Volcanic-associated Massive Sulfide Research Articles

Evaluation of non-destructive tools for preliminary environmental risk assessment during mining exploration

Environmental assessment is generally performed when a mining project is at an advanced development stage, such as the prefeasibility study. It involves several laboratory tests such as detailed characterisation and geochemical mobility prediction tests, which require many samples considered representative of the deposit. Having early characterisation information could be useful to select the most relevant samples for the overall environmental assessment. The present study proposes a selection of non destructive and portable tools for improving the early environmental assessment of a mineral deposit. Three tools (x-ray fluorescence (XRF), mineral spectrometer, carbonate staining) were identified to form a preliminary environmental assessment methodology that can be performed directly on the exploration site. This methodology was applied to two different mining projects: i) a well developed mine, LaRonde zone 5, with available geochemical data in a volcanic-associated massive sulfide (VMS) context, and ii) an exploration project, O’Brien, with ongoing geochemical acquisition in an Au-quartz vein context. Both mine sites are in the south of the Blake River Group within the Abitibi greenstone belt, Quebec, Canada. The first site was used to validate the developed methodology, whereas the second acted as a test site to apply the methodology as a preliminary environmental assessment. The results on the first site confirmed that the selected tools provide geochemical and mineralogical data sets comparable to those of traditional testing methods. The developed methodology then enabled the classification of preliminary geo-environmental domains for the second site. Standard static and kinetic tests were performed on the second site samples to confront the preliminary assessment protocol. The proposed preliminary protocol made it possible to discriminate low-risk samples versus those with a potentially higher risk for the selection of subsequent environmental assessments.

Tonian-Cryogenian bimodal volcanism and related sulfide ores in the Arabian-Nubian Shield: An example from the Dendekan prospect in the Eastern Desert of Egypt

The Dendekan prospect is located in the southern segment of the Eastern Desert of Egypt, which constitutes the northwestern part of the Arabian-Nubian Shield. The volcanic rocks of the Dendekan prospect are considered to be the eastern part of the Shadli-Ranga bimodal volcanic belt. These volcanic rocks include massive basaltic flows that are intruded by porphyritic rhyolite. The porphyritic rhyolite yielded a SIMS U-Pb zircon age of 750 ± 10 Ma. Both basalt and rhyolite have a low-K tholeiitic affinity and their mantle-normalized trace element patterns show enrichment of large ion lithophile elements (LILE), U and Th over high field strength elements (HFSE) and pronounced negative Nb anomaly. These geochemical characteristics along with the bimodal nature of the volcanic rocks are consistent with incipient rifting in an intra-oceanic island arc tectonic setting. The onset of rifting promoted hydrous melting of depleted mantle as indicated by the low Nb/Yb ratio of the Dendekan basalt. Geochemistry of the Dendekan rhyolite and its high zircon εHf (T) values (9.5 average) suggest melting of mainly juvenile mafic lower crust. The Hydrothermal alteration in the prospect is represented by patchy and vein-like epidotization as well as silicification of basalt, while the porphyritic rhyolite exhibits extensive sericitization along the wall of old exploited trenches extending close to the contact between the rhyolite and the basalt. Pyrite occurs as disseminated crystals and aggregates in association with minor pyrrhotite and chalcopyrite. Pyrite is commonly altered to ferric oxyhydroxide, locally with native gold inclusions. Sulfides in the Dendekan prospect may represent a pyrite-rich deep part of a volcanic-associated massive sulfide system that was affected by weathering. Compared with the Tonian bimodal volcanic rocks of the Dendekan prospect, the volcanic assemblage from the western part of the Shadli-Ranga bimodal belt exhibits a younger Cryogenian age and a less pronounced subduction geochemical signature suggesting the evolution form Tonian incipient arc rifting to Cryogenian rifting in a back-arc setting.

Generation and structural modification of the giant Kengdenongshe VMS-type Au-Ag-Pb-Zn polymetallic deposit in the East Kunlun Orogen, East Tethys: Constraints from geology, fluid inclusions, noble gas and stable isotopes

