António Olímpio Gonçalves

Agostinho Neto University

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Joan Carles Melgarejo i Draper

Universitat de Barcelona

Octávio Mateus

Universidade Nova de Lisboa

Michael J. Polcyn

Southern Methodist University

Louis L. Jacobs

Southern Methodist University

Marc Campeny

Natural Science Museum of Barcelona

Anne S. Schulp

Naturalis Biodiversity Center

María Pura Alfonso Abella

Universitat Politècnica de Catalunya

José Mánuel

Agostinho Neto University

Maria Luísa Morais

Agostinho Neto University

Alessandra Costanzo

Ollscoil na Gaillimhe – University of Galway

Cooperative Institutions

Universitat de Barcelona

Agostinho Neto University

Southern Methodist University

Universidade Estadual Paulista (Unesp)

Macquarie University

Australian Research Council

ARC Centre of Excellence for Core to Crust Fluid Systems

Museu da Lourinhã

Universidade Nova de Lisboa

Instituto de Geociencias

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Geological setting and paleoecology of the Upper Cretaceous Bench 19 Marine Vertebrate Bonebed at Bentiaba, Angola

Netherlands Journal of Geosciences – Geologie en Mijnbouw (2014)

C. Strganac Louis L. Jacobs Michael J. Polcyn Octávio Mateus Timothy S. Myers

Abstract The Bench 19 Bonebed at Bentiaba, Angola, is a unique concentration of marine vertebrates preserving six species of mosasaurs in sediments best correlated by magnetostratigraphy to chron C32n.1n between 71.4 and 71.64 Ma. The bonebed formed at a paleolatitude near 24°S, with an Atlantic width at that latitude approximating 2700 km, roughly half that of the current width. The locality lies on an uncharacteristically narrow continental shelf near transform faults that controlled the coastal outline of Africa in the formation of the South Atlantic Ocean. Biostratigraphic change through the Bentiaba section indicates that the accumulation occurred in an ecological time dimension within the 240 ky bin delimited by chron 32n.1n. The fauna occurs in a 10 m sand unit in the Mocuio Formation with bones and partial skeletons concentrated in, but not limited to, the basal 1–2 m. The sediment entombing the fossils is an immature feldspathic sand shown by detrital zircon ages to be derived from nearby granitic shield rocks. Specimens do not appear to have a strong preferred orientation and they are not concentrated in a strand line. Stable oxygen isotope analysis of associated bivalve shells indicates a water temperature of 18.5°C. The bonebed is clearly mixed with scattered dinosaur and pterosaur elements in a marine assemblage. Gut contents, scavenging marks and associated shed shark teeth in the Bench 19 Fauna indicate biological association and attrition due to feeding activities. The ecological diversity of mosasaur species is shown by tooth and body-size disparity and by δ 13 C analysis of tooth enamel, which indicate a variety of foraging areas and dietary niches. The Bench 19 Fauna was formed in arid latitudes along a coastal desert similar to that of modern Namibia on a narrow, tectonically controlled continental shelf, in shallow waters below wave base. The area was used as a foraging ground for diverse species, including molluscivorus Globidens phosphaticus , small species expected near the coast, abundant Prognathodon kianda , which fed on other mosasaurs at Bench 19, and species that may have been transient and opportunistic feeders in the area.

10.1017/njg.2014.32

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Citations (15)

Niobium and rare earth minerals from the Virulundo carbonatite, Namibe, Angola

Mineralogical Magazine (2012)

Lisard Torró C. Villanova M.K. Castillo Marc Campeny António Olímpio Gonçalves

Abstract The Virulundo carbonatite in Angola is one of the largest in the world and contains pyrochlore as an accessory mineral in all of the carbonatite units (calciocarbonatites, ferrocarbonatites, carbonatite breccias and trachytoids). The primary magmatic pyrochlore is fluorine dominant and typically contains about equal molar quantities of Ca and Na at the A site. High-temperature hydrothermal processes have resulted in the pseudomorphic replacement of the primary pyrochlore by a second generation of pyrochlore with less F and Na. Low-temperature hydrothermal replacement of the first and second generation pyrochlore, associated with quartz-carbonate-fluorite vein formation in the carbonatite, has produced a third generation of pyrochlore, with a high Sr content. The Sr appears to have been released by low-temperature hydrothermal replacement of the primary magmatic carbonates. Finally, supergene alteration processes have produced late-stage carbonates, goethite, hollandite and rare earth element ( REE ) minerals (mainly synchysite-(Ce), britholite-(Ce), britholite-(La), cerite-(Ce)). Cerium separated from the other REE s in oxidizing conditions and Ce 4+ was incorporated into a late generation of supergene pyrochlore, which is strongly enriched in Ba and strongly depleted in Ca and Na.

Carbonatite

Nepheline

Rare-earth element

10.1180/minmag.2012.076.2.08

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Citations (44)

Use and misuse of Mg- and Mn-rich ilmenite in diamond exploration: A petrographic and trace element approach

Lithos (2017)

Montgarri Castillo-Oliver Joan Carles Melgarejo i Draper Salvador Galí Vladimir Pervov António Olímpio Gonçalves

Ilmenite

Trace element

Metasomatism

Xenolith

10.1016/j.lithos.2017.09.021

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Citations (19)

Recent carbonatitic magmatism in Angola: the dykes of the Chiva lagoon maar

Boletín de la Sociedad Geológica Mexicana (2017)

Marc Campeny Joan Carles Melgarejo i Draper José Mangas José Mánuel António Olímpio Gonçalves

fluorapatite (35 %), titaniferous magnetite (35 %), augite (15 %), phlogopite (15 %)

