Therefore, the prograde metamorphism
of these rocks is marked by the transition from the greenschist facies (chlorite + plagioclase + clinozoisite [+ o -] quartz [+ o -] titanite [+ o -] graphite and actinolite + clinozoisite + quartz + plagioclase [+ o -] epidote [+ o -] titanite) through the epidote-amphibolite facies (actinolite + hornblende + epidote + clinozoisite + zoisite + quartz + plagioclase [+ o -] garnet [+ o -] titanite [+ o -] rutile [+ o -] muscovite) to the amphibolite facies (hornblende + garnet + plagioclase [+ o -] quartz).
Field occurrence and textural relations of staurolite with other mineral phases, as well as microstructural evidence observed in the investigated metapelites, reveal that these rocks underwent (1) prograde metamorphism during a complex polyphase deformation suggested by several foliations, as well as inclusion trails in staurolite porphyroblasts and (2) extensive retrograde metamorphism after the [P.
Muscovite pseudomorphs after staurolite as a record of fluid infiltrating during prograde metamorphism.
Metamorphic fluids produced from prograde metamorphism
flowed upwards along major faults, fractures and shear zones, mixing with meteoric component in the shallower levels.
These garnet features, monazite trace-element signatures, and monazite ages suggest that prograde metamorphism was still underway at 29 Ma, but that decompression or cooling was occurring by 25 Ma, consistent with the interpretation that peak metamorphism and mid-crustal ductile extension began at ~35 Ma, was ongoing at ~23 Ma, and had ceased by ~16 Ma [Lee and Whitehouse, 2007].
These monazite trace-element signatures and ages suggest that prograde metamorphism at Kangmar was later than in Mabja, but of similar duration-or, perhaps because of their small size-closed after prograde metamorphism.
Comment on "Redistribution of trace elements during prograde metamorphism from lawsonite blueschist to eclogite facies; implications for deep subduction-zone processes" by C.
2003, Redistribution of trace elements during prograde metamorphism from lawsonite blueschist to eclogite facies; implications for deep subductionzone processes: Contributions to Mineralogy and Petrology, v.
Widespread garnet and cordierite in these rocks formed by breakdown of biotite and sillimanite, which indicates prograde metamorphism
The metamorphic rocks in the Arquia valley were affected by prograde metamorphism, which was followed by a retrograde event after reaching maximum temperature and pressure conditions.
The relationships among the various types of rocks that form the Arquia Group are consistent with prograde metamorphism.
The prograde metamorphism was followed by a retrograde metamorphic event that affected the mineral associations formed at the metamorphic peak.