Decoupling of isotopes between magmatic zircons and their mafic host rocks: A case study from the ca. 830 Ma Jiabang dolerite, South China

•Whole-rock geochemistry suggests crustal contamination played only a minor role in producing the Jiabang dolerite.•Zircon Hf-O isotopes of the Jiabang dolerite suggest significant crustal contamination, however this is not shown by the whole-rock Hf-Nd data.•This decoupling of zircon Hf-O isotopes from the whole-rock isotopic composition may be more widespread in mafic magma systems.