辽西凌源河坎子碱性杂岩体的成因  

Petrogenesis of Hekanzi Alkaline Complex in Lingyuan,West Liaoning

作　　者：陆露[1,2] 钱程 赵珍[4] Lu;Qian Cheng;Zhao Zhen(College of Paleontology Shenyang Normal University,Shenyang 110034,China;Key Laboratory of Evolution of Past Life in Northeast Asia,Ministry of Land and Resources,Shenyang 110034,China;Shenyang Center,China Geological Survey,Shenyang 110034,China;Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]沈阳师范大学古生物学院,辽宁沈阳110034 [2]自然资源部东北亚古生物演化重点实验室,辽宁沈阳110034 [3]中国地质调查局沈阳地质调查中心,辽宁沈阳110034 [4]中国地质科学院,北京100037

出　　处：《地球科学》2023年第10期3671-3688,共18页Earth Science

基　　金：中国地质调查局项目(Nos.DD20190039,DD20160048-01);辽宁省教育厅科研项目(No.LQN201915);沈阳师范大学博士引进人才科技项目启动基金项目(No.BS201705).

摘　　要：为了较全面地认识华北克拉通早中生代碱性岩浆活动的性质,对河坎子碱性杂岩体进行了锆石U-Pb测年、地球化学和Sr-Nd-Hf同位素特征研究.河坎子碱性杂岩体中花岗斑岩和辉石正长岩的锆石U-Pb测年结果分别为227.7±1.5 Ma、225.8±1.2 Ma,为晚三叠世.花岗斑岩为过铝质岩石,具有钾玄岩特征;辉石正长岩为准铝质岩石,具有钾玄岩-高钾钙碱性特征;这两类岩石均具有右倾的球粒陨石标准化配分曲线、均为正铕异常.花岗斑岩和辉石正长岩的ε_(Nd)(t)值分别为-6.9~-5.5,-5.4~-4.7;ε_(Hf)(t)值分别为-4.32~-1.65,-1.01~-0.01.河坎子碱性杂岩体是由受俯冲影响的富集地幔部分熔融形成,其源区残留金云母、角闪石和石榴子石;该岩体的形成与古亚洲洋的闭合有关,是岩石圈地幔发生对流减薄和软流圈物质上涌的结果.The Hekanzi alkaline complex in Lingyuan,West Liaoning,is one important Early Mesozoic alkaline complex on the northern margin of the North China craton.In this paper,the Hekanzi alkaline complex was studied in detail by zircon U-Pb geochronology,major and trace elemental compositions and Sr-Nd-Hf isotopic compositions.The zircons from the granite porphyry and pyroxene syenite yielded U-Pb data of 227.7±1.5 Ma and 225.8±1.2 Ma,respectively.These results show that the rocks formed in the Late Triassic.Geochemical results show that the granite porphyries belong to perauminous rocks and shoshonite series.The pyroxene syenites belong to metaluminous rocks and high K shoshonite series.They both have similar rightleaning chondrite-normalized distribution curves and show obviously positive Eu anomalies.The Sr-Nd isotopic results show thatε_(Nd)(t)values of the granite porphyries vary from-6.9 to-5.5,andε_(Nd)(t)values of the pyroxene syenites vary from-5.4 to-4.7.The zirconε_(Hf)(t)values of the granite porphyries range from-4.32 to-1.65.The zirconε_(Hf)(t)values of the pyroxene syenites are negative(ε_(Hf)(t)=-1.01 to-0.01).These geochemical signatures,along with Sr-Nd-Hf isotopic compositions,reveal that the alkaline complex was derived from the partial melting of enriched lithospheric mantle which contained phlogopite,horblende and garnet.Combined with the previous research,it is suggested that the formation of the Hekanzi alkaline complex from Lingyuan,West Liaoning,is related to the closure of paleo-Asian Ocean,and the Early Mesozoic alkali-rich magmatism is the result of as the nospheric upwelling,following the thinning of mantle lithosphere.

关 键 词：碱性杂岩体 岩石成因 凌源河坎子 华北克拉通北缘 早中生代 岩石学 构造 

分 类 号：P581[天文地球—岩石学]