Geochemical discrimination and petrogenetic affinities of dykes intruding the Ladakh batholith, NW India
Published:September 25, 2019
A. R. Heri, J. Bahl, I. M. Villa, 2019. "Geochemical discrimination and petrogenetic affinities of dykes intruding the Ladakh batholith, NW India", Crustal Architecture and Evolution of the Himalaya–Karakoram–Tibet Orogen, Rajesh Sharma, Igor M. Villa, Santosh Kumar
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Eocene dykes extending over 50 km along the southern margin of the Ladakh batholith (NW India) fall into two main groups showing different orientations, as well as different isotope and trace element geochemistry. Both dyke families formed in the same tectonic setting over a time span of approximately 4 Ma. However, each family is far from monolithic, and therefore we tested several statistical approaches to identify geochemical subgroups from rare earth element (REE) data and relate them to magmatogenetic processes.
Hierarchical clustering and multidimensional scaling calculate similarities/dissimilarities among individuals of a population. Both statistical tools, when applied to the Ladakh dykes, reflect the east–west dichotomy. However, detailed quantification of the resulting grouping varies according to input data. Normalization to chondrites yields slightly different groupings from unnormalized concentration data. Population internal REE normalization provides the most accurate grouping, as revealed by the fact that multiple samples from the same dyke are assigned the closest relatedness. Independently from normalization, east–west dichotomy is mirrored by marked differences in the degree of crustal assimilation and magma evolution, pointing to kilometre-scale geological heterogeneity. Finally, dykes intruding the Ladakh batholith 150 km SE of the present samples are geochemically similar, but cluster as a distinct group.
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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.