地质通报2013，Vol.32Issue(2)：399-407,9.
大兴安岭中段玛尼吐组火山岩LA-ICP-MS锆石U-Pb年龄及地球化学特征
W.Zircon U-Pb dating and geochemical study of volcanic rocks in Manitu Formation of central Da Hinggan Mountains
摘要
Abstract
In this study, LA-ICP-MS zircon U-Pb dating results and geochemical data were obtained from the volcanic rocks in Mani-tu Formation of Chaihe area lying in southwest Zhalantun City of central Da Hinggan Mountains. Zircon U-Pb dating results show that they were formed in early Cretaceous(135Ma). The volcanic rocks belonging chemically to the shoshonite series have SiO2 59.5%～70.8% and are enriched in alkali and potassium, with Rittman index from 3.2 to 4.7(σ=3.2～4.7). In addition, they are characterized by low total rare earth elements (EREE=112×10-6～172×10-6), significant fractionations of REE(La/Yb)N=6.5～9.2), moderate negative Eu anomalies (δEu=0.54～0.77), enrichment of large ion lithophile elements (LILEs, such as Ba and K) and light rare earth elements (LREEs) and depletion of high field strength elements (HFSEs, such as Nb, Ti and P). The values of such iron family elements as Cr, Co and Ni are all low (Cr=6.55×10-3, Cr=6.97×10-6, Ni=4.35× 10-6 on average). Recent researches show that the volcanic rocks might have been formed in an extensional setting after the closure of the Mongol-Okhotsk Ocean. Considering the regional resources, the authors have reached the conclusion that the volcanic rocks in Manitu Formation of central Da Hinggan Mountains region were formed in two structural environments. Total REE amounts are relatively law(∑REE=112×10-6～M72×10-6), fractionation between LREE and HREE (La/Yb)N=6.5～9.2) is obvious, and there exist moderate negative Eu anomalies (δEu=0.54～0.77). They are enriched in high LILE (e.g., Ba, K) and LREE, and depleted in HFSE (e.g., Nb, Ti, P) and iron family elements such as Cr, Co and Ni(Cr=6.55×10-6, Cr=6.97×10-6, Ni=4.35×10-6 on average). The research above shows that the tectonic background of Manitu Formation volcanics in the study area are formed on the lithospheric extensional structure after the closure orogeny of Mongolia -Ehucike, which is similar to the north section of the Great Xing'an Range but different from the south section generated in the compression and uplift.关键词
大兴安岭/玛尼吐组/地球化学Key words
Da Hinggan Mountains/Manitu Formation/ geochemistry分类
天文与地球科学引用本文复制引用
李世超,徐仲元,刘正宏,李永飞,王兴安,张超,范志伟..大兴安岭中段玛尼吐组火山岩LA-ICP-MS锆石U-Pb年龄及地球化学特征[J].地质通报,2013,32(2):399-407,9.基金项目
国家自然科学基金《辽西医巫闾山变质核杂岩形成与岩浆活动》(批准号:41272223)和中国地质调查局项目《古亚洲洋构造体制与滨太平洋构造体制叠加转变的综合调查和研究》(编号:1212011085473)、《东北地区晚古生代以来构造演化特征综合研究》(编号:1212011121085) （批准号:41272223）
