Simulation of rock mass balance of two typical altered rocks in Wulong gold deposit of Liaoning, China

Wulong gold deposit hosted in granite and fine-grained d io rite dikes, is a typical gold deposit of quartz vein type. Granite and fine-gra ined diorite dikes in the ore deposit were altered by metallogenic fluid. Based on the altered zoning, the samples of petrochemistry were collected and major an d trace elements were analyzed systematically. Calculation of rock mass balance shows that the major elements (SiO 2, K 2O, P 2O 5, Fe 2O 3) in the two ty pical altered rocks are clearly added into the altered system, and that trace el ements (V, Y, Zr, Ni, Co, Sr) assume an increasing and decreasing tendencies in the altered granite and altered diorite dike, respectively. The fluid/rock ratio s are 30.17-181.00 and 115.44-692.67 respectively for altered granite and alte red diorite dike, they have profoundly effects on metallogenesis.

Characteristics of Element Migration in the Process of Wall-Rock Alteration in the Shibangou Gold Deposit,Western Henan

Abstract The Shibangou gold deposit in western Henan is associated with irregular quartz veinlets occurring in altered shear zones dissecting a dioritic intrusion. The altered shear zones are characterized by silicification, pyritization, sericilization, chloritization and K-feldspar alteration. Zoning of altered rocks adjacent to the Au-bearing quartz veins is obviously exhibited. Fine-grained sulphides and quartz veinlets of different ages and small-scale fissures are widely distributed in the central part of the altered zones. Major mineralization types in this gold deposit are Au-bearing quartz veinlets and altered rocks in the shear zones. Samples were collected from drilling cores according to the alteration zoning and mineralization type and all samples were analyzed for major and trace elements. Mass balance, volume change (fv=97.3–71.9%) and major element variation sequences are studied in terms of major elements. The changes of mobile components (SiO2, K2O, Fe2O3) and CaO) and immobile component (Al2O3) in the wall-rock alteration are discussed. The gold mineralization is associated with the enrichment of As, Ag, Hg and Pb and depletion of Cu and Zn. The study of compositional variation of altered rocks proves to be a very efficient method for defining the extent of wall-rock alteration, fluid activity and mineralization and enrichment.

CRUSTOBODY STRUCTURE OF CHINA AND DISTRIBUTION OF ROCK GOLD ORE DEPOSITS

CRUSTOBODY STRUCTURE OFCHINA AND DISTRIBUTION OFROCK GOLD ORE DEPOSITSHuang Ruihua(Changsha Institute of Geotectonics, Academia Sinica, 410013, Hunan, China)rock gold ore deposit, crustobody structure, China.China continent is divided into four crustobodies from east to west. There is well-known Jinguashi rock gold deposit in East Asia continental margin crustobody. Gold met-allization is very well developed in East Asia crustobody. There are mainly rock gold ore de-posits related to Archean greenstone formation and Mesozoic-Cenozoic rock gold ore deposits in it. There are mainly Palaeozoic rock gold ore deposits of geosynclinal type and Cenozoic rock gold ore deposits of diwa (depression) type in Central Asia crustobody. South Asia crustobody possesses great potential in rock gold metallization. As a whole, prospecting exploration and exploitation of rock gold are very well of future in China.

The Structure of Ore-controlling Strain and Stress Fields in the Shangzhuang Gold Deposit in Shandong Province,China

The Shangzhuang altered-rock type gold ore deposit is located in the middle segment of and controlled by the Wang＇ershan fault zone in the northwestern part of the Jiaodong gold province, China. The deformation evolution, the structure of strain and stress fields and its ore-controlling effect in the Shangzhuang deposit are discussed in this paper. It is revealed that the deformation evolution has mainly undergone four phases： the early ductile deformation, the second NE-striking horizontal simple shear, the third NE-striking compression-shear and the final NW-striking compression. The mineralization happened during the third stage in which the maximum principal stress gradually transited from NE to NW. The 3-D numerical simulations of the stress field show that, on the condition that the maximum principal stress is NE-striking, the fracture development in the fault zone is favored, while when the maximum principal stress is NW-striking, the fault zone is relatively extensional and it is suitable for the influx and emplacement of ore-forming fluids. The compression-shear strain field during the mineralization is characterized by the λ-type structure, the positive flower structure, etc. Orebodies are mostly equidistantly located in the dilatational spaces, which are distributed in the integral compressional circumstances. And the dilatational spaces are developed where the fault attitude changes or shear joint systems develop. In the overall compression-shear stress field, the strain field bears self-similarity at multiple scales, including the orebody, ore deposit and orefield. The selfsimilarity of the structure comprises the subequidistant distribution of fractures at the same scale and the similar shape of the fractures at various scales. Yet, due to the special geological structure, the orebodies are mostly located in the hanging wall in the Shangzhuang deposit, which is different from most deposits in the Jiaodong gold province. Analyses of the ore-controlling stress and strain fields in the deposit provide an important basis for deposit seeking.

