Experimental study of concentration dependence of Ta2O5 and Nb2O5 solubility in the alkaline and carbonate solutions at T=550oC, P=500 bar and low oxygen fugacity (Co-CoO buffer)

2011 ◽  
Vol 3 (Special Issue) ◽  
pp. 1-7 ◽  
Author(s):  
N. P. Kotova
Keyword(s):  
Experimental Study ◽  
Oxygen Fugacity ◽  
Concentration Dependence ◽  
Low Oxygen ◽  
Carbonate Solutions

Experimental study of trace element partitioning between enstatite and melt in enstatite chondrites at low oxygen fugacities and 5GPa

2014 ◽  
Vol 130 ◽  
pp. 167-187 ◽  
Author(s):  
Camille Cartier ◽  
Tahar Hammouda ◽  
Régis Doucelance ◽  
Maud Boyet ◽  
Jean-Luc Devidal ◽  
...  
Keyword(s):  
Experimental Study ◽  
Trace Element ◽  
Low Oxygen ◽  
Trace Element Partitioning ◽  
Element Partitioning ◽  
Enstatite Chondrites

Problems of iron gain and loss during experimentation on natural rocks: the experimental crystallization of five lunar basalts at low pressures

1977 ◽  
Vol 286 (1336) ◽  
pp. 313-330 ◽  
Keyword(s):  
Oxygen Fugacity ◽  
Glass Tube ◽  
Oxide Content ◽  
Low Oxygen ◽  
Lunar Basalts ◽  
Purity Iron ◽  
High Purity Iron ◽  
Low Pressures ◽  
Melting Experiments ◽  
Iron Bearing

It is extremely difficult to conduct melting experiments on iron-bearing silicate compositions under conditions where the oxygen fugacity and iron oxide content of the charges are controlled precisely at the relevant values, due to reactions between the charge, the container and the adjacent atmosphere. Possible effects are illustrated by discussion of the experimental data for five lunar basalts. At low oxygen fugacities the techniques using molybdenum capsules in an atmosphere whose oxygen fugacity is controlled by passage of a CO 2 /H 2 mixture, and that of enclosing (better, sealing) the charge inside a high purity iron capsule inside a sealed, evacuated silica glass tube yield results which are relatively close to the desired run conditions.

Experimental study of NiO electrical conductivity changes under low oxygen pressures

1978 ◽  
Vol 12 (2) ◽  
pp. 183-190 ◽  
Author(s):  
R. L. Lalauze ◽  
J. H. Meunier
Keyword(s):  
Electrical Conductivity ◽  
Experimental Study ◽  
Low Oxygen

scholarly journals Experimental study of amphibole crystallization from the highly magnesian melt of Shiveluch volcano

2019 ◽  
Vol 27 (5) ◽  
pp. 476-495 ◽  
Author(s):  
A. G. Simakin ◽  
V. N. Devyatova ◽  
T. P. Salova ◽  
O. Yu. Shaposhnikova
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Oxygen Fugacity ◽  
Volcanic Rocks ◽  
Maximum Size ◽  
Rapid Quenching ◽  
Shiveluch Volcano ◽  
Modified Technique ◽  
Before And After ◽  
Partial Transfer

The paper reports results of an experimental study of amphibole crystallization from the highly magnesian andesite melt of Shiveluch volcano, Kamchatka. The experiments were carried out in IHPV at 300 MPa and 940–980°С in iron-saturated platinum capsules, using rapid quenching and temperature oscillations (in some experiments). The redox state of iron in the system was measured before and after the experiments using Mössbauer spectroscopy. The maximum size of the experimental amphibole crystals (up to 200 μm) was close to those of natural amphibole phenocrysts in the volcanic rocks of Shiveluch volcano. The experimental data show that the content of octahedrally coordinated Al (Al6) in the amphibole considerably varies with small variations in the intensive parameters (P, T, and fO2) and composition of the melt, and the maximum Al6 concentration can be evaluated only by using a reasonably large dataset of amphibole analyses. A modified 13eCNK method is suggested to calculate the values of Al6 and Fe3+/Fe2+ with regard for the Ti concentration and the probable partial transfer of Mg into site B in high-Mg amphibole. Calculations with this modified technique yield lower Fe3+/Fe2+ and higher Al6 values. Our experimental data show that the temperature of amphibole liquidus crystallization decreases from about 990 to 960°C when the oxygen fugacity drops from NNO + 1.5 to NNO + 0.4. In view of this, the transition from amphibole-bearing to anhydrous mineral assemblage in the magmas of Shiveluch volcano might have been caused by variations of the oxygen fugacity but not water. The application of our geobarometer to amphiboles from Shiveluch volcano (extrusions Krasnaya and Karan) yields the highest pressure estimate of above 1 GPa, corresponding to the P-T conditions of the melting of garnet-bearing amphibolite in the lower crust.

