Open AccessLong‐term stability of fracture systems and their behaviour as flow paths in uplifting granitic rocks from the J apanese orogenic field
Author(s) -
Yoshida H.,
Metcalfe R.,
Ishibashi M.,
Minami M.
Publication year - 2013
Publication title -
geofluids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.44
H-Index - 56
eISSN - 1468-8123
pISSN - 1468-8115
DOI - 10.1111/gfl.12008
Subject(s) - pluton , geology , carbonate , geochemistry , fracture (geology) , meteoric water , carbonate rock , mineral , magma , skarn , hydrothermal circulation , mineralogy , geotechnical engineering , seismology , sedimentary rock , volcano , tectonics , fluid inclusions , materials science , metallurgy
In granitic rocks, fracture networks typically provide pathways for groundwater flow and solute transport that need to be understood to assess the long‐term performance of deep underground storage or disposal facilities such as radioactive waste repositories. However, relatively little is known about the long‐term processes of fracturing and/or the longevity of flow paths ( FP ) in granitic rocks distributed within orogenic belts. To clarify these issues, J apanese plutons of different ages and in situ fractures in granite at the M izunami U nderground R esearch L aboratory ( MIU ) located in central J apan were studied. Detailed structural characterization and geochemical analysis of in situ fracture fillings sampled from a depth of 300 m were carried out to clarify the relationship between fracturing and mineral infilling processes. Different plutons show identical episodes of fracturing and fracture filling, consisting of: brittle tensile fracturing, due to decreasing temperature through the ductile–brittle transition after plutonic intrusion (Stage I); relatively rapid uplifting (ca. a few mm/year) accompanied by hydrothermal water circulation, which produced uncrushed layered mineral fillings (Stage II ); and a period of low‐temperature meteoric water circulation following exposure after uplift (Stage III ). The parageneses of carbonate mineral fracture fillings and their carbon isotopic compositions ( 14 C, δ 13 C) show that there were distinct episodes of carbonate mineral precipitation during the rapid uplifting of a pluton. The carbonate minerals that formed during each episode incorporated carbon from a distinct source. The evolution of fillings identified here enables development of a specific model of fracturing and persistence of fluid‐conducting systems in the plutons of the orogenic field.