冀北康保县北沙城岩体岩石成因及成矿潜力讨论——U-Pb年龄、矿物学及岩石地球化学证据  

A discussion on petrogenesis and ore-forming potential of Beishacheng pluton in Kangbao County,northern Hebei Province——U-Pb age,mineralogical and petrogeochemical evidences

作　　者：李康硕 陈公正 王金芳 成义 杨良森 井新奎 李元申 刘辰雨 陆泽芊 宋宇桐 LI Kangshuo;CHEN Gongzheng;WANG Jinfang;CHENG Yi;YANG Liangsen;JING Xinkui;LI Yuanshen;LIU Chenyu;LU Zeqian;SONG Yutong(Hebei Province Collaborative Innovation Center for Strategic Critical Mineral Research,Hebei GEO University,Shijiazhuang,050031;Innovation base for Metallogenic Theory and Prospecting Techniques of Ophiolite Belt,Hebei GEO University,Shijiazhuang,050031;Hebei Province Bureau of Geology and Mineral Resources Exploration and Development Xiong’an Geological Survey Monitoring Center,Langfang,Hebei,065201;China Gold Association,Beijing,100000;China Gold Group Geological Co.,Ltd,Beijing,100000)

机构地区：[1]河北地质大学河北省战略性关键矿产研究协同创新中心,石家庄050031 [2]河北地质大学蛇绿岩带成矿理论与找矿技术创新基地,石家庄050031 [3]河北省地质矿产勘查开发局雄安地质调查监测中心,河北廊坊065201 [4]中国黄金协会,北京100000 [5]中国黄金集团地质有限公司,北京100000

出　　处：《地质论评》2025年第2期488-510,共23页Geological Review

基　　金：河北省高等学校科学技术研究项目(编号:BJK2023077);国家自然科学基金青年基金资助项目(编号:42202080);河北省战略性关键矿产研究协同创新中心开放基金资助项目(编号:HGUXT2023-6);河北地质大学博士科研启动基金项目(编号:BQ2024017);河北省地矿局地质科技项目(编号:13000022P0069B410038J)的成果。

摘　　要：冀北康保县北沙城岩体位于华北克拉通北缘,主要岩石类型为花岗斑岩和似斑状花岗岩,是北沙城铅锌银铜矿床的主要赋矿围岩之一。为查明北沙城岩体成因及其与北沙城矿床之间的成因关系,笔者等对北沙城岩体开展LA-ICP-MS锆石U-Pb定年、岩石地球化学、锆石Lu—Hf同位素及矿物地球化学研究。锆石U-Pb测年结果表明,花岗斑岩和似斑状花岗岩分别形成于276.1±0.6 Ma、274.9±0.7 Ma,为早二叠世晚期岩浆活动产物,均具有高硅、富碱、过铝质的特征,其稀土配分曲线呈右倾式,具中等Eu负异常(0.44~0.62),富集Rb、Th、U、K等大离子亲石元素,亏损Nb、Ti、P、Sr等高场强元素,二者为同一岩浆系统不同演化程度的产物。北沙城岩体ε_(Hf)(t)值为-7.37~-14.54之间,Hf同位素两阶段模式年龄(T_(DM2))在1763~2215 Ma之间,表明北沙城岩体源区主要为古元古代地壳物质。岩浆氧逸度(NNO)在-4.78~-0.11之间,黑云母结晶温度和压力分别为740~766℃和280~441 MPa,似斑状花岗岩含水量在11.3%~13.2%,花岗斑岩含水量在8.00%~8.30%之间。低氧逸度和过早的流体出溶不利于Pb、Zn、Cu的富集,北沙城岩体可能并非成矿岩体。The Beishacheng intrusion located in the northern margin of the North China Craton,mainly comprising granite porphyry and porphyritic granite,is the primary ore-hosting rock of the Beishacheng Pb—Zn—Ag—Cu deposit.In order to ascertain the genesis of the Beishacheng intrusion and its relationship with the Beishacheng deposit,this paper carried out LA-ICP-MS zircon U-Pb dating,petroleum geochemistry,zircon Lu—Hf isotope and mineral geochemistry studies on the Beishacheng intrusion.Zircon U-Pb dating results indicate that the granite porphyry and porphyritic granite were formed at 276.1±0.6 Ma and 274.9±0.7 Ma,respectively.Both granite porphyry and porphyritic granite are characterized by high silicon,rich alkali,and peraluminous.The rare earth distribution curve is right-leaning,with moderate Eu negative anomaly(0.44~0.62),enrichment of large ion lithophile elements such as Rb,Th,U,and K,and depletion of high field strength elements such as Nb,Ti,P,and Sr.The granite porphyry and porphyritic granite formed in different evolution degrees of the same magmatic system.Theε_(Hf)(t)value of the Beishacheng intrusion is distributed between-7.37 and-14.54,and the two-stage Hf isotope model age(T_(DM2))is from 1763 to 2215 Ma,indicating that the Beishacheng intrusion is formed by partial melting of a source dominated by Paleoproterozoic basement.The value of magma oxygen fugacity(NNO)is from-4.78 to-0.11.The crystallization temperature and forming pressure of biotite are 740~766°C and 280~441 MPa,respectively.The water content of porphyritic granite and granite porphyry range from 11.3%to 13.2%and 8.00%to 8.30%,respectively.The presence of low oxygen fugacity and premature fluid exsolution of the Beishacheng intrusion impedes the enrichment of Pb,Zn,and Cu,which suggests that the Beishacheng intrusion may not be a primary factor in the mineralization process.

关 键 词：北沙城岩体 锆石U-Pb定年 岩石地球化学 Ⅰ型花岗岩 岩浆氧逸度 

分 类 号：P61[天文地球—矿床学]