T83 Geochemical Signatures of Fluid-Rock Interaction: Earth Surface Weathering to Hydrothermal Systems I

Tuesday, 27 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

δD VALUES OF SHEAR ZONE MICAS FROM THE LHAGOI KANGRI DOME SUGGEST HIGHER REGIONAL ELEVATION IN THE NORTHERN HIMALAYA DURING THE MID-MIOCENE

Paper number: T83-9
Program: Technical Sessions
Time: 3:20 PM – 3:35 PM

Authors

Abstract

The uplift history of the Himalayan – Tibetan orogen is crucial to understanding the geodynamic evolution of the orogen and its influence on the Asian climate system. Here we reconstruct paleoelevation ~13 Ma in the northern Himalaya using the hydrogen isotope composition (δD) of synkinematic micas in mylonitic quartzite and paragneiss. These micas equilibrated at high temperatures (447 ± 48°C, determined by oxygen isotope fractionation of quartz-muscovite mineral pairs) with a water composition (δDw = -179 ± 5‰ VSMOW) consistent with high elevation precipitation that infiltrated into the ductile shear zone bounding the Lhagoi Kangri dome. We used multiple lapse rates to compare this value with contemporaneous sea-level precipitation recorded in Siwalik paleosol carbonate. These lapse rates provide paleoelevation estimates ranging from 5.8 – 6.5 km for the regional catchment that provided water to the shear zone during displacement, close to 1 km higher than the modern catchment average elevation (~5 km). This result is similar to late Miocene paleoelevation data from the Zhada basin ~850 km along strike to the west and shows that more than one area of the northern Himalaya experienced elevation loss during the late Neogene.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-356192

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