Fluid Inclusion Investigations of the Masjed Daghi Copper-Gold Porphyry-Epithermal Mineralization, East Azerbaijan Province, NW Iran

The Masjed Daghi mineralization is located 30 km southeast of Jolfa city at the bank of Araxes River, northwest Iran. This area is situated in the Alborz-Azarbaijan structural zone of Iran. The most widespread rocks in the mineralization area are andesite and trachyandesite, while there are rock units of latite tuff, andesitic agglomerate, and hornblende porphyry basalt in eastern hills and Eocene flysch in the southern part of the area. Several intrusive bodies are present in the study area, from which the dominant intrusive rock hosting the mineralization is diorite porphyry. The mineralized rock units of the area are cut by different diorite ad mafic dikes. The most prevalent texture of mineralization is dissemination, while open space filling textures including veins and veinlets, are common as well. Diverse types of alteration including potassic, phyllic, argillic, silicification, and a little of carbonatization were recognized in the field and microscopic observations as well as by XRD. In addition to thick silica veins and stockwork zones, some silica, barite, sulfide, and calcite veins and veinlets have occurred in the Masjed Daghi mineralization area. In this research, 26 doubly polished thin sections (wafers) were prepared and investigated. Four samples were taken from surface veins, while 22 samples were chosen from core samples (of 6 boreholes) of white and grey-white silica, and silica-barite veins. The fluid inclusion studies on 105 primary fluid inclusions indicated five phases for inclusions including: 1) liquid or gas, 2) liquid and gas, 3) liquid, gas, and solid, 4) liquid, gas, halite, and solid, and 5) liquid, gas, halite, and two types of solids. The data gained from fluid inclusions approved two mineralization fluids which caused porphyry and epithermal mineralizations. The porphyry fluid inclusions were homogenized in temperatures of 122°C to 550°C with a maximum of 700°C and average salinity of 55 wt% NaCl equivalent, while the epithermal inclusions indicated an average homogenization temperature of 186°C with an average salinity of 6.23 wt% NaCl equivalent.

Genetic links of porphyry Mo-epithermal Pb–Zn–Ag mineralization system:a case study of the Shipingchuan polymetallic deposit,South China

Compared with the porphyry Cu-epithermal Au mineralization system,detailed studies on the porphyry Mo-epithermal Pb–Zn–Ag–Au mineralization are rare due to limited exposures.The Shipingchuan polymetallic deposit,located in the South China Mo Province(SCMP)represents a typical example containing both porphyry Mo and epithermal Pb–Zn–Ag mineralization.The Mo mineralization mainly occurs as molybdenite-quartz veins in veinlets or as disseminated molybdenite within the potassic,silicic,and sericitic syenogranite.The Pb–Zn–Ag mineralization is characterized by veinlet-type sphalerite–galena–pyrite–quartz–calcite vein within the volcanic rocks accompanied with silicifi cation and propylitization.Five molybdenite samples yield a Re–Os isochron age of 104.7±0.7 Ma that is consistent with the zircon age(107.5±2.1 Ma)of the ore-bearing syenogranite within errors.Together with previous reported Ar–Ar ages(106.6–121.8 Ma)of Pb–Zn–Ag related volcanic rocks,the Mo and Pb–Zn–Ag mineralization belong to a magmatic-hydrothermal event in the Early Cretaceous.Meanwhile,the total Re contents of molybednite range from 1.28 to 45.55 ppm,indicating the ore-forming materials were from a mixture between the mantle and crustal material.Moreover,previous sulfur isotopic values(3.7–4.3‰)of the pyrites from the porphyry Mo mineralization were consistent with the reported range of 4.0–6.1‰of the sphalerites from the Pb–Zn–Ag mineralization,implying that the sulfur of two-types of mineralization was derived from magma.The above-mentioned spatial,temporal,and isotopic lines of evidence suggest that the Mo and Pb–Zn–Ag mineralization of the Shipingchuan deposit was formed from the same metallogenic system.In consideration of regional tectonic evolution history,we propose that the porphyry Mo-epithermal Pb–Zn–Ag mineralization formed in an extensional tectonic setting caused by the continued rollback and the eventual slab break-off of the subducting PaleoPacifi c plate.

