【摘要】 华北克拉通北缘中段窟窿山花岗岩与火山岩构成了一个完美的岩浆演化系列，晚期花岗岩中赋存多个Be-Nb-U-Pb-Zn矿床（点），但有关Be-Nb的矿化年龄及成因机制尚不清楚。Be-Nb矿化蚀变带明显受NNE向、NEE向断裂控制，硅化、绿泥石化、萤石化与Be-Nb矿化关系密切。本文通过锡石及铌铁矿微区U-Pb定年、热液石英流体包裹体显微测温和H-O同位素、全岩及硫化物S同位素分析，确定与主要铍矿物日光榴石共生的铌铁矿和锡石的U-Pb年龄为134～132Ma，与赋矿花岗岩锆石U-Pb年龄（134Ma）一致，Be-Nb矿化是同一岩浆-热液系统在不同演化阶段的产物。气液两相（VL）流体包裹体均与成矿过程密切相关，成矿流体温度为220～430℃，盐度为2.56%～13.44%，属中高温、中低盐度的H₂O-NaCl热液体系。H-O同位素显示成矿流体来源于岩浆水和大气降水的混合。全岩δ³⁴S值变化较大为2.85‰～13.46‰，闪锌矿和黄铁矿的δ³⁴S值分别为8.33‰～9.06‰和6.77‰～8.07‰，指示硫源与窟窿山花岗岩浆活动密切相关。研究表明窟窿山酸性岩浆经历了显著的分离结晶作用，促进了Be、Nb初始富集。在岩浆-热液阶段，萤石的结晶降低了成矿元素的溶解度，导致铌铁矿、日光榴石和锌日光榴石的形成，热液阶段外来流体的加入致使铍矿物与硫化物矿物共存。研究区早白垩世岩浆活动及成矿作用受到与古太平洋板块后撤有关的伸展构造体制控制。更多还原

【Abstract】 The Kulongshan granite and its associated volcanic rocks,located in the central section of the northern margin of the North China Craton,represent an exemplary series of magmatic evolution.Several beryllium-niobium-uranium-lead-zinc deposits occurred within the most evolved granite;however,the mineralization age and genetic mechanism associated with beryllium and niobium remain poorly understood.The Be-Nb mineralized alteration zone is clearly influenced by faults trending in the NNE and NEE directions.The processes of silicification,chloritization and fluoritization are closely associated with Be-Nb mineralization.This study utilizes U-Pb dating of cassiterite and columbite,micro-temperature measurements of fluid inclusions,H-O isotope analysis of quartz,and S isotope analysis of whole rock and sulfides to reveal these processes.The U-Pb ages of columbite and cassiterite,which coexist with helvine,range from 134Ma to 132Ma.This finding is consistent with the U-Pb age of zircon（134Ma） extracted from the orebearing granite,suggesting that the mineralization is a product of the same magma-hydrothermal series at different evolutionary stages.There exist gas-liquid two-phase（VL） primary inclusions within hydrothermal quartz,which are closely related to the mineralization processes.The temperature of the ore-forming fluid ranges from 220℃ to 430℃,while the salinity varies between 2.56% and 13.44%eqv.This fluid is classified as part of the H₂O-NaCl hydrothermal system,characterized by medium to high temperatures and medium to low salinity.The H-O isotope analysis of quartz suggests that the ore-forming fluid is a mixed hydrothermal solution derived from both magmatic water and atmospheric precipitation.The whole rock δ³⁴ S values of measured samples vary greatly from 2.85‰ to 13.46‰.while the δ³⁴S values of sphalerite and pyrite range from 8.33‰ to 9.06‰ and from 6.77‰ to 8.07‰,respectively,indicating the sulfur source of the samples closely associated with Mesozoic magmatic activity.The Kulongshan granitic magma experienced significant fractional crystallization,which facilitated the initial concentration of niobium and beryllium.During the magma-hydrothermal stage,the crystallization of fluorite reduced the solubility of these elements,leading to the formation of columbite,helvine and genthelvite.External fluids during the hydrothermal stage led to the coexistence of beryllium minerals with sulfide minerals.The magmatic and mineralization activities in the study area during the Early Cretaceous were influenced by an extensional tectonic regime associated with the retreat of the Paleo-Pacific plate.更多还原