Brazilian Quartz Research Articles

Analysis of fluid inclusion leachates from quartz by ion chromatography

20 chemical species have been detected and quantified in standard solutions using a Dionex 2000i-SP ion Chromatograph. These species are (minimum detection limits in ppb in injected sample follow each species; anions and cations listed in order of increasing retention time): F − (14), CH 3COO − (12), HCOO − (4), Cl − (6), NO − 2 (9), Br - ̊ (19), NO − 3(16), HPO 2− 4 (28), SO 2− 4 (26), C 2O 2− 4 oxalate (250), I − (20), Li + (0.5), Na +(0.7), NH + 4 (0.6), K + (1.6), Rb + (3.5), Cs + (5.9), Mg 2+ (5), Ca 2+ (15) and Sr 2+ (100). A technique has been developed to clean fluid inclusion-bearing samples and obtain fluid inclusion leachates by hand crushing ~1–2 g samples under leaching solutions in an agate mortar and then separating the leachates by vacuum filtration. High-efficiency ion removal from the crushed sample is required since gas Chromatographic H 2O analyses of sample splits have been used to calculate species concentrations in fluid inclusions. Three separate crushes using different leaching solutions are required for a complete analysis. Cleaning procedures have been established for all components involved in the crush/leach procedure, and a system blank has been obtained by crush/leach analysis of heat-treated Brazilian quartz. The contact time between the leachate and the component (i.e., agate mortar) has been established as an important control on blank levels. The technique has been applied to three samples from the Tanco granitic pegmatite: the analyses show both a ‘pegmatitic’ and a possibly external fluid component. A combined, single sample, gas and ion Chromatographic procedure has been developed to link directly the fluid inclusion volatile and leachate data.

Fluid inclusion volatile analysis by gas chromatography with photoionization micro-thermal conductivity detectors: Applications to magmatic MoS 2 and other H 2O-CO 2 and H 2O-CH 4 fluids

