Geology and Geochemistry of K-feldspar Veins in Lamprophyre at the Zhenyuan Gold Deposit,Yunnan,Southwest China:Implications for Gold Mineralization

Lamprophyres typically appear in hydrothermal gold deposits.The relationship between lamprophyres and gold deposits is investigated widely.Some researchers suggest that the emplacement of lamprophyres triggers gold mineralization,whereas others hypothesize that the formation of lamprophyres increases the fertility of mantle sources and ore-forming fluids.K-feldspar veins,with ages between those of lamprophyres and gold deposits,appear in lamprophyres in Zhenyuan.Therefore,K-feldspar veins are ideal for investigating the relationship between lamprophyres and gold deposits.Phlogopite in K-feldspar veins has lower Mg#,Ni,and Cr contents and higher TiO2,Li,Ba,Sr,Sc,Zr,Nb,and Cs contents than phlogopite in lamprophyres.The in-situ Sr isotopic values of apatites(0.7063–0.7066)in K-feldspar veins are within the range for apatites(0.7064–0.7078)from lamprophyres.High large-ion lithophile element concentrations and low Nb and Ta concentrations in phlogopite from lamprophyres,in addition to high(87Sr/86Sr)i values of apatite(0.7064–0.7078),indicate that the magma parental to these phlogopite and apatite crystals is derived from an enriched mantle.Kfeldspar veins are genetically correlated with lamprophyres,whereas sulfide mineral assemblage and trace element compositions of pyrite in K-feldspar veins suggest that K-feldspar veins in lamprophyres are not directly related to gold mineralization of the Zhenyuan deposit.

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.

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.

Microstructural analysis of a subhorizontal gold-quartz vein deposit at Donalda,Abitibi greenstone belt,Canada:Implications for hydrodynamic regime and fluid-structural relationship

The Donalda gold deposit in the southern part of the Archean Abitibi greenstone belt consists mainly of a subhonzontal gold-quartz vein perpendicular to subvertical shear zones.The 0.3—0.5 m thick vein is characterized by vein-parallel banding structures indicating multiple episodes of fracture opening and mineral precipitation.Measurement of the c-axis of primary growth quartz indicates that quartz preferentially grew perpendicular to the fracture,suggesting open space filling and/or extensional nature of the fracture.Measurement of the orientations of microfractures,veinlets and fluid—inclusion planes（FIPs） crosscutting primary growth quartz indicates that the vein minerals were subject to a vertical maximum principal stress（σ_1）,which is inconsistent with the subhorizontalσ_1 inferred from the regional stress field with N—S shortening.This apparent discrepancy is explained by invoking episodic fluid pressure fluctuation between supralithostatic and hydrostatic regimes accompanied by episodic opening and closing of the sub-horizontal fracture.When fluid pressure was higher than the lithostatic value,the fracture was opened and primary growth minerals were precipitated,whereas when fluid pressure decreased toward the hydrostatic value,the hanging wall of the fracture collapsed,causing collision of protruding primary growth minerals from both sides of the fracture and resulting in formation of vein-parallel deformation bands.The columns where the two facing sides of the fracture collided were subject to higher-than-lithostatic stress due to the bridging effect and reduced support surface area,explaining the development of verticalσ_1.This hypothesis is consistent the fault-valve model,and explains the flipping ofσ_1 without having to change the regional stress field.

Geochemical Trace of Silicon Isotopes of Intrusions and Ore Veins Related to Alkali-rich Porphyry Deposits in Western Yunnan, China

Western Yunnan is the well-known polymetallic province in China. It is characterized by copper-gold mineralization related to Cenozoic alkali-rich porphyry. This paper analyzes the silicon isotope data obtained from four typical alkali-rich porphyry deposits based on the dynamic fractionation principle of silicon isotope. The study shows that the ore materials should originate mainly from alkali-rich magmas, together with silicon-rich mineralizing fluids. The process of mineralization was completed by auto-metasomatism, i.e. silicon-rich mineralizing fluids (including alkali-rich porphyry and wall-rock strata) replaced and altered the country rocks and contaminated with crustal rocks during the crystallization of alkali-rich magmas. Such a process is essentially the continuance of the metasomatism of mantle fluids in crust's mineralization. This provides important evidence of silicon isotopic geochemistry for better understanding the mineralization of the Cenozoic alkali-rich porphyry polymetallic deposits

