Abstract
AbstractWe used a multidisciplinary approach integrating major, trace and rare earth element geochemistry, mineralogy of rocks and sediments along with the ionic composition of water reservoirs of Admiralty Bay, King George Island, to evaluate the record of water-rock interactions under Maritime Antarctic conditions. Our results showed that the ionic compositions of the streams and meltwaters predominantly reflect the atmospheric inputs, while lake waters have higher Na/Cl, Ca/Mg and HCO3/Cl ratios related to chemical weathering in lake sediments, but this did not allow for distinguishing purely silicate sources. Consistent with the trace and rare earth element data, various alteration indices and Index of Compositional Variability values denote the low degree of chemical weathering in the lake sediments. The records from the previously unexplored Mud Lake and Upper Lake suggest that the lakes of Admiralty Bay are better places to trace the impacts of a succession of environmental changes that have occurred in the watershed, while the stream channel sediments, when accompanied by water chemistry data, may provide a more representative composition of the source rocks than the lake sediments. These findings may help revealing the intensity of contemporary weathering in a colder climate with relatively few mineralogical changes accompanied by a lesser degree of elemental loss.
Highlights
Mafic rock weathering, involving chemical and physical processes, is a major process that governs the release and mobility of elements, profoundly impacting the geochemical compositions of rivers, seawater, soils and sediments under the various surface conditions of the Earth, which feed back into the long-term evolution of Earth's climate (Sharp et al 1995, Elango & Kannan 2007)
Revealing the geochemical records of mafic rock weathering in cold and dry regions such as Continental Antarctica and the sub-Antarctic has been the focus of intensive research (Marra et al 2015, Kim et al 2020), as they have implications for the effects of changing climatic conditions on the global carbon cycle on Earth and for sedimentary processes on Mars dominated by a basaltic crust (Rutledge et al 2018, Thorpe et al 2019)
The Gibbs plots constructed from the water chemistry data and the relatively higher Na+/Cl- (> 2) and Ca2+/Mg2+ (> 4) ratios of the lake waters and their outflow waters suggest that lakes waters are under the influence of both bedrock weathering and atmospheric precipitation, while the major ions of the streams and meltwaters reflect predominantly atmospheric precipitation
Summary
Mafic rock weathering (e.g. basalt), involving chemical and physical processes, is a major process that governs the release and mobility of elements, profoundly impacting the geochemical compositions of rivers, seawater, soils and sediments under the various surface conditions of the Earth, which feed back into the long-term evolution of Earth's climate (Sharp et al 1995, Elango & Kannan 2007). Revealing the geochemical records of mafic rock weathering in cold and dry regions such as Continental Antarctica and the sub-Antarctic has been the focus of intensive research (Marra et al 2015, Kim et al 2020), as they have implications for the effects of changing climatic conditions on the global carbon cycle on Earth and for sedimentary processes on Mars dominated by a basaltic crust (Rutledge et al 2018, Thorpe et al 2019). There are few studies dealing with the water and sediment geochemistry records of different
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