Magmatic and Hydrothermal Controls on the Mineralogy of the Basal Zone, Nechalacho REE-Nb-Zr Deposit, Canada☼
Bibliographic record
Abstract
Research Article| December 01, 2017 Magmatic and Hydrothermal Controls on the Mineralogy of the Basal Zone, Nechalacho REE-Nb-Zr Deposit, Canada☼ Volker Möller; Volker Möller 1Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec H3A 0E8, Canada †Corresponding author: e-mail, volker.moeller@mail.mcgill.ca Search for other works by this author on: GSW Google Scholar Anthony E. Williams-Jones Anthony E. Williams-Jones 1Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec H3A 0E8, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Volker Möller 1Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec H3A 0E8, Canada Anthony E. Williams-Jones 1Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec H3A 0E8, Canada †Corresponding author: e-mail, volker.moeller@mail.mcgill.ca Publisher: Society of Economic Geologists Accepted: 06 Aug 2017 First Online: 15 Nov 2017 Online Issn: 1554-0774 Print Issn: 0361-0128 © 2017 Economic GeologyEconomic Geology Economic Geology (2017) 112 (8): 1823–1856. https://doi.org/10.5382/econgeo.2017.4531 Article history Accepted: 06 Aug 2017 First Online: 15 Nov 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Volker Möller, Anthony E. Williams-Jones; Magmatic and Hydrothermal Controls on the Mineralogy of the Basal Zone, Nechalacho REE-Nb-Zr Deposit, Canada. Economic Geology 2017;; 112 (8): 1823–1856. doi: https://doi.org/10.5382/econgeo.2017.4531 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Abstract The Nechalacho rare metal deposit, and in particular its heavy rare earth element (HREE)-enriched Basal zone, constitute a world-class resource of REEs, zirconium, and niobium. The deposit formed by magmatic accumulation and interstitial crystallization of eudialyte in the upper part of a 2176 Ma layered agpaitic nepheline syenite intrusion. Its endowment in HREEs compared to later-crystallized units in the intrusion is a result of emplacement-level fractionation combined with the compatibility of HREEs in the eudialyte deposited in the Basal zone. Despite the enrichment of REEs, Nb, and Zr by igneous processes and evidence for the immobility of these elements in the Basal zone, hydrothermal alteration had a major impact on the mineralogy of the deposit: eudialyte was completely replaced by a quasi-miaskitic hydrothermal assemblage consisting of REE-Nb-enriched zircon and secondary REE and Nb minerals, mainly fergusonite-(Y) and bastnäsite-(Ce). The host aegirine-nepheline syenite was metasomatically altered to a biotite + quartz + magnetite ± ankerite ± fluorite assemblage. Sodium was lost in large proportions during the alteration, and substantial amounts of Mg were introduced. Mineral equilibria calculated for the hydrothermal conditions (300°C and 4 kbar) indicate that the fluid was mildly reducing (fo2 was 2.0–3.6 log units above the quartz-fayalite-magnetite buffer) and that pH was moderately acidic to mildly alkaline (between 3.7 and 5.7). It is likely that the hydrothermal fluid was initially acidic and neutralized upon reaction with the nepheline syenites. In contrast, the pH for magmatic fluids in equilibrium with fresh nepheline syenite was alkaline, owing to the reaction of nepheline to analcime. Hence, we conclude that the acidic, Mg-bearing hydrothermal fluid responsible for the in situ replacement of eudialyte and alteration of the host syenites was externally derived, likely a crustal fluid introduced during a 1871 to 1835 Ma, regionally pervasive hydrothermal event. The identity and composition of the secondary REE-Nb minerals that now make up the mineral resource were controlled by the original composition of eudialyte and the fluids. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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 teacher head, 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".