【作者】 朱志新；

【导师】 李锦轶；

【作者基本信息】 中国地质科学院 ， 构造地质学， 2007， 博士

【摘要】 南天山地处塔里木板块和哈萨克斯坦板块交界处,为乌拉尔—南天山造山带在中国境内的延伸,为一典型的古生代造山带,是在塔里木板块和哈萨克斯坦板块之间的一个开阔洋盆演化而来的古生代碰撞带,由南北两条蛇绿岩及其周围的陆缘岩系及古老结晶基底组成。南天山造山带构造属性与形成演化历来是众多地质学家研究的重点,对其构造属性与形成演化的研究是解决本区板块构造活动及资源评价的基础。本文以板块构造理论为指导,在系统研究近年的区域地质调查成果和科研成果的基础上,重点开展对南天山蛇绿岩、侵入岩和火山岩的地质学、年代学和岩石学的研究,结合地层、构造、古地磁研究等,从而重塑南天山地质发展史。以综合分折类比法研究为主,结合野外考察,进行岩石学、地质特征的研究。通过对南天山物质组成的系统研究,探讨南天山古生代造山带构造属性与形成演化。南天山是由多个不同时代不同成因的地质体拼合的一个复杂造山带,北以那拉提山南缘断裂为界与那拉提山相邻,南以南天山山前断裂与塔里木盆地相邻,由额尔宾山、哈尔克山、虎拉山三个既独立又相互成生联系的山脉组成。其间夹有多条大型右行韧性剪切变形带,各个山系均呈正扇型构造样式组成南天山一个大型扇型构造样式.通过野外地质调查和室内综合研究,对南天山蛇绿混杂带的区域地质特征、岩石学特征、形成时代和环境进行了系统的研究.认为南天山洋盆从晚震旦世就已具有一定规模,在晚石炭世闭合。南天山存在南北二条蛇绿混杂带,这两条蛇绿混杂带分别代表了南天山北缘洋盆和南缘洋盆的消亡的洋壳残片。南带蛇绿混杂带又可分为南北二支,北支为库勒湖经铁力买提达坂向东裙它力克达坂、过虎拉山北缘的虎拉沟,向东延入焉耆盆地。南支为从吉尔吉斯斯坦境内进入中国阿合奇,经米斯布拉克、黑英山满达勒克过欧西达坂、色日牙克依拉克、虎拉山南缘乌陆沟向东延伸。该带是南天山蛇绿岩出露主体,它与前苏联南天山蛇绿岩带费尔干纳南缘剖面可综合对比研究。本文认为中间可能存在库尔干洋岛将其分隔,从运动学及两侧的岛弧认为该两支蛇绿混杂岩是南天山南缘洋盆向南、北俯冲的残片。本文在那拉提山前人划分的华力西期侵入岩中识别出志留纪的酸性侵入岩,锆石SHRIMP U-Pb定年为436±8Ma,岩石学和地球化学研究显示该区早中志留纪侵入岩具同碰撞后造山花岗岩的特征,说明在早古生代那拉提山岛弧就增生到伊犁地块的南缘。同时还确定那拉提山370±7Ma、366±8Ma钙碱性侵入岩的存在,结合研究的晚志留世巴音布鲁克组和早石炭世的大哈拉边山组的钙碱性的火山岩,认为晚古生代那拉提山是伊犁地块南的一个活动陆缘。在额尔宾山发现并确定了约300Ma同碰撞-后碰撞的花岗岩,同时通过对南天山石炭纪、二叠纪的侵入岩的年代学和岩石学的研究,结合区域资料,通过研究对比认为南天山石炭纪的花岗岩基本为以壳源为主富铝的同碰撞花岗岩,总体和地壳加厚有关,和该区石炭纪残余海盆的发展基本同步,时限为300-340Ma,而二叠纪的花岗岩为后造山富钾花岗岩,与后造山带张性环境有关,时限为250-290Ma间。确定南木札尔特-黑英山-色日牙克依拉克-虎拉山南缘一带和那拉提山具有相同的构造属性,具有一套早古生代的同碰撞后造山带花岗岩,同时还在该带色日牙克依拉克一带前人划的石炭纪花岗岩中取得该处花岗闪长岩锆石同位素SHRIMP定年387±8 Ma,为一套中泥盆世钙碱性侵入岩,其形成主要与板块的俯冲作用有关。根据岩石组合、岩石化学、地球化学等特征,首次明确提出晚志留-早泥盆世在哈尔克山和额尔宾山形成岛弧带。在晚志留-早泥盆世由于南天山南缘洋盆向哈尔克山和额尔宾山微陆块下俯冲,在开都河两岸形成了一套早泥盆世火山岩和陆源碎屑岩。该套火山岩主要为中基性火山岩与中酸性火山岩,岩石化学显示为为低钾的钙碱性玄武岩系列,地球化学也显示火山岩具有岛弧火山岩的特征。在哈尔克山北缘也形成大量的中酸性火山岩碎屑岩和酸性熔岩,形成一条晚志留-早泥盆世的钙碱性火山岩带。对黑英山-虎拉山洋壳残片的研究中,确定一套洋岛型的火山岩组合,岩石组合为碱性中基性熔岩和火山碎屑岩。和深海沉积物一起组成黑英山-虎拉山洋壳残片。在洋壳上部的硅质岩中发现大量的放射虫,时代早泥盆世-早石炭世。初步确定南天山古生代洋盆中存在多个微陆块,从而使南天山在古生代洋盆中出现多个洋盆并存的局面,并在不同时期俯冲闭合。早古生代存在三列并行的岛弧带,从北向南,分别为那拉提山岛弧带、哈尔克山-额尔宾山岛弧带、色日牙克依拉克-虎拉山南缘岛弧带。在早古生代那拉提山岛弧增生到伊犁中天山地块的南缘,而色日牙克依拉克-虎拉山南缘岛弧带增生到塔里木板块北缘。至晚古生代,那拉提山和色日牙克依拉克-虎拉山南缘进入活动陆缘的演化阶段。在系统总结和研究南天山物质组成的基础上,确定黑英山-色日牙克依拉克一带蛇绿混杂带为塔里木板块与哈萨克斯坦板块的古生代板块缝合线,并系统的划分了中南天山的构造单元,在此基础上提出了南天山造山模式并重建了南天山的地质演化历史。认为南天山洋盆是古亚洲洋的一部分,其和古亚洲洋北部其它洋盆一起在元古的联合古陆基础上,从震旦纪开始裂解,由多列岛弧向两侧板块经多次不断增生碰撞,至晚石炭世最终闭合。更多还原

【Abstract】 South Tianshan is located in the junction of Tarim and Kazakhstan plates as the east extension in the Chinese territory of the Urals - South Tianshan orogenic belt which is a typical Paleozoic orogenic belt. South Tianshan is a Paleozoic collision zone which was developed from a broad ocean basin between the Tarim and Kazakhstan plates, composed of two ophiolite belts and their surrounding continental rocks and ancient crystalline basement. The tectonics and evolution of South Tianshan have always been the focus of the geological study. The reconstruction of the tectonics and evolution is the key to solving the plate tectonic activity and resource evaluation of South Tianshan Region.Based on the theory of plate tectonics and recent regional