volcanogenic massive sulfide ore deposit
   HOME

TheInfoList



OR:

Volcanogenic massive sulfide ore deposits, also known as VMS ore deposits, are a type of
metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
sulfide Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds lar ...
ore deposit Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 April 2 ...
, mainly
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
-
zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
which are associated with and created by
volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...
-associated
hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...
events in submarine environments. These deposits are also sometimes called volcanic-hosted massive
sulfide Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds lar ...
(VHMS) deposits. The density generally is 4500 kg/m3. They are predominantly stratiform accumulations of sulfide minerals that precipitate from hydrothermal fluids on or below the seafloor in a wide range of ancient and modern geological settings. In modern oceans they are synonymous with sulfurous plumes called
black smokers A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspot ...
. They occur within environments dominated by volcanic or volcanic derived (e.g., volcano-sedimentary) rocks, and the deposits are coeval and coincident with the formation of said volcanic rocks. As a class, they represent a significant source of the world's copper, zinc,
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
,
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...
and
silver Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
ores, with
cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...
,
tin Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
,
barium Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Th ...
,
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
,
selenium Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, ...
,
manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...
,
cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
,
indium Indium is a chemical element with the symbol In and atomic number 49. Indium is the softest metal that is not an alkali metal. It is a silvery-white metal that resembles tin in appearance. It is a post-transition metal that makes up 0.21 parts p ...
,
bismuth Bismuth is a chemical element with the Symbol (chemistry), symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental ...
,
tellurium Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally fou ...
,
gallium Gallium is a chemical element with the symbol Ga and atomic number 31. Discovered by French chemist Paul-Émile Lecoq de Boisbaudran in 1875, Gallium is in group 13 of the periodic table and is similar to the other metals of the group (aluminiu ...
and
germanium Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors s ...
as co- or by-products. Volcanogenic massive sulfide deposits are forming today on the seafloor around
undersea volcano Submarine volcanoes are underwater vents or fissures in the Earth's surface from which magma can erupt. Many submarine volcanoes are located near areas of tectonic plate formation, known as mid-ocean ridges. The volcanoes at mid-ocean ridges ...
es along many
mid ocean ridge A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a diverge ...
s, and within back-arc basins and forearc rifts. Mineral exploration companies are exploring for
seafloor massive sulfide deposits Seafloor massive sulfide deposits or SMS deposits, are modern equivalents of ancient volcanogenic massive sulfide ore deposits or VMS deposits. The term has been coined by mineral explorers to differentiate the modern deposit from the ancient. SM ...
; however, most exploration is concentrated in the search for land-based equivalents of these deposits. The close association with volcanic rocks and eruptive centers sets VMS deposits apart from similar ore deposit types which share similar ''source'', ''transport'' and ''trap'' processes. Volcanogenic massive sulfide deposits are distinctive in that ore deposits are formed in close temporal association with submarine volcanism and are formed by hydrothermal circulation and exhalation of sulfides which are independent of sedimentary processes, which sets VMS deposits apart from sedimentary exhalative ( SEDEX) deposits. There is a subclass of VMS deposits, the volcanic- and sediment-hosted massive sulfide (VSHMS) deposits, that do share characteristics that are hybrid between the VMS and SEDEX deposits. Notable examples of this class include the deposits of the Bathurst Mining Camp,
New Brunswick New Brunswick (french: Nouveau-Brunswick, , locally ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. It is the only province with both English and ...
, Canada (e.g., Brunswick #12); the deposits of the
Iberian Pyrite Belt The Iberian Pyrite Belt is a vast geographical area with particular geological features that stretches along much of the south of the Iberian Peninsula, from Portugal to Spain. It is about 250 km long and 30–50 km wide, running northwe ...
,
Portugal Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...
and
Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...
, and the Wolverine deposit,
Yukon Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...
, Canada.


Genetic model

* The ''source'' of metal and sulfur in VMS deposits is a combination of incompatible elements which are leached from the volcanic pile in the sub-seafloor hydrothermal alteration zone by hydrothermal circulation. Hydrothermal circulation is generally considered to be driven via heat in the crust often related to deep-seated gabbro intrusions. * ''Transport'' of metals occurs via convection of hydrothermal fluids, the heat for this supplied by the
magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...
chamber which sits below the volcanic edifice. Cool ocean water is drawn into the hydrothermal zone and is heated by the volcanic rock and is then expelled into the ocean, the process enriching the hydrothermal fluid in sulfur and metal ions. * The ore materials are trapped within a
fumarole A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...
field or a
black smoker A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspot ...
field when they are expelled into the ocean, cool, and precipitate sulfide minerals as stratiform sulfide ore. Some deposits show evidence of formation via deposition of sulfide via replacement of altered volcanosedimentary rocks and may also form by invasion of sulfur-rich brines into unconsolidated sediments.


