Journal ArticleDOI
A general equation for estimating Fe3+ concentrations in ferromagnesian silicates and oxides from microprobe analyses, using stoichiometric criteria
TLDR
In this article, a simple general equation is presented for estimating the Fe 3 § concentrations in ferromagnesian oxide and silicate minerals from microprobe analyses, assuming that iron is the only element present with variable valency.Abstract:
A simple general equation is presented for estimating the Fe 3 § concentrations in ferromagnesian oxide and silicate minerals from microprobe analyses. The equation has been derived using stoichiometric criteria assuming that iron is the only element present with variable valency and that oxygen is the only anion. In general, the number of Fe 3 + ions per X oxygens in the mineral formula, F, is given by; F = 2X(1 - T/S) where T is the ideal number of cations per formula unit, and S is the observed cation total per X oxygens calculated assuming all iron to be Fe 2 § Minerals for which this equation is appropriate include pyralspite and ugrandite garnet, aluminate spinel, magnetite, pyroxene, sapphirine and ilmenite. The equation cannot be used for minerals with cation vacancies (e.g. micas, maghemite) unless, as in the case of amphiboles, the number of ions of a subset of elements in the formula can be fixed. Variants of the above equation are presented for some of the numerous published schemes for the recalculation of amphibole formulae. The equation is also inappropriate for minerals showing SP += 4H § substitution (e.g. staurolite, hydrogarnet), minerals containing an unknown proportion of an unanalysed element other than oxygen (e.g. boron-bearing kornerupine) and minerals containing two or more elements with variable valency.read more
Citations
More filters
Journal ArticleDOI
A duality of timescales: Short-lived ultrahigh temperature metamorphism preserving a long-lived monazite growth history in the Grenvillian Musgrave–Albany–Fraser Orogen
TL;DR: In situ LA-ICP-MS U-Pb monazite geochronology from the eastern Musgrave Inlier, central Australia, suggests that high- T, suprasolidus conditions were maintained for >70 myr during the Grenvillian (c. 1220-1140) Ma.
Journal ArticleDOI
207Pb-206Pb, 40Ar-39Ar and Fission-Track Geothermochronology Quantifying Cooling and Exhumation History of the Kaman-Kırşehir Region Intrusions, Central Anatolia, Turkey
TL;DR: The Kaman-Kirsehir region intrusions were generated in a post-collisional extensional setting following Cenomanian-Turonian docking of an oceanic island arc, comprising the supra-subduction zone (SSZ) Central Anatolian ophiolite (CAO), onto the Tauride-Anatolide Platform (TAP).
Journal ArticleDOI
Role of H2O in the formation of garnet coronas during near‐isobaric cooling of mafic granulites: the Tasiusarsuaq terrane, southern West Greenland
TL;DR: The Mesoarchaean Tasiusarsuaq terrane of southern West Greenland consists of Tonalite-trondhjemite-granodiorite gneisses and, locally, polymetamorphic mafic and ultramafic rocks.
Journal ArticleDOI
Compositional variation of Fe-Ti oxides from the Sokli complex, northeastern Finland
TL;DR: The phoscorite-carbonatite complex at Sokli, northeastern Finland, is composed of five stages of intrusions of phoscarites and carbonatites (P1-C1, P2-C2, P3-C3, D4 and D5 dolomite carbonatite) which are cut by numerous lamprophyric dikes as discussed by the authors.
Journal ArticleDOI
Contrasting P-T-t paths from a Paleoproterozoic metamorphic orogen: Petrology, phase equilibria, zircon and monazite geochronology of metapelites from the Jiao-Liao-Ji belt, North China Craton
Yi Zou,Mingguo Zhai,M. Santosh,M. Santosh,Li-Gang Zhou,Lei Zhao,Jun-Sheng Lu,Bo Liu,Houxiang Shan +8 more
TL;DR: In this paper, an isobaric cooling followed by a final decompression is defined from high grade metapelites in the Jingshan Group at the southern part of the Jiao-Liao-Ji belt.
References
More filters
Journal ArticleDOI
Origin of Basalt Magmas: An Experimental Study of Natural and Synthetic Rock Systems
H. S. Yoder,C. E. Tilley +1 more
Journal ArticleDOI
The iron-titanium oxides of salic volcanic rocks and their associated ferromagnesian silicates
TL;DR: In this article, the coexisting microphenocrysts of magnetite and ilmenite together with the ferromagnesian silicates in salic volcanic rocks have been analyzed with the electron microprobe.
Journal ArticleDOI
Omphacite in Californian metamorphic rocks
TL;DR: Omphacite is a common mineral in greenstones, metasediments and related Franciscan rocks of the glaucophane schist facies as discussed by the authors, and it also occurs in late veins cutting amphibolites, glaucaphane schists, eclogites, greenstones and occasionally metagraywackes.