福建福安上后洋叶蜡石矿床地质特征及找矿标志

福建福安上后洋叶蜡石矿呈似层状，赋存于晚侏罗世南园组中部火碎屑岩中，共发现有4个矿体，矿石可分为2种类型。即石英叶蜡石型和伊利石质叶蜡石型，以石英叶蜡石型为主，矿体明显受地层岩性控制，属火山热液顺层交代蚀变的似层状叶蜡石矿床。     

Quaternary Volcanic-Related Acid Hydrothermal Alteration in the Ugusu Silica Stone Deposit, Western Izu Peninsula, Central Japan: Geology and Alteration

Acid alteration areas accompanying Quaternary volcanoes are widespread in the western Izu Peninsula, central Japan. The Ugusu alteration area is the largest among them and is mined for “silica stone” at the silica body in the core of the alteration area. Silica zone defined by previous studies is subdivided into highly leached brecciated silica zone and residual silica zone, which extend along a NNW‐SSE–NNE‐SSW direction of fractures/faults. Fe‐rich, alunite, advanced argillic alteration, and intermediate argillic alteration zones occur toward the outside surrounding the two silica zones. The ascent of acid hydrothermal fluid would be responsible for the silica zones and surrounding alteration zones at an earlier stage, while the hydrothermal brecciation and silica veins were caused by a limited supply of silica‐saturated fluids at later stages. Based on the available mineral stability relations and fluid inclusion thermometries, the formation temperatures are estimated to be: >300°C for the residual silica zone; >290°C for the diaspore association in the advanced argillic alteration zone; and <260°C for the kaolinite association in the intermediate argillic alteration zone. The later stage quartz druses have been formed at 200–260°C. The Ugusu–Fukata acid hydrothermal systems were active at 1.5–1.2 Ma, which were temporally related to the Tanaba Andesite volcanism. Hydrothermal system at the Seikoshi gold–silver deposit survived until 0.7 Ma after the volcanism. In the western half of the Izu Peninsula, subduction of the Philippine Sea plate underneath the Suruga Trough caused nearly N–S‐trending maximum horizontal compressive stress (σ_Hmax) and the resultant formation of similarly trending alteration areas and Au‐Ag vein‐type deposits in the Ugusu‐Toi‐Seikoshi area. From a practical viewpoint, at the Ugusu silica stone deposit, the fracture‐controlled vertical morphology of the silica body provides an important guide for exploration. Because the alteration zones occur both in the lower and upper sides of the silica bodies, it is important to make sure to which side the alteration zones correspond.     

寿山叶蜡石矿床中叶蜡石的多型及其转变

叶蜡石具有1Tc和2M_1两种多型。寿山叶蜡石矿床中的叶蜡石不但具有普遍报道的2M_1型及1Tc与2M_1的混合型,而且具有同类矿床中少见的、但在本区却大量出现的1Tc型。本文对寿山叶蜡石多型变体的X射线衍射特征、镜下特征及化学成分特征作了写实性描述,指出本区叶蜡石存在着2M_1型向1Tc型转变的客观事实,并可能存在二者的中间类型;探讨了叶蜡石多型转变的条件,提出“表生溶液”是实现该转变的主要因素。     

相山李家岭铀矿床热液蚀变作用地球化学特征

李家岭铀矿床是最近几年在相山西部发现的一个铀矿床。矿床热液蚀变特别发育并存在明显的蚀变分带现象,在对钻孔岩心样详细的野外和室内岩相学观测基础上,将李家岭铀矿床铀矿化段分为矿化中心带、矿旁蚀变带、近矿蚀变带和远矿蚀变带,其热液蚀变强度依次减弱。运用标准化Isocon图解法表明,热液蚀变带中,CaO、FeO、Fe₂O₃、Na₂O明显增加,这与发育赤铁矿化、钠长石化、碳酸盐化相一致;K₂O明显降低,这是由于钠长石交代钾长石造成K的大量迁出;而MnO、MgO在各蚀变带中呈现“此消彼长”的特征,显示出热液蚀变交代过程中并不是简单地扩散渗滤交代,可能存在对流平衡的元素迁移方式。Th、Y、Zr、Hf等微量元素变化与铀含量一致,对铀矿化具有很好地指示作用。HREE与铀矿化关系密切,随着蚀变程度增强,HREE明显增加,显示成矿流体富含HREE,并具有深源性。     