geological survey results, the author focused on the studies of geology, chronology and petrology of the ophiolite, intrusive rocks and volcanics in South Tianshan. Coupled with stratigraphy, tectonics and paleomagnetism, the author reconstructed the history of geological evolution and the tectonic features of South Tianshan.South Tianshan is a complicated orogenic belt composed of geological units of various ages, bounded by the fault named Nalati Mountain South in the north, by South Tianshan Fault and Tarim Basin in the south, composed of Eerbin Mountain, Haerke Mountain and Hula Mountains. Many dextral shear zones developed among the three mountains. Each mountain occurs as a normal fan style in profile and the whole South Tianshan forms a large fan tectonic style.The author conducted field geological survey and indoor comprehensive study on the Southern Tianshan ophiolite belt and the regional geology including pretrology, chronology and tectonic environment of South Tianshan and proposed that the south Tianshan ocean basin had already developed into substantial scale in the Late Sinian and closed in late Carboniferous. There exist two ophiolite belts, one in north and one in south, both represent the relics of the oceanic crust. The South ophiolite belt can be divided into two sub-belts in the North and the South, the North Belt starts from Kule lake through Tielimaidaban, Hulagou extending to Yanqi Basin; The south belt starts from Kyrgyzstan and enter China at Aheqi, through Mishibulake, south Hulashan to the east. This sub-belt contains the main ophiolite in the South Tianshan, which can be correlated to the ophiolite belt at south Fergana section in former Russia. The author thinks that may exist Kuergan oceanic island which separate the south and north ophiolite belts. The island arcs and the kinetics both support that the two ophiolite belts are the oceanic crust relics after the south oceanic basin was subducted into north and south.This study presented Silurian acidic intrusions through SHRIMP zircon U-Pb dating (436±Ma) which was thought to be Hercinian intrusions. Petrology and geochemistry studies indicate there were early Silurian intrusive rocks which has the features of syn-collision orogenic granite and there exist calc-alkaline intrusions at ages 370±7Ma and 366±8Ma in the Nalati mountains. Coupled with the calc-alkaline volcanics of late Silurian and Early Conbonniferous, the author proposed that the Nalati Mountain is a active continental margin in later Paleozoic.The author identified syn- and post-collision granites at about 300Ma in the Erben Mountains and proposed that the granites of Carboniferous in south Tianshan are mainly crustal sourced syncollision granite, related to the crust thickening and synchronized to the development of Carboniferous remaining oceanic basin with an age ranging between 300 and 340Ma. The Permian granites are post orogenic K-rich granites a t ages between 