SMOW Research Articles

Radiation-related retrograde hydrogen isotope and K—Ar exchange in clay minerals

Hydrogen and oxygen isotope studies have been widely applied to characterize the origin of fluids during ore-forming processes1–4. The primary isotope record, however, may be disturbed by retrograde exchange reactions, thus complicating the interpretation of the data. The susceptibility of minerals to retrograde isotope and chemical exchange is variable5, reflecting differences in the mechanism and rate of isotope exchange. These depend on several factors, including mineralogy, surface area, temperature, pressure, nature and concentration of fluid phase, water/rock ratio. In the Cluff-D uranium deposit within the Athabasca basin (Saskatchewan, Canada) illites and chlorites associated with uranium mineralization are strongly depleted in deuterium (–90 > δD > – 170‰ SMOW (standard mean ocean water)) and have young K/Ar apparent ages ( δD > –62‰; 1,265 Myr)6–8. Both the δD values and K/Ar 'ages' decrease with increase in the uranium content of the rock. The H2O+ content of illite from mineralized samples is higher than the theoretical value as well as samples from the barren zone. These relationships are interpreted in terms of radiation-catalysed retrograde hydrogen isotope and K–Ar exchange of the clays at low temperatures with post-Cretaceous meteoric waters.

Eolian Additions to Soils and Sediments of Japan

Significance of the eolian additions to soils and sediments of Japan was evaluated. Soils overlying Paleozoic limestone, Ando soils developed on volcanic ashes, eolian dusts in a mud rain deposit, snow melt and ombrogenous Sphagnum peats from Japan and South Korea, and loes! from North China were analyzed for the particle-fize distribution and oxygen isotopic composition of a marker mineral quartz. The total quartz content of the soils overlying limestones was much higher in the surface horizons (30 to 40%) than the subsurface horizons (3 to 14%). The whole quartz content within cumulative Ando soils varied from 9–11% in the lower buried horizons (8,000–l50,000 years B.P.) to 1–2% in the upper recent horizons (<ca. 8,000 years B.P.). Quartz grain-size cumulative curves for most soil and sediment samples from Japan and South Korea fell within a relatively narrow range (2 to 50 μm) which was between that of loess and loess-derived soil of North China (20 to 50 μm) and Hawaiian soils (1 to 10 μm), suggesting a grain-size sorting by prevailing Westerly Wind systems of the mid-latitude zone of the Northern Hemisphere. Quartz of the underlying limestones from six localities showed marked variations in the particle-size distribution indicating the soils overlying limestones were not derived from the residuum of the limestones weathered away. The oxygen isotopic compqsition (δ18O value, expressed as parts per thousand variation relative to Standard Mean Ocean Water, SMOW) of fine quartz silt (1 to 10 μm in diameter, characteristic of long-distance aerosolic dust) of soil and sediment samples showed values of +16.3 to +17.0‰ (North China) and +14.7 to +16.1‰ (Japan). Those values are in agreement with those previously reported for fine quartz from the North Pacific pelagic sediments and the Hawaiian soils, and characteristic of the eolian dusts of the mid-latitude zone of Eurasia. These values correspond to the average composition of quartz of the earth’s crust. A well-mixed reservoir in the source is inferred for the soil quartz. The quartz from underlying limestones and volcanic material has totally different isotopic compositions, and cannot be the source of the soil quartz. The correspondence between the two parameters of quartz strongly suggests their common eolian input from arid and semi-arid regions in Asian interiors to the soils. Local eolian contribution from dry-river bed and/or beach and volcanic ash, quartz of whose predominant size is 30 to 40 μm is evident for some Ando soils from Kagoshima, Shizuoka and Hokkaido. The framework of 14C dating, together with the stratigraphic correlation of marker tephras, suggests that the long-distance eolian additions were much greater in the last glacial maximum period (18,000 years B.P.) than in the Holocene.

