Deformation of rhyolite lava crust associated with intermittent inner flow of lava: palaeomagnetic evidence
| Autor: | Kuniyuki Furukawa, Koji Uno, Kotaro Nakai, Takuma Kamio, Tatsuo Kanamaru |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Paleomagnetism
Asia 010504 meteorology & atmospheric sciences Pleistocene Lava Palaeomagnetism Crust Deformation (meteorology) 010502 geochemistry & geophysics 01 natural sciences Volcanic hazards and risks Rock and mineral magnetism Geophysics Geochemistry and Petrology Remanence Pumice Rhyolite Petrology Geology 0105 earth and related environmental sciences |
| Zdroj: | Geophysical Journal International. 220:190-200 |
| ISSN: | 1365-246X 0956-540X |
| DOI: | 10.1093/gji/ggz432 |
| Popis: | SUMMARY A palaeomagnetic study has been conducted to examine the deformation of thick crusts of rhyolite lava while its inner portions continue to flow. The Sanukayama rhyolite lava, which erupted in the Pleistocene in Kozushima Island, Japan, was chosen as the investigation site because of its well-exposed vertical lithofacies variations classified into three distinct zones (pumiceous, obsidian and crystalline). The targets of this study are the pumiceous and obsidian zones, which constitute the crust of the lava. Thermal demagnetization reveals three remanent magnetization components from the pumiceous and obsidian samples but only a single magnetization component from the inner crystalline rhyolite samples. Alternating field demagnetization is ineffective in isolating the magnetization components in the pumiceous and obsidian samples. The multiple components of remanent magnetization of the crust are interpreted to have been acquired during cooling as thermoremanent magnetizations. We suspect intermittent lava transport of the inner portions, the primary mode of rhyolite lava advancement, to be responsible for the presence of multiple components in pumice and obsidian of the lava crust. When the inner portions of the lava retain mobility to flow out of the crust, the solidified crust of the lava surface below the magnetite Curie temperature remains susceptible to deformation. Analysis of palaeomagnetic directions from the crust allows the deformation of the crust to be described in terms of rotation. Although the mode of rhyolite lava advancement is not well understood, because of its infrequent occurrence, our observations offer an important insight on how the mobile part of the lava is associated with the deformation of the crust during continued lava advance. |
| Databáze: | OpenAIRE |
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