Hydrothermal evolution of Daraloo porphyry copper deposit, Iran: evidence from fluid inclusions

The Daraloo field is located in the southeast of Iran (Kerman province). It is associated with Oligomiocene diorite/granodiorite to quartz monzonite stocks. Copper mineralization is basically relevant to potassic and phyllic alteration zones. Petrographic and geologic studies imply that mineralization is restricted to two major parts locating in the center and east of district. The larger central mineralization has a northwest–southeast trend perpendicular to the smaller one. Hydrothermal ore fluid formation occurred in relatively deep levels thereafter faulting and fracturing provided appropriate conduits to ascend fluids through shallower depths. Early hydrothermal alteration produced a confined potassic assemblage in the central and eastern parts of the stock. Two main fluid inclusion groups in relationship with alteration ore fluids have been identified. They are liquid-rich inclusions containing solid phases, with high temperatures (257°C to 554°C) and high salinities (31 to 67 wt.% NaCl equiv.), and vapor-rich inclusions with high temperatures and low salinities without any solid phases. These magmatic source fluids are responsible for boiling and also potassic and phyllic alteration zone. They also resulted in the formation of quartz groups I and II veins and chalcopyrite deposition. Propylitic alteration is attributed to a Ca-rich meteoric fluid. Inclusions originated from this fluid are liquid-rich having low temperatures (161°C to 269°C) and low salinities (1 to 13 wt.% NaCl). Mixing descending meteoric water with magmatic fluids reduces considerably the salinity of magmatic fluid. Mixing is also the impetus of leaching copper from potassic to the phyllic zone. It is possible to conclude that all these procedures are controlled by the main faults of district having NW–SE trend. Two fundamental events affecting the mineralization are cooling ore-bearing fluids and magnetite (±pyrite) emplacement. The latter one is formed in potassic and phyllic alteration zone in which copper-bearing fluids have interaction with magnetite minerals and so chalcopyrite minerals have been formed nearby magnetites. Temperature and pressure of hydrothermal fluid differentiation could be applied as a predictive tool to discriminate between barren and productive copper porphyry deposits. A simple comparison of temperature and pressure variations between Daraloo deposit and other copper porphyry deposits located in the same belt of Iran (Sahand-Bazman belt) illuminates that Daraloo system has high range of pressure implying deeper exsolution of hydrothermal fluid. On the other hand, economic mineralization has direct relationship with temperature range of orthomagmatic fluids so that if a deposit has a wide range of high temperature fluids, it could be inferred as a barren deposit. In conclusion, it could be inferred that Daraloo district can be categorized as a sub-economic porphyry deposit. On the other hand, restricted formation of chalcopyrite and the other copper-bearing minerals besides large amounts of magnetite and pyrite can approve obviously the low grade of mineralization in Daraloo district.     

Geology,Alteration, and Mineralization of the Kay Tanda Epithermal Gold Deposit,Lobo, Batangas,Philippines

The Kay Tanda epithermal Au deposit in Lobo, Batangas is one of the Au deposits situated in the Batangas Mineral District in southern Luzon, Philippines. This study aims to document the geological, alteration, and mineralization characteristics and to determine the age of the mineralization, the mechanism of ore deposition, and the hydrothermal fluid characteristics of the Kay Tanda deposit. The geology of Kay Tanda consists of (i) the Talahib Volcanic Sequence, a Middle Miocene dacitic to andesitic volcaniclastic sequence that served as the host rock of the mineralization; (ii) the Balibago Diorite Complex, a cogenetic intrusive complex intruding the Talahib Volcanic Sequence; (iii) the Calatagan Formation, a Late Miocene to Early Pliocene volcanosedimentary formation unconformably overlying the Talahib Volcanic Sequence; (iv) the Dacite Porphyry Intrusives, which intruded the older lithological units; and (v) the Balibago Andesite, a Pliocene postmineralization volcaniclastic unit. K‐Ar dating on illite collected from the alteration haloes around quartz veins demonstrated that the age of mineralization is around 5.9 ± 0.2 to 5.5 ± 0.2 Ma (Late Miocene). Two main styles of mineralization are identified in Kay Tanda. The first style is an early‐stage extensive epithermal mineralization characterized by stratabound Au‐Ag‐bearing quartz stockworks hosted at the shallower levels of the Talahib Volcanic Sequence. The second style is a late‐stage base metal (Zn, Pb, and Cu) epithermal mineralization with local bonanza‐grade Au mineralization hosted in veins and hydrothermal breccias that are intersected at deeper levels of the Talahib Volcanic Sequence and at the shallower levels of the Balibago Intrusive Complex. Paragenetic studies on the mineralization in Kay Tanda defined six stages of mineralization; the first two belong to the first mineralization style, while the last four belong to the second mineralization style. Stage 1 is composed of quartz ± pyrophyllite ± dickite/kaolinite ± diaspore alteration, which is cut by quartz veins. Stage 2 is composed of Au‐Ag‐bearing quartz stockworks associated with pervasive illite ± quartz ± smectite ± kaolinite alteration. Stage 3 is composed of carbonate veins with minor base metal sulfides. Stage 4 is composed of quartz ± adularia ± calcite veins and hydrothermal breccias, hosting the main base metal and bonanza‐grade Au mineralization, and is associated with chlorite‐illite‐quartz alteration. Stage 5 is composed of epidote‐carbonate veins associated with epidote‐calcite‐chlorite alteration. Stage 6 is composed of anhydrite‐gypsum veins with minor base metal mineralization. The alteration assemblage of the deposit evolved from an acidic mineral assemblage caused by the condensation of magmatic volatiles from the Balibago Intrusive Complex into the groundwater to a slightly acidic mineral assemblage caused by the interaction of the host rocks and the circulating hydrothermal waters being heated up by the Dacite Porphyry Intrusives to a near‐neutral pH toward the later parts of the mineralization. Fluid inclusion microthermometry indicates that the temperature of the system started to increase during Stage 1 (T = 220–250°C) and remained at high temperatures (T = 250–290°C) toward Stage 6 due to the continuous intrusion of Dacite Porphyry Intrusives at depth. Salinity slightly decreased toward the later stages due to the contribution of more meteoric waters into the hydrothermal system. Boiling is considered the main mechanism of ore deposition based on the occurrence of rhombic adularia, the heterogeneous trapping of fluid inclusions of variable liquid–vapor ratios, the distribution of homogenization temperatures, and the gas ratios obtained from the quantitative fluid inclusion gas analysis of quartz. Ore mineral assemblage and sulfur fugacity determined from the FeS content of sphalerite at temperatures estimated by fluid inclusion microthermometry indicate that the base metal mineralization at Kay Tanda evolved from a high sulfidation to an intermediate sulfidation condition.     

