碾子沟金红石矿床基本地质特征

碾子沟金红石矿区地层主要为上太古界变粒岩、斜长角闪片岩及榴闪岩 ;岩浆岩主要为晋宁期基性岩 ;构造主要为断裂。矿区蚀变岩发育 ,主要为细晶直闪片岩、粗晶直闪岩、中细晶滑石岩及细晶绿泥片岩。矿体呈似纺锤状、似板状及透镜状。矿石类型有浅褐色细晶直闪石型片状矿石、灰白色粗晶直闪石型块状矿石、灰绿色或灰白色中细晶滑石型块状矿石、黑色中细晶角闪石型片状矿石及灰绿色巨晶直闪石型块状矿石等 5种。以前 3种为主 ,矿石品位一般 2 %～ 15 %。矿床规模为大型 ,矿床为变质蚀变成因。     

山西代县碾子沟金红石矿床蚀变温度

测试山西代县碾子沟金红石矿床细晶直闪石中原生气体包裹体和气液包裹体均一温度分别为790～825℃、756～780℃,分别代表了细晶直闪石化早期、中后期的温度。镁电气石中原生气体包裹体均一温度高于800℃,据气液比分析,相当于细晶直闪石化早期的温度,其形成的时空分离性主要由蚀变介质物质成分差异所致。类比分析了其它蚀变阶段的温度。总体上看,矿床蚀变属高温蚀变。蚀变温度明显高于围岩变质温度和高温热液矿床的温度,略低于矽卡岩化温度。高温使钛、铁离子的动能和活性大幅度提高,蚀变介质的存在使离子具备了良好的迁移条件,从而使钛铁离子完全分离、钛进一步富集并形成了金红石矿床。     

青海茫崖石棉矿区变质超基性岩的蚀变演化序列：岩石化学及矿物学证据

青海茫崖石棉矿区超基性岩体是由原岩以纯橄岩、辉橄岩和橄辉岩为主体组成的富镁质超基性岩体,经历自变质和后期多期热液的叠加变质蚀变作用,经蛇纹石化后形成蚀变完全的蛇纹岩岩体,其中部分蛇纹岩又进一步发生滑石化及碳酸盐化蚀变为滑石菱镁片岩、菱镁滑石片岩、滑石片岩和菱镁岩等。本文在野外地质调查基础上,在室内通过镜下岩矿综合鉴定、全岩化学成分分析以及电子探针成分分析等手段进行了岩石化学特征、矿物学特征及其蚀变演化过程研究。结果表明,该变质超基性岩体蛇纹岩主要特征组合矿物为蛇纹石(利蛇纹石、叶蛇纹石、纤蛇纹石)、磁铁矿、菱镁矿、滑石、水镁石、铬铁矿,变余矿物有斜方辉石、单斜辉石和铬铁矿,滑石菱镁片岩类主要组成矿物为菱镁矿、滑石、蛇纹石及磁铁矿,局部可见石英脉。该地区变质超基性岩体较完整地记录了橄榄岩水化、滑石化及碳酸盐化作用过程的各个阶段,超基性岩蚀变演化过程主要有两个作用阶段:(Ⅰ)橄榄石、辉石类矿物的蛇纹石化作用及蛇纹石绿泥石化作用;(Ⅱ)富Ca、CO2流体交代蛇纹石、滑石及水镁石的碳酸盐化作用。蛇纹石化等变质蚀变作用促进了Si、Mg及Fe元素化学活动性,使元素发生富集与迁移,对于次生矿物的形成与演化起到了一定的催化作用。多期不同组成流体热液的交代作用过程,清晰地展示了利蛇纹石、纤蛇纹石和叶蛇纹石的演化序列,以及滑石、水镁石、铬铁矿和磁铁矿的形成过程及标形特征。     

