EXTRACTION METHOD AND SIGNIFICANCE OF AUTHIGENIC CLAY MINERALS IN SEDIMENTARY ROCKS FOR K-Ar AGE DATING

A new method was used to separate authigenic clay minerals in sedimentary rocks-a repetitive free zing thawing process.The aim of this process was to disaggregate rock samples using the volume expansion of water that impregnates samples.The new method can avoid the shortcoming that a conventional crushing produces an over crushing of the larger grains of a rock,creating artificially clay sized particles which become intimately mixed with the natural clay component of the rock.For the most of our samples,fractions smaller than 1μm,the new method already remove the presence of K feldspar,while the conventional method can not achieve;In addition,with the reduction of grain size,the content of detritus illite in clay mineral component decreased gradually.For our samples,in the most of fractions smaller than 0.2μm,the content of detritus illite 5%,in some of them,the detritus illite already removed.