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1.
造山带具有复杂的动力学环境、俯冲交代历史和热力学状态,其地幔源区物质组成、熔融机制和岩浆产物明显不同于地幔柱和大陆裂谷带,因此造山带环境中与镁铁-超镁铁质岩浆有关的铜镍成矿作用有别于板内环境。本文综述了交代地幔源区与造山带铜镍成矿关系的新进展,重点聚焦于：(1)岩石圈与软流圈的贡献。成矿岩浆来源于上涌的软流圈驱动交代岩石圈地幔不同程度的混合熔融,其中后俯冲阶段岩浆产物的成矿作用最为普遍、规模最大;岩石圈地幔经历不同比例俯冲板片沉积物熔体(富钙沉积物)和低温蚀变洋壳流体交代,具有显著的富挥发分和碳酸盐特征。(2)幔源岩浆氧化还原状态对成矿的约束。显生宙造山带成矿初始岩浆(硫化物未发生饱和)可能普遍为氧化性岩浆,岩浆体系硫化物饱和前后存在氧逸度骤降,导致岩浆体系硫化物饱和时硫的溶解度呈指数级下降,直接触发硫化物熔离,或者为达到熔离创造低的硫溶解度条件,其中岩浆还原作用由碳质物在岩浆期的有效混染造成。(3)挥发分对岩浆硫化物的运载汇聚。挥发分显著降低熔体粘度,从而减小粘滞阻力对岩浆超压的消耗;岩浆在上侵减压过程中挥发分能够发生出溶-成核作用,形成大量低密度气泡并与硫化物液滴形成复合液滴,促进... 相似文献
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塔里木克拉通东北缘坡北、磁海等地二叠纪幔源岩浆活动形成了镍钴硫化物矿床和铁钴氧化物矿床，两者赋矿镁铁 超镁铁岩体的年龄相近(290~260 Ma)，主、微量元素和Sr Nd Hf同位素组成相似，分配系数接近的微量元素比值分布于相同趋势线，揭示两者岩浆源区相同，可能为俯冲板片流体交代的亏损地幔或软流圈地幔。两类矿床镁铁 超镁铁质岩中Co与Ni含量正相关，Co主要富集在基性程度高的岩石中；块状硫化物与磁铁矿矿石中Co与Ni相关性差，Co和Ni具有不同的富集机制，Co热液富集作用明显。北山镁铁 超镁铁杂岩体是地幔柱相关软流圈上涌，诱发俯冲板片交代的亏损岩石圈地幔发生部分熔融，形成的高镁母岩浆演化过程中经历壳源混染、硫化物饱和富集镍钴形成铜镍钴硫化物矿床，富铁母岩浆氧逸度高、富水，岩浆分离结晶磁铁矿、叠加热液作用富集钴，形成铁钴氧化物矿床。 相似文献
3.
四川丹巴县独狼沟金矿床是扬子陆块西缘金成矿带上的一个大型金矿床。矿体呈较高品位、较厚单体石英脉充填于构造破碎带之间,呈透镜状、似层状和层状产出,受断层构造影响极为明显,具热液矿床特征。矿物学、锆石U-Pb测年成果和稀土元素及微量元素等方面研究显示矿床主要受两期热液成矿作用影响,早期热液成矿作用形成以磁黄铁矿、黄铁矿等高温热液矿物为主的金矿体,时限限定于184.2±1.1 Ma;晚期热液成矿作用则形成以黄铜矿、叶碲铋矿等中温热液矿物为主的金矿体,时限限定于156.5±4.3 Ma。成矿流体氢氧同位素组成表明其与该时期区域岩浆作用存在一定关联而与区域变质作用关系不密切。S同位素组成反映出其来源为深部来源的属性,在Pb同位素组成的研究中也对这一观点进行了验证。成矿流体被认为是来自交代岩石圈地幔,在早侏罗世软流圈上涌事件影响下交代岩石圈地幔中挥发分上涌并活化上覆地层中的金,从而形成富金成矿流体并沿区域性深大断裂上移就位于地壳岩石地层中成矿。成矿动力学机制与区域碰撞造山后由挤压向伸展转换的大地构造背景密切关联,认为独狼沟金矿床为典型造山型金矿床。 相似文献
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5.
