Mineralogy of long drill core from Darkhad Basin in northern Mongolia

Darkhad Basin in northern Mongolia was former dammed lake during Pleistocene glaciations.The basin is located in the inside of continent where is sensitive to the climate change.The lake sediments are expected to possess the paleo-environmental records like the sediments from Lake Baikal and Hovsgol.Three long drill cores were obtained from the Darkhad Basin at winter of 2010.This study is first report for the mineralogy of the long drill core from the Darkhad Basin.DDP10-3 core(alternatively "Hodon core";51°20’11 "N,99°30’4" E;length about 164 m) was used for the mineralogical investigation.The sample was cut into 3 cm and analyzed from top to 30 m by means of X-ray powder diffraction(XRD) after freeze-drying.XRD analyses of bulk sample show that the constituent minerals present in the sediments were quartz,feldspar,amphibole,calcite,dolomite,mica chlorite and smectite.Quartz,feldspar,amphibole,chlorite,mica and smectite were found in samples from all depths.However some samples contain carbonate minerals(calcite and dolomite) whereas some samples do not.The samples with calcite usually contain dolomite.There is no systematic tendency of the presence or absence of carbonate minerals with depth.The formation and dissolution rate of carbonate minerals are much higher than the other constituent minerals.This indicates that carbonate minerals disappear(or appear) during some periods as response to changes of water chemistry of the paleo-lake.The water chemistry is usually affected by surround environment.This preliminary study suggests that the carbonate mineralogy can be regarded as possible proxy for the paleo-environment in Darkhad Basin.