Eighteen fluid inclusion volatile peaks have been detected and identified from 1–2 g samples (quartz) by gas chromatography using heated (~105°C) on-line crushing, helium carrier gas, a single porous polymer column (HayeSep R; 10′ × 1 8 ″: 100 120 #; Ni alloy tubing), two temperature programme conditions for separate sample aliquots, micro-thermal conductivity (TCD) and photoionization detectors (PID; 11.7 eV lamp), and off-line digital peak processing. In order of retention time these volatile peaks are: N 2, Ar, CO, CH 4, CO 2, C 2H 4, C 2H 6, C 2H 2, COS, C 3H 6, C 3H 8, C 3H 4 (propyne), H 2O (22.7 min at 80°C), SO 2, ± iso- C 4 H 10 ± C 4 H 8 (1-butene) ± CH 3 SH, C 4H 8 (iso-butylene), (?) C 4H 6 (1,3 butadiene) and ± n- C 4 H 10 ± C 4 H 8 (trans-2-butene) (80 and −70°C temperature programme conditions combined). H 2O is analysed directly. O 2 can be analysed cryogenically between N 2 and Ar, but has not been detected in natural samples to date in this study. H 2S, SO 2, NH 3, HCl, HCN, and H 2 ca nnot be analysed at present. Blanks determined by crushing heat-treated Brazilian quartz (800–900°C/4 h) are zero for 80°C temperature programme conditions, except for a large, unidentified peak at ~64 min, but contain H 2O, CO 2, and some low molecular weight hydrocarbons at −70°C temperature conditions due to cryogenic accumulation from the carrier gas and subsequent elution. TCD detection limits are ~30 ppm molar in inclusions; PID detection limits are ~ 1 ppm molar in inclusions and lower for unsaturated hydrocarbons (e.g., ~0.2 ppm for C 2H 4; ~ 1 ppb for C 2H 2; ~0.3 ppb for C 3H 6). Precisions (1σ) are ~ ±1–2% and ~ ± 13% for H 2O in terms of total moles detected; the latter value is equivalent to ±0.6 mol% at the 95 mol% H 2O level. Major fluid inclusion volatile species have been successfully analysed on a ~50 mg fluid inclusion section chip (~7 mm × ~10 mm × ~100 μm). Initial inclusion volatile analyses of fluids of interpreted magmatic origin from the Cretaceous Boss Mtn. monzogranite stock-related MoS 2 deposit, central British Columbia of ~97 mol% H 2O, ~3% CO 2, ~ 140–150 ppm N 2, and ~16–39 ppm CH 4 (~300–350°C) are reasonable in comparison with high temperature (~400–900°C) volcanic gas analyses from four, active calc-alkaline volcanoes; e.g., the H 2O contents of volcanic gases from the White Island (New Zealand), Mount St. Helens (Washington, USA), Merapi (Bali, Indonesia), and Momotombo (Nicaragua) volcanoes are 88–95%, >90% (often >95%), 88–95% and ~93%, respectively; CO 2 contents are ~3–10%, 1–10%, 3–8%, and ~3.5%. CO 2/N 2 ratios for the Boss Mtn. MoS 2 fluids of ~ 190–220 are in the range for known volcanic gas ratios (e.g., ~ 150– 240; White Island). The ∑S content of the Boss Mtn. MoS 2 fluid prior to S loss by sulphide precipitation may have been ~2 mol% since CO 2/∑S molar ratios of analysed high-temperature volcanic gases are ~ 1.5. This estimate is supported by ∑S contents for White Island, Merapi and Momotombo volcanic gases of ~2%, ~0.5–2.5%, and ~2%. COS has been determined in H 2O-CO 2 fluid inclusions of interpreted magmatic origin from the Boss Mtn. MoS 2 deposit and the Tanco zoned granitic pegmatite, S.E. Manitoba at ~50–100 ppm molar levels, which are consistent with levels in volcanic gases. It appears that low, but significant, concentrations of C 2-C 4 alkanes (~ 1–20 ppm), C 2-C 4 alkenes (~ 1–480 ppb) and alkynes (e.g., C 3H 4) have been detected in magmatically derived fluids (Boss Mtn. MoS 2 deposit; Tanco granitic pegmatite). Significantly higher, low molecular weight hydrocarbon concentrations have been determined in a CH 4-rich (~ 2%), externally derived fluid of possible metamorphic or deep crustal origin trapped as inclusions in metasomatic wall-rock tourmaline adjacent to the Tanco pegmatite (e.g., 300/470 ppm C 2H 6; 50 90 ppm C 3H 8; 3–60 ppm C 2H 4 C 3H 6 n-C 4H 10 ).

Fluid inclusion volatile analysis by heated crushing, on-line gas chromatography; applications to Archean fluids

