This paper reports zircon U-Pb dating, geochemical and Hf isotope data of the biotite diorite and syenogranite at the Jinchanggou gold orefield in southern Jilin, NE China. Zircon grains from the biotite diorite and syenogranite are euhedral-subhedral prisms, display oscillatory- zoning, and have Th/U ratios ranging from 0.48 to 1.54, indicating a magmatic origin. Zircon U-Pb dating results indicate that both the biotite diorite and syenogranite were formed in the Late Triassic. The syenogranite has SiO2=71.58%‒72.74%, Al2O3=10.89%‒13.09%, K2O=6.03%‒5.55%, (K2O+Na2O)= 6.11%‒6.68%, A/CNK=0.75‒1.32, and Ca, Mg, and Fe are low. The syenogranite is characterized by right-dipping chondrite- normalized REE patterns, with LREE/HREE=5.56‒9.53, (La/Yb)N=6.33‒10.12 andδEu=0.55‒0.63. In trace element spider diagram, large ion lithophile elements (LILEs), such as Rb, Ba and K are enriched, and high field strength elements (e.g. Nb, Ta and Ti) and P are depleted. The syenogranite has low Sr concentration of 58.5×10–6 to 113.5×10–6 and high Yb of 2.97×10–6 to 3.91×10–6. The zircon grains from the syenogranite haveεHf(t) values of –15.3 to –9.0, and two-stage model agesof 1.83 Ga to 2.22 Ga. These data suggest that the syenogranite belongs to peraluminous shoshonitic series, which is generally similar to S-type granite. Thus, we conclude that the primary magma of the syenogranite was likely derived from partial melting of felsic lower crust. The biotite diorite have SiO2=54.86%‒63.01%, Al2O3=15.70%‒16.55%, (K2O+Na2O)=6.64%‒8.66%, A/CNK=0.84‒0.96, CaO=3.05%‒4.90% and MgO=2.79%‒4.67%. The biotite diorite is characterized by right-dipping chondrite-normalized REE patterns, with LREE/HREE=15.94‒24.57, (La/Yb)N=24.61‒43.09,δEu=0.78‒0.95. Large ion lithophile elements (LILEs), such as Rb, Ba and K are enriched, while the high field strength elements (e.g. Nb, Ta and Ti) and P are depleted. The biotite diorite has high Sr=735×10–6‒1560×10–6, and low Yb=0.92×10–6‒1.23×10–6. TheεHf(t) values of zircon grains from the biotite diorite range from –12.9 to –8.5, and their Hf two-stage model agesvary from 1.82 Ga to 2.07 Ga. Based on the characteristics mentioned above, it is concluded that the primary magma of the biotite diorite is likely derived from partial melting of mafic crustal materials. In combination with the published data, the Mesozoic magmatism in Southern Jinlin has chronological framework similar to that of Eastern Liaoning and Eastern Shandong peninsula, meaning that plutons in the three areas constitute a NE-trending Mesozoic magmatic belt. Considering the tectonic history, we propose that that the formation of the Late Triassic plutons was related to the collision the Yangtze and North China cratons.%本文报道了吉林南部金厂沟矿区黑云母闪长岩和正长花岗岩的锆石LA-ICP-MS U-Pb年龄、锆石Hf同位素和岩石地球化学资料,以确定该区岩体的形成时代、源区性质和构造背景。黑云母闪长岩和正长花岗岩的锆石U-Pb年龄分别为221.5±1.1 Ma和227.4±1.9 Ma,表明岩体形成于晚三叠世。正长花岗岩富硅、铝、碱和贫钙、钠、镁及铁,稀土元素配分曲线为右倾型,微量元素蛛网图上表现为大离子亲石元素(Rb、Ba、K)富集和高场强元素(Nb、Ta、Ti)及P亏损,锆石εHf(t)介于–15.3~–9.0之间, Hf二阶段模式年龄(tDM2)介于1.83~2.22 Ga之间。以上特征表明,该期正长花岗岩为准铝质‒过铝质钾玄岩系列,与 S 型花岗岩特征相似,岩浆起源于古元古代长英质下地壳在低压环境下的部分熔融。黑云母闪长岩具有富硅、铝、钾、钠和贫镁的特点,稀土元素配分曲线为右倾型,微量元素蛛网图上表现为富集大离子亲石元素Rb、Ba、K 及活泼的不相容元素 Th 和 U,相对亏损高场强元素 Nb、Ta、P 和 Ti,具有高 Sr(735×10–6~1560×10–6),低Yb(0.92×10–6~1.23×10–6)的特征。锆石εHf(t)为–12.9~–8.5,二阶段Hf模式年龄(tDM2)为1.82~2.07 Ga。结合前人研究成果,认为黑云母闪长岩起源于深部的古元古代镁铁质下地壳的部分熔融。综合分析吉南地区已有的年代学资料和区域构造研究成果,认为吉南中生代岩浆作用主要发生在晚三叠世、早中侏罗世和早白垩世,与辽东和胶东地区具有相同的年代学格架并构成一条北东向岩浆岩带。吉南地区晚三叠世黑云母闪长岩和正长花岗岩是扬子板块与华北板块碰撞拼合的产物。
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