长江中下游贵池地区燕山期侵入岩发育,与成矿关系密切.本文对该区侵入岩开展了详细的锆石U-Pb年代学、地球化学及Sr-Nd-Hf同位素研究.结果表明,马头花岗闪长斑岩形成于147±2Ma,而花园巩石英二长岩形成于127±1Ma,比花岗闪长斑岩晚约20Ma.早期的花岗闪长斑岩(147 ～ 145Ma)为高钾钙碱性系列,具有高Al2O3、Sr含量和Sr/Y、La/Yb比值,以及低的Y、Yb含量,与埃达克质岩的地球化学特征一致；而晚期石英二长岩(127Ma)和石英正长岩为钾玄岩系列,具有高的(Na2O+ K2O)、Zr、Nb、Y含量和Y/Nb、Yb/Ta比值,与造山带A2型花岗岩地球化学特征相似；碱长花岗岩(125～124Ma)同样具有A型花岗岩的地球化学特征,但与石英二长岩、石英正长岩相比,碱长花岗岩的Y/Nb、Yb/Ta比值相对较低,具板内环境A1型花岗岩的地球化学特征.因此,贵池地区岩浆岩从早期的埃达克质岩变为晚期的A型花岗岩,反应了晚中生代时期长江中下游地区的构造环境由大陆边缘环境向伸展环境的转变.%Zircon U-Pb ages, elemental and Sr-Nd-Hf isotopic data are reported for Late Mesozoic plutons in the Guichirnmetallogenic district in the Middle and Lower Reaches of the Yangtze River Region, attempting to constrain their age, petrogenesis, and tectonic implications. The Matou granodiorite porphyry and the Huayuangong quartz monzonite were dated at 147 ±2Ma and 127 ± 1Ma, respectively. The early Matou and Tongshan granodiorite porphyries are high-K calc-alkaline, and exhibit adakite-like geochemical features, such as high A12O3, Sr, Sr/Y and La/Yb values, and low Y and Yb contents. The 127Ma Huayuangong quartz monzonites and quartz syenites are shoshonitic, and characterized by high ( Na2O + K2O), Zr, Nb, Y, Y/Nb and Yb/Ta values, indicating A2-type granite affinity at convergent margins. The 125 ~ 124Ma Huangyuangong alkali feldspar granites also exhibit A-type granite geochemical features, while are characterized by lower Y/Nb and Yb/Ta values, resembling A,-type granite affinity in interplate settings. The change of geochemical features from adakitic rocks to A-type granite is magmatic response to tectonic transition, switching from a continental margin environments to a lithosphere extensional regime.
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