Crustal development of the Hida belt, Japan: Evidence from Nd–Sr isotopic and chemical characteristics of igneous and metamorphic rocks

Abstract

Chemical and Sr–Nd isotopic investigations were performed on the igneous and metamorphic rocks in the Hida belt (central Japan) to clarify their ages and possible sources, and to provide constraints on the crustal evolution of the eastern margin of the Asian continent. Igneous rocks of three main stages in the Hida belt, represented by the late Silurian amphibolites (first stage), the middle Carboniferous mafic dikes (second stage) and the late Triassic to early Jurassic granite-gabbro plutons (third stage), show alkaline to calc-alkaline chemical affinity. Major and trace element characteristics show that the three stages of igneous rocks were emplaced in a continental margin or continental arc environment. The mafic igneous rock suites have relatively high ε Nd (−0.5 to +5.5) and low 87Sr/ 86Sr (0.7049 to 0.7061) values, indicating their origin from upper mantle sources, though the third stage granitoids contain recycled crustal components. The Hida gneisses of clastic origin show two groups of model ages ( T DM): middle Proterozoic (1.4–2.2 Ga), and late Proterozoic to early Paleozoic (0.55–0.74 Ga). Consistent with geological, geochemical and radiometric age data are that the sedimentation and basaltic volcanism occurred in early to middle Paleozoic, and the protoliths with middle Proterozoic model ages are detritals from the Proterozoic continental provenances. A synthesis of available geological and geochemical data for the basement metamorphic and igneous rocks in eastern Asia suggests two possibilities for the Paleozoic to early Mesozoic history of the Hida belt: (1) the Hida belt was formed at the eastern margin of the North China Block with later evolution as a suture zone between the North and South China blocks; or (2) it evolved as a part of the East-Central Asian Orogenic Belt (ECAOB) to the north.