【作者】 代军治；

【导师】 毛景文； 张作衡；

【作者基本信息】 中国地质科学院 ， 矿物学、岩石学、矿床学， 2008， 博士

【摘要】 燕辽地区是华北地北缘一条重要的多金属成矿带,也是我国第二大钼矿带。成矿带内已发现钼（铜）矿床（点）20余处,这些矿床主要分布于冀北和辽西地区,矿床成因类型包括斑岩型、斑岩-矽卡岩型、矽卡岩型和石英脉型。本论文在前人研究成果的基础上,重点选择了成矿带内兰家沟、肖家营子、撒岱沟门3个典型矿床进行研究。通过对燕辽成矿带内区域地质背景、矿床地质特征、流体包裹体、稳定同位素、成岩成矿年代学及综合分析对比等多种手段,研究了成矿流体来源、演化及成因机制,总结了成矿规律,探讨了燕辽钼矿带成矿地球动力学背景及其演化,并与东秦岭钼矿带进行了对比,取得了如下成果:1、燕辽成矿带钼（铜）矿床主要分布于华北板块北缘的弧形构造带内,受区域性EW向、NE向和NNE向断裂控制。赋矿地层主要为蓟县系雾迷山组白云质灰岩和寒武系-奥陶系灰岩、页岩,与钼（铜）矿化有关的岩体主要是中生代中酸性复式侵入体（肖家营子除外）。钼矿床多产于含钼花岗质岩石之中或与地层的接触带之中。侵入岩与地层条件对矿床的形成具有一定的制约性,产于花岗斑岩、长英质或中酸性火山岩内的钼矿床多为斑岩型,而产在花岗质岩类与碳酸盐岩地层接触带的钼或铜（铜）矿床为矽卡岩型或斑岩-矽卡岩型。2、兰家沟钼矿床矿体主要赋存于细粒花岗岩体内部及与粗粒花岗岩的接触部位,矿石类型以石英-辉钼矿大脉为主,围岩蚀变主要是钾化、硅化、云英岩化和水白云母化。含钼石英脉中流体包裹体以气液两相为主,包裹体的均一温度为160～405℃;盐度w(NaCl_eq)为2.4%～16.5%,成矿流体属NaCl-H₂O±（CO₂）体系。石英的δD为-81‰～-101‰,δ¹⁸O_H2O为-0.1‰～4.5‰,表明成矿流体来自岩浆水与大气降水的混合。成矿流体在演化过程中发生了中等盐度和低盐度流体的混合作用,2种不同组分流体的混合作用使得辉钼矿大量沉淀而成矿。通过与典型斑岩型钼矿床地质特征、矿化、围岩蚀变、流体包裹体特征及同位素组成的对比,认为兰家沟钼矿床属于石英脉型钼矿床。3、肖家营子矿床是一个与中-基性侵入岩有关的矽卡岩型钼（铁）矿床,矿体主要赋存于细粒闪长岩与雾迷山组白云岩接触部位的矽卡岩体中。石榴石矽卡岩阶段和磁铁矿化阶段流体包裹体主要为含子矿物包裹体,含子矿物包裹体通过气泡消失而均一,均一温度分别为505～560℃和435～541℃,盐度w(NaCl_eq)分别为43.4%～50.0%和44.9%～56.9%;辉钼矿化阶段以含子矿物包裹体和气液两相包裹体为主,含子矿物包裹体通过子矿物消失而完全均一,均一温度为203～440℃,盐度w(NaCl_eq)为32.0%～52.0%,气液两相包裹体通过气泡消失而均一,均一温度为146～402℃,盐度w(NaCl_eq)为4.3%～18.4%。肖家营子矿床成矿流体属于H₂O-NaCl±（KCl）高盐度体系。流体包裹体和氢氧同位素分析表明,成矿早期为高温、高盐度的岩浆流体;辉钼矿阶段流体为中温、高盐度流体和中-低温、低盐度的混合流体。含矿流体在演化的过程中,高温、高盐度流体由于压力和密度的转化对磁铁矿沉淀富集具有重要影响;中温、高盐度与低盐度流体的混合有利于辉钼矿富集成矿。4、撒岱沟门矿床矿体主要以网脉状、细脉状、星散浸染状或条带状赋存于二长花岗岩体内,属于斑岩型钼矿床。钼矿化与微斜长石化、硅化、白云母化关系密切。撒岱沟门钼矿床石英脉中主要发育气液两相、含CO₂三相和CO₂相包裹体。成矿前与成矿期后流体以气液两相包裹体为主,包裹体均一温度、盐度w(NaCl_eq)分别为280～452℃、5.4%～18.4%和153～279℃、3.9%～9.7%;成矿期流体中3类包裹体都发育,包裹体均一温度为170～370℃,盐度w(NaCl_eq)为4.3%～14.4%,成矿流体属于NaCl-H₂O-CO₂不混溶体系。含钼石英脉的δD为-82‰～-98‰,δ¹⁸O_H2O为0.1‰～6.2‰,表明成矿流体以岩浆水为主,晚期有大气水的混入。成矿流体在形成过程中经历了3个阶段的流体演化:早期为岩浆脱水、脱气阶段,成矿期为流体不混溶阶段,晚期为大气水混合阶段。其中,流体的不混溶作用对辉钼矿沉淀成矿产生了积极的影响。5、分别采用SHRIMP锆石U-Pb定年法、锆石U-Pb定年法和辉钼矿Re-Os同位素测年方法对兰家沟、肖家营子、撒岱沟门矿床的成岩成矿年龄进行了精测。获得兰家沟细粒花岗岩的SHRIMPU-Pb年龄为（188.9±1.2）Ma与辉钼矿Re-Os年龄（186.5±0.7）Ma相似:肖家营子细粒闪长岩的SHRIMP U-Pb年龄为（169.9±1.4）Ma,辉钼矿Re-Os等时线年龄为（165.5±4.6）Ma;撒岱沟门二长花岗岩的U-Pb年龄为227 Ma,辉钼矿Re-Os模式年龄为237～238 Ma;大草坪钼矿床花岗闪长岩U-Pb年龄为137 Ma,辉钼矿Re-Os模式年龄为136～146 Ma。通过与成矿带内其它钼矿床的对比发现,燕辽成矿带内大规模的钼（铜）矿化事件主要集中于225±Ma、185±Ma、140±Ma,这些矿床形成的地球动力学背景分别为西伯利亚板块与华北板块后碰撞造山作用的短期挤压阶段;蒙古—鄂霍茨克洋消减、闭合时期:中国东部地球动力学机制大调整晚期。6、对比研究表明,华北板块南北缘钼矿床的形成在区域地球化学背景、赋矿层位、构造、岩浆岩和成岩成矿年龄方面存在一定的差异性。华北板块北缘燕辽钼矿带区域钼、铜地球化学异常背景高,地层层位对钼（铜）矿床的控制作用较华北板块南缘东秦岭钼矿带明显。华北板块北缘区域性EW向、NE向、NNE向断裂控制着燕辽地区的岩浆活动与钼（铜）矿床的展布,与钼（铜）矿化有关的岩浆系列从基性→中性→酸性都有,而东秦岭钼矿带构造格局以NWW向和NE向断裂为主,与钼矿化有关的岩体主要为一些中酸性花岗岩类小岩体。在成矿时代方面,燕辽成矿带早侏罗世钼矿床成矿事件较为强烈,早白垩世成矿作用弱。而东秦岭成矿带内早侏罗世钼成矿事件弱,晚侏罗-早白垩世成矿作用强烈。更多还原

