中国南方发现大型文石笋

中国南方大量石笋剖面研究表明,石笋矿物组成有方解石、文石、方解石-文石三种类型。石笋沉积纹(微)层结构构造特征大同小异,但是文石石笋的放射状纹(微)层构造更显著。文石石笋沉积生长的气候环境是滴水多而稳定,水温低、气温略高的冷、湿的洞穴气候条件。文石转变为方解石常保留文石的针状、柱状晶形,并存在于石笋沉积生长的始终。文石结构构造转化在常温或低温、常压或低压下自调整作用的成晶成岩环境进行,其强度取决于所在洞穴气候环境、滴水在石笋的渗流和石笋的含水度。转化作用不影响同位素分馏,石笋同时全面记录古气候环境信息。研究文石石笋对重建古气候环境、成岩成矿作用都有重要理论和实践意义。

Large aragonite stalagmites found in South China

The study of stalagmites in the South China indicates that they are made of calcite, aragonite or the combination of calcite and aragonite. The radial symmetry structure of aragonite is clearly shown. The environment of aragonite stalagmite formation is characterized by cool temperatures and humid conditions with abundant and steady drop water. An additional requirement is that water temperature must be lower than air temperature. The acicular and columnar shapes of aragonite crystals are preserved even after aragonite changes into calcite. The change of aragonite to calcite usually occurs under lower temperature and pressure. This change is controlled by the cave environment, the character of drop water's run on the stalagmite and the water content of the stalagmite. This change does not disturb isotopic fractionation, and during the process the stalagmite is able to keep environment information. The study of aragonite stalagmites is important to reconstruct the paleoclimate and know mineralization in both theory and practice.