The Kengdenongshe giant Au-Ag-Pb-Zn polymetallic deposit is located in the East Kunlun Orogen (EKO). It contains about 42.2 t of Au, 608.6 t of Ag and 1.05 Mt of Pb and Zn with an average grade of Au 2.31 g/t, Ag 19.29 g/t and Pb + Zn 3.49 wt% (Pb: 1.23 wt%, Zn: 2.26 wt%). The NWW-trending ore bodies are predominantly hosted in Late Permian to Triassic rhyolitic tuff, which formed during Late Permian back-arc extension to Triassic arc-continental collision. The ore bodies are subdivided into Pb-Zn rich ore bodies on the top with high grades of Pb and Zn and low grades of Au and Ag, and Au-Ag rich ore bodies below with high grades of Au and Ag and low grades of Pb and Zn. The Pb-Zn rich ore bodies occur as vein, stockwork, and in breccia, and comprise quartz, pyrite, galena, sphalerite, and small amounts of chalcopyrite. The Au-Ag rich ore bodies consist of auriferous barite-sulfide-oxide veins and contain barite, pyrite (early strawberry and oolitic pyrite and later eu- to subhedral pyrite), galena, sphalerite, chalcopyrite, tetrahedrite and covellite. Gold is present as electrum, kustelite and native gold and silver is present as polybasite, pearceite, kongsbergite, and as minor native silver in microfractures in sulfides. The hydrothermal alteration minerals include, from bottom to top, quartz + barite + calcite around the Au-Ag rich orebodies, quartz + chlorite + epidote around the Pb-Zn rich orebodies, and quartz + K-feldspar within the tuff. Fluid inclusions from both the Pb-Zn rich and the Au-Ag rich orebodies consist of two phases (V–L-type) fluid inclusions of which the vapor phase has a size of 10–40 vol%. Fluid inclusions microthermometry reveal homogenization temperatures of fluid inclusions in Pb-Zn rich and Au-Ag rich ore bodies of 128–230 °C and 110–320 °C, with corresponding salinities of 0.7–9.9 and 0.2–18.3 wt% NaCl equivalent, respectively. H-O-S-Pb stable isotope and He-Ar noble gas isotope data indicate a mixed magmatic water-seawater source for both the Pb-Zn and Au-Ag rich ore bodies, and an additional meteoric water component for the Au-Ag rich ore bodies. The Pb-Zn and Au-Ag rich ore bodies share the same sulfur and lead sources, i.e. sulfur is derived from crustal magma and seawater/marine sulfate, and the lead originated from a mixed magmatic-ancient crustal sedimentary source. Collectively, the regional geology, mineralogy, alteration, and geochemistry indicate that the Kengdenongshe Au-Ag-Pb-Zn polymetallic deposit can be characterized as a VMS-type (volcanic-associated massive sulfide) deposit. Formation of the ore-hosting rhyolite tuff and mineralization are associated with Late Permian to Triassic marine volcanic exhalation. Middle to Late Triassic basin closure and arc-continent collision modified the deposit and resulted in the location inversion of the Pb-Zn and Au-Ag rich orebodies.

Age and Tectonic Setting of Mesothermal Magmatic Hydrothermal Vein‐Type Pb–Zn–(Ag) Mineralization in the Xiaohongshilazi Deposit, Central Jilin Province, Northeast China

AbstractThe Xiaohongshilazi deposit located in central Jilin Province, Northeast China, is a newly discovered and medium‐scale Pb–Zn–(Ag) deposit with ore reserves of 34,968 t Pb, 100,150 t Zn, and 158 t Ag. Two‐stage mineralization has been identified in this deposit. Stratiform volcanic‐associated massive sulfide (VMS) Pb–Zn mineralization interbedding with the marine volcanic rocks of the Late Carboniferous–Early Permian Daheshen Formation was controlled by the premineralization E–W‐trending faults. Vein‐type Pb–Zn–(Ag) mineralization occurs within or parallel to the granodiorite and diorite porphyries controlled by the major‐mineralization N–S‐trending faults that cut the stratiform mineralization and volcanic rocks. To constrain the age of vein‐type Pb–Zn–(Ag) mineralization and determine the relationship between mineralization and magmatism, we conducted LA–ICP–MS U–Pb dating on zircon from the ore‐bearing granodiorite and diorite porphyries and Rb–Sr dating on metal sulfide. Granodiorite and diorite porphyries yield zircon U–Pb weighted‐mean 206Pb/238U ages of 203.6 ± 1.8 Ma (Mean Standard Weighted Deviation [MSWD] = 1.8) and 225.6 ± 5.1 Ma (MSWD = 2.3), respectively. Sulfides from four vein‐type ore samples yield a Rb–Sr isochron age of 195 ± 17 Ma (MSWD = 4.0). These results indicate a temporal relationship between the granodiorite porphyry and vein‐type Pb–Zn–(Ag) mineralization. The granodiorite associated with vein‐type mineralization has high SiO2 (68.99–70.49 wt.%) and Na2O (3.9–4.2 wt.%; Na2O/K2O = 1.07–1.10) concentrations, and A/CNK values of 0.95–1.04; consequently, the intrusion is classified as a high‐K, calc‐alkaline, metaluminous I‐type granite. The granodiorite porphyry is enriched in large‐ion lithophile elements (e.g. Rb, Th, U, and K) and light REE and is depleted in high‐field‐strength elements (e.g. Nb, Ta, P, and Ti) and heavy REE, indicating that it represents a subduction‐related rock that formed at an active continental margin. Furthermore, the granodiorite porphyry has Mg# values of 31–34, indicating a lower crustal source. Based on petrological and geochemical features, we infer that the ore‐bearing granodiorite porphyry was derived from the partial melting of the lower crust. In summary, mineralization characteristics, cross‐cutting relationships, geochronological data, and regional tectonic evolution indicate that the region was the site of VMS Pb–Zn mineralization that produced stratiform orebodies within the Late Carboniferous–Early Permian marine volcanic rocks of the Daheshen Formation, followed by mesothermal magmatic hydrothermal vein‐type Pb–Zn–(Ag) mineralization associated with granodiorite porphyry induced by the initial subduction of the Paleo‐Pacific Plate beneath the Eurasia Plate during the Late Triassic–Early Jurassic.

