本文選題：造山帶 + 南秦嶺�。� 參考：《中國(guó)科學(xué)技術(shù)大學(xué)》2016年博士論文

【摘要】：南秦嶺構(gòu)造帶是秦嶺造山帶的重要組成部分,前人的研究結(jié)果表明南秦嶺和揚(yáng)子板塊有很大的相似性,因此,南秦嶺地體是理解秦嶺兩階段碰撞造山過(guò)程的關(guān)鍵因素,記錄兩個(gè)相鄰地體裂解而后又拼合的歷史。本文研究了南秦嶺相關(guān)巖石單元的三個(gè)主要內(nèi)容。其一,研究了南秦嶺結(jié)晶基底陡嶺雜巖兩類主要的巖石類型,厘定了形成時(shí)代和經(jīng)歷的主要演化歷史,并與揚(yáng)子板塊前寒武的演化歷史對(duì)比,探討兩個(gè)相鄰板塊的不同演化歷程。其二,研究了侵入陡嶺雜巖的新元古侵入巖的不同源區(qū)和巖石成因,結(jié)合廣泛分布于揚(yáng)子北緣的新元古構(gòu)造事件,探討其形成構(gòu)造背景。其三,研究了侵入到南秦嶺過(guò)渡型基底中的鎂鐵質(zhì)巖墻群,準(zhǔn)確限定其形成年齡以及巖石成因,并探討其動(dòng)力學(xué)背景和秦嶺造山活動(dòng)的關(guān)系。陡嶺雜巖主要由副片麻巖以及花崗質(zhì)正片麻巖構(gòu)成。三個(gè)正片麻巖的巖漿成因的鋯石顯示年齡為～2.5 Ga,表明為太古代和古元古代交界的巖漿活動(dòng)。Nd-Hf同位素證明殼幔分異發(fā)生在～3.0 Ga。這一期的巖漿活動(dòng)在揚(yáng)子板塊沒(méi)有發(fā)現(xiàn),暗示了南秦嶺和揚(yáng)子板塊不同的早期演化歷史。副片麻巖中包含不同成因的復(fù)雜來(lái)源的碎屑鋯石,鋯石的主要的年齡峰值集中在2.5 Ga,2.0 Ga,1.5 Ga和800 Ma,其中2.0 Ga和800 Ma的鋯石Th/U比值很低,沒(méi)有環(huán)帶,表明存在兩次變質(zhì)疊加。其中2.5 Ga的碎屑鋯石與正片麻巖中的鋯石年齡和Hf同位素相似,并與揚(yáng)子板塊新元古沉積巖中2.5 Ga的鋯石特征類似,表明陡嶺雜巖正片麻巖可能是這些沉積巖的重要源區(qū)。古元古晚期的變質(zhì)作用在揚(yáng)子板塊也廣泛分布,證明了南秦嶺和揚(yáng)子的密切聯(lián)系,而800 Ma的角閃巖相的變質(zhì)作用也制約了南秦嶺和揚(yáng)子板塊由擠壓轉(zhuǎn)向伸展環(huán)境的的時(shí)間,與Rodinia超大陸的聚合和裂解過(guò)程可能密切相關(guān)。侵入到陡嶺雜巖的新元古侵入體,未顯示變質(zhì)變形的特征,雖然包含從輝長(zhǎng)巖到花崗巖的多種巖石類型,形成時(shí)代卻集中在750-720 Ma。所研究的侵入巖具有不同的源區(qū),其中鎂鐵質(zhì)巖石分為兩類,一類是高Ti的輝長(zhǎng)巖,巖漿系列為堿性或拉斑質(zhì),具有高Fe含量,較低的Mg“,沒(méi)有明顯的Nb-Ta虧損,同位素特征顯示虧損的特征,表明為軟流圈地幔部分熔融的產(chǎn)物；另外一類為鈣堿性輝長(zhǎng)巖和輝長(zhǎng)閃長(zhǎng)巖,具有較高的MgO含量以及Mg#,微量元素具有典型的島弧巖漿特征,如富集輕稀土,大離子親石元素,虧損高場(chǎng)強(qiáng)元素特征,Nd同位素顯示較大的范圍,εNd(t)為-3.0到6.2,表明來(lái)自不均一交代的巖石圈地幔熔融的產(chǎn)物。長(zhǎng)英質(zhì)巖石也分為兩類,一類是Ⅰ型花崗巖,Nd-Hf同位素表明來(lái)自于幔源巖漿和殼源巖漿混合成因,另一類是S型花崗巖,源區(qū)主要是類似于陡嶺雜巖變沉積巖的地殼巖石部分熔融形成。地幔到地殼巖石發(fā)生廣泛熔融,表明南秦嶺新元古中晚期處于伸展背景。結(jié)合揚(yáng)子北緣的新元古構(gòu)造活動(dòng),將新元古的演化歷史可以歸納如下：800 Ma之前的加積俯沖階段,-800 Ma的弧陸碰撞階段,800-700 Ma的裂谷活動(dòng)階段以及700-620 Ma大陸裂解階段。南秦嶺武當(dāng)?shù)貐^(qū)存在大量的基性巖墻群,鋯石U-Pb定年表明存在兩期不同的侵位時(shí)代,-460Ma以及～220Ma,遠(yuǎn)小于前人的獲得的～680-650Ma的結(jié)果。兩期基性巖脈表現(xiàn)為相似的主量元素特征,但是截然不同的微量元素和同位素特征。早古生代的巖漿富集LREEs, LILEs以及HFSEs,具有EMⅡ型地幔同位素特征,顯示來(lái)自于類似OIB的富集地幔源區(qū)。早中生代的基性巖脈分為兩類,其中一類虧損LREEs, LILEs以及HFSEs,具有DM型地幔同位素特征,表明來(lái)自于軟流圈地幔源區(qū),第二類相比于第一類巖脈有更高的Rb, Ba, K含量,同時(shí)具有EMI型同位素特征,表明它們的源區(qū)包含了顯著的揚(yáng)子板塊下地殼巖石貢獻(xiàn)。這些鎂鐵質(zhì)巖漿記錄了南秦嶺顯生宙漫長(zhǎng)的演化歷史,古生代的基性巖脈可能與分隔南秦嶺和揚(yáng)子板塊的勉略洋的形成相關(guān),而早中生代的基性巖脈來(lái)源于兩者碰撞拼合后伸展階段軟流圈上涌部分熔融,俯沖的大洋板片斷離模型不僅可以來(lái)用解釋中生代武當(dāng)?shù)貐^(qū)的鎂鐵質(zhì)巖脈成因,也可以解釋秦嶺中生代造山東西兩側(cè)的差異。在東側(cè)的大別蘇魯?shù)貐^(qū),板塊斷裂的深度較大,沒(méi)有明顯的同造山巖漿活動(dòng),而在東秦嶺地區(qū),板片斷離的深度較小,軟流圈上涌至較淺位置,引起地殼廣泛熔融,形成大量的花崗質(zhì)巖漿活動(dòng)。武當(dāng)?shù)貐^(qū)的基性巖脈記錄了勉略洋從形成到閉合的歷史。
[Abstract]:The southern Qinling Mountains tectonic belt is an important part of the Qinling Mountains orogenic belt. The results of previous studies show that the southern Qinling Mountains and the Yangtze plate are very similar. Therefore, the southern Qinling Mountains earth body is the key factor in understanding the two stage of the collision orogenic process in Qinling Mountains, and records the history of the splitting and splitting of the two adjacent areas. In this paper, the related rocks in southern Qinling Mountains are studied. Three main contents of the stone unit. First, we studied two main types of rock types of the crystalline basement dling complex in southern Qinling Mountains, determined the main