福建紫金山矿田西南铜钼矿段蚀变矿化特征及SWIR勘查应用研究

西南铜钼矿段位于中国著名的福建上杭县紫金山矿田内,是该矿田最新发现的另一个典型的斑岩型矿床。该矿床形成于白垩纪,矿化(浸染状和细脉浸染状)与成矿同期花岗闪长斑岩密切相关。围岩蚀变由深到浅分别为青磐岩化带、绢英岩化带、高级泥化-泥化蚀变带和氧化带。蚀变矿化期次可划分为:(早期)绢英岩化期、斑岩矿化期、浅成低温热液叠加期、成矿后期脉和表生期。其中,斑岩矿化期又可分为钾硅酸盐化阶段、青磐岩化阶段和(晚期)绢英岩化阶段;浅成低温热液叠加期主要为泥化-高级泥化蚀变。对比研究发现,西南矿段具有与典型斑岩矿床相似的矿化蚀变特征,但缺失钾化带且矿化规模小,成矿斑岩以岩枝状(非岩株状)水平侵位,产生非对称蚀变分带,据此推测西南矿段深部可能存在真正的成矿斑岩岩株和大储量及高品位的矿化中心。通过短波红外光谱(SWIR)研究发现,从矿化中心到外围,伊利石结晶度值(IC)和伊利石2200 nm吸收峰位值(Pos2200)均有明显的从高值到低值的变化趋势。此外,研究发现高IC值(2.1)和高Pos2200值(2203 nm)可作为紫金山地区勘查该类矿床的找矿标志。本研究可以为紫金山地区斑岩矿床的成矿规律认识和找矿勘查提供科学依据。     

造山带背景铜镍矿床蚀变过程与水的来源——东天山黄山南矿床氢氧同位素的指示

造山带背景铜镍矿床以富水为主要特征,但水(流体)在成矿中的作用以及其对岩石的改造过程仍不明确。本文以黄山南铜镍矿床为例,通过辉橄岩和橄辉岩等超镁铁岩的蚀变矿物组合和H-O同位素变化规律,限定蚀变过程与流体性质及来源。黄山南超镁铁岩原生矿物主要有尖晶石、橄榄石、斜方辉石、单斜辉石和少量填隙状角闪石、云母,蚀变矿物有角闪石(浅闪石、阳起石、透闪石、普通角闪石以及镁闪石)、滑石、绿泥石和蛇纹石等。根据岩石结构与蚀变矿物比例,将超镁铁岩分为弱蚀变、中等蚀变和强蚀变3类。蚀变矿物组合与角闪石成分指示超镁铁岩经历了高温蚀变阶段(>700℃),形成了镁质闪石+滑石+绿泥石;中温蚀变阶段(700～550℃)和低温蚀变阶段(<550℃),分别形成了钙质闪石+滑石+绿泥石+蛇纹石与滑石+碳酸盐+蛇纹石的矿物组合。蚀变岩石普遍以中低温蚀变为主,可能与中低温阶段的叠加-改造作用相关。岩石随蚀变程度增加,Si、Na、K、Mn等主量元素和Rb、Ba等微量元素呈现明显降低趋势,表明大多数元素在流体改造过程中从岩石中迁出,说明蚀变过程为开放体系。中-强蚀变岩石中,硫化物矿物边部的形态呈锯齿状,但主体仍为磁...     

新疆鄯善小尖山金矿区地质特征及控矿构造

小尖山金矿位于康古尔金矿中东段，矿体主要有含金蚀变岩和含金花岗细晶岩两类，以蚀变岩型金矿为主，发育于变质岩区，具有低温绿片岩相的面貌，受韧性剪切带控制并以剪切作用为主要的成矿机制。     

