Range Of Delta Research Articles

Sulfur and oxygen isotope studies of melt-country rock interaction, Babbitt Cu-Ni deposit, Duluth Complex, Minnesota

The Babbitt Cu-Ni deposit, formerly known as Minnamax, occurs within troctolitic and gabbroic rocks of the Precambrian Duluth Complex. Both massive and disseminated mineralizations are found in the deposit. Pyrrhotite, cubanite, chalcopyrite, and minor pentlandite mineralization occurs near the basal contact with pelitic metasedimentary rocks of the Virginia Formation or higher in the igneous sequence associated with abundant country-rock xenoliths (cloud zones). Sulfur and oxygen isotope studies have been carried out to evaluate the importance of melt-country rock interaction in localizing sulfide mineralization.The delta 34 S values of pyrrhotite plus pyrite from the Virginia Formation located outside the contact aureole range from 5.6 to 13.7 per mil. Pyrrhotite from footwall Virginia Formation hornfels or inclusions in the basal zone exhibits delta 34 S values ranging from 1.5 to 6.2 per mil, whereas delta 34 S values of pyrrhotite from xenoliths in cloud zones range from 2.6 to 21.4 per mil. Isotopic values of basal zone Cu-Ni sulfides range from 6.0 to 13.0 per mil, with a mode at 8 to 9 per mil. Two features highlight basal zone delta 34 S values. First, delta 34 S values of sulfide mineralization are higher than those of pyrrhotite in immediately adjacent Virginia Formation hornfels. Second, higher grade ore areas (> 1% Cu) show 34 S enrichment, with delta 34 S values in the range of 9 to 13 per mil. Sulfides in cloud zones show a wide range in delta 34 S values, from 0.7 to 19.7 per mil. Sulfur isotope data suggest that most of the sulfur found in the deposit has been derived from sedimentary country rocks. However, an in situ process of sulfur derivation is not indicated. Sulfur in basal mineralized zones must have been derived at depth within an auxiliary magma chamber or during magma ascent and emplacement. Isotopic homogenization was not achieved during the sulfide-forming process as evidenced by the spatial variability of delta 34 S values.Oxygen isotope values of both mildly metamorphosed Virginia Formation and footwall hornfels range from 8.2 to 14.0 per mil. Inclusions of Virginia Formation show pronounced isotopic effects due to interaction with melt. Xenolith margins may have values as low as 7 to 8 per mil and are depleted in 18 O with respect to xenolith interiors. The delta 18 O values of igneous rocks from the Babbitt deposit range from 3.9 to 12.2 per mil. Zones of 18 O depletion are rare and suggest that exchange with a low 18 O fluid phase was spatially restricted. Anomalous delta 18 O values in excess of 7 to 7.5 per mil are common throughout the deposit but are limited to within 3 m of Virginia Formation xenoliths. A model of diffusion-controlled 18 exchange between igneous material and xenoliths best describes the delta 18 O distribution. Devolatilization and desilicification of the xenoliths occurred early in their history, when physical mixing in the host magma was possible. Addition of high 18 O material from these processes into a large volume of melt affected delta 18 O distributions only slightly. Continued exchange of oxygen after major cation transfer produced the observed delta 18 O profiles.In the case of basal zone Cu-Ni mineralization at Babbitt, isotopic evidence indicates that sulfide saturation was not caused by in situ addition of sulfur, silica, or oxygen. Sulfide saturation is thought to have been achieved at depth, triggered by assimilation of large quantities of sulfide liberated through devolatilization reactions occurring in country rocks.

Oxygen isotope evidence for the mixing of magmatic and meteoric waters during tin mineralization in the Mole Granite, New South Wales, Australia

Oxygen isotope measurements of quartz in the tin-mineralized, Permian Mole Granite, New South Wales, support a model of progressive mixing of magmatic water and surface-derived water of meteoric origin in mineralizing hydrothermal circulation systems.The magmatic water, observed as multiphase fluid inclusions in hydrothermal quartz-biotite-orthoclase-topaz-bearing pegmatites, had a high temperature (550 degrees C), high salinity (55-75 wt %), and a delta 18 O SMOW value of about 8.7 per mil. The initial magmatic delta 18 O SMOW value of the granite is estimated to be about 9 per mil.The meteoric water, observed as liquid-rich fluid inclusions in quartz from late veins of quartz-sphalerite-galena, had a low temperature (250 degrees C), low salinity (3-5 wt %), and a delta 18 O SMOW value of-15 per mil. Permian meteoric water is expected to be light isotopically, owing to a near polar (70 degrees ) palcolatitude for the New England fold belt.Quartz from cassiterite-quartz-chlorite-sericite ores has a wide range of delta 18 O values, from -2.8 to +6.7 per mil. This is intermediate between the values for quartz deposited from magmatic and from meteoric waters. The fluid inclusions in these samples have homogenization temperatures of about 300 degrees C and a wide range of salinities (25-35 wt %). The variation in isotopic composition observed for quartz is attributed to a fluctuating isotopic composition of the hydrothermal solutions resulting from variable degrees of mixing of magmatic and meteoric water. Cassiterite has a narrow range of delta 18 O (-5.9--7.2ppm), which suggests precipitation of cassiterite over a narrow range of mixing of the hydrothermal fluids. Three cassiterite-quartz mineral pairs, with textures indicating synchronous crystallization, imply cassiterite-water fractionations of -2.2 per mil at 300 degrees C and -4.1 per mil at 370 degrees C.Hydrogen isotope data are less systematic due to postcrystallization isotopic exchange of hydrous minerals and the presence of younger fluids in secondary fluid inclusions in quartz.

