Framboidal and idiomorphic pyrite in the upper Maastrichtian sedimentary rocks at Gabal Oweina, Nile Valley, Egypt: Formation processes, oxidation products and genetic implications to the origin of framboidal pyrite

Soliman, Mamdouh F.; Goresy, A. El

doi:10.1016/j.gca.2012.05.004

Cited by 41 publications

(9 citation statements)

References 53 publications

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“…Pyrite oxidation accounted for the acidic character of percolating fluids as well their enrichment in dissolved sulphate [49]. Such oxidation follows Reaction (1) [50], which is attested by the general replacement of pyrite by jarosite in Gavà [51,52]. (Figure 6).…”

Section: Formation Of the Gavà Supergene Mineralisationsmentioning

confidence: 89%

Critical Elements in Supergene Phosphates: The Example of the Weathering Profile at the Gavà Neolithic Mines, Catalonia, Spain

et al. 2019

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The essential role of Critical Elements (CE) in 21st century economy has led to an increasing demand of these metals and promotes the exploration of non-conventional deposits such as weathering profiles. The present work is focused on the study of a weathering profile located at the Archaeological Park of the Gavà Neolithic Mines, Barcelona, Catalonia, Spain. In the Gavà deposit, acid and oxidising meteoric fluids generated intense weathering during the early Pleistocene, affecting series of Llandoverian black shales and associated syn-sedimentary phosphates. The circulation of these acid fluids at deeper levels of the profile generated supergene vein-like mineralisations comprised of secondary phosphates (e.g., variscite, perhamite, crandallite, phosphosiderite) and sulphates (e.g., jarosite, alunite). This supergene mineralisation is significantly enriched in certain CE (e.g., Ga, Sc, REE, In, Co and Sb) that were mobilised from host rock components and later hosted in the crystal lattice of supergene minerals. Weathering processes and corresponding supergene enrichment of CE at the Gavà deposit could be used as an example to determine exploration guidelines of CE in weathering profiles and associated supergene phosphates worldwide.

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Section: Formation Of the Gavà Supergene Mineralisationsmentioning

confidence: 89%

Critical Elements in Supergene Phosphates: The Example of the Weathering Profile at the Gavà Neolithic Mines, Catalonia, Spain

et al. 2019

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“…2 ), because sedimentary pyrite formed in the water column is typically framboidal in morphology 28 . Although euhedral pyrite could be generated by the overgrowth of framboidal pyrite 29 , no framboidal cores have been identified (Supplementary Fig. 3e , f).…”

Section: Discussionmentioning

confidence: 99%

Transient marine euxinia at the end of the terminal Cryogenian glaciation

et al. 2018

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Termination of the terminal Cryogenian Marinoan snowball Earth glaciation (~650–635 Ma) is associated with the worldwide deposition of a cap carbonate. Modeling studies suggest that, during and immediately following deglaciation, the ocean may have experienced a rapid rise in pH and physical stratification followed by oceanic overturn. Testing these predictions requires the establishment of a high-resolution sequence of events within sedimentary records. Here we report the conspicuous occurrence of pyrite concretions in the topmost Nantuo Formation (South China) that was deposited in the Marinoan glacial deposits. Sedimentary facies and sulfur isotope data indicate pyrite precipitation in the sediments with H2S diffusing from the overlying sulfidic/euxinic seawater and Fe (II) from diamictite sediments. These observations suggest a transient but widespread presence of marine euxinia in an ocean characterized by redox stratification, high bioproductivity, and high-fluxes of sulfate from chemical weathering before the deposition of the cap carbonate.

