Determination and estimation of magnesium content in the single phase magnesium-calcite [Ca(1−x)MgxCO3(s)] using electron probe micro-analysis (EPMA) and X-ray diffraction (XRD)

Fahad, Muhammad; Saeed, Sundas

doi:10.1007/s12303-017-0059-8

“…We can imagine that other organisms such as calcareous algae, sponges or even rare corals continue this construction of the reef today. Figure 5 X-ray analysis of the beachrocks recovered on Site 11; relative intensity of the main minerals and mole percent MgCO 3 in calcite according to the position of d( 211) peak (Fahad and Saeed, 2018). Various diffractograms relating the position and the intensity of the d(211) peak of calcites from beachrocks cements (dive 11).…”

Section: Discussionmentioning

confidence: 99%

Beachrocks of the last low sea level, substrate of the barrier reef system along the outer Guiana shelf

Giresse

¹

,

Loncke

²

,

Heuret

³

et al. 2022

Preprint

0

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The Great Amazon Reef System is a living biogenic mesophotic reef ecosystem that has been recently described along the shelf break of Brazil. An exploration mission was carried out in 2019 along the outer edge of the French Guiana Shelf. A side-scan sonar survey was conducted to locate reef outcrops and allowed twelve in situ 80 to 120 m depth dives and sampling of the reef rocks and peripheral sands. The majority of the hard-rocks are composed of biological concretions. However several fragments revealed the inside presence of sandstone clasts. These clasts, more or less enveloped by biogenic coatings, probably represent destroyed clasts of underlying or neighboring beachrock banks. Their dominant cement is micritic (high-magnesian calcite); the intergranular or extragranular porous field was later filled with low-magnesian sparry calcite. The sand or gravel that accumulated near the barrier mainly consist of the blunt debris of coastal fauna and flora associated with different carbonate or ferruginous neoformed ooids. At 104 m depth, ooids extracted from Dive 11 samples dated from the start of MIS2 (27,370 cal yr BP) and attest to the presence of a significant coastal accumulation. At this same site, cementing did not take place until about 3,500 years later (23,990 cal yr BP). The cement of a nearby beachrock indicates a much more recent age (16,170 cal yr BP). Lastly, the age of 4,100 year BP measured on the barnacles attached to the top of the reef attests to the late Holocene reef's biological activity.

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“…It is infact low-Mg magnesian calcite, with 2% mol MgCO 3 in most of the samples, as was established as follows (Supplementary Figure S1). Low-Mg calcite showed a d 104 reflection at 3.04-3.02 Å (Zhang et al, 2010;Fahad and Saeed, 2018;Stanienda Pilecki, 2018). The mol% of MgCO 3 has been calculated using the data of Fahad and Saeed (2018) since low-Mg calcite in relation to the Mg content of calcite has been correlated to an increase in temperature (Burton and Walter, 1987).…”

Section: Mineralogymentioning

confidence: 99%

Analysis of a travertine system controlled by the transpressional activity of the Alhama de Murcia fault: The Carraclaca site, eastern Betic Cordillera, Spain

Canora

¹

,

Rodríguez

²

,

Díaz

³

et al. 2023

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Continental carbonates, such as travertines and tufas, formed from CO2-rich groundwater degassing as it emerges at the Earth’s surface, are often associated with major crustal-scale faults. The Carraclaca site, in the Lorca-Totana section of the Alhama de Murcia Fault, Spain, presents a complex geomorphological landscape controlled by active tectonics. The geology here records the interaction between Quaternary alluvial fans, travertines, and a pop-up structure developed in a transpressional section of the fault. The Alhama de Murcia Fault is an 80 km long left-lateral strike-slip fault that is one of the main seismogenic structures in the Iberian Peninsula. In this work, we examined the relation between travertine precipitation in the Carraclaca site and the tectonic activity of this fault zone through morphological and geochemical studies. The δ13C and δ18O isotopic signals indicate that the carbonate deposits are hydrothermal. In addition, the 87Sr/86Sr ratios in the samples suggest subsurface fluid interaction with the Miocene sediments and the Alpujárride basement, located below the alluvial deposits. Tectonic activity in the Alhama de Murcia Fault might generate the opening of deep water circulation in the crust every time a seismic event occurs, giving rise to hydrothermally derived carbonates precipitation. Deep waters rise and reach the surface interacting with meteoric waters, resulting in travertine formation. Therefore, the Carraclaca carbonate deposits study can inform us about the seismogenic cycle of the fault in the Lorca-Totana section.

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“…Low-magnesian calcite is characterized by a lattice spacing ranging from 3.03 Å to 3.05 Å. Three of the sandstones contain signi cant contents of high-magnesian calcite; according to the mole % MgCO 3 in a calcite with the position of the d(211) peak (Goldsmith et al 1961;Fahad and Saeed 2018), one can determine the shift of the calcite peak to respectively 14, 16 and 24 mole % MgCO 3 (Fig. 5).…”

Section: X-ray Diffractionmentioning

confidence: 99%

Beachrocks of the last low sea level, substrate of the barrier reef system along the outer Guiana shelf

Giresse

¹

,

Loncke

²

,

Heuret

³

et al. 2022

Preprint

View full text Add to dashboard Cite

The Great Amazon Reef System is a living biogenic mesophotic reef ecosystem that has been recently described along the shelf break of Brazil. An exploration mission was carried out in 2019 along the outer edge of the French Guiana Shelf. A side-scan sonar survey was conducted to locate reef outcrops and allowed twelve in situ 80 to 120 m depth dives and sampling of the reef rocks and peripheral sands. The majority of the hard-rocks are composed of biological concretions. However several fragments revealed the inside presence of sandstone clasts. These clasts, more or less enveloped by biogenic coatings, probably represent destroyed clasts of underlying or neighboring beachrock banks. Their dominant cement is micritic (high-magnesian calcite); the intergranular or extragranular porous field was later filled with low-magnesian sparry calcite. The sand or gravel that accumulated near the barrier mainly consist of the blunt debris of coastal fauna and flora associated with different carbonate or ferruginous neoformed ooids. At 104 m depth, ooids extracted from Dive 11 samples dated from the start of MIS2 (27,370 cal yr BP) and attest to the presence of a significant coastal accumulation. At this same site, cementing did not take place until about 3,500 years later (23,990 cal yr BP). The cement of a nearby beachrock indicates a much more recent age (16,170 cal yr BP). Lastly, the age of 4,100 year BP measured on the barnacles attached to the top of the reef attests to the late Holocene reef's biological activity.

show abstract

Determination and estimation of magnesium content in the single phase magnesium-calcite [Ca(1−x)MgxCO3(s)] using electron probe micro-analysis (EPMA) and X-ray diffraction (XRD)

Cited by 16 publications

References 37 publications

Beachrocks of the last low sea level, substrate of the barrier reef system along the outer Guiana shelf

Beachrocks of the last low sea level, substrate of the barrier reef system along the outer Guiana shelf

Analysis of a travertine system controlled by the transpressional activity of the Alhama de Murcia fault: The Carraclaca site, eastern Betic Cordillera, Spain

Beachrocks of the last low sea level, substrate of the barrier reef system along the outer Guiana shelf

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