【作者】 门兰静；

【导师】 迟效国； 孙景贵；

【作者基本信息】 吉林大学 ， 地球化学， 2011， 博士

【摘要】 延边-东宁地区位于兴蒙造山带东端,狭于华北板块,佳木斯地块以及兴凯地块之间,是一个经历了古亚洲洋演化、兴蒙造山对接以及新生代超壳断裂作用叠加而成的复合构造区,多期的构造、岩浆作用使得本区成为我国内生浅成热液金铜等多金属重要矿产地之一,长期以来倍受国内外地质学家关注和研究。为了深入揭示浅成热液金属矿床的成矿规律和找矿方向,本文以该地区的超大型-大(中)型浅成热液金铜矿床为研究对象,深入开展了典型矿床以及与成矿关系密切的中酸性火成岩的地质、地球化学、同位素、年代学研究,取得了如下重要进展。矿床地质研究得出：斑岩型金厂18号脉、农坪和类斑岩型小西南岔金铜矿床矿体类型为细脉型、细脉浸染型,浅成高硫化矿床矿体类型为角砾岩型和蚀变岩型；研究区斑岩型-浅成高硫化型矿床的控矿构造均为线性断裂或次级断裂,矿体产在断裂交汇的角砾岩筒内或次级断裂中；矿化阶段上,除类斑岩型小西南岔金铜矿床外,斑岩型和浅成高硫化型均分为4个矿化阶段：斑岩型和浅成高硫化型金铜矿床Ⅰ矿化阶段分别为钾长石化阶段、黄铁绢英岩阶段,其余三个矿化阶段均分别为：石英-黄铁矿±黄铜矿±辉钼矿阶,多金属硫化物阶段,石英-方解石脉阶段；小西南岔分为5个阶段,第Ⅰ和第Ⅴ矿化阶段和斑岩型第Ⅰ和第Ⅳ矿化阶段相同,Ⅱ-Ⅳ(主成矿)矿化阶段分为浸染状硫化物蚀变岩阶段、硫化物阶段、纯硫化物阶段；围岩蚀变上,三类矿床除斑岩型和类斑岩型早期发育钾长石化、阳起石化、电气石化及黑云母化,均发育绿泥石、绿帘石化,硅化,绢云母化,泥化和碳酸盐化。流体包裹体的研究表明：浅成高硫化矿床包裹体类型为气液两相、含子晶多相及(富)纯气相,富液相；子晶类型主要为石盐、钾盐、硬石膏、重晶石等硫酸盐,黄铜矿及赤铁矿等金属子晶；金厂0号脉、1号脉和杜荒岭、九三沟的均一温度分别为120℃-490℃,110℃-490℃,90-530℃,140-560℃；初始成矿流体的盐度分别为35.66-65.85 wt%(NaCl), 62.38±wt%(NaCl),60.03～64.49 wt%(NaCl);主成矿古深度为<1.5km。斑岩型金厂18号、农坪金铜矿床包裹体除发育浅成高硫化包裹体类型外,金厂18号矿体还存在熔融包裹体,子晶种类与高硫化型相同；其均一温度分别为230℃-600℃、170-490℃；初始成矿流体的盐度分别为31.75-69.82 wt%(NaCl),2.89 wt%(NaCl)±；主成矿阶段古深度分别为3.5-1.0km,2.0-0.5km.小西南岔北山、南山及与成矿关系密切的角闪花岗闪长岩包裹体类型与斑岩型相同,子晶种类还有方解石和水合物；北山、南山及角闪花岗闪长岩均一温度分别为150℃-500℃、150℃-390℃,90℃-530℃,显示北山具有高温气相成矿特征；北山获得初始成矿流体盐度为9.45-20.15(wt%NaCl),与角闪花岗闪长岩原生流体包裹体的盐度10.49-15.55(wt%NaCl)接近；北山开始成矿深度为4km,南、北山主成矿古深度均小于2.0kmm。这三类矿床主成矿阶段流体盐度均出现低盐度和高盐度两个区间,晚期为低盐度流体。激光拉曼结果显示五个矿床的气体成分主要为H20,C02,CH4,小西南岔南、北矿区和金厂0号脉,杜荒岭气体成分还有N2。氢氧同位素显示小西南岔南、北矿区和金厂0号脉的δ18O(H2O)分别为0.048-6.125‰,-0.09-3.78‰,4.1-7.14‰；δDV-SMOW分别为-46--99.5%o,-38--82.5%0,-73-86.62。这些结果表明早期成矿流体均为含CO2的高温高氧化的幔源岩浆热流体,浅成高硫化矿床和斑岩型金厂18号脉初始成矿流体具有高盐度性质,而斑岩型农坪和类斑岩型小西南岔金铜矿床初始成矿流体为中低盐度,成矿过程中均有不同程度的地壳流体和大气水的混入。三类矿床的成矿过程中均有沸腾作用发生,450-400℃,30Mpa,高盐流体与大气水的加入是浅成高硫化矿床形成的前提,350-200℃,15-5Mpa流体沸腾是该类矿床主要成矿机制；斑岩型金厂18号脉和农坪经先沸腾后大气水混合形成细脉浸染状斑岩型矿床,沸腾条件分别为450-300℃,35-10Mpa和350-300℃,20-10Mpa；温度370-400℃,压力20Mpa时流体的瞬间沸腾是小西南岔矿床形成的前提,随后350℃±,15Mpa时高温气相与地壳流体混合交代是北山形成的主要机制,400-200℃,20-5Mpa随温压变化在裂隙中脉状充填结晶是南山主要成矿机制,5Mpa大气水加入造成局部不混溶是小西南岔中晚期成矿机制。成矿关系密切的中酸性火成岩的主量、痕量元素显示Si02含量≥53%,A1203≥17%,富集大离子、轻稀土元素,亏损重稀土元素的特征；Sr-Nd-Pb同位素结果显示：金厂九三沟和小西南岔脉岩的(87Sr/86Sr)i,INd和εNd(t)的值分别为0.70414-0.70487,0.51258～O.51264,1.56-2.88;206Pb/204Pb为18.3481～18.4682,207Pb/204Pb为15.5438～15.6198,208pb/204Pb为38.2316-38.4177。这些结果显示脉岩为钙碱性和埃达克质岩共生特征,为俯冲洋壳脱流体过程中,可能伴生有埃达克质熔体的产生,它们与上覆地幔楔和地幔熔体不同程度的混合、混染形成。成岩成矿年代学研究显示金厂金铜矿和九三沟金矿的成矿时代上限分别为110±1.1Ma,109.8±2.2Ma,杜荒岭金矿床的成矿时代为107±6 Ma；小西南岔和农坪矿床成矿时代上限分别为102.1±2.2Ma,96.9±1.4Ma;显示成矿集中在两个时间,110Ma和100Ma,均与早白垩世晚期伊泽奈奇板块不同方向的俯冲有关。结合与成矿有关的岩浆的成因和形成时代,成矿流体的演化,归纳成矿动力学背景和成矿过程为：110Ma伊泽奈奇板块北北西向下俯冲古亚洲洋大陆,俯冲洋壳脱流体过程中,可能伴生有埃达克质熔体的产生,它们与上覆地幔楔和地幔熔体不同程度的混合、混染过程中,岩浆房逐渐卸载岩浆带来的铜等成矿元素,中低盐度的超临界含矿流体库聚集形成。随着岩浆结晶金厂和杜荒岭,九三沟矿区的临界流体发生相分离均形成高盐度流体和低盐度岩浆气；在岩石圈地幔伸展情况下,岩浆和成矿流体上升,高盐度流体经过沸腾和大气水混合以结晶和充填方式在金厂形成细脉浸染状18号脉,金厂矿区、杜荒岭和九三沟矿区的低盐度岩浆气上升过程中浓缩出高盐度液相再经大气水混合转变为中低盐度流体,1.5km处经沸腾分别形成0号、1号角砾岩筒矿体,杜荒岭和九三沟角砾岩型矿体；100Ma伊泽奈奇板块北西向俯冲,经历上述过程形成的埃达克质岩浆和中低盐度流体在小西南岔和农坪矿区上升,经沸腾和大气水混合形成农坪细脉浸染状铜金矿体,而在小西南岔沸腾后的高温气相流体与年轻地壳流体混合交代、结晶在北山形成细脉浸染状矿体,沸腾的中温含矿流体在南山以充填方式形成磁黄铁矿为主的硫化物石英脉,在中晚期南、北山均有大气水的加入,在南山造成局部不混溶形成纯硫化物脉和角砾岩,北山不混溶形成的高温气相流体以充填方式形成胶黄铁矿石英脉,上升的埃达克质岩浆随着矿体形成也在浅部就位。因此,延边-东宁地区晚中生代在相同的动力学背景下,通过不同的流体演化过程形成了三种不同类型的热液金铜矿床。更多还原

