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Sample records for quartz vein gold

  1. The Laramide Caborca orogenic gold belt of northwestern Sonora, Mexico; white mica 40Ar/39Ar geochronology from gold-rich quartz veins

    USGS Publications Warehouse

    Izaguirre, Aldo; Kunk, Michael J.; Iriondo, Alexander; McAleer, Ryan; Caballero-Martinez, Juan Antonio; Espinosa-Arámburu, Enrique

    2016-02-12

    The COGB is approximately 600 kilometers long and 60 to 80 km wide, trends northwest, and extends from west-central Sonora to southern Arizona and California. The COGB contains mineralized gold-rich quartz veins that contain free gold associated with white mica (sericite), carbonate minerals (calcite and ankerite), and sulfides such as pyrite and galena. Limited geochronologic studies exist for parts of the COGB, and previous work was concentrated in mining districts. These previous studies recorded mineralization ages of approximately 70 to 40 Ma. Therefore, some workers proposed that the orogenic gold mineralization in the region occurred during a single pulse that was associated with the Laramide Orogeny that took place during the Cretaceous to early Eocene in the western margin of North America. However, the geochronologic dataset was quite limited, making any regional interpretations tenuous. Accordingly, one of the objectives of this geochronology study was to get a better representative sampling of the COGB in order to obtain a more complete record of the mineralization history. The 63 samples presented in this work are broadly distributed throughout the area of the COGB and allow us to better test the hypothesis that mineralization occurred in a single pulse.

  2. Relationship between amorphous silica and precious metal in quartz veins

    NASA Astrophysics Data System (ADS)

    Harrichhausen, N.; Rowe, C. D.; Board, W. S.; Greig, C. J.

    2015-12-01

    Super-saturation of silica is common in fault fluids, due to pressure changes associated with fracture, fault slip, or temperature gradients in hydrothermal systems. These mechanisms lead to precipitation of amorphous silica, which will recrystallize to quartz under typical geologic conditions. These conditions may also promote the saturation of precious metals, such as gold, and the precipitation of nanoparticles. Previous experiments show that charged nanoparticles of gold can attach to the surface of amorphous silica nanoparticles. Thus, gold and silica may be transported as a colloid influencing mineralization textures during amorphous silica recrystallization to quartz. This may enrich quartz vein hosted gold deposits, but the instability of hydrous silica during subsequent deformation means that the microstructural record of precipitation of gold is lost. We investigate a recent, shallow auriferous hydrothermal system at Dixie Valley, Nevada to reveal the nano- to micro-scale relationships between gold and silica in fresh veins. Fault slip surfaces at Dixie Valley exhibit layers of amorphous silica with partial recrystallization to quartz. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) show amorphous silica can contain a few wt. % gold while areas recrystallized to quartz are barren. At the Jurassic Brucejack deposit in British Columbia, Canada we observe the cryptocrystalline quartz textures that may indicate recrystallization from amorphous silica within quartz-carbonate veins containing high grade gold. Comb quartz within syntaxial veins, vugs, and coating breccia clasts indicate structural dilation. Vein geometry is investigated to determine relative importance of fault slip in creating dilational sites. By comparing quartz-carbonate veins from the Dixie Valley to Brucejack, we can determine whether amorphous silica formed in different environments show similar potential to affect precious metal mineralization.

  3. 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)

    Harraz, Hassan Z.; Hamdy, Mohamed M.

    2015-01-01

    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

  4. 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)

    Mueller, Andreas G.

    2015-02-01

    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

  5. New Peak Temperature Constraints Using RSCM Geothermometry on Lucia Subterrane in Franciscan Complex (California, USA): Detection of Thermal Anomalies in Gold-Bearing Quartz Veins Surrounding.

    NASA Astrophysics Data System (ADS)

    Lahfid, A.; Delchini, S.; Lacroix, B.

    2015-12-01

    The occurrence of deposits hosted by carbonaceous materials-rich metasediments is widespread. Therefore, we aims in this study to investigate the potential of the Raman Spectroscopy of Carbonaceous Material (RSCM) geothermometry to detect thermal anomalies in hydrothermal ore deposits environment and to demonstrate the ability of warm fluids, migrating through the sedimentary sequence to locally disturb the thermal gradient and associated peak temperatures. For this purpose, we have chosen the Lucia subterrane in the Franciscan Complex (California, USA), which includes gold-bearing quartz veins that witness a hydrothermal overprint (Underwood et al., 1995).The sediments in this zone essentially comprise greywacke and shale-matrix mélange (e.g. Frey and Robinson, 1999), which have undergone high-pressure, low-temperature metamorphism. The thermal history of the Lucia subterrane has been previously proposed by Underwood et al. (1995), essentially using vitrinite reflectance method (Rm). Rm values increase from the south to the north; they vary between 0.9 and 3.7 % (~150-280°C). All these results suggest that the Lucia subterrane underwent a regional increase of thermal gradient toward the north. Anomalous Rm values from 4.5% to 4.9% (~305-315°C) are recorded near Cape San Martin. These highest temperatures estimated are likely, associated with a late hydrothermal event (Underwood et al., 1995). Estimated Raman temperatures 1) confirmed the increase in the metamorphic grade towards the north already shown by Underwood et al. (1995), using classical methods like mineralogy and vitrinite reflectance and 2) exhibit anomalous values (temperatures reach 350°C). These anomalies are probably due to the later hydrothermal event. This result suggests that RSCM could be used as a reliable tool to determine thermal anomalies caused by hot fluid-flow.

  6. Metamorphic origin of ore-forming fluids for orogenic gold-bearing quartz vein systems in the North American Cordillera: constraints from a reconnaissance study of δ15N, δD, and δ18O

    USGS Publications Warehouse

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

    2003-01-01

    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 δ15N 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 δ15N values of 1 to 6 per mil. The δ18O 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 δD values of hydrothermal micas are between -110 and -60 per mil. Ore fluids have calculated δ18O values of 8 to 16 per mil and δD values of -65 to -10 per mil at an estimated temperature of 300δC; δD 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 δDH2O 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

  7. Tracking the Mineralogical Fate of Arsenic in Weathered Sulfides from the Empire Mine Gold-Quartz Vein Deposit by using Microbeam Analytical Techniques

    NASA Astrophysics Data System (ADS)

    Burlak, T.; Alpers, C. N.; Foster, A. L.; Brown, A.; Hammersley, L. C.; Petersen, E.

    2010-12-01

    Several complementary microbeam analytical techniques are being employed to determine the mineralogical fate of arsenic (As) released by weathering of primary sulfide minerals from waste rock at a California gold mine. Because of the known association of As with Fe-oxides, special attention was paid to the fate of Fe during weathering of arsenian pyrite [Fe(S,As)2], arsenopyrite (FeAsS), and ferroan dolomite [Ca(Mg,Fe)(CO3)2]. Samples were collected from waste rock dumps at the Empire Mine State Historic Park in Grass Valley, California, and polished thick (60-μm) sections were prepared for analysis. Micro-X-ray fluorescence (µXRF) investigations at the Stanford Synchrotron Radiation Lightsource (SSRL) involved mapping element distribution at the 100-μm pixel scale (beamline 10-2) and 2-µm pixel size (beamline 2-3) at four energies spanning the range of As valence states (11,867-11,890 eV). The maps provide spatial data on several elements (As, Ca, Fe, K, Mn, Ni, S, and Zn), but without standardization this information remains qualitative. Good correspondence was found between the results of principal component analysis of the maps and the distribution of the two main As valence states, As(III) and As(V). X-ray absorption fine structure (XAFS) spectra collected on beamline 2-3 at the As and Fe K-edges show reduced and oxidized species of both elements and no evidence for secondary arsenate phases such as scorodite (FeAsO4 ● 2H2O). Spectra of As(III) were rare, and not often mixed with As(V). The same thick sections were also analyzed by electron microbeam methods. Chemical and element analysis using a Cameca SX-100 microprobe quantified mineral compositions at selected spots in the sections by comparison to well-characterized reference materials. Concentrations of As in pyrite ranged from less than 0.01% to 3.1 wt. % and pyrite and was heterogeneous at the sub-µm scale. Arsenopyrite and ferroan dolomite were also found to be heterogeneous in composition

  8. Crystallochemical and structural evolution of tourmaline in auriferous quartz veins of the Iskel terrane prospect (western Hoggar, Tamanrasset, South Algeria)

    NASA Astrophysics Data System (ADS)

    Talbi, Mohamed; Chaouche, Ismahane; Fuchs, Yves

    2016-04-01

    A mylonite zone limits the Iskane Terrane tectonic unit (Western Hoggar). This zone is intruded by granitic units belonging to the Taourirt cycle. North -South and North East-South West trending auriferous quartz veins are hosted in the cataclased areas. Visible gold can be observed but gold is also present in sulfides (pyrite, chalcopyrite). Tourmaline is abundant in these veins. Mossbauer spectrometry as well as FTIR spectrometry shows that in some sectors tourmaline underwent an oxidation process posterior to its formation. The general structure of tourmaline studied, shows the coexistence of ferric iron Fe3+ with ferrous iron Fe2+ in the Y site. This represents a tourmaline "deprotonated". This oxidation induced a partial transformation of Fe2+ in Fe3+ that is charge compensated by a deshydroxylation of the central OH group. The relationship of the gold deposition with the oxidation of tourmaline is discussed. Key words: Tourmaline, oxidation, "deprotonation-deshydroxylation", sulfides, gold.

  9. Establishment of gold-quartz standard GQS-1

    USGS Publications Warehouse

    Millard, Hugh T.; Marinenko, John; McLane, John E.

    1969-01-01

    A homogeneous gold-quartz standard, GQS-1, was prepared from a heterogeneous gold-bearing quartz by chemical treatment. The concentration of gold in GQS-1 was determined by both instrumental neutron activation analysis and radioisotope dilution analysis to be 2.61?0.10 parts per million. Analysis of 10 samples of the standard by both instrumental neutron activation analysis and radioisotope dilution analysis failed to reveal heterogeneity within the standard. The precision of the analytical methods, expressed as standard error, was approximately 0.1 part per million. The analytical data were also used to estimate the average size of gold particles. The chemical treatment apparently reduced the average diameter of the gold particles by at least an order of magnitude and increased the concentration of gold grains by a factor of at least 4,000.

  10. Evolution of ore forming fluid in the orogenic type gold deposit in Tavt, Mongolia: trace element geochemistry and fluid inclusions in quartz

    NASA Astrophysics Data System (ADS)

    Lee, K.; Oyungerel, S.; Lee, I.

    2011-12-01

    The Tavt gold deposit of Dzhida-Selengisky metallogenic belt is located in the Dzhida terrane, northern Mongolia. This deposit commonly occurs with massive auriferous quartz veins that contain sulfides and less commonly occurs with disseminated- and stockwork-type quartz veins. Such gold-bearing quartz veins have an average grade of 6.3 g/t Au, 29.4 g/t Ag, and 1.3% Cu. This gold deposit is composed of three stages of quartz vein groups. The first stage quartz group is widely spread with medium to large grain size, showing white-grey and milky white colors. It underwent intensive cataclasis with strong cuts via fractures and includes a small amount of sulfides, secondary minerals and Au. The second stage quartz group is grey and includes an oxidation zone. The oxidation zone distributed on the outside of the vein is brown and green-grey; it is also enriched with sulfide minerals containing gold. This quartz group is located in a brittle and cataclastic zone with the first stage quartz group. The main mineralization process for gold is related to this second stage quartz group. The transition between the first and second groups is not clear, and their contact relationship is complex. The third stage quartz group is transparent to translucent, and has small euhedral crystals that were formed in the second stage quartz group. The third stage of quartz is partly associated with chlorite and montmorillonite that was formed in the latest stage. Each generation of quartz was analyzed by SEM-CL, EPMA, and ICP-MS. Fluid inclusion data were collected from the USGS gas-flow heating/freezing stage and Raman-spectroscopy. The electron microprobe data show the distribution of Al, Ca, K and Fe among distinguished CL intensities and textures of quartz from different stages. The prepared pure quartz samples were analyzed by ICP-MS. The analysis also shows different patterns of trace elements according to the quartz stages.

  11. Geology and mineralization at the Ishmas Kabir gold prospect, Ishmas gold district, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Walker, B.M.; Ben Talib, Majed; El Komi, Mohamed; Hussain, M.A.; Christian, R.P.

    1990-01-01

    Quartz veins intersected by drill holes are surrounded by mylonite schist. Quartz and carbonate veins less than 5 mm thick are boudined, whereas thick quartz veins (£ 1.2 m) have disrupted and brecciated margins; mylonitized country rock envelops quartz-vein fragments. Sulfide mineralization associated with vein formation predates this rock-deformation event. Contemporaneous brittle and ductile deformation of quartz veins and country rocks occurred during the Nabitah orogeny. Supergene gold enrichment took place much later.

  12. Analysis of Rare Earth Elements (REE) in vein quartz and quartz-sandstone host rock in the Zhelannoe high purity quartz deposit, Russia

    NASA Astrophysics Data System (ADS)

    Zemskova, Marina; Prokofiev, Vsevolod; Bychkov, Andrey

    2015-04-01

    The Zhelannoe high purity quartz deposit is located on the western slope of the Polar Urals. It is one of the largest deposits of vein quartz and rock crystal in Russia. Most of the mineralization is hosted within a single horizon of very firm quartz-sandstone, where plastic deformation did not occur almost entirely. All tectonic stress was released by the development of numerous thrust faults of different scales. Cavities formed during this process were later filled with quartz and rock crystal. In order to obtain more details on conditions under which mineralization took place, analysis of trace element contents in vein quartz and host rocks, and the micro-thermometric study of fluid inclusions in quartz have been carried out. The trace element composition of vein quartz and of the host rock has been determined by ICP-MS. The results have shown that concentrations of most of the 46 studied elements in quartz are two orders of magnitude lower than in chondrite, and more than three orders of magnitude lower than in the upper crust. Even though Pb and Li have the highest concentrations in quartz samples, levels are only nearly comparable in chondrite, and substantially lower in the upper crust. At the same time, negative anomalies of Pb and Li concentrations in the host rock may indicate the removal of these elements during vein quartz formation. Contents of most REEs are two orders of magnitude lower than in chondrite, and three orders of magnitude lower than in the host rock. Generally, the patterns of REE distribution in vein quartz and the host rock express a clear correlation; confirming the genetic link between vein quartz and quartz-sandstone host rock. However, the process of quartz recrystallization led to an intense decrease of REEs content, and of all other impurities, which consequently influenced industrial value of the Zhelannoe deposit. As a result of the micro-thermometric study of fluid inclusions in quartz, the following physical

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

    NASA Astrophysics Data System (ADS)

    Akawy, Ahmed

    2007-02-01

    Several quartz vein sets with varying orientation, geometry and internal structure were recognized in the Atalla area. The veins were associated with the deformation phases affecting the area. En echelon and extensional veins are the main geometrical types. Syn-kinematic veins associated with the major northeast-over-southwest thrust faults were later boudinaged, folded and re-folded. En echelon veins, fibrous veins, and extensional veins are associated with the NNW-SSE faults. Other veins are associated with the NW-SE, N-S, NE-SW and E-W faults. Veins are concentrated at the intersection zones between faults. The internal structure of the veins comprises syntaxial, antitaxial, and composite types and reflects a change from a compressive stress regime to an extensional one. Chocolate-tablet structures and synchronous and co-genetic vein networks indicate later multi-directional extension of the area. Interaction between cracking and sealing of fractures is a common feature in the study area indicating that it was easy for the pore pressure to open pre-existing fractures instead of creating new ones. The reopening of pre-existing fractures rather than creating new ones is also indicated by the scattering of vein data around σ3. There is an alteration and change in characteristics of the wall rock due to increase in fluid flow rate. Fault-valving probably is also a cause of the complex geometry of some veins.

  14. Different carbon reservoirs of auriferous fluids in African Archean and Proterozoic gold deposits? Constraints from stable carbon isotopic compositions of quartz-hosted CO2-rich fluid inclusions

    NASA Astrophysics Data System (ADS)

    Lüders, Volker; Klemd, Reiner; Oberthür, Thomas; Plessen, Birgit

    2015-04-01

    Stable carbon (and when present, nitrogen) isotope ratios of fluid inclusions in quartz from selected gold deposits in Ghana and Zimbabwe have been analyzed using a crushing device interfaced to an isotopic ratio mass spectrometer (IRMS) in order to constrain possible sources of the auriferous fluids. The study revealed a striking difference in stable carbon isotopic compositions of CO2 in quartz-hosted fluid inclusions from Archean and Paleoproterozoic orogenic gold deposits and points to diverse sources of CO2 in the studied deposits. Whether this finding can be generalized for other Archean and Proterozoic orogenic gold deposits worldwide remains open. However, a significant CO2 contribution by mantle degassing can be ruled out for every deposit studied. Devolatilization of greenstone belt rocks is the most likely source for CO2 in some Archean Au deposits in Zimbabwe, whereas CO2 in Proterozoic vein-type Au deposits in the West African Craton is most likely derived from Corg-bearing metasedimentary rocks. The δ13CCO2 values of high-density CO2-rich, water-poor inclusions hosted in quartz pebbles from the world-class Au-bearing conglomerate deposits at Tarkwa (Ghana) differ considerably from the δ13CCO2 values of similar high-density CO2-rich inclusions in vein quartz from the giant Ashanti deposit (Ghana) and disprove the idea of derivation of the Tarkwaian quartz (and gold?) from an older equivalent to the Ashanti vein-type gold deposit.

  15. SEM-Cathodoluminescence and fluid inclusion study of quartz veins in Hugo Dummett porphyry Cu-Au deposit,South Mongolia

    NASA Astrophysics Data System (ADS)

    Sanjaa, M.; Fujimaki, H.; Ken-Ichiro, H.

    2010-12-01

    The Hugo Dummett porphyry copper-gold deposit in Oyu Tolgoi, South Mongolia is a high-sulfidation type deposit which consists of Cu-Au bearing quartz veins. Cathodoluminescence (CL) analysis using scanning electron microscope (SEM) and fluid inclusion microthermometer were performed to elucidate the relationship between CL structures, fluid inclusion microthermometer of different quartz generations, and ore forming process of the Hugo Dummett deposit. Hydrothermal quartz from quartz-sulfide veins in the porphyry Cu-Au deposit in Hugo Dummett, revealing the following textures: (1) euhedral growth zones (2) embayed and rounded CL-bright cores, with CL-dark and CL-gray overgrowths, (3) concentric and non concentric growth zones, and (4) CL dark/bright microfractures. These textures indicate that many veins have undergone fracturing, growth of quartz into fluid-filled space and quartz dissolution of quartz. SEM-CL imaging indicates vein quartz in the Hugo Dummett deposit, initially grew as individual CL-bright crystals 356 ± 10°C liquid-reservoir (average Th value for fluid inclusions in the crystal cores is 359°C). In contract, SEM-CL imaging shows the edges of the micron-scale growth zones of varying CL intensity, reflecting quartz precipitation at some later time, when the Hugo Dummett deposit hydrothermal system had cooled, when reservoir conditions were about 211 ± 25°C (average Th value of 212°C). Crystal growth is SEM-CL evidence of the vein quartz having been partly dissolved. Pressure change has a large effect on quartz solubility and may have been responsible for quartz dissolution and precipitation textures in the cooling hydrothermal system. CL-dark microfractures homogenization temperatures lower 169 ± 16°C (average Th value 170°C) than CL bright and CL gray. Temperature and pressure of the mineralized fluid estimates a pressure of formation of 0.3-0.5 kbar (lithostatic), was formed at approximately 2 km depth, as well as a formation temperature

  16. Trace elements in hydrothermal quartz: Relationships to cathodoluminescent textures and insights into vein formation

    USGS Publications Warehouse

    Rusk, B.G.; Lowers, H.A.; Reed, M.H.

    2008-01-01

    High-resolution electron microprobe maps show the distribution of Ti, Al, Ca, K, and Fe among quartz growth zones revealed by scanning electron microscope-cathodoluminescence (SEM-CL) from 12 hydrothermal ore deposits formed between ???100 and e1750 ??C. The maps clearly show the relationships between trace elements and CL intensity in quartz. Among all samples, no single trace element consistently correlates with variations in CL intensity. However in vein quartz from five porphyry-Cu (Mo-Au) deposits, CL intensity always correlates positively with Ti concentrations, suggesting that Ti is a CL activator in quartz formed at >400 ??C. Ti concentrations in most rutile-bearing vein quartz from porphyry copper deposits indicate reasonable formation temperatures of 2000 ppm, but in high-temperature quartz, Al concentrations are consistently in the range of several hundred ppm. Aluminum concentrations in quartz refl ect the Al solubility in hydrothermal fluids, which is strongly dependent on pH. Aluminum concentrations in quartz therefore reflect fluctuations in pH that may drive metal-sulfide precipitation in hydrothermal systems. ?? 2008 The Geological Society of America.

  17. Formation of Archean batholith-hosted gold veins at the Lac Herbin deposit, Val-d'Or district, Canada: Mineralogical and fluid inclusion constraints

    NASA Astrophysics Data System (ADS)

    Rezeau, Hervé; Moritz, Robert; Beaudoin, Georges

    2016-07-01

    The Lac Herbin deposit consists of a network of mineralized, parallel steep-reverse faults within the synvolcanic Bourlamaque granodiorite batholith at Val-d'Or in the Archean Abitibi greenstone belt. There are two related quartz-tourmaline-carbonate fault-fill vein sets in the faults, which consist of subvertical fault-fill veins associated with subhorizontal veins. The paragenetic sequence is characterized by a main vein filling ore stage including quartz, tourmaline, carbonate, and pyrite-hosted gold, chalcopyrite, tellurides, pyrrhotite, and cubanite inclusions. Most of the gold is located in fractures in deformed pyrite and quartz in equilibrium with chalcopyrite and carbonates, with local pyrrhotite, sphalerite, galena, cobaltite, pyrite, or tellurides. Petrography and microthermometry on quartz from the main vein filling ore stage reveal the presence of three unrelated fluid inclusion types: (1) gold-bearing aqueous-carbonic inclusions arranged in three-dimensional intragranular clusters in quartz crystals responsible for the main vein filling stage, (2) barren high-temperature, aqueous, moderately saline inclusions observed in healed fractures, postdating the aqueous-carbonic inclusions, and considered as a remobilizing agent of earlier precipitated gold in late fractures, and (3) barren low-temperature, aqueous, high saline inclusions in healed fractures, similar to the crustal brines reported throughout the Canadian Shield and considered to be unrelated to the gold mineralization. At the Lac Herbin deposit, the aqueous-carbonic inclusions are interpreted to have formed first and to represent the gold-bearing fluid, which were generated contemporaneous with regional greenschist facies metamorphism. In contrast, the high-temperature aqueous fluid dissolved gold from the main vein filling ore stage transported and reprecipitated it in late fractures during a subsequent local thermal event.

  18. Formation of Archean batholith-hosted gold veins at the Lac Herbin deposit, Val-d'Or district, Canada: Mineralogical and fluid inclusion constraints

    NASA Astrophysics Data System (ADS)

    Rezeau, Hervé; Moritz, Robert; Beaudoin, Georges

    2017-03-01

    The Lac Herbin deposit consists of a network of mineralized, parallel steep-reverse faults within the synvolcanic Bourlamaque granodiorite batholith at Val-d'Or in the Archean Abitibi greenstone belt. There are two related quartz-tourmaline-carbonate fault-fill vein sets in the faults, which consist of subvertical fault-fill veins associated with subhorizontal veins. The paragenetic sequence is characterized by a main vein filling ore stage including quartz, tourmaline, carbonate, and pyrite-hosted gold, chalcopyrite, tellurides, pyrrhotite, and cubanite inclusions. Most of the gold is located in fractures in deformed pyrite and quartz in equilibrium with chalcopyrite and carbonates, with local pyrrhotite, sphalerite, galena, cobaltite, pyrite, or tellurides. Petrography and microthermometry on quartz from the main vein filling ore stage reveal the presence of three unrelated fluid inclusion types: (1) gold-bearing aqueous-carbonic inclusions arranged in three-dimensional intragranular clusters in quartz crystals responsible for the main vein filling stage, (2) barren high-temperature, aqueous, moderately saline inclusions observed in healed fractures, postdating the aqueous-carbonic inclusions, and considered as a remobilizing agent of earlier precipitated gold in late fractures, and (3) barren low-temperature, aqueous, high saline inclusions in healed fractures, similar to the crustal brines reported throughout the Canadian Shield and considered to be unrelated to the gold mineralization. At the Lac Herbin deposit, the aqueous-carbonic inclusions are interpreted to have formed first and to represent the gold-bearing fluid, which were generated contemporaneous with regional greenschist facies metamorphism. In contrast, the high-temperature aqueous fluid dissolved gold from the main vein filling ore stage transported and reprecipitated it in late fractures during a subsequent local thermal event.

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

    NASA Astrophysics Data System (ADS)

    Sintubin, Manuel; Wenk, Hans-Rudolf

    2013-04-01

    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

  20. Hydrothermal Fluid Evolution During Vein Formation in Arghash Gold Prospect, Northeast Of Iran

    NASA Astrophysics Data System (ADS)

    Alirezaei, S.; Ashrafpour, E.; Ansdell, K. M.

    2009-05-01

    The Arghash gold prospect consisting of five gold-bearing vein systems is hosted by Eocene intermediate volcanic and pyroclastic rocks and Late Eocene-Oligocene granitic and dioritic rocks. The vein materials consist mostly of quartz, calcite and minor pyrite. Gold occurs as native particles in quartz, as well as submicroscopic particles in arsenian pyrite, as indicated by microprobe analyses. All auriferous vein systems show similar vein mineralogy and hydrothermal alteration assemblages, implying that they all belong to the same mineralization event in the region. The ä18O compositions of hydrothermal fluid(s) in equilibrium with vein quartz vary from +6.3 to +10.5 per mil. The äD values of the fluid in equilibrium with kaolinite from the immediate altered wall rocks vary from -53 to - 62 per mil. The oxygen isotope values fall in the range commonly accepted for magmatic waters; the calculated äD values overlap between meteoric and magmatic waters. Oxygen and hydrogen isotope compositions similar to those in Arghash can be produced from meteoric waters evolved through interaction with country rocks, boiling, and mixing with magmatic water. The effects of various water/rock ratios on the isotopic composition of the exchanged meteoric water could explain a shift of about +14 per mil in the ä18O values of the mineralizing fluids in the Arghash prospect. Water/rock interaction would also change the äD values of the hydrothermal fluids at low water/rock ratios. In the case of igneous country rocks, as in the Arghash, this process should lead to a shift in the äD of the presumed meteoric waters toward higher values. Boiling will increase the ä18O and äD values of hydrothermal fluids due to fractionation of 16O and H into the vapor phase and decreasing temperature. The magnitude of the enrichment depends on the boiling path and the mechanism of vapor separation. Boiling in Arghash is supported by mineralogical and textural evidences. Gold assays are highest

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    1993-11-01

    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).

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

    Quartz-carbonate veins are common in a variety of moderate temperature hydrothermal systems and ore deposits. Associated fluid inclusions have a wide range of compositions, including liquid carbon dioxide fillings. Examination of chemical and physical conditions which result precipitation of quartz and carbonate in veins raises several key questions about multiphase fluid processes and reaction rates. We have been experimentally investigating physical-chemical reaction processes of mixed brine-carbon dioxide fluids for the shallow crust. Synthetic arkose (microcline + oligoclase + quartz + biotite) plus argillaceous shale were reacted with 5.5 molal NaCl brine. The system was held at 200 C and 200 bars for 32 days to approach steady state, then injected with carbon dioxide and allowed to react for an additional 45 days. In a parallel experiment, the system was allowed to react for 77 days without injection of carbon dioxide. Trace ions initially absent from NaCl brine appeared in solution at mM (K, Ca, and silica) to uM (Mg, Al, Fe and Mn) quantities, reflecting reaction of brine with rock. Without carbon dioxide injection, the silica concentration (2.4 mM) was stable below calculated quartz solubility (3.9 mM). Injection of carbon dioxide resulted in decreased pH and increased silica concentration to a level near calculated chalcedony solubility (5.4 mM). Dissolution of silicate minerals is apparently coupled to the acidity, and concomitant inhibition of the precipitation of quartz (and other silicates). A significant increase in concentration of trace metals is consistent with in-situ pH decrease and increased carbon dioxide dissolved in brine. Multi-phase fluid reaction relationships between supercritical carbon dioxide and brine-rock systems allow formation of carbonate vein precipitates in substantial quantities. Brine and continued rock reactions provide a substantial reservoir for Ca, Mg and Fe components. A separate carbon dioxide liquid allows

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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 (50μm) within the amorphous silica layers. The porosity (Φ) gradually decreases with minimal porosity (Φ = 0.4) at ˜ 38mm from

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

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

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

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

    PubMed

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

    2009-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Jørgen Kjøll, Hans; Viola, Giulio; Menegon, Luca; Sørensen, Bjørn

    2015-04-01

    A coarse grained, statically crystallized quartz vein with a random CPO, embedded in a phyllonitic matrix, was studied by optical microscopy, SEM imaging and EBSD to gain insights into the processes of strain localization in quartz deformed under low greenschist facies conditions at the frictional-viscous transition. The vein is located in a high strain zone at the front of an imbricate stack of Caledonian age along the northwesternmost edge of the Repparfjord Tectonic Window in northern Norway. The vein was deformed within the Nussirjavrri Fault Zone (NFZ), an out-of-sequence thrust with a phyllonitic core characterized by a ramp-flat-ramp geometry, NNW plunging stretching lineations and top-to-the SSE thrusting kinematics. Deformation conditions are typical of the frictional-viscous transition. The phyllonitic core 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, related to the development of a mesoscopic pervasive extensional crenulation cleavage, was accommodated within the vein initially by basal slip of suitably oriented quartz crystals, which produced e.g. undulose extinction, extinction bands and bulging grain boundaries. In the case of misoriented quartz crystals, however, glide-accommodated dislocation creep resulted soon inefficient and led to localized dislocation tangling and strain hardening. In response to 1) hardening, 2) progressive increase of fluid pressure within the actively deforming vein and 3) increasing competence contrast between the vein and the surrounding weak, foliated phyllonitic fault core, quartz crystals began to deform frictionally along specific lattice planes oriented optimally with respect to the imposed stress field. Microfaulting generated small volumes of gouge along

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

    NASA Astrophysics Data System (ADS)

    Kerrich, R.; Feng, R.

    1992-01-01

    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.

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

    SciTech Connect

    Zeitler, P.K. ); Barreiro, B.; Chamberlain, C.P. ); Rumble, D. III )

    1990-07-01

    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.

  10. Nature and composition of gold-forming fluids at Umm Rus area, Eastern Desert, Egypt: evidence from fluid inclusions in vein materials

    NASA Astrophysics Data System (ADS)

    Harraz, H. Z.; El-Dahhar, M. A.

    1993-04-01

    The Umm Rus gold lode is housed along fractures in granitoid-gabbroic rocks, being largely controlled by a NE-SW trending fracture system that affected the Eastern Desert. Mineralogically, the gold lode consists of quartz and carbonate gangue enclosing minor amounts of auriferous pyrite and arsenopyrite. Trace amounts of sphalerite, galena, marcasite and pyrrhotite are also present. The lode can be divided into: (i) Au-poor, pyrite-quartz vein, (ii) Au-rich, pyrite-arsenopyrite-quartz vein and (iii) gangue dominant. Inspection of primary inclusions from the Umm Rus gold lode showed that the ore was formed from CO 2-H 2O-rich fluids (ca. 30-46 mol % CO 2) of low salinity (6.75-7.75 wt. % NaCl equiv.) and alkaline to neutral pH with a density of 0.76-0.85 g/cc. These data are consistent with dissolution of gold as a bisulphide complex. Deposition of Au most likely occurred over a temperature range of 250-300°C and at pressures around 0.35 Kbars. The deposition may have occurred in response to separation of a liquid CO 2-phase from an originally CO 2-H 2O-rich aqueous fluids. The style of mineralization at Umm Rus bears certain resemblances to Au-bearing quartz veins in the Archaean deposits of Canada and Australia and the "Mother Lode" deposits of the U.S.A.

  11. Alteration and fluid flow around a sulfide-carbonate-quartz vein, Lucky Friday mine, Northern Idaho

    SciTech Connect

    Gitlin, E.C.

    1985-01-01

    Wall rocks at the Lucky Friday mine, Coeur d'Alene district, Idaho, contain a >500m wide zone about a steeply dipping Pb-Zn-Ag vein. This zone has experienced local conditions distinct from the regional metamorphism of the quartzite + argillite host rock. Within the district, the host rock (Precambrian Revett Formation) has undergone low grade metamorphism and contains varying proportions of quartz, phengitic muscovite, detrital alkali feldspar, magnetite, hematite, ilmenite, rutile, zircon, tourmaline, +/- calcite, +/- ankeritic dolomite. In contrast, the Lucky Friday wall rocks lack feldspar and Fe-bearing oxides, and contain Fe-poor muscovite and up to 40% carbonate: siderite, ankerite, and/or calcite. A comparison of district-wide Revett rocks with Lucky Friday wall rocks suggests that the wall rocks have undergone localized dephengitization with concomitant Fe-enrichment in the carbonates and Fe-depletion of the oxides. Pertinent metamorphic reactions consume CO/sub 2/ and liberate H/sub 2/O. Fluid inclusions from the vein and wall rock stringers have homogenization temperatures from approx. =200/sup 0/ to <375/sup 0/C, but they define no temperature gradient. With few exceptions, compositions of the carbonates are identical throughout the altered wall rock. These observations suggest that the carbonate subzone contacts are not isograds but isofluxes: the loci of equivalent fluid/reactant mineral ratio. The disposition of isofluxes around a dominant fluid channelway, i.e. the vein, affords an opportunity to interpret fluid flow pathways during low temperatures metamorphism.

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

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

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

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

    USGS Publications Warehouse

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

    1993-01-01

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

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

    SciTech Connect

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

    1988-07-01

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

  15. Fluid inclusion and stable isotopes studies of epithermal gold-bearing veins in the SE Afar Rift (Djibouti)

    NASA Astrophysics Data System (ADS)

    Moussa, N.; Boiron, M. C.; Grassineau, N.; Fouquet, Y.; Le Gall, B.; Mohamed, J.

    2015-12-01

    The Afar rift results from the interaction of a number of actively-propagating tectono-magmatic axes. Recent field investigations in the SE Afar rift have emphasized the importance of hydrothermal system in rift-related volcanic complexes. Mineralization occur as gold-silver bearing veins and are associated with felsic volcanism. Late carbonate veins barren of sulfides and gold are common. The morphologies and textures of quartz show crustiform colloform banding, massive and breccias. Microthermometric measurements were made on quartz-hosted two phases (liquid + vapor) inclusions; mean homogenization temperature range from 150°C to 340°C and ice-melting temperatures range from -0.2° to 1.6°C indicating that inclusion solutions are dilute and contain 0.35 to 2.7 equivalent wt. % NaCl. Furthermore, δ18O and δ13C values from calcite range from 3.7 to 26.6 ‰ and -7.5 to 0.3‰, respectively. The presence of platy calcite and adularia indicate that boiling condition existed. This study shows that precious-metal deposition mainly occurred from hydrothermal fluids at 200°C at around 300 and 450 m below the present-day surface in a typical low-sulphidation epithermal environment.

  16. Development of discrete aggregates of recrystallization along micro-shear zones in quartz ribbons during multistage ductile evolution of a quartz vein

    NASA Astrophysics Data System (ADS)

    Ceccato, Alberto; Pennacchioni, Giorgio; Bestmann, Michel

    2016-04-01

    The post-magmatic ductile deformation of the Rieserferner pluton (Eastern Alps) includes localized ductile shear zones exploiting a set of joint-filling quartz veins. These deformed veins show different stages of evolution, from coarse grained vein quartz to the fine grained recrystallized aggregates of ultramylonites, locally recorded in different domains of heterogeneously sheared veins. The microstructural evolution includes, with increasing strain: (i) Development of ribbon mylonites consisting of elongated grains, oblique to the shear zone boundary, derived from different quartz veins crystals. The individual ribbons have different crystallographic orientations and aspect ratios. (ii) Dismantling of ribbons along a fracture-like network of fine grained recrystallized quartz aggregates, that commonly represent micro-shear zones (μSZ). These discrete recrystallization zones are preferentially developed in ribbons whose crystallographic axis is oriented either parallel or normal to ribbon elongation. (iii) Extensive dynamic recrystallization to fine-grained (10-20 μm) aggregates leading to quartz ultramylonites. Typically ultramylonites show a layered texture with bands having different crystallographic preferred orientation (CPO) that probably reflect the original heterogeneity in crystallographic orientations of the vein. Electron backscattered diffraction analysis indicates that the μSZ within quartz ribbons are mainly parallel to {r} or {z} planes of the host grain, and the new grain inside μSZ show a weak CPO with their basal plane parallel to the μSZ boundary. There is no systematic relationships between the Dauphiné twinning and the μSZ. Misorientation analysis suggests that in the host grain dislocation creep is dominant on {m} slip system, whereas it is probably a minor mechanism within μSZ. Subgrains and low-angle boundaries (LAB) are heterogeneously developed at the border of the μSZ, and more commonly occur around the tips of

  17. Zinc oxide nanorod growth on gold islands prepared by microsphere lithography on silicon and quartz.

    PubMed

    Blackledge, Charles W; Szarko, Jodi M; Dupont, Aurélie; Chan, George H; Read, Elizabeth L; Leone, Stephen R

    2007-09-01

    Gold islands, vapor deposited on silicon and quartz by microsphere lithography patterning, are used to nucleate arrays of ZnO nanorods. ZnO is grown on approximately 0.32 microm2 Au islands by carbothermal reduction in a tube furnace. Scanning electron microscopy (SEM) and energy dispersive atomic X-ray spectroscopy (EDS) confirm that the gold effectively controls the sites of nucleation of ZnO. Atomic force microscopy (AFM) shows that approximately 30 nm diameter nanorods grow horizontally, along the surface. Alloy droplets that are characteristic of the vapor-liquid-solid (VLS) mechanism are observed at the tips of the nanorods. The spatial growth direction of VLS catalyzed ZnO nanorods is along the substrate when they nucleate from gold islands on silicon and quartz. The energy of adhesion of the VLS droplet to the surface can account for the horizontal growth.

  18. Lubricity of gold nanocrystals on graphene measured using quartz crystal microbalance

    PubMed Central

    Lodge, M. S.; Tang, C.; Blue, B. T.; Hubbard, W. A.; Martini, A.; Dawson, B. D.; Ishigami, M.

    2016-01-01

    In order to test recently predicted ballistic nanofriction (ultra-low drag and enhanced lubricity) of gold nanocrystals on graphite at high surface speeds, we use the quartz microbalance technique to measure the impact of deposition of gold nanocrystals on graphene. We analyze our measurements of changes in frequency and dissipation induced by nanocrystals using a framework developed for friction of adatoms on various surfaces. We find the lubricity of gold nanocrystals on graphene to be even higher than that predicted for the ballistic nanofriction, confirming the enhanced lubricity predicted at high surface speeds. Our complementary molecular dynamics simulations indicate that such high lubricity is due to the interaction strength between gold nanocrystals and graphene being lower than previously assumed for gold nanocrystals and graphite. PMID:27554595

  19. Lubricity of gold nanocrystals on graphene measured using quartz crystal microbalance

    NASA Astrophysics Data System (ADS)

    Lodge, M. S.; Tang, C.; Blue, B. T.; Hubbard, W. A.; Martini, A.; Dawson, B. D.; Ishigami, M.

    2016-08-01

    In order to test recently predicted ballistic nanofriction (ultra-low drag and enhanced lubricity) of gold nanocrystals on graphite at high surface speeds, we use the quartz microbalance technique to measure the impact of deposition of gold nanocrystals on graphene. We analyze our measurements of changes in frequency and dissipation induced by nanocrystals using a framework developed for friction of adatoms on various surfaces. We find the lubricity of gold nanocrystals on graphene to be even higher than that predicted for the ballistic nanofriction, confirming the enhanced lubricity predicted at high surface speeds. Our complementary molecular dynamics simulations indicate that such high lubricity is due to the interaction strength between gold nanocrystals and graphene being lower than previously assumed for gold nanocrystals and graphite.

  20. Combined optical second harmonic generation/quartz crystal microbalance study of underpotential deposition processes: copper electrodeposition on polycrystalline gold.

    PubMed

    Lakkaraju, S; Bennahmias, M J; Borges, G L; Gordon Ii, J G; Lazaga, M; Stone, B M; Ashley, K

    1990-11-20

    Optical second harmonic generation and quartz crystal microbalance techniques are used as in situ probes of copper underpotential deposition on polycrystalline gold surfaces in sulfuric acid electrolyte. The second harmonic signal from a polished bulk gold substrate is observed to decrease by >60% as a result of copper underpotential deposition on gold. Also, the mass of an underpotentially deposited copper adlayer is monitored in situ by an oscillating quartz crystal microbalance, yielding an estimated coverage of ~8.0 x 10(-10) mol cm(-2) and an electrosorption valency of 1.5 for a copper adlayer on the surface of vapor-deposited polycrystalline gold.

  1. Fluid evolution in a volcanic-hosted epithermal carbonate-base metal-gold vein system: Alto de la Blenda, Farallón Negro, Argentina

    NASA Astrophysics Data System (ADS)

    Márquez-Zavalía, M. Florencia; Heinrich, Christoph A.

    2016-10-01

    Alto de la Blenda is a ˜6.6-Ma intermediate-sulphidation epithermal vein system in the Farallón Negro Volcanic Complex, which also hosts the 7.1-Ma porphyry-Cu-Au deposit of Bajo de la Alumbrera. The epithermal vein system is characterised by a large extent and continuity (2 km × 400 m open to depth × 6 m maximum width) and an average gold grade of ˜8 g/t. The vein is best developed within an intrusion of a fine-grained equigranular monzonite, interpreted as the central conduit of a stratovolcano whose extrusive activity ended prior to porphyry-Cu-Au emplacement at Bajo de la Alumbrera, which is in turn cut by minor epithermal veins. The Alto de la Blenda vein consists predominantly of variably Mn-rich carbonates and quartz, with a few percent of pyrite, sphalerite, galena and other sulphide and sulphosalt minerals. Four phases of vein opening, hydrothermal mineralisation and repeated brecciation can be correlated between different vein segments. Stages 2 and 3 contain the greatest fraction of sulphide and gold. They are separated by the emplacement of a polymictic breccia containing clasts of quartz feldspar porphyry as well as basement rocks. Fluid inclusions in quartz related to stages 2 to 4 are liquid rich with 2-4 wt% NaCl(eq). They homogenise between 160 and 300 °C, with very consistent values within each assemblage. Vapour inclusions are practically absent in the epithermal vein. Quartz fragments in the polymictic breccia contain inclusions of intermediate to vapour-like density and similar low salinity (˜3 wt% NaCl(eq)), besides rare brine inclusions containing halite. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analyses of epithermal inclusions indicate high concentrations of K, Fe, As, Sb, Cs, and Pb that significantly vary within and through subsequent vein stages. Careful consideration of detection limits for individual inclusions shows high gold concentrations of ˜0.5 to 3 ppm dissolved in the ore fluid, which

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  3. Recrystallization fabrics of sheared quartz veins with a strong pre-existing crystallographic preferred orientation from a seismogenic shear zone

    NASA Astrophysics Data System (ADS)

    Price, Nancy A.; Song, Won Joon; Johnson, Scott E.; Gerbi, Christopher C.; Beane, Rachel J.; West, David P.

    2016-07-01

    Microstructural investigations were carried out on quartz veins in schist, protomylonite, and mylonite samples from an ancient seismogenic strike-slip shear zone (Sandhill Corner shear zone, Norumbega fault system, Maine, USA). We interpret complexities in the microstructural record to show that: (1) pre-existing crystallographic preferred orientations (CPO) in the host rock may persist in the new CPO patterns of the shear zone and (2) the inner and outer parts of the shear zone followed diverging paths of fabric development. The host rocks bounding the shear zone contain asymmetrically-folded quartz veins with a strong CPO. These veins are increasingly deformed and recrystallized with proximity to the shear zone core. Matrix-accommodated rotation and recrystallization may position an inherited c-axis maximum in an orientation coincident with rhomb < a > or basal < a > slip. This inherited CPO likely persists in the shear zone fabric as a higher concentration of poles in one hemisphere of the c-axis pole figure, leading to asymmetric crossed girdle or paired maxima c-axis patterns about the foliation plane. Three observed quartz grain types indicate a general trend of localization with decreasing temperature: (1) large (> 100 μm), low aspect ratio (< 5) and (2) high aspect ratio ( 5-20) grains overprinted by (3) smaller (< 80 μm), low aspect ratio (< 4) grains through subgrain rotation-dominated recrystallization. In the outer shear zone, subgrain rotation recrystallization led to a well-developed c-axis crossed girdle pattern. In the inner shear zone, the larger grains are completely overprinted by smaller grains, but the CPO patterns are relatively poorly developed and are associated with distinctively different misorientation angle histogram profiles ("flat" neighbor-pair profile with similar number fraction for angles from 10 to 90°). This may reflect the preferential activation of grain size sensitive deformation processes in the inner-most part of the

  4. Theoretical prediction of gold vein location in deposits originated by a wall magma intrusion

    NASA Astrophysics Data System (ADS)

    Martin, Pablo; Maass-Artigas, Fernando; Cortés-Vega, Luis

    2016-05-01

    The isotherm time-evolution resulting from the intrusion of a hot dike in a cold rock is analized considering the general case of nonvertical walls. This is applied to the theoretical prediction of the gold veins location due to isothermal evolution. As in previous treatments earth surface effects are considered and the gold veins are determined by the envelope of the isotherms. The locations of the gold veins in the Callao mines of Venezuela are now well predicted. The new treatment is now more elaborated and complex that in the case of vertical walls, performed in previous papers, but it is more adequated to the real cases as the one in El Callao, where the wall is not vertical.

  5. Gold volatile species atomization and preconcentration in quartz devices for atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Arslan, Yasin; Musil, Stanislav; Matoušek, Tomáš; Kratzer, Jan; Dědina, Jiří

    2015-01-01

    The on-line atomization of gold volatile species was studied and the results were compared with thermodynamic calculations in several quartz atomizers, namely: diffusion flame, flame-in-gas-shield, flame-in-plain-tube, externally heated T-tube and externally heated flame-in-T-tube. Atomization mechanism in the explored devices is proposed, where volatile species are converted to thermodynamically stable AuH at elevated temperature over 500 °C and then atomized by an interaction with a cloud of hydrogen radicals. Because of its inherent simplicity and robustness, diffusion flame was employed as a reference atomizer. It yielded atomization efficiency of 70 to 100% and a very good long time reproducibility of peak area sensitivity: 1.6 to 1.8 s μg- 1. Six and eleven times higher sensitivity, respectively, was provided by atomizers with longer light paths in the observation volume, i.e. externally heated T-tube and externally heated flame-in-T-tube. The latter one, offering limit of detection below 0.01 μg ml- 1, appeared as the most prospective for on-line atomization. Insight into the mechanism of atomization of gold volatile species, into the fate of free atoms and into subsequent analyte transfer allowed to assess possibilities of in-atomizer preconcentration of gold volatile species: it is unfeasible with quartz atomizers but a sapphire tube atomizer could be useful in this respect.

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

    NASA Astrophysics Data System (ADS)

    Jacques, Dominique; Muchez, Philippe; Sintubin, Manuel

    2014-05-01

    Research on ancient fluid systems mainly focuses on veins, because they offer the opportunity to combine macro- and microstructural data with geochemical data to gain insight into the P-T-X conditions present during veining. By applying such an integrated petrographic and microthermometric methodology to syn- to late-orogenic quartz veins in the Palaeozoic High-Ardenne slate belt (Belgium), we were able to define the relative timing and related P-T-X conditions of different quartz vein generations, despite of the absence of any mutual cross-cutting relationships in the field (Jacques et al., 2014). The different quartz vein generations represent the meso-scale brittle accommodation during fold initiation, amplification and locking. The presence of free polycrystal growth in cavities at a midcrustal depth, and fluid-assisted brecciation indicate that veining occurred under overpressured fluid conditions during the orogeny. Significant differences in crystal-plastic deformation microstructures and P-T trapping conditions indicate that the different processes accommodating folding occurred in a progressive manner along a retrograde deformation path. While vein quartz in an extrados vein and in the peripheral part of a lenticular, fault-accommodating vein shows moderate crystal-plastic deformation (e.g. bulging recrystallisation, deformation lamellae, shear bands), crystal-plastic deformation is relatively absent in the vein quartz of a saddle reef and the core of the lenticular vein (i.e. no to minor undulose extinction). Successive veining occurred from peak metamorphic conditions (ca. 300 ° C and 190 MPa), measured in the extrados vein, to lower P-T conditions in the periphery of the lenticular vein (ca. 275 ° C and 180 MPa), the late-orogenic saddle reef (ca. 245 ° C and 160 MPa) and the core of the lenticular vein (ca. 220 ° C and 150 MPa). The relative timing and accompanying decrease in P-T conditions of the different quartz vein generations reflect the

  7. Diagnosis of environmental problems related to vein gold mining in Colombia

    NASA Astrophysics Data System (ADS)

    Prieto, Gloria R.; Gonzalez, Myriam L.

    Since 1985 the annual gold production in Colombia has been fluctuating between 30 and 35 tons (1-1.4 million ounces troy). Exploitation plants can be found in vein and placer gold deposits. During 1992 a preliminary study was undertaken, resulting in a diagnosis of problems in small scale mining in 6 gold areas (vein type) of Colombia. In order to evaluate the general impact caused to the environment due to mining activities, six gold districts located in Nariño, Antioquia, Bolivar, Valle and Caldas Departments were visited. Geochemical analysis (ES, AAS, HGAAS, GFAAS) of orebodies, tailings and waters were carried out, with results that showed high levels of heavy metals in the environmental compartments studied.

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

    NASA Astrophysics Data System (ADS)

    Barbosa, Paola; Lagoeiro, Leonardo

    2013-04-01

    The evidences of fluid activity in rocks are well recognized. In many cases, the fluid is responsible to remobilize many elements (e.g. Au, Mn, Si) that may be transported over a long distance and precipitated as new minerals in regions of low stress of the rock. In many deformed rocks, the origin of a large number of structures (veins, pressure shadows, dissolved grain boundaries, etc) may be correlated to the fluid activity. However, the fluids are important not only during the crack-and-seal process but also after the sealing ceases. As an example of how the fluids are responsible to rearrange the structure of the rock, we studied many quartz veins of one iron-formation from Brazil. The rocks were collected in Quadrilátero Ferrífero (QF), Brazil, that is one of the most important metalogenetic provinces in the world. It is assumed the existence of a deformational and metamorphic gradient in the rocks of QF, increasing the occurrence of penetrative structures from southwest to northeast. However, the effects of the local shear zones in the deformation pattern of QF may not be neglected. Shear zones are generally recognized as structures that accommodate deformation, eventually with intense fluid percolation. It is indubitable that there is a relationship between the fluid activity and the deformation accommodation in shear zones. So, to investigate how the fluid activity can affect the mechanisms of accommodation of deformation in rocks of shear zones from QF, we characterized the crystallographic preferred orientation (CPO) of some quartz vein by EBSD (electron backscattering diffraction). All the samples came from the same outcrop and from the same dextral shear zone, localized in the low-deformation region of QF, under greenschist metamorphic conditions. The samples were oriented according to the XYZ reference system, with X parallel to the foliation and Z normal to the XY plane. The veins are quartz-rich layers parallel to the rock foliation. They do not

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

    NASA Astrophysics Data System (ADS)

    Fukunari, Tetsuzo; Gudmundsson, Agust

    2014-05-01

    Orthogonal fractures can easily make networks in geological formations and are of great importance for permeability and fluid transport in subsurface reservoirs. Despite many studies focusing on the formation of orthogonal fractures, no clear and generally accepted model has been established as yet although their formation is widely believed to occur during crustal uplift or exhumation. Here we provide new insights into their mechanism of formation based on the results of a fieldwork and analytical study of orthogonal fractures and quartz veins in alternating sand-shale layers in the South Wales coalfield, which is one of foreland basins developed in relation with north-south compression of the Variscan Orogeny. More than 3,000 fractures were measured at various localities extending from southern end to northern end of the basin. Most of the fractures in the sandstone layers, are extension fractures (mode I cracks), and become arrested at contacts with shale layers. The fractures strike north-south and east-west. Some fractures are filled with shale, probably supplied from adjacent shale layers, suggesting the shale behaved as semi-ductile material at the time of fracture formation. A remarkable observation is that most of the fractures are perpendicular to bedding planes throughout the basin. This is despite the fact that the beds are strongly folded as a result of the Variscan Orogeny. The perpendicular attitude suggests that the fracture formation somewhat predates or coincides with that of folding. This implies that the orthogonal fractures in this area did not form during crustal uplift/exhumation but rather during basin growth at the time of regional north-south convergence and associated compression of the Variscan Orogeny. By using aspect (length/thickness) ratios of quartz veins of the same geometry as the orthogonal fractures, fluid overpressure (driving pressure) at the time of fracture formation is estimated at around 33 MPa for fractures striking north

  10. A new LA-ICP-MS method for Ti-in-Quartz: Implications and application to HP rutile-quartz veins from the Czech Erzgebirge

    NASA Astrophysics Data System (ADS)

    Cruz-Uribe, A. M.; Mertz-Kraus, R.; Zack, T.; Feineman, M. D.; Woods, G.

    2014-12-01

    Experimental determination of the pressure and temperature controls on Ti solubility in quartz provide a calibration of the Ti-in-quartz (TitaniQ) geothermometer applicable to geologic conditions up to ~20 kbar (Thomas et al. (2010) Contrib Mineral Petrol 160, 743-759). One of the greatest limitations to analyzing Ti in metamorphic quartz by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is the lack of a suitable matrix-matched reference material. Typically LA-ICP-MS analyses of Ti in minerals use 49Ti as a normalizing mass because of an isobaric interference from 48Ca, which is present in most well characterized reference glasses, on 48Ti. The benefit of using a matrix-matched reference material to analyze Ti in quartz is the opportunity to use 48Ti (73.8 % abundance) as a normalizing mass, which results in an order of magnitude increase in signal strength compared to the less abundant isotope 49Ti (5.5 % abundance), thereby increasing the analytical precision. Here we characterize Ti-bearing SiO2 glasses from Heraeus Quarzglas and natural quartz grains from the Bishop Tuff by cathodoluminescence (CL) imaging, electron probe microanalysis (EPMA), and LA-ICP-MS, in order to determine their viability as reference materials for Ti in quartz. Titanium contents in low-CL rims in the Bishop Tuff quartz grains were determined to be homogenous by EPMA (41 ± 2 µg/g Ti, 2σ), and are a potential natural reference material. We present a new method for determining 48Ti concentrations in quartz by LA-ICP-MS at the 1 µg/g level, relevant to quartz in HP-LT terranes. We suggest that natural quartz such as the homogeneous low-CL rims of the Bishop Tuff quartz are more suitable than NIST reference glasses as an in-house reference material for low Ti concentrations because matrix effects are limited and Ca isobaric interferences are avoided, thus allowing for the use of 48Ti as a normalizing mass. Titanium concentration from 33 analyses of low

  11. Cyclical Stress Field Switching and (Total?) Relief of Fault Shear Stress Recorded in Quartz Vein Systems Hosted by Proterozoic Strike-Slip Faults, Mt Isa, Australia

    NASA Astrophysics Data System (ADS)

    Sibson, R. H.; Begbie, M. J.; Ghisetti, F. C.; Blenkinsop, T. G.

    2003-12-01

    The Proterozoic Mt Isa inlier ( ˜50,000 km2) in NW Queensland, Australia, underwent a complex tectonothermal history involving multiple episodes of intracontinental rifting, sedimentation, and magmatism that culminated in the Isan Orogeny (1590-1500 Ma) where strong E-W shortening led to compressional inversion of former rift basins. The resulting metamorphic complex of subgreenschist to amphibolite facies assemblages is disrupted by brittle, late-orogenic (1500-1450 Ma?) strike-slip faults. The faults occur in two mutually cross-cutting sets; a set of dextral strike-slip faults striking NE-SW to NNE-SSW with offsets <20 km, and a conjugate set of sinistral faults striking NW-SE to NNW-SSE. The two contemporaneous fault sets therefore lie at +/-45-60° to inferred E-W maximum compression, approaching the expected lock-up angle for 'Byerlee' friction coefficients. The faults commonly outcrop as linear blade-like ridges extending for many kilometres across the semi-arid terrain. Transects across the NE-SW Fountain Range and Overlander Faults which crosscut Corella Formation amphibolite facies assemblages and granites have shown that the fault zones are about 100 m in width with a composite brittle fabric comprising: (1) subvertical silicified cataclastic shear zones (cataclasites plus microbreccias containing vein fragments); (2) innumerable subvertical quartz-veins (cm to m thickness) lying subparallel to the principal shear zones (some retain purely dilational textures; others are multiply recemented fault-breccias with wallrock fragments); (3) highly irregular non-systematic veins; and (4) a systematic set of predominantly extensional, steep planar quartz veins oriented 080-120° at moderate angles to the main faults. Mutual cross-cutting relationships occur between all structural components, indicating broad contemporaneity. Recorded dextral separations along shear fracture components are commonly of the order of 1-10 cm, consistent with small-moderate seismic

  12. 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)

    Sintubin, M.

    2013-12-01

    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

  13. Tourmalines from the siderite-quartz-sulphide hydrothermal veins, Gemeric unit, western Carpathians, Slovakia: crystal chemistry and evolution

    NASA Astrophysics Data System (ADS)

    Bačík, P.; Uher, P.; Dikej, J.; Puškelová, Ľ.

    2017-03-01

    Tourmaline is an important gangue mineral in a large number of Cretaceous siderite-quartz-sulphide hydrothermal veins in the Gemeric Unit, Slovak Ore Mountains, Slovakia, such as Dobšiná, Vlachovo, Rožňavské Bystré, Hnilčík, Rakovnica, Novoveská Huta, Gretla, Rudňany, and Bindt. In this study we combine by electron microprobe analysis, powder X-ray diffraction, Mössbauer and optical emission spectroscopy to determine the range of tourmaline compositions in the deposits and constrain the mechanisms of its precipitation. Selected samples from the mentioned deposits belong mostly to the alkali group, schorl to dravite series, rarely dominant X-site vacant foititic tourmaline (Vlachovo and Bindt) and oxy-dravite compositions (Hnilčík) were detected. Rim zones of some schorlitic tourmalines show high concentrations of Ti (up to 2.35 wt.% TiO2, 0.30 apfu; Rožňavské Bystré). The chemical composition is mostly controlled by alkali-deficient X □AlNa-1(Mg,Fe2+)-1 and proton-deficient AlO(Mg,Fe2+)-1(OH)-1 substitutions. Titanium is incorporated into the structure by Y Ti Y (Mg,Fe) Y Al-2, Y Ti Z Mg Y Al-1 Z Al-1, Y TiO( Y AlOH), and X Ca Y Ti Z MgO2 X □-1 Y,Z Al-2(OH)-2 substitutions. Along trace elements, Sr and V attain concentrations of 80-450 and 70-320 ppm, respectively. The unit-cell parameter a varies between 15.960 and 15.985 Å; variations in c are larger, between 7.177 and 7.236 Å indicating the presence of Fe3+ and Mg2+ at Z site. Mössbauer spectroscopy has shown variable Fe3+ proportions (0.17-0.55 apfu) in all samples. The gathered dataset suggests some qualitative considerations on the mechanisms controlling tourmaline compositions at the regional scale. The highest Fe3+ concentrations occur in samples from Rudňany and Gretla in the external part of Gemeric unit, suggesting higher oxidation during longer transport of fluids. We propose that the determined XFe in the samples are correlated with the compositions of the host rocks, as

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    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.

  15. Evaluation of anisotropy in physical/mechanical properties of metabasalts from Gadag (Southern India) - implications for vein emplacement and gold mineralization

    NASA Astrophysics Data System (ADS)

    Satheesan Vishnu, C.; Mamtani, Manish A.

    2016-04-01

    Foliated rocks have anisotropic physical and mechanical properties. In the case of foliated metamorphic and bedded sedimentary rocks, it is easy to decipher this anisotropy. However, this is not readily possible in the case of massive rocks. Vishnu et al. (2010) used Anisotropy of Magnetic Susceptibility (AMS) analysis to identify magnetic fabric in massive quartzites and established that the rocks have a lower strength parallel to the magnetic foliation, than perpendicular to it. In the present study, the authors have extrapolated the same concept to the metabasalts of Gadag region (West Dharwar Craton, Southern India), which is replete with quartz veins that are gold bearing. These metabasalts are massive and are devoid of visible foliation. Mondal and Mamtani (2013, 2014) did AMS analysis of the metabasalts and showed that the magnetic foliation is NW-SE striking, and the quartz veins also have similar strike. It was inferred by the above authors that the magnetic foliation developed during D1/D2 deformation (regional NE-SW compression) and the veins emplaced during D3 (NW-SE compression). This implies (a) dilation of pre-existing anisotropic elements during D3 and (b) rock strength anisotropy must have been important in controlling this dilation. To test this oriented blocks (each approximately 50 × 40 × 25 cm in size) of metabasalts were collected. A portion of the sample was used for AMS analysis. Subsequently, the magnetic foliation identified from AMS analysis was marked on the remaining sample block, and NX size (Diameter = 54.7 cm) cylindrical cores were drilled parallel and perpendicular to the magnetic foliation for various rock physical/mechanical tests - uniaxial compressive strength (UCS), point load test (PLT), P-wave velocity and Brazilian tensile strength. Results so far indicate that average point load index parallel and perpendicular to the foliation is 8.47 MPa, and 9.93 MPa, respectively, while UCS is 172.77 kN and 212.95 kN, respectively

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    Stable isotope (O, H, C), radiogenic isotope (Sr, Nd) and trace element analyses have been applied to quartz-dolomite veins and their uranium(U)-bearing fluid inclusions associated with Proterozoic unconformity-related UO2 (uraninite) ores in the Athabasca Basin (Canada) in order to trace the evolution of pristine evaporated seawater towards U-mineralizing brines during their migration through sediments and basement rocks. Fluid inclusion data show that quartz and dolomite have precipitated from brines of comparable chemistry (excepted for relatively small amounts of CO2 found in dolomite-hosted fluid inclusions). However, δ18O values of quartz veins (δ18O = 11‰ to 18‰) and dolomite veins (δ18O = 13‰ to 24‰) clearly indicate isotopic disequilibrium between quartz and dolomite. Hence, it is inferred that this isotopic disequilibrium primarily reflects a decrease in temperature between the quartz stage (˜180 °C) and the dolomite stage (˜120 °C). The δ13C values of CO2 dissolved in dolomite-hosted fluid inclusions (δ13C = -30‰ to -4‰) and the δ13C values of dolomite (δ13C = -23.5‰ to -3.5‰) indicate that the CO2 dissolved in the mineralizing brines originated from brine-graphite interactions in the basement. The resulting slight increase in the fluid partial pressure of CO2 (pCO2) may have triggered dolomite precipitation instead of quartz. δ18O values of quartz veins and previously published δ18O values of the main alteration minerals around the U-ores (illite, chlorite and tourmaline) show that quartz and alteration minerals were isotopically equilibrated with the same fluid at ˜180 °C. The REE concentrations in dolomite produce PAAS-normalized patterns that show some similarities with that of UO2 and are clearly distinct from that of the other main REE-bearing minerals in these environments (monazite, zircon and aluminum phosphate-sulfate (APS) minerals). The radiogenic isotope compositions of dolomite (87Sr/86Sri = 0.7053 to 0

  17. Adsorption kinetics of an engineered gold binding Peptide by surface plasmon resonance spectroscopy and a quartz crystal microbalance.

    PubMed

    Tamerler, Candan; Oren, Ersin Emre; Duman, Memed; Venkatasubramanian, Eswaranand; Sarikaya, Mehmet

    2006-08-29

    The adsorption kinetics of an engineered gold binding peptide on gold surface was studied by using both quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) spectroscopy systems. The gold binding peptide was originally selected as a 14-amino acid sequence by cell surface display and then engineered to have a 3-repeat form (3R-GBP1) with improved binding characteristics. Both sets of adsorption data for 3R-GBP1 were fit to Langmuir models to extract kinetics and thermodynamics parameters. In SPR, the adsorption onto the surface shows a biexponential behavior and this is explained as the effect of bimodal surface topology of the polycrystalline gold substrate on 3R-GBP1 binding. Depending on the concentration of the peptide, a preferential adsorption on the surface takes place with different energy levels. The kinetic parameters (e.g., K(eq) approximately 10(7) M(-1)) and the binding energy (approximately -8.0 kcal/mol) are comparable to synthetic-based self-assembled monolayers. The results demonstrate the potential utilization of genetically engineered inorganic surface-specific peptides as molecular substrates due to their binding specificity, stability, and functionality in an aqueous-based environment.