近年来,东北地区地幔热演化过程的相关研究相对较少,而揭示东北地区地幔热演化过程的有效手段就是研究东北地区玄武岩的成分变异特征.系统总结并对比了大兴安岭北段早白垩世玄武质岩石和新生代玄武质岩石的化学成分变异,以便揭示研究区中生代晚期-新生代的地幔热演化过程.大兴安岭北段早白垩世玄武岩在化学上属于拉斑玄武岩系列,以亏损Nb、Ta、Ti等高场强元素为特征,它们的La/Nb和La/Ta比值分别介于1.8~5.6和30~87,暗示岩浆起源于岩石圈地幔;它们的初始87Sr/86Sr值、εNd（t）和εHf（t）值分别介于0.704 5~0.706 9、-1.52~+3.60和+1.74~+7.77,表明岩浆源区属于弱亏损-弱富集的岩石圈地幔;早白垩世玄武质岩石的Sr-Nd-Pb同位素成分指示岩浆源区是由DM和EMⅡ型地幔端元混合而成,并经历了俯冲流体的交代.表明大兴安岭北段早白垩世玄武质岩浆源区为受早期俯冲流体交代的岩石圈地幔.新生代超钾质和钾质玄武岩具有Nb-Ta的弱负异常,87Sr/86Sr值为0.704 7~0.705 7、εNd（t）值为-6.3~-0.8,而地幔捕掳体具有Sr-Nd同位素亏损特征;钠质玄武岩具有Nb-Ta的正异常,较超钾质和钾质玄武岩具有低的87Sr/86Sr（0.703 5~0.704 2）以及高的εNd（t）值（+3.4~+6.6）,类似MORB的同位素组成,这些特征说明大兴安岭北段新生代玄武质岩石起源于软流圈地幔.综上所述,大兴安岭北段早白垩世和新生代玄武质岩石成分的差异不仅指示其岩浆源区从岩石圈地幔转变为软流圈地幔,更为重要的是它揭示了研究区地幔的热演化过程——从早白垩世高的地温梯度到新生代低的地温梯度的转变.这一过程也是岩石圈从中生代晚期到新生代逐渐增厚的过程.结合区域构造演化,可以得出大兴安岭北段早白垩世的玄武质岩浆作用与岩石圈伸展、减薄形成的裂陷作用相关,而新生代玄武质岩浆作用则与陆内裂谷作用相关. 相似文献
6.
胶东型金矿具有独特的成矿特征和成因机制,不同于国际已知金矿类型。为了深化认识控制矿床形成、变化和保存的地质要素及成矿过程,本文综合分析了胶东半岛晚中生代岩浆作用、构造活动和成矿特征及其构造背景,提出该区深部岩浆活动与地壳快速隆升及浅部变质核杂岩、张性断层、断陷盆地等伸展构造,共同控制了以Au为主的矿床成矿系列及成矿演化过程,谓之热隆-伸展成矿系统。阐明了晚中生代岩浆演化过程中的元素变化规律,发现了金矿化蚀变带中的低Ba、Sr含量异常及早白垩世胶东地壳中金丰度的显著变化,揭示了壳幔物质混合和伟德山型花岗岩岩浆活动对金成矿的贡献。认为这一成矿系统形成于古太平洋板块俯冲后撤的后俯冲伸展环境,由于软流圈上涌导致岩石圈地幔性质由富集向亏损转化,从而引起岩浆岩地球化学特征变化,地球化学元素重新调整,幔源含金流体与由重熔下地壳析出的壳源含金流体混合形成富金流体库,并产生贫金花岗岩。大规模岩浆活动为成矿元素的活化、迁移提供了热动力条件,上地壳伸展产生的断裂构造则为成矿元素聚集提供了良好空间。热隆-伸展成矿系统是中国东部晚中生代重要的成矿系统。 相似文献
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南秦岭地区在早古生代经历了大规模且持续性的碱性岩浆活动,其丰富的碱性岩石记录为探索深部地幔物质组成、壳内岩浆演化过程以及地球动力学演化机制提供了珍贵的地质载体。文章基于团队近期对于区域上典型碱性岩的地球化学分析结果和成因机制探讨,旨在对南秦岭早古生代碱性岩浆的源区和演化过程进行全面地约束。南秦岭早古生代碱性岩石类型主要包括一套成分从碱性玄武质向粗面质变化,呈双峰式分布的碱性火山- 侵入岩组合,以及少量与碱性硅酸岩（角闪辉石岩、正长岩）- 碳酸岩共生杂岩体。