Evidence of mantle-rooted fluids and multi-level circulation ore-forming dynamics: A case study from the Xiadian gold deposit,Shandong province,China

Metallogensis of the Xiadian gold deposit in Shandong Province has been a question under dispute for a long time. There are many points such as metamorphic hydrothermal, magamatic hydrothermal and meteoric water. Detailed study shows that mantle-rooted fluids were involved in the ore-forming processes. Evidence for this argumentation comes from: (1) discor-dogenic fault; (2) intersecting and accompanying of basic veins and lodes; (3) geochemistry of stable isotopes; (4) geochemistry of fluid inclusions; and (5) multi-level circulation and exchanging of mantle-rooted fluids. Based on the characteristics of the circulation system of mantle-rooted fluids and its close relation to magmatic hydrothermal fluids and meteoric water, ore-bearing fluids are divided into three subsystems: (1) C-H-O-rich fluid circulation subsystem in mantle, (2) Si-rich fluid circulation subsystem in the middle and lower crust; and (3) S-rich fluid circulation subsystem in shallow and surface crust. Ore-forming functions of these subsystems are controlled respectively by their different geodynamic settings.     

Evidence of mantle-rooted fluids and multi-level circulation ore-forming dynamics: A case study from the Xiadian gold deposit, Shandong Province, China

Metallogensis of the Xiadian gold deposit in Shandong Province has been a question under dispute for a long time. There are many points such as metamorphic hydrothermal, magamatic hydrothermal and meteoric water. Detailed study shows that mantle-rooted fluids were involved in the ore-forming processes. Evidence for this argumentation comes from: (1) discordogenic fault; (2) intersecting and accompanying of basic veins and lodes; (3) geochemistry of stable isotopes; (4) geochemistry of fluid inclusions; and (5) multi-level circulation and exchanging of mantle-rooted fluids. Based on the characteristics of the circulation system of mantle-rooted fluids and its close relation to magmatic hydrothermal fluids and meteoric water, ore-bearing fluids are divided into three subsystems: (1) C-H-O-rich fluid circulation subsystem in mantle, (2) Si-rich fluid circulation subsystem in the middle and lower crust; and (3) S-rich fluid circulation subsystem in shallow and surface crust. Ore-forming functions of these subsystems are controlled respectively by their different geodynamic settings.     

Sources of ore-forming fluids and metallic materials in the Jinwozi lode gold deposit, eastern Tianshan Mountains of China

This paper presents gas compositions and H-, O-isotope compositions of sulfide- and quartz-hosted fluid inclusions, and S-, Pb-isotope compositions of sulfide separates collected from the principal Stage 2 ores in Veins 3 and 210 of the Jinwozi lode gold deposit, eastern Tianshan Mountains of China. Fluid inclusions trapped in quartz and sphalerite are dominantly primary. H- and O-isotopic compositions of pyrite-hosted fluid inclusions indicate two major contributions to the ore-forming fluid that include the degassed magma and the meteoric-derived but rock 18O-buffered groundwater. However, H- and O-isotopic compositions of quartz-hosted fluid inclusions essentially suggest the presence of groundwater. Sulfide-hosted fluid inclusions show considerably higher abundances of gaseous species CO2, N2, H2S, etc. Than quartz-hosted ones. The linear trends among inclusion gaseous species reflect the mixing tendency between the gas-rich magmatic fluid and the groundwater. The relative enrichment of gaseous species in sulfide-hosted fluid inclusions, coupled with the banded ore structure indicating alternate precipitation of quartz with sulfide minerals, suggests that the magmatic fluid has been inputted to the ore-forming fluid in pulsation. Sulfur and lead isotope compositions of pyrite and galena separates indicate an essential magma derivation for sulfur but the multiple sources for metallic materials from the mantle to the bulk crust.     

Sources of ore-forming fluids and metallic materials in the Jinwozi lode gold deposit,eastern Tianshan Mountains of China