Use of Solubility Parameters of Drug and Vehicle to Predict Flux Through Skin

The solubilities of theophylline in, and fluxes through skin from, isopropyl myristate, octanol, dimethylformamide, propylene glycol, ethylene glycol, and formamide have been determined experimentally. Values for experimental permeability coefficients (Kp) corresponding to the respective fluxes were determined from, flux/solubility = Kp, which were then compared with values for the respective theoretical partition coefficients (PC) calculated from the known solubility parameters for the vehicles (delta v), theophylline (delta i) and skin (delta s). There was a good correlation for theoretical log PC - 2.52 = experimental log Kp for vehicles exhibiting solubility parameters in the range of delta v = 12-18 (cal/cm3)1/2. This allows relative fluxes to be determined from calculated theoretical partition coefficients and experimentally determined solubilities in that range. For vehicles or mixtures of vehicles exhibiting solubility parameters in the range of delta v = 8-12 (cal/cm3)1/2 large increases in fluxes and permeability coefficients, compared with those predicted from the results in the delta v = 12-18 (cal/cm3)1/2 range, were observed because of vehicle effects on the skin caused by the similarity in solubility parameters of those vehicles to that of skin. Qualitatively, fluxes and permeability coefficients were found to be inversely dependent on drug solubility in the vehicles with a minimum that corresponded approximately to the point where delta i = delta v.

Geologic, sulfur isotope, and fluid inclusion studies of the Sannae W-Mo Mine, Republic of Korea; comparison of sulfur isotope systematics in Korean W deposits

The Sannae tungsten-molybdenum mine is located approximately 60 km north of Pusan within the Gyeongsang basin of the southern Korean peninsula. The hydrothermal vein-type deposits which comprise the mine occur within an Upper Cretaceous magnetite series quartz monzonite stock which intrudes Middle Cretaceous sedimentary and volcanic rocks. Mineralization can be separated into three stages (with declining temperature): early molybdenum, main tungsten, and late carbonate stages. Fluid inclusion data suggest that most of the molybdenite was deposited at temperatures between 550 degrees and 350 degrees C; wolframite and scheelite, between 450 degrees and 300 degrees C; and carbonates, between 300 degrees and 180 degrees C. Salinities of mineralizing hydrothermal fluids ranged from 5 to 25 equiv wt percent NaCl, with a marked decrease in salinity between main tungsten and late carbonate stages. Fluid inclusion evidence of boiling suggests a range of pressures from about 100 to 300 bars. This range is consistent with a depth of mineralization near 1,250 m under pressure conditions that alternated between hydrostatic and lithostatic.Sulfur isotope compositions of sulfides from the mine have the following ranges of delta 34 S values: molybdenite, 5.2 to 6.0 per mil; and pyrite, 6.0 to 7.1 per mil. The delta 34 S (sub H 2 S) values calculated for these minerals are consistent with an igneous source of sulfur with a delta 34 S (sub Sigma S) value near 4.0 to 5.0 per mil.The geology, mineral paragenesis, and sulfur isotope and fluid inclusion data of the Sannae W-Mo mine are very similar to data from other Korean tungsten deposits. The total range of delta 34 S (sub H 2 S) values of sulfides for all the Korean tungsten deposits is -2 to +7 per mil; however, there is a narrow range of delta 34 S values for individual deposits. The sulfur isotope compositions and systematics of Korean tungsten deposits are nearly identical to those of Japanese deposits associated with magnetite series granitoids and may be explained by the separation of a sulfur-bearing magmatic fluid from a granitic melt under different oxidizing conditions.

Stable isotope geochemistry and metal zonation at the Iron Mountain Mine, West Shasta District, California