【Abstract】 The Yan-Liao（Yanshan-western Liaoning） area is an important metallogenic belt for Au,Ag,Pb-Zn on the northern margin of the North China Block and is also the second largest Mo metallogenic belt in China where more than 20 Mo（Cu） deposits have been explored.Those Mo（Cu） deposits are present in the northern Hebei province and western Liaoning province and are mainly porphyry types,skarn types and quartz vein types.Base on the pervious researchers and detail field investigation in Yan-Liao area,we selected three types of representative Mo deposits such as Lanjiagou（quartz vein types）,Xiaojiayingzi （skarn type） and Sadaigoumen（porphyry type） to detail study.Focusing on the geological characteristics, fluid inclusions analyses,stable isotope,chronology and synthetically comparative study etc,we studied the source and evolution of ore fluids of representative Mo deposit,summarized the metallogenic regularities of Mo（Cu） deposits,discussed the metallogenic mechanism and the relation between geodynamics evolution and the Mo（Cu） mineralization of the Yan-Liao area,and compared with the Mo deposits in east Qinling Mo metallogenic belt in the southern margin of North China Block.The main advance achievements from this study are as followings:1.Located in the Yan-Liao area,the Mo（Cu） deposits occurred in an arc structure belt in the northern margin of North China Block,which were controlled by the EW-trending,NE-trending and NNE-trending regional faults.The host rocks of these deposits are Mesoproterozoic Wumishan Formation,comprising dolomitic limestone and Cambrian-Ordovician limestone and shale.Most these Mo（Cu） deposits were temporally and spatially associated with intermediate-felsic rocks（except Xiaojiayingzi deposit）,and occurred in the inner of felsic rocks or the contact zone between the felisc with host rocks.Intrusive rocks and host rocks play an important role for the metal mineralization.Those Mo（Cu） deposits,occurring in the inner of granite porphyry,felsic rocks and intermediate-felsic volcanic rock are mainly porphyry type, whereas the Mo（Cu） deposits,occurring in the contact zone between felsic rocks and carbonate rocks are mainly skarn type or porphyry type deposits.2.The Lanjiagou Mo deposit is located in Liaoning province.Its major molybdenite orebodies are situated at the inner of fine granite of Hongluoshan and the contact zone between fine granite and coarse granite.Molybdenite quartz large veins are the primary mineralization type in Lanjiagou deposits.The wallrock alteration consists of potassium alteration,silicification,greisenization and hydromuscovite alteration.Petrographic observation shows that aqueous two-phase inclusion is the mainly fluid inclusion type in molybdenite quartz veins and the homogenization temperatures and salinities of the inclusion in ore-forming stage range from 160 to 405℃,2.4～16.5%NaCl equivalent,respectively.Laser Raman Spectroscopic analysis of fluid inclusions suggest that the ore-forming fluids once were of NaCl-H₂O±（CO₂） system.The hydrogen and oxygen isotopic components of typical ores indicate that theδD values of ore-forming fluids from -81‰to -101‰and theδ¹⁸O_H2O values vary from -0.1‰to 4.5‰,which suggested that the ore-forming fluids could be produced by mixing magmatic