本文選題：安山質(zhì)巖漿作用 + 雙峰式火山作用�。� 參考：《中國科學(xué)技術(shù)大學(xué)》2016年博士論文

【摘要】：板塊構(gòu)造理論可以很好地解釋現(xiàn)代匯聚板塊邊緣弧巖漿作用的發(fā)生機制,但是對于大陸弧鎂鐵質(zhì)巖漿巖的地幔源區(qū)性質(zhì)、俯沖板片物質(zhì)加入到地幔楔的具體機制以及大陸弧巖漿從源區(qū)提取之后在上覆板塊發(fā)生的分異演化過程等問題仍不是很清楚。在大陸內(nèi)部,具有弧型地球化學(xué)特征的鎂鐵質(zhì)巖漿巖也很常見,這些巖漿巖在形成時遠離現(xiàn)今活動大陸邊緣,它們的成因是受古代消亡板塊板塊俯沖構(gòu)造控制還是受現(xiàn)今活動板塊構(gòu)造控制,已經(jīng)成為一個亟待解決的問題。本博士學(xué)位論文選取華南長江中下游地區(qū)晚中生代火山巖作為對象進行系統(tǒng)的巖石地球化學(xué)研究,結(jié)果不僅對長江中下游地區(qū)晚中生代火山巖的成因機制提供了新的系統(tǒng)的認識,而且建立了古大洋俯沖帶殼幔相互作用與現(xiàn)今陸內(nèi)弧型巖漿巖之間的成因聯(lián)系本文第一章到第四章分別系統(tǒng)介紹了選題研究背景、區(qū)域地質(zhì)背景、樣品采集和描述以及所采用的一系列分析方法。第五章以長江中下游地區(qū)廬樅盆地晚中生代安山巖為例,通過系統(tǒng)的全巖主微量、Sr-Nd-Pb-Hf同位素、鋯石U-Pb年齡以及Hf-O同位素研究。探討了古安第斯型俯沖帶富集地幔源區(qū)的形成過程及其對大陸弧安山巖成因的指示意義。在第六章中,通過對寧蕪火山巖進行鋯石U-Pb年齡和Hf-O同位素分析、全巖主微量元素和Sr-Nd-Hf同位素分析,驗證了廬樅安山質(zhì)火山巖的成因機制是否適用于寧蕪盆地安山巖。第七章對寧蕪火山巖中的單斜輝石斑晶進行了巖石學(xué)和地球化學(xué)分析,以期對寧蕪火山巖的巖漿演化過程有系統(tǒng)的認識,從而進一步制約源區(qū)組成和巖漿過程對寧蕪安山質(zhì)火山巖地球化學(xué)成分的相對貢獻。在第八章中對繁昌盆地晚中生代雙峰式火山巖進行了系統(tǒng)的U-Pb定年和Hf-O同位素分析,以期確定它們的巖石成因。第九章中通過編輯文獻發(fā)表的長江中下游地區(qū)火山巖地球化學(xué)數(shù)據(jù),對比了該地區(qū)玄武巖、安山巖以及英安巖-流紋巖的地球化學(xué)組成,對該地區(qū)晚中生代火山巖的成因給出了系統(tǒng)的解釋,同時也對這些火山巖形成的構(gòu)造背景進行了限定。論文根據(jù)江南造山帶北部在長江中下游地區(qū)的構(gòu)造出露,提出在新元古代時期華夏洋向揚子克拉通南緣的北向俯沖過程中發(fā)生了俯沖洋殼衍生熔體與地幔楔-橄欖巖之間的化學(xué)反應(yīng)。因此,長江中下游地區(qū)晚中生代巖漿作用本質(zhì)上就是古老安第斯型俯沖帶形成的富集富沃巖石圈地幔在晚中生代太平洋板塊西向俯沖引發(fā)華南陸塊巖石圈伸展背景下再活化的產(chǎn)物。廬樅盆地火山巖主要由玄武質(zhì)粗面安山巖和粗面安山巖組成,伴隨有少量的粗面玄武巖和粗面巖。這些巖石具有變化的SiO2(48.66-63.43 wt.%), MgO (0.39-4.85 wt.%), Na2O (1.22-6.07 wt.%)和K2O (2.53-10.10 wt.%)含量,其同時具有高的變化的K2O/Na2O比值(0.45-7.39).廬樅火山巖具有弧型徽量元素分布特征,表現(xiàn)為富集LILE、Pb和LREE,虧損HFSE.它們還具有富集的Sr-Nd-Pb-Hf同位素組成,其87Sr/86Sr初始比值介于0.7050和0.7066之間,εNd(t)值介于-8.0和-3.1之間,εHf(t)值介于-11和-1.1之間；在給定的206Pb/204Pb比值下.具有顯著高出北半球參考線的207Pb/204Pb和207Pb/204Pb比值。 鋯石U-Pb定年給出了127：1：2至137±1 Ma的巖漿結(jié)晶年齡,這些鋯石具有高的δδ18O值(5.3-7.6%以及高度變化的ε:Hf(t)值從-13.1變化到2.6。這些地球化學(xué)特征表明,廬樅晚中生代火山巖源自富集富沃地幔源區(qū)的部分熔融,這一地幔源區(qū)形成于古安第斯型俯沖帶沉積物來源熔體與上覆地幔楔橄欖巖之間的相互作用,類似現(xiàn)今大陸弧之下的殼幔相互作用過程。因此,該研究結(jié)果表明,大量沉積物來源的熔體加入到地幔楔橄欖巖中形成富集富沃的地幔源區(qū)可能是安山巖形成的重要前提條件。結(jié)合大洋弧玄武巖的成因機制,我們認為大陸弧安山巖與大洋弧玄武巖的成分差別本質(zhì)上受控于交代介質(zhì)的化學(xué)成分,前者以沉積物來源含水熔體為主,后者以蝕變洋殼來源的富水流體為主。寧蕪火山巖主要由粗面安山巖和粗面巖組成,包含少量的玄武質(zhì)粗面安山巖。這些火山巖具有低的變化的MgO含量(0.11-3.73wt.%),低的Mg#值(1.60-51.18),高的K20含量(1.99-9.88wt.%)。它們具有弧型微量元素配分模式,表現(xiàn)為富集LILE,Pb和LREE,虧損HFSE,它們還具有富集的Sr-Nd-Pb-Hf同位素特征,其初始87Sr/86Sr比值介于0.7050和0.7082之間,εNd(t)值介于-8.1和-1.8之間,εHf(t)值介于-6.7和0.39之間；在給定的206Pb/204pb比值(17.76-18.28)下,具有顯著高出北半球參考線的207pb/204pb(15.47-15.61)和208Pb/204Pb(37.75-38.44)比值。 锫石U-Pb定年給出了128±2到133±2 Ma的巖漿結(jié)晶年齡,這些鋯石具有高的8190值(5.7-7.8‰)以及變化的εHf(t)值從-5.8變化到0.7。根據(jù)其截然不同的成分特征,可以將這些安山巖劃分為兩組。相對組Ⅱ樣品,組1樣品具有更為富集的Sr-Nd-Pb-Hf同位素組成和相對低的不相容元素含量。對這些地球化學(xué)特征的綜合分析表明,組Ⅰ火山巖形成于富集程度較高、含有大量金云母地慢源區(qū)較高程度的部分熔融；相反,組Ⅱ火山巖形成于富集程度相對較低、金云母含量較少的地幔源區(qū)較低程度的部分熔融。