摘要
Binggou ophiolite mélange,the eastern part of Hongliugou ophiolite,Altyn Tagh,is composed of serpentinites,harzburgites,pyroxenites and gabbros etc.Geochemistry analysis shows that the serpentinites are characterized by high Mg contents,with Mg/Fe ratio greater than 9,and low Al,Ca,Na,K contents.Determined by rare earth elements and trace elements compositions,the gabbro is very similar to MORB,and ultrabasic rocks are close to PRIMA.The SHRIMP U-Pb age of zircon from the gabbro is 449.5±10.9Ma which is belongs to Middle to Late Ordovician.The country rocks of Binggou ophiolite mélange are mainly composed of clastic rocks,pyroclastics,volcanics,and part of carbonates which combined to be a huge thick sequence.These rocks contain basalt which has characteristics of MORB and the pillow structure,and radiolarian cherts which formed in Middle to Late Ordovician that is consistent with the gabbro SHRIMP age.These evidences further convinced that the Early Paleozoic ocean basin has been existed in the Hongliugou area.
