摘要
浸铜湖斑岩铜(钼)矿床位于福建紫金山矿田的北东侧,本文分析了出露于该矿床的石英正长斑岩的主量元素、稀土和微量元素组成,Nd同位素组成,并对其进行锆石LA-ICP-MS U-Pb定年。研究结果显示,岩石SiO2含量变化于57.59%~71.19%,岩石全碱含量为7.73%~10.01%,里特曼指数σ为2.21~6.05,铝饱和指数A/CNK为1.24~1.53,为过铝质、高钾钙碱性系列。稀土元素总量为152×10-6~212×10-6,具有弱Eu负异常(Eu/Eu*=0.71~0.97),(La/Yb)N为16.62~33.49,表现出轻稀土富集,重稀土亏损。微量元素具有亏损Nb、Ta、P、Ti等高场强元素,富集大离子亲石元素的特点,显示弧岩浆作用特点。岩石具有低的εNd(t)值和低的Nd模式年龄,分别为-6.60^-4.37和1.25~1.43Ga,显示壳-幔相互作用特征。对石英正长斑岩两个样品的锆石进行激光探针等离子体质谱(LA-ICP-MS)U-Pb微区测定,结果分别为95.3±0.9Ma和96.7±0.9Ma,为晚白垩世早期岩浆活动产物。结合已有的研究成果,本文认为石英正长斑岩形成于拉张的构造背景之下,由受到俯冲组分改造或影响的岩石圈地幔物质与中、下地壳物质部分熔融形成的花岗质岩浆混合形成。
The Jintonghu porphyry Cu （Mo） deposit locates in the northeastern Zijinshan ore field. Whole-rock major, rare and trace elements, Nd isotopic composition and zircon LA-ICP-MS U-Pb age of quartz-syenite porphyry from Jintonghu deposit are analyzed in this paper. The major elements results show that the contents of SiO2 and alkali range from 57.59% to 71.19% and 7.73% to 10.01%, respectively. The Rittmann Index and Aluminum Saturation Index are from 2.21 to 6.05 and 1.24 to 1.53 respectively, indicating that the rock belong to peraluminous and high-K calc-alkaline series. The quartz-syenite porphyry have ∑REE range from 15210-6 to 21210-6, and negative Eu anomalies （Eu /Eu＊=0.71~0.97）, with （La/Yb）N values from 16.62 to 33.49, exhibiting relative LREE enrichment and HREE depletion. Compared to primitive mantle values, all the rocks are enriched in LILEs and depleted in HFSEs （Nb, Ta, P, Ti）. The geochemical results show characteristic of arc volcanic rock. The low εNd（t） values and low Nd isotopic model ages, which range from -6.60 to -4.37 and from 1.25Ga to 1.43Ga respectively, indicate the characteristic of crust-mantle interaction. In situ zircon U-Pb LA-ICP-MS dating on the two quartz-syenite porphyry samples yielded ages of 95.30.9Ma and 96.70.9Ma. Combined with former researches, we conclude that the quartz-syenite porphyry formed in an extensional tectonic setting, and was a product of mixing of lithospheric mantle material （modified or influenced by subduction components） and granitic magma （derived from partial melting of middle and lower crust）.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第12期4151-4166,共16页
Acta Petrologica Sinica
基金
国家973项目(2012CB416705)
国家自然科学基金项目(41103023)
中国科学院“百人计划”项目联合资助
