Ag Vein Deposits Research Articles

Determination of structural lineaments of the mafic-ultramafic belt of the Southern Argentine Precordillera

In central-western Argentina, an Early Paleozoic belt including mafic-ultramafic bodies and marine metasedimentary rocks occurs along the western margin of the Precordillera and in the eastern Frontal Cordillera. In this paper, we present the analysis of aeromagnetic data and its processing focused on mapping geological limits, structures and the relation at depth of the southern Precordillera. With this main objective were applied filtering algorithms, reduction to the pole, tilt derivative, analytic signal, and particularly, the use of Improved Logistic Function (IL) as a new method of edge detection, in combination with the inversion map obtained from the Magnetization Vector Inversion (MVI) method. The results allow us to describe at depth the main trend of the Southern Precordillera Mafic Ultramafic Belt as two separated bocks, one in Peñasco and another in Cerro (Co.) Cortaderas, passing through Cerro (Co.) Pozos with a possible NNE-SSW direction. The combination of this techniques also can be used as prospecting guide to Pb–Zn–Ag vein deposits and High sulfidation Au-Epitermal deposits.

The Cerro Negro epithermal district, northwestern Deseado Massif (Patagonia, Argentina): New insights from telescoped volcanic-hydrothermal systems

The Cerro Negro district, northwestern Deseado Massif (Patagonia, Argentina), is one of two world-class Au–Ag epithermal mines in the Patagonian region, with combined reserves, resources, and production of about 8 Moz of Au equivalent. The epithermal deposits are hosted by volcanic and intrusive rocks and are related to the evolution of distinct Jurassic magmatic events. Major WNW trending depocenters were filled by a thick sequence of andesitic-dacitic flows and ignimbrites. In the western part of the district, the sequence is intruded by subvolcanic bodies of the same composition and is grouped into the 159-156 Ma Eureka Volcanic Subvolcanic Complex (EVSC). Hydrothermal activity took place during the last stages of the EVSC, producing epithermal Au- and Ag-rich veins of low to intermediate sulfidation style in the Eureka West (156 Ma) and the Marianas-San Marcos veins (155-154 Ma) that were emplaced in NW striking extensional faults and in WNW to E-W trending strike-slip faults. In the eastern part of the district, basal units of the EVSC are overlain by a thick package of 154 Ma rhyodacitic ignimbrites, hosting the NW to EW-striking Vein Zone deposit and the NW-striking Bajo Negro, Silica cap and Gato Salvaje veins. NNE-trending block faulting formed horsts in the western and eastern parts of the district, separated by a central graben. Uplift of the western and eastern horst blocks lowered the water table and caused erosion, exhumation, and telescoping of the vein systems. Volcanism culminated in a late-to post-mineral rhyolitic event composed of lava-domes and volcaniclastic deposits grouped into the Eureka Rhyolitic Complex (ERC). Continued hydrothermal-volcanic explosive activity produced breccias which cap some of the Au–Ag vein deposits. The high geothermal gradient during ERC volcanism generated renewed hydrothermal activity, and hot springs discharged along the boundary faults of the central graben and within the graben in a fluvio-lacustrine environment.The Au–Ag epithermal veins associated with the EVSC (Eureka and Marianas-San Marcos) show a complex paragenetic history. High Au–Ag grades are related to early sulfide-rich ginguro bands formed at 290–230 °C from meteoric and volcanic fluids due to boiling/flashing mechanism at ~600–800 m below the paleowater table. Low-grade to barren quartz stages followed the early Au–Ag stage, and late calcite was deposited due to the collapse of steam heated CO2 waters. The highest Au–Ag grades are related to a late supergene event extending to 400 m depth. The eastern group of epithermal deposits (Vein Zone, Bajo Negro, Silica cap and Gato Salvaje) were emplaced ~300–400 m below the paleowater table indicated by a silica cap on Cerro Negro hill. They are dominated by silica replacement after lattice calcite texture with high Au grades related to low temperature quartz and late hematite-stained brecciation. We conclude that all deposits are genetically related to intrusive activity, and that additional Au–Ag mineralization may be concealed beneath post-mineral volcanic and sedimentary rocks in the central graben.