250 and 290Ma, related to post orogenic extensional environment.The author identified Nanmuzhaerte-Heiyingshan-Seriyakeyilake-Hulashan and Nalatishan have the same tectonic features and developed early Paleozoic syncollision granites and obtained an age of 387±8Ma using SHRIMP zircon dating for the granodiorite which was thought to be Carboniferous in age. is for a Middle Devonian calc - alkaline intrusion which is related to the plate subduction.Based on rock assemblages, rock chemistry and geochemistry characteristics, the author first presented that the region between Haerkeshan and Ererbinshan was an arc in late Silurian and early Devonian. As the result of the subduction of the south Tianshan oceanic basin to the Haerkeshan and Ererbinshan plate, volcanics and terrestrial clastics were developed at the Kaidu River in Devonian. These volcanics are mainly intermediate and basic volcanics and intermediate and acidic volcanics and are low K sub-alkaline series and calc-alkaline basalt series by rock chemistry and indicate arc volcanics by geochemistry. The intermediate and acidic volcanoclastics and acidic lava in the north Haerkeshan formed a Late Silurian and Early Devonian calc-alkaline volcanic belt.The oceanic crust relics at Heiyingshan and Hulashan are identified to be a volcanic assemblage of oceanic island type with an association of intermediate and basic lava and volcanoclastics, together with the deep sea sediments formed the oceanic crust relics at Heiyingshan and Hulashan. A lot of radiolarian has been found in the silicious rocks at the upper part of oceanic crust and was dated Early Devonian–Early Carboniferous.The author presented that there existed many small continents within the Paleozoic oceanic basin in south Tianshan which resulted into the coexistence of many oceanic basins and subduction and closure at different ages. In Ealrly Paleozoic, there were three parallel arc belts, Nalati, Haerkeshan-Eerbinshan and Seriyakeyilake -Hulashan arc belts from north to south. Nalatishan arc accreted to Middle Tianshan block at Yili in early Paleozoic, while the Seriyakeyilake -Hulashan accreted to the north edge of Tarim Plate. In late Paleozoic, south rim of the Nalatishan and Seriyakeyilake arc entered into stage of active contimental margin.Based on systematic studies of rock components of south Tianshan, the author proposed that the ophiolite complex at Heiyingshan- Seriyakeyilake is the suture zone of Tarim plate and Hasakeshitan plate and classified the tectonic units for middle and south Tianshan and presented the orogenic model for south Tianshan and reconstructed the evolution history. The author proposed that the south Tianshan ocean basin was a part of the ancient Asian ocean, together with other oceanic basins in the north of the ancient Asian ocean, south Tianshan oceanic basin broke up in Sinian into many island arc and accreted to lateral plates and closed in late Carboniferous.更多还原