摘要
满洲里南部塔木兰沟组火山岩主要由橄榄玄武岩、辉石玄武岩和玄武安山岩组成。LA-ICP-MS锆石U-Pb定年结果显示,火山岩形成于164～161Ma的中侏罗世末期。岩石主体属高钾钙碱性系列,镁含量较低[w(MgO)=1.64%～9.59%],镁指数较小(Mg#=0.26～0.66);稀土元素配分模式呈轻稀土富集右倾型,轻重稀土分馏明显[(La/Yb)N=6.86～22.29],存在微弱的Eu异常(δEu=0.70～0.93);微量元素以富集大离子亲石元素(如Rb、Ba、K)和轻稀土元素(LREE)、亏损高场强元素(如Nb、Ta、P、Ti)和相容元素(Cr、Co、Ni)为特征;锆石176 Hf/177 Hf值为0.282 691～0.282 740,εHf(t)值为0.67～2.30。综合研究表明:岩浆源区为俯冲板片流体交代过的岩石圈地幔,岩浆上升过程中未受到地壳物质的明显混染,但经历了一定程度的橄榄石和单斜辉石分离结晶作用。结合区域地质构造演化特征,认为交代作用流体来自蒙古—鄂霍茨克洋壳,塔木兰沟组火山岩是蒙古—鄂霍茨克洋闭合造山后岩石圈伸展环境下的产物。
The volcanic rocks of Tamulangou Formation in southern Manchuria are composed mainly of olivine basalt,pyroxene basalt and basaltic andesite.LA-ICP-MS zircon U-Pb dating results show that the volcanic rocks formed at the end of Middle Jurassic,ranged from 164 Ma to 161 Ma.Geochemical data show that the volcanic rocks belong to high-K calc-alkaline series,have low contents of MgO（1.64%-9.59%） and small Mg#（0.26-0.66）;The chondrite-normalized rare earth element（REE） patterns indicate that the volcanic rocks are enriched in light rare earth elements（LREE） with significant fractionation of HREE and LREE（（La/Yb）N=6.86-22.29） and weak Eu anoalies（δEu=0.70-0.93）;The trace element geochemistry are characterized by enrichment in large ionic lithophile elements（e.g.Rb,Ba,K） and LREEs,depletion in high field strength elements（e.g.Nb,Ta,P,Ti） and compatible elements（Cr,Co,Ni）;The initial 176Hf/177Hf ratios of the magmatic zircons from volcanic rocks vary from 0.282 691 to 0.282 740,and the corresponding εHf（t） values range from 0.67 to 2.30.The geochemical data suggest that the magma could be derived from partial melting of lithosphere mantle which had been metasomatized by subduction fluids,and probably experienced fractional crystallization of olivine and clinopyroxene,and insignificant crustal contamination.Combined with the regional research results,we suggest that the metasomatic fluids could be originated from the oceanic crust of Mongol-Okhotsk Ocean,and these volcanic rocks formed under a lithospheric extension after the closure of Mongol-Okhotsk Ocean.
出处
《吉林大学学报（地球科学版）》
EI
CAS
CSCD
北大核心
2011年第6期1865-1880,共16页
Journal of Jilin University：Earth Science Edition
基金
中国核工业地质局项目(200805)
国家自然科学基金项目(41172058)
国家'973'计划项目(2009CB19303)
中国地质调查局项目(121201112108)
西北大学大陆动力学国家重点实验室开放基金
关键词
塔木兰沟组
年代学
地球化学
岩石成因
满洲里
Tamulangou Formation
chronology
geochemistry
petrogenesis
Manchuria
