胶西北地区钻孔揭露隐伏郭家岭期花岗岩的地球化学、锆石U- Pb年龄及Lu- Hf同位素特征

胶东矿集区是世界著名的金矿资源基地,截止2019年累计查明金资源储量达5000余吨,区内广泛分布的中生代花岗岩与金矿有着密切的时间、空间关系。前人利用高精度重磁、CSAMT等物探方法解译,认为焦家成矿带、招平成矿带深部可能有隐伏郭家岭期花岗岩存在。本文通过近几年勘查施工钻孔揭露的胶西北三条主要金成矿带隐伏郭家岭期花岗岩,表现为较高的Na₂O+K₂O(5.80%～11.27%)、Al₂O₃(14.01%～16.36%)含量,高的Sr含量(632×10^-6～1224×10^-6)、Ba含量(1641×10^-6～3512×10^-6)和高的Sr/Y比值(185～435),CaO(1.25%～2.44%)、TiO₂(0.08%～0.23%)、MgO(0.17%～0.84%)、全Fe₂O₃(0.67%～1.94%)、Rb(46×10^-6～1...     

胶东地区郭家岭岩体岩石构造组合特征及地质意义

通过对前人就郭家岭花岗岩构造地质学、岩石化学、同位素年代学等地质信息资料的分析、研究,认为胶东地区郭家岭花岗闪长岩一花岗岩总体上归属于幔源岩浆与壳源岩浆混合后经分异作用而成的同熔深成型花岗岩类;主要形成于由洋壳俯冲引起的火山岛弧环境、大陆碰撞环境和弧后拉张性质的大陆边缘环境;其定位机制为：沿着NEE向挤压带从小面积到大面积频率式脉动或涌动热轻气球膨胀式定位;该岩石构造组合主体形成于早白垩世。从岩石构造组合的概念,将其定义为造山中期郭家岭弱片麻状花岗闪长岩～花岗岩组合。     

郭家岭岩体壳幔岩浆混合作用与侵位机制的动力学研究

暗色包体、岩石地球化学及Nd.Sr同位素的研究一致表明,胶东金矿区的郭家岭岩体是由壳幔岩浆混合形成的,混合比大体为3:2.该岩体岩性均一,缺少长英质端元和过渡性岩石类型正是壳幔岩浆混合程度高的表现。以胶东群地层150MPa.850℃条件下的部分熔融产物(熔体分数约35%)作为长英质端元,最偏基性的闪长质包体作镁铁质端元,按3:2的混合比较好地模拟了该岩体的成分,同时也满足了分层岩浆房发生整体对流的动力学条件。根据暗色包体计算了岩体的侵位速度,结果表明该岩体很可能是沿着现在的艾山岩体所占据的断裂通道侵位的。岩体呈EW向带状产出反映了基底构造——栖霞复背斜对该岩体形成的控制作用。     

招远金山金矿特征及深部含矿性探讨

金山金矿位于招掖金矿带的中西部,该区岩性为元古代震旦期玲珑超单元九曲单元弱片麻状细粒石榴二长花岗岩和中生代燕山早期郭家岭超单元大草屋单元斑状细粒角闪黑云花岗闪长岩。断裂构造发育,规模较小。矿床成因为热液型,属小型蚀变岩型金矿,形成于玲珑岩体侵入后期,主要分布有两条矿体,长分别为112 m和370 m,斜深104 m和133 m,真厚度0.40 m和1.54 m,平均品位分别为19.68×10-6及3.67×10-6。矿体分别赋存在80 m及-15 m标高之上。根据其成因分析及深部钻孔控制,认为本区深部含矿性不大。     

Gold mineralizing efficiency during hydrothermal alteration of the Mesozoic granitoids in the northwest Jiaodong Peninsula: Contrasting conditions between the Guojialing and Linglong plutons

Mesozoic granitoids were extensively altered by hydrothermal fluids in the northwest Jiaodong Peninsula, and gold precipitated from the fluids developing prevalent mineralization in this district. The 160–158 Ma Linglong granite and 130–120 Ma Guojialing granodiorite are the major Mesozoic granitoids in this district, both of which are hydrothermally altered and intimately associated with gold mineralization. Although numerous studies were carried out by previous researchers, mainly focusing on tectonics, lithology, mineralogy, geochronology, and fluid geochemistry, knowledge about hydrothermal alteration processes of these granitoids and their gold mineralization efficiency (i.e. which one is more effective to precipitate the gold from its parent solution) is far beyond clear illumination. Geochemical simulation software GEM-Selektor (based on the Gibbs energy minimization algorithm) was applied in this study, which aims to test the gold mineralization efficiency of these two granitoids during the hydrothermal alteration processes. Simulation results indicate that solutions in equilibrium with the Linglong granite are capable of hosting more sulfur than that with the Guojialing granodiorite, since the latter contains more Fe. However, the solutions with these two granitoids display similar gold solubility. “Bulk cooling” simulation results show that the gold mineralization pattern is similar between the Linglong and Guojialing case; “Rock titration” simulation results reveal that the Guojialing granodiorite is prone to precipitate gold more strongly than the Linglong granite, as gold-bearing solutions (or ore-forming fluids) flowing-through at high temperature, equivalent to a deeper level, implying that if the gold mineralization is developed at depth, the Guojialing rock will precipitate more gold. If the gold-bearing solution flow-through the wall rocks relatively fast, and gold mineralization fails to take place, then the Guojialing granodiorite is probably unfavorable for subsequent gold enrichment of the ore-forming fluid. The Linglong granite will precipitate the gold more efficiently from its parent solution at low temperature or at a shallower level, and this is consistent with previous mining prospecting results. Therefore, we suggest that the Guojialing granodiorite should be treated as the main target during future deep prospecting project.     