Maar

10.18268/bsgm2017v69n1a10

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Citations (0)

The Distribution of Rare Metals in the LCT Pegmatites from the Giraúl Field, Angola

Minerals (2019)

António Olímpio Gonçalves Joan Carles Melgarejo i Draper María Pura Alfonso Abella Sandra Amores A. Paniagua

The Giraúl granitic pegmatite field in Angola is composed of five pegmatite types, the most evolved belong to the beryl-columbite, beryl-columbite-phosphate and spodumene types. Pegmatites are concentrically zoned with increased grain size toward a quartz core; the most evolved pegmatites have well-developed replacement units. These pegmatites are rich in Nb-Ta oxide minerals and the field has a moderate interest for critical elements such as Ta and Hf. Tourmaline, garnet and micas occur as accessory minerals. The abundance of Zr and Nb-Ta minerals increases with the evolution of the pegmatites, as well as the proportions of beryl and Li-rich minerals. The Ta/(Ta + Nb) ratio in Nb-Ta oxide minerals and the Hf/(Hf + Zr) ratio in zircon also increase with the evolution of the pegmatites and within each pegmatite body from border to inner zones, and especially in the late veins and subsolidus replacements. Textural patterns and occurrence of late veins with Ta-rich minerals suggest that Nb and especially Ta can be enriched in late hydrothermal fluids exsolved from the magma, along with Hf and other incompatible elements as Sn, U, Pb, Sb and Bi.

Pegmatite

Columbite

Tourmaline

Spodumene

10.3390/min9100580

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Citations (11)

New aristonectine elasmosaurid plesiosaur specimens from the Early Maastrichtian of Angola and comments on paedomorphism in plesiosaurs

Netherlands Journal of Geosciences – Geologie en Mijnbouw (2015)

Ricardo Araújo Michael J. Polcyn Johan Lindgren Louis L. Jacobs Anne S. Schulp

Abstract New elasmosaurid plesiosaur specimens are described from the Early Maastrichtian of Angola. Phylogenetic analyses reconstruct the Angolan taxon as an aristonectine elasmosaurid and the sister taxon of an unnamed form of similar age from New Zealand. Comparisons also indicate a close relationship with an unnamed form previously described from Patagonia. All of these specimens exhibit an ostensibly osteologically immature external morphology, but histological analysis of the Angolan material suggests an adult with paedomorphic traits. By extension, the similarity of the Angolan, New Zealand and Patagonian material indicates that these specimens represent a widespread paedomorphic yet unnamed taxon.

Neoteny

Sister group

10.1017/njg.2014.43

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Citations (47)

Comparative anatomy and systematics of Cretaceous mammal tracks of Angola

Marco Marzola Octávio Mateus Anne S. Schulp Louis L. Jacobs Michael J. Polcyn

Mammal

Source

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Citations (4)

Subsolidus processes as a key factor on the distribution of Nb species in plutonic carbonatites: The Tchivira case, Angola

Lithos (2012)

Joan Carles Melgarejo i Draper Alessandra Costanzo Aurora C.J.M. Bambi António Olímpio Gonçalves Andrés B. Neto

Carbonatite

Fluorite

Columbite

10.1016/j.lithos.2012.06.024

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Citations (32)

Lamprophyre-Carbonatite Magma Mingling and Subsolidus Processes as Key Controls on Critical Element Concentration in Carbonatites—The Bonga Complex (Angola)

Minerals (2019)

Sandra Amores-Casals Joan Carles Melgarejo i Draper Cosimo Bambi António Olímpio Gonçalves Eduardo Alves Morais

The Bonga complex is composed of a central carbonatite plug (with a ferrocarbonatite core) surrounded by carbonatite cone sheets and igneous breccias of carbonatitic, fenitic, phoscoritic and lamprophyric xenoliths set in a carbonatitic, lamprophyric or mingled mesostase. To reconstruct the dynamics of the complex, the pyrochlore composition and distribution have been used as a proxy of magmatic-hydrothermal evolution of the complex. An early Na-, F-rich pyrochlore is disseminated throughout the carbonatite plug and in some concentric dykes. Crystal accumulation led to enrichment of pyrochlore crystals in the plug margins, phoscoritic units producing high-grade concentric dykes. Degassing of the carbonatite magma and fenitization reduced F and Na activity, leading to the crystallization of magmatic Na-, F- poor pyrochlore but progressively enriched in LILE and HFSE. Mingling of lamprophyric and carbonatite magmas produced explosive processes and the formation of carbonatite breccia. Pyrochlore is the main Nb carrier in mingled carbonatites and phoscorites, whereas Nb is concentrated in perovskite within mingled lamprophyres. During subsolidus processes, hydrothermal fluids produced dolomitization, ankeritization and silicification. At least three pyrochlore generations are associated with late processes, progressively enriched in HFSE, LILE and REE. In the lamprophyric units, perovskite is replaced by secondary Nb-rich perovskite and Nb-rich rutile. REE-bearing carbonates and phosphates formed only in subsolidus stages, along with late quartz; they may have been deposited due to the release of the REE from magmatic carbonates during the hydrothermal processes.

Carbonatite

Lile

Breccia

Metasomatism

Dolomitization

10.3390/min9100601

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Citations (13)

Petrology, metallogeny and U-Pb geochronology of the paleoproterozoic mafic-ultramafic Hamutenha intrusion, Angolan Shield

Journal of African Earth Sciences (2022)

Marc Campeny Joaquín A. Proenza Montgarri Castillo-Oliver Lisard Torró Cristina Villanova-de-Benavent

Metallogeny