Alteration and mineralization styles of the orogenic disseminated Zhenyuan gold deposit, southeastern Tibet: Contrast with carlin gold deposit

Orogenic disseminated and Carlin gold deposits share much similarity in alteration and mineralization.The disseminated orogenic Zhenyuan Au deposit along the Ailaoshan shear zone,southeastern Tibet,was selected to clarify their difference.The alteration and mineralization from the different lithologies,including meta-quartz sandstone,carbonaceous slate,meta-(ultra)mafic rock,quartz porphyry and lamprophyre were researched.According to the mineral assemblage and replacement relationship in all types of host rocks,two reactions show general control on gold deposition:(1) replacement of earlier magnetite by pyrite and carbonaceous material;(2) alteration of biotite and phlogopite phenocrysts in quartz porphyry and lamprophyre into dolomite/ankerite and sericite.Despite the lamprophyre is volumetrically minor and much less fractured than other host rocks,it contains a large portion of Au reserve,indicating that the chemically active lithology has played a more important role in gold precipitation compared to structure.LA-ICP-MS analysis shows that Au mainly occurs as invisible gold in fine-grained pyrite disseminated in the host rocks,with Au content reaching to 258.95 ppm.The diagenetic core of pyrite in meta-quartz sandstone enriched in Co,Ni,Mo,Ag and Hg is wrapped by hydrothermal pyrite enriched in Cu,As,Sb,Au,Tl,Pb and Bi.Different host rock lithology has much impact on the alteration and mineralization features.Carbonate and sericite in altered lamprophyre show they have higher Mg than those developed in other of host rocks denoting that the carbonate and sericite incorporated Mg from phlogopite phenocrysts in the primary lamprophyre during alteration.The ore fluid activated the diagenetic pyrite in meta-quartz sandstone leading the hydrothermal pyrite enriched in Cu,Mo,Ag,Sb,Te,Hg,Tl,Pb and Bi,but the hydrothermal pyrite in meta-(ultra)mafic rock is enriched in Co and Ni as the meta-(ultra)mafic rock host rock contain high content of Co and Ni.However,Au and As shear similar range in both types of host rocks indicating that these two elements most likely come from the deep source fluid rather than the host rocks.It was shown in the disseminated orogenic gold deposit that similar hydrothermal alteration with mineral assemblage of carbonate (mainly dolomite and ankerite),sericite,pyrite and arsenopyrite develops in all types of host rocks.This is different from the Nevada Carlin type,in which alteration is mainly dissolution and silicification of carbonate host rock.On the other hand,Au mainly occur as invisible gold in both disseminated orogenic and Carlin gold deposits.

The geology, structure and mineralisation of the Oyu Tolgoi porphyry copper-gold-molybdenum deposits, Mongolia： A review