Preserved stable isotopic signature of subaerial diagenesis in the 1.2-b.y. Mescal Limestone, central Arizona: Implications for the timing and development of a terrestrial plant cover

A Precambrian exposure surface in the 1.2-b.y. Mescal Limestone has been isotopically examined for indications of a carbon isotopic signature that might indicate the presence of a subaerial vegetative cover in the middle Proterozoic. δ 18 O values of the Mescal carbonates show two distinct data sets: (1) dolomites from an unaltered zone which were unaffected by sub-aerial diagenesis having δ 18 O values ranging from +19.9 to +25.6‰ Standard Mean Ocean Water (SMOW) with cherts averaging +30‰, and (2) dolomites from a dissolution zone subaerially exposed in the Precambrian with δ 18 O values ranging from +13.9 to +22.4‰ and cherts averaging +25‰. δ 13 C of dolomite ranges from +3.7‰ Pee Dee Belemnite (PDB) in the unaltered zone to 0‰ in the dissolution zone. The dissolution zone consists of a karst breccia of recemented dolomite and chert fragments with numerous clastic solution dikes. Isotopic and field data indicate that the δ 18 O of the unaltered dolomite was fixed during early meteoric-water diagenesis, including dissolution-silicification of evaporites and dolomitization. During a later subaerial exposure event, a large flux of meteoric water flushed through the dissolution zone and produced the same isotopic patterns that Allan and Matthews documented for younger examples as indicative of a vegetatively covered land surface. Alternative explanations for producing the observed δ 13 C variations in the absence of vegetation do not seem feasible. We therefore suggest that the subaerial environment 1.2 b.y. ago was a biologically active zone.

Simultaneous stratospheric measurements of H2O, HDO, and CH4 from balloon‐borne and aircraft infrared solar absorption spectra and tunable diode laser laboratory spectra of HDO

High‐resolution infrared solar absorption spectra recorded from a balloon‐borne platform at 33‐km altitude and an aircraft at 12‐km altitude have been analyzed to derive simultaneous stratospheric concentrations of H2O, HDO, and CH4. The data were obtained near 33°N with the University of Denver interferometer during a balloon flight in October 1979 and with the NCAR interferometer aboard a Sabreliner aircraft in September 1982. The analysis of the balloon spectra indicates the H2O mixing ratio increased from 3.5 to 4.8 ppmv and the CH4 mixing ratio decreased from 1.15 to 0.70 ppmv between 18 to 38 km. Tunable diode laser laboratory spectra were recorded and analyzed to derive absolute intensities and air‐broadened half widths of selected lines of the v2 band of HDO. With these parameters, which are reported here, an HDO profile that increases from 0.61 ppbv near 18 km to 0.88 ppbv near 29 km is inferred from the balloon spectra, corresponding to a D/H ratio, normalized to the reference value of 158 atomic parts per million of Standard Mean Ocean Water (SMOW), of 0.55 to 0.67. The average D/H value of 0.40 above 12 km, derived from the aircraft spectra, provides additional spectroscopic evidence for a large depletion in the D content of water vapor in the lower stratosphere. The simultaneous vertical profiles for the three gases retrieved from the balloon spectra are consistent, within the estimated precision of the data (±10%), with methane oxidation as the sole source of stratospheric H2O in addition to H2O transported upward through the tropopause. However, there is an indication of a small increase in the total hydrogen in H2O and CH4 with altitude, and we believe more precise simultaneous measurements are required.

Isotopic and related studies of Antarctic ice samples

The ice samples obtained from Dakshin Gangotri, Antarctica show the presence of nuclear debris, attributed mainly to French nuclear explosions. Cosmogenic7Be occurs at levels of 30 dpm/L. The vertical profile ofδD in 6 m long drill core ranges between −130 and −180‰ compared to Standard Mean Ocean Water (SMOW). No systematic change with depth is seen. Small amounts of dust obtained by filtering melt water show presence of metallic spherules. Absence of elements characteristic of meteoritic or cometary debris suggests that most of them are of volcanic or industrial origin.

Comparison of stable isotope reference samples

Use of light stable isotope ratio measurements has proliferated in the past decade. The need for procuring additional stable isotope reference materials was recognized at an International Atomic Energy Agency (IAEA) consultants' meeting convened in 19761. This group recommended acquisition of two carbonates, two carbon dioxide samples, a biotite, a sulphate, and other reference materials. We report here on the mass-spectrometric analysis of these and other reference samples in a single laboratory to minimize interlaboratory calibration errors. A result of this work is an improved equation for relating the PDB isotope scale (belemnite from the Peedee Formation of South Carolina adopted in the 1950s as a reference in palaeotemperature studies2) to the V-SMOW (Vienna-Standard Mean Ocean Water) scale1.

