El Espino Iron-Oxide Copper Gold District, Coastal Cordillera of North-Central Chile, The
Bibliographic record
Abstract
The El Espino Iron Oxide Copper Gold (IOCG) mining district is located in the Coastal Cordillera of north-central Chile and includes the El Espino deposit which has a measured plus indicated geologic resource of 145 Mt @ 0.55% Cu and 0.22 g/t Au.Mineralized bodies are distributed in a 7 x 10 km 2 area and range in geometry from single veins to stockworks and breccias to manto-type deposits.The ore bodies are hosted primarily by Early Cretaceous volcanic, volcaniclastic, and sedimentary units, with fewer mineralized zones within a Late Cretaceous multi-phase intermediate pluton.Hydrothermal alteration and mineralization was coeval with plutonism at 88 Ma.Both plutonism and hydrothermal alteration/mineralization were localized within a dilatational jog along a major transtensional north-south fault system that controlled the distribution of alteration and mineralization.Sodic alteration is the most extensive style of alteration in the district and is best developed at stratigraphically deep levels.Sodic-calcic alteration is spatially more restricted and grades inward into a calcic alteration assemblage at intermediate levels, displaying a zoned pattern around the Late Cretaceous pluton.Potassic alteration is relatively restricted in extent and is not always spatially related to sodic, sodic-calcic, and calcic alteration zones.Late hydrolytic alteration is concentrated in the middle and upper portions of the stratigraphis sequence while argillic alteration is restricted to the highest part of the alteration system.Iron oxides and sulfides are largely confined to calcic and hydrolytic alteration assemblages.The fluids responsible for sulfide precipitation ranged in temperature from 350 to 425°C with salinities between 32 and 34 wt% NaCl equivalent.Mineralization probably took place at a minimum depth of 3-4 km.Early high temperature fluids were magmatically derived while later hydrothermal fluids may have contained mixed meteoric fluids with marine-derived sulfate.The close spatial and temporal association of alteration zones with a plutonic suite suggests that plutons provided heat and contributed fluid and sulfur to the hydrothermal system.Lithogeochemical mass balance analyses indicate that early and deep alteration events leached elements that were fixed at later times higher in the stratigraphic sequence during the waning stages of hydrothermal alteration.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".