Mineralogical And Origin Of Juhongtu Boron Deposit And Mud Volcanos In Yashatu, Qinghai

With the development of science and technology, boron and its compounds is widely used in various fields such as chemical industry, building materials, light industry, et al, due to its special physical and chemical properties. The demand of boron is increasing around the world.High quality ascharite oreis close to exhaustion in northern ascharite ore in our country after mining for more than50years, the foreign boron-depending is high to79%.According to previous research results, Tataleng River is the main source of replenishment of boron and lithium in Da Qaidam and Xiao Qaodam Lake. We studied the mineralogical and origin of Juhongtu boron deposit, Wulanbaomu mud volcano and Wubaotu mud volcano, hope to provide a clue of exploration for boron.We used microscopy, X-ray diffraction (XRD) analysis and other methods to study weathering products of qilianshanite and found that the weathering process of qilianshanite contains two stages. The weathering products of qilianshanite in the field are nahcolite and tincalconite, and then nahcolite changed into trona in a laboratory in Beijing.In this study we obtained ettringite samples from abandoned boron mine slags in Juhongtu, the composition of slags are borax and thermonatrite. We for the first time found that ettringite shows pronounced pleochroism and parallel extinction. The refractive index of ettringite is Ng≈1516; Nm≈1.482; Npv^1.446, Ng-Np=0.07. After high-temperature calcination, ettringite lost part (even all) of crystallization water and the refractive index rose significantly, thus leading the mineral to change from uniaxial negative to biaxial positive.Through the study of the hydrolysis process,Juhongtu ettringite is broken up into aragonite and alumina gel in carbonate environment. A comparison between the hydrolysis process of Juhongtu ettringite and that of cement ettringite indicates that the process of its hydrolytic carbonization will accelerate greatly under the background of higher CO32-contents. This has indicative significance for the study of the stability of cement.We found the honeycombgeyserite for the first time in bottom of Juhongtu boron deposit. Geyserite’s formation needs hot water with the temperature higher than180℃. We speculated that the formation of Juhongtu boron deposit should contains3stages. At first, the boron-rich and lithium-rich hot water upwelling along the fracture, it forms geyserite at the ground surface after the temperature reduction. The residual water and surface water converged in a depression, with gravel layer formed.Water in depression cooled and concentrated, borate minerals such as qilianshanite, ulexite, inyoite et al. At last, the fracture moved under the gravel layer, with the adarce formation above the gravel layer. The boron-rich water in the caps of afrace and the depression further concentrated. In the end, the main ulexite layer formed.We also studied the Wulanbaomu and Wubaotu mud volcano near Juhongtu boron deposit, considered that the origin of mud volcano is duo the boron-rich confined water upwelling along the fracture.After research of the boron and lituium contents of water sampleing in the Tataleng river system, the sediments sampleing in the northern and southern sections, the results show the positive anomaly of boron and lithium. Tataleng river basin will be the prospective project of boron deposit.According our research on occurrence state of lithium and potash of Jurassic sediments in Khukh Del, Mongolia, it contain almost no solubility potash, the"potassium resource" is not available; while lithium is kept in muscovite. It is not the real deposit under the condition of current technology. So the resource estimation of potash and lithium makes no economic sense.