**3. Occurrence of tectonic mélange and Cataclasites with pseudotachylyte**

The occurrence of tectonic melanges and cataclasites with pseudotachylyte in outcrop scale is represented in Fig. 3.

Fig. 3. Occurrences of tectonic melanges (host rocks) and cataclasites with pseudotachylyte in outcrop scale. A) A photo of tectonic melanges. Color bar indicates 1 m length. B) A closeup photo of tectonic melanges. White interval represents 10 cm. C) A photo of cataclasites showing quartz grains surrounded by black matrices. D) A photo of cataclasite. Very thin faults are developed within the cataclasites.

The melanges show blocks in matrix textures, as commonly reported from other tectonic melange zones. The blocks are asymmetrically shaped, indicating that the shear deformation is strongly related to the texture formation (Figs. 3A and B). The melange blocks of sandstone range from a few cm to about 2–3 m in diameter in outcrop scale (Figs. 3A and B). Foliations are well developed in the shale matrices, representing composite planar fabrics, with the interval between foliations on the scale of mm. Micro-faults, with a thickness of less than 1 cm and a displacement of less than 1 m, can also be observed cutting into the melange fabrics in outcrop scale (Figs. 3A and B). Most of the micro-faults are accompanied by quartz and calcite veins. Some mineral veins in the study area are ankerite (Fe–Mg carbonate). The relationship between the micro-faults and cataclasites containing pseudotachylyte is unknown.

The cataclasites with pseudotachylyte are composed of relatively small grains (less than a few cm diameter) of quartz and calcite surrounded by black material (Figs. 3C and D). These blocks also have an asymmetric shape, and the long axis of the blocks is aligned in the same direction as the melange fabrics (Figs. 3C and D). In some parts, very thin (less than 1 mm), continuous faults are observed within the cataclasites, although these thin faults are obscure (Fig. 3D).

Fig. 4. Micro-textures of tectonic melanges. A) Black seams (Pressure solution cleavages) are well developed in shale matrices. B) A photo of Fig. 4A under cross poralized light. C) Very weak anastomosed pressure solution cleavage in sandy shale matrices. D) A photo of Fig. 4C under cross polarized light.

At the microscopic scale, the occurrence of tectonic melanges and cataclasites with pseudotachylyte is also distinctive.

Foliations are well developed in the shale matrices, representing composite planar fabrics, with the interval between foliations on the scale of mm. Micro-faults, with a thickness of less than 1 cm and a displacement of less than 1 m, can also be observed cutting into the melange fabrics in outcrop scale (Figs. 3A and B). Most of the micro-faults are accompanied by quartz and calcite veins. Some mineral veins in the study area are ankerite (Fe–Mg carbonate). The relationship between the micro-faults and cataclasites containing pseudotachylyte is

The cataclasites with pseudotachylyte are composed of relatively small grains (less than a few cm diameter) of quartz and calcite surrounded by black material (Figs. 3C and D). These blocks also have an asymmetric shape, and the long axis of the blocks is aligned in the same direction as the melange fabrics (Figs. 3C and D). In some parts, very thin (less than 1 mm), continuous faults are observed within the cataclasites, although these thin faults are obscure

Fig. 4. Micro-textures of tectonic melanges. A) Black seams (Pressure solution cleavages) are well developed in shale matrices. B) A photo of Fig. 4A under cross poralized light. C) Very weak anastomosed pressure solution cleavage in sandy shale matrices. D) A photo of Fig.

At the microscopic scale, the occurrence of tectonic melanges and cataclasites with

unknown.

(Fig. 3D).

4C under cross polarized light.

pseudotachylyte is also distinctive.

Microscopic occurrence of tectonic melanges is characterized by a weak pressure solution cleavage within shale matrices (Fig. 4). The pressure solution cleavages develop along melange foliations, also representing composite planar fabrics. In coarser grained areas, pressure solution cleavages are weakly observed, showing anastomosed networks of pressure solution cleavages (Figs. 4C and D).

Fig. 5. Micro-texture of cataclasites with pseudotachylyte. A) Quartz grains are surrounded by shale matrices. Thin faults and micro-folding are identified within the shale matrices. B) Embayed grains surrounded by shale matrices. C) Injection vein from main fault surface (Horizontal). The boundary with host rocks is embayed. D) A photo of Fig. 5C under crosspolarized light.

