Electrical structure across the Indus Tsangpo suture and Shyok suture zones in NW Himalaya using magnetotelluric studies

Abstract

[1] Magnetotelluric studies in the NW Himalayan region have shown anomalously high conductance of about 20,000 siemens in the crust beneath the Indus Tsangpo suture (ITS) and the adjoining Tso-Morari dome in the depth range of 1 -20 km. High heat flow and high attenuation of the seismic waves in the Himalayan crust, together with the observed high conductance indicate presence of wide spread partial melt generated from the subducted Indian crust. The Ladakh batholith appears as a resistive block to the north of ITS. A moderately conductive zone demarcates the Ladakh batholith from Karakoram batholith to the north. The similarity in the resistive structure with the results reported from the Tibetan region by Wei et al. [2001] about 1500 km to the east is rather significant, indicative of a two dimensional nature of the Himalayan collision belt, at least to the first order.

Crustal imaging of the Northwest Himalaya and its foredeep region from teleseismic events

“…The ratio is high for DDI station (> 0.30) located in the Northwest Himalaya. The medium-to-high value in the Northwest Himalaya region are consistent with a mafic/ ultramafic lower crust as inferred from other geophysical surveys (Gokarn et al 2002;Arora et al 2007). …”

“…They have found out that the Moho depth reached up to 75 km on LadakhÀKarakoram and the thickness of Moho decreased southward to 40 km near the Indo-Gangetic basin. Caldwell et al (2009) reported a mid-crustal channelized liquid flow or a lowvelocity layer (LVL) from the southern Tibet detachment to the Northwest Himalaya region, in agreement with the previous magnetotelluric (MT) study by Gokarn et al (2002) and Arora et al (2007). The MT study by Arora et al (2007) inferred the presence of a low-resistivity (5À10V) layer in the middle crust from the southern detachment to Karakoram fault (KF).…”

“…An additional source of uncertainty in the average crustal P velocity is required as a necessary input for the algorithm. For consistency, we constrained Vp to 6.8 km/sec for stations located on the Northwest Himalaya based on previous MT and seismic studies (Gokarn et al 2002;Arora et al 2007) and to 6.4 km/sec for stations located on the Indo-Gangetic plain. The parameters 'H', 'Vp/Vs' and 's' along with tectonic features are presented in table 1.…”

“…The MT study by Arora et al (2007) inferred the presence of a low-resistivity (5À10V) layer in the middle crust from the southern detachment to Karakoram fault (KF). Gokarn et al (2002) and Harinarayana et al (2004) inferred from their studies that the presence of a low-resistivity layer can be attributed to partial melts, aqueous fluid or graphite in the region. Although MT data cannot distinguish between the magmatic flow and aqueous flow, but it points to the fact that there is a large viscosity drop in the Northwest Himalaya.…”

Magnetotelluric Studies of Active Continent–Continent Collisions

“…The North West Himalaya in India has been studied as part of the HIMPROBE project that included teleseismic receiver function studies (Rai et al 2006) and MT surveys (Gokarn et al 2002a;Arora et al 2007). As in the Central Himalaya, the MT data image a dipping conductor located at the top of the underthrusting Indian Plate (Arora et al 2007).…”