Hydrothermal Alteration and Mineralization of Middle Jurassic Dexing Porphyry Cu-Mo Deposit, Southeast China

The Dexing deposit is located in a NE‐trending magmatic belt along the southeastern margin of the Yangtze Craton. It is the largest porphyry copper deposit in China, consisting of three porphyry copper orebodies of Zhushahong, Tongchang and Fujiawu from northwest to southeast. It contains 1168 Mt of ores with 0.5% Cu and 0.01% Mo. The Dexing deposit is hosted by Middle Jurassic granodiorite porphyries and pelitic schist of Proterozoic age. The Tongchang granodiorite porphyry has a medium K cal‐alkaline series, with medium K₂O content (1.94–2.07 wt%), and low K₂O/(Na₂O + K₂O) (0.33–0.84) ratios. They have high large‐ion lithophile elements, high light rare‐earth elements, and low high‐field‐strength elements. The hydrothermal alteration at Tongchang is divided into four alteration mineral assemblages and related vein systems. They are early K‐feldspar alteration and A vein; transitional (chlorite + illite) alteration and B vein; late phyllic (quartz + muscovite) alteration and D vein; and latest carbonate, sulfate and oxide alteration and hematite veins. Primary fluid inclusions in quartz from phyllic alteration assemblage include liquid‐rich (type 1), vapor‐rich (type 2) and halite‐bearing ones (type 3). These provide trapping pressures of 20–400 ´ 10⁵ Pa of fluids responsible for the formation of D veins. Igneous biotite from least altered granochiorite porphyry and hydrothermal muscovite in mineralized granodiorite porphyry possess δ¹⁸O and δD values of 4.6‰ and ?87‰ for biotite and 7.1–8.9‰, ?71 to ?73‰ for muscovite. Stable isotopic composition of the hydrothermal water suggests a magmatic origin. The carbon and oxygen isotope for hydrothermal calcite are ?4.8 to ?6.2‰ and 6.8–18.8‰, respectively. The δ³⁴S of pyrite in quartz vein ranges from ?0.1 to 3‰, whereas δ³⁴S for chalcopyrite in calcite veins ranges from 4 to 5‰. These are similar to the results of previous studies, and suggest a magmatic origin for sulfur. Results from alteration assemblages and vein system observation, as well as geochemical, fluid inclusion, stable isotope studies indicate that the involvement of hydrothermal fluids exsolved from a crystallizing melt are responsible for the formation of Tongchang porphyry Cu‐Mo orebodies in Dexing porphyry deposit.     

胶东三山岛北部海域金矿蚀变特征与微量元素迁移规律

胶东地区是中国最重要的金矿矿集区,区内众多大型–超大型金矿集中产出,已探明金矿资源量占全国30%以上。构造蚀变岩型金矿是胶东区内重要的类型之一,三山岛北部海域金矿是该类型的典型代表。胶东三山岛北部海域金矿是近年来新发现的超大型金矿,对该矿床的蚀变岩石进行研究具有重要意义。通过详实地岩心编录与室内研究,查明了该矿床的主要蚀变类型及矿物组合特征,系统采集了典型蚀变岩石样品并进行了微量元素地球化学分析,运用质量平衡技术方法总结了热液蚀变过程中的元素迁移规律,同时探讨了黄铁绢英岩中微量元素特征。结果表明,在标高−1200～−1400 m 范围内蚀变强烈。蚀变类型有钾化、绢英岩化和黄铁绢英岩化等,其中与成矿关系最为密切的是绢英岩化和黄铁绢英岩化;从原岩到黄铁绢英岩的整个蚀变过程中,流体向围岩提供了大量（迁移量＞2）的As、Sb、Te等低温元素,中量（迁移量为1～2）的Pb、Zn、Cu等中温元素,少量（迁移量＜1）的Co、Ni、Cr等高温元素,表明在标高−1200～−1400 m处,流体以中低温元素组合为主,预测−1200～−1400 m处矿体仍处于中上部,深部还有很好的找矿潜力。     

Relationship Between Hydrothermal Alteration Index and Geological Attributes at Chuquicamata Cu–Mo Porphyry Deposit,Chile

