Natural Occurrence of MgSiO 3 -Ilmenite and Evidence for MgSiO 3 -Perovskite in a Shocked L Chondrite
1997; American Association for the Advancement of Science; Volume: 277; Issue: 5324 Linguagem: Inglês
10.1126/science.277.5324.352
ISSN1095-9203
AutoresT. G. Sharp, C. M. Lingemann, C. Dupas-Bruzek, D. Stöffler,
Tópico(s)Geological and Geochemical Analysis
ResumoShock-induced melt veins in the Acfer 040 L5-6 (S6) chondrite contain a previously unknown set of high pressure phases consisting of amorphous grains similar in composition to majorite, MgSiO 3 -ilmenite, and ringwoodite. The amorphous grains have compositions that are similar to those of synthetic MgSiO 3 -perovskites from chemically complex systems and are inferred to be MgSiO 3 -perovskite that crystallized from the melt at high pressure and temperature and subsequently amorphized after pressure release. The ilmenite represents a natural occurrence of a potentially important mineral in Earth's mantle. The MgSiO 3 -perovskite–MgSiO 3 -ilmenite–ringwoodite assemblage is not predicted by phase equilibria studies, but appears to result from crystallization of a melt at pressures above 26 gigapascals.
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