This paper presents gas compositions and H-, O-isotope compositions of sulfide- and quartz-hosted fluid inclusions, and S-, Pb-isotope compositions of sulfide separates collected from the principal Stage 2 ores in Veins 3 and 210 of the Jinwozi lode gold deposit, eastern Tianshan Mountains of China. Fluid inclusions trapped in quartz and sphalerite are dominantly primary. H-and O-isotopic compositions of pyrite-hosted fluid inclusions indicate two major contributions to the ore-forming fluid that include the degassed magma and the meteoric-derived but rock ¹⁸O-buffered groundwater. However, H- and O-isotopic compositions of quartz-hosted fluid inclusions essentially suggest the presence of groundwater. Sulfide-hosted fluid inclusions show considerably higher abundances of gaseous species CO₂, N₂, H₂S, etc. than quartz-hosted ones. The linear trends among inclusion gaseous species reflect the mixing tendency between the gas-rich magmatic fluid and the groundwater. The relative enrichment of gaseous species in sulfide-hosted fluid inclusions, coupled with the banded ore structure indicating alternate precipitation of quartz with sulfide minerals, suggests that the magmatic fluid has been inputted to the ore-forming fluid in pulsation. Sulfur and lead isotope compositions of pyrite and galena separates indicate an essential magma derivation for sulfur but the multiple sources for metallic materials from the mantle to the bulk crust.     

Sources of ore-forming fluids and metallic materials in the Jinwozi lode gold deposit,eastern Tianshan Mountains of China

This paper presents gas compositions and H-, O-isotope compositions of sulfide- and quartz-hosted fluid inclusions, and S-, Pb-isotope compositions of sulfide separates collected from the principal Stage 2 ores in Veins 3 and 210 of the Jinwozi lode gold deposit, eastern Tianshan Mountains of China. Fluid inclusions trapped in quartz and sphalerite are dominantly primary. H-and O-isotopic compositions of pyrite-hosted fluid inclusions indicate two major contributions to the ore-forming fluid that include the degassed magma and the meteoric-derived but rock ¹⁸O-buffered groundwater. However, H- and O-isotopic compositions of quartz-hosted fluid inclusions essentially suggest the presence of groundwater. Sulfide-hosted fluid inclusions show considerably higher abundances of gaseous species CO₂, N₂, H₂S, etc. than quartz-hosted ones. The linear trends among inclusion gaseous species reflect the mixing tendency between the gas-rich magmatic fluid and the groundwater. The relative enrichment of gaseous species in sulfide-hosted fluid inclusions, coupled with the banded ore structure indicating alternate precipitation of quartz with sulfide minerals, suggests that the magmatic fluid has been inputted to the ore-forming fluid in pulsation. Sulfur and lead isotope compositions of pyrite and galena separates indicate an essential magma derivation for sulfur but the multiple sources for metallic materials from the mantle to the bulk crust.

     

Geophysical exploration for interlayer slip breccia gold deposits: example from Pengjiakuang gold deposit, Shandong Province, China

Interlayer slipping breccia‐type gold deposit – a new type of gold deposit, defined recently in the northern margin of the Jiaolai Basin, Shandong Province, China – occurs in interlayer slip faults distributed along the basin margin. It has the features of large orebody thickness (ranging from 14 m to 46 m, with an average thickness of 30 m), shallow embedding (0–50 m thickness of cover), low tenor of gold ore (ranging from 3 g/t to 5 g/t), easy mining and ore dressing. This type of gold deposit has promising metallogenic forecasting and potential for economic exploitation. A ground gamma‐ray survey in the Pengjiakuang gold‐ore district indicates that the potassium/thorium ratio is closely related to the mineralization intensity, i.e. the larger the potassium/thorium ratio, the higher the mineralization. The gold mineralized alteration zone was defined by a potassium/thorium ratio of 0.35. A seismic survey confirms the location of the top and bottom boundaries and images various features within the Pengjiakuang gold mineralization belt. The gold‐bearing shovel slipped belt dips to the south at an angle of 50–55° at the surface and 15–20° at depth. The seismic profile is interpreted in terms of a structural band on the seismic section characterized by a three‐layered model. The upper layer is represented by weakly discontinuous reflections that represent the overlying conglomerates. A zone of stronger reflections representing the interlayer slip fault (gold‐bearing mineralized zone) is imaged within the middle of the section, while the strongest reflections are in the lower part of the section and represent metamorphic rocks at depth. At the same time, the seismic reflection survey confirms the existence of a granite body at depth, indicating that ore‐forming fluids may be related to the granite. A CSAMT survey showed that the gold‐bearing mineralized zone is a conductive layer and contains a low‐resistivity anomaly ranging from 2 Ωm to 200 Ωm.     

