西藏高原盐湖的构造地球化学和生物学研究

Tectonogeochemical and Biological Aspects of Salt Lakes on the Tibetan Plateau

按盐湖的盐类组分和地质构造背景差别,将其概分为普通盐湖和特种盐湖。前者产于克拉通、地台等稳定构造区;后者分布于活动构造区,包括大陆边缘火山弧后盆地或陆-陆碰撞带,板块转换带后盆地。西藏高原盐湖产于陆-陆碰撞带;盐湖硼和稀碱元素主要来自高原深部壳层重熔岩浆,热水成为输入盐湖中的重要载体;盐湖水化学类型和组分特征控制了不同的成矿专属性。笔者等对藏北高原作了大范围盐湖生物概查,在调查的125个湖泊中,确定30个盐湖有卤虫繁衍。在羌塘北部21个湖泊中,已鉴定出浮游植物95种,主要种类有Gloeothece linearis,Doctylococcopsis rhaphichoidesHansg,Chroococcus minor,Naviculasp.,Cymbella pusilla,Dunaliellasalina,Chlorella rulgaris,Diatoma elongatum。浮游动物共鉴定出原生动物16种,主要种类有Voriticellaspp.,Epistylisspp.,Keratella quadrata,Daphniopsis tibetana,Artemiasp.等。

Based on saline minerals and geological settings, ordinary salt lakes and special salt lakes may be distinguished. The former occur in stable tectonic regions such as cratons and platforms; while the latter in tectonically active regions, including continental-margin back-arc basins or collision zones and basins at the rear of plate transform fault zones. Salt lakes of the Tibetan Plateau occur in a continent-continent collision zone. Boron and rare alkali elements mainly came from anatectic magma at the depth of the crust below the plateau, especially in the partial melting layer and recent anatectic magma in the Himalaya-south Qiangtang area, and hydrothermal water was the major carrier for transporting B and rare alkali elements from the depth to the salt lakes. Hydrochemical types and composition of the salt lakes constrain different minerogenetic specializations. An extensive investigation of 125 salt lakes in the northern Tibetan Plateau detected Artemia spp. in 30 lakes. In 21 lakes in the northern part of Qiangtang, 95 species of planktonic algae including Gloeothece linearis, Doctylococcopsis rhaphichoides Hansg, Chroococcus var. minor, Navicula sp. , Cymbella pusilla , Dunaliella salina , Chlorella rulgaris and Diatoma elongagtum , and 16 species of planktonic animals, such as Voriticella spp., Epistylis spp., Keratella quadrata, Daphnkiopsis tibetana and Artemia sp. were found.