Ore Genesis for Stratiform Ore Bodies of the Dongfengnanshan Copper Polymetallic Deposit in the Yanbian Area, NE China: Constraints from LA‐ICP‐MS in situ Trace Elements and Sulfide S–Pb Isotopes

The Dongfengnanshan Cu polymetallic deposit is one representative deposit of the Tianbaoshan ore district in the Yanbian area, northeast (NE) China. There occur two types of ore bodies in this deposit, the stratiform ore bodies and vein‐type ones, controlled by the Early Permian strata and the Late Hercynian diorite intrusion, respectively. Due to the ambiguous genetic type of the stratiform ore bodies, there has been controversy on the relationship between them and vein‐type ore bodies. To determine the genetic type of stratiform ore bodies, laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) in situ trace elements and S–Pb isotope analysis have been carried on the sulfides in the stratiform ore bodies. Compared with that in skarn, Mississippi Valley‐type (MVT), and epithermal deposits, sphalerite samples in the stratiform ore bodies of the Dongfengnanshan deposit are significantly enriched in Fe, Mn, and In, while depleted in Ga, Ge, and Cd, which is similar to the sphalerite in volcanic‐associated massive sulfide (VMS) deposits. Co/Ni ratio of pyrrhotites in the stratiform ore bodies is similar to that in VMS‐type deposits. The concentrations of Zn and Cd of chalcopyrites are similar to those of recrystallized VMS‐type deposits. These characteristics also reflect the intermediate ore‐forming temperature of the stratiform ore bodies in this deposit. Sulfur isotope compositions of sulfides are similar to those of VMS‐type deposits, reflecting that sulfur originated from the Permian Miaoling Formation. Lead isotope compositions indicate mixed‐source for lead. Moreover, the comparison of the Dongfengnanshan stratiform ore bodies with some VMS‐type deposits in China and abroad, on the trace elements and S–Pb isotope characteristics of the sulfides reveals that the stratiform ore bodies of the Dongfengnanshan deposit belong to the VMS‐type, and have closely genetic relationship with the early Permian marine volcanic sedimentary rocks.

The Society of Economic Geologists Awards for 2014 R. A. F. Penrose Gold Medal for 2014 Citation of James M. Franklin

Mr. President, SEG members, and friends: Jim Franklin’s career has encompassed all of the criteria applicable to the terms of reference for the Penrose Gold Medal with his outstanding contributions to scientific research, to the profession, and to the development of mineral resources. All three were achieved through a full career in economic geology as practiced in academia, government, and industry. Although his scientific achievements are wide ranging and easily documented, I believe his singular technical contribution has been the establishment of the link between the geological attributes of volcanic-associated massive sulfide deposits, as preserved in the rock record ranging back to the Archean, with hydrothermal processes in modern oceanic environments. His penchant for documentation of key features associated with massive sulfide deposits, particularly things geochemical, dates back to his employment as a student at the Geological Survey of Canada with the late S.M. Roscoe, who was one of the earliest proponents of a syngenetic origin for deposits at Noranda and Mattagami Lake. Jim later put this experience to work in documenting the geology of the newly discovered Mattabi deposit at Sturgeon Lake in northern Ontario in the early 1970s, showing a geological setting and style of alteration that differed in many respects from the more familiar examples at Noranda and Kuroko. Similar work elsewhere at the time was focused on the site of metal deposition but Jim’s work at Sturgeon Lake pointed the way to two broader and more critical aspects: the presence of a …

Metallogenesis and geodynamics of the Lachlan Orogen: New (and old) insights from spatial and temporal variations in lead isotopes

Analysis of the distribution patterns of Pb isotope data from mineralised samples using the plumbotectonic model of Carr et al. (1995), which invokes mixing between crustal and mantle reservoirs, indicates systematic spatial patterns that reflect major metallogenic and tectonic boundaries in the Paleozoic Lachlan and Delamerian orogens in New South Wales and Victoria, Australia. This distribution pattern accurately maps the boundary between the Central and Eastern Lachlan subprovinces. The Central Lachlan Subprovince is characterised by Pb isotope characteristics with a strong crustal signature, whereas the Eastern Lachlan Subprovince is characterised by variable crustal and mantle signatures. The Macquarie Volcanic Province is dominated by Pb with a mantle signature: known porphyry Cu–Au and high sulphidation epithermal Au–Cu deposits in the province are associated with a zone characterised by the strongest mantle signatures. In contrast, granite-related Sn deposits in the Central Lachlan Subprovince are characterised by the strongest crustal signatures. The Pb isotope patterns are broadly similar to Nd isotope model age patterns derived from felsic magmatic rocks, although a lower density of Nd isotope data locations makes direct comparison difficult.The two reservoirs identified by Carr et al. (1995) do not appear to be isotopically linked: the crustal source was not formed via extraction from the mantle source. Rather, the two reservoirs formed separately. The mantle reservoir may have been sourced from a subducting proto-Pacific plate, whereas the crustal reservoir is most likely to be extended Australian crust. The data allow the possibility that the proto-Pacific mantle source was isotopically linked to the western Tasmanian crustal source.Comparison of Pb isotope data from the Girilambone district, Central Lachlan Subprovince, (e.g., Tritton and Avoca Tank Cu deposits) with those from the Cobar Cu–Au–Zn–Pb district, Eastern Lachlan Subprovince, in north central New South Wales indicates a less radiogenic signature, and probably older age, for deposits in the Girilambone district. Hence, a syngenetic volcanic-associated massive sulphide origin for these deposits is preferred over a syn-tectonic origin. The data are also consistent with formation of the Girilambone deposits in a back-arc basin inboard from the earliest phase of the Macquarie Volcanic Province.

