loading page

Development and use of garnet-based high-resolution P-T-t paths to constrain the dynamics of Himalayan orogenesis
  • +1
  • Elizabeth Catlos,
  • Theresa Perez,
  • Thomas Etzel,
  • Oscar Lovera
Elizabeth Catlos
University of Texas at Austin

Corresponding Author:[email protected]

Author Profile
Theresa Perez
University of Texas at Austin
Author Profile
Thomas Etzel
University of Texas at Austin
Author Profile
Oscar Lovera
University of California Los Angeles
Author Profile

Abstract

Tectonic models as a universal outcome generate predictions regarding the travel time paths of rocks as they are displaced due to the application of particular input parameters and boundary conditions. A need for most of these models, either as a constraint for realistic input conditions or to gauge their relevance to a particular natural system, is pressure‐temperature‐time (P‐T‐t) paths from individual rock samples that track the conditions they experienced during displacement. Although arguments can be made that P‐T paths and absolute peak P‐T conditions may not necessarily be diagnostic of processes involved, this type of information is clearly a valuable addition to other types of data, such as timing and microstructural information regarding strain recorded during rock deformation. Low‐resolution P‐T paths can be limited in their ability to test ideas regarding lithospheric response to perturbations, including motion within fault zones. Here we apply advances in thermodynamic modeling to acquire high‐resolution P‐T paths that show the conditions responsible for garnet growth within one of the Himalayas’ major fault systems. The approach we outline can be applied to any garnet‐bearing assemblage using bulk rock and mineral compositions and have the potential to significantly increase the understanding of the dynamics of field areas that contain garnet, from the mineral’s crystallization to erosion‐driven or tectonically-driven exhumation. Overall, high-resolution garnet-based P-T paths were generated for two transects across the Himalayan Main Central Thrust (MCT) spaced ~850 km apart (along the Bhagirathi and Marsyangdi drainages) and monazite grains were dated in situ to help constrain crystallization time. Rocks collected at equivalent structural positions to the MCT along both transects show similar paths and a shear zone imbrication model suggest the MCT zone has very high exhumation rates, up to 12 mm/yr since the Pliocene.