evolution history of the formation time and experience, compared with the evolution history of the Precambrian of the Yangtze plate, and discussed the different evolution course of the two adjacent plates. Secondly, the new elements of the intrusion of the dash complex were studied. The non homologous region and petrogenesis of the paleo intrusive rocks are combined with the Neoproterozoic tectonic events widely distributed in the northern margin of the Yangtze River, and the formation of its tectonic setting is discussed. Thirdly, the mafic rock wall group invading into the transitional basement of South Qinling Mountains is studied, the age of formation and the cause of rock formation are accurately defined, and its dynamic background and Qinling Mountains orogenic activities are discussed. The dling complex is mainly composed of paraplastic gneiss and granitic positive gneiss. The magmatic zircon of three positive magma shows a age of ~ 2.5 Ga, indicating that the magmatism.Nd-Hf isotopes at the junction of Archaean and Palaeoproterozoic showed that the magmatic activity of the crust and mantle differentiation occurred in the period of ~ 3 Ga., and that there was no hair in the Yangtze plate. It is suggested that the early evolution history of southern Qinling Mountains and Yangzi plate is different. Parisneis contains complex sources of detrital zircon from different origins. The main peak age of zircon is 2.5 Ga, 2 Ga, 1.5 Ga and 800 Ma, of which 2 Ga and 800 Ma zircon Th/U ratio is very low, and there is no belt, indicating that there is two metamorphic superposition. 2.5 of them. The detrital zircon of Ga is similar to the zircon age and Hf isotopes in the ortho Proterozoic, similar to the zircon features of the 2.5 Ga in the Neoproterozoic sedimentary rocks of the Yangtze plate, indicating that the dling complex is probably an important source of these sedimentary rocks. The metamorphic action of the late Proterozoic was also widely distributed in the Yangtze plate, proving that southern Qinling Mountains and the Yangtze were also proved. The metamorphism of the 800 Ma amphibolite facies also restricts the time of the southern Qinling Mountains and the Yangtze plate from the extrusion to the extensional environment, which is closely related to the process of polymerization and cracking of the Rodinia supercontinent. The Neoproterozoic intrusions into the dling complex have not shown the characteristics of metamorphic deformation, although it contains from gabbro to granite. A variety of rock types, the formation age is concentrated in 750-720 Ma., the intrusive rocks have different source areas, of which mafic rocks are divided into two types, one is high Ti gabbro, the magma series is alkaline or pulla, with high Fe content, low Mg ", no obvious Nb-Ta loss, isotopic characteristics show loss characteristics, isotopic characteristics show loss characteristics, the isotope characteristics show loss characteristics. The latter is the product of partial melting of the asthenosphere mantle; the other is calc alkaline gabbro and gabbro, with high MgO content and Mg#. The trace elements have typical island arc magma characteristics, such as the enrichment of light rare earth, large