Acraman impact ejecta and host shales: Evidence for low-temperature mobilization of iridium and other platinoids

Abstract

Research Article| February 01, 1990 Acraman impact ejecta and host shales: Evidence for low-temperature mobilization of iridium and other platinoids Malcolm W. Wallace; Malcolm W. Wallace 1Department of Geology and Geophysics, University of Adelaide, G.P.O. Box 498, Adelaide, South Australia 5001, Australia Search for other works by this author on: GSW Google Scholar Victor A. Gostin; Victor A. Gostin 1Department of Geology and Geophysics, University of Adelaide, G.P.O. Box 498, Adelaide, South Australia 5001, Australia Search for other works by this author on: GSW Google Scholar Reid R. Keays Reid R. Keays 2Department of Geology, University of Melbourne, Parkville, Victoria 3052, Australia Search for other works by this author on: GSW Google Scholar Author and Article Information Malcolm W. Wallace 1Department of Geology and Geophysics, University of Adelaide, G.P.O. Box 498, Adelaide, South Australia 5001, Australia Victor A. Gostin 1Department of Geology and Geophysics, University of Adelaide, G.P.O. Box 498, Adelaide, South Australia 5001, Australia Reid R. Keays 2Department of Geology, University of Melbourne, Parkville, Victoria 3052, Australia Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1990) 18 (2): 132–135. https://doi.org/10.1130/0091-7613(1990)018<0132:AIEAHS>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Malcolm W. Wallace, Victor A. Gostin, Reid R. Keays; Acraman impact ejecta and host shales: Evidence for low-temperature mobilization of iridium and other platinoids. Geology 1990;; 18 (2): 132–135. doi: https://doi.org/10.1130/0091-7613(1990)018<0132:AIEAHS>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Geochemical investigations of a widely dispersed Late Proterozoic impact ejecta horizon and its host shales (Bunyeroo Formation, Australia) have provided strong evidence for low-temperature mobilization of the platinum group elements (PGE), including Ir. PGE anomalies are associated with both the ejecta horizon (Ir up to 2.0 ppb, Pt up to 270 ppb) and the green shales that envelop it. Several PGE anomalies (0.073-0.45 ppb Ir, 3.11-314 ppb Pt) also occur in thin green shale beds at other stratigraphic levels within a predominantly red shale sequence (average red shale background of 0.019 ppb Ir and 0.89 ppb Pt). All green shale horizons analyzed, regardless of their stratigraphic position, have relatively high levels of Ir and other PGE. The nonextraterrestrial, postdepositional origin of the PGE at other stratigraphic levels away from the impact ejecta horizon is indicated by their occurrence in thin, permeable, green beds in a predominantly red shale sequence, their association with enrichments in Cu-V-Zn-Ni, and their nonchondritic PGE interelement ratios. The impact ejecta horizon has a more chondritic PGE geochemistry consistent with a meteoritic origin. A redox precipitation model similar to that invoked for redbed Cu-U-V deposits is proposed to explain the PGE anomalies in the green shales. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.