Tropospheric origin of quartz in ando solls and red-yellow soils on basalts, Japan

Abstract Fine quartz silt (1-10 pm diameter, characteristic size of aerosolic dust) isolated from two Ando soils from volcanic ashes (Fukuoka and Iwate), two Red-Yellow soils on basalts (Saga and Nagasaki) and one loess deposit (Saga) exhibited a very narrow range of oxygen isotopic ratios (expressed as parts per thousand relative to Standard Mean Ocean Water, SMOW, σ18O) varying from 15.8 to 16.1\%0. These values were almost identical with those reported for a mud-rain deposit (σ180=16.2\%0) and two north Pacific pelagic sediments near the Japanese Islands (d180= 16.2 and 16.6%0)' all derived from continental aerosolic dusts, carried by Westerly Winds. The quartz oxygen isotopic ratios of the selected Ando soils preclude both an indigenous volcanic ash (magmatic) origin and secondary crystallization under the ambient temperature. The oxygen isotopic results together with the covariant relationship between the fine-grained-quartz and 2 : 1 type day mineral contents suggest that the great bulk of the 2 : 1 day mineral-bearing phase of Ando soils of Japan is also of tropospheric origin, resulting from long distance eolian transport from Asian semi-arid and arid regions.

The origin of continental shelf and slope water in the New York Bight and Gulf of Maine: Evidence from H218O/H216O ratio measurements

The H218O/H216O ratio of meteoric water in eastern North America decreases with increasing latitude. The annual weighted average δ18O content of the Middle Atlantic Bight (MAB) and Gulf of Maine (GOM) rivers are −9.33‰ and −10.89‰, respectively. The δ18O compositions of the major east coast rivers are 2‰ enriched during summer months. By using H218O and salinity measurements, both conservative properties of sea water, the geographic origin of continental shelf water can be identified. The isotope‐salinity tracer method, which has been used so successfully in polar regions, is also an effective method in the temperate MAB because subpolar waters are exported to this region. The apparent dilutent of slope water is −22‰ δ18O relative to standard mean ocean water. Water of this composition is presently forming in the Labrador Sea. Melt water from sea ice has nearly the same isotopic composition as the sea water from which it formed and thus may be distinguished from meteoric water. In March 1977, the New York Bight cold pool contained as much as 2.5% sea ice melt water. The Gulf of St. Lawrence is the nearest source of sea ice. The New York Bight ‘cold pool’ was renewed from the north between March and July, which was the extent of our sampling period.

Hydrogen isotopic composition of MnO(OH) minerals from manganese oxide and massive sulfide (Kuroko) deposits in Japan

The hydrogen isotopic composition of structural water in MnO(OH) minerals from manganese oxide and massive sulfide deposits (Kuroko) in Tertiary formations fall within a narrow range from -261 to -275 permil relative to standard mean ocean water (SMOW). The δD of two manganites from manganese deposits in Paleozoic formations were -236 and -298 permil, indicating a wider range than in those of Tertiary manganese deposits. The MnO(OH) minerals are more deuterium-depleted. than any other hydrothermal minerals reported to date. Hydrogen isotopic fractionation factors between manganite and water were experimentally determined to be 0.7894, 0.7958, and 0.8078 at 150°, 200°, and 250° C, respectively, under hydrothermal conditions at 500 bars. The present experimental results indicate that if manganites were formed at temperatures below 250° C under isotopic equilibrium conditions, then most manganite mineralization in the ore deposits must have precipitated from meteoric hydrothermal solutions.

Availability of large quantities of low-deuterium hydrogen, and possible uses

Hydrogen produced electrolytically is isotopically light (depleted in deuterium) relative to the water in the electrolysis cell. Samples of the hydrogen by-product from two caustic soda/chlorine plants in New Zealand have been collected; one plant uses diaphragm cells and the other mercury cells. The hydrogen from one plant has been burnt to produce light water. These samples, commercial compressed hydrogen and Antarctic snow-melt (previously recommended as a source of light water) are approx 80, 50 and 35%, respectively, depleted in deuterium, relative to standard mean ocean water. The water produced by burning hydrogen from the caustic/chlorine plants, could be available in tonnage quantities anywhere in the industrialised world. Work with this water has failed to confirm previous claims of accelerated germination of seeds and subsequent growth of plants, when using light water.

