Episodes 2022; 45(2): 147-159
Published online June 1, 2022
Copyright © International Union of Geological Sciences.
Hafiz Ur Rehman1*, Hiroshi Yamamoto1, Tayyaba Mateen1, Kazuaki Okamoto2, Tzen-Fu Yui3, Masaru Terabayashi4, Kazuaki Nanamura5
1 Graduate School of Science and Engineering, Kagoshima University, Kagoshima, Japan
2 Department of Earth Sciences, Faculty of Education, Saitama University, Saitama, Japan
3 Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan
4 Faculty of Engineering and Design, Kagawa University, Takamatsu, Japan
5 Division of Instrumental Analysis Research Support Center, Kagoshima University, Japan
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Oxygen isotope data (δ18O) of quartz are reported for the San-yo and Ryoke belt granites, metamorphic rocks, and late-stage siliceous veins. The analyzed quartz showed δ18O values of 9.7-12.9‰ (relative to VSMOW) in granites, 15.1-17.3‰ in biotite schist, 16.4-17.8‰ in siliceous schist. The δ18O values of quartz in foliation-parallel and -normal veins are 16.6‰ and 17.3‰, respectively. The δ18O values of quartz in the granite samples are relatively higher than those crystallized from I-type granite magma (ca. 5–8‰) and similar with values of S-type granite magma (ca. 9–12‰). These features suggest partial melting of the chemically modified crust with sedimentary precursors to form the parental magma of granites. Hafnium isotope data of zircons from those granites, reported in an earlier publication, exhibited by εHf (t) values between +1.1 and -4.8, provide additional evidence for the formation of the granites from a continental crust with some incorporation of hydrothermally altered reworked crust before partial melting. The relatively higher δ18O values (> 15‰) of quartz in siliceous veins indicate their precipitation from silica- and 18O-rich fluids that were extracted from the slab-dehydration process during late-stages of their evolution.