汉南杂岩与金成矿特征

汉南杂岩区位于扬子地台北缘,围岩为元古界绿片岩 勉县—洋县深大断裂系统在成岩、成矿与盆地形成方面占有重要的地位.杂岩体由斜长花岗岩、二长花岗岩、钾长花岗岩、石英闪长岩和辉长辉绿岩组成.金矿化类型主要有石英脉型和蚀变岩型,与接触带、断裂带、蚀变带有关,蚀变后岩石矿物成分变化.使金重新分布,砂金分布与金源、地貌和新构造运动关系密切.     

河南桐柏县彭家老庄金矿矿化地质特征及控矿地质因素分析

通过系统总结彭家老庄金矿成矿地质背景和矿化地质特征,分析成矿控制要素,认为矿区内中元古界信阳群龟山岩组变质绿片岩、NW向脆韧性剪切带和老湾花岗岩体三位一体的地质环境有利于成矿,而龟山组地层与老湾花岗岩的接触带、脆韧性构造的局部引张和构造交叉及倾向上倾角由陡变缓部位有利于富矿体的形成与定位,为下一步找矿工作提供方向。     

吉林海沟金矿床同位素地球化学和成矿规律研究

同位素地球化学研究表明,中元古界色洛河群绿片岩相变质岩系是海沟金矿床的重要矿源层,它经历了多次构造、变质和混合岩化作用,特别是在燕山早期强烈构造活动中发生了局部深熔作用,形成了海沟二长花岗岩。受热大气降水的淋滤作用,使岩体内金元素活化、迁移和富集,以含金硫化物石英脉群形式沿NE向裂隙带充填于海沟二长花岗岩中,形成了大型沉积变质、深熔岩浆岩源大气降水热液金矿床。     

河南省前河构造蚀变岩型金矿的矽卡岩化及其找矿意义

前河金矿床位于秦岭造山带内,矿体赋存于低绿片岩相变质的中元古界熊耳群安山质火山岩地层中,严格受断裂控制。通过对前河金矿深部和外围找矿工作发现,石家岭矿段发育有矽卡岩化岩石,主要发育于合峪花岗岩体北部赋存金矿体的F4断裂附近,围岩是低绿片岩相的安山质火山岩,并且在前河大桥附近有石榴子石脉产出;岩相学特征及电子探针成分分析表明,该矽卡岩化岩石由钙铁石榴子石、透辉石-钙铁辉石、绿帘石、绿泥石、阳起石、石英和方解石等矿物组成,经历了干矽卡岩阶段、湿矽卡岩阶段以及石英硫化物阶段这一典型演化过程;褐帘石电子探针成分和穆磁铁矿具赤铁矿的假象表明,湿矽卡岩阶段具有还原性特征。因此,前河金矿矽卡岩化可能由附近合峪花岗岩岩浆热液交代形成。     

汉中地区金矿特征

汉中地区位于秦岭地槽中段与扬子准地台北缘交界处,地质构造复杂,成矿作用期次多,矿产资源丰富,作者近来收集了大量金矿资料,并进行了初步整理与研究,现将汉中地区金矿地质及金矿分布特征论述如下; 一、汉中地区金矿地质特征 (一) 地层 1.元古界蓟县系:主要有西乡群及三花石群,它们构成了扬子区地台结晶基底。碧口群属地槽区海底火山喷发产物。与金矿有关的地质特征是: (1)西乡群:主要分布于西乡西南,为一套火山岩系,主要岩性为绿片岩和片理化凝灰岩,下段夹铁矿,上段含铜矿;在柳树店一带见有较富的砂金,北侧有沙河坎岩体侵入,在其与较基性的围岩接触时,产生强烈的混染而变成石英闪长岩,在接触带见有较多的钍矿化。     

