Tectonic Discrimination of Granitoids

Research Article| May 01, 1989 Tectonic discrimination of granitoids PAPU D. MANIAR; PAPU D. MANIAR 1Department of Geology and Planetary Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 Search for other works by this author on: GSW Google Scholar PHILIP M. PICCOLI PHILIP M. PICCOLI 1Department of Geology and Planetary Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 Search for other works by this author on: GSW Google Scholar Author and Article Information PAPU D. MANIAR 1Department of Geology and Planetary Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 PHILIP M. PICCOLI 1Department of Geology and Planetary Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1989) 101 (5): 635–643. https://doi.org/10.1130/0016-7606(1989)101<0635:TDOG>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation PAPU D. MANIAR, PHILIP M. PICCOLI; Tectonic discrimination of granitoids. GSA Bulletin 1989;; 101 (5): 635–643. doi: https://doi.org/10.1130/0016-7606(1989)101<0635:TDOG>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 SocietyGSA Bulletin Search Advanced Search Abstract Granitoids as categorized by tectonic environment are (1) island arc granitoids (IAG), (2) continental arc granitoids (CAG), (3) continental collision granitoids (CCG), (4) postorogenic granitoids (POG), (5) rift-related granitoids (RRG), (6) continental epeirogenic uplift granitoids (CEUG), and (7) oceanic plagiogranites (OP). Of these, the IAG, CAG, CCG, and POG are considered orogenic granitoids, and the RRG, CEUG, and OP are considered anorogenic granitoids.The discrimination of granitoids is based on the major-element chemistry. Various discrimination plots are presented which sequentially discriminate the different tectonic environments. OP are separated from all other granitoids on the K2O versus SiO2 plot. Discrimination between group I (IAG + CAG + CCG), group II (RRG + CEUG), and group III (POG) granitoids can be achieved by using plots of Al2O3 versus SiO2, FeO(T)/ [FeO(T) + MgO] versus SiO2, and AFM and ACF ternary diagrams. In the figures, group I and group II plot in individual fields. Identification of group III is different, in that group III does not have a unique field in which it plots. Group III is identified because it consistently displays characteristics of both group I and group II. Further discrimination within group I can be accomplished on the basis of Shand's index. Only CCG have A/CNK [AL2O3/(CaO + Na2O + K2O)] values greater than 1.15. It is not possible to discriminate between IAG and CAG. Further discrimination within group II is done using the TiO2 versus SiO2 plot.The proposed discrimination scheme is applied to the Proterozoic granitoids of the midcontinent of the United States. It is shown that the Arbuckle granitoids are not anorogenic as previously thought. 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.