Vein Formation and Deformation in Greenstone Gold Deposits
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
Abstract Veins are common components of greenstone gold deposits. Their analysis is one key aspect in understanding the sequence of events leading to the formation or deformation of gold deposits. This analysis is essential for the determination of controls on mineralization and ore-forming processes, and for the prediction of the geometry and plunges of deposits and orebodies. Many greenstone gold districts have experienced a common structural evolution: D1 thin skin-style shortening and D2 thick skin-style shortening are largely responsible for the structural trend and penetrative fabrics in a district, whereas D3 and D4 transcurrent deformation are largely focused along preexisting major fault zones. A majority of greenstone gold deposits consists of quartz-carbonate veins in or adjacent to high-angle reverse, and less commonly transcurrent, shear zones, viewed as splays or subsidiaries of major, complex, belt-scale fault zones. In other deposits, veins simply overprint gold mineralization and provide important information about the postore deformation history. Three main types of veins occur in greenstone gold deposits and each records small increments of bulk strain. Laminated fault-fill veins form by slip along the central parts of active shear zones in low-angle di-lational bends, or less commonly by extensional opening of foliation planes. Extensional and oblique-extension veins form within or adjacent to shear zones, at high angles to foliation and elongation lineation. They represent opening and filling of extensional and hybrid extensional-shear fractures, respectively. In more competent host rocks, extensional veins can form arrays of en echelon planar or sigmoidal veins, or of stacked planar veins, and can also combine into multiple sets to form stockwork and breccia bodies. Multiple types and sets of auriferous veins commonly combine to form variably complex vein networks, especially in large deposits. These vein networks record deposit-scale bulk incremental strain, with axes of elongation and shortening that can be compared with those of the main deformation increments in the district as a further way of constraining their timing of formation. The formation of vein networks in many districts is compatible with D2, and in a number of others with D3, reflecting their formation in contractional or transcurrent deformation regimes, likely involving subhorizontal compressional stress under high fluid pressures. Veins in many districts also systematically display evidence of overprinting deformation, in the form of folds, boudins, striated vein margins, and a number of internal vein textures such as recrystallized quartz and stylolites. Overprinting deformation is a natural consequence of vein formation in active shear zones, but it can also result from overprinting of veins by a younger increment of regional deformation. This can lead to local shear zone reactivation or wholesale folding or boudinage of a deposit. The confident determination of the structural timing of veins in deposits is critical but challenging, and is at the center of divergences of interpretation of the origin of many greenstone gold deposits. A number of guidelines are offered to help distinguish pre-orogenic veins and deposits from those with syn- to postorogenic timing.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.001 | 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 it