Evaluation of Coexisting Garnet-Biotite, Garnet-Clinopyroxene, and Other Mg-Fe Exchange Thermometers in Adirondack Granulites

Abstract

Research Article| February 01, 1980 Evaluation of Coexisting Garnet-Biotite, Garnet-Clinopyroxene, and Other Mg-Fe Exchange Thermometers in Adirondack Granulites Steven R. Bohlen; Steven R. Bohlen 1Department of Geology and Mineralogy, University of Michigan, Ann Arbor, Michigan 48109 Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, California 90024. Search for other works by this author on: GSW Google Scholar Eric J. Essene Eric J. Essene 1Department of Geology and Mineralogy, University of Michigan, Ann Arbor, Michigan 48109 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1980) 91 (2_Part_II): 685–719. https://doi.org/10.1130/GSAB-P2-91-685 Article history received: 06 Aug 1979 accepted: 15 Aug 1979 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Steven R. Bohlen, Eric J. Essene; Evaluation of Coexisting Garnet-Biotite, Garnet-Clinopyroxene, and Other Mg-Fe Exchange Thermometers in Adirondack Granulites. GSA Bulletin 1980;; 91 (2_Part_II): 685–719. doi: https://doi.org/10.1130/GSAB-P2-91-685 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract INTRODUCTIONOf the many thermometers that have been proposed for metamorphic and igneous rocks, those that depend on the distribution of a pair of cations or groups of cations between two coexisting phases are perhaps the most widely appled and yet the most poorly calibrated for natural compositions. The most attractive feature of these systems is the apparent simplicity of their application, requiring only an analysis of the coexisting phases. Unfortunately, the partitioning of cations between co-exiting phases may depend on bulk compositions as well as temperature. In some systems—for example, Mg-Fe2+ exchange between olivine and orthopyroxene—bulk composition has a more important effect than temperature on the distribution co-efficient (Ramberg and DeVore, 1951; Medaris, 1969; Matsui and Nishizawa, 1974). Consequently, it is important to test the effect of bulk composition as well as temperature when applying cation exchange (KD) thermometry. (KD is defined as the ratio of a pair of cations between co-existing phases. For example, KD(Fe-Mg)(garn-cpx) = (Fe garnet/Mg garnet) (Mg cpx/Fe cpx).)The effect of pressure, on the other hand, is generally quite small, because the δV is usually very small for a given reaction of the type A (in phase X) + B (in phase Y) = B (in phase X) + A (in phase Y). Most often, the pressure dependence of KD is ignored for extrapolations within the crust—that is, for δP of less than 10 kb. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.