treatment of primary symptomatic varicose veins (VV). Background The Ontario Health Technology Advisory Committee (OHTAC) met on November 27, 2009 to review the safety, effectiveness, durability and cost-effectiveness of ELT for the treatment of primary VV based on an evidence-based review by the Medical Advisory Secretariat (MAS). Clinical Condition VV are tortuous, twisted, or elongated veins. This can be due to existing (inherited) valve dysfunction or decreased vein elasticity (primary venous reflux) or valve damage from prior thrombotic events (secondary venous reflux). The end result is pooling of blood in the veins, increased venous pressure and subsequent vein enlargement. As a result of high venous pressure, branch vessels balloon out leading to varicosities (varicose veins). Symptoms typically affect the lower extremities and include (but are not limited to): aching, swelling, throbbing, night cramps, restless legs, leg fatigue, itching and burning. Left untreated, venous reflux tends to be progressive, often leading to chronic venous insufficiency (CVI). A number of complications are associated with untreated venous reflux: including superficial thrombophlebitis as well as variceal rupture and haemorrhage. CVI often results in chronic skin changes referred to as stasis dermatitis. Stasis dermatitis is comprised of a spectrum of cutaneous abnormalities including edema, hyperpigmentation, eczema, lipodermatosclerosis and stasis ulceration. Ulceration represents the disease end point for severe CVI. CVI is associated with a reduced quality of life particularly in relation to pain, physical function and mobility. In severe cases, VV with ulcers, QOL has been rated to be as bad or worse as other chronic diseases such as back pain and arthritis. Lower limb VV is a common disease affecting adults and estimated to be the seventh most common reason for physician referral in the US. There is a strong familial predisposition to VV with the risk in offspring being 90% if both parents affected, 20% when neither is affected, and 45% (25% boys, 62% girls) if one parent is affected. Globally, the prevalence of VV ranges from 5% to 15% among men and 3% to 29% among women varying by the age, gender and ethnicity of the study population, survey methods and disease definition and measurement. The annual incidence of VV estimated from the Framingham Study was reported to be 2.6% among women and 1.9% among men and did not vary within the age range (40-89 years) studied. Approximately 1% of the adult population has a stasis ulcer of venous origin at any one time with 4% at risk. The majority of leg ulcer patients are elderly with simple superficial vein reflux. Stasis ulcers are often lengthy medical problems and can last for several years and, despite effective compression therapy and multilayer bandaging are associated with high recurrence rates. Recent trials involving surgical treatment of superficial vein reflux have resulted in healing and significantly reduced recurrence rates. Endovascular Laser Therapy for VV ELT is an image-guided, minimally invasive treatment alternative to surgical stripping of superficial venous reflux. It does not require an operating room or general anesthesia and has been performed in outpatient settings by a variety of medical specialties including surgeons (vascular or general), interventional radiologists and phlebologists. Rather than surgically removing the vein, ELT works by destroying, cauterizing or ablating the refluxing vein segment using heat energy delivered via laser fibre. Prior to ELT, colour-flow Doppler ultrasonography is used to confirm and map all areas of venous reflux to devise a safe and effective treatment plan. The ELT procedure involves the introduction of a guide wire into the target vein under ultrasound guidance followed by the inse

2010-01-01

339

SIMS analyses of silicon and oxygen isotope ratios for quartz from Archean and Paleoproterozoic banded iron formations  

NASA Astrophysics Data System (ADS)

Banded iron formations (BIFs) are chemical marine sediments dominantly composed of alternating iron-rich (oxide, carbonate, sulfide) and silicon-rich (chert, jasper) layers. Isotope ratios of iron, carbon, and sulfur in BIF iron-bearing minerals are biosignatures that reflect microbial cycling for these elements in BIFs. While much attention has focused on iron, banded iron formations are equally banded silica formations. Thus, silicon isotope ratios for quartz can provide insight on the sources and cycling of silicon in BIFs. BIFs are banded by definition, and microlaminae, or sub-mm banding, are characteristic of many BIFs. In situ microanalysis including secondary ion mass spectrometry is well-suited for analyzing such small features. In this study we used a CAMECA IMS-1280 ion microprobe to obtain highly accurate (±0.3‰) and spatially resolved (˜10 ?m spot size) analyses of silicon and oxygen isotope ratios for quartz from several well known BIFs: Isua, southwest Greenland (˜3.8 Ga); Hamersley Group, Western Australia (˜2.5 Ga); Transvaal Group, South Africa (˜2.5 Ga); and Biwabik Iron Formation, Minnesota, USA (˜1.9 Ga). Values of ? 18O range from +7.9‰ to +27.5‰ and include the highest reported ? 18O values for BIF quartz. Values of ? 30Si have a range of ˜5‰ from -3.7‰ to +1.2‰ and extend to the lowest ? 30Si values for Precambrian cherts. Isua BIF samples are homogeneous in ? 18O to ±0.3‰ at mm- to cm-scale, but are heterogeneous in ? 30Si up to 3‰, similar to the range in ? 30Si found in BIFs that have not experienced high temperature metamorphism (up to 300 °C). Values of ? 30Si for quartz are homogeneous to ±0.3‰ in individual sub-mm laminae, but vary by up to 3‰ between multiple laminae over mm-to-cm of vertical banding. The scale of exchange for Si in quartz in BIFs is thus limited to the size of microlaminae, or less than ˜1 mm. We interpret differences in ? 30Si between microlaminae as preserved from primary deposition. Silicon in BIF quartz is mostly of marine hydrothermal origin (? 30Si < -0.5‰) but silicon from continental weathering (? 30Si ˜ 1‰) was an important source as early as 3.8 Ga.

