Widespread Mesozoic granitic plutons in the North China Craton (NCC) are products of remelting of the crust associated with large-scale Mesozoic destruction of the NCC. Mafic microgranular enclaves (MMEs) are common in these plutons and are attributed to magma mixing. However, the involved magmatic processes of the mixing are poorly known. In this paper, we reported complex zoning patterns, in situ UPb ages, and elemental and Nd isotopic compositions of titanite grains in the MMEs and host monzogranite of the Sanguliu pluton in the NCC. Titanite grains in the MMEs and monzogranite have similar UPb ages of ca.130 Ma, and display different internal textures and compositions. They can thus be divided into four types, i.e., types 1 and 2 from the host monzogranite, and types 3 and 4 from the MMEs. Type 1 is euhedral in shape, whereas type 2 has a euhedral inner domain and a thin deuteric rim with a sharp contact between them. Types 3 and 4 are angular grains. Type 3 shows a typical core-mantle-rim texture with a resorbed core, a mantle and an irregular rim, whereas type 4 contains a homogeneous inner domain and a discontinuous rim. Most titanite grains of the four types display oscillatory, fir-tree and sector zoning and have crystallization temperatures ranging from 680 to 750 °C based on the Zr-in-titanite thermometry, indicating a magmatic origin. The core of type 3 titanite has the highest ε_Nd(t) of −11.3 to −12.5 among others, close to that of the mafic dykes (ε_Nd(t) = −7.8 to −11.6) that intrude the Sanguliu pluton. The core can be interpreted as crystallized from the mixed magmas with more mafic components that were derived from metasomatized subcontinental lithospheric mantle (SCLM) beneath the NCC. The mantle of type 3 and the inner domain of type 4 titanite have ε_Nd(t) (−13.0 to −15.3) nearly identical to that of the MMEs (−14.3 to −15.4), but distinctly higher than that of types 1 and 2 titanite (−15.9 to −18.3). The rims of types 3 and 4 titanite have ε_Nd(t) (−16.1 to −18.3), identical to that of type 1 and the inner domain of type 2 titanite, however, they have REE concentrations and Th/U and Nb/Ta similar to the rim of type 2 titanite, clearly indicative of crystallization from evolved, hydrated, granitic magmas. A three-stage growth model is thus proposed to explain the core-mantle-rim texture of the titanite in the MMEs by a magma mixing process. The core likely crystallized from the mixed magma with more mafic components. It was then partially or totally resorbed by mixed, dioritic magma due to chemical disequilibrium, which was followed by the re-precipitation from the dioritic magma, forming the mantle. The rim is an overgrowth from the evolved, hydrated, granitic magma. This study demonstrates that the complex zoning patterns and compositions of titanite in the MMEs can be used to investigate magmatic processes including magma mixing.

华北克拉通（NCC）中广泛分布的中生代花岗岩体是重熔壳的产物，伴随着NCC的大规模中生代破坏。镁铁质微颗粒飞地（MMEs）在这些岩体中很常见，并归因于岩浆混合。然而，所涉及的混合的岩浆作用过程是鲜为人知的。在本文中，我们报告了复杂的分区模式，原位U Pb年龄以及NCC中Sanguliu岩体中MME和宿主Monzogranite中钛矿晶粒的元素和Nd同位素组成。MME中的钛铁矿颗粒和辉长花岗岩具有相似的U铅的年龄约为130 Ma，并显示出不同的内部纹理和组成。因此，它们可以分为四种类型，即主体蒙脱石的类型1和2，以及MME的类型3和4。1型为正面体形状，而2型为内面体域，氘核边缘较薄，且两者之间有紧密的接触。类型3和4是角粒。类型3显示了典型的芯-幔-边缘纹理，具有重吸收的芯，幔和不规则边缘，而类型4包含均匀的内部区域和不连续的边缘。根据钛矿中Zr的测温法，这四种类型的大多数钛矿晶粒均显示出振荡，枞树和扇形区带，且结晶温度范围为680至750°C，表明岩浆成因。3型榍的核心具有最高的ε_钕（t）的-11.3 -12.5到除其他外，接近于镁铁质堤坝（ε的_钕该侵入的Sanguliu岩体（T）= -7.8到-11.6）。岩心可以解释为是由混合岩浆结晶而成的，这些岩浆中含有更多的镁铁质组分，这些组分是由交联后的亚大陆岩石圈地幔（SCLM）演化而来的。类型3的地幔和类型4榍有无ε的内结构域_的Nd（T）（-13.0 -15.3到）几乎相同的的MME（-14.3 -15.4到），但比类型1和明显更高的2钛铁矿（-15.9至-18.3）。的类型3和4榍有无ε轮缘_的Nd（t）（-16.1至-18.3），与1型和2型钛矿的内部区域相同，但是，它们的REE浓度和Th / U和Nb / Ta与2型钛矿的边缘相似，很明显指示从演化的，水合的花岗岩岩浆中结晶。因此，提出了一种三阶段生长模型，通过岩浆混合过程来解释MME中钛矿的核幔边缘结构。岩心可能从具有更多铁镁质成分的混合岩浆中结晶出来。然后由于化学不平衡作用，它被混合的闪长岩浆部分或全部吸收，然后再由闪长岩浆重新沉淀，形成地幔。轮缘是演化的，水合的花岗岩岩浆的过度生长。