本文選題：南海擴(kuò)張期后 + 雷瓊地區(qū)��； 參考：《中國地質(zhì)大學(xué)(北京)》2017年碩士論文

【摘要】：南海擴(kuò)張期后在其周邊陸域特別是西北緣所發(fā)生的大規(guī)模巖漿活動(dòng)系一重大的區(qū)域特色,它所代表的構(gòu)造意義及深部過程值得予以重點(diǎn)關(guān)注。本論文以雷州半島、瓊北地區(qū)和越南昆嵩地區(qū)出露的晚新生代玄武巖為研究對(duì)象,在巖相學(xué)和地球化學(xué)工作的基礎(chǔ)上,結(jié)合同時(shí)期區(qū)域斷裂的展布特點(diǎn)和活動(dòng)規(guī)律,就中中新世(~16Ma)南海擴(kuò)張停止之后的區(qū)域地質(zhì)過程提出新的認(rèn)識(shí)。雷瓊地區(qū)和越南昆嵩地區(qū)的玄武巖噴發(fā)年代接近,性質(zhì)相似,富集大離子親石元素(LILE),高場(chǎng)強(qiáng)元素(HFSE)和輕稀土元素(LREE),毫無爭(zhēng)議地接近于板內(nèi)成因。應(yīng)用高M(jìn)g#值首先得到雷瓊和昆嵩地區(qū)的原始巖漿組分,進(jìn)一步依據(jù)原始巖漿組分中的MgO含量求得兩地的地幔潛在溫度分別為T雷瓊 p=1552.02℃,T越南p=1546.70℃,其中,瓊北的溫度還得到橄欖石-熔體平衡計(jì)算方法的支持。這一結(jié)果顯示,研究區(qū)與MORB相比較的ΔT值高達(dá)200~300℃,超過冰島而逼近夏威夷的地幔潛在溫度,暗示研究區(qū)存在堪與世界著名熱點(diǎn)媲美的地幔柱,與近期地球物探資料所得到的結(jié)果基本吻合。源自下地幔的“海南地幔柱”的存在極為可能。南海西北緣陸緣斷裂構(gòu)造非常發(fā)育。中中新世以后南海停止擴(kuò)張,正斷層代替走滑斷層成為區(qū)域斷裂體系的主要元素。在越南,正斷層主要呈N-S向展布,而在雷瓊地區(qū)呈NW-SE向展布,它們都是地幔隆升后巖漿上升的主要通道。南海停止擴(kuò)張后在其西北緣即本文研究區(qū)所顯示的巖漿-構(gòu)造活動(dòng)構(gòu)成的典型的主動(dòng)型陸內(nèi)裂谷體系,但這一體系的形成在時(shí)代順序上與南海擴(kuò)張并無關(guān)聯(lián)。
[Abstract]:The large-scale magmatism occurring in the continental area around the South China Sea, especially in the northwestern margin, is a major regional feature after the expansion period of the South China Sea. The tectonic significance and deep process represented by the magmatism deserve to be paid more attention to. In this paper, the late Cenozoic basalt exposed in Leizhou Peninsula, Qiongbei area and Kunsong area, Vietnam, is taken as the research object. On the basis of petrographic and geochemical work, combined with the distribution characteristics and activity law of regional faults in the same period, A new understanding of the regional geological process following the cessation of South China Sea extension in Miocene is presented. The eruption age of basalt in Leiqiong area is close to that in Kunsong area of Vietnam, and its properties are similar. The rich large ion lithophile element LILEN, high field strength element (HFSE) and light rare earth element (LREE) are indisputably close to the intraplate origin. Using high Mg# value, the primitive magmatic components in the Leiqiong and Kunsong areas were first obtained, and the potential temperatures of the mantle in the two places were obtained from the MgO content of the original magmatic components, respectively, at 1552.02 鈩，

本文編號(hào)：1790131