Gold Mineralization in Izu Peninsula, Central Japan, during Crustal Extension in Response to Double Subduction

AbstractIzu Peninsula in central Japan, the northern tip of the Izu‐Bonin arc, hosts numerous epithermal Au–Ag vein deposits of low‐sulfidation style. All have similar vein textures, mineralogy, and alteration. Geochemical data from fluid inclusions in vein quartz, the mineralogy and mineral chemistry of alteration, and stable isotope data indicate that auriferous hydrothermal activity occurred under subaerial conditions. The K–Ar ages of auriferous vein minerals are <1.5 Ma, indicating that the mineralization took place after extensive submarine volcanism for the host rocks. These observations suggest that Au–Ag mineralization was synchronous with the development of an extensional regime of the Izu block after its collision with the Honshu arc after 1.5 Ma. This collision resulted in the shifting of the Izu block far from the trench to the rear position, and the subduction of the Izu block along the Suruga trough to the west and along the Sagami trough to the east. The reararc position of the Izu block and double subduction resulted in crustal extension, upwelling of asthenospheric mantle, and tholeiitic magmatism reflected by mafic dyke swarms and subsequent monogenetic volcanic activity in the Izu peninsula. The timing of the Au mineralization in the Izu Peninsula during the beginning of lithospheric extension is similar to that of the Sado Au–Ag deposit on Sado island in the Japan Sea. Two mineralization events coincide with extensive tholeiitic mafic volcanism and injections of dyke swarms related to the back‐arc opening of the Japan Sea. The geological setting of the Au–Ag mineralization in Izu and Sado is also similar to that of the epithermal Au–Ag deposits in northern Nevada, where mineralization was contemporaneous with crustal extension and tholeiitic mafic magmatism derived from the asthenospheric mantle. This study suggests that epithermal Au mineralization at shallow crustal depths is a product of large‐scale lithospheric evolution.

Major types and time–space distribution of Mesozoic ore deposits in South China and their geodynamic settings

The ore deposits of the Mesozoic age in South China can be divided into three groups, each with different metal associations and spatial distributions and each related to major magmatic events. The first event occurred in the Late Triassic (230–210 Ma), the second in the Mid–Late Jurassic (170–150 Ma), and the third in the Early–Mid Cretaceous (120–80 Ma). The Late Triassic magmatic event and associated mineralization is characterized by peraluminous granite-related W–Sn–Nb–Ta mineral deposits. The Triassic ore deposits are considerably disturbed or overprinted by the later Jurassic and Cretaceous tectono-thermal episodes. The Mid–Late Jurassic magmatic and mineralization events consist of 170–160 Ma porphyry–skarn Cu and Pb–Zn–Ag vein deposits associated with I-type granites and 160–150 Ma metaluminous granite-related polymetallic W–Sn deposits. The Late Jurassic metaluminous granite-related W–Sn deposits occur in a NE-trending cluster in the interior of South China, such as in the Nanling area. In the Early–Mid Cretaceous, from about 120 to 80 Ma, but peaking at 100–90 Ma, subvolcanic-related Fe deposits developed and I-type calc-alkaline granitic intrusions formed porphyry Cu–Mo and porphyry-epithermal Cu–Au–Ag mineral systems, whereas S-type peraluminous and/or metaluminous granitic intrusions formed polymetallic Sn deposits. These Cretaceous mineral deposits cluster in distinct areas and are controlled by pull-apart basins along the South China continental margin. Based on mineral assemblage, age, and space–time distribution of these mineral systems, integrated with regional geological data and field observations, we suggest that the three magmatic–mineralization episodes are the result of distinct geodynamic regimes. The Triassic peraluminous granites and associated W–Sn–Nb–Ta mineralization formed during post-collisional processes involving the South China Block, the North China Craton, and the Indo-China Block, mostly along the Dabie-Sulu and Songma sutures. Jurassic events were initially related to the shallow oblique subduction of the Izanagi plate beneath the Eurasian continent at about 175 Ma, but I-type granitoids with porphyry Cu and vein-type Pb–Zn–Ag deposits only began to form as a result of the breakup of the subducted plate at 170–160 Ma, along the NNE-trending Qinzhou-Hangzhou belt (also referred to as Qin-Hang or Shi-Hang belt), which is the Neoproterozoic suture that amalgamates the Yangtze Craton and Cathaysia Block. A large subduction slab window is assumed to have formed in the Nanling and adjacent areas in the interior of South China, triggering the uprise of asthenospheric mantle into the upper crust and leading to the emplacement of metaluminous granitic magma and associated polymetallic W–Sn mineralization. A relatively tectonically quiet period followed between 150 and 135 Ma in South China. From 135 Ma onward, the angle of convergence of the Izanagi plate changed from oblique to parallel to the coastline, resulting in continental extensional tectonics and reactivation of regional-scale NE-trending faults, such as the Tan-Lu fault. This widespread extension also promoted the development of NE-trending pull-apart basins and metamorphic core complexes, accompanied by volcanism and the formation of epithermal Cu–Au deposits, granite-related polymetallic Sn–(W) deposits and hydrothermal U deposits between 120 and 80 Ma (with a peak activity at 100–90 Ma).