由于沉積物來源的長英質(zhì)熔體組分的加入,這兩種地幔源區(qū)在巖石化學(xué)上比正常橄欖巖地幔都相對富沃。對寧蕪火山巖中的單斜輝石斑晶進行了系統(tǒng)巖石學(xué)和地球化學(xué)分析,結(jié)果對寧蕪火山巖的巖漿演化過程有了系統(tǒng)的認識,從而進一步認識到源區(qū)成分和巖漿過程對寧蕪安山質(zhì)火山巖地球化學(xué)成分的相對貢獻。分析發(fā)現(xiàn),這些斑晶具有復(fù)雜的結(jié)構(gòu)和成分環(huán)帶,且不同的環(huán)帶對應(yīng)于不同的REE配分形式。根據(jù)其截然不同的REE配分模式,可以將這些單斜輝石分為三類。第一類單斜輝石具有平坦的REE配分模式和強烈的Eu負異常,第二類單斜輝石具有LREE-MREE富集的右傾的REE配分模式以及中等程度的Eu負異常,第三類單斜輝石具有MREE虧損的REE配分模式和強烈的Eu負異常。這三類輝石呈現(xiàn)出兩種截然不同的成分演化趨勢,指示它們結(jié)晶自兩種截然不同的熔體。其中,第一類單斜輝石結(jié)晶自由REE富集程度較弱的初始熔體演化形成的熔體,第二類和第三類輝石則結(jié)晶自由REE富集程度較高的初始熔體演化形成的熔體。第二類輝石和第三類輝石的成分差異表明,在二者結(jié)晶的間隙存在大量的斜長石和角閃石的結(jié)晶。然而,這些輝石的寄主巖石均具有微弱的Eu負異常和MREE鍕不虧損的REE配分模式,表明其成分沒有受到斜長石和角閃石分離結(jié)晶的影響。因此,第三類輝石所記錄的斜長石和角閃石結(jié)晶改變了第三類輝石結(jié)晶時的熔體的成分特征,但是這些斜長石和角閃石在結(jié)晶之后直至噴發(fā)之前并沒有從熔體中分離出去,因此對寧蕪安山質(zhì)火山巖的最終成分沒有顯著的影響。輝石斑晶廣泛發(fā)育的補丁狀環(huán)帶和反環(huán)帶記錄了貫穿整個寧蕪火山作用的巖漿注入過程,這一長期存在的巖漿注入過程導(dǎo)致了火山作用晚期的巖石相對早期的巖石具有更為狹窄的成分變化范圍,也導(dǎo)致了寧蕪火山巖整體上相對長江中下游地區(qū)其它火山巖具有更為狹窄的成分變化范圍。在繁昌盆地還發(fā)育一套晚中生代雙峰式火山巖,其地球化學(xué)成分與同時代安山巖有很多相似性。因此.對這些雙峰式火山巖的研究不僅有助于理解整個長江中下游地區(qū)晚中生代巖漿作用的實質(zhì),而且能夠?qū)υ摰貐^(qū)安山質(zhì)火山巖的成因做更進一步的限定。繁昌盆地鎂鐵質(zhì)火山巖主要由玄武巖、粗面玄武巖和堿性玄武巖組成,它們均具有玄武質(zhì)成分特征,其長英質(zhì)火山巖主要由粗面巖、流紋巖以及少量的粗面安山巖組成,它們具有英安質(zhì)或者流紋質(zhì)成分特征。本文鋯石U-Pb定年結(jié)果表明,繁昌盆地雙峰式火山作用發(fā)生在129到125 Ma之間。鎂鐵質(zhì)火山巖具有如下特征：(1)弧型微量元素分布模式,高度富集流體活動性元素：(2)中等程度富集的Sr-Nd-Hf同位素組成,具有非常均一的(87Sr/86Sr)i值0.7065-0.7067,低的εNd(t)值-5.61至-3.5 1以及低的εHf(t)值-3.01至-2.73：(3)變化范圍極大的鋯石εHf(t)值-20.5至7.9。上述這些特征表明,這些鎂鐵質(zhì)巖來自含角閃石的富集地幔源區(qū)的部分熔融,該源區(qū)是以流體為主、熔體為輔的俯沖板片來源物質(zhì)與地幔楔橄欖巖反應(yīng)形成的富集地幔。另一方面,該地區(qū)長英質(zhì)巖石具有與鎂鐵質(zhì)巖類似但變化范圍稍大的(87Sr/86Sr)i比值0.7060至0.7076,比玄武巖更負的εNd(t)值-8.26至-6.62,更負的εHf(t)值-8.01至-7.77。其鉆石同樣具有高度變化的εHf(t)值-17.9至-1.8,這些鋯石還具有相對高的81s0值6.3至9.2%o。這些地球化學(xué)特征表明,長英質(zhì)火山巖來自陸源沉積物的部分熔融。鎂鐵質(zhì)和長英質(zhì)火山巖在某些地球化學(xué)組成上具有親緣性,表明二者具有成因上的聯(lián)系,這一點在鋯石Hf同位素上體現(xiàn)的尤為明顯,表明二者源區(qū)含有同一來源的沉積物組分。因此,繁昌盆地雙峰式火山巖的成因可以解釋為古俯沖隧道中的交代地幔和俯沖洋殼沉積物在碰撞后環(huán)境下的分別再活化。盡管本文實測樣品研究對長江中下游地區(qū)安山巖和雙峰式火山巖的成因有了一定的認識,但是它們之間的相互聯(lián)系以及對整個長江中下游地區(qū)晚中生代火山巖成因的含義有待探索。為此,通過統(tǒng)計編輯文獻發(fā)表的相關(guān)數(shù)據(jù),可以對比該地區(qū)玄武巖、安山巖以及英安巖-流紋巖的地球化學(xué)組成,對該地區(qū)晚中生代火山巖的成因給出了系統(tǒng)的解釋,同時也對長江中下游晚中生代火山巖形成的構(gòu)造背景進行進一步的限定。結(jié)果發(fā)現(xiàn),長江中下游地區(qū)晚中生代火山巖均具有弧型微量元素分布特征,富集的Sr-Nd-Pb-Hf同位素特征�？傮w上,安山巖具有顯著高于玄武巖的Th和U的含量,安山巖與玄武巖具有類似的Sr和Pb同位素組成,但其Nd和Hf同位素組成比玄武巖顯著富集。同時,安山巖具有低的Ba/Th比值和高的(La/Sm)N比值,玄武巖則剛好相反。這些特征表明,安山巖的地幔源區(qū)受到了沉積物來源的含水熔體為主、富水流體為輔的俯沖地殼來源物質(zhì)的交代,而玄武巖地幔源區(qū)則恰恰相反。英安巖-流紋巖在Sr-Nd-Hf同位素組成上比玄武巖和安山巖更為富集,但缺乏同位素與分異指標之間的相關(guān)性,表明該特征不能用鎂鐵質(zhì)巖漿的AFC過程來解釋。其富集且高度變化的鋯石Hf同位素以及高的鋯石氧同位素組成表明,這些英安巖-流紋巖來自陸源沉積物的部分熔融。至此,長江中下游晚中生代火山巖的形成可以概括為古大洋俯沖隧道內(nèi)不同介質(zhì)交代形成的富集地幔源區(qū)和俯沖洋殼沉積物共同熔融的結(jié)果。因此,長江中下游地區(qū)晚中生代弧型玄武質(zhì)-安山質(zhì)巖漿作用實質(zhì)上是新元古代古安第斯型俯沖隧道內(nèi)形成的地幔源區(qū)在晚中生代太平洋板塊西向俯沖誘發(fā)華南區(qū)域性巖石圈拉張及軟流圈上涌背景下的再活化,這個地幔源區(qū)的形成機制與現(xiàn)代活動大陸邊緣類似,但是再活化時間滯后了700百萬年以上。從這個角度來說,長江中下游地區(qū)晚中生代火山巖成因模型對現(xiàn)代活動大陸邊緣玄武巖-安山巖的成因具有借鑒意義。
