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All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Pb loss from Apollo 17 glassy samples and Apollo 16 revisited

U-Th-Pb analyses of bulk samples of soil breccia 70019, when compared to KREEP data, indicate that different lunar samples are sometimes characterized by distinctly different initial Pb isotopic compositions. U-Th-Pb analyses on nonglassy samples and a glassy separate of soil breccia 70019, and bulk and agglutinate samples of soil 72701 showed that the glassy samples did lose considerable Pb relative to U less than 200 million years ago. These data support the contention of other investigators that vaporization of volatile elements owing to impact events significantly alters the chemistry of the lunar regolith. Metaclastic rock 60315 was reanalyzed and was found to be concordant at 3.93 billion years rather than slightly discordant, as was previously reported.

Nunes, P. D.↗
NASA NTRS1992

U-Th-Pb, Rb-Sr, and Sm-Nd isotopic systematics of lunar troctolitic cumulate 76535 - Implications on the age and origin of this early lunar, deep-seated cumulate

The U-Th-Pb, Rb-Sr, and Sm-Nd isotopic systematics of four lightly leached residues of pristine, high-Mg, troctolitic cumulate 76535 were analyzed in order to determine their ages and magma sources. The data indicate that the cumulate was in isotopic equilibrium with a fluid or magma characterized by a high U-238/Pb-204 (mu) value of 600 at 4.236 Ga. Two and three stage Pb evolution calculations define even greater source mu values of about 1000, assuming low lunar initial mu values between 5 and 40 prior to about 4.43 Ga. These results are similar to mu values for KREEP sources and are also consistent with values from 78235, suggesting that at least some high-Mg suite rocks were derived from magma sources with high-mu values similar to KREEP, and support that idea that these rocks postdate primary lunar differentiation and formation of ferroan anorthosites.

Premo, Wayne R.↗
NASA NTRS2015

Investigation of Benthic Foraminiferal Non-Traditional Stable Isotopes to Reconstruct Methane Fluxes in Sedimentary Environments

Methane (CH4) is an important greenhouse gas, with a global warming potential much higher than carbon dioxide (CO2) on a short time scale. Even if the residence time of CH4 in the atmosphere is relatively short (tens of years), one of the products of CH4 oxidation is CO2, a greenhouse gas with a much longer residence time in the atmosphere (tens to hundreds of years). CH4 has been proposed as one of the trigger mechanisms for rapid global climate change today and in the geological past. With regards to the geological past, numerous studies proposed the benthic foraminiferal carbon isotope ratio (Delta13C) as a tool to reconstruct the impact of marine CH4 on rapid climate changes; however, the investigation of modern benthic foraminiferal Delta13C have produced inconclusive results. CH4 has a distinctive hydrogen isotope (Delta(D)) and Delta13C signature compared to seawater, and sulfate reduction, often coupled to CH4 anaerobic oxidation in sediments, changes the sulfur isotope signature (Delta34S) of the remaining sulfate in porewater. Therefore, we hypothesize that the Delta(D) and Delta34S signature of infaunal benthic foraminiferal species can provide a complementary approach to Delta13C to study CH4 dynamics in sedimentary environments. Here, we present the preliminary results obtained analyzing Uvigerina peregrina Delta(D) and Delta34S from three different locations at Hydrate Ridge, offshore Oregon. Unfortunately, the lack of chemical data related to the moment of foraminiferal calcification makes difficult to build a robust relationship among the U. peregrina stable isotopes and the CH4 fluxes at the sampling sites. However, our results look very promising, as each site is characterized by a different Delta(D) and Delta34S signature. We emphasize that this study represents the first step in the development of new proxies (Delta(D)) and Delta34S), which may complement the more traditional benthic foraminiferal Delta13C values, to reconstruct marine CH4 fluxes in the geological past.

