铜陵舒家店地区中生代中酸性侵入岩锆石Hf同位素特征及其地质意义

通过锆石LA-MC-ICP-MS Lu-Hf同位素分析，结合前人地球化学资料对舒家店地区中酸性侵入岩进行了研究.主量、微量元素地球化学特征表明区内侵入岩为准铝质，具有岛弧岩浆岩的特征，区内岩浆的演化可能经历了同化混染与分离结晶（AFC）过程.通过分析，我们认为舒家店地区的早白垩世岩浆活动可能与早白垩世初太平洋板块的斜向俯冲相关，侵入岩的形成演化受到了区域构造应力场的制约.Hf同位素分析及计算结果表明，除两个继承性锆石核外，本区侵入岩锆石的ε_Hf（t）均为负值，橄榄安粗岩系列侵入岩的ε_Hf（t）值为-8.6~-4.1，高钾钙碱性系列ε_Hf（t）值为-13.4~-4.7.与高钾钙碱性系列相比，橄榄安粗岩系列侵入岩的ε_Hf（t）更接近球粒陨石演化线.从ε_Hf（t）值的变化特征来看，两个系列侵入岩均为来源于富集地幔，且在演化过程中混染了地壳物质，而高钾钙碱性系列在这个过程中混入了更多的地壳物质. 

Geochemical and Zircon Hf Isotopic Characteristics of Mesozoic Intermediate-Acid Intrusive Rocks in Shujiadian Area,Tongling and Their Geological Significance

In this paper, we carry out research on intermediate-acid intrusive rocks in Shujiadian area in aspect of zircon LA-MC-ICP-MS Lu-Hf isotopes combining previous geochemical data. The characteristics of major and trace elements show that the rocks belong to metaluminous series with attributes of island arc magmatic rocks, and may have experienced assimilation-fractional crystallization (AFC) process. We considered that the Early Cretaceous magmatic activity might relate to the oblique subduction of the Pacific plate in the beginning of the Cretaceous, and the evolution of the intrusive rocks in the area were subject to the regional tectonic stress field. The Hf isotope analysis shows that except two inherited zircon cores, the ε_Hf(t) values are negative, with shoshonite series being -8.6 to -4.1 and High-K calc-alkaline series -13.4 to -4.7. Comparing to the high-K calc-alkaline series rocks, the ε_Hf(t) values of the shoshonite series are closer to chondrite evolution line. Considering from the variance of ε_Hf(t) values for the two series, though they both originated from enriched mantle and were contaminated with crustal material during magmatic evolution, the high-K series was contaminated more during this process.