The Geochemistry and Cosmochemistry of Impacts

Abstract-Suevite and melt breccia compositions in the boreholes Enkingen and Polsingen are compared with compositions of suevites from other Ries boreholes and surface locations and discussed in terms of implications for impact breccia genesis. No significant differences in average chemical compositions for the various drill cores or surface samples are noted. Compositions of suevite and melt breccia from southern and northeastern sectors of the Ries crater do not significantly differ. This is in stark contrast to the published variations between within-crater and out-of-crater suevites from northern and southern sectors of the Bosumtwi impact structure, Ghana. Locally occurring alteration overprint on drill cores-especially strong on the carbonate-impregnated suevite specimens of the Enkingen borehole-does affect the average compositions. Overall, the composition of the analyzed impact breccias from Ries are characterized by very little macroscopically or microscopically recognized sediment-clast component; the clast populations of suevite and impact melt breccia are dominated consistently by granitic and intermediate granitoid components. The Polsingen breccia is significantly enriched in a dioritic clast component. Overall, chemical compositions are of intermediate composition as well, with dioritic-granodioritic silica contents, and relatively small contributions from mafic target components. Selected suevite samples from the Enkingen core have elevated Ni, Co, Cr, and Ir contents compared with previously analyzed suevites from the Ries crater, which suggest a small meteoritic component. Platinum-group element (PGE) concentrations for some of the enriched samples indicate somewhat elevated concentrations and near-chondritic ratios of the most immobile PGE, consistent with an extraterrestrial contribution of 0.1-0.2% chondrite-equivalent.

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“…Normalization factors from Lodders (). For comparison, a PGE pattern for Upper Continental Crust (after Koeberl ; open squares) has been plotted.…”

Section: Platinum‐group Element Analysesmentioning

confidence: 99%

Geochemical studies of the SUBO 18 (Enkingen) drill core and other impact breccias from the Ries crater, Germany

Reimold

McDonald

Schmitt

et al. 2013

Meteorit & Planetary Scien

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“…This list is an updated assemblage of previous compilations (Grieve and Shoemaker, 1994;Koeberl, 1998Koeberl, ,2007Tagle and Hecht, 2006). Only craters larger than 0.1 km in diameter are listed.…”

Section: Current Situation: Projectile Identification At Impact Cratementioning

confidence: 99%

Projectile Identification in Terrestrial Impact Structures and Ejecta Material

Goderis¹,

Paquay²,

Claeys³

2012

Impact Cratering

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“…Impact cratering studies include analyses of processes and mechanisms of crater formation, modification and structural development of the craters, mineralogical and geochemical study of the impactites, and numerical modeling of the physical processes of crater formation (Melosh, 1989;French, 1998;Melosh and Ivanov, 1999;Koeberl, 2002Koeberl, , 2007Shuvalov and Trubestkaya, 2002;Shuvalov et al, 2005Shuvalov et al, , 2012French and Koeberl, 2010). Sedimentary processes of the crater-filling successions have, however, been less widely discussed.…”

Section: Introductionmentioning

confidence: 98%