| Part of a series on |
| Biogeochemical cycles |
|---|
 |
The lithium cycle (Li) is the biogeochemical cycle of lithium through the lithosphere and hydrosphere.
| Part of a series on |
| Biogeochemical cycles |
|---|
| |
The lithium cycle (Li) is the biogeochemical cycle of lithium through the lithosphere and hydrosphere.
In the diagram above, lithium sinks are described in concentrations (ppm) and displayed as boxes. [1] Fluxes are shown as arrows and are in units of moles per year. [2] Continental rocks containing lithium are dissolved, transferring lithium to rivers or secondary minerals. [2] Dissolved lithium in run-off travels to the ocean. [2] Fluid release from hydrothermal vents contributes to oceanic lithium reserves while lithium is removed from the ocean by secondary mineral formation. [2]
Lithium is widely distributed in the lithosphere and mantle as a trace element in silicate minerals. [1] Lithium concentrations are highest in the upper continental and oceanic crusts. Chemical weathering at Earth’s surface dissolves lithium in primary minerals and releases it to rivers and ground waters. Lithium can be removed from solution by formation of secondary minerals like clays, oxides, or zeolites. [1]
Rivers eventually feed into the ocean, providing approximately 50% of marine inputs. [2] The remainder of lithium inputs come from hydrothermal venting at mid-ocean ridges, where lithium is released from the mantle. [1] Secondary clay formation removes dissolved lithium from seawater to the authigenic clays [3] and to the altered oceanic crust. [1]
Lithium isotopes have potential as viable geochemical tracers for processes such as silicate rock weathering and crust/mantle recycling due to significant lithium isotope fractionation during these processes. [2]
Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the entire Solar System, and has made important contributions to the understanding of a number of processes including mantle convection, the formation of planets and the origins of granite and basalt. It is an integrated field of chemistry and geology.
A lithosphere is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time scales of up to thousands of years or more. The crust and upper mantle are distinguished on the basis of chemistry and mineralogy.
An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed, and often emplaced onto continental crustal rocks.
Isotope geochemistry is an aspect of geology based upon the study of natural variations in the relative abundances of isotopes of various elements. Variations in isotopic abundance are measured by isotope ratio mass spectrometry, and can reveal information about the ages and origins of rock, air or water bodies, or processes of mixing between them.
The iron cycle (Fe) is the biogeochemical cycle of iron through the atmosphere, hydrosphere, biosphere and lithosphere. While Fe is highly abundant in the Earth's crust, it is less common in oxygenated surface waters. Iron is a key micronutrient in primary productivity, and a limiting nutrient in the Southern ocean, eastern equatorial Pacific, and the subarctic Pacific referred to as High-Nutrient, Low-Chlorophyll (HNLC) regions of the ocean.
A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about 2,600 meters (8,500 ft) and rises about 2,000 meters (6,600 ft) above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a divergent plate boundary. The rate of seafloor spreading determines the morphology of the crest of the mid-ocean ridge and its width in an ocean basin.
The sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element (CHNOPS), being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. The global sulfur cycle involves the transformations of sulfur species through different oxidation states, which play an important role in both geological and biological processes. Steps of the sulfur cycle are:
Lithogenic silica (LSi) is silica (SiO2) derived from terrigenous rock (Igneous, metamorphic, and sedimentary), lithogenic sediments composed of the detritus of pre-existing rock, volcanic ejecta, extraterrestrial material, and minerals such silicate. Silica is the most abundant compound in the Earth's crust (59%) and the main component of almost every rock (>95%).
Fractional crystallization, or crystal fractionation, is one of the most important geochemical and physical processes operating within crust and mantle of a rocky planetary body, such as the Earth. It is important in the formation of igneous rocks because it is one of the main processes of magmatic differentiation. Fractional crystallization is also important in the formation of sedimentary evaporite rocks or simply fractional crystallization is the removal of early formed crystals from an Original homogeneous magma so that the crystals are prevented from further reaction with the residual melt.
The Troodos Ophiolite on the island of Cyprus represents a Late Cretaceous spreading axis that has since been uplifted due to its positioning on the overriding Anatolian plate at the Cyprus arc and ongoing subduction to the south of the Eratosthenes Seamount.
Reverse weathering generally refers to the formation of a clay neoformation that utilizes cations and alkalinity in a process unrelated to the weathering of silicates. More specifically reverse weathering refers to the formation of authigenic clay minerals from the reaction of 1) biogenic silica with aqueous cations or cation bearing oxides or 2) cation poor precursor clays with dissolved cations or cation bearing oxides.
Marine biogeochemical cycles are biogeochemical cycles that occur within marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. These biogeochemical cycles are the pathways chemical substances and elements move through within the marine environment. In addition, substances and elements can be imported into or exported from the marine environment. These imports and exports can occur as exchanges with the atmosphere above, the ocean floor below, or as runoff from the land.
