Subduction-related Manipur Ophiolite Complex, Indo-Myanmar Ranges: elemental and isotopic record of mantle metasomatism
Published:September 25, 2019
Oinam Kingson, Rajneesh Bhutani, S. Balakrishnan, J. K. Dash, Anil D. Shukla, 2019. "Subduction-related Manipur Ophiolite Complex, Indo-Myanmar Ranges: elemental and isotopic record of mantle metasomatism", Crustal Architecture and Evolution of the Himalaya–Karakoram–Tibet Orogen, Rajesh Sharma, Igor M. Villa, Santosh Kumar
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This study reports, for the first time, Sr and Nd isotope ratios from the mafic rocks in the Manipur Ophiolite Complex (MOC), along with new elemental abundances to show the subduction zone influence. The initial 87Sr/86Sr ratios (for t = 127 Ma) range from 0.705230 to 0.709734. The initial 143Nd/144Nd and ɛNdt (t = 127 Ma) range from 0.512611 to 0.512900 and +2.7 to +8.3, respectively. The high field strength element (HFSE) ratios vary widely, with Nb/Ta ranging from c. 3 to 18 and Zr/Hf ranging from 20 to 41, indicating fluid–rock interaction in the presence of rutile. The correlated variation in the Nd and Sr isotope ratios and the HFSEs, including TiO2, reflects the variation in the slab-derived fluids. The light rare earth element (LREE) enriched and flat patterns yielded by the mafic rocks are modelled by varying the degree of melting of the fluid-metasomatized mantle. The subsequent influx of the slab-derived fluid at a greater depth caused the re-melting of the previously depleted wedge to produce the LREE-depleted patterns.
We propose that the geochemical variation recorded in the MOC rocks indicates the changing nature of fluid metasomatism of the mantle wedge across the subduction zone with time.
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Crustal Architecture and Evolution of the Himalaya–Karakoram–Tibet Orogen
CONTAINS OPEN ACCESS
This volume comprises 17 contributions that address the architecture and geodynamic evolution of the Himalaya–Karakoram–Tibet (HKT) system, covering wide aspects, from the active seismicity of the present day to the remnants of the Proterozoic orogen. The articles investigate the HKT system at different scales, blending field research with laboratory studies. The role of various lithospheric components and their inheritance in the geodynamic and magmatic evolution of the HKT system through time, and their links to global geological events, are studied in the field. The laboratory research focuses on the (sub-)micrometre scale, detailing micro-structural geology, crystal chemistry, geochronology, and the study of circulating fluids, their preservation (trapped in fluid inclusions) and their evolution, distribution, migration and interaction with the solid host. An orogen over 2000 km long can be understood only if the processes at the nanometre and micrometre scales are taken into account. The contributions in this volume successfully combine these scales to enhance our understanding of the HKT system.