Hydrogeochemistry, Geothermometry, and Sourcing of High Dissolved Boron, Tungsten, and Chlorine Concentrations in the Trans-Himalayan Hotsprings of Ladakh, India

Boron (B) and Tungsten (W) are often found enriched in high-temperature geothermal waters associated with the development of subduction-related mafic to felsic arc magma. However, knowledge about the sourcing and transportation of these elements from such hydrothermal systems is sparse and ambiguous. Being the only active continental collision site in the world, the Trans-Himalaya offers a unique chance to study how continental collision sources the high boron and tungsten concentrations in geothermal fluids. This study investigated the distribution of trace elements, major cations, and anions in three physicochemically distinct hotspring sites in the Ladakh region. The results were integrated with the existing geochemical and isotopic data to address the research problem more effectively. This study exhibits that the extreme concentrations of boron, sodium, chlorine, potassium, and tungsten in the hotspring waters were primarily governed by magmatic fluid inputs. In addition, this study recorded the highest-ever chlorine and boron concentrations for the Trans-Himalayan hotspring waters. The highest-ever boron and chlorine concentrations in the hotspring waters probably represented an increase in magmatic activity in the deeper source zone

Large-scale mass wasting on the Miocene continental margin of western India

A giant mass-transport complex was recently discovered in the eastern Arabian Sea, exceeding in volume all but one other known complex on passive margins worldwide. The complex, named the Nataraja Slide, was drilled by International Ocean Discovery Program (IODP) Expedition 355 in two locations where it is ∼300 m (Site U1456) and ∼200 m thick (Site U1457). The top of this mass-transport complex is defined by the presence of both reworked microfossil assemblages and deformation structures, such as folding and faulting. The deposit consists of two main phases of mass wasting, each consisting of smaller pulses, with generally fining-upward cycles, all emplaced just prior to 10.8 Ma based on biostratigraphy. The base of the deposit at each site is composed largely of matrix-supported carbonate breccia that is interpreted as the product of debris-flows. In the first phase, these breccias alternate with well-sorted calcarenites deposited from a high-energy current, coherent limestone blocks that are derived directly from the Indian continental margin, and a few clastic mudstone beds. In the second phase, at the top of the deposit, muddy turbidites dominate and become increasingly more siliciclastic. At Site U1456, where both phases are seen, a 20-m section of hemipelagic mudstone is present, overlain by a ∼40-m-thick section of calcarenite and slumped interbedded mud and siltstone. Bulk sediment geochemistry, heavy-mineral analysis, clay mineralogy, isotope geochemistry, and detrital zircon U-Pb ages constrain the provenance of the clastic, muddy material to being reworked, Indus-derived sediment, with input from western Indian rivers (e.g., Narmada and Tapti rivers), and some material from the Deccan Traps. The carbonate blocks found within the breccias are shallow-water limestones from the outer western Indian continental shelf, which was oversteepened from enhanced clastic sediment delivery during the mid-Miocene. The final emplacement of the material was likely related to seismicity as there are modern intraplate earthquakes close to the source of the slide. Although we hypothesize that this area is at low risk for future mass wasting events, it should be noted that other oversteepened continental margins around the world could be at risk for mass failure as large as the Nataraja Slide