In-situ optical reflectance characterization of ion beam irradiation damage on crystalline (quartz) and amorphous (silica) SiO2

Outline: • Motivation, aim • Complement waveguide data on silica • Optical data in quartz • Detailed analysis, i.e. both fluence kinetics and resolution • Efficiency of irradiation and analysis, samples, time... • Experimental set-up description • Reflectance procedure • Options: light source (lasers, white light..), detectors, configurations • Results and discussion • Comparative of amorphous and crystalline phases

Comparative study of ion beam-irradiation effects on silica and α-quartz: evidences for excitonic mechanisms

Introduction - SiO 2 •Simple composition and structure; Crystalline and amorphous phases •Adequate for atomistic simulations •Abundant in nature. Relevant for many technologies -Irradiation with swift heavy ions: •They provide EXTREME physical conditions •Very high excitation densities similar to high power lasers •Very high local temperatures •By playing with high energy and heavy mass (SHI) : •One can go from low electronic excitations (collisions regime) to high electronic excitations (electronic regime

A critical force constant of the structural phase transition in quartz

Long wavelength optical phonons of quartz were analyzed by a Born-Von Karman model not previously used. It was found that only one force constant associated with the turning of the Si-O bonds has a critical effect on the soft-mode frequency and the α-β transition in quartz. The square of the soft-mode frequency was found to depend linearly on this force constant which has the temperature dependence K(T)= -5.33+225.3x10-4(851-T)2/3 in units of 104 dyn/cm2.

Helium in solubility equilibrium with quartz and porefluids in rocks - a new approach in hydrology

Quartz crystals in sandstones at depths of 1200 m–1400 m below the surface appear to reach a solubility equilibrium with the 4He-concentration in the surrounding pore- or groundwater after some time. A rather high 4Heconcentration of 4.5x10E-3 cc STP 4He/cm3 of water measured in a groundwater sample would for instance maintain a He pressure of 0.47 atm in a related volume. This value is equal within analytical error to the pressure deduced from the measured helium content of the quartz and its internal helium-accessible volume. To determine this volume, quartz crystals of 0.1 to 1 mm were separated from sandstones and exposed to a helium gas pressure of 32 atm at a temperature of 290°C for up to 2 months. By crushing, melting or isothermal heating the helium was then extracted from the helium saturated samples. Avolume on the order of 0.1% of the crystal volume is only accessible to helium atoms but not to argon atoms or water molecules. By monitoring the diffusive loss of He from the crystals at 350°C an effective diffusion constant on the order of 10E-9 cm2/s is estimated. Extrapolation to the temperature of 70°C in the sediments at a depth of 1400 m gives a typical time of about 100 000 years to reach equilibrium between helium in porewaters and the internal He-accessible volume of quartz crystals. In a geologic situation with stagnant pore- or groundwaters in sediments it therefore appears to be possible with this new method to deduce a 4He depth profile for porewaters in impermeable rocks based on their mineral record.

Morphology and surface texture of quartz grains from ODP Site 105-645

The shapes and surface textures of sand-sized quartz grains from the sediments cored at Site 645 in southern Baffin Bay during ODP Leg 105 were studied to characterize the terrigenous materials and the settling processes involved in the deposition of these sediments. Here, we show a homogeneous sand fraction that results from mixing grains from various provenances. The characteristics inherited from terrestrial processes (varying degrees of wear; fluviatile, aeolian, and diagenetic features) dominate the characteristics that result from evolution in a high-energy marine environment. Thus, the influence of the last stage of sedimentation in a deep-marine environment was difficult to distinguish. However, fluctuations in the relative proportions of particular features reveal that the terrigenous material derived from sedimentary formations of Baffin Island and East Greenland or from direct abrasion of the crystalline shield, which changed through time as the dominant settling processes evolved. In particular, this study confirms the onset of major ice rafting as old as late Miocene.

Sediment constituents and quartz in the sand-sized fraction, West Florida slope and Mississippi Fan sediments

The interval between 488.2 and 513.7 m below seafloor at Deep Sea Drilling Project (DSDP) Site 615 is interpreted as a single carbonate gravity-flow deposit. The deposit has characteristics of both a debris flow and a high-density turbidity current. Comparison of the sedimentary constituents in 15 samples from this site with samples from 26 core tops from the upper West Florida continental slope and eastern Mississippi Fan shows many similarities. Shallow-water indicators, such as mollusk and echinoid fragments, occur in both suites of samples. The West Florida continental margin, therefore, is a potential provenance area. The Yucatan slope is also a possible source, but data from it are limited. The recognition of carbonate gravity-flow deposits intercalated within the Mississippi Fan refines our understanding of Pleistocene sedimentation within the Gulf basin. Deposition in the deep Gulf is dominated by the construction of the Mississippi Fan. However, this marine terrigenous depocenter is located between two large carbonate depocenters, the West Florida continental margin on the east and the Yucatan peninsula on the southwest. Periodically, the carbonate slope in these two regions fails, injecting carbonate gravity flows into the accreting terrigenous deep-sea fan.

Tongass National Forest (N.F.), Quartz Hill road access, bulk sampling permit D,Dapp,Dsup,F,Fapp; Draft mining development concepts B1; Mining development concepts : environmental impact statement.

Mode of access: Internet.

Fused-quartz fibers : a survey of properties, applications, and production methods /

Bibliography: p. 18-26.

High temperature infra-red transmission studies of ultrasil fused quartz for Project FIRE /

Photocopy.

Quartz from the uplands,

Published anonymously in 1905; now issued with slight alterations.

Rapport sur la mine de quartz aurifere de Santa Ernestina (en Cunapiru) Departamente de Tacuarembo, Republique Orientale de l'Uruguay

Mode of access: Internet.