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新疆冰达坂含金剪切带内高品位金矿体更倾向定位于低应变带.选取典型剖面,对比蚀变围岩、矿石、未蚀变花岗质初糜棱岩及花岗质原岩组分特征,结果表明花岗质岩石容矿的金矿床剪切变形过程中组分发生分异,动力分异与流体分异对金矿化所起作用及相对程度不同,研究区金成矿主要与流体分异作用有关.流体分异作用过程中,相对于高应变带,低应变带内强分异形成的高Fe环境及扩容空间为金矿化、沉淀提供更有利条件,且碱(Na)交代排出的Si为浅层次硅化蚀变糜棱岩型及石英脉型矿化提供物源基础,K、 Ca、 Mg形成绢云母化、碳酸盐化、绿泥石化等蚀变,从而为区内金矿化定位及共生蚀变提供了合理解释.结合已有研究成果,认为钠长石化带下部应发育钾长石化带,且作为矿根相存在,矿带东、西段深部均有较好金矿化前景 相似文献
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金平龙脖河铜矿位于哀牢山-金沙江构造带的东南端。赋矿围岩为变钠质火山岩,成矿主要类型为构造破碎蚀变岩型铜矿;围岩蚀变以绿泥石化、碳酸盐化、硅化、磁铁矿化等为主。通过对产于变钠质火山岩中不同蚀变程度和矿化程度岩、矿石的地球化学组分进行对比,计算不同岩、矿石体积的变化和组分的迁移。计算结果表明：从弱矿化变钠质火山岩到强矿化变钠质火山岩,随蚀变和矿化的增强,岩石体积分别扩容了14%、12%;组分SiO2、HREE及成矿物质Cu和S等的含量具有逐渐增加的趋势,微量元素中亲铁元素Cr、Ni也有不同程度的迁入富集;而组分CaO、MnO和LREE等的含量则逐渐降低,说明成矿过程中SiO2、HREE及成矿物质Cu和S等是由流体带入的,而CaO、MnO和LREE等则是由流体从围岩中带出的,以及成矿物质主要来源于深部流体。 相似文献
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构造形变类型与金矿化类型的关系 总被引：14，自引：0，他引：14
含金构造形变类型决定或控制金矿化类型,深层次的韧性超韧性变莆为元素迁出区,一般不利于金矿化;韧性含金构造控制蚀变糜棱岩型金矿化,韧脆性变形含金构造控制构造蚀变岩型金矿化,脆性含金构造控制石英脉型金矿化。对于韧性剪切带和未来发生叠加蚀变矿化的糜棱岩来说,往往是构造变形越强,金元素含量越低。但在蚀变糜棱岩型金矿床中,已经叠加蚀变矿化的糜棱岩若幅度,石英变形机制与金矿富集程度都有密切的关系,而且含金构造 相似文献
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扬子地块东南缘板岩带中剪切带金矿床主要有三种成因类型,即糜棱岩型、石英脉型及蚀变岩型,剪切带对其形成具有明显控制作用.矿体主要受控于如下构造：1-4级多级构造,是由韧性剪切带和脆-韧性剪切带或脆性断层所组成,构造形态变化地段,包括弧形剪切带顶部扩容区及剪切带交汇部位;构造强应变及其叠加部位,这些地段系由超糜棱岩、糜棱岩、碎裂岩所组成;构造多期变形地段。本文还建立了板岩带剪切带型金矿床的动力成矿模式;划分了金矿形成四个阶段,即背景岩石形成;成矿物质运移;主期动力成矿及矿床改造、再造阶段。 相似文献
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赛坝沟金矿是青海省柴北缘构造带东段重要的金矿床,矿体受NW-NNW向韧-脆性断裂构造组控制,主要赋存于奥陶系英云闪长岩中,矿化蚀变主要有硅化、黄铁矿化、绢英岩化、绿泥石化、绿帘石化和碳酸盐化等。本文在厘定赛坝沟金矿热液蚀变类型、矿物组合特征以及蚀变空间变化关系的基础上,选取Ⅳ-4主矿体在AZK3901钻孔深部见矿岩心及底板蚀变围岩进行研究,通过对蚀变岩及其原岩的地球化学分析,剖析热液蚀变作用过程与机理。研究结果表明,赛坝沟金矿床钻孔深部蚀变中,绿泥石化绿帘石化及强糜棱岩化岩石表现为主量元素K_(2)O、CaO的明显带入和Na_(2)O的带出,大离子亲石元素Pb、Ba、Sr的带出以及过渡族金属元素Bi、Co、Cr的带入;黄铁矿绢英岩化、硅化岩石中,主量元素K_(2)O、SiO_(2),大离子亲石元素Rb、Ba、Cs、Pb以及过渡族金属元素均表现出不同程度的带入;各蚀变岩石中稀土元素以及高场强元素并未表现变化,仅在近矿体处出现了轻重稀土的解耦以及高场强元素Zr元素的带入。综合研究认为,赛坝沟金矿强糜棱岩化绿泥石化英云闪长岩为强烈的韧性剪切和脆性断裂叠加改造作用的产物,对流体成矿物质的运移形成了一定的屏障,使得成矿物质大部分沉淀在硅化、绢英岩化带内,局部发育的方解石细脉与成矿晚期碳酸盐化作用相关。金的沉淀主要是由于含矿流体温度、压力的下降和氧逸度的升高,使得含矿流体与围岩强烈反应形成硅化、绢云母化,同时伴随成矿流体pH值的增大和H^(+)的减少,热液中含硫组分与Fe元素发生反应形成黄铁矿等硫化物,破坏了含金络合物的稳定性,导致金的大量沉淀。 相似文献
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西藏东窝东矿床矿化蚀变过程元素迁移及绢云母~(40)Ar-~(39)Ar年代学及其地质意义 总被引：2，自引：2，他引：0
东窝东铜多金属矿床位于羌塘地体南缘,多龙铜金矿集区东侧。该矿床尚未开展矿化蚀变时限、成矿作用中元素迁移特征等问题的研究。为确定矿床的蚀变矿化作用时限,本文对东窝东矿床的黄铁绢英岩化蚀变带中的蚀变绢云母进行了~(40)Ar-~(39)Ar年代学测试,获得~(40)Ar-~(39)Ar坪年龄为122.20±0.84 Ma,该年龄与已有的斑岩体侵位时代(122 Ma)一致,说明东窝东矿床黄铁绢英岩化蚀变与斑岩体侵位有密切联系。此外,对比分析地表弱蚀变和钻孔中强黄铁绢英岩化花岗闪长斑岩的岩石地球化学结果,运用"等浓度线(isocon)方程"及其推导方程,探讨黄铁绢英岩化蚀变过程中的不同元素的带入、带出特点及元素迁移特征。结果表明:高场强元素质量基本守恒;轻稀土元素较重稀土元素迁移量较大,但总体上稀土元素的迁移程度较弱;主要的成矿元素Cu、Pb、Zn为带入元素。东窝东矿床含矿斑岩侵位时代和热液蚀变时限均与多龙矿集区内多不杂、波龙、铁格隆南等多个超大型-大型铜金矿床一致,说明东窝东矿床和多龙矿集区内的多个矿床受控于同一构造-岩浆成矿背景,东窝东矿区具有重要的找矿潜力。 相似文献
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与韧性剪切带有关的不同金矿化类型地质地球化学特征对比研究 总被引：7，自引：0，他引：7
与韧性剪切带有关的金矿化类型主要有蚀变糜棱岩型、构造蚀变岩型和石英脉型。不同金矿化类型具有不同的控矿构造类型,蚀变糜棱岩型金矿化受韧性变形带控制,构造蚀变岩型金矿化受脆性碎裂岩控制,石英脉型金矿化则受浅部裂 隙带控制;未矿化糜 棱岩变形越强,金元素含量就越低,超糜棱岩明显低于粗糜 棱岩,但强烈变形的糜 棱岩容易叠加后期的矿化蚀变;在时空关系上,同一厉矿期内石英脉型金矿化稍晚于构造蚀变岩型和蚀变糜棱 相似文献
