Convergence history of the Jiamusi and Songnen-Zhangguangcai Range massifs: Insights from detrital zircon U-Pb geochronology of the Yilan Heilongjiang Complex, NE China

摘要

The Heilongjiang Complex, located between the Jiamusi and Songnen-Zhangguangcai Range massifs, has become a focus of tectonic research in recent years. Here we document new U-Pb detrital zircon age data for metasedimentary rocks from the Heilongjiang Complex in Yilan-Huanan counties. These data not only provide important constraints on the depositional timing and provenance, but also give further insights into the complicated convergence history of the Jiamusi and Songnen-Zhangguangcai Range massifs. Most zircons from the Heilongjiang Complex show "magmatic-like" zircon rare earth element patterns, with enrichment in heavy rare earth elements and positive Ce and negative Eu anomalies, suggesting a magmatic origin. Laser ablation-inductively coupled plasma-mass spectrometry zircon U-Pb analysis indicates that the youngest detrital zircons in these metasedimentary rocks have concordant Pb-206/U-238 ages of ca. 230-130 Ma. Based on this finding and the Middle Jurassic metamorphic ages of the Heilongjiang Complex, we conclude that metasedimentary rocks of the Yilan Heilongjiang Complex were deposited during the Late Triassic-Early Jurassic. Approximately 55% of the detrital zircons yield ages of 297 to 180 Ma, with peaks at 270-245 Ma, 230-200 Ma and 200-180 Ma. while 27% of the detrital zircons yield ages of 544-412 Ma with a peak at 500-480 Ma. Proterozoic detrital zircons (similar to 15%) were also identified, yielding ages of 2352 to 595 Ma, with most being of Neoproterozoic age. These results, combined with field relationships and previously published ages, suggest that detrital zircons in the Yilan Heilongjiang Complex were sourced mainly from igneous rocks in the Jiamusi and Songnen-Zhangguangcai Range massifs. Moreover, the protoliths of the metasedimentary rocks in the Yilan Heilongjiang Complex were most likely deposited in a forearc basin setting during convergence between the Jiamusi and Songnen-Zhangguangcai Range massifs. (C) 2018 International Association