REE geochemistry of auriferous quartz carbonate veins of Neoarchean Ajjanahalli gold deposit,Chitradurga schist belt,Dharwar Craton,India

REE composition of the carbonates of the auriferous quartz carbonate veins（QCVs） of the Neoarchean Ajjanahalli gold deposit.Chitradurga schist belt.Dharwar Craton,is characterized by U-shaped chondrite normalized REE patterns with both LREE and HREE enrichment and a distinct positive Eu anomaly.As positive Eu anomaly is associated with low oxygen fugacity,we propose that the auriferous fluids responsible for gold mineralization at Ajjanahalli could be from an oxygen depleted fluid.The observed positive Eu anomaly is interpreted to suggest the derivation of the auriferous fluids from a mantle reservoir.The location of Ajjanahalli gold deposit in a crustal scale shear zone is consistent with this interpretation.

Isotopic Chronological Study of the Huangsha-Tieshanlong Quartz Vein-Type Tungsten Deposit and Timescale of Molybdenum Mineralization in Southern Jiangxi Province,China

The Huangsha-Tieshanlong quartz-vein tungsten polymetallic ore deposit, located in the northern Pangushan-Tieshanlong tungsten ore field in eastern Ganxian-Yudu prospecting areas of the Yushan metallogenic belt, is a well-known tungsten deposit in southern Jiangxi province, China. SHRIMP-determined dating of zircons from the Tieshanlong granite yields ages of 168.1±2.1 Ma （n=11, MSWD-1.3）. Rhenium and osmium isotopic dating of molybdenite from the Huangsha quartz-vein tungsten deposit determined by ICP-MS yields a weighted average ages of 153-3 Ma and model ages of 150.22.1 Ma - 155.4-2.3 Ma. The age of the Huangsha tungsten deposit is 10 to 15 Ma later than the Tieshanlong granite, which shows that there might have been another early Late Jurassic magmatic activity between 150 and 160 Ma, a process which is closely related with tungsten mineralization in this area. The Tieshanlong granite, the Hnangsha tungsten deposit and the Pangushan-Tieshanlong ore field were all formed around 150-170 Ma, belonging to products of a Mesozoic second large-scale mineralization. According to the collected molybdenite Re-Os dating results in southern Jiangxi province, the timescale of the associated molybdenum mineralization is 2-6 Ma in the tungsten deposit and the timescale of independent molybdenum mineralization is 1-4 Ma, implying the complexity of tungsten mineralization. Times of molybdenum mineralization are mainly concentrated in the Yanshanian, which includes three stages of 133-135 Ma, 150-162 Ma, and 166-170 Ma, respectively. The 150-162 Ma-stage is in accordance with ages of large-scale WoSn mineralization, which is mainly molybdenum mineralization characterized by associated molybdenum mineralization with development of an even greater-intensity independent molybdenum mineralization. Independent molybdenum mineralization occurred before and after large-scale W-Sn mineralization, which indicates that favorable prospecting period for molybdenum may be in Cretaceous and early late Jurassic.

Auriferous Quartz Veins from the Dongping Gold Deposit, NW Hebei Province and Metallogenesis—Fluid Inclusion Rb-SrIsochron Evidence

The Dongping gold deposit, situated on the northern margin of the North China Platform, is a composite deposit composed of auriferous quartz vein-type and altered rock-type ore bodies. It is hosted in the inner contact zone of an alkaline intrusion which was intruded into Archean metamorphic rocks and was formed not later than the Hercynian peried. Auriferous quartz veins of the deposit are dated with the fluid inclusion Rb-Sr isochron method at 103 ±4Ma, indicating that the gold deposit was formed in the Yenshanian period. 87Sr/86Sr sourcetracing shows the ore-forming materials came dominantly from alkaline intrusions. These results, combined with other isotope and REE data, suggest that the Dengping gold deposit is not a traditional magmatic hydrothermal deposit, but a reworked hydrothermal deposit related to heated and evoved meteoric water.