胶东西北部玲珑、郭家岭超单元花岗岩成因探讨

玲珑、郭家岭超单元花岗岩的源岩均为胶东岩群变质岩；玲珑超单元花岗岩表现出岩石的不均匀性，其成因为原地、半原地交代一重熔型花岗岩；郭家岭超单元花岗岩则属于有幔源物质参人的同熔型花岗岩。两个花岗岩均经历了多期构造一岩浆作用，最终形成于燕山期；郭家岭超单元最终形成晚于玲珑超单元花岗岩。     

胶东招掖郭家岭型花岗岩锆石SHRIMP年代学研究

采用世界上最先进的SHRIMP锆石U-Pb测年技术,对招掖地区郭家岭型花岗岩及成矿后花岗斑岩脉进行了年代学研究,精确地测定了郭家岭型花岗岩的年龄为130-126Ma,成矿后花岗斑岩脉的年龄为120±2Ma,金矿化被限定在126-120Ma之间。结合岩体年龄和与金矿化密切的空间关系及地球化学上的亲缘关系,认为郭家岭型花岗岩属造山晚期花岗岩,金矿化主要与郭家岭型花岗岩有关。该花岗岩异常高的Ba、Sr含量可作为太古宙绿岩地体环境下判别与金矿化有关花岗岩的地球化学标志。     

胶东地区郭家岭岩体岩石构造组合特征及地质意义

通过对前人就郭家岭花岗岩构造地质学、岩石化学、同位素年代学等地质信息资料的分析、研究,认为胶东地区郭家岭花岗闪长岩-花岗岩总体上归属于幔源岩浆与壳源岩浆混合后经分异作用而成的同熔深成型花岗岩类;主要形成于由洋壳俯冲引起的火山岛弧环境、大陆碰撞环境和弧后拉张性质的大陆边缘环境;其定位机制为:沿着NEE向挤压带从小面积到大面积频率式脉动或涌动热轻气球膨胀式定位;该岩石构造组合主体形成于早白垩世。从岩石构造组合的概念,将其定义为造山中期郭家岭弱片麻状花岗闪长岩-花岗岩组合。     

胶西北丛家花岗闪长岩体SHRIMP锆石U-Pb年代学研究

胶西北地区是我国最重要的金矿集中区,区内大量展布的中生代花岗岩与金矿关系十分密切,本文通过对郭家岭序列的丛家花岗闪长岩体的地质背景和SHRIMP锆石年代学研究,获得该岩体的成岩年龄为(127±1)Ma,地质时代属早白垩世。郭家岭序列各个岩体所测得的年龄值相差不大,表明它们近于同时侵位,侵位时间为127.9 Ma。丛家岩体锆石样品中测得Ar_3、Pt_1、J_3等多个期次的继承锆石年龄。结合前人研究,表明郭家岭序列岩浆源区成分非常复杂,既有来自胶辽陆块的前寒武纪基底、晚侏罗世玲珑序列,也有来自胶南—威海造山带的三叠纪同碰撞花岗岩类,还有幔源组分的加入。其中,壳源组分以玲珑序列为主。郭家岭序列与胶西北地区金矿的关系十分密切。从时间上看,郭家岭序列的形成年龄早于胶西北地区金矿的形成年龄5~10 Ma,符合同源岩浆成因金矿的成岩成矿时间差。从空间上看,胶西北地区三条主要控矿断裂带下均有隐伏郭家岭序列存在,金矿与郭家岭序列形影不离。从物质成分上看,与其他早白垩世岩浆岩类相比,郭家岭序列相对富Na,有可能是郭家岭序列在侵位之前,经历了含Au的富K热液组分分离的结果。因此,郭家岭序列更接近于胶西北地区金矿的成矿母岩。     

胶东地区早白垩世郭家岭期花岗岩

胶东地区早白垩世郭家岭期花岗岩指形成时代为早白垩世,形成年龄为123～135Ma的一期岩浆活动事件的产物,从西到东由莱州三山岛、招远上庄、招远北截、招远丛家、龙口七甲、栖霞郭家岭及蓬莱范家店7个岩体组成.主要岩性为二长花岗岩和花岗闪长岩,少量的石英二长岩和二长闪长岩,多数具有钾长石斑晶和暗色包体,为一套准铝质—过铝质高...