Provenance and tectonic setting of siliciclastic rocks associated with the Neoproterozoic Dahongliutan BIF: Implications for the Precambrian crustal evolution of the Western Kunlun orogenic belt, NW China

Abstract

The Late Neoproterozoic Dahongliutan BIF is associated with siliciclastic rocks in the Tianshuihai terrane of the Western Kunlun orogenic belt (WKO), NW China. The sedimentary rocks have various weathering indices (e.g., CIA=57–87, PIA=61–96 and Th/U=4.85–12.45), indicative of varying degrees of weathering in the source area. The rocks have trace element ratios, such as Th/Sc=0.60–1.21 and Co/Th=0.29–1.67, and light rare earth element (LREE) enriched chondrite–normalized REE patterns, suggesting that they were mainly sourced from intermediate and felsic rocks. Available U–Pb ages of detrital zircon from these rocks reveal that the detrital sources may have been igneous and metamorphic rocks from the WKO and the Tarim Block. Our study suggests that the Dahongliutan BIF and hosting siliciclastic rocks may have deposited in a setting transitional from a passive to active continental margin, probably related to the Late Neoproterozoic–Early Cambrian seafloor spreading and subduction of the Proto–Tethys Ocean. U–Pb dating of 163 detrital zircons defines five major age populations at 2561–2329Ma, 2076–1644Ma, 1164–899Ma, 869–722Ma and 696–593Ma. These age groups broadly correspond to the major stages of supercontinent assembly and breakup events widely accepted for Columbia, Rodinia and Gondwana. Some zircons have TDM2 model ages of 3.9–1.8Ga and negative εHf(t) values, suggesting that the Archean to Paleoproterozoic (as old as Eoarchean) crustal materials were episodically reworked and incorporated into the late magmatic process in the WKO. Some Neoproterozoic zircons have TDM2 model ages of 1.47–1.07Ga and 1.81–1.53Ga and positive εHf(t) values, indicating juvenile crustal growth during the Mesoproterozoic. Our new results, combined with published data, imply that both the Tianshuihai terrane in the WKO and the Tarim Block share the same Precambrian tectonic evolution history.