Silver Deposits of the Pamir Region, Tajikistan: Metallogeny, Mineralogy, and Genesis

Silver deposits of the South Pamir region of Tajikistan occur as siderite veins with sulfosalts and sulfides, and formed during a late Mesozoic-early Alpine cycle of rifting and orogenesis. Three mineral-geochemical types of ore deposits that occur in several ore districts are recognized: Ag-Sb, Ag-Pb, and Ag-Hg. The Ag vein deposits all occur in terrigenous-carbonate sedimentary rocks and in intrusive granites. The veins are controlled by late Mesozoic faults, and are the products of the last endogenous event in the region. The most significant group of Ag-Sb vein deposits is located in the Bazardara ore district. Three stages of mineralization are recognized in this region: siderite-tetrahedrite, quartz-tetrahedrite, and quartz-galena-freibergite. Most of the veins were deposited during the first stage. Tetrahedrite is the prevailing and most economically important mineral, and contains 0.2 to 15.5% Ag. Associated freibergite contains from 19.5 to 32% Ag. Fluid-inclusion studies indicate that Ag-Sb ore deposits formed over a temperature interval of 280-100°C and pressure of 750-450 bars. Ore deposits were formed from saline solutions (up to 38%) that in late stages were diluted (1.5%). Considerable fluctuations apparently occurred in the associated regional hydrothermal system. Temperature gradients ranged from 8-10°C/100 meters to 14-15°C/100 meters. Temperatures and concentrations of hydrothermal solutions significantly decreased from the main ore-controlling fault toward the north and south flanks of the ore districts.

Lithophile-element systematics of Archean greenstone belt Au–Ag vein deposits: implications for source processes: Reply

Potassic alteration domains of greenstone belt lode gold deposits are characterized by systematic partitioning between lithophile elements. K, Rb, and Ba are generally co-enriched and linearly correlated over almost three orders of magnitude in abundance, where K/Rb = 220–400 and K/Ba = 30–85; K/Cs (~104) and K/Tl (~2 × 104) are also correlated, though more weakly. Lithium abundances and Rb/Sr ratios are erratic in altered rocks. These interelement trends, collectively, are present in deposits variously hosted by ultramafic, mafic, or felsic volcanic rocks and sediments or granitoids. Magmatic processes involving crystal fractionation of biotite, K-feldspar, and plagioclase generate trends to systematically diminished K/Rb (≥50), K/Li, K/Cs, and K/Tl but enhanced K/Ba (≤8 × 103) and Rb/Sr in most differentiates. Such late-stage trends are the rule in magmatophile deposits, including the Archean Cadillac molybdenite deposit, Phanerozoic Cu- and Mo-porphyry deposits, Sn–W greisens, and most...

Lithophile-element systematics of Archean greenstone belt Au–Ag vein deposits: implications for source processes: Discussion

Lithophile-element systematics of Archean greenstone belt Au–Ag vein deposits: implications for source processes: Discussion

Carbon-isotope systematics of Archean Au–Ag vein deposits in the Superior Province