Geochemistry of ore-forming fluids and geological significance of the Kuoerzhenkuola gold field in Xinjiang, China

The Kuoerzhenkuola gold field (including the Kuo- erzhenkuola and the Buerkesidai gold deposits), lo- cated 68 km east of Jimunai County in northern Xing- jiang, China, is an important component of the Sawuer gold belt which is the eastward extending part of the Zarma-Sawur gold-copper belt in Kazakhstan. Some studies are concerned with the geology of the gold ores[1―3], the associated volcanic rocks[4], radiogenic isotope[5―8], and the ore-forming environment[8]. Most researchers inferr…     

Isotopic indication to source of ore materials and fluids of the Wangfeng gold deposit in Tianshan: A case study of metallogenesis during collisional orogenesis

The Wangfeng gold deposit is one of the five most important gold deposits in the Tianshan. Studies of its metallogenic time, space, geodynamic background, ore feature and ore fluid have proved that the deposit formed in the late Paleozoic continental collision, and consequently is a suitable delegate to probe mineralizing regularities during collisional orogenesis. Isotopic studies including O, D, C, S, Pb and Sr reveal ore materials derived from sedimentary association (including carbonate and sulfate), which further refers to the Hercynian carbonate-silicolite-argillite formation north to Wangfeng camp. At the end of Paleozoic, the southward intracontinental subduction of Hercynian synthem along the Hongwuyueqiao fault down to the Central Tianshan terrane induced large-scale fluidization which extracted and out-transported ore materials from Hercynian synthem upto shallow fair positions, and finally resulted in the formation of the Wangfeng deposit. This study excludes the possibility of other tectonic metallogenic models other than the tectonic model for collisional metallogenesis, petrogenesis and fluidization.     

安徽省霍山县东溪-南关岭金矿地质特征与成矿条件

东溪-南关岭金矿为北淮阳东段发现的第一个原生金矿,产于磨子潭-晓天中生代火山盆地边缘,容矿围岩为安山质-英安质火山岩,矿化和蚀变受桐柏-桐城深大断裂带的次级构造带控制。该金矿发育陡倾斜的脉状矿体和缓倾斜的似层状矿体,成因类型为冰长石-绢云母型浅成低温热液金矿。火山岩盆地之下的变质基底可能起到了初始矿源层作用,桐柏-桐城断裂带及其次级构造破碎带为重要的导岩导矿构造,早白垩世强烈的岩浆活动提供了热源、动力源和部分矿源。参照国内外类似金矿的特征,认为本区成矿地质条件良好,有可能隐伏着与石英正长岩体有关的细脉浸染型矿化,晓天火山盆地具有良好的找矿前景。     

A preliminary study on ore-forming environments of Xianglushan-type iron deposit and the weathering mineralization of Emeishan basalt in Guizhou Province,China

Xianglushan-type iron deposits are one of the new types of iron deposits found in the Weining Area of Western Guizhou. The iron-bearing rock system is a paleo-weathered crustal sedimentary(or accumulating) stratum between the top of the Middle-Late Permian Emeishan basalt formation and the Late Permian Xuanwei formation. Iron ore is hosted in the Lower-Middle part of the rock system. In terms of the genesis of mineral deposit, this type of deposit should be a basalt paleo-weathering crustal redeposit type, very different from marine sedimentary iron deposits or continental weathering crust iron deposits. Based on field work and the analytical results of XRD Powder Diffraction, Electron Probe, Scanner Electron Microscope, etc., the geological setting of the ore-forming processes and the deposit features are illustrated in this paper. The ore-forming environment of the deposit and the Emeishan basalt weathering mineralization are also discussed in order to enhance the knowledge of the universality and diversity of mineralization of the Emeishan Large Igneous Province(ELIP), which may be a considerable reference to further research for ELIP metallogenic theories, and geological research for iron deposits in the paleo-weathering crust areas of the Emeishan basalt,Southwestern, China.     

Crude oil as carrier of gold: petrological and geochemical evidence from Lannigou gold deposit in southwestern Guizhou, China

Organic matter is related closely to mineralization of Lannigou gold deposit in southwestern Guizhou, China. Regionally, the distribution of organic carbon agrees well with that of faults within which gold deposits are hosted. Studies on organic petrology show that pyrobitumen, which is related most closely to mineralization, adheres to quartz vein or fills quartz veinlet. Proton-induced X-ray emission (PIXE) analysis shows an evident abundance of Au in pyrobitumen. Pyrobitumen paragenetically associates with pyrite and arsenopyrite which are the main carrier minerals of Au. The thermal simulation experiment indicates that about 99% of Au will be concentrated in oil phase in the coexisting system of oil and brine and rock. The role of crude oil in ore-forming process is: as carrier of Au, crude oil moves upwards, and undergoes thermal decomposition and thermochemical reduction when it encounters the oxidizing fluid within the Trassic turbidity; Au is thus released from crude oil, reduced and precipitated. Project supported by the Climbing Project (No. PA30) and the National Natural Science Foundation of China (Grant No. 49673190).     

