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U-Pb geochronologic analyses have been conducted on 413 detrital-zircon grains collected from 16 samples in the Altun Shan, Nan Shan, and Qilian Shan. The samples come primarily from quartz arenites and metaturbidites of Middle to Late Proterozoic age and from feldspathic and volcanic clast-rich sandstones of early Paleozoic age. Zircon grains in Proterozoic strata resting on Tarim basement yielded mainly 2.0–1.9 Ga ages, whereas Proterozoic strata of the Qaidam and Qilian terranes yielded mainly ca. 930–820 Ma and ca. 1.9–1.1 Ga ages. The younger grains were apparently shed from local igneous rocks, whereas the grains older than 1.1 Ga were shed from an undetermined continental source. Grains in the lower Paleozoic strata are mainly ca. 500–430 Ma and were shed from nearby plutonic and possibly volcanic rocks that formed in a magmatic arc setting.

Our detrital-zircon ages are …