Clay mineralogy and diagenesis of the Miocene-Pleistocene sedimentary rocks, NW Taiwan
Speaker: An-Ho Huang
Abstract
The study discussed the properties of clay minerals in the same sediments but burial in the different depths. The materials of the study were collected from the core Kuanyin-1 which locates in Taoyuan tableland, and from the foothill belt (the Dahan river, Chengfu profile, and Tsouho profile were included).The cored samples in Kuanyin-1 ranged from Toukeshan to Daliao Formation (181-2603 m deep), and there were 35 shales and 5 sandstones. By X-ray powder diffraction analysis for clay minerals, results showed that the abundances of the expanded minerals like smectite and illite/smectite mixed-layer minerals (I-S) in Kuanyin-1 were just a little. These trends stand for the growths of clay minerals in core Kuanyin-1 were not mainly controlled by diagenesis. By Chen ， s (1998) study of metamorphic divisions , through Toukeshan to Kueichulin Formation in Kuanyin-1, illite crystallinities ranged generally in anchizone, and this suggests the sediments might came from the anchizone in Taiwan orogenic belt. In the foothill belt, the abundances of clay minerals such as smectite and illite/smectite mixed-layer minerals were extremely low, whereas illite contents were generally high. The obvious trends of properties of clay minerals appeared in the foothill belt were illite crystallinities , smectite I-S contents, both degraded with burial depths. Furthermore, there are 11 samples from Tsouho profile for petrographic analysis, results showed that quartz were most abundant; whereas feldspar and lithic fragments were very low. From scanning electron microscope images, detrital clay minerals such as smectite, illite/smectite mixed-layer minerals, and kaolinite were appeared in the samples. Some of sandstones contain pyrite framboids in individual grain or lined in sheet silicates. Detrital clay minerals might imply the contents of parent rocks and growth of framboidal pyrite might indicate properties of environment.
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