Abundant carbonate is a characteristic feature of most Archean mesothermal Au–Ag vein deposits, but the source of the C is controversial. For Superior Province deposits collectively, the maximum variation of average δ13C values is from −9.0 ± 0.7‰ (1σ, n = 19; Darius) to −0.6 ± 1.6‰ (1σ, n = 7; Cochenour–Willians), and limiting δ13C values are−13.6 and + 1.3‰. At the deposit scale, Fe dolomites in nongraphitic lithologies are for the most part isotopically uniform, where δ13C = −3.4 ± 0.4 (1σ) (Hollinger), −3.2 ± 0.3 (McIntyre), −4.7 ± 1.7 (Dome), −2.8 ± 0.6 (Buffalo Ankerite), −3.6 ± 0.5 (Macassa), −3.2 ± 0.3 (Bousquet), −5.4 ± 0.9 (Lamaque), and −5.3 ± 0.5‰ (Hasaga): the restricted individual ranges of δ13C values imply a corresponding uniformity to the ambient temperature and δ13CΣC of the ore-forming fluids.Within individual deposits, small systematic variations of δ13C carbonate arise from (i) interaction of hydrothermal fluids with carbonaceous rocks, (ii) immiscible separation of CO2 + CH4, or (iii) Rayleigh fractionation effects. Positive shifts in δ13C result from buffering of the fluid to lower Eh by reaction with reduced C, whereas negative shifts reflect partial isotopic equilibration between 13C-depleted C (δ13C ≈ −26‰) and aqueous hydrothermal C species. Transient immiscibility of CO2 + CH4 acts to precipitate carbonates enriched relative to the main population of Fe dolomites. The δ13C values of carbonates in unmineralized alteration halos (−2.2 ± 1.1‰, n = 42) at the McIntyre deposit are enriched in 13C relative to the main gold-bearing vein systems (δ13C = −3.2 ± 0.3‰): the enrichment is attributed to a Rayleigh fractionation accompanying progressive consumption of CO2 as hydrothermal fluids infiltrate laterally from veins into wall rocks. Fe dolomite and calcite are variably enriched in 18O with respect to equilibrium quartz-carbonate fractionations for ambient temperatures of 270–340 °C. Carbonate δ18O values diminish in an irregular manner with depth, converging on values of ~11‰ (Fe dolomite, 6800 ft (2073 m), McIntyre). Variable degrees of oxygen-isotope disequilibrium represent overprinting of carbonates by post-Archean brines in the Canadian Shield.Synvolcanic vesicle calcite in three groups of metabasalts (δ13C = −4.3 ± 2.1; −2.8 ± 1.5; −2.7 ± 1.3‰) and calcite in two groups of clastic sediments (−6.4 ± 1.8; −4.6 ± 2.5‰) remote from deposits are systematically depleted of 13C relative to average Precambrian limestones (~0 ± 1‰), owing to the involvement of CO2 derived from 13C-depleted organic matter. Consequently, calcite in greenstone belt supracrustal rocks is not restricted to approximately 0‰. The total spread of average δ13CFe dol values (−9.0 ± 0.7 to −0.6 ± 0.6‰) in the Au deposits, which goes in hand with a geographical provinciality in O-, Sr-, and Pb-isotope compositions of the ore-forming fluids, is too large to be accounted for by mantle CO2 (−6 ± 2‰) or magmatic CO2 (−6 ± 2‰) alone but rather is interpreted as reflecting generation of hydrothermal fluids in crustal or subcreted rocks heterogeneous in terms of the distribution of 13C-enriched (carbonate) and 13C-depleted (reduced C) lithologies.

Lithophile-element systematics of Archean greenstone belt Au – Ag vein deposits: implications for source processes: Reply

Lithophile-element systematics of Archean greenstone belt Au – Ag vein deposits: implications for source processes: Reply

Lithophile-element systematics of Archean greenstone belt Au–Ag vein deposits: implications for source processes: Discussion

Lithophile-element systematics of Archean greenstone belt Au–Ag vein deposits: implications for source processes: Discussion

Genetic implications of stable isotope characteristics of mesothermal Au deposits and related Sb and Hg deposits in the Canadian Cordillera