Geology

The typical location for VMS deposits is at the top of the felsic volcanic sequence, within a sequence of volcaniclastic
tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock cont ...
aceous epiclastics,
chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...
s, sediments or perhaps fine tuffs which are usually related to the underlying volcanics. The hangingwall to the deposit is broadly related to a more mafic sequence of volcanic rocks, either
andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomi ...
(examples being Whim Creek & Mons Cupri, Western Australia or Millenbach,
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
), or
basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
(Hellyer,
Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...
) or absent or sediments only (Kangaroo Caves, Western Australia). VMS deposits are associated spatially and temporally with
felsic In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted with mafic rocks, whi ...
volcanic rocks Volcanic rock (often shortened to volcanics in scientific contexts) is a Rock (geology), rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of Volcano, volcanic origin. Like all rock types, ...
, usually present in the stratigraphy below the deposit, and often as the direct footwall to the deposit. Sediments are usually contiguous with VMS deposits in some form or another and typically are present as (manganiferous)
chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...
s and chemical sediments deposited within a submarine environment. The hanging wall to the deposit can be volcanic units essentially contiguous and coeval with the footwall rocks, indicating mineralisation was developed in an inter-eruptive pause; it may be volcanic rock dissimilar to the footwall volcanics in bimodal volcanic subtypes, or it could be sedimentary strata if mineralisation occurred toward the end of an eruptive cycle. Hybrid VMS-SEDEX deposits of the siliciclastic associations (see below) may be developed within interflow sediments or within units of sedimentary rocks which are present discontinuously throughout a larger and essentially contiguous volcanic package. Altogether, these geological features have been interpreted to show an association of VMS deposits with hydrothermal systems developed above or around submarine volcanic centres.


Morphology

VMS deposits have a wide variety of morphologies, with mound shaped and bowl shaped deposits most typical. The bowl-shaped formations formed due to venting of hydrothermal solutions into submarine depressions - in many cases, this type of deposit can be confused with
sedimentary exhalative deposits Sedimentary exhalative deposits (SEDEX or SedEx deposits) are zinc-lead deposits originally interpreted to have been formed by discharge of metal-bearing basinal fluids onto the seafloor resulting in the precipitation of mainly stratiform ore ...
. The mound-shaped deposits formed in a way similar to that of modern massive sulfide deposits - via production of a hydrothermal mound formed by successive black smoker chimneys. Deposits that have formed in environments dominated by sedimentary rocks or highly permeable volcanic rocks can show a tabular morphology that mimics the geometry of the surrounding rocks. VMS deposits have an ideal form of a conical area of highly altered volcanic or volcanogenic sedimentary rock within the feeder zone, which is called the stringer sulfide or stockwork zone, overlain by a mound of massive exhalites, and flanked by stratiform exhalative sulfides known as the apron. The stockwork zone typically consists of
vein Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated b ...
-hosted sulfides (mostly
chalcopyrite Chalcopyrite ( ) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mo ...
,
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...
, and
pyrrhotite Pyrrhotite is an iron sulfide mineral with the formula Fe(1-x)S (x = 0 to 0.2). It is a nonstoichiometric variant of FeS, the mineral known as troilite. Pyrrhotite is also called magnetic pyrite, because the color is similar to pyrite and it is ...
) with
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...
,
chlorite The chlorite ion, or chlorine dioxide anion, is the halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as salts of chlorous ac ...
and lesser
carbonates A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...
and
barite Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate ( Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...
. The mound zone consists of laminated massive to
breccia Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of di ...
ted pyrite,
sphalerite Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in Sedimentary exhalative deposits, sedimen ...
(+/-
galena Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver. Galena is one of the most abundant and widely distributed sulfide minerals. It cryst ...
),
hematite Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...
, and barite. The mound can be up to several tens of metres thick and several hundred metres in diameter. The apron zone is generally more
oxidised Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
, with stratiform, laminated sulfidic sediments, similar to SEDEX ores, and is generally
manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...
, barium and hematite enriched, with
chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...
s,
jasper Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases,Kostov, R. I. 2010. Review on the mineralogical systematics of jasper and related rocks. – Archaeometry Workshop, 7, 3, 209-213PDF/ref> ...
s and chemical sediments common.


