scholarly journals Hydrous fluid metasomatism in spinel dunite xenoliths from the Bearpaw Mountains, Montana, USA

2019 ◽  
Keyword(s):  
Hydrous Fluid

Formation of chlor- and fluor-apatite in layered intrusions

1994 ◽  
Vol 58 (391) ◽  
pp. 299-306 ◽  
Author(s):  
R. Grant Cawthorn
Keyword(s):  
Bushveld Complex ◽  
Layered Intrusions ◽  
Early Separation ◽  
Hydrous Fluid ◽  
Interstitial Liquid ◽  
Igneous Intrusions ◽  
Analogous Process ◽  
Fluor Apatite ◽  
Mineralogical Evidence

AbstractApatite in most igneous intrusions has a high Cl/F ratio. However, chlor-apatite has been reported in the lower portions of the Bushveld and Stillwater Complexes. This has been used as evidence supporting the early separation of a Cl-rich discrete hydrous fluid in these intrusions. Mineralogical evidence is presented here to demonstrate that the Bushveld Complex, at least, formed from a nearly anhydrous magma, and did not release a hydrous fluid before apatite began to crystallize. It is suggested that apatite in the earliest cumulates equilibrated with trapped interstitial liquid, which converted it from the typical F-rich composition of cumulus apatite to a Cl-rich composition. This is an analogous process to that in which cumulus mafic minerals may become more Fe-rich on cooling and reaction with interstitial liquid.

Monazite-(Ce) and xenotime-(Y) microinclusions in fluorapatite of the pegmatites from the Volta Grande mine, Minas Gerais state, southeast Brazil, as witnesses of the dissolution–reprecipitation process

2019 ◽  
Vol 83 (4) ◽  
pp. 595-606 ◽  
Author(s):  
Felipe Emerson André Alves ◽  
Reiner Neumann ◽  
Ciro Alexandre Ávila ◽  
Fabiano Richard Leite Faulstich
Keyword(s):  
Electron Probe ◽  
Minas Gerais ◽  
Compositional Variation ◽  
Partial Removal ◽  
Hydrous Fluid ◽  
Southeast Brazil ◽  
Pegmatite Body ◽  
Minas Gerais State ◽  
Fluorapatite Structure ◽  
Mineralogical Assemblage

AbstractFluorapatite with monazite-(Ce) and xenotime-(Y) microinclusions occurs in the lithium–caesium–tantalum pegmatite body A of the Volta Grande mine, Minas Gerais state, Southeast Brazil. The fluorapatite displays faint zoning, detected mainly by cathodoluminescence. Electron probe and laser ablation analyses indicate that zoning in the fluorapatite corresponds to variation in Mn and rare-earth element (REE) content. Such compositional variation is attributed to partial removal of the REE from the fluorapatite structure during a dissolution–reprecipitation process, forming monazite-(Ce) and xenotime-(Y) microinclusions in the REE-depleted zones of the fluorapatite. These inclusions exhibit an inherited geochemical signature, manifested by low Th and U concentrations when compared to monazite and xenotime crystallised from melts. Rhodochrosite and calcite inclusions are also associated with monazite-(Ce) and xenotime-(Y) and are probably products of the same process, recycling Ca, Mn, and CO32− from the fluorapatite through the following reaction: [Ca(5–2a–b–½x),Naa,(Y + REE)a,Mnb][(PO4)3–x(CO3)x(F)] + Fluid[a(2Ca2+ + P5+) + (x–b)(Ca2+) + H2O)] → [Ca5(PO4)3(F,OH)] + a[(Y + REE)PO4] + b[Mn(CO3)] + (x–b)[Ca(CO3)] + Fluid a[Na+].On the basis of new fluid-inclusion analyses, we propose that a hot (T > 204.5°C), salty (16 wt.% eq. NaCl, attributed to LiCl), hydrous fluid mediated the dissolution–reprecipitation of the fluorapatite. This fluid corresponds to similarly described Li-rich fluids which were suggested to have re-equilibrated the mineralogical assemblage at the Volta Grande mine.

scholarly journals Multiple origins for mantle harzburgites: examples from the Lewis Hills, Bay of Islands ophiolite, Newfoundland

1995 ◽  
Vol 32 (7) ◽  
pp. 1046-1057 ◽  
Author(s):  
Stephen J. Edwards ◽  
John Malpas
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Rock Type ◽  
Left Behind ◽  
Hydrous Fluid ◽  
Multiple Origins ◽  
Geochemical Studies ◽  
Investigative Process ◽  
Basaltic Melts

