Petrogenesis of the olivine cumulate outcrop Issole – The missing link between the Séítah and Máaz formations in Jezero crater, Mars
Bibliographic record
Abstract
Two lithologic units have been mapped and studied on the floor of Jezero crater, Mars: Séítah, which consists of layered olivine-rich cumulates, and Máaz, a series of basaltic to trachyandesitic lava flows. While Séítah and Máaz are close in proximity and stratigraphy, their potential geologic and petrological relationship remains unclear. Here, we present observations from the Planetary Instrument for X-ray Lithochemistry (PIXL) of an olivine cumulate outcrop – Issole – within the Séítah formation. The rock analyzed at Issole is a wehrlite dominated by olivine (Fo 46±1 ) and interstitial phases, including augite, late olivine, spinel, and feldspathic material. Compared to other outcrops from Séítah, Issole is more iron-rich and records substantial alteration processes. We combine mineral chemistry, textural analysis, and thermodynamic modeling to show that Séítah olivines crystallized from a basaltic parent magma, compositionally similar to the most primitive basalts in the Máaz formation. Crystallization of this parent magma produces residual melts that follow the magmatic differentiation trend defined by Máaz basalts. Moreover, the mineral assemblages predicted by our model during crystallization are consistent with observations from Séítah rocks but show some differences in composition. These differences can be reconciled by considering post-cumulus processes that modified the mineral assemblage in Séítah, including Fe Mg exchange between olivine and pyroxene. Our results indicate that Séítah and Máaz are likely genetically related, and their formation involved both accumulation of crystals at depth and eruption of lavas. The emplacement of Séítah likely occurred as a near-surface, sill-like igneous intrusion into previously erupted Máaz lava flows. The relationship between Séítah and Máaz demonstrates that magmatic differentiation processes, similar to those responsible for the formation of some Martian meteorites, can produce highly diverse lithologies and mineral textures in the Martian crust. • The Quartier abrasion analyzed by PIXL at the Issole outcrop is a wehrlite dominated by olivine (Fo 46±1 ). • Issole/Quartier olivine crystallized from a basaltic magma, similar to the most primitive basalts in the Máaz formation. • The Séítah and Máaz formations are likely petrogenetically related. • Séítah likely intruded into Máaz lava flows as a near-surface intrusion, with both units sharing the same magma source.
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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 | 0.000 | 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".