山东焦家金成矿带地球物理特征及找矿预测

本文以焦家断裂带为研究目标,综合利用地质、重力、磁法、大地电磁等资料,总结了区域物性、重磁场特征,并选择典型剖面,利用实测MT数据,开展了2.5D重磁电联合精细反演,推断了控矿断裂构造的深部变化特征.A-A′剖面重磁电特征显示,焦家断裂带上盘呈现低阻-中磁特征,而下盘呈现高阻-高磁特征,焦家断裂带和三山岛断裂带的视电阻率异常梯度带在4 km以浅非常清晰,分界线走势基本沿焦家断裂带深部延伸,呈现"漏斗"形状.本文根据建立的地质-地球物理找矿预测模型推断,焦家断裂带剖面上低磁异常向高磁异常的过渡带、布格重力异常梯级带的转弯部位和视电阻率等值线同步向下弯曲、间距变大及由陡变缓部位都是成矿的有利部位,为今后该地区金矿勘查提供重要技术指导.     

基于多元信息约束的隐伏矽卡岩型铁矿床的定位——以云南北衙金矿区红泥塘矿段为例

矽卡岩型矿床是云南北衙金多金属矿区的一种主要矿床类型,受岩体、构造及层位等控制,其有利找矿空间为中酸性岩体与碳酸盐岩的接触带.以岩石物性为纽带,实现目标地质体与地球物理场的转换,提取有效信息.接触带中低电阻率、岩体的低密度性、铁矿的高磁性和高极化率等都是矽卡型铁矿床的特有地球物理属性.通过地质地球物理等多元信息的层层约束,解析不同级次的成矿要素问题,实现对隐伏矽卡岩型铁矿床的定位,建立地球物理勘探模式,并在矿区外围开展方法有效性的验证,取得了良好的勘探效果,提出一套适应于北衙地区及类似成矿地质背景下的隐伏矽卡岩型铁矿床定位预测方法.     

A step metallogenetic model for gold deposits in the northwestern Shandong Peninsula, China

Based on our study of the nature and variation of mineralization-controlling faults in their deep extension and the spatial distribution of gold orebodies in the northwestern Shandong Peninsula (NSP), here we propose that the gold deposits in the Jiaojia gold belt are controlled by listric faults and the gold deposits in the NSP are controlled by extensional fault system. We also suggest that there is a multiple mineralization space in the deep part of the NSP gold belt. As steps or benches occur along the deep extention of the listric fault where its dipping angle changes from steep to gentle, a number of gold deposits are correspondingly distributed as a steplike pattern, which is named as a step metallogenetic model for gold deposits in the NSP. The gold deposits in Shandong Peninsula were formed in the Cretaceous when the crust in the region experienced extention and thinning following the strong collision between North China Plate and Yangtze Plate during the Triassic. Crust anataxis, fluid remobilization, and extention-detachement of the crust are the leading factors for the gold mineralization.     

Characteristics and origins of primary fluids and noble gases in mantle-derived minerals from the Yishu area, Shandong Province, China

springerlink.com Studies of mantle fluids are currently one of the hot topics in the earth science, greatly contributing to re-vealing origins and evolutions of fluids. In general, the concept of mantle fluids refers to their active compo-nents, such as CO2, H2O, N2, etc., while the noble gases inert in chemical properties belong to another research system. Due to their marked differences in various fluid sources of the Earth[1], the isotopic sig-natures of He and Ar have been widely used a…     

N2-Ar-He systematics and source of ore-forming fluid in Changkeng Au-Ag deposit, central Guangdong, China*

Changkeng Au-Ag deposit is a newly-discovered new type precious metal deposit. N₂-Ar-He systematics studies and³He/⁴He and δD- δ¹⁸O composition analyses show that the ore-forming fluid of the deposit is composed mainly of formation water (sedimentary brine) but not of meteoric water, which was thought to be source of the ore-forming fluid by most previous researchers. The content of mantle-derived magmatic water in the ore-forming fluid is quite low, usually lower than 10%. According to the source of the ore-forming fluid, the Changkeng Au-Ag deposit should belong to sedimentary brine transformed deposits. From the Late Jurassic to the Early Cretaceous Period, with deposition and accumulation of thick sediments in Sanzhou Basin, the formation water in the sedimentary layers was expelled from the basin because of overburden pressure and increasing temperature. The expelled fluid moved laterally along sedimentary layers to the margin of the basin, and finally moved upward along a gently-dipping interlayer fault. Because of a decline in pressure and temperature, ore minerals were deposited in the fault. Project supported by the National Natural Science Foundation of China (Grant No. 495020291, the Natural Science Foundation of Zhongshan University, the Research Foundation of National Key Laboratory of Metallogenesis in Nanjing University (Grant No. 039704) and the Lingnan Foundation.     