山西恒山巨晶状直闪石岩的成因:来自地球化学和Sm-Nd同位素的证据

山西恒山地区的巨晶状直闪石岩由石榴石、直闪石、蓝晶石、十字石、堇青石、石英、金红石、钛铁矿和少量斜长石和普通角闪石组成,岩石SiO2含量类似于中-基性岩,但比后者更富镁铁而贫钙和碱。岩石可分为Ⅰ、Ⅱ两种类型:Ⅰ类直闪石岩含有石榴石变斑晶,并相对低镁、钛和碱,而含有较高铝、铁,其高场强和稀土元素特征类似于岛弧玄武岩,岩石的143Nd/144Nd为0.511361～0.511894,tDM(Nd)=2.39～2.60Ga,Nd同位素特征与五台杂岩中的基性变质岩一致。Ⅱ类直闪石岩富含直闪石,一般不出现石榴石,相对高镁、钛和碱,而含有较低铝和铁,高场强和稀土元素特征类似于大洋中脊拉斑玄武岩。岩相学和地球化学对比表明,本区直闪石岩的原岩是由与五台杂岩变质基性岩类似的火山岩经受海水热液蚀变的产物,这种水热蚀变引起基性岩中钙、碱丢失和镁(铁)富集,并可能形成大量绿泥石等富水矿物。直闪石岩的现有矿物组合是经历高压角闪岩相变质和接续的等温降压作用形成的,其中巨晶结构是由于这种极富流体岩石在峰期之前的前进变质过程中大量脱水所致,与这种大量脱水伴随的变质分异作用导致了直闪石岩成分的进一步改造。     

新疆鄯善小尖山金矿区地质特征及控矿构造

小尖山金矿位于康古尔金矿中东段,矿体主要有含金蚀变岩和含金花岗细晶岩两类,以蚀变岩型金矿为主,发育于变质岩区,具有低温绿片岩相的面貌,受韧性剪切带控制并以剪切作用为主要的成矿机制.     

云南香格里拉春都斑岩铜矿区围岩蚀变及矿化特征

春都斑岩铜矿床地处著名的印支期中甸-义敦岛弧成矿带南端。矿区出露闪长玢岩-花岗闪长斑岩复式岩体,成矿岩体为印支晚期的花岗闪长斑岩。围绕成矿岩体,围岩蚀变强烈,蚀变分带明显,由中心向外,依次出现硅化钾化带→绢英岩化带→硅化带→硅化黑云母化带→青磐岩化带→绢云母化及泥化带。区内蚀变与矿化关系密切,蚀变类型决定矿化程度,蚀变...     

海南省罗葵洞钼矿围岩蚀变找矿标志

海南省罗葵洞钼矿是一处特大型斑岩型钼矿床,赋存于陆相火山岩与隐伏似斑状花岗岩接触界面及其外围,呈隐伏状产出,地表很难见到钼矿化露头.矿区最常见的蚀变是硅化和黄铁矿化,其次有钾化、绢云母化、绢英岩化、云英岩化、伊利石-水白云母化、黑云母化、绿帘石化、次闪石化、绿泥石化、碳酸盐化等,局部尚有叶腊石化、萤石化.其中硅化、钾化、绢英岩化、云英岩化与钼矿成矿关系密切.据初步研究,该区蚀变从火山口相中心,由内向外大致可分为不十分明显的4个蚀变带：强硅化蚀变带、硅钾蚀变带、硅化蚀变带、绿帘石-绿泥石化带.在详查工作中根据面形硅化细脉带,可以确定矿化范围,钾化强烈发育地段为钼矿富集部位.     

法国比利牛斯山Trimouns滑石-绿泥石矿床地质与成因

位于法国比利牛斯山的Trimouns矿床是世界上最大的滑石-绿泥石矿床之一。对该矿床形成的条件及滑石和绿泥石矿石的含量已较清楚。它是由不同类型的岩石通过热液交代蚀变而形成的，主要包括白云岩蚀变为滑石为主的矿石和硅铝质岩石(云母片岩和伟晶岩)蚀变为绿泥石为主的矿石。滑石矿石显示片理化结构(滑石片岩)或压实块状结构(块滑石)。由伟晶岩蚀变而来的绿泥石矿石为呈绿色的球状矿体，而由云母片岩蚀变而来的绿泥石矿石呈块状或片理状、颜色为灰绿色和深灰色。本文对欧洲这个独一无二的滑石和绿泥石矿床的地质特征和成因进行了总结和讨论。流体包裹体研究表明成矿流体为高盐度(20to30％eq．wt％NaCl)、中温(320℃)、压为为2．5kbars。磷钇矿和独居石的U—Ph定年结果表明，成矿年代为112—97Ma，成矿作用可能持续了16Ma以上。     