and meteoric water.During mineralization stages,the fluid inclusions with lower salinities underwent mixing processes with the fluid inclusion with middle salinities,which brought positive influence to molybdenite mineralization and concentrate.Comparative studies on geological features,mineralization,wallrock alteration,fluid inclusions characteristics and H,O isotope,the author confirm that there are many differences between Lanjiagou Mo deposit and porphyry Mo deposit.The genesis of Lanjiagou deposits is of quartz vein type Mo deposit.3.The Xiaojiayingzi Mo（Fe） deposit is temporally and spatially associated with intermediate to mafic rocks and the mineralization hosted in skarn.Detail fluid inclusion studies show that there are mainly two types primary fluid inclusion occurred in this deposit.The fluid inclusion in granet and chondrodite from garnet skarn stage and magnetite mineralization stage are mainly daughter crystal-bearing polyphase,which homogenized to the liquid phase by disappearance of vapor phase and homogenization temperatures from 505 to 560℃and 435 to 541℃,salinity from 43.4 to 50.0%NaCl equiv and 44.9 to 56.9%NaCl equiv, respectively.The fluid inclusions occured in calcite and quartz from molybdenite mineralization stage: daughter crystal-bearing polyphase inclusion and aqueous two-phase inclusion.The former homogenized to liquid phase by dissolution of daughter minerals,with homogenization temperatures from 203 to 440℃and salinity ranging from 32.0%to 52.0%NaCl equiv.The latter homogenized to the liquid phase by disappearance of the vapor bubble at homogenization temperatures from 146 to 402℃,salinity between 4.3%to 18.4%NaCl equiv.Fluid inclusion and H,O isotope analysis show that the ore-forming fluid from pre-ore stage is characterized by high temperature and high salinity.The ore-forming fluid from molybdenite mineralization stage are characterized by mixed fluid of high temperature and high salinity fluid end and medium to lower temperature and lower salinity fluid end.During the evolutional processes of ore-forming fluid,the transformed of the pressure and density of high temperature and high salinity fluid play an important role to magnetite minealization,and the mixing of fluid between high salinity and lower salinity take a positive influence to molybdenite deposition.4.The Sadaigoumen deposit lies in Hebei province and is the largest molybdenum deposit in this region thus far reported.Its major molybdenite orebodies are mainly hosted inside monzogranite and occurred as veinlet,disseminated structure or banding structure.Molybdenite mineralization is closely associated with microclinization,silicification and muscovitization.Fluid inclusion studies suggest that three types of fluid inclusion are present in this deposit:aqueous two-phase inclusions,CO₂-bearing three-phase inclusions and CO₂ phase inclusions.Fluid inclusions in quartz in the pre-ore stage