Metal zonation

Most VMS deposits show metal zonation, caused by the changing physical and chemical environments of the circulating hydrothermal fluid. Ideally, this forms a core of massive
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...
and
chalcopyrite Chalcopyrite ( ) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mo ...
around the throat of the vent system, with a halo of chalcopyrite-
sphalerite Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in Sedimentary exhalative deposits, sedimen ...
-pyrite grading into a distal sphalerite-
galena Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver. Galena is one of the most abundant and widely distributed sulfide minerals. It cryst ...
and galena-
manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...
and finally a
chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...
-manganese-
hematite Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...
facies. Most VMS deposits show a vertical zonation of
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...
, with the cooler upper portions generally more enriched in gold and silver. The
mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the proces ...
of VMS massive sulfide consists of over 90% iron sulfide, mainly in the form of
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...
, with
chalcopyrite Chalcopyrite ( ) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mo ...
,
sphalerite Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in Sedimentary exhalative deposits, sedimen ...
and
galena Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver. Galena is one of the most abundant and widely distributed sulfide minerals. It cryst ...
also being major constituents.
Magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the ...
is present in minor amounts; as magnetite content increases, the ores grade into massive oxide deposits. The
gangue In mining, gangue () is the commercially worthless material that surrounds, or is closely mixed with, a wanted mineral in an ore deposit. It is thus distinct from overburden, which is the waste rock or materials overlying an ore or mineral body t ...
(the uneconomic waste material) is mainly
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...
and
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...
or
pyrrhotite Pyrrhotite is an iron sulfide mineral with the formula Fe(1-x)S (x = 0 to 0.2). It is a nonstoichiometric variant of FeS, the mineral known as troilite. Pyrrhotite is also called magnetic pyrite, because the color is similar to pyrite and it is ...
. Due to the high density of the deposits some have marked gravity anomalies ( Neves-Corvo,
Portugal Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...
) which is of use in exploration.


Alteration morphology

Alteration haloes developed by VMS deposits are typically conical in shape, occur mostly stratigraphically below the original fluid flow location (not necessarily the ore itself), and are typically zoned. The most intense alteration (containing the stringer sulfide zone) is generally located directly underneath the greatest concentration of massive sulfides, within the footwall volcanic sequence. If the stringer zone is displaced from the sulfides, it is often the product of tectonic deformation, or the formation of a hybrid SEDEX-like distal pool of sulfides. The alteration assemblages of the footwall alteration zone is, from core outwards; * ''Silica alteration zone'', found in the most intensely altered examples, resulting in complete silica replacement of the host rocks, and associated with chalcopyrite-pyrite stringer zones. * ''Chlorite zone'', found in nearly all examples, consisting of chlorite +/- sericite +/- silica. Often the host rock is entirely replaced by chlorite, which may appear as a chlorite schist in deformed examples. * ''Sericite zone'', found in nearly all examples, consisting of sericite +/- chlorite +/- silica, * ''Silicification zone'', often gradational with background silica-albite metasomatism. In all cases these alteration zones are
metasomatism Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a rock by hydrothermal and other fluids. It is the replacement of one rock by another of different mineralogical and chemical com ...
effects in the strictest sense, resulting in addition of potassium, silica, magnesium, and depletion of sodium. Chlorite minerals are usually more magnesian in composition within the footwall alteration zone of a VMS deposit than equivalent rocks within the same formation distally. The hangingwall to a VMS deposit is often weakly sodium depleted. Alteration not associated with the ore forming process may also be omnipresent both above and below the massive sulfide deposit. Typical alteration textures associated with devitrification of submarine volcanic rocks such as rhyolitic
glasses Glasses, also known as eyeglasses or spectacles, are vision eyewear, with lenses (clear or tinted) mounted in a frame that holds them in front of a person's eyes, typically utilizing a bridge over the nose and hinged arms (known as temples or ...
, notably formation of
spherulites In petrology, spherulites () are small, rounded bodies that commonly occur in vitreous igneous rocks. They are often visible in specimens of obsidian, pitchstone, and rhyolite as globules about the size of millet seed or rice grain, with a dul ...
, of
perlite Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. It is an industrial m ...
,
lithophysae A lithophysa (plural lithophysae, from Greek ''lithos'' "stone" + ''physan'' "to blow") is a felsic volcanic Rock (geology), rock with a spherulitic structure and interior cavity with concentric chambers. Its outer shape is spherical or lenticula ...
, and low-temperature prehnite-pumpellyite facies sub-seafloor alteration is ubiquitous though often overprinted by later metamorphic events. Metamorphic mineralogical, textural and structural changes within the host volcanic sequence may also further serve to disguise original metasomatic mineral assemblages.


