Petrogénesis de los Thudereggs en domos rioliticos del centro de chubut, Ptagonia

ARAGON, E.; SAADI, J.A.; UBALDON, M.C.; KUCK, A.M.; CAVAROZZI, C.E.; AGUILERA, Y.E.; RIBOT, A.; GONZALEZ, S.

Revista de la Asociación Geológica Argentina

Asociacion Geologica Argentina

Lugar: Buenos Aires; Año: 2006 vol. 61 p. 347 - 354

0004-4822

Thundereggs at the glass domes of Piedra Parada Caldera are described. Their geological, petrological and geochemical characteristics suggest growth from immiscible liquid drops that devitrified as anorthoclase spherulites. The expansion of the segregated vapor phase of the devitrified immiscible drops broke the spherulites and made large vesicles lined with the broken pieces of the spherulite. Further cooling of the rest of the magma yielded a glass dome with perlitic texture. Low temperature water lixiviated the perlitic glass and spherulites, filling the cavities within the vesicles and broken spherulite with opal and/or chalcedony.