Earth system
Mineral systems
How metals become concentrated: the source of the components, what mobilised and carried them, what focused the flow, what made them stop, and what happened to the result afterwards. Six systems, each drawn from a published deposit model, and nothing here is a target.
A mineral system is the machinery that concentrates a metal, and a deposit is one very small part of it. The signatures of a system extend well beyond any deposit it may contain — which makes the system easier to find, and makes finding part of a system very different from finding a deposit.[1]
The six systems recorded here share no mechanism. Their carriers range from a supercritical magmatic fluid to a sulfide melt to rainwater; their temperatures from over a thousand degrees to ambient; their drivers from a pluton to the weather. What they share is a shape, and it is the shape that Lithoen encodes.[1, 2, 3, 4]
Ore is not a geological word. The definition Lithoen cites includes value and recoverability, so nothing in this corpus is called ore, no ground is ranked, no probability is assigned and no drilling is recommended. Phase 3 exists to make one question well-formed — what evidence would we expect if this system operated here? — not to answer it about a place.[1, 2, 3]
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What a mineral system is
A mineral system is the whole machinery that concentrates a metal: where the components came from, what moved them, what focused the flow, what made them stop, and what happened to the result afterwards. A deposit is a small part of it, and most of a system is not a deposit.
Ore is not a geological word
Mineralisation, deposit, resource, reserve and ore are five different things, and only the first two are geological. Lithoen can describe rock; it cannot say what is worth mining, and this article explains why the distinction is enforced by machine rather than left to good intentions.
What an indicator can and cannot tell you
Alteration, structure, a favourable host, the right tectonic setting: each of these is commonly found around mineralisation, and each is also found, far more often, around nothing at all. This is why Lithoen records associations and refuses to score them.
Formation is not preservation
A mineral system can run to completion and leave nothing behind. What survives to be found is decided long after the metal stopped moving, by oxidation, uplift, erosion, metamorphism and burial — and what is found today is never quite what formed.
Porphyry copper systems
The archetype: a shallow granitoid porphyry, an exsolving magmatic fluid, kilometres of altered rock, and copper spread thinly through an enormous volume. It supplies most of the world’s copper and the model that describes it says many of its controls are still poorly understood.
Volcanogenic massive sulfide systems
Seawater sinks into hot ocean crust, comes back up at 400 degrees, and drops its metal when it hits cold water. It is the one ore-forming system whose engine can be watched running today — which is exactly why its ancient products are so hard to read.
Mississippi Valley-type systems
No magma, no heat source, no volcano. Warm salty water moving through limestone deposits lead and zinc at temperatures a domestic oven would exceed — and this system supplies the clearest evidence in the corpus that a geological control is not a geological prediction.
Magmatic nickel-copper systems
Metal that never touches water. A mantle-derived magma swallows enough crustal sulfur to become sulfide-saturated, an immiscible liquid separates, and it collects wherever the flow slows. Occurrences are on most continents; deposits worth the name are in five countries.
Stratiform chromite systems
Layers of chromite metres thick and tens of kilometres long, holding most of the world’s chromium. How they form is not settled — the deposit model says so in its own words, and this article keeps that sentence in view.
Nickel-cobalt laterites
The only system here whose engine is the weather. Rainwater removes magnesium and silicon from ultramafic rock over millions of years and leaves nickel behind — and the same uplift that exposes the rock destroys the profile that concentrates it.
The systems
Six published deposit models, chosen for the diversity of their mechanisms rather than for their economic importance: magmatic-hydrothermal, seafloor, basinal, magmatic, and surficial.
Mineral system
Porphyry copper system
A magmatic-hydrothermal system in which fluids exsolved from a crystallising granitoid porphyry carry copper, sulfur and other components into the surrounding rock, producing large volumes of weakly mineralised, strongly altered ground. It is the archetype against which other hydrothermal systems are described.
Mineral system
Volcanogenic 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.
Mineral system
Mississippi Valley-type system
A low-temperature system in which brines expelled from a sedimentary basin migrate through platform carbonates and precipitate lead and zinc sulfides where fluids mix or conditions change. It involves no magmatism at all, which is precisely why it belongs in the canon.