Geochronology and Ore‐Forming Fluids of the Baizhangyan W–Mo Deposit in the Chizhou Area,Middle‐Lower Yangtze Valley,SE‐China

The Baizhangyan skarn‐porphyry type W–Mo deposit is located in a newly defined Mo–W–Pb–Zn metallogenic belt, which is in the south of Middle‐Lower Yangtze Valley Cu–Fe–Au polymetallic metallogenic belt in SE China. The W–Mo orebodies occur mainly within the contact zone between fine‐grained granite and Sinian limestone strata. There are two types of W–Mo mineralization: major skarn W–Mo mineralization and minor granite‐hosted disseminated Mo mineralization which was traced by drilling at depth. Eight molybdenite samples from Mo‐bearing ores yield Re–Os dates that overlap within analytical error, with a weighted average age of 134.1 ± 2.2 Ma. These dates are in close agreement with SIMS U–Pb concordant zircon age for fine‐grained granite at 133.3 ± 1.3 Ma, indicating that crystallization of the granite and hydrothermal molybdenite formation were coeval and likely cogenetic. The Baizhangyan W–Mo deposit formed in the Early Cretaceous extensional tectonic setting at the Middle‐Lower Yangtze Valley metallogenic belt and the Jaingnan Ancient Continent. Based on mineral compositions and crosscutting relationships of veinlets, hydrothermal alteration and mineralization, the ore mineral paragenesis of the Baizhangyan deposit is divided into four stages: skarn stage (I), oxide stage (II), sulfide stage (III), and carbonate stage (IV). Fluid inclusions in garnet, scheelite, quartz and calcite from W–Mo ores are mainly aqueous‐rich (L + V) type inclusions. Following garnet deposition at stage I, the high‐temperature fluids gave way to progressively cooler, more dilute fluids associated with tungsten–molybdenite–base metal sulfide deposition (stage II and stage III) (162–360°C, 2.7–13.2 wt % NaCl equivalent) and carbonate deposition (stage IV) (137–190°C, 0.9–5 wt % NaCl equiv.). Hydrogen‐oxygen isotope data from minerals of different stages suggest that the ore‐forming fluids consisted of magmatic water, mixed in various proportions with meteoric water. From stage I to stage IV, there is a systematic decrease in the homogenization temperature of the fluid‐inclusion fluids and calculated δ¹⁸O values of the fluids. These suggest that increasing involvement of formation water or meteoric water during the fluid ascent resulted in successive deposition of scheelite and molybdenite at Baizhangyan.     

San Rafael, Peru: geology and structure of the worlds richest tin lode

The San Rafael mine exploits an unusually high grade, lode-type Sn–Cu deposit in the Eastern Cordillera of the Peruvian Central Andes. The lode is centered on a shallow-level, Late Oligocene granitoid stock, which was emplaced into early Paleozoic metasedimentary rocks. It has a known vertical extent exceeding 1,200 m and displays marked vertical primary metal zoning, with copper overlying tin. The tin mineralization occurs mainly as cassiterite–quartz–chlorite veins and as cassiterite in breccias. The bulk of it is hosted by a K-feldspar megacrystic, biotite- and cordierite-bearing leucomonzogranite, which is the most distinctive phase of the pluton. Copper mineralization occurs predominantly in the veins that straddle the metasedimentary rock–intrusion contact or are hosted entirely by slates. Both tin and copper mineralization are associated with strong chloritic alteration, which is superimposed on an earlier episode of sericitization and tourmaline–quartz veining. Based on the distribution of alteration and ore mineralogy, cassiterite deposition and subsequent chalcopyrite precipitation are believed to have been the result of a single, prolonged hydrothermal event. The source of the metals is inferred to be a highly evolved, peraluminous magma, related to the leucomonzogranitic phase of the San Rafael pluton. Preliminary fluid inclusion microthermometry suggests that ore deposition took place during the mixing of moderate and low salinity fluids, which were introduced in a series of pulses. Several large fault-jogs, created by sinistral-normal, strike-slip movement, are interpreted to have focused synkinematic magmatic fluids and permitted their effective mixing with meteoric waters. It is proposed that this mixing led to rapid oxidation of Sn (II) chloride species and caused supersaturation of the fluids in cassiterite, resulting in the development of localized, high-grade ore shoots. A favorable structural regime that promoted large-scale mixing of two fluids originating under very different physico-chemical conditions appears to have been the key factor responsible for the unusual richness of the deposit.     

