Cosmochemistry; Part 1, Meteorites

Mason, Brian

doi:10.3133/pp440b1

Cited by 59 publications

(28 citation statements)

References 96 publications

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“…This Cl content is about an order of magnitude higher compared to the ordinary chondrite range of 15-177 ppm (Garrison et al 2000). Thus, we find that compared to average H chondrites (Mason 1979), Devgaon is significantly enriched in Cl and Br and depleted in I. In Table 7, the ratios of I/Cl and Br/Cl of Devgaon are compared with Kesen (H4) (a normal H chondrite), Zag (H3) (a chondrite having halites), and CI chondrites.…”

Section: Halogen Contents and Neutron Fluencementioning

confidence: 50%

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

Murty

Vinai

Shukla

et al. 2004

Meteorit & Planetary Scien

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Abstract-The Devgaon meteorite fell in India on February 12, 2001 and was immediately collected. It is an ordinary chondrite having a number of SiO 2 -rich objects and some Ca, Al-rich inclusions. Olivines ) are fairly equilibrated, while pyroxenes ) 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 ( 52 Mn) to 7.3 × 10 5 yr ( 26 Al), 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) × 10 6 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 38 Ar, 83 Kr, and 126 Xe. 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 60 Co, high ( 22 Ne/ 21 Ne) c , and large neutron produced excesses at 80 Kr, 82 Kr, and 128 Xe indicate a complex exposure history of the meteoroid. In the first stage, a meter-sized body was exposed for nearly 10 8 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. FALL, PETROGRAPHY, AND MINERALOGYA single stone weighing about 12 kg fell in the village of Devgaon, Bastar district, Chattisgarh, Central India on February 12, 2001 at about 16:00 hours IST. The meteorite was fully covered with fusion crust (Fig. 1) at the time of recovery. The meteorite was quickly recovered and delivered to the district Collectorate from whom one of us (G. Srinivasan) got a piece weighing about 3.8 kg.Devgaon is an ordinary chondrite consisting of abundant chondrules and chondrule fragments embedded within a moderately recrystallized fine-grained matrix (Fig. 2). Studies of thin sections show that most constituents of the meteorite are fragmented. In contrast, the hand specimen of Devgaon looks quite homogeneous without any indication of brecciation. Occasionally, shock veins are visible (Fig. 3), although the bulk rock is very weakly shocked and is classified as shock grade S2 (Stöffler et al. 1991). The Olivines show undulatory extinction and irregular fractures but no planar deformation. The multiple degrees of shock effects indicate that the event responsible for the formation of shock veins is not responsible for the fragmentation of the meteorite components. Therefore, we conclude that the process of fragmentation must have occurred before accumulation of the material on the parent body from which the Devgaon meteoroid is derived. In thin section, many type...

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Section: Halogen Contents and Neutron Fluencementioning

confidence: 50%

“…To estimate the amount of 36 Ar n , we use 82 Kr n . Assuming the (Cl/Br) atom ratio in Devgaon to be 700, the same as in average H chondrites (Mason 1979), and using (n, γ) cross sections from Göbel et al (1982), we calculate 36 Ar n = 3.58 × 10 −8 ccSTP/g.…”

Section: Nucleogenic Componentmentioning

confidence: 99%

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

Murty

Vinai

Shukla

et al. 2004

Meteorit & Planetary Scien

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“…Although these experiments provide interesting results, it should be kept in mind that the amount of schreibersite reaching the Earth today is low. Schreibersite occurs only in iron meteorites as macroscopic inclusions, making up 0.5-1.3% of sample volume [70] . Metallic meteorites comprise not more than 7.4% of the total meteorite flux.…”

Section: A Cellular Origin Of Lifementioning

confidence: 99%

Stochastic Prebiotic Chemistry within Realistic Geological Systems

et al. 2016

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This review introduces its readers to a ‘stochastic approach’ to origins of life research, from the viewpoints of both prebiotic chemistry and geology. The idea of a “primordial soup” has been subject to extensive criticism from thermodynamic, biochemical and geochemical perspectives, yet recent advancements have made clearer the plausibility of this theory. Herein, we review the theoretical and experimental approaches which have previously been explored, among these modelling, laboratory‐confined and geologically motivated experimentation. Of these, we consider organo‐mineral interactions, uniting aspects of prebiotic chemistry and geology, to be an especially promising way forward. However, we aim here to advance current approaches by advocating a methodology involving chemical systems and their stochastic reactivity on heterogeneous geological surfaces. This models the origins of life as a continuity of chemical reactions in an analogue to the early Earth (Hadean) environment.

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“…Hence, normalization of the saturated activity observed to the oxygen content works well. We estimated the saturated activity for a given class of meteorite by normalizing the mean value of the 14 C content of Bruderheim (51.1 dpm/kg) to the oxygen content of the meteorite determined from bulk chemistry or from average compositions (Mason 1979). The scatter in measurements on saturated falls suggests that an uncertainty of ±15% should be included in estimates of the terrestrial age to account for uncompensated shielding or depth effects, as well as experimental uncertainty (Jull et al 1993a).…”

Section: Meteorite Studies and Terrestrial Agesmentioning

confidence: 99%

Radiocarbon Beyond this World

et al. 2000

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ABSTRACT. In this paper, we review the production of radiocarbon and other radionuclides in extraterrestrial materials. This radioactivity can be produced by the effects of solar and galactic cosmic rays on solid material in space. In addition, direct implantation at the lunar surface of 14 C and other radionuclides can occur. The level of 14 C and other radionuclides in a meteorite can be used to determine its residence time on the Earth's surface, or "terrestrial age". 14 C provides the best tool for estimating terrestrial ages of meteorites collected in desert environments. Age control allows us to understand the time constraints on processes by which meteorites are weathered, as well as mean storage times. Third, we discuss the use of the difference in 14 C/ 12 C ratio of organic material and carbonates produced on other planetary objects and terrestrial material. These differences can be used to assess the importance of distinguishing primary material formed on the parent body from secondary alteration of meteoritic material after it lands on the earth.

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Cosmochemistry; Part 1, Meteorites

Cited by 59 publications

References 96 publications

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

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

Stochastic Prebiotic Chemistry within Realistic Geological Systems

Radiocarbon Beyond this World

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