The Oyu Tolgoi cluster of seven porphyry Cu-Au-Mo deposits in southern Mongolia,define a narrow,linear,12 km long,almost continuously mineralised trend,which contains in excess of 42 Mt of Cu and1850 t of Au,and is among the largest high grade porphyry Cu-Au deposits in the world.These deposits lie within the Gurvansayhan island-arc terrane,a fault bounded segment of the broader Silurian to Carboniferous Kazakh-Mongol arc,located towards the southern margin of the Central Asian Orogenic Belt,a collage of magmatic arcs that were periodically active from the late Neoproterozoic to PermoTriassic,extending from the Urals Mountains to the Pacific Ocean.Mineralisation at Oyu Tolgoi is associated with multiple,overlapping,intrusions of late Devonian（～372 to 370 Ma） quartzmonzodiorite intruding Devonian（or older） juvenile,probably intra-oceanic arc-related,basaltic lavas and lesser volcaniclastic rocks,unconformably overlain by late Devonian（～370 Ma） basaltic to dacitic pyroclastic and volcano sedimentary rocks.These quartz-monzodiorite intrusions range from earlymineral porphyritic dykes,to larger,linear,syn-,late- and post-mineral dykes and stocks.Ore was deposited within syn-mineral quartz-monzodiorites,but is dominantly hosted by augite basalts and to a lesser degree by overlying dacitic pyroclastic rocks.Following ore deposition,an allochthonous plate of older Devonian（or pre-Devonian） rocks was overthrust and a post-ore biotite granodiorite intruded at～365 Ma.Mineralisation is characterised by varying,telescoped stages of intrusion and alteration.Early A-type quartz veined dykes were followed by Cu-Au mineralisation associated with potassic alteration,mainly K-feldspar in quartz-monzodiorite and biotite-magnetite in basaltic hosts.Downward reflux of cooled,late-magmatic hydrothermal fluid resulted in intense quartz-sericite retrograde alteration in the upper parts of the main syn-mineral intrusions,and an equivalent chlorite-muscovite/illite-hematite assemblage in basaltic host rocks.Uplift,facilitated by syn-mineral longitudinal faulting,brought sections of the porphyry deposit to shallower depths,to be overprinted and upgraded by late stage,shallower,advanced argillic alteration and high sulphidation mineralisation.Key controls on the location,size and grade of the deposit cluster include（i） a long-lived,narrow faulted corridor;（ii） multiple pulses of overlapping intrusion within the same structure;and（iii） enclosing reactive,mafic dominated wall rocks,focussing ore.

An integrated ore prospecting model for the Nyasirori gold deposit in Tanzania

The Nyasirori gold deposit,located in the middle-western end of the Musoma-Mara Archean greenstone belt in Tanzania,is a tectonic altered rock type gold deposit controlled by shear tectonic zone.This work conducted high-precision ground magnetic measurements to delineate fault structures and favorable prospecting targets,utilized induced polarization(IP)intermediate gradient to roughly determine the distribution and extension of the tectonic altered zone and gold ore(mineralized)bodies,and further carried out IP sounding and magnetotelluric sounding to locate the tectonic altered zone and gold ore(mineralized)bodies.The anomalous gradient belt of the combination of positive and negative micromagnetic measurements reflects the detail of shallow surface tectonic alteration zone and gold mineralization body.Micromagnetic profile anomalies indicate the spatial location and occurrence of concealed tectonic alteration zone and gold(mineralized)ore bodies.Soil geochemical measurements indicate that the ore-forming element Au correlates well with As and Sb,and As and Sb anomalies have a good indication to gold orebodies.Based on the multi-source geological-geophysical-geochemical information of the Nyasirori gold deposit,this work established an integrated prospecting model and proposed a set of geophysical and geochemical methods for optimizing prospecting targets.

GEOCHEMICAL KINETIC SIMULATION ON WALL-ROCK ALTERATION ZONING IN THE BAOBAN GOLD FIELD, SOUTH CHINA

The Baoban gold field, located in the area of Hainan Island, South China, bears three gold de-posits: Tuwaishan, Baoban, and Erjia, which belong to the wall-rock alteration type. In terms of the petrography data, four alteration zones can be recognized from the ore-vein outwards: (1) the silicification zone; (2) the sericitization zone, (3) the chloritization zone; and (4) the calcitization zone. The geochemical kinetic simulation was carried out on sericitization and chloritization . Results of the study showed that the formation of the alteration zones is connected with the properties of hydrothermal fluids: the initial concentration of Al (O H)3, the diffusion coefficient and the velocity of fluid flow. The alteration zones in this field are the result of multiple interaction between hydrothermal fluids and wall rocks.

Important Geological Factors Controlling the Formation of Gold Deposits in East China

The major gold deposits in East China are characterized by their occurrence in pre-Cambrian host metamorphic rocks, restriction in some specific stratigraphic-structural terranes,tendentious localization in ductile or ductile-brittle shear zones, association with the syntexis-type granitoids, and significant remobilization, superimposition and enrichment by the later-stage Mesozoic tectono-magmatic activities.

