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Paragould

LL5
standby for paragould photo
Fell February 17, 1930
36° 4′ N., 90° 30′ W. At about 4:00 in the morning, a bright fireball with accompanying detonations pierced the predawn sky, its path visible over several states. Some witnesses believed it to be a crashing airplane, but it was a meteorite that ended its fall near Paragould, Arkansas. The first stone that was discovered was found by farmer Raymond Parkinson at the bottom of a 3½ foot hole, southwest of Finch in the Poland Township. Three men spent half the following day digging the 80-pound stone out of Parkinson’s pasture. Parkinson sent a sample to H. H. Nininger asking if he would like to purchase the meteorite, but before Nininger could complete the trip, the stone was covertly sold by local high school teacher L.V. Rhine, to which it was on loan for exhibit. Nevertheless, while he was in the area, Nininger was able to calculate the meteorite’s trajectory and arrange for the purchase of any additional masses that he suspected might eventually be found.

Four weeks later, an 820-pound mass was discovered three miles from the first mass, and within 300 yards of a farmhouse. The mass was found lying in a crater eight feet wide and eight feet deep. It was presumed by the homeowner, J. Fletcher, that the large hole had been dug by dogs, but its true nature was quickly realized by his neighbor, W. Hodges. The removal of the mass took three hours and required five men and a team of horses. The 820-pound mass was purchased by Nininger for the large sum of $3,600 and subsequently sold to the Chicago Field Museum for $6,200.

Prior to the events surrounding the fall and recovery of the Paragould meteorite, Nininger was forced to balance his passion for finding meteorites with his necessity for earning a regular salary, which he accomplished by teaching biology and geology at McPherson College in Kansas. The profitable sale of the Paragould main mass to Stanley Field and its subsequent donation to the Field Museum of Natural History in Chicago became the impetus for him to resign from his teaching job and dedicate his life full-time to the search for meteorites, ultimately becoming the most successful meteorite hunter of the century. The following quote from his book Find A Falling Star is telling: ‘The Paragould meteorite had profound effects on our lives. I have never ceased to regret parting with it, but I had paid a price too high, and was forced to give up either the specimen or my dream of making meteorites a new vocation. And Paragould, with the $2,000 profit it brought, was the way to my dream.’ The 80-pound Paragould stone was purchased by Stuart Perry for his collection and then donated it to the Smithsonian National Collection in 1935. At the time of its fall, the Paragould meteorite was the largest known witnessed fall and the largest intact stony meteorite in existence. It has been highly shocked (S4–5) causing plagioclase to recrystallize, resulting in a wide range of An compositions (A. Rubin, 1992; A. Brearley and R. Jones, 1998). The rare identification of L-chondrite clasts in the Paragould breccia has been reported by Fodor and Keil (1978).

The photo above shows a 2.374 g partial slice of Paragould that was removed from the 820 pound mass which once belonged to H. H. Nininger. A magnificent Paragould section can be seen on display at the Smithsonian Institution, Washington D.C. standby for paragould main mass photo
Paragould main mass on display in Mullins Library at the University of Arkansas


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Parnallee

LL3.7
standby for parnallee photo
Fell February 1857
9° 14′ N., 78° 21′ E. On February 28, 1857, at 12:00 noon, sonic booms were heard followed by the fall of two stones weighing 134 pounds and 37 pounds. Parnallee is said to be 16 miles south of Madura, India, but no village with this name can be traced in the area. The place of fall is probably Perunali, Ramnad district, 52 miles SSE of Madura.

This is a very primitive chondrite full of slightly flattened chondrules (ave. 10% deformation) ranging in size from 0.2 mm to 2.5 mm, but some as large as 4 mm have been identified. They include radial pyroxene, barred olivine, and porphyritic types. Shock effects include fractured olivine and extensive undulatory extinction, likely the result of the impact shock that also produced the chondrule foliation. In a study of two LL chondrites, NWA 1701 and LAR 06298, Weirich et al. (2009) determined an Ar–Ar age of ~1 b.y., possibly reflecting the last major impact on the LL chondrite parent body. A shock stage of S3 was determined for Parnallee.

