The Kennack Gneiss of the Lizard Peninsula, Cornwall, SW England: commingling and mixing of mafic and felsic magmas accompanying Givetian continental incorporation of the Lizard ophiolite
Bibliographic record
Abstract
The Kennack Gneiss comprises a suite of interlayered mafic and felsic igneous rocks that intruded the 397 Ma Lizard Ophiolite Complex, Cornwall, at 376.4±1.7 Ma (U–Pb single-zircon date) and were shortly thereafter ( c. 370 Ma) metamorphosed to the amphibolite facies. Weakly deformed examples at the type-locality of Kennack Sands reveal net-veining of the mafic by the felsic component, dispersed enclaves of the former in the latter and flame-like interfingering of the two, features indicative of magmatic commingling and mixing. The silicic components of the Kennack Gneiss range from granodiorite to syenogranite and from metaluminous to peraluminous, the least silicic rocks being the most peraluminous. They were generated through anatexis of a predominantly metasedimentary crustal source having trace element and isotopic compositions comparable to those of the Devonian Gramscatho Group of South Cornwall. The mafic component of the gneiss includes members (group 1) which are weakly enriched in light REE, have minor negative Ta, Nb, P and Ti anomalies in extended trace element plots, and display primitive, time-corrected 143 Nd/ 144 Nd and 87 Sr/ 86 Sr values, and others (group 2) which are more strongly enriched in all incompatible trace elements, exhibit more prominent negative Ta, Nb, P and Ti anomalies, and have isotopic ratios intermediate between group 1 mafic components and the associated felsic gneiss. Group 2 represents mixtures of group 1 and granitic melts, whereas group 1 rocks are comparable to EMORB and were probably generated through partial melting of a weakly enriched mantle source. Emplacement of two commingled magmas into the base of the Lizard ophiolite, one representing the products of crustal anatexis, implies that the ophiolite was removed from its oceanic setting and was in the process of obduction in the Givetian.
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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 | 0.001 | 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".