Fig. 4
From: Reduced and unstratified crust in CV chondrite parent body
Silica activity vs. temperature diagrams of mineral stability fields. a Mineral stability in the system Ca-Fe-Si-O associated with characteristic assemblages in CV3 chondrites; b Mineral stability in the systems Ca-Fe-Si-O without water (black) and Ca-Fe-Si-O-H with excess water. Stability field are calculated at IM redox conditions and an indicative pressure of 2000 bar. Green lines and green area for hydrous phases. The silica activity buffer curve nepheline/albite is also plotted. Characteristic Ca-Fe-rich assemblages in CV3 chondrites allow depicting Log aSiO2–T pathway for each CV3 lithologies. As illustrated in b, a single trend matches the diversity of Ca-Fe secondary phases in all CV3 subgroup, suggesting a unique allochemical metamorphism in CV3 chondrites parent body (gray area and dashed arrow). Ca-Fe-rich anhydrous phases crystallize first at the highest aSiO2 due to the intrinsic composition of the unprocessed matrix while rare serpentine-like hydrous phases (Fe-serpentine field in green) should witness the low temperature part of the fluid-assisted metamorphic trend (dashed arrow)
