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At least 55 records · Page 3Linked to original sources
USGS2010

Comment on: “New” lunar meteorites: Impact melt and regolith breccias and large‐scale heterogeneities of the upper lunar crust, by P. H. Warren, F. Ulff‐Møller, and G. W. Kallemeyn

We described lunar meteorite Dhofar 026 (Cohen et al. 2004) and interpreted this rock as a strongly shocked granulitic breccia (or fragmental breccia consisting almost entirely of granulitic‐breccia clasts) that was partially melted by post‐shock heating. Warren et al. (2005) objected to many aspects of our interpretation: they were uncertain whether or not the bulk rock had been shocked; they disputed our identification of the precursor as granulitic breccia; and they suggested that mafic, igneous‐textured globules within the breccia, which we proposed were melted by post‐shock heating, are clasts with relict textures. The major evidence for shock of the bulk rock is the fact that the plagioclase in the lithologic domains that make up 80–90% of the rock is devitrified maskelynite. The major evidence for a granulitic‐breccia precursor is the texture of the olivine‐plagioclase domain that constitutes 40—45% of the rock; Warren et al. apparently overlooked or ignored this lithology. Textures of the mafic, igneous‐textured globules, and especially of the vesicles they contain, demonstrate that these bodies were melted and crystallized in situ. Warren et al. suggested that the rock might have originally been a regolith breccia, but the textural homogeneity of the rock and the absence of solar wind—derived noble gases preclude a regolith‐breccia precursor. Warren et al. classified the rock as an impact‐melt breccia, but they did not identify any fraction that was impact melt.

Meteoritics and Planetary Science↗
USGS1976

Thermomagnetic analysis of meteorites, 3. C3 and C4 chondrites

Thermomagnetic analysis was made on samples of all known C3 and C4 chondrites in a controlled oxygen atmosphere. Considerable variation was noted in the occurrence of magnetic minerals, comparable to the variation observed earlier in the C2 chondrites. Magnetite was found as the only major magnetic phase in samples of only three C3 chondrites (2–4 wt.%) and the Karoonda C4 chondrite (7.7 wt.%). The magnetite content of these three C3 chondrites is only about one-third that observed in the C1 and C2 chondrites which were found to contain magnetite as the only magnetic phase. Five C3 chondrites were observed to undergo chemical change during heating, producing magnetite: this behavior is characteristic of troilite oxidation. Upper limits on initial magnetite content of about 1–9% were established for these meteorites. Samples of the remaining five C3 chondrites and the Coolidge C4 chondrite were found to contain both magnetite and metallic iron. In two samples, iron containing ≤2% Ni was observed, while in the other four, the iron contained 6–8 wt.% Ni. In addition to containing both magnetite and iron metal, three of these samples reacted during heating to form additional magnetite. Variations in the magnetic mineralogy and, hence by inference bulk mineralogy, of C3 and C4 chondrites indicate a more complex genesis than is evident from whole-rock elemental abundance patterns.

Earth and Planetary Science Letters↗
USGS1989

Isotopic determinations of rhenium and osmium in meteorites by using fusion, distillation and ion-exchange separations

A stable isotope-dilution method using resonance ionization mass spectrometry is suitable for the determination of rhenium and osmium abundances and osmium isotopic composition in carbonaceous chondrites and iron meteorites. The chemical procedure involves sodium peroxide fusion, followed by distillation of osmium from sulfuric acid/hydrogen peroxide and subsequent anion-exchange separation of rhenium from the same solution. ?? 1989.

Analytica Chimica Acta↗
USGS1997

Radiation-induced diamond crystallization: Origin of carbonados and its implications on meteorite nano-diamonds

Ten carbonados from Central Africa were studied for U-Th-Pb systematics. To extract U, Th, and Pb from the samples, we developed a cold combustion technique wherein diamond was burnt in liquid oxygen. The technique gave low blanks; 25–50 pg for Pb, 3 pg for U, and 5 pg for Th. After very thorough acid treatments of the carbonados with hot HNO 3 , HF, and HCl over one week, most of U, Th, and Pb were removed from the samples. Lead in the acid-leached diamonds was highly radiogenic ( 206 Pb/ 204 Pb up to 470). However, the amounts of U and Th in the acid-leached diamonds are too low to account for the radiogenic Pb even if we assume 4.5 Ga for the age of the diamonds. Therefore, we conclude that the radiogenic Pb was implanted into the diamonds from surroundings by means of recoil energy of radioactive decays of U and Th. From the radiogenic lead isotopic composition, we estimate a minimum age of 2.6 Ga and a maximum age of 3.8 Ga for the formation of the carbonados. The above findings of the implantation of recoiled radiogenic Pb into carbonados is consistent with the process of radiation-induced crystallization which was proposed for carbonado by Kaminsky (1987). We show from some theoretical considerations that when highly energetic particles, such as those emitted from radioactive decay of U and Th, interact with carbonaceous materials, they give rise to cascades of atomic disturbance (over regions of about a few nanometer), and the disturbed atoms are likely to recrystallize to form micro-diamonds because of increasing surface energy due to small size. The radiation-induced diamond formation mechanism may be relevant to the origin of nano-diamonds in primitive meteorites.

