【作者】 陈静；

【导师】 孙丰月；

【作者基本信息】 吉林大学 ， 矿物学、岩石学、矿床学， 2011， 博士

【摘要】 小兴安岭地区位于中亚—兴蒙巨型造山带的东段,西伯利亚板块、华北板块和太平洋板块三大板块的交汇区域,是经多次相互作用的复合造山带,其前中生代主要受古亚洲洋构造域的影响,中生代以来又受到太平洋板块活动的强烈改造与叠加增生,因此构成了此区独特的构造演化背景。本次工作对小兴安岭地区与成矿有关的岩浆岩进行了岩石学、地球化学、年代学的研究,获得了本区中生代侵入岩锆石U-Pb年龄的200-170Ma和120-100Ma两个范围。200-170Ma间形成大规模花岗岩类,主要沿伊春—延寿褶皱带呈近南北向展布,岩石类型总体为钙碱性—高钾钙碱性系列的I型(包括高分异I型)花岗岩,且大多数岩体属于氧化程度高的磁铁矿系列,形成与太平洋板块的俯冲有关；120-100Ma间与成矿有关的主要为火山岩和浅成侵入岩,岩石学特征和地球化学分析表明其形成于俯冲后岩石圈伸展减薄环境。集中在分布在野外工作和室内研究的基础上,我们对研究区内典型矿床成因类型及成矿特征进行了重新认识：小西林铅锌矿原定矽卡岩型,经项目组野外调查初步认为I号主矿体成因类型为以碳酸盐岩为容矿围岩的热水喷流沉积型铅锌矿床(银矿山型SMS),老道庙沟铅锌矿为小西林矿田内不同于主矿体的热液脉型铅锌矿；翠宏山矽卡岩型铁钼多金属矿床原定是加里东期成矿作用叠加印支期和燕山期岩浆热液活动的结果,本次研究认为它很可能与霍吉河、鹿鸣钼矿同时产出于燕山早期,是太平洋俯冲背景下岩浆侵入碳酸岩地层的产物。根据Westra等(1981)对斑岩型钼矿的分类,霍吉河、鹿鸣斑岩型钼矿属于钙碱性系列的深成侵入体型,钼矿化主要有两种类型：石英—辉钼矿脉(花岗岩未蚀变)和薄膜状矿化(花岗岩蚀变成绢英岩),根据成矿岩体和钼矿化特征,我们建议将此类深成侵入体型钼矿定义为细网脉型钼矿,拓宽寻找斑岩型矿床的思路,即大岩基也可以成矿。在对小兴安岭地区成岩成矿年龄的修正及典型矿床成因的重新认识之后,对研究区典型矿床进行了成矿系列的重新划分,可划分为2个成矿系列：与燕山早期中酸性岩浆侵入活动有关的钼铁铅锌钨铜矿床成矿系列、与燕山晚期中酸性火山岩、次火山岩有关的金、银矿床成矿系列。最后,本文总结了小兴安岭地区成矿的空间和时间规律：空间上,可划分为伊春—延寿MoFePbZnWSnCuAg成矿亚带和小兴安岭北西向AuAg成矿亚带。前者成矿作用既受中生代岩浆活动控制,又受特定时代地层(如寒武系西林群铅山组、奥陶系小金沟组等)控制,北东向、北北东向和北西向构造都是成矿的主要控制条件；后者受燕山晚期北西向小兴安岭盆岭边界断裂火山喷发带控制,产出低硫化型浅成低温热液型矿床。时间上可分为3个成矿期：早寒武世成矿期、早燕山成矿期、晚燕山成矿期,其中最主要的是燕山成矿期。在上述成矿分析的基础上,我们在吉林大学地球科学学院地质流体实验室采用Linkam THSM-600型冷热台,对各矿床进行了大量的流体包裹体测试,确定了各典型矿床(点)成矿流体的均一温度、盐度、密度、压力,并计算了成矿的深度,为小兴安岭地区的研究工作积累了大量的资料。鹿鸣钼矿与霍吉河斑岩型钼矿的成因类型及成矿特征基本一致,矿石类型主要以辉钼矿石英细网脉为主,包裹体均一温度表明成矿温度总体集中在180-360℃之间,辉钼矿沉淀温度集中在280-360℃之间,富液相水溶液包裹体盐度集中在3.05-6.58wt%NaCleqiv之间；含子矿物多相包裹体大多数通过子矿物的消失而均一,盐度范围为39.23-47.60 wt%NaCleqiv。各阶段包裹体特征表明,成矿流体总体演化过程可能为岩浆房最先分离出一个单一相的高温、中低盐度的流体相,当流体系统由静岩向静水压力演化过程中,由于减压导致流体局部沸腾,分离出高盐度的流体及其与之共生的气相两种流体,钼在残余流体中富集并沉淀,同时,温度的降低使钼在300-360℃间迅速沉淀。总体上,随着成矿流体不断演化,成矿物质不断沉淀,成矿系统逐步降温,盐度也随之降低。翠宏山铁钼多金属矽卡岩型矿床流体包裹体测试样品均来自石英硫化物期,其中,早阶段包裹体以含子矿物包裹体和富液相水溶液包裹体为主,含子矿物多相包裹体均一温度为291-330.5℃,相应的流体盐度为(NaCleq)37.29%-40.17%,富液相水溶液包裹体均一温度集中于240-315℃,盐度为6.44%-9.60%；辉钼矿化阶段和铜铅锌矿化阶段以大量发育富气相水溶液包裹体为特征,类型主要为富液相水溶液包体和富气相水溶液包体,少量含子矿物多相包体,包裹体均一温度为180-234℃和252-288℃。浅成低温热液型矿床中三道湾子金矿床形成温度集中在230-270℃问,结合地质特征和矿物组合特征该温度区间大致相当与硫化物一石英脉和石英—金—碲化物形成的温度；东安金矿成矿温度主要集中在220-280℃,属于中低温矿床；乌拉嘎金矿主矿区矿床形成温度主要集中在150-220℃区间内,为主矿化阶段的含金玉髓状石英-多金属硫化物形成的温度。上述三个矿床成矿流体均为低盐度低密度流体。更多还原

【Abstract】 Lesser Hinggan Mountain is located in the eastern section of giant Central Asia-Hing Meng orogenic belt, the intersection area of Siberia plate, North China plate and the Pacific plate. It is a composite orogenic belt undergoing interactions of the three plates, mainly influenced by Paleo-Asian Ocean tectonic domain before the Mesozoic, and reconstruction and superposition activities of the Pacific plate since the Mesozoic, therefore constitutes a unique tectonic evolution background in this area.Petrology, geochemistry, chronology researches on