The Yarle Lakes 001 meteorite: A H5 chondrite from South Australia

Abstract— The Yarle Lakes 001 meteorite was a single stone of 913 g found approximately 20 km north of Watson, South Australia, in 1990 October. It consists of olivine (Fa_{18.7 ± 0.4}, n = 30), low-Ca pyroxene (Fs_{16.6 ± 0.2} Wo _{12 + 0.4}, n = 15). feldspar, high-Ca pyroxene, metallic Fe-Ni and troilite. Based on texture and mineral chemistry, Yarle Lakes 001 is classified as a H5 chondrite of shock stage S3.     

The Loxton meteorite: A new olivine-bronzite chondrite from South Australia

Abstract— The Loxton meteorite is a single stone of 22 g found in South Australia in 1968. It has been classified as an L5 chondrite, shock facies ‘a,’ and contains olivine (Fa₂₄), orthopyroxene (Fs_21–22), clinopyroxene (Wo_44.7En_45.9Fs_9.4), nickel-iron, troilite, chromite and chlorapatite.     

Mineral and chemical composition of the Jezersko meteorite—A new chondrite from Slovenia

The Jezersko meteorite is a newly confirmed stony meteorite found in 1992 in the Karavanke mountains, Slovenia. The meteorite is moderately weathered (W2), indicating short terrestrial residence time. Chondrules in partially recrystallized matrix are clearly discernible but often fragmented and have mean diameter of 0.73 mm. The meteorite consists of homogeneous olivine (Fa_19.4) and low‐Ca pyroxenes (Fs_16.7Wo_1.2), of which 34% are monoclinic, and minor plagioclase (Ab₈₃An₁₁Or₆) and Ca‐pyroxene (Fs₆Wo_45.8). Troilite, kamacite, zoned taenite, tetrataenite, chromite, and metallic copper comprise about 16.5 vol% of the meteorite. Phosphates are represented by merrillite and minor chlorapatite. Undulatory extinction in some olivine grains and other shock indicators suggests weak shock metamorphism between stages S2 and S3. The bulk chemical composition generally corresponds to the mean H chondrite composition. Low siderophile element contents indicate the oxidized character of the Jezersko parent body. The temperatures recorded by two‐pyroxene, olivine‐chromite, and olivine‐orthopyroxene geothermometers are 854 °C, 737–787 °C, and 750 °C, respectively. Mg concentration profiles across orthopyroxenes and clinopyroxenes indicate relatively fast cooling at temperatures above 700 °C. A low cooling rate of 10 °C Myr^?1 was obtained from metallographic data. Considering physical, chemical, and mineralogical properties, meteorite Jezersko was classified as an H4 S2(3) ordinary chondrite.     

The Wilder H5 chondrite: A 1982 find from Idaho

Abstract— The Wilder chondrite, a single stone of 1970 g, was found in southwestern Idaho in 1982. A classification of H5 is indicated by the mean compositions of olivines (Fa_18.4) and orthopyroxenes (Fs_16.3), and the narrow range in mineral compositions, recrystallized nature of the matrix, and mean Wo content of the orthopyroxenes (Wo_1.34).     

Rumanová H5 chondrite,Slovaki

Abstract— An H5 chondrite was found near the village of Rumanová, Slovakia. dominant minerals of the meteorite are enstatite, olivine, kamacite, taenite and troilite. The minor minerals are oligoclase, augite, pigeonite, accessory chromite, whitlockite and chlorapatite. The composition of olivine (Fa_19.0) and low-Ca orthopyroxene (Fs_17.0), and the density and chemical composition of the meteorite correspond to those of an H chondrite. Normal zoning of Ni in metal grains and parallel planar fractures in olivine suggest weak shock metamorphism of stage S3. Due to moderate oxidation of metal, iron hydroxides were formed corresponding to weathering stage W2.     

The Linum Chondrite

Abstract— Based on optical microscopy and electron microprobe analysis, Linum is classified as an L6b chondrite that contains olivine (Fa₂₄), orthopyroxene (Fs₂₀), clinopyroxene (Wo₄₅En₄₇Fs₈), plagioclase (An₁₀Ab₈₄Or₆), nickel-iron, troilite, chromite and accessory amounts of chlorapatite and whitlockite.     

