Generation of metaluminous A-type granites by low-pressure melting of calc-alkaline granitoids

Abstract

Research Article| August 01, 1997 Generation of metaluminous A-type granites by low-pressure melting of calc-alkaline granitoids Alberto E. Patiño Douce Alberto E. Patiño Douce 1Department of Geology, University of Georgia, Athens, Georgia 30602 Search for other works by this author on: GSW Google Scholar Author and Article Information Alberto E. Patiño Douce 1Department of Geology, University of Georgia, Athens, Georgia 30602 Publisher: Geological Society of America First Online: 02 Jun 2017 Online Issn: 1943-2682 Print Issn: 0091-7613 Geological Society of America Geology (1997) 25 (8): 743–746. https://doi.org/10.1130/0091-7613(1997)025<0743:GOMATG>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 Alberto E. Patiño Douce; Generation of metaluminous A-type granites by low-pressure melting of calc-alkaline granitoids. Geology 1997;; 25 (8): 743–746. doi: https://doi.org/10.1130/0091-7613(1997)025<0743:GOMATG>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 Melting experiments on two calc-alkaline rocks, a tonalite and a granodiorite, demonstrate that shallow dehydration melting of hornblende- and biotite-bearing granitoids generates metaluminous A-type granitic melts. Profuse crystallization of calcic plagioclase + orthopyroxene during low pressure (P ≤ 4 kbar) incongruent melting explains all of the major and trace element characteristics of A-type granites (e.g., their low Al, Ca, Mg, Sr, and Eu contents, and high Ga/Al and K/Na ratios), as well as their common association with anorthositic and mangeritic rocks. The residual assemblage produced during melting of the same rocks in the deep crust (P ≥ 8 kbar) is dominated by clinopyroxene, and, as a consequence, most of the chemical features diagnostic of A-type granites are lost. The high temperatures (>900 °C) and low H2O contents (≤ 4 wt%) that are characteristic of A-type magmas are adequately explained by the H2O-poor nature of the granitoid source materials, and require neither a granulitic nor a F-rich source. Previous attempts to explain the origin of A-type granites have focused on the nature of the source material. These experiments show that pressure of melting is at least as important as source composition in engendering A-type melts. 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.