| 长江中下游地区九瑞矿集区邓家山花岗闪长斑岩的地球化学与成因研究 |
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| 引用本文： | 李亮,蒋少涌.长江中下游地区九瑞矿集区邓家山花岗闪长斑岩的地球化学与成因研究[J].岩石学报,2009,25(11):2877-2888. |
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| 作者姓名： | 李亮 蒋少涌 |
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| 作者单位： | 南京大学地球科学系内生金属矿床成矿机制研究国家重点实验室,南京,210093 |
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| 基金项目： | 科技部973计划课题，十一五科技支撑项目课题 |
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| 摘 要： | 邓家山是长江中下游成矿带九瑞矿集区西北部的一处矽卡岩型Cu-Au-Mo矿床.矿区与成矿关系密切的岩体为花岗闪长斑岩.本文通过锆石SHRIMP U-Pb定年确定,该岩体侵位于早白垩世早期(138.2±1.8Ma).常微量元素分析结果表明,邓家山花岗闪长斑岩具有埃达克质岩的地球化学特征,表现为高Sr(＞650×10~(-6))、Ba(＞700×10~(-6)),低Y(＜12×10~(-6)),Yb(＜1×10~(-6)),Nb(＜10×10~(-6)),Ta(＜0.7×10~(-6)),富集轻稀土而强烈亏损重稀土(LREE/HREE=12.2～13.5).邓家山花岗闪长斑岩的~(87)Sr/~(86)Sr,为0.7068～0.7071,ε_(Nd)(t)为-2.7～-2.3,Nd同位素两阶段模式年龄T_(2DM)为1.13Ga～1.15Ga.锆石的Hf同位素分析结果表明,~(176)Ht/~(177)Hf值为0.282475～0.282539,计算的ε_(Hf)(t))值为-5.2～-7.5,Hf同位素两阶段模式年龄T2DM为1.52Ga～1.67Ga.全岩ε_(Nd)(t)与锆石ε_(Hf)(t))之间出现了较为明显的Nd-Hf同位素解耦.根据以上特征,我们认为邓家山花岗闪长斑岩是壳幔相互作用的产物,即增厚下地壳拆沉并部分熔融,岩浆在上升过程中又与地幔橄榄岩发生大规模混染.
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| 关 键 词： | Nd-Hf同位素解耦 下地壳拆沉 壳幔相互作用 邓家山 长江中下游成矿带 |
Petrogenesis and geochemistry of the Dengjiashan porphyritic granodiorite, Jiujiang-Ruiehang metallogenie district of the Middle-Lower Reaches of the Yangtze River |
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| LI Liang,JIANG ShaoYong.Petrogenesis and geochemistry of the Dengjiashan porphyritic granodiorite, Jiujiang-Ruiehang metallogenie district of the Middle-Lower Reaches of the Yangtze River[J].Acta Petrologica Sinica,2009,25(11):2877-2888. |
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| Authors: | LI Liang JIANG ShaoYong |
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| Abstract: | Dengjiashan skarn Cu-Au-Mo deposit is located in the northwest part of Jiujiang-Ruichang metallogenic district of the Middle-Lower Reaches of the Yangtze River.The ore-related granitic body is the Dengjiashan porphyritic granodiorite.Zircon SHRIMP U-Pb dating suggests an emplacement age of 138.2±1.8Ma.The geochemical analyses indicate this rock belongs to adakite,with high concentrations of Sr(＞ 650×10~(-6))and Ba(＞ 700×10~(-6)),low concentrations of Y(＜ 12×10~(-6)),Yb(＜ 1×10~(-6)),Nb(＜ 10×10~(-6)),and Ta(＜ 0.7×10~(-6)),enrichment of light rare earth element(LREE)and depletion of heavy rare earth element(HREE)with a LREE/HREE ratio of 12.2～13.5.The rocks show a ~(87) Sr/~(86) Sri of 0.7068～0.7071,ε_(Nd)(t)of-2.7～-2.3,and T2DM of 1.13～1.15Ga.The Hf isotope analyses of zircon show a ~(176) Hf/~(177) Hf ratio of 0.282475～0.282539,_(Hf)(t))value of-5.2～-7.5,and T_(2DM) age of 1.52～1.67Ga.The bulk-rock ε_(Nd)(t)and zircon ε_(Hf)(t)show a distinct decoupling feature.Based on these characteristics,we prefer a mantle-crust interaction origin for the Dengjiashan porphyritic granodiorite:i.e.,the magma,possibly derived from partial melting of delaminated lower crust,reacted strongly with the surrounding mantle peridotite during its ascent. |
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| Keywords: | Nd-Hf isotope decoupling Delaminated lower crust Mantle-crust interaction Dengjiashan Middle-Lower Reaches of the Yangtze River |
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