本文選題：黑河 + 河漫灘碎屑鋯石　； 參考：《中國地質(zhì)大學(xué)(北京)》2015年碩士論文

【摘要】：本文通過碎屑鋯石的U-Pb年齡來研究北祁連地區(qū)巖漿事件的發(fā)生時(shí)間;通過Hf同位素分析巖漿事件中新生地殼和被改造古老地殼的信息,并用來估算新生地殼的產(chǎn)生時(shí)間;結(jié)合主微量元素,獲得源區(qū)區(qū)域地殼的基本特征、形成演化歷史及其地球化學(xué)意義。得出如下認(rèn)識(shí):(1)黑河河漫灘沉積物中的碎屑鋯石U-Pb年齡主要分為232~551Ma(54.9%),982~1163Ma(1.5%),1500~2202Ma(34.7%)和2350~2681Ma(8.9%)四個(gè)年齡段。(2)前寒武紀(jì)年齡主要分布在元古代,黑河河漫灘沉積物碎屑鋯石900~1200Ma的年齡可與同時(shí)期全球的Rodinia超大陸裂解事件做對(duì)比,另外根據(jù)1800Ma左右的峰值年齡信息推斷物源區(qū)存在該時(shí)期明顯的巖漿作用事件。(3)新元古代末-古生代年齡信息里面,晚震旦紀(jì)到早奧陶紀(jì)形成祁連洋盆,且北祁連洋盆于奧陶紀(jì)開始俯沖消減,并且貫穿整個(gè)奧陶紀(jì);于早志留紀(jì)已經(jīng)發(fā)生碰撞造山作用,且持續(xù)到泥盆紀(jì)時(shí)期;而黑河河漫灘碎屑鋯石測(cè)年工作獲得了海西期的年代學(xué)信息,印證了前人關(guān)于北祁連西段存在海西期巖漿活動(dòng)的報(bào)告,且北祁連地區(qū)加里東中期和晚期的侵入花崗巖體都有經(jīng)歷海西期的巖漿熱事件的改造。(4)黑河河漫灘沉積物樣品13HH-1與HH1-1和HH2相比缺少980~1160Ma的年齡數(shù)據(jù),主要是由于碎屑鋯石隨著水遷移距離的增加,粒度逐漸變小,甚至滯留在上游,不易被檢測(cè)。(5)黑河河漫灘沉積物中明顯虧損Nb、Ta等高場(chǎng)強(qiáng)元素,輕度富集Cs、Rb、Nd、La等大離子親石元素。(6)祁連地塊提供了黑河河漫灘碎屑沉積物的幾乎全部物源貢獻(xiàn)。(7)黑河河漫灘沉積物物源區(qū)平均大陸地殼各時(shí)期均有新生地殼的產(chǎn)生和古老地殼的重熔。具體來說2350-2681Ma期間以新生地殼為主,兼有部分古老地殼的重熔;1500-2202Ma期間以古老地殼的重熔為主;顯生宙以來主要以古老基底巖石的重熔再造為主。
[Abstract]:In this paper, the occurrence time of magmatic events in North Qilian area is studied by U-Pb age of clastic zircon, the information of new crust and reformed old crust in magmatic event is analyzed by HF isotope, and the generation time of new crust is estimated. Combined with main trace elements, the basic characteristics, evolution history and geochemical significance of the regional crust in the source area are obtained. The main results are as follows: (1) the zircon U-Pb ages in the sediments of the Heihe River floodplain are mainly divided into four age groups: 232A551 Ma (54.9%), Precambrian ages (1.5%), 1500220Ma (34.7%), and 2350,2681Ma (8.9%). (2) the Precambrian ages are mainly distributed in Proterozoic. The age of 900 ~ (200 Ma) zircon from sediments of Heihe River floodplain can be compared with the Rodinia supercontinental pyrolysis event of the same period. In addition, it is inferred from the peak age information of about 1800 Ma that magmatism events occurred in the source area of this period. (3) in the information of Neoproterozoic and Paleozoic ages, the Qilian ocean basin was formed from late Sinian to early Ordovician. The North Qilian ocean basin began to subduction in Ordovician and ran through Ordovician, and collisional orogeny occurred in early Silurian and lasted until Devonian. The dating of detrital zircon in the Heihe River floodplain obtained the chronological information of the Hercynian period, which confirmed the previous reports on the existence of the Hercynian magmatic activity in the western part of North Qilian. Moreover, the intrusive granite bodies in the middle and late Caledonian periods in North Qilian area have undergone the transformation of the Hercynian magmatic thermal events. (4) the age data of 13HH-1 in the sediment samples of Heihe River floodplain are less than those of HH1-1 and HH2 at 980,1160Ma. The main reason is that the grain size of the detrital zircon becomes smaller with the increase of water migration distance, and even stays upstream, which is not easy to detect. (5) the high field strength elements, such as NB, Ta and so on, are obviously depleted in the sediments of Heihe River floodplain. (6) the Qilian massif provides almost all the contribution of the detrital sediments of the Heihe River floodplain. (7) the average continental crust of Heihe River floodplain sediment source area has the occurrence of new crust in every period. And the remelting of the ancient crust. Specifically, during 2350-2681 Ma, the new crust dominated, and part of the ancient crust was remelted during 1500-220Ma, and since the Phanerozoic, the remelting of the ancient basement rocks was the main one.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P597.3;P588.21

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本文編號(hào)：2085352