辽东五龙重融型花岗质岩体锆石U-Pb年代学、岩石地球化学、Sr-Nd-Pb-Hf同位素特征及地质意义

在华北克拉通东北缘的辽东半岛广泛发育一套形成于侏罗纪的花岗质岩体，出露于丹东地区的五龙花岗质岩体为五龙大型金矿床的围岩，岩体内分布有古元古界辽河岩群变质岩残留体和古元古代侵入岩残留体，多数发育碎裂岩化和糜棱岩化构造.对五龙岩体进行详细解体，认为其是由黑云母二长花岗岩、二云母二长花岗岩、黑云母花岗岩和花岗闪长岩组成的一套酸性侵入岩组合.根据锆石SHRIMP U-Pb测年结果，获得4种岩性的岩浆结晶年龄分别为162±3 Ma、169.3±3.1 Ma、157.5±1.7 Ma、158.0±2.7 Ma，形成于中-晚侏罗世.岩石地球化学特征显示，五龙岩体属于钙碱性-高钾钙碱性、过铝质、中温花岗质岩浆系列，富集Rb、Th、U、K等大离子亲石元素（LILE），亏损Nb、Ta、P、Ti等高场强元素（HFSE），δEu为0.56~1.97，异常变化范围较大，ε_Hf（t）值为-39.7~-22.9，二阶段模式年龄t_DM2为3 711~2 653 Ma，ε_Nd（t）值为-23.8~-20.2，t_DM2为2 782~2 487 Ma，显示岩浆源区来自太古代~古元古代壳源物质；结合Pb同位素特征以及石英、长石、云母的显微结构特征，认为五龙岩体是古元古代花岗岩和辽河岩群地层受侏罗纪~160 Ma陆壳重熔事件于上地壳原地重新结晶所形成的S型花岗质岩体，形成于中-晚侏罗世时期受古太平洋板块俯冲影响的挤压-造山构造背景. 

Zircon U-Pb Ages,Elements Geochemistry and Sr-Nd-Pb-Hf Isotopic Characteristics of Wulong Remelting Granite Intrusive Rocks in Liaodong Peninsula and Geological Significance

Jurassic granitic intrusions are widely exposed on the Liaodong Peninsula on the northeastern margin of the North China craton. The Wulong granitic pluton in the Dandong area is the wall rock of the Wulong gold deposit,which contains residues of Paleoproterozoic Liaohe Group metamorphic rocks and Paleoproterozoic intrusive rocks,with fragmentation and mylonitization developed locally. In this paper,the Wulong pluton is studied in detail,revealing that it is an assemblage of acid intrusive rocks containing biotite monzonitic granite,two-mica monzonitic granite,biotite syenite granite and granodiorite. According to zircon SHRIMP U-Pb isotope dating,the crystallization ages of these four rock types are 162±3 Ma,169.3±3.1 Ma,157.5±1.7 Ma and 158.0±2.7 Ma,respectively,or Middle-Late Jurassic. The geochemistry of the rocks shows that the Wulong pluton belongs to the calc-alkaline to high-K calc-alkaline,peraluminous and mesothermal granitic magma series,with enrichments in large ion lithophile elements (LILE) such as Rb,Th,U and K and depletions in high field strength elements (HFSE) such as Nb,Ta,P,and Ti. The ε_Hf(t) values range from -39.7 to -22.9,and the t_DM2 values are between 3 711 Ma and 2 653 Ma. The ε_Nd(t) values vary from -23.8 to -20.2,and the t_DM2 values are between 2 782 Ma and 2 487 Ma. These results show that the magma source is Archean to Paleoproterozoic crustal materials. Combining this information with Pb isotopes and the microstructural characteristics of quartz,feldspar and mica,it is believed that the large-scale Jurassic Wulong pluton on the Liaodong Peninsula is S-type granite,which recrystallized from Paleoproterozoic granites and Liaohe Group rocks in-situ in the upper crust affected by Late Jurassic (ca. 160 Ma) crustal remelting. The pluton was formed in a compressional orogenic tectonic setting influenced by the subduction of the Paleo-Pacific plate during the Middle-Late Jurassic.