In cataclasites with pseudotachylyte, highly fractured grains surrounded by shale matrices are observed (Figs. 5A and B). The grains are composed mainly of quartz aggregates, with grain size ranging from tens of µm to a few mm. The shale matrices represent highly deformed fabrics with lighter and darker brownish materials (Figs. 5A and B). Very thin and sharp faults are recognized within the shale matrices of the cataclasites (Fig. 5A and B). The shape of grains is embayed (Fig. 5B), and injection veins from the main shear surface can also be seen (Figs. 5C and D). Along the main shear surface, highly fractured cataclasites are observed. The boundary between host rocks and cataclasites shows embayed texture. Injection veins from the main shear surface also have an embayed boundary with the host rocks (Figs. 5C and D).

#### **4. Method**

We analyzed the clay and other minerals using an X-ray diffractometer (MultiFlex, RIGAKU) for randomly oriented and oriented samples. Randomly oriented samples were analyzed for bulk rock samples. The oriented samples were prepared using <1.4 µm grains as clay size fraction. Oriented samples were further analyzed using an ethylenglicoled treatment. The XRD analysis was conducted under the following conditions: 45 kV, 40 mA of Cu kα radiation, step size of 0.01°, and a 2θ range of 2-35°.

From the XRD charts obtained, we examined bulk and clay mineralogy, iron and magnesium substitution in chlorite, and illite crystallinity, and performed a semiquantification of illite and chlorite in the samples. The peak intensities were obtained using MacDiff 4.2.5. Twenty samples each of tectonic melanges and cataclasites were analyzed.

Illite crystallinity is expressed by a width of the illite 001 peak at half of the peak height above the background for an oriented, < 2 µm fraction of sample (Kubler, 1969). The width is controlled by X-ray-scattering-domain size and percentage of expandable layers (Srodon and Eberl, 1984; Eberl and Velde, 1989). A smaller scattering domain and/or more expandable layers would lead to a wider peak.

The chlorite in the study is Fe–Mg chlorite from both the host melanges and cataclasites with pseudotachylyte, based on the bulk rock analysis. Chlorite is composed of silicate and hydroxide layers, both layers having three sites for positive ions. The substitution of iron and magnesium in the chlorite layers was estimated from the XRD charts, following the method of Moore and Reynolds (1989). I(003)/I(005) gives the symmetry of the Fe distribution (the D value in Moore and Reynolds (1989)) and [I(002) + I(004)]/I(003)′ gives the total number of Fe atoms in six octahedral sites (the Y value in Moore and Reynolds (1989)). I(003)′ is calculated from the following equation (Brown and Brindley, 1980):

$$I(003)' = \frac{I(003)(114)^2}{\left(114 - 12.1D\right)^2} \tag{1}$$

Reference frame in the configuration described above for the number of iron and magnesium from 0 to 3 at intervals of 0.5 in the silicate and hydroxide layers (the total number of patterns is 49), respectively, were calculated by NEWMOD (Reynolds Jr, 1985). The results of the NEWMOD calculations in the I(003)/I(005) vs. [I(002) + I(004)]/I(003)′ space are shown in Fig. 7 as dotted lines.

For the semi-quantitative analysis of illite and chlorite, we used the Mineral Intensity Factor (MIF) method (Moore and Reynolds, 1989). To obtain the MIF value, we computed the mineral reference intensities for illite and chlorite also using the NEWMOD (Moore and Reynolds, 1989). As the MIF value for chlorite depends on its composition, we used the result from the examination of iron-magnesium substitution in chlorite described above. We used an illite composition of 0.1 Fe and 0.75 K as a reference mineral. Values of µ\* = 14 and sigma\* = 25 were used in the NEWMOD calculations, as suggested by Moore and Reynolds (1989).

Injection veins from the main shear surface also have an embayed boundary with the host

We analyzed the clay and other minerals using an X-ray diffractometer (MultiFlex, RIGAKU) for randomly oriented and oriented samples. Randomly oriented samples were analyzed for bulk rock samples. The oriented samples were prepared using <1.4 µm grains as clay size fraction. Oriented samples were further analyzed using an ethylenglicoled treatment. The XRD analysis was conducted under the following conditions: 45 kV, 40 mA

From the XRD charts obtained, we examined bulk and clay mineralogy, iron and magnesium substitution in chlorite, and illite crystallinity, and performed a semiquantification of illite and chlorite in the samples. The peak intensities were obtained using MacDiff 4.2.5. Twenty samples each of tectonic melanges and cataclasites were

