scholarly journals Modelling of melt segregation processes by high-temperature centrifuging of partially molten granites-I. Melt extraction by compaction and deformation

1996 ◽  
Vol 127 (3) ◽  
pp. 616-626 ◽  
Author(s):  
N. S. Bagdassarov ◽  
A. M. Dorfman ◽  
D. B. Dingwell
Keyword(s):  
High Temperature ◽  
Melt Extraction ◽  
Melt Segregation

scholarly journals Transient rhyolite melt extraction to produce a shallow granitic pluton

2021 ◽  
Vol 7 (21) ◽  
pp. eabf0604
Author(s):  
Allen J. Schaen ◽  
Blair Schoene ◽  
Josef Dufek ◽  
Brad S. Singer ◽  
Michael P. Eddy ◽  
...  
Keyword(s):  
Time Scales ◽  
Explosive Eruptions ◽  
Upper Crust ◽  
Saturation Model ◽  
Granitic Pluton ◽  
Melt Extraction ◽  
High Silica ◽  
Melt Segregation ◽  
Zircon Saturation

Rhyolitic melt that fuels explosive eruptions often originates in the upper crust via extraction from crystal-rich sources, implying an evolutionary link between volcanism and residual plutonism. However, the time scales over which these systems evolve are mainly understood through erupted deposits, limiting confirmation of this connection. Exhumed plutons that preserve a record of high-silica melt segregation provide a critical subvolcanic perspective on rhyolite generation, permitting comparison between time scales of long-term assembly and transient melt extraction events. Here, U-Pb zircon petrochronology and 40Ar/39Ar thermochronology constrain silicic melt segregation and residual cumulate formation in a ~7 to 6 Ma, shallow (3 to 7 km depth) Andean pluton. Thermo-petrological simulations linked to a zircon saturation model map spatiotemporal melt flux distributions. Our findings suggest that ~50 km3 of rhyolitic melt was extracted in ~130 ka, transient pluton assembly that indicates the thermal viability of advanced magma differentiation in the upper crust.

Tourmaline and boron as indicators of the presence, segregation and extraction of melt in pelitic migmatites: examples from the Ryoke metamorphic belt, SW Japan

2004 ◽  
Vol 95 (1-2) ◽  
pp. 111-123 ◽  
Author(s):  
Tetsuo Kawakami
Keyword(s):  
High Temperature ◽  
Partial Melting ◽  
Correct Recognition ◽  
High Temperature Side ◽  
Metamorphic Belt ◽  
Melt Extraction ◽  
Mode Of Occurrence ◽  
Temperature Side ◽  
Sw Japan

The mode of occurrence of borosilicates and the breakdown fronts of prograde tourmaline (tourmaline-out isograd) in three anatectic migmatite regions of the Ryoke metamorphic belt, SW Japan, are reported. The breakdown of tourmaline in the migmatite zones and release of boron into the melts, followed by the extraction of the boron-bearing melts from the migmatite zones occurred throughout the Ryoke metamorphic belt. Retrograde, magmatic tourmaline in interboudin partitions filled with leucosome is useful for calculating the degree of partial melting in the migmatites. Using boron contents in the leucosomes and pelitic schists, the degree of partial melting at the migmatite front of the Aoyama area is estimated to be 12 wt.%. Extraction of the boron-bearing melt is suggested by the boron-depleted nature of the migmatites. Connection of boudinage structures probably supplied the vertical pathways of the segregated melts, and major transport of the melts was accomplished by dyking. Irregularly shaped, amoeboid tourmaline locally occurs on the high-temperature side of the tourmaline-out isograds in the Yanai and Komagane areas, implying incomplete extraction of boron-bearing melts from those areas. Discriminating retrograde from prograde tourmaline enables correct recognition of the tourmaline-out isograd. The amount of retrograde tourmaline in migmatites can potentially be used as an indicator of the degree of melt extraction from them.

scholarly journals Plagioclase peridotite or olivine-plagioclase assemblage in orogenic peridotites: its implications on high-temperature decompression of the subcontinental lithosphere-asthenosphere boundary zone