  18. Fluid fractionation of tungsten during granite-pegmatite differentiation and the metal source of peribatholitic W quartz veins: Evidence from the Karagwe-Ankole Belt (Rwanda)

    NASA Astrophysics Data System (ADS)

    Hulsbosch, Niels; Boiron, Marie-Christine; Dewaele, Stijn; Muchez, Philippe

    2016-02-01

    The identification of a magmatic source for granite-associated rare metal (W, Nb, Ta and Sn) mineralisation in metasediment-hosted quartz veins is often obscured by intense fluid-rock interactions which metamorphically overprinted most source signatures in the vein system. In order to address this recurrent metal sourcing problem, we have studied the metasediment-hosted tungsten-bearing quartz veins of the Nyakabingo deposit of the Karagwe-Ankole belt in Central Rwanda. The vein system (992 ± 2 Ma) is spatiotemporal related to the well-characterised B-rich, F-poor G4 leucogranite-pegmatite suite (986 ± 10 Ma to 975 ± 8 Ma) of the Gatumba-Gitarama area which culminated in Nb-Ta-Sn mineralisation. Muscovite in the Nyakabingo veins is significantly enriched in granitophile elements (Rb, Cs, W and Sn) and show alkali metal signatures equivalent to muscovite of less-differentiated pegmatite zones of the Gatumba-Gitarama area. Pegmatitic muscovite records a decrease in W content with increasing differentiation proxies (Rb and Cs), in contrast to the continuous enrichment of other high field strength elements (Nb and Ta) and Sn. This is an indication of a selective redistribution for W by fluid exsolution and fluid fractionation. Primary fluid inclusions in tourmaline of these less-differentiated pegmatites demonstrate the presence of medium to low saline, H2O-NaCl-KCl-MgCl2-complex salt (e.g. Rb, Cs) fluids which started to exsolve at the G4 granite-pegmatite transition stage. Laser ablation inductively coupled plasma mass-spectrometry shows significant tungsten enrichment in these fluid phases (∼5-500 ppm). Fractional crystallisation has been identified previously as the driving mechanism for the transition from G4 granites, less-differentiated biotite, biotite-muscovite towards muscovite pegmatites and eventually columbite-tantalite mineralised pegmatites. The general absence of tungsten mineralisation in this magmatic suite, including the most differentiated

  19. Competitive surfactant adsorption of AOT and Tween 20 on gold measured using a quartz crystal microbalance with dissipation.

    PubMed

    Thavorn, Jakkrit; Hamon, Joshua J; Kitiyanan, Boonyarach; Striolo, Alberto; Grady, Brian P

    2014-09-23

    Competitive surfactant adsorption of anionic surfactant AOT and nonionic surfactant Tween 20 on gold was investigated by using a quartz crystal microbalance with dissipation (QCM-D) at 25 °C. The adsorption isotherm of pure AOT did not reach a plateau at the CMC, but rather adsorption continued to increase gradually at concentrations higher than the CMC before reaching a plateau. This behavior is evidence of competitive adsorption between AOT and impurities. The adsorbed layer of AOT on gold became more viscoelastic as the concentration of AOT increased. Tween 20 reached the plateau adsorption on gold before its concentration reached the CMC, suggesting that the attraction between Tween 20 and gold is very strong. The Tween 20 adsorbed layer was rigid when compared to the AOT adsorbed layer, as indicated by low dissipation. The addition of Tween 20 to a surface covered by AOT resulted in an increase in adsorbed mass, suggestive of the insertion of Tween 20 into the AOT adsorbed layer as expected because Tween 20 is able to separate the repulsive headgroups of AOT. When AOT was added to a preformed Tween 20 layer, a drop in the adsorbed amount was found between 0 and 0.1 CMC, and then no change was observed until the CMC of AOT was reached; the adsorbed amount then increased, reaching a final adsorption greater than that of pure AOT. All data support the formation of mixed surfactant layers on the surface. Although a two-step model fit both AOT and Tween 20 adsorption kinetic data well, AOT was found to adsorb much more slowly than Tween 20.

  20. The Sarylakh and Sentachan gold-antimony deposits, Sakha-Yakutia: A case of combined mesothermal gold-quartz and epithermal stibnite ores

    NASA Astrophysics Data System (ADS)

    Bortnikov, N. S.; Gamynin, G. N.; Vikent'eva, O. V.; Prokof'ev, V. Yu.; Prokop'ev, A. V.

    2010-10-01

    New mineralogical, thermobarometric, isotopic, and geochemical data provide evidence for long and complex formation history of the Sarylakh and Sentachan Au-Sb deposits conditioned by regional geodynamics and various types of ore mineralization, differing in age and source of ore matter combined in the same ore-localizing structural units. The deposits are situated in the Taryn metallogenic zone of the East Yakutian metallogenic belt in the central Verkhoyansk-Kolyma Fold Region. They are controlled by the regional Adycha-Taryn Fault Zone that separates the Kular-Nera Terrane and the western part of the Verkhoyansk Fold-Thrust Belt. The fault extends along the strike of the northwest-trending linear folds and is deep-rooted and repeatedly reactivated. The orebodies are mineralized crush zones accompanied by sulfidated (up to 100 m wide) quartz-sericite metasomatic rocks and replacing dickite-pyrophyllite alteration near stibnite veinlets. Two stages of low-sulfide gold-quartz and stibnite mineralization are distinguished. The formation conditions of the early milk white quartz in orebodies with stibnite mineralization at the Sarylakh and Sentachan deposits are similar: temperature interval 340-280°C, salt concentration in fluids 6.8-1.6 wt % NaCl equiv, fluid pressure 3430-1050 bar, and sodic bicarbonate fluid composition. The ranges of fluid salinity overlapped at both deposits. In the late regenerated quartz that attends stibnite mineralization, fluid inclusions contain an aqueous solution with salinity of 3.2 wt % NaCl equiv and are homogenized into liquid at 304-189°C. Syngenetic gas inclusions contain nitrogen 0.19 g/cm3 in density. The pressure of 300 bar is estimated at 189°C. The composition of the captured fluid is characterized as K-Ca bicarbonatesulfate. The sulfur isotopic composition has been analyzed in pyrite and arsenopyrite from ore and metasomatic zones, as well as in coarse-, medium-, and fine-grained stibnite varieties subjected to

  1. Ore mineralogy and textural zonation in the world-class epithermal Waihi Vein System, Hauraki Goldfield

    USGS Publications Warehouse

    Mauk, Jeffrey L.; Skinner, Erin G; Fyfe, Sarah J; Menzies, Andrew H; Lowers, Heather A.; Koenig, Alan E.

    2016-01-01

    The Waihi district in the Hauraki Goldfield of New Zealand contains adularia-sericite epithermal gold-silver veins that have produced more than 7.7 Moz gold. The outermost veins of the district (Martha, Favona, Moonlight, and Cowshed) contain abundant colloform, cherty, and black quartz fill textures, with minor crustiform and massive quartz. The central veins (Amaranth, Trio, and Union) contain predominantly massive and crustiform textures, and these veins are also commonly coarser grained than outermost veins. Pyrite, sphalerite, galena, chalcopyrite, electrum, and acanthite occur in both outermost and central veins; base metal sulfide minerals typically increase in abundance in deeper samples. Antimony-, arsenic-, and selenium-bearing minerals are most abundant in the Favona and Moonlight veins, whereas base metal sulfide minerals are more abundant in the central veins at Correnso. Throughout the Waihi vein system, electrum is by far the most widespread, abundant, and significant gold-bearing mineral, but LA-ICP-MS analyses show that arsenian pyrite also contains some gold. Mineralogical and textural data are consistent with the central veins forming at a deeper structural level, or from hydrothermal fluids with different chemistry, or both.

  2. Mercury Sorption and Desorption on Gold: A Comparative Analysis of Surface Acoustic Wave and Quartz Crystal Microbalance-Based Sensors.

    PubMed

    Kabir, K M Mohibul; Sabri, Ylias M; Esmaielzadeh Kandjani, Ahmad; Matthews, Glenn I; Field, Matthew; Jones, Lathe A; Nafady, Ayman; Ippolito, Samuel J; Bhargava, Suresh K

    2015-08-04

    Microelectromechanical sensors based on surface acoustic wave (SAW) and quartz crystal microbalance (QCM) transducers possess substantial potential as online elemental mercury (Hg(0)) vapor detectors in industrial stack effluents. In this study, a comparison of SAW- and QCM-based sensors is performed for the detection of low concentrations of Hg(0) vapor (ranging from 24 to 365 ppbv). Experimental measurements and finite element method (FEM) simulations allow the comparison of these sensors with regard to their sensitivity, sorption and desorption characteristics, and response time following Hg(0) vapor exposure at various operating temperatures ranging from 35 to 75 °C. Both of the sensors were fabricated on quartz substrates (ST and AT cut quartz for SAW and QCM devices, respectively) and employed thin gold (Au) layers as the electrodes. The SAW-based sensor exhibited up to ∼111 and ∼39 times higher response magnitudes than did the QCM-based sensor at 35 and 55 °C, respectively, when exposed to Hg(0) vapor concentrations ranging from 24 to 365 ppbv. The Hg(0) sorption and desorption calibration curves of both sensors were found to fit well with the Langmuir extension isotherm at different operating temperatures. Furthermore, the Hg(0) sorption and desorption rate demonstrated by the SAW-based sensor was found to decrease as the operating temperature increased, while the opposite trend was observed for the QCM-based sensor. However, the SAW-based sensor reached the maximum Hg(0) sorption rate faster than the QCM-based sensor regardless of operating temperature, whereas both sensors showed similar response times (t90) at various temperatures. Additionally, the sorption rate data was utilized in this study in order to obtain a faster response time from the sensor upon exposure to Hg(0) vapor. Furthermore, comparative analysis of the developed sensors' selectivity showed that the SAW-based sensor had a higher overall selectivity (90%) than did the QCM

  3. Creating gold nanoprisms directly on quartz crystal microbalance electrodes for mercury vapor sensing

    NASA Astrophysics Data System (ADS)

    Sabri, Y. M.; Ippolito, S. J.; O'Mullane, A. P.; Tardio, J.; Bansal, V.; Bhargava, S. K.

    2011-07-01

    A novel electrochemical route is used to form highly {111}-oriented and size-controlled Au nanoprisms directly onto the electrodes of quartz crystal microbalances (QCMs) which are subsequently used as mercury vapor sensors. The Au nanoprism loaded QCM sensors exhibited excellent response-concentration linearity with a response enhancement of up to ~ 800% over a non-modified sensor at an operating temperature of 28 °C. The increased surface area and atomic-scale features (step/defect sites) introduced during the growth of nanoprisms are thought to play a significant role in enhancing the sensing properties of the Au nanoprisms toward Hg vapor. The sensors are shown to have excellent Hg sensing capabilities in the concentration range of 0.123-1.27 ppmv (1.02-10.55 mg m - 3), with a detection limit of 2.4 ppbv (0.02 mg m - 3) toward Hg vapor when operating at 28 °C, and 17 ppbv (0.15 mg m - 3) at 89 °C, making them potentially useful for air monitoring applications or for monitoring the efficiency of Hg emission control systems in industries such as mining and waste incineration. The developed sensors exhibited excellent reversible behavior (sensor recovery) within 1 h periods, and crucially were also observed to have high selectivity toward Hg vapor in the presence of ethanol, ammonia and humidity, and excellent long-term stability over a 33 day operating period.

  4. Gold gradients and anomalies in the Pedro Dome-Cleary Summit area, Fairbanks district, Alaska

    USGS Publications Warehouse

    Forbes, Robert B.; Pilkington, H.D.; Hawkins, D.B.

    1968-01-01

    Anomalous gold values have been discovered in hydrothermally altered quartz diorite, quartz monzonite, and quartz mica schist at the head of Fox Creek; and in similarly altered quartz diorite in the Granite Creek area. Channel samples across some of these altered zones have produced anomalous gold values over widths which merit further investigation as potential large tonnage low-grade gold deposits. Trace gold gradients have also been detected in the wall rocks adjacent to mineralized veins and in hydrothermal alteration zones in the Pedro Dome-Cleary Summit area. Although most of the gradients may not materially increase the mineable width of the deposit under current economic conditions, such gradients can be used to locate auriferous quartz veins and altered zones by geochemical methods. Gold enrichment is accompanied by anomalous concentrations of arsenic and antimony, and gold bearing quartz veins and altered zones are frequently signaled by peripheral haloes of these metals before trace gold is detectable. Hydrothermally altered and/or sheared zones in both granitic and metamorphic rocks should be carefully prospected, along the trend of the Cleary Antiform.

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

    NASA Astrophysics Data System (ADS)

    Morteani, G.; Voropaev, A.

    2007-01-01

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

  6. VOC and VOX in fluid inclusions of quartz: New chemical insights into hydrothermal vein mineralization by GC-MS and GC-IRMS measurements

    NASA Astrophysics Data System (ADS)

    Sattler, Tobias; Kirnbauer, Thomas; Keppler, Frank; Greule, Markus; Fischer, Jan; Spiekermann, Patrik; Schreiber, Ulrich; Mulder, Ines; Schöler, Heinz Friedrich

    2015-04-01

    Fluid inclusions (FIs) in minerals are known to contain a variety of different liquids, gases, and solids. The fluids get trapped during mineral growth and can preserve the original mineral-forming fluid or fluids of later events. A new analytical technique developed by Mulder et al. (2013) [1] allows to measure trace gases in FIs. For the measurements, grains of 3-5 mm diameter are ground in an airtight grinding device, releasing the volatiles from FIs into the gas phase, where they can be measured by GC-MS, GC-FID and GC-IRMS. The Taunus covers the southeastern part of the thrust-and-fold-belt of the Rhenish Massif (Germany). The Variscan rock sequences comprise sedimentary and volcanic units ranging from Ordovician to Lower Carboniferous. Several types of hydrothermal mineralization can be distinguished, which are - in regard to the Variscan orogeny - pre-orogenic, orogenic, late-orogenic, post-orogenic and recent in age [2]. They include SEDEX, vein, Alpine fissure, disseminated and stockwerk mineralizations. Thus, the Taunus mineralizations enable investigations of different hydrothermal systems at different age in one region. For most of them extensive studies of stable and radiogenic isotopes exist. Quartz crystals of post-orogenic quartz veins and Pb-Zn-Cu bearing veins [3] were selected for our FI investigation. Sulphur containing compounds like COS and CS2 dominate the FIs but there are also volatile hydrocarbons (VOC) like different butenes, benzene, toluene and cyclopentene that were found very often. In some samples volatile halogenated organic carbons (VOX) like chloro- and bromomethane were found. Some FIs even contain iodomethane, chlorobenzene, vinyl chloride and -bromide. The non-fossil-fuel subsurface chemistry of VOC and VOX is not fully understood. There are a lot of unknown geogenic sources [4][5]. For a better understanding δ13C- and δ2H-values of CH4 were measured by GC-IRMS to examine if the detected organic compounds are formed biotic

  7. Simultaneous detection of surface coverage and structure of krypton films on gold by helium atom diffraction and quartz crystal microbalance techniques

    SciTech Connect

    Danisman, M. Fatih; Oezkan, Berrin

    2011-11-15

    We describe a quartz crystal microbalance setup that can be operated at low temperatures in ultra high vacuum with gold electrode surfaces acting as substrate surface for helium diffraction measurements. By simultaneous measurement of helium specular reflection intensity from the electrode surface and resonance frequency shift of the crystal during film adsorption, helium diffraction data can be correlated to film thickness. In addition, effects of interfacial viscosity on the helium diffraction pattern could be observed. To this end, first, flat gold films on AT cut quartz crystals were prepared which yield high enough helium specular reflection intensity. Then the crystals were mounted in the helium diffractometer sample holder and driven by means of a frequency modulation driving setup. Different crystal geometries were tested to obtain the best quality factor and preliminary measurements were performed on Kr films on gold surfaces. While the crystal structure and coverage of krypton films as a function of substrate temperature could successfully be determined, no depinning effects could be observed.

  8. Simultaneous detection of surface coverage and structure of krypton films on gold by helium atom diffraction and quartz crystal microbalance techniques.

    PubMed

    Danışman, M Fatih; Özkan, Berrin

    2011-11-01

    We describe a quartz crystal microbalance setup that can be operated at low temperatures in ultra high vacuum with gold electrode surfaces acting as substrate surface for helium diffraction measurements. By simultaneous measurement of helium specular reflection intensity from the electrode surface and resonance frequency shift of the crystal during film adsorption, helium diffraction data can be correlated to film thickness. In addition, effects of interfacial viscosity on the helium diffraction pattern could be observed. To this end, first, flat gold films on AT cut quartz crystals were prepared which yield high enough helium specular reflection intensity. Then the crystals were mounted in the helium diffractometer sample holder and driven by means of a frequency modulation driving setup. Different crystal geometries were tested to obtain the best quality factor and preliminary measurements were performed on Kr films on gold surfaces. While the crystal structure and coverage of krypton films as a function of substrate temperature could successfully be determined, no depinning effects could be observed.

  9. Electrical Characterization of a Thiol SAM on Gold as a First Step for the Fabrication of Immunosensors based on a Quartz Crystal Microbalance

    PubMed Central

    Tlili, Asma; Abdelghani, Adnane; Hleli, Salwa; Maaref, Mhamed A.

    2004-01-01

    In order to develop a robust biosensor based on quartz crystal microbalance technique for antigen detection, a control of the steps of the surface functionalization has been performed by impedance spectroscopy. The gold electrode is functionalized with the self-assembled monolayer technique. The high insulating properties of the acidic thiol monolayer has been characterized with cyclic voltammetry and impedance spectroscopy. The modified surface is activated with N-hydroxysuccinimide(NHS) and 1-(3-(dimethylamino)propyl)-3-ethylcarbodimide hydrochloride(EDC) cross-linker for antibody coupling. The non-specific sites are blocked with bovin serum albumine molecules. Different concentrations of antigen can be detected with a good reversibility in real time with the quartz crystal microbalance.

  10. Tectonic setting of Late Cenozoic gold mineralization in the gold belt of Costa Rica

    SciTech Connect

    Deruyter, V.D.

    1985-01-01

    The Gold Belt of Costa Rica is a northwest-elongated zone 15 km wide by 120 km long containing numerous auriferous quartz veins and pyritic silicified patterns upon which abundant small mines are developed. Gold veins are related principally to northeast-southwest and north-south striking, steeply dipping faults. Higher grade ore and thicker veins invariably occur at intersections of these fracture orientations, indicating simultaneous opening at the time of gold introduction. Restriction of gold veins to the northwest-trending arc of Miocene Aguacate Group andesite volcanic rocks, a product of Cocos Plate subduction, suggested approximately coeval formation, but recognition by the writer of the important role played by 2-5 m.y. old altered, gold mineralized rhyolite dikes intruded along north-south gold vein structures and intimately involved with high grade ores at the Esperanza Mine and Rio Chiquito prospect, for example, suggest a much younger period of fracturing and gold introduction. The rhyolite intrusions are more brittle and stockwork mineralized than andesite host rocks and form bulk tonnage gold targets. Initiation of right-lateral movement along the north-south Panama Fracture Zone at 5 m.y.a. within the pattern of northeastward Cocos Plate subduction may have tapped rhyolites from subvolcanic magma chambers into new faults.

  11. Strike-slip fault reactivation as a control on epithermal vein-style gold mineralization

    NASA Astrophysics Data System (ADS)

    Henley, R. W.; Adams, D. P. M.

    1992-05-01

    Epithermal precious metal mineralization develops within contemporaneously active tectonic and volcanic terranes in which co-active faults focus fluids from deep high-temperature reservoirs and magmas into shallower environments. Recognition of such structural controls through analysis of the architecture of prospective volcanic belts and basins is therefore important in the exploration for epithermal gold deposits. Field and high-resolution aeromagnetic data suggest that gold mineralization at Bimurra and Wirralie in the late Paleozoic Drummond Basin (northeast Queensland, Australia) is primarily controlled by reactivation of a northeast-striking strike-slip fault array that may have developed as a transfer fault in the early history of the basin. Gold mineralization is hosted by volcaniclastic and sedimentary rocks whose distribution was also controlled by this reactivated structure.

  12. Characteristics of gold deposits in northern Sonora, Mexico: a preliminary report

    USGS Publications Warehouse

    Silberman, M.L.; Giles, D.A.; Graubard, C.

    1988-01-01

    The complex geology of northern Sonora has a variety of environments suitable for gold mineralisation, and many of the gold prospects occur within or adjacent to the southwestern boundary of the megashear in Precambrian, Mesozoic and Tertiary rocks. The characteristics types of gold deposits have been delineated by reconnaissance field investigations of the authors. There are four main environments of lode gold deposits present in Sonora: epithermal veins and breccias; discontinuous quartz veins; structurally controlled Au; and carbonate sedimentary-hosted disseminated Au. -after Authors

  13. Biogenic Iron-Rich Filaments in the Quartz Veins in the Uppermost Ediacaran Qigebulake Formation, Aksu Area, Northwestern Tarim Basin, China: Implications for Iron Oxidizers in Subseafloor Hydrothermal Systems.

    PubMed

    Zhou, Xiqiang; Chen, Daizhao; Tang, Dongjie; Dong, Shaofeng; Guo, Chuan; Guo, Zenghui; Zhang, Yanqiu

    2015-07-01

    Fe-(oxyhydr)oxide-encrusted filamentous microstructures produced by microorganisms have been widely reported in various modern and ancient extreme environments; however, the iron-dependent microorganisms preserved in hydrothermal quartz veins have not been explored in detail because of limited materials available. In this study, abundant well-preserved filamentous microstructures were observed in the hydrothermal quartz veins of the uppermost dolostones of the terminal-Ediacaran Qigebulake Formation in the Aksu area, northwestern Tarim Basin, China. These filamentous microstructures were permineralized by goethite and hematite as revealed by Raman spectroscopy and completely entombed in chalcedony and quartz cements. Microscopically, they are characterized by biogenic filamentous morphologies (commonly 20-200 μm in length and 1-5 μm in diameter) and structures (curved, tubular sheath-like, segmented, and mat-like filaments), similar to the Fe-oxidizing bacteria (FeOB) living in modern and ancient hydrothermal vent fields. A previous study revealed that quartz-barite vein swarms were subseafloor channels of low-temperature, silica-rich, diffusive hydrothermal vents in the earliest Cambrian, which contributed silica to the deposition of the overlying bedded chert of the Yurtus Formation. In this context, this study suggests that the putative filamentous FeOB preserved in the quartz veins might have thrived in the low-temperature, silica- and Fe(II)-rich hydrothermal vent channels in subseafloor mixing zones and were rapidly fossilized by subsequent higher-temperature, silica-rich hydrothermal fluids in response to waning and waxing fluctuations of diffuse hydrothermal venting. In view of the occurrence in a relatively stable passive continental margin shelf environment in Tarim Block, the silica-rich submarine hydrothermal vent system may represent a new and important geological niche favorable for FeOB colonization, which is different from their traditional

  14. Geology of the Ar Rahail ancient gold mine, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    White, Willis H.; Samater, Rashid M.; Doebrich, Jeff L.

    1987-01-01

    Pre-existing northwest-trending faults, possibly re-opened by stock emplacement, were invaded by later fluids that precipitated barren quartz veins and, in the adjacent faulted wall rocks, anomalous gold and arsenic. Gold, however, is restricted to the narrow structures, and, although values as much as 4.2 g/t are present, the tonnages are inadequate for profitable mining. No further work is recommended, because the hoped for dissemination of gold between faults does not exist.

  15. Potential-dependent adsorption/desorption behavior of perfluorosulfonated ionomer on a gold electrode surface studied by cyclic voltammetry, electrochemical quartz microbalance, and electrochemical atomic force microscopy.

    PubMed

    Masuda, Takuya; Ikeda, Kota; Uosaki, Kohei

    2013-02-19

    Potential-dependent adsorption/desorption behavior of perfluorosulfonated ionomer (PFSI) on a gold electrode was investigated by cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), and electrochemical atomic force microscopy (EC-AFM) in a Nafion (i.e., PFSI) dispersed aqueous solution without any other electrolyte. It was found that PFSI serves as an electrolyte and that electrochemical measurements can be performed in this solution without any significant IR drop. PFSI molecules were adsorbed on the Au surface in the lying-down configuration in the potential range between 0 and 0.45 V, the amount of adsorbed PFSI increased when the potential was made more positive than 0.75 V, and the adsorbed PFSI fully desorbed from the surface at potentials more positive than 1.4 V where gold oxide was formed. Once the gold oxide had been reduced, PFSI readsorbed on the surface, albeit slowly. PFSI desorbed from the surface as the potential was made more negative than 0 V. These processes took place reversibly.

  16. Colorado quartz: occurrence and discovery

    USGS Publications Warehouse

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

    1991-01-01

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

  17. Gold of the Pharaohs 6000 years of gold mining in Egypt and Nubia

    NASA Astrophysics Data System (ADS)

    Klemm, Dietrich; Klemm, Rosemarie; Murr, Andreas

    2001-08-01

    The legendary wealth in gold of ancient Egypt seems to correspond with an unexpected high number of gold production sites in the Eastern Desert of Egypt and Nubia. This contribution introduces briefly the general geology of these vast regions and discusses the geology of the different varieties of the primary gold occurrences (always related to auriferous quartz mineralization in veins or shear zones) as well as the variable physico-chemical genesis of the gold concentrations. The development of gold mining over time, from Predynastic (ca. 3000 BC) until the end of Arab gold production times (about 1350 AD), including the spectacular Pharaonic periods is outlined, with examples of its remaining artefacts, settlements and mining sites in remote regions of the Eastern Desert of Egypt and Nubia. Finally, some estimates on the scale of gold production are presented.

  18. Epigenetic lead, zinc, silver, antimony, tin, and gold veins in Boulder Basin, Blaine and Custer counties, Idaho; potential for economic tin mineralization

    USGS Publications Warehouse

    Ratchford, Michael E.

    2002-01-01

    Boulder Basin is in a northwest-trending belt of allochthonous Paleozoic rocks in the Boulder Mountains of central Idaho. Regional Tertiary extension resulted in widespread normal faulting and coeval emplacement of shallow-level intrusions and extrusive rocks of the Challis Volcanic Group. Epigenetic lead-zinc-silver-antimony-tin-gold vein deposits formed during Tertiary extension and are hosted within Paleozoic strata. The major orebodies are in the lower plate of the Boulder Basin thrust fault, in massive quartzite of the Middle Pennsylvanian to Lower Permian Wood River Formation. Anomalous concentrations of tin are present in the base-metal mineral assemblage of the Boulder Basin ore deposits. The tin-bearing veins in Boulder Basin are strikingly similar to Bolivian tin deposits. The deposit model for Bolivian tin deposits identifies buried tin porphyry below the tin-bearing vein system.

  19. A geological and geophysical study of the gold-silver vein system of Unga Island, Southwestern Alaska

    USGS Publications Warehouse

    Riehle, James R.

    1999-01-01

    The topic of this CD-ROM is the geologic framework of gold-silver vein deposits on Unga Island, in the Shumagin Islands, southwestern Alaska. The core of the publication is a new geologic map at a scale of 1:63,360 and aeromagnetic and electromagnetic survey data acquired by industry over the area of mineralization. Both the geologic map as well as a preliminary interpretation of the geophysical data - which are included by permission of the owner - are aimed towards deciphering the relations among volcanism, tectonism, and mineralization. Data and discussions are organized in seven chapters, titles of which are outlined in the table of contents. The chapters consist of viewable text and figure images; postscript versions of the frontispiece figures and all chapter figures are included on the CD-ROM as well. The geologic map is a large viewable figure (Plate 1) that accompanies chapter 2. The map was constructed in ARC and its component coverages are provided in the folder 'Geology' for users who may wish to modify the geologic data or add their own data.

  20. Gold geochemical anomaly in the Cortez district, Nevada

    USGS Publications Warehouse

    Erickson, Ralph Leroy; Van Sickle, G.H.; Nakagawa, H.M.; McCarthy, J.H.; Leong, K.W.

    1966-01-01

    An area in the Cortez district, Nevada, previously established to be anomalous in arsenic, antimony, and tungsten has been found to be anomalous also in mercury and gold. Samples from narrow quartz veins, calcite veins, and shear zones in partially silicified limestone in the lower plate of the Roberts thrust fault (Cortez window) contain as much as 3.4 ounces gold per ton. The richest samples are from an outcrop, about 100 feet long, surrounded by gravels. Their economic significance is yet to be established.

  1. Meteoric incursion and oxygen fronts in the Dalradian metamorphic belt, southwest Scotland: a new hypothesis for regional gold mobility

    NASA Astrophysics Data System (ADS)

    Craw, D.; Chamberlain, C. P.

    1996-07-01

    Post-metamorphic quartz veins which occur over hundreds of square kilometres in the biotite zone of the Dalradian metamorphic belt consist of three principal types: anhedral quartz with pyrite, anhedral quartz with hematite, and prismatic quartz with hematite or rutile. The oxide minerals in anhedral veins have formed by oxidation of pre-existing sulphides, and gold was mobilized during this oxidation. Anhedral quartz veins formed from an aqueous fluid with up to 5 wt% dissolved salts and 16 wt% CO2 at about 300 °C. Texturally later prismatic quartz crystals formed from a compositionally similar fluid which was undergoing phase separation at the H2O-CO2 solvus at 160 200 °C and 500 to 1200 bars fluid pressure. Oxygen isotope ratios for quartz from the veins range from 12.0 to 15.3‰, with hematite-bearing veins generally isotopically heavier than pyrite-bearing veins. Calculated fluid oxygen isotope ratios range from +8‰ for pyrite-bearing veins to -2‰ for late prismatic crystals. The mineralizing fluid contained a substantial component of meteoric water whose isotopic and chemical composition evolved with progressive water-rock interaction. Evolution of meteoric fluid composition involved migration of oxidation and oxygen isotope fronts in the down-flow direction as head-driven water passed through structurally controlled fractures in the schist pile. A gold solubility trough occurs for the observed fluid in the oxidation frontal zone. Gold remobilization and reprecipitation occurred progressively as the oxidation front migrated through the schist pile.

  2. Geology of epithermal silver-gold bulk-mining targets, bodie district, Mono County, California

    USGS Publications Warehouse

    Hollister, V.F.; Silberman, M.L.

    1995-01-01

    The Bodie mining district in Mono County, California, is zoned with a core polymetallic-quartz vein system and silver- and gold-bearing quartz-adularia veins north and south of the core. The veins formed as a result of repeated normal faulting during doming shortly after extrusion of felsic flows and tuffs, and the magmatic-hydrothermal event seems to span at least 2 Ma. Epithermal mineralization accompanied repeated movement of the normal faults, resulting in vein development in the planes of the faults. The veins occur in a very large area of argillic alteration. Individual mineralized structures commonly formed new fracture planes during separate fault movements, with resulting broad zones of veinlets growing in the walls of the major vein-faults. The veinlet swarms have been found to constitute a target estimated at 75,000,000 tons, averaging 0.037 ounce gold per ton. The target is amenable to bulkmining exploitation. The epithermal mineralogy is simple, with electrum being the most important precious metal mineral. The host veins are typical low-sulfide banded epithermal quartz and adularia structures that filled voids created by the faulting. Historical data show that beneficiation of the simple vein mineralogy is very efficient. ?? 1995 Oxford University Press.

  3. Gold, base-metal, and related deposits of North Carolina

    USGS Publications Warehouse

    Luttrell, Gwendolyn Werth

    1978-01-01

    Gold, silver, copper, lead, zinc, pyrite, tin, cobalt, molybdenum, tungsten, barite, and rare-earths have been mined in North Carolina. Gold, with by-product silver, occurs in veins and mineralized shear zones in metamorphic rocks of the Piedmont province and in placers derived from these deposits. Copper occurs with complex sulfide ores in quartz veins in the metamorphic rocks of the Piedmont province and in massive pyrrhotite-pyrite deposits in crystalline rocks west of the Blue Ridge. Lead and zinc occur in complex ores of gold, copper, lead, zinc, and silver in veins and replacements in metamorphic rocks. Pyrite occurs in crystalline metamorphic rocks. Tin occurs in pegmatite and placer deposits in crystalline rocks near Kings Mountain. Cobalt minerals with ores of iron or gold have been reported in a few areas in the Piedmont. Molybdenum occurs along the borders of a granite body in Halifax County. Tungsten minerals occur with copper sulfide ores in Cabarrus and Vance Counties. Barite occurs in quartz veins and associated with sulfide minerals in Orange, Madison, Cleveland, and Gaston Counties. Ore-earths occur with sulfides in vein deposits in Cabarrus County.

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

    USGS Publications Warehouse

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

    2006-01-01

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

  5. Flash vaporization during earthquakes evidenced by gold deposits

    NASA Astrophysics Data System (ADS)

    Weatherley, Dion K.; Henley, Richard W.

    2013-04-01

    Much of the world's known gold has been derived from arrays of quartz veins. The veins formed during periods of mountain building that occurred as long as 3 billion years ago, and were deposited by very large volumes of water that flowed along deep, seismically active faults. The veins formed under fluctuating pressures during earthquakes, but the magnitude of the pressure fluctuations and their influence on mineral deposition is not known. Here we use a simple thermo-mechanical piston model to calculate the drop in fluid pressure experienced by a fluid-filled fault cavity during an earthquake. The geometry of the model is constrained using measurements of typical fault jogs, such as those preserved in the Revenge gold deposit in Western Australia, and other gold deposits around the world. We find that cavity expansion generates extreme reductions in pressure that cause the fluid that is trapped in the jog to expand to a very low-density vapour. Such flash vaporization of the fluid results in the rapid co-deposition of silica with a range of trace elements to form gold-enriched quartz veins. Flash vaporization continues as more fluid flows towards the newly expanded cavity, until the pressure in the cavity eventually recovers to ambient conditions. Multiple earthquakes progressively build economic-grade gold deposits.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  7. Late-Hercynian intrusion-related gold deposits: An integrated model on the Tighza polymetallic district, central Morocco

    NASA Astrophysics Data System (ADS)

    Éric, Marcoux; Khadija, Nerci; Yannick, Branquet; Claire, Ramboz; Gilles, Ruffet; Jean-Jacques, Peucat; Ross, Stevenson; Michel, Jébrak

    2015-07-01

    Gold have been recently recognized in the Tighza (formerly Jebel Aouam) district, in the Hercynian belt of central Morocco. This district has long been known for its W mineralization, as well as major Pb-Ag-Zn, and minor Sb-Ba deposits, all geographically associated with late-Hercynian calc-alkaline magmatism. Gold mineralization in the district is mainly hosted by thick W-Au quartz veins located around the "Mine granite" small granitic plug. Within the veins, gold grade is highest (up to 70 g/t) close to the granite but rapidly decreases going outward from the granite, defining a perigranitic zoning. Anomalous gold grades have also been measured in hydrothermal skarn layers close to two other granitic plugs (Kaolin granite and Mispickel granite), associated with disseminated As-Fe sulfides. The paragenetic sequence for the W-Au quartz veins shows three stages: (1) an early oxidized stage with wolframite-scheelite associated with early quartz (Q1), (2) an intermediate Bi-As-Te-Mo-Au sulfide stage with loellingite, bismuth minerals and native gold with a later quartz (Q2), restricted to a narrow distance from the granite, and (3) a late lower temperature As-Cu-Zn-(Pb) stage with abundant massive pyrrhotite, arsenopyrite and sphalerite, locally forming independent veins ("pyrrhotite vein"). Both Q1 hyaline and Q2 saccharoidal gold-bearing quartz display aqua-carbonic fluids with minor H2S and Cu and an homogeneous composition (81 mole% H2O, 18 mole% CO2 and about 1 mole% NaCl). The trapping pressure is estimated to 1.5-2 kbar with temperature ranging from 300 to 350 °C. Q1 inclusions have exploded indicating an uplift of the Tighza block, that lead to saccharoidal Q2 quartz deposition with multiphase NaCl-saturated fluid inclusions. 40Ar/39Ar dating demonstrates that the "Mine granite", tungsten skarnoid, scheelite-molybdenite veins, and very likely gold-bearing veins are coeval, emplaced at 286 ± 1 Ma. Multiple and widespread metal sources are indicated by

  8. Gold

    USGS Publications Warehouse

    Kirkemo, Harold; Newman, William L.; Ashley, Roger P.

    1998-01-01

    Through the ages, men and women have cherished gold, and many have had a compelling desire to amass great quantities of it -- so compelling a desire, in fact, that the frantic need to seek and hoard gold has been aptly named "gold fever." Gold was among the first metals to be mined because it commonly occurs in its native form -- that is, not combined with other elements -- because it is beautiful and imperishable, and because exquisite objects can be made from it.

  9. Quartz crystal microbalance study of bovine serum albumin adsorption onto self-assembled monolayer-functionalized gold with subsequent ligand binding.

    PubMed

    Thourson, Scott B; Marsh, Caitlin A; Doyle, Brian J; Timpe, Shannon J

    2013-11-01

    Adsorption characteristics of the model protein bovine serum albumin (BSA) onto gold surfaces were examined using a 5 MHz quartz crystal microbalance. Protein immobilization was executed in the presence and absence of a homogenous self-assembled monolayer (SAM) of NHS-terminated alkanethiols. BSA concentrations in the range of 3.2 × 10(-6) to 1.0 × 10(-3)mol/L were found to saturate both SAM-functionalized and non-functionalized surfaces with similar densities of 450 ± 26 ng/cm(2). The lack of functionalization dependence is attributed to the large protein size relative to the density of available binding sites in either surface condition. The BSA ligand 8-anilino-1-naphthalenesulfonic acid (ANS) was subsequently introduced to the immobilized BSA to determine any effects of the protein immobilization conditions on ligand binding. The rate of ANS binding to BSA was found to increase with increasing BSA concentration used in the immobilization step. This suggests that protein concentration affects morphology and ligand binding affinity without significantly altering adsorption quantity.

  10. EPITHERMAL GOLD-SILVER MINERALIZATION RELATED TO VOLCANIC SUBSIDENCE IN THE CUSTER GRABEN, CUSTER COUNTY, IDAHO.

    USGS Publications Warehouse

    Johnson, Kathleen M.; McIntyre, David H.

    1984-01-01

    The Custer graben is a 13 by 32 km northeast-trending volcano-tectonic graben in the Challis volcanic field of central Idaho. Andesites, rhyolites, and associated pyroclastic rocks host vein and disseminated gold-silver deposits that are localized along discrete northeast- and northwest-trending fracture zones. Ore minerals in vein deposits are electrum, native gold and silver, chalcopyrite, and various sulfosalts in a gangue of pyrite and fine-grained quartz. At the Sunbeam Mine, near the center of the graben, vein and disseminated gold-silver mineralization occurred in hydrothermally altered rhyolite and pyroclastic rocks. The host rock has been pervasively silicified, and the feldspars altered to clay minerals. Analyses of surface and drill-core samples show that altered rocks are variably enriched in gold, silver, molybdenum, arsenic, zirconium, and selenium. Intense silicification is shown by SiO//2 values at high as 93%.

  11. A method of layer-by-layer gold nanoparticle hybridization in a quartz crystal microbalance DNA sensing system used to detect dengue virus

    NASA Astrophysics Data System (ADS)

    Chen, Sz-Hau; Chuang, Yao-Chen; Lu, Yi-Chen; Lin, Hsiu-Chao; Yang, Yun-Liang; Lin, Chih-Sheng

    2009-05-01

    Dengue virus (DENV) is nowadays the most important arthropod-spread virus affecting humans existing in more than 100 countries worldwide. A rapid and sensitive detection method for the early diagnosis of infectious dengue virus urgently needs to be developed. In the present study, a circulating-flow quartz crystal microbalance (QCM) biosensing method combining oligonucleotide-functionalized gold nanoparticles (i.e. AuNP probes) used to detect DENV has been established. In the DNA-QCM method, two kinds of specific AuNP probes were linked by the target sequences onto the QCM chip to amplify the detection signal, i.e. oscillatory frequency change (ΔF) of the QCM sensor. The target sequences amplified from the DENV genome act as a bridge for the layer-by-layer AuNP probes' hybridization in the method. Besides being amplifiers of the detection signal, the specific AuNP probes used in the DNA-QCM method also play the role of verifiers to specifically recognize their target sequences in the detection. The effect of four AuNP sizes on the layer-by-layer hybridization has been evaluated and it is found that 13 nm AuNPs collocated with 13 nm AuNPs showed the best hybridization efficiency. According to the nanoparticle application, the DNA-QCM biosensing method was able to detect dengue viral RNA in virus-contaminated serum as plaque titers being 2 PFU ml-1 and a linear correlation (R2 = 0.987) of ΔF versus virus titration from 2 × 100 to 2 × 106 PFU ml-1 was found. The sensitivity and specificity of the present DNA-QCM method with nanoparticle technology showed it to be comparable to the fluorescent real-time PCR methods. Moreover, the method described herein was shown to not require expensive equipment, was label-free and highly sensitive.

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

    USGS Publications Warehouse

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

    2004-01-01

    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

  13. Gold deposits in the late Archaean Nzega-Igunga greenstone belt, central plateau of tanzania

    SciTech Connect

    Feiss, P.G.; Siyomana, S.

    1985-01-01

    2.2 m oz of gold have been produced, since 1935, from late Archaean (2480-2740 Ma) greenstone belts of the Central Plateau, Tanzania. North and east of Nzega (4/sup 0/12'S, 3/sup 0/11'E), 18% of the exposed basement, mainly Dodoman schists and granites, consists of metavolcanics and metasediments of the Nyanzian and Kavirondian Series. Four styles of mineralization are observed. 1. Stratabound quartz-gold veins with minor sulfides. Host rocks are quartz porphyry, banded iron formation (BIF), magnetite quartzite, and dense, cherty jasperite at the Sekenke and Canuck mines. The Canuck veins are on strike from BIF's in quartz-eye porphyry of the Igusule Hills. 2. Stratabound, disseminated gold in coarse-grained, crowded feldspar porphyry with lithic fragments and minor pyrite. At Bulangamilwa, the porphyry is conformable with Nyanzian-aged submarine (.) greenstone, volcanic sediment, felsic volcanics, and sericite phyllite. The deposits are on strike with BIF of the Wella Hills, which contains massive sulfide with up to 15% Pb+Zn. 3. Disseminated gold in quartz-albite metasomes in Nyanzian greenstones. At Kirondatal, alteration is associated with alaskites and feldspar porphyry dikes traceable several hundred meters into post-Dodoman diorite porphyry. Gold is with pyrite, arsenopyrite, pyrrhotite, minor chalcopyrite, and sphalerite as well as tourmalinite and silica-cemented breccias. 4. Basal Kavirondian placers in metaconglomerates containing cobbles and boulders of Dodoman and Nyanzian rocks several hundred meters up-section from the stratabound, disseminated mineralization at Bulangamilwa.

  14. A Palaeoproterozoic multi-stage hydrothermal alteration system at Nalunaq gold deposit, South Greenland

    NASA Astrophysics Data System (ADS)

    Bell, Robin-Marie; Kolb, Jochen; Waight, Tod Earle; Bagas, Leon; Thomsen, Tonny B.

    2017-03-01

    Nalunaq is an orogenic, high gold grade deposit situated on the Nanortalik Peninsula, South Greenland. Mineralisation is hosted in shear zone-controlled quartz veins, located in fine- and medium-grained amphibolite. The deposit was the site of Greenland's only operating metalliferous mine until its closure in 2014, having produced 10.67 t of gold. This study uses a combination of field investigation, petrography and U/Pb zircon and titanite geochronology to define a multi-stage hydrothermal alteration system at Nalunaq. A clinopyroxene-plagioclase-garnet(-sulphide) alteration zone (CPGZ) developed in the Nanortalik Peninsula, close to regional peak metamorphism and prior to gold-quartz vein formation. The ca. 1783-1762-Ma gold-quartz veins are hosted in reactivated shear zones with a hydrothermal alteration halo of biotite-arsenopyrite-sericite-actinolite-pyrrhotite(-chlorite-plagioclase-löllingite-tourmaline-titanite), which is best developed in areas of exceptionally high gold grades. Aplite dykes dated to ca. 1762 Ma cross-cut the gold-quartz veins, providing a minimum age for mineralisation. A hydrothermal calcite-titanite alteration assemblage is dated to ca. 1766 Ma; however, this alteration is highly isolated, and as a result, its field relationships are poorly constrained. The hydrothermal alteration and mineralisation is cut by several generations of ca. 1745-Ma biotite granodiorite accompanied by brittle deformation. A ca. 1745-Ma lower greenschist facies hydrothermal epidote-calcite-zoisite alteration assemblage with numerous accessory minerals forms halos surrounding the late-stage fractures. The contrasting hydrothermal alteration styles at Nalunaq indicate a complex history of exhumation from amphibolite facies conditions to lower greenschist facies conditions in an orogenic belt which resembles modern Phanerozoic orogens.

  15. A Palaeoproterozoic multi-stage hydrothermal alteration system at Nalunaq gold deposit, South Greenland

    NASA Astrophysics Data System (ADS)

    Bell, Robin-Marie; Kolb, Jochen; Waight, Tod Earle; Bagas, Leon; Thomsen, Tonny B.

    2016-07-01

    Nalunaq is an orogenic, high gold grade deposit situated on the Nanortalik Peninsula, South Greenland. Mineralisation is hosted in shear zone-controlled quartz veins, located in fine- and medium-grained amphibolite. The deposit was the site of Greenland's only operating metalliferous mine until its closure in 2014, having produced 10.67 t of gold. This study uses a combination of field investigation, petrography and U/Pb zircon and titanite geochronology to define a multi-stage hydrothermal alteration system at Nalunaq. A clinopyroxene-plagioclase-garnet(-sulphide) alteration zone (CPGZ) developed in the Nanortalik Peninsula, close to regional peak metamorphism and prior to gold-quartz vein formation. The ca. 1783-1762-Ma gold-quartz veins are hosted in reactivated shear zones with a hydrothermal alteration halo of biotite-arsenopyrite-sericite-actinolite-pyrrhotite(-chlorite-plagioclase-löllingite-tourmaline-titanite), which is best developed in areas of exceptionally high gold grades. Aplite dykes dated to ca. 1762 Ma cross-cut the gold-quartz veins, providing a minimum age for mineralisation. A hydrothermal calcite-titanite alteration assemblage is dated to ca. 1766 Ma; however, this alteration is highly isolated, and as a result, its field relationships are poorly constrained. The hydrothermal alteration and mineralisation is cut by several generations of ca. 1745-Ma biotite granodiorite accompanied by brittle deformation. A ca. 1745-Ma lower greenschist facies hydrothermal epidote-calcite-zoisite alteration assemblage with numerous accessory minerals forms halos surrounding the late-stage fractures. The contrasting hydrothermal alteration styles at Nalunaq indicate a complex history of exhumation from amphibolite facies conditions to lower greenschist facies conditions in an orogenic belt which resembles modern Phanerozoic orogens.

  16. Geological setting of the Paleoproterozoic Rosebel gold district, Guiana Shield, Suriname

    NASA Astrophysics Data System (ADS)

    Daoust, Caroline; Voicu, Gabriel; Brisson, Harold; Gauthier, Michel

    2011-10-01

    The Rosebel gold district is hosted in a Paleoproterozoic greenstone belt of the Guiana Shield and has many characteristics that enable classification of the ores as an orogenic gold deposit. Host rocks have undergone several phases of deformation. However, gold deposition occurred late in the structural history of the belt, and is considered part of a late regional metallogenic event with respect to the geotectonic evolution of the Guiana Shield. Economic gold mineralization is hosted in felsic to mafic volcanic rocks and two sedimentary successions that are differentiated into turbiditic and arenitic depositional packages. The detailed lithostratigraphic characterization and the geochemistry enable the correlation of the local rock types with the Paramaka, the Armina, and the Rosebel formations respectively. The Rosebel district comprises eight discrete gold deposits distributed along two major structures. The northernmost structure is a sub-vertical WNW-ESE shear zone that preserves evidence of dextral strike-slip followed by normal faulting. The southern structure is an east-west reverse fault along which gold deposits are mainly hosted in the footwall. Gold mineralization is associated with quartz vein arrays developed along pre-existing structural heterogeneities, such as stratigraphic contacts and fold hinges. Four main sets of veins are recognized in the district: shear veins, north-south tension veins, stacks of north-dipping tension veins, and anticline-hosted tension veins. Mineralized quartz veins are typically associated with a wallrock alteration assemblage comprising sericite, chlorite, carbonate, tourmaline, pyrite, pyrrhotite, and plagioclase. The presence of a WNW-ESE dextral strike-slip structure, an east-west reverse fault, and north-south tension veins are consistent with the formation of a Riedel system during a simple shear event. All vein sets cut deformed sedimentary rocks that were deposited in a pull-apart basin, which together with their

  17. Noble gases, K, U, Th, and Pb in native gold

    NASA Astrophysics Data System (ADS)

    Engster, O.; Niedermann, S.; Thalmann, C.; Frei, R.; Kramers, J.; KräHenbühl, U.; Liu, Y. Z.; Hofmann, B.; Boer, R. H.; Reimold, W. U.; Bruno, L.

    1995-12-01

    We present determinations of the noble gas and Pb isotopic abundances and of K, Th, and U concentrations of native gold. Our results demonstrate that gold is an excellent carrier for crustal volatiles, but direct dating of gold using the U, Th-4He, 40K-40Ar, and U fission Xe methods was not successful for various reasons. The main significance of this work is the great sensitivity of gold for trapped gases as well as for gases that were produced in situ which gives the prospects of using gold and its fluid and solid inclusions for the study of paleogas composition. Numerous nuclear effects characterize the noble gas inventory of placer gold from Switzerland and Italy, vein gold from Italy, South Africa, and Venezuela, and lode gold from South Africa. The degassing patterns obtained by mass spectrometry show a low-temperature release of volatiles around 500°C from fluid inclusions mainly in vein gold and a high-temperature release from solid inclusions and the gold itself. The low-temperature volatiles represent species that were trapped when the gold crystallized. We investigated the following trapped species: the isotopes of He, Ne, Ar, Kr, Xe, and Pb, and the abundances of K, U, Th, H2O, and CO2. The crustal gases trapped by gold comprise 3He from 6Li(n,α)3H → β- → 3He, 4He and 40Ar from the U, Th, and K decay, and Xe from 238U fission. We observe 4He/40Ar = 3.9 for the radiogenic trapped gases of tertiary gold and a ratio of 1.4 for Archean gold. These ratios are consistent with the production ratios from U and K at the respective times and demonstrate that gold can be used as a sampler of ancient atmospheric gases. The concentrations of U and Th range from a few parts per billion to a few parts per million, and those of K and Pb range up to some tens of parts per million. The antiquity of trapped Pb is indicated by the Pb-Pb model age of about 3000 Ma for the lead extracted from vein gold and quartz of the Lily gold mine (South Africa). Gold also

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

    USGS Publications Warehouse

    Foley, Nora K.; Ayuso, Robert A.

    1994-01-01

    Pb isotope compositions from the late stage of the North Amethyst vein system and from the Bondholder and central and southern Creede mining districts are more radiogenic than the host volcanic rocks of the central cluster of the San Juan volcanic field. Our Pb isotope results indicate that early Au mineralization of the North Amethyst area may represent the product of an older and relatively local hydrothermal system distinct from that of the younger base metal and Ag mineralization found throughout the region. Fluids that deposited Au minerals may have derived their Pb isotope composition by a greater degree of interaction with shallow, relatively less radiogenic volcanic wall rocks. The younger, base metal and Ag-rich mineralization that overprints the Au mineralization in the North Amethyst area clearly has a more radiogenic isotopic signature, which implies that the later mineralization derived a greater component of its Pb from Proterozoic source rocks, or sediments derived from them.Paragenetically early sulfide-rich vein assemblages have the least radiogenic galenas and generally also have the highest Au contents. Thus, identification of paragenetically early vein assemblages with relatively unradiogenic Pb isotope compositions similar to those of the North Amethyst area provides an additional exploration tool for Au in the central San Juan Mountains area.

  19. Quartz-sericite and argillic alterations at the Peschanka Cu-Mo-Au deposit, Chukchi Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Marushchenko, L. I.; Baksheev, I. A.; Nagornaya, E. V.; Chitalin, A. F.; Nikolaev, Yu. N.; Kal'ko, I. A.; Prokofiev, V. Yu.

    2015-05-01

    The porphyry Peschanka copper-molybdenum-gold deposit and the Nakhodka ore field located in the Baimka ore trend on the western Chukchi Peninsula are spatially related to monzonitic rocks of the Early Cretaceous Egdykgych Complex. Two types of quartz-sericite metasomatic rocks (QSR) have been identified at both the deposits and the ore field: (I) chlorite-quartz-muscovite rock with bornite and chalcopyrite (porphyry type) and (II) tourmaline-quartz-carbonate-muscovite ± phengite rock accompanied by veins with base-metal mineralization (subepithermal or transitional type), as well as carbonate-quartz-illite rock (argillic alteration) accompanied by veins with precious metal mineralization (epithermal type). The QSR I chlorite evolves from chamosite to clinochlore, which is caused by increasing H2S activity in mineralizing fluid and precipitation of sulfide minerals. The QSR I clinochlore is significantly depleted in silica as compared with that from the rocks affected by argillic alteration. The chemical composition of muscovite from both quartz-sericite alterations is similar. The QSR II carbonates evolve from calcite through dolomite to siderite, which results from the increasing activity of CO2 followed by the decreasing activity of H2S in mineralizing fluid. The Mn content in dolomite is similar to that in beresite (quartz-muscovite-carbonate-pyrite metasomatic rock) of the intrusion-related gold deposits. Illite from argillic alteration is depleted in Al as compared with that of postvolcanic epithermal Au-Ag deposits. However, carbonates from the discussed argillic alteration rhodochrosite and Mn-rich dolomite are similar to those from quartz-illite rock at postvolcanic epithermal Au-Ag deposits.

  20. Varicose Veins

    MedlinePlus

    ... has surface (superficial) veins that are connected to deep veins by bridging (perforator) veins. Unlike arteries, which ... the valve leaflets and can develop in the deep, perforator, or superficial veins. View this table: View ...

  1. First Evidence of Epithermal Gold Occurrences in the SE Afar Rift, Republic of Djibouti

    NASA Astrophysics Data System (ADS)

    Moussa, Nima; Fouquet, Yves; Caminiti, Antoine Marie; Le Gall, Bernard; Rolet, Joel; Bohn, Marcel; Etoubleau, Joel; Delacourt, Christophe; Jalludin, Mohamed

    2010-05-01

    The Republic of Djibouti, located at the SE part of the Afar volcanic Triangle, is characterized by intense tectonic and bimodal volcanic activity, and is emplaced over an earlier magmatic rift system, as old as 25-30 Ma. Each magmatic event is accompanied by hydrothermal activity. Few works have been so far published on hydrothermal mineralization in the Afar area. Mineralization generally occur as veins and are mainly associated with acidic volcanic intrusions along the fractures at the edges of grabens established during the last 4 Ma. Eighty samples from hydrothermal quartz ± carbonate veins and breccias were studied on 9 different sites representative of 4 main volcanic events ranging in age from early Miocene up to Present. Gold was found in excess of 200 ppb in 30% of the samples. Mineralogical analyses based on optical reflected light microscopy, X-Ray diffractometry, X-Ray fluorescence, inductively coupled plasma mass spectroscopy and electron microprobe, led us to identify two types of gold mineralization (i) native gold, electrum, hessite and sulfides (chalcopyrite, pyrite, bornite, ± sphalerite, and galena) in massive quartz breccias and banded chalcedony, (ii) gold, electrum, hematite, magnetite, trace minerals (argentite) and adularia in banded chalcedony. Another group without gold is characterized by quartz, pyrite ± goethite. Secondary minerals are characterized by goethite, native silver and native copper. Arsenic is enriched in pyrite in samples with a high gold content. The bimodal volcanism, the occurrence of adularia, the native gold and electrum in banded silica veins, are classically observed in neutral epithermal systems. The discovery of this type of mineralization in a recent-active continental rift system supplies new insights about hydrothermal processes associated with volcanic activity in a spreading context. Keywords: Republic of Djibouti, Afar Triangle, Hydrothermal, Epithermal system, Gold

  2. First evidence of epithermal gold occurrences in the SE Afar Rift, Republic of Djibouti

    NASA Astrophysics Data System (ADS)

    Moussa, N.; Fouquet, Y.; Le Gall, B.; Caminiti, A. M.; Rolet, J.; Bohn, M.; Etoubleau, J.; Delacourt, C.; Jalludin, M.

    2012-06-01

    The geology of the Republic of Djibouti, in the SE Afar Triangle, is characterized by intense tectonic and bimodal volcanic activity that began as early as 25-30 Ma. Each magmatic event was accompanied by hydrothermal activity. Mineralization generally occurs as gold-silver bearing chalcedony veins and is associated with felsic volcanism. Eighty samples from mineralized hydrothermal chalcedony, quartz ± carbonate veins and breccias were studied from ten sites representing four major volcanic events that range in age from early Miocene to the present. The most recent veins are controlled by fractures at the edges of grabens established during the last 4 Myr. Gold in excess of 200 ppb is present in 30% of the samples, with values up to 16 ppm. Mineralogical compositions allowed us to identify different types of mineralization corresponding to different depths in the hydrothermal system: (1) surface and subsurface mineralization characterized by carbonate chimneys, gypsum, silica cap and quartz ± carbonate veins that are depleted in metals and Au; (2) shallow banded chalcedony ± adularia veins related to boiling that contain up to 16 ppm Au, occurring as native gold and electrum with pyrite, and tetradymite; (3) quartz veins with sulfides, and (4) epidote alteration in the deepest hydrothermal zones. Samples in which pyrite is enriched in As tend to have a high Au content. The association with bimodal volcanism, the occurrence of adularia and the native Au and electrum in banded chalcedony veins are typical of epithermal systems and confirm that this type of mineralization can occur in a young intracontinental rift system.

  3. SIMS Investigations on Growth and Sector Zoning in Natural Hydrothermal Quartz: Isotopic and Trace Element Analyses

    NASA Astrophysics Data System (ADS)

    May, E.; Vennemann, T. W.; Baumgartner, L. P.; Meisser, N.

    2014-12-01

    Quartz is the most abundant mineral in the Earth's crust and is found in virtually every geological context. Despite its ubiquity and the detailed studies on the conditions of quartz crystallization, some questions concerning its growth and sector zoning with regard to trace element incorporation and oxygen isotope fractionations and the implications thereof for interpretations on the conditions of formation remain (e.g., Jourdan et al., 2009). This study presents new in-situ measurements of trace element and oxygen isotope ratios on natural hydrothermal quartz from an extensional gold-bearing quartz vein in the western Swiss Alps. The temperature of formation of the veins is estimated by quartz-hematite oxygen isotope thermometry to be about 360°C. A detailed SEM-CL study of this sample shows cyclic lamellar growth, alternating with phases of dissolution that are directly followed by macro-mosaic growth of the quartz, before returning to a cyclic lamellar growth again. Trace element concentrations (measured for Na, K, Li, Al, and Ti) notably showed Al/Si variations of three orders of magnitude and coupled Al and Li variations, likely substituting for Si in different growth zones with lower values in macro-mosaic zones precipitating after the period of dissolution. The oxygen isotope composition of the crystal, in contrast, is homogeneous through all growth zones (δ18O values between 15.6‰ and 16.2‰) indicating that the fluid must have been buffered by the host-rock and/or the source of the fluid remained the same despite the period of quartz dissolution. Furthermore, the temperature during crystallization of the quartz crystal has likely also remained similar. The fact that no variations are measured in oxygen isotope compositions but some variations in trace element contents may suggest that changes in pressure were important during the formation of this quartz crystal. Give the pressure effects on the solubility of quartz (Fournier and Potter, 1982), both

  4. Geology and geochemistry of the shear-hosted Julie gold deposit, NW Ghana

    NASA Astrophysics Data System (ADS)

    Amponsah, Prince Ofori; Salvi, Stefano; Béziat, Didier; Siebenaller, Luc; Baratoux, Lenka; Jessell, Mark W.

    2015-12-01

    The Leo Man Craton in West Africa is host to numerous economic gold deposits. If some regions, such as the SW of Ghana, are well known for world-class mineralizations and have been extensively studied, gold occurrences elsewhere in the craton have been discovered only in the last half a century or so, and very little is known about them. The Julie gold deposit, located in the Paleoproterozoic Birimian terrane of NW Ghana, is one such case. This deposit is hosted in a series of granitoid intrusives of TTG composition, and consists of a network of deformed, boudinaged quartz lodes (A-type veins) contained within an early DJ1 E-W trending shear zone with dextral characteristics. A conjugate set of veins (C-type) perpendicular to the A-type veins contains low grade mineralization. The main ore zone defines a lenticular corridor about 20-50 m in width and about 3.5 km along strike, trending E-W and dipping between 30 and 60°N. The corridor is strongly altered, by an assemblage of sericite + quartz + ankerite + calcite + tourmaline + pyrite. This is surrounded by a second alteration assemblage, consisting of albite + sericite + calcite + chlorite + pyrite + rutile, which marks a lateral alteration that fades into the unaltered rock. Mass balance calculations show that during alteration overall mass was conserved and elemental transfer is generally consistent with sulfidation, sericitization and carbonatization of the host TTG. Gold is closely associated with pyrite, which occurs as disseminated grains in the veins and in the host rock, within the mineralized corridor. SEM imagery and LA-ICP-MS analyses of pyrites indicate that in A-type veins gold is associated with bismuth, tellurium, lead and silver, while in C-type veins it is mostly associated with silver. Pyrites in A-type veins contain gold as inclusions and as free gold on its edges and fractures, while pyrites from C-type veins contains mostly free gold. Primary and pseudosecondary fluid inclusions from both

  5. Geology and geochemistry of the Clear Creek intrusion-related gold occurrences, Tintina Gold Province, Yukon, Canada

    USGS Publications Warehouse

    Marsh, E.E.; Goldfarb, R.J.; Hart, C.J.R.; Johnson, C.A.

    2003-01-01

    The Clear Creek gold occurrences lie within deformed lower greenschist-facies rocks of the western Selwyn basin. They consist of auriferous, sheeted quartz veins that cut six Cretaceous stocks and their hornfels. The veins contain 1-2% combined pyrite and arsenopyrite, with lesser pyrrhotite, bismuthinite, and scheelite, as well as 2-5 g/t Au. New 40Ar/39Ar geochronology of hydrothermal micas indicates that the veins formed within 1-2 million years of granitoid emplacement. Fluid inclusion microthermometry defines a parent ore fluid of -81 mol.% H2O, 14 mol.% CO2, 4 mol.% NaCl ?? KCl, and 1 mol.% CH4, which unmixed into a low- and high-salinity immiscible pair. This suggests a more saline parent fluid and a greater degree of fluid unmixing relative to the other occurrences in the eastern Tintina Gold Province. Inclusions trapped in As- and Bi-rich, high-gold grade veins have homogenization temperatures of 300-350??C, whereas inclusions found in more Ag- and Pb-rich veins are characterized by temperatures of 250-300??C. Fluid inclusion geobarometry suggests hydro-fracturing and gold deposition at 5-7 km depth. The ??18O values of quartz samples range from 13-16??? (per mil) and ??34S for sulfides are also consistent between -3.0???, 0???, with the exception of some outliers from the Contact Zone of the Pukelman stock that indicate a lower temperature second phase of mineralization. It remains uncertain as to whether the Clear Creek ore fluids were exsolved from magmas at depth or from devolatilization reactions within the contact metamorphic aureoles of the intrusions.

  6. Anomalous concentrations of gold, silver, and other metals in the Mill Canyon area, Cortez quadrangle, Eureka and Lander Counties, Nevada

    USGS Publications Warehouse

    Elliott, James E.; Wells, John David

    1968-01-01

    The Mill Canyon area is in the eastern part of the Cortez window of the Roberts Mountains thrust belt in the Cortez quadrangle, north-central Nevada. Gold and silver ores have been mined from fissure veins in Jurassic quartz monzonite and in the bordering Wenban Limestone of Devonian age. Geochemical data show anomalies of gold, silver, lead, zinc, copper, arsenic, antimony, mercury, and tellurium. Geologic and geochemical studies indicate that a formation favorable for gold deposition, the Roberts Mountains Limestone of Silurian age, may be found at depth near the mouth of Mill Canyon.

  7. Shock metamorphism of deformed quartz

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  8. Magmatic-hydrothermal origin of the early Triassic Laodou lode gold deposit in the Xiahe-Hezuo district, West Qinling orogen, China: implications for gold metallogeny

    NASA Astrophysics Data System (ADS)

    Jin, Xiao-ye; Li, Jian-wei; Hofstra, Albert H.; Sui, Ji-xiang

    2016-12-01

    The Xiahe-Hezuo district in the West Qinling orogen contains numerous Au-(As-Sb) and Cu-Au-(W) deposits. The district is divided into eastern and western zones by the Xiahe-Hezuo Fault. The western zone is exposed at a shallow level and contains sediment-hosted disseminated Au-(As-Sb) deposits, whereas the eastern zone is exposed at a deeper level and contains Cu-Au-(W) skarn and lode gold deposits within or close to granitic intrusions. The Laodou gold deposit in the eastern zone consists of auriferous quartz-sulfide-tourmaline and minor quartz-stibnite veins that are structurally controlled by fault zones transecting the Laodou quartz diorite porphyry stock and enveloped by potassic and phyllic alteration. Both the veins and alteration halos commonly contain quartz, sericite, tourmaline, pyrite, and arsenopyrite, with minor galena, sphalerite, chalcopyrite, tetrahedrite, and enargite. Gold occurs mainly as invisible gold in pyrite or arsenopyrite and locally as inclusions less than 50 μm in diameter. The zircon U-Pb age of 247.6 ± 1.3 Ma (2σ) on the host quartz diorite porphyry and the sericite 40Ar/39Ar plateau ages of 249.1 ± 1.6 and 249.0 ± 1.5 Ma (2σ) on two ore-related hydrothermal sericite samples are within analytical errors of one another. At the formation temperature (275 °C) inferred from microthermometric measurements of fluid inclusion, sericite and tourmaline yield calculated δDH2O values of -70 to -45‰ and δ 18OH2O of 5.8 to 9.7‰, while quartz yields calculated δ 18OH2O values of 5.1˜5.7‰. Hydrothermal tourmaline in quartz-sulfide-tourmaline veins has δ 11B of -11.2 to -0.9‰ (mean of -6.3‰) that are similar to the values of magmatic tourmaline (-8.9 to -5.5‰ with a mean of -6.8‰) in the host quartz diorite porphyry. The δ 34S values of sulfide minerals range from -5.9 to +5.8‰ with a mean of -0.6‰ that is typical of magmatic sulfur. Pyrite from hydrothermally altered quartz diorite porphyry and quartz

  9. Age constraints on Tarkwaian palaeoplacer and lode-gold formation in the Tarkwa-Damang district, SW Ghana

    USGS Publications Warehouse

    Pigois, J.-P.; Groves, D.I.; Fletcher, I.R.; McNaughton, N.J.; Snee, L.W.

