洛川黄土纳米尺度观察：纳米棒状方解石

本文对洛川黄土剖面典型样品进行了透射电镜分析，发现黄土中存在纳米棒状方解石。此类方解石直径30～50nm，长度几百纳米至几微米。纳米棒状晶体有圆滑地粗细变化和弯曲现象，偶见晶体连接成树枝状或晶体直角连接形成框架状形态。X-射线能谱分析显示方解石有少量的镁、磷和硫，这种纳米棒状方解石在国内外文献中鲜有报道。根据纳米尺度研究结果推测，这种纳米棒状方解石形成与生物衍生物诱导的定向结晶有关。纳米棒状方解石是一种重要的黄土堆积时期干旱环境指示矿物，其碳、氧稳定同位素组成代表黄土堆积时气候参数。纳米棒状方解石的发现，对环境中纳米矿物研究、黄土中碳酸盐碳成因及古气候研究具有重要价值。

Nanometer-scale Investigation on the Loess of Luochuan: Nano-rod Calcite

Nano-rod calcite was discovered in a loess-paleosol sequence with the TEM investigation for the samples from the Luochuan section. The diameter of the calcite is 30- 50 nanometer and the length from hundreds nanometer to several micrometer. Nano-rod calcite crystals are round fibers with varying thicknesses. The crystals are bended along the direction of the crystal length. They sometimes have interlaced arrangement, and arborescent or frame forms. The EDS reveals small amounts of magnesium, phosphorous and sulfur. Morphology and composition analysis indicate that the formation of the nano-rod calcite is involved in matter derived from microorganisms and mineralization. The forming condition of the nano--rod calcite should be an indicator of paleoclimate, paleoenvironment and paleoecology. Therefore, the discovery of nano-rod calcite in the loess-paleosol sequence provides a new clue for reconstructing the paleoclimate and is of significance in the research of nanometer minerals in environment, genesis of carbonate in loess and paleoclimate reconstruction.