Material Source,Migration Process And Formation Model Of Boron-rich Salt Lake In Qinghai-tibet Plateau

Boron ore is an important non-metallic mineral in China,boron and its compounds have the properties of high hardness,fusion resistance and high electrical conductivity,which are widely used in the fields of national defense,chemical industry,agriculture,material science and nuclear industry.The salt lake of Qinghai-Tibet Plateau(QTP)is endowed with a large amount of solid and liquid boron ore resources,and the research on the material source,migration and enrichment pattern and formation mode of boronrich salt lake of QTP is of great theoretical significance and application value for the exploration and development of boron resources.In this paper,we investigate the formation mode of boron-rich salt lake on the QTP from the source of boron mineralization material and boron-rich mechanism of bedrock,the activation and release process of boron in bedrock,migration and enrichment process and influencing factors.Taking the source area of Da Qaidam Lake as the main research area,we use zircon chronology and trace element geochemistry to identify the boron-rich bedrock in Da Qaidam Lake and study its boron-rich mechanism.The activation and release process of bedrock boron is explored by using the weathering profile boron migration pattern study,high temperature and high pressure water-rock action experiment and other simulations.Through the geochemical study of the recharge water in the source area of Da Qaidam Lake,the main activation and release forms of boron in bedrock and the migration and enrichment process of boron are investigated.The tectonic background of the formation of boron-rich bedrock in the source area of boron-rich salt lakes on the Tibetan Plateau is systematically analyzed by exploring the distribution pattern and tectonic background of the salt lakes on the Tibetan Plateau and the formation process of boron-rich bedrock.Starting from the distribution relationship between boron-rich salt lake and hot spring activity in the northern Tibetan plateau,the main recharge form of boron-rich salt lake formation in the northern Tibetan plateau is discussed.The two boron-rich salt lakes,Lakkor Co and Bangor Co,northern Tibetan plateau,are selected for supplementary study,and the tectonic background of the formation of boron-rich bedrock and the migration and enrichment process of boron to the salt lakes are compared and studied.These studies are combined to characterize the formation pattern of boron-rich salt lakes on the QTP.The research in this paper is of great significance to fully understand the formation conditions and influencing factors of boron-rich salt lakes,and provides an important scientific basis for the resource development,evaluation and exploration of modern salt-lake type boron ores.The research results show that.1,The boron element of Da Qaidam Lake has two main sources,namely the tourmaline-bearing granite in the eastern part of the lake and the boron-rich bedrock of the high-pressure metamorphic zone gneiss,peridotite and serpentinite assemblage in the west,and the boron-rich minerals in the bedrock are mainly tourmaline,muscovite and serpentine.2,Bedrock boron release process mainly exists in two forms,namely surface weathering and deep water rock action,deep water rock action has a high boron release efficiency,while the surface weathering process boron release efficiency is low and boron element is easy to assign in the new carbonate minerals and fine grained sediments.3,Boron-rich salt lake in northern Tibetan plateau is mainly distributed in Longmucuo-Shuanghu suture zone(LSSZ)and Bangong-Nujiang suture zone(BNSZ),the tectonic background of these two regions is similar to the western part of Da Qaidam Lake,both are related to the participation of mantle material,forming high-pressure metamorphic rocks and ophiolite mingled rocks.The boron-rich salt lake in the interior of Lhasa massif is mainly distributed near the tourmaline-bearing pale granite,which is also related to the participation of mantle material and belongs to the continental Itype granite,and its formation mechanism is similar to the tourmaline-bearing granite in the eastern part of Da Qaidam Lake.There is a certain positive correlation between the distribution of boron-rich salt lake and the distribution of hot springs in the northern Tibetan plateau,and the boron-rich hot springs formed by the process of deep waterrock action may be the main recharge form of boron resources in the salt lake,which has an important influence on the formation of boron-rich salt lake.4、The formation of boron-rich salt lake on Qinghai-Tibet Plateau is a kind of "Internal-source and ex-converged" model.