Evidencia de un pequeño impacto meteorítico en Extremadura: El «volcán» de El Gaseo (Las Hurdes)

Abstract

A small outcrop of pumice-like rocks in northern Ciceres province (Extremadura, Spain) is totally unrelated >

to Cenozoic volcanism in the whole Iberian Peninsula. Microscope petrography, SEM-EDX, and XRD studies

reveal a highly-vesiculated glass with abundant quartz, and minor amounts of orthcpyroxene and

ringwoodite, a high-pressure polymorph of olivine. According to this evidence, we interpret this rock as a

result of a hypervelocity impact of a small meteorite. Under this preliminary interpretation, glass and

vesicles resulted from melting and vaporization of the target metasedimentary clastic rocks and pore

water, quartz grains are unmelted relics of quartz from the target rock, and ringwoodite originated from a

Mg-bearing mineral phase during and immediately after shock-wave passage. The reduced size and

geological uniqueness of the outcrop merits its highest protection as part of the geological heritage of

meteorite impacts in Spain, and any extraction of material from the site should be restricted and strictly controlled