内蒙古曹四夭钼矿花岗斑岩地质地球化学特征及 U-Pb 同位素测年

摘要

内蒙古兴和县曹四夭超大型钼矿床的成矿岩体花岗斑岩为微型岩株,岩石为强酸性花岗岩,富含 Rb,Li,Be,Nb,Zr 和 Mo,其中 Mo 的含量为克拉克值的20倍,岩石稀土总量较低,为轻稀土富集型,Eu 严重亏损；U-Pb 同位素测年结果显示,加权平均年龄为(133.5±7.4)Ma,时代为中生代白垩纪早期,花岗斑岩的形成年龄基本上代表了钼矿床的成矿年龄；岩体侵入的构造背景为燕山晚期的板内造山环境；花岗斑岩的成因为 S 型与 I 型的过渡类型,岩浆物质原始来源于上地幔以浅,岩浆沿深大断裂上侵形成花岗斑岩,揭示出上地壳基底物质与岩浆的同熔过程。%The super-large Mo deposit-hosted granitic porphyry body is the stronger acidic granite occur-ring in mini stock with less porphyritic crystals.It is rich in Rb,Li,Be,Nb,Zr and Mo.Its Mo content is as 20 times as clarke value.∑REE is low (122.388×10 -6 )belonging to LREE enrichment type with Eu depletion.The weighted U-Pb isotopic average age is 133.5 ±7.4 Ma corresponding to Early Cretaceous epoch.Rock-forming age of the granitic porphyry represents the ore-forming age.The intrusion occurred under intra-plate orogenic background during Late Yanshanian Period.It is a transitional type of S and I-type granite.The material source of magma is derived above the upper mantle and intrudes up along huge fault as syntactic granitic porphyry.