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韧性剪切带型金矿是一种成矿机制与控矿因素都与韧性剪切带及其演化密切相关的金矿床类型。阿尔金北缘地区不同层次剪切带发育,金矿床受韧性剪切带控制明显,在区域上,韧性剪切带控制金矿床(点)的分布;在矿床范围内,韧性剪切带及其演化过程中形成的韧脆性剪切带既是唯一的赋(含)矿构造,也对矿化带、矿体的形态、产状、规模及分布起决定性的控制作用;压扭性韧性剪切变形特点决定了金矿化类型以蚀变糜棱岩型为主,交代蚀变作用发育。含矿构造裂隙以P型为主,少量D型和R型,个别为R~1型和T型;构造变形所引发的动力分异作用及其形成的动力变质热液是金矿成矿流体的主要来源之一,这与地球化学和成矿流体包裹体研究显示的大平沟金矿床成矿物质主要来源于变质岩、成矿流体有相当部分来源于变质水的特征相吻合。结合糜棱岩磁组构研究,发现磁各向异性度P值与金元素含量呈负相关关系,说明构造变形早于金矿化蚀变作用,这种时序关系进一步佐证了韧性剪切带型金矿床的成矿模式。即大面积的韧性变形构造动力分异作用形成的含金热液不是就地原位矿化,而是向上迁移并集中到范围比较窄小的韧-脆性或脆性裂隙中才发生金元素富集,最终形成金矿床。 相似文献
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安徽铜陵桂花冲斑岩铜矿围岩蚀变与矿化作用 总被引：1，自引：0，他引：1
桂花冲铜矿为安徽铜陵地区新发现的斑岩型铜矿,斑岩体为准铝质高钾钙碱性的花岗闪长斑岩。围岩蚀变与矿化作用是斑岩型矿床成矿过程研究的一项重要内容,对蚀变带岩石开展元素地球化学成分的迁移研究,是分析热液交代蚀变过程的基础。桂花冲铜矿区内围岩蚀变作用比较强烈,蚀变类型主要有钾化、绢云母化、硅化、绿泥石化和碳酸盐化等。蚀变分带比较明显,由内向外依次为钾化带、绢英岩化带和青磐岩化带,矿体主要产于绢英岩化带内。矿化蚀变自早至晚划分为钾长石、石英-绢云母、石英多金属硫化物和碳酸盐4个阶段。蚀变带物质组分迁移结果表明,在蚀变过程中,岩石的主量元素除TiO2、MnO、MgO外,其他元素迁移量发生了明显改变;微量元素除Sr和Cu外,迁移量变化较小,稀土元素在矿化强的部位亏损,在矿化弱的地带富集。岩体及蚀变带岩石稀土元素球粒陨石标准化配分模式一致,说明岩体与蚀变岩石经历了相同来源流体的交代蚀变,是岩浆流体连续作用的结果。 相似文献
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Discriminations in a local chemical,fluidal,mechanical and thermal processes in a shear zone will lead to metallogenic differentiation in a local section.This paper,based on the general geological setting of the Shibangou gold deposit in Xixia,Henan,deals with petrological and petrochemical samples of altered rocks in the metallogenic section and of mylonites in the non-metallogenic section of a selected shear zone.The discriminations in fluid-rock interaction and petrological mass balance between altered rocks near the orebody and mylonites in the shear zone are discussed as well.The results show that the petrological volume of altered rocks in the metallogenic section of the shear zone is almost always dilatant and the mylonite volume in the non-metallogenic section is almost always lost.Major elements in altered rocks from the metallogenic section and in mylonites from the non-metallogenic section always show a tendency of being enriched and depleted,respectively.Fluid-rock ratios in the mylonites(Nu=93.68-468.40)are larger than those of the altered rocks(NC(Ⅳ）^s=36.11-216.67).The gain and loss of major and trace elements from the altered rocks and mylonites in the shear zone are a composite process to be imported and exported by percolating fluids as well as of the loss and dilatancy of rock volume. 相似文献
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Fluid-Rock Interaction of Shear Zones in Continental Crust:as Evidenced by Xincheng-Xishui and Hetai Shear Zones 总被引：1，自引：0，他引：1
Zhong Zengqiu You Zhendong Xu QidongFaculty oj Earth Sciences China University of Geosciences Wuhan 《中国地质大学学报(英文版)》1995,(2)
There is a coupling of thermal, mechanical, chemical and fluidal processes in a continental shear zone. Both Xincheng-Xishui and Hetai shear zones are typical continental crust shear zones of greenschist facies environment. The representative mylonite zones of the shear zones are studied with whole rock major and trace element analyses. The chemical compositional variation tendencies in both shear zones are very similar and the gain-loss ratios of various components in the mylonitic rocks are reflected in the mass balance equations. The enrichment of those immobile high-field-strengh elements is considered to he related to the volume loss of the myionitic rocks in a shear zone. Based on the volume loss expression C_s/C_o=1/(1-V),the fractional volume losses (V)are 37.5％ and 36.5％-42.3％ respectively for mylonites and ultramylonites in the Xincheng-Xishui shear zone and 11％ and 28％ respectively for mylonites and phyllonites in the Hetai shear zone. The high volume loss and large removal of SiO_2 from 相似文献