The Juancheng chondrite: A new meteorite fall from China

Abstract— A new meteorite, the Juancheng chondrite, fell recently in Juancheng County, Shandong Province, China. It is classified as an H5 (S2) chondrite on the basis of the compositions of olivine (Fa 19.2, σ_Fa 0.46), low-Ca pyroxene (Fs 16.9, σ_Fs 0.4) and Co contents of kamacite (0.36–0.47 wt%). Plagioclase is compositionally heterogeneous.     

Compositional diversity of ordinary chondrites inferred from petrology,bulk chemical,and oxygen isotopic compositions of the lowest FeO ordinary chondrite,Yamato 982717

We performed a petrologic, geochemical, and oxygen isotopic study of the lowest FeO ordinary chondrite (OC), Yamato (Y) 982717. Y 982717 shows a chondritic texture composed of chondrules and chondrule fragments, and mineral fragments set in a finer grained, clastic matrix, similar to H4 chondrites. The composition of olivine (Fa_{11.17 ± 0.48 (1σ)}) and low‐Ca pyroxene (Fs_{11.07 ± 0.98 (1σ)}Wo_{0.90 ± 0.71(1σ)}) is significantly more magnesian than those of typical H chondrites (Fa_16.0‐20, Fs_14.5‐18.0), as well as other known low‐FeO OCs (Fa_12.8‐16.7; Fs_13‐16). However, the bulk chemical composition of Y 982717, in particular lithophile and moderately volatile elements, is within the range of OCs. The bulk siderophile element composition (Ni, Co) is within the range of H chondrites and distinguishable from L chondrites. The O‐isotopic composition is also within the range of H chondrites. The lack of reduction textures indicates that the low olivine Fa content and low‐Ca pyroxene Fs content are characteristics of the precursor materials, rather than the result of reduction during thermal metamorphism. We suggest that the H chondrites are more compositionally diverse than has been previously recognized.     

The mineralogy of the Yaringie Hill meteorite—A new H5 chondrite from South Australia

Abstract— The Yaringie Hill meteorite is a new H5 ordinary chondrite found in the Gawler Ranges, South Australia. The meteorite, which shows only minor signs of terrestrial weathering, is predominantly composed of olivine (Fa_17.2), orthopyroxene (Fs_15.1Wo_1.1), and three distinct phases of nickeliferous iron metal (kamacite, taenite, tetrataenite). Other minerals include troilite, plagioclase (Ab₈₁An₁₆Or₃), clinopyroxene (En₅₂Wo₄₂Fs₆), chlorapatite, merrillite, ilmenite, and native copper. Three types of spinel with distinctive textures (coarse, skeletal aggregates, rounded aggregates) and with compositions close to the join MgAl₂O₄‐FeCr₂O₄ are also present. Chondrules within the Yaringie Hill meteorite, which often have poorly defined boundaries, are placed in a recrystallized matrix. Shock indicators suggest that the meteorite experienced only weak shock metamorphism (S3).     

Fuc Bin–an L5 chondrite fall from Vietnam

Abstract— A stony meteorite fell near the Fuc Bin village, Vietnam, in July, 1971. Based on optical microscopy, scanning electron microscopy and electron probe microanalysis, the meteorite is classified as an L5 chondrite that contains olivine (Fa_23.6), low-Ca pyroxene (Fs_20.3 Wo_1.3), high-Ca pyroxene (Fs_7.5 Wo_44.2), plagioclase (Ab_83.8 Or₅), chlorapatite, merrillite and opaque minerals: chromite, troilite, kamacite, taenite, tetrataenite and native copper.     

