Provenance and Tectonic Setting Study of the Maerzheng Formation at the Delistan of Buqingshan Area in the Southern Margin of East Kunlun

The flysch of Maerzheng Formation in the Buqingshan Area is located in the southern margin of the East Kunlun region,and its main body contains a set of turbidite of deposition in the bathyal-abyssal environment.This paper studied the characteristics of sandstone of the flysch formation.The framework component of the Maerzheng Formation sandstones statistical results show that feldspathic litharenite,quartz,feldspar and lithic is 42%,37%,21%,respectively,and the provenance is mainly derived from recycled island arc and orogenic belt in category.The sandstones of Maerzheng Formation are characterized by SiO2values of 50.18%~74.05%(average value of 66.69%),CIA=43~69,∑REE values of 59.99×10-6~171.07×10-6,∑LREE/∑HREE=6.6~8.8;(La/Yb)N=6.6~10.7,(La/Sm)N=3.2~4.6,andδEu=0.59~1.04.The sandstone′s geochemical characteristic indicates that the flysch was formed in the tectonic setting of the active continental margin;the sandstone belongs to continental island arc type;the provenance is the volcanic-plutonic magmatic island arc orogene and metamorphic basement of northern East Kunlun block;the protolith of sandstone dominantly derived from felsic volcanic rocks,cogenetic plutonic and metamorphic rock of basement;the sedimentary basin is the ancient trench or fore-arc setting in the outside subduction complex.Consequently,it indirectly records the process of Buqingshan-A′nyemaqen Ocean from continuous expansion,to northward subduction,and finally to closure.