Eighteen fluid inclusion volatile peaks have been detected and identified from 1–2-g samples (quartz) by gas chromatography using heated (∼ 105°C) on-line crushing, helium carrier gas, a single porous polymer column (HayeSep R; 10′ × 1/8″; 100/120#; Ni alloy tubing), two temperature programme conditions for separate sample aliquots, micro-thermal conductivity (TCD) and photoionization detectors (PID; 11.7 eV lamp) and off-line digital peak processing. In order of retention time these volatile peaks are: N 2, Ar, CO, CH 4, CO 2, C 2H 4, C 2H 6, C 2H 2, COS, C 3H 6, C 3H 6, C 3H 4 (propyne), H 2O (22.7 mins at 80°C), SO 2, ±iso-C 4H 10±C 4H 8 (1-butene) ± CH 3SH, C 4H 8 (iso-butylene), (?) C 4H 6 (1,3 butadiene), and ± n-C 4H 10 ±C 4H 8 (trans-2-butene) (80°C and −70°C temperature programme conditions combined). H 2O is analysed directly. O 2 can be analysed cryogenically between N 2 and Ar, but has not been detected in natural samples to date. H 2S, SO 2, NH 3, HCl, HCN and H 2 cannot be analysed at present. Blanks determined by crushing heat-treated Brazilian quartz (800–900°C/4hrs) are zero for 80°C temperature programme conditions, except for a large, unidentified peak at ∼ 64 mins, but contain H 2O, CO 2 and some low molecular weight hydrocarbons at −70°C temperature conditions due to cryogenic accumulation from the carrier gas and subsequent elution. TCD detection limits are ∼30 ppm molar in inclusions; PID detection limits are ∼ 1 ppm molar in inclusions and lower for unsaturated hydrocarbons (e.g. ∼ 0.2 ppm for C 2H 2; ∼ 0.3 ppb for C 3H 6). Precisions are ∼±1–2%, except for H 2O (∼±13%). Major fluid inclusion volatile species have been successfully analysed on a ∼50 mg fluid inclusion section chip (∼ 7 m × ∼ 10 m × ∼ 100 μm). Two distinct end-member Archean fluids, one internal and one external, have been found related to the Tanco zoned, granitic pegmatite, SE Manitoba. The former is an H 2O (∼96%)-CO 2 (∼40%)-CH 4-N 2 fluid (S species not included) with a moderate salinity of 6.6 ± 1.3 eq. wt.% NaCl which is interpreted to be magmatic in origin, whereas the latter is an H 2O (∼97%)-CH 4 (∼2%)-CO 2 (∼0.4%)-C 2H 6-N 2 fluid with a distinctly higher salinity of ∼10–20 eq. wt% NaCl which is interpreted to be of metamorphic/lower crustal (∼2,900 bar/∼10km) origin. The volatile compositions of H 2O (∼87–94%)-CO 2 (∼6–13%)-CH 4-N 2 fluids with ∼5–6 eq. wt.% NaCl from primary inclusions from three structurally controlled, mafic-ultramafic rock hosted Archean Au-quartz vein deposits in the Barberton greenstone belt, southern Africa ( n=9) are distinctly different from the composition of the Tanco external fluid, but similar to the composition of primary fluids of interpreted

Experimental post-entrapment water loss from synthetic CO 2-H 2O inclusions in natural quartz

Artificial fluid inclusions were hydrothermally synthesized by crack healing in natural Brazilian quartz. Two original experiments E421 and E679 with a H 2O-CO 2 fluid were carried out at 835 K, 200 MPa, over 38 days, and at 856 K, 211 MPa, over 35 days, respectively. In both experiments homogeneous three-phase (a vapor and two liquids) fluid inclusions were synthesized with 22 and 20 mol% CO 2, respectively. The CO 2 phases homogenize to the vapor phase at 302.2 ± 0. l K (E679, cores 1 and 2), and to the liquid phase at 303.6 ± 0.3 K (E421, core 3), 303.9 ± 0.2 K (E421, core 4). The CO 2-H 2O phases homogenize to the vapor phase at 573.6 ± 0.4 K (E679, core 1 and 2), 575.6 ± 1.5 K (E421, core 3), and 576.1 ± 0.8 K (E421, core 4). Micro cracks and the new hydrothermally precipitated quartz, which directly surrounds the inclusions, were studied with TEM and SEM. The healed cracks have numerous growth imperfections that provide many possible routes for fluid transport. Dislocation arrays and small channels were observed and are often connected to the inclusions. Quartz cores 3 and 4 were subsequently re-equilibrated for 21 and 27 days respectively under hydrothermal conditions with pure H 2O, at both a lower pressure of 100 MPa (E463) and a higher pressure of 365 MPa (E490) than that of the original experiment E421. The temperatures of the re-equilibration experiments were equal to the original (835 K). In E463, the internally overpressured re-equilibration, only traces of solution and precipitation of quartz were evident with minor transformation of the angular walls to more rounded forms. Volume increase for some inclusions resulted from decrepitation. The homogenization of the CO 2-H 2O phases to the gas phase occurred at higher temperatures, up to 604 K. In E490, the internally underpressured re-equilibration, major solution and precipitation resulted in the transformation of irregular shaped inclusion walls and formation of secondary inclusions halos. The homogenization of the CO 2-H 2O phases to the gas phase occurred at lower temperatures, down to 565 K. The fluids in inclusions from both re-equilibration experiments were found to have lower densities than the original fluids synthesized. This is quantified by the increased volumetric proportions of CO 2 vapor. The CO 2 fraction in inclusions was found to have increased, by up to 54 mol%. The change in homogenization temperatures and the decrease in the proportions of H 2O in the original inclusions favours a model in which preferential transport of H 2O occurs along mobile dislocation lines, small intercrystalline nanocracks, and/or channels. Results from experiment V1 and V4, using cores 1 and 2, indicate that the changes observed in the re-equilibration experiments are not artifacts of the experimental method.

