The Bulong Gold Deposit-a Quartz-Barite Vein Type Gold Deposit in Xinjiang:Geological Characteristics and S, He and Ar Isotopic Compositions

The Bulong gold deposit, located in the southwest Tianshan in China, occurs in the Upper Devonian finegrained clastic rocks. The gold orebodies are controlled by an gently inclined interlayer fractured zone. They are hosted only in quartz-barite veins though there are barite veins and quartz veins in the ore district. The δ34S values of pyrite in the ores range from 14.6‰ to 19.2‰ and those of barite from 35.0‰ to 39.6‰, indicating that the sulfur was derived from the strata. 3He/4He ratios of fluid inclusions in pyrite are 0.24-0.82 R/Ra, approximating to that of the crust. The 40Ar/39Ar ratios range from 338 to 471, slightly higher than that of the atmosphere. 40Ar /4He ratios of ore fluids range from 0.015 to 0.412 with a mean of 0.153. Helium and argon isotope compositions of fluid inclusions show that the ore fluids of the Bulong gold deposit were mainly derived from the crust.

Geochemical Characteristics of the Jinjiazhuang Ultrabasic Rock-Type Gold Deposit in Chicheng County, Hebei Province

The Jinjiazhuang gold deposit occurs in the Zhangjiakou gold field, Northwest Hebei. The ore bodies are mostly hosted in Xiaozhangjiakou ultrabasic rocks dominated by diopsidite. Electron microprobe analyses indicate that the deposit is characterized by the enrichment of some platinum group elements in principal metallic minerals such as chalcopyrite, galena, sphalerite and pyrite, and the presence of millerite. Stable isotope studies show that carbon, sulfur and most of the metallogenic elements were probably derived largely from the host Xiaozhangjiakou ultrabasic rocks and that it is possible that the ore\|forming fluid was predominated by meteoric water.

U-Pb SHRIMP Dating of Zircon from Quartz Veins of the Yangshan Gold Deposit in Gansu Province and Its Geological Significance

The Yangshan gold deposit is a super-large fine-grained disseminated gold deposit located in southern Gansu Province. Its metallogenic age has been determined by using the cathodoluminescence image and ion probe U-Pb dating techniques. It is found that zircons from quartz veinlet of the fine-grained disseminated gold ore show characters of magmatic origin with prism idiomorphism, oscillatory zoning and dominant Th/U ratios of 0.5-1.5. Three main populations of zircons are obtained, giving average 206Pb/238U ages of 197.6±1.7 Ma, 126.9±3.2 Ma and 51.2±1.3 Ma respectively. The first age corresponds to the K-Ar age of the plagiogranite dike, while the latter two ages indicate that buried Cretaceous and Tertiary intrusives exist in the orefield, suggesting that the Yangshan gold deposit was genetically related to the three magmatic hydrothermal activities. By contrast, zircons from coarse gold-bearing quartz vein in the mining area are much older than the host rock, indicating that the vein was formed earlier and was not contaminated by later magmatic fluids. It is concluded that the coupling of multiperiodic hydrothermal activities in the mining area has contributed a lot to mineralization of the Yangshan gold deposit.

Fluid inclusion, siliceous rock geochemistry of Shewushan lateritic gold deposit, Hubei Province, eastern China: Implication for the genesis of primary orebody

The Shewushan gold deposit is located 16 km southwest of Jiayu County, Hubei Province, eastern China, which is the largest lateritic gold deposit in Asia, consisting of a series of mineralized faults containing gold grades of 1.0–19.5 g/t set within a larger, lower-grade(0.2–1.0 g/t) zone. According to the fluid inclusions study, the homogenization temperature ranges from 70–350℃, and concentrates between 140–220℃. The laser Rama results show that the CO2 and CH4 exist in mineralized fluid. In addition, the major and trace element and REE geochemical data show that the genesis of the siliceous rocks is hydrothermal genesis, formed by mineralized fluid bearing SiO2 transmitted along faults to the surface, and replace the carbonate rocks to begin deposition. Primary gold mineralization is attributed to hydrothermal activity that followed the main period of tectonic deformation of the Indosinian orogeny, which caused the regional detachment regime in southeast Hubei. The reversed fold and the fault system formed the fluid migration channel in the Shewushan area. EPMA results show that Au exists in arsenopyrite(850×10-6–1550×10-6 Au) and pyrite(470×10-6–1340×10-6 Au). Therefore, based on the above results and combined with the field observation, we suggest that the genesis of primary orebody in Shewushan deposit is carlin type, while not weathered residual type.