The Iron Mountain volcanogenic massive sulfide deposit is contained in a Devonian bimodal suite of island-arc volcanic rocks in the southern end of the West Shasta mining district. It is the largest of the West Shasta ore deposits and is composed of a series of structurally related orebodies that have been separated by a series of high-angle normal faults. The ore deposits are predominantly pyritic with subordinate chalcopyrite and sphalerite. The major gangue mineral of the massive sulfide is quartz which occurs in veins and lenses as well as interstitial to the sulfides in the orebody. The deposit shows metal zonation with copper and zinc grade increasing in the central and upper portions of the orebody.Whole-rock oxygen and hydrogen isotope analyses of the rocks underlying the orebodies show the effects of hydration and silicification, from a hydrothermal fluid composed of seawater. Pyrite from the massive ore has a narrow range in delta 34 S values from 3.2 to 5.3 per mil and shows no variation with texture, stratigraphic position, or grade of ore. The narrow range can be explained by a single hydrothermal event of relatively constant isotopic composition, whose principal source of sulfur was leached magmatic sulfur from the underlying rocks. Calculated temperatures from coexisting chalcopyrite-pyrite mineral pairs yield temperatures predominantly in the 400 degrees to 700 degrees C range. The unrealistically high temperatures indicate disequilibrium conditions although clustering of temperatures suggests some regularity governing the isotopic relations.The isotopic values of interstitial quartz in the orebodies show a trend of decreasing delta 18 O values with depth. This isotopic trend along with the similarity in isotopic values between the lower portion of the orebody and the quartz veins in the underlying rock suggests that the quartz was deposited from fluids moving through a temperature gradient of approximately 150 degrees C.From the isotopic and metal zonation data, Iron Mountain is interpreted to have formed from continued zone refining in which successive replacement of sulfides has accounted for both the isotopic relationship in the coexisting sulfide mineral pairs, the isotopic trends in interstitial quartz, and the metal zonation.

Oxygen and carbon isotope variations in gold-bearing hydrothermal veins in the Kushikino mining area, southern Kyushu, Japan

The Kushikino mine is located in the Tertiary gold mining areas of southern Kyushu, Japan. The ore deposits occur in andesitic volcanics as fissure-filling epithermal veins, consisting of gold- and silver-bearing quartz and calcite with minor amounts of adularia, sericite, and sulfides. Quartz and calcite are dominant throughout the mineralization. Three major stages of mineral deposition are recognized as follows; (I) first opening of fractures and deposition of translucent quartz, (II) repeated fracturing and the main stage of the Au-Ag mineralization with deposition of milky quartz and calcite, and (III) deposition of barren calcite.Oxygen and carbon isotope compositions were determined for quartz and calcite from the Kushikino 1 (the Champion vein) and the Arakawa 4 veins. The ranges of the isotopic compositions of the minerals are as follows (numbers of determination are given in parentheses):Vein Mineral delta 18 O SMOW (ppm) delta 13 C PDB (ppm)Kushikino 1 Quartz 5.5 to 9.7 (29) Calcite 2.3 to 8.5 (13) -11.2 to -8.3 (13)Arakawa 4 Quartz 8.4 to 10.7 (8) Calcite 5.6 to 9.9 (5) -9.7 to -8.9 (5)No distinct difference in oxygen isotope compositions is observed between the stage I translucent quartz and the stage II milky quartz. In stage II both quartz and calcite have wide ranges in delta 18 O values, extending for the entire compositional ranges of the veins mentioned above. The stage III calcite has higher delta 18 O values than does the stage II calcite.The wide range in the delta 18 O values of the stage II minerals corresponds to a temperature decrease from 220 degrees to 140 degrees C. The isotopic data can be interpreted to indicate a mixing of deep hydrothermal fluid and low-temperature meteoric ground water, if the deep hydrothermal water was unexchanged or partially exchanged meteoric water with a limited range of delta 18 O values (lower than - 3ppm at 300 degrees C). Incorporation of a large quantity of high delta 18 O thermal waters is not plausible. The delta 13 C-delta 18 O trend of calcite is interpreted to show a temperature decrease and a change in the carbon species of the fluid. Calcite crystallized in equilibrium with a fluid in which H 2 CO 3 was dominant at temperatures higher than 140 degrees or 150 degrees C, whereas HCO (super -) 3 was dominant at lower temperatures. This accords with inferences based on phase equilibria. The stage III calcite crystallized in a lower temperature range of the HCO (super -) 3 -dominant field.Judging from fluid inclusion data and mineral assemblages, changes in pressure or pH of the fluid were not so important in stage II. The quartz-calcite deposition and Au-Ag mineralization in Stage II may have taken place as a result of rapid cooling of the fluid due to mixing. Mixing of two fluids, both of which were saturated with calcite but which had different temperatures, caused supersaturation of the calcite and, thus, deposition of it along with a temperature decrease. Deposition of a large quantity of calcite in stage III would be due to a pressure decrease caused by the opening of fractures at shallow depths. A subsequent decrease in pH of the fluid may have caused the kaolinite alteration near the surface.

