The composition of the Earth

The Lu–Hf and Sm–Nd isotopic composition of CHUR: Constraints from unequilibrated chondrites and implications for the bulk composition of terrestrial planets

Biogenic methane formation in marine and freshwater environments: CO2 reduction vs. acetate fermentation—Isotope evidence

Magmatic fluids, both vapour and hypersaline liquid, are a primary source of many components in hydrothermal ore deposits formed in volcanic arcs. These components, including metals and their ligands, become concentrated in magmas in various ways from various sources, including subducted oceanic crust. Leaching of rocks also contributes components to the hydrothermal fluid—a process enhanced where acid magmatic vapours are absorbed by deeply circulating meteoric waters. Advances in understanding the hydrothermal systems that formed these ore deposits have come from the study of their active equivalents, represented at the surface by hot springs and volcanic fumaroles.

The role of magmas in the formation of hydrothermal ore deposits

[1] We present an estimate for the composition of the depleted mantle (DM), the source for mid-ocean ridge basalts (MORBs). A combination of approaches is required to estimate the major and trace element abundances in DM. Absolute concentrations of few elements can be estimated directly, and the bulk of the estimates is derived using elemental ratios. The isotopic composition of MORB allows calculation of parent-daughter ratios. These estimates form the “backbone” of the abundances of the trace elements that make up the Coryell-Masuda diagram (spider diagram). The remaining elements of the Coryell-Masuda diagram are estimated through the composition of MORB. A third group of estimates is derived from the elemental and isotopic composition of peridotites. The major element composition is obtained by subtraction of a low-degree melt from a bulk silicate Earth (BSE) composition. The continental crust (CC) is thought to be complementary to the DM, and ratios that are chondritic in the CC are expected to also be chondritic in the DM. Thus some of the remaining elements are estimated using the composition of CC and chondrites. Volatile element and noble gas concentrations are estimated using constraints from the composition of MORBs and ocean island basalts (OIBs). Mass balance with BSE, CC, and DM indicates that CC and this estimate of the DM are not complementary reservoirs.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2003GC000597

Composition of the depleted mantle

A Review of Hydrogen, Carbon, Nitrogen, Oxygen, Sulphur, and Chlorine Stable Isotope Fractionation Among Gaseous Molecules

Carbon and nitrogen isotopes in the mantle

https://www.ipgp.fr/~kaminski/web_doudoud/JavoyEA_EPSL_2010.pdf

The chemical composition of the Earth: Enstatite chondrite models

Using data on naturally occurring oxygen isotope fractionation among coexisting minerals in igneous and metamorphic rocks and previously derived relations, the authors deduce expressions for the temperature dependence of the isotopic disproportionation among the minerals quartz, feldspar, pyroxene, olivine, garnet, muscovite, biotite, amphibole, ilmenite, and magnetite. The expressions are only valid at temperatures greater than about 500°C. Oxygen isotope analyses on separated minerals (quartz, feldspar, pyroxene, olivine, garnet, muscovite, biotite, amphibole, ilmenite, magnetite) published prior to 1974 are reviewed and listed. The great majority of igneous and metamorphic rock samples for which three or more coexisting minerals have been analyzed separately has conserved a state of oxygen isotopic exchange equilibrium. Retrograde effects are common in plutonic and acidic volcanic rocks.

Marc Javoy

Papers

A Review of Hydrogen, Carbon, Nitrogen, Oxygen, Sulphur, and Chlorine Stable Isotope Fractionation Among Gaseous Molecules

Carbon and nitrogen isotopes in the mantle

The chemical composition of the Earth: Enstatite chondrite models

Oxygen isotope partitioning among the minerals in igneous and metamorphic rocks

The volatiles record of a “popping” rock from the Mid-Atlantic Ridge at 14°N: chemical and isotopic composition of gas trapped in the vesicles