Geochemical and isotopic constraints on the origin and evolution of the Matum-Das tonalite and mafic enclaves from the Kohistan Batholith, Northern Pakistan
Bibliographic record
Abstract
Granitoids at subduction zones play a significant role in the generation and evolution of continental crust . The Kohistan Batholith in the Kohistan Island Arc is, in large part, comprised of granitoids with various sizes, amongst which the Matum-Das tonalitic pluton stands out as the most enigmatic due to its emplacement age and unique geochemical signatures. The genesis and formation mechanism of the Matum-Das tonalite is still unclear. In addition, the Matum-Das tonalite hosts abundant mafic microgranular enclaves (MMEs), which have rarely been mentioned in previous studies. Here, a combined investigation of the petrological characteristics, mineral chemistry , zircon U Pb geochronology and Hf isotope, whole-rock major, trace element and Sr Nd isotope geochemistry has been conducted on the Matum-Das tonalite and the MMEs. Zircon U Pb dating indicates that the Matum-Das tonalite was emplaced at ∼150 ± 2 Ma, comparable with the age of the MMEs (∼149 ± 1 Ma). The consistent isotopic signatures of the host tonalite (I Sr = 0.7046∼–0.7053; ε Nd (t) = +6.0 ∼ +7.8; ε Hf (t) = +13.9 ∼ +18.0) with the MMEs (I Sr = 0.7034∼–0.7048; ε Nd (t) = +6.6 ∼ +9.4; ε Hf (t) = +11.2 ∼ +20.4) indicate the same parental magma source, which was mainly derived from the depleted mantle. The tonalite displays highly acidic signatures with SiO 2 contents ranging from 73.72 to 76.06 wt% and low alkali (Na 2 O + K 2 O) contents of from 3.62 to 5.04 wt%. It has low Sr and high Y contents with low Sr/Y ratios. Compared to the host tonalite, the MMEs are dioritic in composition and have metaluminous affinity. Combined with the non-adakitic traits and high-water contents (9.07–11.68 wt%) inferred from the amphibole chemistry, we propose that the Matum-Das tonalite was most likely formed by fractional crystallization of hydrous magma derived from the metasomatized asthenosphere mantle. The associated MMEs were formed in the earlier stage of magma evolution from the same parental magma. The onset of intra-oceanic subduction of the Neo-Tethys Ocean in the late Jurassic is responsible for the island arc volcanism . The studied tonalitic rocks yielded the oldest ages within the KIA, and they represented the magmatic products in the initial stage of the Neo-Tethys intra-oceanic subduction.
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.
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 | 0.001 |
| 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 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".