【作者】 王伟；

【导师】 万渝生；

【作者基本信息】 中国地质科学院 ， 地球化学， 2010， 博士

【副题名】地质、SHRIMP锆石年代学和地球化学制约

【摘要】 鲁西新太古代花岗-绿岩带位于华北克拉通东部,主要由泰山岩群和花岗质岩石组成。早期研究认为,泰山岩群雁翎关组、山草峪组和柳杭组形成时代相同(-2.7 Ga),自下而上整合接触,构成单斜地层。表壳岩系以较小规模分布于不同时代花岗质岩石“海”中。七星台是鲁西花岗-绿岩带典型代表,泰山岩群表壳岩和各类太古宙花岗质岩石都有出露,是研究鲁西花岗-绿岩带形成演化的最理想地区之一。本论文以七星台地区为研究对象,在详细野外地质工作基础上,以SHRIMP锆石U-Pb年代学和岩石地球化学为主要研究手段,对泰山岩群和周边各类花岗质岩石的组成和形成时代进行了研究,重新拟定了柳杭岩组与山草峪岩组的含义和界线,确定了深熔作用的空间分布和时代,探讨了鲁西花岗-绿岩带的形成构造环境以及构造演化。取得主要成果和认识如下。(1)在原1：50000地质图基础上,对重点研究区进行了详细野外工作,获得许多新的重要发现,对原地质图作了重大修改。(2)“柳杭岩组”主要由变质块状和枕状玄武岩组成,存在火山凝灰质与沉积岩夹层。变质玄武岩具MORB组成特征。形成时代为2.71—2.75 Ga。(3)“山草峪岩组”主要由黑云变粒岩和细粒片麻岩(黑云变粒岩受变质深熔作用改造产物)组成,与“柳杭岩组”为构造接触。变质原岩主体为碎屑沉积岩,但具岛弧中酸性岩浆岩组成特征。碎屑锆石最小年龄(2.52—2.53 Ga)限制了最大沉积时代。(4)划分出三套TTG片麻岩,形成时代分别为2.71 Ga、2.62 Ga和2.52 Ga。前两者以较大规模分布于表壳岩系西侧,后者以脉状侵入“山草峪岩组”,限定了“山草峪岩组”最大沉积时代。(5)确定深熔岩石带,并把其进一步划分为四个亚带。发生深熔的主要地质体为“山草峪岩组”表壳岩。深熔作用时代为～2.51 Ga。大面积二长花岗岩的形成与之有关。(6)将鲁西花岗-绿岩代的形成演化划分为两个阶段。第一阶段(2.60—2.75 Ga),在洋底高原环境形成“柳杭岩组”,洋内俯冲导致～2.7 Ga的TTG花岗质岩石形成。第二阶段(2.50—2.60 Ga),在岛弧环境形成“山草峪岩组”,大范围～2.5 Ga壳源花岗岩形成标志着鲁西地块克拉通化的结束。更多还原

【Abstract】 The Archean granite-greenstone belt of Western Shandong Province (WSP) is located in the eastern North China Craton and is mainly composed of the Taishan Group and surrounding granitoid association. In early studies, the Taishan group, formed at～2.7 Ga, was subdivided into the Yanglingguan, Shancaoyu and Liuhang formations, which are considered to be comfortable to each other and constitute a monoclinal strata. Qixingtai is one of the typical areas of the WSP granite-greenstone belt, where the Taishan Group and different kinds of granitoids of Archean are well exposed. Based on geological mapping, this paper carried out a series of research, including SHRIMP zircon U-Pb chronology and geochemistry, in the Qixingtai Area And arrived some important conclusions as follows.(1) "The Liuhang Formation" was mainly composed of massive meta-basalt and pillow meta-basalt intercalated with some thin tuff and sedimentary layers. The meta-basalts are same in geochemistry as MORB, derived form depleted mantle source at 2.75-2.71Ga.(2) "The Shancaoyu Formation" was composed of leptite and fine-grained gneiss, with the latter being formed by anatectic reconstruction of the former. It shows a tectonic contact with "the Liuhang Formation". All the meta-sedimentary rocks of "the Shancaoyu Formation" show the geochemical charactaristics of magmatic rocks formed in island arc environmnet. Nd isotope compositions suggest a short crustal residence time in their source region. The meta-sediments contain detrital zircons of 2.56-2.53 Ga,-2.7 Ga and 2.53-2.52, limiting the deposition age of "the Shancaoyu Formation".(3) Three suites of TTG rocks, formed at 2.71Ga,2.62Ga and 2.52Ga respectively, have been identified in the area.(4) An anatectic belt has been identified. It can be further divided from west to east into four sub belts, namely the belts of lepite, leptite+felsic or granitic veins, fine-grained gneiss+felsic or granitic veins and migmatite. It is probably the anatexis at～2.51 Ga that resulted in the formation of crustally-derived granites which are widely distributed in the east of the anatectic belt.(5) The WSP granite-greenstone belt is considered to undergo two evolution periods. First period (2.75-2.6 Ga), "the Liuhang Formation" was formed in oceanic plateau environment, and the TTG of～2.7 Ga was formed as a result of intra-ocean subduction. Second period (2.6-2.5Ga), "the Shancaoyu Formation" was formed in island arc environment. The large-scale crustally-derived granites were produced at～2.5 Ga, remarking the cratonization of the WSP Block.更多还原