Impact glasses, irghizites and zhamanshinites, from the Zhamanshin crater have been analyzed in-situ by ion microprobe to determine the trace and REE composition. Irghizites are markedly different from acid zhamanshinites in their content of a number of trace elements. This is due to a combination of factors: liquation of the primordial impact melt (separation of Ti, Zr, Nb, Ca, Mg, Fe) and subsequent participation of this melt portion to form irghizites; contamination of irghizites by meteoritic matter (the increase in Ni, Co, Cr abundance and the different Cr/V ratio); and the special conditions of irghizite formation (removal of the volatiles B, Na, K). Ratios of some trace elements (e. g. Ba/Y, Figure) suggest that irghizites and zhamanshinites could not differ from each other as a result of the difference in the composition of the target rocks. The Zhamanshin crater was formed by two impacts close in time. The material formed by the second impact can be distinguished from that of the first impact. Irghizites produced by the second impact show traces of meteoritic matter. Irghizites also exhibit a complicated pattern of trace element zoning. They show a marked similarity to tektites found elsewhere in the world relative to the F/B ratio and the B content.
Mendeley saves you time finding and organizing research
There are no full text links
Choose a citation style from the tabs below