![]() ![]() Vent fluids have salinities of 0.1–6 wt% salts, which provide evidence for phase separation and segregation of vapours and brines in hydrothermal systems. In contrast, Cl is usually assumed to behave conservatively in pore waters and F is precipitated in authigenic sedimentary minerals meaning it is not significantly advected into the underlying basement. Regeneration of organic matter during diagenesis releases I⁻ and Br⁻ to marine sediment pore waters, which acquire Br/Cl and I/Cl ratios of higher than seawater and can be advected into the underlying crust and lithosphere. ![]() Sequestration of I and Br by phytoplankton lead to the storage of these elements in marine sediments, which are the Earths dominant I reservoir. Seawater (3.4–3.5 wt% salt) is depleted in F, weakly enriched in I and strongly enriched in Cl and Br compared to the primitive mantle. It reviews the concentrations of F, Cl, Br and I in seawater, marine sediment pore waters, hydrothermal vent fluids, fluid inclusions from deeper in the crust, and the complementary solid-phase reservoirs of organic matter and minerals present in sediments and crustal/mantle rocks from varying depths. This chapter aims to provide a framework for understanding the distribution of halogens in the oceanic lithosphere. It is important that obtained exposure ages are carefully scrutinized in the framework of detailed field studies, including local terrace or moraine stratigraphy and regional morphostratigraphic relationships as well as in light of independent age constraints. As a result focus can shift to the geomorphic questions. The power of cosmogenic nuclide methods lies in the number of nuclides available (the radionuclides 10Be, 14C, 26Al, and 36Cl and the stable noble gases 3He and 21Ne), which allows almost every mineral and hence almost every lithology to be analyzed. Sampling strategies as well as information on individual nuclides are discussed in detail. In this paper the history and theory of surface exposure dating are reviewed followed by an extensive outline of the fields of application of the method. Landforms ranging in age from a few hundred years to tens of millions of years can be dated (depending on rock or landform weathering rates) by measuring nuclide concentrations. Cosmogenic nuclides are produced in rocks and sediment due to reactions induced by cosmic rays. In the last decades surface exposure dating using cosmogenic nuclides has emerged as a powerful tool in Quaternary geochronology and landscape evolution studies. The activity of the thyroid gland changes with age, and alterations in its function can be associated with longevity thus, peculiarities of iodine metabolism in older age are of particular interest. Iodine deficiency in organism has multiple adverse health consequences, including goitre, hypothyroidism and an increased risk of developing several types of cancer. ![]() Iodine exhibits some effects not mediated by its action in the composition of thyroid hormones and can be involved in the prevention and inhibition of tumour growth. The adequate iodine status is also an important factor in preventing thyroid disorders and maintaining proper mental and physical health in adulthood. As a component of thyroid hormones, iodine has a crucial role in prenatal and early postnatal ontogenesis due to its involvement in the regulation of neurodevelopment, maturation of the musculoskeletal and respiratory systems and the formation of cognitive function. The major effects of iodine in the organism are mediated by its action as a structural constituent of thyroid hormones, thyroxine and triiodothyronine, potent regulators of cellular metabolism and growth and development processes. Iodine is an essential micronutrient for health and maintenance of thyroid function in humans and other vertebrates. ![]()
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