Laumontitization as an Exploration Indicator of Epithermal Gold Deposits: A Case Study of the Axi and Other Epithermal Systems in West Tianshan, China

In the light of field investigation, microscopic study, X\|ray phase analysis and mineral infrared spectral analysis, it is considered that laumontitization is of extensive occurrence in the Axi gold orefield. The development of laumontitization and its relationship to mineralization show that the laumontitization appeared mainly at the top of and in the periphery of orebodies, and occurred at the edge of the epithermal system or at the late stage of epithermal system evolution. Therefore, laumontitization can be used as an exploration indicator of epithermal gold deposits. The fluids responsible for laumontitization in the Axi gold orefield are similar to those producing hot spring\|type gold deposits or those from modern geothermal fields. Epithermal mineralization of the Axi gold deposit was dated at Carboniferous, indicating that the West Tianshan of China is a region favorable to epithermal\|type gold mineralization and preservation. Hence the West Tianshan of China is a target area for exploring epithermal gold deposits.

Epithermal Ageing Mechanism of Gussasphalt

The normal asphalt index test, DSR test, FTIR and the GPC distribution analysis of molecular weight on the extraction and recovery of asphalt of the gussasphalt, SMA extraction and recovery of asphalt and the rotary-thin-film-oven-aged asphalt above 240 ℃ were introduced. The results indicate the rutting factor and fatigue factor of the extraction and recovery of asphalt of the gussasphalt are greatly improved, and an obvious absorption peak of carbonyl and a further decrease of the SBS molecular weight of the gussasphalt are found.

Genesis of the Ciemas Gold Deposit and Relationship with Epithermal Deposits in West Java,Indonesia:Constraints from Fluid Inclusions and Stable Isotopes

The Ciemas gold deposit is located in West Java of Indonesia, which is a Cenozoic magmatism belt resulting from the Indo-Australian plate subducting under the Eurasian plate. Two different volcanic rock belts and associated epithermal deposits are distributed in West Java： the younger late Miocene-Pliocene magmatic belt generated the Pliocene-Pleistocene epithermal deposits, while the older late Eocene-early Miocene magmatic belt generated the Miocene epithermal deposits. To constrain the physico-chemical conditions and the origin of the ore fluid in Ciemas, a detailed study of ore petrography, fluid inclusions, laser Raman spectroscopy, oxygen-hydrogen isotopes for quartz was conducted. The results show that hydrothermal pyrite and quartz are widespread, hydrothermal alteration is well developed, and that leaching structures such as vuggy rocks and extension structures such as comb quartz are common. Fluid inclusions in quartz are mainly liquid-rich two phase inclusions, with fluid compositions in the NaCI-H2O fluid system, and contain no or little CO2. Their homogenization temperatures cluster around 240℃-320℃, the salinities lie in the range of 14-17 wt.% NaCI equiv, and the calculated fluid densities are 0.65-1.00 g/cm^3. The values of δ18OH2O-VSMOW for quartz range from ＋5.5%0 to ＋7.7‰, the δDVSMOW of fluid inclusions in quartz ranges from -70‰ to -115‰. All of these data indicate that mixing of magmatic fluid with meteoric water resulted in the formation of the Ciemas deposit. A comparison among gold deposits of West Java suggests that Miocene epithermal ore deposits in the southernmost part of West Java were more affected by magmatic fluids and exhibit a higher degree of sulfidation than those of Pliocene-Pleistocene.

The first discovery of Xinlong epithermal gold deposit in southern margin of the Bangonghu-Nujiang metallogenic belt: A new expansion of gold prospecting in Northern Tibet