右江盆地大际山U-(Mo)矿床围岩蚀变特征及微量元素迁移规律——对区域内U、Au成生关系的指示

位于扬子地块西南缘的右江盆地,是全球第二大的卡林型Au矿(共伴生有Sb、Hg、Tl异常/矿化)矿集区,有着滇黔桂“金三角”的美誉。值得注意的是,该区除发育Au(-Sb-Hg-Tl)矿床外,还产有大量赋矿岩性和控矿构造相似的U矿床(点),成矿特色鲜明。前人对该区Au矿开展了大量研究,而U矿研究较少,对U、Au的成生关系尚不清楚。基于此,文章选取右江盆地内典型的U矿床——大际山U-(Mo)矿床为研究对象,通过开展岩矿相学研究和地球化学分析,厘定了矿化的围岩蚀变为硫化、沥青质化、磷铝锶石化、硅化和伊利石化,揭示了矿化过程中Re、Tl、Mo、U、Cd、Ni、Co、As、Sb、MREE的相对富集。蚀变矿物组合及元素迁移规律约束大际山U-(Mo)矿床中成矿物质可能来源于牛蹄塘组,成矿流体应为还原性有机流体与地表-近地表酸性、氧化性流体的混合,矿质沉淀发生在低温、酸性、还原环境中。综合分析认为,右江盆地内U、Au分布特征及矿床成因具有明显差异,二者应是不同成矿事件的产物。

宁陕县某金矿地质特征及富集规律

宁陕县某金矿地处秦岭中段南坡山地,金矿体主要赋存在燕山期NE-NNE向破碎蚀变带内的破碎蚀变岩及石英脉体中。目前,该矿正处于勘查阶段,只进行了基本的地质工作,研究程度较低。本文采用激电中梯测量和1:10000土壤化学测量圈定矿体后,通过钻探验证、槽探揭露、地质测量、取样分析等工作,查明金矿地质特征,分析成矿地质条件和矿床形成机制,概括矿物富集规律和找矿标志,为后期外围探矿和深部找矿提供真实可靠的理论依据。

胶西北新东庄金矿床蚀变岩岩石地球化学特征与成矿作用

新东庄金矿床位于招平断裂中段,矿体主要沿中生代玲珑型花岗岩与胶东群变质岩接触带展布。黄铁绢英岩是主要矿化岩石,矿体下盘玲珑型花岗岩主要发育红化蚀变,上盘胶东群变质岩发育青磐岩化蚀变。主量元素分析结果显示,红化花岗岩、黄铁绢英岩、绢英岩中K_(2)O、SiO_(2)、SO_(3)含量及LOI较原岩玲珑型花岗岩普遍增加,为带入成分,且在黄铁绢英岩、绢英岩等与矿化密切相关的岩石中增幅更大。在微量元素中,Rb、U在红化花岗岩和黄铁绢英岩、绢英岩中普遍带入。新东庄金矿床的金成矿与氧逸度、酸碱性条件的变化密切相关,金富集主要发生在还原性和偏酸性条件。

河南嵩县九仗沟金矿床地球化学特征与勘查模式

九仗沟金矿位于熊耳山—外方山矿集区内的蛮峪—店房金矿带北段,是典型的大型构造蚀变岩型金矿床。采用1/5万水系沉积物测量圈定了找矿靶区,1/1万土壤地球化学测量确定了矿化富集部位,岩石地球化学(原生晕)测量识别出构造破碎带和矿化强度,并预测矿体相对剥蚀程度。研究表明:不同尺度地球化学测量为该金矿勘查提供了不同阶段的找矿信息,找矿效果显著。其中,利用水系沉积物测量在九仗沟矿区范围内圈定了11-丙-Au异常,利用土壤地球化学测量发现了九仗沟1-甲_(1)-Au-Ag-Pb-Cu-Hg-As-Bi-Ni异常,利用原生晕剖面微量元素峰值部位确定了F_(1)构造矿化蚀变带。通过总结该矿床地球化学异常特征和找矿标志,建立了勘查地球化学模式,为区域及矿区周边相同类型的金矿勘查提供理论指导。

豫西前河金矿床构造原生晕特征及其对深部找矿的指示

前河金矿床是典型构造蚀变岩型金矿床,矿体受近东西向构造控制。构造研究表明,该矿区经历了多期演化,形成近东西向、北东向、南北向等3个方向的构造,不同构造对矿体起着控制或破坏作用。F_(4)断裂为近东西向构造的典型代表,为Ⅳ号矿带的容矿构造。通过对Ⅳ号矿带进行构造原生晕分析,认为头晕元素整体以中、内带异常为主,近矿晕元素以内带异常为主,尾晕元素分布差别较大,可能与元素变异系数变化较大有关。葚沟矿段00中段83勘探线深部、石家岭矿段260中段43勘探线—45勘探线深部均具有较好的找矿前景。

