花岗岩是大陆地壳最主要的组成部分，记录了大陆地壳的再造和生长。因此对花岗岩的成因及源区性质的探究，对于解析大陆地壳的形成以及造山带深部地球动力学过程具有重要的意义。本文选取北秦岭造山带古生代和晚中生代花岗岩为研究对象，进行了详细的锆石U-Pb年代学、全岩Sr-Nd-Pb同位素和矿物化学研究，探讨了物质源区和不同岩浆过程对花岗岩成分的影响。本文获得的主要认识如下： (1)选取北秦岭古生代灰池子和商南岩体为研究对象，探究古生代北秦岭地体花岗岩成因及地壳演化。锆石年代学研究表明，灰池子岩体侵位于423±7 Ma～424±10 Ma。地球化学特征表明灰池子岩体为I型花岗岩，全岩⁸⁷ Sr／⁸⁶Sr〓 (0.7050～0.7054)和ε〓(t)(2.9～0.4)值显示灰池子岩体是起源于新元古代新生下地壳部分熔融的产物。灰池子花岗岩具有相对高的Sr／Y、(La／Yb)〓比值，不明显的Eu的负异常，显示较深的岩浆源区。商南岩体侵位于424±11 Ma与灰池子岩体同期，商南岩体样品可以分为两组，地球化学特征显示，第一组样品具有高的SiO₂含量，为S型花岗岩。相对高的⁸⁷ Sr／⁸⁶Sr(0.7131-0.7158)初始值和低的ε〓(t)值(-7.1～10.5)，显示其源区为富斜长石而贫粘土矿物的杂砂质岩石，类似于北秦岭内出露的成熟度较低的变沉积岩：另一样品具有相对低的SiO₂含量，具有类似于灰池子岩体的Sr-Nd同位素特征(⁸⁷ Sr／⁸⁶Sr〓=0.7057；ε〓(t) =1.0；T〓=1.1 Ga)，说明新生地壳在源区的贡献。结合北秦岭古生代花岗岩的地球化学特征和时空分布特点，我们认为，灰池子和商南岩体形成于伸展环境初期，新元古代新生地壳部分熔融形成灰池子岩体，熔融的基性岩石不完全混染表壳岩石形成商南岩体。 (2)源区物质成分是决定花岗岩岩石学和地球化学特征的首要因素。本文选取侵位于北秦岭地体北缘的牧护关和蟒岭岩体的锆石U-Pb年代学和地球化学成分的研究，为探究北秦岭地体基底物质组成和晚中生代构造演化提供了契机。两个岩体中的二长花岗岩具有高的SiO₂含量(69.3—77.0 wt.％)，低Mg〓值(0.21—0.38)，富集LREE，Th，U和Pb元素，亏损HFSE，且存在Eu的负异常。蟒岭岩体二长花岗岩具有较高的Sr／Y、(Dy／Yb)〓和(La／Yb)〓比值，较低的SiO₂含量和不明显的Eu的负异常，推测蟒岭岩体二长花岗岩比牧护关岩体二长花岗岩具有更深的形成深度。Sr-Nd同位素特征表明，牧护关和蟒岭岩体花岗岩具有相似的岩浆来源，均来源于不均一的岩浆源区(牧护关岩体花岗岩⁸⁷ Sr／⁸⁶Sr〓=0.7070～0.7103，ε〓(t)=-7.0～15.0；蟒岭岩体花岗岩⁸⁷ Sr／⁸⁶Sri= 0.7054～0.7083，ε〓(t)=-7.9～16.0)。锆石U-Pb定年结果可以分为两类：(1)岩浆锆石(153-140 Ma)；(2)继承锆石，可以分为五个群组，分别为新太古代-古元古代(2633—2103 Ma)、古元古代-中元古代(1988—1377 Ma)、新元古代(975—605 Ma)，古生代(535—382 Ma)，晚古生代-早中生代(329—187 Ma)。牧护关和蟒岭岩体花岗岩的地球化学特征显示，它们来源于类似于北秦岭新元古代新生下地壳与古老的基底物质(类似于华北南缘熊耳群)的混合。牧护关和蟒岭岩体较低的放射性成因Pb同位素组成也支持了华北南缘基底物质的参与。结合北秦岭晚中生代花岗岩的时空分布特点，北秦岭地体内广泛分布的晚侏罗-早白垩世花岗质岩石形成于伸展环境中，地幔物质的上涌。形成这些花岗岩的熔体来源于逆冲俯冲至北秦岭地体之下的华北南缘基底物质与新元古代新生变基性岩的混合。 关键词：北秦岭；中生代；花岗岩；古生代；锆石U-Pb；Sr-Nd-Pb同位素；矿物化学

 Granite is the most important component of the continental crust, which records the reconstruction and growth of the continental crust. Therefore, the genesis of granites might provide great significance to explore the continental crust structure and composition. And provide an optimal window to unraveling the geodynamic process. In this study, we present zircon U-Pb age, whole-rock Sr-Nd-Pb isotopic and mineral element analysis for the late Mesozoic and Paleozoic granites in the North Qinlng terrane. The main achievements are obtained as follows: (1)The Huichizi and Shangnan plutons are selected from the North Qinling terrane, to explore the genesis and crustal evolution of granites in the Paleozoic North Qinling terrane. New LA-ICPMS zircon U-Pb age dating results indicate that the Huichizi pluton was emplaced at ca. 423 ± 7 Ma. Geochemical characteristics indicate that the Huichizi pluton belong to I-type granite. Sr-Nd isotopic data (⁸⁷ Sr／⁸⁶Sr〓= 0.7050～0.7054; ε〓(t) = 2.9～-0.4) indicate that the Huichizi pluton is the product of partial melting of the Neoproterozoic juvenile lower crust. They have relatively high Sr/Y and (La/Yb)〓 ratios, and not obvious Eu negative anomaly, showing a deep magma source with garnet stability in source area. LA-ICPMS zircon U-Pb age dating results indicate that the Shangnan pluton was emplaced at 424 ± 11 Ma, coeval with Huichizi pluton. According to geochemical characteristics, the Shangnan pluton could divided into two group. The first group samples belong to