内蒙古大青山新地沟金矿地质特征、成矿条件及成矿规律

新地沟金矿是华北地台北缘大青山段绿岩型金矿的代表性矿床,矿体主要产于上太古界色尔腾山岩群绿片岩组合中的蚀变糜棱岩带中。矿石类型有:蚀变糜棱岩、千糜岩、石英脉等。主要蚀变为硅化、钾化、黄铁矿化、绢云母化。矿体与围岩糜棱面理产状基本一致,绿片岩为矿源层。影响成矿的主要因素是两期不同层次的韧性剪切变形变质作用和早期同构造侵位的晚太古代二长花岗岩。矿床形成是上述地质事件综合作用的产物。显生宙以来的花岗岩侵位对成矿影响不大,基底硬化后脆性断裂对矿体起破坏作用。     

白乃庙金矿床构造特征

白乃庙金矿床矿体围岩有白乃庙群绿片岩和长英片岩、石英闪长岩和斜长花岗岩等。矿床构造专题研究表明,控矿构造是白乃庙断层和次级断裂组成的帚状构造,并在断层交汇部位形成富矿柱。     

内蒙古中部早古生代白乃庙群韧性剪切变形特征

内蒙古中部地区早古生代白乃庙群地层主要由绿泥片岩段(Ob~1、Ob~3)和长英片岩段(Ob~2)组成,花岗闪长斑岩(386Ma)侵入于地层之中。白乃庙群和花岗闪长斑岩一同遭受了推覆型韧性剪切作用。     

小秦岭金矿田成因的锶同位素约束

本文报道了前人对小秦岭金矿田部分金矿床流体包裹体、赋矿围岩(太华群)、文峪花岗岩的锶同位素结果以及作者新获得的中-新元古界地层(官道口群-栾川群)的缌同位素测试结果。鉴于小秦岭金矿田的金矿床和文峪花岗岩均形成于130Ma 左右,作者将所有~(87)Sr/~(86)比值返算为130Ma 时的初始值,即 I_(Sr-130)比值。文峪花岗岩的8件 I_(Sr-130)=0.7077～0.7084, 平均0.7082;太华群的12件 l_(Sr-130)=0.7073～0.8090,平均0.7557;中-新元古界地层的15件 I_(Sr-130)=0.7119～0.8373,平均0.7623;赋存于太华群中的金矿床流体包裹体的22件 I_(Sr-130)值变化于0.7334～0.7519,平均0.7440:赋存于文峪花岗岩中的矿脉流体包裹体7件 I_(Sr-130)=0.7135～0.71 85,平均0.7162。由此可见,赋存于太华群的金矿床 I_(Sr-130)值远高于文峪岩体,而落入太华群和中-新元古界地层的 I_(Sr-130)值范围,表明成矿流体不可能源于文峪花岗岩岩浆分异,而源于太华群和/或中-新元古界地层的变质脱水;赋存于文峪岩体中的含矿石英脉 I_(Sr-130)值低于太华群和/或中-新元古界地层,也低于太华群中的金矿床,但显著高于文峪岩体,应是高 I_(Sr-130)的成矿流体与低 I_(Sr-130)值的文峪花岗岩围岩相互作用的结果如此,碰撞造山成岩成矿与流体作用模式可较好阐释小秦岭金矿田的成因,即,中生代扬子与华北板块碰撞过程中,由中-新元古界地层及下伏太华群组成的陆壳板片沿小河断裂向北 A 型俯冲到小秦岭金矿田之下,俯冲板片经变质脱水作用为小秦岭金矿田形成提供了成矿流体,成矿流体与赋矿围岩的相互作用造成太华群中的矿脉与文峪岩体中的矿脉具有明显不同的 I_(Sr-130)值。     

