Episodic Neoproterozoic Magmatism in the Northeastern Yangtze Craton: Implications for the Breakup of the Rodinia Supercontinent

Abstract. The composition and evolution of Precambrian basement are pivotal for understanding global continental crustal growth and supercontinent cycles, representing a key frontier in geological research. Although ancient basement exposures have been documented along the periphery of the Yangtze Craton, its northern margin exhibits limited and sporadic Precambrian outcrops, resulting in poorly constrained crustal evolution history for this critical period. This study identifies a series of magmatic rocks with mid-Neoproterozoic ages along the northeastern margin of the Yangtze Craton, which provides new constraints on the tectonic evolution of the Yangtze Craton in Neoproterozoic. This discovery provides critical constraints on the crystalline basement attributes and tectonic evolution during this stage, while offering vital evidence for investigating its linkage with the Rodinia supercontinent. Geochronological results reveal two magmatic episodes: 781–776 Ma granitic gneisses (Feidong Complex) and 753–730 Ma bimodal volcanic rocks (spilite-keratophyre association; Zhangbaling Group). Contrasting geochemical signatures and isotopic compositions indicate complex melting conditions and tectonic stages: the Feidong granitic gneisses exhibit highly enriched zircon Lu-Hf isotopes (ε_Hf(t) = −16.9 to −10.9) and ancient crustal model ages, attesting to remelting of ancient continental material, elevated Sr/Y, (La/Yb)ₙ ratios coupled with significantly fractionated REE patterns showing significant HREE depletion imply high-pressure melting conditions. During this phase, decompression melting of the lithospheric mantle occurred, inducing lower crustal melting via underplating. In contrast, the Zhangbaling bimodal volcanics display diagnostic A-type granite geochemical affinities, depleted zircon Lu-Hf isotopes (ε_Hf(t) = −3.9 to +4.3), and shallower melting depths. This upward shift in magmatic source records the transition of the northeastern Yangtze margin from initial extension to a mature rift system, directly recording the Rodinia supercontinent breakup process.