Crustal mass transfer and index mineral growth in Barrow's garnet zone, northeast Scotland
1997; Geological Society of America; Volume: 25; Issue: 1 Linguagem: Inglês
10.1130/0091-7613(1997)025 2.3.co;2
ISSN1943-2682
Autores Tópico(s)Geochemistry and Geologic Mapping
ResumoResearch Article| January 01, 1997 Crustal mass transfer and index mineral growth in Barrow's garnet zone, northeast Scotland Jay J. Ague Jay J. Ague 1Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, Connecticut 06520-8109 Search for other works by this author on: GSW Google Scholar Author and Article Information Jay J. Ague 1Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, Connecticut 06520-8109 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 (1): 73–76. https://doi.org/10.1130/0091-7613(1997)025 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 Jay J. Ague; Crustal mass transfer and index mineral growth in Barrow's garnet zone, northeast Scotland. Geology 1997;; 25 (1): 73–76. doi: https://doi.org/10.1130/0091-7613(1997)025 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 The Barrovian metamorphic sequence of northeastern Scotland plays a critical role in our understanding of regional metamorphism at middle and lower crustal levels. The importance of regional temperature and pressure gradients in producing the sequence is well established, but the petrogenetic significance of mass transport of nonvolatile elements by metamorphic processes remains controversial. This paper focuses on the impact of fluid flow through fractures (now quartz veins) on the geochemical and petrologic evolution of metamorphosed clastic rocks in the northeastern part of Barrow's garnet zone, Scotland. The veins constitute ∼13 vol % of the total rock mass and are generally surrounded by zones rich in plagioclase. A traverse along a typical metasedimentary bed cut by a vein reveals that, as one approaches the vein, (1) plagioclase porphyroblast size and An content increase, (2) the modal plagioclase/muscovite ratio increases, (3) bulk rock Na/K, Ca/K, Sr/Rb, (Na + Ca + K)/Al, Mg/FeT, and (Mg + FeT)/Al increase, and (4) bulk rock Si/Ti decreases. The plagioclase-rich zones are interpreted to be alteration selvages that developed as a result of fluid infiltration through fractures; the alteration reaction destroyed muscovite and produced plagioclase. Furthermore, in some rocks the assemblage garnet + biotite + chlorite was stable in the most intensely altered areas directly adjacent to vein margins, whereas chloritoid + biotite + chlorite was stable in less-altered and unaltered areas. Geochemical relations suggest that the fluid flow was in a direction of increasing temperature and that the vein quartz was mostly derived from local wall rocks. It appears that open-system transport of nonvolatile elements can exert important, previously unrecognized controls on rock chemistry and the growth of common regional metamorphic mineral assemblages. 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.
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