A hydrogen and oxygen isotope study of the San Cristobal Mine, Peru; implications of the role of water to rock ratio for the genesis of wolframite deposits

Oxygen and hydrogen isotope ratios were measured from vein minerals and extracted fluid inclusion waters from the San Cristobal wolframite-base metal deposit in Peru. Oxygen isotope values for quartz range from 9.8 to 14.4 per mil and for wolframite from 0.6 to 4.6 per mil. The calculated delta values at 300 degrees C for water in equilibrium with quartz and wolframite are delta 18 O = 2.8 to 7.3 per mil for quartz and 1.4 to 5.4 per mil for wolframite. Hydrogen isotope values show an overall range of delta D = -58 to -148 per mil, but the range for any given mineral is much smaller. These data are interpreted in light of a model which examines the effect of temperature and water to rock ratio on the isotopic compositions of meteoric waters exchanging with granite. In a rock-dominated system an isotopically exchanged water becomes depleted in delta 18 O and enriched in delta D as the temperature of exchange decreases. When the water to rock ratio is also allowed to vary, a wide variety of water compositions is generated. The isotopic composition of minerals from San Cristobal can be interpreted as the result of deposition from a meteoric water which has undergone isotopic exchange with a granite at 400 degrees C, with a water to rock ratio ranging from 0.01 to 0.003. Isotopic data taken from two other wolframite deposits, Pasto Bueno (Landis, 1972) and Panasquiera (Kelly and Rye, 1979) are reinterpreted using the model developed for San Cristobal. Both sets of data are consistent with the hypothesis that wolframite deposits are formed by meteoric waters which have experienced exchange at very low water to rock ratios (<0.05). The importance of the low water to rock ratio may be related to the way in which tungsten is leached from a crystallized pluton.

Fluid inclusion and stable isotope studies on some Caledonian sulfide-bearing veins in Sweden

Sulfur isotope measurements have been made on sulfides from Caledonian sulfide-bearing calcite veins in the Precambrian basement of the Swedish Caledonides and from sulfide-bearing quartz veins within the Caledonides in Sweden. The calcite veins show a narrow range in delta 34 S of the sulfides, between -7 and +1 per mil vs. CDT, whereas the quartz veins show a much wider range, from -12 to +14 per mil. A more detailed study of sulfide sulfur in one quartz vein deposit, Nasafjll, however, shows little variation within that deposit, with most delta 34 S values in a narrow range between 7 and 10 per mil. No vein deposits with sulfur as heavy as that of the sandstone-hosted impregnation ores of Vassbo and Laisvall (delta 34 S = 17-28) have been found in this study.Fluid inclusion data from the Aakerlandet calcite vein suggest that it formed at temperatures between 75 degrees and 165 degrees C (not corrected for pressure) during mixing between two hot saline brines. Carbon isotope values, with delta 13 C of the calcite close to -15 per mil vs. PDB, point to a significant contribution of reduced carbon to the ore-forming fluid. These data are used to reconstruct the chemical environment in terms of pH and oxygen fugacity for the formation of the Aakerlandet deposit. A similar tentative reconstruction is also made for the Nasafjll quartz vein deposit.The sulfur in the calcite veins is probably derived from leaching of sulfides in the granitic basement, in contrast to the organic reduction of seawater sulfate which has been proposed for the sandstone-hosted impregnation ores. Sulfide sulfur in the quartz veins may be a mixture of sulfide and sulfate sulfur leached both from the granitic basement and the overlying metasediments and metavolcanics of the Caledonian nappes, the sulfate being inorganically reduced through reactions with wall rocks prior to sulfide precipitation. The sulfur isotope data thus suggest different processes to have been involved in the formation of the different types of deposits. Together with lead isotope data, the sulfur data show that the Caledonian quartz and calcite veins in Sweden are not directly related to the Caledonian strata-bound ores but form distinct ore types of their own.

Opioid peptides and central control of blood pressure.

The role of endogenous opioids in central modulation of baroreceptor reflex function has been assessed in rabbits and in man using stable enkephalin analogues and synthetic opiates with a range of mu, delta and kappa opiate receptor agonist specificity. In addition the effects of naloxone, a mu opiate receptor antagonist, have been studied. In rabbits descarboxy-leu-enkephalin (RX783016) given by intracisternal injection reduced baroreflex sensitivity as assessed by heart rate responses to phenylephrine, sodium nitroprusside and controlled haemorrhage. These effects were prevented by intravenous naloxone. Naloxone alone increased the slope of the heart period: mean arterial pressure relationship and thus increased baroreflex sensitivity. In conscious man essentially similar results were found following intravenous dosing with a stable met-enkephalin analogue (DAMME, FK33824) or naloxone with decreases and increases respectively in the sensitivity of baroreflex responses to sodium nitroprusside. In rabbits and man arterial baroreceptor reflexes mediating heart rate responses can be pharmacologically modified by exogenous opiates and may be under some tonic endogenous opiate peptide influences.

