云南兰坪—思茅盆地红层中温泉和盐泉的水文地质特征

Hydrogeological characteristics of the hot springs and salty springs occurring in the redbeds in the Lanping-Simao Basin of Yunnan

云南西部兰坪—思茅盆地位于藏南—滇西地热带和羌北—滇西盐类成矿带东南部,红层分布广泛,盆地内温泉、盐泉和咸泉数量众多,有些温泉沉积钙华。分析了红层的岩性特征和地下水类型,出露于红层泉水的成因机制以及钙华的成因和控制因素,盆地盐泉或咸泉的找钾特征系数及其在预测找钾远景中的应用。盆地内红层地下水的分布受到岩性、构造和地貌的控制,风化裂隙水分布局限,以夹层型层间裂隙水和溶孔水为主。温泉均为深循环泉,盐泉或咸泉多为溶滤成因的浅循环泉。影响温泉附近钙华沉积的水化学因素主要包括pH、CO_2含量或CO_2分压、Ca^(2+)和HCO_3^-含量,可以用Ca^(2+)/HCO_3^-毫克当量比值和方解石饱和指数判断钙华沉积趋势。盐泉或咸泉的比例系数有助于预测找钾远景。

The Lanping-Simao Basin in western Yunnan is located in the southeast part of the Southern TibetWestern Yunnan geothermal zone and the Qiangbei-Western Yunnan salt mineralization zone,where red strata widely occur. There are many hot springs,salty springs and saline springs in the basin,and some of the hot springs deposit travertines. This paper briefly introduces the lithology of the red layers and types of groundwater occurrence in the red beds,and describes the formation mechanism of the springs occurring in the red beds and the control factors for deposition of the travertines. The hydrochemical characteristic ratios of salty or saline springs for prediction of the prospect of potash ore are also briefly described. The distribution of groundwater in the red beds in the basin is controlled by lithology,tectonics and topography. The distribution of weathering fissure water is limited,and the interlayer fissure water and dissolution pore water are the main types. The hot springs are all of the deep-circulation type,while the salty and saline springs are mainly of theshallow-circulation type and undergo incongruent dissolution of the salt-bearing red beds. The chemical factors affecting the deposition of travertine near the hot springs mainly include pH,content of CO2 or partial pressure of CO2,and contents of Ca^（2＋）and HCO3^-. The values of equivalent ratio of Ca^（2＋）/HCO3^- and saturation index of calcite can be used to predict the trend of travertine deposition. The ion ratios of the salty and saline springs are helpful in predicting the prospects of potash exploration.