安徽繁昌浮山钾长花岗岩成因及其构造意义——来自锆石U-Pb年龄、岩石地球化学和Hf同位素的证据
发布时间：2019-08-09 11:27
【摘要】：安徽繁昌地区是长江中下游铜铁金多金属成矿带的重要组成部分。对繁昌浮山钾长花岗岩开展了详细的岩石学、岩石地球化学、锆石U-Pb年代学和Lu-Hf同位素分析,并在此基础上探讨了岩石成因及动力学背景。岩石地球化学研究表明,浮山钾长花岗岩为硅过饱和的准铝质-弱过铝质富碱富钾岩石,具有较高的Ga/Al值、TFeO/MgO值、Zr+Nb+Ce+Y和稀土元素含量,显示出A型花岗岩的地球化学特征。此外,浮山钾长花岗岩具有低(~(87)Sr/~(86)Sr)_i、高δ~(18)O、负ε_(Nd)(t)和ε_(Hf)(t)、负Eu异常等地球化学特征。繁昌浮山钾长花岗岩LA-ICP-MS锆石~(206)Pb/~(238)U年龄为124.9±2.0Ma(n=15,MSWD=0.20),被解释为钾长花岗岩的形成年龄。与长江中下游地区A型花岗岩带中的其他岩体为同期岩浆活动的产物,均形成于早白垩世。结合岩石学和区域地质资料,表明浮山钾长花岗岩可能是新生下地壳物质部分熔融作用形成的,形成浮山钾长花岗岩的新生下地壳可能由来源于富集地幔岩石圈的玄武质-安山质岩浆和少量结晶变质基底物质组成。根据锆石U-Pb年龄,结合区域地质资料分析,晚侏罗世—早白垩世,长江中下游地区经历挤压向伸展构造应力场的转变,随时间推移,伸展作用逐渐增大,至125Ma左右该区岩石圈可能达到了伸展的高峰期。
[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 卤2.0Ma (n 鈮，
本文编号：2524761
[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 卤2.0Ma (n 鈮，
本文编号：2524761
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