辽东石庙沟岩体岩石地球化学特征、锆石U-Pb年龄、Hf同位素及其地质意义

辽东石庙沟地区位于华北陆块东部的辽吉造山/活动带上，该带经历了十分复杂的构造演化过程，记录了多期岩浆-构造-变质事件。石庙沟岩体为花岗斑岩，富SiO₂、Na₂O和K₂O，贫CaO、MgO及Al₂O₃，亏损高场强元素（Nb、Ti、Ta、P），富集大离子亲石元素（K、Rb、Ba、U），A/CNK值大于1，REE配分曲线呈"海鸥"式分布，以具有显著的负Eu异常为特征，高Ga/Al值，与典型A型花岗岩特征一致。花岗斑岩中锆石的LA-ICP-MS U-Pb测年结果表明其成岩年龄为（123.0±1.6）Ma，为早白垩世。锆石Hf同位素分析表明，ε_Hf（t）值均为负值，介于-15.72~-12.85之间，平均值为-14.14，二阶段模式年龄（T_DM2）在2 164~1 989 Ma之间，平均为2 067 Ma，反映源岩以大陆壳成分为主。结合花岗斑岩高SiO₂，低Mg、Co、Cr、Ni，且富集LREE和LILE，亏损HFSE等特征，表明早白垩世花岗斑岩岩浆应为大陆地壳物质熔融的产物。根据年代学和岩石地球化学研究认为，早白垩世花岗斑岩是古太平洋板块向欧亚大陆板块俯冲所形成的活动大陆边缘弧花岗岩。研究区早白垩世花岗斑岩的形成主要受太平洋构造域的影响，形成环境受板块俯冲造山后伸展作用和下地壳拆沉作用的联合制约，是辽东地区岩石圈减薄的直接证据。

Geochemical,Zircon U-Pb Age,Hf Isotope and Geological Significance of Early Cretaceous Granite-Porphyry in Shimiaogou Area,Eastern Part of Liaoning Province

The Shimiaogou area in Liaodong is tectonically located in the Liao-Ji orogenic/active belt in the eastern part of the North China block, which has experienced a very complex tectonic evolution with multiple magma-tectono-metamorphic events. The Shimiaogou rock mass is of granite porphyry, rich in SiO2,Na2O, and K2O,poor in CaO, MgO, and Al2O3;It lacks high field strength elements(Nb, Ti, Ta and P) but is rich in large ion lithophile elements(K, Rb, Ba, U)with A/CNK values greater than 1;The REE distribution curve shows"seagull"type, characterized by significant negative Eu anomaly, and Ga/Al value is consistent with the typical characteristics of type A granite. The granite-porphyry magmatic zircon LA-MC-ICP-MS U-Pb dating results show that its rock age was(123.0±1.6) Ma in the Early Cretaceous. Through Hf isotope analysis, the εHf(t)values are between-15.72 and-12.85 with the average of-14.14 and the two stage model age(TDM2)is between 2 164 and 1 989 Ma with an average of 2 067 Ma, reflecting the main continental crust composition of the source rock. Furthermore, combined with the characteristics of high SiO2,low Mg, Co, Cr, Ni, enrichment of LREE and LILE and loss of HFSE,it is suggested that the Early Cretaceous granite porphyry magma should be the melting product of continental crust material formed under the subduction of the Pacific plate beneath the Eurasian plate in the active continental margin. The Early Cretaceous environment of Liaodong region is affected by the subduction post-tectonic extension and lower crust delamination. The formation of the Early Cretaceous granite porphyry is controlled by Pacific tectonic domain, the dynamic environment formed in the lithosphere stretching is a direct evidence of lithospheric thinning in Liaodong area.