The Canadian Cordillera hosts a large number of mesothermal, Au + or - Ag vein deposits. The deposits are scattered throughout accreted and suspect terranes of the cordillera and often have a distinct spatial association with strike-slip faults. These vein deposits possess a striking degree of homogeneity in delta 18 O values on vein, district, and regional scales. In most districts, delta 18 O values for mineralized quartz veins vary only by 2 to 3 per mil across the entire district. Over the Canadian Cordillera as a whole, delta 18 O values for such veins range from 13 to 18 per mil (SMOW). In contrast to the high degree of homogeneity evident in the delta 18 O values of the veins, alteration zones in adjoining wall rocks possess distinctive zoning patterns, indicating isotopic exchange between ore fluids and host units.Deposits of Hg and Sb are also closely associated with strike-slip faults in the Canadian Cordillera area. The delta 18 O studies of quartz from these deposits indicate average values of 29 + or - 2.0 per mil (SMOW) for quartz from the Hg deposits and 21.0 + or - 1.5 per mil for quartz from the Sb deposits. When corrected for isotopic fractionation assuming equilibrium conditions, average delta 18 O values for ore-forming fluids of the various deposit types all fall within a 5 per mil range, indicating a probable common fluid source for the three deposit types. All three deposit types have delta 13 C values for carbonates in the range of -10 to +2 per mil (PDB), which are believed to reflect a heterogeneous source for the carbon. The delta D values from serpentinites associated with Au deposits and inclusion fluids from all three deposit types are lighter than - 100 per mil and latitudinally dependent, indicating the involvement of chemically evolved, meteoric water in the ore-forming process.A model for formation of these deposits is presented involving the convection of meteoric water in the brittle crust to depths of 12 to 15 km and temperatures of 300 degrees to 400 degrees C. During descent, the fluid evolves in delta 18 O and acquires constituents involved in the later ore-forming process. Fluids ascend in highly permeable zones associated with strike-slip faults, depositing quartz, sulfides, and Au at a depth of approximately 10 km and a temperature of 300 degrees + or - 50 degrees C. At shallower levels and cooler temperatures, Sb quartz + or - Au veins are formed and near the surface, cinnabar and carbonate are deposited at temperatures near 150 degrees C. Similarities in geology and geochemistry of mesothermal Au deposits of the Canadian Cordillera and deposits of the Mother Lode, California, and the Archecan cratons suggest that the model proposed herein may also be applicable to those deposits.

Source processes for Archean Au–Ag vein deposits: evidence from lithophile-element systematics of the Hollinger–McIntyre and Buffalo Ankerite deposits, Timmins

Potassic alteration domains of Archean greenstone belt lode gold deposits, typified by the Hollinger–McIntyre and Buffalo Ankerite mines, Timmins, are characterized by systematic partitioning between different groups of incompatible elements such that Al, Ga, Th, U, Ti, and V are decoupled from K, Rb, Ba, Li, Cs, and Tl. The former group of elements has concentrations and interelement ratios in alteration domains that reflect host-rock control, implying approximately isochemical behaviour. In contrast, the lithophile elements K, Rb, and Ba are generally coenriched and are linearly correlated over three orders of magnitude in abundance, where K/Rb = 230–380 (r = 0.92–0.99) and K/Ba = 34–97 (r = 0.82–0.99), values close to average crustal ratios of 285 and 36, respectively. K/Rb and K/Ba ratios trend towards higher values with respect to increasing concentrations of Rb and Ba, possibly because of mixing between host rock and hydrothermal reservoirs of the lithophile elements. Cs and Tl contents average 1.4 and 1.1 ppm, respectively, such that K/Cs and K/Tl, as well as K/Rb and K/Ba, trend to higher than bulk crustal ratios, signifying a mafic to ultramafic source variably depleted in Cs, Tl, Rb, and Ba relative to K. Lithium is generally not coenriched with K but rather correlates with Mg content, reflecting the primary magmatic substitution of Li1+ for Mg2+ in the parent magmas. Al and Ga are highly correlated: Al/Ga = 2070–3790 and r = 0.85–0.98. Accordingly, Al and Ga were not fractionated during mineralization. These interelement trends, collectively, are present in deposits variously hosted by ultramafic, mafic, or felsic volcanic rocks and by sediments or granitoids.Magmatic processes involving crystal fractionation of biotite, K-feldspar, and plagioclase generate trends to systematically diminished K/Rb (≥50), K/Li, K/Cs, and K/Tl but enhanced K/Ba (≤8 × 103) and Rb/Sr ratios in most late-stage differentiates. Al/Ga ratios diminish systematically during late-stage magmatic evolution, and Th–U and Ti–V display mutual partitioning governed by crystallization of trace phases. Such "late-stage" trends are the rule in "magmatophile" deposits, including the Archean Cadillac molybdenite deposit, Phanerozoic Cu- and Mo-"porphyry" deposits, Sn–W greisens, and most pegmatites. Accordingly, magmatic processes of this type can be ruled out as the dominant source of volatiles for gold-forming systems. There is no complementarity between large-ion lithophile-element (LILE) (K, Rb, Ba, Cs, U, Th) depletion patterns in granulites and K, Rb, and Ba enrichment in Au deposits. The enhanced K/Rb, K/Cs, and Rb/Cs ratios but diminished K/Ba ratios, characteristic of many granulites, are not reflected in the gold deposits, where K/Rb and K/Ba ratios approximate average crustal values and Th and U behave isochemically. In many granulites, especially Archean examples, LILE depletion is a primary feature; accordingly, the granulitization model for Au–Ag vein deposits can also be ruled out.The compliance of K/Rb and K/Ba ratios in potassic alteration domains of Au deposits with values characteristic of main-trend igneous rocks or "average" crust implies that K, Rb, and Ba were partitioned into the hydrothermal ore-forming fluids in approximately the same ratios as in the source rocks, consistent with known fluid–mineral distribution coefficients. Dehydration reactions in dominantly mafic to ultramafic source rocks under amphibolite-facies conditions or equilibration of ore-forming fluids with source rocks under conditions of low water/rock ratio, rather than either purely magmatic or granulitization processes, may satisfy the requirement for proportional K, Rb, and Ba coenrichment, Li retention, and the absence of Al–Ga fractionation.

