Geobarometric constraints on the depth of emplacement of granite from the Ladakh batholith, Northwest Himalaya, India.

Thermal evolution and exhumation of the Ladakh Batholith, northwest Himalaya, India

“…Cations were initially calculated on the basis of 23 oxygens and then recalculated to account for ferric iron. The measured amphibole compositional data are in excellent agreement with published data (Jowhar, 2001;Singh et al, 2007) (Fig. 3).…”

“…The recalculated pressure and depth calculations from the studies of Jowhar, (2001) and Singh et al (2007) vary from those previously published due to the temperature effect and the fact that Fe 2+ and Fe 3+ are calculated by charge balance and normalised amphibole composition to 13 cations. Samples with Na+Ca (M4) < 2.0±0.1 were not considered further due to potential alteration, this included LB17 (Singh et al, 2007).…”

“…The batholith has been studied in some detail; from its origin and the timing of crystallisation (Honegger et al, 1982;Rolland et al, 2002;Singh et al, 2007;St. Onge et al, 2010) to its emplacement (Jowhar, 2001;Singh et al, 2007) and exhumation history (Choubey, 1987;Kirstein et al, 2006;Kumar et al, 2007) making it an ideal location to investigate the thermal evolution of part of the potentially dissected plateau region and question the apparent regional steady and slow denudation since the Eocene. Previous models of emplacement and exhumation are complex and vary significantly.…”

“…The Al-in-hornblende barometer is specifically calibrated for the assemblage quartz + alkali feldspar + plagioclase + hornblende + biotite + iron oxide + titanite + melt + fluid (Schmidt, 1992;Anderson and Smith, 1995) and is ideal for application to the granites and granodiorites of Ladakh. Here we present new amphibole compositional data from five samples across the Ladakh Batholith and recalculate previously published depth of emplacement data (Jowhar, 2001;Singh et al, 2007) using the Al-in-hornblende equation of Anderson and Smith (1995) which incorporates the effect of temperature for samples of appropriate bulk mineral assemblage (Table 1, 2).…”

Computer Programs for P-T History of Metamorphic Rocks using Pseudosection Approach

“…Conventional geothermobarometry (inverse modeling) uses the equilibrium thermodynamics of balanced chemical reactions between end-members of minerals, combined with the observed compositions of minerals [5] [6] [7]. Whereas in contrast, pseudosections involve a forward calculation of mineral equilibria for a given rock composition.…”