| 粤西晚侏罗世花岗质岩体及其暗色微粒包体的成因及意义:年代学、矿物学和地球化学约束 |
| |
| 引用本文： | 刘梓,张玉芝,崔翔,甘成势,王岳军.粤西晚侏罗世花岗质岩体及其暗色微粒包体的成因及意义:年代学、矿物学和地球化学约束[J].地球科学,2020,45(4):1243-1265. |
| |
| 作者姓名： | 刘梓 张玉芝 崔翔 甘成势 王岳军 |
| |
| 作者单位： | 1.中山大学地球科学与工程学院, 广东广州 510275 |
| |
| 基金项目： | 国家自然科学基金项目U1701641国家自然科学基金项目U1701641中国科学技术部国家重点研发计划课题2016YFC0600303广东省自然科学基金项目2018B030312007 |
| |
| 摘 要： | 粤西阳江市八二花岗质岩体中广泛发育似斑状细粒闪长质暗色微粒包体，这些暗色微粒包体形态多样，与寄主岩具相似的矿物组合，对研究花岗岩成因和壳-幔相互作用具有十分重要的意义.为了探讨它们的岩石成因及构造属性，对寄主岩和暗色微粒包体开展了系统的岩相学、年代学和地球化学研究.LA-ICP-MS锆石U-Pb定年结果表明，寄主岩年龄为160.0±1.0 Ma，暗色微粒包体年龄为159.3±1.1 Ma，均为晚侏罗世的产物.全岩地球化学特征显示，寄主岩属于富钾的准铝质I型花岗岩，寄主岩和暗色微粒包体均富集轻稀土元素和大离子亲石元素，亏损重稀土元素和Nb、Ta、Ti等高场强元素.此外，两者具相似的Sr-Nd同位素组成，寄主岩的εNd（t）值为-5.73~-5.67，（87Sr/86Sr）i值为0.707 63~0.707 67；而暗色微粒包体的εNd（t）值为-5.81~-4.35，（87Sr/86Sr）i值为0.707 04~0.707 74.锆石饱和温度计和角闪石全铝压力计表明八二花岗质岩体结晶于730~754℃和19.8~20.6 km.综合寄主岩及其暗色微粒包体的岩石学、地球化学、同位素特征，晚侏罗世八二花岗质岩体可能形成于陆内伸展背景，由于软流圈物质上涌底侵，导致中下地壳变基性岩为主的源岩部分熔融，并且源区有少量幔源物质的加入，局部可能存在岩浆混合作用；暗色微粒包体是由镁铁质岩浆与长英质岩浆混合形成的.
|
| 关 键 词： | 华南 晚侏罗世 暗色微粒包体 U-Pb年龄 地球化学 |
| 收稿时间： | 2019-05-19 |
Petrogenesis and Implications of the Late Jurassic Granitoid and Its Mafic Microgranular Enclaves in West Guangdong Province: Constraints from Geochronological,Mineralogical and Geochemical Evidence |
| |
| Abstract: | Mafic microgranular enclaves (MMEs) are widespread in the host granitoid from the Ba'er pluton in the west of the Guangdong Province. The MMEs have variable shapes and share similar mineral compositions with their host rocks, but are not fully understood. Petrographic study, zircon U-Pb dating and geochemical data are reported for the host granitoid and its MMEs, to constrain their petrogenesis and tectonic setting. LA-ICP-MS zircon U-Pb dating results yield weighted mean 238U/206Pb ages of 160.0±1.0 Ma and 159.3±1.1 Ma for the host rocks and the MMEs, respectively. The host granitoid is characterized by high SiO2(61.04%-65.84%), K2O(1.60%-4.97%), low A/CNK(1.59-1.99), belonging to metaluminous, K-enriched I-type granitoid. Both host rocks and MMEs are enriched in LREE and LILE, and are depleted in HREE and HFSE (e.g., Nb, Ta and Ti). In addition, they also have indistinguishable Sr-Nd isotopic compositions. The granitoid has εNd(t) values of -5.73 to -5.67 and (87Sr/86Sr)i values of 0.707 63-0.707 67. The MMEs have εNd(t) values of -5.81 to -4.35 and (87Sr/86Sr)i values of 0.707 04-0.707 74. The calculated crystallization temperatures and depths of the Ba'er pluton are 730-754℃ and 16.8-20.6 km, respectively. According to comprehensive analysis of their tectonic settings as well as petrographic characteristics and geochemical data, the magma produced by partial melting of predominantly mafic middle-lower crust, with the input of minor mantle-derived materials, experienced different degrees of fractional crystallization in an intraplate extensional setting of Late Jurassic, Southeast China, which was accompanied by local magma mixing. The MMEs are generated by the mixing of the mafic magma with felsic magma. |
| |
| Keywords: | |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《地球科学》浏览原始摘要信息 |
|
点击此处可从《地球科学》下载全文 |
|
