tashtab mountain is located 25 km from the city of khur in northeastern isfahan province. several bentonite mines formed in this area as a result of the eocene volcanic alteration. these mines are classified as the khur bentonite horizon. studies on trace elements in parent rock and clays show that the studied bentonites formed from andesite-basaltic parent rocks. the xrd analysis shows that st...

Measurements of natural cosmogenic Si (t1/2 ~ 140 years) in tropical deltaic sediments demonstrate for the first time that most Si is present in rapidly formed authigenic clays and not biogenic opaline silica (bSi). The burial of bSi in deltaic and continental margin sediments has likely been greatly underestimated because of diagenetic alteration of bSi to clay, little of which dissolves in th...

White saponite occurs in joints and open fracture zones in metamorphosed dolomitic limestone near Ballarat, California. The saponite appears to have formed by hydrothermal alteration, possibly during Pliocene times. The material shows a 06l X-ray powder diffraction peak at 1.529 ]k, A1203 and MgO contents of about 4.4 and 23.5%, respectively, and a half-cell octahedral atoms summation value of ...

High-resolution mapping by visible and near-infrared orbital spectrometers has revealed a diversity of hydrated mineral deposits on the surface of Mars. Quantitative analysis of mineral abundances within these deposits has the potential to distinguish depositional and diagenetic processes. Such analysis can also provide important constraints on the nature of putative global and local-scale mine...

Microscopic soft tissues have been identified in fossil vertebrate remains collected from various lithologies. However, the diagenetic mechanisms to preserve such tissues have remained elusive. While previous studies have described infiltration of biofilms in Haversian and Volkmann’s canals, biostratinomic alteration (e.g., trampling), and iron derived from hemoglobin as playing roles in the pr...