【作者】 蔡志慧；

【导师】 许志琴；

【作者基本信息】 中国地质科学院 ， 构造地质学， 2010， 博士

【摘要】 塔里木盆地东北缘位于中亚造山带的南缘,经历复杂增生造山过程,是研究增生型造山带的理想场所。同时它又处于联结东天山造山带与塔里木盆地的特殊构造位置,是研究盆山耦合关系的一个重要区域。作者结合野外考察与室内研究,对塔里木盆地东北缘造山带进行构造分析,结合年代学、岩石学、地球化学、地层学及沉积学等。对塔里木盆地东北缘造山带的造山过程以及与塔里木盆地的关系进行研究和探讨。主要研究成果及认识如下：1)建立塔里木盆地东北缘造山带的基本构造格架。根据南天山内榆树沟-铜花山缝合带及相邻单元之间大型韧性走滑剪切带(断裂)的空间位置,将塔里木盆地东北缘造山带划分为：(Ⅰ)北天山晚古生代增生体(NTSA)、(Ⅱ)中天山复合增生弧地块(CTSB)、(Ⅲ)南天山早古生代增生楔(STSA),及(Ⅳ)塔里木北部陆缘(NTRMM)(在研究区内主要指库鲁克塔格隆起)。它们之间的界限为中天山北缘剪切带(断裂)、中天山南缘剪切带(断裂)榆树沟-铜花山缝合带及辛格尔剪切带(断裂)。2)确定塔里木盆地东北缘库鲁克塔格地区前南华纪的多次变质岩浆事件,发现前南华纪基底中存在一条大型韧性滑脱剪切带。塔里木盆地东北缘库鲁克塔格地区广泛出露前南华基底岩石。锆石LA-ICP-MS测试获得2505 Ma和1161～811 Ma的年龄,结合前人同位素测年结果,认为库鲁克塔格地区存在晚太古代-早元古代基底(2400-2800 Ma,或更老),经历元古代的1880-1817 Ma,1161～811 Ma的变质岩浆事件。库鲁克塔格地区基底与盖层之间存在一条E-W走向、厚度约2 km的韧性滑脱带,韧性滑脱带内普遍发育糜棱岩及“A”型剪切褶皱等,糜棱岩面理向N或S缓倾、拉伸线理向NW或SE倾伏,不对称旋转构造及糜棱岩中石英晶格优选方位图(EBSD测试)指示韧性滑脱带上盘滑脱方向为自NW向SE。韧性滑脱带中糜棱岩内白云母的Ar-Ar测年结果表明滑脱时代早于383 Ma。3)确定库鲁克塔格震旦纪-早古生代岩石经历多期构造变形叠加。库鲁克塔格震旦纪-早古生代岩石经历多期构造变形可分为4期：(1)N-S向挤压变形；(2)右行走滑韧脆性变形；(3)库鲁克塔格地区东部NE-SW向挤压变形与左行走滑韧脆性变形；(4)新生代陆内逆冲推覆和舒缓褶皱变形。4)库鲁克塔格早古生代盖层由底部到顶部早期变形程度逐渐变弱。由N到S呈逆冲席状展布,向S逆冲推覆。采用层长守恒原理对震旦纪-早古生代盖层缩短率进行估算结果为19.0-22.1%。5)塔里木盆地东北缘造山带中4条大型右行走滑剪切带(断裂)的厘定及形成时限的确认。确定中天山北缘剪切带、中天山南缘剪切带、辛格尔剪切带以及兴地剪切带为韧性-脆性右行剪切带。塔里木盆地东北缘造山带中物质存在自西向东运动的轨迹。这些右行走滑剪切带形成于368～340 Ma (Ar-Ar测年结果),再次活动于290～241 Ma (Ar-Ar测年结果)。6)确定塔里木盆地东北缘造山带中存在加里东造山事件。塔里木盆地东北缘造山带中存在加里东造山事件,证据为：(1)中天山南缘存在一条早古生代的蛇绿岩带：榆树沟-铜花山蛇绿岩带；(2)库鲁克塔格寒武-奥陶系为早古生代被动陆缘深海-斜坡相沉积；(3)库米什地区出露古南天山洋盆的俯冲产物-早古生代深海沉积增生楔；(4)中天山广泛出露早古生代岩浆弧型花岗岩：(5)库鲁克塔格在早古生代形成向南逆冲极性的褶皱冲断带；(6)塔里木盆地东北缘造山带与盆地内发育有一定规模的志留-泥盆系砾岩；(7)以角度不整合接触的石炭系与奥陶系-志留系具有不同的构造变形特征,石炭系变形多为宽缓直立褶皱,而奥陶-志留系为具有流劈理的直立紧密褶皱；(8)库鲁克塔格“铲”式盖层与基底基底组成的滑脱-褶皱构造,是塔里木地块与中天山岩浆弧带碰撞(早于383 Ma)后发生陆内俯冲的产物。(9)由于碰撞后大型陆内平移作用引起的大型右行走滑剪切带在泥盆纪368-340 Ma(Ar-Ar测年结果)之前已经形成,说明开始在碰撞作用很可能发生在早古生代。7)探讨了在加里东期塔里木盆地与塔里木盆地东北缘造山带之间存在相互制约的关系。早古生代造山结束后,形成前陆盆地。以塔里木盆地东北缘造山带中以及塔里木盆地中普遍存在的早-中古生代砂岩、砂砾岩及泥质岩等为证据；碰撞造山后,盆-山结合部位发生陆内平移兼挤压。盆地内发生明显沉降。8)提出塔里木盆地东北缘造山带的构造演化模式。(1)震旦纪南天山洋开启；(2)震旦纪-早古生代,南天山洋盆收缩,塔里木地块开始向准噶尔地块俯冲,在中天山位置形成增生弧；(3)加里东期,塔里木地块与中天山增生岩浆弧带碰撞。形成一系列北倾南冲的不对称相似褶皱、北倾流劈理。同时形成磨拉石盆地,但这些盆地大部分仍在海平面以下；(4)弧-陆碰撞刚结束时,在塔里木盆地东北缘造山带处发生陆内平移兼逆冲过程,盖层与基底之间形成大规模韧性滑脱带；(5)受到北部古亚洲洋向S俯冲作用的影响,在塔里木盆地东北缘普遍发育石炭纪的具有弧后位置拉张裂解形成环境的火山岩；(6)早二叠世大规模沿造山带平行分布的陆相红色磨拉石(舒良树等,2004)是由于弧-陆碰撞造山而形成的磨拉石盆地由海相转为陆相的标志；(7)碰撞造山后二叠纪-早三叠世塔里木盆地东北缘造山带内发生大型右行韧脆性走滑；(8)受到阿尔金断裂系统的影响塔里木盆地东北缘造山带东部具有左行走滑的变形特征；(9)中生代在塔里木盆地东北缘造山带普遍发生大规模抬升剥蚀；(10)新生代由于印度板块向青藏高原挤压作用,塔里木盆地东北缘发生陆内再挤压再造山过程。更多还原

【Abstract】 The northeastern margin of Tarim basin is located along the southern margin of the Central Asia Orogenic belt, has undergone an accretional orogenic process, connects the East Tianshan Orogen and Tarim Basin, it is an important area that geologists study accretion-type orogens and basin-mountain coupling relations.With field investigation and lab study, the author analyzed the orogenic process of orogenic belt and its relations with Tarim Basin combining studies on structural geology, chronology, petrology, geochemistry, stratigraphy and sedimentology.1) Establish structural framework of the orogenic belt on the northeastern margin of Tarim basinAccording to the locations of Yushugou-Tonghuashan suture zone in South Tishan