Lithophile-element systematics of Archean greenstone belt Au–Ag vein deposits: implications for source processes

Potassic alteration domains of greenstone belt lode gold deposits are characterized by systematic partitioning between lithophile elements. K, Rb, and Ba are generally co-enriched and linearly correlated over almost three orders of magnitude in abundance, where K/Rb = 220–400 and K/Ba = 30–85; K/Cs (~104) and K/Tl (~2 × 104) are also correlated, though more weakly. Lithium abundances and Rb/Sr ratios are erratic in altered rocks. These interelement trends, collectively, are present in deposits variously hosted by ultramafic, mafic, or felsic volcanic rocks and sediments or granitoids. Magmatic processes involving crystal fractionation of biotite, K-feldspar, and plagioclase generate trends to systematically diminished K/Rb (≥50), K/Li, K/Cs, and K/Tl but enhanced K/Ba (≤8 × 103) and Rb/Sr in most late-stage differentiates. Such "late-stage" trends are the rule in "magmatophile" deposits, including the Archean Cadillac molybdenite deposit, Phanerozoic Cu- and Mo-"porphyry" deposits, Sn–W greisens, and most pegmatites. Accordingly, magmatic processes of this type can be ruled out as the dominant source of volatiles for gold-forming systems. The compliance of K/Rb and K/Ba ratios in potassic alteration domains of Au deposits with values characteristic of main-trend igneous rocks, or "average" crust, implies that K, Rb, and Ba were partitioned into the hydrothermal ore-forming fluids in approximately the same ratios as in the source rocks. Dehydration reactions in the source rocks or equilibration of fluids with source rocks under conditions of low water/rock ratio, rather than magmatic processes, may satisfy the requirement for proportional K, Rb, and Ba co-enrichment.

The genesis of the Deer Trail Zn–Pb–Ag vein deposits, northeast Washington, U.S.A.: evidence from fluid-inclusion and stable-isotope studies

The Zn–Pb–Ag-bearing vein deposits of the Deer Trail mine, northeastern Washington, U.S.A., are hosted by Beltian metasediments that have been intruded by the Jurassic–Cretaceous Loon Lake granitoid batholith.Vein infilling took place in three stages: pre-ore, ore, and post-ore. Fluid-inclusion studies revealed homogenization temperatures and salinities of approximately 300 °C and 6.5–8.5 wt. % NaCl equivalent, respectively, for the pre-ore stage; 250–150 °C and 4–7.5 wt. % NaCl equivalent for the ore stage; and less than 150 °C and 3 wt. % NaCl equivlent for the post-ore stage. The calculated δ18O values of the hydrothermal fluids and δD values of fluid inclusion waters were +8 to +11‰ (SMOW) and −128 to −134‰ (SMOW), respectively, for the pre-ore stage; 0 to +10‰ and −89 to −143‰ for the ore stage; and 0 to −5‰ and −139‰ for the post-ore stage. The δ34S(ΣS) of the hydrothermal fluids was approximately +10‰(CDT).The results provide insight into the evolution of a geothermal system dominated by meteoric waters and driven thermally by the cooling batholith. The chemical and isotopic compositions of the veins were influenced by chemical reactions and isotope exchange of the hydrothermal fluids with the Precambrian metasedimentary rocks.