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.

Barrovian-grade pelites in the Greater Himalayan Crystallines and Lesser Himalayan Formations exposed in the Himalayan core are separated by the Main Central Thrust (MCT). This fault system accommodated a significant amount of India-Asia convergence and is the focus of several models that explore ideas about the development of the range and collisional belts in general. Units separated by the MCT provide critical information regarding the mechanisms of heat transfer within collisional belts. Garnets collected across the MCT record their growth history through changes in chemistry. These chemical changes can be extracted and modeled using a variety of thermodynamic approaches. Here we describe and apply particular thermobarometric techniques to decipher the metamorphic history of several garnet-bearing rocks collected across the MCT in central Nepal, the Sikkim region, and NW India. Comparisons are made between the results of previously-reported conventional rim P-T conditions and P-T paths extracted using the Gibb’s method to isopleth thermobarometry and high-resolution P-T path modeling using the same data and assemblages. Regardless of calibrations used, the P-T conditions and paths, along with previously-reported timing constraints, are consistent with an imbrication model that suggest the MCT shear zone developed as rock packages within the LHF were progressively transferred. In this model, samples within the LHF travel along the MCT at a 5 km/Ma speed rate from 25 to 18 Ma. The hanging wall speed rate is 10 km/Ma, and topography progressively accumulates until a maximum height of 3.5 km. Once the topography is achieved at 18 Ma, a period of cessation is applied to the MCT between 18 and 15 Ma, and topography is reduced at a rate of 1.5 km/Ma. The model returns to activity within the MCT shear zone with the activation of the MCT footwall slivers from 8 to 2 Ma. P‐T changes recorded by the footwall garnets result from thermal advection combined with alterations in topography. For most MCT footwall samples, the P-T paths match the model predictions remarkably well. The P-T paths for some samples in central Nepal are also consistent high exhumation rates (>12mm/year) within the MCT shear zone since the Pliocene, a scenario predicted by this imbrication model.