胶北地区古元古代基性——超基性岩锆石U-Pb定年Hf同位素组成及其构造岩浆演化意义  

Determination of Hf Isotope Components and Tectonic by Using Zircon U-Pb Dating and Magmatic Significance of Paleoproterozoic Mafic-Ultramafic Rocks in Jiaobei Area

作　　者：田京祥 侯建华[2] 郭瑞朋[2] 万渝生[3] 于晓卫[2] 王立功[2] 祝德成[2] 李秀章[2] 黄永波[2] 董春艳[3] 颉颃强[3] 谢士稳[3] 宋志勇[2] TIAN Jingxiang;HOU Jianhua;GUO Ruipeng;WAN Yusheng;YU Xiaowei;WANG Ligong;ZHU Decheng;LI Xiuzhang;HUANG Yongbo;DONG Chunyan;XIE Hangqiang;XIE Shiwen;SONG Zhiyong(Shandong Institute of Geological Sciences,Key Laboratory of Gold Mineralization Processes and Resources Utili.zation Subordinated to the Ministry of Land and Resources,Shandong Key Laboratory of Geological Processes and Resource Utilization in Metallic Minerals,Shandong Jinan 250013,China;Shandong Geological Surveying Insti.tute,Shandong Jinan 250014,China;Beijing SHRIMP Center in Geology Institute of Chinese Academy of Geo.logical Sciences,Beijing 100037,China)

机构地区：[1]山东省地质科学研究院,国土资源部金矿成矿过程与资源利用重点实验室,山东省金属矿产成矿地质过程与资源利用重点实验室,山东济南250013 [2]山东省地质调查院,山东济南250013 [3]中国地质科学院地质研究所北京离子探针中心,北京100037

出　　处：《山东国土资源》2018年第5期14-27,共14页Shandong Land and Resources

基　　金：国家重点研发计划(2017YFC0601506);国土资源部公益性行业专项(201511029);国家自然科学基金项目(41672084;41503038;41772076);中国地质调查局项目(1212011220485;12120114034901);山东省地质勘查项目(鲁勘字[2014]7号)联合资助

摘　　要：胶北地区位于古元古代胶-辽-吉构造岩浆岩带的南段,前人对该区的早前寒武纪地质事件进行了较多研究,然而,对古元古代基性—超基性岩研究较少。通过对该区基性—超基性岩岩石地球化学、锆石U-Pb定年及Hf同位素分析,讨论了其成因、形成时代及其对构造岩浆演化意义。基性—超基性岩为偏铝质岩石,具有低硅贫钾的特征,无明显Eu异常,轻重稀土分馏不明显。获得岩浆锆石年龄~2.1 Ga,形成时代为古元古代,与区域上古元古代构造热事件一致。同时获得变辉长岩~2.4 Ga,~2.7 Ga的2组继承锆石年龄和1.8~1.9 Ga的变质年龄。一个变辉长岩样品的岩浆锆石的ε_(Hf)(t)值和T_(DM2)分别为-11.1^-2.1和2 859~3 408 Ma(10个数据点),一个超基性岩样品的外来锆石ε_(Hf)(t)值和T_(DM2)分别为4.6~5.3和2 355~2 398 Ma(2个数据点)。研究表明,基性岩来自于地幔但受到陆壳物质的强烈影响,变质超基性主要为古元古代亏损地幔或其新生地壳组分,岩浆熔融程度较高。总体反映该地区由早期的挤压机制转为古元古代的伸展机制。Jiaobei area is located in the south part of Paleoproterozoic Jiaodong-Liaoning-Jilin tectonic and magmatic belt.In the past years,early Precambrian geological events have been studied,but the study on mafic-ultramafic rocks in the Paleoproterozoic period is very lack.In this paper,through analysis on geochemitry of mafic-ultramafic rocks,zircon U-Pb dating and Hf isotope analysis,the origin,ore-forming age and the significance of tectonic and magmatic evolution have been discussed.It is regarded that mafic-ultramafic rocks are partial aluminous rock with the characteristics of low silicon and poor potassium.The La/Yb differentiation is weak,and there is no obvious Eu anomaly.The age of zircon is^2.1 Ga,and the forming age is Palaeoproterozoic,which is consistent with regional Proterozoic tectonic thermal events.At the same time,two generations of inherited zircon ages of gabbro are^2.4Ga and^2.7 Ga,and metamorphic ages of 1.8~1.9 Ga have been obtained.TheεHf(t)value and TDM2 of magmatic zircon of a metamorphic gabbro sample are-11.1^-2.1 and 2859~3408 Ma(10 data points)respectively;while theεHf(t)value and TDM2 of an ultra-basic rock sample are 4.6~5.3 and 2355~2398 Ma(2 data points)respectively.It is showed that basic rocks are derived from the mantle,but are strongly influenced by the materials of the continental crust.The metamorphic ultrabasic is mainly composed of Paleoproterozoic depleted mantle or its new crust components.The degree of magma melting is high.It is generally reflected that the area changed from the early extrusion mechanism to the Paleoproterozoic extension mechanism.

关 键 词：胶北地区 基性-超基性岩 古元古代 锆石U-PB定年 HF同位素 

分 类 号：P618.5[天文地球—矿床学]