[Abstract]:The theory of plate tectonics can explain the mechanism of the magmatism of the marginal arc of the modern converging plate, but for the nature of the mantle source area of the continental arc mafic magmatism, the specific mechanism of the subduction plate material added to the mantle wedge and the differentiation and evolution process of the overlying plate after the extraction of the continental arc magma from the source area. It is still not clear that the mafic magmatic rocks with the characteristics of arc geochemistry are also common in the continent. These magma rocks are far from the active continental margin at present, and their genesis has become an urgent problem to be controlled by the subduction of the plate plate subduction of the ancient disappearing plate or the structure of the present active plate. In this thesis, the late Mesozoic volcanic rocks in the middle and lower reaches of the Yangtze River, Southern China, were selected as the object of systematic rock geochemical study. The results not only provided a new systematic understanding of the genetic mechanism of the late Mesozoic volcanic rocks in the middle and lower reaches of the Yangtze River, but also established the crust mantle interaction in the paleo oceanic subduction zone and the present land. In the first chapter to the fourth chapter, the research background, the regional geological background, the sample collection and description and the series of analysis methods are introduced. The fifth chapter takes the late Mesozoic andesite in the middle and lower reaches of the Yangtze River in the middle and lower Yangtze River as an example, through the system of the main trace of the whole rock, Sr-Nd-Pb-Hf Isotopes, zircon U-Pb age and Hf-O isotopes study. The formation process of the source area of the enriched mantle in the ancient Andean subduction zone and its directive significance to the genesis of the continental arc andesite are discussed. In the sixth chapter, the analysis of U-Pb age and Hf-O isotopes of zircon from Ningwu volcanic rocks, the analysis of the trace elements and Sr-Nd-Hf isotopes of the whole rock It is verified whether the genetic mechanism of the luzongan mountain quality fire rock is applicable to andesite in the Ningwu basin. In the seventh chapter, the petrography and geochemical analysis of the monoclinic pyrophyla in the Ningwu volcanic rocks are carried out to make a systematic understanding of the magma evolution process in Ningwu volcanic rocks and further restrict the source area composition and the magma process to Ningwu. The relative contribution of the geochemical