澜沧江南带火山岩系侏罗纪火山岩的存在及其地质意义
投稿时间:2019-09-09  修订日期:2019-10-10  点此下载全文
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唐波浪 中国地质大学(北京)自然资源部深地动力学重点实验室,中国地质科学院地质研究所 1554057877@qq.com 
刘英超 自然资源部深地动力学重点实验室,中国地质科学院地质研究所 lychappy@126.com 
马旺 自然资源部深地动力学重点实验室,中国地质科学院地质研究所  
岳龙龙 自然资源部深地动力学重点实验室,中国地质科学院地质研究所  
黄世强 中国地质大学(北京)  
庄亮亮 自然资源部深地动力学重点实验室,中国地质科学院地质研究所  
吴志旖 中国地质大学(北京)  
周梦林 山东省地质测绘院  
基金项目:国家重点研发计划(2016YFC0600306)、国家自然科学基金(41773042,41922022,41773043,41772088,41472067)、自然资源部深地动力学重点实验室自主研究课题(J1901-6)、国际地质对比计划(IGCP-662)
中文摘要:澜沧江南带火山岩系是古特提斯构造演化的产物,是反演古特提斯演化的利器。本文选择了带内南段普洱地区那澜村剖面火山岩进行了系统的年代学和地球化学研究,为古特提斯洋演化过程提供了新的认识。那澜村火山岩为一套发育斑状结构、流纹构造的流纹岩,其斑晶由半自形板柱状钾长石和石英组成,基质为隐晶质长石、石英。主量元素中SiO2含量介于75.59%~77.40%,Al2O3含量介于11.69%~12.20%,K2O含量(4.13%)大于Na2O(3.72 %),属过铝质高钾钙碱性-钙碱性系列火山岩。主量元素CaO/Na2O值为0.01~0.04, Al2O3/(MgO+TFeO)为0.03~0.06,CaO/(MgO+TFeO)为5.51~6.66,微量元素Nb/Ta比值集中在12.27-13.08,放射性同位素组87Sr/86Sr比值为0.714~0.719,207Pb/204Pb为15.733~15.760,206Pb/204Pb为18.903~19.400,表明火山岩源区为重熔的含(变质)泥岩地壳。微量元素标准化配分曲线呈不规则锯齿状且具高度一致性,Rb、Nb、Ta、Y、Yb等数据具富Rb低Nb、Ta、Y、Yb特征,表明澜沧江南带火山岩具有陆缘弧火山岩属性。LA-ICP-MS测定锆石U-Pb年代学表明那澜村火山岩协和年龄为200.6±2.8 Ma,和澜沧江南带北段火山岩活动(210-280Ma)具有一致性,说明澜沧江南带火山活动至少延伸至早侏罗世,也即古特提斯洋的俯冲活动至少持续到早侏罗世。
中文关键词:澜沧江南带火山岩系  流纹岩  地球化学特征  年代学  地质意义  普洱地区
 
The existence of the Jurassic volcanic rocks in the southern part of the Lancangjiang belt and its geological significance
Abstract:The volcanic rock series in the south of the Lancangjiang is a product of the evolution of the Paleo-Tethys and it’s a tool for inverting the evolution of the Paleo-Tethys. This paper selects the systematic chronology and geochemistry of the volcanic rocks in the Nanancun section of the Pu'er area, which provides a new understanding of the evolution of the Paleo-Tethys ocean. The volcanic rock in the area is a rhyolite of plaque-like structure and rhyolite structure. Its phenocrysts are composed of semi-automorphic slab-like K-feldspar and quartz. The matrix is cryptocrystalline feldspar and quartz. The main element analysis showed that the content of SiO2 was 75.59%~77.40%, the content of Al2O3 was 11.69%~12.20%, and the content of K2O (4.13%) was more than Na2O (3.72%), indicating that the rhyolite is Peraluminous high potassium calc-alkaline, calc-alkaline series volcanic rocks. The main elements of CaO/Na2O ratio is 0.01~0.04, Al2O3/(MgO+TFeO) is 0.03~0.06, and CaO/(MgO+TFeO) is 5.51~6.66, The ratio of trace element Nb/Ta is concentrated at 12.27~13.08, with an average of 12.79, and the date of radioactive?isotope 87Sr/86Sr is 0.714~0.719, 207Pb/204Pb is 15.733~15.760, 206Pb/204Pb is 18.903~19.400, indicating that the volcanic source is derived from the remelted (metamorphic) mudstone crust. The standardized trace element distribution curve is irregularly jagged and highly consistent, the date of Rb, Nb, Ta, Y and Yb is rich Rb and low Nb, Ta, Y and Yb, indicate that the volcanic rocks in the southern part of the Langcangjiang have the property of volcanic rocks in the continent marginal arc. The LA-ICP-MS zircon U-Pb chronology shows that the concord age of volcanic rocks is 200.6±2.8Ma, It is consistent with the volcanic rock activity (210-280Ma) in the northern section of the southern Lancangjiang belt, indicating that the volcanic activity in the southern Lancangjiang belt extends at least to the early Jurassic, that is, the subduction activity of the Paleo-Tethys ocean lasts at least to the early Jurassic.
keywords:Volcanic rock series in the south of Lancangjiang  rhyolite  geochemical characteristics  chronology  geological significance  Pu'er area
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