Ore textures and remobilization mechanisms of the Hongtoushan copper–zinc deposit, Liaoning, China

The Hongtoushan copper–zinc deposit is a volcanic-associated massive sulfide deposit in the Archean greenstone belt in Liaoning, China. Polymetamorphism has resulted in changes to the composition and textures of minerals in the deposit, along with remobilization. During metamorphism, the original alteration minerals that formed with the ore minerals, such as chlorite and sericite, were transformed into cordierite, anthophyllite, and phlogopite. After further remobilization, new minerals, such as gahnite and actinolite, were formed. In this process, the original textures were destroyed and new textures were formed, including recrystallization and growth textures, brittle and ductile deformation textures, durchbewegung textures, replacement textures, chalcopyrite disease, and retrograde textures. The ore-forming components underwent two periods of remobilization. In the first (early) stage, mechanical remobilization was important, and formed a high grade Cu–Zn–Au–Ag “ore pillar” along the vertical hinge of a synformal fold. In the second (late) stage, the mixed hydrothermal–mechanical remobilization affected the ores, and was typically characterized by matrix sulfides, together with silicate minerals, moving from the matrix into individual fractured pyrite metablasts and replacing them to varying degrees.

Volcanic-associated Besshi-type copper sulfide deposits

Besshi-type volcanic-associated massive sulfide deposits (VMSD) are associated with undifferentiated basaltic formations. They form within the mid-ocean ridges near the continental margins, in back-arc spreading zones, and rarely in intracontinental rift basins. They are characterized by a wide spread of turbidites in ore-bearing strata, Co-rich copper-zinc ores, the predominance of subvolcanic sills, sheet-like ore bodies, an absence of clear structural control, relatively low Cu, Zn, Ag, and Au grades, enrichment in Pb, and relatively large ore and metal reserves.

The Pb-rich sulfide veins in the Boccassuolo ophiolite: Implications for the geochemical evolution of hydrothermal activity across the ocean-continent transition in the Ligurian Tethys (Northern-Apennine, Italy)

Galena bearing sulfide veins have been discovered coexisting with Fe–Cu–Zn dominated veins in the hydrothermal stockwork of the Boccassuolo ophiolite (External Ligurides, Northern Apennine, Italy). The galena-rich veins cut across a volcanic pile composed of pillow lava flows, pillow breccia, and ophiolitic sandstone. Bulk-ore analyses indicate significant enrichment in Pb giving raise to mantle normalized Pb–Ag–Au–Zn–Cu patterns with unusual negative slope, in contrast with the average flat pattern of most sulfide deposits in the Internal Liguride ophiolites which reflect the Fe–Cu–Zn assemblage of ophiolite-hosted Volcanic-associated Massive Sulfide (VMS) deposits all over the world. A wide literature shows that, in contrast with the Internal Ligurides, plutonic and volcanic rocks of the External Ligurides display less depleted and even enriched geochemical characters, not consistent with common oceanic crust at mid oceanic ridges (MOR), but probably originated in the ocean–continent transition of the Adria continental margin. In this geodynamic context, pillow basalts become locally enriched in Pb with high Pb/Cu ratios, and other crustal-compatible elements such as Mo and U. The Pb enrichment observed in the veins Boccassuolo is interpreted to be a result of leaching of such anomalous volcanics forming the ophiolitic substrate. The case of Boccassuolo supports the conclusion that the geochemical character of hydrothermal activity evolved from Cu–Zn rich in MOR-type assemblages of the Internal Ligurides, towards composition enriched in Pb in the External Liguride domain, representing the transition from the Ligurian ocean to the Adria continental margin.

Sulfur-isotope variations in sulfide minerals from massive sulfide deposits of the northern Apennine ophiolites: inorganic and biogenic constraints

Sulfur isotope analysis of sulfide minerals has been carried out for the first time on ore samples from Volcanic-associated Massive Sulfide (VMS) deposits in Tethyan Jurassic ophiolites of the Northern Apennine. The average d34S value is +5.2‰ in pyrite (n. 22), +6.7‰ in chalcopyrite (n. 23), +6.1‰ in sphalerite (n. 9), and 4.6‰ in pyrrhotite (n. 2). The overall average d34S of +5.9‰ (n = 30, s = 3.7) is consistent with data from other sulfide deposits of the Eastern Mediterranean Tethys, although the Apennine ores display a distinctive range from +11.4‰ to the negative field (min. -2.9). The highest d34S‰ values are found in stockwork veins crosscutting basalt and gabbro, and in stratabound ores within basalt (av., +8.9‰). The d34S decreases in serpentinite-hosted stockwork veins (av., +5.8‰) and in stratiform deposits lying on ancient seafloors (av., +2.5‰), in which the negative values were detected. Inorganic reduction of seawater sulfate is assumed to be the primary source of sulfur in the deposits, with some exception however. The low d34S values of serpentinite-hosted veins indicate mixing with sulfur derived from the leaching of magmatic sulfides (av., d34S = +0.8‰). The negative values detected in seafloor-stratiform ores correlate with sulfide textures indicative of the activity of sulfate-reducing bacteria causing preferential fractionation of the light sulfur isotope. The sulfur isotope variations observed in the Northern Apennine VMS deposits reflect the influence of the different environments of sulfide deposition (seafloor vs. subseafloor) and different lithologies of the host rocks (basalt vs. serpentinite).

