本文選題：巖石成因　切入點：Hf-O同位素　出處：《合肥工業(yè)大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：皖南地區(qū)位于揚子板塊東南緣,江南隆起帶東段。本文選取青陽-九華山復(fù)式巖體和太平-黃山復(fù)式巖體,開展主量元素、鋯石U-Pb年代學(xué)和Hf-O同位素研究。LA-ICPMS鋯石U-Pb定年結(jié)果顯示青陽-九華山復(fù)式巖體與太平一黃山復(fù)式巖體分別可以劃分為三個不同的期次,早期侵入產(chǎn)出的為花崗閃長巖(青陽巖體、太平巖體),形成年齡在149.3±2.4 Ma到138.3±1.4 Ma之_間；中期為二長花崗巖(青陽巖體、太平巖體),形成年齡在145.1±1.7 Ma到132.8±1.5 Ma之間;晚期為鉀長花崗巖(九華山巖體、黃山巖體),形成年齡在134.9±2.6 Ma到128.4±1.4 Ma之間。結(jié)合已發(fā)表的其他高精度年代學(xué)數(shù)據(jù)表明,皖南地區(qū)燕山期巖漿作用可劃分為三期,早期153～136 Ma、中期136～129 Ma和晚期129～122 Ma。早期花崗閃長巖Si02變化范圍為66%～67%,MgO含量較低(1.2%～1.5%),全堿含量在7.1%至7.5%之間,K2O/Na2O1, A/CNK1, ANK屬于高鉀鈣堿性系列,為準鋁質(zhì)Ⅰ型花崗巖；中期二長花崗巖具有較花崗閃長巖略高的Si02含量,在68%～69%之間,其它主量元素特征較類似,全堿含量在7.7%-8.6%之間, K2O/Na2O1, A/CNK1, ANK屬于高鉀鈣堿性系列,為弱過鋁質(zhì)Ⅰ型花崗巖;晚期鉀長花崗巖富硅(Si02=73%-77%),低鈣(CaO=0.2%-0.8%), A/CNK1, ANK, K2O/Na2O1,同樣為高鉀鈣堿性系列巖石,具有A型花崗巖特征�；◢忛W長巖的鋯石εHf(t)值在-9.54～-4.86之間,對應(yīng)的δ18O值在6.68‰～8.42‰之間；二長花崗巖的鋯石εHf(t)值在-11.40-9.43之間,對應(yīng)的818O值在7.16‰～8.04‰之間；鉀長花崗巖的鋯石Hf-O同位素表現(xiàn)出不同的特征,九華山巖體的鋯石εHf(t)值較低,為-7.62-4.78,鋯石818O值介于7.03‰和8.84‰之間,而黃山巖體具有較九華山巖體略高的鋯石εHf(t)值(-6.56～-1.20),鋯石δ18O值介于6.27‰和8.34‰之間。主量元素和鋯石Hf-O同位素綜合研究表明,在太平洋板塊低角度俯沖背景下,受到板片析出流體交代的巖石圈地幔發(fā)生部分熔融,玄武巖漿的底侵導(dǎo)致晚太古代-早元古代地殼也發(fā)生部分熔融,這兩種巖漿發(fā)生不同程度的混合形成皖南早期花崗閃長巖-二長花崗巖巖體；隨著俯沖板片的后撤和俯沖角度的加大,皖南地區(qū)的構(gòu)造背景轉(zhuǎn)變?yōu)榛『罄瓘?引起板撕裂形成板片構(gòu)造窗,軟流圈地幔物質(zhì)沿著斷裂上涌,部分熔融揚子地塊中元古代基底,形成晚期鉀長花崗巖。
[Abstract]:The southern Anhui area is located in the southeast margin of the Yangtze plate and the eastern section of the Jiangnan uplift belt. In this paper, the Qingyang-Jiuhuashan complex rock mass and the Taiping Huangshan complex rock mass are selected to carry out the main elements. Zircon U-Pb geochronology and Hf-O isotopic study. The results of LA-ICPMS zircon U-Pb dating show that the Qingyang-Jiuhuashan complex and Taiping-Huangshan complex can be divided into three different stages, and the early intrusions occurred in the granodiorite (Qingyang pluton). The formation age of Taiping rock body is 149.3 鹵2.4 Ma to 138.3 鹵1.4 Ma, the middle stage is monzogranite (Qingyang rock body, Taiping rock body), the age range is 145.1 鹵1.7 Ma to 132.8 鹵1.5 Ma, and the late stage is potassium feldspar granite (Jiuhuashan rock body). The formation age of Huangshan rock body ranges from 134.9 鹵2.6 Ma to 128.4 鹵1.4 Ma. The Yanshanian magmatism in southern Anhui can be divided into three periods, combined with other published high accuracy geochronological data. The range of Si02 variation of early granodiorite is 660.The Si02 content of early granodiorite is relatively low, and the total alkali content is between 7.1% and 7.5%. The content of K _ 2O / Na _ 2O _ 1, A / CNK _ 1 and ANK belong to high-potassium calc-alkaline series and quasi-aluminous I-type granite. The Si02 content of the monzomorphic granodiorite is slightly higher than that of the granodiorite, and between 68% and 69%, the other major elements are similar. The total alkali content is between 7.7% and 8.6%. K _ 2O / Na _ 2O _ 1, A / CNK _ 1 and ANK belong to the high-potassium calc-alkaline series and belong to weakly peraluminous I-type granite. The late K-feldspar granites are Si-rich in Si _ (02) ~ (73) ~ (-77) and low in calcium content (0.2 ~ 0.8). A / C _ (CNK1), ANK, K _ 2O / Na _ 2O _ (1), which is also a high-potassium calc-alkaline series, has the characteristics of A-type granite. The zircon 蔚 Hft value of granodiorite ranges from -9.54 to 4.86, and the corresponding 未 ~ (18) O value is between 6.68 鈥，

本文編號：1640754