本文選題：阿爾山 + 奧陶紀(jì)火山巖　； 參考：《吉林大學(xué)》2015年碩士論文

【摘要】：頭道橋-新林-塔原斷裂帶位于額爾古納地塊與興安地塊之間，沿?cái)嗔褞С雎队行铝稚呔G巖、環(huán)宇蛇綠巖和頭道橋藍(lán)片巖，近年來(lái)的研究認(rèn)為它是兩大地塊的縫合帶，然而額爾古納和興安地塊的碰撞時(shí)代和模式一直存在爭(zhēng)議。多寶山奧陶紀(jì)島弧位于頭道橋-新林-塔原蛇綠巖帶的東南側(cè)，它的成因及性質(zhì)可以為區(qū)域構(gòu)造演化提供較好的約束。由于缺少對(duì)該島弧西南延伸區(qū)奧陶紀(jì)火山巖的系統(tǒng)的年代學(xué)和地球化學(xué)研究，致使多寶山奧陶紀(jì)島弧的成因及性質(zhì)一直不明。因此，論文對(duì)多寶山島弧南段阿爾山地區(qū)的代表性的奧陶紀(jì)火山巖進(jìn)行了系統(tǒng)的巖石學(xué)、年代學(xué)和地球化學(xué)研究，旨在為區(qū)域構(gòu)造演化提供依據(jù)。 阿爾山地區(qū)多寶山組火山巖由變玄武巖、變玄武安山巖和變英安巖組成，變玄武安山巖和變英安巖的鋯石U-Pb年齡分別為469±6Ma和475±4Ma。巖石富集Th、U、Zr、Hf等高場(chǎng)強(qiáng)元素，Nb、Ta弱虧損，顯示出弧火山巖向OIB過(guò)渡的地球化學(xué)特征。阿爾山地區(qū)佳疙疸組變玄武巖的鋯石U-Pb年齡為464±7Ma，變玄武巖按地球化學(xué)特征可以分為兩類，第一類高鈦玄武巖富集Rb、Ba、Th、U、K等強(qiáng)不相容元素，Nb、Ta正異常，具有與OIB型玄武巖一致的地球化學(xué)特征；第二類低鈦玄武巖則與本區(qū)多寶山組火山巖具有相似的地球化學(xué)特征，也體現(xiàn)出弧火山巖向OIB過(guò)渡的特征。綜合分析認(rèn)為多寶山組和佳疙疸組低鈦玄武巖的源區(qū)具有OIB深部上涌地幔和俯沖洋殼釋放的流體組分的雙重貢獻(xiàn)，但佳疙疸組高鈦玄武巖的巖漿源區(qū)則以O(shè)IB地幔性質(zhì)為主。結(jié)合阿爾山地區(qū)構(gòu)造位置，本文認(rèn)為阿爾山地區(qū)奧陶紀(jì)火山巖產(chǎn)生于弧后盆地的早期階段。 綜上所述，頭道橋-新林-塔原蛇綠巖帶早古生代構(gòu)造演化特征如下：寒武紀(jì)末額爾古納地塊與洋內(nèi)島弧或是興安地塊拼貼形成頭道橋藍(lán)片巖，，早中奧陶世古亞洲洋向北俯沖，形成多寶山火山弧，在弧后伸展盆地形成區(qū)內(nèi)的奧陶紀(jì)過(guò)渡型+OIB的火山巖組合，典型的弧火山巖應(yīng)該位于阿爾山地區(qū)的東南側(cè)。
[Abstract]:The Toutaoqiao-Xinlin-Tarim fault zone is located between the Erguna block and the Xingan block. Along the fault zone, there are Xinlin ophiolite, Huanyu ophiolite and Toutaoqiao blue schist, which have been considered to be suture zones of the two major landmasses in recent years. However, the era and model of collision between Erguna and Xingan landmasses have been controversial. The Ordovician island arc in Dobaoshan is located on the southeast side of the Tudaoqiao-Xinlin-Tarim ophiolite belt. Its genesis and properties can provide a good constraint for the regional tectonic evolution. Due to the lack of systematic geochronology and geochemistry of Ordovician volcanic rocks in the southwestern extension of the island arc, the origin and nature of the Ordovician island arc in Dobaoshan have been unknown. Therefore, the representative Ordovician volcanic rocks in the Arshan area in the southern segment of the island arc of Dobaoshan are systematically studied in petrology, geochronology and geochemistry in order to provide the basis for the regional tectonic evolution. The volcanic rocks of the Dobaoshan formation in the Alshan area are composed of metamorphic basalt, altered Black Tortoise andesite and metamorphic andesite. The zircon U-Pb ages of altered Black Tortoise andesite and metamorphic andesite are 469 鹵6Ma and 475 鹵4Marespectively. The low depletion of high field strength elements such as Th _ (U) U _ (Zr) ~ (H _ f) _ f shows the geochemical characteristics of the transition from arc volcanic rocks to OIB. The zircon U-Pb age of the metabalts of Jiakujing formation in Alshan area is 464 鹵7 Ma.The metabalts can be divided into two types according to their geochemical characteristics. The second type of low titanium basalt has similar geochemical characteristics to that of Dobaoshan formation volcanic rocks in this area, which also shows the transition of arc volcanic rocks to OIB. It is considered that the source regions of the low titanium basalts of the Dobaoshan and Jiakuji formations have dual contributions from the deep upwelling mantle of OIB and the fluid released from the subduction oceanic crust, but the magmatic source of the high-titanium basalts of the Jiakuji formation is dominated by the OIB mantle. Based on the tectonic location of the Alshan area, it is believed that the Ordovician volcanic rocks in the Alshan area originated in the early stage of the back-arc basin. To sum up, the early Paleozoic tectonic evolution characteristics of the Tudaoqiao-Xinlin-Tarim ophiolite belt are as follows: the late Cambrian Erguna block and the intraoceanic island arc or Xingan block collage together to form the Toutaoqiao blue schist, and the early middle Ordovician ancient Asian ocean subducts north. The formation of the Dobaoshan volcanic arc and the formation of the Ordovician transitional OIB volcanic rock assemblage in the back-arc extensional basin, the typical arc volcanic rocks should be located on the southeast side of the Alshan area.
【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)】：P588.14

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