The history of ordinary chondrites from the data on stable isotopes of noble gases (a review)

Alexeev, V. A.

doi:10.1007/s11208-005-0028-z

Cited by 19 publications

(7 citation statements)

References 103 publications

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“…Furthermore, according to Alexeev (1998) non-Antarctic finds have (16 ± 4)% less 4 He on average compared to falls, whereas Antarctic finds have only (5 ± 3)% less. Finally, the average nominal cosmic ray exposure age of non Antarctic H chondrite finds belonging to the ~7 Ma exposure peak is about 15% lower than that of falls, for which terrestrial weathering is the most likely reason (Alexeev 2005). Laboratory experiments simulating the effect of rainwater on enstatite chondrites, however, have not supported these results so far for cosmogenic He and Ne (Patzer and Schultz 2001), while, on the other hand, significant losses of cosmogenic Ar were observed.…”

Section: Influence Of Terrestrial Weatheringmentioning

confidence: 82%

“…The ratio of ( 4 He/ 3 He) cosm reported by Heymann (1967) is 5.2 ± 0.3, while Alexeev (1998) report 6.1 ± 0.3 and Welten et al (2003) 6.2 ± 0.2. Alexeev (2005) reports a variation in L-chondrites of 5.5 ± 0.8 (Antarctic finds) to 6.7 ± 0.5 (falls). In our case the lowest measured ratio is 4.1 (pyroxene of ALHA77005; ), which we take as pure cosmogenic composition for partitioning 4 He into cosmogenic and radiogenic components.…”

Section: Partitioning Of Measured 4 He Into Its Cosmogenic and Radiogmentioning

confidence: 99%

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Helium loss from Martian meteorites mainly induced by shock metamorphism: Evidence from new data and a literature compilation

Schwenzer

Fritz

Stöffler

et al. 2008

Meteorit & Planetary Scien

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available online at http://meteoritics.org Helium loss from Martian meteorites mainly induced by shock metamorphism:Evidence from new data and a literature compilation Abstract-Noble gas data from Martian meteorites have provided key constraints about their origin and evolution, and their parent body. These meteorites have witnessed varying shock metamorphic overprinting (at least 5 to 14 GPa for the nakhlites and up to 45-55 GPa (e.g., the lherzolitic shergottite Allan Hills [ALH] A77005), solar heating, cosmic-ray exposure, and weathering both on Mars and Earth. Influences on the helium budgets of Martian meteorites were evaluated by using a new data set and literature data. Concentrations of 3 He, 4 He, U, and Th are measured and shock pressures for same sample aliquots of 13 Martian meteorites were determined to asses a possible relationship between shock pressure and helium concentration. Partitioning of 4 He into cosmogenic and radiogenic components was performed using the lowest 4 He/ 3 He ratio we measured on mineral separates ( 4 He/ 3 He = 4.1, pyroxene of ALHA77005). Our study revealed significant losses of radiogenic 4 He. Systematics of cosmogenic 3 He and neon led to the conclusion that solar radiation heating during transfer from Mars to Earth and terrestrial weathering can be ruled out as major causes of the observed losses of radiogenic helium in bulk meteorites. For bulk rock we observed a correlation of shock pressure and radiogenic 4 He loss, ranging between ~20% for Chassigny and other moderately shocked Martian meteorites up to total loss for meteorites shocked above 40 GPa. A steep increase of loss occurs around 30 GPa, the pressure at which plagioclase transforms to maskelynite. This correlation suggests significant 4 He loss induced by shock metamorphism. Noble gas loss in rocks is seen as diffusion due to (1) the temperature increase during shock loading (shock temperature) and (2) the remaining waste heat after adiabatic unloading (post shock temperature). Modeling of 4 He diffusion in the main U,Th carrier phase apatite showed that post-shock temperatures of ~300 °C are necessary to explain observed losses. This temperature corresponds to the post-shock temperature calculated for bulk rocks shocked at about 40 GPa. From our investigation, data survey, and modeling, we conclude that the shock event during launch of the meteorites is the principal cause for 4 He loss.