Analyse isotopique de concrétions sous-glaciaires de l'inlandsis laurentidien et teneur en oxygène 18 de la glace

Calcareous concretions occurring on Grenvillian gneiss have been discovered north of Hull, Quebec. Their structure and isotopic composition ([Formula: see text]; [Formula: see text]; 14C age &gt; 35 000 BP) indicate subglacial conditions of precipitation. It is concluded that they were deposited at the base of the Laurentide ice sheet. Assuming equilibrium conditions with the subglacial film of water during precipitation of calcite, it is possible to define a −27.5 to −31.8‰ (vs. "standard mean ocean water" (SMOW)) range for the oxygen-18 content of the ice.

Deduction of Past Geothermal Gradients in Neogene Siliceous Rocks in Circum-Pacific Region: ABSTRACT

Zones of diagenetic silica record past geothermal gradients in Neogene diatomaceous sediments and siliceous rocks in the Circum-Pacific region and are useful in evaluating the petroleum potential of these important source rocks. In many areas burial diagenesis has produced the well-known lithologic and mineralogic progression: diatomite (opal-A) ^rarr chert and porcelanite (opal-CT) ^rarr chert and porcelanite (quartz). Temperature is an important control of these transformations. The range in temperature for the conversion of opal-A to opal-CT, calculated from measured values of heat flow and thermal conductivity, is 25 to 56°C. Opal-CT transforms to quartz in the range 43 to 81°C. Similar ranges of temperatures are calculated from oxygen isotopes of opal-CT an quartz from cherts and porcelanites using the experimental fractionation for quartz and water, assuming the transformations occurred in isotopic equilibrium with water whose oxygen isotopic composition differed only slightly from standard mean ocean water. Taking the top and base of the opal-CT zone as approximate isotherms, the past geothermal gradient for any area equals the difference between these isotherms divided by the thickness of the opal-CT zone. In addition, both the thickness and the depth (reconstructed maximum overburden) to the top of this zone decrease with increasing geothermal gradient. Because depth and thickness are related by a simple linear expression, either may be used to estimate past geothermal gradients in Neogene siliceous rocks. End_of_Article - Last_Page 510------------

Oxygen Isotope Composition of Subglacially Precipitated Calcite: Possible Paleoclimatic Implications

Isotopic analyses of subglacially precipitated calcite from near a modern temperate glacier show that the delta(18)O (= (18)O/(16)O relative to standard mean ocean water) of the calcite records the delta(18)O of the ice from that glacier. It may therefore be possible to determine the delta(18)O of Pleistocene ice sheets on the basis of isotopic analyses of calcite formed under that ancient ice. This, in turn, would allow estimation of the delta(18)O of Pleistocene oceans and correction of the paleotemperature scale based on foraminiferal oxygen isotopic analyses.

Standards for stable isotope measurements in natural compounds

RESEARCH based on stable isotope variations in natural compounds is expanding in scientific fields such as geochemistry, hydrology, environmental studies and biochemistry. However, intercomparison of results obtained in different laboratories is often not fully reliable and therefore to improve the intercalibration of deuterium and 18O measurements in natural waters, two water standards have been distributed by the International Atomic Energy Agency since 1968. The two standards, called V-SMOW (Vienna Standard Mean Ocean Water) and SLAP (Standard Light Antarctic Precipitation), were prepared, following a recommendation by an Advisory Group Meeting convened by the IAEA in 1966. Information on the two standards is given here.

Geochemical and petrogenetic study of the Girnar igneous complex, Deccan volcanic province, India

Representative rocks of gabbro, diorite, lamprophyre, and syenite from the Girnar complex, Deccan volcanic province, India, and associated silicic porphyritic rocks have been analyzed for major and trace (including rare earth) elements and for strontium and oxygen isotopic composition. Variation diagrams of the major elements against the Fe/Mg index suggest a systematic evolution in the complex. Silicic porphyry, on the other hand, forms a separate group in the variation diagrams. Rare earth elements (REEs) increase in abundance from gabbro to syenite and become increasingly fractionated. REE patterns and Th/Ta ratios in the silicic porphyritic rocks differ from the others. The initial 87 Sr/ 86 Sr ratios of the rocks show bimodal distribution — that is, silicic porphyry with an average value of 0.7275, whereas the other rocks have a range from 0.7051 to 0.7080. δ 18 O values range from +5.37 per mil to +8.68 per mil relative to standard mean ocean water. Variation of the strontium isotopic composition within the gabbro-syenite group is inferred to be related to crustal contamination. The silicic porphyry may be derived by partial fusion of the Precambrian granitic basement. New K-Ar age determinations show a range from 63.8 to 56.2 m.y. and suggest that the igneous complex was emplaced immediately after the eruption of the Deccan basalts.

