小兴安岭伊东林场金多金属矿床火山-次火山岩年代学、岩石地球化学及构造背景  

Zircon U-Pb Geochronology, Geochemistry and Tectonic Environment of the Volcanic-Subvolcanic Rocks at Yidong Linchang Gold Polymetallic Deposit, Lesser Xing’an Range (Northeast China)

作　　者：赵忠海 梁杉杉 孙景贵[2] 王兴 李成禄 周佳峥 荆曌怡 Zhao Zhonghai;Liang Shanshan;Sun Jinggui;Wang Xing;Li Chenglu;Zhou Jiazheng;Jing Zhaoyi(College of Mining,Liaoning Technical University,Fuxin 123000,Liaoning,China;College of Earth Sciences,Jilin University,Changchun 130061,China;Heilongjiang Institute of Natural Resources Survey,Harbin 150036,China)

机构地区：[1]辽宁工程技术大学矿业学院,辽宁阜新123000 [2]吉林大学地球科学学院,长春130061 [3]黑龙江省自然资源调查院,哈尔滨150036

出　　处：《吉林大学学报（地球科学版）》2023年第3期785-808,共24页Journal of Jilin University：Earth Science Edition

基　　金：国家重点研发计划项目(2017YFC0601306);辽宁省自然科学基金项目(2020-BS-258);辽宁省教育厅科学研究经费项目(LJ2020JCL010);辽宁工程技术大学学科创新团队资助项目(LNTU20TD-14);黑龙江省重点研发计划项目(GA21A204);2022年辽宁工程技术大学研究生创新实践竞赛培育项目(LNTU2022A023)

摘　　要：伊东林场金多金属矿床是小兴安岭地区新发现的浅成低温热液型金矿,矿区内火山-次火山岩分布广泛,其中闪长玢岩和英安岩与成矿具有成因联系。为了厘定闪长玢岩和英安岩与成矿的关系,制约成矿时代,本文对其进行了岩石地球化学、锆石U-Pb年代学和Sr-Nd-Hf同位素等研究。岩石地球化学研究结果表明,与成矿密切相关的火山-次火山岩为一套过铝质钙碱性火山岩系,具有轻稀土富集和弱的Eu负异常,富集Rb、Ba大离子亲石元素和Th、U等不相容元素,亏损Nb、P、Ti等高场强元素等与俯冲有关的弧岩浆特征。锆石U-Pb定年结果显示,闪长玢岩与英安岩的成岩年龄分别为(99.60±0.62)Ma和(98.50±0.50)Ma,均形成于早白垩世。Sr-Nd-Hf同位素分析结果显示,样品具有高的(^(87)Sr/^(86)Sr)i值(0.70720~0.70770),低ε_(Nd)(t)值(-3.47~-2.42)以及ε_(Hf)(t)值(-2.22~4.11),反映形成源区以幔源为主,但受较强的地壳混染。研究结果揭示,研究区早白垩世火山-次火山岩形成于活动大陆边缘的陆缘弧环境下,为受俯冲洋板片脱水释放的流体交代上覆地幔楔发生部分熔融的产物,并在演化过程中受到较强的地壳混染。结合区域地质背景,推测认为该套早白垩世火山-次火山岩形成于区域伸展构造背景下,与古太平洋板块俯冲回撤的动力学背景有关。Yidong Linchang gold polymetallic deposit is a recently discovered gold deposit in Lesser Xing’an range.The volcanic-subvolcanic rocks are widely distributed in the mining area,among which the diorite porphyrite and dacite are closely related to the mineralization.In this contribution,we reported petrogeochemistry,zircon U-Pb ages and Sr,Nd and Hf isotope compositions of the diorite porphyrite and dacite at Yidong Linchang gold polymetallic deposit.Geochemical studies show that the volcanic-subvolcanic rocks closely related to mineralization are peraluminous calc-alkaline volcanic rocks.All these rocks have arc magma characteristics related to subduction and are enriched in LREEs and weak negative Eu anomaly,enriched in large-ion lithophile elements(Rb,Ba)and incompatible elements(Th,U),and relatively depleted of high field-strength elements(Nb,P and Ti).Zircon U-Pb ages of diorite porphyrite and dacite are(99.60±0.62)Ma and(98.50±0.50)Ma,respectively,both formed in the Early Cretaceous.Sr-Nd-Hf isotope analysis showed that the samples have high(^(87)Sr/^(86)Sr)i ratios(0.70720-0.70770),low ε_(Nd)(t)values(-3.47--2.42)and ε_(Hf)(t)values(-2.22-4.11),revealing that the source area is mainly mantle with the strong contamination of crustal materials.Research results reveal that the diorite porphyrite and dacite in Yidong Linchang gold polymetallic deposit were formed in the continental arc environment of the active continental margin.The magmas were likely derived from deep-formed magmas by the partial melting of the overlying mantle wedge by the fluids released by the dehydration of the subducting Pacific Oceanic plate,and are strongly contaminated by the crust during the evolution process.On the basis of the above research and combined with the regional geological background,it is inferred that the volcanic-subvolcanic rocks of the Early Cretaceous were formed in the tectonic background of lithospheric extension as a consequence of the rollback of the subducted Paleo-Pacific Oceanic plate.

关 键 词：锆石U-PB定年 地球化学 岩石成因 浅成低温热液型金矿 小兴安岭地区 

分 类 号：P581[天文地球—岩石学]