Detection of liquid H2O in vapor bubbles in reheated melt inclusions: Implications for magmatic fluid composition and volatile budgets of magmas?

The different generations of calc‐silicate assemblages formed during sequential metasomatic events make the Campiglia Marittima magmatic–hydrothermal system a prominent case study to investigate the mobility of rare earth element (REE) and other trace elements. These mineralogical assemblages also provide information about the nature and source of metasomatizing fluids. Petrographic and geochemical investigations of granite, endoskarn, and exoskarn bodies provide evidence for the contribution of metasomatizing fluids from an external source. The granitic pluton underwent intense metasomatism during post‐magmatic fluid–rock interaction processes. The system was initially affected by a metasomatic event characterized by circulation of K‐rich and Ca(‐Mg)‐rich fluids. A potassic metasomatic event led to the complete replacement of magmatic biotite, plagioclase, and ilmenite, promoting major element mobilization and crystallization of K‐feldspar, phlogopite, chlorite, titanite, and rutile. The process resulted in significant gain of K, Rb, Ba, and Sr, accompanied by loss of Fe and Na, with metals such as Cu, Zn, Sn, W, and Tl showing significant mobility. Concurrently, the increasing fluid acidity, due to interaction with Ca‐rich fluids, resulted in a diffuse Ca‐metasomatism. During this stage, a wide variety of calc‐silicates formed (diopside, titanite, vesuvianite, garnet, and allanite), throughout the granite body, along granite joints, and at the carbonate–granite contact. In the following stage, Ca‐F‐rich fluids triggered the acidic metasomatism of accessory minerals and the mobilization of high-field-strength elements (HFSE) and REE. This stage is characterized by the exchange of major elements (Ti, Ca, Fe, Al) with HFSE and REE in the forming metasomatic minerals (i.e., titanite, vesuvianite) and the crystallization of HFSE‐REE minerals. Moreover, the observed textural disequilibrium of newly formed minerals (pseudomorphs, patchy zoning, dissolution/reprecipitation textures) suggests the evolution of metasomatizing fluids towards more acidic conditions at lower temperatures. In summary, the selective mobilization of chemical components was related to a shift in fluid composition, pH, and temperature. This study emphasizes the importance of relating field studies and petrographic observations to detailed mineral compositions, leading to the construction of litho‐geochemical models for element mobilization in crustal magmatic‐hydrothermal settings.

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Composition and origin of nodules from the ≈20 ka Pomici di Base (PB)-Sarno eruption of Mt. Somma — Vesuvius, Italy

Open Geosciences ◽

10.2478/s13533-011-0059-6 ◽

2012 ◽

Vol 4 (2) ◽

Author(s):

Rita Klébesz ◽

Robert Bodnar ◽

Benedetto Vivo ◽

Kálmán Török ◽

Annamaria Lima ◽

...

Keyword(s):

Melt Inclusions ◽

Alkali Feldspar ◽

Sem Analysis ◽

Chemical Compositions ◽

Type I ◽

Type Ii ◽

Vapor Bubbles ◽

Ti Oxides ◽

Basaltic Composition ◽

Dark Green

AbstractNodules (coarse-grain “plutonic” rocks) were collected from the ca. 20 ka Pomici di Base (PB)-Sarno eruption of Mt. Somma-Vesuvius, Italy. The nodules are classified as monzonite-monzogabbro based on their modal composition. The nodules have porphyrogranular texture, and consist of An-rich plagioclase, K-feldspar, clinopyroxene (ferroan-diopside), mica (phlogopite-biotite) ± olivine and amphibole. Aggregates of irregular intergrowths of mostly alkali feldspar and plagioclase, along with mica, Fe-Ti-oxides and clinopyroxene, in the nodules are interpreted as crystallized melt pockets.Crystallized silicate melt inclusions (MI) are common in the nodules, especially in clinopyroxenes. Two types of MI have been identified. Type I consists of mica, Fe-Ti-oxides and/or dark green spinel, clinopyroxene, feldspar and a vapor bubble. Volatiles (CO2, H2O) could not be detected in the vapor bubbles by Raman spectroscopy. Type II inclusions are generally lighter in color and contain subhedral feldspar and/or glass and several opaque phases, most of which are confirmed to be oxide minerals by SEM analysis. Some of the opaque-appearing phases that are below the surface may be tiny vapor bubbles. The two types of MI have different chemical compositions. Type I MI are classified as phono-tephrite — tephri-phonolite — basaltic trachy-andesite, while Type II MI have basaltic composition. The petrography and MI geochemistry led us to conclude that the nodules represent samples of the crystal mush zone in the active plumbing system of Mt. Somma-Vesuvius that were entrained into the upwelling magma during the PB-Sarno eruption.