Parnallee was previously classified as an LL3.6 ordinary chondrite, consistent with results from the technique of induced thermoluminescence. However, utilizing Raman spectroscopy along with other independent petrologic tracers (i.e., noble gas content, presolar grain abundance, and zoning of olivine phenocrysts), Bonal et al. (2006) concluded that the actual petrologic type of Parnallee should lie between 3.7 and 3.8, and they suggested a classification of LL3.7 as most appropriate.

Most of the metal and sulfide in this meteorite occurs between chondrules, but some resides in both the interior and along the rims of chondrules. Much of the glassy mesostasis within the chondrules has been devitrified to very fine-grained aggregates, but some chondrules preserve a transparent, isotropic, brown glass. Light brown limonitic staining around metal particles is widespread but not pervasive, and does not mask the primary textures of the chondrules. Investigators have identified an achondritic clast (a microgabbro), as well as a chondritic clast that is isotopically related to carbonaceous chondrites (Sokol et al., 2007 and references therein). The presence of nepheline replacing anorthite in some porphyritic chondrules in Parnallee is an indication of early alkali metasomatism on the LL parent body (Lewis and Jones, 2014). These metasomatic fluids might have been introduced through the infall of carbonaceous chondrite material.

Trapped primitive noble gases in various components of Parnallee comprise primordial Q-gas, Ar-rich gas, and a subsolar component (Matsuda et al., 2010). Based on these noble gases, a CRE age of 6.8–10 m.y. was calculated for Parnallee. The specimen of Parnallee shown above is a 2.4 g partial slice, while the photo below shows a large cut slab, courtesy of the Elbert A. King Collection, which shows the rich concentration of chondrules in this meteorite.

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NWA 5206

LL3.05
standby for nwa 5206 photo
Purchased October 2007
no coordinates recorded A single weathered (W3) meteorite weighing 1,276 g was found in Algeria and sold to a meteorite dealer in Erfoud, Morocco. Analysis and classification of the stone was conducted at Northern Arizona University (T. Bunch and J. Wittke), and it was determined that NWA 5206 is a very weakly shocked (S2), terrestrially weathered (W3), highly unequilibrated LL3.05 (or possibly lower) chondrite.

Chondrules of both type-I and type-II compositions are present in a ratio of 3:1, respectively. Chondrule textures span a broad range; porphyritic types predominate, while the remainder comprises granular, radial, cryptocrystalline, barred, and a number of unique types, some with thick mantles. In addition to the primitive compositional heterogeneity of this chondrite, other petrographic and chemical characteristics, such as the alkali-poor glassy chondrule mesostasis and the Cr distribution in ferroan olivine, has led investigators to conclude that NWA 5206 is highly unequilibrated with a subtype <3.1. A more extensive review of the most recent techniques used to discriminate among the lowest petrologic types can be found on the NWA 1756 page.

Utilizing Al–Mg chronometry for a broad sampling of unequilibrated ordinary chondrites, Pape et al. (2019) ascertained that five type-II chondrules from NWA 5206 provide 26Al–26Mg isochron ages of ~1.97 to ~2.64 m.y. after formation of CAIs. The total age range for the entire sample set is ~1.76 to ~2.92 m.y. after CAIs, attesting to chondrule formation occurring over an interval of ~1.2 m.y., or ~1.5 m.y. when including the oldest known chondrules. standby for nwa 5206 chondrule age diagram
Diagram credit: Pape et al., GCA, vol. 244, p. 429 (2019)
‘Time and duration of chondrule formation: Constraints from 26Al-26Mg ages of individual chondrules’
(https://doi.org/10.1016/j.gca.2018.10.017)
Very few ordinary chondrites have been classified as petrologic subtype 3.05 or lower, and NWA 5206 is the only LL chondrite designated as such. A comprehensive pictorial review of NWA 5206 can be found on the Meteorites Australia page showing examples of the many chondrule types and exotic components such as metallic chondrules armored with troilite, xenolithic chondrule fields, and dark inclusions. The specimen of NWA 5206 shown above is a 7.47 g partial slice. The photo below shows a view of the main mass, courtesy of M. Cimala. standby for nwa 5206 photo
Photo courtesy of Marcin Cimala—Polish Meteorite Laboratory


