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Crystal size distribution of amphibole grown from hydrous basaltic melt at 0.6–2.6 GPa and 860–970 °C

Zhang, Bo and Hu, Xianxu and Asimow, Paul D. and Zhang, Xin and Xu, Jingui and Fan, Dawei and Zhou, Wenge (2019) Crystal size distribution of amphibole grown from hydrous basaltic melt at 0.6–2.6 GPa and 860–970 °C. American Mineralogist, 104 (4). pp. 525-535. ISSN 0003-004X. https://resolver.caltech.edu/CaltechAUTHORS:20190403-085027141

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Abstract

We carried out three series of amphibole crystallization experiments from hydrous basaltic melt to calibrate the dependence of crystal growth rate on temperature and pressure in amphibole-bearing igneous rocks. One series of 100 h duration multi-anvil experiments were carried out at a constant pressure of 0.6 GPa and variable temperatures from 860 to 970 °C. The second series was conducted at a constant temperature of 970 °C and variable pressures from 0.6 to 2.6 GPa. The third series examined the time dependence at 970 °C and 0.6 GPa, with durations from 1 to 100 h. A verification experiment showing both reproducibility and the ability of these three series to predict behavior at novel conditions was performed in a piston cylinder at 1.0 GPa and 900 °C for 63 h. All experiments yielded mostly amphibole in a quenched glass of granitic to granodioritic composition. We used the two-dimensional thin section method to measure the crystal size distribution (CSD) of amphibole in the experimental products. Concave-down CSD curves at small sizes indicate a textural coarsening process during the crystallization. The CSD data were inverted using canonical CSD theory for CSD growth rate; maximum and average growth rates of amphibole were also inferred directly from the maximum and average grain size and crystallization time. The maximum growth rate is, of course, always larger than the average growth rate, which is in turn slightly larger than the CSD growth rate, suggesting that CSD growth rate is an adequate measure of the average growth rate of a mineral in magmatic rocks. The CSD growth rate increases with increasing temperature in the isobaric series and with increasing pressure at constant temperature. However, the growth rate is negatively correlated with crystallization time at constant temperature and pressure. Based on the experimental results, a functional form for evaluating growth rate at known pressure and temperature from an observed amphibole CSD was developed and applied to a diorite collected from the eastern Tianshan Mountains, Xinjiang Uygur autonomous region, NW China. The estimated growth rate of amphibole is between 1.6 × 10^(–9) mm/s and 5.6 × 10^(–7) mm/s, and combined with petrological constraints on pressure and temperature, the corresponding crystallization time was between 0.1 and 4.3 yr in the natural diorite.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.2138/am-2019-6759DOIArticle
ORCID:
AuthorORCID
Zhang, Bo0000-0003-0212-8879
Asimow, Paul D.0000-0001-6025-8925
Additional Information:© 2019 Mineralogical Society of America. Funding: This work benefited from the financial support of the National Natural Science Foundation of China (Grant No. 41772043 and 41802043), the Joint Research Fund in Huge Scientific Equipment (U1632112) under cooperative agreement between NSFC and CAS, the Chinese Academy of Sciences “Light of West China” Program (Dawei Fan, 2017), Youth Innovation Promotion Association CAS (Dawei Fan, 2018434), the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (XDB 18010401), the CPSF-CAS Joint Foundation for Excellent Postdoctoral Fellows (Grant No. 2017LH014), and China Postdoctoral Science Foundation (Grant No. 2018M631104). Experiments in the Caltech lab and participation of PDA in this work were supported by the U.S. NSF through award EAR-1550934. The authors thank Michael Zieg and Michael Higgins for their very insightful and thorough reviews, and sincere thanks are extended to Associate Editor Erik Klemetti. We thank Hongfeng Tang for providing the important diorite sample, Neng Jiang for his assistance during EMP analyses. We warmly thank Yijin Yang and Wei Mao for their linguistic assistance during the preparation of this manuscript.
Funders:
Funding AgencyGrant Number
National Natural Science Foundation of China41772043
National Natural Science Foundation of China41802043
Joint Research Fund in Huge Scientific EquipmentU1632112
Youth Innovation Promotion Association CAS2018434
Chinese Academy of SciencesXDB 18010401
CPSF-CAS Joint Foundation for Excellent Postdoctoral Fellows2017LH014
China Postdoctoral Science Foundation2018M631104
NSFEAR-1550934
Subject Keywords:Amphibole, basalt, high temperature–high pressure, crystal-size distribution, growth rate, crystallization time
Issue or Number:4
Record Number:CaltechAUTHORS:20190403-085027141
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190403-085027141
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94393
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:03 Apr 2019 16:14
Last Modified:09 Mar 2020 13:19

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