2020 ◽  
Author(s):  
Kazuhito Ozawa ◽  
Carlos Garrido ◽  
Karoly Hidas ◽  
Jean-Lois Bodinier ◽  
Tomo Aoki ◽  
...  
Keyword(s):  
High Temperature ◽  
Partial Melting ◽  
Thermal Processing ◽  
Stability Limit ◽  
Stability Field ◽  
Lithosphere Thinning ◽  
Plagioclase Peridotite ◽  
Orogenic Peridotite ◽  
Garnet Stability Field ◽  
Melt Segregation

<p>Orogenic peridotites are expected to provide direct information with high spatial resolution for a better understanding of the processes taking place in the lithosphere and asthenosphere boundary zones (LABZ), where the transfer mechanisms of heat, material, and momentum from the Earth’s interior to the surface drastically change. Plagioclase peridotite or olivine-plagioclase assemblage <em>sensu lato</em> has been reported from some orogenic peridotites. The olivine-plagioclase assemblage in fertile systems is in principle not stable even at the depth of the upper most subcontinental lithospheric mantle (SCLM) because (1) the common crustal thickness in normal non-cratonic SCLM is ~35km, (2) the Moho temperature for the mean steady-state continental geotherm is much lower than 600°C, (3) the upper stability limit of plagioclase (plagioclase to spinel facies transition) becomes shallower with decrease in temperature, and (4) kinetic barrier for subsolidus reactions in the peridotite system becomes enormous at temperatures below 600°C. The occurrence of olivine-plagioclase assemblage in some orogenic peridotite bodies, therefore, implies transient and dynamic high-temperature (>800°C) processing at depth shallower than 20km (plagioclase-spinel facies boundary at ~800°C), i.e., high-temperature decompression of LABZ up to the depth closer to the Moho. Adiabatic decompression of high-temperature LABZ leading to decompressional melting with inefficient melt segregation may give rise to plagioclase peridotite. Decompression along moderately high temperature adiabatic path or heating to allow subsolidus reactions leading to transformation of either spinel peridotites or garnet peridotites may give rise to plagioclase peridotite. However, decompression of LABZ associated with efficient cooling does not produce any olivine-plagioclase assemblage. Plagioclase peridotites thus could provide precious information on the dynamics of shallowing LABZ and underlying asthenosphere.</p><p>We have examined several orogenic peridotite complexes, Ronda, Pyrenees, Lanzo, and Horoman, to clarify the extent of shallow thermal processing based on olivine-plagioclase assemblage. The key approach of this study is searching olivine-plagioclase assemblage not only in various lithologies but also in microstructures, whose scale and mode of occurrence provide extent and strength of thermal processing in the shallow upper mantle. The wide-spread occurrence of plagioclase peridotites and localized partial melting in Lanzo suggest exhumation along high temperature adiabatic paths from the thermally structured <span>LABZ in the </span>Seiland subfacies; the predominance of plagioclase peridotites and its localized partial melting in Horoman <span>suggest </span> exhumation along variously heated paths from the garnet stability field; the moderate development of plagioclase peridotites without partial melting in Ronda suggest exhumation along variously but weekly heated paths from the spinel-garnet stability field, and the occurrence of minor plagioclase peridotites in Pyrenees suggests exhumation along cold path from the garnet-spinel facies boundaries. We propose that the extent of shallower thermal processing decreases, and thus lithosphere thinning becomes less extensive in this order.</p>

The permeability of magma mush assembled from anisotropic tabular crystals

2021 ◽  
Author(s):  
Eloïse Bretagne ◽  
Fabian B. Wadsworth ◽  
Katherine J. Dobson ◽  
Jérémie Vasseur ◽  
Jason P. Coumans
Keyword(s):  
Numerical Simulation ◽  
Granular Medium ◽  
Granular Media ◽  
Pore Space ◽  
A Priori ◽  
Spherical Particles ◽  
Natural Systems ◽  
Melt Extraction ◽  
Melt Segregation ◽  
Melt Accumulation

