Low-temperature thermochronology of the Izu collision zone, central
Japan: Implications for mountain building at an active arc-arc collision
zone
Abstract
Arc-arc collision plays an important role in the formation and evolution
of continents (e.g., Yamamoto et al., 2009; Tamura et al., 2010). The
Izu collision zone central Japan, an active collision zone between the
Honshu Arc and the Izu-Bonin Arc since the middle Miocene (Matsuda,
1978; Amano, 1991; Kano, 2002; Hirata et al., 2010), provides an
excellent setting for reconstructing the earliest stages of continent
formation. Multi-system geo-thermochronometry was applied to different
domains of the Izu collision zone, together with some previously
published data, in order to reveal mountain formation processes, i.e.,
vertical crustal movements. For this study nine granitic samples yielded
zircon U–Pb ages of 10.2–5.8 Ma (n = 2), apatite (U–Th)/He ages of
42.8–2.6 Ma (n = 7), and apatite fission-track (AFT) ages of 44.1–3.0
Ma (n = 9). Thermal history inversion modelling based on the AFT data
using HeFTy ver. 1.9.3 (Ketcham, 2005), suggests rapid cooling events
confined to the study region at ~5 Ma and
~1 Ma. The Kanto Mountains are thought to be uplifted
domally in association with collision of the Tanzawa Block at
~5 Ma. But this uplift may have slowed down following
migration of the plate boundary and late Pliocene termination of the
Tanzawa collision. The Minobu Mountains and possibly adjacent mountains
may have been uplifted by collision of the Izu Block at
~1 Ma. Mountain formation in the Izu collision zone was
mainly controlled by collisions of the Tanzawa and Izu Blocks and
motional change of the Philippine Sea plate at ~3 Ma
(Takahashi, 2006). Earlier collisions of the Kushigatayama Block at
~13 Ma and Misaka Block at ~10 Ma appear
to have had little effect on mountain formation. Together with
~90° clockwise rotation of the Kanto Mountains at 12-6
Ma (Takahashi & Saito, 1997), these observations suggest that
horizontal deformation predominated during the earlier stage of arc-arc
collision, whereas vertical movements due to buoyancy resulting from
crustal shortening and thickening developed at a later stage.
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