崂山早白垩世高分异Ⅰ型花岗岩地球化学特征及岩石成因机制  

Geochemical characteristics and petrogenetic mechanism of Early Cretaceous highly fractionated I-type granites in Laoshan

作　　者：杜娟[1] 于胜尧 高翔宇 蒋兴洲 彭银彪 纪文涛 李传志 DU Juan;YU Sheng-yao;GAO Xiang-yu;JIANG Xing-zhou;PENG Yin-biao;JI Wen-tao;LI Chuan-zhi(MOE Key Lab of Submarine Geosciences and Prospecting Technique,Institute for Advanced Ocean Study,College of Marine Geosciences,Ocean University of China,Qingdao 266100,China;Laboratory for Marine Geology,Pilot National Laboratory for Marine Science and Technology,Qingdao 266237,China;School of Resources and Environmental Engineering,Shandong University of Technology,Zibo 255022,China)

机构地区：[1]中国海洋大学海洋高等研究院,海洋地球科学学院,海底科学与探测技术教育部重点实验室,山东青岛266100 [2]青岛海洋科学与技术国家实验室,海洋地质过程与环境功能实验室,山东青岛266237 [3]山东理工大学资源与环境工程学院,山东淄博255022

出　　处：《岩石矿物学杂志》2024年第4期821-846,共26页Acta Petrologica et Mineralogica

基　　金：国家自然科学基金委创新群体项目(42121005);111项目(B20048);泰山学者项目(Notstp20221112)。

摘　　要：崂山花岗岩出露于胶东区域,目前对其花岗岩的类型划分、源区、成因仍存在争议,而对高分异花岗岩成因、演化过程尚缺乏研究。本文以崂山早白垩世花岗岩为研究对象,对其进行岩石学与岩相学、全岩主微量及稀土元素、锆石U-Pb定年与Lu-Hf同位素分析、电子探针长石成分分析。LA-MC-ICP-MS锆石U-Pb测年结果表明,崂山石英二长岩、二长花岗岩、正长花岗岩、花岗斑岩成岩年龄分别为128.6±2.7 Ma、122.8±2.5 Ma~118.6±1.2Ma、121.5±2.7 Ma~121.3±1.2Ma和114.5±1.2 Ma,指示它们均为早白垩世岩浆活动产物。地球化学组成上表现为高硅富碱,不同程度的贫铝、镁、铁,富集轻稀土元素和Rb、Th、U,亏损Ba、Sr,显著Eu负异常。崂山花岗岩锆石εHf(t)值介于-21.0~-15.1之间,Hf同位素二阶段模式年龄t_(DM2)介于2 482~2 149 Ma之间。结合矿物学、岩石学和地球化学证据,石英二长岩、二长花岗岩为I型花岗岩,正长花岗岩、花岗斑岩为高分异I型花岗岩。结合胶东区域研究资料,认为崂山早白垩世高分异I型花岗岩是在古太平洋板块俯冲作用产生的伸展构造环境下,软流圈地幔来源的岩浆底侵,诱发下地壳物质部分熔融形成长英质岩浆,后期受到斜长石、钾长石、磷灰石等矿物分离结晶作用的控制,经历高程度的分异形成。Laoshan granites are widely distributed in Jiaodong area.Their typology,magma source and petrogenesis are still controversial,and the magmatic evolution and petrogenesis of highly fractionated I-type granite have not been well constrained.In this study,the Laoshan Early Cretaceous granites are selected as the research theme.The granites are analyzed by petrology and petrography,whole rock major and trace elements,zircon U-Pb dating and Lu-Hf isotopes,plagioclase electron probe analysis.LA-MC-ICP-MS zircon U-Pb dating results show that the diagenetic ages of quartz monzonite,monzogranite,syenogranite and granitic porphyry in Laoshan are 128.6±2.7 Ma,122.8±2.5 Ma~118.6±1.2 Ma,121.5±2.7 Ma~121.3±1.2 Ma and 114.5±1.2 Ma,respectively,indicating that they were all emplaced during the Early Cretaceous.The geochemical composition of Laoshan granites show high contents of silicon and alkali,low abundances of aluminum,magnesium and iron.They are also depleted in Rb,Th,U,Ba and Sr,with significant negative Eu anomaly.The zirconsεHf(t)values of Laoshan granites range from-21.0 to-15.1,and Hf isotope second-stage model ages(t_(DM2))range from 2482 to 2149 Ma.Based on mineralogical,petrological and geochemical evidence,the quartz monzonite and monzogranite are I-type granites,and the syenogranite and granitic porphyry are classified are high fractionated I-type granites.Combined with the previous researches results in Jiaodong area,in the extensional tectonic setting generated by the subduction of the Paleo-pacific plate,magmas from the asthenosphere underplated into the lower crust,inducing partial melting of the lower crust material to form felsic magmas.After different degrees of fractional crystallization and evolution of felsic magmas,granites with varying degrees of differentiation in Laoshan area are formed ultimately.

关 键 词：胶东地区 高分异Ⅰ型花岗岩 岩石成因 岩浆分异 古太平洋俯冲 

分 类 号：P588.121[天文地球—岩石学] P597[天文地球—地质学]