Detrital-zircon geochronology and Hf isotope of Paleozoic sedimentary rocks in the Jilin Province, NE China: tectonic significance for microcontinental blocks of eastern Central Asian Orogenic Belt

摘要

We undertook U-Pb-Hf isotope testing of detrital zircons from Late Paleozoic sedimentary rocks in the Jilin Province, NE China, with the aim of constraining the tectonic evolution of eastern Central Asian Orogenic Belt. The age populations of the detrital zircons from the sandstone of the Jiefangcun Formation in the Songliao Block are similar to 2234, similar to 1782, similar to 1030-921, similar to 817, similar to 540, and similar to 381-254 Ma, whereas those of the zircons from the greywacke of the Permian Kedao Formation in the Songliao Block yield are similar to 2436, similar to 1905, similar to 1692, 1146-1170, similar to 554-498, and similar to 342-255 Ma. Combined Hf isotope characteristics, these ages reveal that: (1) rocks from the Jiefangcun and Kedao formations were deposited after 254 and 255 Ma, respectively; (2) these formations were sourced mainly from the Songliao Block and the Jiamus Terrane in the eastern CAOB and to a lesser amount, from the northern margin of the NCC; and (3) it appears that several remnants of ancient Precambrian basement occur adjacent to these Late Paleozoic strata that occur within the microcontinental blocks. Detrital zircons from the silty sandstone of the Miaoling Formation in the western margin of the Khanka Terrane yield peak age populations of 508-476, 463-396, and 348-258 Ma, having similar epsilon(Hf(t)) values to those obtained from zircons within the Jiamusi Terrane. These data indicate that (1) deposition of the Miaoling Formation in the western margin of the Khanka Terrane had started by 258 Ma, and (2) these sediments were sourced mainly from the Jiamusi Terrane and local magmatic rocks. The widespread occurrence of detrital zircons with ages of 480-550 Ma and positive epsilon(Hf(t)) values within the Late Paleozoic strata in the Songliao Block and the Jiamusi-Khanka Terrane, indicates that the amalgamation of these blocks took place during the middle stage of the Paleozoic, probably after the Silurian, prior to the Late Permian.