Experimental Study Of Phase Relations In The Ca-Ongonite From Ary-Bulak Massive (Transbaykal Region, Russia) at 700–800 °C

2020 ◽  
Author(s):  
Anna Novikova ◽  
Yana Alferyeva
Keyword(s):  
Experimental Study ◽  
Oxygen Fugacity ◽  
Phase Relationship ◽  
Phase Relations ◽  
General Tendency ◽  
Rock Samples ◽  
Volcanic Body

<p>An experimental study of three examples of the sub-volcanic body of Ary-Bulak ongonite was carried out to determine the composition of the liquidus phases and the order of crystallization of minerals. Phase relations in the samples of porphyritic ongonites (1), porphyritic ongonites with a high content of Ca and F (2)  and aphyric rocks with a high content of Ca and F (3) were studied at temperatures of 700–800 °C, a pressure of 1 kbar in Ni-NiO and Mt– Hem buffer conditions.</p><p>Rock samples have specific petrochemical aspects. In this series of rocks from (1) to (3), the general tendency is directed towards a decrease in the content of alkalis and silicon and an increase in the content of F and Ca.</p><p>Liquidus is achieved for porphyritic and aphyric ongonites with a high content of Ca and F. The liquidus phases for them are fluorite, topaz and plagioclase. Crystallization of porphyry ongonites begins at a temperature below 700 ° C.</p><p>The phase relationship and composition of the liquidus phases are independent of oxygen fugacity.</p>

Rare sulfides enriched in K, Tl and Pb from the Noril'sk and Salmagorsky complexes, Russia: new data and implications

2015 ◽  
Vol 79 (3) ◽  
pp. 799-808 ◽  
Author(s):  
Andrei Y. Barkov ◽  
Robert F. Martin ◽  
Louis J. Cabri
Keyword(s):  
Oxygen Fugacity ◽  
Compositional Data ◽  
Low Oxygen ◽  
Coexisting Phases ◽  
Hydrothermal Stage ◽  
Coupled Substitution ◽  
Natural Series

AbstractNew results (compositional data and reflectance values) are reported for some rare sulfides enriched in K, Tl and Pb, which are related to djerfisherite, thalfenisite, bartonite, a “Cl-bearing bartonite”, or chlorbartonite, and also for shadlunite, from the Noril'sk and Salmagorsky complexes, Russia. Our observations and comparisons with relevant data in the literature imply that: (1) bartonite is probably a S-dominant (or Cl-free) analogue of djerfisherite; and a “Cl-bearing bartonite” and chlorbartonite are probably compositional variants of the djerfisherite–bartonite series. (2) The most probable formulae of bartonite and djerfisherite are (K,Me2+)6(Fe,Cu,Ni)25–xS26(S,Cl) and (K,Me2+)6(Fe,Cu,Ni)25–xS26(Cl,S), where 0 ≤ x ≤ 5, respectively. (3) Two independent substitution mechanisms probably operate in the natural series. A coupled substitution [Me2+ + S2– ↔ K+ + Cl–] is reflected by an observed deficit in K, accompanied by the incorporation of Me2+(Pb, Fe, or Ni) in the K site. Another mechanism is inferred to be [2Fe3+ + 〈 ↔ 3Fe2+], which assumes the existence of vacancy-type defects at the Me site. Thus, the second mechanism could possibly control the existing variations of Σ(Fe, Cu, Ni) in the range of ∼21 to 25 a.p.f.u., documented in djerfisherite- and bartonite-type minerals. The minerals analysed from Noril'sk, which are free of Cl and related to bartonite and to a Tl-dominant analogue of bartonite (unnamed species), probably crystallized from microvolumes of late fluid rich in K and Tl, under conditions of relatively low oxygen fugacity in the environment. Uniform contentss of Fe and Cu, observed in coexisting phases of normal (Cl-bearing) djerfisherite and bartonite (or Cl-free analogue of djerfisherite) at Salmagorsky imply that they reached equilibrium with regard to the distribution of these elements during crystallization. These phases probably formed as a result of fluctuations in the ratios of sulfur and chlorine fugacity in a fluid at a postmagmatic hydrothermal stage.

