Alteration Reaction and Mass Transfer via Fluids with Progress of Fracturing along the Median Tectonic Line, Mie Prefecture, Southwest Japan

Abstract

We have analyzed mass transfer in the cataclasite samples collected from the Median Tectonic Line, southwest Japan, in which the degree of fracturing is well correlated with the bulk rock chemical compositions determined by the X-ray fluorescence (XRF) analysis. The results of "isocon" analysis indicate not only a large volume increase up to 110% but also the two-stage mass transfer during cataclasis. At the first stage from the very weakly to weakly fractured rocks, the weight percents of SiO 2 ,N a 2 O, and K 2 O increase, while those of TiO 2 , FeO, MnO, MgO, and CaO decrease. At the second stage from the weakly to moderately and strongly fractured rocks, the trend of mass transfer is reversed. The principal component analysis reveals that the variation of chemical compositions in the cataclasite samples can be mostly interpreted by the mass transfer via fluids and by the difference in chemical composition in the protolith rocks to lesser degree. Finally, the changes in the modal composition of minerals with increasing cataclasis analyzed by the X-ray diffraction (XRD) with the aid of "RockJock" software clearly elucidate that the mass transfer of chemical elements was caused by dissolution and precipitation of minerals via fluids in the cataclasite samples.

Kinematic Analyses and Radiometric Dating of the Large‐Scale Paleogene Two‐Phase Faulting Along the Median Tectonic Line, Southwest Japan

“…Although non-isochoric deformation could have occurred in the studied fault zones (cf. Kaneko et al, 2017), this aspect can be tested from the orientation of Riedel shears. These analyses are beyond the scope of this study.…”

The architecture of long-lived fault zones: insights from microstructure and quartz lattice-preferred orientations in mylonites of the Median Tectonic Line, SW Japan

“…In some samples (likely those with a more mafic bulk composition), former hornblende porphyroclasts have been replaced by coarse-grained dark blue chlorite (cf. Takagi 1985;Kaneko et al 2017). Mylonitic samples are typically overprinted by cataclasis and contain < 50% feldspar porphyroclasts.…”

“…5d; cf. Kaneko et al 2017). Cataclastic samples contain clasts of ultramylonite and show evidence for fracturing, granulation, clast rotation, and diffusive mass transfer.…”

Coseismic fluid–rock interactions in the Beichuan-Yingxiu surface rupture zone of the Mw 7.9 Wenchuan earthquake and its implication for the fault zone transformation

“…Thermal pressurization refers to the thermal pressurization effect of the fluid caused by rapid frictional heating, which substantially weakens the effective normal stress acting on the fault surface and the friction between two fault planes, which affects dynamic fault weakening and propagation of earthquake rupture (Sibson et al, 1973(Sibson et al, , 1990Andrews, 2002;Wibberley and Shimamoto, 2003;Rice, 2006;Hayman et al, 2006;Mishima, 2009;Moore et al, 2013). Fluid-rock interaction means that the coseismic frictional heating intensifies the process of the fluid-rock interaction, changes the mineral composition, which mainly includes the mineral alteration/decomposition and dehydration (deaeration) (Forster et al, 1991;Hickman et al, 1995;Chen et al, 2007;Kaneko et al, 2017), and generates a large amount of layered silicate minerals (such as clay) with relatively low friction coefficient (Wintsch et al, 1995;Vrolijk et al, 1999;Fu et al, 2008;Lockner et al,2011), which weakens the fault. The fluid action within the fault zone affects the earthquake nucleation, dynamic rupture propagation, and postseismic fault healing (Brace and Byerlee , 1966;Sibson, 1973;Beach, 1976;Bruhn et al, 1990;McCaig, 1988;Forster et al, 2007;Rice, 2006;Caine et al, 1996;Evens et al, 1995;Faulkner et al, 2003;Ishikawa et al, 2008;Hamada et al, 2009;Paola et al, 2011), the study of which has important significance.…”

“…CC BY 4.0 License. mainly use geochemical approaches to trace the sources of fluids and analyze the infiltration and fuildrock interaction processes of fluids (Anderson et al, 1983;Evans et al, 1995;Goddard and Evans, 1995;Roland et al, 1996;Chen et al, 2007;Pili et al, 2002Pili et al, , 2011Ishikawa et al, 2008;Chen et al, 2013b;Duan et al, 2016;Kaneko et al, 2017). The geochemical characteristics of fault zones cutting clastic sedimentary rocks differ from those cutting carbonate and magmatic rocks.…”