Late Neoarchean magmatic record of the Jiamusi–Khanka Block, Northeast China: New clues from amphibolite zircon U–Pb geochronology and Lu–Hf isotopes

Abstract

Precambrian microcontinents represent key tectonic units in the accretionary collages of the eastern Central Asian Orogenic Belt (ECAOB), and possess a wealth of information about the geological evolution. Here, we describe newly discovered late Neoarchean amphibolite of the Huangsong Group collected from drillhole ZK4301 at the Sishanlinchang gold mining area in the Jiamusi-Khanka Block. LA-ICP-MS U-Pb dating for zircons from the amphibolite yields a weighted-mean 207 Pb/ 206 Pb age of 2539 ± 4 Ma, which can be referred to as its protolithic age. Zircons in the 2.54-Ga amphibolite show high and positive ε Hf (t) values ranging from +4.2 to +6.8 and single-stage Hf model ages (TDM1) of 2.60 to 2.68 Ga, suggesting that a depleted mantle source might have been metasomatized by fluids/melts from subducted crustal materials. The amphibolite displays low SiO 2 and alkalis, and high TFe 2 O 3 and Mg# (0.50-0.52), and is classified as a subalkaline series, medium-to high-K calc-alkaline basaltic rock. Our geochemical and geochronological data reveal that a late Archean tectono-magmatic event is preserved in the Jiamusi-Khanka Block, providing robust evidence for the existence of an Early Precambrian basement. The 2.54-Ga basaltic magmatism likely took place in an active continental margin/island arc setting.