mineralization-related magmatic rocks are carried out within Lesser Hinngan Mountain. It is suggested that ages of these intrusive rocks center on 200-170Ma and 120-100Ma. Great amounts of granitoids formed during 200-170Ma, mainly distributed nearly north-south trending along the Yichun-Yanshou fold belt, belong to calc-alkaline-high-K calc-alkaline series, I type (including the highly fractionated I-type) granites, magnetite series,with a high degree of oxidation, forming by subduction of the Pacific plate; volcanic and shallow intrusive rocks are contributed to mineralization during 120-100Ma, and formed due to lithospheric thinning after subduction.Based on the field work and laboratory study, we are approaching a new understanding on the genesis types and characteristics of deposits in studying area:Xiaoxilin lead-zinc skarn deposit is sedimentary exhalative lead-zinc deposits (Silver mine type SMS); Laodaomiaogou lead-zinc deposit is of hydrothermal vein type, different from the type of main ore body within Xiaoxilin ore field; Cuihongshan Fe-Mo polymetallic skarn deposit is formed during early Yanshanian, due to the Pacific subduction, instead of originally concerned as the product of the Caledonian superimposed Indosinian and Yanshanin magmatic hydrothermal activities.According to Westra et al (1981) on the classification of porphyry molybdenum deposit, we consider Huojihe, Luming porphyry molybdenum deposit are belong to the calc-alkaline series, pluton type. There are two types of molybdenum mineralization:quartz-molybdenite veins (Granite is not altered) and film-like mineralization (granite is altered into phyllic), according to rock and molybdenum mineralization characteristics, we propose to redefine this type as stockwork molybdenum deposit, in order to expand the idea of for porphyry deposit prospecting.After revising diagenetic mineralization ages and reunderstanding of ore genesis, we again reclassify the metallogenic series in the study area, two series can be divided: magmatism-related Mo-W-Cu-Pb-Zn deposit series in Early Yanshanian and volcanic-subvolcanic rocks related Au-Ag mineralization series in the late Yanshan.Finally, the paper summarizes the regional mineralization laws in space and time:in space, it can be divided into Yichun-Yanshou Mo-Fe-Pb-Zn-W-Sn-Cu-Ag metallogenic subzone and Lesser Hinggan Mounain NW-trending Au-Ag ore subzone. Mineralization in former subzone is well controlled by Mesozoic magmatic activity, also by specific strata (such as Cambrian Qianshan group, Ordovician Xiaojingou group, etc.), and NE, NNE and NW structures; the latter is controlled by volcanic eruption zone along NW-trending Basin and Range boundary