【作者】 董晓杰；

【导师】 张兴洲； 徐仲元；

【作者基本信息】 吉林大学 ， 构造地质学， 2012， 博士

【摘要】 内蒙古大青山地区是华北克拉通早前寒武纪基底的重要组成部分，也是华北克拉通基底岩石保留较好的区域之一。最新的区域地质调查成果表明，该区域早前寒武纪岩石地层发育齐全，主要由太古代花岗-绿岩地体、太古代麻粒岩-紫苏花岗岩地体以及早元古代孔兹岩组成。除此之外，在孔兹岩系中还发现了大量的早元古代变质火山岩及侵入岩。花岗-绿岩地体主要分布在大青山北麓的固阳-武川一带。红山子地区出露的花岗-绿岩岩石组合是其中的典型代表。红山子地区出露的太古代侵入岩主要由片麻状石英闪长岩、片麻状花岗闪长岩、片麻状斜长花岗岩以及片麻装花岗岩组成。地球化学特征表明，该区域的太古代侵入岩组合不仅包括典型的TTG岩石，还包括与俯冲作用有关的高镁闪长岩、赞岐岩类。另外，研究区还发现了可能代表同（后）碰撞阶段的高铝花岗岩。绿岩地体的岩石组成较为复杂，根据其组成，推测其是由太古代蛇绿岩残片及当时的岛弧火山岩共同变质而成。根据锆石年代学研究，红山子一带花岗-绿岩地体可能是一套2.55-2.4Ga期间板块俯冲-碰撞-后碰撞演化阶段的综合产物。太古代麻粒岩-紫苏花岗岩地体主要分布于大山北麓的西乌兰不浪地区。该区域岩石以穹窿构造形式产出，穹窿构造的核部岩石为紫苏花岗质片麻岩，麻粒岩系展布于穹形构造四周。岩石地球化学特征表明，紫苏花岗岩是麻粒岩深熔作用的产物。变质作用研究表明，该区域的麻粒岩-紫苏花岗岩不仅保留着代表逆时针等压降温P-T轨迹的矿物共生组合，还发现了代表顺时针恒温减压P-T轨迹的“白眼圈”结构。根据年代学研究，这些麻粒岩-紫苏花岗岩地体形成于～2.7-2.5Ga，变质作用为一连续的年代学记录，分布于～2.5-2.4Ga之间。根据年代学及变质作用特征分析，麻粒岩-紫苏花岗岩地体反映研究区在～2.55-2.4Ga是一个连续的演化过程，并且在演化过程中经历了岛弧模式的俯冲向弧陆碰撞或陆陆碰撞的转变。早元古代岩石单元主要产出在研究区南部的孔兹岩相带中，它们彼此之间关系密切。早元古代变质火山岩主要由斜长角闪岩、角闪斜长片麻岩、黑云角闪片麻岩、黑云片麻岩和长英片麻岩组成。地球化学特征显示其成因与大陆裂谷活动有关。年代学证据表明他们形成时间为～1980-1950Ma。早元古代侵入岩由一套具A-型花岗岩性质的侵入体及一套黑云角闪花岗岩组成。A型侵入体的形成与伸展作用有关，年代学证据表明他们的形成时间与早元古代变质火山岩基本同期。黑云角闪花岗岩形成于后期的一次陆内造山事件。早元古代孔兹岩为一套中高级变质地层，主要由榴云片麻岩、透辉片麻岩、大理岩三个岩石系列组成。地球化学特征表明孔兹岩系一套变质沉积地层。年代学研究表明孔兹岩系的碎屑物源主要由～2.0Ga和～2.55~2.4Ga两个时间段的岩石组成；而变质时代记录多在～1.95-～1.80Ga之间，并且发育～1.92Ga的超高温变质作用。超高温变质作用与孔兹岩系顺时针型“P-T”轨迹不同，表现为逆时针的变质作用演化。超高温变质作用多与基性辉长岩岩脉侵位相伴生，并被认为是区域伸展作用导致的软流圈地幔大规模上涌铁镁质岩浆板底垫拖作用的结果。超高温变质作用、裂谷性质的变质火山岩及A-型花岗岩性质的侵入体共同限定研究区在1.98-1.90Ga期间处于伸展的构造背景下，可能是一次大陆裂谷事件，根据孔兹岩中碎屑锆石的分布规律，裂谷事件可能在2.0Ga就已经开始。然而，孔兹岩最终却显示出与碰撞有关的顺时针P-T轨迹，并普遍发育近东西向的陡倾叶理。这些特征都暗示出孔兹岩系经历了南北向的挤压变形。因此我们判断在裂谷作用结束后有一期陆内造山作用，该期造山作用的时限应该大致与华北克拉通中部碰撞带的碰撞时间相同(1.85-1.8Ga)。上述研究表明，大青山地区从新太古代末期-早元古代末期应该经历了从“弧陆俯冲-陆陆碰撞-稳定克拉通-大陆裂谷-陆内造山”的连续演化历史。更多还原

