西藏当雄错盐湖卤水中硼的来源研究  

Origin of Boron in the Dangxiong Co Salt Lake,Tibet,China

作　　者：雒洋冰[1] 郑绵平[1] 

机构地区：[1]中国地质科学院矿产资源研究所,国土资源部盐湖资源与环境重点实验室,北京100037

出　　处：《地质学报》2016年第8期1900-1907,共8页Acta Geologica Sinica

基　　金：自然科学基金重点项目(编号:U1407207);中国地质调查局大地调项目(编号:1212011085524)项目联合资助的成果

摘　　要：当雄错盐湖为大型硼矿床。大气降水、地表径流和地下径流以及蚀源区岩石是当雄错盐湖卤水中硼等稀有、稀散元素的三个来源途径。本文通过国标法(GB/T8538-2008)、电感耦合等离子光谱法(ICP-AES)、电感耦合等离子质谱法(ICP-MS)对当雄错硼的这三个来源分别进行元素地球化学研究,发现:1大气降水对当雄错B_2O_3的年估算输入量约为0.05×10^(-3)t^1.5×10^(-3)t,与地表径流和地下径流893t相比可以忽略不计;2河流对当雄错B_2O_3的贡献量最大,其中湖南岸的3条河流B_2O_3的年估算输入量达10个水源的95%,这3条河流的地球化学特征与热泉马尔作相同,B同位素δ^(11)B值也与热泉马尔作相同。说明当雄错地表径流和地下径流中的B_2O_3主要来自热水;3当雄错湖周蚀源区岩石主要为二叠纪,白垩纪岩石与第四纪碳酸盐粘土与钙华。其中二叠纪与白垩纪岩层中B_2O_3的含量较中国东部同类岩石低,不是当雄错B_2O_3的主要来源。第四纪碳酸盐粘土与钙华B_2O_3含量较高,高于世界碳酸盐岩与中国东部富泥碳酸盐岩。碳酸盐粘土稀土元素分布模式与已报道的热水湖相沉积的白云岩相同,都是中稀土富集,Dy的正异常,说明碳酸盐粘土是主要受热水影响。当雄错碳酸盐粘土是热水湖相沉积的一个典型实例。综上可知,热水是当雄错硼的主要来源。这一研究不仅为探索盐湖硼的成因提供重要依据,也为扩大寻找硼酸盐矿床指明方向。Boron （B） resources in Dangxiong Co （DC） salt lake of Tibet, China. It is a large-sized borate deposit. Atmospheric deposition, surface runoff, groundwater and rocks in erosion source area are sources of trace and dispersed elements （including B） in DC salt lake in Tibet. Geochemical characteristics of these sources were studied using GB/T8538-2008, ICP-AES, and ICP-MS in this paper. Results show that, ① The annual input of B2O3 from atmospheric deposition to the DC salt lake is 0.05×10^-3t～1.5×10^-3t, which is negligible compared to 893 t from surface runoff and groundwater inputs. ②Rivers are the most contributors of B2Oa to DC salt lake. The three rivers on the south bank of the DC salt lake contribute 95% of Be Oa. The geochemical characteristics of the water of these three rivers are the same to the Maerzuo hot spring. In addition, the δ^11B value is also same to that of Maerzuo hot spring. These results indicate that B2O3 in surface runoff and groundwater is from hot spring. ③The rocks in erosion source area are mainly Permian and Cretaceous strata rocks and Carbonate clay and travertine of Quaternary strata. The B2O3 concentrations of of Permian and Cretaceous strata around DC salt lake are lower than that in similar rocks in eastern China, that indicate the Permian and Cretaceous strata in DC are not the main source of Boron in DC salt lake. Carbonate clay and travertine of Quaternary strata around DC salt lake have a high content of B2O3, higher than carbonate rocks in the world and eastern China. The rare earth elements （REE） distribution patterns of carbonate clay are same as that of reported thermal water lacustrine deposit dolomite, characterized by middle REE enrichment and Dy positive anomaly. This indicates that carbonate clay around DC salt lake is lacustrine deposit affected by hot spring. The carbonate clay in DC is a typical example of lacustrine hydrothermal deposits. All these results above prove that thermal water is the main source for boron in DC salt lake. This

关 键 词：西藏 当雄错 盐湖 硼 热水 元素地球化学 硼同位素 

分 类 号：P619.2[天文地球—矿床学]