Geology and Geochemistry of Reworking Gold Deposits in Intrusive Rocks of China-I.Features of the Intrusive Rocks

Most gold deposits in intrusive rocks were formed as a result of reworking processes.The intrusive rocks containing gold deposits and consisting of ultramafic-mafic, intermediate-acid and alkaline rocks of the Archean, Proterozoic, Caledonian, Hercynian and Yenshanian periods occur in cratons, activated zones of cratons and fold belts. Among them, ultramafic-mafic rocks, diorite, alkaline rocks, and anorthosite are products of remelting in the mantle or mantle-crust or mantle with crustal contamination. However, auriferous intermediate-acid rocks are products of metasomatic-remelting in auriferous volcanic rocks or auriferous volcano-sedimentary rocks in the deep crust.

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.

Genesis and Geological-Geochemical Characters of the Rushan Gold Deposit, Shandong, China

The Rushan gold deposit, explored in recent years in the Jiaodong area, Shandong Province is a quartz vein-type gold deposit hosted in granite. The temperature of its major mineralization episode is between 220℃ and 280℃. The salinity of the ore-forming fluid is 5 % to 9% NaCl equivalent, with H2O and CO2 as the dominant gas constituents. The fluid is rich in Na+, Ca+ and Cl-, but relatively impoverished in K+ and F-, characterized by either Ca2+ >Na+ >K+ (in three samples) or Na+ > Ca2+ > K+ (in six samples). Hydrogen and oxygen isotopes in the ore-forming fluid are highly variable with δ18 OH2O ranging between -7. 70‰ and 5. 97‰ and δDH2O between - 128‰ and - 71‰. The possibility of lamprophyre serving as the source of gold can be excluded in view of its low gold content on the order of 2. 5 × 10 -9. Rb-Sr isochron ages of the deposit and the host Kunyushan granite are (104. 8±1. 5) Ma and 134. 6 Ma respectively with the respective initial Sr ratios of 0. 71307 and 0. 7096. It is considered that the emplacement of the lamprophyre under a tensile environment had provided sufficient heat energy to facilitate deep circulation of meteoric water by which ore metals were extracted from the Kunyushan granite through long-term water-rock reaction.

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.

Genesis and Geological and Geochemical Characteristics of Qixia Gold Deposit, Shandong, China

The Qixia gold deposit is one of the important quartz vein-type deposits hosted inmetamorphic rocks in the east of Shandong, China. Compositionally the wolframite which isassociated with gold mineralization in the deposit is rich in iron, but poor in manganese, showing that this mineral crystallized from hydrothermal solution at low temperature. The temperatures at the main metallogenic stage of the Qixia gold deposit are Within the range of 160 -270t. The gaseous phases in fluid inclusions are dominated by H2O and CO2, while Na+,Ca2+ and Cl- are the major species in the fluid phase with K+ and F- present in relativelysmall amounts. The salinities of fluids are 4. 2 wt% - 8. 0 wt% NaCl equiv. Meanwhile, thefluid is characterized by either Ca2+ > Na+ > K+ (in five samples) or Na+ > Ca2 + > K+ (in twosamples), quite similar to the composition of ore-forming fluid derived from meteoric water.Primary data on the hydrogen and oxygen isotopic compositions of the ore-forming fluid fallwithin a wide range: δ%H2o = - 56‰-95‰ and δ18OH2O=- 3.6‰-4. 5‰ relative toSMOW. These isotopic values fully reflect the distribution features of meteoric water which hasexchanged with the metamorphic rocks of the Jiaodong Group at different temperatures and W/R ratios, and the metallogenic process is characterized by low W/R ratios. The Rb-Sr isochronage of the Qixia gold deposit is 125. 8 ± 1. 7 Ma, with (87Sr/86Sr) being 0. 7168, and the timeinterval between the gold deposit and its country rocks (granite or metamoprhic rocks) is verylarge. The formation Of the Qiaxia gold deposit is directly related to the evolution of geologicalhistory in eastern Shandong, and a genetic model in which the deep convective circulating meteoric water reacts with the country rocks can be used to explain the metallogenic mechanism ofthe deposit.

辽东半岛五龙金矿外围电性特征及找矿意义

辽东五龙金矿经过80余年的开采,矿山资源储备严重下滑,后备资源不足问题日益突出,亟需查明矿区深部和外围矿产资源。通过在v163号脉西北和东南两侧以及100号断裂南侧开展瞬变电磁法测量工作,构建了相应的二维和三维地电模型,分析了矿区低阻异常特征;结合前人研究成果,推断出金矿成因类型和下一步找矿方向。研究结果表明:v163号脉西北方向P0剖面上低阻区是由包括163号脉西北段的细粒闪长岩脉群引起的,属于石英脉型成矿的可能性较大;100号断裂南侧三维地电模型中的低阻区域与大孤顶子金矿矿化点相对应,该低阻区向北侧深部规模增大,异常未封闭,表明该区域北侧深部具有良好的找矿前景,值得进一步开展研究工作;v163号脉东南方向的三维地电模型中,低阻异常值在数量级上明显低于前二者,推测为蚀变带引起,后经工程验证孔揭露,该区域纵向存在多层不连续的硅化蚀变岩,最大厚度为41m,蚀变类型有硅化、绢云母化、绿泥石化以及不同程度的黄铁矿化。研究表明,五龙金矿不仅存在石英脉型金矿体,还有蚀变岩型金矿体,后者可能是该矿区下一个找矿的主要方向。

