本文選題：南海北部陸緣 + 火成巖��； 參考：《中國科學院研究生院(海洋研究所)》2014年博士論文

【摘要】：南海及其周邊廣泛發(fā)育的火山活動記錄了南海演化以及相關的深部動力學過程的重要信息,開展南�；鸪蓭r的研究對于理解南海地區(qū)張裂陸緣的構造性質(zhì)、海底擴張、殼幔作用、以及資源效應均有重要的科學意義。本文利用2D/3D地震資料,并參考最新的鉆井和大洋鉆探資料以及重磁數(shù)據(jù),結合區(qū)域地質(zhì)背景,重點研究了南海北部陸緣火成巖的地震特征,分析了巖漿巖的幾何產(chǎn)狀、形成時間和分布規(guī)律。討論了火成巖的形成機制,南海北部大陸邊緣的類型及構造性質(zhì)以及地幔柱對裂后巖漿活動的影響。取得以下成果:1)建立火成巖識別標準,在南海北部識別出兩大類火成巖-侵入型和噴出型,并精細刻畫各類火成巖體的地震反射特征。根據(jù)能量的強弱,進一步將侵入型分為刺穿型和隱刺穿型。根據(jù)外形特征,進一步將噴出型分成平頂海山和尖頂錐狀海山。統(tǒng)計了各類火成巖體在南海北部分布的數(shù)量和規(guī)模。在地震數(shù)據(jù)包含的可分辨尺度信息的前提下,總結了三種判別火成巖形成時期的標準。據(jù)此,將南海北部陸緣巖漿活動分為三期,并討論各期次的分布規(guī)律;2)分析本區(qū)巖床復合體的組合形式和形成機制,指出本區(qū)巖床復合體幾何產(chǎn)狀多為碟狀,以個體或互相結合的方式在白云凹陷西部下中新統(tǒng)中廣泛分布。判斷形成時間為15.5Ma,表明海底擴張結束后,殘余巖漿將裂谷期斷層作為巖漿通道,深部大巖床成為其上小巖床的根部巖漿供給。巖漿通過水平不連續(xù)面,由內(nèi)巖床放射性的向外巖床提供巖漿,形成新的巖床;3)總結四點支持南海北部陸緣為非典型巖漿匱乏型大陸邊緣的證據(jù):南海北部陸緣存在接近洋殼廣泛的分布于下陸坡并明顯集中在向海一側的巖漿巖帶;存在與裂谷盆地相關的高角度鏟式斷層,并終止于斷凹轉(zhuǎn)換面S23.8即存在裂后延遲;OCT處地殼厚度明顯減薄;裂谷期間沒有地幔柱的作用和影響。討論晚中新世以來出現(xiàn)在瓊東南盆地,鶯歌海盆地及西沙海區(qū)的異常熱沉降與巖漿活動的關系;4)刻畫自晚燕山期至今巖漿活動演化圖,表明南海北部陸緣的巖漿作用受太平洋板塊俯沖和歐亞碰撞共同影響。討論海底擴張結束后,地幔柱可能作為主導因素影響著巖漿活動的發(fā)生時間和規(guī)模。結合海南地幔柱半徑小、上升速度慢、溫度低等特點分析其引起大規(guī)模巖漿活動延遲的原因。
[Abstract]:The extensive volcanic activity in and around the South China Sea records the important information of the evolution of the South China Sea and related deep dynamic processes. The study of the igneous rocks in the South China Sea is useful in understanding the tectonic properties of the extensional continental margin in the South China Sea and the undersea expansion.Crust-mantle interaction, as well as resource effects, are of great scientific significance.Based on the 2D/3D seismic data, the latest drilling and ocean drilling data and gravity and magnetic data, combined with the regional geological background, the seismic characteristics of igneous rocks in the northern continental margin of the South China Sea are emphatically studied, and the geometric occurrence of magmatic rocks is analyzed.Formation time and distribution.The formation mechanism of igneous rocks, the types and tectonic properties of the continental margin in the northern part of the South China Sea and the influence of mantle plume on post-rift magmatic activity are discussed.The following results are obtained: 1) establish the igneous rock identification standard, identify two major types of igneous rocks-intrusive and ejection types in the northern part of the South China Sea, and characterize the seismic reflection characteristics of various igneous rocks in detail.According to the strength of energy, the invasive type is further divided into piercing type and implicit piercing type.The ejection type is further divided into flat-topped seamounts and pointed conical seamounts according to their shape characteristics.The quantity and scale of distribution of various igneous rocks in the northern part of the South China Sea are calculated.On the premise of the discernible scale information contained in seismic data, three criteria for distinguishing igneous rocks are summarized.Based on this, the magmatic activity in the northern margin of the South China Sea is divided into three stages, and the distribution of each stage is discussed. (2) the assemblage form and formation mechanism of the rock bed complex in this area are analyzed, and it is pointed out that the geometric occurrence of the rock bed complex in this area is mostly disheveled.It is widely distributed in the lower Miocene in the west of Baiyun sag.The judging time of formation is 15.5Ma. it shows that the residual magma takes the rift fault as the magmatic channel and the deep rock bed becomes the root magma supply of the upper and smaller rock bed after the undersea expansion.Magma passes through horizontal discontinuities, providing magma from the radioactive inner rock bed to the outer rock bed,The formation of a new rock bed 3) summarizes the evidence that the northern margin of the South China Sea is an atypical magmatic deficient continental margin: the northern margin of the South China Sea has a magmatic belt close to the oceanic crust and widely distributed on the lower slope and obviously concentrated on the seaward side;There are high-angle shovel faults related to rift basins, and the crust thickness is obviously thinned at post-crack delay Oct when it terminates at S23.8, and there is no effect of mantle plume during the rift.The relationship between anomalous thermal subsidence and magmatic activity in the Yinggehai basin and Xisha sea area since the late Miocene is discussed.It shows that the magmatism in the northern margin of the South China Sea is influenced by the subduction of the Pacific plate and the Eurasian collision.It is discussed that the mantle plume may be the dominant factor influencing the occurrence time and scale of magmatic activity after the undersea expansion.According to the characteristics of Hainan mantle plume, such as small radius, slow rising speed and low temperature, the reasons for the delay of large-scale magmatic activity are analyzed.
【學位授予單位】：中國科學院研究生院(海洋研究所)
【學位級別】：博士
【學位授予年份】：2014
【分類號】：P736.1

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本文編號：1763893