Continental growth in eastern Central Asian Orogenic Belt: Evidence from Middle Permian–Middle Jurassic magmatism

The Zhangguangcai Terrane, Northeast China, provides an ideal site to investigate Phanerozoic continental crustal growth through the Permian to Jurassic tectono-magmatic evolution of Northeast China. A systematic review of the 266–163 Ma magmatic rocks in the Zhangguangcai Terrane, integrating geochronology, geochemical, and whole-rock Sr-Nd and zircon Hf isotopic data, reveals a four-stage magmatic history. Adakitic and I-type rocks characterize the 266–240 Ma magmatic pulse, whereas 229–210 Ma, 209–185 Ma, and 184–163 Ma magmatic rocks exhibit three distinct suites of adakitic, I-type and A-type rocks. Geochemical features are indicative of a lower crustal source, with some mantle-derived materials. The petrogenetic history of these rocks, integrated with temporal changes in crustal thickness and evidence from previous studies, suggests that the tectono-magmatic history of the Zhangguangcai Terrane was dominated by the westward subduction and ultimate closure of the Heilongjiang Ocean. Convergent plate interaction occurred from 266 to 210 Ma, leading to prolonged crustal growth and reworking. A magmatic lull at ca. 240–230 Ma is ascribed to low-angle (or flat-slab) subduction of the Heilongjiang oceanic plate. Closure (209–180 Ma) of the Heilongjiang Ocean and obduction of ocean fragments (180–163 Ma) culminated in the final amalgamation of the Jiamusi-Khanka Block with the Central Asian Orogenic Belt, and the tectonic exhumation and emplacement of blueschist in the Heilongjiang Accretionary Complex. Our analysis of the Zhangguangcai Terrane indicates that it represents a combination of Paleozoic to early Mesozoic accretionary complex and continental arc intruded by multi-stage granites, which contrasts with previous models that argued that it constitutes a Neoproterozoic basement block.