岩相学、年代学和地球化学证据显示这些碱性岩具有相同的地幔源区,其中演化程度较低的镁铁质端元记录了南秦岭早古生代交代岩石圈地幔的部分熔融事件,交代介质主要为硅酸盐熔体。演化程度较高的碱性岩端元（粗面- 正长岩、碳酸岩）来源于初始镁铁质组分的岩浆分异过程,其中粗面- 正长岩类主要受到以长石和单斜辉石为主的分离结晶作用控制。中生代热液交代过程主要记录在北大巴山东部和武当地块西南缘的早古生代碱性岩体中,热液交代作用促进了碳酸岩杂岩体中稀土元素的富集成矿。副矿物年代学和独居石Nd同位素特征反映了热液可能形成于岩体本身的再活化事件,晚三叠世秦岭地区的造山运动可能对此过程具有促进作用。 相似文献
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小秦岭、熊耳山金矿区中基性岩墙的岩石化学研究 总被引：4，自引：0，他引：4
通过对小秦岭、熊耳山金矿区岩墙的地质学、岩石学、地球化学的综合研究,查明该岩墙主要由辉绿岩和煌斑岩类组成,属钾质、中等铝质岩石并富含挥发份(>2%)的中基性岩。岩石富集LILE和LREE,与原始地幔相比具有明显的Ti、Nb负异常和Pb正异常。对形成岩墙的岩浆演化过程研究后认为,其岩浆演化大致分为三个关键环节:(1)早中生代时期富钾、富硅熔体交代秦岭造山带岩石圈地幔,导致具富集地幔特征的玄武质岩浆的形成;(2)玄武质岩浆与区域热效应形成的花岗质岩浆的混合(混染)作用;(3)混合岩浆在深部热力学和动力学机制下的结晶分异和连续演化过程。 相似文献
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前人对金沙江-红河构造带上的煌斑岩研究工作主要集中在南段哀牢山地区.对构造带中段鲁甸地区新发现的煌斑岩脉进行了锆石U-Pb年代学和全岩地球化学研究.结果表明,煌斑岩形成时代为始新世末期,与滇西新生代富碱斑岩高峰期一致.鲁甸煌斑岩具有高钾、富碱、高Mg#,富集大离子亲石元素（LILE）和轻稀土元素（LREE）,亏损高场强元素（HFSE,尤其是Ta-Nb-Ti）的特征.其岩浆源区为受俯冲流体和熔体交代的岩石圈地幔,源区组分为含金云母的尖晶石相方辉橄榄岩.结合同期的镁铁质火山岩和富碱斑岩研究成果,滇西区域的岩石圈地幔富集过程可能为元古宙时期与罗迪尼亚超大陆聚合相关的俯冲作用.始新世时期,在印度和亚洲大陆碰撞过程中,金沙江-红河构造带的富集岩石圈地幔发生拆沉或对流减薄,软流圈物质上涌,引发富集的岩石圈地幔部分熔融,形成本期煌斑岩岩浆作用. 相似文献
10.
幔源玄武岩及地幔捕虏体中所含的地幔流体挥发分对于认识岩浆源区特征及岩石圈地幔演化具有重要意义。本文对东北地区双辽新生代玄武岩及其携带的地幔捕虏体中流体挥发分进行研究,探究地幔流体特征与来源。双辽玄武岩橄榄石斑晶和地幔捕虏体内发育早期、晚期两类流体包裹体,早期流体包裹体中的挥发分代表矿物形成时捕获的岩浆原始流体挥发分,主要在高温段(600~1200℃)释出,晚期流体包裹体中的挥发分代表矿物形成后捕获的交代或蚀变流体挥发分,主要在低温段(200~600℃)释出。地幔捕虏体原始流体挥发分主要为H_2O、CO和H_2,其次为CO_2,并含有少量CH_4等烃类。地幔捕虏体交代流体挥发分与双辽玄武岩橄榄石斑晶原始流体挥发分相似,主要为CO_2和H_2O,其次为CO和H_2,含有少量烃类。地幔捕虏体原始流体挥发分、交代流体挥发分及玄武岩橄榄石斑晶原始流体挥发分中,CO_2和烃类碳同位素均具有有机成因特征,表明岩石圈地幔及玄武岩岩浆源区内均存在有机质热解产物的混入,玄武岩岩浆源区及岩石圈地幔交代流体中的有机成因挥发分主要来自于俯冲太平洋板片之上的沉积有机质。双辽玄武岩斜长石斑晶和基质流体挥发分含量较高,主要为H_2O和CO_2,相对于橄榄石原始流体挥发分具有较轻的CO_2碳同位素组成,这种现象表明岩浆上升过程中发生了明显的脱气作用。 相似文献
11.