老湾金矿带金成矿地质背景

老湾金矿带岩浆活动强烈,形成了老湾花岗岩体及一系列酸性岩脉。老湾花岗岩岩性为黑云母二长花岗岩,可分内部相、过渡相和边缘相,为同熔型复式岩体。成矿带两侧是松扒断裂带和老湾断裂带,两断裂带之间低序次构造裂隙发育,并伴有强烈的韧性剪切作用。含矿岩系是信阳群龟山组,主体岩性是二云母石英片岩和斜长角闪片岩,原岩是一套(含)碳泥质陆源碎屑一钙质沉积建造夹基性火山岩建造,经历了至少五期变质作用。二云母石英片岩含金量为5.08×10^-9,斜长角闪片岩平均含金量为4.80×10^-9,它们为金成矿提供了物质来源。金矿成矿依赖于含金建造、构造活动及岩浆活动这三个基本条件。     

Palaeoproterozoic metamorphism in the Jeori-Wangtu Gneissic Complex (JWGC), western Himalayas

The Jeori-Wangtu Gneissic Complex (JWGC) exposed as a tectonic window in the Lesser Himalayas represents one of the oldest Gneissic Complex of the Himalayas. Foliated granite and the metapelite constitute the dominant lithologies of the JWGC. The western margin of the JWGC is bounded by a brittle shear while in the east, the tectonic surface is a ductile shear zone.Kyanite schist, chloritoid schist, staurolite schist (St-1), garnet schist and staurolite schist (St-2) are present in a west to east sequence beginning from near to the Jhakhri thrust and up to the contact with the JWGC granite. Mica schist is intermittently present and is the dominant metapelite. Low to medium grade regional metamorphic conditions has been inferred for these rocks.Calc silicate enclaves within the JWGC granite preserve the contact metamorphic effects. These are reflected in development of narrow zones of disequilibrium assemblages of calcareous garnet (grs₅₃), clinopyroxene, K feldspar, calcic plagioclase (An₈₆), quartz, zoned sphene, zoned allanite, amphiboles, calcite and epidote.Recording of contact metamorphic assemblage of 1.80 Ga granite witin the enclave calc silicates and in the host metapelites over an earlier, relict low to medium grade assemblage indicates that the JWGC preserves palaeoproterozoic metamorphic imprints.     

内蒙古巴彦哈尔金矿床地质特征及成因初探

内蒙古巴彦哈尔金矿床位于华北陆块北缘艾力庙-锡林浩特中间地块西北缘.矿床赋存于中元古代温都尔庙群的绢云石英片岩和绿泥石片岩中.矿床的形成与区内韧性剪切带及华力西期岩浆活动关系密切.矿区内共圈定出5个矿体,总体走向为北西向,矿体呈似层状或透镜状产出,矿石类型包括石英脉型和糜棱蚀变岩型.金矿化与硅化和黄铁绢英岩化蚀变关系密切.结合矿床的矿体地质、矿物成分、矿物嵌布及围岩蚀变特征以及前人包裹体测温结果,认为矿床类型为浅成低温热液型金矿.     

Mineral chemistry and geochemistry of vanadian silicates in the Hemlo gold deposit,Ontario, Canada

Some of the most vanadium-rich silicate minerals known are present in green mica schist from the Hemlo gold deposit, Ontario, Canada. Vanadium-rich silicate minerals include green mica (up to 17.6 wt. % V₂O₃), phlogopite (10.1 wt. % V₂O₃), pumpellyite (25.7 wt. % V₂O₃), garnet (18.5 wt. % V₂O₃), epidote-group minerals (9.1 wt. % V₂O₃), antimonian vesuvianite (4.3 wt. % V₂O₃), and titanite (18.5 wt. % V₂O₅). In addition, minor amounts of V (<2 wt. % V₂O₃) are present in tourmaline, chlorite, talc and tremolite in other lithologies of the Hemlo deposit. The principal substitution that incorporates V into most of these silicate minerals is Al³⁺=V³⁺ in octahedral positions. Vanadium is incorporated into phlogopite mainly by the two substitutions: 3Mg²⁺ =2V³⁺+ and ^VIMg²⁺+^IVSi⁴⁺=^VIV³⁺ +^IVAl³⁺, and all of the three substitutions Ti⁴⁺+O^2- =V³⁺+(OH,F)^-, Ti⁴⁺=V⁴⁺, and 5Ti⁴⁺=4V⁵⁺ + may have operated in titanite.Vanadium-enriched green mica schist from the Hemlo gold deposit is characterized by uniform Ti/Zr ratios, systematically low Ti, Ni, Co and Sc abundances, and low levels of incompatible elements Th, U, Hf and Zr and is distinct in these respects from its Cr-enriched counterpart. These geochemical features, along with textural evidence (relict quartz and oligoclase phenocrysts), indicate that the V-enriched green mica schist from Hemlo was most likely derived mainly from quartz-oligoclase porphyry. However, its anomalously high V and Cr contents were probably introduced metasomatically from local maficultramafic sources and were fixed in green mica and oxides during the waning of a second regional metamorphism. Vanadium was further remobilized, and its concentration probably enhanced, during the late hydrothermal alteration, which resulted in the formation of the characteristic V-rich calc-silicate minerals.     

