Pyroxene structures, cathodoluminescence and the thermal history of the enstatite chondrites

Testing an integrated chronology: I‐Xe analysis of enstatite meteorites and a eucrite

“…Khairpur belongs to the EL6 meteorite group that shows textural evidence for a greater degree of metamorphism than the EH4 meteorites, while mineralogical thermometers suggest that the EH4 and EL6 meteorites experienced similar equilibration temperatures (600-800 °C, Zhang et al 1996), i.e., the temperature at which their mineral systems underwent closure. Following this, the EHs and ELs apparently experienced very different thermal histories, with very rapid cooling of EHs (>6 °C/h, Skinner and Luce 1971) and slower cooling of ELs (10 3 -10 4 °C/Ma, Rubin 1984).…”

Cathodoluminescence characterization of enstatite

“…Therefore, Fe ions of terrestrial enstatite should diminish luminescence efficiency derived from activators even with high density. Extraterrestrial enstatite with low FeO contents (<5 wt%) in E-chondrites shows obvious CL caused by various emission centers due to a negligibly small of quencher (Keil, 1968;Leitch and Smith, 1982;McKinley et al, 1984;Weisberg et al, 1994;Zhang et al, 1996). Terrestrial enstatite with luminescence have considerably low FeO contents (<1 wt%) on the same level with that of extraterrestrial enstatite (Sah97096 and Aub1), suggesting almost absence of quenching effect in the luminescent process (Table 1).…”

“…1). Extraterrestrial enstatite has been reported as a variety of CL colors emitted with red, magenta and blue (e.g., Zhang et al, 1996). In the previous studies (Crookes, 1879;Reid et al, 1964), however, terrestrial enstatite has not emitted any luminescence even by the excitation of any energy sources such as ion and X-ray beams.…”

“…CL, a visible light of emissions when a material is irradiated by an electron beam, has a high advantage to reveal growth textures in the crystals of enstatite such as domain and zonation, most of which are difficult to be identified by conventional optical examinations. Therefore, CL of enstatite in E-chondrite has been used for the identification of its petrographic type and the studies of its thermal history (e.g., Zhang et al, 1996). Enstatite in meteorites occasionally shows various CL emissions with red, purple and blue (Reid et al, 1964), whereas terrestrial enstatite has no CL emission.…”

“…Cathodoluminescence (CL) of the enstatite has been investigated mainly in E-chondrite and Aubrite (e.g., Zhang et al, 1996). CL, a visible light of emissions when a material is irradiated by an electron beam, has a high advantage to reveal growth textures in the crystals of enstatite such as domain and zonation, most of which are difficult to be identified by conventional optical examinations.…”