The role of fluids in the metamorphism of komatiites,Agnew nickel deposit,western Australia

The Agnew nickel sulfide deposit is spatially associated with a lenticular body of ultramafic rocks which shows a concentric zonation in metamorphic mineralogy. Olivine + tremolite + chlorite + cummingtonite ±enstatite assemblages occur at the margin of the ultramafic lens, giving way to olivine + anthophyllite, olivine + talc and olivine + antigorite assemblages successively inwards. These rocks are interpreted as having crystallized from komatiitic lavas, and exhibit a spectrum of compositions from those of original flow tops to pure olivine adcumulates. The relative modal abundances of metamorphic olivine, tremolite and chlorite reflect original proportions of cumulus olivine and komatiite liquid in the protolith. Peak metamorphic conditions are estimated at 550° C, based on garnet-biotite thermometry, at a maximum pressure of 3 kb. This temperature falls within the narrow range over which metamorphic olivine may co-exist with enstatite, anthophyllite, talc or antigorite depending upon the fugacity of water in the metamorphic fluid. The observed mineralogical zonation is therefore attributed to infiltration by CO₂-rich fluids, generated by decarbonation of talc-carbonate rocks formed during pre-metamorphic marginal alteration of the ultramafic lens. Metamorphic fluids were essentially binary mixtures of water and CO₂, with minor H₂S having a maximum partial pressure less than 1 percent of total pressure. Enstatite-bearing assemblages formed in the presence of CO₂-rich fluids at fluid: rock volume ratios close to one, while anthophyllite, talc and antigorite bearing assemblages formed in the presence of progressively more water-rich fluids at progressively lower fluid-rock ratios.     

X射线粉晶衍射仪在辽宁瓦房店金伯利岩蚀变矿物鉴定中的应用

瓦房店金伯利岩热液蚀变强烈,原岩矿物组分几乎蚀变殆尽,显微镜下对蚀变矿物鉴定相当困难.利用X射线粉晶衍射技术对蚀变金伯利岩物相进行系统检测,结果显示：42号岩管金伯利岩主要矿物为蛇纹石、金云母和滑石,有少量方解石、锐钛矿、磷灰石、石英、钛铁矿、钙钛矿、榍石、磁铁矿和绿泥石;石灰窑1号无矿金伯利岩岩管主要矿物为蛇纹石、金云母和白云石,有少量方解石、锐钛矿、磷灰石、滑石、磁铁矿和绿泥石;9号无矿金伯利岩岩脉主要矿物为方解石和石英,有少量绿泥石和重晶石;51号贫矿金伯利岩岩管主要矿物为蛇纹石和金云母,方解石化作用不均匀,白云石化作用普遍,有少量锐钛矿、滑石、磁铁矿、绿泥石、磷灰石、钛铁矿、石英;30号贫矿岩管样品风化严重,主要矿物为蒙脱石,有少量方解石、滑石、蛇纹石、榍石、磷灰石.实践证明,采用X射线粉晶衍射仪鉴定金伯利岩蚀变矿物组合是一种非常可行的技术手段.     

