Hydrothermal chloritization processes from biotite in the Toki granite, Central Japan: Temporal variations of of the compositions of hydrothermal fluids associated with chloritization

Abstract

This paper describes the biotite chloritization process with a focus on mass transfer in the Toki granitic pluton, Central Japan, and also depicts the temporal variations in chemical characteristics of hydrothermal fluid associated with chloritization during the sub-solidus cooling of the pluton. Singular value decomposition (SVD) analysis results in chloritization reaction equations for eight mineral assemblages, leading to the quantitative assessment of mass transfer between the reactant and product minerals, and inflow and outflow of components through the hydrothermal fluid. The matrices for SVD analysis consist of arbitrary combinations of molar volume and closure component in the reactant and product minerals. The eight reactions represent the temporal variations of chemical characteristics of the hydrothermal fluid associated with chloritization: the progress of chloritization results in gradual increase of silicon, potassium, and chlorine and gradual decrease of calcium and sodium in the hydrothermal fluid with temperature decrease. The biotite chloritization involves two essential formation mechanisms: chlorite formation (CF) mechanism 1, small volume decrease from biotite to chlorite and large inflow of metallic ions such as Al 3+ , Fe 2+ , Mn 2+ , and Mg 2+ from the hydrothermal fluid, and CF mechanism 2, large volume decrease and large outflow of the metallic ions into hydrothermal fluid. Chlorite produced with CF mechanism 1 dominates over that of CF mechanism 2, resulting in the gradual decrease of the metallic components in the hydrothermal fluid with chloritization progress. The chloritization reactions also give the temporal variations in physicochemical parameter of the hydrothermal fluid: a gradual decrease of pH and a gradual increase of redox potential in the hydrothermal fluid as chloritization proceeds. The combination of continuous reactions based on compositional variations in chlorite together with corresponding continuous Al IV variations gives an indication of the temporal variations in rates of decreasing and increasing concentration of chemical components in the hydrothermal fluid associated with chloritization. The biotite chloritization and resultant temporal variations of chemical and physicochemical characteristics in hydrothermal fluid act as a trigger for the successive dissolution-precipitation process of a granitic rock.

Pre‐orogenic upper crustal softening by lower greenschist facies metamorphic reactions in granites of the central Pyrenees

“…The calculated range of temperatures (200–350°C) is also consistent with hydrothermal conditions typically associated with the appearance of prehnite and titanite in the cleavages of biotite (e.g. Eggleton & Banfield, ; Morad, Sirat, El‐Ghali, & Mansurbeg, ; Yuguchi et al, ) and with temperatures calculated for the overlying sediments, suggesting that fluids were freely circulating between the basement and the overlying sediments. In detail, thermometric results indicate that the pre‐kinematic greenschist facies metamorphism occurred at a higher temperature (270–350°C) than later syn‐kinematic fluid–rock interaction (200–280°C, Figure b), with spatial variations (east and west of Lake Urdiceto, Figure a) due to local variations in fluid composition.…”

“…Static or quasi‐static hydrothermal alteration is also observed in granites and has been widely documented, especially in large igneous provinces (e.g. Cathelineau, ; Parneix, Beaufort, Dudoignon, & Meunier, ; Yuguchi, Sasao, Ishibashi, & Nishiyama, ). However, static alteration is rarely characterized, and hardly ever dated and placed in a regional orogenic context.…”

Interplay of irreversible reactions and deformation: a case of hydrofracturing in the rodingite–serpentinite system

“…Table 6 shows the results for the SiO 2 -AF-FM system. It should be noted that a row consisting of molar volumes of corresponding minerals was added to the composition matrix for SVD analysis to ensure the constant solid volume condition, as per the method in Yuguchi et al (2015). The molar volume data were taken from Helgeson et al (1978), considering the chlorite as clinochlore and the garnet as grossular.…”

“…Because the isocon is occasionally difficult to define in the isocon plot, this method is not universally applicable. The analysis of reaction relations among minerals by the singular value decomposition (SVD) method is an alternative way by means of determining the mass transfer due to metasomatism (Fisher 1989;Lang et al 2004;Shigeno et al 2012;Yuguchi et al 2015). The SVD method is a type of least square method that systematically surveys reaction relations among minerals.…”

Enhancement of Permeability Activated by Supercritical Fluid Flow through Granite

“…Fluids responsible for the quartz dissolution are little known. Hydrothermal chloritization of biotite during the subsolidus cooling of the Toki granitic pluton has been reported [34]. Mineralogical effects of hydrothermal alteration, such as partial dissolution of plagioclase, biotite dissolution, and illite precipitation, were also investigated.…”