and large strike-slip ductile shear zones between neighboring units, orogenic belt in the northeastern margin of Tarim is divided into several parts including the North Tianshan unit, the Central Tianshan unit, the South Tianshan unit and the Kuruktag unit with the boundaries:the north Central Tianshan shear zone, the south Central Tianshan shear zone, Yushugou-Tonghuashan suture zone, Xinger shear zone and Xingdi shear zone.2) Identify pre-Sinian metamorphic and magmatic events in Kuruktag, discover a large ductile detachment shear zone in the basement of the orogenic belt at the northeast Margin of Tarim Basin.The basement rocks outcrop widely in Kuruktag. With zircon dating result of 2505 Ma and 1161-811 Ma and other previous isotope dating results, it is believed that Kuruktag terrane has late archean-early proterozoic (2565-2296 Ma) or older basement and experienced major metamorphic and magmatic events of proterozoic period at 1880-1817 Ma and 1161-811 Ma. (2) A decollement exists between the cover rocks and the basement stretches in E-W direction with a width of 2 km, is characterized by "A" type fold, mylonites, gently mylonite foliation, stretching lineation plunging to northwest or southeast. Studies on asymmetrical rotational structure and crystallographic preferred orientations of quartz in mylonites (EBSD analysis) indicate a movement of the ductile decollement in a top-to SE direction. (3) Ar-Ar dating result of the muscovite in the mylonite from the ductile decollement shows the decollement formed before 383 Ma.3) Sinian-early Paleozoic rocks in orogenic belt in the northeastern margin of Tarim experienced several deformation envents.The deformation events can be divided into 4 periods, including (1) N-S compressional deformation, (2) dextral strike-slip ductile-brittle deformation, (3) NE-SW compressional deformation and sinistral strike-slip ductile-brittle deformation in the east of this area, (4) intra-continental thrusting and gently folding deformation occurred in Cenozoic.4) Early Paleozoic cap rocks thrusting southward spread sheet-like from N to S and are deformed weaker increasingly from bottom to top.5) Redefine four large dextral strike-slip shear zones in orogenic belt of the northeastern margin of Tarim Basin and identify their formation duration time.The north Central Tianshan shear zone, the south Central Tianshan shear zone, Xinger shear zone and Xingdi shear zone are identified as ductile-brittle dextral shear zones. These dextral strike-slip shear zones formed before 368-340 Ma (Ar-Ar dating results), and large scale Intra-continental ductile dextral strike-slipping event occurred at 290-241 Ma (Ar-Ar dating results).6) Identify Caledonian orogenic event on the orogenic belt in the northeastern margin of Tarim, the northeastern margin of Tarim Basin.The evidences are:(1) An early Paleozoic suture zone (Yushugou Tonghuashan suture zone) exists in the south Tianshan; (2) The Cambrian and Ordovician rocks in Kuruktag (south part of the orogeny) have the feature of passive continental margin abyssal and slope facies. (3) Early