GEOCHEMISTRY OF PELITIC ROCKS. PART III: MAJOR ELEMENTS AND GENERAL GEOCHEMISTRY

Abstract

Research Article| July 01, 1956 GEOCHEMISTRY OF PELITIC ROCKS. PART III: MAJOR ELEMENTS AND GENERAL GEOCHEMISTRY DENIS M SHAW DENIS M SHAW MCMASTER UNIVERSITY, HAMILTON, ONTARIO Search for other works by this author on: GSW Google Scholar Author and Article Information DENIS M SHAW MCMASTER UNIVERSITY, HAMILTON, ONTARIO Publisher: Geological Society of America Received: 17 Jun 1955 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1956, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1956) 67 (7): 919–934. https://doi.org/10.1130/0016-7606(1956)67[919:GOPRPI]2.0.CO;2 Article history Received: 17 Jun 1955 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation DENIS M SHAW; GEOCHEMISTRY OF PELITIC ROCKS. PART III: MAJOR ELEMENTS AND GENERAL GEOCHEMISTRY. GSA Bulletin 1956;; 67 (7): 919–934. doi: https://doi.org/10.1130/0016-7606(1956)67[919:GOPRPI]2.0.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 Compilation of 155 analyses gives the following average composition of all pelitic rocks in per cent, from low to high grade (standard deviations in parentheses): SiO2, 61.54 (4.68); TiO2, 0.82 (0.61); A12O3, 16.95 (4.21); Fe2O3, 2.36 (1.97); FeO, 3.90 (2.25); MgO, 2.52 (1.91); CaO, 1.76 (2.03); Na2O, 1.84 (1.18); K2O, 3.45 (1.32); H20, 3.47 (2.25); CO2, 1.67 (2.37).After classifying the analyses into two groups (clays, shales, and slates; phyllites, schists, and gneisses) statistical discrimination tests showed no change in composition during regional metamorphism, beyond loss of H20 and CO2.The Littleton formation of New Hampshire is a series of pelitic rocks, but is not completely representative of the group, since it forms a sedimentary petrographic province. Thus, the formation is somewhat deficient in CaO, Na2O and CO2, contains more Al2O2 and possibly TiO2, and is in a more reduced state at the low-grade level than the average pelitic rock. It is also more restricted in composition. Moreover this formation underwent minor metasomatism during metamorphism, resulting in the addition of about half a per cent of CaO and Na2O and the loss of H2O, as well as minor element changes.Comparison of pelitic rocks with the average igneous rocks shows that the alkalies and alkaline earths are relatively concentrated in shales as follows: Li > K > Na; Sr > Ba > Mg > Ca. These relations cannot be explained solely on the basis of relative ionic potentials. 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.