Mixed-valent iron [Fe(II)-Fe(III)] minerals such as magnetite and green rust have received a significant amount of attention over recent decades, especially in the environmental sciences. These mineral phases are intrinsic and essential parts of biogeochemical cycling of metals and organic carbon and play an important role regarding the mobility, toxicity, and redox transformation of organic and inorganic pollutants. The formation pathways, mineral properties, and applications of magnetite and green rust are currently active areas of research in geochemistry, environmental mineralogy, geomicrobiology, material sciences, environmental engineering, and environmental remediation. These aspects ultimately dictate the reactivity of magnetite and green rust in the environment, which has important consequences for the application of these mineral phases, for example in remediation strategies. In this review we discuss the properties, occurrence, formation by biotic as well as abiotic pathways, characterization t...

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Magnetite and Green Rust: Synthesis, Properties, and Environmental Applications of Mixed-Valent Iron Minerals

https://eps.mcgill.ca/~crowe/downloads/Rowe_etal_2012a.pdf

Signature of coseismic decarbonation in dolomitic fault rocks of the Naukluft Thrust, Namibia

Examination of schorlomite from ijolite at Magnet Cove (USA) and silicocarbonatite at Afrikanda (Russia), using electron-microprobe and hydrogen analyses, X-ray diffraction and Mossbauer spectroscopy, shows the complexity of substitution mechanisms operating in Ti-rich garnets These substitutions involve incorporation of Na in the eightfold-coordinated X site, Fe2+ and Mg in the octahedrally coordinated Y site, and Fe3+, Al and Fe2+ in the tetrahedrally coordinated Z site Substitutions Ti4+Fe3+Fe3+−1Si−1 and Ti4+Al3+Fe3+−1Si−1 are of major significance to the crystal chemistry of schorlomite, whereas Fe2+ enters the Z site in relatively minor quantities (<3% Fe∑) There is no evidence (either structural or indirect, such as discrepancies between the measured and calculated Fe2+ contents) for the presence of [6]Ti3+ or [4]Ti4+ in schorlomite The simplified general formula of schorlomite can be written as Ca3Ti4+2[Si3-x(Fe3+,Al,Fe2+)
 x
 O12], keeping in mind that the notion of end-member composition is inapplicable to this mineral In the published analyses of schorlomite with low to moderate Zr contents, x ranges from 06 to 10, ie Ti4+ in the Y site is 15 mol%) proportions of andradite (Ca3Fe3+2Si3O12), morimotoite (Ca3Fe2+TiSi3O12), and Ca3MgTiSi3O12 The importance of accurate quantitative determination and assignment of Fe, Ti and other cations to the crystallographic sites for petrogenetic studies is discussed

Schorlomite: a discussion of the crystal chemistry, formula, and inter-species boundaries

Petrology and geochemistry of Zijinshan alkaline intrusive complex in Shanxi Province, western North China Craton: Implication for magma mixing of different sources in an extensional regime

The Sung Valley alkaline complex is a relatively small intrusion of Lower Cretaceous age emplaced slightly before or during the India–Antarctica break-up. It consists of ultramafic rocks (dunites, wehrlites, clinopyroxenites, uncompahgrites), mafic rocks (ijolites sensu lato ), felsic rocks (nepheline syenites) and carbonatites. The chemical composition of the mafic minerals indicates the expected enrichment in iron toward the felsic rocks. On the other hand, carbonatites feature very Mg-rich minerals, generally Cr-rich, indicating that their genesis is completely unrelated to that of mafic and felsic rocks (ijolites and nepheline syenites). The parageneses indicate that this complex was formed by batches of primitive magmas with a distinct magmatic affinity (olivine melilitites and olivine nephelinites, basanites, and possibly also carbonatites) which evolved independently, generating the observed spectrum of intrusive rocks. Clinopyroxenites have interstitial alkali feldspar and titanite, indicating that they formed from evolved feldspar-normative (phonotephritic, tephriphonolitic) magmas. The sequence perovskite–titanite and titanite–garnet noted in some ijolitic rocks indicates changes in the chemical composition of coexisting silicate melts and, most likely, an increasing f (O 2 ). The trace-element profiles of coexisting phases in interesting associations in a sample of ijolite were documented by means of LA–ICP–MS analyses.

Mineral compositions and petrogenetic evolution of the ultramafic-alkaline – carbonatitic complex of sung valley, northeastern india

Complexly zoned Ti-rich melanite-schorlomite garnets from Ambadungar carbonatite-alkalic complex, Deccan Igneous Province, Gujarat State, Western India

A note on the occurrence and formation of magnetite in the carbonatites of Sevvattur, North Arcot district, Tamil Nadu, Southern India

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R Ramasamy

Papers

Complexly zoned Ti-rich melanite-schorlomite garnets from Ambadungar carbonatite-alkalic complex, Deccan Igneous Province, Gujarat State, Western India

A note on the occurrence and formation of magnetite in the carbonatites of Sevvattur, North Arcot district, Tamil Nadu, Southern India

Problems Faced on the Exploration and Exploitation of Lignite Deposits for Thermal Power Plants near Jayamkondacholapuram, Tamil Nadu, India