The oxygen fugacity of a magma controlling element distribution and mobility is influenced by multiple factors including source composition and magmatic processes (e.g., assimilation and degassing). Here, whole-rock and in situ mineral analyses of the alkaline complex from the northern North China Craton are reported to investigate the influence of source composition and magmatic processes on the evolution of the melt oxidation state. The alkaline complex comprises orthoclase pyroxenites, pyroxene syenites, and syenites with similar mineral assemblages and trace element patterns. Consistent zircon and titanite U-Pb age of ~234 Ma is presented for the alkaline rocks. Their high large ion lithophile elements content, negative high field strength element anomalies, and high ⁸⁷Sr/⁸⁶Sr ratio suggest a metasomatized mantle origin by recycled crustal material. Magnetite and hematite inclusions were found in the early-crystallized minerals including clinopyroxene and apatite. Fluorapatites are characterized by high S (SO₃ up to 0.64 wt%) and low Mn contents, with estimated ΔFMQ higher than +3. These features together indicate a primary oxidized magma inherited from the metasomatized mantle.

However, inclusion-rich fluorapatites with decreasing S and increasing Mn content from the core to the rim were found in some pyroxene syenites. Moreover, the S content of inclusion-rich fluorapatite from these pyroxene syenites is lower than that of other rock types in the complex, which may correspond to a decrease in oxygen fugacity of ~2.5 log units. These features suggest that the oxidized magma was later transformed into reduced magma. Oriented Cu-rich sulfide in inclusion-rich fluorapatite formed during the reducing event. δ⁶⁵Cu of the pyroxene syenite with inclusion-rich fluorapatite (−0.06 to −0.24‰) and sulfides in fluorapatite (−0.26‰) are lighter than those of other rock types (+0.30 to +0.43‰), suggesting that the sulfides were derived from extraneous materials via magma assimilation. Variable and high ⁸⁷Sr/⁸⁶Sr ratios (0.7071–0.7085) in titanites and high-²⁰⁷Pb/²⁰⁶Pb rims of zoned K-feldspar in the pyroxene syenite imply that the reduced extraneous materials were derived from ancient crust. Overall, in situ mineral analyses and Cu isotopes indicate a direct link between the transformation of alkaline magma from an oxidized to a reduced state with source composition and magmatic processes, and improve our understanding of element mobility and distribution.

岩浆控制元素分布和迁移率的氧气逸度受多种因素影响，包括源组成和岩浆过程（例如，同化和脱气）。在这里，据报道华北克拉通北部碱性复合物的全岩石和原位矿物分析，以研究源组成和岩浆作用对熔体氧化态演化的影响。碱性配合物包括原矿型辉石，辉石正长岩和具有相似矿物组成和痕量元素形态的正长岩。对于碱性岩石，锆石和钛铁矿的U-Pb年龄一致，约为234 Ma。它们具有高的大离子亲石元素含量，负的高场强元素异常和高的⁸⁷ Sr / ⁸⁶Sr比值表明地壳物质是由回收的地壳物质交代而成的。在早结晶的矿物中发现了磁铁矿和赤铁矿夹杂物，包括斜铁辉石和磷灰石。氟磷灰石的特征在于高S（SO ₃高达0.64 wt％）和低Mn含量，估计ΔFMQ高于+3。这些特征共同表明，从交代地幔继承了原始的氧化岩浆。

然而，在一些辉石正长岩中发现了富集的氟磷灰石，其从芯层到边缘的S含量降低且Mn含量增加。此外，这些辉石正长岩中富含夹杂物的氟磷灰石中的S含量低于该复合物中其他岩石类型的S含量，这可能对应于氧逸度降低了约2.5 log个单位。这些特征表明，氧化的岩浆随后被转化为还原的岩浆。在还原过程中形成的富夹杂物氟磷灰石中的定向富铜硫化物。δ ⁶⁵具有富夹杂物氟磷灰石（-0.06至-0.24‰）和氟磷灰石中的硫化物（-0.26‰）的辉石正长岩中的铜比其他类型的岩石（+0.30至+ 0.43‰）更轻，表明硫化物是衍生出来的。通过岩浆吸收从外来物质中提取。钛铁矿和高²⁰⁷ Pb / ^206的可变和高⁸⁷ Sr / ⁸⁶ Sr比（0.7071–0.7085）辉石正长岩中带钾长石的Pb边缘暗示还原的外来物质是从古代地壳中提取的。总的来说，原位矿物分析和铜同位素表明，碱岩浆从氧化源到还原态的转变与源成分和岩浆过程之间存在直接联系，并增进了我们对元素迁移率和分布的理解。