大兴安岭中段根多河地区早白垩世花岗岩地球化学特征及构造背景
发布时间：2019-06-16 18:23
【摘要】：论文选取广泛发育于内蒙古根多河地区的早白垩世花岗质侵入岩为研究对象,通过野外调研、测试分析和综合研究,确定了其形成的时代,地球化学特征,探讨了该时期花岗岩的岩浆源区性质、岩石成因以及形成的构造背景,为大兴安岭地区早白垩世侵入岩的活动时间及构造演化历史提供了新的资料。野外调研结果表明,根多河地区以新立屯岩体为代表的花岗闪长岩集中分布于新立屯林场一带,总体呈近南北向岩基展布,切割了区内北东、北北东向断裂,由11个侵入体组成,出露面积45.12km2;以根多河岩体为典型代表的二长花岗岩主要分布在根多河林场、济沁河林场一带及零星出露于研究区东部、东南部,根多河岩体总体呈近北东向岩基展布,由11个侵入体组成,出露面积59.07km2。采用锆石LA-ICPMS U-Pb测年方法,测得新立屯岩体形成时代为135.6±1.3Ma、根多河岩体形成时代为130.3±2.4Ma,表明其形成时代为早白垩世,而非前人认为的印支期或燕山早期。不同岩体主量元素、微量元素和稀土元素测试结果表明,新立屯岩体的SiO2含量65.64%~67.09%;里特曼指数(σ)2.40~2.92,属钙碱性岩石;A/CNK值在0.92~0.97之间,呈准铝质特点;稀土元素总量(ΣREE)102.3~159.13×10-6,平均值为122.86×10-6,轻稀土元素分馏作用较强,重稀土元素分馏作用相对较弱。Tm出现弱的正异常,Er、Yb、Eu呈负异常,δEu值0.61~0.80,为弱亏损,说明源区岩浆发生过斜长石的分离结晶,导致残余熔体中Eu的亏损。根据Sr和Yb的富集和亏损程度,可将本区花岗闪长岩定为高Sr低Yb型花岗岩,Sr462μg/g,Yb2.04μg/g。根多河岩体SiO2含量66.88~76.53%;里特曼指数(σ)2.27~3.13,属钙碱性岩石;A/CNK值在1.05~1.17之间,为铝过饱和岩石;稀土元素总量(ΣREE)141.53~194.03×10-6,轻重稀土分馏明显,为轻稀土富集型;Ce、Gd出现相对明显的正异常;δEu值0.23~0.92,暗示源区残留相存在斜长石;微量元素球粒具有贫Ba、Nb、C、P、Ti,富K、Rb、Th、Nd的特点;Ba相对于Rb、Th明显亏损。上述地球化学特征显示本区白垩纪中酸性侵入体的源区存在斜长石而缺乏石榴石和角闪石,表明本期岩浆源区比较浅。Nb显负异常,表明其与消减有关。综合研究发现,新立屯岩体的花岗闪长岩为准铝质、高钾钙碱性系列的I型花岗岩,呈高Sr低Yb型,形成于较高压的下地壳,具有类似于活动大陆边缘花岗岩的岩石组合特征,暗示其可能形成于活动大陆边缘构造背景,即与古太平洋板块的俯冲有关。根据构造判别推测,该地区的根多河二长花岗岩形成于造山后的拉张环境,地壳减薄,促使软流圈的物质上涌和幔源岩浆的底侵作用,导致地壳的温度升高,减压熔融形成该地区的二长花岗岩。
[Abstract]:In this paper, the early Cretaceous granitic intrusive rocks, which are widely developed in Gendohe area, Inner Mongolia, are selected as the research object. Through field investigation, test analysis and comprehensive research, the age and geochemical characteristics of granitic intrusive rocks in this period are determined, and the magmatic origin, petrogenesis and tectonic background of granites in this period are discussed. It provides new data for the activity time and tectonic evolution history of early Cretaceous intrusive rocks in Daxinganling area. The results of field investigation show that the granodiorite represented by Xinlitun rock mass in Gendohe area is concentrated in the area of Xinlitun Linchang, which is distributed in the north-south direction, and cuts the north-east and north-east faults in the area, which is composed of 11 intrusions and the exposed area is 45.12 km ~ 2. The monzonitic granite represented by the Gentuohe rock mass is mainly distributed in the Gentuohe forest farm. The JiQinhe forest farm area and sporadic exudation in the eastern part of the study area. In the southeast, the Gentuohe rock mass is distributed in the near-east-eastward rock base, which is composed of 11 intrusions with an exposed area of 59.07km2.The Gentuohe rock mass is distributed in the east of the study area in the east and southeast of the study area. By using zircon LA-ICPMS U-Pb dating method, the formation age of Xinlitun rock mass is 135.6 卤1.3 Ma, and that of Gendohe rock mass is 130.3 卤2.4 Ma, indicating that its formation age is early Cretaceous, rather than the Indochina or early Yanshanian period. The test results of main elements, trace elements and rare earth elements of different rock masses show that the SiO2 content of Xinlitun rock mass is 65.64% 鈮，
本文编号：2500732
[Abstract]:In this paper, the early Cretaceous granitic intrusive rocks, which are widely developed in Gendohe area, Inner Mongolia, are selected as the research object. Through field investigation, test analysis and comprehensive research, the age and geochemical characteristics of granitic intrusive rocks in this period are determined, and the magmatic origin, petrogenesis and tectonic background of granites in this period are discussed. It provides new data for the activity time and tectonic evolution history of early Cretaceous intrusive rocks in Daxinganling area. The results of field investigation show that the granodiorite represented by Xinlitun rock mass in Gendohe area is concentrated in the area of Xinlitun Linchang, which is distributed in the north-south direction, and cuts the north-east and north-east faults in the area, which is composed of 11 intrusions and the exposed area is 45.12 km ~ 2. The monzonitic granite represented by the Gentuohe rock mass is mainly distributed in the Gentuohe forest farm. The JiQinhe forest farm area and sporadic exudation in the eastern part of the study area. In the southeast, the Gentuohe rock mass is distributed in the near-east-eastward rock base, which is composed of 11 intrusions with an exposed area of 59.07km2.The Gentuohe rock mass is distributed in the east of the study area in the east and southeast of the study area. By using zircon LA-ICPMS U-Pb dating method, the formation age of Xinlitun rock mass is 135.6 卤1.3 Ma, and that of Gendohe rock mass is 130.3 卤2.4 Ma, indicating that its formation age is early Cretaceous, rather than the Indochina or early Yanshanian period. The test results of main elements, trace elements and rare earth elements of different rock masses show that the SiO2 content of Xinlitun rock mass is 65.64% 鈮，
本文编号：2500732
本文链接：https://www.wllwen.com/kejilunwen/diqiudizhi/2500732.html