Understanding the geochemical behavior of chalcophile elements in magmatic processes is hindered by the limited partition coefficients between sulfide phases and silicate melt, in particular at conditions relevant to partial melting of the hydrated, metasomatized upper mantle. In this study, the partitioning of elements Co, Ni, Cu, Zn, As, Mo, Ag, and Pb between sulfide liquid, monosulfide solid solution (MSS), and hydrous mantle melt has been investigated at 1200 °C/1.5 GPa and oxygen fugacity ranging from FMQ−2 to FMQ+1 in a piston-cylinder apparatus. The determined partition coefficients between sulfide liquid and hydrous mantle melt are: 750–1500 for Cu; 600–1200 for Ni; 35–42 for Co; 35–53 for Pb; and 1–2 for Zn, As, and Mo. The partition coefficients between MSS and hydrous mantle melt are: 380–500 for Cu; 520–750 for Ni; ∼50 for Co; <0.5 for Zn; 0.3–6 for Pb; 0.1–2 for As; 1–2 for Mo; and >34 for Ag. The variation of the data is primarily due to differences in oxygen fugacity. These partitioning data in conjunction with previous data are applied to partial melting of the upper mantle and the formation of magmatic-hydrothermal Cu–Au deposits and magmatic sulfide deposits.I show that the metasomatized arc mantle may no longer contain sulfide after >10–14% melt extraction but is still capable of producing the Cu concentrations in the primitive arc basalts, and that the comparable Cu concentrations in primitive arc basalts and in MORB do not necessarily imply similar oxidation states in their source regions.Previous models proposed for producing Cu- and/or Au-rich magmas have been reassessed, with the conclusions summarized as follows. (1) Partial melting of the oxidized (fO2 > FMQ), metasomatized arc mantle with sulfide exhaustion at degrees >10–14% may not generate Cu-rich, primitive arc basalts. (2) Partial melting of sulfide-bearing cumulates in the root of thickened lower continental crust or lithospheric mantle does not typically generate Cu- and/or Au-rich magmas, but they do have equivalent potential as normal arc magmas in forming magmatic-hydrothermal Cu–Au deposits in terms of their Cu–Au contents. (3) It is not clear whether partial melting of subducting metabasalts generates Cu-rich adakitic magmas, however adakitic magmas may extract Cu and Au via interaction with mantle peridotite. Furthermore, partial melting of sulfide-bearing cumulates in the deep oceanic crust may be able to generate Cu- and Au-rich magmas. (4) The stabilization of MSS during partial melting may explain the genetic link between Au-Cu mineralization and the metasomatized lithospheric mantle.The chalcophile element tonnage, ratio, and distribution in magmatic sulfide deposits depend on a series of factors. This study reveals that oxygen fugacity also plays an important role in controlling Cu and Ni tonnage and Cu/Ni ratio in magmatic sulfide deposits. Cobalt, Zn, As, Sn, Sb, Mo, Ag, Pb, and Bi concentrations and their ratios in sulfide, due to their different partitioning behavior between sulfide liquid and MSS, can be useful indices for the distribution of platinum-group elements and Au in magmatic sulfide deposits. 相似文献
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《地学前缘(英文版)》2022,13(2):101339
The current margins of the North China and Yangtze Cratons provide arguably the best examples globally of anomalously high mineral endowment within a 100 km buffer zone, hosting 66 diverse world-class to giant ore systems that help explain China’s premier position as a producer of multiple metal and mineral commodities. After the cratonization of these crustal blocks during the Neoarchean-Paleoproterozoic, with incorporation of iron ores on assembled micro-block margins, the margins of the cratons experienced multiple convergence and rifting events leading to metasomatism and fertilization of their underlying sub-continental lithospheric mantle. The rifted margins with trans-lithosphere faults provided pathways for Cu-Au (Mo-W-Sn)-bearing felsic to Ni-Cu-bearing ultrabasic intrusions and REE-rich carbonatite magmas, and for the development of marginal sedimentary basins with both Cu-Pb-Zn-rich source units and reactive carbonate or carbonaceous host rocks. There was diachronous formation of hydrothermal orogenic gold, antimony, and bismuth systems in the narrow orogenic belts between the cratons. Complexity in the Mesozoic Paleo-Pacific subduction systems resulted in asthenosphere upwelling and lithosphere extension and thinning in the North China Craton, leading to anomalous heat flow and formation of orogenic gold deposits, including those of the giant Jiaodong gold province on its north-eastern margin. These gold deposits, many of which formed from fluids liberated by devolatilization of previously metasomatized sub-continental lithospheric mantle, helped propel China to be the premier gold producer globally. The thick sub-continental lithospheric mantle of the cold buoyant cratons helped the preservation of some of the world’s oldest porphyry-skarn and epithermal mineral systems. Although craton margins globally control the formation and preservation of a diverse range of mineral deposits, China represents the premier example in terms of metal endowment due to the anomalous length of its craton margins combined with their abnormally complex tectonic history. 相似文献
13.
