新疆北山西段红石山镁铁—超镁铁质岩带成岩成矿作用

发布时间：2018-03-20 02:32

  本文选题：红石山镁铁-超镁铁质岩　切入点：铜镍矿床　出处：《中国地质大学》2017年博士论文　论文类型：学位论文

【摘要】：新疆北山西段红石山地区发育了一系列二叠纪镁铁-超镁铁质岩和红石山、红镍山镍矿床及一些矿化异常。矿化多以稀疏浸染状为主,品位较低,近年来找矿工作未有太大突破。此外该地区成岩动力学背景存在争议,岩浆起源与演化研究不足,硫化物熔离作用未有系统研究,矿化规律总结薄弱。本论文旨在详细野外地质调查的基础上,通过系统岩石学、矿物学、年代学和地球化学手段深刻认识成岩动力学背景和成岩成矿作用,总结矿化规律,建立成矿模式,提高找矿理论上认识,为下一步勘探工作提供科学依据。镁铁-超镁铁质岩沿着红柳河-依格孜塔格深大断裂南缘成群成带产出,大多侵位于下石炭统红柳园组和下寒武统双鹰山组一套变质岩中。主要岩石类型有苏长岩、辉长岩、橄榄辉长岩、橄长岩、单辉橄榄岩、辉橄岩、纯橄岩等。含矿晚期辉橄岩和纯橄岩相发育在岩体中心部位偏下。岩石低Si高Mg,低碱贫Ca,多属亚碱性、拉斑玄武系列,整体稀土含量偏低,轻重稀土分异不太明显。岩石富集Zr、Hf、Th、U等高场强元素,亏损Rb,Nb,Ta,同时具明显的Pb,Sr正异常。PGE含量主要受控于岩浆作用,与后期热液事件关系不大。成岩过程以结晶分异为主,同时发生了明显的地壳混染,后期遭受了强烈的蚀变和风化作用。橄榄石主要为贵橄榄石,最高Fo值90.3。单斜辉石主要为普通辉石和透辉石,斜方辉石主要为斜顽辉石。橄榄辉长岩和橄长岩中的早于硅酸盐矿物结晶,包裹于橄榄石和辉石中的铬铁矿颗粒受后期改造最微弱,最能代表原始铬铁矿,因而可用来反演母岩浆性质。镁铁质岩浆作用有两期:大部分岩体侵位于早二叠世(271-284Ma);蚕头山岩体、旋窝岭岩体、罗东镁铁质岩脉侵位于晚二叠世(261-266Ma)。相关的中酸性岩侵位于早二叠世(271-280Ma)。早二叠世镁铁质岩的Rb-Sr同位素组成较宽,(87Sr/86Sr)i为0.702949-0.712714,初始Nd较低且集中(143Nd/144Nd)i=0.512219-0.512843,εNd(t)=-1.29-11.2。锆石176Hf/177Hf=0.28274-0.28282,计算的εHf(t)=4.9-7.8,一阶段模式年龄TDM1=618-742Ma。镁铁质岩地幔源区为亏损地幔,同时受到了EMII改造。北山地幔源区受改造影响较东天山、中天山地区明显。早二叠世镁铁质岩母岩浆起源于受俯冲流体交代改造的亏损地幔在相对浅的深度发生16.5-17.0%的部分熔融,其具高镁(14.5%wt.%MgO)、高温(1368℃)、含水特征。晚二叠世岩石母岩浆具类似性质,只是源区受改造程度更高,熔融程度稍低(14.3%)。综合镁铁质侵入岩、玄武岩、中酸性岩石的岩石学、矿物学、年代学和地球化学特征及与东天山、塔里木地区相关岩石的对比,北山地区早二叠世大规模镁铁-超镁铁质岩浆作用并非形成于岛弧环境,亦非地幔柱成因,而更可能是后碰撞伸展环境下板片断裂造成的软流圈地幔上涌。部分岩浆上侵至地表形成钙碱性玄武岩、英安岩等火山岩组合。此外幔源岩浆与新生地壳脱水熔融岩浆的混合,同时裹入古老地壳物质,除了形成A型花岗岩外,还形成了I型、S型花岗岩组合。镁铁-超镁铁质岩浆作用一直持续到晚二叠世。矿体主要呈悬浮状产于辉橄岩底部。3D磁法反演显示岩浆通道方向为南西深部至北东浅部。Se、Te等中低温元素与矿体产出吻合可能反映了低温热液作用对矿化富集有一定贡献。珠滴状硫化物显示岩浆演化过程中发生了硫化物熔离,Cu/Zr比值、PGE含量和橄榄石成分模拟表明橄榄石发生4%结晶时硫已达饱和并发生熔离,熔离程度为0.015-0.02%,形成低品位浸染状矿化。坡北岩带在橄榄石结晶之前即发生硫化物熔离,且熔离一直持续到橄榄石结晶过程中,分别形成高品位贯入式脉状矿化和低品位浸染状矿化。硅质钙质地层混染有利于硫化物熔离,但贡献有限。岩浆早期铬铁矿、橄榄石的结晶导致岩浆体系中FeO含量和硫溶解度的降低,促使硫饱和并发生熔离。综合镁铁质岩石产出构造背景、岩浆源区及性质、硫化物熔离及岩浆侵位序次,北山岩浆型铜镍矿床的成矿模式为“深部熔离+就地熔离多期次脉动成矿”。深大断裂与次级断裂的交汇部位是寻找镁铁质岩的构造条件。岩相分异明显,含有辉橄岩等超镁铁质岩相,其橄榄石中Ni含量不能太高,这些地质信息在找矿勘探中应该重点关注。拉斑玄武质母岩浆、岩体低Ti高Mg、高m/s和m/f、母岩浆MgO含量大于11.5%、部分熔融程度不低于12-15%、固结指数SI大于40、TiO2含量小于1%,均是有利含矿的地球化学指标。
[Abstract]:The western part of Xinjiang Beishan Hongshishan area developed a series of Permian mafic ultramafic rocks and red hill, red hill nickel nickel deposit and mineralization anomalies. Mineralization in sparse disseminated, low grade ore prospecting work in recent years not much breakthrough. In addition the diagenetic dynamic controversial background, the origin and evolution of magma, the sulfide liquation mineralization rules no system research, this paper aims to summarize the weak. Based on detailed field geological survey, through systematic mineralogy, petrology, geochronology and geochemistry means a profound understanding of diagenetic dynamics background and mineralization, summed up the mineralization regularity and metallogenic mode is established, improve prospecting theory knowledge, and provide scientific basis for the next exploration. Mafic