GeoScienceWorld Lithosphere Volume 2020, Article ID 8854615, 26 pages https://doi.org/10.2113/2020/8854615 Research Article Fluid-Present Partial Melting of Paleoproterozoic Okbang Amphibolite in the Yeongnam Massif, Korea Yuyoung Lee 1,2 and Moonsup Cho3 1Research Center for Geochronology and Isotope Analysis, Korea Basic Science Institute, Cheongju 28119, Republic of Korea 2Geology Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Republic of Korea 3Department of Earth and Environmental Sciences, Chungbuk National University, Cheongju 28644, Republic of Korea Correspondence should be addressed to Yuyoung Lee;
[email protected] Received 24 April 2019; Revised 11 December 2019; Accepted 18 May 2020; Published 1 September 2020 Academic Editor: Sarah M. Roeske Copyright © 2020 Yuyoung Lee and Moonsup Cho. Exclusive Licensee GeoScienceWorld. Distributed under a Creative Commons Attribution License (CC BY 4.0). The waning stage of a long-lived collisional orogeny is commonly governed by an extensional regime in association with high-temperature metamorphism, anatexis, and magmatism. Such a late-orogenic process is well-recorded in the Okbang amphibolite, Yeongnam Massif, Korea, where thin layers or irregular patches of tonalitic leucosomes are widespread particularly in association with ductile shear zones. Various microstructures including interstitial felsic phases and former melt patches indicate that leucosomes are the product of partial melting. These leucosomes are aligned en echelon and contain large (up to ~2 cm) grains fl of peritectic hornblende, suggesting synkinematic uid-present anatexis. The leucosomes are enriched in Na2O and Sr contents compared to the amphibolite but depleted in rare earth and high field-strength elements. P - T conditions of the anatexis were estimated at 4.6–5.2 kbar and 650–730°C, respectively, based on hornblende-plagioclase geothermobarometry.