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NWA 4290

LL3.10
standby for nwa 4290 photo
Found March 2004
no coordinates recorded A single fusion-crusted stone weighing 1,101 g was found in Kelb Ellouz, Morocco by the French team of Caillou Noir, under the organization of Michel Franco. A portion was sent for analysis to the Museum National d’Histoire Naturelle, France (M. Denise), the Universite Blaise Pascal, France (B. Devouard), and the Université des Sciences et de la Technologie Houari Boumediene, Algeria (M. Messaoudi).

Northwest Africa 4290 was determined to be a highly unequilibrated ordinary chondrite, and was published as the first known LL3.10 chondrite (NWA 1756 was previously classified as type LL3.0/3.2, but on-going studies have revealed that it is most consistent with type LL3.10). Northwest Africa 4290 has been shocked to stage S3 and has been weathered to grade W3. The main mass of NWA 4290 was subsequently purchased by collector S. Turecki, from which the specimen above was derived.

Northwest Africa 4290 is a primitive chondrite, among the very few to have escaped significant metamorphic processes on its parent asteroid. It preserves many primordial features such as the following: 1) a wide range of olivine fayalite compositions (Fa0.4–Fa47), and ferrosilite compositions (Fs0.7–Fs35); 2) a high chondrule/matrix ratio with 65% Type-II (FeO-rich, oxidized) chondrules; 3) well-defined chondrules (0.1 mm to 3 mm, with some up to 10 mm) having dark fine-grained rims; 4) chondrule mesostasis consists of isotropic glass; 5) whereas Cr is rapidly lost from chondrules as metamorphism increases, NWA 4290 contains an average of 0.38 (± 0.21) wt% Cr (in olivines from type-II chondrules).

Recently, a new petrologic scheme was proposed by J. Grossman (2004) and J. Grossman and A. Brearley (2005). It is more discriminating at the lowest petrologic types, those associated with the highly unequilibrated chondrites (3.0–3.2). This new classification scheme, based on a sensitive technique utilizing the variation in the distribution of Cr in ferroan olivine, is virtually unaffected by the processes of terrestrial weathering and aqueous alteration. The petrologic scale of the new decimal system has been extended as follows:

3.00–3.05–3.10–3.15–3.2

In subsequent studies of chromite zoning profiles along with the chromite content of individual ferroan olivine grains, Grossman (2008) was able to further resolve the petrologic type for chondrites at the lowest metamorphic stages. These two petrographic features provide a reference for a sequencial history of increasing thermal metamorphism that is consistent among olivine grains within each meteorite. For metamorphic types 3.00–3.03, chromite zoning profiles are smooth and correlate with igneous FeO zoning profiles. In addition, at this lowest metamorphic stage chromite contents account for 0.3–0.5 wt% in the chondrite groups studied. While chromite contents in type 3.05–3.10 chondrites still reflect the lowest degrees of metamorphism, chromite now exhibits igneous zoning profiles which are no longer smooth. Upon reaching a degree of metamorphism equivalent to type 3.15, chromite zoning has diminished considerably, and chromite abundance is now only 0.1–0.2 wt%. With metamorphic types of at least 3.2, no zoning is observed and chromite abundance is mostly less than 0.1 wt%.

Following the scheme of J. Grossman and A. Brearley (2005), only the LL chondrite Semarkona and the ungrouped (probably CO-related; Simon and Grossman, 2015) carbonaceous chondrite Acfer 094 (Kimura et al., 2006) were assigned to the least equilibrated subtype 3.00; however, Semarkona has more recently been determined to represent a petrologic subtype 3.01 (Kimura et al., 2008). This specific metamorphic type for Semarkona is also consistent with findings based on the FeNi-metal component, the features of which provide one of the most sensitive indicators for the onset of thermal metamorphism. The technique reveals that primary martensite decomposes to fine-grained plessite during very low degrees of thermal metamorphism in Semarkona, but which did not occurred in Acfer 094. Furthermore, they found that metal in and around Semarkona chondrules does not show a solar ratio of Co/Ni like that in Acfer 094, reflecting the greater degree of metamorphism that affected Semarkona. Moreover, low temperature aqueous alteration has occurred in Semarkona as attested by the presence of secondary alteration products such as smectite.