Impurity Content Characterization of Brazilian Quartz Lascas

Lattice impurities (Al, Li, Fe) free from the influence of cations in inclusion liquid were evaluated by atomic absorption spectrophotometry (AAS) in quartz lascas taken from 10 deposits with known localities in three states, Minas Gerais, Tocantins and Bahia. Levels of Al content and associated Li content depend on the localities of deposits. Quartz deposit regions with high Al content are composed of granite, gneiss, and pegmatite as surrounding rocks. It was concluded that the charge compensation for Al-Si substitution in quartz lascas was realized substantially by the formation of Al-Li and Al-OH centers which were confirmed from the linear relation of Al-Li plots by AAS data and IR spectra due to Al-OH center. The variety in Al-Li and Al-OH correlations was attributed to the fluctuation of growing conditions of quartz in nature.

Oxygen diffusion in quartz: Dependence on temperature and water fugacity

Oxygen self-diffusion coefficients ( D) were determined in single crystals of Brazilian quartz by measuring 18O concentration profiles with an ion microprobe. In the α-quartz field at 450–590°C and 100-MPa confining pressure, for diffusion parallel to c, the Arrhenius relation is described by the parameters D 0 = 2.9 · 10 −5 m 2 s −1 and Q = 243 ± 17 kJ (g-at. O) −1. The diffusion rate was also measured in β-quartz from 5- to 350-MPa confining pressure and at 700°C as a function of water, hydrogen and oxygen fugacities as well as for different proton activities. There is a good correlation of D with water fugacity, no correlation with oxygen nor hydrogen fugacities, and no correlation with proton activity over the range for which this parameter could be fixed independent of the water fugacity, The available evidence suggests that the oxygen-bearing species responsible for the rapid transport of oxygen under hydrothermal conditions is molecular water. The rate controlling step for oxygen diffusion may be either the rate of migration of water molecules, or the rate of oxygen exchange between the water molecules and the quartz structure.

The Role of Organic Acids in Feldspar and Quartz Dissolution at 100 degree C/347 Bars: An Experimental Study

Water-soluble organic anions are capable of dissolving feldspar and quartz under diagenetic conditions and maintaining high levels of Al and Si in solution. It has been shown that abundant organic acids are released prior to and possibly during hydrocarbon generation. The combination of dissolution and complexing capacity suggests that organic acids may be of significant importance in mineral dissolution and secondary porosity development in sandstones in the diagenetic environment. Dissolution of albite and quartz was studied using flow-through hydrothermal vessels at 100C and 347 bars. Buffered 5,000 ppm acetate/500 ppm oxalate solutions (pH = 4.7) were passed through sand packs of 250-500 {mu}m Amelia albite (Ab{sub 97-99}) and Brazilian hydrothermal quartz. The solid starting material was cleaned ultrasonically to remove any adhering ultrafine particles. Organic species were analyzed using ion chromatography. Steady-state concentrations of SiO{sub 2} and Al average 237 ppm and 50 ppm, respectively. These values are significantly higher than predicted by the solubilities of common aluminosilicate clay minerals in water. This suggests that the amount of Al held in solution by complexing is very high, significantly reducing the amount of Al available for clay precipitation. The lack of authigenic aluminosilicates indicates the efficiency of the organics in removingmore » and transporting Al and Si. Future work with aliphatic and aromatic organics, as well as inorganic acids, will allow comparison of the role of various aqueous species in mineral dissolution and secondary porosity development.« less

