滇东南富宁地区基性侵入岩与峨眉山地幔柱存在成因关系吗?——来自1∶5万洞波幅和皈朝幅地质填图的证据  

Are the mafic intrusive rocks in the Funing area,Southeast Yunnan(Southwest China),really derived from the Emeishan plume?New evidence from geological surveys of the Dongbo and Guichao sheets(1∶50000)

作　　者：江文 向忠金[2] 夏文静 夏磊 张慧 PHAM Van Tho 闫全人 卫巍 JIANG Wen XIANG ZhongJin XIA WenJing XIA Lei ZHANG Hui PHAM Van Tho YAN QuanRen WEI Wei(College of Earth Sciences, University of Chinese Academy of Sciences, Beijing 100049, China Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China)

机构地区：[1]中国科学院大学地球科学学院,北京100049 [2]中国地质科学院地质研究所,北京100037

出　　处：《岩石学报》2017年第10期3109-3122,共14页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40472119;40872147);中国地质调查局项目(12120113067500;DD20160201-07)联合资助

摘　　要：在滇东南富宁地区,出露一系列以辉绿岩为主、含少量辉长辉绿岩和辉绿玢岩的基性侵入岩。根据地球化学、同位素地球化学以及锆石U-Pb年代学等分析结果,前人将这些基性侵入岩视作峨眉山大火成岩省的组成部分,源自峨眉山地幔柱。国内外研究的共识认为,峨眉山地幔柱活动发生于263~252Ma之间,持续时间极短。在开展1∶2.5万大比例尺地质调查与填图(洞波幅和皈朝幅1∶5万地质调查手图)过程中,我们发现,这些基性侵入岩不仅侵入古生代地层,还侵入了富宁县皈朝一带的晚二叠世-中三叠世岛弧玄武安山岩(255~241Ma)以及早-中三叠世地层。这些地质事实表明,富宁地区基性侵入岩的形成时代至少晚于中三叠世Anisian期或更晚,与峨眉山地幔柱活动时代存在很大的时差,岩石类型与组合上也与峨眉山大火成岩省的有很大差异。根据我们填图过程中获得的基本地质事实分析,滇东南富宁地区的基性侵入岩是华南地块与北越地块间的古特提斯分支洋盆闭合、两个地块碰撞造山(即印支造山)后的岩浆活动产物,与峨眉山地幔柱没有成因关系。The mafic intrusive rocks in the Funing area,Southeast Yunnan Province（Southwest China）,are dominated by diabase with a small amount of gabbro-diabase.Previous workings interpreted them as part of the Emeishan Large Igneous Province,based on geochemical,isotopic and zircon U-Pb analyses.Geological surveys（the Guichao and Dongbo Sheets at a scale of 1∶50000） in the Funning area conducted by this study show that diabase sheets or dikes not only intrude into Paleozoic strata,but also penetrate arcrelated basaltic andesites（ca.255~241 Ma） and low-middle Triassic strata（the Luolou Formation and Beifeng Formation,respectively）.These geological facts clearly indicate that the emplacement of the mafic intrusive rocks in the Funing area was occurred after the Middle Triassic and significantly later than the Emeishan plume（ca.263~252 Ma）.In addition,these mafic rocks are also significantly distinct from the Emeishan Large Igneous Province in the rock types and assemblages.Therefore,the geological facts presented in this study come to a conclusion that the mafic intrusive rocks in the Funing area are the product of magmatism after collision orogeny between the South China and Indochina blocks（Indosinian orogeny）,rather than the part of the Emeishan Large Igneous Province.

关 键 词：云南富宁 基性侵入岩 古特提斯 印支造山后 峨眉山地幔柱 

分 类 号：P542[天文地球—构造地质学] P588.124[天文地球—地质学]