Borrelli, C.↗
NASA NTRS2005

Lunar and Planetary Science XXXVI, Part 19

The topics include: 1) The abundances of Iron-60 in Pyroxene Chondrules from Unequilibrated Ordinary Chondrites; 2) LL-Ordinary Chondrite Impact on the Moon: Results from the 3.9 Ga Impact Melt at the Landing Site of Appolo 17; 3) Evaluation of Chemical Methods for Projectile Identification in Terrestrial and Lunar Impactites; 4) Impact Cratering Experiments in Microgravity Environment; 5) New Achondrites with High-Calcium Pyroxene and Its implication for Igneous Differentiation of Asteroids; 6) Climate History of the Polar Regions of Mars Deduced form Geologic Mapping Results; 7) The crater Production Function for Mars: A-2 Cumulative Power-Law Slope for Pristine Craters Greater than 5 km in Diameter Based on Crater Distribution for Northern Plains Materials; 8) High Resolution Al-26 Chronology: Resolved Time Interval Between Rim and Interior of a Highly Fractionated Compact Type a CAI from Efremovka; 9) Assessing Aqueous Alteration on Mars Using Global Distributions of K and Th; 10) FeNi Metal Grains in LaPaz Mare Basalt Meteorites and Appolo 12 Basalts; 11) Unique Properties of Lunar Soil for In Situ Resource Utilization on the Moon; 12) U-Pb Systematics of Phosphates in Nakhlites; 13) Measurements of Sound Speed in Granular Materials Simulated Regolith; 14) The Effects of Oxygen, Sulphur and Silicon on the Dihedral Angles Between Fe-rich Liquid Metal and Olivine, Ringwoodite and Silicate Perovskite: Implications for Planetary Core Formation; 15) Seismic Shaking Removal of Craters 0.2-0.5 km in Diameter on Asteroid 433 Eros; 16) Focused Ion Beam Microscoopy of ALH84001 Carbonate Disks; 17) Simulating Micro-Gravity in the Laboratory; 18) Mars Atmospheric Sample Return Instrument Development; 19) Combined Remote LIBS and Raman Spectroscopy Measurements; 20) Unusual Radar Backscatter Properties Along the Northern Rim of Imbrium Basin; 21) The Mars Express/NASAS Project at JPL; 22) The Geology of the Viking 2 Lander Site Revisited; 23) An Impact Genesis for Loki Patera? 24) Mars Polar Cap Edges Tracked over 3 Full Mars Years; 25) Elemental Abundance in Presolar SiC: Comparing Grains Separated by Acid Residue and Gently Separation Procedures; 26) First Results from the Descent Imager/Spectral Radiometer (DISR) Experiment on the Huygens Entry Probe of Titan; 27) Minor Element Behavior of Pallasite Olivine: Understanding Pallasite Thermal History and Chronology; 28) Canonical Anorthite in a Grosnaja Forsterite-bearing CAI; 29) Experimental Evidence for Condensation of 'Astrophysical' Carbonate; 30) Distribution and Classification of Multiple Coronae on Venus; 31) Recognition of Rayed Craters on Mars in THEMIS Thermal Infrared Imagery: Implications for Martian Meteorite Source Regions; 32) Geochemical Modeling of Evaporites on Mars: Insight from Meridiani Planum; 33) Hadean Crustal Processes Revealed from Oxygen Isotopes and U-Th-Pb Depth Profiling of Pre-4.0 Ga Detrital Zircons from Western Australia; 34) On Modeling the Seepage of Water into the Martian Subsurface; 35) Martial Gullies and Groundwater: A Series of Unfortunate Exceptions; 36) Olivine and Carbonate Globules in ALH84001: A Terrestrial Analog, and Implications for Water on Mars; 37) A Reevaluation of Mass Movements Within the Valles Marineris Region of Mars Using MOLA and MOC Data; 38) Evidence of Hydrated 109P/Swift-Tuttle Meteoroids from Meteor Spectroscopy; 39) Cr-54 Anomalies in the Solar System: Their Extent and Origin; 40) Reevaluation of the Mn-53-Cr-53 Systematic in the Basaltic Achondrites; 41) Effective Liquid Metal-Silicate Mixing Upon Shock by Power-Law Droplet Size Scaling in Richtmyer-Meshkov Like Perturbations; 42) Post-Impact Deformation of Impact Craters: Towards a Better Understanding Through the Study of Mjolnir Crater; 43) Cutting Silica Aerogel for Particle Extraction; 44) Liquid Hydrocarbons on Titan's Surface? How Cassini ISS Observations Fit into the Story (So Far); and 45) Mesoscale Simulations of Polar Circulations: Late Spring to Late Summe

