Titanite petrochronology of the Pamir gneiss domes: Implications for middle to deep crust exhumation and titanite closure to Pb and Zr diffusion

• Published in: Tectonics (Washington, D.C.) D.C.), 2015-04, Vol.34 (4), p.784-802
• Main Authors: Stearns, M. A., Hacker, B. R., Ratschbacher, L., Rutte, D., Kylander-Clark, A. R. C.
• Format: Article
• Language: English
• Subjects: Cenozoic; collapse; Diffusion; India-Asia collision; Lithosphere; Magma; Metamorphic rocks; orogenic plateau; Pamir Plateau; petrochronology; titanite closure; Trace elements
• ISSN: 0278-7407; 1944-9194
• DOI: 10.1002/2014TC003774

The Pamir Plateau, a result of the India‐Asia collision, contains extensive exposures of Cenozoic middle to lower crust in domes exhumed by north‐south crustal extension. Titanite grains from 60 igneous and metamorphic rocks were investigated with U‐Pb + trace element petrochronology (including Zr thermometry) to constrain the timing and temperatures of crustal thickening and exhumation. Titanite from the Pamir domes records thickening from ~44 to 25 Ma. Retrograde titanite from the Yazgulem, Sarez, and Muskol‐Shatput domes records a transition from thickening to exhumation at ~20–16 Ma, whereas titanite from the Shakhadara dome records prolonged exhumation from ~20 to 8 Ma. The synchronous onset of exhumation may have been initiated by breakoff of the Indian slab and possible convective removal of the Asian lower crust and/or mantle lithosphere. The prolonged exhumation of the Shakhdara and Muztaghata‐Kongur Shan domes may have been driven by continued rollback of the Asian lithosphere concurrent with shortening and northwestward translation of the Pamir Plateau. Key Points Titanite ages record different durations of gneiss dome exhumation from 20 to 8 Ma Independent exhumation was driven by two tectonic events rather than GPE alone Titanite retained Pb and Zr > 650 C for ~25 Myr