Short-lived orogenic cycles and the eclogitization of cold crust by spasmodic hot fluids

Area of Science:

• Geology
• Tectonics
• Metamorphic Petrology

Background:

• Collision tectonics transforms continental crust into high-pressure rocks (eclogites).
• Existing tectonothermal models conflict with petrological-isotopic data from these rocks.
• Contradictions arise from assumptions of thermal equilibrium in thickened crust.

Purpose of the Study:

• To reconcile discrepancies between tectonothermal models and petrological-isotopic data.
• To constrain the duration of orogenic cycles and associated metamorphic events.
• To develop a non-steady-state model for crustal evolution during collision.

Main Methods:

• Utilized 40Ar-39Ar geochronology.
• Employed thermal modeling.
• Integrated geochronological data with thermal models to analyze metamorphic timescales.

Main Results:

• Orogenic cycles constrained to <13 Myr duration.
• Metamorphic events determined to last ~20 kyr.
• Individual heat pulses identified as short as 10 years.
• Evidence for rapid tectonic processes and transient heat advection via hot fluids along shear zones.

Conclusions:

• Short timescales indicate rapid tectonic processes, possibly linked to seismic events.
• Transient heat advection by hot fluids in shear zones explains rapid heating.
• A non-steady-state, cold-crust model better explains geological observations than equilibrium models.