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Geological mapping using extreme gradient boosting and the deep neural networks: application to silet area, central Hoggar, Algeria

Elbegue Abderrahmane Aref, Allek Karim, Zeghouane Hocine

Acta Geophysica

2022

Vol. 70, no 4

1581--1599

Nowadays, machine learning algorithms are considered a powerful tool for analyzing big and complex data due to their ability to deliver accurate and fast results. The main objective of the present study is to prove the effectiveness of the extreme gradient boosting (XGBoost) method as well as employed data types in the Saharan region mapping. To reveal the potential of the XGBoost, we conducted two experiments. The first was to use different combinations of: airborne gamma-ray spectrometry data, airborne magnetic data, Landsat 8 data and digital elevation model. The objective is to train 9 XGBoost models in order to determine each data type sensitivity in capturing the lithological rock classes. The second experiment was to compare the XGBoost to deep neural networks (DNN) to display its potential against other machine learning algorithms. Compared to the existing geological map, the application of XGBoost reveals a great potential for geological mapping as it was able to achieve a correlation score of (78%) where igneous and metamorphic rocks are easily identified compared to sedimentary rocks. In addition, using different data combinations reveals airborne magnetic data utility to discriminate some lithological units. It also reveals the potential of the apparent density, derived from airborne magnetic data, to improve the algorithm’s accuracy up to 20%. Furthermore, the second experiment in this study indicates that the XGBoost is a better choice for the geological mapping task compared to the DNN. The obtained predicted map shows that the XGBoost method provides an efficient tool to update existing geological maps and to edit new geological maps in the region with well outcropped rocks.

Pleistocene neotectonics and Fe-mineralizations in the Ahnet-Mouydir area (northern margin of the Hoggar Massif, Algerian Sahara)

Wendt J., Neumann U., Schulz H.

Acta Geologica Polonica

2008

Vol. 58, no. 1

13-26

Strongly mineralized lithologies were found in 4 different depositional settings along the northern margin of the Hoggar Massif in southern Algeria: (1) Pleistocene fluvial terraces, (2) pebble-filled erosional furrows in marine Silurian and Upper Devonian shales, (3) sedimentary dykes in Givetian mud buildups and (4) tectonic fault fissures and cracks in Upper Devonian shales. In spite of the contrasting sedimentary environment, all these rocks display very similar properties and are considered as contemporaneous. They are characterized by high porosities, intense Fe-mineralization and a great variety of accompanying, secondary minerals formed in a subrecent continental regime under pluvial to arid conditions. The dykes, faults and cracks are direct evidence of tensional stress during the early and middle Pleistocene which has not been observed so far. The complex sedimentary and diagenetic history of conglomerates, breccias, sandstones, ferricretes, calcretes and claystones in these settings was analyzed using SEM, EDX-microprobe, XRD, transmitted and reflected light petrography and is documented in hitherto unknown details.