Paleozoic abyssal sedimentary accretionary wedge, the product of paleo South Tianshan Ocean subduction, outcrops in Kumish (in the south Tianshan). (4) Early Paleozoic magmatic arc-type granites outcrop widely in Central Tianshan. (5) Fold-thrust belt thrusting southward formed at early Paleozoic in Kuruktag. (6) Silurian-Devonian conglomerates develop widely in orogenic belt and basin, northeastern margin of Tarim Basin. (7) Carboniferous rocks and Ordovician-Silurian rocks contacted with an angular unconformity have different structural features. Deformation in Carboniferous rocks occur broad and gentle upright folds and Ordovician-Silurian upright compact folds with flow cleavage. (8) The spade-like cap rocks and the decollement bellow them is the product of the intercontinental subduction after the collision event (before 383 Ma). (9) Dextral strike-slip fault system in Central Tianshan and Kuruktag, the product of intra-continental deformation after early Paleozoic close of the south Tishan Ocean, formed at 368-340 Ma (Ar-Ar dating results).7) The relation between Tarim Basin and the northeastern margin orogenic belt at the early paleogenic.After early Paleozoic orogeny foreland basin formed and massive sandstone, sandy conglomerate and mudstone deposited. After collisional orogeny intra-continental translation and compression happened in basin-mountain binding site. Apparent subsidence occurred in basin.8) Propose a structural evolution pattern of the orogenic belt on the northeastern margin of Tarim(1) At Sinian the South Tianshan Ocean opened. (2) Paleo South Tianshan ocean shrinked at Sinian-early Paleozoic period and the Tarim block subducted underneath the Jungar block resulting accretionary arc formed at Central Tianshan. (3) At Caledonian Tarim block and Central Tianshan accretionary magma arc collided which lead to formation of a series of asymmetric similar folds and flow cleavages. Molasses basins formed at the same time, the majority part of which was still under the sea level. (4) After the end of arc-continental collision, intra-continental translational thrusting occurred at orogenic belt, and large ductile detachment belt formed between cap and basement. (5) Carboniferous igneous rocks, indicating formation setting of extensional cracking at back-arc, develop widely in northeastern margin of Tarim due to subduction southward of paleo Asia Ocean at north. (6) Early Permian massive continental red molasses along orogenic belt are the signal that molasse basins began to change from marine to continental. (7) At Permian-early Triassic, large dextral ductile-brittle strike slip happened in northeastern margin of Tarim. (8) The east part of orogenic belt in northeastern margin of Tarim shows deformation characteristics of sinistral strike slip. (9) During Mesozoic period large uplift erosion occurred commonly in the orogenic belt of northeastern margin of Tarim. (10) At Cenozoic, the northeastern margin of Tarim experienced intra-continental compressinal orogenic process again due to the compression of India plate towards Tibetan plateau.更多还原