Preliminary Geochimical Investigation on Banded Iron-Formations from Southern-Somalia

The article shows the results of a preliminary geochemical study on metamorphosed banded iron-formations of the Bur area (southern Somalia) in order to investigate environmental and depositional conditions for their genesis.Maqaalku wuxuu muujinayaa natiijooyinka daraasaadka geochemistry-ga ee bidaayiga ah ee ku saabsan bir-samaysanka degaanka Buur, koofur Soomaaliya, si loo baaro degaanka iyo xaaladda samaysanka ciid macdaneedda.L'articolo illustra i risultati di uno studio geochimico preliminare sulle formazioni ferrifere a bande (BIF) nell'area di Bur, Somalia meridionale, allo scopo di indagare le condizioni ambientali e sedimentarie per la loro genesi.Document provided to the Somali Studies Centre by Prof. Carmignani, University of Siena.Prof. Carmignani, oo ka mid ah Jamaacadda Siena, ayaa dokumentigan ku deeqay xarunta cilmibaarista (Centro Studi Somali).Documento messo a disposizione del Centro Studi Somali dal Prof. Carmignani, Università di Siena

Terrestrial target and melting site of Libyan Desert Glass: New evidence from trace elements and Sr isotopes

Strontium isotopes and selected trace elements (Rb, Sr, REE, Zr, Hf, Th, and U) were measured on samples of Libyan Desert Glass (LDG) and a series of terrestrial materials (rocks, LDG-bearing soils, eolic sand) collected over a large area of southwestern Egypt to identify the LDG terrestrial parent material and the site where impact melting occurred. Samples include Upper Cretaceous hypersilicic sandstones outcropping at or near the LDG strewn field and Lower Cretaceous to Silurian sandstones from the Gilf Kebir Plateau highlands. Strontium isotopes and partially Zr, Hf, Th, and U, possibly reflecting the composition of detrital zircon grains, are effective indicators of the geochemical affinity between terrestrial materials and LDG, unlike Rb, Sr, and REE abundances. The best geochemical affinity with LDG was found in LDG-bearing soils collected at the base of intradunal corridors in the Great Sand Sea. Remarkably, abundances of the Zr group elements of the LDG Zr-bearing phase are distinct from all terrestrial detrital zircons from the area. We suggest a mixture of weathering products from sandstones of different ages, including Devonian and Silurian rocks from the Gilf Kebir highlands, as the most likely source for LDG. A loose sedimentary formation exposed 29 Ma ago at the Earth\u2019s surface, superimposed over hard bedrock, might have been the true terrestrial target of the impact, but because of its incoherent nature, it was rapidly destroyed, explaining the complete absence of any evidence of an impact structure

Anatomy of carbonate turbidite megabeds (M. Cassio Formation, Upper Cretaceous, Northern Apennines, Italy)

Mem. Descr. Carta Geol. d'Itali