The distribution of mineral zones, hydrothermal alteration assemblages and ore associations are important geological attributes of the Chuquicamata Porphyry Cu–Mo deposit. The development and morphology of these attributes were influenced by syn‐mineralization structures with later modification of post‐mineralization tectonism to yield the present day form. In this work we evaluate the elemental mass transfer index due to hydrothermalism by using Pearce Element Ratios, using a database of 1110 samples consisting of elemental concentrations by chemical analysis. We study the relationship of the aforementioned index with the geological attributes in the porphyry as well as evaluate the type of information that the index provides according to its distribution, magnitude and variability. The magnitudes of the alteration index are organized into deciles, each of which represents a source of information, or macrostate. Within these, the geological attribute, or microstate, has a probability to participate that depends on the possible categorization of a particular attributes. The amount of information or uncertainty that each geological attribute provides to each decile of the distribution of the alteration index is determined by measuring the value of entropy. The results indicate that this distribution is controlled by the geometric–kinematic properties of syn‐mineralization structures that generate the primary pattern related to potassic alteration that develops in the hanging wall of the East Shear Zone. Subsequently the shape of the potassic alteration is modified by the kinematic effect imposed by the Americana and Estanques Blancos faults, and this broadly defines the geometry of the Qz–Mo event and the shape of the phyllic alteration. In addition, the sinistral‐inverse shear of the West Fault Zone allows the construction of an enriched blanket and also generates the drag fold that is characteristically observed in the south wall of the mine. All of the above events combine to yield the final geometry of the geological attributes that controls the shape and magnitude of the alteration index in the porphyry. The magnitude of the alteration index is mainly driven by the potassic and phyllic alteration stages. Potassic alteration is dominant in the first four deciles, while phyllic alteration is dominant in the last six deciles. Supergene mineralization attributes contribute discreetly to the average magnitude of the alteration index for each decile. The distribution of the probability of participation of the geological attributes in the distribution of the alteration index suggests that in the potassic alteration, biotite and green‐gray sericite facies contribute to strengthen the index in an associated manner, while in the phyllic alteration, the Qz–Ser textural type is the most significant.     

伊犁京希—伊尔曼德金矿床的热液蚀变及成矿流体演化特征

京希－伊尔曼德金矿床的热液蚀变在空间上有明显的分带性，中心蚀变带以强烈的硅化为主，典型的蚀变矿物组合为石英或玉髓和地开石，中间带为高级泥化带，以地开石－高岭石－石英或玉髓为特征；外带为以蒙脱石－高岭石－伊利石－其他粘土矿物等矿物组合为主的泥化带，蚀变强度和矿物组合的分带性是温度、压力和化学梯度的反映，是流体在不断的水或流体－岩石反应和成分交换的产物。该矿床成矿流体演化过程为：早期酸性（pH=2-3)含矿流体在沿断裂上升过程中，受围岩灰岩中的流体（pH为中性）缓冲，在其进入高渗透性的碎屑岩层时，流速和水－岩石或流休－岩石反应大大加快，并在与大气降水的混合作用下，pH值逐步升高（3－5），产生了流体的温度及成分梯度，在温度和压力迅速下降的条件下，金及蚀变矿物沉淀、结晶生长，形成了蚀变空间分带，中心带保存完好的多孔状石英和地开石等高级泥化矿物组合说明该矿床是高硫化热液体系作用下的产物。     

西藏古堆地热田水热蚀变类型、分布特征及对勘探方向的启示

水热蚀变与泉华作为地热流体水-岩反应和化学沉积的产物,其相关研究可为水热活动发展史、恢复地热流体古温度及水岩反应过程等方面研究提供重要信息。古堆地热田位于错那—沃卡裂谷中部,是继羊八井地热田之后我国大陆最具发电潜力的非火山岩型高温地热田之一,极具开发潜力。为了解古堆地热田泉华和水热蚀变的类型、分布特征及判断有利的勘探方向,本文在野外地热地质调查的基础上,结合室内镜下鉴定和扫描电镜分析等工作,识别出绿泥石化、硅化、高岭石化和碳酸盐化等水热蚀变类型。研究发现,古堆地热田水热蚀变呈现出从蚀变中心向外由酸性蚀变过渡为弱酸性-中性蚀变的分带模式,蚀变中心常由强烈蚀变的硅化带或高岭石带组成;水热蚀变分布受断裂构造的控制,蚀变在断裂交汇处最为强烈,蚀变中心常沿着断裂延伸;根据水热蚀变的分布及蚀变强度,初步判断布雄朗古和杀嘎朗嘎的渗透性相对较好且热储温度高,具有较好的开发前景。在泉华沉积方面,古堆地热田西区主要为钙华区,东区为钙华和硅华叠加区;结合青藏高原动力学背景,认为古堆地热田水热发展史与陆陆碰撞的隆升过程及错那—沃卡裂谷活动密切相关且存在明显的耦合关系。     