内蒙古包日汗区温都尔庙群变质岩系的构造演化特点

<正> 内蒙古自治区二连浩特以东,自二道井经巴音敖包、包日汗、红格尔庙至锡林浩特一带(以下简称集二线北带),下古生代的温都尔庙群呈北东东向断续分布(图1)。它们产出在构造地质学上著名的“蒙古弧”东翼,习惯上多称为内蒙古华力西褶皱带。我们同意将温都尔庙群出露区划为加里东优地槽褶皱带的意见。温都尔庙群岩石主要为细碧岩、块状绿泥闪帘石岩、绿泥闪市片岩、石英千枚岩(片岩)夹变质碧玉岩、石英岩以及磁铁赤铁石英岩，常伴有基性、超基性岩体的侵入。岩层变形强烈，发育有不同级别和不同型式的褶皱及断裂。1978年，我们在研究温都尔庙群层序及铁矿分布规律时，重点研究了包日汗地区的褶皱构造。     

Lithological and Structural Controls on the Genesis of Emerald Occurrences and their Exploration Implications in and around Gurabanda Area,Singhbhum Crustal Province,Eastern India

Emerald, the green gem variety of beryl (Be₃Al₂Si₆O₁₈), is the third most valuable gemstone after diamond and ruby. The green colour appearance of the crystal is due to trace of Cr³⁺ and V³⁺, which replaces Al³⁺ ions in the crystal lattice of beryl. The hue of green colour of emerald depends on the quantity of Cr³⁺ and V³⁺ present in the crystal. Be is incorporated along with Cr and/or V during the process of crystallization. Since Be is relatively rare in the upper continental crust, therefore specific geological and geochemical parameters are required for Be to be incorporated in the crystal lattice of emerald.The present work was carried out to understand the lithological and structural control of emerald occurrences in and around Gurabanda area within the Singhbhum shear zone (SSZ) of Singhbhum crustal province, eastern India. The biotite and serpentine schist belong to the Paleoproterozoic Dhanjori Group and constitute the major lithology of the area. Pegmatite and biotite schist contains a variety of gem minerals in abundance in the area and the gem quality emerald occur at the contact zone of quartz vein and mica-schist. Lithology and structure are the main controlling factors of gem-mineralization in the study area. The study indicates that regional metamorphism and deformation processes along the shear zone played a significant role in the formation of emerald deposits. It is inferred that Singhbhum shear zone facilitated a favourable condition, where the Be bearing pegmatites interacted with Cr bearing mica schist or ultramafic rocks to produce emerald crystal.     

