Geochemical Characteristics and Geological Significance of Eclogite in Airikehansen Area, Dulan County, Qinghai Province

The eclogite discovered in the Airikehansen area of Dulan County Qinghai Province, is about 12km northwest of northern Dulan eclogite belt. It is the newly discovered large-scale eclogite producing area and is a part of the HUP metamorphic belt in the Northern Qaidam. Most eclogites in the belt have a high degree of retrograde metamorphism. Its zircon U-Pb age is 435+4Ma, which represents the peak metamorphic age of the eclogite. The content of SiO₂ in eclogite ranges from 48.36% to 49.22%, (Na₂O+K₂O) from 3.28% to 3.65%(w(Na₂O)>w(K₂O). The original rocks of eclogites are basic basalts, subalkaline tholeiite series. The tectonic setting is mid-ocean ridge environment. The REE distribution curve of eclogite shows a right-leaning pattern, with weak enrichment of light REE and deficiency of heavy REE, (La/Sm)N=1.70-2.34, (La/Yb)N=1.18-2.54, which belongs to mantle-derived E-MORB type. The trace elements of eclogites show strong depletion of high field strength elements such as Th, P and Zr, and enrichment of large ion lithophile elements such as Rb and Ba. This indicates the deep subduction and orogenic collision background of the Qaidam block and the Olongbluk micro-block in the northern Qaidam basin from Late Ordovician to Early Silurian.