EVIDENCE FROM OLIVINE/MELT ELEMENT PARTITIONING THAT NONBRIDGING OXYGEN IN SILICATE MELTS ARE NOT EQUIVALENT
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dc.contributor.author | Mysen B.O. | |
dc.contributor.author | Shang J. | |
dc.date.accessioned | 2023-11-18T10:28:21Z | |
dc.date.available | 2023-11-18T10:28:21Z | |
dc.date.issued | 2005 | |
dc.identifier | https://www.elibrary.ru/item.asp?id=12092211 | |
dc.identifier.citation | Geochimica et Cosmochimica Acta, 2005, 69, 11, 2861-2875 | |
dc.identifier.issn | 0016-7037 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/41888 | |
dc.description.abstract | Partitioning of Ca, Mn, Mg, and Fe2+ between olivine and melt has been used to examine the influence of energetically nonequivalent nonbridging oxygen in silicate melts. Partitioning experiments were conducted at ambient pressure in air and 1400°C with melts in equilibrium with forsterite-rich olivine (Fo >95 mol%). The main compositional variables of the melts were NBO/T and Na/(Na+Ca). In all melts, the main structural units were of Q4, Q3, and Q2 type with nonbridging oxygen, therefore, in the Q3 and Q2 units.For melts with high Q3/Q2-abundance ratio (corresponding to NBO/T near 1), increasing Na/(Na+Ca) [and Na/(Na+Ca+Mn+Mg+Fe2+)] results in a systematic decrease of the partition coefficients, KCaol/melt, KMnol/melt, KMgol/melt, and KFe2+ol/melt, because of ordering of the network-modifying Ca, Mn, Mg, and Fe2+ among nonbridging oxygen in Q3 and Q2 structural units. This decrease is more pronounced the smaller the ionic radius of the cation. With decreasing Q3/Q2 abundance ratio (less-polymerized melts) this effect becomes less pronounced.Activity-composition relations among network-modifying cations in silicate melts are, therefore, governed by availability of energetically nonequivalent nonbridging oxygen in individual Qn-species in the melt. As a result, any composition change that enhances abundance of highly depolymerized Qn-species will cause partition coefficients to decrease. | |
dc.title | EVIDENCE FROM OLIVINE/MELT ELEMENT PARTITIONING THAT NONBRIDGING OXYGEN IN SILICATE MELTS ARE NOT EQUIVALENT | |
dc.type | Статья | |
dc.identifier.doi | 10.1016/j.gca.2004.12.028 |
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