Ontogenic development of autoregressive component waves of waking EEG in normal infants and children

Waking EEGs of 150 normal children aged from 20 days to 15 years were subjected to analysis. Discrete time series of an artifact free segment of the EEG record at 50 samples/sec for twenty seconds was generated and autoregressive (AR) and component analyses were carried out with a minicomputer PDP 11/40 (DEC). The results may be summarized as follows: 1) In the group of 1 year old and less, the power increased with the monthly age, whereas the bio-informing activity amount decreased. In those older than 1 year, both parameters showed maximal values at 1 year and then decreased with age, and the decreases were marked from 1 to 3 years. 2) The first- and second-order component activities of 129 and 677 waves, respectively, were obtained by applying component analysis to 152 EEG records. The frequency polygons of natural frequency of second-order component waves verified several modes, each of which was enhanced in the frequency range of the well-known delta 0, delta 1, theta 1, theta 2, alpha 1, alpha 2, beta 1, beta 2 and beta 3 waves, respectively. 3) The average percent-power of the delta wave (delta 0 + delta 1) decreased with age, especially from 1 to 3 years old, whereas those of beta- and alpha-waves increased with advancing age. That of the theta wave tended to increase from 2 to 4 years of age, and thereafter decreased gradually with increasing age. 4) With increasing age, the durations of damped oscillations were significantly lengthened in delta 1, alpha 1 and beta 3 waves, whereas that in the theta 1 wave was significantly shortened. 5) The bio-informing activity amounts of alpha waves increased from 1 to 3 years with increasing age, whereas those of delta and theta waves decreased. No significant developmental change in the parameters, however, was observed in the beta wave. The results indicate that AR-power spectral and component analyses of EEG are sensitive methods for obtaining valuable information regarding the electrical brain maturation in childhood.

Stable Isotope Study of Karstic-Related Dolomitization: Jurassic Rocks from the Coastal Plain, Israel

The Middle-Upper Jurassic section in Israel contains scattered areas of dolomitization within predominantly limestone formations. One of these dolomitization sites, in the subsurface in the Ashdod-Gan Yavne area is associated with karst features as well as Mississippi Valley type mineralization (saddle dolomite-fluorite-quartz-bituminous clay-calcite) and hydrocarbons. Four distinct carbonate phases--limestone, coarsely crystalline brown host rock dolomite, white sparry saddle dolomite, and white vein calcite--were analyzed for stable isotopes of carbon and oxygen. These phases are believed to represent successive stages of diagenesis--epigenesis of the Ashdod-Gan Yavne deposits. Water taken from fluid inclusions from saddle dolomite and calcite was analyzed for stable isotopes of hydrogen as well. In all but a few samples, the carbon isotope ratio +1 + or - 1 per thousand was identical for all the carbonate phases studied. The oxygen isotope ratio for the limestones in all but a few cases was much heavier (-4.5 to -7.0 per thousand ) than that of the host rock dolomites (-5.7 to - 11.3 per thousand ) and is interpreted as reflecting dolomitization following limestone deposition. The oxygen isotopes in the host rock dolomites show geographic as well as stratigraphic variations. The host rock dolomites in the Zohar Formation in the Ashdod area have characteristically less negative delta 18 O values (-6.7 to -9.0 per thousand ) than the host rock dolomites in the Shderot Formations in the Ashdod area and the dolomites from both the Zohar and Shderot Formations in the Ashqelon area (delta 18 O < -9.2 per thousand ). The oxygen isotope results can be interpreted as evidence for either two different events of dolomitization, one regional and the other restricted to the Ashdod area, or a single event of dolomitization affecting two separate aquifers which differ in their oxygen isotope composition. Saddle dolomites, which were earlier thought to be a separate phase of epigenesis representing the earliest stage of mineralization postdating dolomitization, showed isotopic values identical to the host rock dolomites and showed the same formational and geographic variations as the host rock dolomites. Isotopic signatures of the vein calcites--believed to be a much later stage of mineralization showed delta 18 O values of (-5.6 to -10.8 per thousand ) similar to the trend expected for dolomite-calcite pairs in the Zohar Formation and the opposite trend in the Shderot Formation. A large range of delta D values (-38 to -58 per thousand ) was measured from fluid inclusions from saddle dolomites and vein calcites. This range is significantly different from the hydrogen isotope composition presently found in formation waters as well as local meteoric water.

Characterisation of membrane vesicles from Paracoccus denitrificans and measurements of the effect of partial uncoupling on their thermodynamics of oxidative phosphorylation.