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Silicate melt inclusions from a mildly peralkaline granite in the Oslo paleorift, Norway

Mineralogical Magazine ◽

10.1180/minmag.1990.054.375.06 ◽

1990 ◽

Vol 54 (375) ◽

pp. 195-205 ◽

Cited By ~ 16

Author(s):

T. H. Hansteen ◽

W. J. Lustenhouwer

Keyword(s):

Fluid Inclusions ◽

Melt Inclusions ◽

Aqueous Fluid ◽

Silicate Melt ◽

Silicate Melts ◽

Magmatic Fluid ◽

Chemical Characteristics ◽

Quartz Crystals ◽

Fluid Interaction ◽

Miarolitic Cavities

AbstractThe mildy peralkaline Eikeren-Skrim granite belongs to the Permian magmatic province of the Oslo rift, south-east Norway. Euhedral quartz crystals from the abundant miarolitic cavities contain primary inclusions of partly crytallized silicate melts and coexisting primary, aqueous fluid inclusions. Micro-thermometric measurements give maximum estimates for the granite solidus of 685–705°C. Quenched silicate melt inclusions are not peralkaline, have normative Or/Ab weight ratios of 1.15–1.44 (compared to 0.49–0.80 in whole-rock samples) and F and Cl contents of 0.1 and 0.21–0.65 wt. %, respectively. Coexisting magmatic fluid inclusions are highly enriched in Na, Cl, S and to some extent K. These chemical characteristics are the results of late-magmatic melt-mineral-fluid interaction in the miarolitic cavities.

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Badzhal tin magmatic-fluid system (Far east, Russia): the transition from the granite crystallization to the hydrothermal ore deposition

Геология рудных месторождений ◽

10.31857/s0016-77706133-30 ◽

2019 ◽

Vol 61 (3) ◽

pp. 3-30

Author(s):

N. S. Bortnikov ◽

L. Ya. Aranovich ◽

S. G. Kryazhev ◽

S. Z. Smirnov ◽

V. G. Gonevchuk ◽

...

Keyword(s):