Precambrian volcanic-associated massive sulfide deposits

Phanerozoic volcanic-associated massive sulfide deposits (VMSD) were subdivided into the Kuroko, Besshi, Cyprus, and Ural types, which differ in their ore geochemistry and mineralogy, in their composition of volcanic ore-hosting rock associations, and in the proportions of felsic and basaltic volcanics and sedimentary rocks in the volcanic successions. The earliest deposits that can be reliably attributed to the above types originated during the Neoproterozoic during the Pangea supercontinental cycle. Archean and Paleoproterozoic VMSD can be accepted as analogues of these types, resembling them in many respects, although differing from the classic deposits of these types in some characteristics. The formation history of Cyprus-type VMSD is traceable to the Paleoproterozoic when deposits in the Outocumpu area dated at approximately 1970 Ma originated during the early stage of Pangea-I amalgamation, whereas the most ancient Besshi-type deposits 1440 million years old originated during the breakup of that supercontinent. Most of the Neoarchean and Paleoproterozoic VMSD are similar in some of their principal features to those of the Ural and Kuroko types. Deposits of both these types and their ancient analogues evolved in the process of the Earth’s evolution and demonstrated unidirectional changes in their ore composition.

Mineral Deposits of Turkey in Relation to Tethyan Metallogeny: Implications for Future Mineral Exploration

The Tethyan metallogeny of Turkey, shaped by the interplay between subduction, collision, postcollision, and rifting processes, is mainly associated with Late Cretaceous to Cenozoic volcanoplutonic and ophiolitic rocks. A wide spectrum of ore deposits is represented from those occurring in island arcs to those associated with continental settings. Though Turkey has been one of the leading producers of chromite, the country is an emerging producer of precious and base metals. This assessment of the metallogeny of Turkey is based on a comprehensive GIS database compilation that contains known mineral deposits and prospects with relevant descriptive data. The data set contains information on major deposit types of economic importance such as porphyry, skarn, epithermal including both high-and low-sulfidation, polymetallic volcanic-associated massive sulfide (VMS) deposits including both Kuroko and Cyprus types, podiform chromite, lateritic nickel, carbonate-hosted lead-zinc with nonsulfide zinc including sedimentary-exhalative (SEDEX) and Mississippi Valley type (MVT), karstic and lateritic bauxite, orogenic gold including both mesothermal and listwanite-hosted types, and placer deposits. Well known deposit types that are less well represented in the database include sediment-hosted Cu, Carlin-type gold, iron oxide copper-gold (IOCG), and detachment-fault related gold systems. Exploration programs in the last two decades have started to reveal the true mineral potential of the country. Turkey is an underexplored country by today’s standards, with a large prospective area with a wide spectrum of mineral deposits reflecting the diverse geological environments that are present. Turkey is the least well explored portion of the Tethyan belt, which hosts Au and Cu endowments comparable with the Andes and the southwest Pacific metallogenic belts.

Geologic Setting of Volcanic-Associated Massive Sulfide Deposits in the Kamiskotia Area, Abitibi Subprovince, Canada

The Upper Archean volcanic succession in the Kamiskotia area (Abitibi greenstone belt, Timmins region) hosts a series of past-producing copper-zinc volcanic-associated massive sulfide (VMS) deposits. All of these occur within a restricted, east-facing stratigraphic interval in the upper part of the Kamiskotia Volcanic Complex. New U-Pb ages for this interval, ranging from 2701.1 ± 1.4 to 2698.6 ± 1.3 Ma, and an age of 2703.1 ± 1.2 Ma from the lower part of the Kamiskotia Volcanic Complex, indicate that the complex is likely part of the Blake River assemblage (2701–2697 Ma) rather than the older Tisdale assemblage (2710–2703 Ma). The Kamiskotia Volcanic Complex consists largely of felsic and mafic lava flows, and VMS mineralization appears to have generally developed at or near the sea floor close to inferred synvolcanic faults. New U-Pb ages of 2714.6 ± 1.2 and 2712.3 ± 2.8 Ma from the northeast-facing volcanic succession in the northern part of the study area (Loveland, Macdiarmid, and Thorburn Townships) indicate that it forms part of the Kidd-Munro assemblage (2719–2710 Ma). A west-northwest–trending faulted contact is inferred between this older succession and the Kamiskotia Volcanic Complex rocks to the south. The Kidd-Munro assemblage rocks are coeval with the Kidd Volcanic Complex, which hosts the giant Kidd Creek VMS deposit 30 km to the east of the study area. The lower part of the succession, in south-central Loveland Township, consists of high silica FIIIb rhyolites. These rocks are geochemically similar to ore-associated FIIIb rocks from Kidd Creek and seem likely to represent the most prospective part of this succession. Future exploration in the Kamiskotia Volcanic Complex is probably best focused on the along-strike extension of the VMS-hosting interval and, in particular, on areas close to the intersections of synvolcanic faults. Mafic and felsic volcaniclastic strata which can be replaced by VMS mineralization, and felsic coherent facies flows and/or domes, appear to be important potential targets.

