BORATE DEPOSITS IN QAIDAM BASIN

Qaidam Basin is situated in the northern border of the Qinghai-Tibet plateau and is ond of the largest inland basin in the world.In this basin, it is enriched in borate deposits.According to their genesis, it can be divided into two types: sedimentary origin and mineralizing water. On the basis of the conditions of its formation, the former may be divided into five subtypes: lacustrine-chemical deposit, lacustrine marsh deposit, deposit of resedimentary origin of oilfield water, deposit of mineralized water and salted soil; The latter may be further classified into four subtypes: brine of the recent salt lake, water of oilfield, mineralized water and water of the mud volcano. The occurrence of ore body and mineral association are different in each one. The lacustrine-chemical borate deposit is the most important among them. There are elevben minerals of borate have been found so far in Qaidam Basin.They are ulexite, pinnoite, inderite, kurnakovite, carboborite, hungtsaoite, macallisterite, inyoite, hydroboracitc, borax, and nodleite.Among them, carboborite, and hungtsaoite were the first found in the world.. The mineralizing water are distributed very wide in Qaidam Basin and it is higher in grade of boron.On account of the boron associated with element K, Li, Mg, I, especially in the brine of salt lake, so it became mineral resource with comprehensive utilization value. According to tje origin and the space distribution of the borate deposits, it may be divided into five minerogcnetic belts in Qaidam Basin as follows: 1, The minerogenetic belt of lacustrine-chemical sedimentary borate of intermont basin on the northern margin of the basin. 2, The minerogenetic belt of sedimentary borate in the region of intermontane valley on the southern of Qilian Mountain. 3.The minerogenetic region of lacustrine marsh-chemical sedimentary borate of the front depression of the mountain on the eastern side of Tirtiary uplift region of the western basin. 4. The minerogenetic belt of resedimented borate of oilfield water and B- bearing oilfield water on the Tertiary uplift of the western basin. S.The minerogenetic belt of lacustrine marsh-chemical sedimented borate on the southern of the basin. 6.The minerogcnetic belt If B-bearing brine associated with K-Mg salt in the Meso-Cenozoic depression belt of the centre basin.