Mineral system
Magmatic nickel-copper-PGE sulfide system
A wholly magmatic system in which a sulfide liquid separates from a silicate magma, scavenges chalcophile metals from it, and accumulates. There is no hydrothermal fluid and no aqueous transport: the concentrating agent is an immiscible liquid.
Mineral system
Stratiform chromite system
A magmatic system in which chromite crystallises and accumulates into laterally extensive layers within a large layered intrusion. How those layers form is genuinely unresolved, which makes the system valuable to the canon as an example of a well-described phenomenon without a settled mechanism.
Mineral system
Nickel-cobalt laterite system
A surface system in which prolonged chemical weathering of ultramafic rock strips away soluble magnesium and silicon and leaves nickel and cobalt behind in the residue and in secondary minerals. Its fluid is rainwater and its energy is climate.
The fluids
What carries a metal is a property of the fluid and its conditions, not of the metal. These records exist so that a transport step can name its medium instead of implying one.
Geological fluid
Magmatic-hydrothermal fluid
An aqueous fluid exsolved from a crystallising magma, carrying water, metals, sulfur and other volatiles away from it. Whether it exists as one supercritical phase or separates into brine and vapour depends on pressure, and that difference changes what it can carry.
Geological fluid
Hypersaline brine
A high-salinity aqueous liquid, whether separated from a magmatic fluid as pressure falls or derived by evaporation in a sedimentary basin. Its dissolved chloride is what allows it to carry base metals in quantity.
Geological fluid
Evolved seawater
Seawater that has been drawn into hot oceanic crust and chemically changed by reacting with it along the flow path. It enters cold, oxidised and sulfate-bearing, and returns hot, reduced and metal-bearing.
Geological fluid
Basinal brine
A saline formation water expelled from a sedimentary basin, typically warm rather than hot. It is the transporting medium of systems that operate entirely without igneous heat.
Geological fluid
Meteoric groundwater
Rainwater circulating through the near-surface and the water table. It is the weakest of the ore-forming fluids and, given enough time and the right climate, one of the most effective.
Geological fluid
Immiscible sulfide liquid
A molten sulfide that separates as a distinct liquid from a silicate magma once that magma becomes saturated in sulfur. It is not an aqueous fluid at all, and it concentrates metals by dissolving them out of the silicate melt it separates from.
Depositional mechanisms
Why transported components stop moving. Cooling, mixing, phase separation, saturation, segregation and residual concentration are different mechanisms leaving different signatures, and a system may use more than one.
Geological process
Cooling
Loss of heat from a fluid, reducing what it can hold in solution. The simplest depositional mechanism, and the dominant one where a hot fluid meets cold water.
Geological process
Fluid mixing
The meeting of two fluids of different composition. Mixing can force precipitation without any change in temperature or pressure, simply because the combined fluid can no longer hold what each carried separately.
Geological process
Fluid phase separation
The splitting of a single supercritical fluid into a dense brine and a low-density vapour as pressure falls. The two phases partition metals and sulfur differently, so where separation happens matters to what is deposited.
Geological process
Sulfide saturation
The point at which a silicate magma can dissolve no more sulfur and an immiscible sulfide liquid separates. Everything chalcophile in the magma then has somewhere better to be.
Geological process
Sulfide segregation
The physical accumulation of dense immiscible sulfide liquid within or beneath a magma body. Saturation makes the sulfide; segregation is what gathers it.
Geological process
Residual enrichment
Concentration by subtraction. Prolonged weathering removes the soluble components of a rock and leaves the insoluble ones behind, so the residue is richer in them than the parent ever was.
Geological process
Supergene enrichment
Redistribution of metal near the surface by descending oxidising water: metal is dissolved from an upper zone and reprecipitated lower down, raising the concentration there above what the original mineralisation held.
Geological process
Crystal accumulation
The gathering of crystals that have separated from a magma into layers or masses. It is the concentrating mechanism of magmatic systems that produce no fluid at all.