甘肃两当县解板沟一带舒家坝群的解体

舒家坝群(D2-3S)是西秦岭北带构造蚀变岩型金矿重要的赋矿地层,为一套浅变质的具类复理石沉积特征的细碎屑岩及少量碳酸盐岩组合,形成时代为中晚泥盆世。通过1∶5万区域地质调查,在西秦岭两当县北解板沟一带原划舒家坝群中新填绘出一套被断裂围限的火山岩-火山碎屑岩系,与舒家坝群的主体岩性差别明显。通过对该火山岩-火山碎屑岩系进行LA-ICP-MS锆石U-Pb测年,分别获得其中流纹质晶屑凝灰岩加权平均年龄为204±2 Ma,英安斑岩加权平均年龄为209±3 Ma,表明该火山岩-火山碎屑岩系形成于晚三叠世。据此,将其从原划舒家坝群中解体,暂划归华日组(T3hr)。     

Dominance of lithogenic effect for nickel,cobalt, chromium and mercury as found in freshly deposited sediments of the river Subernarekha,India

The importance of study of heavy metal distribution in river sediments is a component in understanding the exogenic cycling as well as in assessing the effect of anthropogenic influences of the elements. In India, the river Subernarekha flows over Precambrian terrain of Singhbhum craton in the eastern India. The geological succession in this part of India is through (1) iron ore series, (2) ultrabasic igneous rocks, (3) diorite, (4) granite, (5) newer dolerites, (6) newer tertiary and (7) alluvium. The first four groups belong to the Archaean era, and the representative is the iron ore series consisting of iron ore, manganese and chromite which are abundantly present. The primary rock types are schist and quartzite layers. One main tributary, the Kharkhai flow through granite and schist and quartzite layers. Two important creeks are Gurma and Garra, respectively. The former after originating in basic igneous area travels through schist quartzite, while the later one originates in granite area where some functional but old gold mines are located. Freshly deposited sediments of river were collected upstream and downstream the industrial zone (East Singhbhum district). Samples were collected from four locations and analysed in <63 μm sediment fraction for heavy metals like Ni, Co and Cr by adsorption stripping voltammetry on hanging mercury drop electrode and Hg by anodic stripping voltammetry using polished rotating gold disk electrode. Enrichment of these metals over and above the local natural concentration level (NCL) has been calculated and applied to determine metal-pollution index (MPI) proposed by Goncalves et al. and also geo-accumulation index (I _geo) by Muller. Based on Muller’s classification, Ni, Cr and Hg have been classified from unpolluted to moderately polluted range in pre-monsoon period but for metals Ni and Cr, during the post-monsoon period the values have reached moderately polluted level while Hg has been classified under unpolluted to moderately polluted level except at the monitoring station situated upstream to Gurma Creek where it was found at unpolluted level. Presence of natural resources of the minerals is primarily the reason for their detection in river sediments (lithogenic) but some anthropogenic sources are also contributing for their presence at some sampling stations. Hg is considered to be chalcophilic in nature and is detected wherever known sulphidic ores of copper or nickel are present.     

