Experimental study of phlogopite-forming reactions in the system orthopyroxene+garnet in presence of the H2O-KCl fluids.

2020 ◽  
Author(s):  
Evgeny Limanov ◽  
Valentina Butvina ◽  
Oleg Safonov
Keyword(s):  
Experimental Study ◽  
Mantle Metasomatism ◽  
Model Systems ◽  
Major Mechanism ◽  
Al Content ◽  
Report Result ◽  
Mantle Peridotites ◽  
Gradual Disappearance ◽  
Compositional Changes ◽  
Grossular Garnet

<p>Phlogopite is accepted as a major mineral indicator of the modal metasomatism in the upper mantle within a very wide P-T range and fluid/melt compositions. It extensively forms in mantle peridotites transforming initial harzburgites and lherzolites to phlogopite wehrlites both in garnet and spinel-facies. A reaction 5En + Grt + [K<sub>2</sub>O + 2H<sub>2</sub>O in fluid] = Phl + Di (Grt – pyrope-grossular garnet CaMg<sub>2</sub>Al<sub>2</sub>Si<sub>3</sub>O<sub>12</sub>) is considered as the major mechanism for phlogopite formation in garnet-facies peridotites. This reaction is commonly accompanied by regular compositional changes of primary garnet and pyroxenes. In order to illustrate the regularities, we report result of experimental study of the phlogopite-forming reactions in the model systems pyrope-enstatite, grossular-pyrope-enstatite and knorringite-pyrope-enstatite systems in presence of a H<sub>2</sub>O-KCl fluid at pressure 3 and 5 GPa and temperatures of 900 and 1000°C. The experiments were aimed at the tracing of variations of grossular and knorringite contents in garnet, as well as Al content of pyroxenes, with variations of the KCl content in the fluid.</p><p>The increase of X<sub>KCl</sub> in the fluid is accompanied by gradual decomposition of garnet and Al-bearing enstatite in all systems. The Al<sub>2</sub>O<sub>3</sub> content in orthopyroxene decreases in the pyrope – enstatite system at 5 GPa and 900°C. In the system enstatite-pyrope-grossular at 5 GPa and 1000°C phlogopite forms at the KCl content 10 mol. % in the fluid. Further increase of the KCl content in the fluid results in gradual disappearance of garnet and orthopyroxene and stronger domination of phlogopite and clinopyroxene. Grossular content in garnet increases with the KCl concetration in the fluid up to 10 mol. %, but further increase of the KCl concentration to 20 mol. % results in decrease of the grossular content in garnet. In the system enstatite-pyrope-knorringite at the KCl content in the fluid 0 – 10 mol. %, garnet contains 8-9 mol. % of knorringite. Cr-bearing phlogopite (about 2 wt. % Cr<sub>2</sub>O<sub>3</sub>) appears in this system at 10 mol. % KCl in the fluid, and its formation results in a slight increase of the knorringite content in garnet. Because of relatively high SiO<sub>2</sub> bulk content in comparison to the typical peridotite, Cr-bearing kyanite (not spinel) forms at 20 mol. % KCl in the fluid resulting in a decrease of the knorringite content in garnet down to 3-5 mol. %. The Cr<sub>2</sub>O<sub>3</sub> content in the coexisting phlogopite concomitantly decreases by about 1 wt. %.</p><p>The above experiments reproduced some characteristic regularities in variations of garnet and pyroxene compositions in the course of phlogopite formation in mantle peridotites. The applicability of the experimental results is illustrated by examples from peridotite xenoliths from kimberlites. These effects can be applied for the quantitative and qualitative estimates of variations in K activity during the modal mantle metasomatism.</p>

Experimental Study of the Formation of Chromium-Bearing Priderite and Yimengite as Products of Modal Mantle Metasomatism

2019 ◽  
Vol 486 (2) ◽  
pp. 711-715 ◽  
Author(s):  
V. G. Butvina ◽  
S. S. Vorobey ◽  
O. G. Safonov ◽  
D. A. Varlamov ◽  
G. V. Bondarenko ◽  
...  
Keyword(s):  
Experimental Study ◽  
Mantle Metasomatism

scholarly journals Experimental study of formation of chromian priderite and yimengite as products of modal mantle metasomatism

2019 ◽  
Vol 486 (6) ◽  
pp. 709-713
Author(s):  
V. G. Butvina ◽  
S. S. Vorobey ◽  
O. G. Safonov ◽  
D. A. Varlamov ◽  
G. V. Bondarenko ◽  
...  
Keyword(s):  
Experimental Study ◽  
Upper Mantle ◽  
Mantle Peridotite ◽  
Mantle Metasomatism ◽  
Mantle Minerals ◽  
Silicate Inclusions ◽  
Chromium Spinel ◽  
Series Of Experiments ◽  
Indicator Minerals ◽  
The Relationship