Olympic Dam-type iron-oxide copper–gold deposits are widely recognised in terrains with significant Palaeoproterozoic to
Mesoproterozoic granitic magmatism. Most researchers favour a magmatic association for these deposits, but none of the 100–2000 Mt
recognised copper-bearing deposits has a spatial and/or temporal relationship to an intrusive body of sufficient dimensions
to produce the hosting giant breccia and/or hydrothermal systems. In other words, if the recognised ore-bodies are magmatic-hydrothermal,
they must be classified as distal deposits. The magnetite–copper–phosphate–rare earth element pipe-like carbonatite-hosted
orebody at Loolekop, within the larger Phalabowra Carbonatite Complex, has many features to suggest that it represents an
end member of the Olympic Dam-type deposit class hosted within its magmatic source rock. It (1) falls broadly within the appropriate
age range, (2) has a similar giant size and low copper grade, (3) is dominated by magnetite, (4) has sulfur-poor copper-sulfide
minerals and lacks iron sulfides, (5) is silica-poor, and (6) is enriched in REE, particularly LREE, as well as P, F, U and
Th. As an end member of the Olympic Dam-type deposits, the Loolekop orebody can help explain the common siting of the deposits
at craton edges or other lithospheric boundaries, where decompression melting of metasomatised mantle can produce volatile-rich
alkaline melts (rich in REE, P, F, etc.). Such melts are capable of generating sulfur-deficient volatiles enriched in copper
and gold, among other elements, as well as phreatic breccia pipes and associated intense metasomatism, the most common features
of the Olympic Dam-type deposits.
Received: 27 July 2000 / Accepted: 2 October 2000 相似文献
14.
中国大陆环境斑岩型矿床：基本地质特征、岩浆热液系统和成矿概念模型 总被引：49，自引：5，他引：44
中国大陆环境斑岩型矿床包括斑岩型Cu(-Mo、-Au)、斑岩型Mo、斑岩型Au和斑岩型Pb-Zn等矿床类型,主要产出于青藏高原大陆碰撞带、东秦岭大陆碰撞带和中国东中部燕山期陆内环境,在地球动力学背景、深部作用过程、岩浆起源演化、流体与金属来源等方面与岩浆弧环境斑岩型矿床存在重要差异.在大洋板块俯冲形成的岩浆弧,主要发育斑岩Cu-Au矿床或富金斑岩Cu矿(岛弧)和斑岩Cu-Mo及斑岩Mo矿床(陆缘弧).相比,在大陆碰撞带,晚碰撞构造转换环境发育斑岩Cu、Cu-Mo和Cu-Au矿床,矿床受斜交碰撞带的走滑断裂系统控制,后碰撞地壳伸展环境则主要发育斑岩Cu-Mo矿床,矿床受垂直于碰撞带的正断层系统控制;在陆内造山环境,早期发育斑岩Cu-Au矿床,晚期发育斑岩Pb-Zn矿床,它们主要沿古老的但再活化的岩石圈不连续带分布,受网格状断裂系统控制;在后造山(或非造山)伸展环境,则大量发育斑岩Mo矿和斑岩Au矿,它们则主要围绕大陆基底-克拉通(或地块)边缘分布,受再活化的岩石圈不连续带控制.大陆环境斑岩Cu(-Mo,-Au)矿床的含矿斑岩多为高钾钙碱性和钾玄质,以高钾为特征,显示埃达克岩地球化学特性.岩浆通常起源于加厚的新生镁铁质下地壳或拆沉的古老下地壳.上地幔通过三种可能的方式向岩浆系统供给金属Cu(和Au):①提供大批量的幔源岩浆并底垫于加厚下地壳底部,构成含Cu岩浆的源岩;②提供小批量的软流圈熔体交代和改造下地壳,并诱发其熔融;③与拆沉的下地壳岩浆熔体发生反应.大陆环境含Mo岩浆系统高SiO_2、高K_2O,岩相以花岗斑岩为主,花岗闪长斑岩次之,既不同于Climax型,又有别于石英二长斑岩型Mo矿床,岩浆起源于古老的下地壳.金属Mo主要为就地熔出,部分萃取于上部地壳.大陆环境含Pb-Zn花岗斑岩多属铝过饱和型,与S型花岗岩相当,以高δ~(18)O(>10‰)和高放射性Pb为特征,Sr-Nd-Pb同位素组成反映其来源于中下地壳的深熔作用,金属Pb-Zn主要来源于深融的壳层.大陆环境含Au岩浆系统以富B花岗闪长斑岩为主,常与矿前闪长岩密切共生.Sr-Nd-Pb同位素显示,含Au岩浆主要来源于上部地壳,但曾与幔源岩浆发生相互作用.金属Au部分来源于上地壳,部分来源于地幔岩浆.大陆环境斑岩型矿床显示各具特色的蚀变类型和蚀变分带,其中,斑岩型Cu(-Mo,-Au)矿热液蚀变遵循Lowell and Guilbert模式;斑岩型Mo矿主要发育钙硅酸盐化、钾硅酸盐化和石英-绢云母化;斑岩型Pb-Zn矿主要发育绿泥石-绢云母化和绢云母-碳酸盐化,缺乏钾硅酸盐化;斑岩型Au矿强烈发育中度泥化.斑岩型矿床的成矿流体初始为高温、高fO_2、高S、富金属的岩浆水,由浅成侵位的长英质岩浆房在应力松弛环境下出溶而来,晚期有天水不同程度地混入.Cu、Mo、Pb-Zn通常沉淀于流体分相和流体沸腾过程中,而Au则主要沉淀于岩浆-热液过渡阶段. 相似文献
15.