Source record↗
NASA NTRSDate not supplied

Modeling 238U/204Pb (μ) and Initial Pb of Lunar Meteorite Northwest Africa 12593

Apatite Ca 5 (PO 4 ) 3 (F, Cl, OH) serves as a valuable analytical resource. It is the only nominally hydrous phase on the moon and possesses the capacity to concentrate elements like U, Th, Pb, and rare earth elements (REE). This characteristic facilitates its use in U-Pb and Pb-Pb geochronology, allowing for the determination of the initial isotopic Pb and the -238 U/ -204 Pb ratio (μ) of the parent melt. In situ analysis of apatite grains can provide a detailed record of geochemical changes, revealing the broader petrogenetic and volatile history of the source material. This mineral is particularly informative in understanding the developmental history of its source. In situ analyses are crucial for lunar samples, predominantly composed of breccias, where correlating distinct grains with whole rock analyses poses challenges. This study utilizes in situ apatite isotopic analysis of apatite grains in lunar meteorite Northwest Africa 12593 and model the initial Pb isotopic composition and -238 U/ -204 Pb (μ) of the source. We present in situ Secondary Ionization Mass Spectrometry (SIMS) Pb-Pb analyses of 12 apatite grains in Northwest Africa (NWA) 12593 to test two hypotheses: 1) NWA 12593 clasts and matrix are closely related and from the same source, and 2) the matrix material previously documented as having a highland affinity has a lower modeled μ then KREEP.

K M Lehman Franco↗
NASA NTRS1986

Formation ages and evolution of Shergotty and its parent planet from U-Th-Pb systematics

The isotopic composition of Pb from Shergotty, Zagami, and EETA 79001 meteorites was determined for different phases. Using phases with low U-238/Pb-204 ratio, the initial leads of these meteorites were defined. Samples from all three meteorites were shown to have distinct initial leads, and, thus to have evolved from different reservoirs over most of solar system history in a low U-238/Pb-204 environment. It follows that the parent planet of the shergottites has a high Pb-204 concentration relative to U and must also be high in other volatiles. The possibility of the Martian origin of the SNC-type meteorites is discussed.

Chen, J. H.↗
NASA NTRS1988

U-Pb ages and Sr, Pb and Nd isotope data for gneisses near the Kolar Schist Belt: Evidence for the juxtaposition of discrete Archean terranes

Uranium-lead ages and Sr, Pb, and Nd isotopic data for gneisses near the Kolar Schist Belt and their interpretation as evidence for the juxtaposition of discrete Archean terranes were presented. The granodioritic Kambha gneiss east of the schist belt has a zircon age of 2532 + or - 3 Ma and mantle-like initial Sr, Pb, and Nd isotopic ratios. Therefore these gneisses are thought to represent new crust added to the craton in the latest Archean. By contrast, more mafic Dod gneisses and leucocratic Dosa gneisses west of the schist belt (2632 + or - 7 and 2610 + or - 10 Ma) show evidence for contamination of their magmatic precursors (LREE-enriched mantle-derived for the Dod gneisses) by older (greater than 3.2 Ga) continental crust. Fragments of this older crust may be present as granitic and tonalitic inclusions in the 2.6-Ga gneisses and in shear zones. The antiquity of these fragments is supported by their Nd, Sr, and Pb isotopic compositions and by 2.8 to greater than 3.2 Ga zircon cores.

Krogstad, E. J.↗
NASA NTRS1980

A search for isotopic anomalies in uranium

The U-238/U-235 ratios for nine bulk chondritic meteorites and a terrestrial basalt were measured. The total range in U-238/U-235 determined for both total meteorites and for acid leaches was from 137.2 terrestrial U. The typical errors in a single determination are plus or minus 6 per thousand (2 sigma m) for a 2 ng U sample from a chondrite. Taking the extreme values of delta U-235 for each measurement the maximum amount of excess U-235 that can be allowed to be present ranges from 200 million to 2 billion atoms per gram of bulk meteorite. These results do not support the claims of variations in U-238/U-235 at the percentage levels or number of excess U-235 atoms in some of the same meteorites as reported by several other previous workers.

Chen, J. H.↗
NASA NTRS1992

Age and isotopic relationships among the angrites Lewis Cliff 86010 and Angra dos Reis

The paper presents results of a wide-ranging isotopic investigation of the the Antarctic angrite LEW-86010 (LEW), and reassesses the type angrite Angra dos Reis (ADOR) in order to obtain precise radiometric ages and initial Sr isotopic compositions, and to search for the erstwhile presence of the short-lived nuclei Sm-146 and Al-26 via their daughter products. The isotopic compositions of Sm, U, Ca, and Ti were measured to allow a detailed appraisal to be made of the relations between, and the geneology of, these two angrites. LEW proves to be severely contaminated with modern terrestrial Pb, which is shown to result from terrestrial weathering. Concordant Pb-Pb model ages of pyroxene separates are obtained; uranium isotopic compositions are normal within error. Overall, striking age and isotopic similarities between LEW and ADOR were found, suggesting almost simultaneous production on the same asteroid, even though recent experimental studies imply that the two are not comagmatic.

