Mineral system

Volcanogenic massive sulfide system

Also known as VMS system, Volcanic-hosted massive sulfide system

A seafloor hydrothermal system in which seawater is drawn into hot volcanic crust, evolves chemically by reacting with it, and discharges at the sea floor where abrupt cooling precipitates massive sulfide. Its driver is magmatic heat; its fluid is the ocean.

A dark plume issuing from a mineral chimney on the seafloor, lit by a submersible. — A high-temperature black smoker vent on the seafloor. The USGS occurrence model describes these vents, discharging at about 350 °C and first found on the East Pacific Rise in 1979, as the modern analogue for the volcanogenic massive sulfide deposits Lithoen holds. The analogy runs from the living system to the ancient one and is an interpretation, not an observation of any deposit in this corpus. Locality: Mid-ocean ridge seafloor.

system class: seafloorHydrothermal
model provenance: publishedModel

System architecture

The chain from source to what may be observed. A limb is shown only where Lithoen has recorded it from a source; nothing here identifies a place, ranks ground or implies that a deposit exists.

Source
Where the system draws its components from. Each edge names the component it refers to; source differs between systems and is never generalised.
- Oceanic crustestablished
  component
  Metals, leached from the volcanic pile as convecting seawater reacts with it along the flow path.
- Leachingestablished
  component
  Metals, released from the volcanic pile into convecting seawater along the flow path.
- Magmatic-hydrothermal fluidinferred
  component
  Magmatic water and volatiles, including sulfur species, as a possible additional contribution.
  precisionNote
  The model identifies this as potentially important, not as demonstrated; the edge is inferred and deliberately not established.
- Seawaterestablished
  component
  The mineralising fluid itself, and the sulfate sulfur it carries.
  method
  Chemical and isotopic studies of fluid compositions in modern and ancient deposits.
Transport
What moves the components, and under what conditions. What a medium can carry depends on temperature, pressure, salinity and redox state, so every edge states the conditions it holds under.
- Evolved seawaterestablished
  conditions
  Convecting seawater progressively modified by reaction with host rocks, reaching up to about 400 degrees Celsius in the upflow zone.
Pathway and focusing
What concentrated the flow. The presence of a structure is never on its own evidence that it focused anything, so each edge states the basis for the claim.
- Hydrothermal convectionestablished
  method
  Laboratory experiments on basalt–seawater reaction, followed by direct discovery of active vents on ridges, arcs and back-arc centres.
- Water–rock reactionestablished
  method
  Chemical and isotopic study of fluid compositions, which record the reaction path.
Deposition
Why the components stopped moving. A system may use more than one mechanism, and different mechanisms leave different signatures.
- Coolingestablished
Minerals, in their role here
Mineral role is a property of a mineral in a system, not of the mineral. The same species is an ore mineral in one system and gangue in another.
- Chalcopyriteinferred
  role
  ore mineral
  precisionNote
  Copper is named as a principal product of these deposits; chalcopyrite is inferred as its carrier and is not named in the retrieved passage.
- Pyriteinferred
  role
  gangue
  precisionNote
  Massive sulfide is dominantly iron sulfide; the role is inferred from the deposit description rather than stated in the retrieved passage. In systems where iron itself is sought, the same mineral would not be gangue.
Modification and preservation
What happened after the system finished. Formation is not preservation, and what is observed today is the sum of both.
- Metamorphisminferred
  precisionNote
  Ancient VMS deposits are preserved in deformed and metamorphosed terranes, so what is observed is generally an overprinted system. The cited evidence establishes the preservation problem rather than metamorphic overprinting specifically.
- Oxidationestablished
  precisionNote
  Sulfides on the sea floor oxidise rapidly; this is the process the preservation mechanisms have to defeat.
Commodity association
A geological association only: a commodity characteristically won from this class of system where one is developed and preserved. No statement about any occurrence, and none about value.
- Gold (commodity)established
- Copper (commodity)established
- Lead (commodity)established
- Zinc (commodity)established
Tectonic and geological context
The settings in which this system has been DOCUMENTED. Tectonic context is a necessary or common component of some models; it is not proof that mineralisation is present anywhere. Every entry states what else the setting contains.
- Subductionestablished
  What else the setting contains
  Oceanic and continental-margin arcs and their back-arc basins span every ocean margin with a subduction zone behind it.
  precisionNote
  A documented context, not a prediction. The setting is vastly more extensive than the systems found in it, and this edge asserts only that sources place the system here.
- Seafloor spreadingestablished
  What else the setting contains
  The mid-ocean ridge system is tens of thousands of kilometres long and hydrothermally active along much of it; nearly all of that activity leaves no preserved accumulation.
  precisionNote
  A documented context, not a prediction. The setting is vastly more extensive than the systems found in it, and this edge asserts only that sources place the system here.
Observable expressions
Features commonly associated with this system — and, for each, what else produces the same observation. None of these demonstrates that a system operated anywhere, and Lithoen ranks nothing.
- Global mid-ocean ridge systeminferred
  What else produces this
  Hydrothermal venting occurs along most of the ridge system, and the overwhelming majority of vent sites host no accumulation of the size preserved as an ancient deposit. A ridge setting is a necessary background, not an indication of anything.
  assertionBasis
  MODEL_INHERITED_CONTEXT
  definitionBasis
  Black smoker vents on the East Pacific Rise are described as the modern analogue for the class of system. The indication runs from the class to the ridge, and marks where such systems have been found rather than what this ridge contains.

How this record is known

12
Settled consensus: Cited as the accepted position of the discipline.; 1
Interpretation: Reached by reasoning from evidence, or produced by a named model.

13 of 13 claims on this page cite at least one registered source. Counts describe how each statement is known, not how likely it is to be true.

What Lithoen records

Each claim states how it is known and cites its evidence.

EstablishedAbsence from a compilation is a fact about the compilation.

General principle, shown here for context — not an observation about this record.

A deposit missing from a compilation is missing from that compilation. The USGS volcanogenic massive sulfide database states plainly that "it was not our intent to include every known deposit in the world", and that it excluded bodies whose metamorphic protolith was uncertain or which other investigators classed as sedimentary exhalative. Absence from it is therefore not evidence that a deposit does not exist, and not even evidence that a known deposit is not of this class.

generality: GENERAL_PRINCIPLE
precision note: Lithoen holds 1,090 rows from this compilation and publishes a curated subset of them. Neither number bounds the world.