【作者】 曲凯；

【导师】 董国臣；

【作者基本信息】 中国地质大学(北京) ， 地质工程， 2012， 硕士

【摘要】 木吉村斑岩铜（钼）矿位于华北克拉通中部、太行山的北段，是太行山构造－岩浆岩带一个重要的矿床。本文通过对木吉村斑岩铜（钼）矿床的地质特征、矿化蚀变与流体演化的详细研究，查明了矿床主要的矿化蚀变类型及空间展布特征，厘清了引起各期蚀变事件的热液流体记录。通过同位素年代学及地球化学研究，厘定成岩-成矿时限，并探讨含矿斑岩成因及其地质意义。最后利用流体包裹体显微测温、流体包裹体激光拉曼光谱分析以及H-O、He-Ar、S-Pb同位素示踪成矿流体来源并揭示成矿物质的沉淀机制，进而讨论其矿床成因及其制约因素，初步建立木吉村斑岩铜（钼）矿床的成矿模型。本文研究表明，木吉村矿床含矿岩体为闪长玢岩，具有典型的斑岩型矿床蚀变分带模式：矿床由蚀变中心强烈硅化的石英核，向外依次发育钾硅酸盐化，黄铁绢英岩化以及青磐岩化。矿床中主要赋存A脉、B脉、D脉三期热液流体，矿床发育的硅化核以及钾硅酸盐化与早期A脉的关系密切；Cu-Mo的矿化主要与从钾硅酸盐化蚀变向绢英岩化蚀变转换阶段的B脉有关；晚期的D脉造成以长石分解为主的黄铁绢英岩化蚀变。Mo矿化多以石英+辉钼矿±黄铜矿脉发育于钾硅酸盐化带中，Cu矿化主要以石英+黄铜矿±黄铁矿脉产出，分布在钾硅酸盐化带与黄铁绢英岩化带的过渡带中。含矿斑岩的锆石U-Pb年龄为144±1Ma，代表斑岩的结晶年龄；矿石中辉钼矿Re-Os等时线年龄为140.3±3.9Ma，代表矿床成矿年龄，相近的成岩和成矿年龄，表明木吉村斑岩铜（钼）矿的成岩-成矿是一个持续的岩浆-热液过程。含矿斑岩具有与埃达克岩类似的地球化学性质，结合Lu-Hf等同位素的研究，推测含矿斑岩的起源可能为拆沉的加厚下地壳部分熔融的环境。S-Pb同位素显示：矿床的成矿物质来源以下地壳为主混有少量幔源组分，研究认为金属Cu可能来自壳幔相互作用，金属Mo可能从华北克拉通富Mo古老下地壳的重熔过程中获得；H-O、He-Ar同位素表明：成矿流体早期主要为原生岩浆水，后期有大气降水的参与。早期流体可能来自深部岩浆房的出溶，出溶温度＞590℃，随着流体上侵到斑岩体底部，温度降低至392℃左右形成的A脉，造成矿床的早期蚀变，流体属于高温、高盐度的H₂O-CO₂体系；成矿期的B脉在331℃左右发生沸腾作用，气体大量逸出，伴随钼、铜等硫化物的大规模沉淀；成矿晚期D脉形成于264℃左右，黄铁矿大量沉淀，流体属于低温、低盐度的H₂O-NaCl体系。综上所述，深源流体的加入引起水岩反应加剧形成矿床早期蚀变，随着降温和减压过程，流体在浅部发生沸腾作用，导致铜、钼等成矿元素的大规模沉淀,最终形成了木吉村矿床。更多还原

【Abstract】 Mujicun porphyry copper-molybdenum deposit, located in the northern section of Taihang Mt., is animportant ore district of the Taihang tectonic-magmatic-metallogenic belt. This article describes itsgeological, alteration and mineralization characteristics. Based on detailed study, we recognized the primaryalteration zonation and their spatial distribution characteristics, identified the magmatic and hydrothermalevents which caused the alteration and mineralization. It figures out the dating of diagenesis andmetallogeny by studying the isotope chronology and geochemistry, and probe genesis of ore-formingporphyry and geological significance. By means of the micro-thermometry, Raman component analysis offluid inclusions and H-O, S-Pb, He-Ar isotope tracers, it also discusses the ore-forming fluids and mineralprecipitation mechanism, and further probes into the metallogenic constraints in order to establish thegenetic model of Mujicun porphyry copper-molybdenum deposit.Mujicun diorite-porphyry copper-molybdenum deposit displays a typical alteration-mineralizationpattern. From the center to the edge, it respectively develops silification, K-silicate, beresitization as well asprophylitization. The deposit mainly has three phase hydrothermal fluids （A/B/D veins）. Silification in thecore of the deposit with the potassium in the periphery is closely related to A veins formed in the early stage.The pyrite phyllic alteration zone is characterized by pyrite-chlorite–sericite which due to superposition ofmulti-stage alteration. The isotopic dating yields a LA-ICP-MS zircon U-Pb age of144.7±1Ma forcrystallization of diorite porphyry that hosts the Cu-Mo mineralization, five Re-Os molybdenite ages give aweighted average of140.3±3.9Ma, which suggests that the magmatism, porphyry-type and skarn-typemineralization should form in the continuous process. The ore-bearing porphyry and adakites have similargeochemical properties, and Isotopic Lu-Hf data all implies that the magma and mineralized elementsshould be mainly resulted in partial melting of lower crust.Isotopic S-Pb data implies that the mineralized elements should be mainly from lower crust, the Cuelement may from low crust and exchanged material with the upper mantle, and the Mo element resulted inpartial melting of the lower crust; isotopic He-Ar, H-O results show the ore-forming fluids envolved fromthe primary magmatic water in the early stage, then from the meteoric water in the late stage. The evidenceof the fluid inclusions shows that the early fluid exsolved from ancient depth magma chamber （thetemperature>590℃）. As the fluid intruded into the bottom of porphyry, when the temperature decreased toabout392℃, A vein formed, which belongs to the high temperature and high salinity H₂O-CO₂-NaClsystem. There were a lot of boiling inclusions in the fluid of principle metallogenic stage （B vein）, whichbelongs to the middle temperature, middle salinity H₂O-NaCl system. The inclusions in the late stage （Dvein）, with only broad water peak in the gas phase composition, show the features of H₂O-NaCl systemwith low temperature, low salinity and high density. We conclude that the additional deep source fluidswhich caused a series of mineralization intensify the water-rock interaction, bring heat source and mineralsfor the hydrothermal system, the fluids boiling at a shallow lever induces the precipitation of ore-formingelements, eventually forming the Mujicun porphyry copper-molybdenum deposit.更多还原