【Abstract】 Yanbian-Dongning area is located in the eastern part of Mongolia orogenic belt, adjacent to Jiamusi massifs in the north and North China plate in the South and Khanka massifs in the northeast. The region has undergone the evolution of the Ancient Asian Ocean, Xing’an-Mongorian orogenic process, superposition of Mesozoic subduction of palaeo-Pacific plate and Cenozoic supercrustal faulting. Owing to multi-stage tectonic-magmatism, the study area became one of important Au-Cu-dominated polymetallic mineral producing area in China, and the geologists world-wide have paid much attation to the area for a long period. This paper chooses typical epithermal Au-Cu deposits of Late Mesozoic in the area to further reveal the metallogenic regularity and ore-searching direction. The study, including deposit geology, geochemistry, metallogenic epoch of typical deposits and the geology, geochemistry, isotope and chronology of intermediate-acid igneous associated with the ore, was systemically carried out. The following important developments are obtained.The study on deposit geology indicates that:the orebodies in porphyry type No.18 of Jinchang, Nongping and porphyry-like type Xiaoxinancha Au-Cu deposit are characterized by veinlike and veinlet-dissemination, Those in epithermal high sulfidation deposits (HSD) belong to breccia pipe type and alteration type. The five deposits are all controlled by linear fractures and secondary fracture, and the orebody occurred in breccia pipe and secondary fracture. The porphyry type and HSD type deposit are all divided into four mineralization stage, the first stage for the porphyry type and HSD type deposit are potassic alteration and pyritized phyllite, respectively, the other three stages are quartz-pyrite±chalcopyrite±molybdenite stage, polymetallic sulfide stage, quartz-calcite stage in sequence, whereas Xiaoxinancha can be divided five stages, the first and the end stages are the same to that of the porphyry type deposit, theⅡ-Ⅳstages are disseminated sulfide and alteration rocks stage, sulfide veins stage, pure sulfide stage, in turn. Hydrothermal alteration in five studied deposits are widespread, including argillic alteration, silicification, kaolinization, sericitization, as well as potassic alteration, biotitization and tourmalinization in porphyry type and porphyry-like Au-Cu deposit.Four type fluid inclusions are recognized in HSD deposit, including aqueous inclusion, vapor-rich inclusion, polyphase inclusion and liquid-rich inclusion, the discovered daughter minerals are halite, sylvite, anhydrite, barite, as well as opaque mineral such as hematite, chalcopyrite; the total homogenization temperatures and the salinity of early mineralizing fluids are in the ranges of 90-530℃and 62.38±wt%(NaCl) for Duhuangling, in the ranges of 140-560℃and 60.03-64.49 wt%(NaCl) for Jiusangou,120℃-600℃and 35.66-65.85 wt%(NaCl) for No.0 in Jinchang deposit, and the mineralization depth of the HSD is mainly less 1.5km. The porphyry type deposit in study area have the same fluid inclusion type to HSD, as well as melt inclusion; the range in the salinity of early mineralizing fluids and total homogenization temperatures varies from 31.75-69.82 wt%(NaCl) and 230℃-600℃for