Late Cretaceous U/Pb zircon ages and Precambrian crustal inheritance in Ryoke granitoids, Kinki and Yanai districts, Japan.

Abstract

Ryoke granitoids on Ikoma-yama and Katsuragi-yama in the Kinki District, and on Yashiro jima in the Yanai District, have Late Cretaceous zircon U/Pb isotopic crystallization ages. Older and Younger granites on Ikoma-yama were emplaced within a short time interval between 81 and 82 ± 1 Ma. Younger Ryoke granite on Katsuragi-yama, located south of Ikoma-yama, crystallized at 75 ± 3 Ma. The Gamano grano diorite and Kita-Oshima granite-gneiss on Yashiro-jima have overlapping crystallization ages of 95 to 96 ± 1 Ma. This result supports earlier ideas that the Gamano and Kita-Oshima rocks are cogenetic. An inherited component of Precambrian (1855 to 1953 Ma) radiogenic lead is present in some of the zircons from the Ryoke granitoids analyzed in this study. This result implies that older continental materials were assimilated into the granitic magmas. Possible sources include Precambrian basement or younger upper crustal rocks that contain recycled Precambrian detritus.

Molybdenum isotopes in hydrothermal manganese crust from the Ryukyu arc system: Implications for the source of molybdenum

“…1), is composed of Miocene to Pliocene (17.7-4.5 Ma) tuffs, lava flows, and dikes of calc-alkaline andesite and basalt. In addition, Precambrian-aged zircons are often found from igneous rocks in the Japan archipelago, and have been interpreted as inherited zircons originated from Archean/Paleoproterozoic terranes in South China and Korea (e.g., Herzig et al, 1998;Hidaka et al, 2002). Thus, the old ages likely represent inherited zircons that survived previous intrusive events before they were incorporated into the pumice.…”

Geochronology and geochemistry of Late Cretaceous–Paleocene granitoids in the Sikhote-Alin Orogenic Belt: Petrogenesis and implications for the oblique subduction of the paleo-Pacific plate

“…The ways to test the hypothesis is given by Niu and Tang (2016) Barnes, 2003;Sorokin et al, 2010a;Sun et al, 2013;Wu et al, 2011) and the distribution of Late Cretaceous-Paleocene igneous rocks in the Russian Far East, NE China, SW Japan, and South Korea (Data from Herzig et al, 1998;Hwang, 2011;Nakajima et al, 2004;Jahn et al, 2015;Ji et al, 2007;Xu et al, 2013;Yu et al, 2013;Zhang et al, 2012). ( Boynton (1984) and Sun and McDonough (1989), respectively.…”

Geochronological characterization and petrogenesis of granitoids in the Ryoke belt, Southwest Japan Arc: constraints from K–Ar, Rb–Sr and Sm‐Nd systematics

“…U‐Pb zircon ages are the best technique for obtaining high‐precision dates for granitic rocks to establish their true crystallization ages ( Stern et al 1981 ). However, few such data have been reported from Ryoke granitoids ( Nakajima et al 1993 ; Herzig et al 1998 ), and it is not possible to investigate the general timing with the limited data available. Chemical Th‐U‐total Pb Isochron Method (CHIME) monazite ages have recently been reported for metamorphic and granitic rocks within the Ryoke and San‐yo belts ( Suzuki & Adachi 1998), but in some cases these ages do not reflect crystallization ages ( Yuhara et al 1999b ).…”