    2003-01-01

    Two major epigenetic gold-forming events are recorded in the world-class gold province of southwest Ghana. A pre-Tarkwaian event was the source of the world-class Tarkwa palaeoplacers whereas post-Birimian and Tarkwaian deformation, which was related to the Eburnean orogeny, gave rise to the world-class (e.g. Prestea) to giant (e.g. Obuasi) orogenic gold deposits which have made the region famous for more than 2,500 years. A maximum age of 2133 ?? 4 Ma for Tarkwaian sedimentation is provided by 71 of 111 concordant SHRIMP II U Pb dates from detrital zircons in Tarkwaian clastic rocks from Damang and Bippo Bin, northeast of Tarkwa. The overall data distribution broadly overlaps the relatively poorly constrained ages of Birimian volcanism and associated Dixcove-type granitoid emplacement, indicating syntectonic development of the Tarkwaian sedimentary basin. These zircon ages argue against derivation of the palaeoplacer gold from an orogenic gold source related to the compressional phase of an orogeny significantly older than the Eburnean orogeny. Instead, they suggest that the gold source was either orogenic gold lodes related to an earlier compressional phase of a diachronous Eburnean orogeny or ca. 2200-2100 Ma intrusion-related gold lode. The CO2-rich fluid inclusions in associated vein-quartz pebbles are permissive of either source. At the Damang deposit, an epigenetic, orogenic lode-gold system clearly overprinted, and sulphidised low-grade palaeoplacer hematite magnetite gold occurrences in the Banket Series conglomerate within the Tarkwaian sedimentary sequence. Gold mineralisation is demonstrably post-peak metamorphism, as gold-related alteration assemblages overprint metamorphic assemblages in host rocks. In alteration zones surrounding the dominant, subhorizontal auriferous quartz veins, there are rare occurrences of hydrothermal xenotime which give a SHRIMP U Pb age of 2063 ?? 9 Ma for gold mineralisation. The similar structural timing of epigenetic gold

  10. Mercury contamination from historical gold mining in California

    USGS Publications Warehouse

    Alpers, Charles N.; Hunerlach, Michael P.; May, Jason T.; Hothem, Roger L.

    2005-01-01

    Mercury contamination from historical gold mines represents a potential risk to human health and the environment. This fact sheet provides background information on the use of mercury in historical gold mining and processing operations in California, with emphasis on historical hydraulic mining areas. It also describes results of recent USGS projects that address the potential risks associated with mercury contamination. Miners used mercury (quicksilver) to recover gold throughout the western United States. Gold deposits were either hardrock (lode, gold-quartz veins) or placer (alluvial, unconsolidated gravels). Underground methods (adits and shafts) were used to mine hardrock gold deposits. Hydraulic, drift, or dredging methods were used to mine the placer gold deposits. Mercury was used to enhance gold recovery in all the various types of mining operations; historical records indicate that more mercury was used and lost at hydraulic mines than at other types of mines. On the basis of USGS studies and other recent work, a better understanding is emerging of mercury distribution, ongoing transport, transformation processes, and the extent of biological uptake in areas affected by historical gold mining. This information has been used extensively by federal, state, and local agencies responsible for resource management and public health in California.

  11. Gold placer and Quaternary stratigraphy of the Jabal Mokhyat area, southern Najd Province, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Schmidt, D.L.; Puffett, W.P.; Campbell, W.L.; Al-Koulak, Z. H.

    1981-01-01

    An ancient gold placer at Jabal Mokhyat (lat 20?12.2'N., long 43?28'E.), about 90 km east of Qalat Bishah in the southern Najd Province, Kingdom of Saudi Arabia, was studied in 1973. Seven hundred and twenty-eight samples in 25 measured sections were collected along trenches and pits 2.5 m in depth and 2,600 m in total length. Alluvium was thicker than the excavation depth along about 50 percent of the trench length. The average gold content was 4.4 mg per m3, and the highest grade trench contained 40 mg gold per m 3. Because fine particulate gold is rare in the alluvium, a few large particles, 1 to 5 mm in diameter, greatly affected the sampling results. The ancient placer diggings are in small headwater wadis distributed over a 30-km 2 area, and the total dug area is about 1.2 km2. The placer produced an estimated 50 kg of gold and was worked about 2,600 + 250 years ago. The potential for a present-day placer operation is small. The gold is sparsely distributed in locally derived, flood-deposited, immature gravels throughout a stratigraphic section that consists of 1) calichified, saprolitic bedrock of Precambrian age; 2) basal, intensely calichified, saprolitic gravel (0-3 m thick) of Pleistocene age; 3) disconformable, slightly consolidated gravel and sand (0-1 m thick) of late Pleistocene age containing sparse, disseminated caliche; 4) firm loessic silt (0-1 m thick) of early Holocene age; and 5) loose sand and gravel (0.3-1 m thick) of late Holocene age. The loessic silt accumulated during the Holocene pluvial. The top of the loessic silt unit is dated at about 6,000 years B.P. by using charcoal from hearths of ancient man. Following the Holocene pluvial, the climate became arid, and extreme desiccation resulted in abundant eolian sand that progressively diluted the late Holocene gravels. The remnants of the pre-Holocene stratigraphy suggest similar climatic cycles during the Pleistocene. Abundant, sparsely mineralized, gold-bearing quartz veins (0-1 m wide

  12. Relantionships between gold mineralization and granite - Discussion with the support of a pluridisciplinary study of the Passa Tres gold deposit (South Brazil)

    NASA Astrophysics Data System (ADS)

    Dressel, Bárbara; Chauvet, Alain; Trzaskos, Barbara; Biondi, Joao Carlos; Bruguier, Olivier; Monie, Patrick; Villanova, Sandro; Bazille, Jose

    2016-04-01

    The Passa Três Granite, located at East of the Paraná State is elongated following a NNE-SSW direction. This sienogranite is emplaced within metapelites of the meso to neoproterozoic Açungui Group, between the Morro Agudo and Lancinha transcurrent faults, comprising the N040°E trending Lancinha Transcurrent Fault System. Gold mineralization within the Passa Três Granite is constituted by huge quartz veins with sulfides, variable quantities of fluorite and carbonates, forming orebodies with different internal textures, including massive, banded, sheared and brecciated. Structural data indicate the existence of two major fault systems, one N-S and the other E-W, with dips of 15-45°W and 20-75°S, respectively. Both NS and EW systems are interpreted to be contemporaneous and conjugate. Normal motions are everywhere suspected and main mineralized veins are located at opening sites at these fault systems, such as pull-aparts. The structural model suggests that the normal motion can be initiated by shearing along a "guide" level, in which sulfides and clay minerals are concentrated. This configuration can be observed at several scales, such as field, hand samples and thin section. Mineralized veins mainly contain, in addition to the quartz of the gangue, sulphides (pyrite, chalcopyrite, galena, molybdenite), fluorite, chlorite, muscovite, sericite, and carbonate. The presence of sericite, kaolinite and chlorite indicate the occurrence of, at least, propylitic and phyllic-type alterations, both in core of the granite and best-expressed at the rim of quartz-rich orebodies. Gold occurs as native grains in core of the quartz veins, within fractures that affect pyrite and frequently exhibiting normal motions consistent with the one observed at larger scale and systematically associated with chalcopyrite and galena. Quartz veins are sometimes bordered by aplitic dike. Additionally, some of the veins can exhibit a very thin margin of adularia minerals that seems to

  13. Quartz crystal fabrication facility

    NASA Astrophysics Data System (ADS)

    Ney, R. J.

    1980-05-01

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

  14. Integration of new geologic mapping and satellite-derived quartz mapping yields insights into the structure of the Roberts Mountains allochthon applicable to assessments for concealed Carlin-type gold deposits

    USGS Publications Warehouse

    Holm-Denoma, Christopher S.; Hofstra, Albert H.; Rockwell, Barnaby W.; Noble, Paula J.

    2012-01-01

    Geologic mapping and remote sensing across north-central Nevada enable recognition of a thick sheet of Middle and Upper Ordovician Valmy Formation quartzite that structurally overlies folded and faulted Ordovician through Devonian stratigraphic units of the Roberts Mountains allochthon. In the northern Independence Mountains and nearby Double Mountain area, the Valmy Formation is in fault contact with Ordovician through Silurian, predominantly clastic, sedimentary rocks of the Roberts Mountains allochthon that were deformed prior to, or during, emplacement of the Valmy thrust sheet. Similar structural relations are recognized discontinuously for 200 kilometers along the strike of the Roberts Mountains allochthon in mapping guided by regional remote-sensing-based (ASTER) quartz maps. Overall thicknesses of deformed Roberts Mountains allochthon units between the base of the Valmy and the top of underlying carbonate rocks that host large Carlin-type gold deposits varies on the order of hundreds of meters but is not known to exceed 700 meters. The base of the Valmy thrust sheet is a complimentary datum in natural resource exploration and mineral resource assessment for concealed Carlin-type gold deposits.

  15. Tectonic setting of synorogenic gold deposits of the Pacific Rim

    USGS Publications Warehouse

    Goldfarb, R.J.; Phillips, G.N.; Nokleberg, W.J.

    1998-01-01

    More than 420 million oz of gold were concentrated in circum-Pacific synorogenic quartz loades mainly during two periods of continental growth, one along the Gondwanan margin in the Palaeozoic and the other in the northern Pacific basin between 170 and 50 Ma. These ores have many features in common and can be grouped into a single type of lode gold deposit widespread throughout clastic sedimentary-rock dominant terranes. The auriferous veins contain only a few percent sulphide minerals, have gold:silver ratios typically greater than 1:1, show a distinct association with medium grade metamorphic rocks, and may be associated with large-scale fault zone. Ore fluids are consistently of low salinity and are CO2-rich. In the early and middle Palaeozoic in the southern Pacific basin, a single immense turbidite sequence was added to the eastern margin of Gondwanaland. Deformation of these rocks in southeastern Australia was accompanied by deposition of at least 80 million oz of gold in the Victorian sector of the Lachlan fold belt mainly during the Middle and Late Devonian. Lesser Devonian gold accumulations characterized the more northerly parts of the Gondwanan margin within the Hodgkinson-Broken River and Thomson fold belts. Additional lodes were emplaced in this flyschoid sequence in Devonian or earlier Palaeozoic times in what is now the Buller Terrane, Westland, New Zealand. Minor post-Devonian growth of Gondwanaland included terrane collision and formation of gold-bearing veins in the Permian in Australia's New England fold belt and in the Jurassic-Early Cretaceous in New Zealand's Otago schists. Collision and accretion of dozens of terranes for a 100-m.y.-long period against the western margin of North America and eastern margin of Eurasia led to widespread, lattest Jurassic to Eocene gold veining in the northern Pacific basin. In the former location, Late Jurassic and Early Cretaceous veins and related placer deposits along the western margin of the Sierra Nevada

  16. Preliminary mineralogic, fluid inclusion, and stable isotope study of the Mahd adh Dhahab gold mine, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Rye, Robert O.; Hall, W.E.; Cunningham, C.G.; Czamanske, G.K.; Afifi, A.M.; Stacey, J.S.

    1983-01-01

    The Mahd adh Dhahab mine, located about 280 km northeast of Jiddah, Kingdom of Saudi Arabia, has yielded more than 2 million ounces of gold from periodic production during the past 3,000 years. A new orebody on the southern side of the ancient workings, known as the South orebody, is being developed by Gold Fields-Mahd adh Dhahab Limited. A suite of samples was collected from the newly exposed orebody for preliminary mineralogic, stable isotope, fluid inclusion, and geochemical studies. The Mahd adh Dhahab deposit is in the carapace of a Proterozoic epizonal rhyolite stock that domed pyroclastic and metasedimentary rocks of the Proterozoic Halaban group. Ore of gold, silver, copper, zinc, tellurium, and lead is associated with north-trending, steeply dipping quartz veins in a zone 1,000 m long and 400 m wide. The veins include an assemblage of quartz-chlorite-pyrite-hematite-chalcopyrite-sphalerite-precious metals, which is similar to the mineral assemblage at the epithermal deposit at Creede, Colorado. The primary ore contains abundant chalcopyrite, sphalerite, and pyrite in addition to a complex precious metal assemblage. Gold and silver occur principally as minute grains of telluride minerals disseminated in quartz-chlorite-hematite and as inclusions in chalcopyrite and sphalerite. Telluride minerals include petzite, hessite, and sylvanite. Free gold is present but not abundant. All of the vein-quartz samples contained abundant, minute inclusions of both low-density, vapor-rich fluids and liquid-rich fluids. Primary fluid inclusions yielded homogenization temperatures of from 110? to 238? C. Preliminary light-stable isotope studies of the sulfide minerals and quartz showed that all of the d34S values are between 1.2 and 6.3 per mil, which is a typical range for hydrothermal sulfide minerals that derive their sulfur from an igneous source. The data-suggest that the sulfide sulfur isotope geochemistry was controlled by exchange with la large sulfur isotope

  17. The role of decarbonization and structure in the Callie gold deposit, Tanami Region of northern Australia

    NASA Astrophysics Data System (ADS)

    Williams, Nicholas C.

    2007-01-01

    The Callie deposit is the largest (6.0 Moz Au) of several gold deposits in the Dead Bullock Soak goldfield of the Northern Territory’s Tanami Region, 550 km northwest of Alice Springs. The Callie ore lies within corridors, up to 180 m wide, of sheeted en echelon quartz veins where they intersect the 500-m-wide hinge of an ESE-plunging F1 anticlinorium. The host rocks are the Blake beds, of the Paleoproterozoic Dead Bullock Formation, which consist of a > 350-m-thick sequence of lower greenschist facies graphitic turbidites and mudstones overlying in excess of 100 m of thickly bedded siltstones and fine sandstones. The rocks are Fe-rich and dominated by assemblages of chlorite and biotite, both of which are of hydrothermal and metamorphic origin. A fundamental characteristic of the hydrothermal alteration is the removal of graphite, a process which is associated with bleaching and the development of bedding-parallel bands of coarse biotite augen. Gold is found only in quartz veins and only where they cut decarbonized chloritic rock with abundant biotite augen and no sulfide minerals. Auriferous quartz veins differ from barren quartz veins by the presence of ilmenite, apatite, xenotime, and gold and the absence of sulfide minerals. The assemblage of gold-ilmenite-apatite-xenotime indicates a linked genesis and mobility of Ti, P, and Y in the mineralizing fluids. Geochemical analysis of samples throughout the deposit shows that gold only occurs in sedimentary rocks with high FeO/(FeO+Fe2O3) and low C/(C+CO2) ratios (> 0.8 and < 0.2, respectively). This association can be explained by reactions that convert C from reduced graphitic host rocks into CO2 and reduce ferric iron in the host rocks to ferrous iron in biotite and chlorite. These reactions would increase the CO2 content of the fluid, facilitating the transport of Ti, P, and Y from the host rocks into the veins. Both CO2 and CH4 produced by reaction of H2O with graphite, effervesced under the lower confining

  18. The transition from porphyry- to epithermal-style gold mineralization at Ladolam, Lihir Island, Papua New Guinea: a reconnaissance study

    NASA Astrophysics Data System (ADS)

    Müller, Daniel; Kaminski, Klaus; Uhlig, Stephan; Graupner, Torsten; Herzig, Peter M.; Hunt, Steve

    2002-02-01

    The exceptionally large gold resource at Ladolam (>1,300 metric tons of gold), Lihir Island, resulted from the transition of an early-stage, low-grade porphyry gold system to a low-sulfidation epithermal gold event. This transition was probably triggered by rapid decompression during the partial slope failure of Luise stratovolcano and accompanied by the ingress of seawater. The original porphyry stage is indicated by remnant hydrothermal breccia clasts of strongly biotite-magnetite altered monzodiorite with disseminated pyrite ± chalcopyrite and poorly developed pyrite ± quartz stockwork veins. The breccias are overprinted by biotite-magnetite alteration and their matrix is strongly mineralized with disseminated auriferous pyrite. The breccias are cut by late-stage epithermal quartz-chalcedony-illite-adularia-pyrite veins and associated illite-adularia alteration that locally contain bonanza gold grades of up to 120 g/t. Isotope data suggest a magmatic source of sulfur in the gold-bearing fluids at Ladolam. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00126-001-0230-y

  19. Multistage gold mineralization in the Wa-Lawra greenstone belt, NW Ghana: The Bepkong deposit

    NASA Astrophysics Data System (ADS)

    Amponsah, Prince Ofori; Salvi, Stefano; Didier, Béziat; Baratoux, Lenka; Siebenaller, Luc; Jessell, Mark; Nude, Prosper Mackenzie; Gyawu, Eugene Adubofour

    2016-08-01

    The Bepkong gold deposit is one of several gold camps in the Paleoproterozoic Wa-Lawra greenstone belt in northwest Ghana. These deposits lay along the Kunche-Atikpi shear zone, which is part of the larger transcurrent Jirapa shear zone. The formation of these shear zones can be attributed to the general ESE-WNW major shortening that took place in the Wa-Lawra belt. Gold mineralization in the Bepkong deposit mainly occurs within graphitic shales and volcaniclastic rocks. The ore consists of four N-S trending lenticular bodies, plunging steeply to the south, that are lithologically and structurally controlled. Their shape and thickness are variable, though a general strike length of 560 m and an overall thickness of 300 m can be defined. An alteration mineral assemblage characterises the ore, and consists of chlorite-calcite-sericite-quartz-arsenopyrite-pyrite. Pyrite, as distinct from arsenopyrite, is not limited to the altered rocks and occurs throughout the area. At Bepkong, gold is associated with arsenopyrite and pyrite, which occur disseminated in the mineralized wall rock, flanking Type-1 quartz veins, or within fractures crossing these veins. Textural observations indicate the early formation of abundant arsenopyrite, followed by pyrite, with chalcopyrite, galena, sphalerite and pyrrhotite occurring as inclusions within pyrite and altered arsenopyrite. Detailed petrography, coupled with SEM, LA-ICP-MS and EMP analyses, indicate that gold in the Bepkong deposit occurs in three distinct forms: (i) invisible gold, mostly in arsenopyrite (ii); visible gold as micron-size grains within fractures and altered rims of arsenopyrite, as well as at the interface of sulphide grains; (iii) free visible gold in fractures in quartz veins and their selvages. We interpret the invisible gold to have co-precipitated with the early-formed arsenopyrite. The small visible gold grains observed within the sulphide interfaces, altered arsenopyrite, fractures and grain boundaries

  20. Quartz ball value

    NASA Technical Reports Server (NTRS)

    Goetz, C.; Ingle, W. M.

    1979-01-01

    Quartz ball valve consisting of two quartz joints sealed back-to-back and seated in quartz sockets perform at temperatures of up to 1,250 C and in corrosive chemical environments without contamination or degradation.

  1. Metamorphism and gold mineralization in the Blue Ridge, Southernmost Appalachians

    USGS Publications Warehouse

    Stowell, H.H.; Lesher, C.M.; Green, N.L.; Sha, P.; Guthrie, G.M.; Sinha, A.K.

    1996-01-01

    Lode gold mineralization in the Blue Ridge of the southernmost Appalachians is hosted by metavolcanic rocks (e.g., Anna Howe mine, AL; Royal Vindicator mine, GA), metaplutonic rocks (e.g., Hog Mountain mine, AL), and metasedimentary rocks (e.g., Lowe, Tallapoosa, and Jones Vein mines, AL). Most gold occurs in synkinematic quartz ?? plagioclase ?? pyrite ?? pyrrhotite ?? chlorite veins localized along polydeformational faults that juxtapose rocks with significantly different peak metamorphic mineral assemblages. Mineralogy, chemistry, and O and H isotope studies suggest that the three types of host rocks have undergone differing amounts and types of alteration during mineralization. Limited wall-rock alteration in metavolcanic- and metasediment-hosted deposits, and relatively extensive wall-rock alteration in granitoid-hosted deposits, suggests that most deposits formed from fluids that were close to equilibrium with metavolcanic and metasedimentary rocks. Stable isotope compositions of the fluids calculated from vein minerals and vein selvages are consistent with a predominantly metasedimentary fluid source, but vary from deposit to deposit (-22 to -47??? ??D, 4-5??? ??18O, and 5-7??? ??34S at Anna Howe and Royal Vindicator; -48 to -50??? ??D, 9-13??? ??18O, and ca. 19??? ??34S at Lowe and Jones Vein; and -22 to -23??? ??D, 8-11??? ??18O, 9-10??? ??34S, and -6 ??13C at Hog Mountain). Silicate mineral thermobarometry of vein, vein selvage, and wall-rock mineral assemblages indicate that mineralization and regional metamorphism occured at greenschist to amphibolite facies (480?? ?? 75??C at Anna Howe, 535?? ?? 50??C at 6.4 ?? 1 kbars at Lowe, 530?? ?? 50??C at 6.9 ?? 1 kbars at Tallapoosa, and 460?? ?? 50??C at 5.5 ?? 1 kbars at Hog Mountain). Oxygen isotope fractionation between vein minerals and selvage minerals consistently records equilibration temperatures that are similar to or slightly lower than those estimated from silicate thermometry. Auriferous veins

  2. Textures, trace elements, and Pb isotopes of sulfides from the Haopinggou vein deposit, southern North China Craton: implications for discrete Au and Ag-Pb-Zn mineralization

    NASA Astrophysics Data System (ADS)

    Li, Zhan-Ke; Li, Jian-Wei; Cooke, David R.; Danyushevsky, Leonid; Zhang, Lejun; O'Brien, Hugh; Lahaye, Yann; Zhang, Wen; Xu, Hai-Jun

    2016-12-01

    The Haopinggou deposit in the Xiong'ershan district, southern margin of the North China Craton, comprises numerous Au and Ag-Pb-Zn veins hosted in metamorphic rocks of the Late Archean to early Paleoproterozoic Taihua Group. Two stages of mineralization have been recognized: Stage 1 pyrite-quartz veins and Stage 2 Pb-Zn-sulfide veins. Some pyrite-quartz veins are surrounded or cut by Pb-Zn-sulfide veins, others occur as independent veins. Six generations of pyrite have been identified at Haopinggou: Py1 to Py3 in Stage 1 and Py4 to Py6 in Stage 2. Pyrites from Stage 1 are enriched in Au, As, Co, Ni, and Bi, whereas Stage 2 pyrites contain higher Ag, Pb, Zn, Sn, and Sb. Invisible Au mostly occurs as lattice-bound gold in Py2 (up to 92 ppm Au) and Py3 (up to 127 ppm Au) and has a close relationship with As. Native Au grains are also present in Py3 and likely resulted from mobilization and reprecipitation of the invisible Au previously locked in the precursor pyrite. This view is supported by extensive plastic deformation in Stage 1 pyrite as revealed by electron backscatter diffraction analysis. In Stage 2, Ag is mostly present as lattice-bound silver closely associated with Sb in galena (up to 798 ppm Ag). A variety of silver minerals are also present as inclusions within galena or as interstitial grains. These silver minerals were likely formed via Ag-Cu exchange reaction between tetrahedrite and galena or represent exsolution from galena due to a temperature decrease. Pb isotopic compositions differ remarkably between Stage 1 and Stage 2 sulfides, indicating different sources of lead. Pb in Stage 2 Pb-Zn-sulfide veins is consistent with the Haopinggou porphyry close to the veins. The field, textural, compositional, and lead isotopic data led us to conclude that the early gold-bearing pyrite-quartz veins and late silver-bearing Pb-Zn-sulfide veins likely formed from distinct fluid systems related to discrete mineralization events. Our study suggests that Au and Ag

  3. Spider Veins

    MedlinePlus

    ... Stretch Marks Sun-damaged Skin Unwanted Hair Unwanted Tattoos Varicose Veins Vitiligo Wrinkles Treatments and Procedures Ambulatory ... Stretch Marks Sun-damaged Skin Unwanted Hair Unwanted Tattoos Varicose Veins Vitiligo Wrinkles Treatments and Procedures Ambulatory ...

  4. Gold deposits and occurrences of the Greater Caucasus, Georgia Republic: Their genesis and prospecting criteria

    USGS Publications Warehouse

    Kekelia, S.A.; Kekelia, M.A.; Kuloshvili, S.I.; Sadradze, N.G.; Gagnidze, N.E.; Yaroshevich, V.Z.; Asatiani, G.G.; Doebrich, J.L.; Goldfarb, R.J.; Marsh, E.E.

    2008-01-01

    The south-central part of the Greater Caucasus region, Georgia Republic, represents an extremely prospective region for significant orogenic gold deposits. Gold-bearing quartz veins are concentrated in two extensive WNW-trending belts, the Mestia-Racha and Svaneti districts, within the northern margin of the Southern Slope Zone of the Great Caucasus orogen. This metalliferous region is dominated by Early to Middle Jurassic slates, which are part of a terrane that likely accreted to the continental margin from late Paleozoic to Jurassic. The slates were subsequently intruded by both Middle to Late Jurassic and Neogene granitoids. Quartz veins in the more carbonaceous slate units are most consistently enriched in As, Au, Hg, Sb, and W, and show mineralization styles most consistent with typical orogenic gold deposits. Quartz veins in the Mestia-Racha district were mined in Soviet times for As, Sb, and W, but many of these are now being recognized as gold resource targets. The veins occur in the footwall of a thrust fault between the Southern Slope zone and an earlier accreted terrane, the Main Zone, to the north. Many veins in the district continue along strike for > 1??km and some cut Neogene intrusions, constraining ore formation to the most recent 4 to 5??million years. Gold deposition thus correlates with final collision of the Arabian plate to the south and uplift of the ore-hosting Greater Caucasus. The Zopkhito deposit, previously mined for antimony, contains an estimated 55??t Au at a cutoff grade of 0.5??g/t. The veins are localized in an area where smaller-order structures show a major change in strike from N-S to more E-W trends. A pyrite-arsenopyrite ore stage includes gold concentrated in both sulfide phases; it is overprinted by a later stibnite-dominant stage. Fluid-inclusion studies of ore samples from the Zopkhito deposit indicate minimum trapping temperatures of 300 to 350????C and 200 to 300????C for the two stages, respectively, and minimum

  5. Antimony and arsenic behaviours in soils from three abandoned gold mining areas in northern Portugal

    NASA Astrophysics Data System (ADS)

    Carvalho, Paula; Neiva, Ana; Silva, Maria

    2013-04-01

    The Valongo anticline located 18 km at East of Porto is characterized by the occurrence of several gold deposits, which were exploited until the end of the nineteenth century. This anticline comprises Cambrian to Carboniferous metasediments. The Cambrian schist-graywacke complex crops out in the western limb of the anticline and is intersected by several Sb-Au quartz veins, mainly Montalto and Tapada. At the eastern limb of the anticline, As-Au quartz veins cut Ordovician black slates and were exploited at the Banjas mine. The Sb-Au quartz veins contain mainly quartz, arsenopyrite, pyrrhotite, pyrite, marcasite, sphalerite, chalcophyrite, galena, gold, tetrahedrite, jamesonite, plagionite, berthierite, stibnite, antimony and carbonates. The As-Au quartz veins consist of quartz, arsenopyrite, pyrite, pyrrhotite, cobaltite, glaucodote, sphalerite, boulangerite, tetrahedrite and siderite. Stibnite and arsenopyrite are the most abundant sulphides in Sb-Au and As-Au quartz veins, respectively. Therefore, antimony and arsenic are potential contaminants in the surrounding environments of these old mines. The principal component analysis (PCA) was applied to organic matter, pH, cation exchange capacity, clay size particle and reducible, oxidizable and aqua regia Fe, Mn, As and Sb concentrations obtained by the BCR method in 29 soil samples. The PCA shows a substantial distinction between Sb and As behaviours in soils from the old mining areas of Montalto, Tapada and Banjas. The arsenic concentration ranges between 16.98 mg/kg and 1116 mg/kg, whereas the Sb concentration ranges from 6.4 mg/kg to 21775 mg/kg. The antimony is statistically more correlated with Fe and Mn in the oxides fraction, whereas As in the reducible fraction dependents on pH values. Moreover, Fe and Mn concentrations in the oxidizable fraction are highly correlated with the organic matter, suggesting that pyrite, the main host mineral of Fe, was probably totally altered. However, the As concentration in

  6. Geologic and isotopic investigation of the South Willow creek gold prospect, Madison County, Montana

    SciTech Connect

    Saunders, M.M.; Ripley, E.M.

    1985-01-01

    The South Willow Creek gold prospect is located in the southwestern part of the Potosi tungsten district, southwest Montana. Gold-quartz veins occur in the Bismark shear zone within granodiorite host rocks of the late Cretaceous-early Tertiary Tobacco Root batholith. Four well developed zones of progressive alteration are found adjacent to faults and veins in the area. Gold occurs in solid solution with silver as inclusion in pyrite and alone with quartz. The highest gold assay values occur closest to the Bismark shear zone. Sulfur isotope values for pyrite, galena, and molybdenum range from -6.5 to +1.7 per thousands. Pyrite-galena and pyrite-molybdenum ..delta.. values indicate sulfide deposition temperatures ranging from 220 to 265/sup 0/C. Isotopic values suggest that deposition occurred from a fluid with a delta/sup 34/S value of near 0 per thousand, at redox conditions near those of the ..sigma..sulfate/..sigma..sulfide boundary. Mineral assemblages and delta/sup 34/S values are consistent with gold transport as a chloride complex under acid oxidizing conditions. Increases in pH and decreases in temperature accompanying wallrock alteration are the likely causes of gold deposition. Sericite deltaD values are variable, ranging from -69 to -136 per thousand. Computed delta/sup 18/O/sub H/sub 2/O/ and deltaD/sub H/sub 2/O/ values are most easily interpreted as indicating a predominantly magmatic fluid source, with locally variable contributions of meteoric water. However, non-equilibrium delta/sup 18/O values of coexisting quartz and sericite, and the deltaD values of sericite, both suggest that isotopic exchange rates were variable, and limit the unambiguous determination of fluid source.

  7. Vein Problems Related to Varicose Veins

    MedlinePlus

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

  8. 43 CFR 3864.1-3 - Millsites for quartz mills or reduction works.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Millsites for quartz mills or reduction... APPLICATIONS Millsite Patents § 3864.1-3 Millsites for quartz mills or reduction works. In case the owner of a quartz mill or reduction works is not the owner or claimant of a vein or lode claim the law permits...

  9. 43 CFR 3864.1-3 - Millsites for quartz mills or reduction works.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Millsites for quartz mills or reduction... APPLICATIONS Millsite Patents § 3864.1-3 Millsites for quartz mills or reduction works. In case the owner of a quartz mill or reduction works is not the owner or claimant of a vein or lode claim the law permits...

  10. 43 CFR 3864.1-3 - Millsites for quartz mills or reduction works.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Millsites for quartz mills or reduction... APPLICATIONS Millsite Patents § 3864.1-3 Millsites for quartz mills or reduction works. In case the owner of a quartz mill or reduction works is not the owner or claimant of a vein or lode claim the law permits...

  11. 43 CFR 3864.1-3 - Millsites for quartz mills or reduction works.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Millsites for quartz mills or reduction... APPLICATIONS Millsite Patents § 3864.1-3 Millsites for quartz mills or reduction works. In case the owner of a quartz mill or reduction works is not the owner or claimant of a vein or lode claim the law permits...

  12. Noble Gases in Alpine Gold: U/Th-He Dating and Excesses of Radiogenic He and AR

    NASA Astrophysics Data System (ADS)

    Eugster, O.; Hofmann, B.; Krahenbuhl, U.; Neuenschwander, J.

    1992-07-01

    Gold precipitates in hydrothermal fluids along with other heavy elements, such as Ag and Pt. In order to explore the possibility of dating the formation of gold we determined the concentrations of U, Th, and their decay product ^4He, as well as the K and ^40Ar concentrations in vein-type gold and in placer gold samples. The gold-quartz veins at Brusson in the south-western alps were formed approximately 32 Ma ago during an episode of tectonic uplift (Diamond, 1990). Alpine material was deposited as sediment layers in the region of central Switzerland and placer gold is thus relatively abundant in the rivers of the Napf area. We washed placer gold from the river Grosse Fontanne in 1990 and 1991. Placer gold that had been collected from the river Kruempelgraben in 1933 and a sample of vein-type free gold grown on quartz rock from the Brusson area (Val d'Ayas) have been obtained from the Museum of Natural History in Bern. Table 1 gives the results. Most of the ^4He is released above 1050 degrees C, that is when gold melts, indicating that gold is extremely well retentive for He. From the ^4He concentration of (269 +- 20) x 10^-8 cm^3 STP/g, (0.4 +- 0.1) ppm U, and (0.9 +- 0.3) ppm Th for vein-type gold we calculate a U/Th-He age of (36 +- 8)Ma. This age agrees within errors with the proposed age of 32 Ma. The data given in Table 1 show that all placer gold samples contain excesses of radiogenic ^4He and ^40Ar relative to the concentrations expected from the U/Th and K decay, respectively, if we assume a formation age of 32 Ma. The quartz sample is depleted in ^4He but strongly enriched in radiogenic ^40Ar. The excess of ^40Ar(sub)rad is easier to explain than that of ^4He. Vein-type gold and placer gold contain quartz inclusions (Schmid, 1973). The high ^40Ar(sub)rad content of quartz (Table 1) indicates that the ^40Ar(sub)rad excess of gold originates from quartz inclusions. Excess ^4He in gold must be of radiogenic origin. Taking ^20Ne and ^36Ar as a measure for the

  13. Stable Isotopes (O, H, and S) in the Muteh Gold Deposit, Golpaygan Area, Iran

    SciTech Connect

    Abdollahi, M. J. Karimpour, M. H.; Kheradmand, A.; Zarasvandi, A. R.

    2009-06-15

    The Muteh gold district with nine gold deposits is located in the Sanandaj-Sirjan metamorphic zone. Gold mineralization occurs in a pre-Permian complex which mainly consists of green schists, meta-volcanics, and gneiss rocks. Shear zones are the host of gold mineralization. Gold paragenesis minerals include pyrite, chalcopyrite, pyrrhotite, and secondary minerals. Pyrites occur as pre-, syn-, and post-metamorphism minerals. To determine the source of the ore-bearing fluids, fifty samples were selected for petrographical and stable isotope studies. The mean values of 12.4 per mille , and -42 per mille for {delta}{sup 18}O and {delta}D isotopes, respectively, and a mean value of 7.75 per mille of calculated fractionation factors for {delta}{sup 18}O H{sub 2}O, from quartz veins indicate that metamorphic host rocks are the most important source for the fluids and gold mineralization. Three generations of pyrite can be distinguished showing a wide range of {delta}{sup 34}S. Gold mineralization is closely associated with intense hydrothermal alteration along the ductile shear zones. The characteristics of the gold mineralization in the study area are similar to those of orogenic gold deposits elsewhere.

  14. Orogenic gold deposits: a proposed classification in the context of their crustal distribution and relationship to other gold deposit types

    USGS Publications Warehouse

    Groves, D.I.; Goldfarb, R.J.; Gebre-Mariam, M.; Hagemann, S.G.; Robert, F.

    1998-01-01

    The so-called 'mesothermal' gold deposits are associated with reginally metamorphosed terranes of all ages. Ores were formed during compressional to transpressional deformation processes at convergent plate margins in accretionary and collisional orogens. In both types of orogen, hydrated marine sedimentary and volcanic rocks have been added to continental margins during tens to some 100 million years of collision. Subduction-related thermal events, episodically raising geothermal gradients within the hydrated accretionary sequences, initiate and drive long-distance hydrothermal fluid migration. The resulting gold-bearing quartz veins are emplaced over a unique depth range for hydrothermal ore deposits, with gold deposition from 15-20 km to the near surface environment. On the basis of this broad depth range of formation, the term 'mesothermal' is not applicable to this deposit types as a whole. Instead, the unique temporal and spatial association of this deposit type with orogeny means that the vein systems are best termed orogenic gold deposits. Most ores are post-orogenic with respect to to tectonism of their immediate host rocks, but are simultaneously syn-orogenic with respect to ongoing deep-crustal, subduction-related thermal processes and the prefix orogenic satisfies both these conditions. On the basis of their depth of formation, the orogenic deposits are best subdivided into epizonal (12 km) classes.

  15. Electromagnetic, magnetic, and gravimetric surveys at the Bi'r Jarbuah gold prospect, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Miller, C.H.; Showail, A.A.; Bazzari, M.A.; Khoja, J.A.; Hajour, M.O.

    1990-01-01

    A detailed search for gold and associated minerals was begun in the Bi'r Jarbuah area in 1988. Crone electromagnetic (CEM), magnetic, and gravimetric surveys were run in the areas of greatest interest. Anomalous areas are most interesting in the southern part of the area where linear magnetic and gravity anomalies trend east-northeast and overlap in large part. They are most prominent at or near the south end of a diorite pluton where some quartz veins mined by the ancients also trend northeast. A second area, at the extreme southern end of the survey, contains a large CEM anomaly that coincides with northeast-trending magnetic and gravity anomalies. Although this second area is largely overlain by alluvium, a major quartz vein strikes to the northeast in the adjacent bedrock.

  16. Structural geology mapping using PALSAR data in the Bau gold mining district, Sarawak, Malaysia

    NASA Astrophysics Data System (ADS)

    Pour, Amin Beiranvand; Hashim, Mazlan

    2014-08-01

    The application of optical remote sensing data for geological mapping is difficult in the tropical environment. The persistent cloud coverage, dominated vegetation in the landscape and limited bedrock exposures are constraints imposed by the tropical climate. Structural geology investigations that are searching for epithermal or polymetallic vein-type ore deposits can be developed using Synthetic Aperture Radar (SAR) remote sensing data in tropical/sub-tropical regions. The Bau gold mining district in the State of Sarawak, East Malaysia, on the island of Borneo has been selected for this study. The Bau is a gold field similar to Carlin style gold deposits, but gold mineralization at Bau is much more structurally controlled. Geological analyses coupled with the Phased Array type L-band Synthetic Aperture Radar (PALSAR) remote sensing data were used to detect structural elements associated with gold mineralization. The PALSAR data were used to perform lithological-structural mapping of mineralized zones in the study area and surrounding terrain. Structural elements were detected along the SSW to NNE trend of the Tuban fault zone and Tai Parit fault that corresponds to the areas of occurrence of the gold mineralization in the Bau Limestone. Most of quartz-gold bearing veins occur in high-angle faults, fractures and joints within massive units of the Bau Limestone. The results show that four deformation events (D1-D4) in the structures of the Bau district and structurally controlled gold mineralization indicators, including faults, joints and fractures are detectable using PALSAR data at both regional and district scales. The approach used in this study can be more broadly applicable to provide preliminary information for exploration potentially interesting areas of epithermal or polymetallic vein-type mineralization using the PALSAR data in the tropical/sub-tropical regions.

  17. Gold distribution in As-deficient pyrite and telluride mineralogy of the Yangzhaiyu gold deposit, Xiaoqinling district, southern North China craton

    NASA Astrophysics Data System (ADS)

    Bi, Shi-Jian; Li, Jian-Wei; Zhou, Mei-Fu; Li, Zhan-Ke

    2011-12-01

    The Mesozoic Yangzhaiyu lode gold deposit is situated in the southern edge of the North China craton. Gold mineralization is hosted in Archean amphibolite facies metamorphic rocks, and consists mainly of auriferous quartz veins. Pyrite is the predominant sulfide mineral, with minor amounts of chalcopyrite, sphalerite, and galena. Based on morphology and paragenesis, there are three generations of pyrite, termed as first generation (G1), second generation (G2), and third generation (G3). They have distinct contents, occurrences, and distribution patterns of gold. The coarse-grained, euhedral G1 pyrite contains negligible to low levels of gold, whereas both invisible and visible gold are present in the fine- to medium-grained G2 pyrite that is characterized by abundance of microfractures and porosities, forming a foam-like texture. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) depth profiles indicate that invisible gold occurs either as solid solution or as nanoparticles of gold-bearing tellurides in the G2 pyrite. Visible gold is widespread and present as irregular grains and stringers of native gold mostly along grain boundaries or filling microfractures of pyrite, likely resulting from remobilization of invisible gold once locked in the G2 pyrite. The G3 pyrite, invariably intergrown with chalcopyrite, sphalerite, and galena, contains the highest levels of invisible gold. There is a positive correlation between Au, Ag, and Te, indicating that gold occurs as submicroscopic Au-bearing telluride inclusions in the host minerals. Whenever gold, either invisible or visible, is present, As is always below or only marginally higher than the detection limit of LA-ICP-MS. This indicates that As played an insignificant role in gold mineralization. Tellurides are widespread in the auriferous quartz veins, consisting mainly of petzite, calaverite, hessite, altaite, and tellurobismuthite. Native gold commonly occurs as intergrowths with tellurides

  18. Orogenic gold mineralisation hosted by Archaean basement rocks at Sortekap, Kangerlussuaq area, East Greenland

    NASA Astrophysics Data System (ADS)

    Holwell, D. A.; Jenkin, G. R. T.; Butterworth, K. G.; Abraham-James, T.; Boyce, A. J.

    2013-04-01

    A gold-bearing quartz vein system has been identified in Archaean basement rocks at Sortekap in the Kangerlussuaq region of east Greenland, 35 km north-northeast of the Skaergaard Intrusion. This constitutes the first recorded occurrence of Au mineralisation in the metamorphic basement rocks of east Greenland. The mineralisation can be classified as orogenic style, quartz vein-hosted Au mineralisation. Two vein types have been identified based on their alteration styles and the presence of Au mineralisation. Mineralised type 1 veins occur within sheared supracrustal units and are hosted by garnet-bearing amphibolites, with associated felsic and ultramafic intrusions. Gold is present as native Au and Au-rich electrum together with arsenopyrite and minor pyrite and chalcopyrite in thin alteration selvages in the immediate wall rocks. The alteration assemblage of actinolite-clinozoisite-muscovite-titanite-scheelite-arsenopyrite-pyrite is considered to be a greenschist facies assemblage. The timing of mineralisation is therefore interpreted as being later and separate event to the peak amphibolite facies metamorphism of the host rocks. Type 2 quartz veins are barren of mineralisation, lack significant alteration of the wall rocks and are considered to be later stage. Fluid inclusion microthermometry of the quartz reveals three separate fluids, including a high temperature ( T h = 300-350 °C), H2O-CO2-CH4 fluid present only in type 1 veins that in interpreted to be responsible for the main stage of Au deposition and sulphidic wall rock alteration. It is likely that the carbonic fluids were actually trapped at temperatures closer to 400 °C. Two other fluids were identified within both vein types, which comprise low temperature (100-200 °C) brines, with salinities of 13-25 wt% eq. NaCl and at least one generation of low salinity aqueous fluids. The sources and timings of the secondary fluids are currently equivocal but they may be related to the emplacement of

  19. Sclerotherapy of Varicose Veins and Spider Veins

    MedlinePlus

    ... Index A-Z Sclerotherapy of Varicose Veins and Spider Veins Sclerotherapy uses injections from a very fine, ... Sclerotherapy? What is Sclerotherapy of Varicose Veins and Spider Veins? Sclerotherapy is a minimally invasive treatment used ...

  20. Orogenic-type copper-gold-arsenic-(bismuth) mineralization at Flatschach (Eastern Alps), Austria

    NASA Astrophysics Data System (ADS)

    Raith, Johann G.; Leitner, Thomas; Paar, Werner H.

    2015-10-01

    Structurally controlled Cu-Au mineralization in the historic Flatschach mining district (Styria, Austria) occurs in a NE-SW to NNE-WSW oriented vein system as multiple steep-dipping calcite-(dolomite)-quartz veins in amphibolite facies metamorphic rocks (banded gneisses/amphibolites, orthogneisses, metagranitoids) of the poly-metamorphosed Austroalpine Silvretta-Seckau nappe. Vein formation postdated ductile deformation events and Eoalpine (Late Cretaceous) peak metamorphism but predated Early to Middle Miocene sediment deposition in the Fohnsdorf pull-apart basin; coal-bearing sediments cover the metamorphic basement plus the mineralized veins at the northern edge of the basin. Three gold-bearing ore stages consist of a stage 1 primary hydrothermal (mesothermal?) ore assemblage dominated by chalcopyrite, pyrite and arsenopyrite. Associated minor minerals include alloclasite, enargite, bornite, sphalerite, galena, bismuth and matildite. Gold in this stage is spatially associated with chalcopyrite occurring as inclusions, along re-healed micro-fractures or along grain boundaries of chalcopyrite with pyrite or arsenopyrite. Sericite-carbonate alteration is developed around the veins. Stage 2 ore minerals formed by the replacement of stage 1 sulfides and include digenite, anilite, "blue-remaining covellite" (spionkopite, yarrowite), bismuth, and the rare copper arsenides domeykite and koutekite. Gold in stage 2 is angular to rounded in shape and occurs primarily in the carbonate (calcite, Fe-dolomite) gangue and less commonly together with digenite, domeykite/koutekite and bismuth. Stage 3 is a strongly oxidized assemblage that includes hematite, cuprite, and various secondary Cu- and Fe-hydroxides and -carbonates. It formed during supergene weathering. Stage 1 and 2 gold consists mostly of electrum (gold fineness 640-860; mean = 725; n = 46), and rare near pure gold (fineness 930-940; n = 6). Gold in stage 3 is Ag-rich electrum (fineness 350-490, n = 12), and has a

  1. Mineralogy, mineral chemistry, and paragenesis of gold, silver, and base-metal ores of the North Amethyst vein system, San Juan Mountains, Mineral County, Colorado

    USGS Publications Warehouse

    Foley, Nora K.; Caddey, Stanton W.; Byington, Craig B.; Vardiman, David M.

    1993-01-01

    Mineralogic, lead-isotopic, and fluid-inclusion characteristics of the younger association are similar to those of ores of the southern and central parts of the Creede mining district. In contrast, the gold and manganese-silicate assemblages of the older association are rare to absent in the southern and central parts of the district. The local and early occurrence of the manganese and gold assemblages may indicate that they formed in a small hydrothermal cell that predated the extensive hydrothermal system from which ores of the central and southern parts of the Creede district are proposed to have been deposited (Bethke, 1988). If similar early-stage cells were present in the southern and central parts of the district, they may have been replaced or overprinted by later assemblages, and they may remain to be discovered. In the latter case, mineral assemblages that formed at early stages in the paragenesis hold the most promise for gold exploration.

  2. Geology, mineralization, and geochronology of the Qianhe gold deposit, Xiong'ershan area, southern North China Craton

    NASA Astrophysics Data System (ADS)

    Tang, Ke-Fei; Li, Jian-Wei; Selby, David; Zhou, Mei-Fu; Bi, Shi-Jian; Deng, Xiao-Dong

    2013-08-01

    The Qianhe gold deposit in the Xiong'ershan area is located along the southern margin of the Archean-Paleoproterozoic North China Craton. The deposit consists of six orebodies that are hosted in Paleoproterozoic andesites to basaltic andesites and structurally controlled by roughly EW-trending faults. Individual orebodies comprise auriferous quartz veins and disseminated Au-bearing pyrite within hydrothermally altered rocks on both sides of, or close to, the veins. Ore-related hydrothermal alteration has produced various mixtures of K-feldspar, quartz, sericite, chlorite, epidote, carbonate, and sulfides. Pyrite is the most important ore mineral, associated with minor amounts of galena, sphalerite, and chalcopyrite. Other trace minerals include molybdenite, arsenopyrite, scheelite, rutile, xenotime, and parisite. Gold occurs mostly as native gold and electrum enclosed in pyrite or along microfractures of sulfides and quartz. Microthermometric measurements of primary inclusions in auriferous quartz suggest that gold and associated minerals were precipitated in the range of 160-305 °C from aqueous or carbonic-aqueous fluids with salinities of 6-22 wt% NaCl equiv. Samples of molybdenite coexisting with Au-bearing pyrite have Re-Os model ages of 134-135 Ma, whereas ore-related hydrothermal sericite separates yield 40Ar/39Ar plateau ages between 127 and 124 Ma. The Re-Os and 40Ar/39Ar ages are remarkably consistent with zircon U-Pb ages (134.5 ± 1.5 and 127.2 ± 1.4 Ma; 1 σ) of the biotite monzogranite from the Heyu-intrusive complex and granitic dikes in and close to the Qianhe gold mine, indicating a close temporal and thus possibly genetic relationship between gold mineralization and granitic magmatism in the area. Fluid inclusion waters extracted from auriferous quartz have δD values of -80 to -72 ‰, whereas the calculated δ 18OH2O values range from 3.1 to 3.8 ‰. The hydrogen and oxygen isotopes from this study and previous work indicate that ore fluids

  3. Invisible gold distribution on pyrite and ore-forming fluid process of the Huangshan orogenic-type gold deposit of Zhejiang, SE China: implications from mineralogy, trace elements, impurity and fluid inclusion studies

    NASA Astrophysics Data System (ADS)

    Sundarrajan, Vijay Anand; Li, Zilong; Hu, Yizhou; Fu, Xuheng; Zhu, Yuhuo

    2016-07-01

    The Huangshan orogenic-type gold deposit in Zhejiang of SE China occurred in quartz-pyrite veins. It is hosted by phyllonite that underwent greenschist-facies metamorphism along a large Jiangshan-Shaoxing tectonic belt with a NE-SW direction. Trace elemental characteristics, ore-forming process and invisible gold on different forms of pyrite and quartz are studied. The Au associated pyrite can be classified into two categories; recrystallized pyrite and euhedral pyrite. The precipitation of invisible Au on pyrite is mainly derived by Co and Ni with AuHS2 - complex in the mineralizing fluids in different events. The XPS results revealed that valence states of Au3+ replaced 2Fe2+ in the pyrite and Au0 replaced Si4+ in the quartz structure. The electron paramagnetic resonance and trace elemental results suggested that the element pairs of Ge-Li-Al in quartz and Mn-Co-Ni in pyrite have distinct impurities as identified. A fluid inclusion study showed that the auriferous quartz is characterized by low-saline and CO2-rich fluids. Coexistence of the type I-type III inclusions and same range of homogenization temperature with different mode are evidences of immiscible fluid process. The temperature-pressure values of ca. 250 °C/1250 bar and ca. 220 °C/780 bar for gold precipitation have been calculated by intersection of coexisting fluids during the entrapment. The Huangshan orogenic-type gold deposit may be associated with the Wuyi-Yunkai orogeny during the early Paleozoic, including an upper-mid greenschist-facies metamorphism (450-420 Ma). All the features suggest that the Huangshan gold deposit is probably a product linking with the early Paleozoic orogeny in South China.

  4. Iron isotope constraints on the mineralization processes of the Sandaowanzi telluride gold deposit, NE China

    NASA Astrophysics Data System (ADS)

    Li, Xingxing; Liu, Junlai; Lu, Di; Ren, Shunli; Liu, Zhengyang

    2016-04-01

    Iron isotopes have been widely applied to interpret the fluid evolution, supergene alteration and the metallogenic material sources of the hydrothermal deposit. It may also have significant potentials on the research of the deposit. The Sandaowanzi telluride gold deposit, located in the Great Hinggan Range metallogenic Belt in NE China, is a large epithermal gold deposit of low-sulphidation type. It has a total reserve of ≥25t of Au and an average of 15 g/t. Gold-bearing quartz veins or gold lodes strike to the NW and dip 50-80°northeastward. Ore bodies, including low-grade ores along margins and high-grade ores in the central parts, principally occur in quartz veins. More than the 95 percent Au budgets are hosted in gold-silver tellurides. A six-stage paragenetic sequence of mineralization is revealed according to the compositions and microstructures of the mineral assemblages. Although sulfide minerals in the bonanza quartz veins are rare, pyrite are widespread in quartz veins and altered host rocks. Meanwhile there are always chalcopyrite veins within bonanza quartz veins. Pyrite Fe isotope compositions from different levels (from +50m to +210m) of the main ore body of the Sandaowanzi gold ore deposit are investigated. There is an overall variation in δ57Fe values from -0.09 to +0.99 (av. 0.33). Among them, twenty three samples from different mining levels give positiveδ57Fe values, with the maximum positive value at the economic bonanza ores (level +130m). Four samples, however, possess negative values, one at level 170m, one at level 130m, and two at level 50m, respectively. The two negative values from the levels 170m and 130m are near the cores of the high grade ore body. The two negative values from the level 50m occur at one end of the lode ore body. The above data set shows that the δ57Fe values are not homogeneous at different levels of the ore body. On the other hand, a general trend for the positive values is that the highest δ57Fe value is

  5. Gold remobilisation and formation of high grade ore shoots driven by dissolution-reprecipitation replacement and Ni substitution into auriferous arsenopyrite

    NASA Astrophysics Data System (ADS)

    Fougerouse, Denis; Micklethwaite, Steven; Tomkins, Andrew G.; Mei, Yuan; Kilburn, Matt; Guagliardo, Paul; Fisher, Louise A.; Halfpenny, Angela; Gee, Mary; Paterson, David; Howard, Daryl L.

    2016-04-01

    Both gold-rich sulphides and ultra-high grade native gold oreshoots are common but poorly understood phenomenon in orogenic-type mineral systems, partly because fluids in these systems are considered to have relatively low gold solubilities and are unlikely to generate high gold concentrations. The world-class Obuasi gold deposit, Ghana, has gold-rich arsenopyrite spatially associated with quartz veins, which have extremely high, localised concentrations of native gold, contained in microcrack networks within the quartz veins where they are folded. Here, we examine selected samples from Obuasi using a novel combination of quantitative electron backscatter diffraction analysis, ion microprobe imaging, synchrotron XFM mapping and geochemical modelling to investigate the origin of the unusually high gold concentrations. The auriferous arsenopyrites are shown to have undergone partial replacement (∼15%) by Au-poor, nickeliferous arsenopyrite, during localised crystal-plastic deformation, intragranular microfracture and metamorphism (340-460 °C, 2 kbars). Our results show the dominant replacement mechanism was pseudomorphic dissolution-reprecipitation, driven by small volumes of an infiltrating fluid that had relatively low ƒS2 and carried aqueous NiCl2. We find that arsenopyrite replacement produced strong chemical gradients at crystal-fluid interfaces due to an increase in ƒS2 during reaction, which enabled efficient removal of gold to the fluid phase and development of anomalously gold-rich fluid (potentially 10 ppm or more depending on sulphur concentration). This process was facilitated by precipitation of ankerite, which removed CO2 from the fluid, increasing the relative proportion of sulphur for gold complexation and inhibited additional quartz precipitation. Gold re-precipitation occurred over distances of 10 μm to several tens of metres and was likely a result of sulphur activity reduction through precipitation of pyrite and other sulphides. We suggest

  6. Gangue mineral textures and fluid inclusion characteristics of the Santa Margarita Vein in the Guanajuato Mining District, Mexico

    NASA Astrophysics Data System (ADS)

    Moncada, Daniel; Bodnar, Robert

    2012-06-01

    Successful exploration for mineral deposits requires tools that the explorationist can use to distinguish between targets with high potential for mineralization and those with lower economic potential. In this study, we describe a technique based on gangue mineral textures and fluid inclusion characteristics that has been applied to identify an area of high potential for gold-silver mineralization in the epithermal Ag-Au deposits at Guanajuato, Mexico. The Guanajuato mining district in Mexico is one of the largest silver producing districts in the world with continuous mining activity for nearly 500 years. Previous work conducted on the Veta Madre vein system that is located in the central part of this district identified favorable areas for further exploration in the deepest levels that have been developed and explored. The resulting exploration program discovered one of the richest gold-silver veins ever found in the district. This newly discovered vein that runs parallel to the Veta Madre was named the Santa Margarita vein. Selected mineralized samples from this vein contain up to 249 g/t of Au and up to 2,280 g/t Ag. Fluid inclusions in these samples show homogenization temperatures that range from 184 to 300°C and salinities ranging from 0 to 5 wt.% NaCl. Barren samples show the same range in homogenization temperature, but salinities range only up to 3 wt.% NaCl. Evidence of boiling was observed in most of the samples based on fluid inclusions and/or quartz and calcite textures. Liquid-rich inclusions with trapped illite are closely associated with high silver grades. The presence of assemblages of vapor-rich-only fluid inclusions, indicative of intense boiling or "flashing", shows the best correlation with high gold grades.

  7. Geology of the Ishmas gold district, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Doebrich, Jeff L.; White, Willis M.

    1991-01-01

    The Ishmas gold district was mapped at 1:25,000 scale to place auriferous mineralization into geologic perspective, to assist in creating an ore-deposit model, and to aid in devising a strategy for subsequent exploration elsewhere in the Jabal Ishmas-Wadi Tathlith gold belt. The precratonic evolution of the district began with the deposition of a tholeiitic mafic volcanic and volcaniclastic sequence that was intruded by diabase and gabbro. Basaltic to rhyodacitic volcanism following a calc-alkaline evolutionary trend ensued. Subsequent deposition of a thick wacke and sandstone unit represented the final phase in the volcano sedimentary accumulation. The emplacement of a large lopolithic layered-gabbro complex marked the end of the precratonic evolutionary cycle. The district coincides with the boundary of two allochthonous terranes. The collisional Nabitah orogeny represents the suturing of the two terranes. The effects of this event are manifested by numerous north-trending, steeply dipping faults, shear zones, and mylonite belts, as well as diapiric serpentinite. During the waning stages of the orogeny, auriferous quartz pods were precipitated in dilatant structures within the north-trending shear zones by deep-seated circulating fluids. The emplacement of a tonalite stock was closely followed by the formation of N. 20°-35° W. -trending faults. These faults influenced the emplacement of dacite porphyry stocks and associated auriferous quartz veins. The auriferous veins are massive, tabular open-fracture fillings that are spatially, temporally, and genetically related to the dacite porphyry. The emplacement of a quartz monzodiorite stock was responsible for additional auriferous quartz vein mineralization that is almost exclusively hosted by the intrusion. A nearly random orientation of the veins indicates that no regional structure influenced their formation. The formation of a series of N. 60°-80° W -trending faults represents the final episode in the

  8. Structural and alteration controls on gold mineralization the of the amphibolite facies Detour Lake Deposit, Canada

    NASA Astrophysics Data System (ADS)

    Dubosq, Renelle; Schneider, David

    2016-04-01

    The 15M oz Detour Lake deposit is a Neoarchean orogenic gold ore body located in the northern most region of the Abitibi district within the Superior Province. The mine is an open pit design in the high strain zone of the Sunday Lake Deformation Zone (SLDZ). The ductile-brittle SLDZ parallels the broadly E-W Abitibi greenstone belt and the deposit is situated in a dilation zone between volcanoclastic rocks of the Caopatina Assemblage and Lower Detour Lake Formation, consisting of ultramafic talc-chlorite-sericite schist. The Upper Detour Lake Formation consists of pillowed and massive flows and hyloclastic units crosscut by minor felsic to intermediate dykes. All of the formations are sub-vertical, north-dipping units with stretching lineations indicating dip-slip motion. The Detour deposit differs from other classic ore deposits in the dominantly greenschist facies Abitibi Subprovince by possessing an amphibolite facies metamorphic assemblage of actinolite-biotite-plagioclase-almandine. Consequently, the typical indicator minerals used to identify alteration and mineralization, such as secondary biotite, may not be useful. Petrological and geochemical analyses have revealed at least four populations of biotite: 1) large euhedral crystals located within quartz-carbonate veins, 2) small, euhedral zoned crystals present as alteration haloes, 3) very small, anhedral to subhedral indistinct crystal present in mafic volcanic host rock, and 4) large euhedral crystals defining the main metamorphic foliation in the metasediments. Extensive examination of mineral assemblages, alteration products, and vein structure in rock core across barren and mineralized zones has documented over a dozen vein types which can be grouped into two main categories: 1) sulfidized quartz-carbonate veins associated with biotite alteration and 2) late carbonate veins. Gold grades do not prove to be dependent on vein type but rather on the host rock composition: the highest ore grades are present

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

    USGS Publications Warehouse

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

    1990-01-01

    The Palau and Yap arcs are part of an intra-oceanic island-arc-trench system which separates the Pacific and Philippine plates in the western Pacific Ocean. The 350-km-long Palau arc consists of over 200 islands while the 400-km-long Yap arc located to the north has only four major islands exposed. Four of the largest islands in Palau are composed primarily of early Eocene to mid-Miocene volcanic rocks and the four islands comprising Yap contain only Miocene volcanic rocks. Basalt and basaltic andesites of the Babelthuap Formation are the oldest volcanic rocks in Palau and are characterized by high MgO, Ni and Cr and low TiO2 and have a boninitic affinity. They form the central and southeastern parts of Babelthuap Island. Oligocene arc tholeiite flows having an age of 34-35.5 Ma comprise most of the three smaller volcanic islands in Palau and the western part of Babelthuap. The youngest volcanic rocks are dacitic intrusions having an age of 22.7-23.2 Ma. The Yap arc is unusual in that metamorphic rocks up to amphibolite grade form most of the islands. These are underlain by a melange composed of igneous and volcanic clasts as well as clasts from a dismembered copper-gold skarn deposit. Miocene volcanic rocks consisting of flows and volcaniclastic deposits overlie the melange and metamorphic complex. An epithermal precious-metal vein system hosted by flows and flow breccias of the Babelthuap Formation occurs in an area 1.5 km by 1 km on the southeast side of Babelthuap Island. Over 50 veins and mineralized breccias ranging up to 2 m in width and having a strike length up to 500 m contain from trace to 13.0 ppm gold. The veins consist of quartz with varying amounts of sulfides and iron oxides after sulfides and the mineralized breccias consist of brecciated country rock cemented by quartz and iron oxides after sulfides. The veins and mineralized breccias generally dip within 15?? of vertical and have two preferred orientations, north-northwest and north

  10. Geochemical constraints on the genesis of the Scheelite dome intrusion-related gold deposit, Tombstone gold belt, Yukon, Canada

    USGS Publications Warehouse

    Mair, J.L.; Goldfarb, R.J.; Johnson, C.A.; Hart, C.J.R.; Marsh, E.E.

    2006-01-01

    The Scheelite dome intrusion-related gold deposit, western Selwyn basin, Yukon, is hosted in hornfelsed metasedimentary strata that lie adjacent to the exposed apices of a monzogranite to quartz monzonite plutonic complex of the mid-Cretaceous Tombstone-Tungsten magmatic belt, Tintina gold province, Alaska and Yukon. A variety of mineralization styles occur throughout a 10- ?? 3-km east-trending corridor and include reduced Au- and W-rich skarns, Au, W- and Ag-Pb-Zn-Sb-rich quartz tension-vein arrays, and multiphase fault veins and isolated zones of Au-rich sericite-carbonate altered rock. Integrated U-Pb SHRIMP data for magmatic zircon and Ar-Ar data for magmatic and hydrotbermal biotite indicate that gold mineralization occurred within 1 to 2 m.y. of magma emplacement. Fluid inclusion, oxygen isotope, and arsenopyrite geothermometry data indicate that hydrothermal minerals formed at depths of 6 to 9 km over a temperature range from 550??C. High-temperature Au-rich skarns formed at >400??C, whereas vein-hosted mineralization formed at 280?? to 380??C. In skarns, Au is strongly associated with enrichments of Bi, Te, W, and As, whereas a variety of Au-rich veins occur, with Asrich (type 1), and Te- and W-rich (type 2) end members. Silver-Pb-Zn-Sb veins are typically Au poor and represent the latest and lowest temperature phase in the hydrothermal paragenesis. The fluid inclusion data indicate that all mineralization styles were formed from low-salinity (???4 wt % NaCl equiv) aqueous-carbonic fluids, consistent with the composition of fluid inclusions within infilled miarolitic cavities in the intrusive rocks. However, the nonaqueous fluid was predominantly CH4 in skarn, CO2 in Au-Te and Au-W veins, and a fluid with roughly equal amounts Of CO2, CH4, and N2 in Au-As and Ag-Pb-Zn-Sb veins. Oxygen isotope data are consistent with a mineralizing fluid of predominantly magmatic origin that was variably modified to more positive ??18O values during interaction with 18O

  11. Constraints of mineralogical characterization of gold ore: Implication for genesis, controls and evolution of gold from Kundarkocha gold deposit, eastern India

    NASA Astrophysics Data System (ADS)

    Sahoo, P. R.; Venkatesh, A. S.

    2015-01-01

    Gold mineralization in Kundarkocha gold deposit occurs in the eastern Indian Craton that is hosted by sheared quartz-carbonate-sulfide veins emplaced within the graphitic schist, carbonaceous phyllite and talc-chlorite-serpentine schist belongs to Gorumahisani-Badampahar schist belt of Iron Ore Group. Gold mineralization exhibits both lithological and structural controls in the study area, albeit the stratigraphic control is more ubiquitously observed. Detailed mineralogical characterization coupled with electron probe microanalysis of the sulfide phases reveal the occurrences of gold in three distinct forms (i) as lattice-bound form within sulfides especially enriched in arsenopyrite, loellingite, pyrite, pyrrhotite and chalcopyrite in decreasing order of abundance; (ii) as micro inclusions or nano-scale gold inclusions within pyrite and arsenopyrite especially along the growth zones and micro-fractures as substrates and (iii) as free milling nugget gold grains either along the grain boundaries of sulfides or within the host rocks. Three generations of pyrite (Py-I, Py-II and Py-III) and arsenopyrite (Asp-I, Asp-II, Asp-III) have been identified based on textural, morphological characteristics and mineral chemistry. The lattice-bound gold content in pyrite and arsenopyrite varies from 600 to 2700 ppm and 900 to 3600 ppm respectively and increase in concentration of such refractory gold is seen in the order of chalcopyrite > pyrrhotite > pyrite > loellingite/arsenopyrite. The evolutionary stages of different forms of gold include remobilization of the lattice-bound grains in pyrite and arsenopyrite (Py-I and Asp-I) and re-concentration along the zoned-pyrite and arsenopyrite (Py-II and Asp-II) and ultimately as native gold/nuggets surrounding the sulfides as well as within the main mineralized zone. Lattice-bound gold distribution could have resulted due to metamorphic devolatilization reactions which are further aided by the influx of hydrothermal fluids. These

  12. Varicose Veins and Spider Veins

    MedlinePlus

    ... are sold in medical supply and drugstores. Prescription-strength gradient compression hose, which offer the greatest amount ... the face. Exercise regularly to improve your leg strength, circulation, and vein strength. Focus on exercises that ...

