發(fā)布時間：2018-04-02 19:33

  本文選題：印支運動　切入點：華南　出處：《中國地質(zhì)大學(xué)(北京)》2017年碩士論文

【摘要】：華南板塊位于全球板塊動力學(xué)活動最頻繁的特提斯和太平洋兩大構(gòu)造域之間。華南板塊印支期構(gòu)造巖漿演化過程及其與周緣板塊俯沖和陸塊碰撞等動力學(xué)過程的內(nèi)在聯(lián)系,一直以來是國內(nèi)外地球科學(xué)領(lǐng)域研究的熱點,也是爭議的焦點。本文選取華南大陸西南部的十萬大山構(gòu)造帶為研究區(qū),在詳細(xì)的野外填圖基礎(chǔ)上,結(jié)合構(gòu)造變形、巖石學(xué)、地球化學(xué)及同位素年代學(xué)分析手段,重建了該構(gòu)造帶的二疊紀(jì)-三疊紀(jì)構(gòu)造-巖漿演化史,為了解古太平洋板塊的俯沖作用如何控制華南大陸印支期陸內(nèi)變形-巖漿演化提供了地質(zhì)依據(jù)。野外地質(zhì)填圖及古構(gòu)造應(yīng)力場反演結(jié)果證實,晚二疊世-中三疊世,NW-SE擠壓應(yīng)力場導(dǎo)致十萬大山構(gòu)造帶廣泛縮短變形,形成了一系列自SE向NW逆沖的斷層和相關(guān)褶皺構(gòu)造,和~N-S走向左行和~E-W右行走滑斷裂�？傮w上,構(gòu)造變形由SE向NW強度逐漸變?nèi)?表現(xiàn)為明顯的由SE向NW擴(kuò)展、薄皮逆沖式的變形展布規(guī)律,其可能記錄了古太平洋板塊俯沖作用導(dǎo)致的安第斯型陸內(nèi)造山運動。這期地殼擠壓縮短過程并不是連續(xù)的,其間穿插了一次短暫的巖漿-熱事件,即:大容山-十萬大山花崗巖侵位、抬升和高級變質(zhì)巖的退變質(zhì)作用。大容山-十萬大山花崗巖呈NE-SW向帶狀展布,與十萬大山構(gòu)造帶走向平行。LA-ICP-MS鋯石U-Pb測年顯示,大容山花崗巖體侵位于~250-240 Ma。巖石地球化學(xué)分析表明,該花崗巖體屬高鉀鈣堿性S-型花崗巖類,為古-中元古代殼源物質(zhì)重熔的產(chǎn)物,與區(qū)域內(nèi)的高溫麻粒巖包體和紫蘇花崗巖的形成同期。它們的動力學(xué)成因可能為:古太平洋板塊俯沖過程中,因俯沖板片斷離(slab breakoff)作用影響,高溫巖石圈地幔和軟流圈物質(zhì)沿通道上涌,誘發(fā)上覆地殼發(fā)生超高溫-高溫熔融作用,并在不同層次形成高溫麻粒巖、紫蘇花崗巖和S型花崗巖。本研究還新識別一條寬約300 m的韌性剪切帶,命名為欽州-防城韌性剪切帶,其走向NE-SW,傾角80°,拉伸線理近水平,以右行走滑運動學(xué)為主,剪切變形溫度~400℃,時代為~250 Ma,其形成可能與早三疊世華南板塊與印支地塊陸-陸碰撞作用有關(guān)。
[Abstract]:The South China Plate is located between the Tethys and the Pacific tectonic regions, where the global plate dynamics is most frequent.The evolution of the Indosinian tectonic magma in the South China plate and its internal relationship with the dynamic processes such as the subduction of the peripheral plate and the collision of the continental blocks have been the hot spots in the field of geoscience both at home and abroad and are also the focus of controversy.In this paper, the Shiwandashan tectonic belt in southwestern South China is selected as the study area. On the basis of detailed field mapping, combined with structural deformation, petrology, geochemistry and isotopic geochronology,The history of Permian-Triassic tectonic-magmatic evolution of the tectonic belt has been reconstructed, which provides a geological basis for understanding how subduction of the paleo-Pacific plate controls intra-continental deformation-magmatic evolution in the Indosinian South China continent.Field geological mapping and inversion of paleotectonic stress field confirmed that the late Permian-Middle Triassic NW-SE compressive stress field resulted in extensive shortening and deformation of Shiwandashan tectonic belt, resulting in a series of faults and related fold structures from SE to NW thrust.The N-S strike left and the E-W right strike slip fault.On the whole, the strength of tectonic deformation gradually weakens from SE to NW, which is characterized by the spreading of SE to NW and the distribution of thin crust thrusts, which may record the Andes intracontinental orogeny caused by subduction of the paleo-Pacific plate.The process of crustal compression and shortening in this period is not continuous, during which a brief magma-thermal event, I. e., the emplacement, uplift and retrograde metamorphism of high metamorphic rocks, occurred in Darongshan-Shiwandashan granite.The Dalongshan-Shiwandashan granite distributes in a NE-SW zonal direction, parallel to the strike of Shiwandashan tectonic belt. LA-ICP-MS zircon U-Pb dating shows that the dalongshan granite transgression is located at 250-240 Ma.The petrogeochemical analysis shows that the granitic body belongs to the high-potassium calc-alkaline S- type granitoids and is the product of the remelting of Paleo-Mesoproterozoic crustal materials, which coincides with the formation of the high-temperature granulite inclusions and perilla granites in the region.Their dynamic origin may be that during the subduction process of the paleo-Pacific plate, the high-temperature lithospheric mantle and the asthenosphere material welled up along the channel due to the influence of the subduction plate fragments from the slabs to break off, which induced the super-high-temperature and high-temperature melting of the overlying crust.High temperature granulites, perilla granites and S-type granites were formed at different levels.A ductile shear zone with a width of about 300 m was also newly identified in this study, named Qinzhou Fangcheng ductile shear zone, with a trend of NE-SW, an angle of 80 擄, a near horizontal tensile lineage, mainly a right-strike-slip kinematics, and a shear deformation temperature of 400 鈩，

本文編號：1701801