冀东南部-辽宁南部地区太古宙地壳生长方式研究

This proposal is going to study Archean lithological assemblages of the supracrutal rock series and representative plutonic gneisses, intrusive bodies that exposed in Southern East Hebei and Southern Liaoning provinces, to determine magmatic and metamorphic times, especially emphasized the studies for the mafic and ultramafic rocks, and some representative granitoid lithological associations in the Archean terranes，to ascertain times, petrogenesis of these magmatic rock assemblages,and nature and features of their magmatic source regions, further to analyze their crustal and mantle nature and interactive processes, crustal growth models, including crustal formation,reworking and recycling geodynamic processes by the analyses in petrochemistry, trace elements and Nd-Pb itotopes of representative whole-rock samples, combining with U-Th-Pb-Lu-Hf-O isotopes and trace elements for some accessory minerals of variously genetic zircon and monazite and so on. Integrated with systematic studies in U-Th-Pb-Lu-Hf-O isotopes and trace elements for detrital zircon and other accessory minerals from metamorphic sedimentary rocks of supracrustal rock sequences, nature,timings and features of lithological assemblages consisting of their provenances will be determined, to discover the signatures of older than 3.0 Ga crustal materials. Using the coupling relationships between magmatism and metamorphism in every geological stages determines their thermodynamic backgrouds,to establish geological event series of every geological units in the research terrane, and their tectonic settings of mantle plume, plate or/and mantle plume -plate joint in every developed stages of the geological units，and finally to build up Archean crust growth models in the studied range by synthetic geological comparisions among geological units within the research terrane and between the research regions and other Archean metamorphic basement blocks in the North China Craton.

本申请拟研究冀东南部-辽宁南部变质基底各地块太古宙表壳岩系、代表性深成片麻岩和侵入体的岩石组合，确定不同单元岩浆和变质作用期次，特别注重不同期次铁镁质岩石组合研究，并选择代表性花岗质岩石组合，进行全岩样品微量元素、Nd-Pb同位素体系和不同成因锆石、独居石等副矿物U-Th-Pb-Lu-Hf-O同位素和微量元素的系统研究，确定各岩石组合形成和变质时代、岩石成因、岩浆源区性质与特征，分析不同阶段壳幔性质与作用过程，确定其地壳生长方式，包括地壳形成、活化与再循环及其动力学过程。进行变质沉积岩中碎屑锆石等副矿物同位素和微量元素系统研究，分析其蚀源区岩石组合性质、时代与特征，寻找老于3.0Ga地壳物质记录。通过变质变形演化及变质作用和岩浆作用之间耦合关系确定各单元不同时期热动力学背景，建立各地质单元地质事件序列，分析其不同阶段地幔柱、板块构造或者二者联合作用构造体制，通过对比确定太古宙地壳生长方式。

本项目通过冀东南部-辽宁南部代表性太古宙变质火山岩系和花岗质岩石的岩石组合地质学和岩石学、全岩主、微量元素、锆石U-Th-Pb -Lu-Hf-O同位素研究，确定了各岩石组合形成和变质时代、岩石成因和不同阶段壳幔作用过程。（1）在歪头山地区发现至少~200km2以上的~3.45 Ga的古老地块，证明鞍山-本溪古老地核区大量存在老于~3.3Ga的地质记录；（2）在歪头山地区以北到新宾南地区确定了一系列~2.7 Ga的岩石记录构成了近东西向展布的~2.7Ga TTG片麻岩带，形成于大洋岛弧带构造背景; (3)确定了辽南地块存在的新太古宙变质基底，是被胶-辽-吉构造带和郯庐断裂肢解的新太古代活动大陆边缘残块；（4）冀东-辽西地区太古宙变质基底具有明显的岩石组合分带性，由西北向东南依次分为大洋地壳变质玄武岩带、岛弧构造带、活动大陆边缘和碰撞后伸展带（富钾花岗质岩石带）；（5）其中南部的富钾花岗质岩石带主要由2550-2526 Ma太古宙赞歧岩和2527-2511 Ma二长花岗岩-正长花岗岩组成，前者岩浆起源于交代地幔楔部分熔融，后者岩浆形成于赞岐岩类片麻岩、变质杂砂岩的部分熔融，岩浆作用发生于活动大陆边缘构造背景；（6）辽西-冀东地区存在三个NEE-SWW向构造带形成于多阶段洋壳后展式向南部大陆边缘下俯冲、洋壳多阶段俯冲导致的大洋岛弧带与南部活动大陆边缘拼贴、碰撞的动力学过程。（7）本项目共发表学术论文25篇，其中本项目第一标注国际SCI论文6篇，第一标注的国内SCI论文1篇， 第二标注的国际SCI论文7篇，第二标注的国内SCI论文1篇、第三标注的国际SCI论文7篇，第三标注的国内SCI论文3篇。本项目综合研究成果表明新太古代华北克拉通北部主要是通过大洋岛弧带、大洋弧与活动大陆边缘拼贴与碰撞的侧向增生过程形成的，可能代表了全球新太古代壳幔作用和最主要的大陆地壳生长动力学模式。