No.18, those of Nongping are in the ranges from 170 to 490℃for total homogenization temperature and 2.89 wt%(NaCl)±for the salinity of early mineralizing fluids. In Xiaoxinancha, Hydrate and calcite daughter minerals are also discoveried, except for the same fluid inclusion type to the porphyry type; the total homogenization temperatures are in the ranges of 150℃-500℃for the North mine,150℃-390℃for the South mine,90℃-530℃for the granitic complex associated with the minerazition, and the salinity of early mineralizing fluids is in range from 9.45～20.15 wt%(NaCl), that is consistent with the salinity of the granitic complex (10.49-15.55 wt% NaCl), and the North mine began the mineralization at the depth of 4 km, the main mineralization depth is less 2 km. The salinity in the main mineralizing stage of study deposits all show low- and high-range two regions. The result of Laser raman mainly gives the gas composition of H2O, CO2, CH4, as well as N2 in Xiaoxinancha, Jinchang and Duhuanling. Calculatedδ18O values of H2O in the fluid in equilibrium with quartz and calcite are, respectively,+0.048 to +6.125%o for the South mine, -0.09 to +3.78%o for the North mine in Xiaoxinancha, and +4.1 to +7.14%o for No.0 in Jinchang (SMOW). TheδDH2O of inclusion fluids is -46 to -99.5%o,-38 to -82.5%o, and -73 to -86.62‰, respectively. The result indicated together that early mineralizing fluids of the five deposit are characterized by high temperature, high oxidation, mantle-derived and CO2-bearing, but high salinity for Jinchang, Duhuangling and Jiusangou whereas low salinity for Xiaoxinnach and Nongping. The fluids of three type deposit both experienced boiling; mixing with meteoric water at 450-400℃and 30 Mpa is precondition and fluid boiling at 350-200℃,15-5Mpa is the main mechanism of high sulfidation deposit; fluid boiling is the main mechanism for No.18 of Jinchang and Nongping, and the boiling condition is 450-300℃,35-10Mpa and 350-300℃,20-10Mpa, respectively; and fluid boiling at 370-400℃and 20 Mpa is the prerequisite of the mineralization in Xiaoxinancha, subsequently replacement and crystallization of mixed fluids with young crustal fluid at 15Mpa is the main mechanism of ore precipitation for the North mine whereas filling in fissures with the change of temperature and pressure at 400-200℃and 20-5 Mpa formed sulfide-quartz veins of the South mine, local immiscibility caused by adding of meteoric water at 5Mpa is responsible for middle and late mineralization in North and South mine. The main geochemical characteristics of the intermediate-acid igneous rocks associated with the mineralization are SiO2≥53%, high Al content (Al2O3≥17%), rich in LILE and LREE, and depleted in HREE; the initial Nd and Sr isotopic compositions of the igneous rocks in Jinchang, Jiusangou and Xiaoxinancha are in the ranges of 0.70414-0.70487 for (87Sr/86Sr)i, 0.51258-0.51264 for INd, and 1.56-2.88 forεNd(t); the Pb isotopic ratios of those range from 18.3481 to 18.4682 for 206Pb/204Pb, from 15.5438 to 15.6198 for 207Pb/204Pb, and from 38.2316 to 38.4177 for 208Pb/204Pb. The geochemistry together with petrochemistry is suggested that the igneous rocks are