ultramafic rocks along the southern margin of the Hongliuhe - in lattice MUZTAG deep faults in groups with output, most invasion Located in the lower Carboniferous hongliuyuan formation and lower Cambrian metamorphic rocks in a group of Eagle mountain. The main rock types include Su Changyan, gabbro, olivine gabbro, troctolite, peridotite, harzburgite, dunite. Ore late harzburgite and dunite facies developed in the rock mass center a partial rock. Low Si and high Mg, low alkali and poor Ca, belong to sub alkaline and tholeiitic series, the overall low content of rare earth elements, REE fractionation is not obvious. The enrichment of Zr, Hf, Th, U and other high field strength elements, the loss of Rb, Nb, Ta, at the same time with obvious Pb the content of.PGE, Sr positive anomaly is mainly controlled by magma, and it is a little late hydrothermal event. The diagenetic process dominated by crystallization differentiation, and has significant crustal contamination, later suffered a strong alteration and weathering. Olivine is mainly of olivine, clinopyroxene 90.3. the highest Fo value is mainly ordinary augite and diopside, trapezius Pyroxene is mainly clinoenstatite. Olive gabbro and troctolite in early crystallization in silicate minerals, chromite particles in olivine and pyroxene in the post transformation of the weak, the most representative of the original chromite, and thus can be used to inverse the parent magma properties. Mafic magmatism have two stages: most rock mass emplaced in the early Permian (271-284Ma); silkworm head mountain rock xuanwoling mafic ultramafic intrusion, Luo Dongmei iron dikes emplaced in the Late Permian (261-266Ma). In the acidic rock erosion related in Early Permian (271-280Ma). Early Permian mafic rock Rb-Sr isotopic composition of wide (87Sr/86Sr) I 0.702949-0.712714, initial Nd low concentration (143Nd/144Nd) and i=0.512219-0.512843 Nd (T) =-1.29-11.2., epsilon epsilon zircon 176Hf/177Hf=0.28274-0.28282, calculated by Hf (T) =4.9-7.8, a TDM1=618-742Ma. model age mafic rock mantle depleted mantle, at the same time By the EMII transformation. The mantle source region of Beishan by transformation influence in eastern Tianshan Mountains, in the Tianshan area is obvious. The partial melting of the early Permian mafic rock magma origin 16.5-17.0% occurred at a relatively shallow depth by subduction fluids transformation of the depleted mantle, with its high magnesium (14.5%wt.