Types of Pyrophyllite Deposits in Foldbelts

Abstract. Pyrophyllite deposits can be divided into five types on the basis of geology and genesis. The first two types are associated with hydrothermally altered rocks in felsic and intermediate volcanogenic suites. They are characterized by their metasomatites and their subsequent mineralogic transformations under varying volcanic conditions. The third type includes deposits and occurrences of metamorphic-metasomatic genesis, which is caused by transformations of terrigenous-sedimentary interbeds in felsic volcanics under greenschist facies conditions. The fourth type is associated with low and mid-temperature stages of hydrothermal vein formation at the limits of volcanogenic and metamorphic strata. The fifth type comprises pyrophyllite occurrences in weathering crusts on metamorphic strata and metasomatite.
The formation conditions and distribution of raw pyrophyllite deposits were influenced by the geodynamic situations and geochemical conditions, such as character of tectonic dislocations, volcanism and chemical composition of hydrothermal solutions.     

Hydrothermal Alteration and Fluid Geochemistry of the Tongonan Geothermal Field, Philippines

Abstract: The alteration mineralogy, the present-day fluid chemistry, and some fluid inclusion data are used to make inferences on the chemical changes that have occurred in the fluids during the history of the Tongonan Geothermal Field. Thermal activity in the Tongonan area began in the Miocene when emplacement of many plutons forming a batholith contact metamorphosed the overlying volcanics to hornblende hornfels assemblages. In the early Pliocene, when tectonic uplift occurred along the Philippine Fault, about 2 mole % of mainly carbon dioxide and sulfur gas was released to a geothermal fluid and condensed in groundwater with geothermal steam. The condensate intensely altered the reservoir rock and formed an acid mineral assemblage, which was overprinted by a later, lower temperature, neutral-pH assemblage. Some chlorite, epidote and illite in the reservoir rock formed at temperatures up to 100°C lower than present-day temperatures possibly during the Plio-Pleistocene uplift period, i.e., the system was heating up. The assemblage garnet-anhydrite formed in fractures from a condensate after the gas had nearly completely separated from the deep, CO₂-rich fluid during vigorous boiling possibly during hydrothermal eruptions. The output of gas to the geothermal fluid decreased, while the salinity (10,000 mg/kg or - 2 wt% NaCl) and the temperature of the geothermal fluid remained nearly constant throughout the Quaternary. When this neutral-pH, alkali chloride fluid boiled, it initially precipitated albite or epidote on the rims then anhydrite at the center of fractures at high temperatures (-250–300°C). At lower temperatures (-150–250°C), adularia or wairakite and later calcite were deposited as the proportion of gas in the steam condensate increased. The origin of solutes is also discussed.     

Geological and Geochemical Characteristics of the Hydrothermal Clay Alteration in South Korea

Abstract: Hydrothermally altered areas forming pyrophyllite‐kaolin‐sericite‐alunite deposits are distributed in Chonnam and Kyongsang areas, Cretaceous volcanic field of the Yuchon Group. The Chonnam alteration area is located within depression zone which is composed of volcanic and granitic rocks of late Cretaceous age. The clay deposits of this area show the genetic relationship with silicic lava domes. The Kyongsang alteration area is mainly distributed within Kyongsang Basin comprising volcanic, sedimentary and granitic rocks of Cretaceous and Tertiary age. Most of the clay deposits of this area are closely related to cauldrons. Paleozoic clay deposit occurs in the contact zone between Precambrian Hongjesa granite gneiss and Paleozoic Jangsan quartzite of Choson Supergroup. Cretaceous igneous rocks of the both alteration areas belong to high K calc‐alkaline series formed in the volcanic arc of continental margin by subduction‐related magmatism. Chonnam igneous rocks show more enrichment of crustal components such as K, La, Ce, Sm, Nd and Ba, higher (La/Yb)cn ratio, and higher initial ⁸⁷Sr/⁸⁶Sr ratio (0. 708 to 0. 712) than those of Kyongsang igneous rocks. This might be due to the difference of degree of crustal contamination during Cretaceous magmatism. The most characteristic alteration minerals of Chonnam clay deposits are alunite, kaolin, quartz, pyrophyllite and diaspore which were formed by acidic solution. Those of Kyongsang clay deposits are sericite, quartz and pyrophyllite which were formed by weak acid and neutral solution. The formation ages of the clay deposits of two alteration areas range from 70. 1 to 81. 4 Ma and 39. 7 to 79. 4 Ma, respectively. The Daehyun clay deposit in Ponghwa area of Kyongsang province shows the alteration age range from 290 to 336 Ma. This result shows the different alteration episode from the hydrothermal alteration of Cretaceous to early Tertiary in the Kyongsang and Chonnam alteration areas. These data indicate, at least, three hydrothermal activities of Tertiary (middle to late Eocene), late Cretaceous (Santonian to Maastrichtian) and Paleozoic Carboniferous Periods in South Korea.     