The metallogenic models of gold deposits of quartz vein type and altered rock type

Metallogenic models of gold deposits of quartz vein type and altered rock type will be dis-cussed in this note. They are considered to be closely related to granite spatially andgenetically.

高精度磁测在柴达木盆地北缘三角顶金矿床找矿中的应用

三角顶金矿床位于柴北缘结合带滩间山岩浆弧,是区域造山型金矿成矿事件响应的产物;研究区主要出露寒武系—奥陶系滩间山群火山岩组,岩性主要为玄武岩、硅质岩等;岩浆活动强烈,主要为晚泥盆世花岗闪长岩、二长花岗岩等,岩体中发育辉绿岩脉、石英脉等;基性—酸性岩中磁性由强变弱,其中辉长岩、二长花岗岩磁化率最高分别为8815.6×10^(-6)×4π·SI、5992.4×10^(-6)×4π·SI,可能由磁铁矿化、黄铁矿化引起强磁化率;磁异常呈锯齿状不规则跳跃,强度中等,梯度变化大,幅值为-733~820 nT;高精度磁法测量对与金矿成矿关系密切的断裂构造、破碎蚀变带等地质体有较好的分辨效果,经高精度磁法探测出局部异常呈串珠状分布,沿异常轴部存在断裂构造。经部分工程验证,在区内圈定构造蚀变带12条、金矿体7条、金矿化体40余条,M18-2异常与区内化探异常、深部工程验证等找矿信息相吻合,为区内进一步金矿找矿方向提供了依据。

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。

庄河市新房金矿区找矿方向探讨

庄河市新房金矿区为辽南地区新发现的大型矿床,属庄河-桓仁断裂构造体系,区内褶皱构造发育程度一般,断裂构造较为发育,庄凤构造虽然为区域内规模最大构造,但属导矿构造,其次级构造燕山期构造为成矿期控矿构造,矿体多而分散,研究区域成矿规律对找矿突破有着重要指导意义。通过分析该矿区区的地质特征、矿体特征、矿床成因。明确了该矿床以充填、交代为主,属于中-低温热液交代充填型成因。含金地质体赋存于太古界鞍山群变片麻岩地层内,具明显层控性,主要为石英脉、硅钾蚀变岩二类含金地质体,两者呈迭加过渡关系或单独产出,属石英脉和硅钾蚀变岩型金矿,指出元古代盖层与太古代基底接触带部位是找矿有利靶区。

模糊综合评判法在蚀变岩型金矿床岩体质量评价中的应用

对于工程岩体的质量评价,不论是目前常用的Q系统分类法、地质力学RMR分类法还是国标BQ分类法,都存在一定的局限性。为了得到一个更加准确,更贴近真实岩体质量的评价结果,引用模糊综合评判法进行岩体的稳定性评价。以焦家金矿蚀变岩型金矿床为例,对不同蚀变类型的岩性稳定性进行模糊综合评判。结果表明焦家矿区调查区域为-190中段至-330中段之间,除-270以上黄铁绢英岩化花岗岩为Ⅲ类稳定性一般的岩体外,其余蚀变花岗岩的岩体质量均为Ⅳ类较差和Ⅴ类很差的岩体。品位最高的黄铁绢英岩化碎裂岩岩体稳定性最差,在施工到相应岩性的采场时特别要注意做好采场的相关支护工作。

类比陈家村金矿床浅析高寨岭矿区金矿找矿潜力

为了解湖南省汉寿县高寨岭矿区金矿找矿潜力,采用与岩坝桥岩体周边矿床(点)进行类比的方法,特别是与陈家村(跑马坪)金矿床进行对比,可知岩坝桥岩体周边金矿主攻类型主要为破碎蚀变岩型,次为产于浅变质岩中的石英脉型。对比结果显示陈家村金矿床与高寨岭金矿区属同一“地层-构造-岩体”构成的成矿系统,高寨岭金矿区找矿潜力巨大。