fault in the late Yanshanian, with smoe low-sulfidation epithermal deposits. Three metallogenic periods are determined:Early Cambrian, early Yanshanian and late Yanshanian metallogenic period.Based on mineralization analysis, A lot of fluid inclusions tests have been carried out in geological fluids Laboratory in Earth Sciences department, Jilin University, using Linkam THSM-600 hot and cold units to determine the ore-forming fluids homogenization temperature, salinity, density, pressure of each typical deposit, and calculate the depth of mineralization for the study area, provided large amount of data for further research in Lesser Hing’an area.Luming and Huojihe molybdenum porphyry deposits are comparable, ore types are mainly molybdenite quartz veins, homogenization temperatures of fluid inclusion are concentrated in 180-360℃, molybdenite precipitated between 280-360℃, salinity of L type is concentrated in 3.05-6.58 wt% NaCleqiv whereas S type concentrated in 39.23-47.60wt% NaCleqiv by the disappearance of daughter mineral. Inclusion characteristics of each stage showed the overall evolution of ore-forming fluid may:firstly isolated a high temperature, middle-low salinity single fluid phase from the magma chamber, then isolated a high salinity fluid and coexisting gas phase when pressure changing from lithostatic to hydrostatic due to pressure reducing and fluid boiling. Mo enriched and precipitated in the residual fluid during 300-360℃. Overall, with the evolution of ore-forming fluids, minerals precipitated, ore-forming system was gradually cool down as well as the salinity decreased.Majority S type fluid inclusions in early stage of Chuihongshan Mo polymetallic deposit homogeneous by final dissolution of daughter minerals, a few by disappearing bubbles, homogenization temperature is concerntrated in 291-330.5℃, corresponding fluid salinity (NaCleq) is 37.29%-40.17%, homogenization temperature of L type is concentrated in 240-315℃, salinity in 6.44%-9.60%; Inclusions types of quartz sulfide stage mainly are L and V type, a small amount of S type. Homogenization temperature can be divided into two concentration intervals 180-234℃and 252-288℃, corresponding to molybdenite stage and copper lead zinc mineralization stage.Sandaowanzi gold deposit mainly formed in the 230-270℃, roughly equal to sulfide-quartz veins and quartz-gold-telluride stage; Dongan gold deposit mainly formed in the 220-280℃, belonging to the low-temperature deposit; Wulaga gold deposit forming temperature mainly concentrated in the range 150-220℃, equal to the tempreture of gold-bearing chalcedony quartz-polymetallic sulfides stage. The three deposits are all low salinity low-density.更多还原