Chemical textures on quartz grains: An experimental approach using salts

AbstractTwo groups of fresh crushed Brazilian quartz grains (0.4–0.6 mm) were placed in 10 ml of various saturated salt solutions (sodium sulphate, sodium chloride, magnesium sulphate, sodium carbonate, and sodium carbonate and soil). One group was placed in an environmental cabinet programmed to simulate summer diurnal temperature and relative humidity values recorded in Wheeler Valley, a dry valley in southern Victoria Land, Antarctica. The other group was allowed to remain at normal laboratory conditions. Quartz grains from both groups were removed at pre‐selected intervals for examination using the scanning electron microscope. After 50 hours chemical surface textures were formed on the quartz grains in all but the sodium sulphate solution. At the 140 hour interval all the salt solutions used were producing chemical surface textures on the quartz grains. This paper demonstrates that chemical surface textures can be produced on quartz grain surfaces by saturated salt solutions in a short period of time and may prove to be representative of chemical surface textures produced in a saturated saline environment.

Phase relations in the system NaCl-KCl-H2O. III: Solubilities of halite in vapor-saturated liquids above 445°C and redetermination of phase equilibrium properties in the system NaCl-H2O to 1000°C and 1500 bars

Halite solubilities along the three-phase curve in the binary system NaCl-H2O determined by DTA experiment can be represented by the equation Wt.% NaCl (±0.2) = 19.39 − 0.0364t + 3.553 × 10−4T2 − 2.298 × 10−7T3, where 447≦ T ≦ 800°C. Even though these halite solubilities are up to ~7 wt.% higher than those reported in literature, extrapolated values at temperatures below 447°C merge with the literature values. It is considered that the equation adequately describes halite solubilities between 382 and 800°C. The newly established solubility data are believed to be more reliable because they are compatible with data obtained by using synthetic fluid inclusions and with the observed DTA signals and also because they were measured in a relatively corrosion-free system. In an earlier publication (GUNTER et al., 1983), we were puzzled greatly by multiple and rather unreproducible DTA peaks appearing during isobaric cooling (heating experiments were nondefinitive) at pressures below about 500 bars. These DTA signals apparently suggested that the “halite liquidus” swung sharply upward in temperature as pressure decreased from about 500 bars to that of the halite-saturated boiling curve. Further analysis of the data and helpful discussions with several individuals have revealed that the behavior is a consequence of the initial (precooling) separation of the fluid into NaCl-poor gas and NaCl-rich liquid that failed to homogenize in the short time encompassed by the DTA experiments. The present analysis is based on extrapolations of the dPdT slopes from pressures above 500 bars. Through use of these new halite solubility data and the data from synthetic fluid inclusions [formed by healing fractures in inclusion-free Brazilian quartz in the presence of two coexisting, immiscible NaCl-H2O fluids at various temperatures and pressures (Bodnar et al., 1985)], phase equilibria in the system NaCl-H2O have been redetermined to 1000°C and 1500 bars.

Determination of precise X-ray diffraction angles by fast Fourier transform

A new analytical method is presented for the separation of two or more closely overlapping X-ray diffraction lines using the narrowly distributed Gaussian function and one-dimensional fast Fourier transform pair. To test the method, the diffraction lines associated with characteristic Kα1 and Kα2 rays are measured by an X-ray diffractometer using a Brazilian quartz powder as a standard sample. It is found that the observed diffraction lines can be completely separated into Kα1 and Kα2 lines and that the accuracy of those diffraction angles is better than 2 × 10-4.

Correlation of surface free energy changes and flotability of quartz

Samples of natural Brazilian quartz were variously covered with dodecylamine chloride (DDACl) from methanolic solutions. Then they were subjected to flotation tests and ζ potential measurements in doubly distilled water. In the second series of experiments the samples covered with DDACl were then covered with known amounts of n-hexane or n-hexanol and ζ potentials were determined. From this relationship dispersion and polar components of surface free energy of the quartz samples were calculated. The results obtained allow us to conclude that already at 0.25 statistical monolayer of DDACl the sample of quartz floats in 90%, which is connected with drastic reduction of the polar component of quartz surface free energy from 115 mJ/m 2 (bare surface) to 7.2 mJ/m 2. The maximum flotation activity appears at one statistical monolayer of the amine, and corresponds to complete reduction of the polar interactions at the quartz-water interface.

