發(fā)布時(shí)間：2018-06-05 02:13

  本文選題：大興安嶺中段 + 滿克頭鄂博組�。� 參考：《吉林大學(xué)》2017年碩士論文

【摘要】：本文對(duì)大興安嶺中段五岔溝地區(qū)滿克頭鄂博組火山巖進(jìn)行了LA-ICP-MS鋯石U-Pb年代學(xué)、全巖地球化學(xué)和鋯石原位Lu-Hf同位素的測(cè)試分析,以便探討其形成時(shí)代、巖石成因、源區(qū)性質(zhì)等方面問(wèn)題,為更進(jìn)一步認(rèn)識(shí)大興安嶺晚中生代大規(guī)模巖漿活動(dòng)及其地球動(dòng)力學(xué)背景提供依據(jù)。從巖相學(xué)來(lái)說(shuō),五岔溝地區(qū)滿克頭鄂博組火山巖巖石組合為流紋巖、流紋質(zhì)凝灰?guī)r和少量英安巖。所測(cè)四件火山巖樣品的鋯石呈自形-半自形,發(fā)育清晰的振蕩生長(zhǎng)環(huán)帶,結(jié)合其較高的Th/U比值(0.40~1.54),暗示其典型巖漿成因的特征。LA-ICP-MS鋯石U-Pb定年結(jié)果表明,五岔溝地區(qū)滿克頭鄂博組火山巖形成于早白堊世早期(143~139Ma)。巖石地球化學(xué)方面,滿克頭鄂博組火山巖具有高硅(SiO2=66.70~79.91 wt.%),富堿(Na2O+K2O=5.93~9.72 wt.%),貧鎂(MgO=0.08~1.15wt.%)、鐵(TFeO=0.68~4.50 wt.%)、鈣(CaO=0.10~2.56 wt.%)的特征,總體為高鉀鈣堿性準(zhǔn)鋁質(zhì)至弱過(guò)鋁質(zhì)巖石。這些火山巖富集大離子親石元素(如Rb、Th、U等)和輕稀土元素,虧損高場(chǎng)強(qiáng)元素(如Nb、Ta、Ti等)和重稀土元素,具有高分異I型火山巖的特征。此外,滿克頭鄂博組火山巖鋯石具有較高的176Hf/177Hf比值(0.282900~0.283093),正的εHf(t)值(+7.48~+14.19),年輕的二階段Hf模式年齡(954~344Ma),表明滿克頭鄂博組火山巖源于新元古代—顯生宙期間從虧損地幔中新增生地殼物質(zhì)的部分熔融。在本文研究基礎(chǔ)上,并結(jié)合東北地區(qū)中生代火山巖的時(shí)空分布規(guī)律,認(rèn)為早白堊世期間大興安嶺地區(qū)可能受蒙古-鄂霍茨克洋閉合和古太平洋俯沖的雙重影響,此時(shí)處于蒙古-鄂霍茨克構(gòu)造域向古太平洋構(gòu)造域轉(zhuǎn)化的關(guān)鍵時(shí)期,在早白堊世早期主要受蒙古-鄂霍茨克洋閉合后巖石圈伸展作用的影響,在早白堊世早期之后主要受古太平洋俯沖的控制。
[Abstract]:In this paper, the LA-ICP-MS zircon U-Pb chronology, whole rock geochemistry and zircon in situ Lu-Hf isotopes of the volcanic rocks of the Mankitou Ebo formation in the Wuchagou formation of the central Daxinganling region have been measured and analyzed in order to discuss the formation age and petrogenesis of the volcanic rocks. The characteristics of the source region provide a basis for further understanding of the late Mesozoic magmatic activities and their geodynamic background in the Daxinganling Mountains. In terms of petrography, the volcanic rock assemblage of Mancitou Obo formation in Wuchaigou area is composed of rhyolite, streamline tuff and a small amount of dolomite. The zircon of the four volcanic rock samples showed a self-shape and semi-automorphism with a distinct oscillatory growth ring and a high Th/U ratio of 0.400.401.54, indicating the characteristics of its typical magmatic genesis. LA-ICP-MS zircon U-Pb dating results show that, The volcanic rocks of the Mankitou Ebo formation in Wuchaigou area were formed in early Cretaceous of the early Cretaceous. In terms of rock geochemistry, the volcanic rocks of the Orbo formation in Mankitou have the characteristics of high SiO2SiO66.7079.91wt., alkali-rich Na2O K2O=5.93~9.72 wt., magnesium-poor MgO0.081.15wt., TFeOO 0.68,4.50wt.batt, calcium CaO0.10n2.56wt.), which are generally high potassium calc-alkaline quasaluminite to weakly peraluminous rocks. These volcanic rocks are rich in large ion lithophile elements (such as RbPU, etc.) and light rare earth elements, depleted in high field strength elements (such as NbPU, Ti, etc.) and heavy rare earth elements, and are characterized by high differentiation I type volcanic rocks. In addition, The zircon of the volcanic rocks in Mankitou Ebo formation has a high 176Hf/177Hf ratio of 0.282900 (0.283093) and a positive 蔚 Hfft (7.48 ~ 14.19). The age of the young two-stage HF model is 954 ~ 344 Ma, which indicates that the volcanic rocks of the Orbo formation originated from the Neoproterozoic to Phanerozoic period and were newly added from the depleted mantle during the Neoproterozoic to Phanerozoic period. Partial melting of raw crust material. On the basis of this study and the temporal and spatial distribution of Mesozoic volcanic rocks in Northeast China, it is considered that the Daxinganling area during the early Cretaceous was affected by the closure of Mongolia-Okhotsk Ocean and the subduction of the Paleo-Pacific Ocean. At this time, it is in the key period of the transformation from Mongolia-Okhotsk tectonic domain to paleo-Pacific tectonic domain. In the early Cretaceous, it was mainly influenced by the lithospheric extension after the closure of the Mongolia-Okhotsk Ocean. After the early Cretaceous, it was mainly controlled by the paleo-Pacific subduction.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P588.14

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本文編號(hào)：1979971