滇西勐满金矿床成矿物质来源分析及矿床成因探讨——来自年代学、矿物学及地球化学的证据

勐满金矿床位于云南省勐海县境内,地处临沧-景洪褶皱束之临沧-澜沧复背斜南部,截至2005年探明金矿资源量17t,主矿体属于地表红土型氧化矿,平均品位为0.60×10-6。文章基于对勐满金矿床矿区内新元古界曼来组片岩和中侏罗统花开左组碎屑岩及矿区外围东部的临沧花岗岩的LA-ICP-MS锆石U-Pb年龄测定,探讨了曼来组片岩和花开左组碎屑岩地层的物质来源,追溯母岩的物质源区,并结合矿区普遍发育的硅化岩和硅质脉体的地球化学特征,分析了金成矿的物质来源。勐满金矿床曼来组中主要碎屑锆石年龄为(957.0±9.8)Ma,属新元古代早青白口纪;中侏罗系花开左组主要碎屑锆石年龄为(224.2±2.8)Ma,与临沧花岗岩基中2件黑云母二长花岗岩的年龄(分别为(228.7±2.8)Ma和(229.4±2.0)Ma)一致,表明花开左组地层的物质来源可能与临沧花岗岩有关。微量元素测试结果显示,矿区硅化岩与硅质脉体具有相似的稀土元素配分模式与微量元素组成,均表现为富集U、Th、Pb等大离子亲石元素,亏损Zr、Hf、Nb、Ta等高场强元素,轻稀土元素明显富集,重稀土元素亏损,中-弱的Eu负异常,Ce异常不明显,与矿区围岩及临沧花岗岩体南部的黑云母花岗岩具有相似的变化趋势。硅化岩稀土元素总量为42.3×10-6~311.0×10-6,平均为131.8×10-6;硅质脉体稀土元素总量为5.0×10-6~280×10-6,平均为56.8×10-6,显示硅化岩相对于硅质脉体具有更高的稀土元素总量。硅质脉体((La/Yb)N为4.3~133.4,平均36.7)相对于硅化岩((La/Yb)N为2.1~26,平均为8.5)具有更高的轻、重稀土元素分馏特征。硅化岩的地球化学特征变化介于围岩与硅质脉之间,表明硅化岩既继承了围岩特征,又有经热泉活动改造的痕迹。综合锆石年代学结果与沉积物源分析,认为矿区花开左组砂岩主要为临沧岩体经受风化搬运沉积的产物,曼来组向花开左组提供金的量不足以形成花开左组中的碎屑岩型矿体,热泉活动产生的流体是金成矿的另一重要物质来源,同时是导致金后期富集的重要因素。据此推断,花开左组是赋矿层位,而并非矿源层。结合低硫型矿床标志性矿物冰长石的出现,提出勐满金矿属于典型的与热泉活动有关的低硫型浅成低温热液金矿。     

呼和浩特市大青山区卯独庆金矿床地质特征

卯独庆金矿床赋存在古元古代二道凹岩群的绿片岩层与大理岩层过渡带。金矿化明显受构造片理化带控制。该类金矿化控矿因素是岩性层 构造。     

Microstructures and evolution of folds in SC-mylonites from Dudatoli-Almora crystallines of Garhwal Himalaya

In the Lesser Garhwal Himalaya, the North Almora Thrust separates the overlying medium-grade Dudatoli-Almora crystallines of Precambrian age from the unmetamorphosed to partly metamorphosed rocks of the Garhwal Group of Late Precambrian age. The crystalline nappe sheet consists of flaggy to schistose quartzites, granite gneisses and garnetiferous mica schist members in an ascending order. In different localities. different members of the Dudatoli-Almora crystallines are exposed along the thrust plane. Southwest of Adbadri fine-grained mylonitized schistose quartzites of Dudatoli-AImora crystallines are in contact with the underlying metabasites of the Garhwal Group. The mylonitized schistose quartzites consist of alternating thick (1 to 2m) quartzite and thin (10 to 20cm) micaceous quartzite bands. The micaceous quartzites can be further differentiated into alternating quartz-rich (0-5 to 2.0 cm thick) and mica-rich (0.2 to 1.0 cm thick) layers. In the quartzites the C-surfaces are parallel to the S-surfaces defined by the alternating quartz-rich and mica-rich layers. Further, the S-surfaces exhibit almost similar folds with multiple wavelengths where the axial planes are nearly parallel and enveloping surfaces are oblique to the lithological layering. The evolution of these folds has been envisaged in three phases of deformation on the basis of field evidence, fold geometry and microstructures. During the first phase buckle folds (F ₁) developed in thin micaceous quartzite layers. whereas thick quartzite bands underwent only layer parallel shortening. During the second phase the stress orientation changed and the limbs ofF ₁ folds were folded (F ₂). During the third phase of deformation which coincided with thrusting, the rocks were sheared, mylonitized and developed microstructures exhibiting dynamic recrystallization by the processes of subgrain rotation, and continual and discontinuai grain boundary migration. This phase was also responsible for the development of C-surfaces parallel to the lithological layering. Further, in the folded micaceous quartzite layers shearing resulted in the development of C-surfaces parallel to the axial planes ofF ₂ folds.