| 澜沧江南带三叠纪火山岩岩石学、地球化学特征、Ar-Ar年代学研究及其构造意义 |
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| 引用本文： | 王硕,董国臣,莫宣学,赵志丹,朱弟成,孔会磊,王霞,聂飞.澜沧江南带三叠纪火山岩岩石学、地球化学特征、Ar-Ar年代学研究及其构造意义[J].岩石学报,2012,28(4):1148-1162. |
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| 作者姓名： | 王硕 董国臣 莫宣学 赵志丹 朱弟成 孔会磊 王霞 聂飞 |
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| 作者单位： | 1. 中国地质大学,北京,100083
2. 中国地质大学,北京100083;地质过程与矿产资源国家重点实验室,北京100083 |
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| 基金项目： | 本文受国家重点基础研究发展规划项目(2009CB421002)、111计划项目(B07011)、长江学者和创新团队发展计划(IRT1083)及中国地质调查局研究项目(1212011220920)联合资助. |
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| 摘 要： | 滇西三江地区澜沧江南带广泛发育三叠纪火山岩。在北部云县一带,中晚三叠世火山岩出露齐全,自下而上可划分为中三叠统忙怀组(T2m),上三叠统小定西组(T3x)和上三叠统芒汇河组(T3mh)。忙怀组以酸性火山岩为主,为一套流纹岩夹火山碎屑岩组合;小定西组发育为中基性火山熔岩夹火山碎屑岩;芒汇河组具有流纹质火山碎屑岩与玄武岩共存的"双峰式"火山岩特征。地球化学特征表明,南澜沧江带三叠纪火山岩具有弧火山岩与大陆板内火山岩的双重属性,推测其形成环境为过渡型的大陆边缘造山带环境。对南澜沧江带南部景洪附近采集到的石英安山岩样品进行Ar-Ar年龄测试,得到的坪年龄为236.7±2.2Ma,为中三叠世。结合火山岩年代学结果,推测澜沧江洋主碰撞期为早三叠世,中三叠世与晚三叠世早期分别为碰撞后的应力松弛阶段与洋盆继续俯冲期,到晚三叠世末期,俯冲作用结束,澜沧江洋关闭。
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| 关 键 词： | 三叠纪 弧火山岩 地球化学 Ar-Ar坪年龄 澜沧江南带 |
| 收稿时间： | 2011/4/20 0:00:00 |
| 修稿时间： | 2011/7/10 0:00:00 |
Petrological and geochemical characteristics, Ar-Ar geochronology study and their tectonic significance of Triassic volcanic rocks in southern Lancangjiang zone |
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| WANG Shuo,DONG GuoChen,MO XuanXue,ZHAO ZhiDan,ZHU DiCheng,KONG HuiLei,WANG Xia and NIE Fei.Petrological and geochemical characteristics, Ar-Ar geochronology study and their tectonic significance of Triassic volcanic rocks in southern Lancangjiang zone[J].Acta Petrologica Sinica,2012,28(4):1148-1162. |
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| Authors: | WANG Shuo DONG GuoChen MO XuanXue ZHAO ZhiDan ZHU DiCheng KONG HuiLei WANG Xia and NIE Fei |
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| Institution: | China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China; State Key Laboratory of Geological Processes and Mineral Resources, Beijing 100083, China;China University of Geosciences, Beijing 100083, China; State Key Laboratory of Geological Processes and Mineral Resources, Beijing 100083, China;China University of Geosciences, Beijing 100083, China; State Key Laboratory of Geological Processes and Mineral Resources, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China |
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| Abstract: | Triassic volcanic rocks are widespread in southern Lancangjiang zone of Sanjiang area. Middle-Late Triassic volcanic sequences exposed in full in Yunxian area in the north of southern Lancangjiang zone, can be divided into three formations as Middle Triassic Manghuai Formation (T2m), Late Triassic Xiaodingxi Formation (T3x) and Late Triassic Manghuihe Formation (T3mh) from the bottom to up. Acid volcanics mainly erupted in Manghuai Formation, formed a rhyolite and pyroclastic rock assemblage. Xiaodingxi Formation developed basic-intermediate lavas mixed with pyroclastic rocks. Rhyolite pyroclastic rocks and basalt coexist in Manghuihe Formation, showed "bimodal" volcanic features. Geochemical characteristics indicate that Triassic volcanic rocks from southern Lancangjiang zone have dual characteristics of arc volcanic rocks and continental intraplate volcanic rocks, suggesting that their formation environment is transition-type continental margin orogenic belts. Ar-Ar dating is carried on quartz andesite collected from Jinghong in the south of southern Lancangjiang zone and yields the plateau age of 236.7±2.2Ma, which belong to Middle Triassic. With the dating results, the main collision stage of Lancang River is inferred in Early Triassic. Middle Triassic and early Late Triassic are respectively the stress relaxation stage after collision and continued subduction stage of oceanic basin. Until the end of Late Triassic, subduction ended, Lancang River Ocean closed. |
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| Keywords: | Triassic Arc volcanic rocks Geochemistry Ar-Ar plateau age Southern Lancangjiang zone |
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