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Cl incorporation into successively zoned amphiboles from the Ramnes cauldron, Norway

1997; Mineralogical Society of America; Volume: 82; Issue: 3-4 Linguagem: Inglês

10.2138/am-1997-3-410

1945-3027

Hisao Satô, Yoshiaki Yamaguchi, Kuniaki Makino,

Geochemistry and Geologic Mapping

Other| April 01, 1997 Cl incorporation into successively zoned amphiboles from the Ramnes cauldron, Norway Hisao Sato; Hisao Sato Shinshu University, Department of Geology, Asahi, Japan Search for other works by this author on: GSW Google Scholar Yoshiaki Yamaguchi; Yoshiaki Yamaguchi Search for other works by this author on: GSW Google Scholar Kuniaki Makino Kuniaki Makino Search for other works by this author on: GSW Google Scholar American Mineralogist (1997) 82 (3-4): 316–324. https://doi.org/10.2138/am-1997-3-410 Article history 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 Hisao Sato, Yoshiaki Yamaguchi, Kuniaki Makino; Cl incorporation into successively zoned amphiboles from the Ramnes cauldron, Norway. American Mineralogist 1997;; 82 (3-4): 316–324. doi: https://doi.org/10.2138/am-1997-3-410 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Amphibole from alkali granites in the Ramnes cauldron in the Oslo rift was altered hydrothermally by corrosion and growth through multiple events of fluid circulation. The alteration developed successive zones of amphibole at the crystal margins, resulting in a (1) brownish ferro-edenitic hornblende core (FE), (2) deep bluish-green hastingsitic hornblende zone (HH), and (3) light-greenish Fe-rich actinolite rim (FA). The edenitic core preserves the original igneous amphibole composition. The Cl content of amphibole strongly increases from the FE (0.78–0.82 wt%) to the HH zone (2.07–2.96 wt%) and abruptly decreases in the FA rim (0.01–0.36 wt%). In the Cl-rich HH amphibole zone, amphibole has characteristically high Cl content [2.96 wt%, 0.82 atoms per formula unit (apfu)] and high concentrations in both [4]Al (1.73 apfu) and A-site occupancy (0.86 apfu) with a large K/(Na + K) value of 0.47.Both [4]Al and A-site occupancy increase systematically with positive correlation with Cl content throughout the three amphibole zones. On the other hand, Fe2+ content is not so simply correlated to the Cl content. Based on crystal structure considerations on Cl-rich amphiboles, the cation substitutions are illustrated by structural (geometrical) constraints for [4]Al and by a chemical constraint for Fe2+. These contributions for Cl incorporation are expressed empirically by ln(Cl/OH)amp = ln(Cl/OH)fluid + A·[4]Al·Fe2+/RT + B/RT, where A and B are constant. [4]Al·Fe2+ vs. ln(Cl/OH) plots of the three distinct amphibole zones suggest different fluid conditions in chemistry and temperature for the three zones. The zoning was developed through two stages of hydrothermal alteration. In the early hydrothermal event, a saline and high-temperature fluid altered the original hornblende (FE) to the Cl-rich HH zone. Late stage alteration by a high Fe/Cl and relatively low-temperature fluid partially over-printed the FA zone at the crystal margin. 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.