The use of partial extraction geochemistry for copper exploration in northern Chile
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Bibliographic record
Abstract
Future discoveries of copper resources in the richly endowed porphyry copper belts of northern Chile are likely to occur in areas covered by post-mineral sedimentary and volcanic rock. Most of northern Chile is within a region of interior drainage that has existed since at least mid-Tertiary time when many of the porphyry copper deposits were being uplifted, eroded and supergene enriched. This setting, combined with accumulation of metal-enriched material eroded from the tops of porphyry copper deposits, has produced regions with high geochemical background and geochemically complex post-mineral cover that includes alluvium, lake and playa sediments, evaporites, aeolian material, ignimbrites and volcanic ash. In addition, the climate changed from semi-arid to hyper-arid in mid-Miocene time, creating a surface environment that is saline and slightly alkaline. The geochemical expression of the Chimborazo porphyry copper deposit in northern Chile was studied in detail using the following wet chemical extraction methods: 4-acid (HF-based), aqua regia, bulk cyanide leach, hot hydroxylamine hydrochloride, cold hydroxylamine hydrochloride, enzyme leach and de-ionized water. Limitations affecting several partial extraction methods include poor data quality, lack of pH control, re-adsorption, and the formation of colloids in the leachate. Experimentation with leach time and buffering capacity improved the robustness of some of the methods. Mechanical dispersion is the dominant secondary process in this region although chemical dispersion does occur laterally on a regional scale and vertically on a local scale. Vertical chemical dispersion is associated with dilatancy pumping of metalliferous groundwater along fractures. Supercedency, a process whereby the geochemical fingerprint of transported material is inherited from the underlying material, may have also played a role in the strong signature seen at Chimborazo.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it