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 language | English |
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Pages (from-to) | 123-135 |
Number of pages | 13 |
Journal | Mineralogical Magazine |
Volume | 83 |
Issue number | 1 |
DOIs | |
Publication status | Published - 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