THE RUHOBOBO,RWANDA METEORITE: A NEW L6 CHONDRITE

Ruhobobo is a new meteorite which fell in Rwanda, Africa, in 1976. We found and analyzed olivine (Fa 23.4), opx (Fs 19.7, Wo 1.4), cpx (Fs 7.5, Wo 44.0), plagioclase (An 11.7, Or 5.6), chromite, “whitlockite”, kamacite, taenite and troilite. Based on these analyses and on microscopic observation, Ruhobobo is an unshocked L6 chondrite.     

CLAST-LADEN MELT-ROCK FRAGMENT IN THE ADAMS COUNTY,COLORADO, H5 CHONDRITE

The Adams County, Colorado, H5 chondrite contains a lithic fragment, 1 cm in size, that is texturally and mineralogically quite different from the chondritic host. It is composed of: a groundmass of fine-grained euhedral to subhedral olivine (3–15 μm) and interstitial glass enclosing larger olivine and pyroxene grains (0.15-0.5 mm; about 15 vol %); an assemblage of enstatite grains (subfragment within) and an assemblage of olivine plus orthopyroxene (a second subfragment); and about 11 vol % grains of mixed troilite and nickel-iron metal. Analyses yielded these results: (i) olivine grains of the fragment groundmass have a compositional range (Fa_12–45) and most grains contain substantial CaO and Cr₂O₃ (～ 0.20 and 0.30 avg. wt%, respectively); interstitial glass has ～ 55 wt% SiO₂; (ii) larger olivine grains of the fragment are similarly high in CaO and Cr₂O₃ and also have a wide FeO/MgO range; one unusual pyroxene is an Mg-rich pigeonite; (iii) the metal is martensite in composition (11–14 wt% Ni); and (iv) major and trace element analyses by INAA indicate an H-group bulk composition for the entire 1 cm lithic fragment. On the basis of its texture and bulk and mineral compositions, the fragment is interpreted to represent unequilibrated H-group material that was partly melted by impact. The Ca- and Cr-enriched groundmass olivine and interstitial glass resulted from rapid crystallization of the chondritic melt. The Ca- and Cr-enriched larger silicate grains, including the enstatite sub-fragment and the pigeonite grain, are residual, unmelted clasts from the target material (this is supported by the presence of similar material in actual H3 chondrites). Further impact brecciation of the clast-laden melt material, and resultant impact-splashing accounts for the presence of the fragment in the H-group Adams County host and documents the coexistence of unequilibrated and equilibrated H-group material as surface regolith on one parent body.     

THE MARYVILLE METEORITE: A 1983 FALL OF AN L6 CHONDRITE

The Maryville chondrite fell on January 28, 1983 in eastern Tennessee. Compositions of olivine (Fa 24.5), orthopyroxene (Fs 20.8), plagioclase (An 10.6), along with the bulk composition and siderophile concentrations, indicate L-group classification. The presence of highly equilibrated minerals, strongly recrystallized matrix, and the development of large, clear plagioclase grains suggest petrologic type 6 classification. Subsequent to metamorphism the meteorite was subjected to high transient pressures that converted some feldspar to glass, deformed the silicates, and caused small amounts of melting to occur. The effects of this shock event correspond to shock facies “d” or “e”.     

AN L6 CHONDRITE FOUND NEAR PARACHILNA,SOUTH AUSTRALIA*

An 8.82 kg stony meteorite found on Motpena Station, 31°6' S, 138° 16' E, near Parachilna, South Australia, is shown to be a somewhat weathered L6 (olivine-hypersthene) chondrite. This is listed in The Meteoritical Bulletin, No. 53, June 1975 as MOTPENA, Synonym, Parachilna.     

THE GALATIA,KANSAS, CHONDRITE

The Galatia meteorite was found in August, 1971, approximately 7 km ENE of Galatia, Barton County, Kansas (98° 53′W., 38° 39.5′N). The single stone weighed 23.9 kg and is partially weathered. Olivine (Fa_24.9) and pyroxene (Fs_20.9) compositions indicate L-group classification, and textural observations indicate that the stone is of petrologic type 6. Galatia is similar in many respects to the Otis L6 chondrite (found 20 km to the west), but it does not have the brecciated structure of Otis and, thus, it is not part of the same fall.     