1. Vesicles from Paracoccus denitrificans were prepared by applying an osmotic shock to spheroplasts derived from cells that had been grown anaerobically with succinate as carbon source and nitrate as electron acceptor. In the presence of either phenazinemethosulphate or N,N,N' N',-tetramethyl-p-phenylenediamine, the oxidation of isoascorbate supported the uptake of both S14CN- and 86Rb+ (in the presence of valinomycin), whereas NADH and succinate oxidation resulted only in S14CN- uptake. These observations show that the preparations contain both right-side-out and inside-out vesicles, and are related to the earlier proposal that the stimulation of an NADH-2,6-dichloroindophenol reductase activity by bee venom is an indicator of the proportion of right-side-out vesicles present. The implications impinge on previous conclusions [Burnell, J. N., John. P. and Whatley, F. R. (1975) Biochem. J. 150, 527-536 and FEBS Lett. 58, 215-218] about the mechanisms of sulphate and phosphate transport in P. denitrificans. 2. The relationship between the protonmotive force (delta p; transmembrane proton electrochemical gradient expressed in mV) and the phosphorylation potential (delta Gp) generated by vesicles from P. denitrificans has been studied as a function of the concentration of an uncoupler of oxidative phosphorylation. With either NADH or succinate as substrate, the uncoupler had a more pronounced effect on delta p than on delta Gp, so that the ratio delta Gp/F x delta p increased within a limited range of values of delta p close to the maximum. delta Gp/F x delta p was, however, approximately constant over the remaining range of delta p that was titrated. A fraction of 'highly coupled' vesicles, separated from the initial preparation by centrifugation through a Ficoll pad, showed similar titration behaviour. This demonstrated that heterogeneity within a vesicle preparation was not responsible for significant distortion of the true relationship between delta p and delta Gp. Values of delta p and delta Gp/F x delta p (H+/ATP) from 143-108 mV and 3.9-4.4, respectively, were determined when NADH was substrate, whereas with succinate, delta p ranged from 123-88 mV and delta Gp/F x delta p (H+/ATP) from 4.5-5.6. The variation in the value of delta Gp/F x delta p, which can be equated with a minimum value for the H+/ATP of the ATP synthase enzyme, is similar to, but less pronounced than, some of the data previously reported for mitochondria. Thus the observations with these bacterial vesicles, which represent an experimentally simpler system than mitochondria, might be taken as further evidence that measurements of the bulk phase delta p might not truly reflect the driving force for ATP synthesis sensed by the ATP synthase enzyme. However, other explanations that would make the data consistent with a chemiosmotic mechanism cannot be eliminated...

Sulfur isotopic studies of the Dunka Road Cu-Ni deposit, Duluth Complex, Minnesota

The Dunka Road deposit is one of a series of Cu-Ni occurrences located within troctolitic rocks of the southern portion of the Duluth Complex, Minnesota. Sulfide minerals, principally pyrrhotite, chalcopyrite, cubanite, and minor pentlandite occur interstitially with silicate minerals and average about 2 volume percent in ore-grade horizons. Areas of sulfide concentrations in excess of 1 to 2 percent occur erratically throughout the troctolitic sequence but are in general concentrated near the basal contact with rocks of the metasedimentary Virginia Formation.The delta 34 S values of sulfides in the troctolites range from 0.2 to 15.8 per mil, with an average value near 7.5 per mil. Pyrrhotite in the underlying Virginia Formation hornfels and pyrite from unmetamorphosed Virginia Formation are characterized by a similar range in delta 34 S values. The high positive delta 34 S values and similarity to values found in the Virginia Formation strongly suggest that most of the sulfur in the Dunka Road deposit was derived from the breakdown of pyrite in the Virginia Formation. The sulfur isotopic compositions of minerals in the troctolites show no consistent lateral or vertical trends and are in general characterized by a high degree of variability. Such fluctuations in delta 34 S values indicate that sulfur isotopic homogenization was not attained throughout the troctolitic sequence.Several mechanisms may have contributed to the variations in delta 34 S values found within the troctolites, including mixing of sedimentary and igneous sulfur, assimilation of sedimentary sulfur characterized by variable delta 34 S values, fractionation caused by fluctuations in oxidation states during sulfur volatilization and assimilation, and periodic introduction of isotopically distinct magma batches. In light of the erratic sulfide mineral and delta 34 S distributions, the predominant mechanism is thought to be the introduction of both isotopically and spatially variable country rock sulfur into crystallizing troctolitic magma.

The genesis of sulfide mineralization in a portion of the Potgietersrus Limb of the Bushveld Complex

In the Potgietersrus limb of the Bushveld Complex, South Africa, sulfide mineralization is associated with the intrusive contact between Bushveld pyroxenitic gabbros and floor rocks consisting of Malmani dolomite, the overlying Penge banded ironstone, and sedimentary rocks of the Pretoria series. Whole-rock values of up to 0.5 and 1.8 weight percent copper and nickel, respectively, were obtained in borehole intersections through the contact zone and values of up to 28 ppm platinum group metals have been reported from the area.Petrographic and isotope geochemical studies were undertaken on a representative suite of rocks. It was shown that the pyroxenitic gabbro in contact with the floor rocks was equivalent in composition to the Merensky Reef. Xenoliths of Malmani dolomite incorporated into the Bushveld rocks reacted with the magma and were metamorphosed to calc-silicate and carbonate silicate hornfelses. Increased sulfide concentrations are found in association with the xenoliths. These rocks, together with the Bushveld pyroxenitic gabbros and recrystallized argillaceous sediments of the Pretoria series and the pre-Bushveld noritic sills, constitute a 120-m-thick mineralized zone known as the Platreef.The results of carbon and oxygen isotope determinations on unaltered Malmani dolomite are consistent with values expected for an evaporitic environment of deposition during the Precambrian. Anhydrite normally associated with evaporitic sequences is likely to have been preserved in the Malmani dolomite when it was incorporated as xenoliths into the Bushveld magma. Sulfur isotope studies on sulfides from the Platreef zone give a range of delta 34 S values of from 6.8 to 9.2 per mil. As the delta 34 S values for primary magmatic Bushveld sulfides fall in the range -0.6 to +3.5 per mil, the isotope geochemistry clearly indicates a contribution of sedimentary-derived sulfur to the original Bushveld magma. Sulfide mineralization in the Platreef is considered, therefore, to have been derived from the combined influence of a sulfur-rich Merensky Reef-type magma and the incorporation of additional sulfur from the Malmani dolomite, either through direct diffusion or in association with a carbonate melt.Between the banded ironstone and the Platreef zone there is a 50-m-thick zone of coarsegrained iron- and sulfide-rich pegmatoidal pyroxenite. Pyrrhotite from these rocks gave delta 34 S values of 2.7 and 8.7 per mil which are within the possible range of magmatic sulfur. These rocks may be related to the intrusive pipes found elsewhere in the Bushveld Complex.