  13. Passive airborne EM and ground IP\\resistivity results over the Romero intermediate sulphidation epithermal gold deposits, Dominican Republic

    NASA Astrophysics Data System (ADS)

    Legault, Jean M.; Niemi, Jeremy; Brett, Jeremy S. Zhao, Shengkai; Han, Zihao; Plastow, Geoffrey C.

    2016-04-01

    The Romero gold-copper-zinc-silver deposits are located in the Province of San Juan, Dominican Republic, ~165 km west-north-west of Santo Domingo. Romero and Romero South orebodies contain stratabound gold mineralisation with copper, silver and zinc of intermediate sulphidation (IS), epithermal style. The gold mineralisation is associated with disseminated to semi-massive sulphides, sulphide veinlets and quartz-sulphide veins within quartz-pyrite, quartz-illite-pyrite and illite-chlorite-pyrite alteration. Ground direct current (DC) resistivity and induced polarisation (IP) supported by ground magnetics remain the preferred geophysical targeting tools for drill follow-up along with geologic mapping and geochemistry. However, Z-axis tipper electromagnetics (ZTEM) passive airborne electromagnetics (AEM) and magnetics have recently also been applied with success for reconnaissance mapping of deep alteration and fault structures regionally. The airborne ZTEM-magnetic surveys, supported by three-dimensional (3D) inversions, show good correlation with the ground IP\\resistivity surveys in the Romero and Romero South gold-copper-zinc-silver IS deposit area. The results have provided targets for ground follow-up and deep targeted drilling, and were successful in identifying a previously unknown deep (>500 m) continuity between the Romero and Romero South deposits.

  14. Source of boron in the Palokas gold deposit, northern Finland: evidence from boron isotopes and major element composition of tourmaline

    NASA Astrophysics Data System (ADS)

    Ranta, Jukka-Pekka; Hanski, Eero; Cook, Nick; Lahaye, Yann

    2016-11-01

    The recently discovered Palokas gold deposit is part of the larger Rompas-Rajapalot gold-mineralized system located in the Paleoproterozoic Peräpohja Belt, northern Finland. Tourmaline is an important gangue mineral in the Palokas gold mineralization. It occurs as tourmalinite veins and as tourmaline crystals in sulfide-rich metasomatized gold-bearing rocks. In order to understand the origin of tourmaline in the gold-mineralized rocks, we have investigated the major element chemistry and boron isotope composition of tourmaline from three areas: (1) the Palokas gold mineralization, (2) a pegmatitic tourmaline granite, and (3) the evaporitic Petäjäskoski Formation. Based on textural evidence, tourmaline in gold mineralization is divided into two different types. Type 1 is located within the host rock and is cut by rock-forming anthophyllite crystals. Type 2 occurs in late veins and/or breccia zones consisting of approximately 80% tourmaline and 20% sulfides, commonly adjacent to quartz veins. All the studied tourmaline samples belong to the alkali-group tourmaline and can be classified as dravite and schorl. The δ11B values of the three localities lie in the same range, from 0 to -4‰. Tourmaline from the Au mineralization and from the Petäjäskoski Formation has similar compositional trends. Mg is the major substituent for Al; inferred low Fe3+/Fe2+ ratios and Na values (<0.8 atoms per formula unit (apfu)) of all tourmaline samples suggest that they precipitated from reduced, low-salinity fluids. Based on the similar chemical and boron isotope composition and the Re-Os age of molybdenite related to the tourmaline-sulfide-quartz veins, we propose that the tourmaline-forming process is a result of a single magmatic-hydrothermal event related to the extensive granite magmatism at around 1.79-1.77 Ga. Tourmaline was crystallized throughout the hydrothermal process, which resulted in the paragenetic variation between type 1 and type 2. The close association of

  15. Lebediny gold deposit, Central Aldan: Mineral parageneses, stages, and formation conditions

    NASA Astrophysics Data System (ADS)

    Dobrovol'skaya, M. G.; Razin, M. V.; Prokof'ev, V. Yu.

    2016-07-01

    The mineral parageneses and succession of their formation are considered for the first time for the Zverevsky, Orekhovy, and Vodonosny ore lodes of the Lebediny gold deposit and the Radostny prospect in the Central Aldan ore district, which are genetically related to the epoch of Mesozoic tectonomagmatic reactivation. The orebodies, represented by two morphological varieties—ribbonlike lodes and steeply dipping veins—are hosted in lower part of the Vendian-Cambrian dolomitic sequence, which is cut through by Mesozoic subalkaline intrusive bodies. The chemistry of fahlore and rare minerals, including native gold and bismuth, altaite, aikinite, tetradymite, and sulfosalts of lillianite series, has been studied. Native gold is related to the late hydrothermal process and occurs in skarn and in quartz-tremolite-sulfide and quartz-carbonate-sulfide veins. The data on stable sulfur (δ34S) isotopes of sulfides, oxygen (δ18O) and carbon (δ13C) isotopes of carbonates, as well as on fluid inclusions in various generations of tremolite and quartz, provide evidence for the heterogeneity of ore-bearing solutions, their relationships to magmatism, the depth of the source feeding each specific lode, and different sources of ore-forming hydrothermal solutions.

  16. Mineralogy and geochemistry of the IRG Misky gold deposit, southern Peru

    NASA Astrophysics Data System (ADS)

    Palacios, Silvia; Alfonso, Pura; Proenza, Joaquín Antonio

    2014-05-01

    The Misky gold deposit is one of the several Intrusion Related gold deposits that occur in the ocoña river basin, southern Peru. They are hosted in magmatic rocks from the Nazca-Palpa-Ocoña belt, from the Coastal Batholith. In this study, a petrologic and geochemical characterisation of the host rocks of the Misky deposit is presented to contribute to prove the deposit model. XRD, electron microscopy and electron microprobe analyses were used to characterize the ore and major and trace elements of host rocks were analysed by ICP-Ms. The Misky deposit, Cretaceous in age, consists mainly in quartz veins of lenticular morphology that can be more than 3 Km long and less than 1 m wide. At least two generations of magmatic host rocks are differentiated by the field relationships. The older generation is composed of plutonic rocks of the Incahuasi Unit constituted by diorites, quartz-monzonites, quartz-diorites and granodiorites in minor amounts. These rocks are crosscut by dykes of gabbro, tonalite and quartz diorite porphyries. Parallel to these dykes there is a NEE-SWW fault system. Gold veins are emplaced filling these fractures. Gabbro is rich in hornblende and present titanite reaction rims around ilmenite, which suggests relatively reduced conditions and high H2O contents. Hydrothermal alteration, associated with the gold mineralization, produced sericitization, chloritization and silicification in the surroundings of the veins. The Misky deposit has a Au-As-Pb-Zn-Cu association. Gold appears mainly in veins disseminationed in the host rocks near the contact with these veins. Gold occurs as enclosed grains within pyrite, or as electrum located in fractures of pyrite. In addition other sulphides as sphalerite, galena and chalcopyrite are abundant. Arsenopyrite, sulphosalts, bismuthinite and native bismuth also occur in lesser amounts. Calcocite, malachite and hematite are supergene minerals. The gold content can reach up to 130 pp Au and up to 0.6 wt% Cu. Major

  17. Varicose vein - noninvasive treatment

    MedlinePlus

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

  18. Complex fragmentation and silicification structures in fault zones: quartz mineralization and repeated fragmentation along the Fountain Range Fault (Mt. Isa Inlier, Australia)

    NASA Astrophysics Data System (ADS)

    Seybold, Lina; Blenkinsop, Tom; Heuss, Soraya; Ord, Alison; Kruhl, Jörn H.

    2015-04-01

    In large-scale fault zones fracture networks are commonly generated by high volumes of pressurized fluids, followed by quartz precipitation. In this way large amounts of quartz are formed as microcrystalline masses and as complex vein systems, with partly highly different textures, as a result of different formation processes. Based on field and microstructural data and the quantification of vein patterns, the spatial and temporal connection between fragmentation, quartz crystallization and fluid and material flow along the Fountain Range Fault at Fountain Springs was investigated. Dextral strike-slip led to up to 25 km horizontal displacement along the fault. Due to various fragmentation and quartz formation processes, a ca. 100 m high, 80 - 100 m wide and km-long quartz ridge with numerous vein systems and variable microfabrics was formed. Locally, lenses of highly altered metamorphic wall-rocks occur in the quartz zone. Where exposed, the contact to wall rocks is sharp. Millimetre- to decimetre-thick quartz veins penetrate the wall-rocks only within metre distance from the contact. Several clearly distinguishable fine-grained reddish, brownish to dark and pigment-rich quartz masses form up to 50 m wide and up to several 100 m long steep lenses that build the major part of the silicified fault zone. A chronology can be established. Some of these lenses are oriented slightly oblique to the general trend of the quartz zone, in agreement with the supposed dextral strike slip along the fault. Numerous generations of typically µm-cm thick quartz veins transect the microcrystalline quartz masses and, locally, form anisotropic networks. In the quartz masses, angular fragments often composed of quartz with, again, internal fragmentation structures, indicate earlier fracturing and silicification events. Within the veins, quartz forms geodes, locally filled with fine-grained reddish quartz and palisade structures with feathery textures and fluid-inclusion zoning

  19. Map showing mineral resource assessment for vein and replacement deposits of gold, silver, copper, lead, zinc, manganese, and tungsten in the Butte 1 degree by 2 degrees Quadrangle, Montana

    USGS Publications Warehouse

    Elliott, J.E.; Wallace, C.A.; Lee, G.K.; Antweiler, J.C.; Lidke, D.J.; Rowan, L.C.; Hanna, W.F.; Trautwein, C.M.; Dwyer, J.L.; Moll, S.H.

    1992-01-01

    The purpose of this report is to assess the potential for undiscovered vein and replacement deposits of gold, silver, copper, lead, zinc, manganese, and tungsten in the Butte 1 °X2° quadrangle. This quadrangle, in west-central Montana, is one of the most mineralized and productive regions in the United States. Its mining districts, including the world famous Butte or Summit Valley district, have produced a variety of metallic and nonmetallic mineral commodities valued at more than $6.4 billion. Because of its importance as a mineral producing region, the Butte quadrangle was selected for study by the U.S. Geological Survey under the Conterminous United States Mineral Assessment Program (CUSMAP). Under this program, new data on geology, geochemistry, geophysics, geochronology, mineral resources, and remote sensing were collected and synthesized. The field and laboratory studies were also supported by funding from the Geologic Framework and Synthesis Program and the Wilderness Program. The methods used in resource assessment include a compilation of all data into data sets, the development of a descriptive model for vein and replacement deposits in the quadrangle, and the analysis of data using techniques provided by the Geographic Information System (GIS). This map is one of a number of reports and maps on the Butte 1 °X2° quadrangle. Other publications resulting from this study include U.S. Geological Survey Miscellaneous Investigations Series Maps 1-2050-A (Rowan and Segal, in press) and I-2050-B (Purdy and Rowan, in press); Miscellaneous Field Studies Map MF-1925 (Wallace, 1987); and Open-File Reports 86-292 (Wallace and others, 1986) and 86--0632 (Elliott and others, 1986). Reports on mineral resource assessment for several other types of deposits in the Butte quadrangle are in preparation.

  20. Tectonostratigraphic setting of the Mother Lode gold belt, south of Placerville, California

    SciTech Connect

    Landefeld, L.A.

    1985-01-01

    Gold-quartz veins and alteration of the Mother Lode gold belt south of Placerville are hosted by the Melones fault zone (MFZ) in the south and by its splays in the north. The MFZ changes from south to north in the following manner: ductilely deformed serpentinite-hosted tectonic melange to a broad zone of ductile shearing to a 1 km wide mylonite-phyllonite zone. These strata have common protoliths but differ in metamorphic rank, structural style, gold deposit morphology and production, which can be explained by: 1) greatest uplift of the Sierran block in the south during Basin and Range tilting, 2) irregular shape of the Jura-Triassic convergent margin of western North America coupled with oblique convergence, 3) vertical and lateral variations in age, metamorphic rank and structural style typical of an active arc and basin which is forming while closing, 4) composition and volume of diagenetic, burial and later dynamic metamorphic fluids, 5) rheology and composition of different lithologies. The Mother Lode vein system formed as the MFZ locked up. The ore-forming fluids rose km's up the MFZ to form the vein system during repeated late-stage brittle faulting. As accretion ground to a halt in the MFZ, the accretion shifted west to emplace the Franciscan complex.

  1. Geochemical and mineralogical characterization of the abandoned Valzinco (lead-zinc) and Mitchell (gold) mine sites prior to reclamation, Spotsylvania County, Virginia

    USGS Publications Warehouse

    Hammarstrom, Jane M.; Johnson, Adam N.; Seal, Robert R., II; Meier, Allen L.; Briggs, Paul L.; Piatak, Nadine M.

    2006-01-01

    The Virginia gold-pyrite belt, part of the central Virginia volcanic-plutonic belt, hosts numerous abandoned metal mines. The belt extends from about 50 km south of Washington, D.C., for approximately 175 km to the southwest into central Virginia. The rocks that comprise the belt include metamorphosed volcanic and clastic (noncarbonate) sedimentary rocks that were originally deposited during the Ordovician). Deposits that were mined can be classified into three broad categories: 1. volcanic-associated massive sulfide deposits, 2. low-sulfide quartz-gold vein deposits, 3. gold placer deposits, which result from weathering of the vein deposits The massive sulfide deposits were historically mined for iron and pyrite (sulfur), zinc, lead, and copper but also yielded byproduct gold and silver. The most intensely mineralized and mined section of the belt is southwest of Fredericksburg, in the Mineral district of Louisa and Spotsylvania counties. The Valzinco Piatak lead-zinc mine and the Mitchell gold prospect are abandoned sites in Spotsylvania County. As a result of environmental impacts associated with historic mining, both sites were prioritized for reclamation under the Virginia Orphaned Land Program administered by the Virginia Department of Mines, Minerals, and Energy (VDMME). This report summarizes geochemical data for all solid sample media, along with mineralogical data, and results of weathering experiments on Valzinco tailings and field experiments on sediment accumulation in Knights Branch. These data provide a framework for evaluating water-rock interactionsand geoenvironmental signatures of long-abandoned mines developed in massive sulfide deposits and low-sulfide gold-quartz vein deposits in the humid temperate ecosystem domain in the eastern United States.

  2. Varicose Veins

    MedlinePlus

    ... Wearing loose clothing and avoiding long periods of standing can also help. If varicose veins are painful or you don't like the way they look, your doctor may recommend procedures to remove them. NIH: National Heart, Lung, and Blood Institute

  3. Simulation of quartz resonators

    NASA Astrophysics Data System (ADS)

    Weinmann, M.; Radius, R.; Mohr, R.

    Quartz resonators are suitable as novel sensor elements in the field of profilometry and three dimensional measurement techniques. This application requires a tailoring of the oscillator circuit which is performed by a network analysis program. The equivalent network parameters are computed by a finite element analysis. The mechanical loading of the quartz is modeled by a viscous damping approach.

  4. Preventing Deep Vein Thrombosis

    MedlinePlus

    ... Education & Events Advocacy For Patients About ACOG Preventing Deep Vein Thrombosis Home For Patients Search FAQs Preventing ... Vein Thrombosis FAQ174, August 2011 PDF Format Preventing Deep Vein Thrombosis Women's Health What is deep vein ...

  5. Mineralisation footprints and regional timing of the world-class Siguiri orogenic gold district (Guinea, West Africa)

    NASA Astrophysics Data System (ADS)

    Lebrun, Erwann; Thébaud, Nicolas; Miller, John; Roberts, Malcolm; Evans, Noreen

    2016-10-01

    Siguiri is a world-class orogenic gold district hosted in the weakly metamorphosed Upper Birimian to Lower Tarkwa Group sedimentary rocks of the Siguiri Basin (Guinea). The district is characterised by a protracted deformation history associated with four main deformation events: D1S is a N-S compression; D2S is an E-W compression progressively evolving into an early-D3S transpression and then into a late-D3S NNW-SSE transtension and D4S is a NE-SW compression. Field observations, petrography and geochemistry at three key deposits of the Siguiri district (Bidini, Sintroko PB1 and Kosise) suggest a polyphase hydrothermal history that can be subdivided into four hydrothermal events. The first hydrothermal event was associated with the development of barren bedding-parallel and en-echelon V2S quartz-dominated-(pyrite) veins. The second hydrothermal event is characterised by the development of V3A pyrite-ankerite veins late during D3S. Laser ablation-ICP-MS data show that this vein set contains high gold contents of up to 43.3 ppm, in substitution in pyrite crystal lattice, representing a minor first gold mineralisation event. The third and most prominently developed hydrothermal event is late D3S and represents the second and principal gold mineralisation event. This mineralisation event led to two distinct mineralisation textures. The first texture is best exposed in the Kosise deposit and is characterised by gold-bearing quartz-ankerite-arsenopyrite conjugate V3B veins. Although the bulk of the gold is hosted in native gold grains in V3B veins, LA-ICP-MS analyses show that gold also substitutes in the arsenopyrite crystal lattice (up to 55.5 ppm). The second mineralisation texture is best expressed in the Sanu Tinti deposit and consists of disseminated barren pyrite hosted in a polymict conglomerate. The second and third hydrothermal events are both structurally controlled by a series of early-D3S N-S, NE-SW, WNW-ESE and E-W sub-vertical incipient structures

  6. QUARTZ FIBER ELECTROSCOPES

    DOEpatents

    Henderson, R.P.

    1957-09-17

    An instrument carried unobtrusively about the person such as in a finger ring to indicate when that person has been exposed to an unusual radiation hazard is described. A metallized quartz fiber is electrically charged to indicate a full scale reading on an etched glass background. The quartz fiber and the scale may be viewed through a magnifying lens for ease of reading. Incident radiation will ionize gaseous particles in the sealed structure thereby allowing the charge to leak off the quartz fiber with its resulting movement across the scale proportionally indicating the radiation exposure.

  7. Morphology and composition of gold in a lateritic profile, Fazenda Pison “Garimpo”, Amazon, Brazil

    NASA Astrophysics Data System (ADS)

    Larizzatti, J. H.; Oliveira, S. M. B.; Butt, C. R. M.

    2008-05-01

    This study describes the morphological evolution of gold grains in a lateritic weathering profile in an equatorial rainforest climate. Primary sources of gold are quartz veins associated with shallow granophyric intrusion. Gold grains were found in fresh ore, saprolite, transition zones, ferruginous duricrust, red latosol, and yellow latosol. Irregularly shaped grains predominate, with smaller proportions of dendritic and prismatic forms. Gold grains are weathered in the uppermost 10 m of the regolith. Mean gold grain size is maximum in the duricrust (>125 μm) and decreases progressively upward into the yellow latosol (<90 μm). Voids and corrosion pits appear on grain surfaces, and progressive rounding is observed from the bottom of the profile to the top. Gold grains can be classified as either homogeneous or zoned with respect to their chemical composition. Homogeneous grains contain 2-15% Ag (mean 8.3%). Zoned grains have more variable Ag contents; grain cores have means of approximately 10% or 23% Ag, with Ag-poor zones of approximately 3.7% Ag along internal discontinuities and/or outer rims. Formation of Ag-poor rims is due to preferential depletion of silver. Processes responsible for duricrust formation may preserve some grains as large aggregates, but subsequent transformation into latosol further modifies them.

  8. Geology of the Mother Load gold belt and adjacent foothills metamorphic belt, California

    SciTech Connect

    Landefeld, L.A.

    1985-01-01

    The late Jurassic Mother Lode gold-quartz vein system south of the Consumnes River is hosted by portions of 1) a submarine volcanic arc and overlying epiclastic basin, and 2) the ultramafic-mafic plutonic subarc basement. During accretion to the Paleozoic shelf of western North America, the subarc basement tectonically intruded the disrupted arc basin, incorporating hanging wall lithologies to produce the tectonic melange of the Melones fault zone (MFZ). Late orogenic dikes intrude the margins of the MFZ and adjacent wall rocks. These dikes were altered during the gold-quartz vein formation. The proximal to medial volcanic strata are, from oldest to youngest: 1) island arc tholeiitic pillow basalts, 2) a thin radiolarian chert bed grading into 3) a submarine volcaniclastic sequence, and 4) sporadically distributed flows of calc-alkaline basalt through boninite. Cessation of volcanic activity is marked by the deposition of an organic carbon-rich epiclastic sequence. The intensely folded strata in JT rocks east of the MFZ may be basinward lateral equivalents of the JT strata west of the MFZ. Differences in style of deformation and metamorphic rank in the strata are typical of vertical and lateral variations in basins where one part is passive and another part is tectonically active as the basin closes.

  9. Gold deposits of the northern margin of the North China craton: Multiple late Paleozoic-Mesozoic mineralizing events

    USGS Publications Warehouse

    Hart, C.J.R.; Goldfarb, R.J.; Qiu, Y.; Snee, L.; Miller, L.D.; Miller, M.L.

    2002-01-01

    The northern margin of the North China craton is well-endowed with lode gold deposits hosting a resource of approximately 900 tonnes (t) of gold. The ???1,500-km-long region is characterized by east-trending blocks of metamorphosed Archean and Proterozoic strata that were episodically uplifted during Variscan, Indosinian, and Yanshanian deformational and magmatic events. At least 12 gold deposits from the Daqinshan, Yan-Liao (includes the Zhangjiakou, Yanshan, and Chifeng gold districts), and Changbaishan gold provinces contain resources of 20-100 t Au each. Most deposits are hosted in uplifted blocks of Precambrian metamorphic rocks, although felsic Paleozoic and Mesozoic plutons are typically proximal and host ???30% of the deposits. The lodes are characterized by sulfide-poor quartz veins in brittle structures with low base metal values and high Au:Ag ratios. Although phyllic alteration is most common, intensive alkali feldspar metasomatism characterizes the Wulashan, Dongping, and Zhongshangou deposits, but is apparently coeval with Variscan alkalic magmatism only at Wulashan. Stepwise 40Ar-39Ar geochronology on 16 samples from gangue and alteration phases, combined with unpublished SHRIMP U-Pb dates on associated granitoids, suggest that gold mineralizing events occured during Variscan, Indosinian, and Yanshanian orogenies at circa 350, 250, 200, 180, 150, and 129 Ma. However, widespread Permo-Triassic (???250 Ma) and Early Jurassic (???180 Ma) thermal events caused variable resetting of most of the white mica and K-feldspar argon spectra, as well as previously reported K-Ar determinations. Compiled and new stable isotope and fluid inclusion data show that most ??18O values for ore-stage veins range from 8 to 14???, indicating a fluid in equilibrium with the Precambrian metamorphic basement rocks; ??D values from fluid inclysions range widely from -64 to -154???, which is indicative of a local meteoric component in some veins; and highly variable ??34S data

  10. Vacuum electrolysis of quartz

    DOEpatents

    King, James Claude

    1976-01-13

    The disclosure is directed to a method for processing quartz used in fabricating crystal resonators such that transient frequency change of resonators exposed to pulse irradiation is virtually eliminated. The method involves heating the crystal quartz in a hydrogen-free atmosphere while simultaneously applying an electric field in the Z-axis direction of the crystal. The electric field is maintained during the cool-down phase of the process.

  11. Huebnerite veins near Round Mountain, Nye County, Nevada

    SciTech Connect

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

    1984-01-01

    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.

  12. Pressure, temperature, and timing of mineralization of the sedimentary rock-hosted orogenic gold deposit at Klipwal, southeastern Kaapvaal Craton, South Africa

    NASA Astrophysics Data System (ADS)

    Chinnasamy, Sakthi Saravanan; Uken, Ron; Reinhardt, Jürgen; Selby, David; Johnson, Spencer

    2015-08-01

    Gold mineralization in the Klipwal Shear Zone (KSZ) at the Klipwal Gold Mine is confined to laminated quartz-carbonate lodes, stringers, and associated alteration in sandstone and siltstone of the Delfkom Formation in the upper Mozaan Group of the Mesoarchaean Pongola Supergroup. The moderately dipping brittle-ductile KSZ strikes N-S with an oblique-reverse, sinistral sense of shear. The deformational events that are recognized include an early compressional phase that produced anastomosing shears defined by shear fabrics with numerous shear-parallel laminated quartz-carbonate fault-fill veins and, in places, extensional quartz vein stockworks, and a late brittle reactivation phase that produced fault breccias, displacing earlier extensional veins. Three closely spaced economic reefs (lodes) are developed: the main R-reef constitutes the KSZ, while the J- and H-reefs represent footwall splays. Alteration comprises chlorite, muscovite, epidote, feldspar, and carbonates along with pyrite, arsenopyrite, and chalcopyrite ± pyrrhotite. An inner alteration zone is dominated by laminated quartz-carbonate veins with alternating quartz-carbonate-rich and muscovite-chlorite-rich laminae, whereas the proximal zone is characterized by alteration halos of K-feldspar, albite, epidote, chlorite, and muscovite along with carbonates and associated quartz veins. Chlorite thermometry from the inner and proximal zones yielded temperatures of 267 to 312 °C. Arsenopyrite compositions provide temperatures in the same range, 255 to 318 °C. Fluid inclusion microthermometry and Raman spectrometry of quartz veins in the mineralized reefs reveal the presence of metamorphogenic aqueous-gaseous fluid with an average salinity of 6.5 wt% NaCl equiv. Fluid compositions and estimated pressure-temperature (P-T) range (1.1 to 2.5 kbar at 255 to 318 °C) are typical of orogenic gold deposits. Devolatilization during the regional facies metamorphism of the Pongola Supergroup is considered the likely

  13. Mineralogical and geochemical features of promising types of gold mineralization in the western Altai-Sayany folded region (Russia)

    NASA Astrophysics Data System (ADS)

    Chernykh, Alexandr

    2013-04-01

    The western Altai-Sayany folded region is one of the oldest mining regions of Russia. Typical gold deposits are quartz-viens and skarns, which formation is associated with intrusion of island-arc and collision granitoids. Due to the fact that the traditional gold ore base of the region has already been largely worked out, the necessity of prospecting for new gold deposits has arisen. On the basis of available data, one may state that the outlook for the development of gold-mining industry of the Altai-Sayany region is concerned with gold mineralization in weathering crusts, epithermal gold-silver, gold-porhyry and gold-sulfide formations. The total gold resource potential of these object types is estimated by us at the level of 2000 t. The gold mineralization of epithermal gold-silver formation is confined to Early-Middle Devonian volcanic-plutonic belt. Here, gold-bearing zones of beresitization, argillization, sulfidization and silicification are discovered among volcanites. Maximum contents of noble metals are found in quartz-sulfide veins among sulfidized (arsenic pyrite, pyrite, galenite, sphalerite and fahlore, etc.) and silicified volcanic and subvolcanic rocks. Ore zones are marked by anomalously high content of Au, Ag, Pb, Zn, As, Sb, Hg not only in bedrocks, but also in haloes of dispersion in loose deposits. Gold-sulfide mineralization in terrigenous carbonaceous strata is confined to Late Riphean, Early Cambrian and Devonian metamorphosed complexes. This rocks were formed in the marginal sea basins. Metamorphism and repeated tectono-magmatic activation in the region resulted in redistribution and accumulation of gold. Gold-ore zones are marked by intensive silicification and sulfidization and are characterized mostly by occurrences of multiple generations of pyrite and arsenic pyrite. Gold occurs both in free state and in sulphides. Geochemistry of gold-ore zones can be characterized by associated elevated content of As, Ag, Sb, Cu, Hg. Gold

  14. Geological and Geochemical Criteria for the Estimation of the Area of The Lesser Hinggan for the Endogenous Gold Mineralization (The Far East, Russia)

    NASA Astrophysics Data System (ADS)

    Yurchenko, Yuriy

    2015-04-01

    intergrown with quartz, pyrite, arsenopyrite, galena in areas of intensive dislocation metamorphism and quartz-vein formation, accompanied by hydrothermal-metasomatic alteration of the bedrock in the mineral facies propylite, beresites and argillisites; 4. The transition some alluvial gold from lowland to the talus slope approaching the watershed areas; 5. The structural-geological similarity the area of the Lesser Hinggan with the gold mining areas of China and the northwestern part (Russia) of the Bureya array (Tandzhigou (Juanjiegou) (China), Noninskoe (Russia), Prognoznoe (Russia) and others). The Projected endogenous gold mineralization on the Lesser Hinggan include gold-quartz (including low-sulfide component) ore-formation type in the form of thin and not sustain the strike quartz veins in the surrounding strata (for example, gold deposit Lysoya Gora) and genetically related to the Early Cretaceous Hinggan-Olonoy complex of the subvolcanic felsic small intrusions . The ore-formation types associated with gold-bearing weathering crusts, carbon ("black") schist and ferruginous quartzite are the perspective in the area of the Lesser Hinggan also.

  15. Ore-fluid evolution at the Getchell Carlin-type gold deposit, Nevada, USA

    USGS Publications Warehouse

    Cline, J.S.; Hofstra, A.A.

    2000-01-01

    Minerals and fluid-inclusion populations were examined using petrography, microthermometry, quadrupole mass-spectrometer gas analyses and stable-isotope studies to characterize fluids responsible for gold mineralization at the Getchell Carlin-type gold deposit. The gold-ore assemblage at Getchell is superimposed on quartz-pyrite vein mineralization associated with a Late-Cretaceous granodiorite stock that intruded Lower-Paleozoic sedimentary rocks. The ore assemblage, of mid-Tertiary age, consists of disseminated arsenian pyrite that contains submicrometer gold, jasperoid quartz, and later fluorite and orpiment that fill fractures and vugs. Late ore-stage realgar and calcite enclose ore-stage minerals. Pre-ore quartz trapped fluids with a wide range of salinities (1 to 21 wt.% NaCl equivalent), gas compositions (H2O, CO2, and CH4), and temperatures (120 to >360??C). Oxygen- and hydrogen-isotope ratios indicate that pre-ore fluids likely had a magmatic source, and were associated with intrusion of the granodiorite stock and related dikes. Ore-stage jasperoid contains moderate salinity, aqueous fluid inclusions trapped at 180 to 220??C. Ore fluids contain minor CO2 and trace H2S that allowed the fluid to react with limestone host rocks and transport gold, respectively. Aqueous inclusions in fluorite indicate that fluid temperatures declined to ~175??C by the end of ore-stage mineralization. As the hydrothermal system collapsed, fluid temperatures declined to 155 to 115??C and realgar and calcite precipitated. Inclusion fluids in ore-stage minerals have high ??D(H2O) and ??18O(H2O) values that indicate that the fluid had a deep source, and had a metamorphic or magmatic origin, or both. Late ore-stage fluids extend to lower ??D(H2O) values, and have a wider range of ??18O(H2O) values suggesting dilution by variably exchanged meteoric waters. Results show that deeply sourced ore fluids rose along the Getchell fault system, where they dissolved carbonate wall rocks and

  16. Pan-African shear zone-hosted gold mineralization in the Arabian-Nubian shield

    NASA Astrophysics Data System (ADS)

    Abu-Alam, Tamer; Grosch, Eugene; Abd El Monsef, Mohamed

    2013-04-01

    A new tectonic model of the exhumation mechanism of the Arabian-Nubian Shield will be presented at the EGU2013 by Abu-Alam and Stüwe (2013). According to this new tectonic model, the shear zones of the Arabian-Nubian Shield can be classified into two types; deep-seated and relatively shallow shear zones. The deep-seated shear zones are accompanied with deep sub-horizontal crustal channel flows which are response to the exhumation of the metamorphic complexes from the peak condition depth to a shallower crustal level (ductile-brittle transition). An example of these deep-seated shear zones is the Najd Fault System - the largest shear zone on the Earth. At the ductile-brittle transition crustal level, the deep-seated shear zones were overprinted by a greenschist facies condition or the ?2 and ?3 of the principle stresses may be flipped with each other. This flipping can produce other conjugate shallow shear zones in a greenschist facies conditions. The Egyptian gold deposits can be classified into three main types (Botros, 2004), These are stratabound deposits, non-stratabound deposits and placer gold deposits. The non-stratabound deposits are the most common (ex: Sukari, Wadi Allaqi, Abu Marawat, Atalla, El-Sid and Atud gold mines). They are found in form of vein type mineralization or as disseminated mineralization hosted in volcanics and volcaniclastic rocks (volcanogenic massive sulphides). Spatial and temporal relationships between gold veins and structures in the Arabian-Nubian Shield suggest a genetic relationship between mineralization and major tectonic events. At Sukari, Wadi Allaqi and Abu Marawat areas, the gold is hosted in quartz veins parallel to a deep-seated NW-SE to NNW-SSE shear zones. For Atud, El-Sid and Atalla area, the gold is hosted in NE-SW veins parallel to a shallow shear zone but at the conjugate point with a deep-seated NW-SE shear zone. According to the new tectonic model, we propose the following model for gold formation (non

  17. Spider Vein Removal

    MedlinePlus

    Spider veins: How are they removed? I have spider veins on my legs. What options are available ... M.D. Several options are available to remove spider veins — thin red lines or weblike networks of ...

  18. What Causes Varicose Veins?

    MedlinePlus

    ... weak or damaged, blood can back up and pool in your veins. This causes the veins to ... pressure in your veins due to overweight or obesity or pregnancy. Rate This Content: NEXT >> Updated: February ...

  19. Optical contacting of quartz

    NASA Technical Reports Server (NTRS)

    Payne, L. L.

    1982-01-01

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

  20. Quartz ball valve

    NASA Technical Reports Server (NTRS)

    Goetz, C.; Ingle, W. M. (Inventor)

    1980-01-01

    A ball valve particularly suited for use in the handling of highly corrosive fluids is described. It is characterized by a valve housing formed of communicating segments of quartz tubing, a pair of communicating sockets disposed in coaxial alignment with selected segments of tubing for establishing a pair of inlet ports communicating with a common outlet port, a ball formed of quartz material supported for displacement between the sockets and configured to be received alternately thereby, and a valve actuator including a rod attached to the ball for selectively displacing the ball relative to each of the sockets for controlling fluid flow through the inlet ports.

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

    NASA Technical Reports Server (NTRS)

    Roedder, Edwin

    1990-01-01

    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.

  2. The Wassa deposit: A poly-deformed orogenic gold system in southwest Ghana - Implications for regional exploration

    NASA Astrophysics Data System (ADS)

    Perrouty, Stéphane; Jessell, Mark W.; Bourassa, Yan; Miller, John; Apau, Daniel; Siebenaller, Luc; Velásquez, Germán; Baratoux, Lenka; Aillères, Laurent; Béziat, Didier; Salvi, Stefano

    2015-12-01

    The Ashanti greenstone belt in southwest Ghana hosts many gold deposits distinguished by different timing and structural contexts. This study investigates the evolution of the Wassa system by integrating field and geophysical observations. This 4 million ounces (past production and current resources) gold deposit is interpreted to represent the oldest gold mineralization event in West Africa with gold-bearing pyrites aligned and stretched within the S1 ductile fabric. Mineralized quartz-carbonate veins were strongly deformed during the D1 deformation event. Three additional folding events are characterized by hectometer-scale tight to isoclinal folds, by a kilometer-scale synform fold centered on the mine and by a late recumbent metric-scale folds. Because of its early timing, the Wassa system represents a new poly-deformed deposit type in West Africa and highlights a potential for new discoveries in the underexplored meta-volcanic and meta-sedimentary Sefwi Group. Timing of the gold mineralization at the Wassa mine makes this deposit type a possible candidate for the source of the gold contained in the Tarkwa paleoplacer.

  3. Veins in the northern part of the Boulder batholith, Montana

    USGS Publications Warehouse

    Pinckney, D.M.

    1965-01-01

    About 20 miles north of Butte and extending nearly to Helena, is an area of 350 square miles containing hundreds of veins and altered zones. The bedrock of the area is 1) late Cretaceous volcanic rocks, forerunners of the Boulder batholith, 2) the Boulder batholith of late Cretaceous to early Tertiary age and 3) two groups of Tertiary volcanic rocks lying on the eroded batholith. The veins are post-batholith and pre-Tertiary in age. The veins are largely either quartz-sulfide veins of mesothermal type or chalcedony veins of epithermal type. The relations of these two types of veins have been the subject of conflicting ideas for 60 years. Three workers have proposed three different genetic classifications. This report shows that the quartz veins and the chalcedony veins are closely related parts of a strongly zoned hypogene vein system. Strong zonal patterns were established using the grain size of quartz (or pyrite vs. carbonate in one district) as well as features of the altered rocks. The scale of the zoning ranges from single veins through groups of veins or mining districts to the entire mineralized area. Single veins are zoned around a core of coarse-grained quartz; the quartz outward from the core becoming progressively finer-grained. The cores are zoned around eight major centers and several lesser ones. The centers and their nearby related veins are assigned to central, intermediate, and peripheral zones. Nearly all of the veins around the edge of the mineralized area are chalcedony. Envelopes of altered rocks consist of seven major bands representing three major groups of constituents, aluminum silicates, iron-bearing minerals, and silica. Plagioclase altered successively to montomorillite, kaolinite, and sericite; potassium feldspar altered to sericite (aluminum silicate group). Biotite released iron which formed successively, iron oxides, iron-bearing carbonate, and pyrite (iron-bearing minerals). Excess silica formed silicified bands. Constituents for

  4. Geological and geochemical implications of the genesis of the Qolqoleh orogenic gold mineralisation, Kurdistan Province (Iran)

    NASA Astrophysics Data System (ADS)

    Taghipour, Batoul; Ahmadnejad, Farhad

    2015-03-01

    The Qolqoleh gold deposit is located in the northwestern part of the Sanandaj-Sirjan Zone (SSZ), within the NE-SW trending Qolqoleh shear zone. Oligocene granitoids, Cretaceous meta-limestones, schists and metavolcanics are the main lithological units. Chondrite-normalised REE patterns of the ore-hosting metavolcanics indicate REE enrichment relative to hanging wall (chlorite-sericite schist) and footwall (meta-limestone) rocks. The pattern also reflects an enrichment in LREE relative to HREE. It seems that the LREE enrichment is related to the circulation of SO42- and CO2-bearing fluids and regional metamorphism in the Qolqoleh shear zone. Both positive and negative Eu anomalies are observed in shear-zone metavolcanics. These anomalies are related to the degree of plagioclase alteration during gold mineralisation and hydrothermal alteration. In progressing from a metavolcanic protomylonite to an ultramylonite, significant changes occurred in the major/trace element and REE concentration. Utilising an Al-Fe-Ti isocon for the ore-hosting metavolcanics shows that Sc, Y, K, U, P, and M-HREE (except Eu) are relatively unchanged; S, As, Ag, Au, Ca, LOI, Rb and LREE are enriched, and Sr, Ba, Eu, Cr, Co and Ni decrease with an increasing degree of deformation. Based on geochemical features and comparison with other well-known shear zones in the world, the study area is best classified as an Isovolume-Gain (IVG) type shear zone and orogenic type gold mineralisation. Based on the number of phases observed at room temperature and their microthermometric behaviour, three fluid inclusion types have been recognised in quartz-sulphide and quartz-calcite veins: Type I monophase aqueous inclusions, Type II two-phase liquid-vapour (L-V) inclusions which are subdivided into two groups based on the homogenisation temperature (Th): a) L-V inclusions with Th from 205 to 255°C and melting temperature of last ice (Tm) from -3 to -9°C. b) L-V inclusions with higher Th from 335 to 385

  5. The Kharapeh orogenic gold deposit: Geological, structural, and geochemical controls on epizonal ore formation in West Azerbaijan Province, Northwestern Iran

    USGS Publications Warehouse

    Niroomand, Shojaeddin; Goldfarb, Richard J.; Moore, Farib; Mohajjel, Mohammad; Marsh, Erin E.

    2011-01-01

    The Kharapeh gold deposit is located along the northwestern margin of the Sanandaj–Sirjan Zone (SSZ) in the West Azerbaijan province, Iran. It is an epizonal orogenic gold deposit formed within the deformed zone between central Iran and the Arabian plate during the Cretaceous–Tertiary Zagros orogeny. The deposit area is underlain by Cretaceous schist and marble, as well as altered andesite and dacite dikes. Structural analysis indicates that the rocks underwent tight to isoclinal recumbent folding and were subsequently co-axially refolded to upright open folds during a second deformation. Late- to post-tectonic Cenozoic granites and granodiorites occur northeast of the deposit area. Mineralization mainly is recognized within NW-trending extensional structures as veins and breccia zones. Normal faults, intermediate dikes, and quartz veins, oriented subparallel to the axial surface of the Kharapeh antiform, indicate synchronous extension perpendicular to the fold axis during the second folding event. The gold-bearing quartz veins are >1 km in length and average about 6 m in width; breccia zones are 10–50 m in length and ≤1 m in width. Hydrothermal alteration mainly consists of silicification, sulfidation, chloritization, sericitization, and carbonatization. Paragenetic relationships indicate three distinct stages—replacement and silicification, brecciation and fracture filling, and cataclastic brecciation—with the latter two being gold-rich. Fluid inclusion data suggest mineral deposition at temperatures of at least 220–255°C and depths of at least 1.4–1.8 km, from a H2O–CO2±CH4 fluid of relatively high salinity (12–14 wt.% NaCl equiv.), which may reflect metamorphism of passive margin carbonate sequences. Ore fluid δ18O values between about 7‰ and 9‰ suggest no significant meteoric water input, despite gold deposition in a relatively shallow epizonal environment. Similarities to other deposits in the SSZ suggest that the deposit formed as

  6. Gold deposits in the Xiaoqinling-Xiong'ershan region, Qinling mountains, central China

    USGS Publications Warehouse

    Mao, J.; Goldfarb, R.J.; Zhang, Z.; Xu, W.; Qiu, Y.; Deng, J.

    2002-01-01

    The gold-rich Xiaoqinling-Xiong'ershan region in eastern Shaanxi and western Henan provinces, central China, lies about 30-50 km inland of the southern margin of the North China craton. More than 100 gold deposits and occurrences are concentrated in the Xiaoqinling (west), Xiaoshan (middle), and Xiong'ershan (east) areas. Late Archean gneiss of the Taihua Group, and Middle Proterozoic metavolcanic rocks of the Xiong'er Group are the main host rocks for the deposits. Mesozoic granitoids (ca. 178-104 Ma) are present in most gold districts, but deposits are typically hosted in the Precambrian basement rocks hundreds of meters to as far as 10 km from the intrusions and related hornfels zones. Deposits in the Xiaoqinling and Xiaoshan areas are best classified as orogenic gold deposits, with ores occurring in a number of distinct belts both in quartz veins and disseminated in altered metamorphic rocks. Alteration assemblages are dominated by quartz, sericite, pyrite, and carbonate minerals. The ore-forming fluids were low salinity, CO2-rich, and characterized by isotopically heavy ??18O. Four deposits (Dongchuang, Wenyu, Yangzhaiyu, and Dahu) in the Xiaoqinling area each contain resources of about 1 Moz Au. Some of the gold deposits in the Xiong'ershan area represent more shallowly emplaced tellurium-enriched orogenic systems, which include resources of approximately 1-1.5 Moz Au at Shanggong and Beiling (or Tantou). Others are epithermal deposits (e.g., Qiyugou and Dianfang) that are hosted in volcanic breccia pipes. Isotopic dates for all gold deposits, although often contradictory, generally cluster between 172-99 Ma and are coeval with emplacement of the post-kinematic granitoids. The gold deposits formed during a period of relaxation of far-field compressional stresses, clearly subsequent to the extensive Paleozoic-early Mesozoic accretion of are terranes and the Yangtze craton onto the southern margin of the North China craton. Hydrothermal and magmatic events

  7. Quartz crystal growth

    DOEpatents

    Baughman, Richard J.

    1992-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Cervantes, Pablo; Wiltschko, David V.

    2010-08-01

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

  9. A quartz crystal biosensor for measurement in liquids.

    PubMed

    Kösslinger, C; Drost, S; Aberl, F; Wolf, H; Koch, S; Woias, P

    1992-01-01

    The detection of anti-human immunodeficiency virus (HIV) antibodies by means of synthetic HIV peptide immobilized on a piezoelectric quartz sensor is demonstrated. The measurement set-up consists of an oscillator circuit, a suitably modified AT-cut thickness-shear-mode quartz crystal with gold electrodes, which is housed in a special reaction vessel, and a computer-controlled frequency counter for the registration of the measured frequency values. The quartz crystal is adapted for a steady operation in liquids at a frequency of 20 MHz. In phosphate-buffered saline solution the oscillator reaches a stability of about 0.5 Hz within a few seconds, of about 2 Hz within 10 min and about 30 Hz within 1 h. The frequency shift due to the adsorption of various proteins to the uncoated sensor surface has been investigated. It can be shown that a stable adsorptive binding of proteins to an oscillating gold surface is feasible and can be used for the immobilization of a receptor layer (e.g. HIV peptide). Specific binding of the anti-HIV monoclonal antibody to the HIV peptide immobilized on the quartz sensor is demonstrated. Control experiments show, however, additional unspecific binding. According to the experiments, the Sauerbrey formula gives a sufficiently accurate value for the decrease of the resonant frequency due to adsorption or binding of macromolecular proteins on the quartz crystal surface.

  10. The compression pathway of quartz

    SciTech Connect

    Thompson, Richard M.; Downs, Robert T.; Dera, Przemyslaw

    2011-11-07

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-07-01

    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

  12. Force chain forming quartz in an ultramylonite

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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

  13. Paragenesis and geochemistry of ore minerals in the epizonal gold deposits of the Yangshan gold belt, West Qinling, China

    NASA Astrophysics Data System (ADS)

    Li, Nan; Deng, Jun; Yang, Li-Qiang; Goldfarb, Richard J.; Zhang, Chuang; Marsh, Erin; Lei, Shi-Bin; Koenig, Alan; Lowers, Heather

    2014-04-01

    Six epizonal gold deposits in the 30-km-long Yangshan gold belt, Gansu Province are estimated to contain more than 300 t of gold at an average grade of 4.76 g/t and thus define one of China's largest gold resources. Detailed paragenetic studies have recognized five stages of sulfide mineral precipitation in the deposits of the belt. Syngenetic/diagenetic pyrite (Py0) has a framboidal or colloform texture and is disseminated in the metasedimentary host rocks. Early hydrothermal pyrite (Py1) in quartz veins is disseminated in metasedimentary rocks and dikes and also occurs as semi-massive pyrite aggregates or bedding-parallel pyrite bands in phyllite. The main ore stage pyrite (Py2) commonly overgrows Py1 and is typically associated with main ore stage arsenopyrite (Apy2). Late ore stage pyrite (Py3), arsenopyrite (Apy3), and stibnite occur in quartz ± calcite veins or are disseminated in country rocks. Post-ore stage pyrite (Py4) occurs in quartz ± calcite veins that cut all earlier formed mineralization. Electron probe microanalyses and laser ablation-inductively coupled plasma mass spectrometry analyses reveal that different generations of sulfides have characteristic of major and trace element patterns, which can be used as a proxy for the distinct hydrothermal events. Syngenetic/diagenetic pyrite has high concentrations of As, Au, Bi, Co, Cu, Mn, Ni, Pb, Sb, and Zn. The Py0 also retains a sedimentary Co/Ni ratio, which is distinct from hydrothermal ore-related pyrite. Early hydrothermal Py1 has high contents of Ag, As, Au, Bi, Cu, Fe, Sb, and V, and it reflects elevated levels of these elements in the earliest mineralizing metamorphic fluids. The main ore stage Py2 has a very high content of As (median value of 2.96 wt%) and Au (median value of 47.5 ppm) and slightly elevated Cu, but relatively low values for other trace elements. Arsenic in the main ore stage Py2 occurs in solid solution. Late ore stage Py3, formed coevally with stibnite, contains relatively

  14. Exploration of gold occurrences in alteration zones at Dungash district, Southeastern Desert of Egypt using ASTER data and geochemical analyses

    NASA Astrophysics Data System (ADS)

    Salem, S. M.; El Sharkawi, M.; El-Alfy, Z.; Soliman, N. M.; Ahmed, S. E.

    2016-05-01

    The present study aims at exploration of new gold occurrences in the alteration zones at Dungash district. Processed ASTER images band ratios 7/6 × 4/6 and (7 + 9/8), field geology and mineralogical and geochemical data help characterize three types of alterations in three areas 1 to 3 that may be targeted for Au exploration. Area1 confined to the metavolcanics located in the SE of Dungash gold mine and revealed silicified and sericitized type alterations, composed of quartz, epidote, chlorite, biotite and opaque minerals mainly pyrite and chalcopyrite. Area2 occurs in the gabbro-diorite rocks at Abu Meraiwa area NE of Dungash gold mine, which are rich in kaolinite, illite, sericite, pyrite, arsenopyrite and chalcopyrite that record kaolinitized alteration. Area3 is hosted in carbonaceous listwaenized serpentinite thus indicating the role of listwaenitization type alteration in ore genesis. It is composed of calcite, chromite, pyrite, arsenopyrite, chalcopyrite and Ni-bearing sulphides. Au contents in area 1 range between 0.12 and 14.91 ppm, and between 6.1 and 16.3 ppm in area 2, while gold values in area 3 vary from <0.01 to 0.03 ppm. Dungash district is comprised of Pan-African assemblages of ophiolitic ultramafics thrusted over the island arc metavolcanics of dacitic- andesite composition. Gabbro-diorite rocks are intruded in the ultramafics and the acidic metavolcanics as well as diorite-quartz diorite suite intruded in the intermediate metavolcanics. Several acidic dykes, granitic dykes and quartz veins cut through the different rocks types.

  15. QUARTZ FIBER ELECTROSCOPES

    DOEpatents

    Henderson, R.P.

    1956-04-17

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

  16. Multiple origins of Canadian Cordilleran gold deposits: geologic-tectonic constraints

    SciTech Connect

    Nesbitt, B.E.; Murowchick, J.B.; Muehlenbachs, K.

    1985-01-01

    Detailed examination of geologic and geochemical characteristics of lode gold deposits in the Canadian Cordillera indicates that there are at least two different, yet synchronous styles of gold mineralization: Mother Lode and Epithermal. Epithermal type deposits are hosted by Late Jurassic to Tertiary intermediate to felsic volcanic units in accreted island arc terrains. They have many characteristics in common with the better known US epithermal deposits including potassic, silicic and low pH alteration zones, quartz-chalcedony-calcite-barite gangue and Au/Ag, < 1.0. Mother Lode vein systems are found in most terrains of the Canadian Cordillera and typically show a spatial correlation with major Early Cretaceous to Tertiary transcurrent or thrust faults, but no consistent correlation with felsic plutons. Host rocks for Mother Lode deposits include a wide variety of rock types with a nearly ubiquitous association with serpentinites. All of the units hosting ore have been metamorphosed to low to middle greenschist facies. Mother Lode deposits are accompanied by ankeritic, albitic, sericitic and silicic alteration, have a characteristic gangue assemblage of, Qz, Carb, Alb, Mariposite +/- Scheelite, Asp, Py, Po, Cp and a Au/Ag > 1. The deposits appear to have formed from deep circulation of meteoric water in major fracture zones, typically transcurrent faults. Subsequent upward movement and cooling of the fluids caused deposition of gold and associated gangue. Geologic and geochemical similarities of Mother Lode deposits to Archean gold deposits indicate that such an origin may well have been responsible for many Archean deposits, as well.

  17. Deep Vein Thrombosis

    MedlinePlus

    ... vein swells, the condition is called thrombophlebitis. A deep vein thrombosis can break loose and cause a serious problem in the lung, called a pulmonary embolism. Sitting still for a long time can make ...

  18. Deep vein thrombosis - discharge

    MedlinePlus

    ... this page: //medlineplus.gov/ency/patientinstructions/000027.htm Deep vein thrombosis - discharge To use the sharing features ... page, please enable JavaScript. You were treated for deep vein thrombosis ( DVT ). This is a condition in ...

  19. Varicose vein stripping

    MedlinePlus

    ... noninvasive treatment Varicose veins Venous insufficiency Patient Instructions Surgical wound care - open Varicose veins - what to ask your doctor Review Date 6/6/2016 ... Interventional Radiology & Surgical Critical Care, Philadelphia, PA. Review provided by VeriMed ...

  20. Focus on Varicose Veins

    MedlinePlus

    ... work- ing properly or have evidence of reflux. Measurement of the venous function of the leg may ... Vein stripping was the traditional treatment for bad values in the veins however it is rarely used ...

  1. Portal Vein Thrombosis

    PubMed Central

    Mallet, Thierry; Soltys, Remigiusz; Loarte, Pablo

    2015-01-01

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

  2. ORIGIN OF QUARTZ IN COAL.

    USGS Publications Warehouse

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

    1984-01-01

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

  3. Quartz Crystal Fabrication Facility.

    DTIC Science & Technology

    1980-05-01

    34 platforms. Each platform is supported by four ball coasters engaging a ground plate. The elevation of the chamber end flanges are adjusted by shimming of the...support shaft is rotated and moved in the vertical direction until the source aperture appears centered in the mask and in the skimmer aperture, as...gold source evaporators, and controls for mask head operation. Closed loop temperature regulators with thermocouple sensors are provided for heater

  4. Reconnaissance investigations of ancient gold mines in the southern part of the Wadi Bidah District, Jabal Ibrahim and Al Aqiq quadrangles, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Worl, R.G.; Smith, C.W.

    1982-01-01

    Ancient gold mines in the southern part of the Wadi Bidah district, Kingdom of Saudi Arabia, are located either within lenses of ferruginous chert or in large felsic intrusions of Precambrian age. All are associated with quartz veins, stringers, and stockworks. Samples from both types of deposits have low silver and base-metal contents; samples from deposits within ferruginous chert have anomalous arsenic contents. None of the deposits are large enough to be considered as prime exploration targets at this time. Analytical results from the Bani Sar deposit, which is located within felsic plutonic rocks, are encouraging, but additional surface investigations are needed to define the size and extent of the mineralized zone. Deposits associated with ferruginous chert are also of exploration interest. Anomalous gold contents and other evidence of mineralization were found along a considerable exposure of the metasedimentary unit that contains the chert lenses.

  5. Gold-porphyric mineralization of the Kara ore knot in eastern Transbaikal as a new type of auriferous mineralization in East Siberia

    NASA Astrophysics Data System (ADS)

    Zhmodik, S. M.; Roslyakov, N. A.; Spiridonov, A. M.; Kozachenko, I. V.

    2009-07-01

    On the basis of new data, the authors substantiate the occurrence of gold-porphyric large-volume mineralization, atypical for Transbaikal, within the Sretensk-Kara ore region situated in the zone of the Mongol-Okhotsk suture separating the area of proterozoids of the Stanovoi zone from early mesozoids of Southeastern Transbaikal. The auriferous mineralization is presented by three spatially superposed exploitation-genetic types: (1) veined; (2) mineralized zones; and (3) dispersed and streaky-impregnated (stockwork). All these types and the whole set of granodiorite-dioritic stock with dispersed and streaky-impregnated mineralization, zones of kali-sparization and sulfidization (in fact, by stockwork), and the dykes of quartz dioritic porphyrites were formed as a result of the occurrence of a unified ore-magmatic system and constitute a large-volume deposit corresponding, by all the features, to the gold-porphyric type.

  6. Geology of the world-class Kiaka polyphase gold deposit, West African Craton, Burkina Faso

    NASA Astrophysics Data System (ADS)

    Fontaine, Arnaud; Eglinger, Aurélien; Ada, Koumangdiwè; André-Mayer, Anne-Sylvie; Reisberg, Laurie; Siebenaller, Luc; Le Mignot, Elodie; Ganne, Jérôme; Poujol, Marc

    2017-02-01

    The Kiaka gold deposit is a major resource in West Africa, with measured and indicated resources of 124 Mt at 1.09 g/t Au (3.9 Moz) and inferred resources of 27 Mt at 0.83 g/t Au (0.8 Moz). Located within the Manga-Fada N'Gourma greenstone and plutonic belt in south of the Burkina Faso, the deposit is hosted by a metamorphosed volcano-sedimentary sequence of lithic-, quartz-biotite metagreywackes, aluminosilicate-bearing metapelites and garnet-orthopyroxene-bearing schists and volcanic units. Structural observations indicate four local deformation events: DK1, DK2 and DK3 and DK4. Respectively, these events are linked to regional D1 E-W compression, D2 NW-SE compression and lastly, D3- and D4-related reactivations along D2 shear zones. The S2 foliation and D2 shear zones are developed during lower amphibolite facies metamorphism whereas retrogression occurs during D3-4 reactivations along these shear zones at upper greenschist facies conditions. The emplacement of a dioritic intrusion, dated at 2140 ± 7 Ma (Concordia U-Pb age on magmatic zircon), is interpreted to be contemporaneous with sinistral displacement along mineralized, NE-trending D2 shear zones. The intersection of these shears zones and the Markoye shear zone (dextral-reverse D1 and sinistral-reverse D2 reactivations) controlled the final geometry of the host rocks and the ore zones. Four subparallel elongated ore bodies are mainly hosted within D2-related shear zones and some are developed in an apparent axial plane of a F2 isoclinal fold. Detailed petrographic studies have identified two main types of hydrothermal alteration associated with two stages of gold mineralization. The stage (1) corresponds to replacement zones with biotite and clinozoisite during the D2 event associated with pyrrhotite ± pyrite, chalcopyrite (disseminated gold stage). The stage (2) occurs during reactivations of the D2-related auriferous shear zones (vein stage) and is characterized by diopside ± actinolite D3 veins and

  7. Geology of the Barite Hill gold-silver deposit in the southern Carolina slate belt

    USGS Publications Warehouse

    Clark, S.H.B.; Gray, K.J.; Back, J.M.

    1999-01-01

    hydrothermal activity in a failed massive sulfide system or in a separate event; (3) sulfides and silica-barite rock recrystallized during regional deformation and greenschist facies metamorphism related to the Middle to Late Ordovician collision of the Carolina terrane with the North American continental plate; (4) quartz, barite, and gold were remobilized and formed veins that cut across cleavage; (5) orebodies were offset along high-angle faults; and (6) during weathering, base metal sulfides and barite dissolved and reprecipitated as supergene euhedral barite crystals that line ferric iron oxide-hydroxide gossans.

  8. Quartz resonator processing system

    DOEpatents

    Peters, Roswell D. M.

    1983-01-01

    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.

  9. The Thermal Evolution of the Benton and Broken Bow uplifts, Ouachita Orogen, Arkansas and Oklahoma from Quartz-Calcite Thermometry and Fluid Inclusion Thermobarometry

    NASA Astrophysics Data System (ADS)

    Piper, J.; Wiltschko, D.

    2011-12-01

    To understand the fluid temperature and pressure during the Ouachita orogeny, we use isotopic analysis of syntectonic veins and adjacent host material, quartz-calcite oxygen isotope thermometry and fluid inclusion analysis. The veins were at or near isotopic equilibrium with their host rocks; neither the host nor veins have been isotopically reset. The average isotopic variation in δ18O between vein and host is 2.4% ± 1.7% and 0.7% ± 1.7% for quartz and calcite, respectively. The temperature of vein formation from quartz-calcite oxygen isotope thermometry is about 210°-430°C. Although this is a large range, the temperature does not vary systematically in the exposed Ordovician through Mississippian rocks. The lack of isotopic difference between host and vein suggests that the host oxygen determined that of the veins. This in turn suggests that the fluid in the rocks did not change regionally. The vitrinite reflectance/temperature of the host rocks increases with restored stratigraphic depth more than that calculated with the quart-calcite thermometer in veins. Fluid inclusion analysis in vein quartz constrains homogenization temperatures to be from 106°-285°C. Isochores from fluid inclusion analyses were constrained using quartz-calcite thermometry and vitrinite reflectance temperatures to calculate vein formation pressures of 0.3-4.7 kbars. These pressures correspond to vein formation depths up to 19 km assuming an unduplicated stratigraphic section. Using burial curves and a reasonable range of geothermal gradients places vein formation between 300 to 315 Ma, i.e., Early to Middle Pennsylvanian.

  10. The effect of chrome adhesion layer on quartz resonator aging.

    SciTech Connect

    Wessendorf, Kurt O.; Ohlhausen, James Anthony

    2011-03-01

    This SAND report documents a late start LDRD designed to determine the possible aging effects of a quartz resonator gold adhesion layer. Sandia uses quartz resonators for applications. These applications require a very stable frequency source with excellent aging (low drift) characteristics. These parts are manufactured by one of our qualified vendors outside Sandia Laboratories, Statek Corp. Over the years we, Sandia and the vendor, have seen aging variations that have not been completely explained by the typical mechanisms known in the industry. One theory was that the resonator metallization may be contributing to the resonator aging. This LDRD would allow us to test and analyze a group of resonators with known differentiating metallization and via accelerated aging determine if a chrome adhesion layer used to accept the final gold plating may contribute to poor aging. We worked with our main vendor to design and manufacture a set of quartz resonators with a wide range of metallization thickness ratios between the chrome and gold that will allow us determine the cause of this aging and which plating thickness ratios provide the best aging performance while not degrading other key characteristics.

  11. Application of kinematic vorticity and gold mineralization for the wall rock alterations of shear zone at Dungash gold mining, Central Eastern Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Kassem, Osama M. K.; Abd El Rahim, Said H.; El Nashar, EL Said R.; AL Kahtany, Kaled M.

    2016-11-01

    The use of porphyroclasts rotating in a flowing matrix to estimate mean kinematic vorticity number (Wm) is important for quantifying the relative contributions of pure and simple shear in wall rocks alterations of shear zone at Dungash gold mine. Furthermore, it shows the relationship between the gold mineralization and deformation and also detects the orientation of rigid objects during progressive deformation. The Dungash gold mine area is situated in an EW-trending quartz vein along a shear zone in metavolcanic and metasedimentary host rocks in the Eastern Desert of Egypt. These rocks are associated with the major geologic structures which are attributed to various deformational stages of the Neoproterozoic basement rocks. We conclude that finite strain in the deformed rocks is of the same order of magnitude for all units of metavolcano-sedimentary rocks. The kinematic vorticity number for the metavolcanic and metasedimentary samples in the Dungash area range from 0.80 to 0.92, and together with the strain data suggest deviations from simple shear. It is concluded that nappe stacking occurred early during the underthrusting event probably by brittle imbrication and that ductile strain was superimposed on the nappe structure during thrusting. Furthermore, we conclude that disseminated mineralization, chloritization, carbonatization and silicification of the wall rocks are associated with fluids migrating along shearing, fracturing and foliation of the metamorphosed wall rocks.

  12. Gold Rush!

    ERIC Educational Resources Information Center

    Brahier, Daniel J.

    1997-01-01

    Describes a mathematical investigation of gold--how it is weighed, stored, used, and valued. For grades 3-4, children estimate the value of treasure chests filled with gold coins and explore the size and weight of gold bars. Children in grades 5-6 explore how gold is mined and used, and how the value of gold changes over time. (PVD)

  13. Electrochemical Quartz Crystal Nanobalance

    NASA Astrophysics Data System (ADS)

    Inzelt, György

    The method of piezoelectric microgravimetry (nanogravimetry) using an electrochemical quartz crystal microbalance (EQCM) or nanobalance (EQCN) can be considered as a novel and much more sensitive version of electrogravimetry. The EQCN technique has become a widely used technique in several areas of electrochemistry, electroanalytical chemistry, bioelectrochemistry, etc. [1-10]. Obviously, mass changes occurring during adsorption, sorption, electrosorption, electrodeposition, or spontaneous deposition can be followed, which is very helpful for the elucidation of reaction mechanism via identification of the species accumulated on the surface. These investigations include metal and alloy deposition, underpotential deposition, electroplating, synthesis of conducting polymers by electropolymerization, adsorption of biologically active materials, and analytical determination of small ions and biomolecules. Of course, the opposite processes, i.e., spontaneous dissolution, electrodissolution, corrosion, can also be studied. Electrochemical oscillations, in which the formation and oxidation of chemisorbed molecular fragments play a determining role, have been studied, too. The majority of the investigations have been devoted to ion and solvent transport associated with the redox transformations of electrochemically active polymers. Similar studies have been carried out regarding polynuclear surface layers such as metal hexacyanometalates as well as inorganic and organic microcrystals of different compositions.

  14. Hydrogen speciation in synthetic quartz

    USGS Publications Warehouse

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

    1984-01-01

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

  15. Gold-bearing skarns

    USGS Publications Warehouse

    Theodore, Ted G.; Orris, Greta J.; Hammerstrom, Jane M.; Bliss, James D.