<p>The extraction of melt from a mush in a magma reservoir is of wide interest. All models for melt extraction from a mush require knowledge of mush permeability, and yet this remains poorly constrained. This permeability is typically calculated using the Kozeny-Carman model or variants thereof, which require a priori knowledge of the microstructural geometry. Such models are not calibrated or tested for packs of crystals of a range of shapes found in natural mush piles, leading to the potential for oversimplification of complex natural systems.</p><p>Essentially, a magma mush with minimal crystal-crystal intergrowth is composed of packed crystals where the pore space is filled with interstitial melt. Therefore, this can be studied as a granular medium. We use numerical methods to create domains of closely packed, randomly oriented cuboids in which we keep the short and intermediate axes lengths equal (i.e. square cross section) and vary the long axis magnitude. Our synthetic ‘crystals’ therefore cover the range from oblate to prolate, passing through a cubic shape. We supplement these with 3D numerical packs of spherical particles in cubic lattice arrangements or random arrangements. For the sphere packs we use various polydispersivity of sphere sizes. The permeability of all of these pack types is calculated using a numerical simulation (both LBflow and Avizo-based algorithms) with imposed periodic boundary conditions. The preliminary results suggest that the permeability of a granular medium scales with the specific surface area exclusively, without requiring prior knowledge of the geometry and size distribution of the particles.</p><p>We suggest that the model toward which we are working will allow magma mush permeability to be modelled more accurately. If our approach is embedded in existing continuum models for mush compaction and melt extraction, then more accurate estimates of melt accumulation rates prior to very large eruptions could be found.</p><p>Keywords: melt segregation, compaction, granular media, fluid flow, numerical simulation</p>

Time and tempo of melt segregation from a magma mush: evidence from the Takidani pluton (Japan)

2020 ◽  
Author(s):  
Federico Farina ◽  
Daniela Rubatto ◽  
Eva Hartung ◽  
Luca Caricchi
Keyword(s):  
High Precision ◽  
Time Lag ◽  
Magma Reservoir ◽  
Gradual Transition ◽  
Age Difference ◽  
Central Japan ◽  
Melt Extraction ◽  
Zircon Crystallization ◽  
Melt Segregation ◽  
Residual Melt

<p>The Takidani pluton is a Pleistocene intrusion representing a nearly 2 km-thick shallow level magma reservoir located in the Central Japan Alps. The pluton, which is associated with caldera-forming eruptions, is vertically zoned and composed of six distinct lithological units ranging from hornblende-bearing granodiorite to biotite granite, with silica content varying from ca. 65 to 76 wt.%. In its upper part, the intrusion is characterized by the gradual transition between equigranular and porphyritic granodiorites. Textural and geochemical evidence indicates that the porphyritic unit represents a lens of residual melt extracted from the underlying equigranular granodiorite (Hartung et al., 2017).</p><p>The time and tempo of melt extraction is determined using both high precision and high-spatial resolution U-Pb zircon geochronology, performed by CA-ID-TIMS and SIMS respectively. High precision <sup>206</sup>Pb/<sup>238</sup>U zircon ages for the two units are similar, with grains from both rocks exhibiting an age spread as large as 200-300 kyr, from ca. 1.2 to 1.5 Ma. In-situ U-Pb dating obtained by SIMS using a spot size of 20 μm reveal systematic age difference between cores and rims, highlighting two events of zircon crystallization with no substantial difference between the two units. Zircon cores from the porphyritic and equigranular granodiorites give identical ages at ca. 1.45 ± 0.06 Ma. Spot U-Pb ages from magmatic rims range between 1.29 and 1.07 Ma, with a peak of the distribution density at around 1.20 Ma.</p><p>This information, combined with Zr saturation temperatures and phase equilibria modelling, suggests that zircon cores crystallized from the magma reservoir before rheological locking and melt segregation were achieved. The segregation of the interstitial melt from the mush took place in the ca. 250 kyr between the two events of zircon crystallization. The extracted residual melt was depleted in Zr and carried entrained crystals of plagioclase and zircon from the mush. The low Zr content of this melt hindered zircon crystallization that was only possible after a time lag of 250 kyr. The youngest event of zircon crystallization at ca. 1.2 Ma was contemporaneous in the segregated melt and in the underlying mush.</p><p> </p><p>Reference: Hartung, E., Caricchi, L., Floess, D., Wallis, S., Harayama, S., Kouzmanov, K., Chiaradia, M., 2017. Evidence for residual melt extraction in the Takidani Pluton, Central Japan. J. Petrol.58, 763–788.</p>

scholarly journals Generations of Melt Extraction, Melt–Rock Interaction and High-Temperature Metasomatism Preserved in Peridotites of the ∼497 Ma Leka Ophiolite Complex, Norway