The geochemistry of carbon is the study of the transformations involving the element carbon within the systems of the Earth. To a large extent this study is organic geochemistry, but it also includes the very important carbon dioxide. Carbon is transformed by life, and moves between the major phases of the Earth, including the water bodies, atmosphere, and the rocky parts. Carbon is important in the formation of organic mineral deposits, such as coal, petroleum or natural gas. Most carbon is cycled through the atmosphere into living organisms and then respirated back into the atmosphere. However an important part of the carbon cycle involves the trapping of living matter into sediments. The carbon then becomes part of a sedimentary rock when lithification happens. Human technology or natural processes such as weathering, or underground life or water can return the carbon from sedimentary rocks to the atmosphere. From that point it can be transformed in the rock cycle into metamorphic rocks, or melted into igneous rocks. Carbon can return to the surface of the Earth by volcanoes or via uplift in tectonic processes. Carbon is returned to the atmosphere via volcanic gases. Carbon undergoes transformation in the mantle under pressure to diamond and other minerals, and also exists in the Earth's outer core in solution with iron, and may also be present in the inner core.
Carbonate-associated sulfates (CAS) are sulfate species found in association with carbonate minerals, either as inclusions, adsorbed phases, or in distorted sites within the carbonate mineral lattice. It is derived primarily from dissolved sulfate in the solution from which the carbonate precipitates. In the ocean, the source of this sulfate is a combination of riverine and atmospheric inputs, as well as the products of marine hydrothermal reactions and biomass remineralisation. CAS is a common component of most carbonate rocks, having concentrations in the parts per thousand within biogenic carbonates and parts per million within abiogenic carbonates. Through its abundance and sulfur isotope composition, it provides a valuable record of the global sulfur cycle across time and space.
The silica cycle is the biogeochemical cycle in which biogenic silica is transported between the Earth's systems. Silicon is considered a bioessential element and is one of the most abundant elements on Earth. The silica cycle has significant overlap with the carbon cycle and plays an important role in the sequestration of carbon through continental weathering, biogenic export and burial as oozes on geologic timescales.
Earth's crustal evolution involves the formation, destruction and renewal of the rocky outer shell at that planet's surface.
Trace metal stable isotope biogeochemistry is the study of the distribution and relative abundances of trace metal isotopes in order to better understand the biological, geological, and chemical processes occurring in an environment. Trace metals are elements such as iron, magnesium, copper, and zinc that occur at low levels in the environment. Trace metals are critically important in biology and are involved in many processes that allow organisms to grow and generate energy. In addition, trace metals are constituents of numerous rocks and minerals, thus serving as an important component of the geosphere. Both stable and radioactive isotopes of trace metals exist, but this article focuses on those that are stable. Isotopic variations of trace metals in samples are used as isotopic fingerprints to elucidate the processes occurring in an environment and answer questions relating to biology, geochemistry, and medicine.
The fluorine cycle is the series of biogeochemical processes through which fluorine moves through the lithosphere, hydrosphere, atmosphere, and biosphere. Fluorine originates from the Earth’s crust, and its cycling between various sources and sinks is modulated by a variety of natural and anthropogenic processes.
In geology, silicification is a petrification process in which silica-rich fluids seep into the voids of Earth materials, e.g., rocks, wood, bones, shells, and replace the original materials with silica (SiO2). Silica is a naturally existing and abundant compound found in organic and inorganic materials, including Earth's crust and mantle. There are a variety of silicification mechanisms. In silicification of wood, silica permeates into and occupies cracks and voids in wood such as vessels and cell walls. The original organic matter is retained throughout the process and will gradually decay through time. In the silicification of carbonates, silica replaces carbonates by the same volume. Replacement is accomplished through the dissolution of original rock minerals and the precipitation of silica. This leads to a removal of original materials out of the system. Depending on the structures and composition of the original rock, silica might replace only specific mineral components of the rock. Silicic acid (H4SiO4) in the silica-enriched fluids forms lenticular, nodular, fibrous, or aggregated quartz, opal, or chalcedony that grows within the rock. Silicification happens when rocks or organic materials are in contact with silica-rich surface water, buried under sediments and susceptible to groundwater flow, or buried under volcanic ashes. Silicification is often associated with hydrothermal processes. Temperature for silicification ranges in various conditions: in burial or surface water conditions, temperature for silicification can be around 25°−50°; whereas temperatures for siliceous fluid inclusions can be up to 150°−190°. Silicification could occur during a syn-depositional or a post-depositional stage, commonly along layers marking changes in sedimentation such as unconformities or bedding planes.
Silicon isotope biogeochemistry is the study of environmental processes using the relative abundance of Si isotopes. As the relative abundance of Si stable isotopes varies among different natural materials, the differences in abundance can be used to trace the source of Si, and to study biological, geological, and chemical processes. The study of stable isotope biogeochemistry of Si aims to quantify the different Si fluxes in the global biogeochemical silicon cycle, to understand the role of biogenic silica within the global Si cycle, and to investigate the applications and limitations of the sedimentary Si record as an environmental and palaeoceanographic proxy.