    1991-01-01

    In recent years, a significant proportion of the mining industry's interest has been centered on discovery of gold deposits; this includes discovery of additional deposits where gold occurs in skarn, such as at Fortitude, Nevada, and at Red Dome, Australia. Under the classification of Au-bearing skarns, we have modeled these and similar gold-rich deposits that have a gold grade of at least 1 g/t and exhibit distinctive skarn mineralogy. Two subtypes, Au-skarns and byproduct Au-skarns, can be recognized on the basis of gold, silver, and base-metal grades, although many other geological factors apparently are still undistinguishable largely because of a lack of detailed studies of the Au-skarns. Median grades and tonnage for 40 Au-skarn deposits are 8.6 g/t Au, 5.0 g/t Ag, and 213,000 t. Median grades and tonnage for 50 byproduct and Au-skarn deposits are 3.7 g/t Au, 37 g/t Ag, and 330,000 t. Gold-bearing skarns are generally calcic exoskarns associated with intense retrograde hydrosilicate alteration. These skarns may contain economic amounts of numerous other commodities (Cu, Fe, Pb, Zn, As, Bi, W, Sb, Co, Cd, and S) as well as gold and silver. Most Au-bearing skarns are found in Paleozoic and Cenozoic orogenic-belt and island-arc settings and are associated with felsic to intermediate intrusive rocks of Paleozoic to Tertiary age. Native gold, electru, pyrite, pyrrhotite, chalcopyrite, arsenopyrite, sphalerite, galena, bismuth minerals, and magnetite or hematite are the most common opaque minerals. Gangue minerals typically include garnet (andradite-grossular), pyroxene (diopside-hedenbergite), wollastonite, chlorite, epidote, quartz, actinolite-tremolite, and (or) calcite.

  16. Dating native gold by noble gas analyses

    NASA Technical Reports Server (NTRS)

    Niedermann, S.; Eugster, O.; Hofmann, B.; Thalmann, CH.; Reimold, W. U.

    1993-01-01

    Our recent work on He, Ne, and Ar in Alpine gold samples has demonstrated that gold is extremely retentive for He and could thus, in principle, be used for U/Th-He-4 dating. For vein-type gold from Brusson, Northern Italy, we derived a U/Th-He-4 age of 36 Ma, in agreement with the K-Ar formation age of associated muscovites and biotites. However, in placer gold from the Napf area, Central Switzerland, we observed large excesses of both He-4 and radiogenic Ar-40 (Ar-40 sub rad, defined as Ar-40-295.5-Ar-.36). The gas release systematics indicate two distinct noble gas components, one of which is released below about 800 C and the other one at the melting point of gold (1064 C). We now present results of He and Xe measurements in a 1 g placer gold sample from the river Kruempelgraben, as well as He and Ar data for Brusson vein-type gold and for gold from the Lily Gold Mine, South Africa. We calculate reasonable U/Th-He-4 as well as U-Xe ages based on those gases which are released at approximately 800 C. Probably the low-temperature components represent in-situ-produced radiogenic He and fission Xe, whereas the gases evolving when gold melts have been trapped during gold formation. Therefore, only the low-temperature components are relevant for dating purposes.

  17. Metal and fluid sources in a potential world-class gold deposit: El-Sid mine, Egypt

    NASA Astrophysics Data System (ADS)

    Helmy, Hassan; Zoheir, Basem

    2015-04-01

    Lode gold mineralization at the El-Sid mine area is associated with the ca. 600 Ma Fawakhir granite intrusion, which cuts the ~737 Ma ophiolite nappes in the Central Eastern Desert of Egypt. The mineralized quartz veins are hosted by ~E- and NE-trending fault/fracture sets cutting the western boundary of the intrusion and sheared ophiolites. The results of electron microprobe analyses of gold-associated hydrothermal sulfide and silicate minerals suggest that Au was mobilized alongside Ni, Co, Cr and As from the adjacent ophiolitic serpentinite. After granite emplacement, hydrothermal fluids interacted with the sheared serpentinite, leaching metals and re-depositing them in the faults/fractures and adjacent wall rock in a cyclic process. Low-salinity aqueous-carbonic fluids with significant quantities of volatile species (CO2, CH4, and N2 ± H2S) leached and transported Au from deep to shallow crustal levels. Carbon dioxide had a buffering effect on the Au-bearing hydrothermal solution, maintaining its pH within a narrow near-neutral range, where elevated gold concentration was transported by complexation with reduced magmatic sulfur in a reducing environment. Gold deposition along fault/fracture conduits in the Fawakhir granite and adjacent serpentinite resulted from interplay of pressure drop, fluctuations in oxygen and sulfur fugacities, and exsolution of the volatile phases. Infiltration of meteoric water may have contributed to the formation of the late stage gold-sulfide mineralization that formed at shallower levels during terrane uplift. Sulfidation of the Fe-rich magmatic minerals was, on the other hand, the overriding process in the wall rock as evidenced by abundant disseminated sulfides with gold inclusions. Considering the structural control by regional shear zones (fluid conduits) and the voluminous granitic and ophiolitic rocks (metal sources), a high tonnage gold deposit amenable to open pit mining at the El-Sid mine area is very likely.

  18. Vein of Galen Aneurysms

    PubMed Central

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

    2001-01-01

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

  19. Geology of Unga Island and the northwestern part of Popof Island: Chapter 2 in A geological and geophysical study of the gold-silver vein system of Unga Island, Southwestern Alaska

    USGS Publications Warehouse

    Riehle, James R.; Wilson, Frederic H.; Shew, Nora B.; White, Willis H.

    1999-01-01

    The first geologic map of Unga Island was published by Atwood (1911; scale 1:250,000), who correctly inferred the middle Tertiary age of the volcanic rocks and made the important distinction between the lava flows and the intrusive domes. Although Burk's (1964) reconnaissance map of the Alaska Peninsula (scale 1:250,000) has been modified in some respects, it does correct Atwood's map by replacing the Kenai Formation on northwestern Unga Island with the Unga Conglomerate and by recognizing the older Stepovak Formation elsewhere on Unga and Popof Islands.U.S. Geological Survey (USGS) field studies that were focused on the mineral-resource potential of the Alaska Peninsula began in the late 1970's. These studies led to a geologic map of the Port Moller quadrangle--including Unga Island--at 1:250,000 scale (Wilson and others, 1995), as well as summaries of mineral occurrences and geochronological studies (Wilson and others, 1988, 1994) and a formal revision of the stratigraphic units of the Alaska Peninsula (Detterman and others, 1996). As follow-up to the regional studies, a detailed study of the vein systems on Unga Island was undertaken as a collaborative effort between USGS and private industry (White and Queen, 1989). The fieldwork leading to the present report and geologic map was started in 1978 (Riehle and others, 1982) and was completed as part of the vein study. The objective was a better understanding of the geologic setting of the vein systems: the geologic history of the host rocks, the structural controls on the veins, and the types of processes that likely caused the mineralization.

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

    USGS Publications Warehouse

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

    2015-01-01

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

  1. Microchemical signature of alluvial gold from two contrasting terrains in Cameroon

    NASA Astrophysics Data System (ADS)

    Omang, B. O.; Suh, C. E.; Lehmann, B.; Vishiti, A.; Chombong, N. N.; Fon, A. N.; Egbe, J. A.; Shemang, E. M.

    2015-12-01

    The microchemical signature of alluvial gold particles has wide application in constraining their primary sources. In this study, we apply this concept to investigate the composition of gold-bearing alloys from alluvial samples draining two geologically distinct terrains in southern and eastern Cameroon where the search for primary gold has remained elusive. The first set of gold grains (Lom grains) are from the Lom river drainage system with predominantly metasedimentary Pan-African rocks in the catchment region while the second set of grains (Nyong grains) are from the Mbal and Ebap tributaries of the Nyong river draining over a Paleoproterozoic complex comprising metamorphosed ultramafic rocks, amphibolites and granulitic gneisses. The gold grains recovered from these fluvial networks after panning were first studied under an electron microscope in order to evaluate their morphological features and subsequently embedded in epoxy resin, polished, and their compositions determined by both electron microprobe (EMPA) and laser ablation (LA-ICP-MS) techniques. The Lom grains are irregular to sub rounded with extensively pitted surfaces while the Nyong grains are predominantly rounded, oblong and with smooth surfaces. Nyong grains are devoid of inclusions while galena and pyrite are entombed in the Lom grains. Both set of grains are essentially Au-Ag alloys although the Ag content of the cores of the Nyong grains from both EMPA and LA-ICP-MS analytical techniques are significantly lower (0.05-6.07 wt% Ag; 93.54-99.29 wt% Au) than for Lom gold (0.06-22.75 wt% Ag; 78.76-99.86 wt% Au). X-ray element distribution maps do not show any zonal variation in core composition suggesting the gold grains derived from lode sources with single episode of hydrothermal gold deposition. Also the Nyong grains have significant amounts of Pt, Pd and Cr suggesting a link with ultramafic rocks while the Lom grains have substantial Sb and Zn levels pointing to hydrothermal quartz veining as

  2. Protein adsorption on surfaces: dynamic contact-angle (DCA) and quartz-crystal microbalance (QCM) measurements.

    PubMed

    Stadler, H; Mondon, M; Ziegler, C

    2003-01-01

    Adsorption of the protein bovine serum albumin (BSA) on gold has been tested at various concentrations in aqueous solution by dynamic contact-angle analysis (DCA) and quartz-crystal microbalance (QCM) measurements. With the Wilhelmy plate technique advancing and receding contact angles and the corresponding hysteresis were measured and correlated with the hydrophilicity and the homogeneity of the surface. With electrical admittance measurements of a gold-coated piezoelectrical quartz crystal, layer mass and viscoelastic contributions to the resonator's frequency shift during adsorption could be separated. A correlation was found between the adsorbed mass and the homogeneity and hydrophilicity of the adsorbed film.

  3. Brazil's premier gold province. Part II: geology and genesis of gold deposits in the Archean Rio das Velhas greenstone belt, Quadrilátero Ferrífero

    NASA Astrophysics Data System (ADS)

    Lobato, Lydia; Ribeiro-Rodrigues, Luiz; Vieira, Frederico

    2001-07-01

    Orogenic, gold deposits are hosted by rocks of the Archean Rio das Velhas greenstone belt in the Quadrilátero Ferrífero region, Minas Gerais state, Brazil, one of the major gold provinces in the world. The gold deposits occur at the base of the mafic-ultramafic succession, with the most important orebodies controlled by E-W-striking, strike-slip faults. The main mineralization styles are (1) structurally controlled, sulfide replacement zones in banded iron formation (BIF); (2) disseminated sulfide minerals and gold in hydrothermally altered rocks along shear zones; and (3) auriferous quartz-carbonate-sulfide veins and veinlets in mafic, ultramafic, and felsic volcanic rocks, and also in clastic sedimentary rocks. The most common host rocks for ore are metamorphosed oxide- and carbonate-facies banded iron (± iron-rich metachert) formations (e.g., the Cuiabá, São Bento and Raposos deposits) and the lapa seca unit, which is a local term for intensely carbonatized rock (e.g., the giant Morro Velho mine with >450 t of contained gold). Metabasalts host most of the remaining gold deposits. Mineralogical characteristics and fluid inclusion studies suggest variations in the H2O/CO2 ratio of a low-salinity, near-neutral, reducing, sulfur-bearing, ore fluid. The presence of abundant CH4-rich inclusions is related to reduction of the original H2O-CO2 fluid via interaction with carbonaceous matter in the wallrocks. Oxygen fugacity was close to that of graphite saturation, with variations likely to have been influenced by reaction with the carbonaceous matter. Carbon-rich phyllites and schists, which commonly bound ore-bearing horizons, seem to have played both a physical and chemical role in localizing hydrothermal mineral deposition. Microtextural studies indicate that gold deposition was mainly related to desulfidation reactions, and was paragenetically coeval with precipitation of arsenic-rich iron sulfide minerals. Carbon isotope data are compatible with dissolution of

  4. Yasny lode-placer cluster: Geological and structural features and gold potential

    NASA Astrophysics Data System (ADS)

    Mel'nikov, A. V.; Stepanov, V. A.

    2014-03-01

    The geological and structural features and gold potential of the Yasny lode-placer cluster in Amur province have been investigated. The lode-placer cluster is an intrusive domal uplift elongated in the nearmeridional direction and surrounded by Neogene loose sediments. The cluster comprises placers that yielded 15 t gold mined from there and small occurrences of gold-quartz and gold-base-metal lodes. Association of native gold with cinnabar in the Yasny Creek placer allows us to forecast a new source of gold-mercury mineralization in the basin of this creek, which could be compared with the Kyuchyus deposit in Yakutia. Gold nuggets 79 kg in total weight were mined from Gar-2 River placer. They are comparable in weight and association with quartz to the world's largest Holtermann Plate nugget from Australia. Gold-quartz lodes have been forecasted in the basin of the Gar-2 Creek.

  5. The late cretaceous Donlin Creek gold deposit, Southwestern Alaska: Controls on epizonal ore formation

    USGS Publications Warehouse

    Goldfarb, R.J.; Ayuso, R.; Miller, M.L.; Ebert, S.W.; Marsh, E.E.; Petsel, S.A.; Miller, L.D.; Bradley, D.; Johnson, Chad; McClelland, W.

    2004-01-01

    The Donlin Creek gold deposit, southwestern Alaska, has an indicated and inferred resource of approximately 25 million ounces (Moz) Au at a cutoff grade of 1.5 g/t. The ca. 70 Ma deposit is hosted in the Late Cretaceous Kuskokwim flysch basin, which developed in the back part of the are region of an active continental margin, on previously accreted oceanic terranes and continental fragments. A hypabyssal, mainly rhyolitic to rhyodacitic, and commonly porphyritic, 8- ?? 3-km dike complex, part of a regional ca. 77 to 58 Ma magmatic arc, formed a structurally competent host for the mineralization. This deposit is subdivided into about one dozen distinct prospects, most of which consist of dense quartz ?? carbonate veinlet networks that fill north-northeast-striking extensional fractures in the northeast-trending igneous rocks. The sulfide mineral assemblage is dominated by arsenopyrite, pyrite, and, typically younger, stibnite; gold is refractory within the arsenopyrite. Sericitization, carbonatization, and suffidation were the main alteration processes. Fluid inclusion studies of the quartz that hosts the resource indicate dominantly aqueous ore fluids with also about 3 to 7 mol percent CO2 ?? CH4 and a few tenths to a few mole percent NaCl + KCl. The gold-bearing fluids were mainly homogeneously trapped at approximately 275?? to 300??C and at depths of 1 to 2 km. Some of the younger stibnite may have been deposited by late-stage aqueous fluids at lower temperature. Measured ??18O values for the gold-bearing quartz range between 11 and 25 per mil; the estimated ??18O fluid values range from 7 to 12 per mil, suggesting a mainly crustally derived fluid. A broad range of measured ??D values for hydrothermal micas, between -150 and -80 per mil, is suggestive of a contribution from devolatilization of organic matter and/or minor amounts of mixing with meteoric fluids. Gold-associated hydrothermal sulfide minerals are characterized by ??34S values mainly between -16 and

  6. Thermoelectrically-cooled quartz microbalance

    NASA Technical Reports Server (NTRS)

    Mckeown, D.

    1975-01-01

    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.

  7. The Tintina Gold Belt - A global perspective

    USGS Publications Warehouse

    Goldfarb, Richard J.; Hart, Craig J.R.; Miller, Marti L.; Miller, Lance D.; Farmer, G. Lang; Groves, David I.; Tucker, T.L.; Smith, M.T.

    1999-01-01

    The so-called Tintina Gold Belt extends for more than 1000 km along the length of the northern North American Cordillera. Middle to Late Cretaceous Au deposits within the belt have various similar characteristics, among which are a spatial and temporal association with magmatism; Bi-W-Te signatures in deposits hosted by granitod stocks and As-Sb signatures where hosted by sedimentary rocks and dyke systems; and δ180 values consistently > 12 per mil for Au-bearing quartz. Nevertheless significant differences in structural styles, levels of deposit emplacement, ore-fluid chemistry, and Au grades suggest that the characteristics represent a broad range of deposit types. Many of these are best classified as orogenic Au deposits in the Yukon-Tanana terrane, as epithermal and porphyry-style Au deposits in the Kuskokwim region, and as Au-bearing, granite-related veins and stockworks, replacements, and skarns, as well as associated polymetallic lodes, in central Yukon. The diverse types of Au deposits and associated plutons of the Tintina Gold Belt collectively define a 45-m.y.-long period of arc magmatism that migrated northwesterly, for about 1000 km, across the active collisional margin of Cretaceous northwestern North America. The initiation of fluid flow and plutonism in Albian time seems to correlate with the onset of oblique subduction and dextral strike-slip on the Denali-Farewell, Tintina-Kaltag, and related fault systems. Initial Au-vein formation and subduction-related magmatism at about 115-110 Ma (e.g., including the Goodpaster and Fortymile districts), within the seaward side of the Yukon-Tanana terrane, correlate with the arrival of the Wrangellia superterrane off the continental margin. Dextral translation of the allochthonous Wrangellia block was associated with the migration of the thermal pulse to the northwest at about 95-90 Ma. Orogenic (or so­ called mesotherrnal) and granitoid-related Au deposits formed across the width of the Yukon

  8. Support for varicose veins.

    PubMed Central

    Fentem, P H; Goddard, M; Gooden, B A

    1976-01-01

    A method has been devised to allow reliable comparison of different strengths and constructions of support hosiery. Five garments were evaluated for the compression they exerted on the leg and their ability to limit the distension of a model varicose vein. Stockings and tights which provide modest compression can achieve worthwhile control of vein distension. PMID:1247807

  9. Prepancreatic preduodenal portal vein.

    PubMed

    Lal, N S; Kuruvila, A P; Natesh, P B; Koshy, M M; Anandakumar, M

    1992-10-01

    We report a 17 year old girl with prepancreatic and preduodenal portal vein. She presented with recurrent vomiting. Barium study revealed malrotation of the gut. Laparotomy confirmed malrotation of the gut with a prepancreatic and preduodenal portal vein. The patient is asymptomatic after gastrojejunostomy and vagotomy.

  10. How Are Varicose Veins Diagnosed?

    MedlinePlus

    ... injected into your veins. The dye outlines your veins on x-ray images. An angiogram can help your doctor confirm whether you have varicose veins or another condition. Rate This Content: NEXT >> Updated: ...

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

    USGS Publications Warehouse

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

    1979-01-01

    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

  12. Pb-Sr isotopic evidence for contribution of deep crustal fluid to the Hishikari epithermal gold deposit, southwestern Japan

    NASA Astrophysics Data System (ADS)

    Hosono, Takahiro; Nakano, Takanori

    2004-05-01

    The gold-bearing quartz-adularia veins of the world-class Hishikari mine in southwestern Japan occur in a geological regime where the rocks of the upper to middle crust are simple and their chemical and Sr-Nd-Pb isotopic compositions are well studied. Detailed comparison of Pb and Sr isotopic data of the Hishikari veins with those of all possible source materials demonstrates that metals in the veins were essentially derived from a mixture of magmatic fluid with a deep crustal fluid that originated near the boundary between the Shimanto middle crust and the underlying subcontinental crustal materials. We propose that the release of the deep crustal fluid was triggered by intrusion of the Shishimano rhyodacite magma related to timing of the mineralization. This fluid mixture carried metals to the brittle upper crust along fissures created by extensional stress forming the ore deposits. Although the deep crustal fluid has not been paid much attention, it may be distributed over a large scale in the deep crust from the continent to the arc system and play an important role in the genesis of magmatic-hydrothermal ore deposits and in the generation of flow-induced deep tremor.

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

    SciTech Connect

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

    1985-01-01

    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.

  14. Role of Substrate on Quartz Cementation in Quartz Aggregates

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    Quartz cementation in quartz aggregates has been experimentally investigated. The starting material was disaggregated detrital quartz grains from the well-sorted, mature St. Peter Sandstone. The ‘as-is’ grains have patches of iron oxide coatings and some have euhedral overgrowths that contain iron oxide dust rims. In addition a set of experiments was run using grains that were cleaned by soaking in sodium hydrosulfite and sodium bisulfate solutions to remove exposed iron oxide coatings. Experimental charges consisted of amorphous silica powder (≈30 mg) to provide a source of silica for the quartz cement, AlCl3 powder (≈3 mg) to provide a tracer for Cathodoluminescence (CL) identification of cement formed during the experiment, 25 wt% NaCl brine solution (≈25 mg) to increase the silica solubility and to better mimic oil field brines, and the natural quartz grains (100-130 mg). The charges were weld-sealed in Au capsules and run in cold-seal pressure vessels at 250°C to 450°C at 150 MPa confining pressure for up to 8 weeks. After the experiments, the samples were vacuum impregnated with a low viscosity epoxy containing a blue dye. After curing, the sample charge was sawn in half along its long axis and one half was polished (to 1 micron diamond paste) for analysis. The nature and amount of quartz cement in the samples were determined by a combination of CL, light microscopy, and scanning electron microscopy. Photomosaics of the samples were created and the amount of cement, porosity, and average grain sizes were determined by point-counting. The cement formed during the experiment was easily recognized from the quartz grains (and previous overgrowths) by the difference in luminescence. The results indicate the amorphous silica powder provides a ready source for silica for quartz cementation due to its greater solubility than the quartz. The cementation rates are rapid (>14% cement formed in 2 weeks at 450°C and >7% in 8 weeks at 250°C). Compared to

  15. Constraints on the composition of ore fluids and implications for mineralising events at the Cleo gold deposit, Eastern Goldfields Province, Western Australia

    USGS Publications Warehouse

    Brown, S.M.; Johnson, C.A.; Watling, R.J.; Premo, W.R.

    2003-01-01

    The Cleo gold deposit, 55 km south of Laverton in the Eastern Goldfields Province of Western Australia, is characterised by banded iron-formation (BIF)-hosted ore zones in the gently dipping Sunrise Shear Zone and high-grade vein-hosted ore in the Western Lodes. There is evidence that gold mineralisation in the Western Lodes (which occurred at ca 2655 Ma) post-dates the majority of displacement along the Sunrise Shear Zone, but it remains uncertain if the ore in both structures formed simultaneously or separately. Overall, the Pb, Nd, Sr, C. O and S isotopic compositions of ore-related minerals from both the Western Lodes and ore zones in the Sunrise Shear Zone are similar. Early low-salinity aqueous-carbonic fluids and late high-salinity fluids with similar characteristics are trapped in inclusions in quartz veins from both the Sunrise Shear Zone and the Western Lodes. The early CO2, CO2-H2O, and H2O- dominant inclusions are interpreted as being related to ore formation, and to have formed from a single low-salinity aqueous-carbonic fluid as a result of intermittent fluid immiscibility. Homogenisation temperatures indicate that these inclusions were trapped at approximately 280??C and at approximately 4 km depth, in the deeper epizonal range. Differences between the ore zones are detected in the trace-element composition of gold samples, with gold from the Sunrise Shear Zone enriched in Ni, Pb, Sn, Te and Zn, and depleted In As, Bi, Cd, Cu and Sb, relative to gold from the Western Lodes. Although there are differences in gold composition between the Sunrise Shear Zone and Western Lodes, and hence the metal content of ore fluids may have varied slightly between the different ore zones, no other systematic fluid or solute differences are detected between the ore zones. Given the fact that the ore fluids in each zone have very similar bulk properties, the considerable differences in gold grade, sulfide mineral abundance, and ore textures between the two ore zones

  16. Microscopy and Cathodoluminescence Spectroscopy Characterization of Quartz Exhibiting Different Alkali-Silica Reaction Potential.

    PubMed

    Kuchařová, Aneta; Götze, Jens; Šachlová, Šárka; Pertold, Zdeněk; Přikryl, Richard

    2016-02-01

    Different quartz types from several localities in the Czech Republic and Sweden were examined by polarizing microscopy combined with cathodoluminescence (CL) microscopy, spectroscopy, and petrographic image analysis, and tested by use of an accelerated mortar bar test (following ASTM C1260). The highest alkali-silica reaction potential was indicated by very fine-grained chert, containing significant amounts of fine-grained to cryptocrystalline matrix. The chert exhibited a dark red CL emission band at ~640 nm with a low intensity. Fine-grained orthoquartzites, as well as fine-grained metamorphic vein quartz, separated from phyllite exhibited medium expansion values. The orthoquartzites showed various CL of quartz grains, from blue through violet, red, and brown. Two CL spectral bands at ~450 and ~630 nm, with various intensities, were detected. The quartz from phyllite displayed an inhomogeneous dark red CL with two CL spectral bands of low intensities at ~460 and ~640 nm. The massive coarse-grained pegmatite quartz from pegmatite was assessed to be nonreactive and displayed a typical short-lived blue CL (~480 nm). The higher reactivity of the fine-grained hydrothermal quartz may be connected with high concentrations of defect centers, and probably with amorphized micro-regions in the quartz, respectively; indicated by a yellow CL emission (~570 nm).

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

    USGS Publications Warehouse

    Böhlke, J.K.

    1989-01-01

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

  18. Deep Vein Thrombosis (DVT)

    MedlinePlus

    ... helps reduce the chances that your blood will pool and clot. You should wear these stockings during ... Make lifestyle changes. Lose weight and quit smoking. Obesity and smoking increase your risk of deep vein ...

  19. What Are Varicose Veins?

    MedlinePlus

    ... family history, older age, gender, pregnancy, overweight or obesity , lack of movement, and leg trauma. Varicose veins are treated with lifestyle changes and medical procedures. The goals of treatment ...

  20. Quartz crystal microbalance apparatus for study of viscous liquids at high temperatures

    NASA Astrophysics Data System (ADS)

    Acharya, Biplav; Sidheswaran, Meera A.; Yungk, Ronald; Krim, Jacqueline

    2017-02-01

    A design for a Quartz Crystal Microbalance (QCM) setup for use with viscous liquids at temperatures of up to 300 °C is reported. The system response for iron and gold coated QCM crystals to two common lubricant base oils, polyalphaolefin and halocarbon, is reported, yielding results that are consistent with theoretical predictions that incorporate electrode nanoscale surface roughness into their analysis.

  1. Genesis of the vein-type tungsten mineralization at Nyakabingo (Rwanda) in the Karagwe-Ankole belt, Central Africa

    NASA Astrophysics Data System (ADS)

    Dewaele, S.; De Clercq, F.; Hulsbosch, N.; Piessens, K.; Boyce, A.; Burgess, R.; Muchez, Ph.

    2016-02-01

    The vein-type tungsten deposit at Nyakabingo in the central Tungsten belt of Rwanda is located in the eastern flank of the complex Bumbogo anticlinal structure. The host rock is composed of alternating sequences of sandstones, quartzites, and black pyritiferous metapelitic rocks. Two types of W-mineralized quartz veins have been observed: bedding-parallel and quartz veins that are at high angle to the bedding, which are termed crosscutting veins. Both vein types have been interpreted to have been formed in a late stage of a compressional deformation event. Both vein types are associated with small alteration zones, comprising silicification, tourmalinization, and muscovitization. Dating of muscovite crystals at the border of the veins resulted in a maximum age of 992.4 ± 1.5 Ma. This age is within error similar to the ages obtained for the specialized G4 granites (i.e., 986 ± 10 Ma). The W-bearing minerals formed during two different phases. The first phase is characterized by scheelite and massive wolframite, while the second phase is formed by ferberite pseudomorphs after scheelite. These minerals occur late in the evolution of the massive quartz veins, sometimes even in fractures that crosscut the veins. The ore minerals precipitated from a H2O-CO2-CH4-N2-NaCl-(KCl) fluid with low to moderate salinity (0.6-13.8 eq. wt% NaCl), and minimal trapping temperatures between 247 and 344 °C. The quartz veins have been crosscut by sulfide-rich veins. Based on the similar setting, mineralogy, stable isotope, and fluid composition, it is considered that both types of W-mineralized quartz veins formed during the same mineralizing event. Given the overlap in age between the G4 granites and the mineralized quartz veins, and the typical association of the W deposits in Rwanda, but also worldwide, with granite intrusions, W originated from the geochemically specialized G4 granites. Intense water-rock interaction and mixing with metamorphic fluids largely overprinted the

  2. Laser welding of fused quartz

    DOEpatents

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

    2003-06-10

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

  3. Controls on mineralisation in the Sierra Foothills gold province, central California, USA: A GIS-based reconnaissance prospectivity analysis

    USGS Publications Warehouse

    Bierlein, F.P.; Northover, H.J.; Groves, D.I.; Goldfarb, R.J.; Marsh, E.E.

    2008-01-01

    The assessment of spatial relationships between the location, abundance and size of orogenic-gold deposits in the highly endowed Sierra Foothills gold province in California, via the combination of field studies and a GIS-based analysis, illustrates the power of such an approach to the characterisation of important parameters of mineral systems, and the prediction of districts likely to host economic mineralisation. Regional- to deposit-scale reconnaissance mapping suggests that deposition of gold-bearing quartz veins occurred in second- and third-order, east-over-west thrusts during regional east - west compression and right-lateral transpression. At the district-scale, significant zones of mineralisation correspond with such transpressional reactivation zones and dilational jogs that developed during the Late Jurassic - Early Cretaceous along the misaligned segments of first-order faults throughout the Sierra Nevada Foothills Metamorphic Belt. Field-based observations and interpretation of GIS data (including solid geology, structural elements, deposit locations, magnetics, gravity) also highlight the importance of structural permeability contrasts, rheological gradients, and variations in fault orientation for localising mineralisation. Although this approach confirms empirical findings and produces promising results at the province scale, enhanced geological, structural, geophysical and geochronological data density is required to generate regionally consistent, high-quality input layers that improve predictive targeting at the goldfield to deposit-scale.

  4. Genetic Aspects of Gold Mineralization at Some Occurrences in the Eastern Desert of Egypt

    NASA Astrophysics Data System (ADS)

    Abd El Monsef, M.; Slobodník, M.; Salem, I. A.

    2012-04-01

    The Eastern Desert of Egypt is well known as a gold-mining area since ancient times, there're more than 95 gold deposits and occurrences spread the whole area covered by the basement rocks of Precambrian age. The basement rocks of the Eastern Desert of Egypt constitute the Nubian Shield that has formed a continuous part of the Arabian-Nubian Shield before the opening of Red Sea (Oligocene-Early Miocene). Commonly, the system of gold-bearing quartz veins in the Eastern Desert is clearly structural controlled related to brittle-ductile shear zones that mostly developed during late deformational stages of the evolution history for basement rocks in the Eastern Desert. This running study principally aims to contribute the mineral resource potential of the gold deposits in Egypt, so particularly Fatira, Gidami and Atalla occurrences have been involved into a comprehensive study based on field, structural, mineralogical, geochemical and genetic investigations. It is intended to better understanding for the characteristics, distribution controls, conditions and age of mineralization in relation to the age of the hosting rocks intrusion to find if there're genetic links between the gold mineralization and the evolution of the host intrusive complex. Several authors suggested that the gold mineralization was related to the intrusion of the (postorogenic) Younger granites. Other authors interpret these deposits as products of hydrothermal activity induced either by metamorphism or cooling effects of early Paleozoic magmatism or as combined metamorphic/magmatic episodes. The prime focus will be directed to the ore itself and the associated hydrothermal alteration zones based on detailed maps and well-distributed samples network and geochemical anomalies distribution. The laboratory studies included microscopic examination (reflecting and transmitting microscopy) to allow for determination of the hosting rocks types and mineralogical changes related to the gold mineralization

  5. Mechanical and ultrastructural evaluation of quartz post-endodontic reconstructions.

    PubMed

    Majori, M; Bedini, R; Altamura, C; Filippini, P; Caiazza, S

    2004-01-01

    Aesthetics is a very important element in dentistry, but requires the support of good mechanical performance. Quartz fiber used in post-endodontic reconstruction is an aesthetic material, although there is little research concerning its mechanical properties. This study evaluated the retentive property of post-endodontic reconstruction, composed of a quartz fiber post. Different thermal stresses were applied in vitro to post-endodontic reconstructions, in order to simulate oral thermal action on post-system dental structure linkage. We chose 30 human extracted teeth, endodontically treated and restored, and then divided them into three groups of 10 teeth. A different treatment was applied to each group before mechanical testing: in the 1st group no treatment was done (controls); in the 2nd group teeth were subjected, in a climatic chamber, to 10 thermo-cycles between 4 degrees C and 58 degrees C; in the 3rd group teeth were stored in a saline solution at 37 degrees C for 48 hr. The teeth then underwent tensile shear stress tests at break point using a computerized electronic dynamometer. After mechanical testing, two teeth from each group were longitudinally half-sectioned, sputter-coated in gold and observed by scanning electron microscopy (SEM). The extracted quartz fiber post of each tooth also underwent SEM observation. Mechanical test results demonstrated that thermal cyclic variations could affect bond stability between dental structures and posts in quartz fiber reconstructions, whereas their bond strength seemed unaffected by humidity increases. Quartz fiber post SEM observation demonstrated a homogeneous structure and a regular fiber disposition. Dental root canal morphology SEM images always showed a different thickness in the cement layer. (Journal of Applied Biomaterials & Biomechanics 2004; 2: 156-61).

  6. Site-specific characterization of Castromil Brownfield area related to gold mining activities.

    PubMed

    Ferreira da Silva, Eduardo; Serrano Pinto, Luís; Patinha, Carla; Cardoso Fonseca, Edmundo

    2004-03-01

    Castromil is one of the gold mining areas in Portugal that has been abandoned since 1940. This area, which was first mined in Roman times, is located within a Hercynian granite body near the contact with Silurian metasediments. Gold is essentially disseminated along veins in the silicified granite, running NW-SE, related with a shear zone and frequently associated with sulphides (arsenopyrite and basically pyrite). In paragenetic terms, three stages of mineralization are considered: ferro-arseniferous (quartz + arsenopyrite I + pyrite I + pyrrhotite + bismuth), zinciferous (sphalerite + chalcopyrite), and remobilization (arsenopyrite II + galena + gold). Due to the lack of laws and environmental education, Castromil is today a gold mining heritage site where we can detect the consequences of an incautious exploration (tailings, wells and adits located in the old explored zone) and where a residential area is located. In order to characterize the actual state of the old mining area the trace metal contamination of soils and waters by mining activities was investigated. In the studied area 106 soil samples, 15 waters and 20 plants were sampled and analysed. The soil samples were analysed for 32 elements by ICP-AES. Waters were analysed by ionic chromatography and ICP-MS for major and trace elements. Plants were analysed for As, Fe and Pb by AAS. The results are discussed taking into account the risk-based standards for soils and groundwater's (target and intervention values) proposed by Swartjes (1999). The results show elevated concentration of As and Pb which were found in soils collected from agricultural areas. Foodstuff plants species collected in the Castromil agricultural area show high concentrations of As in the leaves (cabbage and lettuce) and in the tubers (potatoes). Groundwaters in the mining area contain high concentrations of As that exceeds the intervention values. The area must to be subject to a remediation process, considering the actual risks to

  7. Pelvic Vein Embolisation in the Management of Varicose Veins

    SciTech Connect

    Ratnam, Lakshmi A.; Marsh, Petra; Holdstock, Judy M.; Harrison, Charmaine S.; Hussain, Fuad F.; Whiteley, Mark S.; Lopez, Anthony

    2008-11-15

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

  8. Mineralogical and stable isotope studies of gold-arsenic mineralisation in the Sams Creek peralkaline porphyritic granite, South Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Faure, Kevin; Brathwaite, Robert L.

    2006-03-01

    At Sams Creek, a gold-bearing, peralkaline granite porphyry dyke, which has a 7 km strike length and is up to 60 m in thickness, intrudes camptonite lamprophyre dykes and lower greenschist facies metapelites and quartzites of the Late Ordovician Wangapeka formation. The lamprophyre dykes occur as thin (< 3 m) slivers along the contacts of the granite dyke. δ18Omagma values (+5 to +8‰, VSMOW) of the A-type granite suggest derivation from a primitive source, with an insignificant mature crustal contribution. Hydrothermal gold-sulphide mineralisation is confined to the granite and adjacent lamprophyre; metapelite country rocks have only weak hydrothermal alteration. Three stages of hydrothermal alteration have been identified in the granite: Stage I alteration (high fO2) consisting of magnetite-siderite±biotite; Stage II consisting of thin quartz-pyrite veinlets; and Stage III (low fO2) consisting of sulphides, quartz and siderite veins, and pervasive silicification. The lamprophyre is altered to an ankerite-chlorite-sericite assemblage. Stage III sulphide veins are composed of arsenopyrite + pyrite ± galena ± sphalerite ± gold ± chalcopyrite ± pyrrhotite ± rutile ± graphite. Three phases of deformation have affected the area, and the mineralised veins and the granite and lamprophyre dykes have been deformed by two phases of folding, the youngest of which is Early Cretaceous. Locally preserved early-formed fluid inclusions are either carbonic, showing two- or three-phases at room temperature (liquid CO2-CH4 + liquid H2O ± CO2 vapour) or two-phase liquid-rich aqueous inclusions, some of which contain clathrates. Salinities of the aqueous inclusions are in the range of 1.4 to 7.6 wt% NaCl equiv. Final homogenisation temperatures (Th) of the carbonic inclusions indicate minimum trapping temperatures of 320 to 355°C, which are not too different from vein formation temperatures of 340-380°C estimated from quartz-albite stable isotope thermometry. δ18O values

  9. The Tuscarora Au-Ag district: Eocene volcanic-hosted epithermal deposits in the Carlin gold region, Nevada

    USGS Publications Warehouse

    Castor, S.B.; Boden, D.R.; Henry, C.D.; Cline, J.S.; Hofstra, A.H.; McIntosh, W.C.; Tosdal, R.M.; Wooden, J.P.

    2003-01-01

    The Tuscarora mining district contains the oldest and the only productive Eocene epithermal deposits in Nevada. The district is a particularly clear example of association of low-sulfidation deposits with igneous activity and structure, and it is unusual in that it consists of two adjoining but physically and chemically distinct types of low-sulfidation deposits. Moreover, Tuscarora deposits are of interest because they formed contemporaneously with nearby, giant Carlin-type gold deposits. The Tuscarora deposits formed within the 39.9 to 39.3 Ma Tuscarora volcanic field, along and just outside the southeastern margin of the caldera-like Mount Blitzen volcanic center. Both deposit types formed at 39.3 Ma, contemporaneous with the only major intrusive activity in the volcanic field. No deposits are known to have formed during any of the intense volcanic phases of the field. Intrusions were the apparent heat source, and structures related to the Mount Blitzen center were conduits for hydrothermal circulation. The ore-forming fluids interacted dominantly with Eocene igneous rocks. The two deposit types occur in a northern silver-rich zone that is characterized by relatively high Ag/Au ratios (110-150), narrow alteration zones, and quartz and carbonate veins developed mostly in intrusive dacite, and in a southern gold-rich zone that is typified by relatively low Ag/Au ratios (4-14), more widespread alteration, and quartz-fissure and stockwork veins commonly developed in tuffaceous sedimentary rocks. The deposit types have similar fluid inclusion and Pb and S isotope characteristics but different geochemical signatures. Quartz veins from both zones have similar thermal and paragenetic histories and contain fluid inclusions that indicate that fluids cooled from between 260?? and 230??C to less than 200??C. Fluid boiling may have contributed to precious-metal deposition. Veins in both zones have relatively high As and Sb and low Bi, Te, and W. The silver zone has high Ca

  10. Rajkonkoski gold-telluride ore occurrence: A new high prospective type of complex noble metal mineralization in the Karelian Proterozoic

    NASA Astrophysics Data System (ADS)

    Ivashchenko, V. I.; Sundblad, K.; Toritsin, A. N.; Golubev, A. I.; Lavrov, O. B.

    2008-11-01

    The Rajkonkoski ore occurrence is located within the region of the Karelian craton (AR2) and the Svecofennian folded belt (PR1) conjugation. It is presented by quartz-carbonate veins in metadoleriles and a zone of brecciation, crumple, and silification of carbonaceous shales within the volcanites of the Soanlakhtinsky suite (PR1). Ore mineralization in black shales and quartz veins has features of genetic similarity presenting different levels of the ore system controlled by different range strike-slip fault dislocations. At the Rajkonkoski ore occurrence, 41 ore minerals have been identified: 12 tellurides (native tellurium, hedleyite, pilsenite, tsumoite, tellurobismuthite, hessite, stuetzite, radclidzhite, joseite-B, altaite, volynskite, petzite); 4 bismuth-tellurides of the following compositions Bi3Te, Bi3Te2, BiTe4, PbBiTe; 3 selenides (clausthalite, tellurolaitakarite, native selenium); and 12 native metals (gold, silver, electrum, copper, iron, lead, tin, bismuth, osmiridium). The contents of the main ore minerals in places exceed 10%, and the concentrations of elements reach as follows: Cu and Pb, 5%; Zn, Bi, 1%; Se, 219 ppm; Te, 171 ppm; Sb, 3 ppm; As, 5 ppm; Ag, >0.1%; Au, 35.28 ppm. Ore mineralization is formed during the temperature interval from 550°C up to <170oC in the conditions of high activity of Se and Te, and beginning from medium temperatures (>300°C) complete miscibilities galenite-clausthalite and galenite-altaite are observed. In aggregate with a wide temperature interval (>400°C) of ore process evolution and mineral specia variety of telluride and native metal mineralizations, the original “torsion” of different temperature mineralizations makes it possible to determine the affiliation of the Rajkonkoski ore occurrence to the xenothermal type deposits or epithermal “alkaline,” gold-telluride A-type characterized by a close connection with magmatism of increased alkalinity and the original geochemical (Te-V-F) and mineral

  11. Positronium physisorption at quartz surfaces

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

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

  12. The geology of the Morro Velho gold deposit in the Archean Rio das Velhas greenstone belt, Quadrilátero Ferrífero, Brazil

    USGS Publications Warehouse

    Vial, Diogenes Scipioni; DeWitt, Ed; Lobato, Lydia Maria; Thorman, Charles H.

    2007-01-01

    The Morro Velho gold deposit, Quadrilátero Ferrífero region, Minas Gerais, Brazil, is hosted by rocks at the base of the Archean Rio das Velhas greenstone belt. The deposit occurs within a thick carbonaceous phyllite package, containing intercalations of felsic and intermediate volcaniclastic rocks and dolomites. Considering the temporal and spatial association of the deposit with the Rio das Velhas orogeny, and location in close proximity to a major NNW-trending fault zone, it can be classified as an orogenic gold deposit. Hydrothermal activity was characterized by intense enrichment in alteration zones of carbonates, sulfides, chlorite, white mica±biotite, albite and quartz, as described in other Archean lode-type gold ores. Two types of ore occur in the deposit: dark gray quartz veins and sulfide-rich gold orebodies. The sulfide-rich orebodies range from disseminated concentrations of sulfide minerals to massive sulfide bodies. The sulfide assemblage comprises (by volume), on average, 74% pyrrhotite, 17% arsenopyrite, 8% pyrite and 1% chalcopyrite. The orebodies have a long axis parallel to the local stretching lineation, with continuity down the plunge of fold axis for at least 4.8 km. The group of rocks hosting the Morro Velho gold mineralization is locally referred to as lapa seca. These were isoclinally folded and metamorphosed prior to gold mineralization. The lapa seca and the orebodies it hosts are distributed in five main tight folds related to F1 (the best examples are the X, Main and South orebodies, in level 25), which are disrupted by NE- to E-striking shear zones. Textural features indicate that the sulfide mineralization postdated regional peak metamorphism, and that the massive sulfide ore has subsequently been neither metamorphosed nor deformed. Lead isotope ratios indicate a model age of 2.82 ± 0.05 Ga for both sulfide and gold mineralization. The lapa seca are interpreted as the results of a pre-gold alteration process and may be

  13. Integrating geologic and satellite imagery data for high-resolution mapping and gold exploration targets in the South Eastern Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Zoheir, Basem; Emam, Ashraf

    2012-05-01

    The granitoid-greenstone belts of the Arabian-Nubian Shield are well-endowed with lode gold and massive sulfide ores. Although generally characterized by excellent outcrops and arid desert realm, poor accessibility and lack of finance have been always retardant to detailed geologic mapping of vast areas of the shield. Lack of comprehensive geological information and maps at appropriate scales would definitely hinder serious exploration programs. In this study, band ratioing, principal component analysis (PCA), false-color composition (FCC), and frequency filtering (FFT-RWT) of ASTER and ETM+ data have substantially improved visual interpretation for detailed mapping of the Gebel Egat area in South Eastern Desert of Egypt. By compiling field, petrographic and spectral data, controls on gold mineralization have been assessed in terms of association of gold lodes with particular lithological units and structures. Contacts between foliated island arc metavolcanics and ophiolites or diorite are likely to be favorable loci for auriferous quartz veins, especially where the NW-SE foliation is deflected into steeply dipping NNW-trending shear planes. High-resolution mapping of the greenstone belt, structures and alteration zones associated with gold lodes in the study area suggests that dilatation by foliation deflection was related to emplacement of the Egat granitic intrusion, attendant with a sinistral transpression regime (i.e., ˜640-550 Ma?). Gold mineralization associated with granitoid intrusions in transpression-induced pull-apart structures elsewhere in the Eastern Desert (e.g., Fawakhir, Sukari and Hangaliya mines) emphasize the reliability of this setting as a model for gold exploration targets in greenstone terrains of Egypt, and may be elsewhere in the Arabian-Nubian Shield.

  14. Concentration of gold in in situ laterites from Mato Grosso

    NASA Astrophysics Data System (ADS)

    Michel, Dominique

    1987-07-01

    The gold concentration studied is located in lateritic soils overlying Precambrian schists of the Cuiaba Group in Mato Grosso, Brazil. The following five horizons may be recognized from bottom to top: (1) a gray-blue altered schist horizon, (2) a red argillaceous alterite, (3) a horizon characterized by iron oxihydroxide-rich pebbles and quartz fragments in an iron oxihydroxide-rich matrix and clays, (4) an iron crust, and (5) the present soil. The most significant gold content is found in the third horizon just below the iron crust. According to geological study and morphological observations of the gold particles, the gold ore mined today is the result of two combined processes, i.e., the ferrallitic alteration of quartz lodes enclosed in schists and the effect of the red argillaceous alterite which acts as an impervious structure preventing the largest gold grains from migrating downward during their mechanical concentration.

  15. Portal vein thrombosis.

    PubMed

    Chawla, Yogesh K; Bodh, Vijay

    2015-03-01

    Portal vein thrombosis is an important cause of portal hypertension. PVT occurs in association with cirrhosis or as a result of malignant invasion by hepatocellular carcinoma or even in the absence of associated liver disease. With the current research into its genesis, majority now have an underlying prothrombotic state detectable. Endothelial activation and stagnant portal blood flow also contribute to formation of the thrombus. Acute non-cirrhotic PVT, chronic PVT (EHPVO), and portal vein thrombosis in cirrhosis are the three main variants of portal vein thrombosis with varying etiological factors and variability in presentation and management. Procoagulant state should be actively investigated. Anticoagulation is the mainstay of therapy for acute non-cirrhotic PVT, with supporting evidence for its use in cirrhotic population as well. Chronic PVT (EHPVO) on the other hand requires the management of portal hypertension as such and with role for anticoagulation in the setting of underlying prothrombotic state, however data is awaited in those with no underlying prothrombotic states. TIPS and liver transplant may be feasible even in the setting of PVT however proper selection of candidates and type of surgery is warranted. Thrombolysis and thrombectomy have some role. TARE is a new modality for management of HCC with portal vein invasion.

  16. Portal Vein Thrombosis

    PubMed Central

    Chawla, Yogesh K.; Bodh, Vijay

    2015-01-01

    Portal vein thrombosis is an important cause of portal hypertension. PVT occurs in association with cirrhosis or as a result of malignant invasion by hepatocellular carcinoma or even in the absence of associated liver disease. With the current research into its genesis, majority now have an underlying prothrombotic state detectable. Endothelial activation and stagnant portal blood flow also contribute to formation of the thrombus. Acute non-cirrhotic PVT, chronic PVT (EHPVO), and portal vein thrombosis in cirrhosis are the three main variants of portal vein thrombosis with varying etiological factors and variability in presentation and management. Procoagulant state should be actively investigated. Anticoagulation is the mainstay of therapy for acute non-cirrhotic PVT, with supporting evidence for its use in cirrhotic population as well. Chronic PVT (EHPVO) on the other hand requires the management of portal hypertension as such and with role for anticoagulation in the setting of underlying prothrombotic state, however data is awaited in those with no underlying prothrombotic states. TIPS and liver transplant may be feasible even in the setting of PVT however proper selection of candidates and type of surgery is warranted. Thrombolysis and thrombectomy have some role. TARE is a new modality for management of HCC with portal vein invasion. PMID:25941431

  17. [Deep vein thrombosis prophylaxis.

    PubMed

    Sandoval-Chagoya, Gloria Alejandra; Laniado-Laborín, Rafael

    2013-01-01

    Background: despite the proven effectiveness of preventive therapy for deep vein thrombosis, a significant proportion of patients at risk for thromboembolism do not receive prophylaxis during hospitalization. Our objective was to determine the adherence to thrombosis prophylaxis guidelines in a general hospital as a quality control strategy. Methods: a random audit of clinical charts was conducted at the Tijuana General Hospital, Baja California, Mexico, to determine the degree of adherence to deep vein thrombosis prophylaxis guidelines. The instrument used was the Caprini's checklist for thrombosis risk assessment in adult patients. Results: the sample included 300 patient charts; 182 (60.7 %) were surgical patients and 118 were medical patients. Forty six patients (15.3 %) received deep vein thrombosis pharmacologic prophylaxis; 27.1 % of medical patients received deep vein thrombosis prophylaxis versus 8.3 % of surgical patients (p < 0.0001). Conclusions: our results show that adherence to DVT prophylaxis at our hospital is extremely low. Only 15.3 % of our patients at risk received treatment, and even patients with very high risk received treatment in less than 25 % of the cases. We have implemented strategies to increase compliance with clinical guidelines.

  18. Structural setting of gold deposits in the Oudalan-Gorouol volcano-sedimentary belt east of the Markoye Shear Zone, West African Craton

    NASA Astrophysics Data System (ADS)

    Tshibubudze, Asinne; Hein, Kim A. A.

    2013-04-01

    shears crosscut northwest-trending thrust-folds, or where northwest-trending thrust-folds coalesce with north-northeast trending shears. An intimate relationship thus exists between D1 and D2 structures and gold mineralisation in the OGB. Gold in sheeted-stockwork veins is hosted in competent rocks units including conglomerate beds, greywacke, quartzite, monzonite dykes, pyroxenite-gabbro sills and D1 buck quartz veins. Gold in fine veinlets may also be hosted in massive shale units.

  19. Possible genetic link between I-type granite and orogenic gold deposits in Egypt (metamorphic-magmatic interaction?)

    NASA Astrophysics Data System (ADS)

    Abd El Monsef, Mohamed

    2015-04-01

    The orogenic gold deposits are a distinctive type of deposits that revealed unique temporal and spatial association with an orogeny. Where, the system of gold veins and related ore minerals was confined to hydrothermal solutions formed during compressional to transpressional deformation processes at convergent plate margins in accretionary and collisional orogens, with the respect to ongoing deep-crustal, subduction-related thermal processes. In Egypt, most of vein-type and dyke-type gold mineralization are restricted to granitic rocks or at least near of granitic intrusion that seems to have had an important influence on gold mineralization. Shear zone-related, mesothermal gold deposits of Fatira and Gidami mines in the northern Eastern Desert of Egypt are found within granitic bodies or at the contact between granites and metavolcanic rocks. The hosting-granitic rocks in Fatira and Gidami areas are mainly of granodioritic composition (I-Type granite) which is related to calc-alkaline magmatic series. However, Fatira granitoids were developed within island arc tectonic settings related to mature island arc system (Late-orogenic stage), at relatively low temperature (around 660° C) and medium pressure between (5 - 10 Kbar). On the other hand, Gidami granitoids were developed during the collision stage in continental arc regime related to active continental margin (Syn-orogeny), which were crystallized at relatively high temperature (700-720° C) and low pressure (around 0.1 Kbar). The ore mineralogy includes pyrite, chalcopyrite, sphalerite, covellite, ilmenite, goethite ± pyrrhotite ± pentlandite ± galena ± molybdenite. Native gold is detected only in Gidami mineralization as small inclusions within pyrite and goethite or as tiny grains scattered within quartz vein (in close proximity to the sulfides). In Fatira deposits, it is detected only by microprobe analysis within the crystal lattice of pyrite and jarosite. Fluid inclusions study for the mineralized

  20. [Puncture of the brachiocephalic vein].

    PubMed

    Schlarb, K

    1986-09-01

    A specific central vein catheter for puncture of the brachiocephalic vein has been developed which is provided with a valve by which air-embolism and unwanted bleeding from the catheter are eliminated. Typical and often serious complications, which can develop on insertion of central vein catheter, can nearly be totally avoided by the puncture technique described.

  1. Fluid inclusion gas chemistry as a potential minerals exploration tool: Case studies from Creede, CO, Jerritt Canyon, NV, Coeur d'Alene district, ID and MT, southern Alaska mesothermal veins, and mid-continent MVT's

    USGS Publications Warehouse

    Landis, G.P.; Hofstra, A.H.

    1991-01-01

    Recent advances in instrumentation now permit quantitative analysis of gas species from individual fluid inclusions. Fluid inclusion gas data can be applied to minerals exploration empirically to establish chemical (gas composition) signatures of the ore fluids, and conceptually through the development of genetic models of ore formation from a framework of integrated geologic, geochemical, and isotopic investigations. Case studies of fluid inclusion gas chemistry from ore deposits representing a spectrum of ore-forming processes and environments are presented to illustrate both the empirical and conceptual approaches. We consider epithermal silver-gold deposits of Creede, Colorado, Carlin-type sediment-hosted disseminated gold deposits of Jerritt Canyon, Nevada, metamorphic silver-base-metal veins of the Coeur d'Alene district, Idaho and Montana, gold-quartz veins in accreted terranes of southern Alaska, and the mid-continent base-metal sulfide deposits of Mississippi Valley-Type (MVT's). Variations in gas chemistry determine the redox state of the ore fluids, provide compositional input for gas geothermometers, characterize ore fluid chemistry (e.g., CH4CO2, H2SSO2, CO2/H2S, organic-rich fluids, gas-rich and gas-poor fluids), identify magmatic, meteoric, metamorphic, shallow and deep basin fluids in ore systems, locate upwelling plumes of magmatic-derived volatiles, zones of boiling and volatile separation, interfaces between contrasting fluids, and important zones of fluid mixing. Present techniques are immediately applicable to exploration programsas empirical studies that monitor fluid inclusion gas threshold concentration levels, presence or absence of certain gases, or changes in gas ratios. We suggest that the greater contribution of fluid inclusion gas analysis is in the integrated and comprehensive chemical dimension that gas data impart to genetic models, and in the exploration concepts based on processes and environments of ore formation derived from

  2. Sinter-vein correlations at Buckskin Mountain, National district, Humboldt County, Nevada

    USGS Publications Warehouse

    Vikre, P.G.

    2007-01-01

    At Buckskin Mountain (elev 2,650 m, 8,743 ft), Humboldt County, Nevada, a hydrothermal system, imposed on a middle Miocene volcanic sequence with contrasting permeabilities and tensile strengths, produced alteration assemblages controlled by elevation, from Hg-mineralized sinter to subjacent precious metal veins over a vertical distance exceeding 790 m. Sinter and epiclastic deposits, interpreted to be remnant paleosurface basinal strata enclosed by 16.6 to 16.1 Ma rhyolites, overlie older volcaniclastic basinal deposits and were part of a regional fluvial-lacustrine system developed among ca. 16 to 12 Ma basalt-rhyolite eruptive centers throughout the northern Great Basin. Because of contrasting erosional resistance among altered and unaltered rocks, Buckskin Mountain represents inverse topography with sinter and silicified epiclastic deposits at the summit. Sinter and veins, correlated by common elements, similar mineralogy, age constraints, textures, S isotope compositions, and fluid inclusion microthermometry, were deposited by sinter-vein fluid, the first of two sequential hydrothermal fluid regimes that evolved in response to magmatism, tectonism, hydrology, and topography. Thermal quenching of distally derived sinter-vein fluid in planar conduits caused deposition of banded quartz-silicate-selenide-sulfide veins ???270 to > 440 m below sinter at 16.1 Ma; vei??ns were initially enveloped by zoned selvages of proximal K-feldspar + K-mica + quartz + pyrite and distal illite + chlorite + calcite + pyrite. Mixing of sinter-vein fluid with local meteoric water in saturated basinal deposits caused deposition of silica, Hg-Se-S-Cl minerals, and precious metals in sinter and epiclastic deposits. Elevated ???Se/???S in sinter-vein fluid, and the relatively large stability fields of reduced aqueous selenide species in the temperature range of 250?? to <100??C, enabled (but was not the cause of) codeposition of selenide-sulfide minerals and common element associations

  3. Transcutaneous laser treatment of leg veins.

    PubMed

    Meesters, Arne A; Pitassi, Luiza H U; Campos, Valeria; Wolkerstorfer, Albert; Dierickx, Christine C

    2014-03-01

    Leg telangiectasias and reticular veins are a common complaint affecting more than 80% of the population to some extent. To date, the gold standard remains sclerotherapy for most patients. However, there may be some specific situations, where sclerotherapy is contraindicated such as needle phobia, allergy to certain sclerosing agents, and the presence of vessels smaller than the diameter of a 30-gauge needle (including telangiectatic matting). In these cases, transcutaneous laser therapy is a valuable alternative. Currently, different laser modalities have been proposed for the management of leg veins. The aim of this article is to present an overview of the basic principles of transcutaneous laser therapy of leg veins and to review the existing literature on this subject, including the most recent developments. The 532-nm potassium titanyl phosphate (KTP) laser, the 585-600-nm pulsed dye laser, the 755-nm alexandrite laser, various 800-983-nm diode lasers, and the 1,064-nm neodymium yttrium-aluminum-garnet (Nd:YAG) laser and various intense pulsed light sources have been investigated for this indication. The KTP and pulsed dye laser are an effective treatment option for small vessels (<1 mm). The side effect profile is usually favorable to that of longer wavelength modalities. For larger veins, the use of a longer wavelength is required. According to the scarce evidence available, the Nd:YAG laser produces better clinical results than the alexandrite and diode laser. Penetration depth is high, whereas absorption by melanin is low, making the Nd:YAG laser suitable for the treatment of larger and deeply located veins and for the treatment of patients with dark skin types. Clinical outcome of Nd:YAG laser therapy approximates that of sclerotherapy, although the latter is associated with less pain. New developments include (1) the use of a nonuniform pulse sequence or a dual-wavelength modality, inducing methemoglobin formation and enhancing the optical absorption

  4. Frequency retrace of quartz oscillators

    NASA Astrophysics Data System (ADS)

    Euler, F.; Yannoni, N. F.

    Frequency retrace measurements are reported on oven controlled quartz oscillators utilizing AT and SC cut plated and BVA resonators. Prior to full aging, the retrace error is added to the aging effect. With well-aged resonators, after one or several on-off cycles, the frequency settles at a new level characteristic for intermittent operation. Severe frequency shifts have sometimes been found after the first restart following prolonged continuous operation. SC cut resonators appear to show distinctly smaller retrace errors than AT cut.

  5. Colloidal and physical transport textures exhibited by electrum and naumannite in bonanza epithermal veins from western USA, and their significance

    USGS Publications Warehouse

    Saunders, James A.; Vikre, Peter G.; Unger, Derick L.; Beasley, Lee

    2010-01-01

    It is reasonably clear that disequilibrium or “far-from equilibrium” conditions lead to the formation of silica colloids and their deposition in many epithermal deposits. This implies ore-forming solutions had elevated concentrations of dissolved silica, well in excess of amorphous silica saturation. We have previously demonstrated that such colloidal silica particles were deposited in epithermal veins as silica gels and opal, which may later progress along a path to crystallize into more thermodynamically favored (less-soluble) silica phases such as quartz and chalcedony. Also, in some deposits, amorphous silica is co-deposited with precious-metal minerals, such as electrum in the banded super-bonanza ores of the Sleeper deposit (NV). Ore-mineral textures from some western USA bonanza epithermal ores indicate that two precious-metal phases (electrum and naumannite, Ag2Se) form colloidal particles that are transported by ore-forming fluids and are deposited either by aggregation (by sticking to other precious metal-particles) to make dendrites, or are deposited on the “lee” side of protrusion along vein walls (or perhaps by both processes). We can infer by analogy to silica that this also implies that ore-forming solutions contained elevated (supersaturated) dissolved concentrations of both gold and silver that formed colloidal particles under disequilibrium (often chaotic) conditions. Thus physical transport and deposition textures seem to indicate the presence of strongly precious-metal-enriched ore forming fluids, which led to (not surprisingly) the bonanza grades of these remarkable ores. What causes such a precious-metal-rich solution is debatable, but that is the subject of our continued investigations.

  6. Flexural-slip generated bedding-parallel veins from central Victoria, Australia

    NASA Astrophysics Data System (ADS)

    Fowler, T. J.

    1996-12-01

    Thin continuous laminated bedding-parallel quartz veins (BPVs) with slip-striated and fibred vein walls occur within slates, or at their contact with sandstones, on the limbs of chevron folds in the Bendigo-Castlemaine goldfields, southeastern Australia. Two microstructural Types of BPV (I and II) have been previously recognized, and are confirmed in this study. Both types are concluded to have formed during and/or after crenulation cleavage (the first tectonic axial planar structure) in the wallrock slates, and during flexural-slip folding. Type I BPVs consist of syntaxial phyllosilicate inclusion trails, parallel to bedding, enclosing inclined inclusion bands, the latter formed by detachment of wallrock phyllosilicate particles from the walls of pressure solution-segmented discordant tension veins. Type I BPVs are formed by bedding-parallel shear, and grow in width by propagation of the discordant veins into the BPV walls. Type II veins are composed of quartz bands separated by wallrock slate seams which have split away from the vein wall during dilatant shear opening. They incorporate numerous torn-apart fragments of crenulated wallrock slate. Type I BPV inclusion band average spacing of 0.5 mm probably represents the magnitude of slip increments during stick-slip flexural-slip folding activity.

  7. Hydrothermal quartz formation during fluctuations of brittle shear-zone activity and fluid flow: grain growth and deformation structures of the Pfahl shear zone (Germany)

    NASA Astrophysics Data System (ADS)

    Yilmaz, T.; Prosser, G.; Liotta, D.; Kruhl, J. H.

    2012-12-01

    The Bavarian Pfahl shear zone is a WNW-ESE trending dextral strike-slip shear zone at the SW margin of the Bohemian Massif (Central Europe). It was discontinuously active during decreasing PT-conditions, i.e. from ductile to brittle, from the late-Carboniferous to the late-Cretaceous - Paleocene times. Triassic hydrothermal activity produced a 150 km long and 30-100 m wide quartz dyke along the main fault, surrounded by sheared basement rocks. Within a zone of >10 m metasomatism transformed the wall rocks to mostly kaolinite, chlorite and phyllosilicates. The quartz dyke exhibits a layered to lenticular and partly symmetric structure with different types of quartz masses, transected by a complex quartz vein network. This already indicates pulses of fluid flux and fragmentation during the lifetime of the shear zone. Analyses by optical microscopy, cathodoluminescence (CL) and SEM-EDX reveal at least four subsequent stages of quartz crystallization and fragmentation. (i) The oldest generation of quartz is represented by a homogeneous dark grey to reddish quartz mass made up by ~10-20 μm-sized crystals. It contains mm- to cm-sized angular wall-rock fragments, completely altered to kaolinite, indicating intense wall-rock alteration prior to the earliest event of silica precipitation. This rules out the possibility that the quartz mass developed from silicification of the wall rocks. This first type of quartz occurs as cm- to dm-large angular fragments in (ii) a light grey to pink quartz mass formed by ~10-50 μm-sized crystals. The different colours result from variable types and amounts of inclusions. Quartz of both generations shows random crystallographic orientations and complex inclusion structures. It probably developed during two fragmentation events and possibly from a silica gel precursor that crystallized after precipitation. (iii) The third quartz generation formed as a set of mm- to dm-wide veins roughly parallel to the trend of the Pfahl zone

  8. Lode-gold mineralization in the Tanami region, northern Australia

    NASA Astrophysics Data System (ADS)

    Huston, David L.; Vandenberg, Leon; Wygralak, Andrew S.; Mernagh, Terrence P.; Bagas, Leon; Crispe, Andrew; Lambeck, Alexis; Cross, Andrew; Fraser, Geoff; Williams, Nick; Worden, Kurt; Meixner, Tony; Goleby, Bruce; Jones, Leonie; Lyons, Pat; Maidment, David

    2007-01-01

    The Tanami region of northern Australia has emerged over the last two decades as the largest gold-producing region in the Northern Territory. Gold is hosted by epigenetic quartz veins in sedimentary and mafic rocks, and by sulfide-rich replacement zones within iron formation. Although limited, geochronological data suggest that most mineralization occurred at about 1,805-1,790 Ma, during a period of extensive granite intrusion, although structural relationships suggest that some deposits predate this period. There are three main goldfields in the Tanami region: the Dead Bullock Soak goldfield, which hosts the world-class Callie deposit; The Granites goldfield; and the Tanami goldfield. In the Dead Bullock Soak goldfield, deposits are hosted by carbonaceous siltstone and iron formation where a late (D5) structural corridor intersects an early F1 anticlinorium. In The Granites goldfield, deposits are hosted by highly sheared iron formation and are interpreted to predate D5. The Tanami goldfield consists of a large number of small, mostly basalt-hosted deposits that probably formed at a high structural level during D5. The D5 structures that host most deposits formed in a convergent structural regime with σ 1 oriented between E-W and ENE-WSW. Structures active during D5 include NE-trending oblique thrust (dextral) faults and ESE-trending (sinistral) faults that curve into N- to NNW-trending reverse faults localized in supracrustal belts between and around granite complexes. Granite intrusions also locally perturbed the stress field, possibly localizing structures and deposits. Forward modeling and preliminary interpretations of reflection seismic data indicate that all faults extend into the mid-crust. In areas characterized by the N- to NW-trending faults, orebodies also tend to be N- to NW-trending, localized in dilational jogs or in fractured, competent rock units. In areas characterized by ESE-trending faults, the orebodies and veins tend to strike broadly east

  9. Association of gold with uraninite and pyrobitumen in the metavolcanic rock hosted hydrothermal Au-U mineralisation at Rompas, Peräpohja Schist Belt, northern Finland

    NASA Astrophysics Data System (ADS)

    Molnár, Ferenc; Oduro, Harry; Cook, Nick D. J.; Pohjolainen, Esa; Takács, Ágnes; O'Brien, Hugh; Pakkanen, Lassi; Johanson, Bo; Wirth, Richard

    2016-06-01

    The Peräpohja Schist Belt comprises a supracrustal sequence of quartzites, mafic volcanics and volcaniclastics, carbonate rocks, black shales, mica schists and greywackes which were deposited from ca. 2.44 to ~1.91 Ga, during the rifting of the Archaean basement in the eastern part of the Fennoscandian shield. Metamorphism and multiple folding of the basin fill took place during the Svecofennian orogeny (1.9-1.8 Ga) followed by intrusions of late-orogenic (1.84-1.80 Ga) and post-orogenic granitoids (1.79-1.76 Ga). The Rompas Au-U mineralisation is hosted by deformed calcsilicate veins in mafic volcanic rocks and locally contains very high grade (>10,000 g/t Au) gold pockets with strict spatial association of gold minerals to uraninite and pyrobitumen. Chemical ages from the unaltered domains in the structure of uraninite indicate a 1.95-1.90 Ga age for the deposition of the primary, high temperature (e.g. U/Th < 100 in uraninite) hydrothermal uranium mineralisation. These data are in agreement with the results of previous U-Pb dating of uraninite by SIMS. Textural evidence suggests that metamorphic recrystallisation of the uraninite-bearing quartz-dolomite veins into calcsilicate mineral assemblages during the Svecofennian orogeny (1.9-1.8 Ga) was followed by a hydrocarbon-bearing fluid flow event and radiolytic polymerisation of hydrocarbons around grains of uraninite. Gold precipitated during a subsequent hydrothermal process in the fractures of uraninite, as well as in the cracks and on the botryoidal surfaces of uraninite-pyrobitumen nodules. Remobilisation and redeposition of uranium by these hydrothermal events produced secondary uraninite grains with chemical ages between 1.85 and 1.65 Ga. Native gold is associated with galena, altaite, hunchunite, nickeline and rare cobaltite, Pb-bearing maldonite, pyrite, pyrrhotite, chalcopyrite, molybdenite and titanite. Raman spectra show disordered structure of undeformed pyrobitumen nodules in contrast with the well

  10. Polymer-coated quartz crystal microbalance chemical sensor for heavy cations in water.

    PubMed

    Sartore, L; Barbaglio, M; Penco, M; Bergese, P; Bontempi, E; Colombi, P; Depero, L E

    2009-02-01

    A flow type quartz crystal microbalance (QCM) (bio)chemical sensor was developed for the real time determination of heavy metal ions that is suitable for environmental monitoring. A new process has been developed which enables to obtain surface-modified gold electrodes with high heavy metal ions complexing ability. The sensing performances of the piezoelectric sensor used in a flow-through setup were investigated by monitoring the frequency variation induced by the presence of heavy metal ions, such as copper and lead, as model ions, in aqueous media. X-Ray Reflectivity (XRR) and Atomic Force Microscopy (AFM) were carried out to characterize the unmodified and modified gold surfaces.

