A DISCUSSION ON METHODOLOGY TO EXTRACT CLAY MINERALS FROM MARINE SEDIMENTS

Clay minerals, as the most important components of terrigenous fine-grained clastic sediments, play a significant role in the research of sediment sources, oceanic currents, and paleoenvironmental evolution. Therefore, how to extract clay minerals correctly and efficiently from the sediments becomes a prerequisite for further research. In this study we presented two methods i.e. the gravity settling and centrifuged settling respectively to extract clay minerals from marine sediment samples. The two sets of results, compared each other by statistical analysis, show a positive correlation rather than significant difference. Downcore variation of clay mineral assemblages estimated by the two different methods for both ODP Site 1146 and core ZK001 has a very similar overall trend. The diffraction patterns of a clay-sized powder sample obtained by the two extract methods show a similar trend, dominated by clay minerals. Moreover, grain size measurements show that samples obtained by the two extract methods are all in the range of <2 μm. Thus we conclude that the centrifuged settling method can also accurately obtain important information about clay minerals, and is more efficient than traditional gravity settling method to extract clay minerals. Therefore, it is appropriate to promote centrifuged settling method in research of clay minerals in marine sediments.