玄武岩盖层下石林的岩溶动力学特征

KARST DYNAMICS FEATURES OF STONE FOREST UNDER THE BASALT COVER IN SHILIN AREA, YUNNAN

受玄武岩盖层的影响,石林地区的地下水在雨季和旱季对碳酸盐岩都具有侵蚀性,玄武岩盖层空气CO2呈现出低-高-低的双向变化梯度。溶蚀试验表明,地下0～0.6m,水平方向的溶蚀量大于垂直方向的溶蚀量,而随着深度的增加,垂直方向的溶蚀量大于水平方向。富含CO2的水通过具有最大渗透张量和较小主轴倾角的玄武岩裂隙下渗,对碳酸盐岩的溶蚀作用表现为一个脱钙、富铝铁、硅迁移的复杂过程,并在地下0～0.6m形成许多水平凹槽、穿洞等岩溶形态,而地表0.6m以下以垂向溶蚀为主,有利于石柱的形成与发育。

Effected by basalt cover, groundwater in Shilin area was erosive for carbonate in not only rain season but also dry season and the CO2 in basalt cover air had a twoway gradient of lowerhighlower change over the depth. Solution test of limestone showed that the horizontal solution amount of limestone is larger than vertical from the surface to the depth of 0.6 m, and contrary below the depth of 0.6 m. This may suggest that water rich in CO2 percolates down basaltic fracture of largest permeability tensor and smaller dip angle and solution process to carbonate is a complicated process of decalcification, richer aluminium and ferric oxide, and silicon migration. So at the depth less than 0.6m below basalt cover, notch and lightthrough cave etc are dominated, but below the depth of 0.6m dominantly vertical solution is favorable for the formation and development of stone column. 