Oats may grow better in water depleted in oxygen 18 and deuterium

WHILE growing oats at different temperatures in water of different 18O and deuterium (D) abundances, we noticed that oats grown in Antarctic water in which is depleted in 18O and D by −49‰ and −400‰, relative to standard mean ocean water (SMOW used as a comparative reference in hydrogen and oxygen isotope studies), showed initial growth 1–2 weeks sooner than did oats grown in water containing greater 18O and D concentrations. The oats seemed to grow better in water which was most depleted in the stable isotopes throughout the growth period.

Water and Carbon in Rusty Lunar Rock 66095

Lunar rock 66095 contains a hydrated iron oxide and has an unusual amount of water for a lunar rock (140 to 750 parts per million), 90 percent of which is released below 690 degrees C. The deltaof water released at these low temperatures varies from -75 to -140 per mil relative to standard mean ocean water (SMOW). The small amount of water released between 690 degrees and 1300 degrees C has a delta of about -175 +/-25 per mil SMOW. These delta values are not unusual for terrestrial water. The delta(18)O of water extracted from 110 degrees to 400 degrees C has a value of +5+/- I per mil SMOW, similar to the value for lunar silicates from rock 66095 and different from the value of -4 to -22 per mil found for samples of terrestrial rust including samples of rusted meteoritic iron. The amount of carbon varies from 11 to 59 parts per million with a delta(13)C from -20 to -30 per mil relative to Pee Dee belemnite. Only very small amounts of reduced species (such as hydrogen, carbon monoxide, and methane) were found, in contrast to the analyses of other lunar rocks. Although it is possible that most of the water in the iron oxide (goethite) may be terrestrial in origin or may have exchanged with terrestrial water during sample return and handling, evidence presented herein suggests that this did not happen and that some lunar water may have a deltaD that is indistinguishable from that of terrestrial water.

D/H and 18O/16O Ratios in Waters Contained in Geodes from the Basaltic Province of Rio Grande do Sul, Brazil

Analyses of the 18 O and deuterium (D) concentrations in water contained in chalcedony and quartz geodes of Salto do Jacui, in Rio Grande do Sul, Brazil, indicate small variation in the isotopic concentrations of fluid, averaging about − 5.0‰ (per mille) for δ 18 O and −27‰ or δD relative to Standard Mean Ocean Water (SMOW). The geodes studied were collected in primary or sedimentary clay soil resulting from the decomposition of Cretaceous basalt. Comparisons with postulated juvenile and meteoric waters are made in an attempt to obtain further information on the genesis of the studied geodes. The isotopic concentrations indicate that the waters contained in these geodes are meteoric.

Deuterium Distribution in the Gulf of Mexico

Abstract The variations of the stable isotopes of hydrogen (protium and deuterium) were determined in the various water masses of the Gulf of Mexico. Surface waters of the central Gulf were found to have an average δD=5.6‰ relative to Standard Mean Ocean Water (SMOW), whereThe subsurface water masses, Subtropical Underwater, Antarctic Intermediate Water, and Gulf Basin Water, were found to be characterized by deuterium contents of 5.0–5.5, −0.5 and 0.9‰, respectively. In addition, a high deuterium feature (δD=5.5–6.3‰) was shown in the water column at about 100 m depth just above Subtropical Underwater. The δD values for the fresh water contribution to the Gulf via the Mississippi and Coatzacoalcos Rivers were found to be −42.3 and −19.3‰, respectively. The value for the net fresh water addition to the Gulf was ∼−33‰. The isotopic composition of near-shore waters is consistent with a simple mixing model of fresh water from runoff with ocean water modified by the mixing of sea waters from distinct sources.

Oxygen isotope fractionation between biogenic silica and ocean water

The suitability of siliceous radiolaria skeletons in deep sea sediments for oxygen isotope investigations was determined. The δ notation used in this report is defined as: δ O 18 = [( O 18 O 16 ) Sampale/( O 18 O 16 ) smow−1] × 1000 Where SMOW is standard mean ocean water.