An improved extraction system to measure carbon‐14 terrestrial ages of meteorites and pairing of the Antarctic Yamato‐75097 group chondrites

Abstract

Abstract-We examined an improved system for extraction of carbon from meteorites, using a vacuum-tight RF melting method. Meteorite samples mixed with an iron combustion accelerator, including a specific amount of carbon (0.052%), were combusted in a RF furnace (LECO HF-10). 14 CO 2 extracted from the meteorite was diluted with a known amount of nearly 14 C-free CO 2 ,evolved from the iron accelerator on combustion. The 14 C activities of the recently fallen Holbrook (L6) and Mt. Tazerzait (L5) meteorites were measured by this method. The mean value was 56.5 ± 3.0 dpm/kg, which is similar to the values reported for recently fallen L6 chondrites. Furthermore, terrestrial ages were measured for four Antarctic meteorites: 1.8 ± 0. (Honda 1981;Takaoka 1987). The result of this work and literature data for the latter two samples confirmed that they are paired. More discussion and experimental work are needed for other recently fallen meteorites, both for L and H chondrites, and a correction for the shielding effect should be done to determine a more reliable terrestrial age.

AN UPDATE ON THE PERFORMANCE OF THE IN SITU14C EXTRACTION LINE AT THE UNIVERSITY OF BERN

“…We therefore changed the system to its current final setup (see below). Note that the previously mentioned system in Japan (Minami et al 2006) has also undergone many changes over the years. For example, in their system instead of adding pure Fe to the samples, steel with a known carbon concentration of 0.0519±0.0012 wt% is added.…”

“…The reason for choosing this steel is its carbon content, i.e., combustion of 3 g of the steel delivered~1 mg of carbon, an amount necessary for the AMS measurements. In their current system, the Al 2 O 3 -crucible is preheated at 1000°C and the samples are preheated in a muffle furnace at 500°C in air before combustion using RF heating (Minami et al 2006). Though the system gives reliable results, it is still necessary to break the vacuum, and clean and change the crucible after every sample, significantly reducing sample throughput.…”

14C and 14C‐10Be terrestrial age dating system for meteorites—New data for four recently fallen meteorites

“…Carbon-14 and 14 C-10 Be terrestrial age dating has also been applied to mesosiderites (Jull et al, 2009) and iron meteorites (Schnitzer et al, 2012). However, despite the immense potential of this dating system and the importance of the data, there are currently only three laboratories worldwide performing such studies-the University of Arizona, United States (e.g., Jull et al, 2013); the Nagoya University, Japan (Minami et al, 2006); and our group at the University of Bern (Mészáros et al, 2018;Sliz et al, 2019Sliz et al, , 2022.…”

“…The 14 C saturation activities found in the literature for L‐chondrites range between 44 ± 1 dpm kg −1 and 60.1 ± 0.9 dpm kg −1 , that is, they vary by more than 35% (see Minami et al., 2006 for references). In addition, the depth profile for the L/LL5 chondrite Knyahinya ranges from 37 to 58 dpm kg −1 (Jull et al., 1994).…”

Terrestrial ages of seven meteorite strewn fields and two single unpaired meteorites from the Sultanate of Oman determined using 14C and 10Be

“…Currently, many of the meteorites found in the Sultanate of Oman are studied by our group (Mészáros et al., 2018; Sliz et al., 2018, 2019, 2020), particularly with respect to the terrestrial ages, by using the cosmogenic radionuclide 14 C. Note that the systematic investigation of terrestrial ages of meteorites is crucial for studying the time scale of meteorite accumulation (Jull, 2006), effects of erosion on the meteorite population on Earth (Al‐Kathiri et al., 2005; Hutzler et al., 2016; Jull et al., 1993; Pourkhorsandi et al., 2019; Zurfluh et al., 2016), and most importantly for studying the meteorite flux over time (Bland et al., 1996; Halliday et al., 1989). The 14 C terrestrial age dating is a well‐established technique with an immense potential but is currently applied to meteorites only in very few laboratories worldwide (Jull et al., 2013; Mészáros et al., 2018; Minami & Nakamura, 2001; Minami et al., 2006; Sliz et al., 2020).…”