An oxygen‐ and hydrogen‐isotope study of the Panguna porphyry‐copper deposit,Bougainville

Hydrogen‐ and oxygen‐isotope analyses of biotite (19), sericite (8), chlorite (2), quartz (27), and total rocks (37) from the Panguna porphyry‐copper deposit on Bougainville Island, place important constraints on the origin of the hydrothermal fluids responsible for mineralization and alteration in the mine region. Early high‐temperature amphibole‐magnetite alteration resulted from magmatic‐hydrothermal fluids. Several lines of evidence indicate 500°C as a realistic average temperature for mineralization, development of quartz veins, and biotitization processes. On the basis of mineral isotope data, responsible fluids could represent either ¹⁸O‐shifted ground‐waters or magmatic‐hydrothermal fluids at submagmatic temperatures. Independent evidence, as well as total‐rock ¹⁸O data, support the magmatic‐hydrothermal model.

Late‐stage sericitization processes probably resulted from fluids produced by ¹⁸O shifting of groundwaters during the evolution of the propylitic zone. Outermost quartz veins and biotitization conceivably resulted from fluids similar to those that caused sericitization, indicating that some interaction between relatively cool, ¹⁸O‐poor meteoric waters and the ore fluids occurred near the margins of the deposit. The origin of the chlorite‐sericite alteration cannot be resolved solely by isotope studies.     

西藏曲水县色甫金铜矿成矿流体性质与来源

色甫金铜矿是新近在冈底斯南缘新生代斑岩成矿带内揭示的一个叠加于热液脉型铜矿上的浅成低温热液型金矿.详细的野外地质调查显示,色甫金铜矿和邻近的鸡公西矿区范围内先后经历了早始新世磁铁矿化、晚始新世-早渐新世与韧性剪切活动有关、早中新世钼矿化和铜矿化以及稍晚的金矿化等多期热液活动.对各期流体活动形成的石英中流体包裹体的岩相学、显微测温、显微激光拉曼和氢-氧同位素分析显示,与磁铁矿化有关的流体为岩浆热液混合建造水的高温、高盐度富水流体;与钼矿化有关的流体为岩浆热液与大气降水混合的高温、高盐度富水流体;与铜矿体形成有关的流体为具有岩浆贡献的中高温含CO2低盐度流体与大气降水来源的低温低盐度富水流体混合的产物;与金矿体形成有关的流体为具有岩浆贡献的中温含CO2±CH4±N2的中低盐度流体与大气降水来源的低温低盐度富水流体混合的产物.利用流体包裹体显微测温对其捕获温压估算的结果显示,铜矿体和钼矿化体形成前,该地区有过1.5~4.1 km的剥蚀,之后至金矿体形成前时有过近6 km的剥蚀,金矿体形成后剥蚀为0.8~1.2 km.矿区后续工作应优先针对近南北向断裂中赋存的蚀变岩型金矿开展工作.     

Characteristics of Ore-forming Fluid of the Gaoshan Gold-Silver Deposit in the Longquan Area,Zhejiang Province and its Implications for the Ore Genesis

The Gaoshan gold-silver deposit, located between the Yuyao-Lishui Fault and JiangshanShaoxing fault in Longquan Area, occurs in the Suichang-Longquan gold-silver polymetallic metallogenic belt. This study conducted an investigation for ore-forming fluids using microthermometry, D-O isotope and trace element. The results show that two types of fluid inclusions involved into the formation of the deposit are pure liquid phase and gas-liquid phase aqueous inclusions. The homogenization temperature and salinity of major mineralization phase ranges from 156°C to 236°C(average 200°C) and 0.35% to 8.68%(NaCleqv)(average 3.68%), respectively, indicating that the ore-forming fluid is characteristic of low temperature and low salinity. The oreforming pressure ranges between in 118.02 to 232.13'105 pa, and it is estabmiated that the oreforming depth ranges from 0.39 to 0.77 km, indicating it is a hypabyssal deposit in genesis. The low rare earth elements content in pyrites, widely developed fluorite in late ore-forming stage and lack of chlorargyrite(Ag Cl), indicates that the ore-forming fluid is rich in F rather than Cl. The ratios of Y/Ho, Zr/Hf and Nb/Ta of between different samples have little difference, indicating that the later hydrothermal activities had no effects on the former hydrothermal fluid. The chondrite-normalized REE patterns of pyrites from country rocks and ore veins are basically identical, with the characteristics of light REE enrichment and negative Eu anomalies, implying that the ore-forming fluid was oxidative and derived partly from the country rocks. The δD and δ18O of fluid inclusions in quartz formed during the main metallogenic stage range from -105‰ to -69 ‰ and -6.01‰ to -3.81‰, respectively. The D-O isotopic diagram shows that the metallogenic fluid is characterized by the mixing of formation water and meteoric water, without involvement of magmatic water. The geological and geochemical characteristics of the Gaoshan gold-silver deposit are similar to those of continental volcanic hydrothermal deposit, and could be assigned to the continental volcanic hydrothermal gold-silver deposit type.     