The Palaeoproterozoic Kristineberg VMS deposit, Skellefte district, northern Sweden. Part II: chemostratigraphy and alteration

The Kristineberg massive sulfide deposit is hosted by metamorphosed volcanic and subvolcanic rocks of the Palaeoproterozoic Skellefte Group. The deposit consists of: (1) two main massive sulfide horizons, the A-ores and B-ores, which dip steeply southwards and are separated by 100–150 m; and (2) the Einarsson Zone, a complex interval of Cu–Au-rich ‘stockwork‘ sulfides and small massive sulfide lenses in altered and deformed rocks near the 1,000 m level. The Einarsson Zone occurs some 20–100 m south of the B-ores. There are no definite younging indicators in the mine sequence. In many areas of the mine, the original host rocks are impossible to identify petrographically due to the abundance of secondary minerals such as quartz, chlorite, muscovite, cordierite, andalusite, phlogopite, pyrite and talc, combined with variably schistose fabrics. Application of immobile-element methods to 600 recent whole-rock chemical analyses has, however, allowed the original rock types to be identified and correlated. Rhyolite X lies immediately north of the A-ore, while andesitic to dacitic to rhyodacitic rocks make up the 100–150 m interval between the A-ore and B-ore, and massive rhyolite A lies immediately south of the B-ore. The felsic rocks are mostly of calc-alkaline affinity, excluding rhyolite X, which is transitional. The mine porphyry, which lies north of the A-ore and forms the marginal phase of the synvolcanic Viterliden Intrusive Complex, is compositionally similar to dacite and rhyodacite. Mass changes calculated for all rock types indicate that most of the volcanic rocks in the mine area are strongly depleted in Na and Ca, and have gained variable amounts of Mg and Fe, whereas Si changes range from negative to positive. Gains in Fe and changes in Si are largest within 5–10 m of the massive sulfide lenses. Cordierite-bearing schists of andesitic to felsic compositions that lie between massive sulfide lenses A and B are not as altered. The Einarsson Zone commonly shows large gains in Fe and Mg, while Si shows large gains to large losses. Immobile-element ratios indicate that very different secondary assemblages in the mine, e.g. andalusite–quartz–muscovite and cordierite–chlorite–talc, can be produced from the same precursor volcanic unit, e.g., rhyolite. Conversely, the same secondary mineral assemblage can be produced from different rocks, e.g. weakly altered andesite and strongly altered rhyolite. The common presence of cordierite + andalusite in the mine area, without anthophyllite, is unusual in the alteration systems of volcanic-hosted massive sulfide deposits, and is proposed to have formed by the metamorphic reaction of the synvolcanic alteration minerals kaolinite and chlorite to produce cordierite. Where kaolinite was in excess of chlorite, andalusite was also formed. We propose that highly acidic alteration fluids locally produced high-Al minerals such as kaolinite that either overprinted, or occurred in place of, a more typical sericite–chlorite–quartz alteration assemblage that otherwise formed near the massive sulfide lenses. Application of lithogeochemical methods to the altered, deformed and metamorphosed Kristineberg rocks has identified specific volcanic contacts with massive sulfide potential, and quantified the effects of synvolcanic hydrothermal alteration. Such an approach can increase the effectiveness of mineral exploration in metamorphosed terrains.     

The importance of talc and chlorite “hybrid” rocks for volatile recycling through subduction zones; evidence from the high-pressure subduction mélange of New Caledonia

The transfer of fluid and trace elements from the slab to the mantle wedge cannot be adequately explained by simple models of slab devolatilization. The eclogite-facies mélange belt of northern New Caledonia represents previously subducted oceanic crust and contains a significant proportion of talc and chlorite schists associated with serpentinite. These rocks host large quantities of H₂O and CO₂ and may transport volatiles to deep levels in subduction zones. The bulk-rock and stable isotope compositions of talc and chlorite schist and serpentinite indicate that the serpentinite was formed by seawater alteration of oceanic lithosphere prior to subduction, whereas the talc and chlorite schists were formed by fluid-induced metasomatism of a mélange of mafic, ultramafic and metasedimentary rocks during subduction. In subduction zones, dehydration of talc and chlorite schists should occur at sub-arc depths and at significantly higher temperatures (∼ 800°C) than other lithologies (400–650°C). Fluids released under these conditions could carry high trace-element contents and may trigger partial melting of adjacent pelitic and mafic rocks, and hence may be vital for transferring volatile and trace elements to the source regions of arc magmas. In contrast, these hybrid rocks are unlikely to undergo significant decarbonation during subduction and so may be important for recycling carbon into the deep mantle. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