Harzburgite is a common rock type in ophiolites and alpine peridotites. It is considered to be typical of a residual mantle mineralogy, i.e., material left behind after periods of extensive mantle melting and melt–rock and fluid–rock interactions that produce a variety of basaltic melts. The processes by which these melts and residua are produced are complicated; therefore, to fully understand them, it is necessary to undertake detailed and integrated field, petrographic, and geochemical studies of large exposures of mantle material as part of the investigative process. Such a study in the Bay of Islands ophiolite exposed in the Lewis Hills of Newfoundland has enabled the identification of four major types of harzburgite, which represent examples of a complete spectrum of this rock type. Depleted, residual harzburgite and associated dunite, with positive-sloping rare earth element patterns, may develop U-shaped rare earth element patterns and a visible orthopyroxene enrichment by the introduction of a component of high-Mg, quartz-normative melt, or a hydrous fluid component with a high Si/Al ratio. Conversely, U-shaped rare earth element patterns and apparent orthopyroxene depletion may occur by the addition of low-Si/Al, hydrous fluid. Such enrichments and depletions of orthopyroxene by solution–precipitation reactions may result not only in the variety of harzburgite types, which on partial melting might produce a range of melt products, but also in fronts of harzburgite migrating through the mantle.

A celadonite-vermiculite series from the volcanic rocks of the Ochils, Stirlingshire

1977 ◽  
Vol 41 (320) ◽  
pp. 481-485 ◽  
Author(s):  
W. J. French ◽  
M. D. Hassan ◽  
J. E. Westcott
Keyword(s):  
Late Stage ◽  
Volcanic Rocks ◽  
Hydrous Fluid ◽  
Volcanic History ◽  
Sheet Silicates

SummarySpherulitic and felted green to brown minerals are described from various volcanic rocks of the Western Ochils, Stirlingshire. They fill amygdales and replace pyroxenes and appear to be an interlayered series of sheet silicates from celadonite to vermiculite. The minerals are hydrothermal in origin and suggest the presence of a potassium-rich hydrous fluid at a late stage in the volcanic history.

Hydrous fluid as the growth media of natural polycrystalline diamond, carbonado: Implication from IR spectra and microtextural observations

2012 ◽  
Vol 97 (8-9) ◽  
pp. 1366-1372 ◽  
Author(s):  
H. Ishibashi ◽  
H. Kagi ◽  
H. Sakuai ◽  
H. Ohfuji ◽  
H. Sumino
Keyword(s):  
Ir Spectra ◽  
Polycrystalline Diamond ◽  
Growth Media ◽  
Hydrous Fluid

Crystallization of high-Ca chromium garnet upon interaction of serpentine, chromite, and Ca-bearing hydrous fluid

2017 ◽  
Vol 476 (2) ◽  
pp. 1229-1232
Author(s):  
A. A. Chepurov ◽  
A. I. Turkin ◽  
N. P. Pokhilenko
Keyword(s):  
Hydrous Fluid

Stability of Na–Be minerals in late-magmatic fluids of the Ilímaussaq alkaline complex, South Greenland

2001 ◽  
pp. 145-158 ◽  
Author(s):  
Gregor Markl
Keyword(s):  
Phase Diagrams ◽  
Water Activity ◽  
Fluid Inclusions ◽  
Late Stage ◽  
Alkaline Complex ◽  
Quantitative Phase ◽  
Hydrous Fluid ◽  
Silica Activity ◽  
Magmatic Fluids ◽  
Secondary Fluid

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Markl, G. (2001). Stability of Na–Be minerals in late-magmatic fluids of the Ilímaussaq alkaline complex, South Greenland. Geology of Greenland Survey Bulletin, 190, 145-158. https://doi.org/10.34194/ggub.v190.5186 _______________ Various Na-bearing Be silicates occur in late-stage veins and in alkaline rocks metasomatised by late-magmatic fluids of the Ilímaussaq alkaline complex in South Greenland. First, chkalovite crystallised with sodalite around 600°C at 1 kbar. Late-magmatic assemblages formed between 400 and 200°C and replaced chkalovite or grew in later veins from an H2O-rich fluid. This fluid is also recorded in secondary fluid inclusions in most Ilímaussaq nepheline syenites. The late assemblages comprise chkalovite + ussingite, tugtupite + analcime ± albite, epididymite + albite, bertrandite ± beryllite + analcime, and sphaerobertrandite + albite or analcime(?). Quantitative phase diagrams involving minerals of the Na–Al–Si–O–H–Cl system and various Be minerals show that tugtupite co-exists at 400°C only with very Na-rich or very alkalic fluids [log (aNa+/aH+) > 6–8; log (aBe2+/(aH+)2) > –3]. The abundance of Na-rich minerals and of the NaOH-bearing silicate ussingite indicates the importance of both of these parameters. Water activity and silica activity in these fluids were in the range 0.7–1 and 0.05–0.3, and XNaCl in a binary hydrous fluid was below 0.2 at 400°C. As bertrandite is only stable at < 220°C at 1 kbar, the rare formation of epididymite, eudidymite, bertrandite and sphaerobertrandite by chkalovite-consuming reactions occurred at still lower temperatures and possibly involved fluids of higher silica activity.

Sign in / Sign up

Export Citation Format

Share Document