Geochimica et Cosmochimica Acta↗
USGS1980

Sr isotopic fractionation in Ca-Al inclusions from the Allende meteorite

True relative Sr isotopic compositions, determined by double spiking on Ca-Al inclusions from the Allende meteorite show up to 1.5??? per mass unit mass fractionation relative to the Earth and bulk chondrites. All abnormal inclusions are light-isotope enriched. A lack of isotopically heavy Sr in inclusions would place constraints on the time, place and mechanism of origin of these objects. ?? 1980 Nature Publishing Group.

Nature↗
USGS1980

Lu-hf total-rock isochron for the eucrite meteorites

The isotope 176Lu (2.6% of natural lutetium) decays by ??- to 176Hf, with a long half life. We present here the first Lu-Hf isochron. The eucrite meteorites, a suite of planetary igneous rocks of known age, 4,550 Myr, define a 10-point total-rock isochron with a slope of 0.0934 ?? 40, leading to a value of 3.53 ?? 0.14 ??1010yr for the ??--decay half life of 176Lu. The isochron intercept of 0.27973 ?? 12 gives the initial 176Hf/177Hf for the inner Solar System at the time of accretion. ?? 1980 Nature Publishing Group.

Nature↗
USGS1967

Rapid methods of determining cooling rates of iron and stony iron meteorites

Two rapid and simple methods have been developed for determining the approximate cooling rates of iron and stony-iron meteorites in which kamacite formed by diffusion-controlled growth along planar fronts. The first method requires only measurements of the mean kamacite bandwidth and the bulk nickel content. The second method requires the determination of the nickel composition near the taenite-kamacite interface with an electron microprobe.

Science↗
USGS1985

Origin of the Sudbury Complex by meteoritic impact: Neodymium isotopic evidence

Samarium-neodymium isotopic data on whole rocks and minerals of the Sudbury Complex in Canada gave an igneous crystallization age of 1840 ± 21 × 10 6 years. The initial epsilon neodymium values for 15 whole rocks are similar to those for average upper continental crust, falling on the crustal trend of neodymium isotopic evolution as defined by shales. The rare earth element concentration patterns of Sudbury rocks are also similar to upper crustal averages. These data suggest that the Sudbury Complex formed from melts generated in the upper crust and are consistent with a meteoritic impact.

Ontario↗
USGS1971

A meteorite fall near Sakakah, Kingdom of Saudi Arabia

In mid-January 1971, the U. S. Geological Survey Saudi Arabian Project learned that a meteorite fell near the town of Sakakah in northwestern Saudi Arabia during the evening of January 8. The U. S. Geological Survey is cooperating with the Saudi Arabian Directorate General of Mineral Resources in a mineral exploration program that is sponsored by the Kingdom of Saudi Arabia. A field party consisting of William R. Greenwood and Donald H. Johnson, U. S. Geological Survey geologists, and Mohammed Sultan Bahabri, Directorate General of Mineral Resources geologist, set off for Sakakah on February 23 and 24, 1971, after the end of the Islamic Holiday of Eid Al Adha, by Ministry of Petroleum and Mineral Resources helicopter and by Saudi Arabian Airlines commercial airplane. Accomodations were graciously provided at the Tapline pumping station at Badanah through the cooperation of Donald Cole, Acting Station Superintendent at Badanah, and Harry Alter, Acting Chief, Aramco office in Jiddah. The field party visited Amir Abdullah Misha'd bin Jiluwi, Governor of the Northern Frontier Province, in 'Ar'Ar on February 24 to inform him of the proposed search. He graciously offered the considerable assistance of his office.

Open-File Report↗
USGS2023

Using the potassium-argon laser experiment (KArLE) to date ancient, low-K chondritic meteorites

Several laboratories have been investigating the feasibility of in situ K-Ar dating for use in future landing planetary missions. One drawback of these laboratory demonstrations is the insufficient analogy of the analyzed analog samples with expected future targets. We present the results obtained using the K-Ar laser experiment (KArLE) on two old and K-poor chondritic samples, Pułtusk and Hvittis, as better lunar analogs. The KArLE instrument uses laser ablation to vaporize rock samples and quantifies K content by laser-induced breakdown spectroscopy (LIBS), Ar by quadrupole mass spectrometry (QMS), and ablated mass by laser profilometry. We performed 64 laser ablations on the chondrites to measure spots with a range of K 2 O and Ar content and used the data to construct isochrons to determine the chondrite formation age. The KArLE isochron ages on Pułtusk and Hvittis are 5059 ± 892 Ma and 4721 ± 793 Ma, respectively, which is within the uncertainty of published reference ages, and interpreted as the age of their formation. The uncertainty (2 σ ) on the KArLE ages obtained in this study is better than 20% (18% for Pułtusk and 17% for Hvittis). The precision, which compares our obtained ages to the reference ages, is also better than 20% (11% for Pułtusk and 4% for Hvittis). These results are encouraging for understanding the limits of this technique to measure ancient planetary samples and for guiding future improvements to the instrument.

