Genesis and 40Ar/39Ar dating of K-Mn oxides from the Stavelot Massif (Ardenne, Belgium): Insights into Oligocene to Pliocene weathering periods in Western Europe

Dekoninck, Augustin; Monié, Patrick; Blockmans, Sabine; Hatert, Frédéric; Rochez, Gaëtan; Yans, Johan

doi:10.1016/j.oregeorev.2019.103191

Cited by 12 publications

(9 citation statements)

References 108 publications

(261 reference statements)

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“…These minerals occur as small needles of 3-100 μm length and 1-10 μm width ( Fig. 7 b and c), as commonly observed in other supergene Mn deposits (Decrée et al 2010b;Dekoninck et al 2016aDekoninck et al , 2016bDekoninck et al , 2019. There are no differences in the composition of the coronadite group minerals according to their position in sandstones and dolostones, which suggests they originate from the same process.…”

Section: Mineralogy and Petrography Of The Mn Oressupporting

confidence: 68%

Multistage genesis of the late Cretaceous manganese karst-hosted Tasdremt deposit (High Atlas, Morocco)

et al. 2020

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The eastern part of the Souss Basin (Morocco) contains several Mn deposits in the Tasdremt district. Three Mn orebodies occur within the Cenomanian-Turonian dolostones and the Senonian (Coniacian to Maastrichtian) detrital series, the main orebody being located at the boundary between them. The Mn ores consist of coronadite group minerals, mostly coronadite and hollandite, in a karstified dolostone. New field observations, petrographic analyses, and geochemical data define the Tasdremt deposits as a karst-hosted accumulation (11-60 wt.% Mn), particularly enriched in Ba (1.5-8.2 wt.%) and Pb (1.0-5.0 wt.%) with poor contaminations in Al, Fe, and P. This study shows that the ore-forming process is similar to that occurring in the Imini C3 level, located~100 km to the northeast. Such similarities with the high-grade pyrolusite-bearing ore suggest that the Tasdremt deposit is a lateral equivalent of the Imini deposits. However, the scarcity of pyrolusite in Tasdremt results in lower Mn grades, the Tasdremt ores being considered an aborted/ incomplete system in comparison with the Imini deposits. 40 Ar/ 39 Ar geochronology of K-bearing Mn oxides yields late Cretaceous ages, defining three phases at~91.5 Ma,~77.5-82 Ma, and~65-67 Ma. Although the source of metals remains hypothetical, mineralizing fluids were carried by O 2-free groundwater that mixed with O 2-rich shallow meteoric waters at the Tasdremt depositional site. The dissolution of the host dolostones and the karst environment have provided suitable conditions for the precipitation of Mn oxides, causing the coeval increase of pH and Eh, respectively. The Early Atlasic deformation during the Late Cretaceous is associated with mineralization events and was responsible for creation of low stand reliefs from Tasdremt to Imini. This period enabled karstification and mineralization. Connecting the Tasdremt deposits to other African Mn deposits is difficult since the latter consist of laterite resting above Paleoproterozoic Mn protores, and consequently formed under different conditions from karst-hosted deposits. It is likely that other Mn occurrences formed along the Atlas belt in similar settings.

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Section: Mineralogy and Petrography Of The Mn Oressupporting

confidence: 68%

Multistage genesis of the late Cretaceous manganese karst-hosted Tasdremt deposit (High Atlas, Morocco)

et al. 2020

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“…Using 40 Ar- 39 Ar method on cryptomelane in Mn ores of Democratic Republic of Congo, De Putter et al [28], Fontaine et al [45] and De Putter and Ruffet [46] highlighted successive episodes of weathering since Late Cretaceous and concluded that tectonics accounts for most of the recognized supergene ore formation episodes, which are controlled by vertical lithospheric movements that are ultimately responsible for alternating stages of landscape stability and erosion. In the Ardenne (Western Europe), a recent synthesis showed that the uplift of the area was most probably the main factor triggering the development of weathering mantles, together with the increasing seasonality and high precipitation [47], illustrating the role of geodynamics and climate in the weathering.…”

Section: Significance Of the Weathering Episodes At A Regional Scalementioning

confidence: 99%

(U-Th)/He Dating of Supergene Iron (Oxyhydr-)Oxides of the Nefza-Sejnane District (Tunisia): New Insights into Mineralization and Mammalian Biostratigraphy

et al. 2021

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The mining district of Nefza-Sejnane (Tunisia) encloses numerous ores and raw material deposits, all formed in relation with successive Fe-rich fluids of meteoric and/or hydrothermal origins. Here, for the first time in Tunisia, (U-Th)/He ages were obtained on supergene goethite from various localities/deposits of the district highlight direct dating of significant weathering episodes during late Tortonian and late Pleistocene. These weathering events are most likely associated with favorable conditions that combine (i) wet climate displaying sufficient meteoric water/fluid; and (ii) regional exhumation, due to large-scale vertical lithospheric movements enhancing the percolation of fluids. Matched with previous works, these results refine the stratigraphic frame for the polymetallic mineralization and clay deposits in the district, confirming the influence of meteoric fluids circulation during the late Cenozoic. As a consequence of the new (U-Th)/He data, we moreover propose a taxonomic and stratigraphic revision of the well-known mammalian fauna from the Fe-rich Douahria locality, suggesting an early Tortonian age for the fossils, i.e., prior to the first episode of meteoric event in the area.

