【作者】 李怡欣；

【导师】 孙景贵；

【作者基本信息】 吉林大学 ， 矿物学岩石学矿床学， 2012， 硕士

【摘要】 老柞山金矿床区域上位于兴蒙造山带东段佳木斯地块的中北部，由近北东向等间距分布的东矿带、中矿带和西矿带组成。矿区内出露的地质体主要为基底地层麻山群、晚古生代华力西期花岗岩、中生代燕山期闪长玢岩、花岗斑岩、斜长花岗岩等中酸性岩脉；矿区构造主要发育NW、NWW及NE三组断裂，NW、NWW的张性断裂是矿区主要的控矿构造。该矿床的东矿带和中矿带的成因类型为矽卡岩型（铁）金矿床，矿体主要赋存在北西向、北西西向的张性断裂及花岗岩和钙质大理岩、钙质片麻岩的接触构造带内，成矿与矽卡岩密切伴生；西矿带矿体类型为热液脉型金铜矿床，主要赋存在花岗岩内部的北西向、北西西向的张扭性断裂中，金矿化集中发育在东矿带和中矿带。矿石矿物主要有磁黄铁矿、黄铁矿、毒砂、黄铜矿，其次是方铅矿、闪锌矿等，脉石矿物主要为石榴子石、透辉石、绿帘石、绿泥石、石英、方解石等；围岩蚀变类型繁多，以硅化、钾化、绢云母化、矽卡岩化、阳起石与透闪石化、绿帘石、绿泥石化、碳酸盐化为主。野外矿床地质、室内矿相学与流体包裹体特征揭示，流体包裹体的均一温度范围为520-57℃，盐度范围为1.73-39.68％，密度范围为0.19-1.11g/cm-3，压力变化范围为5.6-79Mpa，成矿深度变化范围在2.47-7.25km。成矿过程有五个阶段：从早到晚依次为：（Ⅰ）石榴子石-透辉石阶段（早期矽卡岩阶段），流体包裹体均一温度：520℃-470℃，盐度：1.73-8.9％，密度：0.19-0.47g/cm-3；（Ⅱ）绿帘石-阳起石阶段（晚期矽卡岩阶段），流体包裹体均一温度：470℃-410℃，盐度：4.6-34.8％，密度：0.3-1.1g/cm-3；（Ⅲ）磁黄铁矿-毒砂-黄铁矿-石英脉阶段（早期石英硫化物阶段），流体包裹体均一温度：410-300℃，盐度：3.37-38.64％，密度：0.43-1.11g/cm-3；（Ⅳ）石英-多金属硫化物阶段（晚期石英硫化物阶段），流体包裹体均一温度：300℃-150℃；盐度：1.73-39.68％，密度：0.78-1.08g/cm-3；（Ⅴ）石英-方解石阶段，流体包裹体均一温度<150℃：盐度：3.03-8.67％，密度：0.93-1.04g/cm3。成矿流体气相成分以CO2－CH4－H2O为主，具有岩浆热液流体属性，成矿晚阶段有大气水的加入。整体与国内典型矽卡岩型金矿床的成矿特征基本一致，初步确定为矽卡岩型金矿床。通过赋矿围岩花岗岩、穿切矿体的闪长玢岩脉的LA-ICPMS U-Pb测定，获得年龄分别为262.6±3.9Ma、105Ma，西矿带蚀变矿物绢云母40Ar/39Ar坪年龄为108.76±0.70Ma，结合前人对中矿带的黄铁矿Rb-Sr等时线的测年结果(239±34Ma），确定该矿床有两个内生成矿期，矽卡岩型矿化发生在（262Ma）、叠加热液型矿化发生在（109Ma），早期成矿发生在古亚洲洋向佳木斯地块俯冲消减的末期，与华力西期中二叠世晚期岩浆活动有关，晚期矿化适值晚中生代太平洋板块俯冲的大陆边缘环境，与中酸性岩浆作用有关。上述研究成果进一步得出该矿床金的成矿主要是由古生代花岗岩就位过程与接触的钙质岩系发生交代，在干矽卡岩、湿矽卡岩交代作用的基础上形成，中生代构造岩浆作用对早期成矿影响较小。更多还原

【Abstract】 Laozuoshan gold deposit， which is located in the central-north part of Jiamusimassif，the east section of xing’anling-mongolian orogenic belt，is divided into threeore belts:east belt, middle belt and west belt.outcrop geological bodies in mining areamainly is Mashan Group, Hercynian period granite and Yanshanian intermediate aciddike, such as diorite porphyrite, granite porphyry，plagioclase granite and so on. faultstructure are composed entirely of NW、NWW and NE, while NW and NWW faultare ore-controlling fracture.Study on geological characteristics of the three ore belts can further determinethe genetic type of the east and middle ore belts to be skarn type gold (iron) deposit,the orebody is mainly hosted in NW-NWW tensional fracture, or in the structuralcontact zone of granite and calcareous marble or gneiss, mineralization is closelyassociated with skarn; while the type of the west ore belt is hydrothermal vein typegold-copper deposit, the orebody is also hosted in NW-NWW tension-torsionalfracture, gold mineralization is concentrated in the east and middle ore belts. Themain metallic mineral are pyrrhotite, pyrite, arsenopyrite, chalcopyrite，sphalerite，galena etc. and gangue mineral are garnet, diopside, epidote, chlorite, quartz, calciteetc. wall rock alteration includes silicification, potassic alteration, sericitization，skarnization, actinolitization, epidotization, chloritization and carbonation etc.Study on fluid inclusion and H-O isotopes show that the fluid inclusion fromLaozuoshan gold deposit from with a homogenization temperature520℃to57℃,salinity w (NaCl eq) from1.73%to39.68%. Among them, early skarn stage has aore-forming temperature of520℃to470℃, salinityfrom1.73%to8.9%, late skarnstage has a ore-forming temperature of470℃to410℃, salinity from4.6%to34.8%, early stage of quartz-sulfide with ore-forming temperature of410℃to300℃,salinity from3.37%to38.64%,late quartz-sulfide stage with ore-forming temperatureof300℃to150℃, salinity from1.73%to39.68%, stage of quartz-calcite with a ore-forming temperature of150℃to57℃, salinity from3.03%to8.67%. Theore-forming fluid in the mass is a CO2－CH4－H2O system, with characteristics ofmoderate-high salinity and moderate-low density, and early ore-forming fluids aremainly mantle fluids, late are mainly atmospheric water.Zircon LA-ICPMS U-Pb dating of ore-hosting granite and dioritic porphyritedike that cut gold lodes are262.6±3.9Ma and105Ma separately. The plateau age of40Ar/39Ar of alteration phlogopite from west ore belt is108.76±0.70Ma, togetherwith the Rb-Sr isochron dating results of pyrite from the middle belt，which is239+34Ma, we holds that the deposit has two endogenetic mineralization periods, the skarnmineralization stage occured in239±34Ma, while hydrothermal superimpositionstage occured in102Ma， the early mineralization occurred during subduction ofPaleo-Asian Ocean to Jiamusi massif, and consistent with Hercynian magmatismactivities in late middle Permian, while the late mineralization environment iscontinental marginis, caused by Pacific Plate subducted in Late Mesozoic, and isrelated with intermediate-acid magmatism activitiesc.Based on the study mentioned above, we can come to the conclusion that goldmineralization happens on the base of dry skarn and wet skarn metasomatism ofPaleozoic granites and calcareous rock series and tectonic magmatism.更多还原