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Interdependence of deformation, fluid infiltration and reaction progress recorded in eclogitic metagranitoids (Sesia Zone, Western Alps) 总被引：1，自引：0，他引：1
G. L. FRÜH-GREEN 《Journal of Metamorphic Geology》1994,12(3):327-343
The effects of high-strain deformation and fluid infiltration during Alpine eclogite facies metamorphism have been studied across ductile shear zones in relatively undeformed metagranitoids at Monte Mucrone (Sesia Zone, Western Alps, Italy). Microfabrics together with bulk rock and stable isotope data indicate that the mineralogical and chemical variations are related to the degree of deformation, rather than to changes in P-T conditions or tectonic position. Transformation of meta-quartz diorite to recrystallized eclogitic mylonites involved the breakdown of biotite and plagioclase and required the influx of H2O. Bulk-rock geochemical data show that ductile deformation to form eclogitic mylonites involved an increase in volume with a weight percent gain in H2O and Si and variable loss of K, Na, Ca and Al. δ18O changes systematically across ductile shear zones into the undeformed country rocks. Constant values in shear zone centres indicate advection parallel to the shear zone and within 10 cm of the mylonites. A dominant component of diffusive oxygen exchange perpendicular to the shear zones produced isotopic fronts, evident from a gradual increase in δ18O values to the reference values of the country rocks. The degree of isotopic shift within the shear zones reflects increasing deformation and degree of reaction progress. Multiple phases of Alpine deformation and mineral growth are recognized in the Monte Mucrone metagranitoids, and in some cases, eclogite facies shear zones were reactivated under greenschist facies conditions. The results of this study suggest that high-strain deformation provided pathways for both synkinematic and post-kinematic metamorphic fluids which were necessary for complete reactions. Relict igneous fabrics, as well as the presence of corona textures around biotite and pseudomorphs after primary igneous plagioclase in the least deformed rocks, indicate a paucity of hydrous fluids and support the conclusion that fluid movement was channelled rather than pervasive. 相似文献
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Rock Deformation, Component Migration and ^18O/^16O Variations during Mylonitization in the Southern Tan-Lu Fault Belt 
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下载免费PDF全文 YANG Xiaoyong LIU Deliang FENG Min YU Qingni WANG Kuiren 《《地质学报》英文版》2007,81(2):297-311
