Page 396 - Caldera Volcanism Analysis, Modelling and Response

Facilitating Dike Intrusions into Ring-Faults 371

reactivated ring-faults (Troise et al., 1997, 2003, 2004; Petrazzuoli et al., 1999;
Beauducel et al., 2004; De Natale et al., 2006). In summary, the mechanical
processes that reactivate ring-fractures by dikes may also be of major importance for
hydrothermal activity that follows the same trend (Beauducel et al., 2004). Thus,
understanding the formation and reactivation of ring-faults and their susceptibility
to intruding ring-dikes is of major interest to earth scientists of various disciplines.

5. Conclusion

Periods of caldera unrest mainly reflect tectonic and magmatic processes. This
paper focuses on potential intrusion patterns along caldera ring-faults. A systematic
set of numerical models suggests that caldera deformation may be affected by pre-
existing and reactivated tectonic faults and ring-fractures, and that sites of ring-dike
intrusions are controlled by various tectonic and magmatic loading processes.
A tectonic event like an earthquake may lead to localized displacements at caldera
systems and affect the locations of ring-dike intrusions. The shape of a deflating
magma chamber of ring-fault may also affect the locations of ring-dikes. In view of
this the formation of complete ring-dikes appears to be difficult. Many natural
calderas have ring-dikes that can be better understood by examining the local
volcano-tectonic environment and considering the models summarized in this
paper. The locations and patterns of ring-dike intrusions at caldera volcanoes can
also be applied to the distribution of hydrothermal activity and ore deposition
elsewhere.

ACKNOWLEDGEMENTS

This work benefited from numerous discussions at the International Workshop on Caldera Volcanism
on Tenerife, organized by Joan Marti and Jo Gottsman. Constructive reviews by Brian O’Driscoll and
Shigekazu Kusumoto are greatly appreciated. This work was financially supported by the Deutsche
Forschungsgemeinschaft (DFG WA 1642/1–4).

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