Synthetic fluid inclusions in natural quartz. III. Determination of phase equilibrium properties in the system H 2O-NaCl to 1000°C and 1500 bars

Phase equilibria in the system H 2O-NaCl have been determined to 1000°C and 1500 bars using synthetic fluid inclusions formed by healing fractures in inclusion-free Brazilian quartz in the presence of the two coexisting, immiscible H 2O-NaCl fluids at various temperatures and pressures. Petrographic and microthermometric analyses indicate that the inclusions trapped one or the other of the two fluids present, or mixtures of the two. Salinities of the two coexisting phases were obtained from heating and freezing studies on those inclusions which trapped only a single, homogeneous fluid phase. Results of the present study are consistent with previously published data on the H 2O-NaCl system at lower temperatures and pressures, and indicate that the two-phase field extends well into the P- T range of most shallow magmatic-hydrothermal activity. As a consequence, chloride brines exsolved from many epizonal plutons during the process of “second-boiling” should immediately separate into a high-salinity liquid phase and a lower salinity vapor phase and produce coexisting halite-bearing and vapor-rich fluid inclusions. This observation is consistent with results of numerous fluid inclusion studies of ore deposits associated with shallow intrusions, particularly the porphyry copper deposits, in which halite-bearing and coexisting vapor-rich inclusions are commonly associated with the earliest stages of magmatic-hydrothermal activity.

Selected etching and annealing properties of Brazilian quartz crystals for solid state track recorder applications

The etching and annealing properties of Brazilian quartz crystals are under investigation to determine their suitability for use as solid state track recorders (SSTR) and damage monitors in nuclear reactor environments, where temperatures and neutron fluences are high. Observer objectivity in counting fission tracks has been established at the 1 to 2% level, and a method of standardizing chemical etching from one sample of quartz to another has been found. A method has also been found to make corrections for track loss due to thermal annealing in terms of the effect of the annealing on the track size in the direction of maximum bulk etch rate parallel to the 100 plane, provided the fractional track loss does not exceed approx. 40%.

Transmission electron microscope study of quartz microstructures produced by aeolian bombardment

ABSTRACTThe near‐surface structure produced by laboratory aeolian bombardment of Brazilian quartz has been studied with transmission electron microscopy (TEM). Thin specimens of the abraded surface were prepared by a one‐sided ion etching technique, and control specimens of unabraded material were prepared by standard ion etching methods. The abraded sample exhibited a vastly larger number of defects than the unabraded specimen. The abraded sample contained areas with very little surface disruption, presumably where pieces of material up to several tens of microns in diameter had broken away. Other areas of the abraded surface were extremely disrupted, with open and closed microcracks spaced from a few tens of angstroms to a few microns apart. Electron diffraction indicated significant rotation among submicron blocks bounded by the fractures. These observations suggest that surface disruption occurs primarily by a mechanism involving brittle fracture, rather than plastic deformation.This study demonstrates the feasibility of studying the effects of abrasion on near‐surface structure with TEM. The degree and scale of fracturing also suggest a mechanism for forming submicron particles in quantity during aeolian abrasion.

Stress-dependent morphological features on fracture surfaces of quartz and glass

Stress dependent morphological features have been found on tensile fracture surfaces of natural Brazilian quartz and synthetic quartz specimens which were flexed in air at room temperature. These features are similar to stress dependent morphological features found on fracture surfaces of pyrex, soda-lime and lead glass when deformed in similar experiments. For glass, the relevant morphological feature is the fracture “mirror”, a planar region surrounding the initial flaw. Stress dependent index features chosen for measurement in quartz depend upon the crystallographic orientation on the fracture surface. Their development is related to the crack-system energy but, in contrast to glass, the features are not directly related to crack branching. The experimental results follow an equation of the form: A∗ = σ f r ∗ 1 2 where σ f is the fracture stress, r∗ is the size of a particular morphological feature (e.g. the “mirror” radius in the case of glass) and A∗ is a constant. From the magnitudes of A∗ and the fracture toughness determined in these experiments we conclude that the natural Brazilian quartz used in this study has significantly higher resistance to fracture than synthetic quartz.