The Xinlong gold deposit is located in Niyma County,Naqu area of Tibet and was discovered by the Institute of Mineral Resources,Chinese Academy of Geological Sciences through the 1∶50000 mineral geological survey.The ore bodies occur in the Zenong Group volcanic rocks in the middle section of the central Lhasa subterrane and are structurally controlled by the NNW-striking faults.Four ore bodies have been found,exhibiting cloddy,dense-sparse,disseminated,and breccia structures.The ore minerals are mainly tetrahedrite group minerals,and other ore minerals include pyrite,chalcopyrite,nevskite,bornite,anglesite,native gold,and silver-gold bearing selenide,etc.The types of alteration are dominated by silicification,as well as middle-and high-graded argillization.The alteration mineral assemblages contain quzrtz,pyrophyllite,and kaolinite.The Zaliela Formation volcanic rocks of Zenong Group are silicified by later hydrothermal fluid with vuggy quartz in some fractured zones.The middle-and high-graded argillization are characterized by pyrophyllitization and kaolinization.The Xinlong gold deposit shows great metallogenetic potentiality and has been revealed by 1∶10000 geological mapping,IP sounding,and trial trenching in the mining area.Combined with the regional metallogenic geological setting,we suppose that a potential epithermal gold belt probably exists in the middle of the Lhasa terrane.The discovery of the Xinlong gold deposit opens a new chapter for the gold prospecting in Northern Tibet.

Geological Characteristics of Epithermal Ore Concentrated Areas and Epithermal Ore Deposits in China

The epithermal ore concentrated area is located in Southwestern China. We systematically study the regional geological characteristics such as the basement of Proterozoic, the capping bed, Moho, geothermal feature and tectonics, and discuss the relationship between distributed characteristics of the epithermal ore deposits and ore control factors in this paper. It is concluded that the conditions, under which the epithermal ore deposits form, are huge thick basement of Proterozoic, long time and wide scope developed capping bed and weak magmatic activity. The basement of Proterozoic that enriches volcanic matters and carbon and the carbonaceous bearing and paleo pool bearing capping bed provides main ore source. The large and deep faults and paleopool accordance with gravity anomaly gradient control the distribution of epithermal ore deposits. The lithologic assembles of microclastic rocks and carbonate rocks in the capping bed provide spaces of ore precipitation and create conditions of ore precipitation. The coincidence of many geological factors above forms the epithermal ore concentrated area.

Mineral Geochemistry of Apatite in the Jiama PorphyrySkarn Deposit,Tibet and its Geological Significance

The Jiama deposit,a significant porphyry-skarn-type copper polymetallic deposit located within the Gangdese metallogenic belt in Tibet,China,exemplifies a typical porphyry metallogenic system.However,the mineral chemistry of its accessory minerals remains under-examined,posing challenges for resource assessment and ore prospecting.Utilizing electron microprobe analysis and LA-ICP-MS analysis,this study investigated the geochemical characteristics of apatite in ore-bearing granite and monzogranite porphyries,as well as granodiorite,quartz diorite,and dark diorite porphyries in the deposit.It also delved into the diagenetic and metallogenic information from these geochemical signatures.Key findings include:(1)The SiO_(2) content,rare earth element(REE)contents,and REE partition coefficients of apatite indicate that the dark diorite porphyry possibly does not share a cogenetic magma source with the other four types of porphyries;(2)the volatile F and Cl contents in apatite,along with their ratio,indicate the Jiama deposit,formed in a collisional setting,demonstrates lower Cl/F ratios in apatite than the same type of deposits formed in a subduction environment;(3)compared to non-ore-bearing rock bodies in other deposits formed in a collisional setting,apatite in the Jiama deposit exhibits lower Ce and Ga contents.This might indicate that rock bodies in the Jiama deposit have higher oxygen fugacity.Nevertheless,the marginal variation in oxygen fugacity between ore-bearing and non-ore-bearing rock bodies within the deposit suggests oxygen fugacity may not serve as the decisive factor in the ore-hosting potential of rock bodies in the Jiama deposit.