  11. Deep-Subterranean Microbial Habitats in the Hishikari Epithermal Gold Mine: Active Thermophilic Microbial Communities and Endolithic Ancient Microbial Relicts.

    NASA Astrophysics Data System (ADS)

    Hirayama, H.; Takai, K.; Inagaki, F.; Horikoshi, K.

    2001-12-01

    Deep subterranean microbial community structures in an epithermal gold-silver deposit, Hishikari gold mine, southern part of Kyusyu Japan, were evaluated through the combined use of enrichment culture methods and culture-independent molecular surveys. The geologic setting of the Hishikari deposit is composed of three lithologies; basement oceanic sediments of the Cretaceous Shimanto Supergroup, Quaternary andesites, and auriferous quartz vein. We studied the drilled core rock of these, and the geothermal hot waters from the basement aquifers collected by means of the dewatering system located at the deepest level in the mining sites. Culture-independent molecular phylogenetic analyses of PCR-amplified ribosomal DNA (rDNA) recovered from drilled cores suggested that the deep-sea oceanic microbial communities were present as ancient indigenous relicts confined in the Shimanto basement. On the other hand, genetic signals of active thermophilic microbial communities, mainly consisting of thermophilic hydrogen-oxidizer within Aquificales, thermophilic methanotroph within g-Proteobacteria and yet-uncultivated bacterium OPB37 within b-Proteobacteria, were detected with these of oceanic relicts from the subterranean geothermal hot aquifers (temp. 70-100ºC). Successful cultivation and FISH analyses strongly supported that these thermophilic lithotrophic microorganisms could be exactly active and they grew using geochemically produced hydrogen and methane gasses as nutrients. Based on these results, the deep-subsurface biosphere occurring in the Hishikari epithermal gold mine was delineated as endolithic ancient microbial relicts and modern habitats raising active lithotrophic thermophiles associated with the geological and geochemical features of the epithermal gold deposit.

  12. Effects of accumulated film layers on the accuracy of quartz film thickness monitors

    NASA Technical Reports Server (NTRS)

    Heyman, J. S.; Miller, W. E.

    1978-01-01

    The effect of accumulation layers on the accuracy of quartz thin-film thickness monitors is evaluated. Use of an expanded plane wave ultrasonic propagation theory correctly accounts for observed experimental data. The magnitude of the maximum errors calculated for simply reversing the order of a series of aluminum gold deposits is on the order of 5%. If one totally neglects intervening layers, multiple film propagation and nonlinearity can produce errors greater than 50%.

  13. Using the concentration-volume (C-V) fractal model in the delineation of gold mineralized zones within the Tepeoba porphyry Cu-Mo-Au, Balikesir, NW Turkey

    NASA Astrophysics Data System (ADS)

    Kumral, Mustafa; Abdelnasser, Amr; Karaman, Muhittin; Budakoglu, Murat

    2016-04-01

    The Tepeoba porphyry Cu-Mo-Au mineralization that located at the Biga peninsula (W Turkey) developed around the Eybek pluton concentrated at its southern contact. This mineralization that hosted in the hornfels rocks of Karakaya Complex is associated with three main alteration zones; potassic, phyllic and propylitic alterations along the fault controlled margins of the Eybek pluton and quartz stockwork veining as well as brecciation zones. As well as two mineralized zones were occurred in the mine area; hypogene and oxidation/supergene zone. The hypogene zone has differentiated alteration types; high potassic and low phyllic alteration, while the oxidation/supergene zone has high phyllic and propylitic alterations. This work deals with the delineation of gold mineralized zone within this porphyry deposit using the concentration-volume (C-V) fractal model. Five zones of gold were calculated using its power-law C-V relationship that revealed that the main phase of gold mineralization stated at 5.3083 ppm Au concentration. In addition, the C-V log-log plot shows that the highly and moderately Au mineralization zone developed in western part of deposit correlated with oxidation zone related to propylitic alteration. On the other hand, its weakly mineralization zone has a widespread in the hypogene zone related to potassic alteration. This refers to the enrichment of gold and depletion of copper at the oxidation/supergene zone is due to the oxidation/supergene alteration processes that enrich the deposits by the meteoric water. Keywords: Concentration-volume (C-V) fractal model; gold mineralized zone; Tepeoba porphyry Cu-Mo-Au; Balikesir; NW Turkey.

  14. The Quartz Analog Watch: A Wonder Machine.

    ERIC Educational Resources Information Center

    Crane, H. Richard, Ed.

    1993-01-01

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

  15. Sealed-in-quartz resistance heater

    NASA Technical Reports Server (NTRS)

    Miller, C. G.; Stephens, J. B.

    1980-01-01

    Electric resistance quartz heater operates at 1,400 F without developing excessively hot spots that can fail prematurely. Since resistance element is sealed in quartz, heater can be used in hostile environments. Sealed construction also keeps heater from contaminating heated object.

  16. Precise Sealing of Fused-Quartz Ampoules

    NASA Technical Reports Server (NTRS)

    Debnan, W. J. J.; Clark, I. O.

    1982-01-01

    New technique rapidly evacuates and seals fused-quartz ampoule with precise clearance over contents without appreciably thinning ampoule walls. Quartz plug is lowered into working section of ampoule after ampoule has been evacuated. Plug is then fused to ampoule walls, forming vacuum seal. New technique maintains wall strength and pumping speed.

  17. Magmatic-vapor expansion and the formation of high-sulfidation gold deposits: Chemical controls on alteration and mineralization

    USGS Publications Warehouse

    Henley, R.W.; Berger, B.R.

    2011-01-01

    Large bulk-tonnage high-sulfidation gold deposits, such as Yanacocha, Peru, are the surface expression of structurally-controlled lode gold deposits, such as El Indio, Chile. Both formed in active andesite-dacite volcanic terranes. Fluid inclusion, stable isotope and geologic data show that lode deposits formed within 1500. m of the paleo-surface as a consequence of the expansion of low-salinity, low-density magmatic vapor with very limited, if any, groundwater mixing. They are characterized by an initial 'Sulfate' Stage of advanced argillic wallrock alteration ?? alunite commonly with intense silicification followed by a 'Sulfide' Stage - a succession of discrete sulfide-sulfosalt veins that may be ore grade in gold and silver. Fluid inclusions in quartz formed during wallrock alteration have homogenization temperatures between 100 and over 500 ??C and preserve a record of a vapor-rich environment. Recent data for El Indio and similar deposits show that at the commencement of the Sulfide Stage, 'condensation' of Cu-As-S sulfosalt melts with trace concentrations of Sb, Te, Bi, Ag and Au occurred at > 600 ??C following pyrite deposition. Euhedral quartz crystals were simultaneously deposited from the vapor phase during crystallization of the vapor-saturated melt occurs to Fe-tennantite with progressive non-equilibrium fractionation of heavy metals between melt-vapor and solid. Vugs containing a range of sulfides, sulfosalts and gold record the changing composition of the vapor. Published fluid inclusion and mineralogical data are reviewed in the context of geological relationships to establish boundary conditions through which to trace the expansion of magmatic vapor from source to surface and consequent alteration and mineralization. Initially heat loss from the vapor is high resulting in the formation of acid condensate permeating through the wallrock. This Sulfate Stage alteration effectively isolates the expansion of magmatic vapor in subsurface fracture arrays

  18. Mechanical twinning in small quartz crystals

    NASA Astrophysics Data System (ADS)

    Laughner, J. W.; Newnham, R. E.; Cross, L. E.

    1982-02-01

    Quartz is known to be ferrobielastic; that is, quartz crystals have domain states (Dauphiné twins) which differ in their elastic compliance values and which can be switched by an appropriately oriented stress. Polycrystalline quartz has also been reported (Tullis 1970) to show preferential orientation of these domains following application of large uniaxial stresses. These experiments were designed to study twinning of synthetic quartz “grains” (minimum size 0.07×0.07×0.02 cm) in specially-constructed composites and of grains in three natural quartz aggregates — a quartzite, a novaculite, and a jasper. Backreflection X-ray techniques were used to verify twinning in the composite grains, while special electroding and electrical detection allowed the twinning processes to be examined in “real time.” Small synthetic quartz crystals were found to behave identically to the massive samples previously studied. Electrical pulses due to the reversal of piezoelectric coefficient d 11 in twinned quartz were detected from quartzite and from the man-made composites. Novaculite also gave electrical pulses which were probably from twinning (evidenced by the correlation of expected and observed pulse sizes and shapes), while no pulses from the jaspers indicative of twinning were detected. Grain size distribution differences are considered the main structural reason for the different behaviors.

  19. The economics of vein disease.

    PubMed

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

    2007-09-01

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

  20. Static and Dynamic Behavior of Quartz Resonators

    DTIC Science & Technology

    1979-07-01

    representative of a long line of 110] W. J. Spencer and W. L. Smith , "Precision crystal frequency stan- dards," in Poc. 15th AFC3, May-June 1961, pp...1963, pp. 248- 266. The actual frequency instabilities observed in quartz crystal 1121 W. L. Smith and W. J. Spencer, "Quartz crystal thermometer for...for improved appear in Proc. 33rd AFCS, May-June 1979. quartz crystal oscillator performance," IEEE Trans. Instrum. [411 G. Theobald , G. Marianneau, R

  1. PROCESS FOR THE CONCENTRATION OF ORES CONTAINING GOLD AND URANIUM

    DOEpatents

    Gaudin, A.M.; Dasher, J.

    1958-06-10

    ABS>A process is described for concentrating certain low grade uranium and gold bearing ores, in which the gangue is mainly quartz. The production of the concentrate is accomplished by subjecting the crushed ore to a froth floatation process using a fatty acid as a collector in conjunction with a potassium amyl xanthate collector. Pine oil is used as the frothing agent.

  2. Three sets of crystallographic sub-planar structures in quartz formed by tectonic deformation

    NASA Astrophysics Data System (ADS)

    Derez, Tine; Pennock, Gill; Drury, Martyn; Sintubin, Manuel

    2016-05-01

    In quartz, multiple sets of fine planar deformation microstructures that have specific crystallographic orientations parallel to planes with low Miller-Bravais indices are commonly considered as shock-induced planar deformation features (PDFs) diagnostic of shock metamorphism. Using polarized light microscopy, we demonstrate that up to three sets of tectonically induced sub-planar fine extinction bands (FEBs), sub-parallel to the basal, γ, ω, and π crystallographic planes, are common in vein quartz in low-grade tectonometamorphic settings. We conclude that the observation of multiple (2-3) sets of fine scale, closely spaced, crystallographically controlled, sub-planar microstructures is not sufficient to unambiguously distinguish PDFs from tectonic FEBs.

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

    SciTech Connect

    Hahn, R.; Ikramuddin, M.

    1985-01-01

    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.

  4. Gold Coating

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Epner Technology Inc. responded to a need from Goddard Space Flight Center for the ultimate in electroplated reflectivity needed for the Mars Global Surveyor Mars Orbiter Laser Altimeter (MOLA). Made of beryllium, the MOLA mirror was coated by Epner Technology Laser Gold process, specially improved for the project. Improved Laser Gold- coated reflectors have found use in an epitaxial reactor built for a large semiconductor manufacturer as well as the waveguide in Braun-Thermoscan tympanic thermometer and lasing cavities in various surgical instruments.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Rutilated quartz, aka Venus' hair, is finely-acicular rutile intergrown with host quartz generated by fluid-mediated co-crystallization. It is commonly found in hydrothermal veins, including the renown cleft mineral locations of the Swiss Alps. Previous studies of Alpine cleft mineralizations used rare hydrothermal monazite [1] and titanite [2] to constrain vein formation to ~13.5-15.2 Ma, postdating peak metamorphism by ~2-4 Ma. Temperature (T) estimates of 150-450°C are based on fluid inclusions and bulk quartz-mineral oxygen isotope exchange equilibria, and formation pressures (P) are 0.5-2.5 kbar (for a geothermal gradient of 30°C/km) [2]. The potential of rutilated quartz as a thermochronometer, however, has not been harnessed previously. Here, we present the first results of age and P-T determinations for rutilated quartz from six locations in the Swiss Alps (San Gottardo; Feldbach, Binntal; Pi Aul, Vals; Faido, Leventina; Elm, Steinbach; Binntal). Samples were cut and mounted in epoxy discs to expose rutile (0.03 to 1 mm in diameter) and its host quartz which was also imaged in cathodoluminescence (CL). CL images for half of the samples' host quartz exhibited strong sector zoning, while others reveal only weak CL zonation. Isotopic and trace element analyses were carried out by SIMS using a CAMECA ims1270 for U-Pb, O-isotopes, and Ti-in-quartz, and a LA-ICP-MS system (213 nm New Wave laser coupled to an Agilent 7500a) for Zr-in-rutile. U-Pb rutile ages average 15.5×2.0 Ma (2σ). T estimates are 352-575°C (rutile-quartz oxygen isotopes in touching domains), 470-530°C (Zr-in-rutile assuming P = 0.5 and equilibrium with host-rock zircon), and 251-391°C (Ti-in-quartz at assumed P = 0.5 kbar and aTiO2 = 1). CL zones are isotopically unzoned. Rutile-quartz oxygen isotopes are pressure insensitive, whereas Zr-in-rutile and Ti-in-quartz are minimum temperatures. These results demonstrate that rutilated quartz can constrain timing and conditions of post

  6. Quartz-enhanced photoacoustic spectroscopy: a review.

    PubMed

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

    2014-03-28

    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.

  7. Quartz Mountain/Oklahoma Summer Arts Institute.

    ERIC Educational Resources Information Center

    Frates, Mary Y.; Madeja, Stanley S.

    1982-01-01

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

  8. Fabrication of a novel quartz micromachined gyroscope

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  9. Quartz-Enhanced Photoacoustic Spectroscopy: A Review

    PubMed Central

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

    2014-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  11. Quartz resonator fluid monitors for vehicle applications

    SciTech Connect

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

    1994-09-01

    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.

  12. Method of making a quartz resonator

    DOEpatents

    Vig, John R.; Filler, Raymond L.; Peters, R. Donald; Frank, James M.

    1981-01-01

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

  13. Vein matching using artificial neural network in vein authentication systems

    NASA Astrophysics Data System (ADS)

    Noori Hoshyar, Azadeh; Sulaiman, Riza

    2011-10-01

    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.

  14. Caldera-related gold mineralization of the El Limón mining district, western Nicaragua

    NASA Astrophysics Data System (ADS)

    Malone, Gary B.; Stoiber, Richard E.

    1987-08-01

    The town of El Limón, the center of a small gold mining district, lies 36 km northeast of León, Nicaragua. This paper reports on the sequence of volcanic rocks in the district, the structures in these volcanics and the relationship of the gold veins to them.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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

  16. Fluid inclusions in quartz crystals from South-West Africa

    USGS Publications Warehouse

    Kvenvolden, K.A.; Roedder, E.

    1971-01-01

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

  17. Gold Nanoantennas

    SciTech Connect

    2012-01-01

    An array of gold nanoantennas laced into an artificial membrane enhances the fluorescence intensity of three different molecules when they pass through plasmonic hot spots in the array. Watch for the blue, green and red flashes. The photobleaching at the end of each fluorescence event (white flashes) is indicative of single molecule observations.

  18. Remote sensing detection of gold related alteration zones in Um Rus area, Central Eastern Desert of Egypt

    NASA Astrophysics Data System (ADS)

    Amer, Reda; Kusky, Timothy; El Mezayen, Ahmed

    2012-01-01

    Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Phased Array L-band Synthetic Aperture Radar (PALSAR) images covering the Um Rus area in the Central Eastern Desert of Egypt were evaluated for mapping geologic structure, lithology, and gold-related alteration zones. The study area is covered by Pan-African basement rocks including gabbro and granodiorite intruded into a variable mixture of metavolcanics and metasediments. The first three principal component analyses (PCA1, PCA2, PCA3) in a Red-Green-Blue (RGB) of the visible through shortwave-infrared (VNIR + SWIR) ASTER bands enabled the discrimination between lithological units. The results show that ASTER band ratios ((2 + 4)/3, (5 + 7)/6, (7 + 9)/8) in RGB identifies the lithological units and discriminates the granodiorite very well from the adjacent rock units.The granodiorites are dissected by gold-bearing quartz veins surrounded by alteration zones. The microscopic examination of samples collected from the alteration zones shows sericitic and argillic alteration zones. The Spectral Angle Mapper (SAM) and Spectral Information Divergence (SID) supervised classification methods were applied using the reference spectra of the USGS spectral library. The results show that these classification methods are capable of mapping the alteration zones as indicated by field verification work. The PALSAR image was enhanced for fracture mapping using the second moment co-occurrence filter. Overlying extracted faults and alteration zone classification images show that the N30E and N-S fractures represent potential zones for gold exploration. It is concluded that the proposed methods can be used as a powerful tool for ore deposit exploration.

  19. Geological setting and timing of the cassiterite vein type mineralization of the Kalima area (Maniema, Democratic Republic of Congo)

    NASA Astrophysics Data System (ADS)

    Dewaele, S.; Muchez, Ph; Burgess, R.; Boyce, A.

    2015-12-01

    The Central African Mesoproterozoic Karagwe-Ankole belt in the Great Lakes area (DRCongo, Rwanda, Burundi, Uganda and Tanzania) forms a metallogenic province that hosts a variety of granite-related mineralization, which contains cassiterite, columbite-tantalite, wolframite/ferberite, spodumene and beryl. The Kalima area in the Maniema province of the DRCongo forms one of the most important areas for cassiterite mineralization in the eastern part of the DRCongo, even after many decades of exploitation. The mineralization dominantly consists of quartz veins that are hosted in Mesoproterozoic metasediments at the contact with granitic rocks of the Kalima granite (Avuanga and Yubuli) or directly crosscutting these granitic rocks (Atondo). Only limited - and mainly unmineralized pegmatites - have been described in the Lutshurukuru area. Mineralized quartz veins - and some granite bodies - intruded following the regional tectonic foliation or existing fracture zones, confirming the late-to post-tectonic origin of the fertile granite system. The emplacement of the quartz veins resulted in an alteration of the metasedimentary and granitic host-rocks, mainly resulting in muscovitization, tourmalinization and silicification. Cassiterite itself formed relatively late during vein formation and is associated with muscovite in fractures in or along the margins of the quartz veins. 40Ar-39Ar age dating of muscovite of an unmineralized pegmatite from the Lutshurukuru area gave an excellent plateau age of 1024 ± 5.5 Ma, while the muscovite associated with mineralization gave plateau ages of 986 ± 5.3 Ma for the Atondo deposit and 992.4 ± 5.4 Ma for the Yubuli deposit. The rather large spread in ages between the supposed parental granite/pegmatite and quartz veins is interpreted to reflect different magmatic events in the evolution of a composite granite system, starting at ∼1020 Ma and ending with mineralized quartz vein formation at ∼990 Ma. The latter age corresponds with

  20. Varicose Veins and Venous Insufficiency

    MedlinePlus

    ... that impact a person’s quality of life. Endovenous laser ablation treatment (EVLT) EVLT is a minimally invasive ... ray images ), the interventional radiologist threads a thin laser fiber into the problem vein through a tiny ...

  1. How Are Varicose Veins Treated?

    MedlinePlus

    ... and scarring. Sclerotherapy Sclerotherapy (SKLER-o-ther-ah-pe) uses a liquid chemical to close off a ... Microsclerotherapy Microsclerotherapy (MI-kro-SKLER-o-ther-ah-pe) is used to treat spider veins and other ...

  2. What Is Deep Vein Thrombosis?

    MedlinePlus

    ... deep vein of the leg can break off, travel to the lungs, and block blood flow. Rate This Content: NEXT >> Updated: October 28, 2011 Twitter Facebook YouTube Google+ SITE INDEX ACCESSIBILITY PRIVACY STATEMENT FOIA NO FEAR ACT ...

  3. An experimental verification of the possible influence of gas nano-bubbles on the response of an electrochemical quartz crystal microbalance.

    PubMed

    Tsionsky, Vladimir; Kaverin, Alexander; Daikhin, Leonid; Katz, Galina; Gileadi, Eliezer

    2005-04-21

    Electrochemical removal of oxygen and hydrogen from aqueous solution in the vicinity of gold electrodes, with simultaneous measurements of the response of the quartz crystal microbalance, show no evidence of gas nano-bubbles attached to the surface, irrespective of its roughness and hydrophobicity. The contact between gold and frozen electrolyte, which forms a liquid-like layer between them, also does not contain gas bubbles. These statements could be extended to nano-bubbles with characteristic dimensions larger than a few nanometers.

  4. Prospects of gold mineralization in the Gilgit-Baltistan Province of Pakistan

    NASA Astrophysics Data System (ADS)

    Shah, M. T.; Khan, S. D.; Tahirkheli, T.; Ahmad, L.; Miandad, S.; Rehman, A. U.; Ali, L.

    2012-12-01

    mainly pyrite and chalcopyrite with subordinate amount of bornite and tetrahedrite. Surface leaching of these phases to malachite, azurite and limonite is common. Quartz veining, silicification, carbonization and at places brecciation are the common features of these alteration zones. The concentrations of gold were found in the range of 3ppb to 112ppb, <5- 95ppb, 1ppb to 545ppb, 1ppb to 385 and 1ppb to 318ppb in the alteration zones of Golo Das, Bagrot valley, Shigri Bala, Machulu and Ranthak areas respectively. The barren rock samples have generally <5ppb gold. This is indicative of the multi-times enrichment of gold in the alteration zones. The sulfide mineralization along with gold in the alteration zones could be attributed to the hydrothermal/epithermal activity involving meteoric, igneous and or metamorphic fluid individually or mixture of these. The occurrence of dioritic intrusions (igneous fluid source) and the transitional dilated zones (metamorphic fluid source) on the major reactivated thrust fault (i.e., NSZ) in the vicinity of these alteration zones strengthen these observations. However, isotopic studies are underway to solve this problem. This study suggests that the alteration zones in the studied areas have the potential to be explored in detail for possible economical gold mineralization.

  5. [Surgery of essential varicose veins].

    PubMed

    Maraval, M

    1994-03-15

    Idiopathic varicose veins of the lower limbs are a frequent but benign disorder. Surgery is only a moment in the course of the disease. Although not the only treatment of essential varicose veins, surgery by an experienced team performing crossectomy, stripping by intussusception using a stripper, and phlebectomy gives fully satisfactory results, both to patient and to physician, in over 80% of cases. New techniques were recently developed that, at present, have not confirmed early hopes.

  6. Geology and lithogeochemistry of the Ren gold prospect, Elko County, Nevada - the role of rock sampling in exploration for deep Carlin-type deposits

    USGS Publications Warehouse

    Albino, G.V.

    1994-01-01

    The Ren gold prospect, Elko County, Nevada, is in the northern part of the Carlin trend, two kilometers northwest of the recently-discovered, high-grade Purple Vein deposit. The Ren area is underlain mainly by Paleozoic sedimentary rocks, consisting of limestone, calcareous siltstone, and mudstone of the eastern (carbonate) assemblage, overlain in thrust contact by chert, quartzite, and mudstone of the western (siliceous) assemblage. Cretaceous(?) granodiorite porphyry and hornblende porphyry dikes have intruded the sedimentary rocks along north-striking faults. Three stages of mineralization include a pre- or syntectonic base metal-barite assemblage, a middle stage of Ag- and Sb-rich jasperoid, and a late Au-rich stage responsible for the potentially economic mineralization at the prospect. The latter two stages of alteration and mineralization were focused along steep east-dipping faults and dikes, and the nearly flat-lying contact between lower massive limestone and laminated calcareous siltstone. Mineralization is present between 380 and 500 m below the surface. Alteration includes decalcification and weak silicification in siltstone, and formation of massive jasperoid in the upper part of the limestone unit. Alteration of dikes is mainly sericite-quartz-pyrite, with late pyrite-quartz-kaolinite. The element suite characteristic of Au-stage mineralization includes Au, As, and Hg with minor Ag and Hg; Ag and Sb are most enriched in the earlier jasperoid event. Haloes of As and Hg extend at least 80 m above the Au mineralization, but no anomalies are present at the surface. Gold anomalies are more widespread, and extend to shallower depths, but are less coherent. ?? 1994.

  7. In search of early life: Carbonate veins in Archean metamorphic rocks as potential hosts of biomarkers

    NASA Astrophysics Data System (ADS)

    Peters, Carl A.; Piazolo, Sandra; Webb, Gregory E.; Dutkiewicz, Adriana; George, Simon C.

    2016-11-01

    The detection of early life signatures using hydrocarbon biomarkers in Precambrian rocks struggles with contamination issues, unspecific biomarkers and the lack of suitable sedimentary rocks due to extensive thermal overprints. Importantly, host rocks must not have been exposed to temperatures above 250 °C as at these temperatures biomarkers are destroyed. Here we show that Archean sedimentary rocks from the Jeerinah Formation (2.63 billion yrs) and Carawine Dolomite (2.55 billion yrs) of the Pilbara Craton (Western Australia) drilled by the Agouron Institute in 2012, which previously were suggested to be suitable for biomarker studies, were metamorphosed to the greenschist facies. This is higher than previously reported. Both the mineral assemblages (carbonate, quartz, Fe-chlorite, muscovite, microcline, rutile, and pyrite with absence of illite) and chlorite geothermometry suggest that the rocks were exposed to temperatures higher than 300 °C and probably ∼400 °C, consistent with greenschist-facies metamorphism. This facies leads to the destruction of any biomarkers and explains why the extraction of hydrocarbon biomarkers from pristine drill cores has not been successful. However, we show that the rocks are cut by younger formation-specific carbonate veins containing primary oil-bearing fluid inclusions and solid bitumens. Type 1 veins in the Carawine Dolomite consist of dolomite, quartz and solid bitumen, whereas type 2 veins in the Jeerinah Formation consist of calcite. Within the veins fluid inclusion homogenisation temperatures and calcite twinning geothermometry indicate maximum temperatures of ∼200 °C for type 1 veins and ∼180 °C for type 2 veins. Type 1 veins have typical isotopic values for reprecipitated Archean sea-water carbonates, with δ13CVPDB ranging from - 3 ‰ to 0‰ and δ18OVPDB ranging from - 13 ‰ to - 7 ‰, while type 2 veins have isotopic values that are similar to hydrothermal carbonates, with δ13CVPDB ranging from - 18

  8. Biomineralization of gold: biofilms on bacterioform gold.

    PubMed

    Reith, Frank; Rogers, Stephen L; McPhail, D C; Webb, Daryl

    2006-07-14

    Bacterial biofilms are associated with secondary gold grains from two sites in Australia. 16S ribosomal DNA clones of the genus Ralstonia that bear 99% similarity to the bacterium Ralstonia metallidurans-shown to precipitate gold from aqueous gold(III) tetrachloride-were present on all DNA-positive gold grains but were not detected in the surrounding soils. These results provide evidence for the bacterial contribution to the authigenic formation of secondary bacterioform gold grains and nuggets.

  9. Quartz resonator state-of-charge monitor for lead-acid batteries

    NASA Astrophysics Data System (ADS)

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

    We have demonstrated that a thickness shear mode quartz resonator can be used as a real-time, in situ monitor of the state-of-charge of lead-acid batteries. The resonator is sensitive to changes in the density and viscosity of the sulfuric acid electrolyte. Both of these liquid parameters vary monotonically with the battery state-of-charge. This new monitor is more precise than sampling hydrometers, and since it is compatible with the corrosive electrolyte environment, it can be used for in situ monitoring. A TSM resonator consists of gold electrodes deposited on opposite surfaces of a thin AT-cut quartz crystal. When an RF voltage is applied to the electrodes, a shear strain is introduced in the piezoelectric quartz and mechanical resonance occurs between the surfaces. A liquid in contact with one of the quartz surfaces is viscously entrained, which perturbs the resonant frequency and resonance magnitude. If the surface is smooth, the changes in both frequency and magnitude are proportional to (rho(eta))(exp (1/2)), where rho is the liquid density and eta is the viscosity.

  10. Quartz resonator state-of-charge monitor for lead-acid batteries

    SciTech Connect

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

    1994-06-01

    We have demonstrated that a thickness shear mode quartz resonator can be used as a real-time, in situ monitor of the state-of-charge of lead-acid batteries. The resonator is sensitive to hanges in the density and viscosity of the sulfuric acid electrolyte. Both of these liquid parameters vary monotonically with the battery state-of-charge. This new monitor is more precise than sampling hydrometers, and since it is compatible with the Corrosive electrolyte environment, it can be used for in situ monitoring. A TSM resonator consists of gold electrodes deposited on opposite surfaces of a thin AT-cut quartz crystal. When an RF voltage is applied to the electrodes, a shear strain is introduced in the piezoelectric quartz and mechanical resonance occurs between the surfaces. A liquid in contact with one of the quartz surfaces is viscously entrained, which perturbs the resonant frequency and resonance magnitude. If the surface is smooth, the changes in both frequency and magnitude are proportional to ({rho}{eta}) {sup {1/2}}, where {rho} is the liquid density and {eta} is the viscosity.

  11. Detection of H3N2 canine influenza virus using a Quartz Crystal Microbalance.

    PubMed

    Kim, Yong Kwan; Lim, Seong-In; Cho, Yoon-Young; Choi, Sarah; Song, Jae-Young; An, Dong-Jun

    2014-11-01

    Label-free technology-based Quartz Crystal Microbalance (QCM) is an emerging tool in biological research. In this study, QCM was applied successfully for the rapid diagnosis of H3N2 canine influenza virus (CIV) infection. ProLinker™ B, a calixcrown derivative, enables antibodies to be attached to a gold-coated quartz surface and positioned in a regular pattern with the correct orientation. The ProLinker-coated quartz-based assay detected H3N2 CIV at lower concentrations (2(2) HA unit) than a commercial immunochromatography Ag kit (2(3) HA unit). Three independent experiments in which H3N2 CIV-positive reference samples were applied to an anti-CIV nucleoprotein (NP) monoclonal antibody immobilized on a quartz surface yielded standard deviations (SD) of ≤5%, indicating high reproducibility. In addition, the QCM assay with a cut-off value (-140 Hz) showed 97.1% (34/35) sensitivity and 94.7% (36/38) specificity in testing 73 field saliva samples, respectively. Thus, the QCM assay described herein will be a valuable tool for the rapid diagnosis of H3N2 CIV infection with high sensitivity and specificity, and should overcome several of the disadvantages and limitations inherent in the commercial immunochromatography Ag kit.

  12. [Characteristics of Raman spectra of minerals in the veins of Wenchuan earthquake fault zone].

    PubMed

    Xie, Chao; Zhou, Ben-gang; Liu, Lei; Zhou, Xiao-cheng; Yi, Li; Chen, Zhi; Cui, Yue-ju; Li, Jing; Chen, Zheng-wei; Du, Jian-guo

    2015-01-01

    Quartz in the veins at the Shenxigou section of Wenchuan earthquake fault zone was investigated by micro-Raman spectroscopic measurement, and the distribution of compressive stress in the fault zone was estimated by the frequency shifts of the 464 cm-1 vibrational mode of quartz grains in the veins. It was showed that the 464 cm-1 peak arising from the quartz grains in the veins near the fault plane shifts by 3. 29 cm-1 , and the corresponding compressive stress is 368. 63 MPa, which is significantly lower than the stress accumulation on both sides due to multi-stage events. Stress accumulation increased with moving away from the fault plane in the footwall with the offset of the 464 cm-1 peak arising from the quartz grains in the veins increasing, which can reach 494. 77 MPa at a distance of 21 m with a high offset of 4. 40 cm-1 of the 464 cm-1 peak. The compressive stress gets the maximum value of 519.87 MPa at a distance of 10 m from the fault plane in the hanging wall with the offset of the 464 cm-1 peak arising from the quartz grains in the veins being 4. 62 cm-1, followed by a sudden drop in stress accumulation, and it drops to 359. 59 MPa at a distance of 17 m. Because of moving away from the foult plane at the edge of the foult zone, the stress drops to 359. 59 MPa with a small value of 464 cm-1 peak offset 3. 21 cm-1 at a distance of 27 m from the fault plane in the hanging wall due to the little effect by the fault activity. Therefore, the stress of Wenchuan earthquake fault zone is partially released, but the rest of the stress distribution is uneven, and there is also a high stress accumulation in somewhere in the fault zone, which reflects that the mechanical properties of the rocks in the fault zone have a characteristic of unevenness in space.

  13. Examining the Effect of Water on the Strength of Quartz Using Polycrystalline Quartz Aggregates

    NASA Astrophysics Data System (ADS)

    Barbery, A. M.; Holyoke, C. W., III; Kronenberg, A. K.; Fukuda, J. I.

    2015-12-01

    Quartzite rheology has been extensively studied to model the strength of continental crust. Previous studies have shown that the presence of water in fluid inclusions weakens polycrystalline quartz, and this weakening is usually related to water fugacity. However, no attempt has been made to determine the effect of water content on the strength of quartz. We have deformed hot-pressed quartz aggregates with low water contents at a pressure of 1.5 GPa, a temperature of 1200°C, and strain rates of 10-4 to 10-6/s. Fine synthetic quartz powders were hot-pressed at 1120°C and 1.5 GPa for 24 hours to create quartzites with a grain size of ~20 microns and water contents of <150 H/106Si. The water band in FTIR spectra collected from the hot-pressed quartz aggregates is similar to the broad water band observed in natural quartzites (i.e. free water in fluid inclusions) rather than the spectra observed in synthetic quartz crystals. Results of deformation experiments indicate that the strain rate sensitivity of the strength of these quartz aggregates is consistent with deformation by dislocation creep (n~3.5). Microstructures observed in samples from these experiments include undulatory extinction, flattened grains, and bulging grain boundaries, which are also consistent with dislocation creep. The strength of these quartz aggregates deformed with low water contents (<150 H/106 Si) are an order of magnitude greater than the strengths predicted by polycrystalline quartz flow laws derived from quartzites with high (>2000 H/106Si) water contents. Our results indicate that quartz strength is dependent on water content, in addition to being dependent on water fugacity.

  14. Columbium-, rare-earth-element-, and thorium-bearing veins near Salmon Bay, Southeastern Alaska. Open file report

    SciTech Connect

    Warner, J.D.

    1989-01-01

    In 1984 and 1985 the Bureau of Mines investigated radioactive carbonate veins near Salmon Bay, southeastern Alaska, for concentrations of columbium and associated metals. The veins cut units of graywacke, conglomerate, argillite, and limestone and range in width from less than an inch to greater than 10 ft and have a length ranging from less than a hundred to greater than 1,000 ft. Mineralogy of the veins is complex, and includes thorite, the rare-earth-element minerals monazite, parisite, and bastnaesite, and a columbium mineral that is speculated to be columbite. Gangue minerals include ankerite, dolomite, siderite, quartz and albite. More than seventy veins were sampled but only three contain elevated metal concentrations along a significant strike length. These resources are small compared to columbium, REE, and thorium resources elsewhere in the world.

  15. Scanning hall probe microscopy (SHPM) using quartz crystal AFM feedback.

    PubMed

    Dede, M; Urkmen, K; Girişen, O; Atabak, M; Oral, A; Farrer, I; Ritchie, D

    2008-02-01

    Scanning Hall Probe Microscopy (SHPM) is a quantitative and non-invasive technique for imaging localized surface magnetic field fluctuations such as ferromagnetic domains with high spatial and magnetic field resolution of approximately 50 nm and 7 mG/Hz(1/2) at room temperature. In the SHPM technique, scanning tunneling microscope (STM) or atomic force microscope (AFM) feedback is used to keep the Hall sensor in close proximity of the sample surface. However, STM tracking SHPM requires conductive samples; therefore the insulating substrates have to be coated with a thin layer of gold. This constraint can be eliminated with the AFM feedback using sophisticated Hall probes that are integrated with AFM cantilevers. However it is very difficult to micro fabricate these sensors. In this work, we have eliminated the difficulty in the cantilever-Hall probe integration process, just by gluing a Hall Probe chip to a quartz crystal tuning fork force sensor. The Hall sensor chip is simply glued at the end of a 32.768 kHz or 100 kHz Quartz crystal, which is used as force sensor. An LT-SHPM system is used to scan the samples. The sensor assembly is dithered at the resonance frequency using a digital Phase Locked Loop circuit and frequency shifts are used for AFM tracking. SHPM electronics is modified to detect AFM topography and the frequency shift, along with the magnetic field image. Magnetic domains and topography of an Iron Garnet thin film crystal, NdFeB demagnetised magnet and hard disk samples are presented at room temperature. The performance is found to be comparable with the SHPM using STM feedback.

  16. Synthetic quartz with high ultraviolet transmission.

    PubMed

    Ballman, A A; Dodd, D M; Kuebler, N A; Laudise, R A; Wood, D L; Rudd, D W

    1968-07-01

    Quartz has been synthesized under hydrothermal conditions at rates of 1.78 mm/day in the presence of LiNO(2) in Ag lined and Ag plated systems, and it is shown that such quartz has optical transmission between 1500 A and 3 micro equal, and in some cases superior to, natural quartz. The uv cutoff at about 1500 A has been shown to be associated with Fe whose concentration may be reduced by procedures that reduce the concentration of charge compensating H+ in the lattice (growth in LiNO(2)) and by procedures which reduce the concentration of Fe in solutions (inert conditions). Transmission near 3 micro is affected by OH which can be reduced by LiNO(2).

  17. Adsorption of goethite onto quartz and kaolinite

    USGS Publications Warehouse

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

    1984-01-01

    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.

  18. Gypsum veins in Triassic Moenkopi mudrocks of southern Utah: Analogs to calcium sulfate veins on Mars

    NASA Astrophysics Data System (ADS)

    Young, B. W.; Chan, M. A.

    2017-01-01

    Well-exposed gypsum veins in the Triassic Moenkopi formation in southern Utah, USA, are similar to veins at Endeavour and Gale Craters on Mars. Both Moenkopi and Mars veins are hydrated calcium sulfate, have fibrous textures, and crosscut other diagenetic features. Moenkopi veins are stratigraphically localized with strontium and sulfur isotope ratios similar to primary Moenkopi sulfate beds and are thus interpreted to be sourced from within the unit. Endeavour veins seem to be distributed by lithology and may have a local source. Gale veins cut across multiple lithologies and appear to be sourced from another stratigraphic interval. Evaluation of vein network geometries indicates that horizontal Moenkopi veins are longer and thicker than vertical veins. Moenkopi veins are also generally oriented with the modern stress field, so are interpreted to have formed in the latest stages of exhumation. Endeavour veins appear to be generally vertical and oriented parallel to the margins of Cape York and are interpreted to have formed in response to topographic collapse of the crater rim. Gale horizontal veins appear to be slightly more continuous than vertical veins and may have formed during exhumation. Abrupt changes in orientation, complex crosscutting relationships, and fibrous (antitaxial) texture in Moenkopi and Mars veins suggest emplacement via hydraulic fracture at low temperatures. Moenkopi and Mars veins are interpreted as late-stage diagenetic features that have experienced little alteration since emplacement. Moenkopi veins are useful terrestrial analogs for Mars veins because vein geometry, texture, and chemistry record information about crustal deformation and vein emplacement.

  19. Is It Real Gold?

    ERIC Educational Resources Information Center

    Harris, Harold H.

    1999-01-01

    Features acid tests for determining whether jewelry is "real" gold or simply gold-plated. Describes the carat system of denoting gold content and explains how alloys are used to create various shades of gold jewelry. Addresses the question of whether gold jewelry can turn a wearer's skin green by considering various oxidation reactions.…

  20. Thiol- and biotin-labeled probes for oligonucleotide quartz crystal microbalance biosensors of microalga alexandrium minutum.

    PubMed

    Lazerges, Mathieu; Perrot, Hubert; Rabehagasoa, Niriniony; Compère, Chantal

    2012-07-04

    Two quartz crystal microbalance oligonucleotide biosensors of a toxic microalga gene sequence (Alexandrium Minutum) have been designed. Grafting on a gold surface of 20-base thiol- or biotin-labeled probe, and selective hybridization with the complementary 20-base target, have been monitored in situ with a 27 MHz quartz crystal microbalance under controlled hydrodynamic conditions. The frequency of the set up is stable to within a few hertz, corresponding to the nanogram scale, for three hour experiments. DNA recognition by the two biosensors is efficient and selective. Hybridization kinetic curves indicate that the biosensor designed with the thiol-labeled probe is more sensitive, and that the biosensor designed with the biotin-labeled probe has a shorter time response and a higher hybridization efficiency.

  1. Thiol- and Biotin-Labeled Probes for Oligonucleotide Quartz Crystal Microbalance Biosensors of Microalga Alexandrium Minutum

    PubMed Central

    Lazerges, Mathieu; Perrot, Hubert; Rabehagasoa, Niriniony; Compère, Chantal

    2012-01-01

    Two quartz crystal microbalance oligonucleotide biosensors of a toxic microalga gene sequence (Alexandrium Minutum) have been designed. Grafting on a gold surface of 20-base thiol- or biotin-labeled probe, and selective hybridization with the complementary 20-base target, have been monitored in situ with a 27 MHz quartz crystal microbalance under controlled hydrodynamic conditions. The frequency of the set up is stable to within a few hertz, corresponding to the nanogram scale, for three hour experiments. DNA recognition by the two biosensors is efficient and selective. Hybridization kinetic curves indicate that the biosensor designed with the thiol-labeled probe is more sensitive, and that the biosensor designed with the biotin-labeled probe has a shorter time response and a higher hybridization efficiency. PMID:25585927

  2. Basic Material Quartz and Related Innovations

    NASA Astrophysics Data System (ADS)

    Ballato, A.

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

  3. Quartz: Anomalous Weakness of Synthetic Crystals.

    PubMed

    Griggs, D T; Blacic, J D

    1965-01-15

    The strength of a synthetic quartz crystal drops rapidly at 400 degrees C, and at 600 degrees C is a hundredfold lower than at 300 degrees C. Large plastic deformations can be produced without fracture. The predominant mechanism of deformation is translation gliding. The preferred explanation for this anomalous weakness is that this synthetic quartz contains water which has hydrolyzed the silicon-oxygen bonds. The silanol groups so formed are presumed to be rendered sufficiently mobile by elevating the temperature to 400 degrees C so that they align themselves in dislocation lines and move through the crystal with the dislocation under the small applied shear stress.

  4. Early Yellowstone hotspot magmatism and gold metallogeny

    NASA Astrophysics Data System (ADS)

    Hames, Willis; Unger, Derick; Saunders, James; Kamenov, George

    2009-11-01

    High-grade epithermal gold deposits in the Northern Great Basin have long been associated with regional Miocene basaltic to rhyolitic volcanism. Previous models for the low-sulfidation epithermal gold ores in this region have generally portrayed the bimodal magmas as a source of heat to drive large-scale convection of meteoritic water that leached gold from crustal sources and deposited it in hydrothermal vein systems, or required that the gold evolve from fractionated silicic magmas. New data of the present study indicate a more direct genetic link to the plume-related basaltic magmas of the region. Laser 40Ar/ 39Ar incremental heating plateau ages for single crystals of adularia from several of these low-sulfidation epithermal gold deposits range from 16.6 Ma to 15.5 Ma. Adularia from the Jumbo deposit yields three concordant plateau ages with a combined statistical result of 16.54 ± 0.04 Ma (95% confidence level, MSWD = 0.23). Plateau ages for adularia from other deposits in the region, and from gold-bearing veins in the Owyhee Mountains of southwestern Idaho, yield similar ages up to ~16.5 Ma, however some veins are as young as ca. 15.5 Ma and the grain-to-grain ages for a given sample can vary by up to ca. 0.5 Ma. Observed variations in age among the adularia crystals of a given rock sample indicate varying amounts of extraneous argon, and also loss of radiogenic 40Ar, among the population of grains for a particular sample. The single-crystal results are interpreted to indicate a 16.5-15.5 Ma interval for formation of gold-bearing adularia veins in the region. The initiation and duration of this gold-forming event appears contemporaneous (within uncertainties) with the basaltic volcanism at the Steens Mountain section and an ensuing one-million-year episode of basaltic volcanism from multiple centers in the region ( Brueseke et al., 2007). Trace amounts of lead are alloyed with gold in the deposits studied. The isotopic compositions of this lead are not

  5. Minimally invasive treatments for perforator vein insufficiency

    PubMed Central

    Salazar, Gloria Maria; Prabhakar, Anand M.; Ganguli, Suvranu

    2016-01-01

    Incompetent superficial veins are the most common cause of lower extremity superficial venous reflux and varicose veins; however, incompetent or insufficient perforator veins are the most common cause of recurrent varicose veins after treatment, often unrecognized. Perforator vein insufficiency can result in pain, skin changes, and skin ulcers, and often merit intervention. Minimally invasive treatments have replaced traditional surgical treatments for incompetent perforator veins. Current minimally invasive treatment options include ultrasound guided sclerotherapy (USGS) and endovascular thermal ablation (EVTA) with either laser or radiofrequency energy sources. Advantages and disadvantages of each modality and knowledge on these treatments are required to adequately address perforator venous disease. PMID:28123979

  6. Clinical Trials in Branch Retinal Vein Occlusion

    PubMed Central

    Panakanti, Tandava Krishnan; Chhablani, Jay

    2016-01-01

    Branch retinal vein occlusion (BRVO) is the second most common retinal vascular disorder. The management of macular edema has changed considerably over time. The laser is considered the gold standard treatment for over two decades. However, visual recovery with laser is usually slow and incomplete. The advent of intravitreal agents, specifically anti-vascular endothelial growth factors (VEGF) have heralded a new era which promises rapid recovery of vision and quality of vision. Randomized clinical trials have reported optimal results with anti-VEGF agents (ranibizumab, bevacizumab, and aflibercept) compared to laser therapy or steroids. However, nearly 50% of the patients require repeat intravitreal anti-VEGF therapy up to 4 years after initiating therapy to sustain the visual gains. The adverse events (systemic and ocular) of these agents are minimal. Monotherapy with anti-VEGF agents have been found to provide better results than any combination with laser. This review article summarizes evidence from randomized controlled trials evaluating treatment options for the treatment of macular edema secondary to BRVO with a special focus on anti-VEGF therapy. PMID:26957837

  7. Leiomyosarcoma of the splenic vein.

    PubMed

    Aguilar, Cristian; Socola, Francisco; Donet, Jean A; Gallastegui, Nicolas; Hernandez, Gabriel A

    2013-01-01

    Leiomyosarcomas arising from the wall of blood vessels are rare and aggressive neoplasm. We report a case of a previously healthy 66-year-old woman who presented with intermittent abdominal pain, progressive constipation, and weight loss. Abdominal computed tomography showed a 12 cm solid heterogeneous tumor in the tail of the pancreas. The patient subsequently underwent surgical resection of the pancreatic mass. Surprisingly, histological and immunohistochemical analyses revealed leiomyosarcoma arising from the smooth muscle of the splenic vein. After surgery, she received adjuvant chemotherapy. One year later, there was no evidence of local recurrence. In this paper, we discuss the available information about leiomyosarcomas of splenic vein and its management.

  8. Varicose veins: a critical review of the definition and the therapeutical options.

    PubMed

    Jeanneret, C; Karatolios, K

    2011-09-01

    This review intends to give an overview of the present therapeutic options for varicose vein disease. The definition of varicose vein disease and its recurrence are made and discussed with new aspects including duplexsonography assessment. All therapeutic approaches have developed and refined their treatment modalities, the open surgical as well as the endovenous techniques. In particular the “new” endovenous techniques are described with regard to safety and outcome, the published literature in this respect is summarized. The studies comparing the different techniques are listed, the prospective long term studies comparing the new techniques with the so called gold standard (open surgery) shall decide on the fate of the different techniques.

  9. Quartz crystal microbalances for quantitative biosensing and characterizing protein multilayers.

    PubMed

    Rickert, J; Brecht, A; Göpel, W

    1997-01-01

    The use of quartz crystal microbalances (QCMs) for quantitative biosensing and characterization of protein multilayers is demonstrated in three case studies. Monolayers of QCM-based affinity biosensors were investigated first. Layers of a thiol-containing synthetic peptide constituting an epitope of the foot-and-mouse-disease virus were formed on gold electrodes via self-assembly. The binding of specific antibodies to epitope-modified gold electrodes was detected for different concentrations of antibody solutions. Oligolayers were studied in a second set of experiments. Dextran hydrogels were modified by thrombin inhibitors. The QCM response was used in a competitive binding assay to identify inhibitors for thrombin at different concentrations. Multilayers of proteins formed by self-assembly of a biotin-conjugate and streptavidin were investigated next. The QCM frequency response was monitored as a function of layer thickness up to 20 protein layers. A linear frequency decay was observed with increasing thickness. The decay per layer remained constant, thus indicating perfect mass coupling to the substrate. Frequency changes a factor of four higher were obtained in buffer solution as compared to measurements in dry air. This indicates a significant incorporation of water (75% weight) in the protein layers. This water behaves like a solid concerning the shear mode coupling to the substrate. The outlook discusses briefly the need for controlled molecular engineering of overlayers for subsequent QCM analysis, and the importance of an additional multiparameter analysis with other transducer principles and with additional techniques of interface analysis to characterize the mechanical coupling of overlayers as biosensor coatings. A promising trend concerns the use of QCM-arrays for screening experiments.

  10. A method of calculating quartz solubilities in aqueous sodium chloride solutions

    USGS Publications Warehouse

    Fournier, R.O.

    1983-01-01

    The aqueous silica species that form when quartz dissolves in water or saline solutions are hydrated. Therefore, the amount of quartz that will dissolve at a given temperature is influenced by the prevailing activity of water. Using a standard state in which there are 1,000 g of water (55.51 moles) per 1,000 cm3 of solution allows activity of water in a NaCl solution at high temperature to be closely approximated by the effective density of water, pe, in that solution, i.e. the product of the density of the NaCl solution times the weight fraction of water in the solution, corrected for the amount of water strongly bound to aqueous silica and Na+ as water of hydration. Generally, the hydration of water correction is negligible. The solubility of quartz in pure water is well known over a large temperature-pressure range. An empirical formula expresses that solubility in terms of temperature and density of water and thus takes care of activity coefficient and pressure-effect terms. Solubilities of quartz in NaCl solutions can be calculated by using that equation and substituting pe, for the density of pure water. Calculated and experimentally determined quartz solubilities in NaCl solutions show excellent agreement when the experiments were carried out in non-reactive platinum, gold, or gold plus titanium containers. Reactive metal containers generally yield dissolved silica concentrations higher than calculated, probably because of the formation of metal chlorides plus NaOH and H2. In the absence of NaOH there appears to be no detectable silica complexing in NaCl solutions, and the variation in quartz solubility with NaCl concentration at constant temperature can be accounted for entirely by variations in the activity of water. The average hydration number per molecule of dissolved SiO2 in liquid water and NaCl solutions decreases from about 2.4 at 200??C to about 2.1 at 350??C. This suggests that H4SiO4 may be the dominant aqueous silica species at 350??C, but other

  11. Extrahepatic Portal Vein Obstruction and Portal Vein Thrombosis in Special Situations: Need for a New Classification

    PubMed Central

    Wani, Zeeshan A.; Bhat, Riyaz A.; Bhadoria, Ajeet S.; Maiwall, Rakhi

    2015-01-01

    Extrahepatic portal vein obstruction is a vascular disorder of liver, which results in obstruction and cavernomatous transformation of portal vein with or without the involvement of intrahepatic portal vein, splenic vein, or superior mesenteric vein. Portal vein obstruction due to chronic liver disease, neoplasm, or postsurgery is a separate entity and is not the same as extrahepatic portal vein obstruction. Patients with extrahepatic portal vein obstruction are generally young and belong mostly to Asian countries. It is therefore very important to define portal vein thrombosis as acute or chronic from management point of view. Portal vein thrombosis in certain situations such as liver transplant and postsurgical/liver transplant period is an evolving area and needs extensive research. There is a need for a new classification, which includes all areas of the entity. In the current review, the most recent literature of extrahepatic portal vein obstruction is reviewed and summarized. PMID:26021771

  12. Mass transfer and fluid evolution in late-metamorphic veins, Rhenish Massif (Germany): insight from alteration geochemistry and fluid-mineral equilibria modeling

    NASA Astrophysics Data System (ADS)

    Marsala, Achille; Wagner, Thomas

    2016-08-01

    Element mobility and fluid-rock interaction related to the formation of late-metamorphic quartz veins have been studied by combination of mineral chemistry, whole-rock geochemistry, mass balance analysis and fluid-mineral equilibria modeling. The quartz veins are hosted by very low-grade metasedimentary rocks of the fold-and-thrust belt of the Rhenish Massif (Germany). The veins record two stages of evolution, a massive vein filling assemblage with elongate-blocky quartz, chlorite, apatite and albite, and a later open space filling assemblage with euhedral crystals of quartz, ankerite-dolomite and minor calcite and sulfides. Detailed mass balance analysis of an alteration profile adjacent to a representative quartz vein demonstrates that element mobility is restricted to the proximal zone. The most important element changes are gain of Ca, Fe, Mg, Mn, P and CO2, and loss of Si, K and Na. The data demonstrate that wall-rock carbonation is one of the main alteration features, whereas mobility of Si, K and Na are related to dissolution of quartz and destruction of detrital feldspar and muscovite. The whole-rock geochemical data, in conjunction with fluid composition data and pressure-temperature estimates, were used as input for fluid-mineral equilibria modeling in the system Si-Al-Fe-Mg-Ca-Na-K-C-S-O-H-B-F-Cl. Modeling involved calculation of rock-buffered fluid compositions over the temperature interval 100-500 °C, and reaction-path simulations where a rock-buffered high-temperature fluid reacts with fresh host-rocks at temperatures of 400, 300 and 200 °C. Calculated rock-buffered fluid compositions demonstrate that retrograde silica solubility is a strong driving force for quartz leaching in the temperature-pressure window of 380-450 °C and 0.5 kbar. These conditions overlap with the estimated temperatures for the initial stage of vein formation. Reaction-path models show that high-temperature alteration can produce the observed silica leaching, suggesting that

  13. Coarse muscovite veins and alteration deep in the Yerington batholith, Nevada: insights into fluid exsolution in the roots of porphyry copper systems

    NASA Astrophysics Data System (ADS)

    Runyon, Simone E.; Steele-MacInnis, Matthew; Seedorff, Eric; Lecumberri-Sanchez, Pilar; Mazdab, Frank K.

    2017-02-01

    Veins and pervasive wall-rock alteration composed of coarse muscovite±quartz±pyrite are documented for the first time in a porphyritic granite at Luhr Hill in the Yerington District, Nevada. Coarse muscovite at Luhr Hill occurs at paleodepths of 6-7 km in the roots of a porphyry copper system and crops out on the scale of tens to hundreds of meters, surrounded by rock that is unaltered or variably altered to sodic-calcic assemblages. Coarse muscovite veins exhibit a consistent orientation, subvertical and N-S striking, which structurally restores to subhorizontal at the time of formation. Along strike, coarse muscovite veins swell from distal, millimeter-thick muscovite-only veinlets to proximal, centimeter-thick quartz-sulfide-bearing muscovite veins. Crosscutting relationships between coarse muscovite veins, pegmatite dikes, and sodic-calcic veins indicate that muscovite veins are late-stage magmatic-hydrothermal features predating final solidification of the Luhr Hill porphyritic granite. Fluid inclusions in the muscovite-quartz veins are high-density aqueous inclusions of 3-9 wt% NaCl eq. and <1 mol% CO2 that homogenize between 150 and 200 °C, similar to fluid inclusions from greisen veins in Sn-W-Mo vein systems. Our results indicate that muscovite-forming fluids at Luhr Hill were mildly acidic, of low to moderate salinity and sulfur content and low CO2 content, and that muscovite in deep veins and alteration differs in texture, composition, and process of formation from sericite at shallower levels of the hydrothermal system. Although the definition of greisen is controversial, we suggest that coarse muscovite alteration is more similar to alteration in greisen-type Sn-W-Mo districts worldwide than to sericitic alteration at higher levels of porphyry copper systems. The fluids that form coarse muscovite veins and alteration in the roots of porphyry copper systems are distinct from fluids that formed copper ore or widespread, shallower, acidic alteration

  14. Instantaneous healing of micro-fractures during coseismic slip: Evidence from microstructure and Ti in quartz geochemistry within an exhumed pseudotachylyte-bearing fault in tonalite

    NASA Astrophysics Data System (ADS)

    Bestmann, Michel; Pennacchioni, Giorgio; Mostefaoui, Smail; Göken, Mathias; de Wall, Helga

    2016-06-01

    Exhumed faults within the tonalitic Adamello pluton (Southern Alps) were seismic at depth as indicated by the presence of pseudotachylytes (solidified friction-induced melts). During cooling of tonalite, early-formed joints were first exploited by localized ductile shear zones associated with deposition of quartz veins (at ~ 500 °C), and later by pseudotachylyte-bearing cataclastic faults (at ~ 250-300 °C ambient temperature). Adjacent to pseudotachylytes, quartz of the host tonalite shows pervasive thin (1-10 μm wide) healed micro-fractures and ultra-fine (1-2 μm grain size) recrystallized aggregates along micro-shear zones. Under cathodoluminescence (CL) the healed micro-fractures have a darker gray shade than the host "magmatic" quartz that reflects a change in Ti concentrations ([Ti]) as indicated by NanoSIMS measurements. [Ti] vary from 35-55 ppm in the CL-lighter host quartz to 10-13 ppm along the CL-darker healed micro-fractures. These [Ti] were inherited by the ultra-fine recrystallized aggregates that overprinted both the magmatic quartz and the healed micro-fractures during the high temperature transient related to frictional seismic slip. Based on Ti-in-quartz thermometry, we infer that micro-fracture healing occurred at higher temperatures than the ambient temperatures of faulting (250-300 °C at 0.2 GPa), for which [Ti] < 1 ppm would be expected. Micro-fracture healing can be ascribed to the stage of seismic slip of faults on the basis of the observation that: (i) they are absent in the host rock surrounding high-T quartz veins un-exploited by faults; and (ii) they locally occur at the tip of pseudotachylyte injection veins filling new fractures developed during the propagation of the earthquake rupture. The relatively high [Ti] of micro-fractures are therefore interpreted to reflect quartz healing by a fluid overheated during the initial stages of frictional seismic slip and escaping from fault surface through the damage zone. This suggests that

  15. Deformation and veining processes on the subduction zone; example from the Cretaceous Shimanto accretionary complex in Japan

    NASA Astrophysics Data System (ADS)

    Tokiwa, T.; Kageyama, N.; Yoshida, H.

    2015-12-01

    In this study, the authors discuss the relationship between deformation and veining stages in the accretionary complex in order to understand the deformation and fluid flow process during the subduction. This study deals with the Miyama Formation in the Cretaceous Shimanto accretionary complex located in the Kii Peninsula of Japan. The deformation can be divided three types with four types of vein. Based on the differences, the process can be divided four stage by their cutting relationship as follow. Stage 1; the deformation (D1) in this stage is characterized by the aspect ratio of the deformed clasts with range from 0.1 to 0.4, and pinch-and-swell structure and budinaged structures of the sandstone are developed. The veins (V1) are recognized only within the sandstone, and the veins are cut by muddy matrix. Stage 2; the deformation (D2) is characterized by the aspect ratio is more than 0.4, and is distributed along the unit boundary. The clasts such as sandstone and chert are strongly sheared, and random fabric is often recognized. The vein (V2) in this stage cut the D1, and the V2 and D2 are cut by each other. Stage 3; outcrop-scale faults (D3) cutting D1 and D2 has been progressed in this stage. The vein (V3) is recognized along D3. Stage 4; the vein (V4) cutting D1 to D3 is developed in this stage. From the above-mentioned occurrence and data shown by previous studies of the Miyama Formation, process of each Stage interpreted as follows; Stage 1 developed underthrusting, Stages 2 and 3 correspond to underplating of subducted sediments. In addition, it is considered that Stage 4 is in later stage of underplating. The main components of the V1 to V3 veins are calcite and/or quartz. On the other hand, the V4 vein consists mainly of siderite and ankerite, and contain an abundance of Fe than the other veins. Morphological feature of V1 and V3 veins also show blocky texture suggesting higher rate growth than fracture opening, and V2 vein indicate syn-taxial growth

  16. Angiosarcoma of common iliac vein

    PubMed Central

    Ibis, Kamuran; Usta, Ufuk; Cosar, Rusen; Ibis, Cem

    2015-01-01

    Angiosarcoma is a rare malignant tumour of endothelial cells. Primary angiosarcoma of venous origin is extremely rare, and has a very poor prognosis. A 63-year-old woman with retroperitoneal mass underwent en bloc resection on a part of iliac vein followed by adjuvant radiotherapy. No recurrence was detected during 3 years of follow-up. PMID:25596292

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

    NASA Astrophysics Data System (ADS)

    Urubek, Tomáš; Dolníček, Zdeněk; Kropáč, Kamil

    2015-01-01

    Hydrothermal mineralization hosted by the Lower Cretaceous igneous rock of the teschenite association at Jasenice (Silesian Unit, Flysch Belt, Outer Western Carpathians) occurs in two morphological types - irregular vein filled by granular calcite and regular composite vein formed by both fibrous and granular calcite and minor chlorite, quartz, and pyrite. Crosscutting evidence indicates that the granular veins are younger than the composite vein. The composite vein was formed by two mechanisms at different times. The arrangement of solid inclusions in the marginal fibrous zone suggests an episodic growth by the crack-seal mechanism during syntectonic deformation which was at least partially driven by tectonic suction pump during some stages of the Alpine Orogeny. Both the central part of the composite vein and monomineral veins developed in a brittle regime. In these cases, the textures of vein suggest the flow of fluids along an open fracture. The parent fluids of both types of vein are characterized by low temperatures (Th=66-163 °C), low salinities (0.4 to 3.4 wt. % NaCl eq.), low content of strong REE-complexing ligands, and δ18O and δ13C ranges of + 0.2/+12.5 %. SMOW and -11.8/-14.1 %. PDB, respectively. The parent fluids are interpreted as the results of mixing of residual seawater and diagenetic waters produced by dewatering of clay minerals in the associ-ated flysch sediments. The flow of fluids was controlled by tectonic deformation of the host rock.

  18. How Is Deep Vein Thrombosis Diagnosed?

    MedlinePlus

    ... Vein Thrombosis Diagnosed? Your doctor will diagnose deep vein thrombosis (DVT) based on your medical history, a physical exam, and test results. He or she will identify your risk factors and rule out other causes of your symptoms. ...

  19. What Are Varicose Veins? (For Kids)

    MedlinePlus

    ... Dictionary of Medical Words En Español What Other Kids Are Reading Taking Care of Your Ears Taking ... X-ray What Are Varicose Veins? KidsHealth > For Kids > What Are Varicose Veins? Print A A A ...

