Origin of Materials Erupting from Mud Volcano in Tokamachi City, Niigata Prefecture, Central Japan

Abstract

Mud volcanoes are structures formed as a result of the emissions on a land surface or the sea floor of argillaceous material, which is composed of erupting remobilized mud, petroliferous or magmatic gases, and high-salinity water. Recently, large constructions have been planned deep underground besed on the expectation of geological stability. Therefore, it is important to study the origin of erupted mud and groundwater and the depths from which they ascend when evaluating long-term stability. Three active mud volcanoes and a passive mud volcano are found in the Tertiary Shiiya Formation distributed in Tokamachi City, southern part of Niigata Prefecture. Detailed descriptions of the mud volcanoes are provided by Shinya and Tanaka (2005). However, the origin of erupted mud and the formation mechanism of abnormal pore water pressure have not yet been identified. The authors measured the oxygen and hydrogen isotopic ratio of groundwater and vitrinite reflectance of coal fragments separated from erupted mud of an active mud volcano to investigate the origin of erupted mud, particularly the depth of the origin, and the formation mechanism of abnormal pore water pressure. As a result, 18 O and D values of erupted water are 1.2‰,-5‰ respectively, showing good agreement with those of the Nanatani Formation distributed at a depth of 3400 m in depth in the studied area. Vitrinite reflectance(Ro)shows a bimodal distribution(i.e., 0.3⊖1.2％ and 1.5⊖1.8％). Ro value of coal fragments sampled from the Shiiya Formation at the outcrop in the studied area are 0.3⊖0.45％. High Ro(1.5⊖1.8％)values of coal fragments are obtained in core samples at a depth of 4000 m in the Gimyo SK-1 oil well, which was excavated 2 km NW from the mud volcano. As a result of an investigation of erupted materials at the mud volcano, they were found to have originated at depths of from 3400 m to 4000 m in the studied area. Geothermal temperature of underground at depth of 3400 m to 4000 m in the in the studied area is estimated to be about 120℃ to 150℃. Estimated temperature is high enough to cause diagenetic transition from smectite to illite. Transition from smectite to illite results in the release of a large volume of pore water into the sediment. It is concluded that dehydration due to mineral transition might be the major reason for abnormal pore water pressure formation at depths of 3500 m to 4000 m in the study area.

Seismic and inter-seismic ground surface deformations of the Murono mud volcano (central Japan): a laser scanning approach

“…The activity of the Murono mud volcano can be a key to unraveling the subsurface structure and mud flow dynamics in the area. As a result, various studies have been carried out involving this mud volcano using geodetic, geophysical, and geochemical approaches (e.g., Onishi et al 2009;Shinya and Tanaka 2009;Suzuki et al 2009;Etiope et al 2011). While convex-up relief is commonly observed in large mud volcanoes that are hundreds of meters in length and tens of meters in height (Higgins and Saunders 1974;Chigira and Tanaka 1997), the small Murono mud volcano has a relatively flat surface, with a very small mound having a height of only decimeters.…”

“…A large-scale change in the center of the activity of a mud volcano may be related to the dynamics constrained by the lithological and tectonic structures that exist at depths of hundreds of meters to kilometers (e.g., Kopf 2002;Planke et al 2003;Istadi et al 2009;Shinya and Tanaka 2009). Using the controlled source audiofrequency magneto-telluric (CSAMT) method, low resistivity areas indicating mud chambers, located several hundred meters to kilometers from the surface, have been found around the Murono mud volcano (Suzuki et al 2009).…”

Application of terrestrial laser scanning for detection of ground surface deformation in small mud volcano (Murono, Japan)

“…near an anticline limb of the Naradate syncline (e.g., Noda 1962), with a small coverage area of approximately 130 m × 180 m. The surrounding area is characterized by many fold structures in the NE-SW direction and is known as one of the most important petroleum-producing areas in Japan. The mud volcano has therefore been attracted many interests for geophysical and geochemical researches (e.g., Onishi et al 2009;Shinya and Tanaka 2009;Suzuki et al 2009;Etiope et al 2011). The domain of the mud volcano is used as a practice course for automobile driving, and many areas are paved but others are covered with vegetation including grass and trees ( Fig.…”

The origin of muddy sand sediments associated with mud volcanism in the Horonobe area of northern Hokkaido, Japan

“…Two other onshore MVs are known from Japan: the Niikappu MV in Hokkaido [ Chigira and Tanaka , ] and the Matsudai MV in Niigata which includes the Murono and Kamou MVs [ Shinya and Tanaka , ]. These studies are a source of information on the characteristics of onshore MVs and processes of mud volcanism, thus contributing to an understanding of subsurface flow pathways and transport mechanisms of fluids and sediments.…”