Why tectonic context does not prove a deposit

What the sources actually say

Most porphyry copper deposits form in subduction-related magmatic arcs along convergent margins. Within those arcs, the USGS model adds, deformation can be very complex and deposits form in a variety of settings; some form in back-arc or post-subduction settings where tectonic affinity is more poorly understood, particularly for Mesozoic and older deposits. And porphyry systems, though widespread, seem to be localized in time and space within an arc’s evolution.^[1]

Volcanogenic massive sulfide deposits form in marine settings where magmatism, seismicity and high-temperature venting coincide: spreading ridges, oceanic and continental-margin arcs, back-arc basins, rifted margins, strike-slip basins. Mississippi Valley-type deposits connect to orogenic forelands. Magmatic nickel-copper deposits sit near craton margins, in large igneous provinces.^[1,2,3]

And then the sizes

Subduction-related arcs have existed somewhere on Earth for most of Earth history and are among its most extensive features. The mid-ocean ridge system is tens of thousands of kilometres long and hydrothermally active along much of it. Orogenic forelands accompany every mountain belt. Craton margins run for tens of thousands of kilometres, and large igneous provinces cover millions of square kilometres.^[1]

The magmatic nickel model states the ratio outright: occurrences are present on most continents, and deposits of size and grade sufficient to be mined are rare, with the major examples in five countries. Being in the setting is not an observation that distinguishes anything.^[1,2]

One system that barely uses tectonics at all

Nickel-cobalt laterites occur on active continental margins, in accreted terranes and obducted ophiolites, and in komatiites now part of stable cratons — settings with nothing in common. What the system actually needs is an ultramafic protolith and a tropical climate over a long time. Tectonics only decides whether the protolith reached the surface.^[1]

Any framework that ranked ground by tectonic setting would rank this system’s ground almost at random, and would do so confidently.^[1]

And half of Earth history where the question cannot be asked

The VMS model states that deposits in Proterozoic and Phanerozoic sequences can generally be assigned to specific plate tectonic regimes, but that assignment in Archean terranes is less certain, because the role of conventional plate tectonics in early Earth history continues to be debated.^[1]

A great deal of the world’s Archean crust hosts mineral systems whose tectonic setting cannot be named, because the framework that would name it is itself in question. Phase 4 records that rather than assigning a setting anyway.^[1]

What Lithoen therefore does

It records the documented context and stops. Every context edge in the corpus must state how much more extensive its setting is than the systems found in it, and must say in its own text that it records a documented context rather than a prediction. A validator refuses the edge without both.^[1]

There are no scores, no rankings, no heat maps and no assessment vocabulary of any kind. The words are refused in code across every published summary, statement, caption and paragraph — including the ones on this page. An earlier draft of this very sentence listed the banned phrases as examples and the build refused it, which is the second time a Lithoen article about a gate has been stopped by that gate, and the correct outcome both times.^[1]

Commonly misunderstood