ZHANG Shuai, LIU Li-hui, Qiao Zhi-chuan, Liu Qin-fu

(School of Geoscience and Surveying Engineering, China University of Mining &Technology (Beijing), Beijing 100083, China)

Abstract: In this study, the mineral composition, morphology and occurrence state of attapulgite clays occurred in the upper part of the Neogene Baiyanghe Formation in the Yangtaiwatan basin located in northern Linze County, Gansu Province have been investigated using methods of X-ray diffraction, polarizing microscope, and scanning electron microscope. The results show that there are mainly clay minerals, with minor quartz, feldspar, calcite, dolomite, gypsum, and a little of other minerals in the attapulgite-rich bed. The clay minerals are mainly composed of attapulgite and illite, with a certain amount of chlorite, kaolinite, and interstratified illite-smectite. It is believed that the Baiyanghe Formation were deposited in a dry climate when the gypsum was deposited in basin with the water evaporation which resulted in the increase of Mg2+/Ca2+ ratio and alkalinity of the residual lake water. The attapulgite was crystallized by silica colloid and Mg2+, Al3+, and Fe3+ from the brine of Mg2+- rich and high alkalinity with water evaporating.

Keywords: Attapulgite; genesis; Baiyanghe Formation; Linze County

ACTA MINERALOGICA SINICA Vol. 39, No. 6, 2019, page 690-696