Heck, Philipp R.; Huberty, Jason M.; Kita, Noriko T.; Ushikubo, Takayuki; Kozdon, Reinhard; Valley, John W.

2011-10-01

340

Deep Vein Thrombosis - Multiple Languages: MedlinePlus  

MedlinePLUS

... features on this page, please enable JavaScript. Deep Vein Thrombosis - Multiple Languages Arabic (???????) Bosnian (Bosanski) French ( ... Somali (af Soomaali) Spanish (español) Arabic (???????) Deep Vein Thrombosis (DVT) (Arabic) ??????? Bilingual PDF Health Information ...

341

Varicose and other vein problems - self-care  

MedlinePLUS

... you stand. As a result, you may have: Varicose veins Swelling in your legs Skin changes or even ... at home to: Slow down the development of varicose veins Decrease any discomfort Prevent skin ulcers

342

Are You At Risk for Deep Vein Thrombosis?  

MedlinePLUS

... Are You at Risk for Deep Vein Thrombosis? Language: English Español (Spanish) Share Compartir Deep vein thrombosis occurs ... Address What's this? Submit What's this? Submit Button Language: English Español (Spanish) File Formats Help: How do I ...

343

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

E-print Network

Veins are ubiquitous features in deformed rocks. Despite observations on syntectonic veins spanning two centuries, fundamental questions remain unanswered. Their origin as fractures is largely established but it is still not known why...

Cervantes, Pablo

2009-05-15

344

Retinal vessel classification: sorting arteries and veins.  

PubMed

For the discovery of biomarkers in the retinal vasculature it is essential to classify vessels into arteries and veins. We automatically classify retinal vessels as arteries or veins based on colour features using a Gaussian Mixture Model, an Expectation-Maximization (GMM-EM) unsupervised classifier, and a quadrant-pairwise approach. Classification is performed on illumination-corrected images. 406 vessels from 35 images were processed resulting in 92% correct classification (when unlabelled vessels are not taken into account) as compared to 87.6%, 90.08%, and 88.28% reported in [12] [14] and [15]. The classifier results were compared against two trained human graders to establish performance parameters to validate the success of classification method. The proposed system results in specificity of (0.8978, 0.9591) and precision (positive predicted value) of (0.9045, 0.9408) as compared to specificity of (0.8920, 0.7918) and precision of (0.8802, 0.8118) for (arteries, veins) respectively as reported in [13]. The classification accuracy was found to be 0.8719 and 0.8547 for veins and arteries, respectively. PMID:24111454

Relan, D; MacGillivray, T; Ballerini, L; Trucco, E

2013-01-01

345

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

Federal Register 2010, 2011, 2012, 2013, 2014

...Airworthiness Directives; Quartz Mountain Aerospace, Inc. Model 11E Airplanes AGENCY...directive (AD) for all Quartz Mountain Aerospace, Inc. Model 11E airplanes. This proposed...except Federal holidays. Quartz Mountain Aerospace, Inc. is in liquidation. For...

2010-03-16

346

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

Federal Register 2010, 2011, 2012, 2013, 2014

...Airworthiness Directives; Quartz Mountain Aerospace, Inc. Model 11E Airplanes AGENCY...directive (AD) for all Quartz Mountain Aerospace, Inc. Model 11E airplanes. This AD...this AD. ADDRESSES: Quartz Mountain Aerospace, Inc. is in liquidation. For...

2010-06-01

347

Hydrothermal synthesis of vanadium oxides  

SciTech Connect

The use of mild hydrothermal methods to synthesize vanadium oxides is reviewed, with particular emphasis on those with layer and 3-dimensional structures. A wide range of studies have been performed predominantly in the past decade to grow new materials that might have interesting electrochemical and magnetic properties. Most emphasis has been placed on vanadium oxides that contain organic species or simple cations such as the alkali metals, alkaline earths, zinc and copper. The key parameters determining the structures formed are reviewed, including pH and the organic structure-directing ion. Some initial electrochemical studies are described.

