臺灣西北部中新世-更新世沉積岩中黏土礦物含量與成岩作用之研究

Translated title of the contribution: Clay mineralogy of the Miocene-Pleistocene sedimentary rocks, NW Taiwan

An-Ho Huang, Wei-Teh Jiang, Andrew Tien-Shun Lin, Jong-Chang Wu

Research output: Contribution to journalArticle

Abstract

We analyzed clay minerals and their relative abundances of Miocene to Pleistocene shales sampled from northwestern Taiwan. Results of vertical changes on clay mineral species and abundances yield information on degree of burial diagenesis as well as possible rock types in sediment source terrains. Samples were collected from two localities. One is from the core materials of KY-1 well, locating on the western coast of the Taoyuan Tableland. A series of 30 samples was collected from the Pleistocene Toukoshan Formation to the Miocene Taliao Formation, ranging from 184 m to 2,602 m in depth. The other locale is from three outcrop sections along the Dahan River, Tzukeng River and Sanshia River, respectively, in the NW foothills. We collected 35 samples from the Pliocene Chinshui Shale to the Miocene Mushan Formation with an estimated maximum burial depth range of 2,547-5,193 m. Results from X-ray powder diffraction analyses on collected samples show that KY-1 samples are rich in expandable clays, such as smectite and mixed-layer illite/smectite. There is no characteristic vertical change for the relative abundances of expandable clays and nonexpendable clays (e.g., illite) at the KY-1 well. For the samples from the foothills, the abundance of expandable clays is high in the upper section and decreases when increasing burial depths. In addition, illites are generally high in abundance throughout the composite sections of the foothills with an increase of its abundance at the lower part of the section. It appears that the depth range of 4,000-4,500 m reveals a downward decrease in expandable clays coupled with an increase on non-expandable clays. We therefore interpret that the above depth range is the depth where smectite to illite transformation occurs.
As illite is abundant for all studied samples and it coexists with large amount of expandable clays in rocks experiencing shallow burial, we examined the illite crystallinity to better understand its origin. For burial depths deeper than 4,200 m (i.e. for Shiti and older formations in the foothills), illites show lower crystallinity with a Kübler Index of 0.30-0.53 Δ°2θ, indicating a possible diagenetic origin. For burial depths shallower than 4,500 m (i.e. for all formations at the KY-1 well and Peiliao and younger formations in the foothills), illites show a higher crystallinity with a Kübler Index of 0.27-0.41 Δ°2θ, indicating that most of the illites are sourced from low-grade metamorphic terrains.
Translated title of the contributionClay mineralogy of the Miocene-Pleistocene sedimentary rocks, NW Taiwan
Original languageChinese
Pages (from-to)65-84
Number of pages20
JournalWestern Pacific Earth Sciences
Volume12
Issue number2
Publication statusPublished - 2012 Dec

All Science Journal Classification (ASJC) codes

  • Earth and Planetary Sciences(all)

Fingerprint Dive into the research topics of 'Clay mineralogy of the Miocene-Pleistocene sedimentary rocks, NW Taiwan'. Together they form a unique fingerprint.

  • Cite this