【作者】 石建基；

【导师】 吴淦国； 余心起；

【作者基本信息】 中国地质大学（北京） ， 构造地质学， 2010， 博士

【摘要】 近年的研究已证明长乐-南澳变质带是一条大型的中生代韧性剪切带。但在变形的期次、运动特征及大地构造性质等方面仍有较大的争议。长乐-南澳变质带可分为东、西两个亚带。东亚带变质地层包括前泥盆系亲营山组及上三叠统-下侏罗统(未分)。东亚带的上三叠统-下侏罗统(未分)与西亚带上三叠统-下侏罗统陆相碎屑沉积地层不同,发育大量中性、酸性火山岩,与闽西-粤东北地区下侏罗统藩坑组等火山碎屑-沉积地层相似,仍属浙闽沿海中生代火山岩系的一部分。以地质接触关系为主要依据,结合岩石学、岩石化学、地球化学及锆石微区(LA-ICPMS)U-Pb同位素测年研究,对变质带中变质变形侵入岩进行解体,划分出早侏罗世(早于149.3 Ma)、晚侏罗世(145.4 Ma)、早白垩世早期(139.4~137 Ma)等三期侵入岩。早侏罗世壳-幔混合源花岗岩形成于构造体制由挤压向拉张的转换的环境(;晚侏罗世侵入岩属与俯冲作用有关的同碰撞花岗岩;早白垩世早期侵入岩是在构造体制由挤压向拉张转化期形成的壳-幔混合源花岗岩。三期侵入岩在分布上的叠置关系、不同变质变形特征,糜棱叶理的切割关系等,表明该变质带在中生代发生了三期韧性剪切变形、变质作用:第一期为中侏罗世末-晚侏罗世初(早于149.3 Ma,约165 Ma)低角闪岩相变质、深部构造层次的长石相塑性变形;第二期为晚侏罗世(152~141Ma)高绿片岩相变质、中深部层次的长石-石英相塑性变形;第三期为早白垩世早期(130~115.9 Ma,约120 Ma)低绿片岩相变质、中-浅层次石英相的韧-脆性变形。根据各类面理、线理及指向构造的统计分析,确定韧性剪切带在不同时期的运动特征,并据变形石英、长石斑晶的长短轴统计等方法概算了剪切位移量:第一期为南西西向北东东右行-推覆型韧性剪切变形,位移量约54 km;第二期为北北西向南南东左行—逆冲韧性剪切变形,位移量达84 km;第三期为具正断层性质的右行走滑韧—脆性剪切变形(主剪切面反转倾向南东),位移量不足2 km。结合东南沿海地区地球物理、大地构造学研究成果,认为该变质带是在中侏罗世东南沿海地区由特提斯构造域向太平洋构造域转换的背景下,因伊佐奈崎板块沿日本中央构造线—台湾中央山脉一线俯冲,形成的一系列派生韧性剪切带之一。变质带活动受板块俯冲的方向及速率的制约。更多还原

【Abstract】 Changle-Nan’ao metamorphic zone was proved to be a huge Mesozoic ductile shear zone. However, the geological world is divided on its metamorphic and deformation stages, kinematics characteristics and geotectonic property.By stratigraphic division and correlation, the metamorphic stratum in east sub-zone of this metamorphic zone can be divided into the pre-Devonia Qinyingshan group. The latter, which includes many intermediate and acid volcanic rocks, is different from the the upper Triassic-lower Jurassic stratum in west sub-zone, but is similar to the lower Jurassic Fankeng group in southwestern Fujian. Thus, it belongs still among the volcanic system in the Zhejiang-Fujian coastal.According to the geological contact relations, the petrographica, petrochemical, geochemical characteristics, Metamorphic and deformed granitic rocks in this metamorphic zone was divided to early Jurassic (earlier than 149.3 Ma), late Jurassic (145.4 Ma), and early Cretaceous Intrusive rocks (139.4-137 Ma). The early Jurassic intrusive rocks, which magma belongs to the crust-mantle mixed type (I-type), were formed during changing of tectonic system (PAG-type); The late Jurassic intrusive rocks, which magma belongs to the crust type (S-type), were syn-collisional pluton (ACG-type); The early Cretaceous intrusive rocks, which magma also belongs to the crust-mantle mixed type (I-type), were formed during changing of tectonic system (KCG-type).In Mesozoic, three stages of tectonic deformation and dynamic metamorphism were developed in this Metamorphic zone: the first is characterized by deep structural level plastic deformation and low amphibole facies metamorphism, which took place at the end of middle Jurassic-early stage of late Jurassic (about 165 Ma); the second is characterized by middle-deep structural level ductile shear deformation and high greenschist facies metamorphism , which occurred in late Jurassic (152-141 Ma); The third was characterized by mid-shallow brittle-ductile shear strain and low greenschist facies metamorphism , which happened on the middle period of early Cretaceous (about 125 Ma). Kinematic characteristics of these shear deformation were respectively dextral-thrusting from NWW to SEE (displacement about 52 km), sinistral-thrusting from NNW to SSE (displacement about 84 km), and normal-dextral strike slip (displacement about 2 km).After comprehensive analysis of the geological, geotectonic and geophysical signatures, the author believes that, during changing of the tectonic system from Tethyan tectonic domain to Marginal west-pacific tectonic domain, Changle-Nan’ao metamorphic zone is one of shear zones which derived from the subduction zones along Median-Tectonic-Line in Japan and the Central-Range in eastern Taiwan, where izanag plate divided into the Eurasian plate.更多还原