2015 ◽  
Vol 56 (9) ◽  
pp. 1797-1828 ◽  
Author(s):  
Brian O’Driscoll ◽  
Richard J. Walker ◽  
James M. D. Day ◽  
Richard D. Ash ◽  
J. Stephen Daly
Keyword(s):  
High Temperature ◽  
Ophiolite Complex ◽  
Rock Interaction ◽  
Melt Extraction

A new perspective on cumulate formation and melt extraction from mushy reservoirs: the "melt flush" model

2021 ◽  
Author(s):  
Lyderic France ◽  
Marine Boulanger
Keyword(s):  
Surface Expression ◽  
Mineral Dissolution ◽  
Igneous Rocks ◽  
Main Process ◽  
Porous Flow ◽  
Melt Extraction ◽  
Magma Reservoirs ◽  
New Perspective ◽  
Melt Segregation ◽  
Oceanic Environments

<p>Volcanism is the surface expression of extensive magmatic systems, with their intrusive counterpart representing ~80% of the total magma budget. Our knowledge of igneous processes therefore largely relies on our understanding of deep plutonic processes. In continental or oceanic environments, most of the intrusive igneous rocks bear geochemical cumulate signatures (e.g., depletion in incompatible elements, enrichment in compatible ones) that are commonly explained by minerals-melt segregation during differentiation. Nevertheless, in many cases the processes aiding melt segregation still need to be further constrained.</p><p>In oceanic environments, deformation-assisted compaction aided by melt buoyancy is the main process involved in melt extraction. However, a number of cumulative rocks are lacking any clear compaction evidence, opening the potential for the involvement of other processes. Here, relying on current descriptions of melt dynamics within oceanic magma reservoirs, i.e. the mushy nature of the reservoirs and inferred cyclic replenishment by primitive melts, we propose the involvement of a new igneous process. In the "melt flush" model, repeatedly injected fresh melts hybridize within the injected mush triggering mineral dissolution and crystallization, and concurrent partial extraction of the former interstitial melt forced out of the system by the incoming melts aided by buoyancy.</p><p>This model is consistent with the widespread occurrence of reactive porous flow (RPF) identified in oceanic igneous systems, and matches the petrographical (e.g., olivine and plagioclase dissolution) and geochemical constraints (trace element signatures) brought by natural oceanic samples. More specifically, it has been shown that RPF proceeds following melt consuming reactions that ultimately result in a progressive closure of the mush porosity. The extraction of the evolved interstitial melts replaced by more primitive ones, and the porosity closure are here proposed to account for some of the cumulative signatures observed in igneous rocks. The "melt flush" model we describe eventually adds to the other processes involved in cumulates formation from various settings like magma compaction or crystal settling.</p>

Influence of Thermo-Mechanical Processing on the Microstructure of Beryllia Dispersed Nickel Alloys

1973 ◽  
Vol 31 ◽  
pp. 184-185
Author(s):  
M.S. Grewal ◽  
S.A. Sastri ◽  
N.J. Grant
Keyword(s):  
High Temperature ◽  
Nickel Alloys ◽  
Thermomechanical Processing ◽  
Cold Work ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Mechanical Processing ◽  
Uniform Dispersion ◽  
Oxide Particles ◽  
Nickel Base

Currently there is a great interest in developing nickel base alloys with fine and uniform dispersion of stable oxide particles, for high temperature applications. It is well known that the high temperature strength and stability of an oxide dispersed alloy can be greatly improved by appropriate thermomechanical processing, but the mechanism of this strengthening effect is not well understood. This investigation was undertaken to study the dislocation substructures formed in beryllia dispersed nickel alloys as a function of cold work both with and without intermediate anneals. Two alloys, one Ni-lv/oBeo and other Ni-4.5Mo-30Co-2v/oBeo were investigated. The influence of the substructures produced by Thermo-Mechanical Processing (TMP) on the high temperature creep properties of these alloys was also evaluated.

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