components of the Anshan volcanic rocks. In the eighth chapter, a systematic U-Pb dating and Hf-O isotopic analysis of the late Mesozoic volcanic rocks in the Fanchang basin were carried out to determine their petrogenesis. In the ninth chapter, the geochemical data of the volcanic rocks in the middle and lower reaches of the Yangtze River, published in the edited literature, were compared. The geochemical composition of the basalt, andesite and the anganite rhyolite is made to explain the formation of the late Mesozoic volcanic rocks in this area, and the tectonic setting of these volcanic rocks is limited. During the northern subduction of the Chinese ocean to the southern margin of the Yangtze craton, the chemical reaction between the subducted oceanic crust derived melt and the mantle wedge peridotite occurred during the North subduction of the southern margin of the Yangtze craton, so the late Mesozoic magmatism in the middle and lower reaches of the Yangtze River was essentially the rich fertile lithosphere mantle formed by the ancient Andean subduction zone in the late Mesozoic Pacific plate. The block west subduction leads to the reactivation of the Southern China continental block lithosphere extension background. The Luzong basin is mainly composed of basaltic andesite and rough andesite, accompanied by a small amount of rough basalt and rough rock. These rocks have changed SiO2 (48.66-63.43 wt.%), MgO (0.39-4.85 wt.%), Na2O (1.22-6.07 wt.%) and K. The content of 2O (2.53-10.10 wt.%) has a high variation of K2O/Na2O ratio (0.45-7.39). The Lujiang Fong volcanic rocks are characterized by the distribution of the arc emblem elements, showing the enrichment of LILE, Pb and LREE, and they have a loss HFSE. they also have a enriched Sr-Nd-Pb-Hf isotopes. The initial ratio of 87Sr/ 86Sr is between 0.7050 and 0.7066. Between -3.1 and -3.1, the value of epsilon Hf (T) is between -11 and -1.1; at a given 206Pb/204Pb ratio, the ratio of 207Pb/204Pb and 207Pb/204Pb to the northern hemisphere reference line is significantly higher. The zircon U-Pb year gives a 127:1:2 to 137 + 1 Ma magma crystallization age. These zircon has a high Delta 18O value. The geochemical characteristics of the change from -13.1 to 2.6. indicate that the late Mesozoic volcanic rocks of the Lujiang Fong were derived from the partial melting of the rich fertile mantle source area. This mantle source region was formed in the interaction between the sediments source of the paleandean subduction zone and the overlying mantle wedge peridotite, like the crust mantle interaction under the present continental arc. Therefore, the result of the study shows that the addition of a large amount of sediment source melt into the mantle wedge peridotite