| 安徽滁州地区闪长质岩锆石U-Pb年龄与地球化学:岩石成因和动力学意义 |
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| 引用本文： | 朱强,胡召齐,施珂,吴礼彬,江来利.安徽滁州地区闪长质岩锆石U-Pb年龄与地球化学:岩石成因和动力学意义[J].地质通报,2018,37(6):1101-1112. |
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| 作者姓名： | 朱强 胡召齐 施珂 吴礼彬 江来利 |
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| 作者单位： | 安徽省地质调查院 |
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| 基金项目： | 安徽省国土资源科技项目《明光市管店-全椒县马厂一带金多金属矿控矿构造研究》（编号：2014-K-6） |
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| 摘 要： | 用LA-ICP-MS测得安徽滁州2个闪长玢岩样品中锆石~(206)Pb/~(238)U年龄为126.19±0.44Ma和126.4±0.7Ma,结合前人研究,得出滁州地区岩体的侵位时代应为120~130Ma之间,为早白垩世。岩石地球化学研究显示,Si O_2含量变化范围为56.75%~60.90%,具有高Al_2O_3(14.82%~15.77%)、Mg O(4%)、Sr(750×10~(-6))、Sr/Y(62~110)、La/Yb(20~36),低Y、Yb的特征,同时富集轻稀土元素和大离子亲石元素,亏损高场强元素,Eu异常不明显,属于典型的埃达克质岩。Mg~#值为39~45,K_2O/Na_2O值为0.57~0.96,平均值为0.75,明显低于大别造山带加厚下地壳埃达克岩,Ce/Pb值较低,大多集中在3~5之间,类似于陆壳而明显低于洋壳。研究认为,安徽滁州地区埃达克质岩由拆沉下地壳部分熔融形成,埃达克质岩浆在上升过程中与地幔橄榄岩发生反应,导致熔体Mg O、Cr、Ni等含量增加。早白垩世中国东部地壳伸展减薄导致下地壳拆沉,地幔物质的参与带来铜、金等成矿物质,埃达克质岩可作为该地区重要的找矿标志。
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| 关 键 词： | 闪长质岩 LA-ICP-MS锆石U-Pb测年 地球化学 埃达克质岩 拆沉下地壳 找矿标志 |
| 收稿时间： | 2017/6/12 0:00:00 |
| 修稿时间： | 2017/9/29 0:00:00 |
Zircon U-Pb age and geochemistry of the dioritic rocks in Chuzhou area in Anhui Province: Petrogenesis and dynamics significance |
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| ZHU Qiang,HU Zhaoqi,SHI Ke,WU Libin and JIANG Laili.Zircon U-Pb age and geochemistry of the dioritic rocks in Chuzhou area in Anhui Province: Petrogenesis and dynamics significance[J].Geologcal Bulletin OF China,2018,37(6):1101-1112. |
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| Authors: | ZHU Qiang HU Zhaoqi SHI Ke WU Libin and JIANG Laili |
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| Institution: | Geological Survey of Anhui Province, Hefei 230001, Anhui, China,Geological Survey of Anhui Province, Hefei 230001, Anhui, China,Geological Survey of Anhui Province, Hefei 230001, Anhui, China,Geological Survey of Anhui Province, Hefei 230001, Anhui, China and Geological Survey of Anhui Province, Hefei 230001, Anhui, China |
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| Abstract: | LA-ICP-MS zircon 206Pb/238U ages of two diorite porphyrite samples from Chuzhou area of Anhui Province are 126.19±0.44Ma and 126.4±0.7Ma, respectively. Previous study shows that the emplacement age of dioritic rocks should be 120~130Ma, sug-gesting early Cretaceous. Geochemical study shows the values of SiO2 vary from 56.75% to 60.90%, with the characteristics of high Al2O3(14.82%~15.77%), MgO(>4%), Sr(>750×10-6), Sr/Y(62~110), and La/Yb(20~36) but low Y, Yb, LREE as well as enrichment of LREE and LILE but depletion of HREE, with indistinct Eu anomaly, indicating typical adakitic rocks. Mg# values range from 39 to 45, K2O/Na2O vary from 0.57 to 0.96, 0.75 on average, significantly lower than the values of the adakitic rocks in the thickened crustal of Dabie orogenic belt; Ce/Pb ratios are low, mostly concentrated in the range of 3~5, similar to the values of the continental crust but significantly lower than those of the oceanic crust. The authors hold that the adakitic rocks in Chuzhou area of Anhui was formed by partial melting of delaminated lower crust, and the reaction of upward migrating adakitic magmas and mantle peridotite led to the increase of MgO, Cr and Ni melt content. In Early Cretaceous, eastern China crustal extension thinning resulted in lower crust delamination, and mantle material was involved in bringing Cu, Au and other ore-forming elements; hence adakitic rocks can be used as an important prospecting indicator in this area. |
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| Keywords: | dioritic rocks LA-ICP-MS zircon U-Pb dating geochemistry adakitic rocks delaminated lower crust prospect-ing indicator |
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