Abstract We report the first occurrence of high-pressure metamorphic aragonite in Precambrian carbonates Jabal Akhdar Dome Oman Mountains (northern Oman). propose a model for both its formation at blueschist facies conditions and subsequent preservation to surface within tectonic framework Late Cretaceous obduction Semail Ophiolite. Aragonite formed temperature ~350 °C pressure ≥0.9 GPa is pres...

The uranium isotopic composition (?238U) of bulk marine calcium carbonates has been extensively explored as a promising paleoredox proxy to track the extent global oceanic anoxia in deep time. Multiple studies have examined whether primary can directly capture seawater ?238U and measurements recent ancient preserve U isotope signatures. Here we assess role diagenesis altering signatures sedimen...

Synchronized transitions in the polymorph mineralogy of the major reef-building and sediment-producing calcareous marine organisms and abiotic CaCO3 precipitates (ooids, marine cements) throughout Phanerozoic time are believed to have been caused by tectonically induced variations in the Mg/Ca ratio of seawater (molar Mg/Ca>2=“aragonite seas”, <2=“calcite seas”). Here, I assess the geological e...