A Reconstructed Cretaceous Depositional Setting for Giant Volcanogenic Massive Sulfide Deposits at Tambogrande, Northwestern Peru
Bibliographic record
Abstract
Abstract The Cretaceous Tambogrande volcanogenic massive sulfide (VMS) deposits of northwestern Peru represent some of the largest Cu-Zn-Au-Ag bimodal-mafic VMS deposits in the world. There are currently three known deposits each with approximately 100 million metric tons (Mt) of massive pyrite-rich sulfide. The deposits are intimately associated with dacite lava dome complexes and were deposited within steep-sided basins on the sea floor. Reconstructed sea-floor paleogeomorphic models suggest that sulfide deposition was concentrated in the deepest parts of the basins. Sulfide deposition accompanied synvolcanic faulting and episodic dacitic and basaltic eruptions. A series of time-stratigraphic horizons are defined at the TG1 and TG3 deposits and mark stages in the development of the volcanic complex and massive sulfide bodies. There is only limited evidence for replacement of host rocks during formation of the Tambogrande deposits, in contrast to many other large massive sulfide deposits. The deposits at Tambogrande resulted from focused hydrothermal fluid flow along synvolcanic faults with deposition of sulfide minerals within deep and restricted basins. These depressions, the results of the structural and volcanologic setting, acted as efficient traps for sulfide deposition and were also important for the preservation of the sulfide masses as they acted to shield them from submarine oxidation and weathering. Steep basins and episodic bimodal lava eruptions are key geologic attributes of the depositional setting at Tambogrande and may be necessary for the formation of anomalously large VMS deposits in a volcanic-rock–dominated environment.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".