  20. Ultrasensitive quartz crystal microbalance integrated with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Goyal, Abhijat

    energy loss channel and hence causing an increase in the Q-factor. Measurement of out-of-plane vibrations of the quartz crystals using a laser based optical vibrometer revealed that the out-of-plane vibrations of QCM increase from 13 pm to 26 pm when carbon nanotubes are removed from the surface of the resonator---directly confirming the suppression of the out-of-plane motion on the resonator surface by carbon nanotubes. Additionally, the QCMs were used to study the gas adsorption and desorption behavior of nominally "open-ended" isolated and nominally "close-ended" bundled SWNTs. Using the ultrasensitive QCM, we were able to probe gas storage properties of carbon nanotubes. It was found that carbon nanotubes can adsorb large amount of gas molecules not only in the cylindrical pore that they enclose, but also on their external surface. Four different gases were tested, namely Helium, Nitrogen, Argon, and SF6. It was found that the change in resonance frequency and quality factor for the "fill in" and "evacuation" of gases from carbon nanotubes exhibited a characteristic ˜ MW relationship, where MW is the atomic/molecular weight of gas species adsorbed. Such a behavior was consistently observed both for change in resonance frequency and Q-factor during the events of "fill in" and "evacuation" in the case of bare quartz with gold electrode, gold electrode covered with nominally isolated "open-ended" SWNTs, and gold electrode with nominally bundled "close-ended" SWNTs. In the case of bare quartz with gold electrode, the observed change in resonance frequency and Q-factor and their characteristic ˜ MW relationship can be explained on the basis of the viscous dissipation arising due to gas ambient through the Gordon-Kanazawa equation. In the case of QCM with carbon nanotubes, the change in Q-factor and its characteristic ˜ MW relationship could be explained on the basis of enhanced viscous dissipation arising due to surface roughness or modified Gordon Kanazawa equation

  1. Plastic Deformation of Quartz: Unfinished business?

    NASA Astrophysics Data System (ADS)

    Paterson, M. S.

    2011-12-01

    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

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

    USGS Publications Warehouse

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

    1996-01-01

    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

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

    SciTech Connect

    Hulen, J.B.; Nielson, D.L. )

    1993-08-01

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

  4. Gold grade variation and particle microchemistry in exploration pits of the Batouri gold district, SE Cameroon

    NASA Astrophysics Data System (ADS)

    Vishiti, A.; Suh, C. E.; Lehmann, B.; Egbe, J. A.; Shemang, E. M.

    2015-11-01

    The Batouri area hosts lode-gold mineralization under several-m-thick lateritic cover. Pitting to bed rock on a geochemical Au anomaly defined from previous reconnaissance soil sampling identified five horizons ranging from saprock at the base to laterite at the top. Analysis of bulk samples from each horizon by fire assay shows that most of the horizons are barren although 119 ppb and 48 ppb Au values were obtained from one laterite horizon and one saprolite horizon, respectively, from two separate pits. All the horizons were panned and particulate gold was also recovered only from these two horizons. The gold grains from both horizons are morphologically and compositionally indistinguishable with rare quartz, pyrite and galena inclusions. The grains have irregular, sub-rounded, bean to elongated shapes and they show a remarkable core-rim zonation. Electron microprobe analysis of the grains recorded high gold content in the rims (86.3-100 wt%) and along fissures within the grains (95.1-100 wt%). The cores are relatively Ag rich (11.8-14 wt% Ag) while the rims (0.63-13.7 wt% Ag, most of the values fall within the lower limit of this range) and fissures (0.03-5.02 wt% Ag) are poor in Ag. The low Ag concentration in the rims and along fissures is attributed to preferential leaching of Ag; a process recognized in gold grains and platiniferous alloys from alluvia. The core composition of the grains is similar to that of primary gold composition in the bedrock. These results show that gold in the soil is relic particulate gold derived from the primary source with no evidence of secondary gold precipitation in the weathering cycle. In all the pits no horizon was systematically enriched in gold suggesting there has been no chemical remobilization of gold in this environment. Rather the dispersion of gold here is in the particulate form. Therefore combining particulate gold features with assay data is relevant to exploration in such tropical environments.

  5. Millimeter And Submillimeter-Wave Integrated Circuits On Quartz

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  6. Complex fragmentation and silicification structures in fault zones: quartz crystallization and repeated fragmentation in the Rusey fault zone (Cornwall/UK)

    NASA Astrophysics Data System (ADS)

    Yilmaz, Tim I.; Blenkinsop, Tom; Duschl, Florian; Kruhl, Jörn H.

    2015-04-01

    Silicified fault rocks typically show structures resulting from various stages of fragmentation and quartz crystallization. Both processes interact episodically and result in complex structures on various scales, which require a wide spectrum of analysis tools. Based on field and microstructural data, the spatial-temporal connection between deformation, quartz crystallization and fluid and material flow along the Rusey fault zone was investigated. The fault can be examined in detail in three dimensions on the north Cornwall coast, UK. It occurs within Carboniferous sandstones, siltstones, mudstones and slates of the Culm basin, and is likely to have had a long history. The fault rocks described here formed during the younger events, possibly due to Tertiary strike-slip reactivation. Frequent fragmentation, flow and crystallization events and their interaction led to various generations of complex-structured quartz units, among them quartz-mantled and partly silicified wall-rock fragments, microcrystalline quartz masses of different compositions and structures, and quartz vein patterns of various ages. Lobate boundaries of quartz masses indicate viscous flow. Fragments are separated by quartz infill, which contains cm-sized open pores, in which quartz crystals have pyramidal terminations. Based on frequent occurrence of feathery textures and the infill geometry, quartz crystallization from chalcedony appears likely, and an origin from silica gel is discussed. Fragmentation structures are generally fractal. This allows differentiation between various processes, such as corrosive wear, wear abrasion and hydraulic brecciation. Material transport along the brittle shear zone, and displacement of the wall-rocks, were at least partly governed by flow of mobile fluid-quartz-particle suspensions. The complex meso- to microstructures were generated by repeated processes of fragmentation, quartz precipitation and grain growth. In general, the brittle Rusey fault zone

  7. Optical properties of biaxial nanopatterned gold plasmonic nanowired grid polarizer.

    PubMed

    Aas, Lars Martin Sandvik; Kildemo, Morten; Martella, Christian; Giordano, Maria Caterina; Chiappe, Daniele; Buatier de Mongeot, Francesco

    2013-12-16

    Gold nanoparticles deposited on self-organized nano-ripple quartz substrates have been studied by spectroscopic Mueller matrix ellipsometry. The surface was found to have biaxial anisotropic optical properties. For electric field components normal to the ripples the periodic and disconnected nature of the in plane nanowires gives rise to an optical response dominated by the localized plasmon resonance. In the direction parallel to the ripples the gold nanoparticles are aligned closely leading to localized plasmon resonances in the infrared. As Au was deposited at an angle oblique to the surface normal, the gold nanoparticles were formed on the side of the ripples facing the incoming evaporation flux. This makes the gold particles slightly inclined, correspondingly the principal coordinate system of the biaxial dielectric tensor results tilted. The anisotropic plasmonic optical response results in a strong polarizing effect, making it suitable as a plasmonic nanowired grid polarizer.

  8. phenoVein-A Tool for Leaf Vein Segmentation and Analysis.

    PubMed

    Bühler, Jonas; Rishmawi, Louai; Pflugfelder, Daniel; Huber, Gregor; Scharr, Hanno; Hülskamp, Martin; Koornneef, Maarten; Schurr, Ulrich; Jahnke, Siegfried

    2015-12-01

    Precise measurements of leaf vein traits are an important aspect of plant phenotyping for ecological and genetic research. Here, we present a powerful and user-friendly image analysis tool named phenoVein. It is dedicated to automated segmenting and analyzing of leaf veins in images acquired with different imaging modalities (microscope, macrophotography, etc.), including options for comfortable manual correction. Advanced image filtering emphasizes veins from the background and compensates for local brightness inhomogeneities. The most important traits being calculated are total vein length, vein density, piecewise vein lengths and widths, areole area, and skeleton graph statistics, like the number of branching or ending points. For the determination of vein widths, a model-based vein edge estimation approach has been implemented. Validation was performed for the measurement of vein length, vein width, and vein density of Arabidopsis (Arabidopsis thaliana), proving the reliability of phenoVein. We demonstrate the power of phenoVein on a set of previously described vein structure mutants of Arabidopsis (hemivenata, ondulata3, and asymmetric leaves2-101) compared with wild-type accessions Columbia-0 and Landsberg erecta-0. phenoVein is freely available as open-source software.

  9. Common femoral vein reconstruction using internal jugular vein after blast injury.

    PubMed

    Holt, Andrew M; West, Charles A; Davis, James A; Gilani, Ramyar; Askenasy, Eric

    2014-10-01

    Common femoral vein traumatic injuries are rare. Surgical management is controversial and by nature case specific. In this report, we present an unusual case of an isolated common femoral vein injury from a gunshot blast repaired with an interposition internal jugular vein bypass. To our knowledge, this is the first reported case of an isolated common femoral vein reconstructed in this manner.

  10. Effect of irradiation and thermal annealing on quartz materials luminescence

    NASA Astrophysics Data System (ADS)

    Korovkin, M. V.; Ananyeva, L. G.

    2017-01-01

    X-ray and gamma-quanta irradiation of radiation-resistant quartz materials including natural and synthetic quartz crystals and high-purity quartzite causes the luminescence in the ultraviolet range (365 nm), thermally stimulated luminescence and radiofrequency electromagnetic emission. Preliminary radiation and thermal annealing improves luminescence properties of quartz materials.

  11. Optical processing furnace with quartz muffle and diffuser plate

    DOEpatents

    Sopori, Bhushan L.

    1996-01-01

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

  12. Gold-Silver mineralization in porphyry-epithermal systems of the Baimka trend, western Chukchi Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Nikolaev, Yu. N.; Baksheev, I. A.; Prokofiev, V. Yu.; Nagornaya, E. V.; Marushchenko, L. I.; Sidorina, Yu. N.; Chitalin, A. F.; Kal'ko, I. A.

    2016-07-01

    Mineralogical, fluid inclusion, and geochemical studies of precious metal mineralization within the Baimka trend in the western Chukchi Peninsula have been preformed. Porphyry copper-molybdenum-gold deposits and prospects of the Baimka trend are spatially related to monzonitic rocks of the Early Cretaceous Egdygkych Complex. Four types of precious metal-bearing assemblages have been identified: (1) chalcopyrite + bornite + quartz with high-fineness native gold enclosed in bornite, (2) low-Mn dolomite + quartz + sulfide (chalcopyrite, sphalerite, galena, tennantite-tetrahedrite) ± tourmaline with low-fineness native gold and hessite, (3) rhodochrosite + high-Mn dolomite + quartz + sulfide (chalcopyrite, sphalerite, galena, tennantite- tetrahedrite) with low-fineness native gold, electrum, acanthite, Ag and Au-Ag tellurides, and Ag sulfosalts, and (4) calcite + quartz + sulfide (chalcopyrite, sphalerite, galena) with low-fineness native gold, Ag sulfides and selenides, and Ag-bearing sulfosalts. Study of fluid inclusions from quartz, sphalerite, and fluorite have revealed that hydrothermal ores within the Baimka trend precipitated from fluids with strongly variable salinity at temperatures and pressures ranging from 594 to 104°C and from 1200 to 170 bar, respectively. An indicator of vertical AgPbZn/CuBiMo geochemical zoning is proposed. The value range of this indicator makes it possible to estimate the erosion level of the porphyry-epithermal system. The erosion level of the Baimka deposits and prospects deepens in the following order: Vesenny deposit → Pryamoi prospect → Nakhodka prospect → Peschanka deposit → III Vesenny prospect.

  13. Improved thermoelectrically cooled quartz crystal microbalance

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    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.

  14. Quartz Channel Fabrication for Electrokinetically Driven Separations

    SciTech Connect

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

    1998-12-01

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

  15. Emission polarization study on quartz and calcite.

    NASA Technical Reports Server (NTRS)

    Vincent, R. K.

    1972-01-01

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

  16. THE FRICTION OF QUARTZ IN HIGH VACUUM

    DTIC Science & Technology

    the effects of surface cleanliness . Ultra-high vacuums (to 10 to the minus 10th power torr) and high temperatures (to 350 deg C) were combined with...chemical cleaning and careful handling techniques to produce the maximum surface cleanliness . The coefficient of static friction under varying...on 30-40 mesh glass balls. The coefficient of friction of smooth quartz was found to vary from 0.1 to 1.0 depending on the surface cleanliness . The

  17. Error analysis of quartz crystal resonator applications

    SciTech Connect

    Lucklum, R.; Behling, C.; Hauptmann, P.; Cernosek, R.W.; Martin, S.J.

    1996-12-31

    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.

  18. Varicose veins; a practical approach to treatment.

    PubMed

    ELLENBURG, R

    1958-05-01

    Adequate treatment of varicose veins requires thorough mapping of perforating veins, communicating veins and "blow out" areas. Combined ligations, stripping and injection of sclerotic substances after operation is the most effective regimen of therapy. The technique of stripping is facilitated by isolating the saphenous vein at the ankle, inserting the stripper from below upward, then making a transverse groin incision over the palpable stripper. The tip of the stripper should be twice the diameter of the vein to be removed. Stripping should be done with the patient in the Trendelenburg position. All patients must be examined at regular intervals after operation and injection of sclerosing material carried out as necessary.

  19. Preduodenal portal vein: surgery and radiographic appearance.

    PubMed

    Fernandes, E T; Burton, E M; Hixson, S D; Hollabaugh, R S

    1990-12-01

    Preduodenal portal vein is rare, with 63 cases reported in the literature. In general, this anomaly occurs in children with associated small bowel obstruction. We report a newborn infant who presented with duodenal stenosis, mongolism, and preduodenal portal vein. Treatment consisted of a duodenoduodenal anastomosis without mobilizing the portal vein. The correlation between imaging techniques and the operative findings is discussed. Because identification of preduodenal portal vein at surgery is important, preoperative sonography may be useful in selected cases to define the position of the vein.

  20. Optical processing furnace with quartz muffle and diffuser plate

    DOEpatents

    Sopori, Bhushan L.

    1995-01-01

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

  1. Mouse model of sustained elevation in intraocular pressure produced by episcleral vein occlusion.

    PubMed

    Ruiz-Ederra, Javier; Verkman, A S

    2006-05-01

    We have developed an inducible mouse model of glaucoma based on episcleral vein cauterization (EVC). Intraocular pressure (IOP) elevation in adult mice was produced by cauterizing three episcleral veins. Serial IOP measurements were done by induction-impact tonometry. IOP was significantly elevated by 104+/-20% in 20 out of 23 mice (87%) within the first day after EVC, and remained elevated for 4 weeks, with mean IOP 94% higher in EVC-treated vs. contralateral control eyes. Aqueous outflow blockade was verified from the IOP response to pulsed fluid infusions into the anterior chamber. Retinal ganglion cell (RGC) loss, determined by retrograde labelling using Fluoro-Gold applied to the superior colliculous, was approximately 20% at 2 weeks after EVC. We conclude that episcleral vein occlusion in mice produces significant and sustained elevation in IOP associated with increased outflow resistance and RGC loss, and thus may be useful to model glaucoma in genetically modified and drug-treated mice.

  2. Mechanical buckling of veins under internal pressure.

    PubMed

    Martinez, Ricky; Fierro, Cesar A; Shireman, Paula K; Han, Hai-Chao

    2010-04-01

    Venous tortuosity is associated with multiple disease states and is often thought to be a consequence of venous hypertension and chronic venous disease. However, the underlying mechanisms of vein tortuosity are unclear. We hypothesized that increased pressure causes vein buckling that leads to a tortuous appearance. The specific aim of this study was to determine the critical buckling pressure of veins. We determined the buckling pressure of porcine jugular veins and measured the mechanical properties of these veins. Our results showed that the veins buckle when the transmural pressure exceeds a critical pressure that is strongly related to the axial stretch ratio in the veins. The critical pressures of the eight veins tested were 14.2 +/- 5.4 and 26.4 +/- 9.0 mmHg at axial stretch ratio 1.5 and 1.7, respectively. In conclusion, veins buckle into a tortuous shape at high lumen pressures or reduced axial stretch ratios. Our results are useful in understanding the development of venous tortuosity associated with varicose veins, venous valvular insufficiency, diabetic retinopathy, and vein grafts.

  3. Instantaneous healing of micro-fractures during coseismic slip: evidence from microstructure and Ti in quartz geochemistry within an exhumed pseudotachylyte-bearing fault in tonalite

    NASA Astrophysics Data System (ADS)

    Bestmann, Michel; Pennacchioni, Giorgio; Moustefaoui, Smail; Göken, Mathias; de Wall, Helga

    2016-04-01

    This study presents detailed microstructural and trace element (Ti) analysis of quartz deformation microstructures associated with seismic slip in order to constrain the complex deformation history during an earthquake event. Exhumed faults within the tonalitic Adamello pluton (Southern Alps) were seismic at depth as indicated by the presence of pseudotachylytes (solidified friction-induced melts). During cooling of tonalite, early-formed joints were first exploited by localized ductile shear zones associated with deposition of quartz veins (at ~500 °C), and later by pseudotachylyte-bearing cataclastic faults (at ~250-300 °C ambient temperature). Adjacent to pseudotachylytes, quartz of the host tonalite shows pervasive thin (1-10 μm wide) healed micro-fractures and ultra-fine (1-2 μm grain size) recrystallized aggregates along micro-shear zones. Under cathodoluminescence (CL) the healed micro-fractures have darker gray shade than the host "magmatic" quartz that reflects a change in Ti concentrations [Ti] as indicated by NanoSIMS measurements. [Ti] vary from 35-55 ppm of the CL-lighter host quartz to 11-15 ppm along the CL-darker healed micro-fractures. These [Ti] were inherited by overprinting recrystallization aggregates developed during the high temperature transient related to frictional seismic slip. Based on Ti-in-quartz thermometry, micro-fracture healing occurred at higher temperatures than the ambient temperatures of faulting (250-300 °C at 0.2 GPa). Micro-fracture healing can be ascribed to the stage of seismic slip of faulting on the basis of the observation that: (i) they are absent in the host rock surrounding earlier high-T quartz veins un-exploited by faults; (ii) they locally occur at the tip of pseudotachylyte injection veins filling new fractures developed during the propagation of the earthquake rupture tip. The relatively high [Ti] of micro-fractures are interpreted to reflect quartz healing by a fluid overheated during the initial stages of

  4. Management of varicose veins and venous insufficiency.

    PubMed

    Hamdan, Allen

    2012-12-26

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

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

  6. Mortality after portal vein embolization

    PubMed Central

    Lee, Eung Chang; Park, Sang-Jae; Han, Sung-Sik; Park, Hyeong Min; Lee, Seung Duk; Kim, Seong Hoon; Lee, In Joon; Kim, Hyun Beom

    2017-01-01

    Abstract Portal vein embolization (PVE) is increasingly performed worldwide to reduce the possibility of liver failure after extended hepatectomy, by inducing future liver remnant (FLR) hypertrophy and atrophy of the liver planned for resection. The procedure is known to be very safe and to have few procedure-related complications. In this study, we described 2 elderly patients with Bismuth–Corlette type IV Klatskin tumor who underwent right trisectional PVE involving the embolization of the right portal vein, the left medial sectional portal branch, and caudate portal vein. Within 1 week after PVE, patients went into sepsis combined with bile leak and died within 1 month. Sepsis can cause acute liver failure in patients with chronic liver disease. In this study, the common patient characteristics other than sepsis, that is, trisectional PVE; chronic alcoholism; aged >65 years; heart-related comorbidity; and elevated serum total bilirubin (TB) level (7.0 mg/dL) at the time of the PVE procedure in 1 patient, and concurrent biliary procedure, that is, percutaneous transhepatic biliary drainage in the other patient might have affected the outcomes of PVE. These cases highlight that PVE is not a safe procedure. Care should be taken to minimize the occurrence of infectious events because sepsis following PVE can cause acute liver failure. Additionally, prior to performing PVE, the extent of PVE, chronic alcohol consumption, age, comorbidity, long-lasting jaundice, concurrent biliary procedure, etc. should be considered for patient safety. PMID:28178122

  7. Quartz deformation mechanisms during Barrovian metamorphism: Implications from crystallographic orientation of different generations of quartz in pelites

    NASA Astrophysics Data System (ADS)

    Rahimi-Chakdel, A.; Boyle, A. P.; Prior, D. J.

    2006-12-01

    The behaviour of quartz during metamorphism is studied based on two case studies from the Barrovian terrains of Sulitjelma in arctic Scandinavia and Loch Tay in the Central Highlands Dalradian of Scotland. Both terrains preserve evidence for metamorphism in pelites involving nucleation and growth of garnet at different times in the deformation history. Data are presented on the size, shape and crystallographic orientation of quartz preserved as inclusions in garnet and as grains in the surrounding matrix. While quartz-grains remain small and dispersed between mica grains, deformation appears to be dominated by grain-boundary sliding accommodated by dissolution-precipitation. At amphibolite facies, textural coarsening occurs by dissolution of small quartz grains and growth of larger quartz grains, coupled with segregation of quartz from mica. As a result, quartz deforms by dislocation creep, developing crystallographic preferred orientations (CPO) consistent with both coaxial and non-coaxial strain. Quartz CPOs with <0001> axes lying parallel to foliation and stretching direction are commonly developed, and best explained by mechanical rotation of inequant (detrital?) quartz grains. There is no evidence for selective entrapment of quartz inclusions in garnet on the basis of quartz crystallographic orientation.

  8. The Hatu gold anomaly, Xinjiang-Uygur Autonomous Region, China - testing the hypothesis of aeolian transport of gold

    USGS Publications Warehouse

    Smith, D.B.; Theobald, P.K.; Shiquan, S.; Tianxiang, R.; Zhihui, H.

    1993-01-01

    In 1987, a cooperative project between the U.S. Geological Survey and the Institute of Geophysical and Geochemical Exploration was initiated to evaluate the origin of the Hatu gold anomaly. The anomaly is located in the Hatu mining district in the northwest corner of Xinjiang-Uygur Autonomous Region in northwest China. The climate is semiarid to arid and wind erosion predominates. A regional soil survey of the Hatu district, based on samples collected on a 200 by 500 m grid and composited prior to chemical analysis to a density of one sample per square km, delineated a series of south-southeast-trending Au anomalies. Anomalous Au values range from 5 ppb to more than 700 ppb. The Hatu anomaly, the most prominent of these anomalies, is more than 30 km long and about 5 km wide. The mining town of Hatu and the economic gold deposits of Qiqu 1 and Qiqu 2 are at the northern end of this anomaly. The axis of the Hatu anomaly cuts across mapped structure and stratigraphy in the district, but is parallel to the prevailing wind direction. This observation led to the hypothesis that the Hatu anomaly is the result of acolian dispersion of gold from the vicinity of Qiqu 1 and Qiqu 2. The alternative interpretation, that the anomalies reflected additional primary gold occurrences, was not consistent with existing information on the known occurrences and the geology. The investigation led to the identification of three types of gold in heavy-mineral concentrates derived from stream sediments that were collected along the axis of the Hatu anomaly: (1) free gold, (2) gold in pyrite, and (3) gold included in quartz. Gold in quartz was only observed within 2 km of Qiqu 1. The size of the gold particles and the number of gold particles in these samples did not decrease with distance from Qiqu 1 as would be expected from aeolian or fluvial dispersion from a point source. Instead, both the size and amount of gold increased significantly at a distance of 3.5 km from Qiqu 1 and this

  9. Veins of the thoracic limb of the Van cat.

    PubMed

    Ozüdoğru, Z; Aksoy, G; Soygüder, Z; Ozmen, E

    2003-04-01

    The drainage of the thoracic limb of the Van cat was performed by the superficial and deep vein systems. The superficial system was constituted by the cephalic vein and its branches. The deep vein system was constituted by the axillary vein and its branches. The two vein systems anastomosed with each other at various points along their courses. The cephalic vein emerged from the external jugular vein together with the superficial cervical vein. The axillary vein continued the subclavian vein. It ran caudoventrally and gave off the subscapular vein, at the level of the shoulder joint, then gave off two independent branches, which were the external thoracic veins. Then the rest of the vessel continued as the brachial vein. The thoracodorsal vein was formed by the communicate ramus vein which arose between the subscapular vein and the brachial vein. The cranial circumflex humeral vein arose double from the subscapular vein. One of them anastomosed with the deep brachial vein and the other one drained the biceps and the deep pectoral muscles. The cranial interosseous vein from the caudal aspects of the brachial vein and passed the interosseous space of the antebrachium then ran to the lateral aspect of the forearm. The caudal interosseous vein arose from the ulnar vein (in two specimens) and the median vein together with the ulnar vein (in two specimens) or independently from the median vein (in one specimen). Although many similarities were found in the veins of the thoracic limb of the Van cat as compared with the domestic cat, some significant differences were noted in the origin, course, anastomosing and ramification of veins of the thoracic limb.

  10. Mercury pollution from the artisanal mining in Yani gold district, Northern Bolivia

    NASA Astrophysics Data System (ADS)

    Alfonso, Pura; Freixas, Anna; Bascompta, Marc; María Aranibar, Ana; Villegas, Karla; María García-Noguero, Eva; Higueras, Pablo; Cielito Saraiva, Angela

    2016-04-01

    Artisanal gold mining is the main economic activity in the Yani district, Northern Bolivia. In this area abundant orogenic gold deposits constituted by quartz veins hosted in paleozoic turbiditic series that contain either free gold or associated with pyrite. Gold is recovered in processing plants by gravimetric methods using shaking tables in several communities of this district. Previously, miners ground the mineral in ball mills together with mercury. The present study aims to evaluate the effect of mercury used in the gold recovering process to the environment and human health in the Yani district. The assessment was based on the analysis of human hair, sediments and water from the river nearby the processing plant and drinking water from the fountain that supplies these communities. 47 samples of hair from miners and other people from the Yani and Señor de Mayo communities were obtained in 2014 and 52 samples in 2015. All were analysed to evaluate the mercury exposure in these places. The results from the 2014 sampling show a wide range of Hg concentration in hair, especially in Señor de Mayo, with values up to 136 μg/g THg. However, in 2015 among the 43 residents in Señor de Mayo, 29 (67%) exhibit concentrations higher than 2 μg/g THg, with an average value of 5.36 μg/g THg. On the other hand, in Yani only 40% have concentrations above 2 μg/g THg, with an average value of 2.34 μg/g THg. The content in Hg in most of the hair samples exhibit values above the tolerable limits established by the US Environmental Protection Agency (1 μg/g Hg) and the World Health Organisation (WHO, 2 μg/g Hg). These high Hg concentrations are found not only in miners but also in the other members of the community, in spite of low fish consumption in this area. Part of the hair was analysed before and after cleaning. Usually in the second case the content of Hg is reduced, but still show high Hg levels, then probably the atmosphere is polluted with Hg and population is

  11. Kinetics of the coesite to quartz transformation

    USGS Publications Warehouse

    Mosenfelder, J.L.; Bohlen, S.R.

    1997-01-01

    The survival of coesite in ultrahigh-pressure (UHP) rocks has important implications for the exhumation of subducted crustal rocks. We have conducted experiments to study the mechanism and rate of the coesite ??? quartz transformation using polycrystalline coesite aggregates, fabricated by devitrifying silica glass cylinders containing 2850H/106 Si at 1000??C and 3.6 GPa for 24h. Conditions were adjusted following synthesis to transform the samples at 700-1000??C at pressures 190-410 MPa below the quartz-coesite equilibrium boundary. Reaction proceeds via grain-boundary nucleation and interface-controlled growth, with characteristic reaction textures remarkably similar to those seen in natural UHP rocks. We infer that the experimental reaction mechanism is identical to that in nature, a prerequisite for reliable extrapolation of the rate data. Growth rates obtained by direct measurement differ by up to two orders of magnitude from those estimated by fitting a rate equation to the transformation-time data. Fitting the rates to Turnbull's equation for growth therefore yields two distinct sets of parameters with similar activation energies (242 or 269 kJ/mol) but significantly different pre-exponential constants. Extrapolation based on either set of growth rates suggests that coesite should not be preserved on geologic time scales if it reaches the quartz stability field at temperatures above 375-400??C. The survival of coesite has previously been linked to its inclusion in strong phases, such as garnet, that can sustain a high internal pressure during decompression. Other factors that may play a crucial role in preservation are low fluid availability - possibly even less than that of our nominally "dry" experiments - and the development of transformation stress, which inhibits nucleation and growth. These issues are discussed in the context of our experiments as well as recent observations from natural rocks. ?? 1997 Elsevier Science B.V.

  12. Deformation of ⊥m single quartz crystals

    NASA Astrophysics Data System (ADS)

    Krasner, P.; Holyoke, C. W., III; Kronenberg, A. K.

    2015-12-01

    The rheology of quartz deformed by dislocation creep is essential to understanding the strength of the mid to lower continental crust. Our current understanding of quartz rheology is derived primarily from studies of polycrystalline quartz and little is known about the temperature, strain rate, or water dependence of the individual quartz slip systems. In order to better understand the rheology of quartz slip systems, we have deformed synthetic quartz single crystals with the prism oriented at 45° to the compression direction (⊥m orientation). We converted the gel-type water found in synthetic quartz crystals to free water fluid inclusions, similar to water observed in milky quartz crystals, by annealing the crystals at 900°C/0.1 MPa for 24 hours. The single crystals were deformed at a confining pressure of 1.5 GPa with temperatures of 850 to 1000°C and strain rates of 10-6 to 10-4/s. FTIR measurements of water concentrations in the starting material, annealed synthetic crystals and deformed synthetic quartz crystals indicate that the water concentrations (125-300 H/106Si) are not affected by the annealing process or deformation. However, the spectra in the annealed and deformed samples are similar to those of natural milky quartz rather than those of synthetic quartz. Results of temperature and strain rate stepping experiments indicate that the strength of the crystals decreases with increasing temperature and/or decreasing strain rate. Undulatory extinction is the predominant microstructure observed in deformed samples, which is consistent with deformation by dislocation creep. The strength of the ⊥m oriented quartz crystals deformed in this study with free water is greater than those of the studies of synthetic quartz with gel type water (Linker and Kirby, 1981 and Muto et al., 2011).

  13. The occurrence of quartz in coal fly ash particles

    SciTech Connect

    Meij R.; Nagengast S.; Winkel H.T.

    2000-10-15

    Quartz is present in both coal and residual ash. Ash originates from combustion of pulverised coal and, once removed from the flue gases by electrostatic precipitators (ESPs), it is called pulverized fuel ash (PFA). Thus, occupational exposure to PFA could also include exposure to silica. However, epidemiological studies did not show evidence of progressive massive fibrosis (PMF). In vitro tests demonstrated that PFA is less toxic than silica, and in vivo data of PFA did not support the importance of silica content for toxicity. Commissioned by the Dutch coal-fired power plants, KEMA has started a research project to determine the quartz content in coal and the corresponding PFA. It appears that on average 50% of the alpha-quartz in coal is found again in the total fraction of PFA (D50(ae) 31 {mu}m, where D50(ae) is the aerodynamically mass median diameter), whereas 16% is found in an even finer fraction (D50(ae) 10 {mu}m). The remaining part of the quartz is embedded in a glass phase. Scanning electron microscopy (SEM) with x-ray microanalyses (XMA) of cross-sections of 11,130 ash particles showed that quartz in PFAis present as unmelted sand particles. These quartz particles are angularly shaped. However, two types are to be distinguished: free coarse angular quartz particles (not respirable) and small angular quartz particles within the PFA particles. From the SEM/XMA results, it has to be concluded that the quartz in the respirable fraction is predominantly present within the original molten PFA particle. Since the effects of quartz are surface related, this elucidates the negative results of quartz-related effects of PFA in epidemiological, in vitro and in vivo studies. Besides, the amount of the total alpha-quartz in the respirable fraction of the ashes studied is less than 0.2%, so probably the Dutch occupational quartz standard of 0.075 mg m{sup 3} will not be exceeded.

  14. Spherical quartz crystals investigated with synchrotron radiation

    SciTech Connect

    Pereira, N. R.; Macrander, A. T.; Hill, K. W.; Baronova, E. O.; George, K. M.; Kotick, J.

    2015-10-15

    The quality of x-ray spectra and images obtained from plasmas with spherically bent crystals depends in part on the crystal’s x-ray diffraction across the entire crystal surface. We employ the energy selectivity and high intensity of synchrotron radiation to examine typical spherical crystals from alpha-quartz for their diffraction quality, in a perpendicular geometry that is particularly convenient to examine sagittal focusing. The crystal’s local diffraction is not ideal: the most noticeable problems come from isolated regions that so far have failed to correlate with visible imperfections. Excluding diffraction from such problem spots has little effect on the focus beyond a decrease in background.

  15. Calorimetric thermobarometry of experimentally shocked quartz

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  16. Excitons and Optical Properties of {alpha} -Quartz

    SciTech Connect

    Chang, Eric K.; Rohlfing, Michael; Louie, Steven G. [Department of Physics, University of California at Berkeley, Berkeley, California 94720

    2000-09-18

    We present an ab initio study of the optical properties of {alpha} -quartz. The absorption spectrum is calculated by solving the Bethe-Salpeter equation for the interacting electron-hole system and found to be in excellent agreement with the measured spectrum up to 10 eV above the absorption threshold. We find that excitonic effects are crucial in understanding the sharp features in the absorption spectrum in this energy range. They are also crucial in the ab initio computation of the static dielectric constant, significantly enhancing its value. (c) 2000 The American Physical Society.

  17. Environmental sensitivities of quartz crystal oscillators

    NASA Technical Reports Server (NTRS)

    Walls, Fred L.

    1990-01-01

    The frequency, amplitude, and noise of the output signal of a quartz crystal controlled oscillator is affected by a large number of environmental effects. The physical basis for the sensitivity of precision oscillators to temperature, humidity, pressure, vibration, magnetic field, electric field, load, and radiation is discussed. The sensitivity of crystal oscillators to radiation is a very complex topic and poorly understood. Therefore only a few general results are mentioned. The sensitivity to most external influences often varies significantly from one oscillator type to another and from one unit of given type to another. For a given unit, the sensitivity to one parameter often depends on the value of other parameters and history.

  18. Control of electroosmosis in coated quartz capillaries

    NASA Technical Reports Server (NTRS)

    Herren, Blair J.; Van Alstine, James; Snyder, Robert S.; Shafer, Steven G.; Harris, J. Milton

    1987-01-01

    The effectiveness of various coatings for controlling the electroosmotic fluid flow that hinders electrophoretic processes is studied using analytical particle microelectrophoresis. The mobilities of 2-micron diameter glass and polystyrene latex spheres (exhibiting both negative and zero effective surface charge) were measured in 2-mm diameter quartz capillaries filled with NaCl solutions within the 3.5-7.8 pH range. It is found that capillary inner surface coatings using 5000 molecular weight (or higher) poly(ethylene glycol): significantly reduced electroosmosis within the selected pH range, were stable for long time periods, and appeared to be more effective than dextran, methylcellulose, or silane coatings.

  19. Major brazilian gold deposits - 1982 to 1999

    USGS Publications Warehouse

    Thorman, C.H.; Dewitt, E.; Maron, M.A.; Ladeira, E.A.

    2001-01-01

    Brazil has been a major but intermittent producer of gold since its discovery in 1500. Brazil led the world in gold production during the 18th and early 19th centuries. From the late 19th century to the late 20th century, total mining company and garimpeiro production was small and relatively constant at about 5 to 8 t/year. The discovery of alluvial deposits in the Amazon by garimpeiros in the 1970s and the opening of eight mines by mining companies from 1983 to 1990 fueled a major boom in Brazil's gold production, exceeding 100 t/year in 1988 and 1989. However, garimpeiro alluvial production decreased 'rapidly in the 1990s, to about 10 t/year by 1999. Company production increased about tenfold from about 4 t/year in 1982 to 40 t in 1992. Production from 1992 to the present remained relatively stable, even though several mines were closed or were in the process of closing and no new major mines were put into production during that period. Based on their production history from 1982-1999, 17 gold mines are ranked as major (> 20 t) and minor (3-8 t) mines. From 1982-1999, deposits hosted in Archean rocks produced 66% of the gold in Brazil, whereas deposits in Paleoproterozoic and Neoproterozoic rocks accounted for 19% and 15%, respectively. Deposits in metamorphosed sedimentary rocks, especially carbonate-rich rocks and carbonate iron-formation, yielded the great bulk of the gold. Deposits in igneous rocks were of much less importance. The Archean and Paleoproterozoic terranes of Brazil largely lack base-metal-rich volcanogenic massive sulfide deposits, porphyry deposits, and polymetallic veins and sedimentary exhalative deposits. An exception to this is in the Caraja??s Mineral Province.

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

    NASA Technical Reports Server (NTRS)

    Schmitz, Christopher; Burt, Donald M.

    1990-01-01

    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.

  1. In vivo monitoring of blood oxygenation in large veins with a triple-wavelength optoacoustic system.

    PubMed

    Brecht, H P; Prough, D S; Petrov, Y Y; Patrikeev, I; Petrova, I Y; Deyo, D J; Cicenaite, I; Esenaliev, R O

    2007-11-26

    A noninvasive optoacoustic technique could be a clinically useful alternative to existing, invasive methods for cerebral oxygenation monitoring. Recently we proposed to use an optoacoustic technique for monitoring cerebral blood oxygenation by probing large cerebral and neck veins including the superior sagittal sinus and the internal jugular vein. In these studies we used a multi-wavelength optoacoustic system with a nanosecond optical parametric oscillator as a light source and a custom-made optoacoustic probe for the measurement of the optoacoustic signals in vivo from the area of the sheep neck overlying the external jugular vein, which is similar in diameter and depth to the human internal jugular vein. Optoacoustic signals induced in venous blood were measured with high resolution despite the presence of a thick layer of tissues (up to 10 mm) between the external jugular vein and the optoacoustic probe. Three wavelengths were chosen to provide accurate and stable measurements of blood oxygenation: signals at 700 nm and 1064 nm demonstrated high correlation with actual oxygenation measured invasively with CO-Oximeter ("gold standard"), while the signal at 800 nm (isosbestic point) was independent of blood oxygenation and was used for calibration.

  2. Quartz crystal microbalance biosensor for rapid detection of aerosolized microorganisms

    NASA Astrophysics Data System (ADS)

    Farka, Zdenĕk.; Kovár, David; Skládal, Petr

    2015-05-01

    Biological warfare agents (BWAs) represent the current menace of the asymmetric war. The early detection of BWAs, especially in the form of bioaerosol, is a challenging task for governments all around the world. Label-free quartz crystal microbalance (QCM) immunosensor and electrochemical immunosensor were developed and tested for rapid detection of BWA surrogate (E. coli) in the form of bioaerosol. Two immobilization strategies for the attachment of antibody were tested; the gold sensor surface was activated by cysteamine and then antibody was covalently linked either using glutaraldehyde, or the reduced antibodies were attached via Sulfo-SMCC. A portable bioaerosol chamber was constructed and used for safe manipulation with aerosolized microorganisms. The dissemination was done using a piezoelectric humidifier, distribution of bioaerosol inside the chamber was ensured using three 12-cm fans. The whole system was controlled remotely using LAN network. The disseminated microbial cells were collected and preconcentrated using the wetted-wall cyclone SASS 2300, the analysis was done using the on-line linked immunosensors. The QCM immunosensor had limit of detection 1×104 CFU·L-1 of air with analysis time 16 min, the whole experiment including dissemination and sensor surface regeneration took 40 min. In case of blank (disseminated sterile buffer), no signal change was observed. The electrochemical immunosensor was able to detect 150 CFU·L-1 of air in 20 min; also in this case, no interferences were observed. Reference measurements were done using particle counter Met One 3400 and by cultivation method on agar plates. The sensors have proved to be applicable for rapid screening of microorganisms in air.

  3. The Influence of Calcite on The Mechanical Behavior of Quartz-Bearing Gouge

    NASA Astrophysics Data System (ADS)

    Carpenter, Brett; Di Stefano, Giuseppe; Collettini, Cristiano

    2015-04-01

    Mechanical heterogeneities along faults can result in diverse and complex fault slip. These heterogeneities can vary spatially and temporally and may result from changes in fault structure or frictional properties. The accumulation of calcite in non-carbonate faults, via cementation or entrainment, is likely to alter the frictional properties of that fault gouge. Furthermore, widespread observations of calcite as cement, veins, or cataclasites in non-carbonate hosted faults indicates that calcite is readily available and could play an important role during fault reactivation at shallow- and mid-crustal earthquakes. We report on laboratory experiments designed to explore the mechanical behavior of quartz/calcite mixtures as a means to better understand the evolution in behavior of quartz-bearing gouge in the presence of exotic calcite. We sheared mixtures of powdered Carrara marble (>98% CaCO3) and disaggregated Ottawa sand (99.8% SiO2) at constant normal stresses of 5 and 50 MPa under saturated conditions at room temperature. We performed slide-hold-slide tests, 1-3,000 seconds, and velocity stepping tests, 0.1-1000 µm/s, to measure the amount of frictional healing and velocity dependence of friction respectively. At low normal stress, the addition of calcite to quartz-based synthetic fault gouge results in increases in the steady-state frictional strength, and rates of frictional healing and creep relaxation of the gouge. In particular, with the addition of as little as 2.5 wt% calcite, the frictional healing rate increases by 30%. Microstructural observations indicate that shear is accommodated by distributed deformation throughout the gouge layer and that calcite undergoes significantly more comminution compared to quartz. Large quartz grains frequently show minor rounding of angular edges with fine-grained calcite often penetrating fractures. The in-situ addition of calcite to fault gouge, by either the circulation of fluids or the involvement of carbonate

  4. Positron states and nanoobjects in proton-irradiated quartz single crystals: Positronium atom in quartz

    SciTech Connect

    Grafutin, V. I.; Zaluzhnyi, A. G.; Timoshenkov, S. P.; Britkov, O. M.; Ilyukhina, O. V.; Myasishcheva, G. G.; Prokop'ev, E. P. Funtikov, Yu. V.

    2008-04-15

    The influence of proton bombardment and metal atom impurities on the structure of quartz single crystals has been studied. The related defects have been studied using positron annihilation spectroscopy (angular correlation of positron-annihilation photons), acoustic absorption, and optical absorption measurements. It is shown that the presence of a narrow component f in the angular distribution of annihilation photons (ADAP), which is related to the formation of parapositronium, determines a high sensitivity of this method with respect to features of the crystal structure of quartz. It is established that the defectness of the structure of irradiated quartz crystals can be characterized by the ratio f/f{sub 0} of the relative intensities of narrow components in the ADAP curves measured before (f{sub 0}) and after (f) irradiation. Any process leading to a decrease in the probability of positronium formation (e.g., positron loss as a result of the trapping on defects and the interaction with impurity atoms and lattice distortions) decreases the intensity of the narrow component. Based on the ADAP data, estimates of the radii and concentrations of nanodefects in quartz have been obtained and their variation upon annealing at temperatures up to T = 873 K has been studied.

  5. Preduodenal portal vein: its surgical significance.

    PubMed

    Makey, D A; Bowen, J C

    1978-11-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Ams, D.; Fein, J. B.

    2002-12-01

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

  7. Insitu Calibration of Quartz Crystal Microbalances

    NASA Technical Reports Server (NTRS)

    Albyn, Keith; Burns, Dewit

    2006-01-01

    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.

  8. Shock characterization of quartz phenolic composite

    SciTech Connect

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

    1994-03-01

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

  9. Aqueous Wetting Films on Fused Quartz.

    PubMed

    Mazzoco; Wayner

    1999-06-15

    Using an image analyzing interferometer, IAI, the interfacial characteristics of an isothermal constrained vapor bubble, CVB, in a quartz cuvette were studied as a precursor to heat transfer research. The effects of pH and electrolyte concentration on the meniscus properties (curvature and adsorbed film thickness) and the stability of the aqueous wetting films were evaluated. The surface potential in the electric double layer was a function of the cleaning and hydroxylation of the quartz surface. The disjoining pressure isotherm for pure water was very close to that predicted by the Langmuir equation. For aqueous solutions of moderate electrolyte concentration, the Gouy-Chapman theory provided a good representation of the electrostatic effects in the film. The effect of temperature on the film properties of aqueous solutions and pure water was also evaluated: The meniscus curvature decreased with increasing temperature, while Marangoni effects, intermolecular forces, and local evaporation and condensation enhanced waves on the adsorbed film layer. Pure water wetting films were mechanically metastable, breaking into droplets and very thin films (less than 10 nm) after a few hours. Aqueous wetting films with pH 12.4 proved to be stable during a test of several months, even when subjected to temperature and mechanical perturbations. The mechanical stability of wetting films can explain the reported differences between the critical heat fluxes of pure water and aqueous solutions. The IAI-CVB technique is a simple and versatile experimental technique for studying the characteristics of interfacial systems. Copyright 1999 Academic Press.

  10. Fluid inclusion and noble gas studies of the Dongping gold deposit, Hebei Province, China: A mantle connection for mineralization?

    USGS Publications Warehouse

    Mao, J.; Li, Y.; Goldfarb, R.; He, Y.; Zaw, K.

    2003-01-01

    The Dongping gold deposit (>100 t Au) occurs about 200 km inboard of the northern margin of the North China craton. The deposit is mainly hosted by syenite of a middle Paleozoic alkalic intrusive complex that was emplaced into Late Archean basement rocks. Both groups of rocks are intruded by Late Jurassic to Early Cretaceous crustal-melt granite dikes and stocks, some within a few kilometers of the deposit. The gold ores were deposited during this latter magmatic period at about 150 Ma, a time that was characterized by widespread regional north-south compression that formed the east-west-trending Yanshan deformational belt. The ores include both the telluride mineral-bearing, low sulfide quartz veins and the highly K-feldspar-altered syenite, with most of the resource concentrated in two orebodies (1 and 70). Fluid inclusion microthermometry indicates heterogeneous trapping of low-salinity (e.g., 5-7 wt % NaCl equiv) fluids that varied from a few to 60 mole percent nonaqueous volatile species. Laser Raman spectroscopy confirms that the vapor phase in these inclusions is dominated by CO2, but may be comprised of as much as 9 mole percent H2S and 20 mole percent N2; methane concentrations in the vapor phase are consistently <1 mole percent. The variable phase ratios are consistent with fluid immiscibility during ore formation. Fluid inclusion trapping conditions are estimated to be 250?? to 375??C and 0.6 to 1.0 kbar. Helium isotope studies of fluid inclusions in ore-stage pyrites indicate He/He ratios of 2.1 to 5.2 Ra (Ra = 1.4 x 10-6 for air) for orebody 1 and 0.3 to 0.8 Ra for orebody 70. The former data suggest that at least 26 to 65 percent mantle helium occurs in the fluids that deposited the veins in orebody 1. The lower values for orebody 70, which is characterized by a more disseminated style of gold mineralization, are interpreted to reflect an increased interaction of ore fluids with surrounding crustal rocks, which may have contributed additional He to

  11. The small saphenous vein and other 'neglected' veins of the popliteal fossa: a review.

    PubMed

    O'Donnell, T F; Iafrati, M D

    2007-01-01

    The small saphenous vein (SSV) and other veins in the popliteal fossa merit little discussion in the literature or in didactic programmes regarding their role in chronic venous insufficiency (CVI) and, in this sense, they are neglected. The purpose of this review is to present both duplex ultrasound findings and the associated clinical characteristics of patients with SSV reflux, from several large series. Both the anatomic variations and the epidemiology of the SSV, as well as other veins of the popliteal fossa, the gastrocnemius veins, Gocamini vein, popliteal area veins and popliteal vein, will be discussed. Findings from our review of the current available literature will demonstrate the important role that these veins play in association with CVI. The implications for open and endovenous surgery will be underlined.

  12. Tissue remodeling investigation in varicose veins

    PubMed Central

    Ghaderian, Sayyed Mohammad Hossein; Khodaii, Zohreh

    2012-01-01

    Although the etiology of varicose veins remains unknown, recent studies have focused on endothelial cell integrity and function because the endothelium regulates vessel tone and synthesizes many pro- and anti-inflammatory factors. The aim of this study was to investigate the evidence involving the endothelium in the development of varicose vein disease. In addition, tissue remodeling was investigated in varicose veins to determine the expression of different types of collagen. Tissue specimens of superficial varicose veins and control saphenous vein were used for immunohistochemical and transmission electron microscope (TEM). α-smooth muscle actin, and collagen I, III, IV antibodies were applied for immunohistochemical investigation. Findings of this study showed alterations of the intima, such as focal intimal discontinuity and denudation of endothelium; and the media, such as irregular arrangements of smooth muscle cells and collagen fibres in varicose veins. Our findings showed some changes in terms of distribution of types I, III and IV collagen in the intima and media of varicose vein walls compared with controls. These alterations to the media suggest that the pathological abnormality in varicose veins may be due to the loss of muscle tone as a result of the breakup of its regular structure by the collagen fibres. These findings only described some changes in terms of distribution of these types of collagen in the intima and media of varicose vein walls which may result in venous wall dysfunction in varicosis. PMID:24551759

  13. Small hepatic veins Budd-Chiari syndrome.

    PubMed

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

    2014-05-01

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

  14. Human health risks in an old gold mining area with circum-neutral drainage, central Portugal.

    PubMed

    Carvalho, P C S; Neiva, A M R; Silva, M M V G; Santos, A C T

    2017-02-01

    The former mine of Escádia Grande was active at the middle of 1900 and was exploited for Au and Ag. The mineralized quartz veins consist mainly of quartz, arsenopyrite, pyrite, rare chalcopyrite, galena, sphalerite, gold and argentite. The mine dumps and tailings were deposited close to a stream, and there is a river beach downstream used for recreational proposes. Two villages are also located close to the old mining area. Mine wastes contained up to 8090 mg/kg of As and 70.1 mg/kg of Sb. The waters of the stream that cross the mining area have circum-neutral pH values and contained elevated concentrations of As reaching up to 284 µg/L. However, geochemical speciation modeling (Phreeq C) revealed that As was mainly present as As (V). Arsenic concentrations in waters are attenuated throughout the stream, mainly by the iron-(hydro)-oxides adsorption upstream. However, at 2 km downstream of mine wastes in the river beach, the waters still exceeded 10 µg/L of As, the drinking water limit. The waters also have NO2(-), Cu and Cd concentrations higher than drinking water limit. The stream sediments have As concentrations up to 45 times higher (3140 mg/kg) than the limit of the sediment guideline values of NWQMS (2000). The maximum arsenic concentrations in soils are also up to 27 times higher (5940 mg/kg) than the maximum concentrations in streams from FOREGS Geochemical Atlas of Europe. The use of river beach for recreational purposes causes cancer risk (4.48 × 10(-6)) higher than USEPA limit, mainly due to the arsenic exposure. Even for recreational purposes, stream sediments and soils in the old mining area have high non-carcinogenic effects (2.76 and 4.78, respectively) for children, also related to the arsenic exposure mainly by the ingestion pathway, and the risk is unacceptable according to the limits of USEPA. Moreover, the cancer risk resulting from exposure of adults to arsenic in soils also has unacceptable non-cancer risk (1.13). Arsenic is the

  15. Dual origins of lode gold deposits in the Canadian Cordillera

    NASA Astrophysics Data System (ADS)

    Nesbitt, Bruce E.; Murowchick, James B.; Muehlenbachs, Karlis

    1986-06-01

    From Late Jurassic to late Tertiary time, two geologically, geochemically, and genetically distinct gold mineralization processes were active in the Canadian Cordillera. One group of deposits can be characterized as epithermal because of its association with intermediate to felsic volcanics, regional caldera structures, low pH alteration zones, low Au/Ag values, and quartz-chalcedony-barite-fluorite gangue. The second group of deposits is mesothermal in character and has strong similarities to the Mother Lode deposits of California, being associated with transcurrent faults, intermediate pH alteration zones, and quartz ± carbonate, albite, mariposite, pyrite, arsenopyrite, scheelite gangue. Compared to epithermal deposits, mesothermal deposits have higher As, W, and Au/Ag values, higher CO2 content in fluid inclusions, and δ18O values of ore-forming fluids of +3‰ to +10‰ vs. -14‰ to -7‰ for epithermal deposits. Like the gold deposits in Nevada and Colorado, epithermal mineralization in the Canadian Cordillera formed from the shallow circulation of meteoric water in subaerial, intermediate to felsic volcanic complexes. In contrast, mesothermal gold deposits throughout the North American Cordillera are shown to be the product of deep circulation and evolution of meteoric water in structures associated with major, transcurrent fault zones. Similarities between Archean lode gold deposits and mesothermal deposits of the Cordillera suggest that Archean lode deposits may have been produced by processes similar to those involved in the formation of Cordilleran mesothermal deposits.

  16. Cathodoluminescence of shocked quartz at the Cretaceous-Tertiary boundary

    NASA Astrophysics Data System (ADS)

    Owen, Michael R.; Anders, Mark H.

    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.

  17. Mineral resource of the month: cultured quartz crystal

    USGS Publications Warehouse

    ,

    2008-01-01

    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.

  18. Active feedback cooling of massive electromechanical quartz resonators

    SciTech Connect

    Jahng, Junghoon; Lee, Manhee; Stambaugh, Corey; Bak, Wan; Jhe, Wonho

    2011-08-15

    We present a general active feedback cooling scheme for massive electromechanical quartz resonators. We cool down two kinds of macrosized quartz tuning forks and find several characteristic constants for this massive quartz-resonator feedback cooling, in good agreement with theoretical calculations. When combined with conventional cryogenic techniques and low-noise devices, one may reach the quantum sensitivity for macroscopic sensors. This may be useful for high sensitivity measurements and for quantum information studies.

  19. Quartz technology allows for wider downhole pressure testing range

    SciTech Connect

    Dennis, J.R. ); Zeller, V.P. )

    1991-03-01

    This paper presents a quartz-thickness shear-mode transducer for use in a borehole environment. The pressure sensor is a direct-conversion device that uses a noncylindrical shell to convert and to transmit forces to the quartz-crystal resonator. A brief conceptual description of the transducer is given. Laboratory and field examples illustrate the exceptional performance of the quartz-thickness shear-mode transducer.

  20. Optical processing furnace with quartz muffle and diffuser plate

    DOEpatents

    Sopori, B.L.

    1996-11-19

    An optical furnace for annealing a process wafer is disclosed comprising a source of optical energy, a quartz muffle having a door to hold the wafer for processing, and a quartz diffuser plate to diffuse the light impinging on the quartz muffle; a feedback system with a light sensor located in the wall of the muffle is also provided for controlling the source of optical energy. 5 figs.

  1. Cathodoluminescence of shocked quartz at the Cretaceous-Tertiary boundary

    NASA Technical Reports Server (NTRS)

    Owen, Michael R.; Anders, Mark H.

    1988-01-01

    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.

  2. Clinically silent deep vein thrombosis in patients with superficial thrombophlebitis and varicose veins at legs.

    PubMed

    Jerkic, Zoran; Karic, Alen; Karic, Amela

    2009-01-01

    Although superficial thrombophlebitis is a common disorder until recently it was considered as benign disorder. Also it is associated with varicose vein at legs and it was treated effectively with conservative methods, walking and non-steroid anti-inflammatory drugs. Aims of our investigation were: determine frequency of clinically silent deep vein thrombosis at legs in patient with and without superficial thrombophlebitis, determine correlation between superficial thrombophlebitis and deep vein thrombosis regardless of localization of superficial thrombophlebitis in superficial veins of legs and determine adequacy and safety vein phlebography in early diagnosis clinically silent deep vein thrombosis in patients with superficial thrombophlebitis. Using flebography in prospective study was evaluated incidence of clinically silent deep vein thrombosis in 92 patients with varicose veins at legs. By phlebograpy in patients with varicose veins at legs and superficial thrombophlebitis at legs and without clinical signs of DVT at legs of the 49 patients we detected DVT in 12 patients (24, 48%), in three male and nine female. We detected localization of DVT in ilijacofemoral junction in 4,08% patients, although localization of DVT in femoropopliteal region was observed in 6, 12% patients and localization in crural region was in 14.28% patients. Localization of DVT at legs was detected in iliac vein in 16.66% patients, in femoral vein in 25% patients, popliteal vein 8.33% patients, anterior tibial vein 16.66%, posterior tibial vein in 25% and crural veins 8.33% patients. Also we deduced significant difference between two group of patients (chi2 = 10, 76). Such result proves thesis that in most patients with superficial thrombophlebitis and varicose veins is possibility of developing of DVT.

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

    SciTech Connect

    Mert, Murat Saltik, Levent; Gunay, Ilhan

    2004-08-15

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

  4. Effective antibodies immobilization and functionalized nanoparticles in a quartz-crystal microbalance-based immunosensor for the detection of parathion

    PubMed Central

    Della Ventura, Bartolomeo; Iannaccone, Marco; Funari, Riccardo; Pica Ciamarra, Massimo; Altucci, Carlo; Capparelli, Rosanna; Roperto, Sante; Velotta, Raffaele

    2017-01-01

    Background Biosensor-based detection provides a rapid and low-cost alternative to conventional analytical methods for revealing the presence of the contaminants in water as well as solid matrices. Although important to be detected, small analytes (few hundreds of Daltons) are an issue in biosensing since the signal they induce in the transducer, and specifically in a Quartz-Crystal Microbalance, is undetectable. A pesticide like parathion (M = 292 Da) is a typical example of contaminant for which a signal amplification procedure is desirable. Methods/Findings The ballasting of the analyte by gold nanoparticles has been already applied to heavy target as proteins or bacteria to improve the limit of detection. In this paper, we extend the application of such a method to small analytes by showing that once the working surface of a Quartz-Crystal Microbalance (QCM) has been properly functionalized, a limit of detection lower than 1 ppb is reached for parathion. The effective surface functionalization is achieved by immobilizing antibodies upright oriented on the QCM gold surface by a simple photochemical technique (Photonic Immobilization Technique, PIT) based on the UV irradiation of the antibodies, whereas a simple protocol provided by the manufacturer is applied to functionalize the gold nanoparticles. Thus, in a non-competitive approach, the small analyte is made detectable by weighing it down through a “sandwich protocol” with a second antibody tethered to heavy gold nanoparticles. The immunosensor has been proved to be effective against the parathion while showing no cross reaction when a mixture of compounds very similar to parathion is analyzed. Conclusion/Significance The immunosensor described in this paper can be easily applied to any small molecule for which polyclonal antibodies are available since both the functionalization procedure of the QCM probe surface and gold nanoparticle can be applied to any IgG, thereby making our device of general

  5. Mineral potential tracts for polymetallic Pb-Zn-Cu vein deposits (phase V, deliverable 71): Chapter I in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

    USGS Publications Warehouse

    Beaudoin, Georges

    2015-01-01

    In Mauritania, mineral occurrences of the polymetallic Pb-Zn-Cu vein deposit type are found near the Florence-El Khdar shear zone in northeast Mauritania. The deposits visited were deemed representative of other similar occurrences and consist of quartz veins with trace sulfides. The low sulfide and Pb-Zn-Cu content in the quartz veins is unlike producing polymetallic Pb-Zn-Cu vein deposits, such that the veins are not considered to belong to this deposit type. Mineral potential tracts for polymetallic Pb-ZnCu veins are highly speculative considering the lack of known mineralization belonging to this deposit type. Mineral potential tracts for polymetallic Pb-Zn-Cu veins are associated with and surround major shear zones in the Rgueïbat Shield and zones of complex faulting in the southern Mauritanides, at the exclusion of the imbricated thrust faults that are not considered favorable for this deposit type. No skarn and replacement deposits have been documented in Mauritania and the low mineral potential is indicated by lack of causative Mesozoic and Cenozoic mafic to felsic stocks.

  6. Quartz Crystal Microbalance with Dissipation Monitoring

    DTIC Science & Technology

    2014-11-06

    Module (including reference electrode & accessories), Window Module, Open Module, Humidity Module, Standard Flow Module (extra) • UV/ Ozone cleaner...UV/ Ozone cleaner • Hydroxyapatite, 10 nm, Sensors • Biotin Functionalized on Gold Sensors • His-tag Capturing Sensor QCM-D techniques provide...solutions were pumped through the sensor surface for the first layer coating, after thorough washing steps, Fn solution was pumped through the sensor as

  7. OH zoning in alpine quartz from Austria

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

    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

  8. Dynamics-enabled quartz reference oscillators

    NASA Astrophysics Data System (ADS)

    Chang, David T.; Moyer, Harris P.; Kubena, Randall L.; Joyce, Richard J.; Kirby, Deborah J.; Brewer, Peter D.; Nguyen, Hung D.; Nagele, Robert G.; Stratton, Frederic P.

    2012-06-01

    Stable local oscillators with low phase noise are extremely important elements in high performance military communication and navigation systems. We present the development of compact UHF-band frequency sources capable of maintaining low phase noise under high accelerations or vibrations and over a wide temperature range for handheld portable systems. We also explored nonlinearity in MEMS resonators and attempted to use nonlinear dynamics to enhance phase noise performance. Using the quartz MEMS technology, we have thus far demonstrated a 645 MHz Pierce oscillator with -113 dBc/Hz phase noise at 1 kHz offset with acceleration sensitivity of 5x10-10/g. The controlled oscillation of a nonlinear Duffing resonator in a closed-loop system with improved phase noise is described.

  9. Epidemiology of Blackberry yellow vein associated virus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Blackberry yellow vein disease is one of the most important diseases of blackberry in the United States. Several viruses are found associated with the symptomology but Blackberry yellow vein associated virus (BYVaV) appears to be the most prevalent of all, leading to the need for a better understand...

  10. Element transport in veins during serpentinization

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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 μm and > 200 μm, respectively, from the orthopyroxene. We infer that brucite is not stable in close proximity to orthopyroxene due to elevated SiO2

  11. [Preduodenal portal vein (author's transl)].

    PubMed

    Tovar, J A; Benavent, M; Bachiller, C; Díez-Pardo, J A

    1978-01-01

    Three cases of preduodenal portal vein (PDPV) observed in newborns and young infants are reported. In two patients the diagnosis was made during operations for duodenal stenosis and in the remaining one while operating for midgut volvulus and necrosis. In no case was the PDPV responsible for the clinical picture but in all three patients it was accompanied by other causes of obstruction: annular pancreas, extrinsic adhesive bands and malrotation. In one case there was also an asplenia, and polisplenia was present in another one. Both had malrotation and some degree of abnormal visceral asimmetry. The incidence of associated malformations in 52 previously reported cases is analyzed, and the more convincing embriological explanation for this anomaly is commented upon.

  12. Quartz enhanced photoacoustic spectroscopy based trace gas sensors using different quartz tuning forks.

    PubMed

    Ma, Yufei; Yu, Guang; Zhang, Jingbo; Yu, Xin; Sun, Rui; Tittel, Frank K

    2015-03-27

    A sensitive trace gas sensor platform based on quartz-enhanced photoacoustic spectroscopy (QEPAS) is reported. A 1.395 μm continuous wave (CW), distributed feedback pigtailed diode laser was used as the excitation source and H2O was selected as the target analyte. Two kinds of quartz tuning forks (QTFs) with a resonant frequency (f0) of 30.72 kHz and 38 kHz were employed for the first time as an acoustic wave transducer, respectively for QEPAS instead of a standard QTF with a f0 of 32.768 kHz. The QEPAS sensor performance using the three different QTFs was experimentally investigated and theoretically analyzed. A minimum detection limit of 5.9 ppmv and 4.3 ppmv was achieved for f0 of 32.768 kHz and 30.72 kHz, respectively.

  13. Assessment and management of patients with varicose veins.

    PubMed

    Allen, Louise

    Varicose veins are enlarged superficial veins found in the legs. This article explores the anatomy and physiology of the venous system to assist nurses to assess, manage and treat patients with varicose veins.

  14. The nature of faults and hydrothermal veins in corehole SB-15-D, The Geysers Steam Field, California

    SciTech Connect

    Hulen, J.B.; Nielson, D.L.

    1995-12-31

    Porosity in The Geysers Coring Project corehole SB-15-D is concentrated along vuggy, steeply-dipping, hydrothermal calcite-quartz {plus_minus} adularia veins. There is little difference in the texture and abundance of these veins between the upper two thirds of the core, interpreted as caprock, and the lower two-thirds, in which two, vein-controlled, fluid-loss zones (probable steam entries) were encountered. However, vugs in the caprock veins are locally choked with mixed-layer clay, whereas those in the deeper steam-reservoir veins generally lack this clay but contain calc-silicate minerals. Steeply-dipping, concordant faults concentrated in argillite throughout the core show predominantly strike-slip displacement. Although movement was predominantly along argillites, the lithology appears to have deformed in a ductile manner, and porosity development was minimal. High-angle dilational fractures were developed contemporaneously in the graywackes. These fractures in the graywacke were only partially filled by secondary minerals, and are potential steam conduits in the vapor-dominated geothermal system.

  15. Contrasts in Faulting and Veining Across the Aseismic to Seismic Transition, Kodiak Accretionary Complex, Alaska

    NASA Astrophysics Data System (ADS)

    Rowe, C. D.; Thompson, E.; Moore, J. C.

