【摘要】：安徽繁昌地區(qū)是長江中下游銅鐵金多金屬成礦帶的重要組成部分。對繁昌浮山鉀長花崗巖開展了詳細(xì)的巖石學(xué)、巖石地球化學(xué)、鋯石U-Pb年代學(xué)和Lu-Hf同位素分析,并在此基礎(chǔ)上探討了巖石成因及動力學(xué)背景。巖石地球化學(xué)研究表明,浮山鉀長花崗巖為硅過飽和的準(zhǔn)鋁質(zhì)-弱過鋁質(zhì)富堿富鉀巖石,具有較高的Ga/Al值、TFeO/MgO值、Zr+Nb+Ce+Y和稀土元素含量,顯示出A型花崗巖的地球化學(xué)特征。此外,浮山鉀長花崗巖具有低(~(87)Sr/~(86)Sr)_i、高δ~(18)O、負(fù)ε_(Nd)(t)和ε_(Hf)(t)、負(fù)Eu異常等地球化學(xué)特征。繁昌浮山鉀長花崗巖LA-ICP-MS鋯石~(206)Pb/~(238)U年齡為124.9±2.0Ma(n=15,MSWD=0.20),被解釋為鉀長花崗巖的形成年齡。與長江中下游地區(qū)A型花崗巖帶中的其他巖體為同期巖漿活動的產(chǎn)物,均形成于早白堊世。結(jié)合巖石學(xué)和區(qū)域地質(zhì)資料,表明浮山鉀長花崗巖可能是新生下地殼物質(zhì)部分熔融作用形成的,形成浮山鉀長花崗巖的新生下地殼可能由來源于富集地幔巖石圈的玄武質(zhì)-安山質(zhì)巖漿和少量結(jié)晶變質(zhì)基底物質(zhì)組成。根據(jù)鋯石U-Pb年齡,結(jié)合區(qū)域地質(zhì)資料分析,晚侏羅世—早白堊世,長江中下游地區(qū)經(jīng)歷擠壓向伸展構(gòu)造應(yīng)力場的轉(zhuǎn)變,隨時(shí)間推移,伸展作用逐漸增大,至125Ma左右該區(qū)巖石圈可能達(dá)到了伸展的高峰期。
[Abstract]:Fanchang area of Anhui Province is an important part of copper, iron and gold polymetallic metallogenic belt in the middle and lower reaches of the Yangtze River. The petrology, petrogeochemistry, zircon U-Pb chronology and Lu-Hf isotopic analysis of Fanchang Fushan potassium feldspar granite are carried out in detail. On this basis, the petrogenesis and dynamic background are discussed. The study of petrogeochemistry shows that the Fushan potassium feldspar granite is a quasi-aluminite-weak peraluminous alkali-rich potassium-rich rock with high Ga/ Al value, TFeO/ MgO value, Zr Nb Ce Y and rare earth element content, which shows the geochemical characteristics of A-type granite. In addition, the Fushan potassium feldspar granite has the geochemical characteristics of low (87) Sr/~ (86) Sr) _ I), high 未 ~ (18) O, negative 蔚 _ (Nd) (t) and 蔚 _ (Hf) (t), negative Eu anomalies. The zircon ~ (206) Pb/~ _ (238) U age of Fanchang Fushan potassium feldspar granite is 124.9 鹵2.0Ma (n 鈮，

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