Petrogenesis and tectonic setting of Mingnandong pluton in Yanbian area:Constraints from petro-geochemistry and zircon U-Pb ages
Petrogenesis and tectonic setting of Mingnandong pluton in Yanbian area:Constraints from petro-geochemistry and zircon U-Pb ages
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发表时间：
2014
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通讯作者：
Lei Cong-con
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作者：
Lei Cong-con
本文通过野外观察、LA-ICP-MS锆石U-Pb同位素测定和岩石地球化学等方法，对明南洞岩体进行了深入研究，结果表明，明南洞岩体形成于早侏罗世（180.47±0.71Ma）。SiO_2=60.71%~ 67.72%，Al_2O_3 =15.60%~ 17.44%，Na_2O +K_2O=6.79%~ 7.63%，K_2O/Na_2O=0.61-1.01，A/CNK=0.94- 1.01，为高钾钙碱性I型花岗岩。明南洞岩体富集轻稀土元素和大离子亲石元素，明南洞岩体具有明显的活动大陆边缘和火山弧花岗岩的特征，平行于洋壳俯冲方向的成分分带，使该岩体具有明显的活动大陆边缘和火山弧花岗岩的特征。从盐边、太平山到小兴安岭、张广才山的钙碱性花岗岩、高钾钙碱性花岗岩和双峰式火山岩组合指示了古太平洋板块俯冲的方向，明南洞岩体的侵位受到了早侏罗世古太平洋板块俯冲的影响。
In this paper Mingnandong pluton was studied throughly by such means as field observation,LA-ICP-MS zircon U-Pb isotopic measurement and petro-geochemistry.The results show that Mingnandong pluton was formed in the Early Jurassic(180.47±0.71Ma).Chemical analyses yielded the following data for Mingnandong pluton:SiO_2=60.71%-67.72%,Al_2O_3=15.60%-17.44%,Na_2O+K_2O=6.79%-7.63%,K_2O/Na_2O=0.61-1.01 and A/CNK=0.94-1.01,implying high-potassium calc-alkaline I-type granites.Besides,Mingnandong pluton is enriched in light rare earth elements and large ion lithophile elements,and depleted in heavy rare earth elements and high field strength elements.These features suggest that Mingnandong pluton has obvious characteristics of active continental margin and volcanic arc granites.The ingredient zonation parallel to the orientation of the subduction of oceanic crust made up of cale-alkaine,high-K calc-alkaline granites and the bimodal volcanic rock association from Yanbian and Taiping Mountain to Xiao Hinggan Mountains and Zhangguangcai Mountain indicate the orientation of the subduction of ancient Pacific plate.In a word,the emplacement of Mingnandong pluton was influenced by the subduction of ancient Pacific plate in the Early Jurassic.