Strain interaction effects on the high-spin-low-spin transition of transition-metal compounds

The temperature-induced high-spin(HS)-low-spin(LS) transition of the 3d4-3d7 transition-metal ions in crystals (oxides and sulphides) are investigated on a semiquantitative basis by taking into account the elastic interaction between HS (or LS) clusters produced in a LS (or HS) crystal. The critical temperature at which the discontinuous phase transition takes place is evaluated as a function of the ligand-field strength Delta in units of spin-pairing energy Pi . It is shown that the 'crossover range' where this critical temperature exists is restricted to a finite range of Delta / Pi around the crossover point. The crossover ranges are evaluated for the crystals MO, MS2, M2O3, and LaMO3 where M represents transition-metal ions. The temperature variation of the equilibrium concentrations of HS and LS clusters in LS and HS crystals, respectively, is calculated for several values of Delta / Pi in perovskite LaMO3 crystals. It is pointed out that two discontinuous transitions from HS to LS and LS to HS with decreasing temperature may be expected in the d6 and the d7 systems.

The Tungsten Queen Deposit, Hamme District, Vance County, North Carolina; a stable isotope study of a metamorphosed quartz-huebnerite vein

The Tungsten Queen mine, Vance County, North Carolina, is a large quartz-huebnerite vein deposit of late Precambrian or early Paleozoic age that has undergone middle Paleozoic regional metamorphism of amphibolite grade. The preservation of large banded huebnerite crystals and the low delta 18 O values in the vein minerals and wall rocks indicate a premetamorphic hydrothermal origin for the vein which involves meteoric waters. Quartz-sericite oxygen isotope distributions in the vein and wall rocks indicate metamorphic temperatures of 550 degrees + or - 50 degrees C. All other isotope distributions except possibly those for hydrogen appear to reflect primary hydrothermal distributions that were not significantly disturbed by the metamorphic event. The stable isotope systematics of the vein are remarkably similar to those of younger huebnerite/wolframite-quartz veins associated with shallow intrusions in erogenic belts. Sulfur isotope fractionations among coexisting sulfides in two mineral assemblages may indicate primary mineralization temperatures of about 260 degrees and 320 degrees C. The hydrothermal sulfur was derived from a deep-seated source. The carbon isotope data suggest that a sedimentary organic component was present in the fluids during carbonate deposition. Except for reequilibration between coexisting quartz and sericite, the 18 O systematics of the vein minerals appear to reflect primary hydrothermal distributions and indicate that the vein was largely a closed system during metamorphism. Hydrous minerals and waters in fluid inclusions in the vein minerals show nearly a 50 per mil range in delta D values which may also reflect primary variations in the hydrothermal vein system.

Chromaticity Correction in Large Storage Rings

As the size of storage rings proposed and under construction increases, the chromaticity reaches values which require correction schemes with a new order of sophistication involving sextupoles. The very large chromaticities encountered in storage rings like PEP, PETRA and the ''Very Big Storage Rings'' produce a new set of undesirable characteristics in the beam dynamics which require a more complicated means of correction. The method of attack used at PEP to solve the problem of both satisfactory chromaticity correction and stable non-linear motion is discussed. The analytic expressions developed for calculating the dispersion function through second order in delta and for the tune shifts through third order in delta, agree well with the results of the matrix multiplication method over the range in delta of interest. Analytic expressions for the tune shift with betatron amplitude agree well with the results from the tracking programs and can be used to determine for which amplitudes the tune will be shifted to a resonance.

