Fluid infiltration after seismic faulting: examining chemical and mineralogical composition of the fault rocks in the drilling cores form Nantou well of the Chelungpu fault

• Main Authors: Chung-Bin Lu, 盧崇賓
• Other Authors: Wei-min Donald Chen
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/73222193366789943769

碩士 === 國立中央大學 === 應用地質研究所 === 92 === We defined four fault zones in the depth from 110 to 182m for the southern drilling core of the Chelungpu fault. The following methods are used in the study: X-ray fluorescence analysis (XRF), X-ray diffraction analysis (XRD), Petrographic observation and Isocon method. By integrating the XRD, XRF and petrographic data, we have derived some chemical reactions to explain the chemical input and output between altered rocks and their protoliths. Results of semi-quantitative XRD analysis show that kaolinite increases while montmorillonite decreases from undamaged rocks to seriously faulted rocks. From the whole-rock analyses, SiO2 gradually decrease while Al2O3, Fe2O3 and MgO increase from undamaged rocks to seriously faulted rocks. Volatile contents (LOI and CO2) are increased 1~4 times as high in the pseudotachylite compared to the standard host rock. In the Chelungpu fault zone, we use TiO2 as the immobile reference. A prominent volume loss process possibly caused by mechanical compaction is suggested by chemical isocon analysis. The gradual changes in chemical and mineralogical compositions from undamaged rocks to a fault center is probably due to fluid infiltration after seismic faulting.