Oxygen Isotope ◽

Melt Inclusions ◽

Isotope Composition ◽

Far East ◽

Oxygen Isotope Composition ◽

Magmatic Fluid ◽

Fluid System ◽

Melt And Fluid Inclusions ◽

Isotope System ◽

Ore Deposition

With a view to reveal special characteristics of the transition stage from granite crystallization to rare-metal ore deposition it is studied Badzhal tin-bearing magmatic-fluid system of eponymously-named volcano-plutonic zone of the Middle Priamyrie. For that end the detail research of melt, fluid-melt and fluid inclusions and oxygen isotopes from minerals of granitoids from Verkne-Urmi massif from Badzhal volcano-plutonic zone and also minerals of Sn-W deposits Pravo-Urmi and Blizhnee have been carried out. The formation of greisens and hydrothermal veins were caused by the development of the integrated system associating with establishing of Verkne-Urmi granite massif which is one of a dome fold of Badzhal cryptobatholith. For the first time for tin deposits it has been followed up the transition from the magmatic phase of granite crystallization to the hydrothermal ore formation stage and the evolution of magmatic fluid from its separation from magmatic melt to Sn-W ore deposition. The direct evidence of tin-bearing fluid separation under melt crystallization is combined fluid-melt inclusions. Glass composition in inclusions shows that granites and granite-porphyry were crystallizing from acid and from limited to high-aluminous melts, that is value ASI changes from 0.95 to 1.33 and a content of alkalies varies from 6.02 up to 9.02 mass.%. Cl and F concentrations in glasses are according 0.03–0.14 and 0.14–0.44 mass.% and turned out to be higher of same in the total composition of rocks (0.02 and 0.05–0.13 mass.% in accordance). These differences indicate that Cl and F could be separated from granite melt under its crystallization and degasation. H2O content made from total deficiency electron microprobe analysis is 8–11 mass.%. This evaluation was made inclusive of a probable effect of “Na loss” (Nielsen, Sigurdson, 1981) under aqueous glass crystallization. Considering a high error of a such estimation (Devine et al., 1995), it should take to obtained values as a very approximate evaluation and consider that examined melts contained about 9,5–10,0 mass.% of H2O. The results of melt inclusion examination show that at any rate a part of melt forming magmatic rocks of Badzhal Ore Magmatic System are crystallizing at about T = 650 °C. These melts were acid, limited fluoride and meta- and high aluminous. The reason of low temperatures of its crystallization are likely a high pressure of aqua and also a increased content of F. Most likely that examined inclusions characterize the final stage of establishing of the massif, herewith at the system crystals, residual liquor and magmatic fluid phase coexist. The fluid from which greisens of Pravo-Urmi deposit formed is similar in properties to the supercritical fluid absorbing by magmatic minerals. The salinity of this fluid varying from ~9 to 12 mass.% equiv. NaCl, maximal T = 550 °C (with consideration for the temperature correction of T gom on a pressure ~1 кbar) are similar to such of magmatic fluid, which permit to connect its origin with pluton cooling. The formation of greisens and quartz-topaz veins of Pravo-Urmi deposit is related to fall of temperature of magmatic fluid from 550–450 up to 480–380 °C. The evolution of fluid deposited quartz-cassiterite veins of Blizhnee deposit, which based upon oxygen isotope composition (d18ОН2О ≈ 8.5‰) also separated from magma, was going at more subsurface conditions under much lesser pressure. That led to the gas separation of a fluid with salinity ~13 mass.% equa. NaCl under T = 420–340 °C on thin low salinity vapour and brine with concentration 33.5–37.4 mass.% equiv. NaCl. The research of oxygen isotope system testifies that oxygen isotope composition of ore-forming fluid controlled by equilibrium with granites at wide interval temperatures (from ~700 °С up to the beginning of greisen crystallization). Correspondence of measured and calculation data of the offered model indicates that the considerable volume of external fluid with other isotope characteristics which did not reach the isotope equilibrium with Verkhne-Urmi massif did not come into the magmatic isotope system. The discovered differences of physico-chemical conditions for two studied deposits are not “critical” and support an idea about their formation as the single magmatic-fluid system.

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Periodically Released Magmatic Fluids Create a Texture of Unidirectional Solidification (UST) in Ore-Forming Granite: A Fluid and Melt Inclusion Study of W-Mo Forming Sannae-Eonyang Granite, Korea

Minerals ◽

10.3390/min11080888 ◽

2021 ◽

Vol 11 (8) ◽

pp. 888

Author(s):

Jung Hun Seo ◽

Yevgeniya Kim ◽

Tongha Lee ◽

Marcel Guillong

Keyword(s):

Melt Inclusions ◽

Melt Inclusion ◽

Early Stage ◽

Fluid Pressure ◽

Unidirectional Solidification ◽

Magmatic Fluid ◽

Stability Field ◽

Fluid Loss ◽

Melt And Fluid Inclusions ◽

Magmatic Fluids

The Upper Cretaceous Sannae-Eonyang granite crystallized approximately 73 Ma and hosted the Sannae W-Mo deposit in the west and the Eonyang amethyst deposit in the east. The granite contained textural zones of miarolitic cavities and unidirectional solidification texture (UST) quartz. The UST rock sampled in the Eonyang amethyst mine consisted of (1) early cavity-bearing aplitic granite, (2) co-crystallization of feldspars and quartz in a granophyric granite, and (3) the latest unidirectional growth of larger quartz crystals with clear zonation patterns. After the UST quartz was deposited, aplite or porphyritic granite was formed, repeating the prior sequence. Fluid and melt inclusions occurring in the UST quartz and quartz phenocrysts were sampled and studied to understand the magmatic-hydrothermal processes controlling UST formation and W-Mo mineralization in the granite. The composition of melt inclusions in the quartz phenocrysts suggested that the UST was formed by fractionated late-stage granite. Some of the melt inclusions occurring in the early-stage UST quartz were associated with aqueous inclusions, indicating fluid exsolution from a granitic melt. Hypersaline brine inclusions allowed the calculation of the minimum trapping pressure of 80–2300 bars. Such a highly fluctuating fluid pressure might be potentially due to a lithostatic-hydrostatic transition of pressure-attending fluid loss during UST formation. Highly fluctuating lithostatic-hydrostatic pressures created by fluid exsolution allowed shifting of the stability field from a quartz-feldspar cotectic to a single-phase quartz. The compositions of brine fluid assemblages hosted in the quartz phenocrysts deviated from the fluids trapped in the UST quartz, especially regarding the Rb/Sr and Fe/Mn ratios and W and Mo concentrations. The study of melt and fluid inclusions in the Eonyang UST sample showed that the exsolution of magmatic fluid was highly periodic. A single pulse of magmatic fluids of variable salinities/densities might have created a single UST sequence, and a new batch of magmatic fluid exsolution would be required to create the next UST sequence.

