本文選題：P-T評價 + 鋯石定年　； 參考：《合肥工業(yè)大學》2016年碩士論文

【摘要】：蚌埠隆起區(qū)位于華北克拉通東南緣,是華北克拉通的重要組成部分,然而前人對于蚌埠隆起結晶基底形成的變質(zhì)條件、時限以及構造環(huán)境的分析相對較為薄弱,對五河群形成的構造成因背景仍然存在爭議,制約了人們?nèi)胬斫庠撀∑鸬男纬珊脱莼^程。因此,本文在詳細的野外地質(zhì)調(diào)查基礎上,以變質(zhì)巖石學、同位素年代學以及巖石地球化學等為手段,對在蚌埠隆起東段朱頂-石門山地區(qū)出露的花崗片麻巖、糜棱巖化花崗片麻巖、黑云斜長片麻巖以及新發(fā)現(xiàn)的含石榴石花崗片麻巖進行了較為細致且綜合的研究,并在此基礎上,探討了蚌埠隆起五河群形成的變質(zhì)條件、構造環(huán)境以及演化過程,這對揭示華北克拉通東南緣蚌埠隆起東段的構造演化具有重要意義。通過對含石榴石花崗片麻巖樣品進行電子探針礦物成分分析以及P-T條件估計,得出該樣品的溫壓條件為736-788℃和0.76-0.89GPa,表明其形成于低壓麻粒巖相條件。鋯石LA-ICP-MS U-Pb定年分析記錄了巖漿結晶事件和變質(zhì)事件,它們對應的年齡分別為(2562±34)Ma～(2584±25)Ma、(2433±31)Ma至(2466±31)Ma和(2204±68.0)Ma。上述實驗結果表明蚌埠隆起區(qū)東段具有與華北克拉通演化的一致性,即普遍經(jīng)歷了角閃巖相至麻粒巖相的變質(zhì)環(huán)境以及多階段的演化過程。對研究區(qū)花崗片麻巖進行的巖石地球化學研究結果表明：花崗片麻巖的原巖為巖漿巖,屬正變質(zhì)巖系列,巖石具有富鈉、富鉀的特點,為準鋁質(zhì)-弱過鋁質(zhì)巖,屬鈣堿性系列。該套花崗片麻巖明顯富集Rb、Ba、K等大離子親石元素(LILE),虧損Nb、Ta、Ti等高場強元素(HFSE),具有殼源巖漿的特征。結合鋯石U-Pb定年結果,并通過巖石構造環(huán)境判別圖解得出,花崗片麻巖的原巖為火山弧花崗巖,形成于島弧構造環(huán)境。綜合研究認為華北克拉通東南緣蚌埠隆起區(qū)花崗片麻巖的原巖主要形成于晚太古代島弧環(huán)境,代表了該期板塊俯沖—增生事件。
[Abstract]:The Bengbu uplift is located in the southeastern margin of the North China Craton and is an important part of the North China Craton. However, the metamorphic conditions, time limits and tectonic environment of the crystalline basement of the Bengbu uplift are relatively weak. The tectonic background of the Wuhe Group is still controversial, which restricts the overall understanding of the formation and evolution of the uplift. Therefore, on the basis of detailed field geological investigation, based on metamorphic petrology, isotopic chronology and geochemistry, the granitic gneiss exposed in the eastern section of Bengbu uplift, Zhuding-Shimenshan area, has been studied in this paper. Mylonitic granitic gneiss, black cloud plagioclase gneiss and newly discovered garnet granitic gneiss have been studied in detail and synthetically. On this basis, the metamorphic conditions of Wuhe Group in Bengbu uplift have been discussed. The tectonic environment and evolution process are of great significance to reveal the tectonic evolution of the eastern segment of Bengbu uplift in the southeastern margin of North China Craton. By means of electron probe mineral composition analysis and P-T condition estimation of garnet granitic gneiss samples, the temperature and pressure conditions of the samples are 736-788 鈩，

本文編號：2014912