【摘要】 北山南带沙枣园复式岩体由中细粒黑云母花岗闪长岩、细粒黑云母石英闪长岩、中粒黑云母二长花岗岩和中粗粒黑云母正长花岗岩4个岩相单元组成。LA-ICP-MS锆石U-Pb定年结果表明,中细粒黑云母花岗闪长岩、细粒黑云母石英闪长岩和中粒黑云母二长花岗岩侵位于晚二叠世（252.1±1.9Ma、252.2±2.1Ma和248.8±3.5Ma）,为海西晚期的产物;而中粗粒黑云母正长花岗岩侵位于早三叠世（246.4±2.0Ma）,为印支早期的产物。该花岗质岩石均具有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特征。中细粒黑云母花岗闪长岩和细粒黑云母石英闪长岩具有较高的SiO₂、Al₂O₃和Na₂O含量,以及较低的MgO含量,强烈富集Sr而亏损Yb和Y,具轻微的铕异常（δEu=0.75～1.16）,表现出典型的埃达克岩特征;中粒黑云母二长花岗岩和中粗粒黑云母正长花岗岩总体富硅（SiO₂）、富钾（K₂O）、富碱（K₂O+Na₂O）,Al₂O₃含量中等,铕分别呈现负异常（δEu=0.45～0.73）和强负异常（δEu=0.02～0.08）。年代学及地球化学特征研究表明:①中细粒黑云母花岗闪长岩和细粒黑云母石英闪长岩属准铝质-弱过铝质的钙碱性Ⅰ型花岗岩,并具有典型的埃达克岩特征,中粒黑云母二长花岗岩属弱过铝质的高钾钙碱性Ⅰ型花岗岩,中粗粒黑云母正长花岗岩属弱过铝质的高钾钙碱性A2型花岗岩;②中细粒黑云母花岗闪长岩、细粒黑云母石英闪长岩和中粒黑云母二长花岗岩的岩浆来源于下地壳玄武质岩石部分熔融源区,并在上升过程中混染了下地壳物质,而中粗粒黑云母正长花岗岩的岩浆来源于年轻地壳中富含黑云母的变质泥岩部分熔融源区;③中细粒黑云母花岗闪长岩、细粒黑云母石英闪长岩和中粒黑云母二长花岗岩是俯冲-碰撞构造背景条件下的岩浆产物,而中粗粒黑云母正长花岗岩是同碰撞-碰撞后构造背景条件下的岩浆产物。更多还原

【Abstract】 The Shazaoyuan composite pluton consists of 4 intrusive granitic rocks in the southern Beishan Mountains,which include medium to fine grained biotite granodiorite,fine grained biotite quartz diorite,medium grained biotite monzonite granite,and medium to coarse grained biotite syenogranite.Zircon LA-ICP-MS U-Pb dating result shows that medium to fine grained biotite granodiorite,fine grained biotite quartz diorite and medium grained biotite monzonite granite intrusion occurred in the Late Permian（252.1±1.9 Ma,252.2±2.1 Ma and 248.8±3.5 Ma）,and is the product of the Late Hercynian Period.However,medium to coarse grained biotite syenogranite intrusion occurred in the Early Triassic（246.4±2.0 Ma）,and is the product of the Early Indosinian Period.Geochemically,they are all characterized by the chondrite-normalised REE distribution pattern displaying right skewed shapes,distinct fractionation between LREE and HREE,are enriched in light rare earth elements and depleted in heavy rare earthelements.In addition,medium to fine grained biotite granodiorite and fine grained biotite quartz diorite are characterized by high content of SiO₂,Al₂O₃ and Na₂O,low content of MgO,are strongly enriched in Sr and depleted in Y and Yb,with unobvious Eu anomalies（δEu=0.75～1.16）that are similar to the typical adakites.However,medium grained biotite monzonite granite and medium to coarse grained biotite syenogranite are characterized by high content of SiO₂,K₂O,and K₂O+Na₂O,modertate content of Al₂O₃,with negative Eu anomalies（δEu=0.45～0.73）and strongly negative Eu anomalies（δEu=0.02～0.08）respectively.The geochronological and geochemical features of the Shazaoyuan granitic pluton indicate:① medium to fine grained biotite granodiorite and fine grained biotite quartz diorite belong to peraluminous-weakly metaluminous calc-alkaline Ⅰ-type granites with typical adakite characteristics,medium grained biotite monzonite granite belongs to weakly metaluminous and high K calc-alkaline Ⅰ-type granite,but medium to coarse grained biotite syenogranite belongs to weakly metaluminous and high K calc-alkaline A2 type granite;and②the magmas of medium to fine grained biotite granodiorite,fine grained biotite quartz diorite and medium grained biotite monzonite granite were probably derived from partial melting of the lower crust basaltic rocks,and contaminated by the lower crust materials during magma intrusion,whereas the magmas of medium to coarse grained biotite syenogranite were derived from partial melting of the juvenile crust rich in biotite pelitic source;and ③medium to fine grained biotite granodiorite,fine grained biotite quartz diorite and medium grained biotite monzonite granite were the outcome of emplaced magmas in the subduction-collisional tectonic setting,but medium to coarse grained biotite syenogranite was the outcome of emplaced magmas in the syn-collisional and post-collisional tectonic setting.更多还原