A new type of meteoritic diamond in the enstatite chondrite abee

Diamonds with delta(13)C values of -2 per mil and less than 50 parts per million (by mass) nitrogen have been isolated from the Abee enstatite chondrite by the same procedure used for concentrating Cdelta, the putative interstellar diamond found ubiquitously in primitive meteorites and characterized by delta(13)C values of -32 to -38 per mil, nitrogen concentrations of 2,000 to 12,500 parts per million, and delta(15)N values of -340 per mil. Because the Abee diamonds have typical solar system isotopic compositions for carbon, nitrogen, and xenon, they are presumably nebular in origin rather than presolar. Their discovery in an unshocked meteorite eliminates the possibility of origins normally invoked to account for diamonds in ureilites and iron meteorites and suggests a low-pressure synthesis. The diamond crystals are approximately 100 nanometers in size, are of an unusual lath shape, and represent approximately 100 parts per million of Abee by mass.     

Stable-carbon isotope ratios as a measure of marine versus terrestrial protein in ancient diets

The stable-carbon isotope ratios for the flesh of marine and terrestrial animals from Canada's Pacific coast differ by 7.9 +/- 0.4 per mil, reflecting the approximately 7 per mil difference between oceanic and atmospheric carbon. This difference is passed on to human consumers. The carbon isotopic values (delta(13)C) for human collagen thus yield direct information on the relative amounts of marine and terrestrial foods in prehistoric diets.     

Subduction and recycling of nitrogen along the Central American margin

We report N and He isotopic and relative abundance characteristics of volatiles emitted from two segments of the Central American volcanic arc. In Guatemala, delta15N values are positive (i.e., greater than air) and N2/He ratios are high (up to 25,000). In contrast, Costa Rican N2/He ratios are low (maximum 1483) and delta15N values are negative (minimum -3.0 per mil). The results identify shallow hemipelagic sediments, subducted into the Guatemalan mantle, as the transport medium for the heavy N. Mass balance arguments indicate that the subducted N is efficiently cycled to the atmosphere by arc volcanism. Therefore, the subduction zone acts as a "barrier" to input of sedimentary N to the deeper mantle.     

In situ discovery of graphite with interstellar isotopic signatures in a chondrule-free clast in an L3 chondrite

Optical and scanning electron microscopy of a chondrule-free clast in the unequilibrated L3 chondrite Khohar revealed a spherical object consisting of an aggregate of small ( approximately 2- micrometer diameter), Ni-poor (0.5 to 2.89 weight percent) metal particles and fine-grained graphite (<1-micrometer diameter). The graphite has large D and 15N excesses (deltaD approximately 1500 per mil and delta15N approximately 1300 per mil) with two isotopically distinct signatures: N rich with a high D/H ratio and N poor with a high 15N/14N ratio. These excesses are the largest D and 15N excesses observed in situ in a well-characterized phase in a meteorite. The isotopic characteristics are suggestive of an interstellar origin, probably by ion-molecule reactions at low temperature in the interstellar molecular cloud from which the solar system formed. The structure and nonchondritic composition of the metal particles suggest they did not form under equilibrium conditions in the solar nebula.     

Carbon-13/carbon-12 isotope fractionation of organic matter associated with uranium ores induced by alpha irradiation

Analyses of stable carbon isotopes from two sample suites from sandstone uranium (tabular) ores show interesting variations. Organic carbon associated with high-grade uranium ore is heavy (delta(13)C = -16.9 to -19.6 per mil, where delta(13)C = (13)C/(12)C relative to the Pee Dee belemnite standard) relative to the adjacent lower-grade samples (-22.7 to -26.4 per mil). It is suggested that the heavy isotopic values for the are samples are related to a radiation and chemical isotope effect that has occurred mainly because of an alpha-radiation dose of 10(11) rads.     

Organogenic elements and compounds in surface samples from the sea of tranquillity

Organogenic elements, mainly carbon, nitrogen, phosphorus, and sulfur are present in the particulate material and in a breccia rock from Tranquillity Base in amounts ranging from 5 to 4200 parts per million. The major compounds of carbon released by heating are carbon monoxide and carbon dioxide; the former predominates. Small amounts of other compounds of carbon have also been observed. Sulfur can be released as hydrogen sulfide by treatment with acid. The carbon isotopic delta(13L)C values are definitely nonterrestrial (+ 13 to + 18.5 per mil).     

