| 古太平洋板块早侏罗世俯冲作用:来自吉林延边和龙地区辉长岩年代学和地球化学记录 |
| |
| 引用本文： | 张超1,2,王路远1,耿瑞3,刘正宏2,4,张乐彤5. 古太平洋板块早侏罗世俯冲作用:来自吉林延边和龙地区辉长岩年代学和地球化学记录[J]. 延边大学学报(自然科学版), 2020, 0(6): 819-832. DOI: 10.19814/j.jese.2020.08019 |
| |
| 作者姓名： | 张超1 2 王路远1 耿瑞3 刘正宏2 4 张乐彤5 |
| |
| 作者单位： | 1. 山东理工大学 资源与环境工程学院,山东 淄博 255000; 2. 自然资源部东北亚矿产资源评价重点实验室,吉林 长春 130026; 3. 山东黄金集团有限公司,山东 济南 250101; 4. 吉林大学 地球科学学院,吉林 长春 130061; 5. 黑龙江省地球物理地球化学勘查院,黑龙江 哈尔滨 150036 |
| |
| 摘 要： | 吉林延边地区位于兴蒙造山带南缘东段,是古亚洲洋构造域和环太平洋构造域叠加与改造的地区。为确定吉林延边和龙地区沙松顶子辉长岩侵位时代和成因,探讨其大地构造背景,对沙松顶子辉长岩进行了岩相学、锆石U-Pb年代学、Hf同位素和地球化学分析。结果表明:沙松顶子辉长岩LA-ICP-MS锆石U-Pb加权平均年龄为(175.6±1.1)Ma,为早侏罗世晚期; 辉长岩具低Si、高Al特征和较高的Mg#值,并含有较高的Cr、Ni、V、Co和Sc含量,Zr/Hf和Ba/Rb值具有幔源岩浆岩的特征,Nb/U值接近大陆地壳,反映沙松顶子辉长岩原始岩浆在上升过程中有陆壳物质的加入; 辉长岩稀土元素总含量较低,弱富集轻稀土元素,富集大离子亲石元素Cs、K、Sr等,亏损Nb、Ta等高场强元素,具有正Eu异常,地球化学特征表现出俯冲环境下形成的基性岩浆岩特征; 辉长岩具有显著亏损的Hf同位素组成特征,εHf(t)为2.5～7.0,均为正值,说明辉长岩原始岩浆应起源于高度亏损的地幔。综上所述,沙松顶子辉长岩形成于古太平洋俯冲作用下活动大陆边缘的构造环境,其原始岩浆可能来源于亏损地幔,并遭受俯冲板片析出流体的交代作用和地壳物质的混染。
|
| 关 键 词： | 辉长岩 锆石U-Pb年龄 Hf同位素 早侏罗世 活动大陆边缘 古太平洋板块 兴蒙造山带南缘 吉林 |
Paleo-Pacific Subduction in Early Jurassic: Geochronological and Geochemical Evidences of Gabbros in Helong Area of Yanbian,Jilin, China |
| |
| ZHANG Chao1,' target="_blank" rel="external">2,WANG Lu-yuan1,GENG Rui3,LIU Zheng-hong2,' target="_blank" rel="external">4,ZHANG Le-tong5. Paleo-Pacific Subduction in Early Jurassic: Geochronological and Geochemical Evidences of Gabbros in Helong Area of Yanbian,Jilin, China[J]. Journal of Yanbian University (Natural Science), 2020, 0(6): 819-832. DOI: 10.19814/j.jese.2020.08019 |
| |
| Authors: | ZHANG Chao1,' target=" _blank" rel=" external" >2,WANG Lu-yuan1,GENG Rui3,LIU Zheng-hong2,' target=" _blank" rel=" external" >4,ZHANG Le-tong5 |
| |
| Abstract: | Yanbian area in Jilin, located at the eastern segment of the southern Xing-Meng orogenic belt, is an overlapped and transformed area between the paleo-Asian ocean and paleo-Pacific ocean tectonic domains. In order to confirm the emplaced age and discuss the petrogenesis and tectonic setting of Shasongdizi gabbros in Helong area of Yanbian, Jilin, the petrography, zircon U-Pb geochronology, Hf isotopic data and geochemistry of the gabbros were analyzed. The results show that the emplaced age of Shasongdingzi gabbro is in late Early Jurassic with the weighted mean age of(175.6±1.1)Ma; gabbros are characterized by the low SiO2 contents and high Al2O3 contents, while the samples have high Cr, Ni, V, Co, Sc contents and Mg# values; meanwhile, the ratios of Zr/Hf and Ba/Rb are similar to the ones of mantle igneous rocks, the ratios of Nb/U are similar to the ones of continental crust, indicating that the continental contamination occurs during evolution; gabbros have low total REE contents and positive Eu anomaly; all the samples are slightly enriched in LREE and enriched in LILE such as Cs, K, Sr, and depleted in HFSE such as Nb and Ta. The geochemical features suggest that the gabbros have subduction-reformed lithospheric mantle-derived primary magma contaminated by upper crustal materials during evolution. The gabbros have depleted Hf isotopic compositions with εHf(t)of 2.5-7.0. In summary, the primary magma of gabbros may be from the depleted mantle, which is metasomatized by fluids from subducted oceanic slab and is contaminated by the crustal materials. Furthermore, the Shasongdingzi gabbros form in an active continental margin during the subduction of paleo-Pacific. |
| |
| Keywords: | gabbro zircon U-Pb age Hf isotope Early Jurassic active continental margin paleo-Pacific plate the southern Xing-Meng orogenic belt Jilin |
|
| 点击此处可从《延边大学学报(自然科学版)》浏览原始摘要信息 |
|
点击此处可从《延边大学学报(自然科学版)》下载免费的PDF全文 |
|
