Fluid-chemical studies of gold systems: case studies of an Archean greenstone belt, Nunavut, and a Paleozoic slate belt, Meguma terrane, Nova Scotia.
Bibliographic record
Abstract
Despite several decades of study, the source(s) of gold and mineralizing fluids, and the \nmechanisms responsible for gold precipitation remain controversial. In particular, there is a need \nto improve: (i) the identification of secondary gold upgrading processes that lead to very highgrade gold zones; (ii) the understanding of precipitation mechanisms in carbonaceous material \n(CM)-bearing metasedimentary systems (i.e., slate belts); and (iii) the exploration criteria for the \ncryptic, finely disseminated gold mineralization in CM-bearing metamudstone lithologies. \nThe combined results of an extensive in situ microanalytical protocol (SEM, confocal Raman \nmicrospectroscopy, microthermometry, decrepitate mound analysis, LA-ICP-MS, \ncathodoluminescence, SIMS) has idenitified evidence of secondary gold enrichment at the Madrid \ndeposit, Hope Bay Greenstone Belt, NU, Canada, resulting from the addition of new gold onto an \nearlier orogenic quartz-carbonate vein deposit by magmatic-hydrothermal fluids. This conclusion \nis based on robust textural, mineralogical, and fluid inclusion evidence. The geological setting and \nmineral-chemical features suggest an intrusion-related (i.e., porphyry), or intermediate-sulfidation \nepithermal mineralization style for the later event. This work provides another example of the \nimportance of compositionally distinct cumulative hydrothermal events in the development of \nhigh-grade gold deposits in orogenic settings. \nThe Dufferin deposit, NS, Canada, is a vein-type system hosted in CM-bearing metasedimentary rocks. A detailed fluid inclusion study strongly suggests that Au mineralization occurred through \ncoupled fluid fO2 reduction (via interaction with CM) and pH increase, leading to efficient Au \nprecipitation from an Au-undersaturated aqueous-carbonic fluid. This study presents one of the \nfew examples of measured Au concentrations in ore fluids in an economic orogenic Au deposit and reports direct evidence for the genetic relationship between Au and CM in metasedimentary \nlithologies. The results of this study show that, despite mineralizing fluids being Auundersaturated, they may still produce economic deposits through highly efficient precipitation \nprocesses. The Moose Rive anticline, NS, Canada, hosts a number of, commonly inconspicuous, \nmetasediment-hosted disseminated Au deposits. An initial study using an on-line, rock-crushing \ngas chromatographic technique identified bulk fluid differences (CO2 and hydrocarbon \nabundances) between gold-bearing and gold-barren parcels of metasedimentary rock. This work \nsuggests that bulk fluid characteristics may be a viable exploration vector for disseminated gold \nsystems.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".