Analogue Modeling of Resurgent Calderas: The Role of Prehexisting Tectonic and Volcano-tectonic Structures.
Abstract
Analogue models of block resurgence have been carried out on samples previously de- formed in an extensional setting, in order to better understand the role of pre-existing structures. Two lines of experiments were performed by superposition of two different equipments to simulate: a) resurgence in an area with a simple graben-like structure; b) ersurgence in an area with a caldera collapsed within the previously generated graben- like structure. We used dry sand to simulate the brittle crust and silicone to simulate the intruding magma. It has been observed that in the sample in which no caldera col- lapses were simulated, resurgence occurs through the formation of a discrete number of differentially displaced blocks. The most uplifted block is bordered, along one side, by a newly formed, high-angle, inward dipping reverse fault, that causes horizon- tal shortening of the sample. To accomodate the resulting shortening, normal faults with similar orientations forms in the opposite side together with the reactivation of the pre-existent graben faults. This asymmetric block resurgence that determine the generation of a compressional stress regime along one side and an extensional stress regime along the opposite side has been also observed in the experiments performed with a previous caldera collapse. In this case the reverse ring fault that accommodate the caldera collapse is completely erased along the shortened side, and enhance the effect of the extensional faults on the opposite side, facilitating the intrusion of the silicone. In nature this kind of behaviour has been widely described for the resurgent calderas of Campi Flegrei, Ischia and Pantelleria.
- Publication:
-
EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27.6103D