The Bisha Volcanic-Associated Massive Sulfide Deposit, Western Nakfa Terrane, Eritrea

The Neoproterozoic Bisha volcanic-associated massive sulfide deposit (VMS) is a large (>39 million metric tons (Mt)) relatively high grade Zn-Cu-Au-Ag deposit in a newly discovered VMS district in western Eritrea. The host stratigraphic section comprises a large, possibly coeval and cogenetic intrusion known as the Bisha Gabbroic Complex, ~3 km downsection, a series of mafic to felsic tuffs with minor flows and minor sedimentary rocks in the proximal footwall, and felsic flows, fine tuffs, and volcanic-derived siliciclastic rocks in the proximal hanging wall. Minor siliceous exhalite units extend for several kilometers along strike and are present upsection. Two other VMS deposits are present along strike: Bisha Northwest, 1.5 km to the north-northwest, and Harena, 9.5 km to the south-southwest; additionally, a large, lower grade VMS deposit, Hambok, is present ~15 km to the southwest. The Bisha deposit is a single, nearly inclusion and dike-free lens, 1.2 km along strike, that has been folded and affected by significant, near-surface oxidation and supergene processes. The deposit and host strata form an overturned synform within a probable, west-over east, kilometer-scale nappe structure. It would appear that the strata have been folded and thrust against the gabbroic complex which behaved as a competent buttress during deformation. The oxidation and supergene enrichment have led to the development of four mineralogically and spatially distinct ore types or zones. The hematite-goethite-quartz gossan, from 0- to ~30-m depth, has high gold, silver, and lead contents, with native gold, argentiferous gold, electrum, anglesite, and lesser cerrusite. The kaolinite-quartz-sulfate zone occurs at ~25- to 35-m depth, and also is enriched in gold, silver, and lead, and has the same ore mineralogy as the gossan; additionally it has minor chalcocite and minor to trace amounts of unusual Zn-Pb-Fe carbonate and sulfate minerals. The supergene sulfide zone is present from ~35- to 65-m depth and has significant copper enrichment, with predominant chalcocite, and lesser digenite, covellite, and bornite, along with pyrite, minor pyrrhotite, anglesite, and gangue minerals. The primary massive sulfide, from ~65- to more than 450-m depth, has a significant volume of zinc-rich ore and a typical VMS sulfide assemblage of pyrite, sphalerite, chalcopyrite, and minor to trace galena, pyrrhotite, tetrahedrite, tennantite, arsenopyrite, barite, and gangue. The average ore and trace metal contents of the four ore types are calculated from an extensive assay and whole-rock geochemical database. The average metal contents for primary massive sulfide are comparable to that of other bimodal-siliciclastic deposits using an extended, primitive mantle-normalized plot. The ore metals, Cu, Pb, Zn, Au, and Ag, are 2.5 to 3 orders of magnitude higher than average continental crust, whereas the trace metals are more variable. Manganese is significantly depleted in comparison to the average crustal value. Moderate to strong chloritic alteration and stringer sulfide veins are present in footwall felsic and intermediate tuffs along the entire strike length, immediately east of the eastern massive sulfide lens. This is high-lighted using a chlorite alteration index, in wt percent: (MgO + FeO)*100/(MgO + FeO + CaO + K2O + Na2O). In addition, the chloritic footwall is depleted in silica, alkali, and alkaline earth elements, and europium. In contrast, these elements are enriched in the hanging-wall tuffs, indicating that the Bisha hydrothermal system continued after deposition of the tuffs. Primary geochemistry of mafic to felsic volcanic and nearby intrusive rocks, including the Bisha Gabbroic Complex, indicate a bimodal igneous suite, with evidence for cogenetic and possibly coeval volcanic and intrusive rocks. The suite has tholeiitic to transitional calc-alkalic affinities, with mantle plume-influenced, primitive arc signatures for least altered basalts. Lead isotope ratios of galena and anglesite mineral separates from the Bisha, Bisha Northwest, and Harena deposits have model ages that range from 790 to 770 Ma. This is in contrast to a lead model age of ~720 Ma for the Adi Nefas VMS deposit in the eastern Nakfa terrane and to galena from a nearby gold vein deposit at ~490 Ma. The model ages for the Bisha area VMS deposits indicate that these deposits and their host rocks formed early during the development of the 850 to 550 Ma Nakfa terrane.

