Kinematics of the Greater Himalayan sequence, Dhaulagiri Himal ...

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Gehrels et al. 2003), which is younger than the interpreted Neoproterozoic protolith age of both
the paragneiss and calc-silicate gneiss (Parrish & Hodges 1996; DeCelles et al. 2001). The
orthogneiss is interpreted to have been intruded during Paleozoic orogenesis on the northern
Indian margin (Gehrels et al. 2003) coeval with an Ordovician metamorphic signature preserved
locally in nearby pelitic schist (Godin et al. 2001).
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Structurally below the orthogneiss is a ~2500 m thick unit of calc-silicate gneiss (Figure
2). It is typified by the mineral assemblage: calcite, muscovite, biotite, hornblende, diopside,
scapolite, and epidote (Figure 3b) and locally contains up to 20% (by volume) leucogranitic melt
(Figure 3c). The base of the calc-silicate gneiss is characterized by an interleaving with the
structurally underlying paragneiss.
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Below the calc-silicate gneiss, is a ~1500 m thick unit (Figure 2) of quartz, feldspar,
muscovite, biotite, garnet, kyanite paragneiss (Figure 3d) that includes up to 20% (by volume)
leucogranitic melt (Figure 3e). Analyses of prograde mineral assemblages preserved locally in
these rocks suggest they reached 610˚C and were metamorphosed at a depth of 35 km as a result
of crustal thickening during Eohimalayan deformation (Vannay & Hodges 1996). The
subsequent Neohimalayan metamorphic event, associated with extrusion and decompressional
melting of the Greater Himalayan sequence, is preserved as metamorphic mineral assemblages
that yield a mean temperature 540˚C and equilibrated at a depth of 24 km (Vannay & Hodges
1996).
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The base of the pelitic gneiss is marked by a light grey on weathered and fresh surfaces,
40-50 m thick quartzite unit (Figure 2). At the scale of a hand specimen, this quartzite consists
of ribbon-like lenses of quartz, and it parts along thin biotite-rich layers spaced approximately 4-
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