Fluid Inclusions,Stable Isotopes,and Geochronology of the Haobugao Lead‐Zinc Deposit,Inner Mongolia,China

The Haobugao deposit, located in the southern segment of the Great Xing'an Range, is a famous skarn‐related Pb‐Zn‐(Cu)‐(Fe) deposit in northern China. The results of our fluid inclusion research indicate that garnets of the early stage (I skarn stage) contain three types of fluid inclusions (consistent with the Mesozoic granites): vapor‐rich inclusions (type LV, with V_H2O/(V_H2O + L_H2O) < 50 vol %, and the majority are 5–25 vol %), liquid‐rich two‐phase aqueous inclusions (type VL, with V_H2O/(V_H2O + L_H2O) > 50 vol %, the majority are 60–80 vol %), and halite‐bearing multiphase inclusions (type SL). These different types of fluid inclusions are totally homogenized at similar temperatures (around 320–420°C), indicating that the ore‐forming fluids of the early mineralization stage may belong to a boiling fluid system. The hydrothermal fluids of the middle mineralization stage (II, magnetite‐quartz) are characterized by liquid‐rich two‐phase aqueous inclusions (type VL, homogenization temperatures of 309–439°C and salinities of 9.5–14.9 wt % NaCl eqv.) that coexist with vapor‐rich inclusions (type LV, homogenization temperatures of 284–365°C and salinities of 5.2–10.4 wt % NaCl eqv.). Minerals of the late mineralization stage (III sulfide‐quartz stage and IV sulfide‐calcite stage) only contain liquid‐rich aqueous inclusions (type VL). These inclusions are totally homogenized at temperatures of 145–240°C, and the calculated salinities range from 2.0 to 12.6 wt % NaCl eqv. Therefore, the ore‐forming fluids of the late stage are NaCl‐H₂O‐type hydrothermal solutions of low to medium temperature and low salinity. The δD values and calculated δ¹⁸O_SMOW values of ore‐forming fluids of the deposit are in the range of ?4.8 to 2.65‰ and ?127.3‰ to ?144.1‰, respectively, indicating that ore‐forming fluids of the Haobugao deposit originated from the mixing of magmatic fluid and meteoric water. The S‐Pb isotopic compositions of sulfides indicate that the ore‐forming materials are mainly derived from underlying magma. Zircon grains from the mineralization‐related granite in the mining area yield a weighted ²⁰⁶Pb/²³⁸U mean age of 144.8 ±0.8 Ma, which is consistent with a molybdenite Re‐Os model age (140.3 ±3.4 Ma). Therefore, the Haobugao deposit formed in the Early Cretaceous, and it is the product of a magmatic hydrothermal system.     

Highly Oxidized Magma and Fluid Evolution of Miocene Qulong Giant Porphyry Cu‐Mo Deposit,Southern Tibet,China

The Miocene Qulong porphyry Cu‐Mo deposit, which is located at the Gangdese orogenic belt of Southern Tibet, is the largest porphyry‐type deposit in China, with confirmed Cu ～10 Mt and Mo ～0.5 Mt. It is spatially and temporally associated with multiphase granitic intrusions, which is accompanied by large‐scale hydrothermal alteration and mineralization zones, including abundant hydrothermal anhydrite. In addition to hydrothermal anhydrite, magmatic anhydrite is present as inclusions in plagioclase, interstitial minerals between plagioclase and quartz, and phenocrysts in unaltered granodiorite porphyry, usually in association with clusters of sulfur‐rich apatite in the Qulong deposit. These observations indicate that the Qulong magma‐hydrothermal system was highly oxidized and sulfur‐rich. Three main types of fluid inclusions are observed in the quartz phenocrysts and veins in the porphyry: (i) liquid‐rich; (ii) polyphase high‐salinity; and (iii) vapor‐rich inclusions. Homogenization temperatures and salinities of all type inclusions decrease from the quartz phenocrysts in the porphyry to hydrothermal veins (A, B, D veins). Microthermometric study suggests copper‐bearing sulfides precipitated at about 320–400°C in A and B veins. Fluid boiling is assumed for the early stage of mineralization, and these fluids may have been trapped at about 35–60 Mpa at 460–510°C and 28–42 Mpa at 400–450°C, corresponding to trapping depths of 1.4–2.4 km and 1.1–1.7 km, respectively.     