THE METALLOGENIC STRUCTURE OF VEIN-SHAPED LEAD-ZINCDEPOSIT IN HENGSHANLING-SHEXINGPING,CHENZHOU,HUNAN

ＴＨＥＭＥＴＡＬＬＯＧＥＮＩＣＳＴＲＵＣＴＵＲＥＯＦＶＥＩＮ－ＳＨＡＰＥＤＬＥＡＤ－ＺＩＮＣＤＥＰＯＳＩＴＩＮＨＥＮＧＳＨＡＮＬＩＮＧ－ＳＨＥＸＩＮＧＰＩＮＧ，ＣＨＥＮＺＨＯＵ，ＨＵＮＡＮＳｕｎＺｈｅｎｇｉａＰｅｎｇＥｎｓｈｅｎｇＺｈｕＹｕｄｅ（Ｄｅ...

Rb-Sr Isotopic Chronology of the Au-Bearing Quartz Veins in Gold Deposits in the Eastern Part of North China Platform

In the eastern part of China there had occurred large\|scale gold mineralization during the Mesozoic, resulting in a large number of important gold ore\|concentrated areas. In this paper we have selected some isotope data (including four gold deposits previously studied and two gold deposits in this work) of Au\|bearing quartz veins of the representative gold deposits in six important gold ore\|concentrated areas in the periphery of the North China Platform and calculated their metallogenic ages using the method of Ludwig (2.90 version). The results show that the representative gold deposits in the six gold ore\|concentrated areas were formed during the Mesozoic.

Ore-forming fluid characteristics and genesis of vein-type lead-zinc mineralization of Xiaohongshilazi deposit,Jilin Province, China

The Xiaohongshilazi mineral deposit in Jilin Province,China,is located in the accretion zone in the northern margin of the North China Block. The deposit contains two types of ore bodies: layered Pb-Zn ore bodies in volcanic rock and vein-hosted Pb-Zn ore bodies controlled by fractures. The vein Pb-Zn ore bodies are strictly controlled by tectonic fracture zones trending in S-N direction,which comprise sulfide veins or sulfidebearing quartz veins distributed along faults or structural fissures. The ores mainly appear mesh-vein and vein structures,and also show solid-solution separation and metasomatic textures. The metal minerals are mainly sphalerite,galena,and pyrite,etc. Wall-rock alteration includes mainly sericitization,chloritization,silicification and carbonatization,etc. Microscope observations and Raman spectroscopy analyses indicate that the oreforming fluid of the vein Pb-Zn ore bodies was mainly magmatic water with low temperature,low salinity,and a shallow depth of metallogenesis( ~ 1.5 km). Sulfur and lead isotope analyses indicate that the sulfide source is mainly formation sulfur or biogenic sulfur,which is similar to the sulfur source of hydrothermal deposit( negative( δ^(34) S values),while the main Pb source was the upper crust with some mantle input. This article argues that the vein Pb-Zn ore body of the Xiaohongshilazi deposit is a low-to medium-temperature hydrothermal vein type related to the formation of a shallow magma chamber.

