A non-magmatic iron projectile for the Gardnos impact event     

Steven Goderis  Elin Kalleson  Roald Tagle  Henning Dypvik  Ralf-Thomas Schmitt  Jörg Erzinger  Philippe Claeys 《Chemical Geology》2009,258(3-4):145-156

The goal of this study is to identify the type of projectile responsible for the formation of the late Precambrian Gardnos impact structure in Norway. Fifteen impactite samples, predominantly impact breccias and suevites from the central and northeastern part of the structure, were analyzed for platinum group elements (PGE) and Au using nickel-sulfide fire assay combined with inductively coupled plasma mass spectrometry (ICP-MS). Major and trace elements were measured in the same samples using X-ray fluorescence (XRF). In addition, the concentrations of siderophile elements Ni, Cr, and Co were determined by ICP-MS after acid digestion. The samples collected at the contact between suevite and the sedimentary infill yielded the highest PGE concentrations (Ir = 1.926 ng/g, Ru = 3.494 ng/g, Pt = 4.716 ng/g, Rh = 0.766 ng/g, Pd = 2.842 ng/g for GC6). The CI-normalized PGE patterns are characterized by Ru and Rh enrichments suggesting a non-chondritic impactor. Concentration plots of the different PGE display an excellent correlation (R > 0.99), indicative of a single source for the PGE enrichment. The Ni/Cr ratio of the Gardnos impactor (2.56 ± 0.20) agrees with that of chondrites (2 to 7), whereas Ir is depleted relative to Ni in this projectile (Ni/Ir ratio of 92 000 ± 8000 compared to an average Ni/Ir ratio of 23 150 ± 4250 for chondrites). There is no clear indication of selective post-depositional remobilization of the characteristic highly siderophile elements. The Ni/Ir and Cr/Ir data combined with the non-chondritic PGE ratios probably indicate a differentiated projectile. Based on (1) the similarity of the inter-element ratios of the impactor with the iron phase of non-magmatic iron meteorites and (2) the presence of characteristics of both chondrites and iron meteorites (Ni/Cr and Ni/Ir ratios), an IA or IIIC non-magmatic iron meteorite is a very plausible impactor.  相似文献   

A new look on Imperial Porphyry: a famous ancient dimension stone from the Eastern Desert of Egypt—petrogenesis and cultural relevance     

Abu El-Enen  Mahrous M.  Lorenz  Joachim  Ali  Kamal A.  von Seckendorff  Volker  Okrusch  Martin  Schüssler  Ulrich  Brätz  Helene  Schmitt  Ralf-Thomas 《International Journal of Earth Sciences》2018,107(7):2393-2408

International Journal of Earth Sciences - Imperial Porphyry, a famous dimension stone of spectacular purple color, was quarried in the Mons Porphyrites area north of Jabal Dokhan in the Eastern...  相似文献