Fall, recovery, and characterization of the Novato L6 chondrite breccia

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The Vicência meteorite, a stone of 1.547 kg, fell on September 21, 2013, at the village Borracha, near the city of Vicência, Pernambuco, Brazil. It was recovered immediately after the fall, and our consortium study showed it to be an unshocked (S1) LL3.2 ordinary chondrite. The LL group classification is based on the bulk density (3.13 g cm À3 ); the chondrule mean apparent diameter (0.9 mm); the bulk oxygen isotopic composition (d 17 O = 3.768 AE 0.042&, d 18 O = 5.359 AE 0.042&, D 17 O = 0.981 AE 0.020&); the content of metallic Fe,Ni (1.8 vol%); the Co content of kamacite (1.73 wt%); the bulk contents of the siderophile elements Ir and Co versus Au; and the ratios of metallic Fe 0 /total iron (0.105) versus total Fe/Mg (1.164), and of Ni/ Mg (0.057) versus total Fe/Mg. The petrologic type 3.2 classification is indicated by the beautifully developed chondritic texture, the standard deviation (~0.09) versus mean Cr 2 O 3 content (~0.14 wt%) of ferroan olivine, the TL sensitivity and the peak temperature and peak width at half maximum, the cathodoluminescence properties of chondrules, the content of trapped 132 Xe tr (0.317 9 10 À8 cm 3 STP g À1 ), and the Raman spectra for organic material in the matrix. The cosmic ray exposure age is~72 Ma, which is at the upper end of the age distribution of LL group chondrites. The meteorite is unusual in that it contains relatively large, up to nearly 100 lm in size, secondary fayalite grains, defined as olivine with Fa >75 , large enough to allow in situ measurement of oxygen and Mn-Cr isotope systematics with SIMS. Its oxygen isotopes plot along a mass-dependent fractionation line with a slope of~0.5 and D 17 O of 4.0 AE 0.3&, and are similar to those of secondary fayalite and magnetite in the unequilibrated chondrites EET 90161, MET 96503, and Ngawi. These data suggest that secondary fayalite in Vicência was in equilibrium with a fluid with a D 17 O of~4&, consistent with the composition of the fluid in equilibrium with secondary magnetite and fayalite in other unequilibrated ordinary chondrites. Secondary fayalite and the chondrule olivine phenocrysts in Vicência are not in isotopic equilibrium, consistent with low-temperature formation of fayalite during aqueous alteration on the LL parent body. That alteration, as dated by the 53 Mn-53 Cr chronology age of secondary fayalite, took place 4:0 þ1:4 À1:1 Ma after formation of CV CAIs when anchored to the quenched angrite D'Orbigny.

Section: Resultsmentioning

confidence: 98%

“…), Novato L6 (Jenniskens et al. ), or Soltmany L6 (Schmitt‐Kopplin et al. ), with mainly CHO‐ and CHOS‐type of molecular composition.…”

Section: Resultsmentioning

confidence: 99%

The Vicência meteorite fall: A new unshocked (S1) weakly metamorphosed (3.2)LLchondrite

Keil

Zucolotto

Krot

et al. 2015

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“…), the CAMS network in California (e.g., Jenniskens et al. ), the Croatian Fireball Network (Borovička et al. ), the French Fireball Network (Colas et al.…”

Section: Introductionmentioning

confidence: 99%

Park Forest (L5) and the asteroidal source of shocked L chondrites

Meier

Welten

Riebe

et al. 2017

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The Park Forest (L5) meteorite fell in a suburb of Chicago, Illinois (USA) on March 26, 2003. It is one of the currently 25 meteorites for which photographic documentation of the fireball enabled the reconstruction of the meteoroid orbit. The combination of orbits with pre‐atmospheric sizes, cosmic‐ray exposure (CRE), and radiogenic gas retention ages (“cosmic histories”) is significant because they can be used to constrain the meteoroid's “birth region,” and test models of meteoroid delivery. Using He, Ne, Ar, 10Be, and 26Al, as well as a dynamical model, we show that the Park Forest meteoroid had a pre‐atmospheric size close to 180 g cm−2, 0–40% porosity, and a pre‐atmospheric mass range of ~2–6 tons. It has a CRE age of 14 ± 2 Ma, and (U, Th)‐He and K‐Ar ages of 430 ± 90 and 490 ± 70 Ma, respectively. Of the meteorites with photographic orbits, Park Forest is the second (after Novato) that was shocked during the L chondrite parent body (LCPB) break‐up event approximately 470 Ma ago. The suggested association of this event with the formation of the Gefion family of asteroids has recently been challenged and we suggest the Ino family as a potential alternative source for the shocked L chondrites. The location of the LCPB break‐up event close to the 5:2 resonance also allows us to put some constraints on the possible orbital migration paths of the Park Forest meteoroid.

“…; Jenniskens et al. ). Although the U and Rb enrichment appear slightly higher than the bulk average L and LL chondrites, they fall within the range observed across the entire suite of L and LL chondrites used to construct the average.…”

Section: Resultsmentioning

confidence: 98%

Meteorites found on Misfits Flat dry lake, Nevada

Harlan¹,

Jenniskens

Zolensky

et al. 2016

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Abstract-Meteorites have been found on the small Misfits Flat dry lakebed near Stagecoach, Nevada (119.382W, +39.348N). Since the first find on Sept. 22, 2013, a total of 58 stones of weathering stage W2/3 with a combined mass of 339 g have been collected in 19 visits to the area. This small (3.3 9 3.6 km) lakebed is now a newly designated dense collection area (DCA). Most meteorites were found in a small 350 9 180 m area along the north shore and most are fragments of several broken individual stones. Three of these fragments were classified as an LL4/5 of shock stage S2, now named Misfits Flat 001, one of which (stone MF33) fell 8.1 AE 1.3 ka ago based on the 14 C terrestrial age, assuming it came from a 20-80 cm diameter meteoroid. In addition, a small darkly crusted meteorite MF34, now named Misfits Flat 002, was found 820 m WSW from the main mass. This meteorite is classified as an LL5 ordinary chondrite with shock stage S4/5. The meteorite is saturated in 14 C at 63 dpm kg À1 , suggesting it originated from the center of a 0.5 m diameter meteoroid, or deep inside a~1.0 m meteoroid, less than 300 yr ago. Accounts exist of a fireball seen at 13:15 UT on March 2, 1895, that are consistent with the find location of Misfits Flat 002.