【摘要】：中國(guó)東北地區(qū)處于中亞造山帶的最東段，以廣泛分布的顯生宙花崗質(zhì)侵入巖為特征。傳統(tǒng)認(rèn)為這些花崗質(zhì)巖石形成于晚古生代，主要出露于大興安嶺地區(qū)，沿嫩江-賀根山斷裂帶呈北東向展布。由于缺乏精準(zhǔn)的年代學(xué)和巖石地球化學(xué)資料，嚴(yán)重影響了我們對(duì)其成因和形成構(gòu)造背景的認(rèn)識(shí)。本文對(duì)大興安嶺南部東烏旗地區(qū)5個(gè)具有代表性晶洞堿長(zhǎng)花崗巖體進(jìn)行了鋯石LA-ICP-MS U-Pb年代學(xué)、巖石地球化學(xué)和鋯石原位Hf同位素的測(cè)試分析，確定了研究區(qū)花崗巖的形成時(shí)代和巖石成因，進(jìn)而討論了大興安嶺地區(qū)晚古生代構(gòu)造演化過(guò)程。本文研究的這些堿長(zhǎng)花崗巖主要由石英和堿性長(zhǎng)石組成，含有少量的斜長(zhǎng)石、黑云母，角閃石和副礦物，多數(shù)樣品具有晶洞構(gòu)造，暗示其就位深度較淺并經(jīng)過(guò)較強(qiáng)的結(jié)晶分異作用。新的鋯石U-Pb定年結(jié)果顯示其結(jié)晶于315~300Ma。這些花崗巖富SiO2（73.22%~77.36%）和K2O（3.89%~4.86%），，MgO（0.07%~0.49%）、MnO（0.01%~0.09%）、CaO（0.14%~0.60%）和P2O5（0.01%~0.08%）的含量相對(duì)較低，A/CNK和δEu值分別為0.98~1.14和0.03~0.60。稀土元素配分模式圖顯示輕稀土元素相對(duì)富集，具有明顯的負(fù)銪異常。微量元素原始地幔標(biāo)準(zhǔn)化蛛網(wǎng)圖顯示Ba、Nb、Ta、Sr和Eu相對(duì)虧損，而Zr、Hf、Rb、Th和U較為富集。礦物學(xué)、巖石學(xué)和地球化學(xué)特征表明，它們屬于弱過(guò)鋁質(zhì)高鉀鈣堿性高分異I型花崗巖。另外，花崗巖的εHf(t)和二階段模式年齡分別介于+7.6~+15.1和364Ma~835Ma，表明原始巖漿起源于新增生地殼的部分熔融。根據(jù)地球化學(xué)資料和先前的區(qū)域地質(zhì)調(diào)查研究，我們認(rèn)為這些晶洞堿長(zhǎng)花崗巖形成于活動(dòng)大陸邊緣的背景，其形成可能與興安地塊和松嫩地塊之間的古亞洲洋持續(xù)向西北俯沖有關(guān)。
[Abstract]:Northeast China is located in the easternmost part of the Central Asian orogenic belt, characterized by widely distributed Phanerozoic granitic intrusive rocks. Traditionally, these granitic rocks were formed in the late Paleozoic and mainly appeared in the Daxinganling area, and spread along the Nenjiang-Hegenshan fault zone in a northeasterly direction. The lack of accurate geochronological and petrogeochemical data has seriously affected our understanding of its genesis and tectonic background. In this paper, the zircon LA-ICP-MS U-Pb chronology, geochemistry and in situ Hf isotopes of zircon have been measured and analyzed for five representative crystalline cave alkali feldspar granites in Dongwuqi area, south of Daxing'anling Mountains. The formation age and petrogenesis of granites in the study area are determined, and the late Paleozoic tectonic evolution process in Daxinganling area is discussed. These alkali feldspar granites are mainly composed of quartz and alkaline feldspar, and contain a small amount of plagioclase, biotite, hornblende and accessory minerals. It is suggested that it has a shallow depth and strong crystallization differentiation. The new zircon U-Pb dating results show that the zircon crystallized at 315 Ma. These granites are rich in SiO2 (73.222%) and K2O (3.89%), MgO (0.07%) and 0.49%), MnO (0.01% (0.09%). The contents of CaO (0.14% 0.60%) and P2O5 (0.01%) were relatively low, the values of A/CNK and 未 Eu were 0.981.14 and 0.030.60, respectively. The REE partitioning pattern shows that LREE is relatively enriched and has obvious negative europium anomaly. The trace element primitive mantle-standardized spider webs show the relative depletion of Ba,Nb,Ta,Sr and Eu, but the enrichment of Zr,Hf,Rb,Th and U. Mineralogical, petrological and geochemical characteristics indicate that they belong to weakly peraluminous high-potassium calc-alkaline high-grade iso-I-type granite. In addition, the 蔚 Hf (t) and two-stage model ages of the granites ranged from 7.6 to 15.1 and 364 Ma-835 Ma, respectively, indicating that the primitive magma originated from partial melting of the new accretive crust. Based on geochemical data and previous regional geological surveys, we believe that these granites formed in the background of active continental margin. Its formation may be related to the persistent northwestern subduction of the paleo-Asian ocean between the Xingan and Songnen massif.
【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】：2015
【分類號(hào)】：P588.121

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