Hydrothermal Alteration Related to Silver Mineralization at the Iwami Silver Deposit,Shimane Prefecture,Japan

The Iwami epithermal silver deposit consists of Ag-Cu veins in a dacitic intrusive body at the deep portion of the Eikyu area, and veinlets with disseminated Ag mineralization in dacitic tuff breccia at a shallow portion of the Fukuishi area. Hydrothermal alteration associated with the silver mineralization is characterized by intense potassium metasomatism with oxidizing conditions. An illite zone occurs around the pathways of uprising fluids in both the Eikyu and Fukuishi areas. It grades laterally into the illite/smectite zone, which is surrounded by a broad smectite zone. Because of boiling, abundant adularia associated with silver mineralization overlaps on the altered tuff breccia in the Fukuishi area. The alteration zoning suggests that the western Eikyu area and the eastern Fukuishi area belong to a single hydrothermal system. The data of fluid inclusion microthermometry indicate that the temperatures range 220–270°C, and salinities range 5–7 wt percent NaCl equivalent for the silver mineralization at the upper portion in the Eikyu area and the lower portion in the Fukuishi area. Radiometric ages for volcanic rocks in the area range from 2.19 to 1.64 Ma, and the dacitic intrusion formed at approximately 1.6 Ma. The silver-dominant mineralizing hydrothermal fluids system was active around 1.44 to 1.07 Ma, which formed the Eikyu Ag-Cu veins at depth, and the Fukuishi Ag ores at the shallower portion.     

Numerical Simulation of Hydrothermal Alteration Chemical Reactions During Ore-forming Process of the Jiaojia Gold Deposit,Jiaodong Peninsula,China;

The Jiaojia gold deposit is featured by obvious alteration zonation, and is one of the typical altered-type gold deposits in the Jiaodong gold province. However, the formation conditions of hydrothermal alteration zonation and the spatial location of chemical reaction associated with gold precipitation are still unclear. To quantitatively discuss the hydrothermal process, we used the TOUGHREACT software to simulate the chemical reactions between ore-bearing fluids and wall rocks of the Jiaojia gold deposit. First, we constructed a conceptual mineralization model related to hydrothermal alteration by discussing the chemical reaction between ore-bearing fluids and wall rocks. Subsequently, we simulated the chemical equilibrium concentration of ore-forming fluids and pH changes under different temperature and pressure conditions, which was used to study the dissolution and precipitation mechanism of hydrothermal minerals during ore-forming processes. The simulation results show that the chemical equilibrium concentration of Au+ significantly decreased with temperature from 280 ℃ to 180 ℃, and the chemical equilibrium concentration of Fe2+ showed similar trend, indicating that the favorable gold metallogenic temperature range is 180 ℃ to 280 ℃, and Fe2+ in ore-forming fluids reacts with [Au(HS)2]− to promote gold precipitation. The temperature and pressure conditions influence the chemical equilibrium concentrations of ore elements, nevertheless, temperature is a more critical factor controlling gold precipitation, while the influence of pressure is relatively weak. The pH simulation results show that the pH values of ore-forming fluids increased during the hydrothermal alteration reaction, which means that the ore-forming environment changes from acidic to neutral and/or alkaline. The pH variation during the ore-forming process is consistent with conventional geological observations, and thus validated the simulation results. The above results indicate that the temperature driving lateral migration of ore-forming fluids along the fault resulted in the continuous overprinting alteration. The pyrite-sericite-quartz alteration in the footwall of the fault zone is conducive to gold precipitation and enrichment due to frequent overprinting of various alteration and changes of temperature and pH. © 2023 Science Press. All rights reserved.     

