Electrical impedance measurement of hydrous microcrystalline quartz

Fukuda, Jun; Peach, C. J.; Spiers, Christopher J.; Nakashima, Satoru

doi:10.2465/jmps.081022f

Cited by 8 publications

(5 citation statements)

References 15 publications

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“…These values were estimated from the clear stretching and bending combination bands around 5200 and 4500 cm −1 in their IR spectra. The H 2 O and Si-OH contents of our chalcedony were estimated to be ~ 0.3 wt% each (Fukuda et al 2009a). In addition to the dislocation Si-OH in chalcedony, Si-OH can also be associated with surface Si-OH at grain boundaries because of the fine grain size (e.g., a few hundred nanometers).…”

Section: Discussionmentioning

confidence: 91%

Water distribution in quartz schists of the Sanbagawa Metamorphic Belt, Japan: infrared spectroscopic mapping and comparison of the calibrations proposed for determining water contents

Fukuda

Shimizu

2019

Earth Planets Space

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We evaluated water distributions in deformed quartz in schists along the Asemi River, Central Shikoku, in the Sanbagawa Metamorphic Belt, Japan, using infrared spectroscopic (IR) mapping. The water trapped in quartz as molecular H 2 O showed a broad IR absorption band at 2800-3750 cm −1. A necessary step before assessing the quartz water content was to evaluate and compare six previously proposed IR calibrations in terms of the molar absorption coefficients of H 2 O (L/mol H 2 O cm 2). The coefficients vary from 24,100 to 89,000 L/mol H 2 O cm 2 , and the values of the coefficients show a rough increase with increasing component of structural-OH in the IR spectra. We used Paterson's calibration, which does not require input regarding the mineral species, but which was modified in his paper for measurements of molecular H 2 O in quartz. The absorption coefficient is 38,000 L/mol H 2 O cm 2. IR mapping was performed on Sanbagawa metamorphic rocks with increasing grades of metamorphism, where the mean grain size of quartz increases from ~ 40 to ~ 120 µm. The absorption bands that are only from the quartz can be distinguished on the basis of microstructural observations and the corresponding mapping results. The IR spectra of quartz commonly show dominant molecular H 2 O bands at 2800-3750 cm −1 with no additional bands associated with crystalline-OH when only quartz is measured. The water contents of quartz in all our samples were 40-310 ppm, and these values are about one-third of previously reported values measured using point analyses with the unified Paterson's calibration. This difference seems to reflect the incorporation of phyllosilicates in previous measurements that showed a broad band around 3600 cm −1. The lowest and highest water contents in our quartz samples are associated with intragranular water and grain boundary water, respectively. We estimated the grain boundary widths to be at most ~ 10 nm on the basis of the water contents at grain boundaries.

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Section: Discussionmentioning

confidence: 91%

Water distribution in quartz schists of the Sanbagawa Metamorphic Belt, Japan: infrared spectroscopic mapping and comparison of the calibrations proposed for determining water contents

Fukuda

Shimizu

2019

Earth Planets Space

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“…Another point to consider is the connectivity of molecular H2O at intergranular regions. In our previous study, electrical conductivities at high T were measured for the same sample as the present study to evaluate the connectivity of molecular H2O (Fukuda et al, 2009a). The electrical conductivity obtained at 450°C was lower than the value expected when molecular H2O is completely connected.…”

Section: Measurement O F Dehydration Ratementioning

confidence: 66%

“…This value is thought to be typical for incompletelyconnected grain-boundary diffusion (Farver and Yund, 1992). We have measured the electrical conductivity of the chalcedony and found that intergranular regions in the chalcedony are not completely filled with molecular H2O (Fukuda et al, 2009a). More specifically, a cluster of H2O molecules may dominate a given volume of intergranular regions but not necessarily connect the whole intergranular regions, resulting in patchy distribution of clusters in the chalcedony.…”

Section: Comparison With Previous Studiesmentioning

confidence: 94%

Characterization of the states and diffusivity of intergranular water in a chalcedonic quartz by high-temperature in situ infrared spectroscopy

Fukuda¹,

Yokoyama²,

Kirino³

2009

Mineral. mag.

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Infrared spectroscopy was performed on a thin section of a chalcedonic quartz at high temperature in order to investigate the states and diffusivity of intergranular water. The sample contained 0.3 wt.% of silanol (Si—OH) and 0.3 wt.% of molecular H2O, located mainly at intergranular regions but also as fluid inclusions. We monitored the diffusion of molecular H2O associated with dehydration by in situ analyses at 350—500°C and determined the bulk-diffusion coefficients as expressed by an Arrhenius relationship: Dbulk (m2 sec—1) = 10—4.5 exp(—107±17/RT), where R is the gas coefficient and T the temperature. The activation energy for our sample is similar to those previously reported for diffusion in quartz aggregates with incompletely-connected grain boundaries. This result and our previous measurements of electrical conductivity imply that diffusion of molecular H2O at incompletely- connected intergranular regions is the main mechanism for the dehydration. The diffusion coefficients in chalcedony are larger than those previously reported for rhyolitic glass and other granular aggregates. Intergranular regions, inherent larger pores and cracks created during heating can act as efficient diffusion paths within the chalcedony.

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“…Only silica rocks, like flint, chert and silcrete, benefit from heat-treatment to improve their knapping quality because the thermal transformations in such rocks rely on two characteristics: They contain up to 1 wt% of chemically bound water in the form of silanol (SiOH) (Flörke et al 1982;Graetsch et al 1985;Schmidt et al 2011), and they contain a network of open pores (Micheelsen 1966;Roqué-Rosell et al 2010), most probably intergranular pores (Fukuda et al 2009), that can adsorb fluid water accounting for up to 1 wt% of the total mass of the rock (Schmidt et al 2011(Schmidt et al , 2013b) (i.e. accounting for up to 2.7 vol% of the rock).…”

Section: Introductionmentioning

confidence: 99%

The investment in time needed for heat treatment of flint and chert

Schmidt

Paris

Bellot‐Gurlet

2015

Archaeol Anthropol Sci

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In archaeology, heat treatment is the process of intentionally modifying lithic raw materials to improve their knapping quality. Even though the nature and parameters of the thermal transformations in rocks like flint and chert have been the object of several recent studies, the investment in time needed for heat treatment remains poorly investigated. In our study using time-resolved in situ Raman spectroscopy, we investigate the progression of the reaction that drives the thermal transformations of flint and chert. We found that, although parameters like maximum temperature and heating rate are functions of the content of chemically bound water and pore space in the samples, the duration these samples must be held at maximum temperature is shorter than 1 h, regardless of the maximum heating temperature or the mineralogy of the sample. Combining our results with previously published data on other parameters needed for lithic heat treatment, we propose lower and upper limits of the investment in time required for different heating procedures and discuss their relation to the structure and volume of the heated rocks. The actual duration of heat treatment of flint and chert, as it was practised in different chrono-cultural periods, lies somewhere between 7 h and 2-3 days depending on the type of flint or chert and the heating environment used.

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Electrical impedance measurement of hydrous microcrystalline quartz

Cited by 8 publications

References 15 publications

Water distribution in quartz schists of the Sanbagawa Metamorphic Belt, Japan: infrared spectroscopic mapping and comparison of the calibrations proposed for determining water contents

Water distribution in quartz schists of the Sanbagawa Metamorphic Belt, Japan: infrared spectroscopic mapping and comparison of the calibrations proposed for determining water contents

Characterization of the states and diffusivity of intergranular water in a chalcedonic quartz by high-temperature in situ infrared spectroscopy

The investment in time needed for heat treatment of flint and chert

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