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Predominance of high Th/U, magmatic zircon in Brazilian Shield sandstones

2003; Geological Society of America; Volume: 32; Issue: 1 Linguagem: Inglês

10.1130/g20007.1

1943-2682

Léo Afrâneo Hartmann, João Orestes Schneider Santos,

Geochemistry and Geologic Mapping

Research Article| January 01, 2004 Predominance of high Th/U, magmatic zircon in Brazilian Shield sandstones Léo Afraneo Hartmann; Léo Afraneo Hartmann 1Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Avenida Bento Gonçalves, 9500, 91501-970 Porto Alegre, Rio Grande do Sul, Brazil Search for other works by this author on: GSW Google Scholar João Orestes S. Santos João Orestes S. Santos 2Geological Survey of Brazil (CPRM), Rua Banco da Província, 105, Porto Alegre, Rio Grande do Sul, Brazil Search for other works by this author on: GSW Google Scholar Author and Article Information Léo Afraneo Hartmann 1Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Avenida Bento Gonçalves, 9500, 91501-970 Porto Alegre, Rio Grande do Sul, Brazil João Orestes S. Santos 2Geological Survey of Brazil (CPRM), Rua Banco da Província, 105, Porto Alegre, Rio Grande do Sul, Brazil Publisher: Geological Society of America Received: 10 Jul 2003 Revision Received: 29 Sep 2003 Accepted: 01 Oct 2003 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2004) 32 (1): 73–76. https://doi.org/10.1130/G20007.1 Article history Received: 10 Jul 2003 Revision Received: 29 Sep 2003 Accepted: 01 Oct 2003 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Léo Afraneo Hartmann, João Orestes S. Santos; Predominance of high Th/U, magmatic zircon in Brazilian Shield sandstones. Geology 2004;; 32 (1): 73–76. doi: https://doi.org/10.1130/G20007.1 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 The strong predominance of magmatic (Th/U >0.2) zircon grains in quartz sandstones from 10 locations in the Brazilian Shield, as measured by sensitive high-resolution ion microprobe (SHRIMP), introduces a strong bias in the tectonic interpretation of source terrains, because the metamorphic sources remain undetected in the detrital population. Zircon grains from many mature, and some immature, sedimentary terrains show Th/U ratios >0.2, ratios commonly considered magmatic, complemented by the near absence of metamorphic Th/U ratios <0.1. Metamorphic rims on magmatic zircon grains from the Brazilian Shield are nearly absent from quartz sandstones, only being present in shielded young cores of a few crystals. High-U, metamorphic portions of zircon grains are more defective and liable to undergo comminution by abrasion during weathering and transport, and they do not remain in the sand fraction. Ages obtained from detrital zircon in mature sandstones reflect magmatic sources, not the full spectrum of orogenic events. Only less mature sedimentary rocks preserve a full record of orogenic rocks in the source. Mostly magmatic events were characterized in previous zircon provenance studies. Brazilian Shield detrital zircon may be a proxy for equivalent investigations in other provinces of the world. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.