Original paper

Crystal chemistry and oxidation state of one euhedral Cr-spinel crystal enclosed in a bauxite layer (Trieste Karst: NE Italy): some considerations on its depositional history and provenance

Lenaz, Davide; Carbonin, Susanna; Gregoric, Marko; Princivalle, Francesco


The singular occurrence of a well-preserved euhedral crystal of Cr-spinel has been recognised in a Late Maastrichtian-?Paleocene bauxite layer. Microanalysis and X-ray structural refinement were carried out on the single crystal: determination of oxygen atomic position and electron density in structural sites revealed that this sample did not undergo any oxidation process; this fact may signify that it was wind-blown and deposited after bauxitisation. Chemical parameters, TiO2 contents and compositional variations from core to rim suggest possible magmatic origin. Similarity with other Cr-spinels found in the coeval Julian Basin turbidites (SE Alps) was recognised.


bauxite layercr-spinelcrystal chemistryoxidation statedepositional history