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漳浦复式花岗岩体位于福建东南沿海,为一由多期岩浆作用形成的大岩基,出露面积大于1500km2。按岩性特征,该复式岩体可肢解为长桥黑云母花岗岩、程溪碱长花岗岩和湖西花岗闪长岩3个单元。锆石LA-ICP-MS U-Pb定年结果表明,3个单元岩石的成岩年龄分别为119Ma、101Ma和96Ma。化学组成上,各单元岩石均具有亚碱、准铝或弱过铝、贫磷特征,它们的A/NKC值均在1.10以下,P2O5含量均低于0.20%,均可归为钙碱性的I型花岗岩。各单元岩石均富Cs、Rb、Th、U、Pb和轻稀土,贫Ba、Sr、P、Ti,但长桥和程溪单元较之湖西单元岩石Rb/Sr、Rb/Ba比值高,K/Rb比值低,并表现出更显著的铕负异常,指示各单元岩石的分异演化程度各不相同。3单元岩石具有较均一的Nd同位素组成,εNd(t)=-2.43～-3.24,tDM2=1.11～1.16Ga,但锆石Hf同位素组成普遍具有较大的变化范围,长桥、程溪和湖西3单元岩石的εHf(t)值分别为-8.3～+3.0、+1.7～+10.2和-2.5～+3.5,变化幅度均在6个εHf单位以上,反映岩体的形成存在不同来源物质的贡献。综合分析表明,各单元岩石的形成均经历了幔源岩浆与其诱发地壳物质熔融产生的长英质岩浆在地壳深部混合,随后又经不同程度结晶分异的二阶段成岩过程。各单元岩石之间显著的成岩时差及成分变异趋势指示复式岩体不可能为同一原始岩浆分异演化的产物,而最可能为演化程度各异的壳幔混源岩浆叠次侵位复合的结果。
Zhangpu multi-granite body is located in the southeast coast of Fujian, is a large rock formation formed by multi-stage magmatism, the exposed area is more than 1500km2. According to the lithologic characteristics, the complex rock mass can be disintegrated into three units: Changqiao biotite granite, Chengxi alkali-bearing granite and Hu Xi granodiorite. U-Pb dating of zircons by LA-ICP-MS shows that diagenesis ages of the three unit rocks are 119Ma, 101Ma and 96Ma, respectively. In terms of chemical composition, the rocks of each unit have the features of sub-alkali, quasi-aluminum or weakly over-aluminum and lean phosphorus, all of which have A / NKC values below 1.10 and P2O5 contents below 0.20%, all of which can be classified as calc-alkaline I-type granite. The rocks of each unit are rich in Cs, Rb, Th, U, Pb and light rare earths and are poor in Ba, Sr, P and Ti. However, the Rb / Sr and Rb / / Rb ratio is low and exhibits more pronounced negative anomalies of europium, indicating that the degree of differentiation and evolution of rocks in each unit varies. 3 unit rocks have a more uniform Nd isotopic composition, εNd (t) = -2.43 ~ -3.24 and tDM2 = 1.11 ~ 1.16Ga. However, the Hf isotopic compositions of zircons generally have a wide range of variation. Changqiao, Chengxi and Huxi The values of εHf (t) of units 3 are -8.3 ~ + 3.0, + 1.7 ~ + 10.2 and -2.5 ~ + 3.5 respectively, all of which are above 6 εHf units, reflecting the contribution of different source materials . Comprehensive analysis shows that all unit rocks have undergone two-stage diagenetic process after the mafic magma and its crust-derived magma were mixed in the deep crust and then crystallized at different degrees. The significant diagenetic time difference and variation trend of composition between rocks indicate that the complex rock mass can not be the product of the same original magmatic differentiation, but the most likely result is the superimposed emplacement combination of crust-mantle mixed-source magma with different degrees of evolution .