Geochemical Evolution of Hydrothermal Fluids at the Daejang Cu–Zn–Pb Vein Deposit, Korea

Abstract: The Daejang mine is located within the Cretaceous Gyeongsang basin. Mineral paragenesis can be divided into four stages (stages I, II, III and IV) by major tectonic fracturing. Stages I, III and IV are economically barren. Stage II, at which the precipitation of major ore minerals occurred, is further divided into three substages with paragenetic time based on minor fractures and discernible mineral assemblages: substage IIa, marked by deposition of quartz and Fe–sulfides; substage IIb, by introduction of base-metal sulfides within carbonates and some quartz; substage IIc, by quartz and carbonates with various sulfosalts. Fluid inclusion data indicate a complex geochemical evolution of hydrothermal fluids. Both CO₂–rich and H₂O–rich fluids were trapped in fluid inclusions at stage I and substage IIa. It is suggested that a compositionally heterogeneous fluid was formed by fluid boiling and CO₂ immiscibility at temperatures of about 400° to 300°C. Composite lodes of base-metal sul–fides, carbonates and quartz at substage IIb were deposited in open spaces created by fracturing. The fracturing event prompted rapid decreases in pressure and temperature of residual fluids and resulted in retrograde fluid boiling at about 200 bars and 300°–250°C during substage IIb. The progressive loss of CO₂ by CO₂ effervescence and retrograde boiling from substage IIa and IIb fluids resulted in pH increase and related increase in carbonate activity, causing deposition of abundant carbonates. The change in pH also caused the decrease of stability of hydrogen sulfide with Cu, Zn and Pb chloride complexes (as main transporting agents at Daejang) and resulted in the pricipitation of base-metal minerals. Deposition of Ag– and Sb-bearing sul–fides and sulfosalts of substage IIc occurred at temperatures of about 250° to 150°C from a dominantly aqueous fluid with low salinity (down to 3. 0 equiv. wt % NaCl). At this substage, aqueous fluid formed by mixing with cooler and less saline meteoric groundwater. There is a systematic decrease in caculated δ¹⁸O_water values with the mineralization stage (and decreasing temperature) in the Daejang hydrothermal system, from values of about 11% for stage I, through about 4% for stages II and III, to about –3 per mil for stage IV. The result of stable isotope and fluid inclusion studies are interpreted to indicate progressive less evolved and/or unexchanged meteoric water influx of an early hydrothermal system formed by highly evolved meteoric waters.     

西藏多不杂斑岩铜金矿床地质与蚀变

[摘 要]西藏多不杂斑岩铜金矿是近年来新发现的一个矿床,位于班公湖-怒江成矿带西段。多不杂矿床内发育三期花岗闪长斑岩,侵入到侏罗系曲色组变砂岩中,北东向断层是多不杂矿床的主要控岩断层。多不杂矿床由内向外发育钾化、绢英岩化、青磐岩化,钾化主要发育于第一期花岗闪长斑岩出露区域,绢英岩化环绕钾化带发育,并叠加在钾化带之上,青磐岩化在矿床西侧的玄武安山岩和南侧的火山角砾岩中呈团块状发育。多不杂矿床的的铜矿化以黄铜矿矿化为主,金矿化与铜矿化密切共生。黄铜矿化主要发育于第一期花岗闪长斑岩及其与变砂岩接触带内,第一期花岗闪长斑岩为多不杂矿床的成矿斑岩。     

江西上饶龙门高岭石-叶蜡石矿的矿物组成及稳定同位素特征

在野外地质工作、镜下观察的基础上,采用电子探针、X射线粉晶衍射、氢氧稳定同位素测试等方法对江西上饶龙门高岭石-叶蜡石矿床矿石进行了分析。其主要组成矿物为高岭石族矿物、叶蜡石和石英,其次有少量的绢云母、黄铁矿和赤铁矿等。矿石中高岭石族矿物Hinckley指数为0.33～0.94,整体属于较无序高岭石,叶蜡石有2M型和1Tc型两种多型,以2M型为主。矿石的δ18O值为4.5‰～6.6‰,δD值为-71.7‰～-98.5‰。综合分析认为该矿床为晶屑玻屑凝灰岩受热液蚀变而成,其成矿热液主要来自大气降水,成矿温度为75℃～300℃,压力<1kb。     