Locating Mechanism of Quartz Vein Gold Deposits in Rushan, Shandong Province

According to the differences in ore-controlling structural systems and the characteristics of host rocks, textures and structures of ores and mineral associations of ores, quartz vein-type gold deposits in the Rushan area can be divided into the Rushan and Tongling styles. Rushan style gold deposits, occurring in the Kunyushan complex, include Rushan, Tangjiagou and Tongxishan gold mines. They are distributed along four NNE-trending and sinistral, compresso-shear faults with a right stepping array. A prominent characteristic of the gold mineralization is that the orebodies in neighbouring gold deposits distributed in a single ore-controlling fault zone take opposite pitches. Study of the locating structures of the quartz vein gold deposits shows that the Rushan-style gold deposits are characterized by NNE and NE zoning. Therefore, the intersections of the NE direction of the known gold deposit and the neighbouring NNE-trending fault zones are favourable for looking for gold deposits, and the ends of the curving segments of sinistral and right-stepping faults are favourable for looking for large gold deposits. Tongling-style gold deposits occur in the Sanfosan porphyritic monzonitic granite. Emplacement of gold deposits is controlled by arcuate and radiate structures formed during the intrusion of the Sanfoshan porphyritic monzonitic granite; the radiate faults controlled the distribution of orebodies and the arcuate faults controlled the pitch of the orebodies.

PRELIMINARY STUDY ON THE ORE-FORMING CONDITIONS OF THE Au-Pb-QUARTZ VEIN TYPE ORE DEPOSIT,CHINA

PRELIMINARY STUDY ON THE ORE-FORMING CONDITIONS OFTHE Au-Pb-QUARTZ VEIN TYPE ORE DEPOSIT, CHINAHe Zhili, Xu Jiuhua, Yang Zhenlin and Du Jafeng(Dept. of Geol., Univ. of Scie. and Tech. Beijing, 100083 Beijing, China)Ore-forming condition, Au-Pb-quartz vein, ore deposit, ChinaThere are few Au-Pb-Quartz vein type ore deposits in other countries except China. It might be related to the geohistory and geotectonic background. However, this kind of ore deposit has an important economical significance in China. Its formation is due to the dis-tinctive geological conditions of china. Wendong Au-Pb-Quartz type ore deposit including Wenyu and Dongchuang in Xiaoqinling gold field is the most typical. It is a polygenetic and compound ore deposit, Jintongcha and other deposits lying to the west of it in Xiaoqinling area are Au-Pb-Quartz vein type ore deposits. Others of this area lying to the east of Jintongcha are Au-Quartz vein type. This phenomenon stems from the zonnal distribution of minernal de-posits

^(40)Ar/^(39)Ar Fast Neutron Activation Ages of Quartz from the Jinman Vein Copper Deposit in Western Yunnan and Their Significance

Quartz samples collected from the Jinman vein copper deposit in the Lanping Basin of western Yunnan were determined by \{\}\+\{40\}Ar/\{\}\+\{39\}Ar fast neutron activation techniques, and the spectra are characterized as being saddle\|shaped. The samples yielded a plateau age of \{58.05\}±\{0.54\} Ma, a minimum appearance age of \{56.76\}±\{0.81\} Ma and an isochron age of \{54.30\}±\{0.15\} Ma, the three ages being close to each other, indicating that the ages of the quartz samples so far determined are true and reliable. The plateau age represents the time of formation of Cu\|bearing quartz veins, which is corresponding to Early Himalayan. This age is also consistent with the time at which a tectonically thermal event (60 Ma) took place within the Lanping Basin, Yunnan Province. In consideration of the fact that copper ore and other ore types in the vast area of western Yunnan are concentrated mainly in the Early Himalayan strata, the authors believe that there must have existed some indispensable key factors leading to metallogenesis on a large scale during the Early Himalayan period in western Yunnan and also constraining in union the formation of ore deposits there.

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。

河北省涿鹿县杏园矿区矿床成因及找矿标志

本研究通过系统的地质、地球化学及地球物理分析,深入探讨了河北省涿鹿县杏园矿区的成矿背景、矿床特征及其找矿指标。利用先进的地质勘查技术,首次明确揭示了矿区内斑岩型与热液脉型矿床的共生关系及其空间分布规律,提出了新的成矿模型和勘查方向。研究结果不仅深化了对杏园矿区成矿规律的理解,而且对指导未来的地质勘查工作,推动矿产资源的合理开发与利用具有重要意义。

