U–Pb zircon geochronology of the Hida gneiss and granites in the Kamioka area, Hida Belt

Abstract

A new U–Pb dating and oxygen isotope analysis of zircons collected from a granitic mylonite and an undeformed granite in the Kamioka area, in the Hida Belt of southwest Japan, was conducted using a sensitive high‐resolution ion microprobe (SHRIMP) to restrict the timing of the mylonitization in the Funatsu Shear Zone, which is situated on the eastern and southeastern margins of the Hida Belt. Here, undeformed granite intrudes into the granitic mylonite deformed by mylonitization in the Funatsu Shear Zone. The granitic mylonite and the undeformed granite yielded U–Pb zircon ages of 242.6 ±1.9 Ma and 199.1 ±1.9 Ma, respectively. The granitic mylonite and the undeformed granite also yielded zircon oxygen isotope ratios (δ18OVSMOW) of 7.74 ±0.37 ‰ and 5.74 ±0.17 ‰, which suggests that these rocks are derived from different magmas. Therefore, the timing of the mylonitization in the Funatsu Shear Zone is constrained to be at least 242.6–199.1 Ma, which is consistent with other data from the Tateyama area. The U–Pb zircon ages of the banded gneiss in the Kamioka area also reveals that the protolith is a sedimentary rock deposited at approximately 256 Ma, and regional metamorphism occurred at 245.0 ±6.6 Ma, which indicates that the mylonitization in the Funatsu Shear Zone occurred after the metamorphism in the Hida Belt. These geochronological and geochemical data give new insight into the relationship between the Hida Belt and the eastern margin of the Asian continent: the geochronological and geochemical data in this study support the possibility that the Funatsu Shear Zone is comparable with the Cheongsan Shear Zone located at the center of the Ogcheon Belt on the Korean Peninsula.

Nature and timing of anatectic event of the Hida Belt (Japan): Constraints from titanite geochemistry and U-Pb age of clinopyroxene-bearing leucogranite

“…The Funatsu Shear Zone, which consists of mylonitic granite and augen gneiss, is located between gneissose rocks and granitic rocks (e.g., Kano, 1983;Komatsu et al, 1993). The SHRIMP U-Pb zircon dating of the deformed and undeformed granitic rocks suggests that the mylonitization occurred between 240 Ma and 199 Ma (Takahashi et al, 2010;Takehara and Horie, 2019). The younger granite intruded into the older granite, and a hornfels-like texture of the older granitic rocks at the boundary suggests a contact metamorphism by the younger granitic intrusions (Kano and Watanabe, 1995).…”

“…[4] Undeformed granite of Takehara and Horie (2019). Migmatite*-titanite crystalized from anatectic melt (Chen and Zheng, 2015;Chen et al, 2016).…”

“…However, geological and tectonic correlation among the Hida Belt and Permo-Triassic collisional orogenic belts in East Asia remain controversial. After the pioneering SHRIMP (Sensitive High-Resolution Ion Microprobe) work by Sano et al (2000), ion microprobe and LA-ICPMS zircon U-Pb data has been accumulated in the Hida Belt during the last decade (Cho et al, 2021;Horie, et al, 2010Horie, et al, , 2018Takahashi et al, 2010Takahashi et al, , 2018Takehara and Horie, 2019;Takeuchi et al, 2019;Yamada et al, 2021). Thus far, regional upper amphibolite-to granulite-facies metamorphism and related igneous activity have been dated as ~260-230 Ma.…”

“…Zircon U-Pb ages showing together with reference: [1] Clinopyroxene-bearing leucogranite (so-called 'Inishi'-type migmatite) collected from drill hole ofSakoda et al (2006). [2] Banded gneiss ofTakehara and Horie (2019). [3] Granitic mylonite ofTakehara and Horie (2019).…”

Thematic section: Special topics in 4th IGS ‘Precambrian World 2’

“…Takehara and Horie (2019) report U–Pb ages and oxygen isotope data of zircons collected from a granitic mylonite and an undeformed granite in the Kamioka area in the Hida Belt, southwest Japan. The zircon oxygen isotope ratios suggest that these rocks are derived from different magmas, and the timing of the mylonitization in the Funatsu Shear Zone is constrained to be 242.6–199.1 Ma.…”