Nature, Age, and Emplacement of the Spongtang Ophiolite, Ladakh, NW India

Published on 2018-10-10T22:29:18Z (GMT) by
The Spongtang ophiolite (Ladakh, NW India) constrains the nature of oceanic lithosphere before Indo–Asia collision and key stages in the development of the Himalayas. We report whole-rock <sup>40</sup>Ar/<sup>39</sup>Ar and in-situ zircon <sup>238</sup>U–<sup>206</sup>Pb ages from its crustal, upper and lower mantle sequences. Major and trace elements from harzburgite minerals suggest the ophiolite formed at a mid-ocean ridge-type spreading center, whereas published spinel compositions from Spongtang dunites are consistent with a supra-subduction zone setting. Rare Earth Element-in two-pyroxene thermometry for the harzburgite yields 1058±13°C whereas temperature from solvus-based two-pyroxene and olivine-spinel thermometry is lower (to 656°C). The distribution suggests the mantle section of the ophiolite cooled at rates of 100° Myr<sup>-1</sup> or slower. Based on ages, major and trace element geochemistry, and geospeedometric estimates, we model the origin of the Spongtang ophiolite as forming within a mid-ocean ridge-type spreading center with a spreading rate >2cm y<sup>-1</sup> in the Neo-Tethyan Ocean, possibly from the Late Triassic to Jurassic. By Early Cretaceous, the ridge experienced increasing influence of subduction beneath the Spongtang oceanic lithosphere owing to a subduction polarity reversal. Based on 238U–206Pb ages of the youngest Cenozoic zircon grain, latest obduction occurred between 64.3±0.8 Ma to 42.4±0.5 Ma, in accordance 56.7±5.2 Ma whole-rock <sup>40</sup>Ar/<sup>39</sup>Ar ages.

Cite this collection

Catlos, Elizabeth J.; Pease, Emily C.; Dygert, Nick; Brookfield, Michael; Schwarz, Winfried H.; Bhutani, Rajneesh; et al. (2018): Nature, Age, and Emplacement of the Spongtang Ophiolite, Ladakh, NW India. Geological Society of London. Collection.