【Abstract】 Daqingshan Mountain, Inner Mongolia region is an important part of the EarlyPrecambrian basement of North China Craton, and one of the basement rocks to retainbetter areas. The regional geological survey results indicate that the region earlyPrecambrian rock is complete, mainly composed of Archaean granite-greenstoneterrane, Archean granulite-charnockite terrane and Early Proterozoic khondalite. Inaddition, the Department of khondalite also found a large number of early Proterozoicmetavolcanic rocks and intrusive rocks.Granite-greenstone terrane is mainly distributed in the vicinity of theDaqingshan the northern foot of Guyang-Wuchuan. Hongshanzi area exposed granite-greenstone is a typical representative. Hongshanzi Archean intrusive rocks aremainly composed of gneissic quartz diorite, gneissic granodiorite, gneissicplagiogranite and gneissic installed granite. Geochemical features indicate that theregion of Archean intrusive rocks includes not only typical TTG rocks, including thesubduction-related high-Mg diorite, Sanuki rocks. In addition, to also found highalumina granite may represent the same (after) collision stage. The rocks of thegreenstone terrane composed of more complex, according to its composition,suggesting that its Archean ophiolite fragments and island arc volcanic metamorphism.Zircon geochronology show that hongshanzi Granite-greenstone terrane is acomprehensive product of subduction-collision–after collision in2.55-2.4Ga.Archean granulite-charnockite terrane is mainly distributed in Xi Ulanbulang area in the northern foothills of the Daqingshan Mountain. The output of the rocks isdome constructed in the formation, the core rocks of the dome is granitic gneiss,granulite rock series cloth around the dome. The geochemical characteristics ofcharnockite indicate it is the product of granulite anatexis. Metamorphism studieshave shown that the region granulite-charnockite not only retained counterclockwiseisobaric cooling P-T path mineral assemblages, also found that the clockwisethermostat decompression P-T path of the “white eye socket” structure. According tothe chronological study of granulite-charnockite terrane, the protolith formed in2.7-2.5Ga and metamorphism as a continuous chronology recorded, distributed in2.5-2.4Ga. According to the analysis of the chronology and metamorphism, granulite-charnockite terrane, reaction in the study area is a continuous process of evolution inthe2.55-2.4Ga, and experience the evolution of the subduction of the island arc modeland transform to the arc-continent collision or continent-continent collision.The main outputs of the Early Proterozoic rock units in the study area in southernkhondalite band, the close relationship between them. Early Proterozoic metavolcanicrocks mainly composed of plagioclase amphibolite, hornblende plagioclase gneiss,biotite-hornblende gneiss, biotite gneiss and felsic gneiss. The geochemicalcharacteristics show that the metavolcanic rocks related to continental rift activity.Chronology evidence indicate that they formed in the~1980-1950Ma.Early Proterozoic intrusions include a set of A-type granite and a set of biotiteamphibolite granite. A-type granites indicated that they formed in the extensionalSystem. Chronological evidence indicated that their formation time is the same as theEarly Proterozoic metavolcanic. Biotite amphibolite granite formed in intracontinentalorogenic events in the late.Early Proterozoic khondalite is a senior metamorphic Stratum, mainly composedof garnet gneiss, diopside gneiss and marble, three rock series. Geochemical featuresindicate that the khondalite a metamorphic sedimentary strata. Geochronologicalstudies have shown that the source of khondalite series is of~2.0Ga and~2.55-2.4Ga two periods of rock; metamorphic age record more than~1.95-~1.80Ga anddevelopment~1.92Ga UHT metamorphism. Ultra-high temperature metamorphism is different with khondalite series clockwise “P-T” track, showing the evolution ofmetamorphism of the counter-clockwise. Ultra-high temperature metamorphism andmafic gabbro veins accompanied, and that is considered to be the regional extensioncaused by asthenospheric mantle on a large scale.Ultra-high temperature metamorphism, rift-related metavolcanic rocks andA-type granites limit the study area in~1.98-1.90Ga during extensional tectonicsetting, and is a continental rift event. According to khondalitethe distribution ofdetrital zircons, Rift Valley events may~2.0Ga has already begun. Khondalite series,however, eventually showing the collision-related clockwise P-T path, and generallydeveloped a steep EW foliation. These characteristics imply that the hole is herebyrock series experienced a north-south compressional deformation. Therefore, wedetermine an intracontinental orogenesis after the end of the rifting, and the time limitshould be consistent with the collision time of the Trans-North China Orogen(1.85-1.8Ga).These studies have shown that Daqingshan area experience continuous evolutioncfrom the arc-continent subduction-continental collision-stable craton-continentalrift–orogeny in late Neoarchean–late Paleoproterozoic.更多还原