Continental China is a mosaic of numerous tectonic blocks, which amalgamated from Neoarchean to Cenozoic broadly coeval with the cycles of global supercontinents such as Kenorland, Columbia, Rodinia, Gondwana, and Pangaea. By reviewing the long-lasting geological evolution in the different tectonic blocks, it reveals that more than two episodes of tectonic events, including accretionary and collisional orogeny, and dismantling, as well as mantle plume, occurred successively or simultaneously within a single tectonic belt. This is called superimposed orogeny in this study. Examples of the dominant types of superimposed orogeny in China include: (1) Cenozoic continental collision superimposed on Paleo- to Mesozoic accretionary orogeny in the Tibet and Sanjiang orogenic belts; (2) Reactivation of Paleozoic accretionary orogen in later Mesozoic oceanic subduction in the eastern part of Qinling–Qilian–Kunlun and Central Asian orogenic belts; (3) Mesozoic oceanic subduction under the paleo-suture in the South China Block; (4) Mesozoic demantling along the Paleo- and Neoproterozoic, and Paleozoic sutures in the eastern part of North China Craton; and (5) mantle plume rising through metasomatized lithospheric mantle or stagnant oceanic slab in the Emeishan large igneous province. A comprehensive review of the spatial-temporal distribution of ore deposits and their salient features shows that the superimposed orogeny has exerted significant control on metallogeny in China. The giant porphyry and skarnore deposits, as well as orogenic gold deposits were preferentially formed along previous tectonic suture, craton margin, and arc during later orogenesis due to the remobilization of previously enriched metals. Superimposed orogeny has reworked the lithospheric structure with concomitant granitoid-associated metallogeny. The mixing of magmas from juvenile lower crust, ancient lower crust, and middle crust, which tends to induce the different mineralization of Cu–Au, Mo, and Pb–Zn–W–Sn deposits respectively, was considered to generate a wide variety of combinations of metal species. The superimposed orogeny caused the overlapping of diverse genetic types of deposit formed in different tectonic periods in the same tectono-metallogenic belt. The stratiform ore deposit, including BIF, VMS, SEDEX, or sedimentary sulfide layers, formed from Neoarchean to Paleozoic, were modified by later mineralization, resulting in the enrichment of the various metal species and enhancement of ore resources. This study brings up the concept of composite metallogenic system to summarize the regional metallogeny driven by superimposed orogeny. The composite metallogenic system was dominantly characterized by the multi-episodic and diverse mineralization concomitant with one or more features, including mineralization evolved from the previous metal enrichment, later overlapping or modification on previous ore belt, and diversifying of metal species derived from reworked lithosphere. 相似文献
16.
