【摘要】：華南板塊由華夏地塊和揚子地塊在新元古代早期沿江南造山帶碰撞拼合形成,經歷了自中元古代以來多次造山運動和多期巖漿活動,華南中生代巖漿巖對研究華南板塊的區(qū)域構造及地質演化等科學問題有重要意義。區(qū)域上巖漿巖按時代劃分后大都為北東、北北東向分布,但在江西省東北部發(fā)育一近東西向的巖漿巖帶,其大地構造位置處于揚子地塊的東南部、江南造山帶的東段。本文在前人研究的基礎上通過翔實的野外工作,采集了該巖漿巖帶的系列樣品,開展巖石學、年代學、巖石地球化學及巖漿氧逸度研究,討論其成巖機制及其構造背景。年代學方面,該巖漿巖帶中的巖體鋯石年齡基本一致,形成時代在130~135Ma,都處于白堊紀。其中,樣品D009-1和D011-6與其他樣品的鋯石年齡相差3Ma,反映了一次巖漿涌動作用。所以,取樣的4個巖體屬于同一期次的巖漿活動,該巖漿巖帶形成于燕山期早白堊世。通過鋯石的元素含量來計算巖漿氧逸度,結果表明該巖漿巖帶的巖漿氧逸度低,平均都低于FMQ,反映了巖體的形成環(huán)境為還原型。地球化學方面,樣品的Si2O含量在73.28~77.31,具鋁強過飽和的特點。全堿含量較高,樣品都落在高鉀鈣堿性系列中。微量元素和稀土元素分析顯示,所有分析的樣品都具有相似的REE分布形式,稀土元素配分曲線表現為輕稀土富集的右傾模式,樣品的稀土含量在23.54~131.27之間,LREE/HREE比值范圍在2.21~9.35。具有明顯的Eu負異常,δEu范圍在0.01~0.08之間,反映出殼源特征。且與皖南燕山中期巖體具有相似的地球化學特征,推測它們的來源一致,形成于同期巖漿活動。研究對象形成在大地構造背景由擠壓向伸展轉換的時期,巖石圈減薄,巖漿上涌,其成巖物質來源于地殼深部重融。
[Abstract]:The South China plate was formed by collision of Huaxia block and Yangtze block along the southern Yangtze orogenic belt in the early Neoproterozoic, and experienced many orogenic movements and magmatic activities since the Mesoproterozoic. Mesozoic magmatic rocks in South China are of great significance to the study of regional tectonics and geological evolution of the South China plate. The magmatic rocks in the region are mostly distributed in the north east and north east direction after dividing according to the age, but in the northeast of Jiangxi Province there is a magmatic rock belt near the east west direction. The tectonic position of the magmatic rock belt is located in the southeast of the Yangtze block and the eastern section of the Jiangnan orogenic belt. On the basis of previous studies, a series of samples have been collected from the magmatic zone through extensive field work. The petrology, geochronology, geochemistry and oxygen fugacity of magma have been studied, and the diagenetic mechanism and tectonic setting have been discussed. In terms of geochronology, the zircon ages of the magmatic rocks in this zone are basically the same, and the age of formation is 130135Ma. all of them are in the Cretaceous period. The zircon ages of samples D009-1 and D011-6 differ by 3 MaA, reflecting a magmatic gushing. Therefore, the four samples belong to the same stage of magmatic activity, and the magmatic belt was formed in the early Cretaceous of Yanshanian. The oxygen fugacity of magma is calculated by element content of zircon. The results show that the magmatic oxygen fugacity of the magmatic zone is low, and the average value is lower than that of FMQ, which reflects that the formation environment of the rock mass is reduced. In geochemistry, the Si2O content of the sample is 73.28 ~ 77.31, which is characterized by strong aluminum supersaturation. The total alkali content is high and the samples fall in the high potassium calc-alkaline series. The analysis of trace elements and rare earth elements showed that all the samples had similar REE distribution, and the distribution curve of rare earth elements showed the right tilting pattern of the enrichment of light rare earth elements, and the rare earth contents of the samples ranged from 23.54 to 131.27. The LREE/HREE ratio ranges from 2.21 to 9.35. There are obvious negative Eu anomalies and 未 Eu range from 0.01 to 0.08, which reflects the characteristics of crustal source. The geochemical characteristics are similar to those of the Yanshanian pluton in the south of Anhui, and their origin is the same as that of the Yanshanian rock body, which was formed during the same period of magmatic activity. The object of study was formed in the period of tectonic background transition from compression to extension, lithosphere thinning, magma upwelling, and its diagenetic material originated from deep thawing of the crust.
【學位授予單位】：中國地質大學(北京)
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：P588.1

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