鄂东北花桥金矿构造蚀变特征及成矿规律浅析

花桥金矿是唯一产于鄂东北梅川岩体南缘外接带的构造蚀变岩型金矿,通过分析其构造蚀变特征和控矿因素,重新认识其矿化富集规律,可为梅川岩体南缘的找矿预测提供依据。研究表明,花桥金矿的矿体严格受断裂破碎(蚀变)带控制,NE向断裂破碎带为主要控矿构造,至少经历了3期构造—热液叠加改造,中期形成由黄铁绢英岩、黄铁绢英岩质碎裂岩等组成的矿化蚀变碎裂岩带,赋存了大小不等的矿体,呈现“大带套小带、小带产矿体”的矿化特征。初步分析认为花桥金矿可能形成于早白垩世,梅川岩体提供了成矿热液、成矿物质及热能,郯庐断裂带及其次级剪切带为导矿构造,矿区浅表层次脆性断裂及其裂隙为容矿构造,赋矿围岩主要为构造蚀变岩。建议进一步加强梅川岩体与金多金属矿成矿关系的研究,开展梅川岩体南缘内外接触带深部找矿预测。

黔西南两类容矿围岩金矿对比及对深部找矿勘查的指示

黔西南是中国著名的卡林型金矿集区,已查明金资源量约750 t,特别是近年来在该地区新发现了玄武岩容矿金矿,以架底大型金矿床、大麦地中型金矿床为典型代表,取得了新的找矿突破和认识,至此,该地区原生金矿容矿围岩主要有玄武岩和沉积岩两类。通过对黔西南玄武岩容矿金矿与沉积岩容矿金矿进行对比分析研究,认为:(1)卡林型金矿的定义可能存在一定局限性,需进一步拓展,黔西南玄武岩容矿金矿与沉积岩容矿金矿典型特征相似,可能形成于同一区域成矿事件,是同一区域岩浆热液成矿作用形成的卡林型金矿,在深部勘查与研究工作中应系统考虑;(2)构造(背斜、穹隆、断裂、SBT)+有利岩石组合(厚度大于100 m的碳酸盐岩与上覆厚度大于50 m的碎屑岩或玄武岩/凝灰岩)+Au-As-Sb-Hg-Tl组合异常+围岩蚀变(硅化、黄铁矿化、毒砂化),可能指示深部存在卡林型金矿;(3)玄武质岩石也是卡林型金矿很好的赋矿围岩,卡林型金矿容矿岩石、容矿地层具有多样性,几乎区内所有岩石和地层均可以成为卡林型金矿的容矿岩石和容矿地层,但具体到某一个特定的矿床时,往往有特定的就位地层和特殊的容矿围岩。

湘西雪峰构造带金控矿因素与成矿机理

雪峰构造带发育大量的金矿床,是中国重要的金产地之一。然而,该构造带内金控矿因素问题一直未能厘清。金控矿因素研究对金的成矿规律总结和矿产资源勘查等都具有重要意义。从地层、构造和岩浆岩等方面探讨了雪峰构造带金控矿因素,并结合金矿床的时空分布特征分析了金的成矿机理,结果表明:构造是金成矿的必要条件,而前寒武纪地层和区域岩浆活动仅是金成矿的有利条件,雪峰构造带金成矿期集中在加里东期和印支期—燕山期,支持成矿流体来源为大气降水的观点。雪峰构造带内金矿床类型为变质碎屑岩型。

山东旧店金矿床花岗岩类锆石U-Pb年龄及对招平断裂带南段岩浆活动规律的约束

山东旧店金矿床位于胶东半岛招平断裂带南段,是以石英脉型矿化为主的中型金矿床。矿区内花岗岩类十分发育,类型多样,但是对这些花岗岩类的形成时代和成因一直缺乏深入研究,制约了对该矿床成矿地球动力学背景的认识。对该矿床4号、6号和12号矿脉出露的花岗质片麻岩、含石榴子石二长花岗岩、黑云二长花岗岩及花岗伟晶岩开展了详细的LA-ICP-MS锆石U-Pb定年,获得花岗质片麻岩年龄为709.1±4.1 Ma(6号脉),含石榴子石二长花岗岩年龄为164.1±1.9 Ma(4号脉),黑云二长花岗岩年龄为157.5±1.1 Ma(4号脉)和145.2±1.5 Ma(6号脉),花岗质伟晶岩年龄为146.5±0.7 Ma(12号脉)。综合野外地质特征和前人研究结果表明,旧店金矿床存在新元古代、晚侏罗世和早白垩世3期岩浆活动,其中晚侏罗世含石榴子石二长花岗岩和黑云二长花岗岩形成于岩石圈由挤压向伸展转变阶段,均为S型花岗岩,它们既是该矿床的赋矿岩体,同时可能也是成矿母岩。