Magnetic inference of in situ open microcracks in sandstone samples from the Taiwan Chelungpu Fault Drilling Project (TCDP)

• Published in: Journal of Asian earth sciences Vol. 45; pp. 179 - 189
• Main Authors: Humbert, Fabien, Robion, Philippe, Louis, Laurent, Bartier, Danièle, Ledésert, Béatrice, Song, Sheng-Rong
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 02-02-2012; Elsevier
• Subjects: Anhysteretic remanence; Anisotropy of magnetic susceptibility; Earth Sciences; Ferrofluid; Magnetic mineralogy; Sandstone; Sciences of the Universe; Taiwan Chelungpu Fault Drilling Project (TCDP); Taiwan Chelungpu Fault Drilling Project (TCDP); Ferrofluid; Magnetic mineralogy; Anhysteretic remanence; Sandstone; Anisotropy of magnetic susceptibility
• ISSN: 1367-9120; 1878-5786
• DOI: 10.1016/j.jseaes.2011.10.009

► We investigate the magnetic signature of microcracks in TCDP sandstone. ► Anisotropy of anhysteretic remanent magnetization reflects magnetite neocrystallizations into microcracks network. ► Microcracks in TCDP sandstone are open at depth.
This paper presents a thorough magnetic study of centimeter-sized rock samples from Hole B of the Taiwan Chelungpu Fault Drilling Project (TCDP). Fabrics were obtained from magnetic susceptibility and anhysteretic remanent magnetization are interpreted using whole rock and magnetic mineralogy characterization. We infer the presence in the sandstone lithology of secondary magnetite coating a dense network of microcracks. Using other evidence from ferrofluid saturation experiments, we conclude that this network of microcracks is not sealed but open in situ, and should therefore be incorporated in the interpretation of seismic and borehole scale studies in the TCDP area.