Widespread Mesozoic Au and other hydrothermal polymetal (Zn–Pb–Cu–Mo–Ag–W–Fe–REE) deposits or smaller prospects occur in association with ancient mobile belts surrounding and cutting through the North China Carton (NCC). Among these, the gold ores of the Jiaodong Peninsula, Shandong Province, eastern NCC, represent the largest gold district in China. However, the genesis of these important gold mineralizations has remained controversial, notably their relationships to widespread mafic magmatism of alkaline affinity.The ore bodies of the Guocheng gold deposit on the Jiaodong Peninsula are fracture-controlled, sulfide-rich veins and disseminations, formed contemporaneously with abundant dolerite, lamprophyre and monzonite dikes at ca. 120 Ma. Dolerite dikes possess mantle-like major element compositions and alkaline affinity, associated with prominent subduction-type trace element enrichments. The dikes show petrographic and chemical evidence of magma mixing that triggered exsolution of magmatic sulfide and anhydrite crystallization, preserved as primary inclusions in phenocrysts. LA-ICP-MS analysis of magmatic sulfide inclusions demonstrates that metal abundance ratios (Ag, As, Au, Bi, Co, Cu, Mo, Ni, Pb, Sb, Zn) largely correspond to those of both unaltered bulk rock and bulk ore. Together with identical Pb isotope ratios of dolerite and bulk ore, this demonstrates that gold mineralization and dolerite dikes share a common source.Lead isotope signatures of the ore sulfides are much less radiogenic (17.08 < 206Pb/204Pb < 17.25, 15.41 <207Pb/204Pb < 15.45, 37.55 < 208Pb/204Pb < 37.93) relative to the Pb signature of Phanerozoic convecting mantle and plot to the left of the Geochron and above the MORB-source mantle Pb evolution line. Forward Monte Carlo simulations indicate three events for the U–Th–Pb isotope evolution: (1) late Archean formation of juvenile crust is followed by (2) subduction of this aged crust at ca. 1.85 Ga along with the assembly of Jiao–Liao–Ji mobile belt (suture within Columbia supercontinent). This late-Archean subducted crust released fluids with drastically reduced U/Pb that metasomatized the overlying depleted mantle, which formed cratonic lithospheric mantle. This metasomatized lithospheric mantle was (3) tapped in response to early Cretaceous extensional tectonics affecting notably the eastern margin of the NCC to generate mafic magmas and associated gold mineralization at Guocheng. Similarly non-radiogenic uranogenic Pb isotope data characterize the contemporaneous mafic dikes and gold deposits in the entire Jiaodong Peninsula, suggesting that our genetic model applies to the entire Jiaodong gold district.We propose that early Cretaceous melting of subcontinental lithospheric mantle metasomatized by subduction fluids during Paleoproterozoic amalgamation of terranes to the eastern NCC along with Columbia supercontinent assembly generated mafic magmatism and associated gold deposits. Given the conspicuous association of Phanerozoic hydrothermal ore deposits associated with reactivated Paleoproterozoic mobile belts, we envisage that our genetic model, which largely corresponds to that which is proposed for the Bingham porphyry-Cu–Au–Mo deposit, USA, may explain much of the magmatic-hydrothermal activity and associated ore formation all around the NCC. 相似文献
17.
克拉通边缘岩石圈金属再富集与金-钼-稀土元素成矿作用 总被引：11，自引：6，他引：5
克拉通是大规模成矿的重要构造环境,其边缘产出了众多世界级规模的金、钼、稀土元素矿床。然而,克拉通如何控制巨型矿床的形成与分布尚不十分清楚。文章基于作者和前人的研究成果,探讨了扬子和华北克拉通岩石圈早期金属富集与后期金属活化问题。在全球范围,多数克拉通在其形成之后长期保持稳定,但部分克拉通(如华北、扬子)在克拉通化之后又经历了早期(元古代)增生与晚期(中生代—新生代)改造。在克拉通化及其之后,处于克拉通边缘的大洋岩石圈或克拉通块体间的有限洋盆发生板片俯冲,释放出含金属组分(REE、Cu、Au)的富CO2流体,交代亏损的大陆岩石圈地幔(SCLM),并使之发生交代和金属再富集。俯冲诱发的弧岩浆在大陆下地壳底侵可形成新生下地壳,伴随着少量硫化物的堆积而发生金属(Au、Cu)再富集。由于克拉通相对稳定,新生下地壳在进变质脱水过程中仍能保存部分金属,释放的(含Au)变质流体很可能被封存或固结在地壳的某个部位。在克拉通破坏改造期,软流圈上涌改变克拉通SCLM热结构并诱发其部分熔融,产生富REE的碳酸岩熔体和富水的基性岩浆(如煌斑岩)。前者在浅部地壳侵位并出溶成矿流体,形成碳酸岩型REE矿床;后者在深部地壳脱挥发分(H2O+CO2),诱发新生下地壳重熔和含Au硫化物(和/或含Au流体囊)活化,形成富Au岩浆系统或流体系统。这些深地壳熔/流体沿克拉通边界或岩石圈不连续运移至上部地壳,岩浆系统直接出溶成矿流体,形成以斑岩体为中心的斑岩型Au矿,含Au富CO2流体流沿断裂网络系统活动并沉淀金属,形成石英脉型和蚀变岩型Au矿。伴随克拉通破坏改造,克拉通边界断裂或基底断裂重新活化,并诱发古老下地壳熔融,产生含Mo岩浆系统。这个理论框架不同于已有的造山带成矿理论模式,它解释了克拉通边缘异常富集Au、Mo、REE矿床及其成矿规律,可用于类似克拉通地区的成矿预测。 相似文献
18.