This paper discusses the relationship between the volume loss, fluid flow and component variations in the ductile shear zone of the southern Tan-Lu fault belt. The results show that there is a large amount of fluids flowing through the shear zone during mylonitization, accompanied with the loss of volume of rocks and variations of elements and oxygen isotopes. The calculated temperature for mylonitization in different mylonites ranges from 446 to 484℃, corresponding to that of 475 to 500℃ for the wall rocks. The condition of differential stress during mylonization has been obtained between 99 and 210 MPa, whereas the differential stress in the wall rock gneiss is 70-78 MPa. The mylonites are enriched by factors of 1.32-1.87 in elements such as TiO2, P2O5, MnO, Y, Zr and V and depleted in SiO2, Na2O, K2O, Al203, Sr, Rb and light REEs compared to their protolith gneiss. The immobile element enrichments are attributed to enrichments in residual phases such as ilmentite, zircon, apatite and epidote in mylonites and are interpreted as due to volume losses from 15% to 60% in the ductile shear zone. The largest amount of SiO2 loss is 35.76 g/100 g in the ductile shear zone, which shows the fluid infiltration. Modeling calculated results of the fluid/rock ratio for the ductile shear zone range from 196 to 1192 by assuming different degrees of fluid saturation. Oxygen isotope changes of quartz and feldspar and the calculated fluid are corresponding to the variations of differential flow stress in the ductile shear zone. With increasing differential flow stress, the mylonites show a slight decrease of δ^18O in quartz, K-feldspar and fluid. 相似文献
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以五龙金矿为例，在同一剖面上采集了不同成矿阶段的含金石英脉和近矿蚀变岩样品，．根据矿物流体包裹体和蚀变岩成分地的测定结果，系统地讨论了不同成矿阶段流体包裹体成（K^ 、Na^ 、Ca^＋、CO2等）和不同蚀变岩成分（K2O、Na2O、CaO1、MgO、CO2等）的变化规律，结果表明，从第二成矿阶段到第四成矿阶段，流体中的Na^ 、Ca^ 、Mg^ 含量有明显的升高的趋势，K^ 含量降低，蚀变岩中，K2O由远离矿体的原岩到靠近矿体的蚀变岩其含量增加，而Na2O、CaO、MgO逐渐降低，这种流体包裹体和蚀变岩中的某些相应成分的变化特征，应该是流体－岩石相互作用的结果。 相似文献
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Geological, petrological and structural observations were obtained along a 30-km-long traverse across a segment of the Valle Fértil shear zone, central-western Argentina. On a regional scale, the shear zone appears as numerous discontinues belts over 25 km in width and is approximately 140 km in length, extended on the western section of the Sierras Valle Fértil – La Huerta mountain range. The steeply dipping shear zone with a vertical mylonitic lineation is composed of amphibolite facies ribbon mylonites and amphibolite to greenschist facies ultramylonites derived from Early Ordovician plutonic and metasedimentary parent rocks. Locally, syn-kinematic retrogression of mylonites formed greenschist facies phyllonites. During the later stages of deformation, unstrained parent rocks, mylonites, ultramylonites and phyllonites were affected by pervasive cataclasis under low greenschist facies conditions associated with localized faulting. One new 40Ar/39Ar age on biotite and published 40Ar/39Ar ages on amphibole in the shear zone yield an average cooling rate of 6.2 °C/Ma for a time period that crosses the Silurian–Devonian boundary. Since in metasedimentary rocks the youngest zircon's rims