and post-ore stage are mainly aqueous two-phase.The homogenization temperatures and salinities of the former stage vary from 280 to 452℃and from 5.4%to 18.4%NaCl equivalent respectively,and those of the latter stage vary from 153 to 279℃and from 3.9%to 9.7 wt%NaCl equivalent respectively.During the mineralization stage,all the three types of fluid inclusion were formed in ores.Microthermometric studies indicate that their homogenization temperatures and salinities range from 170 to 370℃and from 4.3 to 14.4 wt%NaCl equivalent respectively.Laser Raman spectrometric and hydrogen and oxygen isotope studies of the fluid inclusions in ores indicate that quartz in the Sadaigoumen deposit contains -82 to -98‰δD and 0.1 to 6.2‰δ¹⁸O_H2O and that the ore-forming fluids once belonged to the immiscible NaCl-H₂O-CO₂ system and were mainly derived from magmatic water,which were mixed with meteoric water in the post-ore stage.During the formation of the ore-forming fluids,three stages of fluid evolution occurred in the Sadaigoumen deposit:magma dehydrating and degassing in the pre-ore stage,fluid immiscibility in the mineralization stage and meteoric waters mixing in the post-ore stage,respectively.The decrease of temperatures and fluid immiscibility are the dominant factors for molybdenite deposition.5.SHRIMP zircon U-Pb,zircon U-Pb and molybdenite Re-Os isotopic dating methods are utilized in order to determine the timing of the mineralization and its relationship intrusive rock.We obtained the SHRIMP zircon U-Pb weighted mean age of（188.9±1.2） Ma for the Lanjiagou fine-grained granite and （169.9±1.4） Ma for the Xiaojiayingzi fine-grained diorite.The molybdenite Re-Os isochron age is （165.5±4.6） Ma for Xiaojiayingzi deposit.The molybdenite Re-Os model age ranges from 237 to 238 Ma for the Sadaigoumen deposit and 136 to 146 Ma for the Dacaoping deposit.The zircon U-Pb for monzonitic granite from Sadaigoumen deposit and for granodiorite from Dacaoping deposit yield modle age of 227 Ma and 137 Ma,respectively.After collecting and documenting the precise radiometric age of the Mo（Cu） deposits in Yan-Liao area,there appear three Mo（Cu） mineralization pulses,i.e.ca.225 Ma,ca. 185 Ma and ca.145 Ma in Mesozoic.Base on the Mesozoic tectonic evolution,we propose these three pulses of large-scale mineralization are the consequences of the short time compression during the postcollisional process of the Siberian Block with the North China Block,the closure of Mongolo-Okhotsk, and the late stage of tectonic regime changing its main stress from NS-trending to EW-trending.6.Based on comprehensive studies and comparison of these Mo deposits between Yan-Liao metallogenic belt and east Qinling Mo mineralization belt,we confirmed that there were significant differences exist in regional geochemical anomaly,the tectonic system,the magmatic composition,the age of magma emplacement and the mineralization pulse.更多还原