Ultra-high-pressure metamorphism

Definition and Characteristics of Ultra-high-pressure Metamorphism

• Metamorphism of rocks at pressures ≥27kbar (2.7GPa) to stabilize coesite
• Diagnostic minerals include coesite and diamond
• Diagnostic mineral assemblage includes magnesite + aragonite
• Mineral compositions can also be used for identification
• Ultra-high-pressure rocks often exhibit unique textures and mineral assemblages
• Ultra-high-pressure metamorphism involves the formation of rocks at depths greater than 100 km
• Rocks undergoing ultra-high-pressure metamorphism experience high temperatures and pressures

Tectonic Settings and Mechanisms of Ultra-high-pressure Metamorphism

• Ultra-high-pressure metamorphism occurs in subduction zones and during collision of continental plates
• Slab break-off and subduction channel processes contribute to ultra-high-pressure metamorphism
• Exhumation of ultra-high-pressure rocks is driven by factors such as slab rollback and bending-related variations in tectonic pressure
• Numerical models and physical experiments help understand the tectonic processes associated with ultra-high-pressure metamorphism

Examples of Ultra-high-pressure Metamorphic Terranes

• The Dabie Shan orogen in China
• The Western Alps
• The Pamir Mountains
• The South Caledonides
• The Pakistan Himalaya
• The Western Gneiss Region in Norway
• The Sulu ultrahigh-pressure terrane in eastern China

Exhumation Processes and Mechanisms of Ultra-high-pressure Rocks

• Exhumation refers to the process of bringing deeply buried rocks to the Earth's surface
• Syn-collisional rock exhumation and associated normal faulting contribute to exhumation
• The hydration of deep slabs and the role of microplate rotation are proposed exhumation mechanisms
• Numerical models and thermomechanical simulations help understand the processes involved in the exhumation of ultra-high-pressure rocks

Significance and Implications of Ultra-high-pressure Metamorphism

• Ultra-high-pressure metamorphism provides insights into deep Earth processes and plate tectonics dynamics
• The study of ultra-high-pressure rocks helps reconstruct ancient tectonic events and understand the evolution of mountain belts
• The presence of ultra-high-pressure minerals in exhumed rocks indicates extreme conditions
• The formation and exhumation of ultra-high-pressure rocks have implications for the recycling of continental crust and the formation of ore deposits
• Understanding ultra-high-pressure metamorphism contributes to our knowledge of Earth's geological history and the processes that shape our planet

Ultra-high-pressure metamorphism Data Sources