Geochemistry and U-Pb Geochronology of the 1450-1425 Ma Large Igneous Province of Eastern Laurentia and 2480-780 Ma Large Igneous Provinces of Western Laurentia
Bibliographic record
Abstract
Mesoproterozoic magmatism that is exposed on the eastern and western margins of Laurentia (North America) are interpreted to be parts of large igneous provinces (LIP). The western margin between Kimberley (British Columbia) and Yellowstone National Park (Wyoming), and the eastern margin between Labrador City and coastal Labrador are herein referred to as western Laurentia (WL) and eastern Laurentia (EL), respectively. WL intraplate magmatism was previously divided into two LIPs the: 1) ca. 1460 Ma Moyie-Purcell LIP (MPL) which consists of the i) Purcell lavas in the USA, ii) Moyie sills of the Belt-Purcell basin iii) dykes of the Tobacco Root Mountains and 2) the ca. 780 Ma Gunbarrel LIP. The MPL is composed of tholeiitic basalts, and associated with the world class Sullivan Pb-Zn deposit. EL consists of basalts of the non-mineralized Michael-Shabogamo Gabbros (MSG).This research demonstrated that at least 17 geochemical groups are present in WL of which some belong to additional previously unrecognized events. Seven geochemical groups belong to the ca. 1460 Ma MPL; 1 with the ca. 780 Ma Gunbarrel LIP, 2 with a 1590-1550 Ma Mammoth-Western Channel LIP (MWCL); 2 with ages of 2480, and 1420 Ma; and 5 undated mafic pulses. The MWCL is similar to contemporaneous volcanic rocks within the South Australia craton, which was adjacent to NW Laurentia ca. 1590 Ma. This study proposes a shared 1590 Ma plume and LIP magmatism between Laurentia, and South Australia cratons.The MSG of EL are subalkaline basalts enriched in P2O5 and K2O and are shown to represent a single event with 2 pulses based on new U-Pb ages. Each pulse is defined by a distinct [P2O5*1000]/Zr (P/Zr) ratio: 1) a high P/Zr group at ca. 1425-1435 Ma; and 2) a low P/Zr group at ca. 1435-1450 Ma. Enrichment of P2O5 and K2O is due to melting of a metasomatized subcontinental lithospheric mantle with melting facilitated by a slab window.
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".