Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, I-50121 Florence, Italy.
CNR-Istituto di Geoscienze e Georisorse, Via La Pira 4, I-50121 Florence, Italy.
Sci Rep. 2017 Feb 15;7:42674. doi: 10.1038/srep42674.
We report the first natural occurrence of the Fe-analogue of akimotoite, ilmenite-structured MgSiO, a missing phase among the predicted high-pressure polymorphs of Fe-pyroxene, with the composition (FeMgCaNaMnAlCr)SiO. The new mineral was approved by the International Mineralogical Association (IMA 2016-085) and named hemleyite in honour of Russell J. Hemley. It was discovered in an unmelted portion of the heavily shocked L6 Suizhou chondrite closely associated to olivine, clinoenstatite and Fe-bearing pyroxene with a composition nearly identical to that of hemleyite. We also report the first single-crystal X-ray diffraction study of a Si-bearing, ilmenite-structured phase. The fact that hemleyite formed in a meteorite exposed to high pressures (<20 GPa) and temperatures (<2000 °C) during impact-induced shocks indicates that it could play a crucial role at the bottom of the Earth's mantle transition zone and within the uppermost lower mantle.
我们报告了 akimotoite 的 Fe 类似物——具有尖晶石结构的 MgSiO 的首次自然出现，这是预测的 Fe 辉石高压多晶型物中缺失的相，其组成式为 (FeMgCaNaMnAlCr)SiO。新矿物已被国际矿物学协会（IMA 2016-085）认可，并以 Russell J. Hemley 的名字命名为 hemleryte。它是在与橄榄石、斜方辉石和 Fe 辉石密切相关的 L6 随州球粒陨石未熔融部分中发现的，其组成与 hemleryte 几乎相同。我们还报告了首例 Si 型、具有尖晶石结构的相的单晶 X 射线衍射研究。在冲击诱发的冲击中，hemleyite 形成于暴露于高压（<20 GPa）和高温（<2000°C）的陨石中，这表明它可能在地幔过渡带底部和最上部下地幔中发挥关键作用。