Cu–Mo Differential Mineralization Mechanism of the Dabate Polymetallic Deposit in Western Tianshan,NW China: Evidence from Geology,Fluid Inclusions,and Oxygen Isotope Systematics

Classic porphyry Cu–Mo deposits are mostly characterized by close temporal and spatial relationships between Cu and Mo mineralization. The northern Dabate Cu–Mo deposit is a newly discovered porphyry Cu–Mo polymetallic deposit in western Tianshan, northwest China. The Cu mineralization postdates the Mo mineralization and is located in shallower levels in the deposit, which is different from most classic porphyry Cu–Mo deposits. Detailed field investigations, together with microthermometry, laser Raman spectroscopy, and O‐isotope studies of fluid inclusions, were conducted to investigate the origin and evolution of ore‐forming fluids from the main Mo to main Cu stage of mineralization in the deposit. The results show that the ore‐forming fluids of the main Mo stage belonged to an NaCl + H₂O system of medium to high temperatures (280–310°C) and low salinities (2–4 wt% NaCl equivalent (eq.)), whereas that of the main Cu stage belonged to an F‐rich NaCl + CO₂ + H₂O system of medium to high temperatures (230–260°C) and medium to low salinities (4–10 wt% NaCl eq.). The δ¹⁸O values of the ore‐forming fluids decrease from 3.7–7.8‰ in the main Mo stage to ?7.5 to ?2.9‰ in the main Cu stage. These data indicate that the separation of Cu and Mo was closely related to a large‐scale vapor–brine separation of the early ore‐forming fluids, which produced the Mo‐bearing and Cu‐bearing fluids. Subsequently, the relatively reducing (CH₄‐rich) Mo‐bearing, ore‐forming fluids, dominantly of magmatic origin, caused mineralization in the rhyolite porphyry due to fluid boiling, whereas the relatively oxidizing (CO₂‐rich) Cu‐bearing, ore‐forming fluids mixed with meteoric water and precipitated chalcopyrite within the crushed zone at the contact between rhyolite porphyry and wall rock. We suggest that the separation of Cu and Mo in the deposit may be attributed to differences in the chemical properties of Cu and Mo, large‐scale vapor–brine separation of early ore‐forming fluids, and changes in oxygen fugacity.     

Mineralization of the Liwu large-scale stratiform copper deposits in Sichuan Province,China: Constraints from fluid inclusions

The Liwu stratiform copper deposit is located in the northwestern Jianglang dome, western China. Current studies mainly focus on the genetic type and mineralization of this deposit. Detailed fluid inclusion characteristics of metallogenic period quartz veins were studied to reveal the ore-forming fluid features. Laser Raman analysis indicates that the ore-forming fluids is a H₂O-NaCl-CH₄ (-CO₂) system. Fluid inclusions microthermometry shows a homogenization temperature of 181–375°C and a salinity of 5.26%–16.99% for the disseminated-banded Cu-Zn mineralization; but a homogenization temperature of 142–343°C and a salinity of 5.41%–21.19% for the massive-veined Cu-Zn mineralization. These features suggest a medium-high temperature and a medium salinity for the ore-forming fluids. H-O isotopic data indicates that the ore-forming fluids were mainly from the metamorphic and magmatic water, plus minor formation water. And sulfur isotopic data indicates that sulfur was mainly derived from the formation and magmatic rocks. Metallogenesis of the disseminated-banded mineralization was mainly correlated with fluid mixing and water-rock reaction; whereas that of the massive-veined mineralization was mainly correlated with fluid boiling. The genetic type of the deposit is a medium-high temperature hydrothermal deposit related to magmatism and controlled by shear zones. This study is beneficial to understand the stratiform copper deposit.©2023 China Geology Editorial Office.     

Metallogenesis and hydrothermal evolution of the Tonggou Cu deposit in the Eastern Tianshan: Evidence from fluid inclusions,H-O-S isotopes,and Re-Os geochronology

The Tonggou Cu polymetallic deposit in the Bogda Orogenic Belt, Eastern Tianshan shows evidence for three stages of hydrothermal mineralization: early pyrite veins (Stage 1), polymetallic sulfide ± epidote–quartz (Stage 2), and late-stage pyrite–calcite veins (Stage 3). Fluid inclusion petrography and microthermometry analyses indicate that the liquid-rich aqueous inclusions (L), vapour-rich aqueous inclusions (V), and NaCl daughter mineral–bearing three phase inclusions (S) formed during the main stage of mineralization, and that the ore fluids represent high-temperature and high-salinity H₂O-NaCl hydrothermal fluids that underwent boiling. Stable isotope (H, O) data indicate that the ore fluids of the Tonggou deposit were originally derived from magmatic water in Stage 2 and subsequently mixed with local meteoric water during Stage 3. Sulphur isotope compositions (6.7‰ to 10.9‰) are consistent with the δ³⁴S values of pyrite from the Qijiaojing Formation sandstone, indicating the primary source of the sulphur ore. Furthermore, chalcopyrite grains separated from the chalcopyrite-rich ore samples yield an isochron age of 303 ± 12 Ma (MSWD = 1.2). These results indicate that the Tonggou deposit is a transition between high–sulfidation and porphyry deposits which formed in the Late Carboniferous. It also suggests an increased likelihood for the occurrence of Cu (Au, Mo) in the Bogda Orogenic Belt, especially at locations where the Cu-Zn deposits are thicker; further deep drilling and exploration are encouraged in these areas.     

