C2 ยท Publication Volume 12

Regional Screening and Project Generation

province, district, tenure, infrastructure and data availability

Learning goals

After this lesson, you should be able to bound a regional search space, distinguish geological permissivity from evidence maturity and practical accessibility, compare information at province, district and target scales, and produce a screening recommendation without disguising missing data as low potential.

Regional screening is a hypothesis filter. It asks where the necessary large-scale processes could have operated and where surviving footprints could be observed. Project generation adds a separate question: where can a coherent, lawful and testable program be defined? A geologically permissive area is not automatically accessible, ranked or economically attractive.

Scale hierarchy and search-space definition

A scale hierarchy may include tectonic domain, metallogenic province, district, corridor, target area and observation support. These terms are descriptive rather than universal legal classes. Each level should have a spatial extent, resolution, time interval and decision question. Evidence cannot be transferred between scales without an explicit rule.

At broad scale, plate setting, crustal architecture, basin evolution, magmatic fertility and preservation may define permissivity. District-scale evidence may include fault intersections, intrusive phases, stratigraphic traps, alteration corridors and regional geochemical gradients. Target-scale observations include geometry, mineralogy, local structure and coherent anomalies. A pixel classified as favourable at regional scale cannot locate a body smaller than the input resolution.

Define exclusions before ranking: outside the scientific search question, unresolved coordinate coverage, prohibited disturbance, unavailable rights, environmentally incompatible work or an observation gap so severe that comparison is meaningless. Exclusion does not mean barren; it means the current decision model does not evaluate the area.

Geological permissivity and system completeness

Permissivity asks whether the geological environment could host the system type under consideration. It should be expressed through processes: source, energy or ligand, pathways, focusing, trap and preservation. A regional analogue is supporting context, not proof that every ingredient coexisted locally or at the same time.

Separate necessary from favourable conditions. If a hypothesis requires a reactive stratigraphic unit, absence established at adequate resolution may exclude it. By contrast, proximity to a mapped structure may be favourable but neither necessary nor sufficient. Broad regional data can identify corridors, yet uncertainty in map age, exposure and interpretation may dominate apparent patterns.

Preservation and visibility are distinct. A system may have formed and been eroded; it may survive beneath cover but lack a surface footprint; or the footprint may exist in a medium not sampled. Regional screening should map formation potential, preservation potential and observation potential separately.

Tenure, infrastructure and data availability

Regional screening keeps geology, observation coverage and practical constraints as separate layers
Regional screening keeps geology, observation coverage and practical constraints as separate layers

Legal rights, land access, environmental restrictions, cultural obligations and permitting requirements are jurisdiction-specific. They must be obtained from current authoritative records and professional advice. A tutorial may represent them as declared constraint layers, but it cannot confer rights or determine consent.

Infrastructure affects whether certain tests are practical, yet it must not be smuggled into geological potential. Record transport, power, water, communications, terrain and seasonal constraints separately from mineral-system evidence. A remote but geologically compelling area and an accessible but weakly supported area represent different trade-offs; neither should be hidden in one opaque score.

Data availability also has two faces. Dense historical data may increase knowledge, but its footprint can reflect prior accessibility and previous targeting beliefs. Sparse data may indicate low attention rather than low potential. Map data density, age, resolution, licence, lineage and null semantics before using the data to rank geology.

Screening matrix and gap map

Use a matrix in which rows are search cells or geological tracts and columns are propositions, not just datasets. Example propositions include: compatible source domain, preserved pathway architecture, suitable trap, observable footprint, interpretable cover, adequate coordinate control and lawful next test. For each cell record evidence status, confidence, resolution and contradiction.

A gap map should distinguish at least: no acquisition, acquisition but unavailable, available but unlicensed, available but obsolete, insufficient resolution, quality failure, conflicting interpretation and genuine negative result. Treating all gaps as zero creates a false low-potential halo around poorly explored areas.

Screening thresholds must be tested for sensitivity. If a tract enters or leaves the portfolio when a poorly known layer changes slightly, flag it as unstable. Report the effect of removing each evidence family. A regional ranking dominated by one inherited dataset is a provenance risk, not a robust synthesis.

Worked synthetic example

Four fictional tracts are compared on three independent dimensions from 0 to 1: geological permissivity G, observation adequacy O and practical readiness R. Missing evidence is not assigned zero. The values are teaching judgements supported by an audit table.

| Tract | G | O | R | Key limitation | |---|---:|---:|---:|---| | T-A | 0.82 | 0.35 | 0.70 | broad geophysics only | | T-B | 0.68 | 0.80 | 0.75 | trap timing uncertain | | T-C | 0.76 | unknown | 0.40 | coordinate lineage unresolved | | T-D | 0.45 | 0.90 | 0.85 | necessary source evidence absent |

A screening rule requires G\ge0.60, no unresolved critical data lineage, and an immediately definable low-disturbance test. Under that rule, T-B advances. T-A remains in the portfolio with a specific observation-gap test. T-C pauses pending lineage resolution; it is not ranked low. T-D drops under the current hypothesis because a necessary source condition was adequately tested and absent, despite good coverage and readiness.

If a simple weighted sum had been used with weights 0.5, 0.3 and 0.2, T-D could appear competitive because coverage and readiness compensate for missing geology. The gate rule prevents a necessary condition from being traded away. This illustrates why screening combines logical gates with transparent scores rather than using one additive index.

Interpretation workflow

  1. State the regional question, system model, spatial extent and scale hierarchy.
  2. Separate formation, preservation and observation potential.
  3. Translate large-scale processes into necessary and supporting propositions.
  4. Inventory geological, geochemical, geophysical, remote and surface-process evidence.
  5. Audit resolution, date, coordinate system, lineage, licence and missing-value meaning.
  6. Map legal, environmental, access and infrastructure constraints separately.
  7. Apply necessary-condition gates before optional weighted comparisons.
  8. Test ranking sensitivity to missing and dependent layers.
  9. Define a next observation for every retained tract.
  10. Record excluded and paused tracts with reasons that do not imply geological absence.

Practice and review

  1. Propose separate maps for formation, preservation and visibility for a buried system.
  2. Explain why historical sample density can be both useful evidence and a source of survivorship bias.
  3. Re-rank the synthetic tracts if T-A observation adequacy becomes 0.65, and state which rule rather than score controls the decision.
  4. Write null semantics for five conditions: not sampled, below detection, censored, inaccessible and confirmed absent.
  5. Give an example of a regional feature whose apparent importance would disappear when evaluated at target scale.

Sources and further reading