S-type granites. They have relatively high ⁸⁷ Sr／⁸⁶Sr〓, ratios (0.7131-0.7158) and low ε〓(t) (-7.1 to -10.5) ratios, implying a plagioclase rich greywacke source, similar to the North Qinling metasedimentary rock; The second group has a relatively low SiO₂ content and has Sr-Nd isotopic characteristics similar to the Huichizi pluton (with ⁸⁷ Sr／⁸⁶Sr〓=0.7057; ε〓(t) =1.0; T〓 =1.1 Ga), indicating the contribution of the juvenile continental crust in the source. Combined with the geochemical characteristics and temporal and spatial distribution characteristics of the Paleozoic granites in the North Qinling terrain, we tend to suggest that the Huichizi and Shangnan pluton formed in an extensional environment, and the Neoproterozoic juvenile crust is partially melted to form the Huichizi pluton, then the mafic melt contaminated with metasedimentary rocks to form the Shangnan pluton. (2)The source material is the primary factor to determine the geochemistry of granite. New zircon U-Pb dating and geochemical characteristics of the Muhuguan and Mangling plutons in the North Qinling terrane, it provide an opportunity for exploring the basement material composition and the tectonic evolution of the North Qinling terrane. Monzogranites from the two plutons are characterized by high SiO₂ contents (69.3-77.0 wt.%), low Mg numbers (0.21-0.38), enriched light rare-earth elements, Th, U, and Pb, depleted high-field-strength elements, and negative Eu anomalies. The source of the Mangling monzogranite is interpreted to have been deeper than that of the Muhuguan monzogranite, on the basis of its higher Sr/Y, (Dy/Yb)〓, and (La/Yb)〓 ratios and lower SiO₂ content. Sr-Nd isotopic compositions indicate similar but heterogeneous magma sources for the two granites: ⁸⁷ Sr／⁸⁶Sr〓= 0.7070-0.7103 and ε〓(t) = -7.0 to -15.0 for the Muhuguan granite, and ⁸⁷ Sr／⁸⁶Sr〓 = 0.7054—0.7083 and ε〓(t) = -7.9 to -16.0 for the Mangling granite. The zircon U-Pb age results fall into two groups: (1) syn-magmatic zircons (153 to 140 Ma); and (2) inherited zircons that define five age clusters, namely Neoarchean-Paleoproterozoic (2633-2103 Ma), Paleoproterozoic to Mesoproterozoic (1988-1377 Ma), Neoproterozoic (975-605 Ma), Paleozoic (535-382 Ma), and Late Paleozoic - Early Mesozoic (329-187 Ma). These data are consistent with a derivation of the granites by mixing between melted underplated juvenile crust within the NQT and melts from basement rocks similar to those of the Xiong'er Group within the southern margin of the North China Craton (S-NCC). The involvement of S-NCC material is also supported by the unradiogenic whole-rock Pb isotopic composition of the Muhuguan and Mangling granites, which is similar to that of the S-NCC basement rocks. These results suggest that the widespread Late Jurassic to Early Cretaceous granitoid intrusions within the NQT were generated in an extensional geological setting associated with mantle upwelling. Melts were derived from underthrust S-NCC basement material and juvenile Neoproterozoic basaltic rocks. Key Words: North Qinling; Late Mesozoic; Granite; Paleozoic; Zircon U-Pb dating; Sr-Nd-Pb isotopes