Petrology, Age, and Alteration of Gabbroic Rocks of the Katangan Large Igneous Province, Central African Copperbelt, Zambia
Bibliographic record
Abstract
Copper and cobalt are essential elements required to support an electrified economy because of their critical role in lightweight electric batteries and transmission lines.Their main global source is the sedimentary rock-hosted deposits of the Central African Copperbelt (CACB), however, the reasons why it occurs in such abundance remain obscure.In addition to copper and cobalt, the CACB deposits also contain significant amounts of other necessary elements for a low-carbon transition such as zinc and nickel.The CACB contains Neoproterozoic Katangan intrusive rock series, comprising gabbro and metagabbro sills and basaltic dykes and flows.They are herein characterized as a large igneous province distributed throughout the 450 km long and 600 km wide arcuate CACB in southeastern Democratic Republic of Congo and northwestern Zambia.Understanding the petrogenesis of these mafic intrusive rocks is vital to assist future studies of their relation to the vast Cu and Co deposits in the CACB and to understand their links to Rodinia's breakup.Lithogeochemical data suggest that these rocks were formed due to an extensional regime with potential plume involvement that developed during a rifting stage of the CACB.Petrological modeling demonstrates how these rocks were derived from primitive magmas and evolved chemically through fractional crystallization, assimilation, and magma mixing, generating a range of compositions with close chemical affinity.Though the Katangan magmatism does not have preserved the areal extent and volume of igneous rocks required to be classified as a large igneous province, it still may represent one that has been severely weathered and only portion of it is left.Other characteristics like chemical composition and geotectonic environment serve as evidence as they are comparable with other large igneous provinces worldwide such as the Paraná-Etendeka large igneous province.The mafic intrusive rocks of the Katangan large igneous province within the Mwashya Subgroup of the Domes region and southeastern Congolese Copperbelt returned two new highprecision U-Pb CA-ID-TIMS zircon ages of 740.3 ± 1.1 Ma and 741.1 ± 1.5 Ma.These results are statistically indistinguishable from but of much higher precision than the previously published U-Pb LA-ICP-MS and SHRIMP zircon ages for Katangan rocks.Lava samples collected near Lwawu in the Western Foreland of the Katangan basin, a geographically, geologically, and geotectonically distinct region from the Domes region and southeastern Congolese Copperbelt, yielded slightly older (765 ± 5 Ma and 763 ± 6 Ma) ages (Key et al., 2001), representing a suite of volcanic rocks potentially unrelated to the ones from the Domes region and southeastern Congolese Copperbelt presented in this research and the ones dated by Barron (2003), Sanz (2005), and MacIntyre (2019).Our more precise data suggest the peak of the igneous activity in the Domes region and southeastern Congolese Copperbelt was concentrated over 3.4 Ma between 742.6 and 739.2 Ma, contradicting previous estimates and interpretations that the magmatism in the region was protracted.Furthermore, this timing is just prior to the initiation of the ca.739-733 Ma Russøya carbon isotope excursion and the ca 735 Ma Kaigas glaciation, suggesting a causal relationship between Katangan magmatism and two, probably inter-related, global climatic swings.Using X-ray maps and laser ablation data, we document widespread removal of Cu, Co, Zn, and Ni from mafic rocks within the metasedimentary basin that hosts the deposits in Zambia.Copper, cobalt, zinc, and nickel were mobilized during post-peak metamorphic leaching of ferromagnesian silicates and oxides ca.536 to 494 Ma caused by widespread albite-carbonate alteration.The results suggest that the critical step required to generate the Cu-Co deposits was the release of base metals by basin-scale albite-carbonate alteration of metagabbroic sills.v Acknowledgments First and foremost, this research was conducted at Carleton University, Ottawa, which campus is on the traditional, unceded territories of the Algonquin nation, and in Victoria, home of the Lək ̓ ʷəŋən (Songhees First Nation and Esquimalt First Nation) Peoples, whose territories I utterly respect.The samples to conduct this research are from Zambia, more specifically from the territories of the Kaonde and Bemba ethnolinguistic groups.May the Zambian people benefit from this research.I wouldn't be here if I haven't had the opportunity of studying and receiving my B.Sc. and M.Sc.degrees from the publicly funded Brazilian federal universities of Santa Catarina and Brasília.I have a deep gratitude for my previous supervisors, Dr.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 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 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".