Nature, age, and emplacement of the Spongtang Ophiolite, Ladakh, NW India

• Published in: Journal of the Geological Society Vol. 176; no. 2; pp. 284 - 305
• Main Authors: Catlos, Elizabeth J, Pease, Emily C, Dygert, Nick, Brookfield, Michael, Schwarz, Winfried H, Bhutani, Rajneesh, Pande, Kachan, Schmitt, Axel
• Format: Journal Article
• Language: English
• Published: Oxford Geological Society of London 01-03-2019; The Geological Society of London; Geological Society Publishing House
• Subjects: absolute age; Ar/Ar; Argon; Asia; Cenozoic; Cretaceous; dates; Earth; Earth mantle; emplacement; Geochemistry; Geochronology; geologic thermometry; harzburgite; igneous and metamorphic rocks; igneous rocks; India; Indian Peninsula; ion probe data; Jammu and Kashmir; Jurassic; Ladakh; Lava; Lead isotopes; Lithosphere; Lower mantle; major elements; Mantle; mass spectra; Mesozoic; Mid-ocean ridges; Mining; Neotethys; Obduction; oceanic lithosphere; Oceans; Olivine; ophiolite; Paleogene; peridotites; petrography; Petrology; plate collision; plutonic rocks; Polarity; Pyroxenes; Radiometric dating; Rare earth elements; Rocks; Seafloor spreading; spectra; Spinel; Spongtang Ophiolite; Spreading; spreading centers; Subduction; subduction zones; Tertiary; Thermometry; Trace elements; Triassic; U/Pb; ultramafics; Zircon; India
• ISSN: 0016-7649; 2041-479X
• DOI: 10.1144/jgs2018-085

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 40Ar/39Ar and in-situ zircon 238U-206Pb 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 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 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 40Ar/39Ar ages. Supplementary material: https://doi.org/10.6084/m9.figshare.c.4261856