The Cascabel Porphyry Cu-Au-Ag District, Northern Ecuador
Bibliographic record
Abstract
Abstract The Cascabel Cu-Au-Ag porphyry cluster is part of the Eocene metallogenic belt of the northern Western Cordillera of Ecuador, and formed during east-directed, low-angle subduction and eastward migration of the Macuchi arc. Cascabel is part of the Imbaoeste mining district, a NE-trending mineralized belt located between the regional-scale Chimbo-Toachi shear zone to the west and the Calacalí-Pujilí-Pallatanga fault to the east. The basement rocks of the Cascabel district are gabbros and mafic volcanic breccias. They are overlain by late Eocene volcanic and volcanosedimentary rocks interpreted to be part of the submarine to transitional Paleocene to late Eocene Macuchi arc. Quaternary conglomerates and alluvial deposits cover the Eocene volcanic rocks locally. Three fault systems—oriented northeast, northwest, and north-northwest—have been identified at Cascabel, with the NW-trending faults being the principal system associated with the emplacement of mineralized dikes, porphyry-style veins, hydrothermal alteration zones, and late breccias. The Cascabel district contains three principal Cu-Au(-Ag) porphyry deposits: Alpala, Tandayama-America, and Aguinaga, together with several other porphyry prospects. Each porphyry deposit has a central potassic alteration domain surrounded by synchronous propylitic alteration assemblages (chlorite ± epidote ± actinolite) and mineralized chlorite-white mica alteration assemblages that overprinted potassic and propylitic alteration. Late alteration assemblages, mainly phyllic, minor argillic, and lesser advanced argillic alteration, developed principally around faults and overprinted the early-formed alteration assemblages. Multiple intrusive phases compose steeply NE-plunging mineralized intrusive complexes at Cascabel’s three major porphyry centers. The intrusions—which vary from equigranular to porphyritic and include diorites, microdiorites, quartz diorites, hornblende quartz diorites, tonalites, and rare granodiorite and granite—have been grouped as early, syn-, intra-, and late mineralization and host porphyry-style veins and Cu-Au(-Ag) mineralization. Several minor postmineralization intrusions have been identified that lack significant mineralization. The intrusive rocks at Cascabel mostly range from subalkaline basalt to dacite compositions and have characteristic primitive mantle-normalized rare earth element (REE) profiles with negative Nb anomalies and subduction-related geochemical signatures, consistent with a magmatic arc origin. They were sourced from a primitive, hydrous parental magma and became progressively more fractionated with each successive intrusive event, from diorites to tonalites and granites, suggesting that magmatic fractionation was fundamental to the intrusive history at Cascabel. New zircon U-Pb dating results from Cascabel indicate multiphase intrusive activity occurred over a period of ~4 m.y., from 39.40 ± 0.60 to 35.07 ± 0.76 Ma. Re-Os geochronological data highlights that mineralization occurred in a more restricted time interval from 39.06 ± 0.20 to 38.36 ± 0.229 Ma. The synmineralization QD10 quartz diorites at Alpala (39.40 ± 0.60 to 38.00 ± 0.80 Ma) have distinctive positive Eu anomalies, listric-shaped REE patterns, and fertile zircon compositions, implying the involvement of oxidized hydrous magmas in mineralization at Cascabel. Mineralization occurred in a compressional continental arc setting, producing a giant Cu-Au deposit at Alpala and providing encouragement for porphyry exploration elsewhere in Ecuador’s Eocene magmatic arc.
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How this classification was reachedexpand
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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.006 | 0.003 |
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; both teacher heads agree on what is shown here.
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".