Chirayil, T.; Zavalij, P.Y.; Whittingham, M.S. [State Univ. of New York, Binghamton, NY (United States)] [State Univ. of New York, Binghamton, NY (United States)

1998-10-01

348

AUTOMATED PLANNING FOR HYDROTHERMAL VENT PROSPECTING USING  

E-print Network

AUTOMATED PLANNING FOR HYDROTHERMAL VENT PROSPECTING USING AUVS by ZEYN A SAIGOL A thesis submitted of searching the ocean floor for hydrothermal vents, using autonomous underwater vehicles (AUVs). This is a hard problem because the AUV's sensors cannot directly measure the range or bearing to vents

Yao, Xin

349

Molecular ecology of hydrothermal vent microbial communities  

Microsoft Academic Search

The study of the structure and diversity of hydrothermal vent microbial communities has long been restricted to the morphological description of microorganisms and the use of enrichment culture-based techniques. Until recently the identification of the culturable fraction required the isolation of pure cultures followed by testing for multiple physiological and biochemical traits. However, peculiar inhabitants of the hydrothermal ecosystem such

Christian Jeanthon

2000-01-01

350

Whole Algae Hydrothermal Liquefaction Technology Pathway  

SciTech Connect

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

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

2013-03-01

351

Hydrothermal synthetic strategies of inorganic semiconducting nanostructures.  

PubMed

Because of their unique chemical and physical properties, inorganic semiconducting nanostructures have gradually played a pivotal role in a variety of research fields, including electronics, chemical reactivity, energy conversion, and optics. A major feature of these nanostructures is the quantum confinement effect, which strongly depends on their size, shape, crystal structure and polydispersity. Among all developed synthetic methods, the hydrothermal method based on a water system has attracted more and more attention because of its outstanding advantages, such as high yield, simple manipulation, easy control, uniform products, lower air pollution, low energy consumption and so on. Precise control over the hydrothermal synthetic conditions is a key to the success of the preparation of high-quality inorganic semiconducting nanostructures. In this review, only the representative hydrothermal synthetic strategies of inorganic semiconducting nanostructures are selected and discussed. We will introduce the four types of strategies based on exterior reaction system adjustment, namely organic additive- and template-free hydrothermal synthesis, organic additive-assisted hydrothermal synthesis, template-assisted hydrothermal synthesis and substrate-assisted hydrothermal synthesis. In addition, the two strategies based on exterior reaction environment adjustment, including microwave-assisted and magnetic field-assisted hydrothermal synthesis, will be also described. Finally, we conclude and give the future prospects of this research area. PMID:23563082

Shi, Weidong; Song, Shuyan; Zhang, Hongjie

2013-07-01

352

TUNABLE HYDROTHERMAL SYNTHESIS OF BAMNO3 NANOCRYSTALS  

Microsoft Academic Search

Although synthesis of nanooxides has been attempted by many different and innovative chemical approaches, further research is still needed to develop inexpensive and mass- production methods capable to provide pure products and thus make nanocrystals' technological applications viable. Hydrothermal synthesis matches these requirements. Under hydrothermal conditions, where an aqueous reaction mixture is heated above 100 ºC in a sealed reaction

Ana Querejeta; Marina Parras; Aurea Varela; Jose González-Calbet

353

Hydrothermal metamorphism in the Larderello Geothermal Field  

SciTech Connect

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

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

1980-01-01

354

REE-bearing minerals in a Ti-rich vein from the Adamello contact aureole (Italy)  

NASA Astrophysics Data System (ADS)