dated at 465 Ma marks the beginning of cooling, nearly continuous uplift of rocks within the shear zone occurred over a minimum time span of 55 Ma. During the period of active deformation, dip-slip movement can explain uplift of several kilometers of the Early Ordovician arc crust. The Valle Fértil shear zone, which was formed near above the inferred suture zone between the Famatinian arc and Cuyania microcontinent, is a major structural boundary nucleated within the Early Ordovician crust. The simplest geodynamic model to explain the evolution of the Valle Fértil shear zone involves the collision of the composite Cuyania/Precodillera microcontinent against the Famatinian arc. 相似文献
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康古尔地区金矿成因类型及其控矿因素 总被引：2，自引：0，他引：2
新疆康古尔地区地质、构造复杂、成矿条件独特,是以金为主的多金属矿成矿有利地段。金矿成因类型多样,有韧性剪切带型、超浅成低温火山－水热型、中低温火山水热型、中低温岩浆－水热型等。剪切带型金矿是本区主要成矿类型。大地构造、地层岩性、侵入岩、火山岩和韧性剪切带等均与金矿形成有着密切关系。中酸性火山岩是本区主要成矿母岩,韧－脆性剪切带是金矿形成的重要导矿构造。成矿物质来源于上地幔和下地壳。主要成矿时代为晚 相似文献
19.
The Yunmeng Shan metamorphic core complex (MCC) is composed of the lower plate, the upper plate and the detachment zone. The detachment zone consists of ductile shear zone (mylonite zone), chloritized microbreccias zone and the brittle fault plane. The ductile shear zone contains mylonitic rocks, protomylonites, and mylonites. Finite strain measurements of feldspar porphyroclasts from those rocks using the Rf/φ method show that the strain intensities increase from mylonitic rocks (Es=0.66–0.72) to protomylonites (Es=0.66–0.83), and to mylonites (Es=0.71–1.2). The strain type is close to flatten strain. Kinematic vorticity estimated by Polar Mohr diagrams suggest that foliations and lineation of mylonite (0.47相似文献
20.
In this paper we present new data on the spatial variability of peridotite composition across a kilometer-scale mantle shear
zone within the Lanzo massif (Western Alps, Italy). The shear zone separates the central from the northern part of the massif.
Plagioclase peridotite shows gradually increasing deformation towards the shear zone, from porphyroclastic to mylonitic textures
in the central body, while the northern body is composed of porphyroclastic rocks. The peridotite displays a large range of
compositions, from fertile peridotite to refractory harzburgite and dunite. Deformed peridotites (proto-mylonite and mylonites)
tend to be compositionally more homogeneous and fertile than weakly deformed peridotites. The composition of most plagioclase
peridotites show rather high and constant (Ce/Yb)
N
ratios, and Yb
N
that cannot be explained by any simple melting model. Instead, refertilization modeling, consisting of melt increments from
spinel peridotite sources, particularly with E-MORB melt, reasonably reproduces the plagioclase peridotite whole rock composition.
Combined with constraints from Ce–Nb and Ce–Th systematics, we speculate that peridotites such as those from Lanzo record
pervasive refertilization processes in the thermal boundary layer. In this scenario, mantle shear zones might act as important
areas of melt focusing in the upper mantle that separates the thermal boundary layer from the conductively cooled mantle. 相似文献