Microfracture Network of Fluids due to Magma Makes Underground Water Pathway
—The First Scientific Evidence of Supercritical Fluid Flow’s Trace in Cretaceous Granite—
Though past studies have reported that fault movements made underground water pathway, some recent researches reveal a high permeability in rock beds without well-developed fractures formed by fault movements. This is probably correlated to gas-like fluid, supercritical fluid, due to igneous activities, and it is important to find the trace of supercritical fluid for the clarification of formation mechanism of underground water pathway..
JAEA and Tohoku University conducted electron-microscopic observations and mineral analyses on rock specimens obtained through a 1,000m-deep boring survey, and then found the trace of supercritical fluids preserved in Cretaceous granite. This is the first scientific evidence.
Additionally, we revealed that microfracture networks developed in the granite bedrock around the trace which makes underground water pathway.
The result can be applied to technological developments of the analysis on long-term geological environment changes for geological disposals, and scientific researches on the migration of fluid in deep underground of a granite rock region and on the generation mechanism of micro-earthquake. These applications can contribute to the improvement in design and construction methods related to countermeasures against spring water for underground structures like tunnels, and the clarification of their correlations with slope disasters.