Frontier Mountain meteorite specimens of the acapulcoite‐lodranite clan: Petrography,pairing, and parent‐rock lithology of an unusual intrusive rock

Abstract— In this paper we reconstruct the heterogeneous lithology of an unusual intrusive rock from the acapulcoite‐lodranite (AL) parent asteroid on the basis of the petrographic analysis of 5 small (<8.3 g) meteorite specimens from the Frontier Mountain ice field (Antarctica). Although these individual specimens may not be representative of the parent‐rock lithology due to their relatively large grain size, by putting together evidence from various thin sections and literature data we conclude that Frontier Mountain (FRO) 90011, FRO 93001, FRO 99030, and FRO 03001 are paired fragments of a medium‐ to coarse‐grained igneous rock which intrudes a lodranite and entrains xenoliths. The igneous matrix is composed of enstatite (Fs_{13.3 ± 0.4} Wo_{3.1 ± 0.2}), Cr‐rich augite (Fs_{6.1 ± 0.7} Wo_{42.3 ± 0.9}), and oligoclase (Ab_{80.5 ± 3.3} Or_{3.2 ± 0.6}). The lodranitic xenoliths show a fine‐grained (average grain size 488 ± 201 μm) granoblastic texture and consist of olivine Fa_{9.5 ± 0.4} and Fe,Ni metal and minor amounts of enstatite Fs_{12.7 ± 0.4} Wo_{1.8 ± 0.1}, troilite, chromite, schreibersite, and Ca‐phosphates. Crystals of the igneous matrix and lodranitic xenoliths are devoid of shock features down to the scanning electron microscope scale. From a petrogenetic point of view, the lack of shock evidence in the lodranitic xenoliths of all the studied samples favors the magmatic rather than the impact melting origin of this rock. FRO 95029 is an acapulcoite and represents a separate fall from the AL parent asteroid, i.e., it is not a different clast entrained by the FRO 90011, FRO 93001, FRO 99030, and FRO 03001 melt, as in genomict breccias common in the meteoritic record. The specimen‐to‐meteorite ratio for the AL meteorites so far found at Frontier Mountain is thus 2.5.     

The Dengli H3 complex breccia: A 1976 find from the Karakoom Desert

Abstract— Dengli is a highly weathered 243.5-g chondrite that was found in 1976 in the Karakoom desert, Turkmenia. The meteorite contains olivine, high-Ca and low-Ca twinned pyroxenes, plagioclase, merrillite, cryptocrystalline material, and opaque minerals: metallic Fe, Ni, troilite, chromite. Based on the texture and the compositions of olivine (Fa_19.6, n = 52, C.V. = 19.3) and low-Ca pyroxene (Fs_18.2, n = 27, C.V. = 17.0), Dengli is classified as an H3.8 breccia.     

Korra Korrabes: A new,large H3 chondrite breccia from Namibia

Abstract— A new, large, ordinary chondrite has been recovered from near the strewn field of Gibeon iron meteorites in Namibia, and is designated Korra Korrabes, after the farm property on which the specimens were found in 1996–2000. A total of ～140 kg of related specimens were recovered, including a large stone of 22 kg, and hundreds of smaller objects between 2 g and several kilograms. Cut surfaces indicate that Korra Korrabes is a breccia, containing 10–20% of light grey‐brown clasts up to 3 cm across in a uniform, darker grey‐brown host that contains abundant round chondrules, and irregular grains of Fe‐Ni metal and troilite up to 1 cm across. The vast majority of the stone is unshocked, although some clasts show mild shock features (stage S2), and one chondrule fragment is moderately shocked (stage S3). Weathering grade varies between W1 and W2. Microprobe analyses indicate variable compositions of olivine (Fa_13.8–27.2, n = 152, percent mean deviation = 7.82%) and low‐Ca pyroxene (multiply twinned clinobronzite, Fs_8.4–27.8, n = 68). There is excellent preservation of magmatic textures and mineralogy within many chondrules, including normally zoned olivine (Fa_13.8–18.9) and low‐Ca pyroxene (Fs_0.2–20.9) phenocrysts, and abundant glass, some of whose compositions are unusually alkaline (Na₂O + K₂O = 13.6–16.3 wt%) and Ca‐deficient (CaO = 0‐0.75 wt%), seemingly out of magmatic equilibrium with associated clinoenstatite or high‐Al calcic clinopyroxene crystals. Textural and mineralogical features indicate that Korra Korrabes is an H3 chondrite breccia, which represents the largest and least equilibrated stony meteorite yet recovered from Namibia; it is now one of the four largest unequilibrated ordinary chondrites worldwide.     

