Paper No. 10
Presentation Time: 4:15 PM
CHARACTERISTICS AND SIGNIFICANCE OF NANO-ROD CALCITES OF BIOMINERALIZATION IN THE LOESS OF CHINA
Nano-rod calcites were discovered in loess-paleosol sequence with field emission scanning electron microscopy and transmission electron microscopy investigation for the samples of Duanjiapo, Luochuan, Lingtai and Xifeng Sections. Nano-rod calcites crystals arrange as bird net like. The mount of nano-rod calcites in loess is more than those of paleosol. Even though large amount of carbonate and various kind of autogenetic calcite in loess-paleosol sequence of China and nano-rod calcite in Tataouine meteorite in South Tunisia had been found, this kind of nano-rod calcites constituting main part of carbonate in loess-paleosol sequence and occurring widely in Chinese Loess Plateau was discovered first time. Diameters of the nano-rod calcites are 30~50 nanometer, length from hundreds nanometer to several micrometer. Nano-rod calcites crystals are roundness fiber, there are minute changed in thickness and minute bend along the direction of crystal length. Crystals of the nano-rod calcites present occasionally interlaced arrangement, arborization and frame by connection with right-angle among crystals. Electron dispersive spectrum shows the peaks of magnesium, phosphorous, and sulfur. Morphology and composition indicate that the formation of the nano-rod calcite is involved in matter derived from microorganism and biomineralization because of organic controlling to growth of calcite in loess deposit environment. Forming conditions of the nano-rod calcites should present paleoclimate, paleoenvironment and paleoecology. So, the discovery of nano-rod calcites in loess-paloesol sequence provide new route for reconstruct paleoclimate by oxygen and carbon isotope employing nano-rod calcites. It will be same important for nanogeoscience because it: (1) provides demonstration data of natural nanometer minerals occurring large mount to research microorganism nanometer mineralization and formation mechanism of natural nanometer minerals; (2) provide novel methods for the synthesis of nano-rod calcite as well as other minerals in material science. The work was supported by the Outstanding Overseas Chinese Scholars Fund of Chinese Academy of Sciences (2003-1-7) and National Science Foundation of China (40331001).