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“…13 B). The hypothesis of erosion of the Eocene laterites is supported by a recent study (Dekoninck et al, 2019) (Aleksiev, 1959) imply that ash fall dissolution in seawater (e.g., Frogner et al, 2001;Randazzo et al, 2009;Censi et al, 2010) may have additionally supplied Mn in the basin before and during Mn-ore deposition (Fig. 13 C).…”

Section: Model Of Formation Of the Obrochishte Mn Depositmentioning

confidence: 67%

Origin of the Oligocene manganese deposit at Obrochishte (Bulgaria): Insights from C, O, Fe, Sr, Nd, and Pb isotopes

Dekov

Maynard

Kamenov

et al. 2020

Ore Geology Reviews

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The large manganese (Mn) deposit at Obrochishte (NE Bulgaria) is part of a cluster of similar Early Oligocene deposits located around present-day Black Sea. They collectively constitute the Earth's second largest endowment of Mn, after the Kalahari Manganese Field in Africa. We have employed a battery of isotopic techniques (C, O, Fe, Sr, Nd, Pb) to help understand the genesis of this deposit. Carbon isotope data indicates that some sections of the Mn-ore layer have diagenetic MnCO3 mineralization, formed by reaction of Mn oxides with organic carbon (Corg), whereas other sections have MnCO3 precipitated directly from the seawater column. Oxygen isotopes show that the high-grade Mn mineralization had seawater as the fluid source, whereas some lower-grade sections had a mix of ground water and seawater as fluid sources. Sr and Nd isotope values of ore leachates also indicate that the Mn deposition occurred in normal Early Oligocene seawater. Nd and Pb isotope values suggest that the clastic host sediments were sourced from continental bedrock rather than younger arc volcanic rocks to the west. Iron isotope composition of the Mn ore implies deposition in a redox-stratified basin, similar to the modern Black Sea, with much of the Fe sequestered in deep, anoxic-euxinic water as sulfides. Similar to the modern Black Sea, most of the detrital Fe was transferred from shallow oxic sediments into deep, anoxic-euxinic water by an "iron shuttle" and remobilized Mn sequestered in the upper suboxic water layer. However, during the Oligocene, the "iron shuttle" operated intermittently due to the chemocline falling mostly below the shelf break, thereby limiting the efficiency of the shuttle mechanism. We propose a model for the Lower Oligocene strata in which intense weathering during the Eocene weathering phase produced a thick lateritic crust on the southern European continent. The drastic sea-level drop at the end of the Eocene initiated downcutting of streams through this weathered material, transferring Fe-and Mn-oxides to the redox-stratified Western Black Sea. Here, these oxides were partly or entirely dissolved in the suboxic Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.(Mn-oxides partly, Fe-oxyhydroxides entirely dissolved) and anoxic-euxinic (Mn-oxides entirely dissolved, dissolved Fe2+ re-precipitated) water layers. Eventually, Fe was re-precipitated as sulfide in the deep anoxic-euxinic water, while Mn accumulated in the suboxic water layer. Transgression in the Early Oligocene brought this Mn-rich water onto the shallow shelf where it precipitated as Mn-oxide, then converted to Mn-carbonates during early diagenesis. Some Mn was also contributed by submarine groundwater discharge. Further transgression brought lower-oxygen water onto the shelf and Mncarbonate precipitated directly from the water column. The findings from this work provide insights about the unique Oli...

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Genesis and 40Ar/39Ar dating of K-Mn oxides from the Stavelot Massif (Ardenne, Belgium): Insights into Oligocene to Pliocene weathering periods in Western Europe

Cited by 12 publications

References 108 publications

Multistage genesis of the late Cretaceous manganese karst-hosted Tasdremt deposit (High Atlas, Morocco)

Multistage genesis of the late Cretaceous manganese karst-hosted Tasdremt deposit (High Atlas, Morocco)

(U-Th)/He Dating of Supergene Iron (Oxyhydr-)Oxides of the Nefza-Sejnane District (Tunisia): New Insights into Mineralization and Mammalian Biostratigraphy

Origin of the Oligocene manganese deposit at Obrochishte (Bulgaria): Insights from C, O, Fe, Sr, Nd, and Pb isotopes

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