% MgO), high temperature (1368 DEG C). Water features. Late Permian rock magma with similar properties, but the source region by transformation of higher degree, degree of melting is slightly lower (14.3%). The comprehensive mafic intrusive rocks, basalt, petrology, mineralogy of acid rocks, geochronology and geochemistry and related rocks in East Tianshan, comparison of Tarim area, Beishan area the large-scale Early Permian mafic ultramafic magmatism is not formed in an island arc environment, nor the causes of mantle plume, but more likely after the collision of asthenospheric mantle stretching plate fracture environment caused by the upwelling of magma. The intrusion to the surface formation of calc alkaline basalt, dacite and volcano rock combination. In addition mixed mantle derived magma and crustal new dehydration melting magma, and wrapped in ancient crust, in addition to the formation of A type granites, formed I type, S type granite assemblage. Mafic ultramafic magmatism has been until the Late Permian. The ore body mainly is suspended from harzburgite at the bottom of the.3D magnetic inversion shows the direction for the magma channel to the North East Nancy deep shallow.Se, Te in the low temperature elements and orebody may reflect a consistent low temperature hydrothermal mineralization has a certain effect on the bead sulfide display contribution. In the process of magmatic evolution occurred in sulfide segregation, Cu/Zr ratio, PGE content and composition of simulation show that olivine occurs 4% olivine crystallization of sulfur has reached saturation and segregation, segregation degree of 0.015-0.02%, the formation of low-grade disseminated mineralization slope. The North rock belt of sulfide segregation that occurs in olivine crystals before and liquation until the olivine crystallization process, the formation of high grade and low grade penetration mineralization disseminated mineralization respectively. Siliceous contamination is conducive to the formation of calcium sulfide segregation, but limited contribution. Early magmatic chromite, olivine crystallization leads to the decrease of the content of FeO and sulfur solubility in the magmatic system, the sulfur saturation and segregation. The comprehensive mafic rocks tectonic background, magma source and nature, sulfide segregation and magmatic emplacement sequence, metallogenic model of Beishan magmatic copper nickel ore bed "deep liquation + in-situ liquation and multi period" the intersection of pulsating mineralization. Deep faults and secondary faults are looking for structural conditions of mafic rocks. The lithofacies are distinct, contains harzburgite and ultramafic lithofacies, the olivine Ni content can not be too high, the geological Information should be paid attention to in prospecting and exploration. The Ti content of the Mg is high, and the content of MgO is more than 11.5%. The partial melting degree is less than 12-15%, the consolidation index is more than 40, and the TiO2 content is less than 1%, which is the geochemical indicator of favorable ore content. The rock mass is low m/s, m/f and high.

【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P611;P587
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本文编号：1637137