Hydrothermal fluid geochemistry at the Chah-Firuzeh porphyry copper deposit,Iran: Evidence from fluid inclusions

The Chah-Firuzeh porphyry copper deposit is located in 35 km north of Shahre Babak (Kerman province). It is associated with granodioriteic intrusive of Miocene age which intruded Eocene volcanosedimentary rocks. Copper mineralization was accompanied by both potassic and phyllic alteration. Field observations and petrographic studies demonstrate that the emplacement of Chah-Firuzeh pluton took place in several intrusive pulses, each with associated hydrothermal ore fluid formation that was also associated with hydrostatic pressure increasing respect to that of lithostatic pressure (and fracturing development-relative boiling) by circulated fluid. Copper is concentrated as a very early hydrothermal mineralized phase in the evolution of the hydrothermal system. Early hydrothermal alteration produced a potassic assemblage (orthoclase–biotite) in the central deep part of the stock. Alteration ore fluids could be classify into two groups of liquid-reach, containing solid phases, high temperature (390 to 500 °C) high salinity (more than 60 wt.% NaCl equiv.) and gas-rich, high temperature (311 to 570 °C), no solid phase and with low salinities. These magmatic source fluids illustrate sever boiling process and also are the responsible for the both potassic alteration, quartz group I and II veins and chalcopyrite deposition. Propylitic alteration occurred by the liquid-rich, low temperature (241 to 390 °C) and Ca-rich fluid with meteoric origin. Continuous decreasing temperature let the meteoric water diffusion into the system, mixed with magmatic fluids and descending the salinities down to the 1 wt.% NaCl equiv. and leaching the Cu from vein groups II and III by sever thermodynamic anarchies from potassic to the phyllic alteration zones. Phyllic alteration and copper leaching resulted from the inflow of oxidized and acidic meteoric waters with decreasing temperature of the system followed by the incursion of this fluid into and its convection in upper part of the system. A late episode of boiling occurred in the apical the phyllic zone, and was associated with significant copper deposition. Based on the field observation on sharp alteration and related mineralization, it is possible to conclude that all these procedures have been controlled by local faults that could be active even before the pluton injection. These faults and the new form ones (which have been formed after injection), could crash the hosted rocks, and act as physical dams to restrict and limit the mineralization in special strikes and zones within the Cah-Firuzeh ore deposit.     

Fluid Inclusions and Hydrogen,Oxygen, Sulfur Isotopes of Nuri Cu‐W‐Mo Deposit in the Southern Gangdese,Tibet

The Nuri Cu‐W‐Mo deposit is located in the southern subzone of the Cenozoic Gangdese Cu‐Mo metallogenic belt. The intrusive rocks exposed in the Nuri ore district consist of quartz diorite, granodiorite, monzogranite, granite porphyry, quartz diorite porphyrite and granodiorite porphyry, all of which intrude in the Cretaceous strata of the Bima Group. Owing to the intense metasomatism and hydrothermal alteration, carbonate rocks of the Bima Group form stratiform skarn and hornfels. The mineralization at the Nuri deposit is dominated by skarn, quartz vein and porphyry type. Ore minerals are chalcopyrite, pyrite, molybdenite, scheelite, bornite and tetrahedrite, etc. The oxidized orebodies contain malachite and covellite on the surface. The mineralization of the Nuri deposit is divided into skarn stage, retrograde stage, oxide stage, quartz‐polymetallic sulfide stage and quartz‐carbonate stage. Detailed petrographic observation on the fluid inclusions in garnet, scheelite and quartz from the different stages shows that there are four types of primary fluid inclusions: two‐phase aqueous inclusions, daughter mineral‐bearing multiphase inclusions, CO₂‐rich inclusions and single‐phase inclusions. The homogenization temperature of the fluid inclusions are 280°C–386°C (skarn stage), 200°C–340°C (oxide stage), 140°C–375°C (quartz‐polymetallic sulfide stage) and 160°C–280°C (quartz‐carbonate stage), showing a temperature decreasing trend from the skarn stage to the quartz‐carbonate stage. The salinity of the corresponding stages are 2.9%–49.7 wt% (NaCl) equiv., 2.1%–7.2 wt% (NaCl) equiv._, 2.6%–55.8 wt% (NaCl) equiv. and 1.2%–15.3 wt% (NaCl) equiv., respectively. The analyses of CO₂‐rich inclusions suggest that the ore‐forming pressures are 22.1 M Pa–50.4 M Pa, corresponding to the depth of 0.9 km–2.2 km. The Laser Raman spectrum of the inclusions shows the fluid compositions are dominated in H₂O, with some CO₂ and very little CH₄, N₂, etc. δD values of garnet are between ?114.4‰ and ?108.7‰ and δ¹⁸O_H2O between 5.9‰ and 6.7‰; δD of scheelite range from ?103.2‰ to ?101.29‰ and δ¹⁸O_H2O values between 2.17‰ and 4.09‰; δD of quartz between ?110.2‰ and ?92.5‰ and δ¹⁸O_H2O between ?3.5‰ and 4.3‰. The results indicate that the fluid came from a deep magmatic hydrothermal system, and the proportion of meteoric water increased during the migration of original fluid. The δ³⁴S values of sulfides, concentrated in a rage between ?0.32‰ to 2.5‰, show that the sulfur has a homogeneous source with characteristics of magmatic sulfur. The characters of fluid inclusions, combined with hydrogen‐oxygen and sulfur isotopes data, show that the ore‐forming fluids of the Nuri deposit formed by a relatively high temperature, high salinity fluid originated from magma, which mixed with low temperature, low salinity meteoric water during the evolution. The fluid flow through wall carbonate rocks resulted in the formation of layered skarn and generated CO₂ or other gases. During the reaction, the ore‐forming fluid boiled and produced fractures when the pressure exceeded the overburden pressure. Themeteoric water mixed with the ore‐forming fluid along the fractures. The boiling changed the pressure and temperature, oxygen fugacity, physical and chemical conditions of the whole mineralization system. The escape of CO₂ from the fluid by boiling resulted in scheelite precipitation. The fluid mixing and boiling reduced the solubility of metal sulfides and led the precipitation of chalcopyrite, molybdenite, pyrite and other sulfide.     