Unveil the Redox Evolution of Ore-forming Fluids using Sulfur Isotope:A Case Study of the Zhengguang Intermediate Sulfidation Epithermal Au-Zn Deposit,NE China

Oxygen fugacity(fO_(2))is a key intensity variable during the entire magmatic-hydrothermal mineralization courses.The redox state and its variations between different stages of the ore-forming fluids of intermediate sulfidation epithermal deposits are rarely deciphered due to the lack of appropriate approaches to determine fO_(2)of the fluids.Here,we reported theδ^(34)S of the sulfides from three different stages(stageⅠ,Ⅱ,Ⅲ)of Zhengguang,an Early Ordovician Au-rich intermediate sulfidation(IS)epithermal deposit,to decipher the redox evolution of the ore-forming fluids.The increasingδ^(34)S values from stageⅠpyrite(pyl,average-2.6‰)through py2(average-1.9‰)to py3(average-0.2‰)indicates a decrease of the oxygen fugacity of the ore-forming fluids.A compilation ofδ^(34)S values of sulfides from two subtypes of IS deposits(Au-rich and Ag-rich)from NE China shows that theδ^(34)S values of sulfides from Au-rich IS deposits are systematically lighter than those of Ag-rich IS Ag-Pb-Zn deposit,indicating the ore-forming fluids of the former are more oxidized than the latter.We highlight that sulfur isotopic composition of hypogene sulfides is an efficacious proxy to fingerprint the oxygen fugacity fluctuations of epithermal deposits and could potentially be used to distinguish the subtypes of IS deposits.

Correction:Gardaneh Salavat porphyry copper system:Is it about metal endowment or fertility of the porphyritic intrusion?

Correction to:Acta Geochim(2022)41(3):496-514 https://doi.org/10.1007/s11631-022-00535-0 In the original publication of the article,under the section“4.1 Proposed hypothesis for Gardaneh Salavat porphyry system”,on page 509,the following sentence“Du and Audétat(2020)believed that early sulfide saturation is not necessarily detrimental to deposit formation or fertility of porphyritic intrusions.Further proving this fact”was included incorrectly.

Gardaneh Salavat porphyry copper system: Is it about metal endowment or fertility of the porphyritic intrusion?

Gardaneh Salavat porphyry copper system is located in the northwest of Iran. It comprises a quartz diorite to diorite porphyritic intrusion that created extensive alteration haloes in the host rocks. Despite all technical considerations, the exploration activities did not yield to ore discovery. As the matter of fact, all of the geological,geophysical, and geochemical characteristics of a porphyry Cu-Au deposit exist but there is no economic mineralization. Detailed examinations suggest that the only reasonable explanation can be related to the infertility or low metal endowment of the porphyritic intrusion. The reasons include(1) anomalous ranges of Cu, Au, and Mo rather than economic ore grades,(2) weakly development of potassic alteration,(3) probably sulfur saturation of magma that occurred before intrusion emplacement in the host rocks, and(4) probably low metal endowment in the regional scale and the lack of known porphyry copper deposits in close neighborhoods. It is tried to test the proposed hypothesis with the introduced fertility indicators based on major and trace element geochemistry. However,current fertility indicators could not prove or reject the proposed hypothesis for Gardaneh Salavat porphyritic intrusion because of the high-K calc-alkaline to shoshonitic nature of the intrusive rocks together with the unavailability of relatively fresh/unaltered samples. This case study is notable to examine because(1) it shows that characterization of fertile from barren intrusions seems to be as important as vectoring towards concealed porphyry copper deposits, especially while dealing with deep exploration targets that are associated with high financial risks, and(2) it highlights the inefficiencies and uncertainties in introduced magma fertility indicators for porphyry copper intrusions. As a result, it is of high importance to conduct an overarching investigation on other possible fertility indicators as a fundamental need for the future of the exploration industry.

A New Genetic Type of Gold Deposits-Meso-Epithermal Carbonate-Type Gold Deposits as Exemplified by the Baguamiao Superlarge Gold Deposit