Lugmair, G. W.↗
NASA NTRS1987

Origin of lead from green glass of Apollo 15426 - A search for primitive lunar lead

Green glass from Apollo 15 lunar clod 15426 (collected from the north rim of Spur Crater), known to be the most primitive among sampled lunar volcanic rocks, was analyzed for Pb isotopic compositions and concentrations of U, Th, and Pb. Hand-picked green glass and yellow impact glass particles were washed with water and a mixture of HBr and HF, and the washes and residues, spiked with a mixure of U-233-U-236-Th-230-Pb-205, were subjected to U-Th-Pb analyses. In contrast to the case of the Apollo 17 orange glass, the isotopic composition of lead from the surfaces of the green glass spherules is totally different from that of the spherules' interiors but is similar to the composition of lunar surface lead. Data for the interior lead yield a Pb-207/Pb-206 age of 3.41 Ga. The data indicate that lunar Pb evolved in an environment with U-238/Pb-204 ratios of 19 to 55, which is considerably lower than those for mare basalts (about 300) but higher than the earth values (6-8).

Tatsumoto, Mitsunobu↗
NASA NTRS1994

Noble gas isotopes and halogens in volatile-rich inclusions in diamonds

Application of the (40)Ar-(39)Ar method and noble gas studies to diamonds has increased our understanding of their age relationships to the host kimberlite or lamproite, and of the source and composition of volatile-rich fluids in the upper mantle. The properties of diamond (inert, high mechanical strength and low gas diffusivities) means they are especially useful samples for studying gases trapped deep within the earth (less than 150 km) as they are unlikely to have undergone loss or exchange of entrapped material since formation. Volatile-rich fluids (H2O-CO2) are important agents for metasomatic processes in the upper mantle, and the noble gases and halogens preferentially partition into this phase leading to a strong geochemical coherence between these groups of elements. The abundances of the halogens in the major reservoirs of the Earth shows a marked progression from chlorine, concentrated in the oceans, through to iodine which, through its affinity to organic material, is concentrated mainly in sediments. Abundances in the upper mantle are low. This is particularly true for iodine which is of special interest in view of its potential significance as an indicator of sediment recycling and by way of its link to (129)Xe amomalies in the mantle through the low extinct isotope (129)I. Extensions of the (40)Ar-(39)Ar technique enable measurements of halogens and other elements (K, Ca, Ba, U) by production of noble gas isotopes from these species during neutron irradiation. Samples analyzed in this way include 15 coated stones from an unknown source in Zaire, 3 boarts from the Jwaneng and 1 boart from the Orapa kimberlites, both in Botswana.

Burgess, Raymond↗
NASA NTRS2004

Endemic Mo Isotopic Anomalies in Iron and Carbonaceous Meteorites

Mo in refractory interstellar grains shows large isotope anomalies. Recent Mo studies showed isotope effects in Allende and Murchison, and in iron meteorites, mesosiderites, and pallasites. Excesses of p- and r-process isotopes (or depletion of sprocess isotopes) of up to 3.5 epsilon units (epsilon u=parts in 10(exp 4)) were reported. We have reported on endemic isotope anomalies in Ru. Other workers have resolved no isotope anomalies for Mo or Ru and have claimed that the work by others is incorrect. Because Ru isotopes can interfere at Mo-96, Mo-98, Mo-100, we improved the chemical separations and eliminated interferences. For Mo work, we used the same solutions from which we separated and analyzed Ru. Three of the iron meteorites (Coahuila, Cape York, and Cape of Good Hope) were chosen for their large Mo isotopic effects. Mo was loaded on outgassed Re filaments, and then reduced; we used Ba(OH)2-NaOH as emitter, and measured Mo in static mode, as MoO3(-). We used Mo-98/Mo-96 for the mass fractionation correction (exponential law). No interferences from Ru or Zr isotopes were detected using the electron multiplier and no corrections were needed. For results on Mo standards we show 2 sigma(not 2 sigma mean) external precision better than: 0.7 epsilon u for Mo-94/Mo-96 and Mo-95/Mo-96; 1.0 epsilon u for Mo-92/Mo-96 and Mo-97/Mo-96; 1.4 epsilon u for Mo-100/Mo-96. Reproducibility for Mo standards is shown as contours (blue lines).

Chen, J. H.↗