THE LOOP CHONDRITE: PETROLOGY,MINERAL CHEMISTRY,AND OPAQUE MINERALOGY

The Loop meteorite was found in 1962 in Gaines County, Texas, at a location very close to that where the Ashmore chondrite was found in 1969. The two specimens were assumed to be fragments of the same meteorite. The Loop meteorite is a type L6 chondrite composed of olivine (Fo_75.4Fa_24.6), orthopyroxene (En_77.6Wo_1.5Fs_20.9), clinopyroxene (En_47.5Wo_45.1Fs_7.4), plagioclase (Ab_84.3Or_5.5An_10.2), Fe-Ni metal, troilite, and chromite. Fe-Ni metal is represented by kamacite (5.8-6.4 wt % Ni, 0.88-1.00 wt % Co), taenite (30.0–52.9 wt % Ni, 0.16-0.34 wt % Co), and plessite (16.8–28.5 wt % Ni, 0.38-0.54 wt % Co). Native copper occurs as rare inclusions in Fe-Ni metal. Both chondrules and matrix have similar mineral compositions. The mineral chemistry of the Loop meteorite is quite different from that of the Ashmore, which was classified as an H5 chondrite by Bryan and Kullerud (1975). Therefore, the Ashmore and Loop meteorites are two different chondrites, even though they were recovered from the same geographic location.     

Northwest Africa 428: Impact‐induced annealing of an L6 chondrite breccia

Abstract— Northwest Africa (NWA) 428 is an L chondrite that was successively thermally metamorphosed to petrologic type‐6, shocked to stage S4–S5, brecciated, and annealed to approximately petrologic type‐4. Its thermal and shock history resembles that of the previously studied LL6 chondrite, Miller Range (MIL) 99301, which formed on a different asteroid. The petrologic type‐6 classification of NWA 428 is based on its highly recrystallized texture, coarse metal (150 ± 150 μm), troilite (100 ± 170 μm), and plagioclase (20–60 μm) grains, and relatively homogeneous olivine (Fa_{24.4 ± 0.6}), low‐Ca pyroxene (Fs_{20.5 ± 0.4}), and plagioclase (Ab_{84.2 ± 0.4}) compositions. The petrographic criteria that indicate shock stage S4–S5 include the presence of chromite veinlets, chromite‐plagioclase assemblages, numerous occurrences of metallic Cu, irregular troilite grains within metallic Fe‐Ni, polycrystalline troilite, duplex plessite, metal and troilite veins, large troilite nodules, and low‐Ca clinopyroxene with polysynthetic twins. If the rock had been shocked before thermal metamorphism, low‐Ca clinopyroxene produced by the shock event would have transformed into orthopyroxene. Post‐shock brecciation is indicated by the presence of recrystallized clasts and highly shocked clasts that form sharp boundaries with the host. Post‐shock annealing is indicated by the sharp optical extinction of the olivine grains; during annealing, the damaged olivine crystal lattices healed. If temperatures exceeded those approximating petrologic type‐4 (?600–700°C) during annealing, the low‐Ca clinopyroxene would have transformed into orthopyroxene. The other shock indicators, likewise, survived the mild annealing. An impact event is the most plausible source of post‐metamorphic, post‐shock annealing because any ²⁶Al that may have been present when the asteroid accreted would have decayed away by the time NWA 428 was annealed. The similar inferred histories of NWA 428 (L6) and MIL 99301 (LL6) indicate that impact heating affected more than 1 ordinary chondrite parent body.     

High‐pressure phases in shock‐induced melt veins of the Umbarger L6 chondrite: Constraints of shock pressure

