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The paper presents experimental data on the impact vaporization of serpentinite. The experiment was carried out on a two-stage light-gas gun at the Institute of Mechanics of the Moscow State University by shooting a copper impactor (~0.5 g) at a speed of ~6 km/s. The vaporized material in the form of a condensate film was analyzed on a scanning electron microscope. The analysis showed that the Mg/Si ratio in the condensate drastically decreased (by ~1.8 times) compared to the initial ratio in the serpentinite target. Thus, it is shown that the evaporation of the impact melt of a silicate target is selective: the vapor is enriched in relatively volatile SiO2, whereas relatively low-volatility MgO is more retained in the residual melt. Our data thus suggest that the shock-explosive bombardment during the accretion of the Earth may have shifted the compositions of rocks at the planet's surface from ultramafic to more acid. An acid trend in rock silicity in the course of accretion is possible if the vaporized matter and/or condensate were accumulated on the surface of the growing planet. [ABSTRACT FROM AUTHOR]

Experimental data on impact vaporization of serpentinite are presented. The experiment was carried out using a two-stage light gas gun with an impact velocity ∼6 km/s. Copper with a mass up to 0.5 g was used as the projectile. Impact-generated vapor in the form of a condensate film was analyzed using a JSM-5610 scanning electron microscope. The analysis showed that the Mg/Si ratio in the condensate decreased sharply (by ∼1.8 times) compared to the initial ratio in the serpentinite target. Thus, it is shown that the evaporation of the impact melt of the silicate target is selective: the vapor is enriched with relatively volatile SiO2, leaving a relatively nonvolatile MgO in the residual melt. [ABSTRACT FROM AUTHOR]