Apatite and zircon (U-Th)/He and fission track ages were obtained from
ridge transects across the central Southern Alps, New Zealand.
Interpretation of local profiles is difficult because relationships
between ages and topography or local faults are complex and the data
contain large uncertainties, with poor reproducibility between sample
duplicates. Data do form regional patterns, however, consistent with
theoretical systematics and corroborating previous observations: young
Neogene ages occur immediately southeast of the Alpine Fault (the main
plate boundary structure on which rocks are exhumed); partially reset
ages occur in the central Southern Alps; and older Mesozoic ages occur
further toward the southeast. Zircon apparent ages are older than
apatite apparent ages for the equivalent method. Three-dimensional
thermokinematic modeling of plate convergence incorporates advection of
the upper Pacific plate along a low-angle detachment then up an Alpine
Fault ramp, adopting a generally accepted tectonic scenario for the
Southern Alps. The modeling incorporates heat flow, evolving topography,
and the detailed kinetics of different thermochronometric systems and
explains both complex local variations and regional patterns. Inclusion
of the effects of radiation damage on He diffusion in detrital apatite
is shown to have dramatic effects on results. Geometric and velocity
parameters are tuned to fit model ages to observed data. Best fit is
achieved at 9 mm a(-1) plate convergence, with Pacific plate
delamination on a gentle 10 degrees SE dipping detachment and more rapid
uplift on a 45-60 degrees dipping Alpine Fault ramp from 15 km depth.
Thermokinematic modeling suggests dip-slip motion on reverse faults
within the Southern Alps should be highest similar to 22 km from the
Alpine Fault and much lower toward the southeast. Citation: Herman, F.,
S. C. Cox, and P. J. J. Kamp (2009), Low-temperature thermochronology
and thermokinematic modeling of deformation, exhumation, and development
of topography in the central Southern Alps, New Zealand, Tectonics, 28,
TC5011, doi: 10.1029/2008TC002367.