ion lithopite elements, the loss of high field and strong elements, Nd isotopes showing a larger range, and the Nd (T) of -3.0 to 6.2 It shows the product of the melting of the lithosphere mantle melt from the inhomogeneous metasomatism. The felsic rocks are also divided into two types, one is type I granite, and the Nd-Hf isotopes indicate that the mixture of mantle derived magma and crust source magma and the other type is S type granite. The source area is mainly formed by partial melting of the crustal rocks similar to the dling complex sedimentary rocks. The extensive melting of the mantle to the crustal rocks indicates that the middle late Neoproterozoic in southern Qinling Mountains is in extensional background. In combination with the Neoproterozoic tectonic activities of the northern margin of the Yangtze, the evolutionary history of the Neoproterozoic can be summed up as follows: the accretion subduction stage before 800 Ma, the arc collision stage of the -800 Ma, the rift stage of the 800-700 Ma and the 700-620 Ma continental fissure. There are a large number of basic rock wall groups in the Wudang region of southern Qinling Mountains. The zircon U-Pb dating shows that there are two different emplacement times, -460Ma and 220Ma, far less than the results obtained by the predecessors to 680-650Ma. The two phases of the basic rock veins are characterized by similar principal elements, but are distinct trace elements and isotopes. The magma of the Palaeozoic was enriched in LREEs, LILEs and HFSEs, characterized by EM II mantle isotopes, showing the origin of the rich mantle derived from similar OIB. The early Mesozoic basic rock veins were divided into two types, including a loss of LREEs, LILEs and HFSEs, with the DM type mantle isotopic characteristics, indicating that the second types were compared to the asthenosphere mantle source region. The first type of vein has a higher Rb, Ba, K content and EMI isotopic characteristics, indicating that their source area contains significant contribution to the lower crust rock of the Yangtze plate. These mafic magma records the long history of the protracted evolution of the southern Qinling Mountains, and the Paleozoic vein may be associated with the delimited ocean of the southern Qinling Mountains and the Yangtze plate. The formation of the early Mesozoic basic rocks originated from the partial melting of the asthenosphere in the extension stage after the collision and combination. The subduction of the oceanic plate fragments from the model can not only explain the genesis of the mafic veins in the Mesozoic Wudang region, but also explain the difference between the two sides of the Mesozoic orogenic East and West in Qinling Mountains. In the region of Shandong, the depth of the plate fracture is larger, and there is no obvious same orogenic magmatic activity. In East Qinling Mountains, the depth of the plate fragment is smaller and the soft flow circle flows to a relatively shallow position, causing extensive melting of the crust and forming a large number of granitic magma activities.
【學(xué)位授予單位】：中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：P548
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本文編號(hào)：1933122