郯庐断裂带中生代以来基性岩墙年代学和地球化学

As one important Fault series, there were many invstigation on the extension of Tan-Lu. However, the stuies were focused on extensional basin and intermediate-acid magmatisms. Nowadays, the mafic dykes has been an important research techniques due to their diagenetic setting-lithosphere extension. Although the close relation between lithosphere extension and mafic dykes during late Cretaceous and early Tertiary in Tan-Lu fault, what is the relation is questionable. Based on the relation between mafic dykes and continental dynamics, as well as on the chemical and physical processes of Tan-Lu extension, this project will select the mafic dykes from Five representative areas during Tan-Lu extension, based on the invigation on chronologcal and geochemistric test, to build a precise chronological framework and define the source, the temporal variation and petrogenesis of the mafic dykes. Moreover, this project will show the time, stage, variation,dynamical mechanism and background of Tan-Lu extension.

郯庐断裂带是我国最重要的断裂带之一，以往对其伸展作用的研究已有较多积累，但这些研究主要偏重于伸展盆地和中酸性岩浆岩方面。作为岩石圈伸展背景下的特征产物，基性岩墙已成为大陆动力学的重要研究手段。虽然已注意到郯庐断裂带晚白垩世-早第三纪岩石圈伸展与基性岩墙之间具有密切的联系，但断裂带伸展与基性岩墙之间究竟存在何种联系，却是尚未很好解决的重要科学问题。本项目从大陆动力学与基性岩墙关系的研究思路出发，围绕中生代以来郯庐断裂带伸展的化学与物理过程，选择断裂带伸展期形成的5个代表性地区基性岩墙为研究对象，通过精确厘定其成岩年龄（40Ar/39Ar和锆石U-Pb原位定年），准确获取地质学和地球化学信息（元素和Sr、Nd、Pb、Hf、O同位素），建立该断裂带中生代以来幔源岩墙精确年代学格架，确定基性岩墙源区性质、时空变化规律及其成因。从而揭示郯庐断裂带伸展活动的时限、期次、变化规律、动力学机制和背景。

郯庐断裂带中生代以来发生了明显的岩石圈伸展，但此方面的研究目前仍相对薄弱。基性岩墙为岩石圈伸展背景的典型产物，其研究对岩石, 圈伸展具有非常重要的意义。郯庐断裂带中生代以来基性岩墙以煌斑岩和辉绿岩为主，辉绿玢岩含量较少。年代学和地球化学研究显示，断裂带上基性岩墙成岩时代范围为215-114 Ma，碱质含量性对较高。另外，基性岩墙以大离子亲石元素富集（Ba、U、K、Pb、Sr）和高场强元素亏损 （Nb、Ta、Ti、P），高的Sr初始比值(0.7055-0.7104)和负的ε Nd (t) (-8.3~-19.6)特征，变化较小的206Pb/204Pb (16.44.15-17.17)、207Pb/204Pb (15.44-15.54) 和208Pb/204Pb (36.49-37.68)，以及负的ε Hf (t) (-31.4~-8.4) 特征。已有研究表明，郯庐断裂带中生代以来基性岩墙皆为富集岩石圈地幔的部分熔融作用的产物，源区受到来自俯冲扬子地壳物质或大陆沉积物以及拆沉大陆下地壳交代作用。母岩浆在上升侵位过程发生了橄榄石、辉石和含Ti相物质的分离结晶作用，但几乎不受地壳物质的混染作用的影响。本项目共发表SCI论文11篇（Precambrian Research, Acta Geologica Sinica, 岩石学报，Journal of Asian Earth Sceicnes、Ore Geology Review、Journal of Geodynamics、矿床地质）、3篇核心期刊论文（矿物学报、矿物岩石地球化学通报）。出版外文专著2部（排名第一）。