Incorporation of Ti into the crystal structures of the high‑pressure dense silicates anhydrous phase B and superhydrous phase Bстатья
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Дата последнего поиска статьи во внешних источниках: 24 января 2020 г.
Аннотация:The crystal structure and chemical composition of crystals of Ti-bearing anhydrous phase B and superhydrous phase B synthesized at 12 – 21 GPa and 1600°C have been investigated. The compounds was found to be orthorhombic. Titanium was found as substitute for Si at the Si1O6 octahedron in both structures, with mean distance Si1–O=1.825 Å (site composition is Si0.84Ti4+0.16) and Si1–O=1.842 (site composition is Si0.92Ti0.08) for AnhB and SuB, respectively. Such substitutions leads to a 4% expansion of the Si1O6 octahedron with respect to the values typically observed for pure AnhB and Fe2+-bearing AnhB and pure SuB. The successful synthesis of Ti-bearing superhydrous phase B indicate that this phase can be stable at temperatures typical of the mantle transition zone and the lower mantle. Thus, water can be transported by Ti-bearing superhydrous B to the lower mantle even at temperatures of the normal mantle geotherm.