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| 华北陆块南缘燕山期花岗岩带岩浆演化:以小秦岭—外方山地区为例 | |
| 引用本文： | 王振强,徐建昌,冯建之,祁冬梅,杨钢,孙卫志.华北陆块南缘燕山期花岗岩带岩浆演化:以小秦岭—外方山地区为例[J].现代地质,2011,25(6):1032-1046. |
| 作者姓名： | 王振强 徐建昌 冯建之 祁冬梅 杨钢 孙卫志 |
| 作者单位： | 1. 河南省金银多金属成矿系列与深部预测重点实验室,河南洛阳471023;河南省地质矿产勘查开发局第一地质调查队,河南洛阳471023 2. 河南省地质矿产勘查开发局第一地质调查队,河南洛阳,471023 3. 河南省地质矿产勘查开发局第一地质调查队,河南洛阳471023;河南省洛阳地质调查院,河南洛阳471023 4. 中国地质大学地球科学学院,湖北武汉,430074 |
| 基金项目： | 国土资源部"小秦岭金矿田深部及外围金矿整装勘查"项目 |
| 摘 要： | 根据华北陆块南缘小秦岭—外方山地区中生代花岗岩的时空分布特征,将其形成过程划分为160～155 Ma(Ⅰ)、150～125 Ma(Ⅱ)、120～110 Ma(Ⅲ)3个期次,与中国北方大规模岩浆活动期次并不完全一致。这3期花岗岩的地球化学元素演化较为特殊,Ⅰ期花岗岩(南泥湖、上房沟等岩体)与Ⅲ期花岗岩的地球化学特征较为相似,均以异常高的K含量、明显的负Eu异常及重稀土元素分馏较弱或不分馏为主要特征,为A型花岗岩。Ⅱ期花岗岩为偏铝质—弱过铝质高钾钙碱性系列花岗岩,富集Rb、Th、U和K等大离子亲石元素,亏损Nb和Ta等高场强元素,P2O5含量随SiO2含量增加呈递减趋势,为I型花岗岩,大部分样品Sr>300.00×10-6,Y<19.00×10-6,Yb<1.90×10-6,具有埃达克岩的属性。时代由老至新,Ⅰ、Ⅱ、Ⅲ花岗岩呈现出A型—I型—A型的演化规律。Ⅰ期花岗岩形成于挤压构造背景下的局部伸展环境;Ⅱ期花岗岩则形成于华北陆块南缘构造体制转换阶段,是地壳加厚导致的下地壳部分熔融的产物;Ⅲ期花岗岩则是扬子与华北陆块拼合后,板块逐渐稳定,岩石圈发生伸展,下地壳岩石减压熔融形成的。 |
| 关 键 词： | 小秦岭—外方山 燕山期花岗岩 岩浆演化 华北陆块南缘 |
Evolution of Yanshanian Granites in Southern Marginal Region of North China Block: A Case Study of Xiaoqinling-Waifangshan Area |
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| WANG Zhen-qiang,XU Jian-chang,FENG Jian-zhi,QI Dong-mei,YANG Gang,SUN Wei-zhi.Evolution of Yanshanian Granites in Southern Marginal Region of North China Block: A Case Study of Xiaoqinling-Waifangshan Area[J].Geoscience——Journal of Graduate School,China University of Geosciences,2011,25(6):1032-1046. | |
| Authors: | WANG Zhen-qiang XU Jian-chang FENG Jian-zhi QI Dong-mei YANG Gang SUN Wei-zhi |
| Institution: | WANG Zhen-qiang1,2,XU Jian-chang2,FENG Jian-zhi2,3,QI Dong-mei4,YANG Gang4,SUN Wei-zhi2,3(1.Key Laboratory of Gold and Silver Polymetallic Mineralization Series and Deep Prediction of Henan,Luoyang,Henan 471023,China,2.No.1 Geological Survey Team,Exploration and Development Bureau of Geological and Mineral Resources of Henan Province,3.Luoyang Institute of Geological Survey,4.Faculty of Earth Sciences,China University of Geosciences,Wuhan,Hubei 430074... |
| Abstract: | According to the time and space distribution characteristics of Mesozoic granites in Xiaoqinling-Waifangshan area in southern marginal region of North China block,the forming process of the Mesozoic granites can be divided into 160-155 Ma(Ⅰ),150-125 Ma(Ⅱ),and 120-110 Ma(Ⅲ),not identical with large-scale magmatic activity periods of North China.The geochemical evolution of the three periods of granites are special: geochemical characteristics of Ⅰ and Ⅲ periods of granites are very similar,and they are abnormally high content of K,obvious negative Eu anomaly and weak heavy rare-earth fractionation,belonging to A-type granites.Ⅱ period of granite is metaluminous-peraluminous and high potassium calcium alkaline series granite,and is rich in big ion lithophile element,such as K,U,and Th,lack in the high field element.P2O5 content decrease with the increasing of SiO2 content,belonging to I-type granite.For the contents of most samples,Sr content is more than 300.00×10-6,Y content is less than 19.00×10-6 and Yb content is less than 1.90×10-6,showing the geochemical characteristics of adakite rock.From early to late period,Ⅰ,Ⅱ and Ⅲ periods of granites show the trend of A-type-I-type-A-type.I period of granite formed in local extensional environment under the extrusion tectonic background.Ⅱ period of granite formed in tectonic setting transition period,being the product of the lower crust melting led by thickening crust.Ⅲ period of granite formed from plate stabilization,lithosphere stretching,and decompression and melting of the lower crust rocks,after Yangtze and North China continental blocks fitting. |
| Keywords: | Xiaoqinling-Waifangshan Yanshanian granite magmatic evolution southern marginal region of North China block |
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