Illite crystallinity is expressed by a width of the illite 001 peak at half of the peak height above the background for an oriented, < 2 µm fraction of sample (Kubler, 1969). The width is controlled by X-ray-scattering-domain size and percentage of expandable layers (Srodon and Eberl, 1984; Eberl and Velde, 1989). A smaller scattering domain and/or more

The chlorite in the study is Fe–Mg chlorite from both the host melanges and cataclasites with pseudotachylyte, based on the bulk rock analysis. Chlorite is composed of silicate and hydroxide layers, both layers having three sites for positive ions. The substitution of iron and magnesium in the chlorite layers was estimated from the XRD charts, following the method of Moore and Reynolds (1989). I(003)/I(005) gives the symmetry of the Fe distribution (the D value in Moore and Reynolds (1989)) and [I(002) + I(004)]/I(003)′ gives the total number of Fe atoms in six octahedral sites (the Y value in Moore and Reynolds

(1989)). I(003)′ is calculated from the following equation (Brown and Brindley, 1980):

*I*

(003)(114) (003)' (114 12.1 ) *I*

Reference frame in the configuration described above for the number of iron and magnesium from 0 to 3 at intervals of 0.5 in the silicate and hydroxide layers (the total number of patterns is 49), respectively, were calculated by NEWMOD (Reynolds Jr, 1985). The results of the NEWMOD calculations in the I(003)/I(005) vs. [I(002) + I(004)]/I(003)′

For the semi-quantitative analysis of illite and chlorite, we used the Mineral Intensity Factor (MIF) method (Moore and Reynolds, 1989). To obtain the MIF value, we computed the mineral reference intensities for illite and chlorite also using the NEWMOD (Moore and Reynolds, 1989). As the MIF value for chlorite depends on its composition, we used the result from the examination of iron-magnesium substitution in chlorite described above. We used an illite composition of 0.1 Fe and 0.75 K as a reference mineral. Values of µ\* = 14 and sigma\* = 25 were used in the NEWMOD calculations, as suggested by Moore

2 2

*<sup>D</sup>* (1)

of Cu kα radiation, step size of 0.01°, and a 2θ range of 2-35°.

expandable layers would lead to a wider peak.

space are shown in Fig. 7 as dotted lines.

and Reynolds (1989).

rocks (Figs. 5C and D).

**4. Method** 

analyzed.


Table 1. Minerals in host melanges


Table 2. Minerals in cataclasites with pseudotachylyte

#### **5. Results**

In this section, we describe the results of our analysis for clay and other mineralogy, iron and magnesium substitution in chlorite, illite crystallinity, and the semi-quantification of illite and chlorite.

### **5.1 Clay and other mineralogy**

262 Earthquake Research and Analysis – Seismology, Seismotectonic and Earthquake Geology

sample Chlorite illite quartz calcite anorthite ankerite

ok060428-2 X X X X

ok060620-4 X X X X

ok060620-13 X X X X

ok060902-13 X X X X

ok061015-7 X X X X

ok061015-8 X X X X

ok061015-9 X X X X

ok061015-10 X X X X X

ok061015-11 X X X X X

ok061015-12 X X X X X

ok060501-8 X X X X X

ok060616-4 X X X X X

ok060902-9 X X X X X

ok060902-12 X X X X X

ok060919-12 X X X X X

ok061004-23 X X X X X

ok061004-24 X X X X X

ok061004-26 X X X X

Table 2. Minerals in cataclasites with pseudotachylyte

**5. Results** 

illite and chlorite.

ok061004-25 X X X X X X

ok061004-27 X X X X X X

In this section, we describe the results of our analysis for clay and other mineralogy, iron and magnesium substitution in chlorite, illite crystallinity, and the semi-quantification of All samples, from both the host melanges and the cataclasites, included quartz, anorthite, illite, and chlorite (Tables 1 and 2), and some of the samples also contained calcite. Ankerite (Fe–Mg carbonates) were found in a number of samples from cataclasites with pseudotachylyte (Tables 1 and 2). On the basis of the bulk powder analysis for XRD, the chlorite are Fe–Mg chlorite. The results from samples analyzed by ethylenglicoled treatment suggest that smectite is not present in any sample (Fig. 6).

Fig. 6. Examples of XRD charts for oriented samples of cataclasites with pseudotachylyte.
