【作者】 刘勇；

【导师】 李廷栋； 肖庆辉；

【作者基本信息】 中国地质科学院 ， 构造地质学， 2011， 博士

【摘要】 本文重点考察湘南地区主要基性岩和花岗岩类岩体,并在深入调研部分关键岩体和全面收集前人研究成果和资料的基础上,通过高精度锆石U-Pb同位素定年统一平台,建立了研究区燕山期火成岩年代学格架；利用TAS分类图解和O’ Conner的CIPW An-Ab-Or方法建立统一命名平台,对研究区花岗岩类进行了统一命名；在此基础上分析厘定了燕山期火成岩组合；利用年代学和岩石地球化学方法,论证了湘南地区燕山期花岗岩是软流层上涌导致的壳-幔岩浆混合作用的产物,初步提出了研究区燕山期花岗岩成因模式,取得了以下成果和认识：1、利用LA-ICPMS U-Pb统一测年平台测试了湘南燕山期花岗岩、基性岩以及暗色闪长质微细粒包体的年龄,据此提出了研究区燕山期火成岩的年代格架。2、应用侵入岩TAS分类图解和O’ Conner(1965)的CIPW An-Ab-Or三角图解,对研究区燕山期花岗岩类进行了统一分类命名,为厘定和修正研究区的花岗岩岩石的命名提供了依据。本文和收集的数据经统一命名处理后表明,研究区燕山期花岗岩的岩石类型主要为花岗岩、花岗闪长岩、石英二长岩,不存在洋壳向陆壳俯冲过程中产生的TTG组合。因此,研究区燕山期花岗岩形成的构造背景可能不是原先多数人认为的是太平洋向西俯冲的结果。3、在统一测年平台和岩石命名平台处理数据的基础上,提出了湘南地区燕山期五个阶段的火成岩组合,它们是：中-晚三叠世火成岩组合、中侏罗世火成岩组合、中-晚侏罗世火成岩组合、晚侏罗世火成岩组合以及早白垩世火成岩组合。4、利用年代学和地球化学等方法确定了研究区宁远碱性玄武岩是亏损地幔软流层上涌的产物。通过对湘南地区花岗岩类、玄武岩类、穿切花岗岩的基性岩脉和花岗岩中的暗色闪长质微细粒包体的岩石学、矿物学、年代学、岩石地球化学、同位素学以及Lu-Hf同位素研究,发现研究区燕山期花岗岩是由于软流层上涌导致的壳幔二源岩浆混合作用的产物。5、在岩相学、年代学、地球化学和同位素研究的基础上,结合区域地质背景,初步厘定了骑田岭、铜山岭岩体壳-幔混合作用的过程。6、在以上研究工作的基础上,初步提出了研究区燕山期花岗岩成因模式和演化阶段。大致可以分为三个阶段,第一阶段是湘南软流层上涌导致岩石圈裂解与加热及软化作用阶段,为中侏罗世大规模花岗岩形成准备了条件；第二阶段是中侏罗世-晚侏罗世岩石圈发生全面拆沉垮塌,以及软流层大规模上涌作用阶段,在大规模软流层上涌形成的基性岩浆底侵作用下,大规模面型花岗岩突然形成；第三阶段是早白垩世岩石圈发生均衡调整,进入全面隆升阶段,在这一阶段,大规模花岗岩浆活动中止,以小规模酸性、基性岩脉岩墙侵入为主。更多还原

【Abstract】 The chronology framework was established preliminary in this paper based on collecting relative comprehensive former researches results and information, and focusing on the main basic rock and acid rock of the southern Hunan area, and carrying out the accurate U-Pb zircon isotopic dating of the samples. The granite in study area was named in unified with using the methods of CIPW An-Ab-Or diagram of the O’Conner. Base on that the igneous petrotectonic assemblages was analyzed and redefined That the results was proofed by using the chronology and the lithogeochemistry method, which the Yanshanian granites in southern Hunan was the intermingling results of the crust-mantle rock magma by the asthenosphere oceanic upwelling. And the diagenetic model of the Yanshanian granite was proposed preliminary. Researches have made the following understanding:1. The chronology framework of the Yanshanian igneous rock in study area was proposed based on that the ages of Yanshanian granite of the southern Hunan province, dark dioritic enclave and basic rock was redefined with the unified platform for dating of LA-ICPMS U-Pb.2. The Yanshanian granite in study area was named in unified with useing TAS classification diagram and CIPW An-Ab-Or Triangular diagram of O’Conner(1965) for the foundation date of redefiniting and correcting of the granite name in study area. The rock types of the Yanshanian granite in study area were mainly including granite, granodiorite and adamellite and without TTG association caused by the downgoing process of the oceanic crust to the continental crust. Thereby, the structural setting of the Yanshanian in the study area is not the former general result of the Pacific downgoing westward.3. The five-stage igneous rock association of the Yanshanian in the southern Hunan area: Middle-Late Triassic igneous association, the association of Jurassic igneous rocks, Middle-Late Jurassic igneous composition, Late Jurassic and Early Cretaceous igneous rock composition.4. The Yanshanian granite in study area was the result of the second source rocks intermingling of crust and mantle owing to asthenosphere upwelling through the researches on Petrology, Mineralogy, Geochronology, Geochemistry, Isotope, and Lu-Hf isotope of the granite, basalts, basic rock, ultrabasic dyke and maficmagmatic enclave of granite in the southern Hunan area5. The process of crust-mantle mixing of the mass of rock in Qitianling and Tongshanling were redefined under the back of regional geology and based on the Petrography, Geochronology, Geochemistry and Isotopic studies.6. The diagenetic model of the Yanshanian granite was proposed preliminary based on the above study. The model included three stages:the one stage was that the lithosphere of the southern Hunan area was being cracked and heated then soften effect. And the second stage was that the lithosphere of the Middle Jurassic-Late Jurassic was dismantled and flopped with effect of asthenosphere upwelling. And the third stage was that the lithosphere of the Early Crataceous begun isostatic adjust and stepped in uplift stage.更多还原