Abstract— We report a previously undocumented set of high‐pressure minerals in shock‐induced melt veins of the Umbarger L6 chondrite. High‐pressure minerals were identified with transmission electron microscopy (TEM) using selected area electron diffraction and energy‐dispersive X‐ray spectroscopy. Ringwoodite (Fa₃₀), akimotoite (En₁₁Fs₈₉), and augite (En₄₂Wo₃₃Fs₂₅) were found in the silicate matrix of the melt vein, representing the crystallization from a silicate melt during the shock pulse. Ringwoodite (Fa₂₇) and hollandite‐structured plagioclase were also found as polycrystalline aggregates in the melt vein, representing solid state transformation or melting with subsequent crystallization of entrained host rock fragments in the vein. In addition, Fe₂SiO₄‐spinel (Fa₆₆‐Fa₉₉) and stishovite crystallized from a FeO‐SiO₂‐rich zone in the melt vein, which formed by shock melting of FeO‐SiO₂‐rich material that had been altered and metasomatized before shock. Based on the pressure stabilities of the high‐pressure minerals, ringwoodite, akimotoite, and Ca‐clinopyroxene, the melt vein crystallized at approximately 18 GPa. The Fe₂SiO₄‐spinel + stishovite assemblage in the FeO‐SiO₂‐rich melts is consistent with crystallization of the melt vein matrix at the pressure up to 18 GPa. The crystallization pressure of ?18 GPa is much lower than the 45–90 GPa pressure one would conclude from the S6 shock effects in melt veins (Stöffler et al. 1991) and somewhat less than the 25–30 GPa inferred from S5 shock effects (Schmitt 2000) found in the bulk rock.     

Fall,classification and cosmogenic records of the Sabrum (LL6) chondrite

Abstract— The petrographic and chemical characteristics of a fresh Indian meteorite fall at Sabrum are described. Its mean mineral composition is defined by olivine (Fa_31.4), orthopyroxene (Fs_25.1,Wo_2.0), clinopyroxene (Wo₄₅En_45.6Fs_9.4) and plagioclase (An_10.6Ab_83.6Or_5.8). The meteorite shows moderate shock features, which indicate that it belongs to the S4 category. Based on mineralogical and chemical criteria the meteorite is classified as an LL6 brecciated veined chondrite. Several cosmogenic radioisotopes (⁴⁶Sc, ⁷Be, ⁵⁴Mn, ²²Na and ²⁶Al), noble gas (He, Ne, Ar, Kr and Xe), nitrogen isotopes, and particle tracks density have been measured. Concentrations of cosmogenic ²¹Ne and ³⁸Ar indicate that its cosmic‐ray exposure age is 24.8 Ma. Small amounts of trapped Kr and Xe, consistent with petrologic class 5/6, are present. The track density in olivines is found to be (1.3 ± 0.3) × 10⁶/cm². Activities of most of the short‐lived isotopes are lower than those expected from solar cycle variation. ²²Na/²⁶Al (1.12 ± 0.02) is found to be significantly anomalous, being ?25% lower than expected from the Climax neutron monitor data. These results indicate that the cosmic‐ray flux during the terminal segment of the meteoroid orbit was low. The activities of ²⁶Al and ⁶⁰Co and the track density indicate small meteoroid size with a radius ?15 cm.     

Petrology and geochemistry of Patuxent Range 91501, a clast‐poor impact melt from the L‐chondrite parent body and Lewis Cliff 88663, an L7 chondrite

Abstract— We have performed petrologic and geochemical studies of Patuxent Range (PAT) 91501 and Lewis Cliff (LEW) 88663. PAT 91501, originally classified as an L7 chondrite, is rather a unique, near total impact melt from the L‐chondrite parent body. Lewis Cliff 88663 was originally classified as an “achondrite (?)”, but we find that it is a very weakly shocked L7 chondrite. PAT 91501 is an unshocked, homogeneous, igneous‐textured ultramafic rock composed of euhedral to subhedral olivine, low‐Ca pyroxene, augite and chrome‐rich spinels with interstitial albitic plagioclase and minor silica‐alumina‐alkali‐rich glass. Only ～10% relic chondritic material is present. Olivine grains are homogeneous (Fa_25.2–26.8). Low‐Ca pyroxene (Wo_1.9–7.2En_71.9–78.2Fs_19.9–20.9) and augite (Wo_29.8–39.0En_49.2–55.3Fs_11.8–14.9) display a strong linear TiO₂‐Al₂O₃ correlation resulting from igneous fractionation. Plagioclase is variable in composition; Or_3.0–7.7Ab_79.8–84.1An_8.2–17.2.‐Chrome‐rich spinels are variable in composition and zoned from Cr‐rich cores to Ti‐Al‐rich rims. Some have evolved compositions with up to 7.9 wt% TiO₂. PAT 91501 bulk silicate has an L‐chondrite lithophile element composition except for depletions in Zn and Br. Siderophile and chalcophile elements are highly depleted due to sequestration in centimeter‐size metal‐troilite nodules. The minerals in LEW 88663 are more uniform in composition than those in PAT 91501. Olivine grains have low CaO and Cr₂O₃ contents similar to those in L5–6 chondrites. Pyroxenes have high TiO₂ contents with only a diffuse TiO₂‐Al₂O₃ correlation. Low‐Ca pyroxenes are less calcic (Wo_1.6–3.1En_76.5–77.0Fs_20.4–21.4), while augites (Wo_39.5–45.6En_46.8–51.1Fs_7.6–9.4) and plagioclases (Or_2.6–5.7Ab_74.1–83.1An_11.2–23.3) are more calcic. Spinels are homogeneous and compositionally similar to those in L6 chondrites. LEW 88663 has an L‐chondrite bulk composition for lithophile elements, and only slight depletions in siderophile and chalcophile elements that are plausibly due to weathering and/or sample heterogeneity.     