Meteoritics & Planetary Science (MAPS)↗
USGS1975

Thermomagnetic analysis of meteorites, 2. C2 chondrites

Samples of all eighteen of the known C2 chondrites have been analyzed thermomagnetically. For eleven of these, initial Fe 3 O 4 content is low (generally <1%) and the J s -T curves are irreversible. The heating curves show variable greater (up to 10 times) than it is initially. This behavior is attributed to the production of magnetite from a thermally unstable phase — apparently FeS. Four of the remaining seven C2 chondrites contain Fe 3 O 4 as the only significant magnetic phase: initial magnetite contents range from 4 to 13%. The remaining three C2 chondrites contain iron or nickel-iron in addition to Fe 3 O 4 . These seven C2 chondrites show little evidence of the breakdown of a thermally unstable phase.

Earth and Planetary Science Letters↗
USGS2004

Photomosaics of the cathodoluminescence of 60 sections of meteorites and lunar samples

Cathodoluminescence (CL) petrography provides a means of observing petrographic and compositional properties of geological samples not readily observable by other techniques. We report the low-magnification CL images of 60 sections of extraterrestrial materials. The images we report include ordinary chondrites (including type 3 ordinary chondrites and gas-rich regolith breccias), enstatite chondrites, CO chondrites and a CM chondrite, eucrites and a howardite, lunar highland regolith breccias, and lunar soils. The CL images show how primitive materials respond to parent body metamorphism, how the metamorphic history of EL chondrites differs from that of EH chondrites, how dark matrix and light clasts of regolith breccias relate to each other, how metamorphism affects eucrites, the texture of lunar regolith breccias and the distribution of crystallized lunar spherules ("lunar chondrules"), and how regolith working affects the mineral properties of lunar soils. More particularly, we argue that such images are a rich source of new information on the nature and history of these materials and that our efforts to date are a small fraction of what can be done. Copyright 2004 by the American Geophysical Union.

Journal of Geophysical Research E: Planets↗
USGS2009

Moon meteoritic seismic hum: Steady state prediction

We use three different statistical models describing the frequency of meteoroid impacts on Earth to estimate the seismic background noise due to impacts on the lunar surface. Because of diffraction, seismic events on the Moon are typically characterized by long codas, lasting 1 h or more. We find that the small but frequent impacts generate seismic signals whose codas overlap in time, resulting in a permanent seismic noise that we term the "lunar hum" by analogy with the Earth's continuous seismic background seismic hum. We find that the Apollo era impact detection rates and amplitudes are well explained by a model that parameterizes (1) the net seismic impulse due to the impactor and resulting ejecta and (2) the effects of diffraction and attenuation. The formulation permits the calculation of a composite waveform at any point on the Moon due to simulated impacts at any epicentral distance. The root-mean-square amplitude of this waveform yields a background noise level that is about 100 times lower than the resolution of the Apollo long-period seismometers. At 2 s periods, this noise level is more than 1000 times lower than the low noise model prediction for Earth's microseismic noise. Sufficiently sensitive seismometers will allow the future detection of several impacts per day at body wave frequencies. Copyright 2009 by the American Geophysical Union.

Journal of Geophysical Research E: Planets↗
USGS1973

Apollo 17 "Orange soil" and meteorite impact on liquid lava

THE “orange soil” from Shorty Crater differs greatly from ordinary lunar soils in that it consists of ∼ 99% 10–300 µm smooth shiny spherules and broken fragments of spherules of transparent orange glass, about 20% of which contain partly crystallized to opaque material. The remaining 1 % is chiefly crystalline basalt fragments. Although the colour of the individual orange spherule varies with thickness from yellow–orange to red–brown, all orange glass in our sample (74220, 70; 0.25 g) has a uniform index of refraction ( ∼ 1.712). By contrast, other lunar soils contain spherules ranging from 1.50 to 1.75. The orange glass is also completely free of bubbles, to the limit of resolution of the light microscope, whereas bubbles are present in many other spherule samples. The spherules generally appear spherical in a normal microscope mount, but when viewed from two directions many are found to be oblate spheroids with axial ratios varying from near 1.00 to as low as 0.42 (Fig. 1 a ). Some have fissioned during free flight 1 and all stages of the fission process are found, as described for the Apollo 11 samples. Only a few spherules seem to have been distorted by landing while still soft. One notable exception is the occurrence of small spherules of orange glass conforming and adhering to the surface of larger black spherules (Fig. 1 b ).

Nature↗