Gold deposits of the meso-epithermal carbonate type were first proposed based on the study of the Baguamiao gold deposit.This new type of gold deposits has many unique characteristics as follows:(1)Obviously strata-bound.The gold deposits are hosted in Middle Devonian turbidite formations;(2)Structrually controlled.Struc-ture is an important factor leading to metallogenesis of this type of gold deposits.The shape and distribution of orebodies are controlled by byittle-ductile shear zones;(3)Multi-stage wall-rock alteration.According to the characteristics of mineral assemblage,gold mineralization can be classified into three stages in association with various wall-rock al-terations.Wall-rock alterations closely genetically related to the gold mineralization are ankerization ,silicification,pyrrhotization and pyritization ;(4)Mineral compositions of the orebodies are mainly pyrrhotite,pyrite,marcasitolite,chalcopyrite,quartz,ankerite,and sericite.Gold mineralization is associated closely in space and time with iron sulfides;(5)Rare elements and REE in ores are low in contents relative to those of the crust.Au content varies from 1.91g/t to 11.15g/t ,averaging 5.5g/t;(6)Studies of sulfur,hydrogen,oxygen and carbon isotopes in main gangue minerals (quartz and ankerite)indicate that fluids and ore-forming materials came from deep-seated sources;(7)Three types of inclusions are recognized in terms of their composition and the vapor amounts of inclusions.The homogenization temperatures of inclusions range from 210℃to 310℃,averaging 230℃,showing that this type of gold deposits belongs to the meso-epithermal type;(8)Metallogenic age of this type of gold deposits is similar to that of the collision between the Yangtze Plate and the North China Plate,indicating that gold deposits of this type are genetically related to continental-margin plate activity.

Qiyugou auriferous breccia pipes: A low-sulphidation epithermal system linked with transition of tectonic regime from collisional compression to extension, Xiong ershan, Henan, China

The Xiong’ershan area,as a part of a metallogenic province in cetral China,contains substantial Leimengou porphyry molybdenite deposit,Qiyugou breccia gold deposits and vein gold deposit occurred in fault zone,as well as previously refer to as orogenic gold deposit.Around or nearby the Mesozoic porphyry granite,the typical porphyry deposit,much more breccia pipes and breccia gold deposit are developed in the area.In this paper we focus on reporting preliminary results obtained from field,petrographic work on the Leimengou porphyry molybdenite and the Qiyugou breccia gold deposit,as well as laser Raman microspectroscopy and microprobe analyses carried out on samples from the Au-bearing Qiyugou breccia pipes.An adularia-calcite assemblage is reported in these breccia gold deposits.Two stages of hydrothermal alteration,pervasive and vein,are identified.The first stage consists of the alteration of the breccia clasts and rock flour by actinolite,green biotite,epidote,chlorite and minor sericite.This hydrothermal activity is likely to relate to the molybdenite mineralisation episode.The second stage is characterised by quartz veining and adularia and calcite filling open-spaces.Vein ores associated with quartz,sericite,and minor calcite alteration occur in NE-trending fault that cut the first stage of alteration.The adularia-calcite alteration is genetically associated with gold mineralization.The adularia-calcite assemblage in the area suggest that the Qiyugou pipes are of low-sulphidation epithermal in nature.The Qiyugou breccia pipes are coeval and spatially associated with the nearby Leimengou porphyry Mo deposit,which together conform to an alkalic mineralising system.We propose a model for the development and evolution of the breccia pipes in conjunction with a model that describes the genesis of the porphyry Mo and auriferous breccia pipes as a unified magmatic-hydrothermal system,which is linked with transition from collisional compressional to extensional geodynamic regime.

Comparison of U-spatial Statistics Method with Classical Statistics Results in the Determination of Geochemical Anomalies of Epithermal Gold in Khoshnameh Area, Hashtjin, Iran

In this study,methods based on the distribution model(with and without personal opinion)were used for the separation of anomalous zones,which include two different methods of U-spatial statistics and mean plus values of standard deviation(X+nS).The primary purpose is to compare the results of these methods with each other.To increase the accuracy of comparison,regional geochemical data were used where occurrences and mineralization zones of epithermal gold have been introduced.The study area is part of the Hashtjin geological map,which is structurally part of the folded and thrust belt and part of the Alborz Tertiary magmatic complex.Samples were taken from secondary lithogeochemical environments.Au element data concerning epithermal gold reserves were used to investigate the efficacy of these two methods.In the U-spatial statistics method,and criteria were used to determine the threshold,and in the method,the element enrichment index of the region rock units was obtained with grouping these units.The anomalous areas were identified by,and criteria.Comparison of methods was made considering the position of discovered occurrences and the occurrences obtained from these methods,the flexibility of the methods in separating the anomalous zones,and the two-dimensional spatial correlation of the three elements As,Pb,and Ag with Au element.The ability of two methods to identify potential areas is acceptable.Among these methods,it seems the method with criteria has a high degree of flexibility in separating anomalous regions in the case of epithermal type gold deposits.