The article presents the data of a series of experiments on the synthesis of exotic titanates (priderite and yimengite) as a result of the reproduction of metasomatic conditions of transformation of mantle minerals (chromite, ilmenite). It was first synthesized chromian priderite not containing Ba. The experiments showed the possibility of crystallization of this mineral as a reaction product of high-chromium spinel and rutile with potassium aqueous carbonate fluid (melt) in the upper mantle. In particular, the obtained experimental data allow us to interpret the relationship between K-Cr-priderite and carbonate-silicate inclusions in chromites of Bohemian garnet peridotites. In the experimental study of the reaction of chromite and ilmenite with aqueous potassium-carbonate fluid (melt) obtained both phases of titanates (priderite and yimengite) - indicator minerals, mantle metasomatism, which directly confirms the possibility of formation of yimengite and K-Cr-priderite and other titanates, the result of mantle metasomatism of upper mantle peridotite under conditions of the highest activity of potassium.

Mineralogy and petrology of ultramafic section of Kukesi Massif, Mirdita Ophiolite (Albania) – preliminary results

2020 ◽  
Author(s):  
Jakub Mikrut ◽  
Magdalena Matusiak-Małek ◽  
Jacek Puziewicz ◽  
Kujtim Onuzi
Keyword(s):  
Chemical Composition ◽  
Chemical Diversity ◽  
Troodos Ophiolite ◽  
Melt Extraction ◽  
Al Content ◽  
Mantle Peridotites ◽  
Wide Range ◽  
Scientific Project ◽  
Composition Of Minerals ◽  
High Degree

<p>Mirdita Ophiolite in northern Albania is a part of 30-40 km wide ophiolitic Pindos Zone in Dinaride-Hellenide part of the Alpine orogenic system (e.g. Dilek & Furnes 2009, Lithos). Mantle and crustal sections in the eastern part of this zone have Supra-Subduction Zone geochemical affinities. The goal of our study is to examine chemical diversity of rocks within Kukesi Massif and to decipher its evolution.</p><p>The Kukesi Massif is composed mostly of coarse- to medium-grained spinel harzburgites and dunite with chromite layers (e.g. Morishita et al. 2011, Lithos), locally  cross-cut by orthopyroxenite veins. Uppermost part of the sequence consist of cumulate pyroxenites and peridotites (composed of olivine, orthopyroxene, clinopyroxene and spinel). Most of the rocks are pervasively serpentinised, but degree of serpentinisation varies within the massive. Samples of peridotites and pyroxenites from over a dozen localities within the massif were collected.</p><p>Olivine occurring in the lower sections of the ophiolite has composition of Fo<sub>89.5-91.2</sub> (NiO 0.28-0.52 wt.%) in peridotites and Fo<sub>90.6-92 </sub>(NiO 0.38-0.52 wt.%) in orthopyroxenite veins. Olivine forming cumulates has Fo<sub>82.4-83.3</sub> and NiO content=0.12-0.23 wt. %. Orthopyroxene (enstatite) in mantle peridotites is Al-poor (0.05-0.08 Al a.p.f.u.) and has Mg# 90.5-91.5. Orthopyroxene from peridotite cut by orthopyroxenite veins is even poorer in Al (0.03-0.04 a.pfu) and has lower Mg# 91.1-91.7 and is chemically indistinguishable from pyroxenitic orthopyroxene. Orthopyroxene forming cumulates has Mg#=82.3-84.0 and the highest Al content among all the lithologies (0.12-0.14 a.p.f.u.). Peridotitic clinopyroxene (diopside) has Al=0.02-0.08 a.p.f.u. which corresponds well to this in orthopyroxene, but Mg# is higher – 92.5-95.4. Clinopyroxene in cumulate rocks has Al content=0.13-0.16 a.p.f.u. and Mg#=87-88. Spinel in mantle peridotites has Cr#=0.47-0.80 and is negatively correlated with Mg# (0.38 to 0.56). The cumulative spinel has lower Cr# (0.18-0.27), but the  Mg# is similar to that forming peridotite (0.38-0.45). </p><p>The orthopyroxene equilibration temperatures calculated with Witt-Eickschen & Seck (1991, CMP) algorithm, yield wide range of temperatures (800-950˚C in mantle peridotites and 950-1020˚C in cumulate peridotites suggesting its magmatic origin). Low Al content in orthopyroxene suggest that peridotites suffered from high degree of melt extraction.</p><p>Chemical composition of minerals forming rocks of Kukesi Massif is typical  for mantle sections of SSZ ophiolites (e.g. Troodos ophiolite, Batanova & Sobolev 2000, Geology). Our preliminary mineral chemical data for Kukesi ultramafics have a wider range than those previously obtained by Morishita et al. (2011, Lithos). The chemical composition of ultramafic rocks within this massif varies, which may result from variable geochemical history, but further studies are required to fully characterize the composition of Kukesi ultramafics and to reconstruct its geochemical and tectonic evolution.</p><p>This study was financed from scientific funds for years 2018-2022 as a scientific project within program “Diamond Grant” (DI 024748).</p>

