Agate gemstones occurring in the Mesoproterozoic volcanic rocks of Priozersk Formation (PrF) within Pasha–Ladoga Basin (Fennoscandian Shield, NW Russia) were investigated to characterize mineral and geochemical composition agates provide new information concerning their origin. Optical scanning electron microscopy, EDS microanalysis, X-ray powder diffraction, fluorescence spectrometry, Raman sp...

—Well-preserved microfossils occur in abundance through more than 1000m of lower Mesoproterozoic siliciclastic rocks composing the Roper Group, Northern Territory, Australia. The Roper assemblage includes 34 taxa, five interpreted unambiguously as eukaryotes, nine as possible eukaryotes (including Blastanosphaira kokkoda new genus and new species, a budding spheromorph with thin chagrinate wall...

The origin of diamonds from Serra do Espinhaço in Diamantina region (State of Minas Gerais) and in Chapada Diamantina, Lençóis region (State of Bahia) remains uncertain, even taking into account the ample research carried out during the last decades. The lack of typical satellite minerals in both districts makes a kimberlitic source for these diamonds uncertain. In mid 18th century the occurren...

Microdigitate stromatolites (MDS) are common in Neoarchean–Paleoproterozoic successions but declined and gradually disappeared in Mesoand Neoproterozoic carbonates. The abundance of well-preserved fibrous fabrics and the absence of identifiable microbial fossils in MDS have been taken as evidence of their abiotic origin in carbonate-supersaturated and anoxic Precambrian oceans. Micronand nanome...

Granitic rocks are commonly used as a means to study chemical evolution of continental crust. In particular, their isotopic compositions reflect the relative contributions of mantle and crustal sources in their genesis. In Laurentia, a distinctive belt of Mesoproterozoic A-type or “anorogenic” granites of ∼1.4 Ga age was emplaced within composite, heterogeneous Proterozoic crust. Zircons are an...

The Saharan Metacraton is a poorly known tract of pre-Neoproterozoic continental crust that occupies the area between juvenile Arabian Nubian Shield, in east, and Tuareg Shield to west. Neoproterozoic orogenesis (i.e. Oubanguides East African orogenies) affect west, south east metacraton, respectively, which led deformation, emplacement igneous bodies, localised episodes rift-related magamatism...

In this contribution we review the possibility of establishing depositional age and tectonic settings metamorphosed carbonate rocks from continental collision zones in East African-Antarctic Orogen. The geochemical characteristics regionally distributed meta-carbonate Highland Complex (HC) Sri Lanka are considered detail compared with similar occurrences Antarctica, India, Madagascar Africa. va...