| 李序贵.云南富宁地区晚二叠世基性火山岩的发现及其构造意义[J].地质与勘探,2020,56(6):1192-1204 |
| 云南富宁地区晚二叠世基性火山岩的发现及其构造意义 |
| Discovery and tectonic significance of Late Permian basic volcanic rocks in the Funing area, Yunnan Province |
| 投稿时间：2019-12-09 修订日期：2020-08-19 |
| DOI：10.12134/j.dzykt.2020.06.008 |
| 中文关键词: 火山岩 晚二叠世 玄武岩 岩石地球化学 富宁 云南 |
| 英文关键词: volcanic rocks, Late Permian, basalt, petrochemistry, Funing area, Yunnan Province |
| 基金项目:中国地质调查局项目《云南1:5万那佐幅、里往幅、大普弄幅、花甲幅（G48E024014、G48E024015、G48E001014、G48E001015）4幅区域地质调查》（编号：121201010000150008-09）资助 |
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| 中文摘要: |
| 笔者在云南富宁地区厘定出一套较大面积展布的火山岩，为讨论该火山岩岩石地球化学特征及其构造意义，对该火山岩进行了地质学、岩石学、地球化学分析。结果表明：（1） 该套火山岩是研究区全新发现，结合其地质学特征及邻近地区测年数据，认为其时代可能为晚二叠世；（2）该火山岩主要由灰色致密状玄武岩、灰色（球颗）玄武岩、灰色气孔状玄武岩等基性岩石构成，多具有间粒结构，致密块状构造、气孔状构造，主要由斜长石、辉石组成，局部可见微弱热液蚀变发育；（3）该火山岩属亚碱性系列，SiO2含量处于46.08%~51.80%之间，全碱alk=2.94~5.21，K2O/Na2O=0.03~1.03，钠质多，为基性中-高钾钙碱性玄武岩；（4）该火山岩呈现轻稀土富集、重稀土亏损的弱分异右倾式稀土元素配分特征，δEu=1.02~1.10，呈现Eu正异常，δCe=0.93~0.96，表现Ce负异常。（Rb/Yb）N=1.6~11.4，强不相容元素富集；（Ce/Yb）N=2.03~7.59，（La/Lu）N=2.4~9.93，稀土元素分异明显；微量元素表现为Sr、Ti、Zr、Nb亏损，而P、Th富集特征。Nb/Ta介于11.8~18.5，显示出岩浆源遭受过来自消减板块的影响；（5）火山岩构造判别图显示该火山岩既具有大陆板内环境特征，又具有大洋板内构造背景，是一种叠加的构造环境，这可能是因为该地区大洋演化过程中同时受到了峨眉山玄武岩影响造成的。 |
| 英文摘要: |
| This work has determined a vast expanse of volcanic rocks in the Funing area, Yunnan Province. Their geochemical characteristics and tectonic significance were revealed by analyses of geology, petrology, and geochemistry. The results show that this volcanic rock set is a new discovery in the study area. Combined with its geological characteristics and the dating data of neighboring areas, its age is considered likely to be Late Permian. The volcanic rock comprises gray dense basalt, gray (globular) basalt, gray stomatal basalt and other basic rocks, most of which have intergranular, dense massive, and stomatal structures. It is composed of plagioclase and pyroxene, with weak hydrothermal alteration locally. The volcanic rock belongs to the subalkaline series, with SiO2 content between 46.08%~51.80%, total alkali alk=2.94~5.21, K2O/Na2O=0.03~1.03, with abundant sodium, being basic medium-high potassium calc alkaline basalt. The volcanic rock shows weak differentiation and a right inclined REE distribution characteristic of light rare earth enrichment and heavy rare earth depletion, with Eu=1.02~1.10, showing an Eu positive anomaly, with δCe=0.93~0.96, showing a Ce negative anomaly. In this rock, (Rb/Yb)N=1.6~11.4, strongly incompatible elements are enriched; (Ce/Yb)N= 2.03~7.59, (La/Lu)N =2.4~9.93, rare earth elements are obviously differentiated; trace elements show Sr, Ti, Zr, and Nb depletion, while P, Th enrichment. Nb/Ta is between 11.8~18.5, indicating that the magma source was affected by a subduction plate. The tectonic discrimination diagram of the volcanic rocks shows a characteristic of a continental plate environment as well as a oceanic plate tectonic background, implying a superimposed tectonic setting, likely due to the influence of the Emeishan basalt during the evolution of the ocean in this area. |
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