is an important precondition for the formation of andesite in the source area of rich fertile soil. Combining the genesis mechanism of the oceanic arc basalt, we think the difference in composition between the continental arc andesite and the oceanic arc basalt is essentially controlled by the intersection. The former is mainly composed of water - bearing melts from sediment sources, and the latter is dominated by water rich fluids derived from altered oceanic shells. The volcanic rocks of Ningwu are mainly composed of rough andesite and rough rock, containing a small amount of basaltic rough andesite. These volcanic rocks have low changing MgO content (0.11-3.73wt.%) and low Mg# value (1.60-51.18 ), high K20 content (1.99-9.88wt.%). They have arc type trace element distribution patterns, which are enriched in LILE, Pb and LREE, and have a loss of HFSE. They also have rich Sr-Nd-Pb-Hf isotopes, whose initial 87Sr/86Sr ratio is between 0.7050 and 0.7082, and the value of E Nd (T) is somewhere between -8.1 and 0.39; Under the 206Pb/204pb ratio (17.76-18.28), the ratio of 207pb/204pb (15.47-15.61) and 208Pb/204Pb (37.75-38.44) to the northern hemisphere reference line is significantly higher than that of the northern hemisphere. U-Pb gives the magma crystallization age of 128 + 2 to 133 + 2 Ma. These zircon has a high 8190 value (5.7-7.8 per 1000) and the change of the value of the Hf (T) from -5.8. These andesite can be divided into two groups. The relative group II samples, the group 1 samples have more enriched Sr-Nd-Pb-Hf isotopes and relatively low incompatible elements. The comprehensive analysis of these geochemical characteristics shows that the group I volcanic rock formed at a high degree of enrichment and contains a large number of gold mica. On the contrary, the group II volcanic rocks are formed in a relatively low degree of partial melting in the mantle source with relatively low enrichment and less gold mica content. The two mantle source regions are relatively rich in rock chemistry than the normal peridotite mantle because of the addition of the long angled melt components from the sediments. A systematic petrographic and geochemical analysis of the monoclinic pyrophyla in the Wuhuo yam rock has been carried out, and the result of the systematic understanding of the magma evolution process of the Ningwu volcanic rocks has further recognized the contribution of the source region composition and the magmatic process to the phase pairs of the geochemical composition of the ningwuan volcanic rocks. The structure and composition ring are corresponding to different REE distribution forms. According to their distinct REE distribution patterns, these monoclinopyroxene can be divided into three types. The