A cleaner production strategy for acid mine drainage prevention of waste rock:A porphyry copper case

An in-process technology approach is proposed to identify the source of acid mine drainage(AMD)generation and prevent its formation in a porphyry copper waste rock(WR).Adopting actions before stockpiling the WR enables the establishment of potential contaminants and predicts the more convenient method for AMD prevention.A WR sample was separated into size fractions,and the WR’s net acidgenerating potential was quantified using chemical and mineralogical characterization.The diameter of physical locking of sulfides(DPLS)was determined,and the fractions below the DPLS were desulfurized using flotation.Finally,the WR fractions and tailing from the flotation test were submitted to acid-base accounting and weathering tests to evaluate their acid-generating potential.Results show that the WR’s main sulfide mineral is pyrite,and the DPLS was defined as 850μm.A sulfide recovery of 91%was achieved using a combination of HydroFloat^(®)and Denver cells for a size fraction lower than DPLS.No grinding was conducted.The results show that size fractions greater than DPLS and the desulfurized WR are unlikely to produce AMD.The outcomes show that in-processing technology can be a more proactive approach and an effective tool for avoiding AMD in a porphyry copper WR.

Reduced magma generation and its implications for the Pulang giant porphyry Cu-polymetallic deposit in Northwest Yunnan,China

The Pulang giant porphyry Cu-Mo polymetallic deposit is located in the Zhongdian area in the center of the Sanjiang Tethys tectonic domain,which was formed by the westward subduction of the Garze-Litang oceanic slab beneath the Zhongza massif.Chalcopyrite-pyrrhotite-pyritemolybdenite occurs as disseminations,veins,veinlets,and stockworks distributed in the K-silicate alteration zone in the monzonite porphyry,which is superimposed by propylitization.The chemical compositions of biotite and amphibole analyzed by electron probe microanalysis(EPMA)indicate that the ore-forming magma and exsolved fluids experienced a continuous decrease in the oxygen fugacity(fO_(2)).Primary amphibolite and biotite(type I)crystallized at relatively high temperatures(744-827°C)and low fO_(2)(log fO_(2)=−12.26 to−11.91)during the magmatic stage.Hydrothermal fluids exsolved from the magma have a relatively lower temperature(621-711°C)and fO_(2)(log fO_(2)=−14.36 to−13.32)than the original magma.In addition,the presence of a high abundance of pyrrhotite and an insufficiency of primary magnetite and sulfate in the ore(i.e.,anhydrite and gypsum)indicate that the deposit may be a reduced porphyry deposit.Magma and fluid fO_(2)results,combined with previous research on magmatic fO_(2)at the Pulang deposit,indicate that the magma associated with the reduced Pulang ore assemblages was initially generated as a highly oxidized magma that was subsequently reduced by sedimentary rocks of the Tumugou Formation.

In situ U-Pb dating and trace elements of magmatic rutile from Mujicun Cu-Mo deposit,North China Craton:Insights into porphyry mineralization

