大别造山带古元古代黑云紫苏斜长片麻岩年代学、地球化学特征及其地质意义  

Geochronology and geochemistry of the Early Proterozoic hypersthene plagioclase gneiss in the Dabie orogen and its geological implications

作　　者：孔令耀 韩庆森 郭盼 邓新[4] 李琳静 徐扬 万俊 陈超 Kong Lingyao;Han Qingsen;Guo Pan;Deng Xin;Li Linjing;Xu Yang;Wan Jun;Chen Chao(Hubei Geological Survey,Wuhan,Hubei 430034,China;Hubei Research Center of Geological Exploration and Engineering Technology,Wuhan,Hubei 430034,China;Institute of Geophysics&Geomatics,China University of Geosciences,Wuhan,Hubei 430074,China;Wuhan Center of China Geological Survey,Wuhan,Hubei 430205,China)

机构地区：[1]湖北省地质调查院,湖北武汉430034 [2]湖北省地质勘查工程技术研究中心,湖北武汉430034 [3]中国地质大学地球物理与空间信息学院,湖北武汉430074 [4]中国地质调查局武汉地质调查中心,湖北武汉430205

出　　处：《地质学报》2023年第5期1463-1477,共15页Acta Geologica Sinica

基　　金：中国地质调查局项目(编号DD20190050,DD20190370);湖北省地质局项目(编号KJ2020-65,KJ2021-4,KJ2021-48)联合资助的成果。

摘　　要：为探讨大别造山带早期结晶基底物质组成及其演化特征,对大别造山带蕙兰山地区出露的黑云紫苏斜长片麻岩的岩石学、地球化学、锆石U-Pb年代学及Lu-Hf同位素组成进行研究,显示其原岩应为石英闪长岩,成岩时代为古元古代早期(2463±22 Ma),且经历了古元古代麻粒岩相变质作用,锆石Ti地质温度计显示其变质温度为767~827℃(平均799℃),变质时间为2002±11 Ma(MSWD=0.46)。岩石地球化学成分显示其SiO_(2)含量为55.16%~57.10%,MgO为4.74%~5.89%,Mg^(#)值为47.5~50.4,钙碱性系列,富Mg贫Si,稀土配分曲线呈现轻稀土相对富集的右倾分布特征((La/Yb)_(N)=19.3~34.1),无明显Eu异常((Eu/Eu^(*))=0.9~1.2),且具较高的Sr、Ni、Cr含量,以及较低的YbN值及Y含量,与镁质闪长岩具相似特征;明显富集Rb、Ba、K等大离子亲石元素,相对亏损Nb、Ta、Zr、Hf等高场强元素;锆石Lu-Hf同位素显示具有较为均一的ε_(Hf)(t)值(+2.69~+3.79),和二阶模式年龄(tDM2=2797~2739 Ma)。该套黑云紫苏斜长片麻岩可能是俯冲板片脱水熔融产生的岩浆与地幔相互作用的产物;岩石记录的2.0 Ga麻粒岩相变质作用可能与Columbia超大陆聚合事件有关,结合前人在北黄陵及大别地区的研究成果,认为扬子陆块北缘在古元古代可能已经存在一个大地构造位置相近的“微陆块群”,这些“微陆块群”在大约2.0 Ga的Columbia超大陆汇聚事件中逐渐拼合形成扬子陆块北缘的早期统一基底。To investigate the composition and evolution characteristics of early crystallization basement in the Dabie orogen,we analyzed the petrology,geochemistry,zircon U-Pb chronology and Lu-Hf isotopic composition of biotite-hypersthene-plagioclase gneiss exposed in the Huilanshan area of this orogen.The result shows that its protolith is quartz diorite with a formation age of Paleoproterozoic(2463±22 Ma),and experienced Paleoproterozoic granulite facies metamorphism with an age of 2002±11 Ma(MSWD=0.46).Zircon Ti geothermometer shows that the metamorphic temperature is about 767~827℃(average 799℃).The quartz diorite gneiss shows low SiO^(2)contents(55.16%~57.10%),high MgO(4.74%~5.89%)and high Mg^(#)values of 47.5~50.4 indicating that it belongs to calc-alkaline series,is enriched in LREE and relatively depleted in HREE((La/Yb)_(N)=19.3~34.1),with no obvious Eu anomaly((Eu/Eu_(*))=0.9~1.2).It also has high Sr,Ni,Cr content,and lower Yb_(N)value and Y content,and is enriched in LILEs(Rb,Ba,K),depleted in HFSEs(Nb,Ta,Zr,and Hf),which is similar to the magnesian diorite.Zircon cores from the gneiss sample have a similar Lu-Hf isotopes value of ε_(Hf)(t)(+2.69~+3.79)and second-stage model ages(t_(DM2)=2797~2739 Ma).We propose that the quartz diorite gneiss may be the product of interaction between the magma produced by dehydration melting of subduction slab and mantle magma.The granulite facies metamorphism at2.0Ga may be related to Columbia supercontinent assembly event.In combination with previous research in the North Huangling and the Dabie area,there may have been a“micro-continent group”with similar geotectonic position since the Paleoproterozoic,and they gradually assembled into a unified basement of the North Yangtze block during the global Columbia supercontinent convergence event.

关 键 词：大别造山带 石英闪长岩 古元古代变质 麻粒岩相 扬子陆块基底演化 

分 类 号：P534.3[天文地球—古生物学与地层学] P588.345[天文地球—地质学] P597.3