大兴安岭南段热液脉状矿床的流体包裹体和稳定同位素特征:对矿床成因的启示

大兴安岭南段发育大井、双尖子山、布金黑、拜仁达坝、维拉斯托等多个具有典型后生特征的热液脉状铅锌银锡多金属矿床。为了查明上述矿床在成矿流体、成矿物质等方面的特征与差异,进而总结大兴安岭南段热液脉状矿床成矿作用特点,本次研究在野外地质调研的基础上,对上述矿床进行了流体包裹体、激光拉曼和氢氧硫同位素的研究,并取得了如下主要的认识:(1)双尖子山银多金属矿床成矿流体属简单盐水体系热液,维拉斯托和布金黑矿床成矿流体属富碳质盐水体系热液,而大井铜矿成矿流体则为含子矿物的不均匀盐水体系热液;(2)大井、布金黑、拜仁达坝和维拉斯托等矿床早期成矿流体均来自于岩浆热液,但布金黑、拜仁达坝和维拉斯托矿床成矿流体在运移过程中明显地受到了大气降水和地层中有机质的影响;(3)大兴安岭南段多数热液脉状多金属矿床矿石硫同位素δ34S值具有岩浆来源特点,个别矿床硫同位素δ34S值偏高可能是由复杂的岩浆源区性质及地层硫混入所引起。总的来说,大兴安岭南段不同热液脉状矿床在物质来源和流体演化方面的差异明显,而这也体现了该区中生代热液成矿作用的多样性和复杂性特点。     

新疆东准噶尔松喀尔苏铜金矿区斑岩型矿床成因研究

松喀尔苏铜金矿区位于卡拉麦里石炭纪陆相火山岩带。文章通过矿床地质、围岩蚀变、含矿斑岩、流体包裹体和同位素研究,探讨了矿床成因类型。研究表明,松喀尔苏矿床具斑岩型矿床的特征,铜金矿化体产于岩体接触带,围岩蚀变具有分带性,从岩体向围岩依次发育绢英岩化带、高岭石化带和青磐岩化带,绢英岩化带与成矿相关。含矿斑岩复式岩体系同期陆相火山活动产物,成矿作用在时间、空间和成因上与复式岩体中晚期花岗斑岩有关。花岗斑岩具有富水、富挥发性组分和岩浆爆破作用的氧化性岩浆特点,具有后碰撞花岗岩类的地球化学亲缘性,其岩浆起源于后碰撞挤压-伸展转换期的壳-幔岩浆过渡带。幔源岩浆注入、软流圈地幔底侵作用和壳-幔岩浆混合作用是形成含矿斑岩岩浆的主导因素。流体包裹体包括液相包裹体、气相包裹体和含子晶多相包裹体,激光拉曼探针分析表明,气相成分以CO₂和CH₄为主。成矿流体具有从高温、高盐度岩浆体系向低温、低盐度与大气降水混合的演化过程,流体沸腾或不混溶作用及温度、盐度降低是导致流体中成矿物质沉淀的主要因素。氢、氧同位素组成表明成矿流体以岩浆水为主,在成矿晚期混有大气降水。硫同位素具幔源硫的特征。铅同位素组成显示成矿作用起源于下地壳-上地幔过渡带的岩浆作用。综上所述,该矿床属于与陆相火山-侵入岩有关的斑岩型铜金矿床。     

内蒙古苏尼特左旗乌日尼图钨钼矿床同位素地球化学特征

乌日尼图钨钼矿位于内蒙古苏尼特左旗境内,是近几年在该区新发现较大规模的钨钼矿床。钨钼矿体主要产于燕山期花岗岩体的内外接触带附近,以细脉状矿化类型为主。同位素测试结果表明:δ34SV-CDT值范围为0.6‰～4.1‰,组成较为稳定;显示钨钼矿体的形成与岩浆作用密切相关,硫可能主要来自岩浆源。矿石样品208Pb/204Pb值范围为38.115～38.353,207Pb/204Pb值范围为15.528～15.591,206Pb/204Pb值范围为18.375～18.528;铅构造模式图解和其参数综合分析表明成矿与岩浆作用密切相关,成矿物质来源于上地壳与地幔的混合,具有壳幔混合特点。热液方解石δ13CPDB=-8.63‰～-6.41‰,δ18OSMOW=-1.49‰～8.72‰,表明热液矿物方解石是2个阶段成矿作用的产物,早期成矿流体碳主要来源于岩浆;成矿作用后期有大气降水的加入。     