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Vapor-bubble growth in olivine-hosted melt inclusions

American Mineralogist ◽

10.2138/am-2020-7377 ◽

2020 ◽

Vol 105 (12) ◽

pp. 1898-1919

Author(s):

Daniel J. Rasmussen ◽

Terry A. Plank ◽

Paul J. Wallace ◽

Megan E. Newcombe ◽

Jacob B. Lowenstern

Keyword(s):

Computational Model ◽

Vapor Bubble ◽

Bubble Growth ◽

Melt Inclusions ◽

Melt Inclusion ◽

Vapor Bubbles ◽

Piston Cylinder ◽

Co2 Diffusion ◽

Inclusion Modification ◽

Similar Accuracy

Abstract Melt inclusions record the depth of magmatic processes, magma degassing paths, and volatile budgets of magmas. Extracting this information is a major challenge. It requires determining melt volatile contents at the time of entrapment when working with melt inclusions that have suffered post-entrapment modifications. Several processes decrease internal melt inclusion pressure, resulting in nucleation and growth of a vapor bubble and, time permitting, diffusion of volatiles (especially CO2) into the vapor bubble. Previous studies have shown how this process may lead to most of the CO2 in the bulk melt inclusion being lost to the bubble. Without reconstruction, most of the melt inclusion data in the literature vastly underestimate the CO2 concentrations of magmas by measuring the glass phase only. Methods exist that attempt to reconstruct the entrapped CO2 contents, but they can be difficult to apply and do not always yield consistent results. Here, we explore bubble growth, evaluate CO2 reconstruction approaches, and develop improved experimental and computational approaches. Piston-cylinder experiments were conducted on olivine-hosted melt inclusions from Seguam (Alaska, U.S.A.) and Fuego (Guatemala) volcanoes at the following conditions: 500–800 MPa, 1140–1200 °C for Seguam and 1110–1140 °C for Fuego, 4–8 wt% H2O in the KBr brine filling the experimental capsules, and run durations of 10–120 min. Heated melt inclusions form well-defined S-CO2 trends consistent with degassing models. CO2 contents are enriched by a factor of ~2.5, on average, relative to those of the glasses in unheated melt inclusions, whereas S contents of heated and unheated melt inclusion glasses overlap, indicating that insignificant amounts of S partition into the vapor bubble. For naturally quenched melt inclusions, relatively low closure temperatures for CO2 diffusion enables some CO2 to enter vapor bubbles during quench, whereas higher closure temperatures for S diffusion limits its loss to vapor bubbles. We evaluate the timescales of post-entrapment processes and use the results to develop a new computational model to restore entrapped CO2 contents: melt inclusion modification corrections (MIMiC). Heated melt inclusion data are used as a benchmark to evaluate the results from MIMiC and other published methods of CO2 reconstruction. The methods perform variably well. Key advantages to our experimental technique are accurate measurements of CO2 contents and efficient rehomogenization of large quantities of melt inclusions. Our new computational model produces more accurate results than other computational methods, has similar accuracy to the Raman method of CO2 reconstruction in cases where Raman can be applied (i.e., no C-bearing phases in the bubble), and can be applied to the vast body of published melt inclusion data. To obtain the most robust data on bubble-bearing melt inclusions, we recommend taking both experimental- and MIMiC-based approaches.