Syntheses of rare K-titanates (yimengite, mathiasite and priderite) at high TP conditions: application to modal mantle metasomatism.

2020 ◽  
Author(s):  
Sofia Vorobey ◽  
Valentina Butvina ◽  
Oleg Safonov
Keyword(s):  
Upper Mantle ◽  
Mantle Metasomatism ◽  
Experimental Fact ◽  
Silicate Material ◽  
Mantle Peridotites ◽  
High Alkali ◽  
End Members ◽  
The Relationship ◽  
Principal Possibility ◽  
Metasomatized Mantle

<p>Magnetoplumbite (yimengite-hawthorneite, HAWYIM), crichtonite (lindsleyite-mathiasite, LIMA) and hollandite (priderite) minerals are exotic titanate phases, which formed during metasomatism at the conditions of high alkali activity, especially K, in the fluids in the upper mantle peridotites. The paper presents data on experiments on formation of K-end-members priderite, yimengite and mathiasite, as the result of the interaction of chromite, chromite+rutile and chromite+ilmenite assemblages in the presence of a small amount of silicate material with H<sub>2</sub>O-CO<sub>2</sub>-K<sub>2</sub>CO<sub>3</sub> fluids at 3.5 and 5 GPa and 1200°C. The experiments demonstrated the principal possibility of the formation of the titanates in the reactions of chromite with alkaline aqueous-carbonic fluids and melts. However, the formation of these phases does not proceed directly on chromite, but requires additional titanium source. The relationship between titanates is found to be a function of the activity of the potassium component in the fluid/melt. Priderite is an indicator of the highest potassium activity in the mineral-forming medium. Titanates in the run products are constantly associated with phlogopite. Experiments prove that the formation of titanates manifests the most advanced or repeated stages of metasomatism in mantle peridotites. Association of titanates with phlogopite characterizes a higher activity of the potassium component in the fluid/melt than the formation of phlogopite alone. The examples from natural associations, reviewed in the paper, well illustrate these conclusions. Experiments revealed the following features of crystallization of these phases and allowed interpretation of the titanate associations in metasomatized mantle peridotites.</p><p>(1) The principal possibility of the formation of minerals of crichtonite and magnetoplumbite groups and priderite in the reactions of chromite with alkaline aqueous-carbonic fluids and melts is confirmed. Such substances are considered as main agents of potassium metasomatism, leading to the formation of titanates in the upper mantle (Konzett et al., 2013; Rezvukhin et al., 2018).</p><p>(2) The formation of these phases does not proceed directly on chromite (e.g. Haggerty et al. 1983; Haggerty, 1983; Nixon, Condliffe, 1989), and requires additional titanium source. They are rutile and ilmenite, which are themselves usually are products of modal metasomatism of peridotites. This experimental fact demonstrates that the formation of titanates marks probably the most advanced or repeated stages of metasomatism in mantle peridotites.</p><p>(3) This is also proved by the relationships of titanates with phlogopite. Association of titanates with phlogopite characterized by a higher activity of the potassium component in the fluid/melt than the formation of phlogopite alone. Such conditions can again be created at the most advanced or repeated stages of mantle metasomatism.</p><p>(4) The relationship between titanates is also a function of the activity of the potassium component in the fluid/melt. Priderite is an indicator of the highest potassium activity in the mineral-forming medium. The above examples from natural associations (Zhou, 1986; Konzett et al., 2013; Almeida et al., 2014) well illustrate this conclusion.</p>

scholarly journals Convective evaporation of vertical films

Soft Matter ◽  
2018 ◽  
Vol 14 (9) ◽  
pp. 1665-1671 ◽  
Author(s):  
François Boulogne ◽  
Benjamin Dollet
Keyword(s):  
Experimental Study ◽  
Model Systems ◽  
Soap Films

Motivated by the evaporation of soap films, which has a significant effect on their lifetime, we performed an experimental study on the evaporation of vertical surfaces with model systems based on hydrogels.

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