TY - JOUR
T1 - Titanium behavior in quartz during retrograde hydration
T2 - Occurrence of rutile exsolution and implications for metamorphic processes in the Sør Rondane Mountains, East Antarctica
AU - Adachi, Tatsuro
AU - Hokada, Tomokazu
AU - Osanai, Yasuhito
AU - Toyoshima, Tsuyoshi
AU - Baba, Sotaro
AU - Nakano, Nobuhiko
N1 - Funding Information:
We would like to express our sincere thanks to the members of the 48 th and 49 th Japan Antarctic Research Expeditions (JARE), and the crew of the icebreaker Shirase . T.A. acknowledges Profs. Y. Motoyoshi and K. Shiraishi for enabling him to participate in JARE. We greatly appreciate the constructive reviews and suggestions of two anonymous reviewers. The cost to T.A. of conducting field work in Antarctica was offset in part by grants-in-aid from the Graduate University for Advanced Studies and the Japan Polar Research Association.
PY - 2010/1
Y1 - 2010/1
N2 - In the central Sør Rondane Mountains, East Antarctica, orthopyroxene felsic gneiss (OPG) was converted to hornblende-biotite felsic gneiss (HBG) by hydration that accompanied the intrusion of pegmatite. The retrograde HBG contains exsolved rutile in quartz. The composition of orthopyroxene and clinopyroxene in OPG suggests a temperature of 840 °C (interpreted as the near-peak temperature), and the composition of hornblende and plagioclase in HBG suggests a temperature of 670-700 °C (interpreted as the temperature during hydration). Ti concentrations in quartz were measured using an electron probe micro-analyzer, and Ti-in-quartz thermometers were applied. Measured Ti concentrations were 110 ppm (equivalent to 760-820 °C) for homogeneous quartz from OPG and 35 ppm (650-700 °C) for an exsolution-free area of a quartz grain from HBG. The pre-exsolution Ti concentration in quartz from HBG was reconstructed with 100 μm beam diameter and 25 kV of accelerating voltage, giving 103 ppm, similar to the value obtained for homogeneous quartz in OPG. The temperatures obtained using a Ti-in-quartz thermometer are consistent with those estimated using other thermometers. Although analysis of the main constitute minerals in HBG yields the conditions of hydration, the reconstructed pre-exsolution Ti content in quartz within HBG yields the pre-hydration conditions. Thus, the Ti-in-quartz thermometer is a potentially powerful tool with which to identify the peak or near-peak temperature conditions, even for retrogressed metamorphic rocks.
AB - In the central Sør Rondane Mountains, East Antarctica, orthopyroxene felsic gneiss (OPG) was converted to hornblende-biotite felsic gneiss (HBG) by hydration that accompanied the intrusion of pegmatite. The retrograde HBG contains exsolved rutile in quartz. The composition of orthopyroxene and clinopyroxene in OPG suggests a temperature of 840 °C (interpreted as the near-peak temperature), and the composition of hornblende and plagioclase in HBG suggests a temperature of 670-700 °C (interpreted as the temperature during hydration). Ti concentrations in quartz were measured using an electron probe micro-analyzer, and Ti-in-quartz thermometers were applied. Measured Ti concentrations were 110 ppm (equivalent to 760-820 °C) for homogeneous quartz from OPG and 35 ppm (650-700 °C) for an exsolution-free area of a quartz grain from HBG. The pre-exsolution Ti concentration in quartz from HBG was reconstructed with 100 μm beam diameter and 25 kV of accelerating voltage, giving 103 ppm, similar to the value obtained for homogeneous quartz in OPG. The temperatures obtained using a Ti-in-quartz thermometer are consistent with those estimated using other thermometers. Although analysis of the main constitute minerals in HBG yields the conditions of hydration, the reconstructed pre-exsolution Ti content in quartz within HBG yields the pre-hydration conditions. Thus, the Ti-in-quartz thermometer is a potentially powerful tool with which to identify the peak or near-peak temperature conditions, even for retrogressed metamorphic rocks.
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U2 - 10.1016/j.polar.2009.08.005
DO - 10.1016/j.polar.2009.08.005
M3 - Article
AN - SCOPUS:74449086915
VL - 3
SP - 222
EP - 234
JO - Polar Science
JF - Polar Science
SN - 1873-9652
IS - 4
ER -