Journal Article

Chemical Weathering Impacts upon the Iron-Bearing Sedimentary Rocks within Sidi-Essaid Formation \Upper Cretaceous\, Sidi-Bujdaria Village, Wadi Gherim, Ghanema, NW Libya

Elgarmadi, Salah Eldin M, Dagdag, Emad Eldin A, Abdelkader, Osama A, Osman, Madiha S. M, Shushan, Ismail Elforjani

2024

Overview

This paper dealt with the study of chemical weathering effects upon Sidi-Bujdaria iron-bearing rock succession outcropped at Sidi-Bujdaria Village, Wadi Gherim, Ghanema Region, NW Libya. This succession consisting of an iron-bearing sedimentary strata and belonging to Sidi-Essaid Formation deposited during the Upper Cretaceous. This work is based on field survey documentations, petrographic studies and chemical analysis as well. Based on lithological variations, ten (10) sedimentary facies is proposed. The twenty (20) meters measured succession is divided vertically into four (4) main parts. The lower part to the bottom (which rests on the wadi's channel) consisting of facies-1 which is sub-divided into three (3) main sections as lower, middle and upper depending on color variations with measured thickness of ~ 2.30 m. The middle part consisted of facies-2, facie-3, facies-4 and facies-5 with measured thickness of ~ 6 m. The upper part of Sidi-Bujdaria consisted of facies-6, facies-7 and facies-8 with total measured thickness of ~ 8 m. The uppermost part (to the top) consisted of facies-9 and facies-10 with measured thickness of ~ 4 m. The middle part of the succession involved abundant iron balls and nodules with varies shapes and sizes. The other parts of the succession showed fossils and parts of fossils replaced by iron-oxide colloidal material with reddish-brown, yellowish-orange and dark-black colors. Iron oxide cementing materials were found to bind and coat large part of the grain framework of the analyzed rock samples. Chemical weathering impact upon Sidi-Bujdaria succession was so strong in which the most active processes included: oxidation, hydration and dehydration that given the rock strata the rusty and various alteration colors. Another special chemical weathering process that had and still has an affection on rock strata is carbonation, which resulted in the formation of varied sizes and shapes of rock cavities, caves and sinkholes and caused rocks to collapse and fall down to the bottom of the succession as well. Solution pipes of varies sizes and shapes with iron oxide alteration features were encountered and resulted due carbonation and water leaching and oxidation actions. The surface of most rock strata is filled-up with reddish-brown, yellowish-orange and grayish-green iron oxide colloidal material whenever voids, fossil casts, sinkhole and vinlets found. According to whole chemical analysis done for the selected rock samples concerning iron-oxide enrichment and as compared with ironstones and iron formations, the succession of Sidi-Bujdaria is better considered as \"ferruginous succession\". According to the other major oxides included in the results, Sidi-Bujdaria succession is considered as formed from ferruginous highly siliceous, calcareous, calcarenitic marl with minor amounts of magnesium and aluminum oxides with. less dolomitic facies. The enhanced secondary rock porosities encountered is due to solution porosity.

• Publisher: جامعة المرقب - كلية التربية بالخمس
• Subject: الصخور الرسوبية / الموارد الكيميائية / عمليات الكربنة / ليبيا