Alteration
Alteration is most of the rock a hydrothermal system touches, and it is produced just as readily by systems that concentrated nothing.
Geological process
Potassic alteration
Alteration that adds potassium phases — potassium feldspar and biotite — to a rock. In porphyry systems it occupies the hot core and is associated with the quartz stockwork veins that carry much of the copper.
Geological process
Sericitic alteration
Alteration producing fine-grained white mica, typically with quartz and pyrite. One of the assemblages that can be mapped remotely because of its distinctive infrared absorption.
Geological process
Propylitic alteration
A low-intensity assemblage of chlorite, epidote and carbonate that forms in the cool outer parts of a hydrothermal system. It is the most widespread alteration around many systems and, on its own, the least diagnostic.
Geological process
Advanced argillic alteration
Intense acid alteration that strips a rock of most of its cations, leaving alumina- and silica-rich residues. It records unusually acidic fluid rather than unusually rich fluid.
Geological process
Intermediate argillic alteration
Clay-dominated alteration formed at lower temperature and lower acidity than advanced argillic alteration.
Geological process
Dolomitisation
Replacement of limestone by dolomite, which increases porosity as it proceeds. In basinal systems it both prepares the pathway and accompanies the mineralisation that uses it.
Geological process
Serpentinisation
Hydration of olivine and pyroxene in ultramafic rock to serpentine minerals. It changes the rock’s density, strength and chemistry, and it is the state in which much lateritic nickel is held before weathering releases it.
Modification and preservation
What is observed today is the sum of formation and of everything since. Preservation is a separate condition, not a consequence of formation.
Geological process
Remobilisation
The movement of already-concentrated material by a later process — deformation, metamorphism or renewed fluid flow. What is observed today may occupy a site the original system never reached.
Geological process
Overprinting
The superposition of a later event on an earlier one, so that the rock records both. Reading a mineralised rock means separating what formed it from what happened to it afterwards.
Geological process
Erosional removal
The destruction of mineralisation by exhumation and erosion. A system that formed successfully and was then stripped away leaves nothing to find, which is why formation and preservation are separate questions.
Geological process
Oxidation
The loss of electrons by an element on exposure to oxygen. In rocks it converts ferrous iron to ferric, which is far less soluble, and fixes it as oxide.
Geological process
Metamorphism
The transformation of existing rock by heat, pressure and chemically active fluids, without melting. It rearranges minerals and fabrics; a rock that melts is no longer being metamorphosed.
Commodities
Geological association only. These records say a commodity is characteristically won from a class of system where one is developed and preserved; they carry no price, no reserve and no assessment.
Resource commodity
Copper (commodity)
Copper as a sought material rather than as a chemical element. The distinction matters: the element is in every crustal rock, and the commodity exists only where a system has concentrated it and left it recoverable.
Resource commodity
Zinc (commodity)
Zinc as a sought material, characteristically won from sediment-hosted and volcanogenic sulfide systems.
Resource commodity
Lead (commodity)
Lead as a sought material, characteristically accompanying zinc in low-temperature carbonate-hosted systems.
Resource commodity
Nickel (commodity)
Nickel as a sought material, won from two entirely different kinds of system: magmatic sulfide accumulations and lateritic weathering profiles.
Resource commodity
Cobalt (commodity)
Cobalt as a sought material, characteristically recovered alongside nickel rather than on its own.
Resource commodity
Gold (commodity)
Gold as a sought material, recovered from a wide range of systems including as a by-product of copper systems.
Resource commodity
Molybdenum (commodity)
Molybdenum as a sought material, characteristically a by-product of porphyry systems.
Resource commodity
Chromium (commodity)
Chromium as a sought material, won almost entirely from chromite accumulated in layered intrusions.
Resource commodity
Platinum-group elements (commodity)
The platinum-group elements as sought materials, characteristically concentrated by immiscible sulfide liquid in magmatic systems.
Hub last updated 2026-09-07. Every entry above is a structured record; the bracketed references link to the entities whose claims support each statement.