THE MADIUN,INDONESIA, CHONDRITE

Madiun is a white, veined olivine-hypersthene, L6 chondrite. It can be classed as such on the basis of its petrography and chemistry, uniform olivine (Fa_24.2) and pyroxene (Fs_21,2) end total iron content of 23.7 wt % Fe.     

THE KRAMER CREEK,COLORADO METEORITE: A NEW L4 CHONDRITE

The Kramer Creek, Colorado, chondrite was found in 1966 and identified as a meteorite in 1972. Bulk chemical analysis, particularly the total iron content (20.36%) and the ratio of Fe_total/SiO₂ (0.52), as well as the compositions of olivine (Fa_21.7) and orthopyroxene (Fs_18.3) place the meteorite into the L-group of chondrites. The well-defined chondritic texture of the meteorite, the presence of igneous glass in the chondrules and of low-Ca clinopyroxene, as well as the slight variations in FeO contents of olivine (2.4% MD) and orthopyroxene (5.6% MD) indicate that the chondrite belongs to the type 4 petrologic class.     

THE IJOPEGA CHONDRITE: A NEW H6 FALL

The Ijopega (Papua New Guinea) meteorite is a new H6 group chondrite fall which contains olivine (Fa 19.9 mole %), bronzite (Fs 17.8 mole %), plagioclase (An 12.1 Or 6.3 Ab 81.6 mole %), diopside, kamacite, taenite, troilite, chromite and whitlockite. The meteorite is extensively recrystallized and brecciated, and shows evidence of moderate shock deformation. Examination of Fe²⁺ and Mg partitioning between ortho- and clinopyroxene indicates a high equilibration temperature (940° or 880 °C). Chemical analysis shows the meteorite to be rich in S, containing about twice the average H-group abundance. Trace elements, including REE, are in accord with established H-group chondrite abundances.     

THE TAMBAKWATU CHONDRITE

According to its petrography, uniform olivine, Fa_23.8, and pyroxene, Fs_20.4, a total iron content of 22.9 wt % Fe, 16.4 wt % FeO and an FeO/FeO + MgO ratio of 24.7 mol %, the Tambakwatu is a veined, intermediate hypersthene (Cia) or L6 chondrite.     

THE SEONI CHONDRITE

The Seoni (India) chondrite is an H6 group ordinary chondrite that contains olivine (Fa, 19.7 mole%), orthopyroxene (Fs, 15.9 mole%), clinopyroxene, plagioclase (An, 10.3; Or, 5.6 mole%), together with chromite, troilite, kamacite, taenite, chlorapatite, and whitlockite. Recrystallization has been quite extensive as indicated by the presence of few remnant chondrules, low abundance of clinopyroxene and relatively high abundance of well formed plagioclase. Treatment of Fe²⁺ and Mg partitioning between clinopyroxene and orthopyroxene and between olivine and chromite indicates equilibration temperatures of between 875–920 °C.     

THE ELLA ISLAND,GREENLAND, CHONDRITE

The Ella Island, Greenland, meteorite was found in August of 1971. Electron microprobe study of the meteorite revealed it to contain olivine, low-calcium pyroxene, high-calcium pyroxene, plagioclase, kamacite, taenite, chromian-hercynite and troilite. On the basis of fayalite and ferrosilite content, poorly-defined chondrules, absence of glass in chondrules, presence of well-developed feldspar in the matrix and chondrules, and degree of recrystallization of the matrix, the Ella Island meteorite is classified as an L-6 chondrite.     

THE PARSA ENSTATITE CHONDRITE

Two meteoritic stones weighing roughly 600 and 200 g fell on 14 April 1942 near Parsa, Bihar, India. The meteorite is a high-Fe (EH) enstatite chondrite on the basis of its large abundance of chondrules, its low concentrations of refractory elements, the Si content of its metal (25–30 mg/g), and its enstatite composition Mg_0.975Ca_0.007Fe_0.018. The high contents of Zn, Cd and In suggest that Parsa is petrologic type 4. A unique feature is an irregular nodule of coarse enstatite, several cm long which is chemically different in its Ca and Fe content compared to the matrix. We have increased the elemental concentrations by 10% to allow for terrestrial oxidation and hydration. The revised siderophile and moderately volatile element concentrations fall within the range observed in EH chondrites and mostly outside the range found in EL chondrites. Terrestrial alteration is indicated by the presence of limonite and other hydrated minerals as well as the morphologies revealed by scanning electron microscopy. The ²⁶Al activity is 51 ± 6 dpm/kg consistent with the calculated production rate. Cosmogenic track densities combined with the ²¹Ne, ³⁸Ar exposure age of 17 Myr indicate 4–10 cm ablation loss, or a preatmospheric mass of about 40 kg.     