云南腾冲地热区主要蚀变矿物含量与蚀变母岩的关系

腾冲地热区出露有众多热泉泉群,地热活动频繁,岩石发生强烈蚀变,形成的主要蚀变矿物包括高岭石、绢云母、蒙脱石、I/M间层矿物、石英和蛋白石。主要蚀变矿物的种类和含量受蚀变母岩性质的控制,花岗质砂砾岩和花岗岩形成高岭石,玄武岩形成伊利石和蒙托石,安山岩中发育硅化作用。泥化作用增强的趋势是安山岩→花岗岩→玄武岩→花岗质砂砾岩。由于花岗质砂砾岩在热区内广泛分布,通过蚀变作用形成了有经济价值的高岭土矿床。     

植被覆盖区高光谱遥感影像上蚀变岩与蚀变矿物信息的提取

在高光谱遥感找矿应用中,从影像上提取的蚀变信息经常包含了很多对找矿无用的信息。为了避免这些无用信息,本研究选取植被覆盖的云南普朗斑岩铜矿区作为研究区,使用该区高光谱遥感数据分别提取蚀变岩和蚀变矿物的信息,分析它们对找矿的有用性。提取蚀变矿物信息使用的是从影像上提取的矿物端元参考光谱,光谱匹配采用的是光谱角方法;提取蚀变岩信息使用的是野外蚀变岩参考光谱,光谱匹配不仅考虑光谱的整体形态,而且考虑吸收谷位置形态。在蚀变岩识别图上,4个典型蚀变岩点的野外验证表明:识别结果与实地地物基本一致。但是,在蚀变矿物信息图中,这4个圈定点无任何信息。这表明:这些点的蚀变岩信息较其表面蚀变矿物信息更丰富,因而能被有效提取出。通过比较蚀变岩、蚀变矿物的信息分布图,发现:一些粘土矿物(比如硬石膏和高岭石)的大量信息分布在沉积岩区,因而可能是假的蚀变信息。这表明:通过蚀变岩光谱获取的蚀变信息比通过蚀变矿物光谱获取的蚀变信息更可靠。在蚀变岩信息提取中,比较吸收谷位置识别前后的结果表明:考虑光谱整体和局部形态比仅考虑整体形态的识别结果具有更高的可靠性。     

弓长岭铁矿蚀变岩及富矿成因

弓长岭铁矿床是鞍山本溪地区最典型的BIF型铁矿床之一,而且是该地区最大的富铁矿产区。从野外产出关系来看,弓长岭矿区的富铁矿与蚀变岩密切相关,蚀变岩与富铁矿基本上是形影相随。蚀变岩具有分带性,由富铁矿向外依次为镁铁闪石岩石榴石岩绿泥石岩弱蚀变斜长角闪岩斜长角闪岩。弱蚀变岩保留了蚀变原岩的岩貌特征,矿物的蚀变并不完全,可见残余的原生矿物。强蚀变岩的蚀变较彻底,基本无原生矿物残留。将蚀变岩与斜长角闪岩、磁铁石英岩的地球化学特征进行对比可以发现弱蚀变岩、石榴石岩、绿泥石岩与斜长角闪岩的痕量元素特征基本一致,而镁铁闪石岩的痕量元素特征更接近磁铁石英岩。再结合镜下特征、野外接触关系、主量元素特征等证据,认为除了镁铁闪石岩是由磁铁石英岩蚀变形成,其余蚀变岩都是由斜长角闪岩蚀变形成。根据各类蚀变岩中主要矿物的(Fe+Mg)/Si值以及蚀变岩的SiO2和Fe2OT3含量变化规律可以发现,在蚀变岩和富矿形成过程中发生了Mg、Fe以及Si的迁移。对本次取样的样品进行原岩恢复和构造环境判别投图,投图结果表明,绿泥石岩和弱蚀变岩的最初原岩都是形成于弧后盆地的玄武岩。