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Three masses of the Chelyabinsk meteorite have been studied with a wide range of analytical techniques to understand the mineralogical variation and thermal history of the Chelyabinsk parent body. The samples exhibit little to no postentry oxidation via Mossbauer and Raman spectroscopy indicating their fresh character, but despite the rapid collection and care of handling some low levels of terrestrial contamination did nonetheless result. Detailed studies show three distinct lithologies, indicative of a genomict breccia. A light-colored lithology is LL5 material that has experienced thermal metamorphism and subsequent shock at levels near S4. The second lithology is a shock-darkened LL5 material in which the darkening is caused by melt and metal-troilite veins along grain boundaries. The third lithology is an impact melt breccia that formed at high temperatures (~1600 °C), and it experienced rapid cooling and degassing of S2 gas. Portions of light and dark lithologies from Chel-101, and the impact melt breccias (Chel-102 and Chel-103) were prepared and analyzed for Rb-Sr, Sm-Nd, and Ar-Ar dating. When combined with results from other studies and chronometers, at least eight impact events (e.g., ~4.53 Ga, ~4.45 Ga, ~3.73 Ga, ~2.81 Ga, ~1.46 Ga, ~852 Ma, ~312 Ma, and ~27 Ma) are clearly identified for Chelyabinsk, indicating a complex history of impacts and heating events. Finally, noble gases yield young cosmic ray exposure ages, near 1 Ma. These young ages, together with the absence of measurable cosmogenic derived Sm and Cr, indicate that Chelyabinsk may have been derived from a recent breakup event on an NEO of LL chondrite composition.

— Samples from a suite of Shergotty—Nakhla—Chassigny (SNC) meteorites were analyzed for their O isotopic ratios by a modified version of the laser fluorination technique. Measured isotopic ratios (17O/16O and 18O/16O) from bulk samples of the Shergottites, EETA79001, Shergotty and Zagami; the Nakhlite Lafayette; and Chassigny are similar to those reported in the literature, as are those from olivine and pyroxene mineral separates from Lafayette. Iddingsite, a preterrestrial alteration product of Lafayette, was measured for the first time as a separate phase. Oxygen isotopic ratios increase with the percentage of iddingsite in a sample to a maximum δ18O of 14.4% for a ∼90% separate. Based on these measurements, end-member iddingsite has a δ18O of 15.6%, which places it among other 18O-enriched secondary phases (carbonate and silica) observed in SNC meteorites. The relatively large difference in δ18O between iddingsite and the olivine and pyroxene it replaces (∼11%) is typical of low-temperature alteration products. A range of crustal fluid δ18O values can be interpreted from the δ18O for end-member iddingsite, assuming isotopic equilibrium was achieved during low-temperature hydrous alteration (

Preliminary investigations have been made on two separate pieces from the Aioun el Atrouss meteorite that fell on April 17, 1974 in southeast Mauritania. The major portion of the meteorite is a brecciated hypersthene achondrite with orthopyroxene (En74) as the major phase. Clasts of eucrite, up to 7 per cent in volume within a single slice, occur within the hypersthene achondrite host. No evidence has been found of reaction between the two meteorite types, nor of the presence of any materials intermediate in composition.

Results of bulk chemical analyses and mineralogical and petrographic studies of a chondrite found at Kramer Creek, Colorado, are reported. The meteorite has been classified as an L-group chondrite on the basis of its bulk chemistry, the fayalite content of its olivine (21.7%) and the ferrosilicate content of its pyroxene (18.3%). The presence of interstitial glass and the iron oxide percent mean deviations for olivine and low-Ca pyroxene (2.4 and 4.6%) place the specimen in petrologic group 4 of the Van Schmus and Wood classification (1967)

Major, minor and trace element analysis as well as noble gas measurements were performed on three Holbrook chondrite samples collected fresh in 1912, in 1931, and in 1968. Decreases in metallic iron and MgO and an increase in total iron were detected. Elemental concentrations of Ti, Ca, Al, P, Mn, Ni, and Cr did not change significantly during weathering. While sodium might have been lost, and K slightly enriched, the trace elements C, Rb, and Sr increased at least two-fold during weathering. Gas abundances decreased, and the concentration ratios of noble gas nuclides varied unpredictably.

Abee chondrite samples were heated at 700 C for one week at 0.00001 to 0.001 atm Ne or at 0.00001 atm H2. Samples heated in Ne showed greater loss of Bi and Se and greater retention of Zn than those heated in H2. An inverse relationship between Zn retention and ambient Ne pressure was found. Seven trace elements (Ag, Co, Cs, Ga, In, Te, and Tl) were retained or lost to the same extent regardless of the heating conditions. Variations in the apparent activation energy for C above and below 700 C suggest that diffusive loss from different hosts and/or different mobile transport processes over the temperature range may have been in effect.

Holbrook chondrite specimen, discussing effects of weathering, leeching and trace elements enrichment over period of time before recovery

Vigarano, a type 3 carbonaceous chondrite, contains a chondrule composed of highly refractory Ca- and Al-rich glass with minor spinel. The chondrule formed from material similar to the Ca-, Al-, Ti-rich aggregates that are common in Vigarano and other type 3 chondrites and formation of these refractory aggregates must predate formation of some Vigarano chondrules. Experiments with synthetic analogs and a comparison with studies in the system CaO-MgO-Al2O3-SiO2 indicate a temperature for formation of the chondrule at or above 1700 C followed by very rapid cooling.