Oxygen isotope ratios in trees reflect mean annual temperature and humidity

Values of the oxygen isotope ratios (delta(18)O) in tree-ring cellulose closely reflect the delta(18)O values in atmospheric precipitation and hence mean annual temperature. The change in delta(18)O in cellulose is 0.41 per mil per degree Celsius for selected near-coastal stations. The values of delta(18)O in precipitation and cellulose also change with altitude, as demonstrated for Mount Rainier, Washington. A temperature lapse rate of 5.2 degrees +/- 0.5 degrees C per 1000 meters calculated from cellulose delta(18)O values agrees with the accepted mean annual lapse rate of 5 degrees C per 1000 meters for this region. Cellulose delta(18)O values and delta(18)O values of carbon dioxide equilibrated with leaf water differ by a fixed 16 per mil.     

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.     

Water, hydrogen, deuterium, carbon, carbon-13, and oxygen-18 content of selected lunar material

The water content of the breccia is 150 to 455 ppm, with a deltaD from-580 to -870 per mil. Hydrogen gas content is 40 to 53 ppm with a deltaD of -830 to -970 per mil. The CO(2) is 290 to 418 ppm with delta (13)C = + 2.3 to + 5.1 per mil and delta(18)O = 14.2 to 19.1 per mil. Non-CO(2) carbon is 22 to 100 ppm, delta(13)C = -6.4 to -23.2 per mil. Lunar dust is 810 ppm H(2)O (D = 80 ppm) and 188 ppm total carbon(delta(13)C = -17.6 per mil). The (18)O analyses of whole rocks range from 5.8 to 6.2 per mil. The temperature of crystallization of type B rocks is 1100 degrees to 1300 degrees C, based on the oxygen isotope fractionation between coexisting plagioclase and ilmenite.     

Carbon, carbides, and methane in an apollo 12 sample

Total carbon in the Apollo 12 sample 12023 fines was 110 micrograms per gram of sample with a carbon isotopic abundance delta(13)C (relative to the Pee Dee belemnite standard) of +12 per mil. Hydrolysis of the fines with deuterium chloride yielded undeuterated methane along with deuterated hydrocarbons, thus confirming the presence of 7 to 21 micrograms of carbon per gram of sample as carbide and about 2 micrograms of carbon per gram of sample as indigenous methane. After vacuum pyrolysis of the fines to 1100 degrees C the following gases were detected in the relative abundance: carbon monoxide carbon dioxide methane. Variations of the delta(13)C value with the pyrolysis temperature indicated the presence of carbon with more than one range of isotopic values. The observed delta(13)C value of +14 per mil for lunar carbide is much higher than that of carbide in meteorites. These results suggest that lunar carbide is either indigenous to the moon or a meteoritic contribution that has been highly fractionated isotopically.     

稳定同位素技术在肉羊产地溯源中的应用

[目的]通过比较不同部位羊肉中碳氮稳定同位素差异,以及对羊肉、全骨粉、脱脂骨粉与骨胶原的稳定同位素分析,为肉羊产地溯源鉴别提供技术支持.[方法]利用同位素比率质谱仪(IRMS)测定不同部位脱脂羊肉中δ13C和δ15N值,进而比较不同产地来源(新西兰和中国宁夏、甘肃、安徽)的羊肉、全骨粉、脱脂骨粉与骨胶原中δ13C和δ1...     

Oxygen isotopes in biogenic silica: global changes in ocean temperature and isotopic composition

A record of oxygen isotopes in biogenic silica from a deep-sea sediment core from the Southern Ocean reveals that marine diatoms retain their primary isotopic composition after burial. As a result, the marine diatom record can be combined with data on coexisting planktonic foraminifera to monitor past surface temperature and isotopic composition of seawater. The coupling of these two records allows the solution of two paleotemperature equations for each core interval. Data from a South Atlantic core show that the average delta(18)O during the glacial period at this site was higher by about 1.3 per mil than average Holocene values, and that average glacial-age temperatures were not significantly different from average Holocene values.     

Endogenous carbon in carbonaceous meteorites

Seven carbonaceous chondrites have been analyzed for soluble organic compounds, carbonate, and residual carbon. Carbon-13/carbon-12 isotopic mneasurements on these fractions gave the following values relative to a marine carbonate standard: carbonate, +40 to +70 per mil; residual carbon, -15 to -17 per mil; soluble organic material, -17 to -27 per mil, with one value of -5.5 per mil. These values are interpreted to indicate that carbonate, residual carbon, and part of the extractable organic material are endogenous to these meteorites.     