    2002-12-01

    Structure and Character of Veined Zones in Kodiak Accretionary Prism Subduction thrust systems produce the world's largest earthquakes. The transition from aseismic to seismogenic faulting occurs at approximately 4 km depth. The chemical and physical controls on this transition are not well understood, but previous research indicates that phase transformations, fluid pressure changes, and formation of authigenic minerals and cements may produce changes in cohesion and coefficient of friction which control fault behavior. We have described and sampled areas of paleo faulting and fluid flow in an ancient subduction thrust system, Kodiak Archipelago, Alaska. We are comparing two formations: the upper Paleocene Ghost Rocks Fm., which previous work has shown to have been exposed to ~ 250° C and 12 km depth (well within the seismogenic zone) and the Eocene Sitkalidak Fm., which has been exposed to 100-125° C at 2.4-3.9 km depth, (accreted before it crossed the aseismic-seismogenic boundary.) Field observations confirmed earlier work and supported project hypotheses. The Ghost Rocks Fm. is characterized by discrete heavily veined zones meters to tens of meters thick. Individual veins in these zones commonly reach thickness of up to several centimeters and are primarily composed of clean calcite and quartz. In contrast, the Sitkalidak Fm. is characterized by a small volume of web-like networks of very fine veins rarely exceeding a few mm in thickness. These veins are composed of laumontite and "dirty" calcite. In the Sitkalidak Fm., stratal disruption is characterized by conjugate shear fracturing, leaving lustrous black residues on shear surfaces, followed by extensional fractures with veining, indicating rising fluid pressures. In the Ghost Rocks Fm., there is little evidence for conjugate shear fracturing. Stratal disruption is accomplished by extensive extensional fracturing and veining as well as ductile deformation and rotation of sediments under non-coaxial strain

  16. Gold deposits of the Carolina Slate Belt, southeastern United States--Age and origin of the major gold producers

    USGS Publications Warehouse

    Foley, Nora K.; Ayuso, Robert A.

    2012-01-01

    Gold- and iron sulfide-bearing deposits of the southeastern United States have distinctive mineralogical and geochemical features that provide a basis for constructing models of ore genesis for exploration and assessment of gold resources. The largest (historic) deposits, in approximate million ounces of gold (Moz Au), include those in the Haile (~ 4.2 Moz Au), Ridgeway (~1.5 Moz Au), Brewer (~0.25 Moz Au), and Barite Hill (0.6 Moz Au) mines. Host rocks are Late Proterozoic to early Paleozoic (~553 million years old) metaigneous and metasedimentary rocks of the Carolina Slate Belt that share a geologic affinity with the classic Avalonian tectonic zone. The inferred syngenetic and epithermal-subvolcanic quartz-porphyry settings occur stratigraphically between sequences of metavolcanic rocks of the Persimmon Fork and Uwharrie Formations and overlying volcanic and epiclastic rocks of the Tillery and Richtex Formations (and regional equivalents). The Carolina Slate Belt is highly prospective for many types of gold ore hosted within quartz-sericite-pyrite altered volcanic rocks, juvenile metasedimentary rocks, and in associated shear zones. For example, sheared and deformed auriferous volcanogenic massive sulfide deposits at Barite Hill, South Carolina, and in the Gold Hill trend, North Carolina, are hosted primarily by laminated mudstone and felsic volcanic to volcaniclastic rocks. The high-sulfidation epithermal style of gold mineralization at Brewer and low-sulfidation gold ores of the Champion pit at Haile occur in breccias associated with subvolcanic quartz porphyry and within crystal-rich tuffs, ash flows, and subvolcanic rhyolite. The Ridgeway and Haile deposits are primarily epithermal replacements and feeder zones within (now) metamorphosed crystal-rich tuffs, volcaniclastic sediments, and siltstones originally deposited in a marine volcanic-arc basinal setting. Recent discoveries in the region include (1) extensions of known deposits, such as at Haile where

  17. Lung Pathology in Pediatric Pulmonary Vein Stenosis.

    PubMed

    Pogoriler, Jennifer E; Kulik, Thomas J; Casey, Alicia M; Baird, Christopher W; Mullen, Mary P; Jenkins, Kathy J; Vargas, Sara O

    2016-01-01

    Pulmonary vein stenosis is a rare progressive narrowing of the extrapulmonary pulmonary veins, presenting predominantly in infancy and virtually always lethal. It typically arises following repair of congenital heart disease, particularly anomalous pulmonary venous return. Histologic characterization of pediatric pulmonary vein stenosis, not previously well described, may provide insight into the disease pathobiology. We retrieved archival lung specimens (biopsy, explant, or autopsy) from patients with pediatric pulmonary vein stenosis. Medical records were reviewed. Microscopic examination included hematoxylin and eosin (H&E)-stained slides, and for a subset of patients, elastic, trichrome, smooth-muscle actin, and D2-40. Groups with different clinical disease features were compared using Fisher's exact test. A total of 33 patients (median age, 7 months) had available tissue and 52% had congenital heart disease; 18% were premature. Within the lungs, interlobular septal veins showed thickened muscular coats (in 58%), proliferation/tortuosity (in 6%), and fibromyxoid intimal proliferation (in 3%). Associated arterial hypertensive changes were seen in 30 (91%). The one patient with intrapulmonary venous fibromyxoid intimal proliferation was the only patient with apparent primary familial disease. Lymphangiectasia and arterial medial hypertrophy were histologic features that correlated with clinical grouping. We conclude that in pediatric pulmonary vein stenosis, intrapulmonary pulmonary veins commonly show muscular thickening, best interpreted as venous hypertensive remodeling. Fibromyxoid intimal proliferation resembling that of the extrapulmonary pulmonary veins is uncommon. Awareness of intrapulmonary features in various clinical subtypes of pulmonary vein stenosis may be diagnostically and therapeutically informative considering that current catheter-based and surgical therapy is directed at the extrapulmonary component of pulmonary vein stenosis.

  18. Recrystallization of quartz after low-temperature plasticity - The record of stress relaxation below the seismogenic zone

    NASA Astrophysics Data System (ADS)

    Trepmann, Claudia A.; Hsu, Chen; Hentschel, Felix; Döhler, Katharina; Schneider, Christian; Wichmann, Veronica

    2017-02-01

    Quartz microfabrics in rocks from the Silvretta basal thrust and the Defereggen-Antholz-Vals (DAV) shear zone in the Eastern Alps, are analysed by polarized light and electron microscopy. The microfabrics from both shear zones record a switch from low-temperature plasticity at transient high stress to recrystallization at relaxing stresses at greenschist facies conditions. The development of new grains is dominantly by subgrain rotation and subsequent strain-induced grain-boundary migration in areas of localized high strain developed during initial low-temperature plasticity. The findings suggest that new grains develop at almost random crystallographic orientations at fast rates of stress relaxation (i.e. at low stress), as indicated by recrystallized quartz zones in the Silvretta fault rocks. In contrast, at slow rates of stress relaxation, new grains develop at moderately high stresses with crystallographic preferred orientation characterized by high Schmid factor for basal glide, as indicated by vein quartz samples from the DAV shear zone. Both recorded histories with transient peak stresses and different rates of stress relaxation are interpreted to be related to seismic activity of the fault systems. This study demonstrates that characteristic microfabrics provide important information about the deformation history of natural shear zones developed in different tectonic regimes.

  19. Assessment of quartz materials crystallinity by x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Korovkin, M.; AnanIeva, L.; Nebera, T.; Antsiferova, A.

    2016-02-01

    The estimated degree of crystallinity of natural and synthetic grown quartz and quartzite by calculating the x-ray diffraction patterns. It is shown that the index of crystallinity of natural quartzite varies widely, reflecting the different degree of their transformation. The highest values of the index of crystallinity are characterized natural and synthetic single crystals of quartz.

  20. Passivation of quartz for halogen-containing light sources

    DOEpatents

    Falkenstein, Zoran

    1999-01-01

    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.

  1. Constraints regarding gold deposition in episyenites: the Permian episyenites associated with the Villalcampo Shear Zone, central western Spain

    NASA Astrophysics Data System (ADS)

    López-Moro, Francisco Javier; Moro, María Candelas; Timón, Susana María; Cembranos, María Luisa; Cózar, Juan

    2013-04-01

    The Villalcampo Shear Zone (around 307 Ma) shows second-order shear zones (420-390 °C) with gold ore bodies hosted by episyenites, which consist of albite episyenites (albitites) and albite-Kfs episyenites, both types with different contents in sulphides and gold. Mass transfer modelling supports higher fluid/rock ratios in albitites than in albite-Kfs episyenites. The study of worldwide barren and gold-bearing episyenites reveals abundant sulphides in the latter as a distinguishing feature. The electrochemical processes at the surface of sulphide would have enhanced gold precipitation, sulphides working as a gold trap. A complex fluid history occurred in gold ore bodies hosted by episyenites, although in essence, it was similar to quartz-sealed faults hosting late Variscan gold deposits: (a) an early fluid equilibrated with the metamorphic pile with sulphides or with a metamorphic fingerprint, resulted in a sulphide deposition and (b) a shallower fluid reservoir of meteoric origin provided gold deposition. In contrast to earlier claims regarding episyenite fluid flow, a down temperature and probably an upwards fluid flow are proposed for the episyenitization process, also in keeping with the early stages of fluid flow in quartz-sealed faults. Fluid inclusions in albite confirm that the striking coupled quartz leaching albitization processes occurred around 400 °C and 60 MPa, crosscutting the retrograde solubility field of silica and yielding a vuggy rock. Initially, albite, and later quartz and sulphide, filled the vugs from the same or a very similar fluid. Uraninites deposited during the albitization and probably the onset of the sulphide deposition afforded the same age (270 ± 12 Ma) as other Spanish episyenites, confirming a synchronous and a regional-scale process and ruling out a relationship with the granite cooling history (324 ± 11 Ma).

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

    SciTech Connect

    Wilson, P.N.; Parry, W.T. )

    1990-09-01

    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.

  3. Petrogenesis and emplacement of the TTG and K-rich granites at the Buzwagi gold mine, northern Tanzania: Implications for the timing of gold mineralization

    NASA Astrophysics Data System (ADS)

    Manya, Shukrani

    2016-07-01

    18 Ma, some 40 Ma years after the emplacement of TTG at 2713 ± 8 Ma. The timing of the Buzwagi mine granitic magmatism falls within the peak crustal growth period in the northern part of the Archaean Tanzania Craton. Gold mineralization at the Buzwagi mine is hosted in quartz veins that are within strongly sheared and hydrothermally altered K-granites in which silica and sericite alterations and sulphides (mainly pyrite and chalcopyrite although chalcocite is also present) are important. The Buzwagi gold deposit is thus a typical Archaean orogenic deposit whose mineralization is hydrothermally and structurally controlled and the abundance of sulphides, silica and sericite alteration assemblages suggests that the deposition conditions were reducing and acidic in nature. Owing to its epigenetic nature, it can be inferred that the maximum age of deposition of gold at the Buzwagi mine is ~ 2674 Ma; which is more or less the same age inferred for the Golden Pride mine (~ 2680 Ma) both of which are found in the Nzega greenstone belt.

  4. Paired stable isotopes (O, C) and clumped isotope thermometry of magnesite and silica veins in the New Caledonia Peridotite Nappe

    NASA Astrophysics Data System (ADS)

    Quesnel, Benoît; Boulvais, Philippe; Gautier, Pierre; Cathelineau, Michel; John, Cédric M.; Dierick, Malorie; Agrinier, Pierre; Drouillet, Maxime

    2016-06-01

    The stable isotope compositions of veins provide information on the conditions of fluid-rock interaction and on the origin of fluids and temperatures. In New Caledonia, magnesite and silica veins occur throughout the Peridotite Nappe. In this work, we present stable isotope and clumped isotope data in order to constrain the conditions of fluid circulation and the relationship between fluid circulation and nickel ore-forming laterization focusing on the Koniambo Massif. For magnesite veins occurring at the base of the nappe, the high δ18O values between 27.8‰ and 29.5‰ attest to a low temperature formation. Clumped isotope analyses on magnesite give temperatures between 26 °C and 42 °C that are consistent with amorphous silica-magnesite oxygen isotope equilibrium. The meteoric origin of the fluid is indicated by calculated δ18Owater values between -3.4‰ to +1.5‰. Amorphous silica associated with magnesite or occurring in the coarse saprolite level displays a narrow range of δ18O values between 29.7‰ and 35.3‰. For quartz veins occurring at the top of the bedrock and at the saprolite level, commonly in association with Ni-talc-like minerals, the δ18O values are lower, between 21.8‰ and 29.0‰ and suggest low-temperature hydrothermal conditions (∼40-95 °C). Thermal equilibration of the fluid along the geothermic gradient before upward flow through the nappe and/or influence of exothermic reactions of serpentinization could be the source(s) of heat needed to form quartz veins under such conditions.

  5. Multi-surface Earthquake Rupture Recorded in Pseudotachylyte Vein Geometries, Norumbega Shear Zone, southern Maine

    NASA Astrophysics Data System (ADS)

    Ross, C.; Rowe, C. D.; Pollock, S. G.; Swanson, M.; Tarling, M.; Backeberg, N. R.; Coulson, S.; Barshi, N.; Bate, C.; Dascher-Cousineau, K.; Scibek, J.; Harrichhausen, N.; Timofeev, A.; Rakoczy, P.; Nisbet, H.; Castro, A.; Smith, H.

    2015-12-01

    Earthquake rupture surfaces are typically treated as single rupture planes. However, the observation of four linked, non-parallel to sub-parallel slip surfaces on a mining induced earthquake in 2004 shows that rupture geometries may be more complicated (Heesakkers et al., 2011). Multiple pseudotachylyte-bearing fault surfaces are exposed within a 1.1 km wide mylonite zone of the Paleozoic Norumbega fault system. The pseudotachylytes are present in two juxtaposed mylonite zones: the Ray Corner mylonite and a mylonite derived from Scarboro Formation metavolcanics. The Ray Corner mylonite crosscuts pelitic schists of the Cape Elizabeth Formation, at upper greenschist-facies conditions (quartz + feldspar + chlorite + muscovite ± titanite ± pyrite). The pseudotachylyte veins formed late in the deformational history, during a period of predominantly brittle dextral offset. The pseudotachylytes are cryptocrystalline and have rounded porphyroclasts of quartz and feldspar. Microstructural observations show evidence for static and dynamic recrystallization overprinting the primary quench textures, suggesting that previous generations of rupture surfaces have been recycled into the mylonitic fabric (Price et al., 2012). Many of the pseudotachylyte veins have a sharp boundary on one side and are poorly defined on the other, providing insight to the propagation direction. This confirms that the paleo-earthquake ruptures occurred at conditions where quartz and feldspar were able to deform plastically, near the base of the seismogenic zone. Using differential GPS, we mapped the geometry of pseudotachylyte fault veins, injection veins, and slip surface intersections. At Ray Corner, there are 7 layer-parallel pseudotachylytes in a 4 m wide zone with linking and subsequent oblique pseudotachylytes. Some intersections between pseudotachylytes are dilational, depending on the intersection angle and relative displacement on the two faults. At these sites, pseudotachylyte melt sourced

  6. Microwave GaAs Integrated Circuits On Quartz Substrates

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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 Roşia 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

  8. Displacement of thiophene by methanethiol observed in situ by scanning tunneling microscopy and quartz crystal oscillator gravimetric analysis on Au(111)

    SciTech Connect

    Dishner, M.H.; Taborek, P.; Hemminger, J.C.; Feher, F.J.

    1998-11-10

    Quartz crystal microbalance and scanning tunneling microscopy experiments have been used to demonstrate that self-assembled monolayers of thiophene on gold can be quantitatively replaced by absorption of methanethiol from the gas phase. Adsorption of thiophene on the gold surface results in the relaxation of the clean gold surface reconstruction and the formation of vacancy islands or pits in the gold. Subsequent annealing of the monolayer can result in the complete removal of the vacancy islands. Methanethiol displacement of thiophene monolayers that have been previously annealed to remove vacancy island pits does not generate additional pits in the gold surface. Thus, ordered methanethiol monolayers which are free from vacancy island pits in the underlying gold surface can be formed by displacement of annealed thiophene monolayers. These results provide strong additional evidence that the formation of vacancy islands in the gold during the formation of alkanethiol SAMs is directly associated with relaxation of the clean surface reconstruction, rather than conventional chemical etching of the surface by alkanethiol.

  9. Multistage crack seal vein and hydrothermal Ni enrichment in serpentinized ultramafic rocks (Koniambo massif, New Caledonia)

    NASA Astrophysics Data System (ADS)

    Cathelineau, Michel; Myagkiy, Andrey; Quesnel, Benoit; Boiron, Marie-Christine; Gautier, Pierre; Boulvais, Philippe; Ulrich, Marc; Truche, Laurent; Golfier, Fabrice; Drouillet, Maxime

    2016-11-01

    Sets of fractures and breccia sealed by Ni-rich silicates and quartz occur within saprock of the New Caledonian regolith developed over ultramafic rocks. The crystallization sequence in fractures is as follows: (1) serpentine stage: lizardite > polygonal serpentine > white lizardite; (2) Ni stage: Ni-Mg kerolite followed by red-brown microcrystalline quartz; and (3) supergene stages. The red-brown microcrystalline quartz corresponds to the very last stage of the Ni sequence and is inferred to have precipitated within the 50-95 °C temperature range. It constitutes also the main cement of breccia that has all the typical features of hydraulic fracturing. The whole sequence is therefore interpreted as the result of hydrothermal fluid circulation under medium to low temperature and fluctuating fluid pressure. Although frequently described as the result of a single downward redistribution of Ni and Mg leached in the upper part of the regolith under ambient temperature, the Ni silicate veins thus appear as the result of recurrent crack and seal process, corresponding to upward medium temperature fluid convection, hydraulic fracturing and subsequent fluid mixing, and mineral deposition.

  10. Personal authentication through dorsal hand vein patterns

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

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

  11. Atypical tryptamine receptors in sheep pulmonary vein.

    PubMed Central

    Eyre, P

    1975-01-01

    Both the pulmonary artery and vein of the sheep contracted dose-dependently to histamine, carbamoylcholine, prostaglandin F2a, noradrenaline and bradykinin and relaxed in the presence of isoprenaline or prostaglandin E1. 2 The effect of 5-hydroxytryptamine (5-HT) on the artery was consistently to produce dose-dependent contractions without tachyphylaxis. The effect on the vein was biphasic. 5HT 5 X 10(-10) to 5 X 10(-8) M relaxed the partially constricted vein. 5-HT 10(-7) to 10(-6) m caused brief venoconstriction followed by relaxation. 5-HT greater than 10(-6) M caused dose-related contraction of the vein. 3 Methysergide effectively blocked the contractile response of the artery to 5-HT, but only weakly inhibited the contractions of the vein (dose-ratio less than 20). 4 Each of ten antagonists tested failed to inhibit the 5-HT-induced relaxation of the vein. Sheep pulmonary vein possesses tryptamine receptors which mediate relaxation and which are not of the classicl M- or D-type. These receptors appear not to be involved directly or indirectly with responses to acetylcholine, catecholamines, histamine or prostaglandins. PMID:1203621

  12. Preduodenal portal vein in the adult.

    PubMed

    Papaziogas, T; Papaziogas, B; Paraskevas, G; Lazaridis, C; Patsas, A

    2000-09-01

    We present three cases of preduodenal portal vein in adult people, which were diagnosed in our department. All of them were identified during elective operation for cholelithiasis, caused some technical difficulties to the performance of the operation, but led to no major intraoperative or postoperative complications. None of them had any preoperative symptoms, which could be related to this anomaly. The preduodenal portal vein is a rare congenital anomaly, which is usually discovered in infants or children due to the obstruction of the duodenum. In adults, it is often asymptomatic, and is usually discovered as an accidental finding during laparotomy for other reason. The postcontrast CT can set the diagnosis, when this anomaly is suspected. Despite its rarity, this anomaly is of great surgical importance, because it can predispose to intraoperative complications including hemorrhage from the abnormal vein, or damage to the biliary tract or the distented duodenum. The anterior position of the portal vein results from the persistence of the ventral anastomosis between the two vitelline veins and the distal portion of the right vitelline vein, with subsequent atrophy of the cranial part of the left vitelline and dorsal anastomotic vein.

  13. Radiological features of azygous vein aneurysm.

    PubMed

    Choudhary, Arabinda Kumar; Moore, Michael

    2014-04-01

    Mediastinal masses are most commonly associated with malignancy. Azygous vein aneurysm is a very rare differential diagnosis of mediastinal mass. We report here three cases of azygous vein aneurysm including children and adult patients. In the pediatric patient it was further complicated by thrombosis and secondary pulmonary embolism. We describe the radiological features on CXR, MRI, CT, PET-CT, US and angiogram and their differential diagnosis. Imaging findings of continuity with azygous vein, layering of contrast medium on enhanced CT and dynamic MRA showing filling of the mass at the same time as the azygous vein without prior enhancement will be strongly suggestive of azygous vein aneurysm with transtracheal ultrasound being the definitive test in these patients. It is important to keep a vascular origin mass in the differential diagnosis of mediastinal masses. Also, in young healthy patients with pulmonary embolism, a vascular etiology such as azygous vein aneurysm should be carefully evaluated. This article will help the clinicians to learn about the imaging features of azygous vein aneurysm on different imaging modalities.

  14. One GHz leaky SAW velocity of metal layers and bilayers evaporated onto fused quartz

    NASA Technical Reports Server (NTRS)

    Walikainen, Dale

    1992-01-01

    An acoustic microscope operating at 1 GHz was used to determine the surface acoustic wave velocities v of thin film metal layers and metal bilayers deposited onto fused quartz. V(0)'s influence was reduced by gating. This produced a calibrated accuracy of 3 percent. A program was constructed from the explicitly solved 6 x 6 theoretical determinant. Single film thicknesses were decided upon by using this theory to produce a v equal to a standard. Since the single film v's were linear with respect to their thickness, half the single film thicknesses were used for the bilayered films. The velocities for these bilayered films agreed with theory. This experimentally confirms the theoretical technique used here to examine bilayered systems, or a prototype composite interphase. No discrepancy was seen for gold films as others have reported. V(z) seemed insensitive to the formation of intermetallics or CuO. Some annealed and unannealed platinum films did not change the v from that of fused quartz. Two platinum films whose v's were in agreement with theory peeled off with the tape test.

  15. GOLD PLATING PROCESS

    DOEpatents

    Seegmiller, R.

    1957-08-01

    An improved bath is reported for plating gold on other metals. The composition of the plating bath is as follows: Gold cyanide from about 15 to about 50 grams, potassium cyanide from about 70 to about 125 grams, and sulfonated castor oil from about 0.1 to about 10 cc. The gold plate produced from this bath is smooth, semi-hard, and nonporous.

  16. A Reappraisal of Saphenous Vein Grafting

    PubMed Central

    Yuan, Shi-Min; Jing, Hua

    2011-01-01

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

  17. Arterialized cephalic vein as a femoropopliteal bypass graft: A case report.

    PubMed

    Stefanov, Georgi; Cheshmedzhiev, Michail; Andreev, Andreia; Denchev, Borislav; Bachvarov, Chavdar; Yordanov, Miroslav; Velinov, Tihomir; Peev, Veselin

    2007-01-01

    The overall therapeutic strategy in patients with diabetes mellitus and peripheral arterial disease affecting several arterial segments is problematic. Usually, the greater saphenous vein (GSV) is the gold standard for bypass. However, alternative venous grafts may be necessary when the GSV is not available. The superficial veins of the arm are not suitable for bypass operations in most cases because of anatomical variations, inadequate diameter or very thin walls. However, arterialization of the cephalic vein can dilate and strengthen the walls, thus avoiding postoperative complications. The present patient, whose case was followed for 20 months postoperatively, suffered both from diabetes and peripheral arterial disease in a setting of gangrene and a lack of the GSV. The treament of the patient and the problems it incurred are discussed. The advantages of preoperative temporary arteriovenous shunting to improve the quality of the cephalic vein as an alternative autogenous graft are analyzed. Currently, the patient has excellent postoperative results, with healing of the ulcers and preserved peripheral pulses.

  18. Intracavity quartz-enhanced photoacoustic sensor

    SciTech Connect

    Borri, S. Galli, I.; Mazzotti, D.; Giusfredi, G.; De Natale, P.; Patimisco, P.; Scamarcio, G.; Spagnolo, V.; Akikusa, N.; Yamanishi, M.

    2014-03-03

    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 μm. 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}.

  19. Distribution of gold, tellurium, silver, and mercury in part of the Cripple Creek district, Colorado

    USGS Publications Warehouse

    Gott, Garland Bayard; McCarthy, J.H.; Van Sickle, G.H.; McHugh, J.B.

    1967-01-01

    Geochemical exploration studies were undertaken in the Cripple Creek district to test the possibility that large low-grade gold deposits might be found. Surface rock samples taken throughout the district indicate that the volcanic rocks between the productive veins contain an average of about 0.6 ppm (part per million) gold. In an area above 3,800 feet long and 500 feet wide near the Cresson mine in the south-central part of the district, scattered surface samples show that the rocks contain an average of 2.5 ppm gold, equivalent to $2.50 per ton. Inasmuch as veins that contain more than 2.5 ppm may also exist in the area, systematic sampling by trenching and drilling is warranted.

  20. Towards a magmatic quartz database: tracing melt sources

    NASA Astrophysics Data System (ADS)

    Tailby, N. D.; Ackerson, M. R.; Watson, E. B.; Thomas, J. B.

    2014-12-01

    Quartz composition has seen increasing interest among the scientific community over the last decade due to new calibrations (e.g., Ti-in-quartz) and the proliferation of trace element analytical facilities. What is presently lacking in the field of quartz research is a quartz composition database. Such a single body of information can be used to evaluate whether variation seen in different crystallization environments is equally manifest in quartz composition. In this study we present >2000 new quartz analyses from >70 different granitoids and volcanic settings from around the globe (Lachlan Fold Belt, High Himalaya, French Massif, Cordilleran, Caledonian, White Mountains, Bishop, Toba, Snake River, Oman ophiolite and a number of other select locations). This dataset also combines data from a number of previous studies and together the data may collectively be used to determine which geochemical characteristics can be used to distinguish quartz from different magma types. A number of trace element concentrations or ratios (e.g., Al/Ti, Ge, Li, P and B) are notably useful when distinguishing peraluminous (e.g., cordierite-bearing granitoid) systems from more metaluminous systems (e.g., hornblende granodiorite) or plagiogranites.

  1. Plastic Deformation of O+ Oriented Quartz Single Crystals

    NASA Astrophysics Data System (ADS)

    Poston, E. J.; Holyoke, C. W., III; Kronenberg, A. K.

    2015-12-01

    The strength of wet quartz deforming by dislocation creep significantly influences the strength of mid to lower crust. Dislocation creep of quartz in Earth's crust is dominated by slip on the basal slip system. However, very little is known about the temperature, strain rate, or water fugacity dependence of this slip system. In order to better understand the rheology of the basal slip system, we deformed single crystals of synthetic quartz, with the basal slip system oriented at 45° to the compression direction (O+ orientation). Each core was annealed at 900°C and 1 atm for 24 hours to convert the gel-type water defects found in synthetic quartz into fluid inclusions, like those observed in milky quartz. FTIR analysis indicate that water contents (200-450 H/106Si) were not affected by the annealing process. The annealed single crystals were then deformed in a Griggs piston-cylinder rock deformation apparatus using a solid salt assembly, at temperatures from 800 to 900°C, strain rates from 10-6 to 10-4/s, and a confining pressure of 1.5 GPa. The strength of the quartz crystals increases with faster strain rates and decreases with increasing temperature. During some of the faster strain rate steps at 800°C, the crystals did not deform plastically before the differential stress reached the confining pressure, whereas they deformed at low stresses at 800°C and 10-6/s. The microstructures visible in the deformed samples are consistent with dislocation creep. The samples exhibit undulatory extinction, and show no deformation lamellae or subgrain formation. The strength of synthetic quartz crystals with low water contents deformed in this study is greater than milky quartz single crystals with high water contents deformed at the same conditions in other studies. These results indicate that the strength of basal slip system in quartz is affected by both water content and water fugacity.

  2. Quartz dissolution in organic-rich aqueous systems

    USGS Publications Warehouse

    Bennett, Philip C.

    1991-01-01

    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 difficult to characterize because of competing interactions in mixed inorganic-organic electrolyte environments. In the experiments reported here, the kinetics of quartz dissolution in dilute aqueous organic-acid solutions between 25 and 70°C were investigated to determine the influence of both organic and inorganic electrolytes.Batch-reactor dissolution experiments in inorganic and organic electrolyte solutions were designed to investigate the hypothesis that organic acids at circum-neutral pH accelerate the dissolution and increase the solubility of quartz in water. Results suggest that multi-functional organic acids such as citrate and oxalate accelerate quartz dissolution by decreasing the activation energy by approximately 20%. The increase in dissolution rate was accompanied by a 100% increase in apparent quartz solubility at 25°C. Experiments using inorganic electrolytes, in contrast, increase the rate of quartz dissolution without decreasing the activation energy, and without increasing solubility.From these data, a model for both a solution complex between dissolved organic acid and monomeric silicic acid, and an activated complex on quartz surfaces is proposed. The model suggests that dissolved organic compounds in natural waters at near-neutral pH and low temperatures are capable of accelerating the dissolution of quartz and increasing its solubility.

  3. Progression of Thrombus in Portal Vein, Superior Mesenteric Vein, and Splenic Vein Even on Anticoagulation in a Patient with Ascending Colonic Malignancy with Liver Metastasis: Portal Vein Thrombosis versus Portal Vein Tumor Thrombosis.

    PubMed

    Sule, Ashish; Borja, Annamarie; Chin, Tay Jam

    2016-12-01

    Portal vein thrombosis (PVT) in a setting of liver metastasis is not easy to treat as it may be portal vein tumor thrombus (PVTT). A 77-year-old male patient was diagnosed as ascending colon carcinoma, underwent right hemicolectomy in 1991 with a recurrence in July 2009. In August 2009, he underwent computed tomography (CT) scan of the abdomen which showed evidence of superior mesenteric vein thrombosis with no liver metastasis. He was started with anticoagulation and decision was to treat long term. He was admitted with mesenteric artery ischemic symptoms in February 2012 on anticoagulation. CT scan abdomen and pelvis in February 2012 showed tumor thrombus involving the superior mesenteric vein, portal vein, and splenic vein with hepatic metastasis. His tumor marker chorioembryonic antigen was 34 µg/L. He was continued on anticoagulation. A repeat CT scan abdomen after 2 years (in January 2014) showed, increase in size of hepatic metastasis, extensive thrombus involving the superior mesenteric vein, portal vein, and splenic vein with collaterals. Mesentery was congested due to extensive superior mesenteric vein thrombus. He finally succumbed in June 2014. It is very important to differentiate PVT from PVTT as the prognosis is different. PVTT progresses despite of long-term anticoagulation with poor prognosis.

  4. Adsorption of cellulose derivatives on flat gold surfaces and on spherical gold particles.

    PubMed

    Amirkhani, Masoud; Volden, Sondre; Zhu, Kaizheng; Glomm, Wilhelm R; Nyström, Bo

    2008-12-01

    The adsorption of hydroxyethylcellulose (HEC), ethyl(hydroxyethyl)cellulose (EHEC), and their hydrophobically modified counterparts HM-HEC and HM-EHEC has been studied on planar gold and citrate-covered gold surfaces by means of quartz crystal microbalance with dissipation monitoring (QCM-D), and on citrate-covered gold particles with the aid of dynamic light scattering (DLS). The QCM-D results indicate that larger amounts of polymer are adsorbed from aqueous solutions of HM-HEC and HM-EHEC on both substrates than from solutions of their unmodified analogues. The adsorption affinity for all the polymers, except EHEC, is higher on the citrate-covered surfaces than on the bare gold substrate. This indicates that more adsorption sites are activated in the presence of the citrate layer. The experimental adsorption data for all the polymers can be described fairly well by the Langmuir adsorption isotherm. However, at very low polymer concentrations significant deviations from the model are observed. The value of the hydrodynamic thickness of the adsorbed polymer layer (delta h), determined from DLS, rises with increasing polymer concentration for all the cellulose derivatives; a Langmuir type of isotherm can be used to roughly describe the adsorption behavior. Because of good solvent conditions for HEC the chains extend far out in the bulk at higher concentrations and the value of delta h is much higher than that of HM-HEC. The adsorption of EHEC and HM-EHEC onto gold particles discloses that the values of delta h are considerably higher for the hydrophobically modified cellulose derivative, and this finding is compatible with the trend in layer thickness estimated from the QCM-D measurements.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  6. Preparing metal-complex surfaces based on self-assembled monolayers of thiols and disulfides on gold

    NASA Astrophysics Data System (ADS)

    Dolzhikova, V. D.; Bogdanova, Yu. G.; Majouga, A. G.; Beloglazkina, E. K.; Kudrinsky, A. A.

    2017-02-01

    The complexation of monolayers of sulfur-containing ligands self-assembled on surface of gold with Co(II) and Cu(II) ions is studied using quartz crystal microbalance (QCM) and wetting measurements. The optimum conditions for obtaining metal-complex surfaces and the compositions of the resulting monolayers are determined.

  7. Who Is at Risk for Varicose Veins?

    MedlinePlus

    ... better within 3 to 12 months of delivery. Overweight or Obesity Being overweight or obese can put extra pressure on your ... lead to varicose veins. For more information about overweight and obesity, go to the Health Topics Overweight ...

  8. Varicose veins - what to ask your doctor

    MedlinePlus

    ... what to ask your doctor References Goldman MP, Weiss RA. Phleblogy and treatment of leg veins. In: ... and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the ...

  9. [Retinal vein occlusion in a young patient].

    PubMed

    Zemba, Mihail; Ochinciuc, Uliana; Sarbu, Laura; Avram, Corina; Camburu, Raluca; Stamate, Alina

    2013-01-01

    We present a case report of a 27 years old pacient with central retinal vein occlussion and macular edema. The pacient has a significant reduction of the macular aedema with complete recovery of vision after the treatment.

  10. Transmission Measurement of the Third-Order Susceptibility of Gold

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Yoon, Youngkwon; Boyd, Robert W.; Crooks, Richard M.; George, Michael

    1999-01-01

    Gold nanoparticle composites are known to display large optical nonlinearities. In order to assess the validity of generalized effective medium theories (EMT's) for describing the linear and nonlinear optical properties of metal nanoparticle composites, knowledge of the linear and nonlinear susceptibilities of the constituent materials is a prerequisite. In this study the inherent nonlinearity of the metal is measured directly (rather than deduced from a suitable EMT) using a very thin gold film. Specifically, we have used the z-scan technique at a wavelength near the transmission window of bulk gold to measure the third-order susceptibility of a continuous thin gold film deposited on a quartz substrate surface-modified with a self-assembled monolayer to promote adhesion and uniformity without affecting the optical properties. We compare our results with predictions which ascribe the nonlinear response to a Fermi-smearing mechanism. Further, we note that the sign of the nonlinear susceptibility is reversed from that of gold nanoparticle composites.

  11. Primary leiomyosarcoma of the innominate vein.

    PubMed

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

    2007-01-01

    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.

  12. Renal Vein Injury During Percutaneous Nephrolithotomy Procedure

    PubMed Central

    Toffeq, Hewa Mahmood

    2016-01-01

    Abstract Background: Percutaneous nephrostolithotomy is an important approach for removing kidney stones. Puncturing and dilatation are two mandatory steps in percutaneous nephrolithotomy (PCNL). Uncommonly, during dilatation, the dilators can cause direct injury to the main renal vein or to their tributaries. Case Presentation: A 75-year-old female underwent PCNL for partial staghorn stone in the left kidney. During puncturing and dilatation, renal vein tributary was injured, and the nephroscope entered the renal vein and inferior vena cava, which was clearly recognized. Injection of contrast material through the nephroscope confirms the false pathway to the great veins (renal vein and inferior vena cava). Bleeding was controlled intraoperatively by applying Amplatz sheath over the abnormal tract, the procedure was continued and stones were removed. At the end of the procedure, a Foley catheter was used as a nephrostomy tube and its balloon was inflated inside the renal pelvis and pulled back with light pressure to the lower calix, which was the site of injury to the renal vein tributaries, then the nephrostomy tube was closed; by this we effectively controlled the bleeding. The patient remained hemodynamically stable; antegrade pyelography was done on the second postoperative day, there was distally patent ureter with no extravasation, neither contrast leak to renal vein, and was discharged home at third postoperative day. After 2 weeks, the nephrostomy tube was gradually removed in the operative room, without bleeding, on the next day, Double-J stent was removed. Conclusion: Direct injury and false tract to the renal vein tributaries during PCNL can result in massive hemorrhage, and can be treated conservatively in hemodynamically stable patients, using a nephrostomy catheter as a tamponade. PMID:27704054

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

    PubMed Central

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

    2013-01-01

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

  14. Improvements of deep vein reflux following radiofrequency ablation for saphenous vein incompetence.

    PubMed

    Kim, Suh Min; Jung, In Mok; Chung, Jung Kee

    2017-02-01

    Objectives The aim of this study was to describe the changes of deep vein reflux after radiofrequency ablation for great saphenous vein incompetence. Method The data on 139 limbs which were treated with radiofrequency ablation for great saphenous vein incompetence were prospectively collected and reviewed. Results Deep vein reflux was present in 43 of 139 limbs (30.9%). There were no significant differences in the rate of successful closure, the incidence of procedure-related complications, and the improvements of symptoms and quality of life between the limbs with or without deep vein reflux. With a mean follow-up of 5.9 months, the peak reflux velocity and duration of reflux were improved in all limbs with deep vein reflux and it was completely corrected in 13 limbs (30.2%) after radiofrequency ablation. Conclusions The presence of deep vein reflux does not affect the treatment outcomes of radiofrequency ablation for great saphenous vein incompetence and is improved in all patients. Deep vein reflux is not a barrier to performing radiofrequency ablation.

  15. High-Frequency Electrodeless Quartz Crystal Microbalance Chip with a Bare Quartz Resonator Encapsulated in a Silicon Microchannel

    NASA Astrophysics Data System (ADS)

    Kato, Fumihito; Ogi, Hirotsugu; Yanagida, Taiji; Nishikawa, Shintaro; Nishiyama, Masayoshi; Hirao, Masahiko

    2011-07-01

    We present a high-frequency electrodeless quartz crystal microbalance (QCM) chip with a bare quartz resonator encapsulated in a silicon microchannel, which is fabricated by micromachining technology. This QCM chip packages an AT-cut quartz plate 2.5 mm long, 1.7 mm wide, and 9.6 µm thick, which is supported by micropillars without fixed parts. There is no issue about destruction during assembly because handling the fragile quartz resonator becomes unnecessary. The quartz resonator is electrodeless and not fixed; therefore, there are no losses due to electrodes and contacting wires. As a result, a high quality factor (Q-factor) and a high signal-to-noise ratio (SNR) can be obtained. The Q-factor is about 800-2800 at 170 MHz in the flow of the carrier solution. In addition, it is possible to reuse the device, because the quartz surfaces can adsorb receptor proteins nonspecifically, which can be removed by a washing procedure with a strong acid solution flowed in the microchannel. The high-frequency quartz resonator (170 MHz) encapsulated in the microchannel can reduce the influence of the viscosity contribution to the frequency shift, achieving highly sensitive and quantitative analysis. The QCM chip is excited and detects the shear vibrations of the quartz resonator by the line antennas without contact. Consequently, both sides of the quartz resonator can be used as the detection area in a solution. We succeeded in detecting the human immunoglobulin G (hIgG) at a concentration of 6 µg/ml via the staphylococcal protein A (SPA) immobilized nonspecifically on the developed QCM chip in real time without any labeling.

  16. Veins improve fracture toughness of insect wings.

    PubMed

    Dirks, Jan-Henning; Taylor, David

    2012-01-01

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

  17. Subclavian vein thrombosis: A continuing challenge

    SciTech Connect

    Hill, S.L.; Berry, R.E. )

    1990-07-01

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

  18. The Enåsen gold deposit, central Sweden

    NASA Astrophysics Data System (ADS)

    Hallberg, A.; Fallick, A. E.

    1994-06-01

    Stable isotope analyses of quartz, sulphides, and magnetite were conducted to provide information on thermal history and source of hydrothermal fluids in the Palaeoproterozoic Enåsen gold deposit. Reequilibration and homogenization of oxygen isotopes throughout the rock have apparently not occurred despite the upper amphibolite to granulite facies regional metamorphism that has affected the rocks. However, oxygen isotope geothermometry on a coexisting quartz-magnetite pair gave a minimum temperature for peak metamorphism of around 650 °C which agrees with Fe-Mg geothermometry. This suggests that grain-scale equilibrium is achieved. The variation in oxygen isotope ratios (δ18O = 7.3 10.5‰) on quartz from the metamorphosed acid sulphate alteration zone is suggested to represent a cooling trend in the fossil hydrothermal system with higher δ18O-values in more superficial parts. Temperatures of alteration and silicification and isotopic composition of hydrothermal fluids could not be defined from the present data but it was recognized that the data is compatible with a epithermal genesis for the deposit. It is suggested that alteration, silicification, and mineralization at the Enåsen gold deposit took place in a high sulphidation epithermal environment at temperatures of around 200 250 °C and that the hydrothermal fluids consisted of meteoric and magmatic water. A tentative reconstruction of the fossil hydrothermal system is presented. Sulphur isotope ratios of sulphides from the fold-bearing quartz-sillimanite gneiss gave δ34S-values close to zero indicating a magmatic source of the sulphur.

  19. Archean high-Mg monzodiorite-syenite, epidote skarn, and biotite-sericite gold lodes in the Granny Smith-Wallaby district, Australia: U-Pb and Re-Os chronometry of two intrusion-related hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Mueller, Andreas G.; Hall, Gregory C.; Nemchin, Alexander A.; Stein, Holly J.; Creaser, Robert A.; Mason, Douglas R.

    2008-03-01

    The Granny Smith (37 t Au production) and Wallaby deposits (38 t out of a 180 t Au resource) are located northeast of Kalgoorlie, in 2.7 Ga greenstones of the Eastern Goldfields Province, the youngest orogenic belt of the Yilgarn craton, Western Australia. At Granny Smith, a zoned monzodiorite-granodiorite stock, dated by a concordant titanite-zircon U-Pb age of 2,665 ± 3 Ma, cuts across east-dipping thrust faults. The stock is fractured but not displaced and sets a minimum age for large-scale (1 km) thrust faulting (D2), regional folding (D1), and dynamothermal metamorphism in the mining district. The local gold-pyrite mineralization, controlled by fractured fault zones, is younger than 2,665 ± 3 Ma. In augite-hornblende monzodiorite, alteration progressed from a hematite-stained alkali feldspar-quartz-calcite assemblage and quartz-molybdenite-pyrite veins to a late reduced sericite-dolomite-albite assemblage. Gold-related monazite and xenotime define a U-Pb age of 2,660 ± 5 Ma, and molybdenite from veins a Re-Os isochron age of 2,661 ± 6 Ma, indicating that mineralization took place shortly after the emplacement of the main stock, perhaps coincident with the intrusion of late alkali granite dikes. At Wallaby, a NE-trending swarm of porphyry dikes comprising augite monzonite, monzodiorite, and minor kersantite intrudes folded and thrust-faulted molasse. The conglomerate and the dikes are overprinted by barren (<0.01 g/t Au) anhydrite-bearing epidote-actinolite-calcite skarn, forming a 600-m-wide and >1,600-m-long replacement pipe, which is intruded by a younger ring dike of syenite porphyry pervasively altered to muscovite + calcite + pyrite. Skarn and syenite are cut by pink biotite-calcite veins, containing magnetite + pyrite and subeconomic gold-silver mineralization (Au/Ag = 0.2). The veins are associated with red biotite-sericite-calcite-albite alteration in adjacent monzonite dikes. Structural relations and the concordant titanite U-Pb age of the skarn

  20. Quartz crystal microbalance immunosensors for environmental monitoring.

    PubMed

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

    2006-10-15

    This paper presents discussion of quartz crystal microbalance (QCM) immunosensors for environmental monitoring. Factors limiting the practical application of antibodies to analytical problems are also presented. Among several candidates for the QCM immunosensor device, selected QCM devices and oscillating circuits were tested thoroughly and developed to obtain highly stable and sensitive frequency signals. The biointerface of QCM immunosensor was designed and controlled to immobilize antibody on the QCM surface, to reduce non-specific binding and to suppress denaturation of immobilizing antibody by self-assembled monolayer technique and artificial phospholipid (2-methacryloyloxyethyl phosphorylcholine (MPC)) polymer. MPC polymer as a antibody-stabilizing reagent was added to reduce non-specific binding of the antigen solution and stabilize the immunologic activity of the antibody-immobilized QCM. In addition, it provides examples for detection and quantitation of environmental samples using QCM immunosensors. The analytical results for fly ash extracted samples of dioxins using the QCM immunosensor indicated a good relationship with GC/MS methods. The integrating protocols of the competitive immunoassay and signal-enhancing step are for detecting low molecular analytes with extremely low detection limits using an QCM immunosensor. Furthermore, its detect limitation was extended from 0.1 to 0.01 ng/ml by the signal-enhancing step when the anti-bisphenol-A antibody conjugated MPC polymeric nanoparticles was used. The QCM immunosensor method has demonstrated its effectiveness as an alternative screening method for environmental monitoring because these results were compared with results obtained through environmental monitoring methods such as ELISA and GC/MS.

  1. Gold recycling and enrichment beneath volcanoes: A case study of Tolbachik, Kamchatka

    NASA Astrophysics Data System (ADS)

    Zelenski, Michael; Kamenetsky, Vadim S.; Hedenquist, Jeffrey

    2016-03-01

    Magmas supply metals to hydrothermal ore deposits, although typical arc basalts may be unable to produce a gold-rich ore-forming fluid, as such basalts rarely exceed 5 ppb Au. Consistent with this, the occurrence of native gold of magmatic origin is extremely rare, and only a few finds of micron-sized gold particles in unaltered basalts have been documented. Surprisingly, some lava flows and scoria cones of the historic basaltic eruptions of Tolbachik volcano (Kamchatka) are unusually gold-rich. Tolbachik basalts contain up to 11.6 ppb Au based on whole rock analyses, nuggets of gold (electrum) up to 900 μm in size and native gold droplets up to 200 μm, plus numerous vapor-deposited gold crystals within fumarolic incrustations and directly on surfaces of basaltic lapilli. Our results demonstrate that the gold nuggets in Tolbachik basalt are of hydrothermal origin and were physically scavenged from epithermal veins hosted by country rocks during intrusion of mafic magmas. Depending on the melt temperature and/or time span of the melt-rock interaction, gold was ejected by the erupting volcano either in the form of abraded nuggets or liquid droplets, or was fully assimilated (dissolved) into the shallow long-lived magma chamber to provide a 4-fold increase in gold content over background concentration of 2.7 ppb Au, characteristic of mafic volcanic rocks in Kamchatka. Upon the end of the eruption, the continued discharge of volcanic vapors enriched in gold deposited abundant crystals of gold on cooling lava and scoria. Similar to Tolbachik, recycling of metals from prior accumulations (ore deposits) in the shallow crust may take place in other long-lived magma reservoirs, thus upgrading the gold and other metal contents and contributing to the ore-forming potential of a magma.

  2. Detection of parathion pesticide by quartz crystal microbalance functionalized with UV-activated antibodies.

    PubMed

    Funari, Riccardo; Della Ventura, Bartolomeo; Schiavo, Luigi; Esposito, Rosario; Altucci, Carlo; Velotta, Raffaele

    2013-07-02

    Photonic immobilization technique (PIT) has been used to develop an immunosensor for the detection of parathion. An antibody solution has been activated by breaking the disulfide bridge in the triad Trp/Cys-Cys through absorption of ultrashort UV laser pulses. The free thiol groups so produced interact with gold lamina making the antibody oriented upside, that is, with its variable parts exposed to the environment, thereby greatly increasing the detection efficiency. PIT has been applied to anchor polyclonal antiparathion antibodies to the gold electrode of a Quartz Crystal Microbalance (QCM) giving rise to very high detection sensitivity once the parathion is made heavier by complexion with BSA (bovine serum albumin), this latter step only required by the mass based transducer used in this case. The comparison of the sensor response with irradiated antibodies against different analytes shows that the high degree of antibody specificity is not affected by PIT nor is it by the complexion of parathion with BSA. These results pave the way to important applications in biosensing, since the widespread occurrence of the Trp/Cys-Cys residues triads in proteins make our procedure very general and effective to detect light analytes.

  3. Real-time evaluation of macromolecular surface modified quartz crystal resonant sensors under cryogenic stress for biological applications.

    PubMed

    Pavey, Karl D; Hunter, A Christy; Paul, Frank

    2003-10-01

    This study presents a novel auto-gain-control based quartz acoustic sensor technology capable of constant quartz crystal operation when cycled between ambient (22 degrees C) and cryogenic temperatures (-196 degrees C), afforded by direct exposure of crystals to bulk liquid nitrogen. The real-time frequency response profiles due to freeze-thaw cycling on crystals of differing surface finish and two model macromolecular surface coatings were studied in order to determine surface events such as water uptake. The quartz crystal surface finishes used were optically polished or lapped to one of two surface finishes. These were used as control native gold electrodes, and these surfaces were further coated with bovine serum albumin or the tri-block copolymer, poloxamer-188 as model macromolecular surface architectures. Crystals were snap frozen in liquid nitrogen and allowed to return to ambient temperature under controlled conditions. The processes of ice formation, thawing and evaporation were followed in real-time and comparisons were made between the test samples in order to assess the capability of this technique for sensing changes in surface characteristics such as the entrapment of water.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    Strongly silicified volcanic rocks and overlying sediments are a common feature in the Mesoarchean Barberton Greenstone Belt, South Africa. The silification predominantly occurs at the top of mafic to ultramafic lava flows at the contact to sedimentary chert horizons, and has been interpreted as a result of fluid circulation in shallow subseafloor convection cells (Hofmann & Harris, 2008). Six samples of silicified rocks of the Mendon Formation were used for a fluid inclusion study to better constrain the conditions of formation and the source and physico-chemical evolution of the fluid that might have been responsible for the alteration. The studied samples consist of silicified ultramafic rock and chemical precipitates with abundant chert and/or quartz veins. The silicified ultramafic rocks are mainly made up of quartz, Cr-muscovite and Cr-Spinell. Tourmaline and chlorite are locally present. Sedimentary cherts are nearly pure quartz with minor accessory minerals such as rutile and Fe-(hydr)oxides. Fluid inclusions are present in coarse-grained quartz in mainly bedding parallel syntaxial veins. Primary fluid inclusions occur as clusters in the crystal's core with an average size of 5-10 µm. They occur as two phase aqueous (liquid-vapour) inclusions at room temperature with a relatively constant vapour fraction (c.15-20 vol.%). Most fluid inclusions from veins crosscutting the silicified ultramafic rocks have a salinity between 0.5 and 11.0. wt.% NaCl equiv., one sample additionally contains inclusions with distinctly higher salinities (18 - 30 wt.% NaCl equiv.). Homogenization into the liquid phase occurs from 110°C to 210°C; with most values ranging between 150 and 180°C. The sample showing two distinct groups in salinity shows the lowest Th ranging from 110°C to 150°C. The sedimentary cherts show substantial differences i.e. the presence of a phase that prohibits freezing with a N-cooled freezing stage; probably CH4 or N2. Independent temperature

  5. Selective transfer of Li-Al-rich phyllosilicate to metamorphic veins (Western Alps): Laser Induced Breakdown Spectroscopy (LIBS) compositional profiles and microstructural characterization

    NASA Astrophysics Data System (ADS)

    Verlaguet, A.; Brunet, F.; Goffé, B.; Menut, D.; Findling, N.; Poinssot, C.; Huet, B.

    2016-11-01

    In convergent settings, fluid-rock interactions generally result in quartz and calcite preferential transfer to metamorphic veins in classical metamarls, while phyllosilicates tend to remain in the host-rock. However, the mechanisms responsible for such a selective mass transfer are poorly discussed in the literature. Here, we study Alpine metabauxites in which phyllosilicates (Li-Al-rich chlorite called cookeite, followed by pyrophyllite) were preferentially transferred to veins at blueschist peak P-T conditions, by a dissolution-diffusion-precipitation process without any fluid infiltration or associated reaction. Cookeite fibrous en-echelon veins formed by extensional shear, and part of them evolved towards thicker fluid-filled veins with euhedral cookeite crystallization. We performed chemical profiles across host-rocks between successive cookeite veins, using Laser Induced Breakdown Spectroscopy (LIBS), associated to a microstructural study. Flat LIBS Li profiles show that about half of the initial cookeite remains homogeneously distributed in host-rocks, which suggests a minimum diffusion distance of 2-4 cm for Li. The availability of an aqueous fluid during most of the metamorphic cycle is demonstrated here. A simple 1D reaction-diffusion model, assuming Li diffusion through a connected fluid-filled porosity network, is able to account for the observed lithium distribution assuming Li diffusion coefficients consistent with literature values in fluid-bearing systems. Chemical potential gradients that drove phyllosilicate transfer to veins can be either interfacial energy driven (i.e., Ostwald ripening), the anhedral phyllosilicate microsheets maintaining high supersaturation levels in the small host-rock pores compared to veins, or stress-induced: phyllosilicates present the highest solubility variations with pressure in the Vanoise bauxites (contrary to quartz-bearing rocks), which may account for their unusual selective transfer to veins. Therefore, mineral

  6. Scattering removal for finger-vein image restoration.

    PubMed

    Yang, Jinfeng; Zhang, Ben; Shi, Yihua

    2012-01-01

    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.

  7. Shock-Induced Effect on Chathodoluminesence of Experimentally Shocked Quartz

    NASA Astrophysics Data System (ADS)

    Chang, Y.; Kayama, M.; Tajika, E.; Sekine, Y.; Sekine, T.; Nishido, H.; Kobayashi, T.

    2015-07-01

    We conducted a series of shock recovery experiments on single crystals of natural and synthetic quartz. In the presentation, we show the results of the variation of Cathodoluminescence (CL) spectral features with increasing shock pressure.

  8. Quartz crystals detect gas contaminants during vacuum chamber evacuation

    NASA Technical Reports Server (NTRS)

    Stephens, J. B.

    1967-01-01

    Piezoelectric quartz crystals detect condensable gas contaminants backstreaming into a vacuum chamber when a pump is evacuating the chamber. One crystal acts as a thermometer, the other detects mass change. They are energized by electronic equipment which records frequency changes.

  9. APPLICATIONS OF CATHODOLUMINESCENCE OF QUARTZ AND FELDSPAR TO SEDIMENTARY PETROLOGY.

    USGS Publications Warehouse

    Ruppert, Leslie F.

    1987-01-01

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

  10. Origin of organism-dependent biogenic silica quartz formation.

    PubMed

    Sato, Kiminori

    2011-12-15

    Organism-dependent biogenic quartz formation in the steady-state environment is a phenomenon that can address the global environmental issues such as diagenetic evolution, biogeochemical cycling, and reservoir formation, but detailed studies have not been performed so far. Here, steady-state quartz formation is studied for amorphous silica of different biogenic origin on the basis of the recently established mechanistic model [Sato et al., J. Phys. Chem. C 2011, 115, 18131]. Amorphous silica originated from rice husks possesses angstrom-scale pores larger by 1.3 Å than those originated from diatom algae. The slight difference of pore size dramatically reduces activation energies of water diffusion by 78% and reactions of water molecules at pore surfaces by 47%, resulting in the reduction of activation energy of biogenic quartz formation by 64%. The present findings evidence that angstrom-scale pores intrinsically residing in the amorphous matrix are the organism-dependent origin of steady-state biogenic quartz formation.

  11. Degradation of glycine and alanine on irradiated quartz.

    PubMed

    Pawlikowski, Maciej; Benko, Aleksandra; Wróbel, Tomasz P

    2013-04-01

    Recent researches suggest participation of minerals in the formation of life under primordial conditions. Among all of the minerals, quartz seems to be one of the most probable to take part in such processes. However, an external source of energy is needed, e.g. electric discharge. A device simulating the proposed conditions was designed and was used to simulate prebiotic conditions. Investigation of processes occurring during the stimulation of quartz with electric discharge was studied by means of Ultraviolet-visible (UV-VIS) spectroscopy, in order to monitor the generation kinetics of free radicals. Additionally, infrared spectroscopy was applied to identify chemical reaction products created in a solution of alanine or glycine, in the presence of quartz treated with electric discharge. Formation of increased amounts of free radicals, compared to experiments performed without quartz and/or amino acid, is reported, along with identification of possible degradation products of alanine. No synthetic reactions were observed.

  12. Structure optimization and simulation analysis of the quartz micromachined gyroscope

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  13. Thermal conductivity calculations of crystalline quartz from the BKS potential

    NASA Astrophysics Data System (ADS)

    Yoon, Young-Gui; Car, Roberto; Srolovitz, David J.; Scandolo, Sandro

    2003-03-01

    We present thermal conductivity calculations from the classical BKS potential[1]. Following a velocity rescaling method for a constant heat flux proposed by P. Jund and R. Jullien[2], thermal conductivity as a heat flux to temperature gradient ratio is directly calculated in periodic simulation cells. Our calculations in a wide temperature range at which crystalline quartz exists are consistent with the experimental trend[3]. The conductivity decreases with temperature in the alpha-quartz regime, and increases after the phase transition to beta-quartz. The temperature dependence is rather small in the beta-quartz regime. [1] B. W. H. van Beest, G. J. Kramer, and R. A. van Santen, Phy. Rev. Lett. 64, 1995 (1990). [2] P. Jund, and R. Jullien, Phy. Rev. B 59, 13707 (1999). [3] H. Kanamori, N. Fujii, and H. Mizutani, J. Geophys. Res. 73, 595 (1968).

  14. Quartz Fibers For Laser Therapy In Tissue Contact

    NASA Astrophysics Data System (ADS)

    Lenz, P.; Sabber, G.; Lambert, R.; Berger, F.

    1984-03-01

    Quartz fibers not protected by a gas stream and used in tissue contact can work virtually indefinitely due to "self cleaning" and "regeneration". Tissue lesions are similar to those obtained with conventional devices.

  15. Syntectonic fluids redistribution and circulation coupled to quartz recrystallization in the ductile crust (Naxos Island, Cyclades, Greece)

    NASA Astrophysics Data System (ADS)

    Siebenaller, Luc; Vanderhaeghe, Olivier; Jessell, Mark; Boiron, Marie-Christine; Hibsch, Christian

    2016-11-01

    The presence of external fluids in metamorphic rocks has been shown to have a profound impact on rock rheology as high fluid pressure processes promote embrittlement and favor ductile deformation by recrystallization. Moreover, it has been proposed that brittle deformation guides fluid circulation and that intracrystalline deformation is responsible for fluid redistribution at the grain scale. Nevertheless, the amount of fluid present in the metamorphic ductile crust is debated and the nature of the interaction between fluids and recrystallization processes are not clearly identified. The aim of this study is to document the spatial distribution of fluid inclusions relative to microstructures in quartz grains and aggregates from veins sampled in amphibolite facies metamorphic rocks, exposed in the island of Naxos in the center of the Attic-Cycladic Metamorphic Complex in Greece. The veins, ranging from discordant structures with sharp contacts to totally transposed structures into the metamorphic foliation, display a large variety of microstructures and fluid evidences interpreted as recording exhumation processes through the ductile/brittle transition: (i) remnants of primary quartz grains contain abundant CO2-H2O fluid inclusions, decrepitated for the most part, distributed in clusters and in fluid inclusion trails, (ii) fluid inclusions with a similar composition are less abundant in recrystallized zones and in subgrains but are concentrated along grain boundaries indicating that grain boundary migration is responsible for redistribution of CO2-H2O fluids, (iii) subgrains of the last generation are almost devoid of fluid inclusions and are characterized by thick grain boundaries with abundant metamorphic fluids locally forming a continuous film. CO2-H2O fluid inclusions aligned in parallel, regularly spaced intragranular trails, locally rooted into grain boundaries, are interpreted as reflecting the spatial redistribution of these fluids in quartz slip planes

  16. Sweeping and Q Measurements at Elevated Temperatures in Quartz,

    DTIC Science & Technology

    1979-05-01

    unsuccessfully. Copper migration is of interest, since neither the metal nor the bipositive ion will migrate. However, the singly charged cuprous ion ...will migrate even though it is larger than the cupric inn. Thus, the charge on the ion seems to be more important than the ionic size. The role of...litn on.. rao ide It n.....wv and idengify by block nanbor) Sweeping Synthetic quartz Solid state electrolysis a-quartz B Elect rodiffus ion Alkali

  17. Elasticity of Single-Crystal Quartz to 10 GPa

    NASA Astrophysics Data System (ADS)

    Wang, J.; Mao, Z.; Jiang, F.; Duffy, T. S.

    2010-12-01

    Quartz is a geologically abundant and technically important mineral. Upon static compression at 300 K, alpha-quartz is found to undergo pressure-driven amorphization and related phase transition, which provide insights into the metastable behavior of materials as a function of pressure [Hemley et al.1988, Haines et al. 2001]. This metastable behavior may be related to the elastic instabilities of quartz. The elasticity of alpha-quartz is also fundamental to a range of solid-state phenomena including elastic wave propagation and the equation of state. Despite this, the single-crystal elastic constants of quartz at high pressures are poorly constrained. Previous studies of quartz elasticity at high pressures by Brillouin scattering, ultrasonic interferometry and density functional theory (DFT) exhibit discrepancies that are unresolved [Gregoryanz et al. 2000, Calderon et al. 2007, Kimizuka et al. 2007]. Here, we report new high-quality Brillouin scattering data using two different orientations of carefully characterized, untwined crystals of pure alpha-quartz compressed in hydrostatic pressure media. Our results provide new insights into the evolution of the mechanical behavior of SiO2 with compression up to 10.2 GPa. Using our measured elastic constants, we directly compared our individual Cijs with previous studies within this pressure range. Our data are more consistent with DFT calculations. Extrapolation of ultrasonic data measured below 1 GPa to high pressure yields poor agreement with our data. Equation of state data obtained from this study match previous synchrotron X-ray studies [Angel et al. 1997, Levien et al. 1980, Hazen et al. 1989] with uncertainties. Calculation of linear compressibility shows that quartz remains strongly anisotropic with compression.

  18. A study of optically contacted quartz at cryogenic temperatures

    NASA Technical Reports Server (NTRS)

    Payne, L. L.

    1982-01-01

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

  19. Surface adsorption of Cs137 ions on quartz crystals

    USGS Publications Warehouse

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

    1954-01-01

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

  20. An effective preprocessing method for finger vein recognition

    NASA Astrophysics Data System (ADS)

    Peng, JiaLiang; Li, Qiong; Wang, Ning; Abd El-Latif, Ahmed A.; Niu, Xiamu

    2013-07-01

    The image preprocessing plays an important role in finger vein recognition system. However, previous preprocessing schemes remind weakness to be resolved for the high finger vein recongtion performance. In this paper, we propose a new finger vein preprocessing that includes finger region localization, alignment, finger vein ROI segmentation and enhancement. The experimental results show that the proposed scheme is capable of enhancing the quality of finger vein image effectively and reliably.

  1. Magmatogene fluids of metal-bearing reefs in the Bushveld Complex, South Africa: Based on research data on fluid inclusions in quartz

    NASA Astrophysics Data System (ADS)

    Zhitova, L. M.; Kinnaird, J. A.; Gora, M. P.; Shevko, E. P.

    2016-01-01

    Fluid inclusions in the Merensky Reef quartz and later pegmatite veins crosscutting the Platreef rocks of the Bushveld Complex are studied by a suite of advanced high-precision methods. Based on the conducted studies, we identify a few types of fluids, some having been separated during the crystallization of volatile matter-rich residual melt of original basic magma, while others are derivatives of later felsic (granite) melts that formed crosscutting veins in fully devitrified ultrabasic and basic rocks. The earliest fluid is captured by quartz in symplectitic intergrowths with intercumulus plagioclase from the Merensky Reef pyroxenite occurs as a homogenous dense dry reduced gas (CH4-N2 ± CO2) mixture separated from the aluminosilicate melt at 800-900°C and 3050 bar. The following heterophase highly concentrated fluids (60-80 wt % NaCl eq.) separated at over 550°C and below 3050 bar transport a large number of metals. Major saline components of such fluids included Na, K, Fe, Ca, and Mn chlorides, Ca and Na sulphates and carbonates. According to LA ICP-MS analysis data, inclusions of these fluids contain high concentrations of Fe, Cr, K, and Na at the level of a few wt % and also significant contents of Cu, Sn, Sb, Mo, Au, Ag, Bi, and Ni in a concentration range from a few to thousands of ppm. Relatively lower-temperature (much higher than 450°C) fluids accompanying the crystallization of crosscutting quartz-feldspar pegmatite veins at the Platreef are also highly concentrated (from 70-80% to 40-14 wt % NaCl eq.), oxidized and metal-bearing. High concentrations of metals such as Na, K, Ca, Mn, Fe, and Pb at the level of wt % and also Ni, Co, Cu, As, Mo, Sn, Sb, and Bi (1-500 ppm) in inclusions in quartz of later pegmatite veins suggest the possible participation of magmatogene fluids related to later felsic intrusions in the redistribution of primary magmatic concentrations of metals. The oxidation of reduced heterophase fluids may be the most important

  2. Application of gold compositional analyses to mineral exploration in the United States

    USGS Publications Warehouse

    Antweiler, J.C.; Campbell, W.L.

    1977-01-01

    Native gold is a mineral composed of Au, Ag and Cu in solid solution and it usually contains one or more trace metals as lattice impurities, as mineral inclusions, in grain boundaries or in surface coatings. Alloy proportions of Au, Ag and Cu, together with certain other elements, can be thought of as constituting a gold "signature". Gold is associated with a great variety of ore deposits and has characteristic signatures for each of several types of ore deposits. Signatures for gold derived from igneous-metamorphic, hypothermal, mesothermal and epithermal deposits reflect conditions of ore formation by their content of Ag, Cu and characteristic associated elements. At higher temperatures of ore formation, gold has low Ag and high Cu content, and Bi and Pb are the most abundant trace elements. But at lower temperatures of ore formation, Ag is high, Cu is low, and P