大兴安岭中南段罕山林场地区玛尼吐组安山岩年代学、地球化学特征及其地质意义  

Geochronology and Geochemistry of the Andesites from the Manitu Formation in the Hanshanlinchang Area,Central-Southern Daxinganling Mountains and their Geological Implications

作　　者：杨海星 高利东 高玉石 隋海涛 柳志辉 赵志飞 赵胜金 于海洋[1] 张维宇 吕晶 郎欣欣 YANG Haixing;GAO Lidong;GAO Yushi;SUI Haitao;LIU Zhihui;ZHAO Zhifei;ZHAO Shengjin;YU Haiyang;ZHANG Weiyu;L Jing;LANG Xinxin(Inner Mongolia Tenth Geological Mineral Exploration and Development Co.,Ltd.,Chifeng,Inner Mongolia 024005;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083)

机构地区：[1]内蒙古第十地质矿产勘查开发有限责任公司,内蒙古赤峰024005 [2]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地质与勘探》2019年第5期1223-1240,共18页Geology and Exploration

基　　金：中国地质调查项目(编号:DD20160048-11、DD20160048-15、DD20160048)资助

摘　　要：玛尼吐组是大兴安岭地区重要的地层单元。本文对大兴安岭中南段罕山林场地区玛尼吐组火山岩进行LA-ICPMS锆石U-Pb定年和岩石地球化学分析。LA-ICPMS锆石U-Pb定年结果显示,四件安山岩样品分别形成于144.0±2.8Ma、144.6±2.1Ma、148.0±2.0Ma及151.4±2.6Ma,说明研究区玛尼吐组安山岩时代归属晚侏罗世。从岩石地球化学特征看,玛尼吐组安山岩与中国安山岩相比,下列成分的含量偏高:SiO2(50.4%~62.38%)、TiO2(0.92%~1.74%)、Al2O3(14.2%~18.34%)、CaO(4.84%~9.39%)、Na2O(2.68%~4.97%);含量相当的成分是:Fe2O3(2.91%~7.83%)、K2O(1.48%~3.27%)、P2O5(0.08%~0.52%;而下列成分的含量偏低:FeO(0.74%~4.67%)、MnO(0.04%~0.16%)、MgO(0.92%~5.06%);因此它是一套准铝质高钾钙碱性系列安山岩。稀土总量(ΣREE)较低,介于95.88×10^-6~186.76×10^-6之间,轻、重稀土分异明显(LREE/HREE=5.24~9.75,(La/Yb)N=4.84~13.21);具轻微负铕异常(δEu=0.78~1.11)。微量元素富集大离子亲石元素(Rb、Ba、K、Pb、Sr)和LREE,亏损高场强元素(Nb、Ta、Ti、P)和HREE。火山岩浆来源于俯冲流体交代的地幔楔部分熔融;形成于大陆边缘弧,与太平洋板块俯冲后的陆内伸展作用相关。The Manitu Formation is an important stratigraphic unit in the Daxinganling Mountains. This paper presents LA-ICPMS ziron U-Pb dating and geochemical analysis of the andesites from the Manitu Formation in the Hanshanlinchang area,central-southern Daxinganling Mountains. Dating results of four samples show ages of 144.0±2.8Ma,144.6±2.1Ma,148.0±2.0 Ma and 151.4±2.6Ma,respectively,indicating that Manitu Formation andesites formed in Late Jurassic. In geochemistry,compared with the general Chinese andesites,the following compositions of Manitu andesites have higher contents:SiO 2 (50.4%~62.38%),TiO 2 (0.92%~1.74%,Al 2 O 3 (14.2%~18.34%),CaO(4.84%~9.39%),Na 2 O(2.68%~4.97%);the compositions with identical contents include Fe 2 O 3 (2.91%~7.83%),K 2 O(1.48%~3.27%),and P 2 O 5 (0.08%~0.52%),while FeO(0.74%~4.67%),MnO(0.04%~0.16%)and MgO(0.92%~5.06%)are relatively low;so they should be a suite of metaluminous high potassium calc-alkaline andesites. Meanwhile,they have low total amount of rare earth elements(Σ REE=95.88×10 ^-6 ~186.76×10 ^-6 );obviously fractionated LREE from HREE(LREE/HREE=5.24~9.75,(La/Yb) N= 4.84~13.21)and negative Eu anomalies(δ Eu=0.78~1.11). Besides,these andesites are enriched in LILE(Rb,Ba,K,Pb,Sr)and LREE,while depleted in HFSE(Nb,Ta,Ti,P)and HREE. Considering the tectonic setting of the Daxinganling Mountains,we suggest that these volcanic rocks have originated from the magma in a partially melting mantle wedge of a subduction zone with fluid replacement,which formed at a continental marginal arc,associated with intracontinental extension after the Pacific underthrusting.

关 键 词：玛尼吐组 安山岩 锆石U-PB年龄 岩石地球化学 地质意义 罕山林场地区 大兴安岭中南段 

分 类 号：P597[天文地球—地球化学] P595[天文地球—地质学]