热液成矿系统构造控矿理论

构造对成矿的控制是热液成矿系统的典型特征之一,系统剖析多重尺度控矿构造的几何学、运动学、动力学、流变学和热力学对认识矿床成因和预测找矿至关重要;而如何实现控矿构造格架、渗透性结构、成矿流体通道和矿化变形网络由静态到多尺度时-空四维动态的转变,查明流体通道和矿床增量生长过程与控制因素,揭示热液成矿系统的构造-流体耦合成矿机制和定位规律是亟待解决的关键科学难题。为此,我们在对已有相关成果系统梳理的基础上,提出了科学构建热液成矿系统构造控矿理论的基本要点与对应方法及应用范畴:(1)流体而非构造是构造控矿理论的中心,热液系统的流体流动与成矿作用受控于断裂带格架及其渗透性结构,其中渗透率是将流体流动与流体压力变化联系起来理解控矿构造的核心;(2)不同控矿构造组合的关键控制是构造差应力和流体压力的大小,而矿化类型的变化可能是由于构造应力场引起的容矿构造方位的不同和赋矿围岩之间的强度差异所致;(3)流体通道的生长始于超压流体储库上游围岩中孤立的微裂隙沿流体压力梯度最大的方向、随裂隙发育且相互连结而形成新的长裂隙,并最终连通形成断裂网络内的流体通道,矿床的增量生长发生在高流体通量的短爆发期,断层反复滑动驱动其内流体压力、流速和应力快速变化,当由此诱发的流体通道生长破坏了流体系统的动态平衡时,随之而来的流体快速降压就成为金属沉淀成矿的关键驱动因素;(4)以热液裂隙-脉系统野外地质观测和构造-蚀变-矿化网络三维填图为基础,通过宏观与微观各级控矿构造相结合、地质历史与构造应力分析相结合、局部与区域点-线-面相结合、浅部与深部相结合、时间与空间相结合、定性和定量相结合,对各种控矿因素开展多学科、多尺度、多层次、全方位综合研究,是应遵循的基本原则;(5)通过构造-蚀变-矿化网络填图,将蚀变-矿化体与控矿构造的类型、形态、规模、产状和间距等几何学特征联系起来,利用热液裂隙-脉系统和断裂网络拓扑学及矿体三维几何结构分析等定量方法查明控矿构造格架和渗透性结构并揭示矿化变形网络的连通性与成矿潜力;(6)合理构建地质模型,选取合适的热力学参数和动力学边界条件,利用HCh和COMSOL等方法,定量模拟成矿过程中的流体流动、热-质传递、应力变形和化学反应等的时-空变化,是揭示构造-流体耦合成矿机理和定位规律、预测矿化中心和确定找矿目标的有效途径。进而提出了构造控矿理论的研究流程:聚焦构造-流体耦合成矿机制和定位规律这一关键科学问题,选择热液裂隙-脉系统和构造-蚀变-矿化网络为重点研究对象;通过几何学描述、运动学判断、流变学分析、动力学解析和热力学综合,厘定控矿构造格架,定位矿化中心,示踪成矿流体通道和多种矿化样式的增量生长过程及其关键控制,揭示渗透性结构的时-空演变规律及构造再活化与成矿定位的成因关联,建立构造-流体耦合成矿模式,服务新一轮战略找矿突破。以胶东焦家金矿田为例,开展控矿构造理论研究和成矿预测应用实践,证实了其科学性和有效性。

瑶岗仙钨矿床两类白钨矿地质特征对比研究

瑶岗仙矿床是南岭地区典型的石英脉型黑钨矿床,并伴生石英脉型和矽卡岩型两类白钨矿化。经过野外地质现象系统的观察以及精细的镜下矿物学研究,厘定了两种类型白钨矿化的成矿阶段,对不同类型白钨矿进行了宏观和微观地质特征对比。结果表明,石英脉型和矽卡岩型白钨矿的成矿环境、成矿规模、显微组构等有着明显区别。通过对比两种矿体白钨矿的岩相学特征,约束不同类型白钨矿的成矿过程与成矿作用。

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。