Discussions On Quaternary Glaciations And Climate Change Characteristics In The Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau is the product of the multi-tectonic north to the orogenic collage,and there are many ophiolite zones.The study of ophiolite has been a hot topic and a frontier issue in the Qinghai-Tibet Plateau.In this paper,the combination of the Longmutou-Shuanghu-Lancangjiang ophiolitic mélange zone,the Bangong Lake-Nujiang ophiolite belt and the Shiquanhe-Nammu-Baimi ophiolite belt in Shuanghu,Dongqiao and Zanzong As well as the petrology and geochemistry of the Moganshan ophiolite,the geostratigraphic environment and its source region properties are analyzed and studied,and the evolution history of each ophiolite zone is discussed.The composition units of the ophiolite in the Shuanghu ophiolite zone are exposed,and they are produced by the later tectonic movement.The geochemical characteristics of the metamorphic diabase and gabbro-based dykes in the ophiolite mélange of the Jiangaidarina Shuanghu show that their geochemical characteristics are derived from the enriched mantle source region,Showing both the mid-ocean ridge basalts and the oceanic basalts,which are the result of the interaction between the mantle plume and the mid-ocean ridge.Zanzongcuo ophiolitic mélange has a relatively complete sequence of ophiolite from bottom to top,but the sequence is seriously damaged by the later tectonic action.Lithology is dominated by mantle peridotite components.The geochemical properties of the ophiolitic rocks are characterized by two different properties of the geochemical composition of the continental margin and the intracontinental rift.Zongzongcuo The first group of basic rock samples derived from the loss of the mantle part of the melting,varying degrees of superimposed on a small amount of subduction fluid,sediment and other substances.Zongzongcuo,The second group of basic rock samples should be derived from the asthenosphere mantle,and superimposed with a small amount of continental crust components.Guomangcuo ophiolite is the Shiquanhe-Namco-Bomi ophiolite belt exposed to a larger area of an ophiolite,the sequence are exposed.Superfine Magnesia complex,where the heap complex shows a significant stacking rhythm,showing a distinct separation of the crystalline characteristics and indicating that it originates from a mantle that is confounded by the enriched component.The basic rock has a high Al characteristic,and the rare earth elements and trace elements have an E-MORB type distribution pattern.The geochemical environment of the petrographic rocks shows that the ophiolitic ophiolite may be formed in the expanded post-arc basin environment.Combined with the regional tectonic characteristics,it is considered that the ShiquanheNamco-Bomi ophiolite belt is the southern subduction The formation of the arc after the small ocean basin,ophiolite unit block is the ancient oceanic subduction damping,collision and tectonic uplift and the formation of today's tectonic rock,not the thrust overturned from the remote transport.Based on the field geological survey,petrographic and geochemical characteristics of ophiolite,this paper constructed the evolution history of ophiolite in northern Tibet in combination with the related achievements of predecessor ophiolite: Shuanghu ophiolite as Longmucuo The part of the Shuanghu-Lancangjiang ophiolitic mélange zone is accompanied by the closed eccentricity of the Late Tertiary in the Late Permian,which is disrupted by the subsequent metamorphic tectonic metamorphic deformation sequence,The exotic Tethys sprang before the Permian and,with the gradual split,began a two-way dive in the southern margin of the Lhasa block and the southern margin of the Qiangtang plots,and induced in the late Triassic Which is related to the subduction of the Dongqiao ophiolite in the Early Jurassic tectonic emplacement,while the Shiquanhe-Namco-Bomi basin continued to crack westward,forming The ophiolitic ophiolite with the background of the post-arc basin is characterized by the subduction of the oceanic crust.The oceanic crust is closed and the ophiolitic tectonic is formed.