【摘要】 算井子埃达克质花岗岩体由中粗粒片麻状黑云母花岗闪长岩、中粗粒黑云母花岗闪长岩和中细粒黑云母二长花岗岩3个岩相单元组成,其为同一次岩浆熔融事件过程中曾经发生过三次岩浆侵入活动而形成的深成岩体。LA-ICP-MS锆石U-Pb定年结果表明,算井子埃达克质花岗岩体侵位于早石炭世（350.0～351.7Ma）,为海西中期的产物。该岩体总体富硅（SiO₂为67.81%～70.93%）,富铝（Al₂O₃为14.94%～16.07%）,全碱含量中等（K₂O+Na₂O为6.01%～6.74%）,K₂O/Na₂O为0.37～0.69,富含钠质成分,而Ti、Ca、Fe和Mg（MgO为0.99%～1.61%）含量较低,（K₂O+Na₂O）/Al₂O₃为0.37～0.45,A/CNK为0.95～1.03,属于准铝质-弱过铝质钙碱性花岗岩。微量元素Sr含量(409×10^-6～548×10^-6)较高,而Y(8.1×10^-6～17.7×10^-6)和Yb(0.83×10^-6～1.73×10^-6)含量较低,总体上富集大离子亲石元素（LILE）K、Rb、Ba和高场强元素（HFSE）Th,而亏损高场强元素Nb、Ta和Ti,稀土元素的球粒陨石标准化配分曲线呈右倾型,轻重稀土分馏大,轻稀土富集且分异明显,而重稀土亏损且分异不显著,具轻微的铕异常（δEu=0.64～1.13）,与典型的埃达克岩特征相似。年代学及地球化学特征研究表明:（1）算井子岩体属准铝质-弱过铝质未分异的Ⅰ型花岗岩,并具有典型的埃达克岩特征;（2）岩浆源于俯冲板片流体交代地幔楔诱发下地壳玄武质岩石部分熔融源区,并在岩浆上升过程中混染了火山弧物质;（3）岩体形成于海西中期活动大陆边缘的火山弧环境,推测其南侧的塔里木板块和哈萨克斯坦板块的俯冲-碰撞效应可能一直持续到早石炭世。更多还原

【Abstract】 The Suanjingzi adakitic granites consist of three intrusive rocks,namely,medium-to coarse-grained gneissic biotite granodiorite,medium-to coarse-grained biotite granodiorite and medium-to fine-grained biotite monzonite granite,which were the products of three magmatic intrusive activities of the same magmatic melting event.Zircon LA-ICP-MS U-Pb dating result shows that the Suanjingzi adakitic granites emplaced in the Early Carboniferous between 350.0 Ma and 351.7 Ma（the Middle Hercynian Period）.Geochemically,the pluton is characterized by high content of SiO₂（67.81% ～70.93%）and Al₂O₃（14.94%～16.07%）,middle content of K₂O+Na₂O（6.01%～6.74%）,lower ratios of K₂O/Na₂O（0.37～0.69）,and low content of Ti,Ca,Fe,and MgO（0.99%～1.61%）,with the ratios of（K₂O+Na₂O）/Al₂O₃ varying between 0.37 and 0.45,and the ratios of A/CNK between 0.95 and 1.03.All these features indicate that the pluton belongs to peraluminous-weakly metaluminous calc-alkaline granites.In respect of trace elements,the rocks have a high content of Sr(409×10^-6～548×10^-6),and the low contents of Y(8.1×10^-6～17.7×10^-6)and Yb(0.83×10^-6～1.73×10^-6),and enriched in LILE（K,Rb,Ba）and HFSE（Th）,but depleted in Ta,Nb and Ti.The chondrite-normalised REE distribution pattern of the Suanjingzi pluton displays a right dipping shape,distinct fractionation between LREE and HREE,enrichment of LREE and depletion of HREE,and unobvious Eu anomalies（δEu=0.64～1.13）,suggesting characteristic of the typical adakites.The geochronological and geochemical features of the Suanjingzi pluton indicate:（1）The Suanjingzi granitic pluton belongs to peraluminous-weakly metaluminous and unfractionated I-type granites with the typical adakite characteristics;（2） magmas were probably derived from partial melting of the lower crust basaltic rocks with the mantle wedge metasomatized by subducted slab-released fluids/melts,and contaminated by the volcanic arc components during magma uprising;（3）the pluton was probably formed in an active continental margin volcanic arc setting in the Middle Hercynian Period,and it can be deduced that the subduction-collision effect between the Tarim Plate and the Kazakhstan Plate continued to the Early Carboniferous in the Beishan Mountains.更多还原