Geochemistry of the Lower Cretaceous limestones in the Eastern Tethys Gyabula Formation (Himalaya, southern Tibet): implications for the depositional environment and tectonic setting

The Tibetan Himalaya region provides crucial sedimentary successions for studying the evolution of the eastern Tethyan depositional area. However, the palaeo-environmental conditions during the Early Cretaceous period in southern Tibet (Tethys Himalaya northern zone) are not well constrained. In this paper, we report on the major, trace, and rare earth elements, as well as the carbon and oxygen isotopic compositions of the limestone successions in the Lower Cretaceous Gyabula Formation of the Rongpo area. The obtained sedimentary rare earth element (REE) profiles suggest that the Rongpo area was situated on a passive continental margin during the Early Cretaceous. The integrated geochemical and sedimentological analyses and results suggest that the limestones were deposited in a non-open marine depositional environment, marked by anoxic conditions. The strong positive europium (Eu) anomalies (Eu/Eu* = 1.77 ± 0.07), high SiO2 contents (average 19.30 ± 2.82%), and the negative δ13C values and δ18O values suggest that hydrothermal fluids may have impacted the Early Cretaceous Neo-Tethyan seawater geochemistry. The combined sedimentological and geochemical data provide new insights on the palaeo-environmental and tectonic setting of the Lower Cretaceous Neo-Tethyan successions of southern Tibet.