He–Ar Isotope Composition of Pyrite and Wolframite in the Tieshanlong Tungsten Deposit,Jiangxi, China: Implications for Fluid Evolution

The Tieshanlong tungsten‐polymetallic deposit is a large wolframite deposit of quartz vein type located in southern Jiangxi, South China. It is genetically related to a high‐K S‐type granite. Seven pyrite and two wolframite samples, selected for He and Ar isotope analyses, yielded ³He/⁴He values of 0.04–0.98 Ra, ⁴⁰Ar/³⁶Ar ratios of 293.5–368.0, and ³⁸Ar/³⁶Ar ratios of 0.176–0.193. These data indicate that the ore‐forming fluids associated with the deposit did not result from a simple mixing of the crustal‐ and mantle‐derived end‐member fluids, but that primeval meteoric fluids were also involved in the generation of the associated granitic magma by partial melting of crustal metasedimentary rocks. Further investigations show that only minimal He from the mantle was added during generation of the associated granitic magma. It is postulated that boiling and second mixing with “new” meteoric fluids took place during migration of magmatic‐hydrothermal fluids into wall‐rock fractures, resulting in a drastic decrease of their metal transport capacity, which triggered the tungsten‐polymetallic mineralization.     

Fluid Inclusion Microthermometry and Implications for the Mechanisms of Ore-Grade Gold Mineralization in Epithermal System, Lalab Orebody, Sibutad, Zamboanga del Norte, Philippines

The Sibutad gold deposit has gold associated in quartz veins. The most important of these is the Lalab orebody, which contains ore‐grade gold, predominantly, in milky quartz veins and veinlets. Here, alteration quartz and fine‐grained crystalline clear and milky quartz were formed from hydrothermal fluids in three stages, namely stages I, II and III. Fluid inclusion microthermometry was carried out on stage I milky quartz, stage II fine‐grained alteration quartz and stage III milky quartz ± barite veins and veinlets. Homogenization temperatures (T_H) are >248°C in stage I, 214–232°C in stage II and 186–239°C in stage III. These fluid inclusions have salinity between 1 and 2 wt% NaCl equivalent. In terms of gold assay, stage I drill‐core samples have gold grades 0.53–0.76 g/ton Au, stage II samples have 1.12–3.70 g/ton Au and stage III samples have 9.06–23.88 g/ton Au. This correlation suggests that gold was precipitated from the stage II and III fluids.     

A Study of Ore-forming Fluids in the Shimensi Tungsten Deposit, Dahutang Tungsten Polymetallic Ore Field, Jiangxi Province, China

The Dahutang tungsten polymetallic ore field is located north of the Nanling W-Sn polymetallic metallogenic belt and south of the Middle—Lower Yangtze River Valley Cu-Mo-Au-Fe porphyry-skarn belt.It is a newly discovered ore field,and probably represents the largest tungsten mineralization district in the world.The Shimensi deposit is one of the mineral deposits in the Dahutang ore field,and is associated with Yanshanian granites intruding into a Neoproterozoic granodiorite batholith.On the basis of geologic studies,this paper presents new petrographic,microthermometric,laser Raman spectroscopic and hydrogen and oxygen isotopic studies of fluid inclusions from the Shimensi deposit.The results show that there are three types of fluid inclusions in quartz from various mineralization stages:liquid-rich two-phase fluid inclusions,vapor-rich two-phase fluid inclusions,and three-phase fluid inclusions containing a solid crystal,with the vast majority being liquid-rich two-phase fluid inclusions.In addition,melt and melt-fluid inclusions were also found in quartz from pegmatoid bodies in the margin of the Yanshanian intrusion.The homogenization temperatures of liquid-rich two-phase fluid inclusions in quartz range from 162 to 363℃ and salinities are 0.5wt%-9.5wt%NaCI equivalent.From the early to late mineralization stages,with the decreasing of the homogenization temperature,the salinity also shows a decreasing trend.The ore-forming fluids can be approximated by a NaCl-H_2O fluid system,with small amounts of volatile components including CO_2,CH_4 and N_2,as suggested by Laser Raman spectroscopic analyses.The hydrogen and oxygen isotope data show that δ5D_(V-smow) values of bulk fluid inclusions in quartz from various mineralization stages vary from-63.8‰ to-108.4‰,and the δ~(18)O_(H2O) values calculated from the δ~(18)O_(V-)smow values of quartz vary from-2.28‰ to 7.21‰.These H-O isotopic data are interpreted to indicate that the ore-forming fluids are mainly composed of magmatic water in the early stage,and meteoric water was added and participated in mineralization in the late stage.Integrating the geological characteristics and analytical data,we propose that the ore-forming fluids of the Shimensi deposit were mainly derived from Yanshanian granitic magma,the evolution of which resulted in highly differentiated melt,as recorded by melt and melt-fluid inclusions in pegmatoid quartz,and high concentrations of metals in the fluids.Cooling of the ore-forming fluids and mixing with meteoric water may be the key factors that led to mineralization in the Dahutang tungsten polymetallic ore field.