Sulfur isotope investigation of the barite, manganese, and lead-zinc-copper-silver deposits of the Walton-Cheverie area, Nova Scotia, Canada

The consolidated rocks underlying the Walton-Cheverie area are mainly sediments of Lower Carboniferous (Mississippian) and Triassic age. Diabase sills, probably of Triassic age, occur in one place. The Mississippian rocks consist of a lower series of terrestrial fluviatile and lacustrine sediments (Horton Group) and an upper sequence of dominantly marine sediments that include evaporites (Windsor Group). The Triassic sediments are entirely of terrestrial origin. The Mississippian rocks are intricately folded in places, and all are extensively faulted; the Triassic rocks are relatively flat lying and have been faulted in many places. The economic deposits of the area are gypsum and anhydrite in sedimentary beds and epigenetic barite and sulfide bodies.The sulfur in the sulfates and sulfides of the country rocks and epigenetic deposits exhibits a wide range in delta 34 S composition, from +33.6ppm to -- 42.0ppm. All of the sulfates, including anhydrite and gypsum in the evaporites, barite in epigenetic deposits, and sulfate dissolved in deep circulating brines, near-surface ground waters, and sea water are enriched in 34 S(delta 34 S range, +33.6ppm to +5.7ppm)- The pyrite in argillites and shales of the Horton Bluff Formation ranges from +18.3ppm to --10.9ppm in delta 34 S; in the calcareous anhydrite beds of the evaporite formation the pyrite is greatly depleted in 34 S(delta 34 S = -- 18.4ppm.). Pyrite in the Triassic diabase is also depleted in 34 S(delta 34 S = --13.1ppm).The average delta 34 S values for the sulfides and sulfosalts in the Magnet Cove deposit are all negative, ranging from -- 0.9ppm to -- 39.6ppm. There is a progressive decrease in 34 S with respect to the paragenetic sequence of minerals, the last sulfosalts and sulfides to be crystallized being significantly depleted in 34 S. Disseminated pyrite in certin coalified plant zones has negative delta 34 S values (average -- 39.6ppm) whereas that in zones devoid of plant remains has positive delta 34 S values (average +11.6ppm).It is concluded that the large massive cryptocrystalline barite body in the Magnet Cove deposit originated mainly by replacement of bedded gypsum and anhydrite (Ba (super 2+) for Ca (super 2+) ) because of similarities in the isotopic composition of the sulfates in the evaporites and in the resultant barite. Other coarsely crystalline barite veins and pods appear to have been deposited from deep circulating brines. The sulfides and sulfosalts in the Magnet Cove deposit appear to have been derived from sulfate in the deep circulating brines by reduction processes, the shift in the isotopic constitution to more negative values being due to these processes which may have been partly aided by bacterial activity.

Fatigue crack propagation in metal-matrix/metal-fibre composites

The growth of fatigue cracks in composites consisting of Al-4%Cu reinforced with strong tungsten wires has been studied during fully reversed tension/compression cycling of double edge-notched plates. The rate of crack growth dc/dN which is related to the range of stress intensity factor Delta K obeys the same power law which describes crack growth in a wide variety of materials, although the exponent is five rather than the theoretically predicted value of four. The stress intensity range for a given crack growth rate appears to vary with fibre volume fraction in the same way as the ordinary fracture toughness K which is determined in monotonic tensile tests on notched samples.

O 18 /O 16 evidence for meteoric-hydrothermal alteration and ore deposition in the Tonopah, Comstock Lode, and Goldfield mining districts, Nevada

Oxygen isotope analyses were obtained for 50 whole-rock samples, 26 vein quartz samples, 4 calcites, and 1 adularia from the volcanic rocks, intrusives, and hydrothermal veins at Tonopah, Goldfield, and the Comstock Lode. At Tonopah, the delta O 18 values are as follows: Mizpah trachyte (-5.9 to +3.3); West End rhyolite (--4.7 to +1.5); Sandgrass andesite (--6.0); main-stage vein quartz (--5.1 to --1.8); late, euhedral quartz crystals (--3.2 to +0.7). The delta D values of 5 of these rocks vary from --135 to --152. These materials are thus depleted in O 18 by about 5 to 15 per mil and in D/H by about 60 to 70 per mil, relative to values in normal igneous rocks. The postmineralization Oddie rhyolite and Fraction volcanic breccia, however, have much higher delta O 18 values (+2.5 to +9.5). The hydrothermal alteration and ore deposition therefore must have been produced by heated meteoric ground waters (delta O 18 [asymp] --13, delta D [asymp] --100) that had undergone very little or no O 18 enrichment as a result of exchange or addition of magmatic water. Various models suggest that this involved very high water/rock ratios (>2) and occurred at about 250 degrees -300 degrees C. Although the delta O 18 of quartz is higher (+1.5 to +3.0), the range of whole-rock delta O 18 values at the Comstock Lode is similar to that at Tonopah: Alta andesite (--4.1 to +4.7); Davidson diorite stock (--2.6 to --0.8). At Goldfield, somewhat higher whole-rock delta O 18 values are observed: altered volcanic rocks (+1.7 to +5.8); ore zones (--3.8 to +3.8). These data also indicate a dominant meteoric ground-water component in the hydrothermal fluids, but they suggest smaller water/rock ratios at Comstock and lower temperatures of alteration at Goldfield. It is concluded that most epithermal gold and silver ore bodies in highly faulted piles of altered volcanic rocks probably were deposited by meteoric-hydrothermal solutions heated and set into convective circulation by interaction with epizonal igneous intrusions.