USTÍ NAD ORLICI: A NEW L6 CHONDRITE FROM CZECHOSLOVAKIA

Ustí nad Orlici (Kerhartice), a meteorite which fell on June 12, 1963 in Czechoslovakia, is classified as a L6 chondrite. Compositions of olivine (Fa 23.4), orthopyroxene (Fs 20, Wo 1.3), plagioclase (Ab₈₅An₁₀Or₅) along with the bulk composition of the meteorite support this classification. Chromite compositions vary with grain size. Large chromites are higher in TiO₂ and lower in Fe³ than small chromites. This may indicate that either these two chromites formed initially under different fO₂ conditions, or that this difference resulted from different equilibration behaviors of both chromites as a function of grain size. The meteorite contains three distinct sulfide assemblages: 1) troilite-pentlandite, 2) troilite, pentlandite-cubanite-chalcopyrite-pyrrhotite-mackinawite, 3) troilite-tetrataenite-(Fe, Cu, Ni)_{1***. 02}S. These assemblages indicate equilibration down to temperatures close to 200 °C.     

THE BROWNELL AND NESS COUNTY (1894) L6 CHONDRITES: FURTHER SORTING-OUT OF NESS COUNTY METEORITES

Brownell is a new, moderately shocked, L6 chondrite from Ness County, Kansas that is petrologically distinct from the other L6 chondrites from Ness County. These latter meteorites, Wellmanville, Franklinville and Ness County (1894), are very similar in their olivine and low-Ca pyroxene compositional distributions, kamacite Co contents, modal abundances of metallic Fe, Ni and presence of martensitic metallic Fe, Ni (∼ 14 wt. % Ni). However, their silicates indicate that they have been shocked to different extents. We suggest that all three probably represent a single, heterogeneously-shocked, L6 fragmental breccia that fell over a large area, > 30 km in length.     

NOBLE GASES IN THE UNIQUE CHONDRITE,KAKANGARI

The Kakangari chondrite has a cosmic-ray exposure age of 5.4 m.y. and a K-Ar age near 4 g.y. Its high cosmogenic ³He/²¹Ne ratio of 7.5 indicates a small preatmospheric mass. The He and Ne are largely of solar-wind origin, presumably implanted during exposure in the regolith of its parent body. The heavy gases Ar, Kr, Xe are largely of planetary origin. Taken together, the low ¹²⁹Xe/¹³²Xe (1.07), low ³⁶Ar/¹³²Xe (225), and high ¹³²Xe content (45 × 10^?10 cc STP/g) are more similar to the values for unequilibrated ordinary chondrites or even C1, C2 chondrites than to enstatite chondrites, and suggest that Kakangari has the same gas-bearing mineral assemblage as the former, in spite of its high degree of reduction (Fa_4.9).     

THE TIMMERSOI†, NIGER,HYPERSTHENE CHONDRITE

The Timmersoi meteorite, a new type L5 hypersthene chondrite from the Niger Republic is described and microprobe analyses of its olivine, orthopyroxene, clinopyroxene, plagioclase, kamacite, taenite, troilite, chromite, whitlockite, chlorapatite and limonite presented. Veins and patches of black “glassy” material are regarded as products of shock melting. In places this material contains immiscible droplets of troilite each with one or more well-formed crystals of taenite. Calculations indicate equilibrium between olivine and orthopyroxene with a temperature of equilibration of about 850 °C.     

THE ATLANTA ENSTATITE CHONDRITE BRECCIA

Atlanta is the fifth known brecciated enstatite chondrite. It contains a centimeter-sized troilite-rich clast, similar to those that occur in Blithfield. All of these clasts probably formed in the solar nebula under high pS₂/pO₂ conditions in a gas of non-cosmic composition. The absence of ordinary or carbonaceous chondrite clasts in any of the enstatite chondrite breccias and absence of enstatite chondrite clasts or materials formed at high pS₂/pO₂ ratios in ordinary and carbonaceous chondrite breccias support the model that enstatite chondrites were formed at a location distant from those of the other chondritic groups.     

THE CLASSIFICATION OF THE BENARES CHONDRITE

The Benares meteorite is an LL4 chondrite, not LL6 as recorded in the literature. Some specimens labelled Benares are misidentified.