Continental hydrothermal sedimentary siliceous rock and genesis of superlarge germanium (Ge) deposit hosted in coal: A study from the Lincang Ge deposit,Yunnan, China

The study on marine hydrothermal sedimentationtends to be perfect at present, and a suit of hydrother-mal sedimentary distinguishing criterions (includingstructure, conformation, geochemistry, etc.) has beenfound[1—12]. While it is unsubstantial on the study ofhydrothermal sedimentation in continental deposi-tional environment, and little was known about therelation between continental hydrothermal sedimenta-tion and metal mineralization. The Lincang Ge deposit,hosted in coal with independent…     

Research on the dynamics of the South China Sea opening:Evidence from analogue modeling

Independent of Indochina extrusion, the South China Sea experienced a process from passive continental rifting to marginal sea drifting. According to the fault patterns in the Beibu Gulf basin and the Pearl River Mouth basin, the continental rifting and early spreading stage from 32 to 26 Ma were controlled by extensional stress field, which shifted clockwise from southeastward to south southeastward. From 24 Ma on, the sea spread in NW-SE direction and ceased spreading at around 15.5 Ma. Integrated geological information with the assumption that the South China Sea developed along a pre-Cenozoic weakness zone, we did analogue experiments on the South China Sea evolu- tion. Experiments revealed that the pre-existing weakness zone goes roughly along the uplift zone between the present Zhu-1 and Zhu-2 depression. The pre-existing weakness zone is composed of three segments trending NNE, roughly EW and NEE, respectively. The early opening of the South China Sea is accompanied with roughly 15° clockwise rotation, while the SE sub-sea basin opened with SE extension. Tinjar fault was the western boundary of the Nansha block (Dangerous Ground), while Lupar fault was the eastern boundary of the Indochina, NW-trending rift belt known as Zengmu basin developed between above two faults due to block divergent of Indochina from Nansha. In the experiment, transtensional flower structures along NW-trending faults are seen, and slight inversion occurs along some NE-dipping faults. The existence of rigid massifs changed the orientations of some faults and rift belt, and also led to deformation concentrate around the massifs. The rifting and drifting of the South China Sea might be caused by slab pull from the proto South China Sea subducting toward Borneo and/or mantle flow caused by India-Asia collision.     

3D electrical structure of porphyry copper deposit: A case study of Shaxi copper deposit

Located in Lu-Zong ore concentration area, middle-lower Yangtze metallogenic belt, ShaXi porphyry copper deposit is a typical hydrothermal deposit. To investigate the distribution of deep ore bodies and spatial characteristics of host structures, an AMT survey was conducted in mining area. Eighteen pseudo-2D resistivity sections were constructed through careful processing and inversion. These sections clearly show resistivity difference between the Silurian sandstones formation and quartz diorite porphyry and this porphyry copper formation was controlled by the highly resistive anticlines. Using 3D block Kriging interpolation method and 3D visualization techniques, we constructed a detailed 3D resistivity model of quartz diorite porphyry which shows the shape and spatial distribution of deep ore bodies. This case study can serve as a good example for future ore prospecting in and around this mining area.     

Emplacement age and PGE geochemistry of lamprophyres in the Laowangzhai gold deposit,Yunnan, SW China

Widely-distributed lamprophyres in the Laowangzhai gold deposit were associated closely with gold ores. Phlogopite⁴⁰Ar/³⁹Ar dating suggests that the emplacement age of lamprophyric magma ranges from (30.8±0.4) to (34.3±0.2) Ma, and gold mineralization took place at (26.4±0.2) Ma. PGE geochemical tracing indicates that gold in the gold deposit did not come from the primitive lamprophyric magma. The tempo-spatial paragenesis between lamprophyres and mesothermal gold deposits along the Jinsha-Red River belt may be attributed to the fact that they formed in the same tectonic setting.