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Geothermal energy and ore-forming potential of 600 °C mid-ocean-ridge hydrothermal fluids

Geology ◽

10.1130/g47791.1 ◽

2020 ◽

Vol 48 (12) ◽

pp. 1221-1225 ◽

Cited By ~ 2

Author(s):

Enikő Bali ◽

László E. Aradi ◽

Robert Zierenberg ◽

Larryn W. Diamond ◽

Thomas Pettke ◽

...

Keyword(s):

Fluid Inclusions ◽

Melt Inclusions ◽

Massive Sulfide ◽

High Energy ◽

Ore Deposits ◽

Convection Cell ◽

Free Fluid ◽

Fluid Composition ◽

Fluid Temperature ◽

In Situ Conditions

Abstract The ∼4500-m-deep Iceland Deep Drilling Project (IDDP) borehole IDDP-2 in Iceland penetrated the root of an active seawater-recharged hydrothermal system below the Mid-Atlantic Ridge. As direct sampling of pristine free fluid was impossible, we used fluid inclusions to constrain the in situ conditions and fluid composition at the bottom of the hydrothermal convection cell. The fluid temperature is ∼600 °C, and its pressure is near-hydrostatic (∼45 MPa). The fluid exists as two separate phases: an H2O-rich vapor (with an enthalpy of ∼59.4 kJ/mol) and an Fe-K–rich brine containing 2000 µg/g Cu, 3.5 µg/g Ag, 1.4 µg/g U, and 0.14 µg/g Au. Occasionally, the fluid inclusions coexist with rhyolite melt inclusions. These findings indicate that the borehole intersected high-energy steam, which is valuable for energy production, and discovered a potentially ore-forming brine. We suggest that similar fluids circulate deep beneath mid-ocean ridges worldwide and form volcanogenic massive sulfide Cu-Zn-Au-Ag ore deposits.

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Mineral-melt-fluid composition of carbonate-bearing cumulate xenoliths in Tertiary alkali basalts of southern Slovakia

Mineralogical Magazine ◽

10.1180/minmag.2007.071.1.63 ◽

2007 ◽

Vol 71 (1) ◽

pp. 63-79 ◽

Cited By ~ 11

Author(s):

V. Hurai ◽

M. Huraiová ◽

P. Konečný ◽

R. Thomas

Keyword(s):

Partial Melting ◽

Central Europe ◽

Melt Inclusions ◽

Fluid Composition ◽

Alkali Basalts ◽

Mantle Mineral ◽

Low Degree ◽

Multiphase Fluid ◽

Textural Evidence ◽

Metasomatized Mantle

AbstractTwo types of carbonatic cumulate xenoliths occur in alkali basalts of the northern part of the Carpatho-Pannonian region, Central Europe. One is dominated by Ca-Fe-Mg carbonates with randomly distributed bisulphide globules (Fe1+xS2, x = 0–0.1), Mg-Al spinel, augite, rhönite, Ni-Co-rich chalcopyrite, and a Fe(Ni,Fe)2S4 phase. The second, carbonatic pyroxenite xenolith type, is composed of diopside, subordinate fluorapatite, interstitial Fe-Mg carbonates, and accessory K-pargasite, F-Al-rich ferroan phlogopite, Mg-Al spinel, albite and K-feldspar. All accessory minerals occur in ultrapotassic dacite-trachydacite glass in primary silicate melt inclusions in diopside, together with calcio-carbonatite and CO2-N2-CO inclusions. Textural evidence is provided for multiphase fluid-melt immiscibility in both xenolith types. The carbonatic pyroxenite type is inferred to have accumulated from differentiated, volatile-rich, ultrapotassic magma derived by a very low-degree partial melting of strongly metasomatized mantle. Mineral indicators point to a genetic link between the carbonatite xenolith with olivine-fractionated, silica-undersaturated alkalic basalt ponded at the mantle-crust boundary.

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Insights from the Depths of Hawaii’s Kīlauea Volcano

Eos ◽

10.1029/2021eo155761 ◽

2021 ◽

Vol 102 ◽

Author(s):

Kate Wheeling

Keyword(s):

Melt Inclusions ◽

Kilauea Volcano ◽

Vapor Bubbles ◽

Kīlauea Volcano

One of the world’s best monitored and most active volcanos still has secrets to yield, and researchers are turning to vapor bubbles trapped in melt inclusions to find them.

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