A hibonite-spinel-corundum-hematite assemblage in plagioclase-clinopyroxene pyrometamorphic rocks, Hatrurim Basin, Israel: Mineral chemistry, genesis and formation temperatures

Victor V. Sharygin

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7 Citations (Scopus)

Abstract

The intergrowths of Fe-rich corundum + Al-rich hematite + spinel + hibonite have been found as an assemblage in a plagioclase-clinopyroxene rock (paralava, former hornfels) at the Hatrurim Basin, Hatrurim combustion metamorphic Formation. Most spinels show oriented exsolution structures and vary from (Mg 0.75 Fe 2+ 0.25 )(Al 1.80 Fe 3+ 0.20 )O 4 (with exsolutions) to (Mg 0.77 )(Al 1.95 Fe 3+ 0.05 )O 4 (homogeneous) indicating a tendency towards magnesioferrite and magnetite, and enrichment in NiO (up to 1.9 wt.%) and ZnO (up to 1.4 wt.%). Hibonite is Ti rich (TiO 2 > 8 wt.%) and close to CaAl 9 Fe 3+ (Mg,Fe 2+ )TiO 19 . Corundum varies in Fe 2 O 3 (4.2-11.8 wt.%). Hematite is also inhomogeneous and contains oriented exsolution structures of corundum. It shows variable concentrations of TiO 2 (0.7-5.6 wt.%), Al 2 O 3 (0.7-8.6 wt.%), Cr 2 O 3 (0.2-1.5 wt.%), V 2 O 3 (0.1-1.0 wt.%) and MgO (0.3-2.0 wt.%). Crystallization of this specific assemblage is assumed to be at 1000-1200°C using evaluations for the corundum hematite pair with reference to published experimental data. The active role of superheated oxidised volatiles is suggested during both crystallisation of this corundum-bearing association and host-rock transformation (melting event for hornfels → paralava).

Original languageEnglish
Pages (from-to)123-135
Number of pages13
JournalMineralogical Magazine
Volume83
Issue number1
DOIs
Publication statusPublished - 1 Feb 2019

Keywords

  • combustion metamorphism
  • corundum
  • corundum-hematite geothermometer
  • Hatrurim Basin
  • hematite
  • hibonite
  • hornfels
  • Israel
  • paralava
  • NATURAL ANALOGS
  • COMBUSTION METAMORPHIC ROCKS
  • NEGEV DESERT
  • PALESTINIAN AUTONOMY
  • LARNITE ROCKS
  • MOTTLED ZONE
  • SOLID-SOLUTION
  • PEROVSKITE
  • DEAD-SEA
  • JABEL HARMUN

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