exhibit calc-alkaline and adakite signatures, and the product of the interaction betweem slightly depleted mantle and subducted fluids and melts.LA-ICP-MS U-Pb dating analysis for zircon grains in the igneous rocks together with 40Ar/39Ar laser probe of dating single quartz particle in sulfide veins indicate that the metallogenic epoch is 107±6 Ma for Duhuangling, the upper limit of metallogenic epoch is 110±1.1Ma for Jinchang,109.8±2.2Ma for Jiusangou,102.1±2.2Ma for Xiaoxinancha, 96.9±1.4Ma for Nongping; they are mainly focused on two stages, one is 110Ma, and the other is 100Ma, both related with the subduction of Izanagi Plate.Based with magmatic genesis, chronology of the intermediate-acid igneous rocks, and the fluid evolution, the dynamic setting and ore-forming process are summarized as following. As a result of Izanagi Plate NNW-trend subduction beneath paleo-Asian continent at 110Ma, mantle wedge contaminated and mixed with dehydration fluids and melts from the subducted oceanic crust, in the process, metal elements such as Cu, Au carried by the magma were gradually unloaded in the magma chamber to form supercritical ore-bearing fluid reservoir. With the crystallization of magma, the critical fluid boiled separating out lower-salinity vapor and hypersaline fluid in magma chamber; As the extension of the lithospheric mantle, the pre-produced magma and the ore-bearing fluids rose along the fractures, the former emplaced at shallow crust to form intermediate-acid igneous rocks, whereas the boiled hypersaline fluid took place "second boiling" and subsequently mixing with meteoric water by crystallization and filling to form No.18 veinlet-dissemination in Jinchang, the hypersaline fluid by condensed out from the lower-salinity vapor in magma chamber, fristly mixed with meteoric water and then "second boiling" in Duhuangling, Jiusangou and No.0 of Jinchang, respectively, which formed breccia pipe type (Cu-) Au orebody. When Izanagi Plate transformed to NW-trend subduction at 100Ma, adakitic magma and low and moderate salinity supercritical fluid generated as the above process in Nongping and Xiaoxinancha rose along the fractures, Nongping Au-Cu deposit was formed as the same way as No.18 of Jinchang. High temperature vapor from boiling was mixed with young crustal fluid, and the mixed fluids metasomatized wall rocks to form veinlet-dissemination orebody in the North mine, with the change of temperature and pressure, moderate temperature mineralizing fluids from boiling formed the South mine sulfide-quartz veins by filling, at middle and late ore-forming stage, local immiscibility was caused by adding of meteoric water, therefore, ore-rich fluids generated in the South mine deposited pure sulfide and breccia, high temperature vapor-like fluids generated in North mine in fissure formed melnicovite-dominated sulfide-quartz veins by filling, as such, the adakitic magma emplaced at shallow crust during the precipation of mineralizing fluids, hence, three types hydrothermal Au-Cu deposits of Late Mesozoic in Yanbian-Dongning area were formed by the similar dynamic setting but different fluids evolving process at the two stage.更多还原