Provenance of the Early–Middle Devonian Shugouzi Formation in the Quruqtagh, Northeastern Xinjiang: Constraints from Sandstone Geochemistry and Heavy Mineral Analysis

Abstract

AbstractThe Early–Middle Devonian Shugouzi Formation in the Quruqtagh block consists mainly of clastic rocks. However, their provenance has been scarcely studied since it was named. Geochemistry of clastic rocks was commonly used to interpret the provenance. Detrital heavy mineral analyses help frame the U‐Pb age from zircon grains, integrated with geochemical data from detrital tourmaline and spinels. These techniques were used to characterize components of the sediment flux and define erosion areas in the Qurugtagh block, further providing evidence about the tectonic evolution of the South Tianshan and Tarim plate. The maximum depositional age constrained by detrital zircon dating was Early–Middle Devonian. Multiple diagrams for sedimentary provenance using major and trace elements indicate that continental island arc‐related felsic rocks were the major source rocks for the Shugouzi Formation. Detrital tourmalines are dravite and schorl. The results of detrital tourmaline electron probe microanalysis (EPMA) show that the source rocks are mainly metasedimentary rocks and granitoids. The detrital chromian spinels within the sediments are characterized by high chroumium (Cr#) and varying magnesium (Mg#). The discrimination plots reveal that these spinels were sourced from island arc magmatic rocks. The laser ablation inductively‐coupled plasma mass spectrometry (LA‐ICP‐MS) U‐Pb chronology of detrital zircons suggests that the sediments were derived mainly from 414–491 Ma and 744–996 Ma magmatic rocks. Paleocurrent restoration, sandstone geochemistry, EPMA, and detrital zircon geochronology indicate that the source rocks were predominantly derived from Late Ordovician and Devonian magmatic rocks and subordinately from recycled Neoproterozoic magmatic rocks. Comprehensive analyses of the source areas suggest that a remnant arc still existed in the Early Devonian and the Shugouzi Formation was deposited in a passive continental margin.