Cloppenburg (H4-5) – first results of a new find

The Cloppenburg meteorite of 141 g was found March 15, 2017 by the facility manager of a school while collecting rocks for the school garden. The rock with a mean density of (3.33 ± 0.03) g/cm³ is a brecciated H-group ordinary chondrite (H4-5) with mean olivine and low-Ca pyroxene of Fa18.5±0.3 and Fs16.4±0.6, respectively. The breccia containing shock veins is weakly shocked (S3) and heavily weathered (W3). The occurrence of vivianite, the oxygen isotopes, and the Ba-enrichment (by INAA) indicate strong weathering in a very wet environment. Radionuclide data evaluation is still ongoing: Accelerator mass spectrometry (AMS) of ¹⁴C, will reveal the terrestrial age. An upper limit of the terrestrial age is yet set by low-level gamma-spectrometry in the Felsenkeller underground lab. No ²²Na (t_1/2=2.6 a) nor ⁴⁴Ti (t_1/2=59 a) could been detected within a counting time of 27 days, whereas ²⁶Al (t_1/2=0.7 Ma) was clearly identified. AMS of ¹⁰Be (t_1/2=1.4 Ma) of ~18 dpm/kg confirms the high cosmic ray exposure age (CRE age) of (7.5 ± 0.4) Ma from noble gas mass spectrometry.