【摘要】：佳木斯地塊是中亞造山帶在中國東北的一個重要構(gòu)造單元，也是興蒙造山帶若干變質(zhì)地體中最著名的一個，地處西伯利亞克拉通和華北克拉通之間。同整個中亞造山帶一樣，佳木斯地塊經(jīng)歷了多期次、多階段的復(fù)雜構(gòu)造演化，形成了大量的花崗質(zhì)巖石。新的鋯石U Pb年齡測定表明，佳木斯地塊很多原被認(rèn)為形成于元古代的花崗巖，實(shí)際上形成于晚古生代，而早古生代花崗巖的時空展布、巖石組合和成因目前尚不清楚，因而有必要加強(qiáng)對早古生代花崗巖的研究。 本文通過對佳木斯地塊東部花崗巖的年代學(xué)、全巖地球化學(xué)和鋯石Hf同位素特征的研究，確定花崗質(zhì)巖石的形成時代及成因，并進(jìn)一步探討佳木斯地塊早古生代花崗巖形成的地球動力學(xué)背景。鋯石LA ICP MS U Pb結(jié)果表明，佳木斯地塊東部早古生代花崗巖的侵位年齡在530~484Ma之間。地球化學(xué)特征顯示：SiO2=64.66%~79.17%、K2O=3.08%~7.33%、MgO=0.14%~2.63%、CaO=0.37%~3.87%、A/CNK=0.89~1.10、 u=0.16~1.77，，富集大離子親石元素（Rb、Nd），虧損高場強(qiáng)元素（Nb、Ta、P、Ti）；鋯石原位Hf同位素分析顯示花崗巖的εHf（t）值介于-5.8~+2.3之間，二階段Hf模式年齡介于2.4~1.3Ga之間。表明其原始巖漿起源于古-中元古代增生的下地殼物質(zhì)的部分熔融。此外，根據(jù)地球化學(xué)及同位素組成的變化，這些花崗巖的巖漿鋯石記錄了一致的鋯石U Pb年齡和不一致的εHf（t）比值，暗示在巖石成因過程中存在分離結(jié)晶作用和地殼混染作用。 結(jié)合區(qū)域研究資料，佳木斯地塊曾發(fā)生過大規(guī)模的泛非期巖漿活動，且該期巖漿事件至少持續(xù)了50Ma，這些花崗巖屬于殼源成因的碰撞后花崗巖，為加厚的造山帶發(fā)生垮塌性伸展導(dǎo)致下地殼物質(zhì)的部分熔融而形成的花崗質(zhì)巖石，反映了佳木斯地塊該期應(yīng)處于碰撞后的伸展構(gòu)造環(huán)境。
[Abstract]:The Jiamusi massif is an important tectonic unit of the Central Asian orogenic belt in northeast China and one of the most famous metamorphic terraces in the Xingmeng orogenic belt, located between the Siberian Craton and the North China Craton. Like the whole Central Asian orogenic belt, the Jiamusi massif underwent multiple stages of complex tectonic evolution and formed a large number of granitic rocks. The new zircon U-Pb dating indicates that many of the Jiamusi blocks were originally considered to have formed in the Proterozoic granite, but in fact they were formed in the late Paleozoic, while the space-time distribution, rock assemblage and genesis of the early Paleozoic granites are still unclear. Therefore, it is necessary to strengthen the study of early Paleozoic granite. Based on the study of geochronology, geochemistry and zircon HF isotopic characteristics of granites in the eastern Jiamusi massif, the forming age and genesis of granitic rocks are determined in this paper. The geodynamic background of the early Paleozoic granite formation in the Jiamusi block is also discussed. The results of zircon ICP and MS U / Pb indicate that the emplacement age of the early Paleozoic granites in the eastern Jiamusi block is between 530~484Ma. The geochemical characteristics show that 79.17K _ 2O-3.08 is 7.33mg _ O _ (0.14) and 2.63 ~ 0.37K ~ 0.370.891.10, U ~ (0.16N) 1.77, enriched in large ion lithophile element (Rbndd), depleted high field strength element (NbLi _ TaPnTi), zircon in-situ HF isotopic analysis shows that the 蔚 Hf (t) value of the granite is between -5.8 ~ 2.3, and the age of the second stage HF model is between -5.8 ~ 2.3, and the age of the second stage HF model is between 2.4~1.3Ga. It is indicated that the primitive magma originated from partial melting of the materials of the lower crust that were accreted in the Paleo-Mesoproterozoic. In addition, according to the changes of geochemistry and isotopic composition, the magmatic zircon of these granites recorded a consistent zircon U-Pb age and inconsistent 蔚 Hf (t) ratio, suggesting that there were segregation crystallization and crustal mixing in the genesis of the rocks. In combination with regional research data, the Jiamusi massif experienced large-scale Pan-African magmatic activity, and the magmatic event lasted at least 50 Ma.These granites belong to post-collision granites of crustal origin. The granitic rocks formed by the collapse extension of the thickened orogenic belt and the partial melting of the material in the lower crust reflect that the Jiamusi massif should be in the post-collision extensional tectonic environment in this period.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P588.121

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