Application of cathodoluminescence to detect productive fracture in geothermal field

• Project/Area Number: 11650962
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 資源開発工学
• Research Institution: Science University of Tokyo
• Principal Investigator: MURAMATSU Yoichi Science University of Tokyo Faculty of Science and Technology, Associate Professor, 理工学部, 助教授 (70266922)
• Project Period (FY): 1999 – 2000
• Project Status: Completed (Fiscal Year 2000)
• Budget Amount: ¥1,700,000 (Direct Cost: ¥1,700,000); Fiscal Year 2000: ¥600,000 (Direct Cost: ¥600,000); Fiscal Year 1999: ¥1,100,000 (Direct Cost: ¥1,100,000)
• Keywords: Cathodoluminescence / Luminoscope / CL-SEM / Productive fracture / Geothermal field / Anhydrite / Calcite / 森地熱地域 / 葛根田地熱地域 / 松川地熱地域

Research Abstract

The purpose of the project is to clarify the application of cathodoluminescence(CL) to geothermal exploration such as detection of productive fracture. The CL of anhydrites and calcites from the different origins or stages in the Kakkonda, Mori and Matsukawa geothermal fields has been studied using the Luminoscope(ELM-3R) and the CL mode of a scanning electron microscope(CL-SEM). The CL images of natural hydrothermal anhydrites have brown, pale green and no colors. The CL images with brown and pale green colors result from both Sm^<3+> and Dy^<3+> emissions, and Mn^<2+> emission, respectively. Calcites from the three different origins or stages such as natural hydrothermal calcite, calcite scale and limestone show CL images with red color, resulting from Mn^<2+> emission. Intensity of CL spectrum of Mn^<2+> in the calcites suggests that Mn content in limestone is little more than those in other calcite. Based on these investigations, it is concluded that the CL of anhydrite and calcite is a useful method to discern the different origins or stages of these minerals, and detect the productive fracture in the Kakkonda, Mori and Matsukawa geothermal fields.