Classification

Deposits of this class have been classified by numerous workers in different ways (e.g., metal sources, type examples, geodynamic setting - see Franklin et al. (1981) and Lydon (1984)). The magmatic assemblages of VMS deposits are associated with varying tectonic setting and geological environment during the formation of the VMS. The following five subclasses have specific petrochemical assemblages that resemble a specific geodynamic environment, during the event of formation:


Mafic associated

VMS deposits associated with geological environments dominated by mafic rocks, commonly
ophiolite An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is found i ...
sequences. The
Cyprus Cyprus ; tr, Kıbrıs (), officially the Republic of Cyprus,, , lit: Republic of Cyprus is an island country located south of the Anatolian Peninsula in the eastern Mediterranean Sea. Its continental position is disputed; while it is geo ...
and
Oman Oman ( ; ar, عُمَان ' ), officially the Sultanate of Oman ( ar, سلْطنةُ عُمان ), is an Arabian country located in southwestern Asia. It is situated on the southeastern coast of the Arabian Peninsula, and spans the mouth of t ...
ophiolites host examples and ophiolite-hosted deposits are found in the Newfoundland
Appalachians The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...
represent classic districts of this subclass.


Bimodal-mafic

VMS deposits associated with environments dominated by mafic volcanic rocks, but with up to 25% felsic volcanic rocks, the latter often hosting the deposits. The Noranda, Flin Flon-Snow Lake and Kidd Creek camps would be classic districts of this group.


Mafic-siliciclastic

VMS deposits associated with sub-equal proportions of mafic volcanic and siliciclastic rocks; felsic rocks can be a minor component; and mafic (and ultramafic) intrusive rocks are common. In metamorphic terranes may be known as or pelitic-mafic associated VMS deposits. The Besshi deposits in Japan and Windy Craggy, BC represent classic districts of this group.


Felsic-siliciclastic

VMS deposits associated with siliciclastic sedimentary rock dominated settings with abundant felsic rocks and less than 10% mafic material. These settings are often shale-rich siliciclastic-felsic or bimodal siliciclastic. The Bathurst Mining Camp in
New Brunswick New Brunswick (french: Nouveau-Brunswick, , locally ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. It is the only province with both English and ...
,
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
;
Iberian Pyrite Belt The Iberian Pyrite Belt is a vast geographical area with particular geological features that stretches along much of the south of the Iberian Peninsula, from Portugal to Spain. It is about 250 km long and 30–50 km wide, running northwe ...
,
Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...
and
Portugal Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...
; and Finlayson Lake areas,
Yukon Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...
, Canada are classic districts of this group.


Bimodal-felsic

VMS deposits associated with bimodal sequences where felsic rocks are in greater abundance than mafic rocks with only minor sedimentary rocks. The Kuroko deposits, Japan; Buchans deposits, Canada; and Skellefte deposits,
Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...
are classic districts of this group.


