摘要
板庙子金矿床位于吉林南部老岭成矿带内,其成因机制长期存在争议,制约了对区域成矿作用的系统认识。为厘清其成矿机制,基于详细的野外调研,选取与成矿密切相关的花岗闪长斑岩为研究对象,系统开展了岩石学、岩石地球化学及锆石U-Pb定年研究。锆石U-Pb定年结果显示,花岗闪长斑岩形成年龄为125.2 Ma±1.1 Ma(即早白垩世)。花岗闪长斑岩地球化学特征表现为高Si、富Na(w(Na_(2)O)/w(K_(2)O)=1.17~1.33)、中等Al、Mg等特征;显著富集大离子亲石元素(Rb、Ba、Th),亏损高场强元素(Nb、Ta、Ti),无明显Eu异常(δEu=1.16~1.22);具备典型的埃达克质岩属性(高Sr(w(Sr)=784.50×10^(-6)~1006.00×10^(-6))、高w(Sr)/w(Y)值(94.14~117.55),低Y(w(Y)=6.94×10^(-6)~9.49×10^(-6))、低Yb(w(Yb)=0.66×10^(-6)~0.78×10^(-6)))。结合区域岩浆活动特征和花岗闪长斑岩较高的地幔相容元素质量分数(w(Ni)=69.11×10^(-6)~127.70×10^(-6)、w(Cr)=204.30×10^(-6)~413.40×10^(-6))及高Mg^(#)值(58~61),认为花岗闪长斑岩形成于古太平洋板块俯冲后撤诱发的区域性伸展构造背景,来源于拆沉下地壳的部分熔融。综合矿床地质特征,认为板庙子金矿床为早白垩世形成的、与埃达克质岩浆活动密切相关的浅成低温热液型矿床。
The Banmiaozi Gold Deposit,located within the Laoling Metallogenic Belt in southern Jilin Province,has long been controversial regarding its genesis,hindering a systematic understanding of regional metallogenesis.Tc clarify its mineralization mechanism,the granodiorite porphyry closely associated with mineralization were studied based on detailed field investigations.Petrological,petrogeochemical,and zircon U-Pb dating studies were systematically conducted.The results of Zircon U-Pb dating show a granodiorite porphyry formation age of 125.2 Ma±1.1 Ma(i.e.,the Early Cretaceous).The granodiorite porphyry exhibits the following geochemical characteristics:high Si and rich Na(w(Na_(2)O)/w(K_(2)O)=1.17-1.33)and moderate Al and Mg;there is also significant enrichment in large-ion lithophile elements(Rb,Ba,and Th)and depletion in high-field-strength elements(Nb,Ta,and Ti),without pronounced Eu anomaly(δEu=1.16-1.22).Moreover,there are typical adakitic rock affinities:high Sr(w(Sr)=784.50×10^(-6)-1006.00×10^(-6)),high w(Sr)/w(Y)ratios(94.14-117.55),low Y(w(Y)=6.94×10^(-6)-9.49×10^(-6)),and low Yb(w(Yb)=0.66×10^(-6)-0.78×10^(-6)).Combined with regional magmatic activity and elevated contents of mantle-compatible elements in granodiorite porphyry(w(Ni)=69.11×10^(-6)-127.70×10^(-6) and w(Cr)=204.30×10^(-6)-413.40×10^(-6))and high Mg^(#)(58-61),it is believed that the granodiorite porphyry is formed in a regional extensional tectonic setting triggered by the rollback of the Paleo-Pacific Plate,originating from partial melting of delaminated lower crust.Based on comprehensive deposit geology,it is concluded that the Banmiaozi Gold Deposit is an epithermal deposit formed during the Early Cretaceous and is genetically closely related to adakitic magmatism.
作者
徐宏伟
王莹
王学阳
冯伟
孙金磊
钱烨
Xu Hongwei;Wang Ying;Wang Xueyang;Feng Wei;Sun Jinlei;Qian Ye(Jilin Banmiaozi Mining Co.,Ltd.;College of Earth Sciences,Jilin University;Changchun Gold Research Institute Co.,Ltd.)
出处
《黄金》
2025年第12期100-110,共11页
Gold
基金
吉林省自然科学基金项目(20220101161JC)。
