美国西尔斯盐湖钙华研究综述

A review on the tufa research in the Searles Salt Lake,USA

钙华具有重要的科研价值。美国加利福尼亚州西尔斯湖内北部、中部和西南部广泛发育钙华丘,丘状体的高度从几厘米至45 m不等,通常高度为5~12 m。钙华丘内存在4种沉积相,分别为多孔海绵状钙华沉积相、结壳状钙华沉积相、柱状钙华沉积相和薄层结壳状钙华沉积相。从时空分布来讲,钙华呈两种沉积层序,分别为多孔海绵状钙华沉积相-结壳状钙华沉积相-薄层结壳状钙华沉积相-多孔海绵状钙华沉积相和多孔海绵状钙华沉积相-柱状钙华沉积相-薄层结壳状钙华沉积相-多孔海绵状钙华沉积相。这些钙华主要由方解石和文石组成,从微观尺度来讲,主要由纳米球晶体和棒状晶体组成,被解释为是微生物作用活动的结果。钙华沉积相中δ^(13)C的测定结果均为正值,表明西尔斯湖钙华属于热成因钙华。对西尔斯湖钙华主要沉积类型及沉积成因的讨论,可以为我国钙华研究提供对比参考资料。

Tufa has a scientific research value. There are wide distributions of the tufa mounds in the north,middle and southwest of Searles Lake,California,USA. The tufa mounds range from a few centimeters to 45 m in height,and most are 5 to 12 m high. There are four tufa facies can be identified from the mounds,including porous spongy tufa facies,nodular tufa facies,columnar tufa facies and finely-laminated crusts tufa facies. In terms of tempospatial distribution,there are two sequences of tufa deposition,including porous spongy tufa facies to nodular tufa facies to finely-laminated crusts tufa facies to porous spongy tufa facies and porous spongy tufa facies to columnar tufa facies to finely-laminated crusts tufa facies to porous spongy tufa facies. These tufa mounds mainly consist of calcite and aragonite. On the microscopic scale,these tufa facies dominantly make up nano-shperes and rod-like crystals,interpreted to be the activities of microorganism,such as bacterial. The values of δ^(13)C in the tufa facies were measured,and the results were positive,proving that the tufa of Searles Lake is the thermogene tufa. The discussion on the main sedimentary types and genesis of tufa in Searles Lake can provide comparative reference for the study of tufa in China.