Distribution

In the geological past, the majority of VMS deposits were formed in
rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-grabe ...
environments associated with volcanic rocks. In particular, they formed throughout geological time associated with mid-ocean ridge spreading centres, back-arc spreading centres, and forearc spreading centres. A common theme to all environments of VMS deposits through time is the association with spreading (i.e., an extensional geodynamic regime). The deposits are typically associated with bimodal sequences (sequences with subequal percentages of mafic and felsic rocks - e.g., Noranda or Kuroko), felsic and sediment-rich environments (e.g., Bathurst), mafic and sediment-rich environments (e.g., Besshi or Windy Craggy), or mafic-dominated settings (e.g.,
Cyprus Cyprus ; tr, Kıbrıs (), officially the Republic of Cyprus,, , lit: Republic of Cyprus is an island country located south of the Anatolian Peninsula in the eastern Mediterranean Sea. Its continental position is disputed; while it is geo ...
and other
ophiolite An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is found i ...
hosted deposits). The majority of world deposits are small, with about 80% of known deposits in the range 0.1-10 Mt. Examples of VMS deposits are
Kidd Creek Kidd Mine or Kidd Creek Mine is an underground base metal mine north of Timmins, Ontario, Canada. It is owned and operated by Swiss multinational Glencore Inc. The mine was discovered in 1963 by Texas Gulf Sulfur Company. In 1981 it was sold to ...
,
Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...
, Canada;
Flin Flon Flin Flon (pop. 5,185 in 2016 census; 4,982 in Manitoba and 203 in Saskatchewan) is a mining city, located on a correction line on the border of the Canadian provinces of Manitoba and Saskatchewan, with the majority of the city located within M ...
in the
Flin Flon greenstone belt The Flin Flon greenstone belt, also referred to as the Flin Flon – Snow Lake greenstone belt, is a Precambrian greenstone belt located in the central area of Manitoba and east-central Saskatchewan, Canada (near Flin Flon). It lies in the central ...
,
Manitoba Manitoba ( ) is a Provinces and territories of Canada, province of Canada at the Centre of Canada, longitudinal centre of the country. It is Canada's Population of Canada by province and territory, fifth-most populous province, with a population o ...
, Canada (
777 777 may refer to: * 777 (number), a number * AD 777, a year of the Julian calendar * 777 BC, a year in the 8th century BC * Boeing 777, a commercial jet airliner :* Boeing 777X, the newer generation of the Boeing 777. Art and entertainment Alb ...
and Trout Lake Mine); Brunswick #12,
New Brunswick New Brunswick (french: Nouveau-Brunswick, , locally ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. It is the only province with both English and ...
, Canada;
Rio Tinto Rio Tinto, meaning "red river", may refer to: Businesses * Rio Tinto (corporation), an Anglo-Australian multinational mining and resources corporation ** Rio Tinto Alcan, based in Canada ** Rio Tinto Borax in America *** Rio Tinto Borax Mine, a ...
,
Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...
; Greens Creek mine,
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
, U.S..


See also

*
Ore genesis Various theories of ore genesis explain how the various types of mineral deposits form within Earth's crust. Ore-genesis theories vary depending on the mineral or commodity examined. Ore-genesis theories generally involve three components: sour ...
*
Ore Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
definition *
Volcanology Volcanology (also spelled vulcanology) is the study of volcanoes, lava, magma and related geological, geophysical and geochemical phenomena (volcanism). The term ''volcanology'' is derived from the Latin word ''vulcan''. Vulcan was the anci ...
*
Hydrothermal vent A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspot ...


References

* Barrie, C. T., and Hannington, M. D., editors, (1999), ''Volcanic-Associated Massive Sulfide Deposits: Processes and Examples in Modern and Ancient Settings'', Reviews in Economic Geology Volume 8, Society of Economic Geologists, Denver, 408 p. * Barrie, C. T., and Hannington, M. D., 1999, Classification of volcanic-associated massive sulfide deposits based on host-rock composition: Reviews in Economic Geology, v. 8, p. 1-11. * Franklin, J. M., Sangster, D. M., and Lydon, J. W., 1981, Volcanic-associated massive sulfide deposits, in Skinner, B. J., ed., Economic Geology Seventy-Fifth Anniversary Volume, Society of Economic Geologists, p. 485-627. * Franklin, J. M., Gibson, H. L., Galley, A. G., and Jonasson, I. R., 2005, Volcanogenic Massive Sulfide Deposits, in Hedenquist, J. W., Thompson, J. F. H., Goldfarb, R. J., and Richards, J. P., eds., Economic Geology 100th Anniversary Volume: Littleton, CO, Society of Economic Geologists, p. 523-560. * Guilbert, John M., and Charles F. Park, Jr., 1986, ''The Geology of Ore Deposits'', pp 572–603, W. H. Freeman, * Gibson, Harold L., James M. Franklin, and Mark D. Hannington, (2000) ''A genetic model for Volcanic-Associated Massive Sulphide Deposits'' https://web.archive.org/web/20050221103926/http://www.cseg.ca/conferences/2000/2000abstracts/758.PDF Accessed 12-20-2005. *Lydon, J. W., 1984, Ore deposit models; 8, Volcanogenic sulfide deposits; Part I, A descriptive model: Geoscience Canada, v. 11, p. 195-202. *Piercey, S. J., 2011, The setting, style and role of magmatism in the formation of volcanogenic massive sulfide deposits, Miner Deposita (2011), v. 46, p. 449-471.


External links


''The dawn of deep ocean mining,'' Steven Scott, Feb. 2006

Treatise on Geochemistry (Second Edition) Volume 13, 2014, Pages 463-488 Treatise on Geochemistry 13.18 - Volcanogenic Massive Sulfide Deposits

''Rethinking the Ancient Sulfur Cycle'' Annual Review of Earth and Planetary Sciences; Vol. 43:593-622 (Volume publication date May 2015)
{{ores Economic geology Ore deposits Plate tectonics