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“…The residual sulfur should attribute to leaching and chemical weathering of pyrite which are very common and have been well documented before (Lu et al, 2005;Soliman & El Goresy, 2012). Most of these researches reported that sulfur in pyrite is transferred to sulfuric and sulfate during oxidation and dissolved in pore water (Weber et al, 2004).…”

Section: Pseudomorphic Transformation From Pyrites To Hematitesmentioning

confidence: 98%

“…Sulfur detected from the hematites could indicate that they were transformed from precursor pyrites (Lu et al, 2005;Soliman & El Goresy, 2012). The preservation of framboidal morphology and bridge-like ferruginous minerals at or near spheroid-to-spheroid contacts also indicates complete pseudomorphic transformation from pyrite to hematite (Lougheed & Mancuso, 1973;Mader, 2006;Huang et al, 2019).…”

Section: Pseudomorphic Transformation From Pyrites To Hematitesmentioning

confidence: 99%

“…Lougheed & Mancuso, 1973;Wilkin & Barnes, 1997;Merinero, Lunar, Somoza, Díaz-del-Río, & Martínez-Frías, 2009;Soliman & El Goresy, 2012;Wang, Huang, Wang, Feng, & Huang, 2013). In many cases, framboidal pyrite aggregates have been observed to completely convert to hematite pseudomorphs (Mader, 2006) or other iron mineral pseudomorphs (Soliman & El Goresy, 2012). Ferruginous minerals at or near spheroid-to-spheroid contacts might be the result of leaching of interstitial hematite, the leaching may exhume the framboidal fabric (Mader, 2006).…”

Section: Pseudomorphic Transformation From Pyrites To Hematitesmentioning

confidence: 99%

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The post-deposition modification of ooids by sulfate-reducing bacteria: Evidence from the Lower Jurassic in the Tethys Himalayas of southern Tibet

Chen

Yao

et al. 2020

Preprint

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Whether ooids are formed through biotic or abiotic progress seems to become increasingly controversial in recent decades. New studies indicate that the microbial effect could make important contributions to the construction, destruction and modification of ooids. Previous studies mainly focused on the organomineralization of carbonate minerals in ooids. This paper investigates the formation process of iron minerals in red oolitic grainstones of the Lower Jurassic Nieniexiongla Formation in the Tethyan Himalaya of southern Tibet. Petrographic studies and electron probe microanalysis revealed that the colorful minerals present in red ooids are hematites. Sulfur was detected in the hematites, which indicates that they were transformed from precursor pyrites. These hematites retain euhedral or framboid shapes of the pyrites. Hematite pseudomorphs distribute randomly in ooids and could not form a whole concentric layer of the ooids. Euhedral crystals usually have larger diameters than amorphous spheres and are scattered mostly in nuclei. Based on the distribution and morphology of hematites, we speculate that precursor pyrites were formed through metabolism of sulfate-reducing bacteria. Moreover, the timing of the pyrite formation was after the deposition but before the lithification. The decomposition of the microorganisms within the ooids by bacterial sulfate-reducing provides the HS-, the degradation of organic matters would produce spaces for the intrusion of pore water with sufficient Fe2+ to facilitate the pyrite deposition. In nuclei, the framboid aggregates of pyrites were transferred to euhedral crystals through continuous growth of the constituent microcrystals. Our study demonstrated organomineralization of sulfate-reducing bacteria mediated pyrites in carbonate ooids. Summary statement This paper investigates the formation process of iron minerals in red oolitic grainstones of the Lower Jurassic Nieniexiongla Formation, demonstrates organomineralization of sulfate-reducing bacteria mediated pyrites in carbonate ooids. We propose that sulfate-reducing bacteria would utilize organic matter within ooids after sedimentation, resulting changes in the mineral composition of ooids.

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Framboidal and idiomorphic pyrite in the upper Maastrichtian sedimentary rocks at Gabal Oweina, Nile Valley, Egypt: Formation processes, oxidation products and genetic implications to the origin of framboidal pyrite

Cited by 41 publications

References 53 publications

Critical Elements in Supergene Phosphates: The Example of the Weathering Profile at the Gavà Neolithic Mines, Catalonia, Spain

Critical Elements in Supergene Phosphates: The Example of the Weathering Profile at the Gavà Neolithic Mines, Catalonia, Spain

Transient marine euxinia at the end of the terminal Cryogenian glaciation

The post-deposition modification of ooids by sulfate-reducing bacteria: Evidence from the Lower Jurassic in the Tethys Himalayas of southern Tibet

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