first type of clinopyroxene has a flat REE distribution pattern and a strong negative Eu anomaly, and the second type of clinopyroxene has a LREE-MREE enrichment right REE partition model. The third type of clinopyroxene has a MREE loss REE distribution pattern and a strong Eu negative anomaly. The three types of pyroxene exhibit two distinct evolutionary trends, indicating that they crystallize from two distinct melts. Among them, the first type of mono clinopyroxene crystallized at the initial concentration of free REE. The melts formed by the melt evolution, the second and third types of pyroxene crystallized the melt formed by the initial melt evolution of the free REE enrichment. The differences in the composition of the second types of pyroxene and third types of pyroxene indicate that there are a large number of plagioclase and amphibolite in the two crystallized spaces. However, the host rocks of these pyroxene are all micro. The weak Eu negative anomaly and the REE distribution pattern of MREE without loss indicate that their components are not affected by the separation and crystallization of plagioclase and hornblende. Therefore, the crystallization of plagioclase and hornblende recorded by the third types of pyroxene changes the composition characteristics of the melts in the crystallization of the third types of pyroxene, but these plagioclase and hornblende are crystallized until after crystallization. It has not been separated from the melt before the eruption, and therefore has no significant influence on the final composition of the ningwuan volcanic rocks. The patched and reverse belt of the pyroxene phenocrysts recorded the magma injection through the whole Ningwu volcano. This long existence of magma injection resulted in the late volcanism. The rock has a more narrower range of composition than the early rocks, and it also leads to a more narrower variation in the composition of the other volcanic rocks in the middle and lower reaches of the Yangtze River. In the Fanchang basin, a set of Late Mesozoic Shuangfeng volcanic rocks was developed, and the geochemical composition of the volcanic rocks is very similar to that of the andesite of the same age. Therefore, the study of these Shuangfeng volcanic rocks is not only helpful to understand the essence of the late Mesozoic magmatism in the middle and lower reaches of the Yangtze River, but also to further restrict the genesis of the Anamic volcanic rocks in this area. The mafic volcanic rocks in the Fanchang basin are mainly composed of Xuan Wuyan, rough Xuan Wuyan and alkaline Xuan Wuyan. All of them are characterized by basaltic composition. Their felsic volcanic rocks are mainly composed of rough rocks, rhyolite and a small amount