發(fā)布時間：2018-02-24 15:04

  本文關(guān)鍵詞： 長江中下游成礦帶 殼幔速度結(jié)構(gòu) 背景噪聲成像 雙平面波成像　出處：《中國地質(zhì)大學(xué)(北京)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：長江中下游地區(qū)主要包括華北克拉通的東南部、大別-蘇魯造山帶、揚子克拉通的中東部以及華夏板塊的東北部。長江中下游成礦帶位于研究區(qū)域的中心,它是我國東部重要的多金屬成礦帶和礦物資源基地,由7個大型礦集區(qū),約200多個大中型礦床組成。為什么在如此狹窄的弧形帶內(nèi)集中產(chǎn)出了眾多的大型、超大型礦床?其深部動力學(xué)背景是什么?深部結(jié)構(gòu)和淺部礦床之間是否存在一定關(guān)聯(lián)?因而探測長江中下游地區(qū)地殼和上地幔速度結(jié)構(gòu),對于加深我們對成礦帶的深部構(gòu)造背景和巖漿活動機制的了解有重要意義。但由于長江中下游地區(qū)地震活動性較低,傳統(tǒng)的地震成像法比較難獲取該地區(qū)高分辨的殼幔速度結(jié)構(gòu),因此該地區(qū)一直缺乏高精度的殼幔速度結(jié)構(gòu)模型。本文首次利用背景噪聲和雙平面波層析成像方法聯(lián)合反演了長江中下游地區(qū)的地殼和上地幔剪切波速度結(jié)構(gòu)。研究中所用數(shù)據(jù)包括從2012年7月至2013年8月共14個月的連續(xù)背景噪聲數(shù)據(jù)以及219個遠震數(shù)據(jù),這些數(shù)據(jù)是由中國地震局區(qū)域數(shù)字地震臺網(wǎng)和中國地質(zhì)大學(xué)(北京)布設(shè)的流動寬頻地震臺站所記錄到的。通過背景噪聲層析成像,獲得了5 s到42 s的瑞利波群速度和相速度。然后,對遠震瑞利波數(shù)據(jù)進行了雙平面波層析成像,獲得了20-143 s的瑞利波相速度頻散。通過將這兩種方法的頻散結(jié)果聯(lián)合起來,反演了5-143 s的瑞利波速度結(jié)果,得到了長江中下游地區(qū)從地表到250 km深度范圍內(nèi)的三維剪切波速度結(jié)構(gòu)。研究結(jié)果表明:在6 km深度,盆地地區(qū)均表現(xiàn)為低速特征,且河淮、蘇北和江漢盆地表現(xiàn)出比南陽和合肥盆地更低的速度,這可能是由于南陽和合肥盆地具有相對較薄的沉積層;大別-蘇魯造山帶和華南褶皺帶表現(xiàn)為高速特征,這些高速可能是由于這些地區(qū)廣泛存在中生代巖漿巖和非常淺的基底而導(dǎo)致的;在上地幔,長江中下游成礦帶下方100 km到200 km深度范圍內(nèi)存在一個明顯的低速區(qū)。該低速區(qū)可能代表由于古太平洋板塊部分熔融或者古太平洋的西向俯沖引起的地幔部分熔融而產(chǎn)生的熱的上地幔物質(zhì),然后這些幔源巖漿上涌從而導(dǎo)致了在長江中下游成礦帶形成大量的花崗巖和豐富的礦床。
[Abstract]:The middle and lower reaches of the Yangtze River mainly include the southeastern part of the North China Craton, the Dabie Sulu orogenic belt, the east-central Yangtze craton and the northeast of the Huaxia plate. It is an important polymetallic metallogenic belt and mineral resource base in the east of China. It is composed of seven large ore concentration areas and about 200 large and medium-sized deposits. Why are there so many large and super large deposits concentrated in such a narrow arc belt? What is the deep dynamic background? Is there a relationship between the deep structure and the shallow deposits? Therefore, it is important to probe the velocity structure of crust and upper mantle in the middle and lower reaches of the Yangtze River to deepen our understanding of the deep tectonic background and the mechanism of magmatic activity in the metallogenic belt, but because of the low seismicity in the middle and lower reaches of the Yangtze River, The traditional seismic imaging method is more difficult to obtain the high resolution crust-mantle velocity structure in this area. Therefore, there has been a lack of accurate crust-mantle velocity structure model in this area. In this paper, the crust and upper mantle shear wave velocity structures in the middle and lower reaches of the Yangtze River are retrieved by using background noise and biplane wave tomography for the first time. The data used in the study included 14 months of continuous background noise data from July 2012 to August 2013 and 219 teleseismic data. These data were recorded by the regional digital seismograph network of the China Seismological Bureau and the mobile broadband seismic stations set up by the China University of Geosciences (Beijing). The Rayleigh wave group velocities and phase velocities of 5 s to 42 s are obtained. Then, the Rayleigh wave data of distant earthquakes are computed by biplane wave tomography, and the dispersion of Rayleigh wave phase velocities of 20-143 s is obtained. By combining the dispersion results of the two methods, The Rayleigh wave velocity of 5-143s is inversed, and the 3-D shear wave velocity structure is obtained in the middle and lower reaches of the Yangtze River from the surface to the depth of 250 km. The results show that at the depth of 6 km, the basin is characterized by low velocity and river and Huaihe River. The north Jiangsu and Jianghan basins show lower velocities than the Nanyang and Hefei basins, which may be due to the relatively thin sedimentary layers in the Nanyang and Hefei basins, while the Dabie Sulu orogenic belt and the southern China fold belt are characterized by high speed. These high speeds may be due to the widespread presence of Mesozoic magmatic rocks and very shallow basements in these areas; in the upper mantle, There is an obvious low velocity zone between 100 km and 200 km below the metallogenic belt in the middle and lower reaches of the Yangtze River. This low speed zone may represent the partial melting of the mantle due to partial melting of the paleo-Pacific plate or westward subduction of the paleo-Pacific Ocean. The hot upper mantle material that melts, Then these mantle magma upwelling resulted in the formation of a large number of granite and rich deposits in the middle and lower reaches of the Yangtze River metallogenic belt.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P617;P542.5

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本文編號：1530684