Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (12) Citing Articles via Google Scholar Google Scholar Articles by SOLOTCHINA, E. P. Articles by WILLIAMS, D. F. Search for Related Content GeoRef GeoRef Citation

Simulation of XRD patterns as an optimal technique for studying glacial and interglacial clay mineral associations in bottom sediments of Lake Baikal

¹ United Institute of Geology, Geophysics and Mineralogy, Siberian Branch of Russian Academy of Sciences, 630090 Acad. Koptyug ave. 3, Novosibirsk, Russia, ² Department of Geological Sciences, University of South Carolina, Columbia, SC 29208, USA, and ³ Institute of Geochemistry, Siberian Branch of Russian Academy of Sciences, Irkutsk, 664033, Russia

^* E-mail: solot{at}uiggm.nsc.ru

(Received 9 September 1999; revised 21 June 2001)

A new method is proposed for modelling complex X-ray diffraction patterns effectively. The method is based on the calculation of the interference function of the one-dimensional disordered crystals with finite thickness. First, we calculated the diffraction effects from structures of individual mineral phases with different layer defects modelled according to the Reynolds’ algorithm. To fit the theoretical to the observed XRD patterns more accurately, we then used a specially developed optimization procedure. This iterative procedure selects the optimal set of chemical and structural parameters (probability and domain size) and yields consistent solutions.

The composition of the clay component in bottom sediments of Lake Baikal relates strongly to glacial/interglacial climate cyclicity. Besides changes in the relative abundance of illite and illite/smectites between glacial and interglacial periods, significant differences are observed in the crystal chemistries and structures of layered minerals. A change from chlorite during glacial periods to chlorite-smectite during interglacials is probably indicative of the weathering processes in the watershed. Changes in the degree of ordering, in domain size and grain-size distribution of illite-smectites imply differences in genesis of this mineral phase in different palaeoenvironments. These findings further strengthen the case for using clay minerals in the sedimentary record of Lake Baikal as palaeoclimate indicators.

One of our findings was that none of the fractions separated by Stokes’ settling is representative of the bulk sample for either the glacial or interglacial intervals. For the interglacial sample, illite-smectite was concentrated in the <2 µm fraction whereas, for the glacial sample, most of illite-smectite is contained in the <1 µm fraction. The selective use of one fraction is yet another potential source of uncontrolled errors that has to be avoided. We suggest using X-ray patterns of bulk samples as a preferred method of analysis of Lake Baikal (and other) sediments.

KEYWORDS: X-ray diffraction, modelling, illite-smectites, Lake Baikal, climate change

This article has been cited by other articles:

				T. Grygar, P. Bezdicka, D. Hradil, M. Hruskova, K. Novotna, J. Kadlec, P. Pruner, and H. Oberhansli CHARACTERIZATION OF EXPANDABLE CLAY MINERALS IN LAKE BAIKAL SEDIMENTS BY THERMAL DEHYDRATION AND CATION EXCHANGE Clays and Clay Minerals, August 1, 2005; 53(4): 389 - 400. [Abstract] [Full Text] [PDF]