The formation and alteration of allanite in skarn from the Beinn an Dubhaich granite aureole, Skye

Martin Smith, Paul Henderson, Teresa Jeffries

Research output: Contribution to journalArticle

Abstract

Allanite-(Ce) occurs as a metasomatic phase in diopside-hedenbergite-anorthite-hastingsite endoskarn from the Beinn an Dubhaich granite aureole, Skye. Fluid-inclusion studies indicate formation of pyroxene at temperatures in the range 600-700oC from Na-K-Fe-Ca bearing brines(45-60wt.%NaCl eq.) assuming pressures of 280-640 bars. Allanite and amphibole formed at much lower temperatures (230-250oC) from low- to moderate-salinity fluids(~ 0-15wt % NaCl eq.) High F contents in both amphibole and vesuvianite indicate that the fluids were F bearing at all stages in the paragenesis. Allanite has textures resulting from growth and alteration. Britholite-(Y) occurs as either a discrete phase, or as an alteration product of allanite. LA-ICP-MS analyses demonstrate that whilst Th remained relatively constant in individual allanite grains, U was leached during alteration. The Th content does vary with zonation, however, and may be altered by processes such as over-growth. The hydrothermal mobility of the REE and Th was almost certainly a result of high-F contents in the hydrothermal fluids. The hydrothermal formation and alteration of allanite may have important consequences for geochronological studies of other allanite occurrences.
Original languageEnglish
Pages (from-to)471-486
Number of pages16
JournalEuropean Journal of Mineralogy
Volume14
Issue number3
Publication statusPublished - 2002

Keywords

  • allanite, Rare Earth Elements, skarn, fluid inclusions

Fingerprint Dive into the research topics of 'The formation and alteration of allanite in skarn from the Beinn an Dubhaich granite aureole, Skye'. Together they form a unique fingerprint.

  • Cite this