Character and genesis of dark residuals in Douzhashan uranium production granite pluton

Study of the dark residual and granite in macro and micro feature, petrochemistry, trace elements and isotopic trace show that the residual and granite have the same U-Pb concord age which exclude the possibility that the dark residual derived from the metamorphic rock in the deep or the xenolith of wallrocks, while the character of trace element and Sm and Nd isotopes excluded the possibility that the dark residual was the dialyse accumulation. Therefore, the dark residual block in Douzhashan granite should be the crystallized block of mixed magma residual of middle-base magma and granite. The middle-base magma should be the comprehensive products of lithosphere mantle rock melting, mixed crustal melting and the isolation of crystallization and also the participation of asthenosphere magma. Thus lead to that Shazijiang-Guanli area was the center of middle-base and granite magma intrusion and mixing which controlled the lithification and uranium mineralization of Douzhashan pluton and even the whole Miaoershan complex orefield. (authors)