富铁玄武岩微观结构与岩浆分异：以褚兰9亿年岩床为例

High-Fe basalts/gabbros occur in the layered complexes, anorthosite complexes and volcanic sequences; and they may occur with bimodal series and/or A-type granites; however, their petrogenesis is controversial as whether their features are originated from source region(s) (e.g., plume head) or magma processes (e.g., immiscibility, fractional crystallization). Here we propose a comprehensive research including petrology, petro-chemistry, mineralogy, isotope geochemistry and geochronology study on the ~900 Ma Chulan sills in North China. Igneous series and petrographic features, variations of whole-rock (e.g., major and trace elements, Sr-Nd-Pb isotopes) and mineral (elemental and Sr-Nd isotopes of rock-forming minerals, and element and Hf-O isotopes of accessory minerals) inside profiles of sills, micro-textures and in-situ compositions of rocks (mineral textures, reactive textures, textures of glasses, etc.), composition of melt inclusions, and controlling factors of crystallization will be analyzed. It aims to reveal the nature and origin of their primary magma and the magma differentiation processes of the high-Fe basalt and the tectonic environments of the Chulan sills, as well as the nature of the Neoproterozoic igneous event. To characterize magma processes through micro-textures and to reveal controlling factors of high-Fe basalt are two key issues of this proposal.

富铁玄武岩/辉长岩常产出于层状侵入杂岩、斜长岩杂岩和火山岩中，可伴生双峰式岩浆岩以及A型花岗岩，其成因或与特殊源区（如，地幔柱头部）有关，或与特定岩浆过程（不混熔作用、结晶分异作用等）有关，备受争议。本项目拟以华北褚兰9亿年岩床为研究对象，运用岩石学、岩石化学、矿物学、同位素地球化学和年代学等方法，围绕岩床群岩浆系列与岩性变化、岩床个体剖面全岩（主微量和Sr-Nd-Pb）及矿物成分（造岩矿物主微量和Sr-Nd同位素、副矿物成分和Hf-O同位素）变异、岩浆岩微观结构（矿物结构、反应结构、隐晶质结构等）及微区成分、熔体包裹体成分、结晶过程控制因素等开展研究，从而揭示富铁基性岩床的母岩浆性质、来源与岩浆分异过程，揭示褚兰岩床的构造背景和新元古代岩浆事件的性质。微观结构对岩浆过程的表征，以及富铁玄武岩形成的控制因素是本项目的关键科学问题。

富铁辉长岩代表的岩浆作用过程在地质历史中有特殊的意义。本项目以华北褚兰9亿年岩床为研究对象，运用岩石学、岩石化学、矿物学、同位素地球化学和年代学等方法，围绕岩床群岩浆系列与岩性变化、岩床个体剖面全岩及矿物成分变异、岩浆岩微观结构及微区成分、结晶过程控制因素等开展研究，从而揭示富铁基性岩床的母岩浆性质、来源与岩浆分异过程，揭示褚兰岩床的构造背景和新元古代岩浆事件的性质。研究揭示，该期富铁辉长岩与其特殊分离结晶过程有关，其岩浆作用指示新元古代重要裂解事件,代表地球中年期结束阶段重要岩浆活动。本项目发表论文十多篇，第1或2标注论文12篇，其中，SCI论文11篇，培养博士生3人。