Petrogenesis and tectonic implications of Late Triassic dikes from the Suolun within the central Great Xing'an Range, NE China: constraints from geochronology and geochemistry.

Dikes are great significance for studying the nature of the crust-mantle and the evolution of continental dynamics. In this paper, we investigated the dikes from the inner part of the Baiyintaohai Basin of the Suolun region in the DaXing'anling Mountains, China. Geochronological and geochemical analyses were performed on selected dike samples. These dikes consist of diorite porphyrite and granite aplites formed in the Late Triassic (221–228 Ma). The diorite porphyrites have low SiO₂ contents of 37.32–58.29 wt%. These rocks are characterized by enrichment in macroionic lithophile elements (LILEs, Rb, K), strong depletion of Sr and Ti, and relative depletion of Nb, Ta. These results indicate that the diorite porphyrites were originated from an enriched lithospheric mantle and was previously accounted for by subduction-related fluids. The primitive magma subsequently underwent varying amounts of fractionated crystallization. In comparison, the granite aplites have relatively high SiO₂ contents of 61.51 to 74.69 wt% (average is 70.15 wt%) and low MgO, CaO contents. Geochemical signatures show the granite aplites enrich LILEs and REEs, display negative Eu anomalies, indicating they were derived from the partial melting of late Mesoproterozoic to Neoproterozoic juvenile crustal material. With this contribution, we suggest that dikes, consisting in granite aplite and diorite porphyrites from the Suolun region, crystallized in a post-closure. Among them, the diorite porphyrites in the Suolun area provide reducing agents for the formation of uranium deposits, and granite aplites provide the material source for uranium ore generation. [ABSTRACT FROM AUTHOR]