Abstract
LA-ICP-MS U–Pb dating of detrital zircons reveals two levels of accumulation of Proterozoic quartzites in the Kyrgyz North Tianshan. The quartzites of the Makbal Formation in the core of the Makbal anticlinorium have a maximum depositional age of 1.7 Ga and characterize the oldest stage of accumulation of quartzites in the western Central Asian Orogenic Belt. Quartzites of the Ovva Formation in the northeastern limb of the Makbal anticlinorium and Djeldysu Formation in the Burkhan anticlinorium have maximum depositional ages of ca. 1.0 Ga. Distributions of detrital zircon ages in these two formations are identical and indistinguishable from detrital zircon age distributions in the Neoproterozoic quartzites of the North Kazakhstan. The latter three quartzitic units have common provenance and, apparently, represent the same stratigraphic level. Distinctly different distributions of detrital zircon ages indicate that Precambrian microcontinents of the Kokchetav-North Tianshan zone represented independent continental massif with respect to Precambrian crustal blocks of the Middle Tianshan and Tarim Craton.
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