Geology and Hydrothermal Alteration of the Duobuza Gold‐Rich Porphyry Copper District in the Bangongco Metallogenetic Belt,Northwestern Tibet

The Duobuza gold‐rich porphyry copper district is located in the Bangongco metallogenetic belt in the Bangongco‐Nujiang suture zone south of the Qiangtang terrane. Two main gold‐rich porphyry copper deposits (Duobuza and Bolong) and an occurrence (135 Line) were discovered in the district. The porphyry‐type mineralization is associated with three Early Cretaceous ore‐bearing granodiorite porphyries at Duobuza, 135 Line and Bolong, and is hosted by volcanic and sedimentary rocks of the Middle Jurassic Yanshiping Formation and intermediate‐acidic volcanic rocks of the Early Cretaceous Meiriqie Group. Simultaneous emplacement and isometric distribution of three ore‐forming porphyries is explained as multi‐centered mineralization generated from the same magma chamber. Intense hydrothermal alteration occurs in the porphyries and at the contact zone with wall rocks. Four main hypogene alteration zones are distinguished at Duobuza. Early‐stage alteration is dominated by potassic alteration with extensive secondary biotite, K‐feldspar and magnetite. The alteration zone includes dense magnetite and quartz‐magnetite veinlets, in which Cu‐Fe‐bearing sulfides are present. Propylitic alteration occurs in the host basic volcanic rocks. Extensive chloritization‐silicification with quartz‐chalcopyrite or quartz‐molybdenite veinlets superimposes on the potassic alteration. Final‐stage argillic alteration overlaps on all the earlier alteration. This alteration stage is characterized by destruction of feldspar to form illite, dickite and kaolinite, with accompanying veinlets of quartz + chalcopyrite + pyrite and quartz + pyrite assemblages. Cu coexists with Au, which indicates their simultaneous precipitation. Mass balance calculations show that ore‐forming elements are strongly enriched during the above‐mentioned three alteration stages.     

基于短波红外勘查技术的西藏甲玛铜多金属矿热液蚀变矿物分布模型研究

甲玛铜多金属矿是西藏冈底斯中段东部取得找矿突破的超大型矿床。通过短波红外测量,确定了矿体中热液蚀变矿物主要有白云母、绿泥石、黑云母、硬石膏、高岭石、地开石、黄玉和方解石。白云母与铜多金属矿化的关系密切,矿体厚度与贫铝白云母的样本数具有正相关关系,代表钾化带的黑云母分布趋势显示甲玛矿体的热源中心位于ZK2416-ZK3216一线以北的位置,富镁绿泥石分布在贫铝绢云母的外侧,与贫铝绢云母具有相同的热源中心指示意义。分布模型中缺少多硅白云母,显示矿区成矿的热源中心较深,因此作为剥蚀程度比较浅的甲玛斑岩系统而言,外围找矿潜力大。     

山东金翅岭金矿蚀变特征与元素迁移规律

胶东地区是中国最重要的金矿集区,区内众多大型-超大型金矿床集中产出,已探明金矿资源量占全国近三分之一。其中石英脉型金矿是区内重要的矿床类型,山东金翅岭金矿就是这一类型的代表之一。通过详细的野外地质观测与室内研究,查明了该金矿床蚀变类型及矿物组合特征,系统采集不同蚀变类型的岩石样品,进行岩石元素地球化学分析,运用质量平衡计算法总结了热液蚀变过程中的元素迁移规律。该矿床原岩为二长花岗岩,含矿热液沿断裂上涌,与围岩发生了强烈的蚀变作用,蚀变类型主要为钾长石化、绢英岩化和黄铁绢英岩化;蚀变过程中的物质交换改变了流体的成分及酸碱度等,流体向蚀变岩提供了大量的Si O2;同时,绢英岩化阶段和黄铁绢英岩化阶段,围岩向流体提供了大量的K、Na,促使流体中的Au活化,引起热液中的Au H3Si O4稳定性降低,造成Au H3Si O4分解,流体中的Fe2+、Fe3+被消耗,形成黄铁矿,导致Au大量沉淀。