of rough andesite. They have the characteristics of the Anglo Amy or rhyolite. The zircon U-Pb dating results showed that the Shuangfeng type volcanism in the Fanchang basin occurred between 129 and 125 Ma. The following characteristics: (1) the distribution pattern of arc trace elements, highly enriched fluid active elements: (2) Sr-Nd-Hf isotopes of moderate enrichment, with a very homogeneous (87Sr/86Sr) I value 0.7065-0.7067, low Nd (T) value -5.61 to -3.5 1 and low I Hf (T) value -3.01 to -2.73: (3) These characteristics indicate that the mafic rocks are partially melted from the rich mantle source area containing amphibole, the source area is a rich mantle derived from the fluid dominated subduction plate source and the mantle wedge peridotite. On the other hand, the felsic rocks in this area are similar to the mafic rock but have a slight variation in range. The larger (87Sr/86Sr) I ratio is 0.7060 to 0.7076, the negative epsilon Nd (T) value is -8.26 to -6.62 more than the basalt, and the negative e Hf (T) value -8.01 to -7.77. its diamond also has a highly variable epsilon Hf (T) value. These zircon also has a relatively high value of 6.3 to the geochemical characteristics indicating that the felsic volcanic rocks come from the terrestrial sediments. The mafic and feldsic volcanic rocks are related to some geochemical compositions, indicating the genetic relationship between the two, which is particularly evident in the zircon Hf isotopes, indicating that the two source areas contain the same source of sediment components. Therefore, the genesis of the Shuangfeng type volcanic rocks in the Fanchang basin can be interpreted as a source of origin. The metasomatic mantle and subducted oceanic sediments in the subducted tunnel are reactivated respectively in the environment after the collision. Although the measured samples have a certain understanding of the genesis of andesite and Shuangfeng type volcanic rocks in the middle and lower reaches of the Yangtze River, the interrelation between them and the late Mesozoic volcanism in the middle and lower reaches of the Yangtze River For this reason, the geochemical composition of the Xuan Wuyan, andesite and the anganite rhyolite in this area can be compared by the relevant data published by the statistical editing literature, and the causes of the late Mesozoic volcanic rocks in this area are explained systematically, and the formation of Late Mesozoic volcanic rocks in the middle and lower reaches of the Yangtze River is also formed. The results show that the late Mesozoic volcanic rocks in the middle and lower reaches of the Yangtze River arc arc trace elements distribution.

【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：P588.14
，

本文編號：1849427