# Experimental grain growth of quartz aggregates under wet conditions and its application to deformation in nature

Grain growth of quartz was investigated using two quartz samples (powder and novaculite) with water under pressure and temperature conditions of 1.0–2.5 GPa and 800–1100 inline-formulaC. The compacted powder preserved a substantial porosity, which caused a slower grain growth than in the novaculite. We assumed a grain growth law of inline-formula $M2inlinescrollmathml{d}^{n}-{d}_{normal 0}^{n}={k}_{normal 0}{f}_{chem{\mathrm{normal H}}_{normal 2}\mathrm{normal O}}^{r}\mathrm{exp}\left(-Q/RT\right)t$ 150pt17ptsvg-formulamathimg360eb1f1682d0a89fc56b42c8640a0cd se-10-621-2019-ie00001.svg150pt17ptse-10-621-2019-ie00001.png with grain size inline-formulad (inline-formulaµm) at time inline-formulat (seconds), initial grain size inline-formulad0 (inline-formulaµm), growth exponent inline-formulan, a constant inline-formulak0 (inline-formulaµminline-formulan MPainline-formular sinline-formula−1), water fugacity inline-formula $M14inlinescrollmathml{f}_{chem{\mathrm{normal H}}_{normal 2}\mathrm{normal O}}$ 22pt14ptsvg-formulamathimg1277ca9ea912fe61f0760abc7ed45444 se-10-621-2019-ie00002.svg22pt14ptse-10-621-2019-ie00002.png (MPa) with the exponent inline-formular, activation energy inline-formulaQ (kJ molinline-formula−1), gas constant inline-formulaR, and temperature inline-formulaT in Kelvin. The parameters we obtained were inline-formula $M20inlinescrollmathmln=normal 2.5±normal 0.4$ 63pt10ptsvg-formulamathimg7455d8bed57ba49d310f3cfabc573513 se-10-621-2019-ie00003.svg63pt10ptse-10-621-2019-ie00003.png , inline-formula $M21inlinescrollmathml{k}_{normal 0}={normal 10}^{-normal 8.8±normal 1.4}$ 71pt16ptsvg-formulamathimg468620545483b5b878aa790e21f79007 se-10-621-2019-ie00004.svg71pt16ptse-10-621-2019-ie00004.png , inline-formula $M22inlinescrollmathmlr=normal 2.3±normal 0.3$ 62pt10ptsvg-formulamathimg6317045305de8e98b8397c3b72ea0395 se-10-621-2019-ie00005.svg62pt10ptse-10-621-2019-ie00005.png , and inline-formula $M23inlinescrollmathmlQ=normal 48±normal 34$ 59pt10ptsvg-formulamathimg5d8d8344c5e9c84959f665b2c7a9ca35 se-10-621-2019-ie00006.svg59pt10ptse-10-621-2019-ie00006.png for the powder and inline-formula $M24inlinescrollmathmln=normal 2.9±normal 0.4$ 63pt10ptsvg-formulamathimgf37bba991e9203756c8a6fa553c2f786 se-10-621-2019-ie00007.svg63pt10ptse-10-621-2019-ie00007.png , inline-formula $M25inlinescrollmathml{k}_{normal 0}={normal 10}^{-normal 5.8±normal 2.0}$ 71pt16ptsvg-formulamathimg84337cf266827e3077f5edd66d7012cc se-10-621-2019-ie00008.svg71pt16ptse-10-621-2019-ie00008.png , inline-formula $M26inlinescrollmathmlr=normal 1.9±normal 0.3$ 62pt10ptsvg-formulamathimg6417f5160417f42ea64c7a2be22618d5 se-10-621-2019-ie00009.svg62pt10ptse-10-621-2019-ie00009.png , and inline-formula $M27inlinescrollmathmlQ=normal 60±normal 49$ 59pt10ptsvg-formulamathimg2c9b29a1c4d49a23e5477ccfb185d677 se-10-621-2019-ie00010.svg59pt10ptse-10-621-2019-ie00010.png for the novaculite. The grain growth parameters obtained for the powder may be of limited use because of the high porosity of the powder with respect to crystalline rocks (novaculite), even if the differences between powder and novaculite vanish when grain sizes reach inline-formula∼70inline-formulaµm. Extrapolation of the grain growth laws to natural conditions indicates that the contribution of grain growth to plastic deformation in the middle crust may be small. However, grain growth might become important for deformation in the lower crust when the strain rate is < 10inline-formula−12 sinline-formula−1.

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Fukuda, Junichi / Raimbourg, Hugues / Shimizu, Ichiko / et al: Experimental grain growth of quartz aggregates under wet conditions and its application to deformation in nature. 2019. Copernicus Publications.

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