The Hashima,Japan H4 chondrite: A newly reported meteorite

Abstract We report a new chondrite that fell in Hashima City in central Japan sometime during the period 1868–1912. The chondrite weighs 1110.64 g and exhibits distinct chondritic structure. Chondrules occupy 24 vol% of the stone and consist of olivine (average Fa_17,8), low-Ca pyroxene (average Fs_15,8 Wo_0.9), devitrified glass and lesser amounts of oligoclase (ca. Ab₈₀Or₄), kamacite, taenite, troilite and chromian spinel. Matrix occupying 76 vol% of the stone consists of olivine, low-Ca pyroxene, kamacite, taenite, troilite, cryptocrystalline minerals and lesser amounts of chromian spinel and chlorapatite. Matrix minerals have the same compositions as those in chondrules. Mineral chemistry, bulk chemistry and magnetic properties indicate that Hashima is an H-group chondrite. Well-defined chondrules, scarcely recrystallized oligoclase and relatively small variations of olivine and low-Ca pyroxene compositions indicate that Hashima is of petrologic type 4.     

Devgaon (H3) chondrite: Classification and complex cosmic ray exposure history

Abstract— The Devgaon meteorite fell in India on February 12, 2001 and was immediately collected. It is an ordinary chondrite having a number of SiO₂‐rich objects and some Ca, Al‐rich inclusions. Olivines (Fa_17–19) are fairly equilibrated, while pyroxenes (Fs_4–20) are unequilibrated. Occasionally, shock veins are visible, but the bulk rock sample is very weakly shocked (S2). Chondrules and chondrule fragments are abundant. Based on chemical and petrological features, Devgaon is classified as an H3.8 group chondrite. Several cosmogenic radionuclides ranging in half‐lives from 5.6 d (⁵²Mn) to 7.3 times 10⁵ yr (²⁶Al), noble gases (He, Ne, Ar, Kr, and Xe), and particle track density have been measured. The track density in olivines from five spot samples varies between (4.6 to 9) × 10⁶ cm^?2 showing a small gradient within the meteorite. The light noble gases are dominated by cosmogenic and radiogenic components. Large amounts of trapped gases (Ar, Kr, and Xe) are present. In addition, (n, γ) products from Br and I are found in Kr and Xe, respectively. The average cosmic ray exposure age of 101 ± 8 Ma is derived based on cosmogenic ³⁸Ar, ⁸³Kr, and ¹²⁶Xe. The track production rates correspond to shielding depths of about 4.9 to 7.8 cm, indicating that the stone suffered type IV ablation. Low ⁶⁰Co, high (²²Ne/²¹Ne)_c, and large neutron produced excesses at ⁸⁰Kr, ⁸²Kr, and ¹²⁸Xe indicate a complex exposure history of the meteoroid. In the first stage, a meter‐sized body was exposed for nearly 10⁸ yr in the interplanetary space that broke up in ?50 cm‐sized fragments about a million years ago (stage 2), before it was captured by the Earth.