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Section: Influence Of Terrestrial Weatheringmentioning

confidence: 82%

Section: Partitioning Of Measured 4 He Into Its Cosmogenic and Radiogmentioning

confidence: 99%

Helium loss from Martian meteorites mainly induced by shock metamorphism: Evidence from new data and a literature compilation

Schwenzer

Fritz

Stöffler

et al. 2008

Meteorit & Planetary Scien

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“…However, the CRE age T 3 , 4.82 ± 0.07 Ma, is less indicating loss of helium. The CRE age of ordinary chondrites (L‐type) commonly range between 1 and 50 Ma (Alexeev ). Although there is no distinct peak in CRE age distribution of L‐type ordinary chondrites, the exposure age of Kamargaon, 7.03 ± 1.6 (Ma), coincides with the 7 Ma peak of H‐type ordinary chondrites in CRE age histogram (Wieler ).…”

Section: Noble Gases and Nitrogen Isotopesmentioning

confidence: 99%

Petrography, classification, oxygen isotopes, noble gases, and cosmogenic records of Kamargaon (L6) meteorite: The latest fall in India

Ray

Mahajan

Shukla

et al. 2017

Meteorit & Planetary Scien

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A single piece of meteorite fell on Kamargaon village in the state of Assam in India on November 13, 2015. Based on mineralogical, chemical, and oxygen isotope data, Kamargaon is classified as an L‐chondrite. Homogeneous olivine (Fa: 25 ± 0.7) and low‐Ca pyroxene (Fs: 21 ± 0.4) compositions with percent mean deviation of <2, further suggest that Kamargaon is a coarsely equilibrated, petrologic type 6 chondrite. Kamargaon is thermally metamorphosed with an estimated peak metamorphic temperature of ~800 °C as determined by two‐pyroxene thermometry. Shock metamorphism studies suggest that this meteorite include portions of different shock stages, e.g., S3 and S4 (Stöffler et al. ); however, local presence of quenched metal‐sulfide melt within shock veins/pockets suggest disequilibrium melting and relatively higher shock stage of up to S5 (Bennett and McSween ). Based on noble gas isotopes, the cosmic‐ray exposure age is estimated as 7.03 ± 1.60 Ma and nitrogen isotope composition (δ15N = 18‰) also correspond well with the L‐chondrite group. The He‐U, Th, and K‐Ar yield younger ages (170 ± 25 Ma 684 ± 93, respectively) and are discordant. A loss of He during the resetting event is implied by the lower He‐U and Th age. Elemental ratios of trapped Ar, Kr, and Xe can be explained through the presence of a normal Q noble gas component. Relatively low activity of 26Al (39 dpm/kg) and the absence of 60Co activity suggest a likely low shielding depth and envisage a small preatmospheric size of the meteoroid (<10 cm in radius). The Kr isotopic ratios (82Kr/84Kr) further argue that the meteorite was derived from a shallow depth.

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“…The initial concentration in radioactive elements depends on the nature of the primordial bricks that formed Iapetus. Following Castillo-Rogez et al (2007), we assume a composition of the silicate fraction corresponding to ordinary chondrites, which represent the vast majority of chondrites falling on Earth (Bischoff, 2001;Alexeev, 2005). Carbonaceous chondrites could also contribute to the silicate budget of Iapetus to some extent.…”

Section: Radioactive Sourcesmentioning

confidence: 99%

Coupling of thermal evolution and despinning of early Iapetus

Robuchon

Choblet

Tobie

et al. 2010

Icarus

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The history of ordinary chondrites from the data on stable isotopes of noble gases (a review)

Cited by 19 publications

References 103 publications

Helium loss from Martian meteorites mainly induced by shock metamorphism: Evidence from new data and a literature compilation

Helium loss from Martian meteorites mainly induced by shock metamorphism: Evidence from new data and a literature compilation

Petrography, classification, oxygen isotopes, noble gases, and cosmogenic records of Kamargaon (L6) meteorite: The latest fall in India

Coupling of thermal evolution and despinning of early Iapetus

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