Spinel‐type aluminosilicate: A new high‐pressure, high‐temperature phase from the Vredefort impact structure

We report a previously unknown aluminosilicate mineral, (Si 0.91 □ 0.09 ) Σ1.00 (Al 1.46 □ 0.54 ) Σ2.00 O 4 with a vacancy‐stabilized spinel‐type structure (henceforth “SiAl‐spinel”). This novel aluminosilicate occurs with coesite, stishovite, and majoritic garnet in a shock melt vein in metaquartzite from the outer collar of the Vredefort Dome, the eroded central uplift of the Vredefort impact structure of South Africa. Formation conditions for this new high‐pressure, high‐temperature phase are around 10 GPa and 1400°C, upon release from peak shock conditions. Based on its composition and formation conditions, this new high‐pressure, high‐temperature phase is predicted to be a common occurrence in terrestrial impactites and in subducted slabs.