First Results of Study of Detrital Zircons from Late Precambrian Quartzite-Schist Sequences of the Aktau-Mointy Block, Central Kazakhstan

摘要

For the first time, the U-Pb age is determined for detrital zircons of quartzite-schist sequences, which are part of the Precambrian basement of the Aktau-Mointy Block (Central Kazakhstan) along with Neoproterozoic felsic volcanic (925-920 Ma) and granitic (945-917 Ma) rocks [6]. We analyzed 219 zircon grains from small-grained quartzites of the northern part of the block (Mt. Bol'shoi Alabas) including 206 grains with concordant age (1149-1273, 1276-1975, 2354-2592 Ma). These ages indicate the Mesoproterozoic, Paleoproterozoic, and Neoarchean rocks as provenances. The youngest statistically significant age peak of 1209 Ma indicates that the quartzite-schist sequences accumulated 1200-900 Ma ago (at the end of the Mesoproterozoic and beginning of the Neoproterozoic) prior to the formation of the Early Neoproterozoic felsic rocks and granites.