Porphyry Cu(Mo-Au)deposit is one of the most important types of copper deposit and usually formed under magmatic arc-related settings,whilst the Mujicun porphyry Cu-Mo deposit in North China Craton uncommonly generated within intra-continental settings.Although previous studies have focused on the age,origin and ore genesis of the Mujicun deposit,the ore-forming age,magma source and tectonic evolution remain controversial.Here,this study targeted rutile(TiO_(2))in the ore-hosting diorite porphyry from the Mujicun Cu-Mo deposit to conduct in situ U-Pb dating and trace element composition studies,with major views to determine the timing and magma evolution and to provide new insights into porphyry Cu-Mo metallogeny.Rutile trace element data show flat-like REE patterns characterized by relatively enrichment LREEs and depleted HREEs,which could be identified as magmatic rutile.Rutile U-Pb dating yields lower intercept ages of 139.3–138.4 Ma,interpreted as post magmatic cooling timing below about 500℃,which are consistent or slightly postdate with the published zircon U-Pb ages of diorite porphyry(144.1–141.7 Ma)and skarn(146.2 Ma;139.9 Ma)as well as the molybdenite Re-Os ages of molybdenum ores(144.8–140.0 Ma).Given that the overlap between the closure temperature of rutile U-Pb system and ore-forming temperature of the Mujicun deposit,this study suggests that the ore-forming ages of the Mujicun deposit can be constrained at 139.3–138.4 Ma,with temporal links to the late large-scale granitic magmatism at 138–126 Ma in the Taihang Orogen.Based on the Mg and Al contents in rutile,the magma of ore-hosting diorite porphyry was suggested to be derived from crust-mantle mixing components.In conjunction with previous studies in Taihang Orogen,this study proposes that the far-field effect and the rollback of the subducting Paleo-Pacific slab triggered lithospheric extension,asthenosphere upwelling,crust-mantle interaction and thermo-mechanical erosion,which jointly facilitated the formation of dioritic magmas during the Early Cretaceous.Subsequently,the dioritic magmas carrying crust-mantle mixing metallic materials were emplaced and precipitated at shallow positions along NNE-trending ore-controlling faults,eventually resulting in the formation of the Mujicun Cu-Mo deposit within an intracontinental extensional setting.

巴布亚新几内亚金元素地球化学特征及成矿预测

巴布亚新几内亚位于太平洋板块和印度-澳大利亚板块的汇聚边缘,由3个构造单元组成。巴布亚新几内亚主要发育两种金矿化类型,即浅成低温热液型和斑岩型。2015—2018年开展的巴布亚新几内亚国家尺度地球化学填图,在高地地区、巴布亚半岛和新几内亚群岛采集了1399件水系沉积物样品。文章研究了巴布亚新几内亚金的地球化学背景、空间分布特征和成矿潜力。巴布亚新几内亚金含量为0.2~6188.0 ng/g,中位数(地球化学基准值)为1.5 ng/g,高于大陆地壳金元素丰度,略低于中国和澳大利亚的金地球化学基准值。由于广泛发育中酸性侵入岩、碱性侵入岩和碱性火山岩,由巴布亚褶皱带、新几内亚逆冲带、奥罗褶皱带、东部褶皱带、东巴布亚复合地体、巴布亚群岛、伯瓦尼-托里塞利地体和菲尼斯特雷地体组成的中央弧陆碰撞带的金基准值高于美拉尼西亚岩浆弧。地球化学图中,新几内亚逆冲带的钙碱性侵入杂岩体、美拉尼西亚岩浆弧中的钙碱性侵入杂岩体和富钾火山-侵入杂岩体与高金含量的区域具有高度耦合对应关系。这次工作圈定了7处金地球化学省和9处金地球化学异常区,主要分布于新几内亚逆冲带。8处异常区均具有发育浅成低温热液型或斑岩型金矿的潜力,可作为下一阶段巴布亚新几内亚金矿找矿方向。

广东省河源铀矿田东部花岗斑岩年代学、地球化学特征及其地质意义

广东省河源铀矿田东部发现大量花岗斑岩,多呈脉状、岩珠状产出,且在空间上与铀矿化关系较为密切;但花岗斑岩的成因及其与铀矿化的关系尚不清楚。文章在野外地质调查基础上,选取花岗斑岩进行LAICP-MS锆石U-Pb年代学及地球化学特征研究。结果表明,花岗斑岩的锆石U-Pb年龄为(161.3±1.2)Ma,属晚侏罗世。花岗斑岩具有高硅、富碱、富铝的特征,为亚碱性过铝质钾玄岩系列。稀土元素总量较高,属轻稀土元素富集型(LREE/HREE=3.09~9.51),明显负铕异常(δEu=0.22~0.37);相对富集Rb、U、Nd、Ti等大离子亲石元素,亏损Ba、Sr、P、Nb等元素。河源铀矿田东部花岗斑岩具有壳源S型花岗岩的特征,形成于后碰撞造山构造环境,为地壳物质发生部分熔融的产物。该花岗斑岩可为铀成矿提供铀源及有利的赋矿空间。

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 Kxiging 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.