Sm–Nd, Rb–Sr and K–Ar geochronology of the Higo metamorphic terrane, west‐central Kyushu, Japan

Abstract

The Higo metamorphic terrane situated in west‐central Kyushu island, southwest Japan, is composed of greenschist‐ to granulite‐facies metamorphic rocks. The southern part of the metamorphic terrane consists mainly of garnet–biotite gneiss and garnet–cordierite–biotite gneiss, and orthopyroxene or cordierite‐bearing S‐type tonalite with subordinate amounts of hornblende gabbro. Rb–Sr, Sm–Nd and K–Ar isotopic ages for these rocks have been determined here. The garnet–biotite gneiss gives an Sm–Nd age of 227.1 ± 4.9 Ma and a Rb–Sr age of 101.0 ± 1.0 Ma. The hornblende gabbro has an Sm–Nd age of 257.9 ± 2.5 Ma and a K–Ar age of 103.4 ± 1.1 Ma. These age differences of the same samples are due to the difference in the closure temperature for each system and minerals. The garnet‐cordierite–biotite gneiss contains coarse‐grained garnet with a zonal structure conspicuously distinguished in color difference (core: dark red; rim: pink). Sm–Nd internal isochrons of the garnet core and the rim give ages of 278.8 ± 4.9 Ma (initial 143Nd/144Nd ratio = 0.512311 ± 0.000005) and 226.1 ± 28.4 Ma (0.512277 ± 0.000038), respectively. These ages are close to formation of the garnet core and the rim. It has been previously suggested that the Higo metamorphic terrane belongs to the Ryoke metamorphic belt. But Sr and Nd isotopic features of the rocks from the former are different from those of the Ryoke metamorphic rocks, and are similar to those of the granulite xenoliths contained in the Ryoke younger granite.

Sm–Nd and Rb–Sr dating of amphibolite from the Nellore–Khammam schist belt, SE India: constraints on the collision of the Eastern Ghats terrane and Dharwar–Bastar craton

“…Experimental procedures used were those of Kagami et al (1987), Kagami, Yokose & Honma (1989) and Hamamoto, Osanai & Kagami (1999). Experimental procedures used were those of Kagami et al (1987), Kagami, Yokose & Honma (1989) and Hamamoto, Osanai & Kagami (1999).…”

Preserved Sm-Nd Isotopic Composition as Useful Provenance Indicators in Neoproterozoic Sandstones in the Voltaian Basin, Ghana

“…T DM (depleted mantle) model ages are calculated by substituting the appropriate DM (deplet place of ( 143 Nd/ 144 Nd) CHUR and ( 147 Sm/ 144 Nd) CHUR in the following equation; CHUR equation is quoted in Rollinson[15]. Parameters used in calculating T DM are those of Goldstein et al,[16]; ( 143 Nd/ 144 Nd) DM,today = 0.51316, ( 147 Sm/ 144 Nd) DM,today = 0.215 and the decay constant l = 6.54 × 10 −12yr−1 .…”

Detrital heavy minerals from Lower Jurassic clastic rocks in the Joetsu area, central Japan: Paleo‐Mesozoic tectonics in the East Asian continental margin constrained by limited chloritoid occurrences in Japan

“…(1999) mentioned that Permo–Triassic metamorphism occurring in the Higo Belt affected the Ryuhozan Metamorphic Rocks because metamorphism of the Higo Metamorphic Rocks took place at 260–230 Ma (e.g. Hamamoto et al . 1999) in addition to at ca 100 Ma (Nakajima et al .…”