Identification of Greigite in the late Pleistocene sediments of Lake Qinghai

In this study,the magnetic mineralogy of a late Pleistocene lake sediment core（1F,ca.18.6 m long） from the southern sub-basin deposition center of Lake Qinghai,the largest lake in China,was studied using multiple rockmagnetic and non-magnetic measurements.There are two distinct magnetic susceptibility peaks at the depths of8.15;.96 m and 15.50;7.28 m.High and low temperature magnetization investigations,coupled with scanning electron microscopy（SEM） and Energy dispersive x-ray（EDX） analyses,suggest that the sediments from these two intervals contain a large number of single domain（SD） and superparamagnetic（SP） greigite particles,which is the primary cause for the enhancement of magnetic susceptibility.These greigite particles are mainly formed due to sulfate reduction.The occurrence of greigite in the late Pleistocene sediments of 1F core implies that the Lake Qinghai could have experienced two intervals favorable for early diagenesis during the late Pleistocene.