Zirconolite, aeschynite-(Ce), titanite and apatite have been found as minor or accessory minerals in a Ti-rich (TiO2=2.1 4.5 wt.%) hydrothermal vein occurring in dolomite marbles at the contact with a tonalite intrusion of the Tertiary Adamello batholith (northern Italy). The vein consists of four distinct mineral zones, comprising from margin to center: (1) forsterite+calcite, (2) pargasite+calcite+titanite+sulfides, (3) phlogopite +calcite+titanite+sulfides, and (4) titanian clinohumite +spinel+calcite+sulfides. Zirconolite occurs in two vein zones only: in the phlogopite zone it is invariably anhedral, often corroded, and exhibits complex chemical zonation patterns. In the titanian clinohumite zone zirconolite is idiomorphic and characterized by a pronounced discontinous chemical zoning, but shows no evidence of corrosion. The considerable compositional variation observed for zirconolite (in wt.%: ?(REE2O3)=0.74 16.8, UO2=0.59 24.0, ThO2=0.67 17.1) is due to the zoning, and may be attributed to four major substitutions described by the exchange vectors: 1. (Th, U) (Mg, Fe2+) Ca-1 Ti-1 2. REE Al Ca-1 Ti-1 3. REE Fe2+ (Nb, Ta) Ca-1 Ti-1 4. Hf Zr-1 Exchange vector (2) is effective at total REE2O3 contents up to approximately 5 wt.%, whereas vector (3) is operating at higher concentrations. Both titanite and aeschynite-(Ce) exhibit, like zirconolite, complex chemical zonation patterns which document that the trace element content of the metasomatic fluid was variable during the vein-forming process. As indicated by thermodynamic analysis of the phase assemblages, the vein zones containing the REE-bearing minerals formed at 500 600°C (Ptotal?2 kbar) from a reducing fluid rich in H2S, HCl°, HF° and phosphorus, but relatively poor in CO2(XCO 2 ?0.2). Geochemical and isotopic data are consistent with the interpretation of the fluid as being derived from the nearby tonalite intrusion. The abundance of idiomorphic fluor-apatite as well as textural relations between apatite, the other REE-bearing minerals and the fluorine-bearing hydrous silicates suggest F- and PO{4/3-}to be the most likely ligands for complexing REE, Ti, Zr and other high-field-strength elements in the veinforming fluid. The corrosive features observed for zirconolite demonstrate that hydrothermal fluids are able to dissolve zirconolite, which is one of the main components of SYNROC-C, the most promising disposal option for high-level nuclear waste. Therefore, immobilization of radioactive waste in zirconolite can be guaranteed only if an effective sealing material prevents any hydrothermal fluid from access to the final disposal site.

Gieré, Reto; Williams, C. Terry

1992-10-01

355

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

SciTech Connect

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

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

2009-08-05

356

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

USGS Publications Warehouse

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

Chou, I.-M.

2003-01-01

357

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

Microsoft Academic Search

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

A. Th. B. Rast

1992-01-01

358

Neovascularization and recurrent varicose veins: more histologic and ultrasound evidence  

Microsoft Academic Search

BackgroundThe recurrence of varicose veins is a common and costly consequence of varicose vein surgery. Despite the long history and vast experience of varicose vein surgery, the exact cause of recurrence is still unknown. This study aims to investigate the cause of recurrence further by correlating findings from duplex ultrasound scans, resin casts, and histologic investigation at the recurrence of

André M van Rij; Gregory T Jones; Gerry B Hill; Ping Jiang

2004-01-01

359

Prevalence and Risk Factors of Varicose Veins in Japanese Women  

Microsoft Academic Search

The prevalence and risk factors of varicose veins in Japan were investigated in 541 Japanese women. Varicose veins were defined as any dilated, tortuous, and elongated veins of the lower extremity and classified into four types. The total prevalence rate was 45%. Saphenous type was observed in 22%, segment type in 35%, reticular type in 28%, and web type in

Masafumi Hirai; Kenichi Naiki; Ryu Nakayama

1990-01-01

360

Development of HIFU Therapy System for Lower Extremity Varicose Veins  

Microsoft Academic Search

High-intensity focused ultrasound (HIFU) treatment utilizing microbubbles was investigated in the present study. It is known that microbubbles have the potential to enhance the heating effects of an ultrasound field. In this study, the heat accompanying microbubble oscillation was used to occlude varicose veins. Alteration of veins was observed after ultrasound irradiation. Veins were resected by stripping. In this study,

Ryuhei Ota; Jun Suzuki; Kiyoshi Yoshinaka; Juno Deguchi; Shu Takagi; Tetsuro Miyata; Yoichiro Matsumoto

2009-01-01

361

Successful use of the inferior mesenteric vein for renal transplantation.  

PubMed

For renal transplantation, the standard venous drainage of the allograft is via the iliac vein. In unusual circumstances, such as thrombosis or agenesis of the iliac veins and the inferior vena cava, portal venous drainage may be a suitable option. We report a case in which the inferior mesenteric vein was used for venous drainage of a cadaveric renal allograft. PMID:12859544

Patel, Pratik; Krishnamurthi, Venkatesh

2003-08-01

362

Congenital intrahepatic portosystemic shunt with variant inferior right hepatic vein.  

PubMed

We present a case of congenital intrahepatic aneurysmal portosystemic shunt in which the right portal vein communicates with both a variant inferior right hepatic vein and the right hepatic vein. We also describe the importance and efficacy of three dimensional computed tomography reconstruction images in determining subtle, small shunt vessels. PMID:18553284

Senocak, Efsun; O?uz, Berna; Edgüer, Tahsin; Cila, Ay?enur

2008-06-01

363

Long-term assessment of cryopreserved vein bypass grafting success  

Microsoft Academic Search

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

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

2001-01-01