Research on the Origin of Eolian Clay Deposits by Means of Thermoluminescence Color Image (TLCI) and Color Image Analysis (TLCI-CIA) Using Quartz Particles

Abstract

A new and TLCI (Thermoluminescence Color Image) and effective TLCI-CIA (Thermoluminescence Color Image-Color Image Analysis) method, using quartz grains to discriminate between eolian and volcanic ash deposits, is proposed in this paper. Experimental results indicate that the coloration of quartz particles can be basically divided into two typical color categories, red and blue, characterized by α-quartz in plutonic rock and β-quartz in ash, respectively.
The source of the clay layers which cover a vast surface of Japan's landforms has been extensively discussed by Quaternary geologists, who have disagreed about whether they come from volcanic materials of the Japan Islands or from loess deposits transported from the inland area of China. To contribute to the discussion, we have used the TLCI method and the TL color quantitative analytical method, which divided the quartz TL coloration into three basic colors (red, blue, and green) by the Nikon LS-1000 system, which is illustrated on the CIE chromaticity diagram.
Three typical kinds of samples were prepared for the TLCI-CIA experiments. The first group is from 8 standard eolian samples selected from the Japanese and Hawaiian Islands. The second and third groups are composed of 6 clay deposits and 8 volcanic ash layers which are distributed in northern Hokkaido. The TLCIs emitted by the first group of standard samples and the second group of clay deposits have been classified similarly into the three different colors 5PB, 10PB, and no-TLCI (dark color), belonging to the blue color region, on the basis of the international color manual (JIS Z 8721). Further, TLCI-CIA research has indicated that 5PB is plotted around 450-495nm and that 10PB is scattered widely in two regions, of 450-495nm and 570-600nm wavelength.
The TLCIs of the third group, tephra layers, has shown a clear 7.5R red color range in the two main grain sizes of 250-590μm or 125-250μm. TLCI-CIA investigations have also shown that the 7.5R grains emitted the wavelength of 570-620nm.
The preliminary TLCI investigation on the blue color region indicated that no-TLCI and 5PB quartz grains originated in different types of source rocks, such as sedimentary, metamorphic, and plutonic rocks.
The experimental conclusion indicates that the majority of clay layers found in the tested area, are derived from eolian deposits originating in blue and no-TL quartz particles associated with small amounts of red-TL quartz particles; however, the tephra layers are mainly composed of red-TL quartz grains. The result also shows the availability of the TLCI-CIA method to identify the sources of deposits.