The relation between the crystallography of quartz, and upturned aeolian cleavage plates

ABSTRACTThe relation between the crystallography of artificially abraded quartz sand grains and aeolian surface textures has been studied using an X‐ray precession camera and the scanning electron microscope (SEM). Crushed Brazilian quartz was sieved to between 250 and 350 μm, eroded in a paddle wheel device which simulated aeolian action at 8 m s−1 for 3 h, and photographed with the SEM. A typical grain was selected and over 1100 photographs were combined to create a 3 × 3 m photomosaic; because of the large size, it was possible to observe and measure the angular and linear relations between the various features. After the c axis direction in the grain was determined by precession X‐ray analysis, the most important aeolian features were related to the crystallography of quartz. The upturned plates or cleavage plates probably represent traces parallel to r(10Ī1) and z(01Ī1) cleavages in quartz. Blocky areas appear to be an expression of a cleavage parallel to m(10Ī0). In addition, plate spacing on thirty‐five experimental, modern, and ancient quartz sand grains is fairly constant. Assuming that abrasion in most sedimentary environments acts in the same manner with respect to quartz crystallography, much of the fine silt and clay in sediments and sedimentary rocks may be the result of cleavage following abrasion parallel to the r and z cleavage planes, while the less common blocky particles are probably the result of cleavage parallel to the m planes.

Application of a new Raman microprobe spectrometer to nondestructive analysis of sulfate and other ions in individual phases in fluid inclusions in minerals

Rosasco et al. (1975), reported the first successful application of laser-excited Raman spectroscopy for the identification and nondestructive partial analysis of individual solid, liquid, and gaseous phases in selected fluid inclusions. We report here the results of the application of a new instrument, based on back-scattering, that eliminates many of the previous stringent sample limitations and hence greatly expands the range of applicability of Raman spectroscopy to fluid inclusions. Fluid inclusions in many porphyry copper deposits contain 5–10 μm ‘daughter’ crystals thought to be anhydrite but too small for identification by the previous Raman technique. Using the new instrument, we have verified that such daughter crystals in quartz from Bingham, Utah, are anhydrite. They may form by leakage of hydrogen causing internal autooxidation of sulfide ion. Daughter crystals were also examined in apatite (Durango, Mexico) and emerald (Muzo, Colombia). Valid analyses of sulfur species in solution in small fluid inclusions from ore deposits would be valuable, but are generally impossible by conventional methods. We present a calibration procedure for analyses for SO 4 2− in such inclusions from Bingham, Utah (12,000 ± 4000 ppm) and Creede, Colo. (probably < 500 ppm). A fetid Brazilian quartz, originally thought to contain liquid H 2S, is shown to contain only HS − in major amounts.

Acoustic emissions from stress-induced dauphiné twinning in quartz

Dauphine (electrical) twins have been introduced into quartz crystals by means of suitably oriented mechanical stresses. Stress-induced twinning was observed optically by means of the photoelastic effect. Accompanying acoustic emission, first detected by ear, was quantitatively measured with a piezoelectric transducer and a suitable filtering and amplification system. Synchronized sound cinematography has been used to correlate the acoustic emission with visual observation of twinning. The resultant motion picture has been used to determine the stress levels required for twinning in Brazilian quartz and to set limits on the twin wall velocity. The possible relevance to rock noise and earthquake precursory phenomena is discussed.

Heat treatment of pure silica glass studied by positron annihilation

The crystallinity of silica glass fused from Brazilian quartz was studied by Doppler-broadening techniques after heat treatment in the temperature range between 1000°C and 1500°C.

Measurement of the Piezoelectric Coefficient of Quartz Using the Fabry-Perot Dilatometer

The piezoelectric strain coefficient d11 has been determined in alpha quartz using a Fabry-Perot dilatometer to measure the strain. The results obtained with eight specimens of Brazilian quartz give an average value of (6.81±0.03) ×10−8 cm/statvolt or (2.27±0.01) ×10−12 m/V. This value is compared with those reported in the literature which range from 5.5 to 7.1×10−8 esu.