Introduction to mineral exploration

List of Contributors. Preface to the Second Edition. Preface to the First Edition. Units, Abbreviations, and Terminology. Part 1: Principles. 1. Ore, Mineral Economics, and Mineral Exploration Charles J. Moon and Anthony M. Evans. 2. The Mineralogy of Economic Deposits Anthony M. Evans. 3. Mineral Deposit Geology and Models Anthony M. Evans and Charles J. Moon. 4. Reconnaissance Exploration Charles J. Moon and Michael K.G. Whateley. 5. From Prospect to Prefeasibility Charles J. Moon and Michael K.G. Whateley. 6. Remote Sensing Michael K.G. Whateley. 7. Geophysical Methods John Milsom. 8. Exploration Geochemistry Charles J. Moon. 9. Mineral Exploration Data Charles J. Moon and Michael K.G. Whateley. 10. Evaluation Techniques Michael K.G. Whateley and Barry C.Scott. 11. Project Evaluation Barry C.Scott and Michael K.G. Whateley. Part 2: Case Studies. 12. Cliffe Hill Quarry, Leicestershire - Development of Aggregate Reserves Michael K.G. Whateley and William L. Barrett. 13. Soma Lignite Basin, Turkey Michael K.G. Whateley. 14. Witwatersrand Conglomerate Gold - West Rand Charles J. Moon and Michael K.G. Whateley. 15. A Volcanic-Associated Massive Sulfide Deposit - Kidd Creek, Ontario Anthony M. Evans and Charles J. Moon. 16. Disseminated Precious Metals - Trinity Mine, Nevada Michael K.G. Whateley, Timothy Bell and Charles J. Moon. 17. Diamond Exploration - Ekati and Diavik Mines, Canada Charles J. Moon. Internet Links. References. Index

Gold in Turkey—a missing link in Tethyan metallogeny

The gold metallogeny of Turkey constitutes a sector of the Tethyan Eurasian Metallogenic Belt (TEMB) within the Alpine–Himalayan orogenic system that formed from Jurassic–Cretaceous to the present. This orogenic system produced many different types of deposits related to subduction, collision, post-collision and rifting processes. Gold deposits, as well as other mineral deposits of Turkey, are mainly concentrated in Late Mesozoic and Tertiary rocks. Evaluation of the gold metallogeny of Turkey is based on a GIS database compilation of known gold deposits and prospects. Currently available data show that Turkey has a gold endowment, including reserves and resources, of approximately 31.5 M oz [979 tonnes] in 51 deposits, 21 of which contain more than 0.2 M oz gold. The other 30 deposits contain a total of approximately 1 M oz [31 tonnes] gold resources. Two recent discoveries, Kisladag and Copler, currently contain total resources of 17.6 M oz Au [549 tonnes], more than 50% of the total Turkish gold endowment. Turkey possesses a wide spectrum of gold deposits related to Mesozoic and Cenozoic volcanoplutonic arcs. However, porphyry gold (copper), epithermal gold (including both high- and low-sulfidation styles), and gold-rich volcanic-associated massive sulfide (including both Kuroko- and Cyprus-types) are the most economically important to date. Orogenic gold, including listwanite-hosted, placer gold and skarn-hosted gold are relatively less important or abundant deposit types. Other potential gold systems for exploration include Carlin-type gold, detachment-fault-related gold, iron oxide–copper–gold, and gold in carbonate-replacement and manganese deposits.

U–Pb Geochronology of VMS mineralization in the Iberian Pyrite Belt

A geochronology study using U–Pb isotope dilution TIMS analyses of zircon has been conducted to determine the ages of volcanic-associated massive sulfide (VMS) deposits in the Iberian Pyrite Belt (IPB), the world's most prolific VMS province. Ages have been determined for host rocks to four VMS systems that span the IPB: the giant Rio Tinto and Aljustrel districts in the central region, Lagoa Salgada to the west, and Las Cruces to the east. A sample of chloritized quartz porphyritic dacite/rhyolite in the footwall of the San Dionisio massive sulfide deposit of the Rio Tinto district is 349.76±0.90 Ma. This is taken as the best age estimate of the mineralization in the Rio Tinto district, probably the world's largest volcanogenic massive sulfide system. Two xenocrystic zircons from the same sample yielded 207Pb/206Pb ages of 414 and 416 Ma, which provide a minimum estimate for the age of the inherited component. A biotite tonalite from the Campofrio area, 3.5 km north of the center of the Rio Tinto district, is chemically similar to the felsic host rock protolith at Rio Tinto. The Campofrio sample has an age of 346.26±0.81 Ma, slightly younger and outside of the 2σ error for the Rio Tinto age; therefore, this phase of this intrusion was not a heat source for the hydrothermal system that formed the deposits of the Rio Tinto district. The Campofrio sample also has three zircon analyses with 207Pb/206Pb minimum ages of 534, 536, and 985 Ma, indicating inheritance from Ordovician and Neoproterozoic sources. In the Aljustrel VMS district, a U–Pb zircon age of 352.9±1.9 Ma characterizes the altered Green Tuff host rock of the Algares deposit, which is slightly older than the Rio Tinto age. Two zircons with 207Pb/206Pb ages of 531 and 571 Ma from this sample indicate inheritance from a Cambrian or older source. The age of mineralization at Lagoa Salgada is given by essentially identical ages of 356.21±0.73 and 356.4±0.8 Ma, for footwall and hanging wall samples, respectively. The hanging wall sample has two zircon analyses with 207Pb/206Pb ages of 464 and 466 Ma, indicating inheritance from an Ordovician or older source. The age for an altered dacite tuff sample from the hanging wall of the Las Cruces deposit is 353.97±0.69 Ma. One zircon analysis from the Las Cruces sample has a 207Pb/206Pb age of 1048 Ma, indicating inheritance from a Neoproterozoic source. These U–Pb ages refine the IPB geochronology provided by previous studies, and they suggest that either volcanism progressed toward the center of the IPB, or that volcanism was broadly static and the strata were progressively rifted to the margins during transtensional basin formation. The zircon inheritance provides direct evidence for Proterozoic to Ordovician sources, reflecting either basement rocks beneath the Phyllite–Quartzite Group during VMS formation in late Tournaisian times, or a Proterozoic to Ordovician detrital component in Phyllite–Quartzite Group source rocks. The presence of an older crustal component is consistent with VMS formation during rift development at a continental margin.

