Magma mixing in Early Jurassic granites in the Lesser Xing'an Range, <scp>NE</scp> China: Evidence from petrology, geochronology, and <scp>Lu–Hf</scp> isotopes

Abstract

The contribution of the mantle to the formation of granites with mantle‐like or juvenile crustal properties having positive ε Hf (t) and ε Nd (t) values remains ambiguous. We have carried out petrologic, geochemical, and zircon U–Pb–Hf–O isotope composition analyses on the Woniuhe and Yuantoupiao granites and associated enclaves with such properties in the northern and southern Lesser Xing'an Range, NE China to determine the crust–mantle interactions involved in the petrogenesis of these host granites and enclaves. The two host granites and their enclaves have identical crystallization ages of ~180–175 Ma within analytical error. The petrological, mineral microstructural, geochronological, Hf–O isotopic, and whole‐rock geochemical data imply that mixing between felsic and mafic magmas occurred in both the Woniuhe and Yuantoupiao plutons. The primary magmas of the enclaves in the two plutons most likely are both mantle‐derived. Hence, mantle materials were directly involved in the genesis of both the Woniuhe and Yuantoupiao host granites through the emplacement of mantle magmas. Combined with the published petro‐geochemical data, our data indicate that large‐scale underplating and emplacement of mantle magmas following crustal growth can occur and may be responsible for the magmatism in the region in the Early Jurassic. This underplating and emplacement might be related to the subduction of the oceanic plate between the Songliao and Jiamusi Massifs beneath the former.

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