Blue glass: A new impactite variety from Zhamanshin crater, U.S.S.R

Aktmct-A new variety of impact giass has been discovered at Zhamansbin impact crater (U.S.S.R.). The crater has been known as the source of different impact glasses such as irghizites and Si-rich zhamanshinites @-rich varieties) and Si-poor (andesitic) zhamanshinites. The newly discovered impact glass is ofdistinct blue color and shows a layered structure with numerous small vesicles. The blue color ranges between the layers from opaque turquoise to very dark blue. The iayers of blue glass are usually connected with layers of greyish or brownish color showing normal Si-rich zhamanshinite composition. The major and tram element chemistry of the blue glass differ from the chemistry of other Sirich impact @asses from the Zhamanshin crater in several ways. One of the ti distinct ftptures is the high CaO content (up to about 7 wt.%), and the different CaO/MgO ratios. Volatile trace elements are generafly intemwdiate betwen i&i&es and Sikh zhamanshinites, or even higher than in Si-rich zhamaMini@, refkcting the inhomogpmity of the blue glass. REE abundancxs anz slightly Iar&r than in Si-rich ~rna~init~ and irghizites and show a les$ monounced Eu anomaly. Impact mixing of country rocks present at the crater seems capable of explaining the chemistry bf the blue glass.