通过锆石U-Pb定年、全岩主微量元素、Sr-Nd-Pb和锆石Hf同位素测试, 对滇西姚安Au-Pb-Ag矿床含矿正长斑岩和粗面岩的地球化学特征进行了分析, 系统探讨了其岩浆起源和演化过程.正长斑岩和粗面岩的锆石U-Pb年龄分别为33.8±0.42 Ma和33.9±0.60 Ma, 它们与同时代滇西镁铁质火山岩和煌斑岩具有相似的稀土和微量元素配分模式和Sr-Nd-Pb同位素组成, 而与区内同时代加厚地壳来源的富碱埃达克质岩石存在Sr-Nd-Pb-Hf同位素组成的明显差异.全岩SiO2与主微量元素关系指示正长斑岩和粗面岩总体上可由矿区内同时代的基性岩浆岩分异演化而来, 表明它们与这些基性岩浆岩起源相似, 较高的Rb/Sr(≥ 0.1)和较低的Ba/Rb(< 20)比值, 指示其源区为富金云母富集地幔, 较低的εHf和古老的模式年龄暗示源区的交代富集发生在中元古代.姚安富碱岩浆活动与矿化关系密切.正长斑岩和粗面岩较滇西镁铁质火山岩和煌斑岩具有稍高的初始Pb同位素组成, 暗示岩浆可能遭受了地壳混染, 从而提高了母岩浆中的金属含量, 增强了岩浆成矿潜力; 适中的氧逸度利于Au富集; 角闪石分离结晶和较多黑云母发育指示母岩浆含水量较高, 利于成矿流体的形成.这些特征综合起来为矿化发育提供了有利条件. 相似文献
19.
张家坪子金矿地质特征初探 总被引：2，自引：0，他引：2
四川省冕宁县张家坪子金矿产于T2.3的一套绿片岩、变质玄武岩、火山角砾岩夹蚀变交代白云岩中的矿床,受金河—程海深断裂影响,金矿化主要位于蚀变带内.经燕山中晚期深源的富Au的多金属地幔流体侵入,在构造有利部位发生交代作用,使Au进一步富集,至喜山期,又发生一次富金热液作用,在有利部位进一步加富而形成矿体. 相似文献
20.
The devolatilization model of the metasomatized lithospheric mantle without pre-enriched gold has been proposed to account for the giant gold mineralization. An excellent example is the world-class Jiaodong gold province with >5000 tonnes Au resources in the eastern North China Craton. The auriferous fluid transport and gold enrichment during wallrock alterations are two vital processes to determine the giant gold mineralization formation in this province. However, the effects of the fluid-rock interaction with alterations on the auriferous fluid transport and gold enrichment still keep poor understanding, which leads the above model to be imperfect. The giant Jiaojia goldfield in this province recorded a wallrock alteration evolution from K-feldspar alteration to pyrite-sericite-quartz alteration, and some parts of the latter can become gold orebodies when the gold grade is >1 ppm. This study conducts thermodynamic fluid-rock interaction modeling to reveal auriferous fluid transport and coupled relationship between gold enrichment and alteration mineral assemblage based on the alteration-mineralization and ore fluid characteristics of the goldfield. The modeling of fluid-rock interaction with cooling indicates the transformation of Au-Cl complexes to Au-S complexes combined with the total sulfur concentration decrease by pyrite precipitation when cooling from ∼460 °C can trigger the dispersive gold precipitation, which should hinder the gold long-range transport to lower ambient temperature. The high oxygen fugacity at >400 °C can enhance Au-Cl complexes stability, and the low pH can maintain high total sulfur concentration in the auriferous fluid, both of which facilitate the long-range gold transport to a lower-temperature environment. The auriferous fluid would acquire higher pH by the buffering of feldspars or sericite, which was beneficial for the high-efficiency precipitations of pyrite and gold. The ankerite-siderite assemblage without pyrophyllite in the pyrite-sericite-quartz alteration zone indicates that a cumulative fluid to rock mass ratio (f/r) of 3.8–4.8 should be needed for the transformation from K-feldspar alteration to pyrite-sericite-quartz alteration according to the fluid-rock interaction modeling at 300 °C and 2000 bar. In the case of auriferous fluids with ≤200 ppb Au concentration, the single fluid-rock interaction can only elevate the gold grade to ≤0.69–0.87 ppm in the pyrite-sericite-quartz alteration zone at f/r 3.8–4.8. Therefore, the fracture-induced fluid flow coupled with fluid-rock interaction is proposed to the prerequisite to elevate the gold grade to >1 ppm in the pyrite-sericite-quartz alteration zone. The metasomatized lithospheric mantle volume for the required ore fluid and Au in the Jiaodong province is estimated according to the modeling results and alteration-mineralization characteristics, which provides a link between the mantle without abnormal Au enrichment and the alteration-mineralization processes. 相似文献