Global comparisons of volcanic-associated massive sulphide districts

AbstractAlthough volcanic-associated massive sulphide (VMS) deposits have been studied extensively, the geodynamic processes that control their genesis, location and timing remain poorly understood. Comparisons among major VMS districts, based on the same criteria, have been commenced in order to ascertain which are the key geological events that result in high-value deposits. The initial phase of this global project elicited information in a common format and brought together research teams to assess the critical factors and identify questions requiring further research. Some general conclusions have emerged.(1)All major VMS districts relate to major crustal extension resulting in graben subsidence, local or widespread deep marine conditions, and injection of mantle-derived mafic magma into the crust, commonly near convergent plate margins in a general back-arc setting.(2)Most of the world-class VMS districts have significant volumes of felsic volcanic rocks and are attributed to extension associated with evolved island arcs, island arcs with continental basement, continental margins, or thickened oceanic crust.(3)They occur in a part of the extensional province where peak extension was dramatic but short-lived (failed rifts). In almost all VMS districts, the time span for development of the major ore deposits is less than a few million years, regardless of the time span of the enclosing volcanic succession.(4)All of the major VMS districts show a coincidence of felsic and mafic volcanic rocks in the stratigraphic intervals that host the major ore deposits. However, it is not possible to generalize that specific magma compositions or affinities are preferentially related to major VMS deposits world-wide.(5)The main VMS ores are concentrated near the top of the major syn-rift felsic volcanic unit. They are commonly followed by a significant change in the pattern, composition and intensity of volcanism and sedimentation.(6)Most major VMS deposits are associated with proximal (near-vent) rhyolitic facies associations. In each district, deposits are often preferentially associated with a late stage in the evolution of a particular style of rhyolite volcano.(7)The chemistry of the footwall rocks appears to be the biggest control on the mineralogy of the ore deposits, although there may be some contribution from magmatic fluids.(8)Exhalites mark the ore horizon in some districts, but there is uncertainty about how to distinguish exhalites related to VMS from other exhalites and altered, bedded, fine grained tuffaceous rocks.(9)Most VMS districts have suffered fold-thrust belt type deformation, because they formed in short-lived extensional basins near plate margins, which become inverted and deformed during inevitable basin closure.(10)The specific timing and volcanic setting of many VMS deposits, suggest that either the felsic magmatic-hydrothermal cycle creates and focuses an important part of the ore solution, or that specific types of volcanism control when and where a metal-bearing geothermal solution can be focused and expelled to the sea floor, or both.This and other questions remain to be addressed in the next phase of the project. This will include in-depth accounts of VMS deposits and their regional setting and will focus on an integrated multi-disciplinary approach to determine how mineralisation, volcanic evolution and extensional tectonic evolution are interrelated in a number of world-class VMS districts.

PALEOSEA-FLOOR VOLCANIC-ASSOCIATED MASSIVE SULFIDE MINERALIZATION RELATED TO A COOLING KOMATIITE FLOW, ABITIBI SUBPROVINCE, CANADA

Paleosea-floor, volcanic-associated massive sulfide mineralization has been discovered 50 to 150 m upsection from a Late Archean peridotitic komatiite flow, where the flow is thickest in a thermal erosion channel. The Terminus massive sulfide occurrence is within carbonaceous argillites that are intercalated with basaltic komatiite flows and flow breccias. It contains appreciable Zn and Cu contents and is associated with silicification and chlorite-epidote alteration. Ultramafic magmas are ideal heat sources for hydrothermal convective systems because of their extremely high liquidus temperatures and their tendency to become less permeable during serpentinization, which impedes advective cooling. Heuristic calculations indicate that there is sufficient enthalpy in the peridotitic komatiite flow to drive the hydrothermal system responsible for the Terminus mineralization. This hypothesis is tested using two-dimensional, finite element heat and fluid-flow simulations. The results suggest that, under the right circumstances (1) relatively thick komatiite flows may take hundreds of years to cool; (2) komatiite flow-driven hydrothermal systems can form sea-floor or subsea-floor deposits comparable in mass to those along the mid-Atlantic Ridge; (3) much of the metal leaching by hydrothermal fluids occurs below, and adjacent to, the flow; and (4) the shape of heat source komatiite flows, or subsea-floor magma chambers, affects the locus and distribution of hydrothermal upwelling. Similar, base metal-precipitating paleohydrothermal systems are present above ponded komatiite flows broadly along strike at the Potter Zn-Cu deposit in Munro township, Ontario. These paleohydrothermal systems, and the calculations presented here, suggest that thick, ponded basaltic flows on the modern sea floor have sufficient enthalpy to form significant hydrothermal sulfide accumulations.