Origin of minor and trace element compositional diversity in anorthitic feldspar phenocrysts and melt inclusions from the Juan de Fuca Ridge Public Deposited

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  • Melt inclusions trapped in phenocryst phases are important primarily due to their potential of preserving a significant proportion of the diversity of magma composition prior to modification of the parent magma array during transport through the crust. The goal of this investigation was to evaluate the impact of formational and post-entrapment processes on the composition of melt inclusions hosted in high anorthite plagioclase in MORB. Our observations from three plagioclase ultra-phyric lavas from the Endeavor Segment of the Juan de Fuca Ridge document a narrow range of major elements and a dramatically greater range of minor and trace elements within most host plagioclase crystals. Observed host/inclusion partition coefficients for Ti are consistent with experimental determinations. In addition, observed values of D[subscript]Ti are independent of inclusion size and inclusion TiO₂ content of the melt inclusion. These observations preclude significant effects from the re-homogenization process, entrapment of incompatible element boundary layers or dissolution/precipitation. The observed wide range of TiO₂ contents in the host feldspar, and between bands of melt inclusions within individual crystals rule out modification of TiO₂ contents by diffusion, either pre-eruption or due to re-homogenization. However, we do observe comparatively small ranges for values of K₂O and Sr compared to P₂O₅ and TiO₂ in both inclusions and crystals that can be attributed to diffusive processes that occurred prior to eruption.
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  • Adams, D. T., R. L. Nielsen, A. J. R. Kent, and F. J. Tepley III (2011), Origin of minor and trace element compositional diversity in anorthitic feldspar phenocrysts and melt inclusions from the Juan de Fuca Ridge, Geochemistry Geophysics Geosystems, 12, Q12T11, doi:10.1029/2011GC003778.
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  • description.provenance : Submitted by Deborah Campbell (deborah.campbell@oregonstate.edu) on 2012-06-18T20:29:32Z No. of bitstreams: 1 NielsenRogerLCEOASOriginMinorTrace.pdf: 805004 bytes, checksum: 3975cf9b1de77c1a82b22e0bcc1bd2d8 (MD5)
  • description.provenance : Made available in DSpace on 2012-06-18T20:29:32Z (GMT). No. of bitstreams: 1 NielsenRogerLCEOASOriginMinorTrace.pdf: 805004 bytes, checksum: 3975cf9b1de77c1a82b22e0bcc1bd2d8 (MD5) Previous issue date: 2011-12-22
  • Vol. 12 no. 12
  • Geochemistry Geophysics Geosystems

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