湖南雪峰弧形构造带字溪金矿床成因及找矿标志

【目的】字溪金矿是湖南雪峰弧形构造带近年来新发现的产于蚀变岩脉中岩的金矿床,探讨其矿床成因,总结找矿标志,对于区内金矿找矿工作有重要指导意义。【方法】通过总结前人的研究成果,综合野外地质特征、岩石地球化学特征观察等方式,探讨了矿床成因,总结了找矿标志。【结果】研究结果表明,区内中基性岩脉岩石类型主要为辉长-闪长岩,其成因与板内大陆裂谷构造环境有密切关系,属于碰撞后伸展活动的产物。矿床形成于雪峰山陆内造山过程中,成矿物质可能主要来源于变质基底。断裂构造、基性岩脉及毒砂化等热液蚀变等是寻找该类型金矿床的重要标志。【结论】研究成果可为区内寻找同类型金矿床提供参考。

甘肃北山斜沟—红柳丘井地区土壤地球化学特征及找矿远景

在斜沟—红柳丘井地区开展1∶50 000土壤测量,采集样品5 625件,粒度为4目至20目。通过样品加工分析和地球化学参数统计,对成矿元素地球化学特征进行研究,圈定单元素异常467处、组合异常3类、综合异常17处。根据异常查证评价情况对综合异常进行了分类及排序。在此基础上,结合区域地质背景、矿产资源分布情况,划分了以Au、Pb、Zn、W、Mo为主的找矿远景区5处,初步评价了其成矿潜力,指出具有找矿潜力的矿床类型为斑岩型钼矿床、蚀变岩型金矿床、火山热液型金矿床。

甘肃大店沟金矿床蚀变矿物特征与金矿化的关系

大店沟金矿床位于西秦岭成矿带上,其矿体类型为石英脉型和构造破碎带蚀变岩型。通过对该区岩石样品进行近红外光谱分析仪测试,确定大店沟金矿床围岩蚀变类型、蚀变矿物含量及特征,并讨论围岩蚀变与金矿化之间的关系。结果表明,该矿床的主要蚀变类型有绢云母化、绿泥石化、黄铁矿化、硅化及碳酸盐化。白云母、锂云母、伊利石、绿泥石等矿物与金矿化呈正相关性,蚀变矿物含量与区内揭露矿体空间位置及规模相对应,后期可作为较好的找矿标志性信息。

构造地质在蚀变岩金矿勘探及采矿中的运用

随着经济的不断发展,我国对于矿产资源的需求也在不断地增加。矿产资源作为人类社会发展过程中必不可少的重要资源,是人类社会进步不可或缺的一部分。尤其是在地质勘探中,对于不同地区的地质情况进行分析,能够对金矿开采提供必要的帮助。对于我国来说,很多地区都存在着蚀变岩金矿。但是由于在构造地质上存在着差异,因此在实际勘探和开采过程中也会出现一定程度上的影响。为此,本文针对构造地质在蚀变岩金矿勘探和开采中应用进行分析,首先阐述了矿区构造特征,其次分析了矿区构造单元的划分及地质特征及矿体产状及空间分布规律,并对蚀变岩金矿勘探及采矿中存在的问题进行了分析,最后提出了优化构造地质在蚀变岩金矿勘探和开采中应用的措施。

广东省广宁县丰木地区金矿地质特征及找矿标志

丰木地区金矿床位于粤西广宁县北部,黄泥坑金矿床的南西部。区内多期次岩浆活动,断裂构造发育,具有良好的构造蚀变岩型金多金属矿床的成矿条件。本文对丰木地区金矿区的地质特征进行研究,判断其为剪切带控制的中低温热液金矿床,并总结了找矿标志,为下一步勘查提供依据。

安徽庐江沙溪铜金矿床蚀变岩地球化学特征和金的赋存状态研究

斑岩型铜金矿床是金资源的重要来源,研究其中载金矿物(如硫化物)的种类其中的金含量是高效回收金的关键。本文通过对沙溪矿床不同类型蚀变岩和工业品位矿石开展系统的矿物学和地球化学成分研究发现,沙溪矿床中钾化蚀变更富集Si、Fe和K、贫Na,青磐岩化蚀变更富集Al和Fe、贫Ca,石英绢云母化更富集Ca和Na、贫Fe和K。矿石内主要脉石矿物为石英含量为37.65 wt%,钠长石含量为17.15 wt%,碱性长石含量为11.35wt%,白云母含量为12.87 wt%,硫化物黄铁矿和黄铜矿含量分别为1.36 wt%、1.17 wt%。金是以类质同象替换的形式存在于黄铁矿和黄铜矿中,在二者中的占比分别为5.98%、2.15%,其他类型占比为91.87%。