scholarly journals Evidence for a dominantly reducing Archaean ambient mantle from two redox proxies, and low oxygen fugacity of deeply subducted oceanic crust

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Sonja Aulbach ◽  
Alan B. Woodland ◽  
Richard A. Stern ◽  
Prokopiy Vasilyev ◽  
Larry M. Heaman ◽  
...  
Keyword(s):  
Oxygen Fugacity ◽  
Published Data ◽  
Low Oxygen ◽  
Efficient Reduction ◽  
Mid Ocean Ridge ◽  
Subducted Oceanic Crust ◽  
Carbon Recycling ◽  
Oxygen Buffer ◽  
Significant Pathway ◽  
Ocean Ridge

AbstractOxygen fugacity (ƒO2) is an intensive variable implicated in a range of processes that have shaped the Earth system, but there is controversy on the timing and rate of oxidation of the uppermost convecting mantle to its present ƒO2 around the fayalite-magnetite-quartz oxygen buffer. Here, we report Fe3+/ΣFe and ƒO2 for ancient eclogite xenoliths with oceanic crustal protoliths that sampled the coeval ambient convecting mantle. Using new and published data, we demonstrate that in these eclogites, two redox proxies, V/Sc and Fe3+/ΣFe, behave sympathetically, despite different responses of their protoliths to differentiation and post-formation degassing, seawater alteration, devolatilisation and partial melting, testifying to an unexpected robustness of Fe3+/ΣFe. Therefore, these processes, while causing significant scatter, did not completely obliterate the underlying convecting mantle signal. Considering only unmetasomatised samples with non-cumulate and little-differentiated protoliths, V/Sc and Fe3+/ΣFe in two Archaean eclogite suites are significantly lower than those of modern mid-ocean ridge basalts (MORB), while a third suite has ratios similar to modern MORB, indicating redox heterogeneity. Another major finding is the predominantly low though variable estimated ƒO2 of eclogite at mantle depths, which does not permit stabilisation of CO2-dominated fluids or pure carbonatite melts. Conversely, low-ƒO2 eclogite may have caused efficient reduction of CO2 in fluids and melts generated in other portions of ancient subducting slabs, consistent with eclogitic diamond formation ages, the disproportionate frequency of eclogitic diamonds relative to the subordinate abundance of eclogite in the mantle lithosphere and the general absence of carbonate in mantle eclogite. This indicates carbon recycling at least to depths of diamond stability and may have represented a significant pathway for carbon ingassing through time.

Two morphologies of pyrophanite in Mn-rich assemblages, Gangpur Group, India

1998 ◽  
Vol 62 (6) ◽  
pp. 847-856 ◽  
Author(s):  
B. R. Nayak ◽  
B. K. Mohapatra
Keyword(s):  
Oxygen Fugacity ◽  
Environmental Conditions ◽  
Low Oxygen ◽  
Fine Needle

AbstractPyrophanite is widely distributed in metamorphic Mn-rich rock assemblages of the Gangpur Group, India. It occurs in two distinct habits: as an independent phase, and as an exsolved phase within hematite. The well developed large sized crystals coexist with spessartine in Mn-silicate facies rocks. In contrast, the exsolved crystals occur as fine needle/bleb-like crystallites intergrown with hematite in Mn-silicate-oxide facies rocks. Compositionally the exsolved crystals are enriched in iron, present in both the ferric and ferrous states. The two morphologies of pyrophanite attest to their formation under different environmental conditions. The independent pyrophanite is formed from a Mn-Ti rich precursor under low oxygen fugacity conditions while the hematite-pyrophanite intergrowth evolved from an Fe-Mn-Ti rich precursor under higher fO2 conditions.

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