Penny ice cap cores, baffin island, canada, and the wisconsinan foxe dome connection: two states of hudson bay ice cover

Ice cores from Penny Ice Cap, Baffin Island, Canada, provide continuous Holocene records of oxygen isotopic composition (delta18O, proxy for temperature) and atmospheric impurities. A time scale was established with the use of altered seasonal variations, some volcanic horizons, and the age for the end of the Wisconsin ice age determined from the GRIP and GISP2 ice cores. There is pre-Holocene ice near the bed. The change in delta18O since the last glacial maximum (LGM) is at least 12.5 per mil, compared with an expected value of 7 per mil, suggesting that LGM ice originated at the much higher elevations of the then existing Foxe Dome and Foxe Ridge of the Laurentide Ice Sheet. The LGM delta18O values suggest thick ice frozen to the bed of Hudson Bay.     

Carbon-13/carbon-12 ratio is relatively uniform among honeys

The variability of the carbon-13/carbon-12 ratio in honeys was evaluated preliminary to use of the ratio to detect the addition of high-fructose corn syrup to honey. Eighty-four honey samples representing 34 states and including 37 floral types from 17 plant families were analyzed. The mean value of the per mil increment in carbon-13 (delta13C) for all samples is -25.2 per mil, and the coefficient of variation is 3.7 percent. This is the smallest variation yet encountered for a honey constituent or physical property. The range and magnitude of the values suggest that the floral sources are C(3) plants.     

Oxygen isotope zoning in garnet

Oxygen isotope zoning was examined within garnet with the use of the stable isotope laser probe. Four metamorphic garnets from the regional metamorphic terrane in Vermont and the skarn deposit at Carr Fork, Utah, were examined and were found to be concentrically zoned in delta(18)O values. The largest variations in delta(18)O values were observed in the regional metamorphic garnets, where delta(18)O values change by 3 per mil from core to rim. These oxygen isotope zoning profiles reflect the changes in the delta(18)O values of the rocks during garnet growth, which are caused by infiltration of fluids and by dehydration reactions during metamorphism.     

Carbon isotopic studies of organic matter in precambrian rocks

Reduced carbon in early Precambrian cherts of the Fig Tree and upper and middle Onverwacht groups of South Africa is isotopically similar (the average value of delta(13)C(PDB) is -28.7 per mil) to photosynthetically produced organic matter of younger geological age. Reduced carbon in lower Onverwacht cherts (Theespruit formation) is anomalously heavy (the average value of delta(13)C(PDB) is -16.5 per mil). This discontinuity may reflect a major event in biological evolution.     

Unexpected changes to the global methane budget over the past 2000 years

We report a 2000-year Antarctic ice-core record of stable carbon isotope measurements in atmospheric methane (delta13CH4). Large delta13CH4 variations indicate that the methane budget varied unexpectedly during the late preindustrial Holocene (circa 0 to 1700 A.D.). During the first thousand years (0 to 1000 A.D.), delta13CH4 was at least 2 per mil enriched compared to expected values, and during the following 700 years, an about 2 per mil depletion occurred. Our modeled methane source partitioning implies that biomass burning emissions were high from 0 to 1000 A.D. but reduced by almost approximately 40% over the next 700 years. We suggest that both human activities and natural climate change influenced preindustrial biomass burning emissions and that these emissions have been previously understated in late preindustrial Holocene methane budget research.     

Pore Fluid Constraints on the Temperature and Oxygen Isotopic Composition of the Glacial Ocean

Pore fluids from the upper 60 meters of sediment 3000 meters below the surface of the tropical Atlantic indicate that the oxygen isotopic composition (delta18O) of seawater at this site during the last glacial maximum was 0.8 ± 0.1 per mil higher than it is today. Combined with the delta18O change in benthic foraminifera from this region, the elevated ratio indicates that the temperature of deep water in the tropical Atlantic Ocean was 4°C colder during the last glacial maximum. Extrapolation from this site to a global average suggests that the ice volume contribution to the change in delta18O of foraminifera is 1.0 per mil, which partially reconciles the foraminiferal oxygen isotope record of tropical sea surface temperatures with estimates from Barbados corals and terrestrial climate proxies.     

Stable isotope enrichment in paleowaters of the southeast atlantic coastal plain, United States

Paleowaters from the Floridan aquifer system in the southeastern Atlantic coastal plain have higher D/H and (18)O/(16)O ratios than local Holocene ground water. Maximum delta(18)O enrichments in ground water having adjusted radiocarbon ages of 20,000 to 26,000 years are 0.7 to 2.3 per mil. The trend in isotopic enrichment in paleowaters is the reverse of that normally observed in continental glacial age ground water. Dissolved nitrogen and argon concentrations indicate, however, that the average recharge temperature was 5.3 degrees C cooler than that today. The data indicate cool conditions in the southeast Atlantic coastal plain during the last glacial maximum, with recharge limited primarily to late summer tropical cyclones and hurricanes.