Another very sensitive method for determining low degrees of metamorphism employs Raman spectra to reveal the maturity of the matrix organic matter (Bonal et al., 2006). Results from this technique for NWA 4290 produce values between that of Semarkona (LL3.00) and Bishunpur (L/LL3.15), again consistent with a value of 3.10.

The CO-group meteorite ALHA77307 is consistent with a subtype 3.03, while three ordinary chondrites—QUE 97008, MET 00526, and EET 90161—have been assigned the next lowest petrologic subtype of 3.05. Several meteorites share the less rigorously defined 3.1 subtype. In addition, Kimura et al. (2008) included the carbonaceous chondrites of groups CR, CH, CB, and CM as probable 3.00 subtype specimens, notwithstanding their current designation of type 2 due to aqueous alteration features. In light of this petrologic typing paradox, they proposed that a separate scale be adopted to describe aqueous alteration which is distinct from the scale currently used for thermal metamorphism.

Further information on the various means of classification of the highly unequilibrated chondrites can be found on the NWA 1756) page. The photo above shows a 0.692 g very thin partial slice of NWA 4290.


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NWA 3127

LL3.10, metal-poor
(possible ungrouped ordinary chondrite)
standby for nwa 3127 photo
Purchased October 2002
no coordinates recorded A single stone weighing 487 g was found in the Sahara Desert and sold to A. and G. Hupé in Safsaf, Morocco in October 2002. This meteorite is very weakly shocked to stage S2 and heavily weathered to grade W3. Through analyses conducted at Northern Arizona University (T. Bunch and J. Wittke) and the U.S. Geological Survey in Reston, Virginia (J. Grossman), it was determined that NWA 3127 is a polymict chondrite consisting of an LL3.1 host with LL4 and LL5 xenoliths.

Studies of the compositional, textural, and other petrographic features of chondrules in NWA 3127 revealed that it had close similarities to those of the LL3.0 Semarkona and the LL3.1 NWA 1756 chondrites. As a sensitive indicator of petrologic subtype (Grossman, 2004; Grossman and Bearley, 2005), the olivine chromite contents of NWA 3127 were measured and found to have values (ave. 0.38 wt%) consistent with an LL3.10 classification. After further analyses conducted by Grossman and Brearley (2007), a reclassification was made for NWA 3127 providing a refined subtype of LL3.10. Northwest Africa 3127 has a very low metal abundance, which was found to be a primary feature rather than an effect of terrestrial weathering.

After the publication of NWA 3127 in MetBull 89 as an LL3.1 chondrite, Rumble III et al. (2007) conducted a survey of the O-isotopic composition of this meteorite and several other metal-poor, ungrouped chondrites in the NWA-series: 960 [ung], 2040 [LL], 2041 [L], 3114 [L], 3127 [LL], 3157 [L], 4294 [LL], 4298 [LL], 4486 [L], and 4531 [LL]. It is demonstrated in the oxygen three-isotope diagram below that these meteorites plot far away from the trend lines for the H, L, and LL ordinary chondrite groups, and they probably represent several previously unrecognized parent asteroids (Irving et al., 2014, #5332). See further details about this ‘supra-TFL’ grouping of meteorites on the HaH 180 page. standby for metal-poor diagram
Diagram credit: Rumble III et al., 38th LPSC, #2230 (2007) Additionally, the ungrouped chondrites NWA 4486 and NWA 5717, as well as the ungrouped achondrites NWA 7835 (Irving et al., 2014, #5332) and NWA 10769 (Moggi Cecchi et al., 2016, #2696), might be related to this metal-poor group of meteorites. The specimen of NWA 3127 shown above is a 1.1 g partial slice.