摘要
研究区作为胶东地区的一个重要地质单元,区内中生代岩浆活动强烈,以往的研究主要集中在玲珑、郭家岭等岩体,而对于小型岩体或者岩脉的研究程度较弱。而这些岩体往往与多金属矿成矿关系密切相关,对其地球化学特征探究可能为揭示研究区成矿物质来源、成矿作用机制、指导找矿等提供关键信息。因此,本文选取臧家庄盆地花岗斑岩开展年代学、地球化学分析,对岩体成因和地质意义进行探究。研究表明,锆石加权平均年龄为125.4±1.2 Ma,形成时代为早白垩世,与位于岩体北部的郭家岭岩体形成年龄近似。地球化学分析显示,样品具有富硅高钾及过铝质花岗岩的特征。地球化学特征和判别图解显示,岩体具有S型花岗岩的亲缘性和埃达克岩的典型特征,结合其富集的Hf同位素组成,亏损Nb、Ta,富集Pb等大陆地壳微量元素特征,以及古老继承锆石存在,表明岩体为古老陆壳熔融的产物。但岩体相对于纯壳源岩浆具有更亏损的Hf同位素组成以及高的Mg^(#)值,表明幔源物质的贡献,岩体可能为壳幔混合成因。结合本文研究的岩体与郭家岭岩体的年代学关系和地球化学相似性,斑岩体可能代表郭家岭期岩体后期的小型浅层侵入体,可能是深部郭家岭期花岗岩体沿构造薄弱带向上伸出的岩枝或岩脉,浅层侵位过程中与围岩的相互作用,可能造成矽卡岩型矿化,形成多金属矿富集沉淀。
As a critical geological unit in the Jiaodong area,the study region exhibits significant Mesozoic magmatic activity.Previous investigations have primarily focused on the Linglong and Guojialing plutons;however,the petrogenesis of small intrusive plutons or dykes remains poorly constrained due to a lack of systematic studies.Notably,these plutons could be linked to the mineralization of polymetallic ores.Thus,elucidating their geochemical characteristics and petrogenesis may offer key insights into the source and mechanism of ore-forming materials,thereby guiding exploration efforts.Accordingly,the granitic porphyry in the Zangjiazhuang Basin has been selected for detailed geochronology and geochemistry investigation to elucidate its genesis and broader geological implications.The zircon dating indicates a weighted average age of approximately 125.4±1.2 Ma,placing it in the Early Cretaceous and aligning with ages determined for the Guojialing plutons in the northern part of the study area.The geochemical analyses show that the samples are enriched in silicon and potassium,and display the characteristics of peraluminous granites.Moreover,discrimination diagrams and geochemical signatures suggest an S-type granitic affinity.The samples also have typical characteristics of adakite features,including enriched Hf isotopic compositions,pronounced depletions in Nb and Ta,and enrichment in Pb and other trace elements,signifying a continental crustal origin.This interpretation is further supported by the presence of ancient inherited zircons,which indicate a contribution from ancient continental crust.Nonetheless,compared with purely crust-derived magma,the granitic porphyry exhibits more depleted Hf isotopic compositions and higher Mg^(#)values,implying an additional contribution from mantle-derived material.Consequently,the granitic porphyry most likely represents a product of crust-mantle mixing.In light of the geochronological consistency and geochemical similarity between the granitic porphyry and the Guojialing plutons,the porphyry may represent a small,shallow intrusion associated with the Guojialing plutonic system.Furthermore,interaction with surrounding rocks during its shallow emplacement may have facilitated skarn-type mineralization,ultimately contributing to the formation of polymetallic ore deposits.
作者
万鹏
王志新
吴凤萍
安茂国
孔祥超
孟元库
孙华芳
Wan Peng;Wang Zhixin;Wu Fengping;An Maoguo;Kong Xiangchao;Meng Yuanku;Sun Huafang(Shandong Provincial Third Exploration Institute of Geology and Mineral Resources,Yantai,Shandong 264000;College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao,Shandong 266590;Yantai Innovation Center for Deep-Seated Gold Mine Exploration Technology,Yantai,Shandong 264000)
出处
《地质科学》
北大核心
2025年第3期682-710,共29页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
山东省自然科学基金面上项目(编号:ZR2023MD021)资助。
