Beschreibung
IDDP-1 demonstrated that non-eruptively degassed rhyolite melt is present at about 2 km depth under Krafla Caldera, raising many questions, as: Is there true magma in IDDP-1, or only a melt ooze that entered the borehole from hypersolidus felsite? If the intrusion formed during the last eruption, why did it not erupt? Ultimately this finding and the questions arising from it triggered KMDP.
The objectives of this proposal are intimately linked to several core objectives of the KMDP and also manifested in the scientific program suggested in the successful KMDP-project. The two central, synergetically interlinked objectives of this proposal are: (1) to constrain the response of rhyolitic magma in general, and Krafla magma in special to slow decompression (in shallow depths). This encompasses the questions if, when and how bubbles will nucleate and grow, the formation of permeable networks, and possibly magma fragmentation. (2) To constrain the mobility of rhyolitic magma towards surrounding host rocks in compressional and tensional (decompression) regimes. This encompasses also the question if a signature of this interaction can be identified that might be used for the monitoring of magma movement
The proposed approach is based on unique laboratory experiments, exploring possible scenarios as the rhyolitic magma responses to slow decompression under P-T conditions relevant to KMDP. Natural and hydrated obsidian from the last rhyolitic eruption of Krafla, and if possible Krafla natural rhyolitic magma from KMPD-well will be investigated for its response to slow decompression in the range of 820-920°C & 16-55 Mpa. Hereby the reaction from ‘nothing’ to minor nucleation to explosive foaming and fragmentation will be mapped out, enabling us to constrain the ’eruptability’ of Krafla magma.
The mobility of Krafla magma will be explored by two complementary approaches, both asking the question if, when and how magma interacts with host-rock (felsite), intruding or fracturing it. The mode how this interaction is forced forms the difference between bot approaches:
- slow decompression, resulting in vesiculation and thus volume increase,
- compressive cycling (loading and unloading) in a uniaxial press, both under magmatic conditions.
In both approaches the acoustic emission of the interactions will be monitored by several AE sensors. The interactions will be further explored using tomography and (micro-)textural techniques. Together these approaches will allow constraining interaction between silicate melt and host-rock and the mobility of the melts, and further give valuable insights for the magma monitoring.
The research proposed here is the second part (continuation project) of a research project that is expected to provide answers critical for understanding how magmas are generated, evolve and interact in the shallow crust as well as how they will react upon disturbance as for instance drilling.
