本文選題：膠北地體 + 鋯石U-Pb年代學(xué)�。� 參考：《中國地質(zhì)大學(xué)(北京)》2015年碩士論文

【摘要】：中生代以來,華北克拉通東部發(fā)生了大規(guī)模的巖石圈減薄以及陸內(nèi)變形與巖漿活動,并伴隨金屬成礦作用,尤其在膠北發(fā)生了金的大規(guī)模聚集,而區(qū)域金成礦作用與地殼增生及再循環(huán)密切相關(guān)。為此,論文通過對晚侏羅世玲瓏黑云母花崗巖和早白堊世郭家?guī)X花崗閃長巖中繼承鋯石U-Pb年代學(xué)和Hf同位素及地球化學(xué)組成分析,厘定區(qū)域巖漿-熱事件和地殼演化歷史,探討古老物質(zhì)再循環(huán)過程和金的可能來源,獲得以下主要認識:(1)郭家?guī)X花崗閃長巖相對玲瓏黑云母花崗巖缺失新元古代-早侏羅世繼承鋯石,這段時間的繼承鋯石主要來自揚子板塊。造成這種差異可能為晚侏羅世俯沖的揚子板塊構(gòu)造板底墊托在膠北地體下造成,而后受熱擾動發(fā)生侵蝕作用發(fā)生部分熔融,花崗質(zhì)熔體被抽取密度增大,而后由于重力不穩(wěn)定發(fā)生拆沉作用,塊體沉入巖石圈地幔,早白堊世拆沉的揚子板塊未為郭家?guī)X花崗閃長巖提供物質(zhì)。(2)膠北地體前寒武紀經(jīng)歷了3.2Ga、~2.9Ga、2.8-2.7Ga、2.5Ga、2.2-1.8Ga巖漿活動,其中活動最為強烈的時間為~2.5Ga和2.2Ga。~3.2Ga為古太古代陸核形成階段,~2.9Ga、2.8-2.7Ga主要為地殼增生階段,~2.5Ga主要為地殼重熔改造,存在少量新生地殼。2.2Ga-1.8Ga為地殼的重熔改造。從古元古代到中生代則主要表現(xiàn)為老地殼的重熔再造,古老基底發(fā)生多次再循環(huán)。另外膠北地體經(jīng)歷了三期主要的變質(zhì)作用,時間為~2.5Ga、1.9~1.8Ga和250~200Ma。~2.5Ga的變質(zhì)事件和同時期巖漿活動可能與地幔柱導(dǎo)致的底侵作用有關(guān)。1.9~1.8Ga的變質(zhì)事件與造山運動有關(guān),另從沉積建造、巖漿活動及變質(zhì)作用的特征,發(fā)現(xiàn)膠北與遼吉地區(qū)具有相似性,表明膠北地體應(yīng)是遼吉地塊向南延伸的一部分,250~200Ma與晚三疊世華北板塊和揚子板塊發(fā)生的碰撞事件及之后超高壓變質(zhì)巖的折返有關(guān)。(3)多期俯沖-碰撞事件為膠北地區(qū)形成陸下富集巖石圈地幔提供了條件,而富集巖石圈地幔低程度部分熔融可產(chǎn)生富金熔體,而由于俯沖的太平洋板塊脫水提供氧化環(huán)境,有利于金從富金熔體中釋放;且膠北老基底發(fā)生重熔改造后,其中的金發(fā)生活化可進一步提供成礦物質(zhì)。因此才造成在如此小范圍內(nèi)形成如此眾多的金礦床。
[Abstract]:Since the Mesozoic, large-scale lithospheric thinning, intracontinental deformation and magmatic activity have occurred in the eastern part of the North China Craton, accompanied by metallization, especially in Jiaobei. The regional gold mineralization is closely related to crustal accretion and recirculation. Therefore, based on the analysis of zircon U-Pb chronology and HF isotopic and geochemical composition of inherited zircon from Linglong biotite granite and early Cretaceous Guojialing granodiorite of late Jurassic, the paper determines the history of regional magmatic and thermal events and crustal evolution. The recirculation process of ancient materials and the possible sources of gold are discussed. The main results are as follows: (1) the granodiorite of Guojialing is relatively Linglong biotite granite without inherited zircon from Neoproterozoic to early Jurassic. This period of inherited zircon mainly comes from the Yangtze plate. The difference may be caused by the subduction of the Yangtze plate in the late Jurassic under the Jiaobei terrane, and then the erosion occurs by thermal disturbance, and the densities of granitic melts are increased. Then, due to gravity instability, the block sank into the lithospheric mantle, and the Yangtze plate did not provide material for the Guojialing granodiorite. (2) the Precambrian magmatic activity of 3.2GaGA-2.8-2.7GA-2.5Ga2.2-1.8Ga was experienced in the Jiaobei area, and the Yangtze plate did not provide material for the Guojialing granodiorite. The most active time is 2.5Ga and 2.2Ga.3.2Ga is the PaleoArchean continental nucleation stage, 2.9Ga 2.8-2.7Ga is the crustal accretion stage and 2.5Ga is mainly crustal remelting transformation, and there is a small amount of newly formed crust. 2.2Ga-1.8Ga is crustal remelting transformation. From Paleoproterozoic to Mesozoic, the remelting of the old crust and recirculation of the ancient basement occurred. In addition, the Jiaobei terrane experienced three major metamorphic events, the metamorphic events of 2.5Ga1.9- 1.8Ga and 250Ga-200Ma.2.5Ga and magmatic activities of the same period may be related to the mantle plume induced underplating. The metamorphic events of 1.9and 1.8Ga are related to the orogenic movement, and from the sedimentary formations, the metamorphic events may be related to the mantle plume, and the metamorphic events of 1.9and 1.8Ga are related to the orogenic movement. The characteristics of magmatic activity and metamorphism show that there are similarities between Jiaobei and Liaoji areas. It is suggested that the Jiaobei terrane is a part of the Liaoji block extending southward with the collision events of the North China plate and the Yangtze plate in the late Triassic and the exhumation of the ultrahigh pressure metamorphic rocks. (3) the multi-stage subduction-collision event is the Jiaobei area. The formation of the subcontinental enriched lithospheric mantle provides the conditions for the formation of the subcontinental lithospheric mantle. The low-degree partial melting of the enriched lithospheric mantle can produce gold-rich melts, and since the subducted Pacific plate dehydration provides the oxidizing environment, it is advantageous for the gold to be released from the gold-rich melts, and after the remelting of the old basement in Jiaobei, One of the blond hair life can provide further mineral formation. As a result, so many gold deposits were formed in such a small range.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P618.51;P548

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