The fourth Arab Impact Cratering and Astrogeology Conference (<scp>AICAC IV</scp>), April 9–12, 2017, Algiers (Algeria)

Belhai, Djelloul; Aoudjehane, Hasnaa Chennaoui; Baratoux, D.; Ferrière, L.; Lamali, A.; Sahoui, R.; Lambert, P.; Ayadi, Abdelhakim

doi:10.1111/maps.12906

Cited by 3 publications

(1 citation statement)

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“…It is worth emphasizing however that despite data rejecting any evidence of melt products and ejecta, other authors have interpreted their petrographic observations as evidence of carbonate melting as a consequence of shock metamorphism (e.g., Sahoui et al, 2016). Others proposed that the remnant‐melted material can have a significant presence within the fracture network or buried beneath the recent sediment of the crater depression, either as a primary phase or as an erosion product (Belhai et al, 2017). Although the work by Lamali et al (2020) did not indicate any anomalous near‐surface electromagnetic signatures of such typical material, the debate about its hidden character is still ongoing.…”

Section: Introductionmentioning

confidence: 99%

Field gamma ray spectrometry as a diagnostic tool for the assessment of hypothetical melt rocks from the Maâdna structure (Talemzane, Algeria): Implications for the crater formation process

Lamali

Hamai

Mokhtar

et al. 2022

Meteorit & Planetary Scien

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Among all geophysical methods, gamma ray spectrometry is not widely used in impact cratering studies, despite its efficiency in the investigation of physical/chemical changes in rocks. The application of gamma ray spectrometry method to data from the Maâdna crater is aimed at detection and verification of the presumed impact‐derived melt rocks or breccias, as well as discussing its implications on process of formation. The resulting information also demonstrates the potential of these specific data regarding our general understanding of impact cratering, while a few case studies have been reported in the literature to date within the impact community. Maâdna crater is dated at 2.6–3.1 Ma of ~1.7 km and is emplaced in Upper‐Cretaceous to Eocene limestones of the northern part of the Algerian Saharan platform. Although originally accepted as an impact crater, its origin is still controversial. Several thousands of field measurements were taken using a field portable gamma ray spectrometer. The measurements can be equivalently expressed by up to about 42 km footpath recordings in real‐time ground acquisitions, covering the entire structure and surrounding areas beyond the crater edge. The collected data included the total count (Tc) and the concentrations of the radionuclides calculated in wt% for K and in ppm for U and Th. The spectra rates recorded inside and outside the crater did not exceed the maximum average concentrations corresponding to 75.3 Cps, 4.94 ppm, 10.5 ppm, and 1.79 wt% for Tc, U, Th, and K, respectively. The database was processed using various gridding data methods, from which the minimum curvature was adopted as it provides a powerful visualization and interpretation of the anomalous distribution of radioactive elements and their corresponding ratios maps. In addition, an improved statistical analysis was carried out in order to extract a maximum of information about the radiometric response of each rock unit. This analysis consisted of a series of multiple linear regression, mean differencing, Q–Q (quantile–quantile) plots, and ternary mapping. Maps and plots of various models allowed us to examine the background variability in the distribution of K, Th, and U concentrations at the surface of the three distinctive litho‐type zones in the surveyed area, which are the central part, the crater edge, and the outside of the crater including the wadi deposits. Observed results of different radiometric responses clearly reflect the effect of various lithological units, especially in the areas with high K concentration. Note that this positive K‐anomaly has been observed in recent deposits that fill the Maâdna depression or external wadi beds. In contrast, the surrounding limestone rocks showed lower levels of radioelement concentrations. Relevant similarities found between the radiometric signatures of the Neogene formations inside and outside the crater can be considered as a strong argument to exclude preferential radionuclides enrichment caused by an impact event. Consequently, the natural...

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Section: Introductionmentioning

confidence: 99%