Artículos de revistas: "Restite"

1

Zeck, H. P. "Restite-melt and mafic-felsic magma mixing and mingling in an S-type dacite, Cerro del Hoyazo, southeastern Spain". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 83, n.º 1-2 (1992): 139–44. http://dx.doi.org/10.1017/s0263593300007823.

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ABSTRACTApproximately 10-15 vol% of the Neogene Hoyazo dacite consists of Al-rich restite rock inclusions (A12O3 = 20–45%) and monocrystal inclusions derived therefrom. Restite material and dacitic melt were formed syngenetically from a (semi-)pelitic rock sequence by means of anatexis. Restite rock fragments and dacite show similar high δ18O values (13–16‰) corresponding to those found for sedimentary material. Striking monocrystal restite inclusions in the dacite rock are graphite crystals measuring a few hundred μm, 0.5–10 mm blue cordierite crystals and 2–10 mm ruby red crystals of almandine-rich garnet (1.1 ± 0.2 vol%). Although the almandine crystals are perfectly euhedral, they are identical in every respect to the crystals found in the Al-rich restite rock inclusions and cannot be crystallisation products of the magmatic melt. The dacite also contains many inclusions of quartz gabbroic and basaltoid material which contains inclusions identical to the restite material found in the dacitic glass base. Many basaltoid inclusions show well-developed chilled borders. These inclusions may represent a more mafic magma of deeper origin which mixed with some dacite magma before mingling into it.

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2

Wyborn, D. y B. W. Chappell. "The petrogenetic significance of chemically related plutonic and volcanic rock units". Geological Magazine 123, n.º 6 (noviembre de 1986): 619–28. http://dx.doi.org/10.1017/s0016756800024134.

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AbstractComagmatic granitic and volcanic rocks are divided into two types depending on whether or not the primary magma contains restite crystals. Examples of both of these types are discussed from the Lachlan Fold Belt of southeastern Australia.Volcanic rocks containing restite phenocrysts are chemically identical to the associated plutonic rocks containing the same amount of restite. The more mafic granitic rocks correspond in composition to the most phenocryst-rich volcanics (up to 60% phenocrysts), and thus cannot be cumulate rocks produced by fractional crystallization, but must represent true magma compositions. These restite-bearing magmas result from partial melting in a source region up to the rheological critical melt percentage, which we estimate to be about 40% in the S-type Hawkins Suite of volcanics.Melts which escape their restite at the source, before the critical melt percentage is reached, are able to undergo fractional crystallization in high level magma chambers by heterogeneous crystallization on chamber walls. In this case volcanic products from the top of the chamber are more felsic than the plutonic products, the plutonics are crystal cumulates and the volcanics are composed of the complementary fractionated liquid. Those phenocrysts present in the volcanics were probably eroded from the chamber walls and are less abundant (< 20%) than in the restite-retentive volcanic products.

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3

White, A. J. R. "Water, restite and granite mineralisation". Australian Journal of Earth Sciences 48, n.º 4 (agosto de 2001): 551–55. http://dx.doi.org/10.1046/j.1440-0952.2001.00878.x.

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4

Matrosova, E. А., А. А. Bendeliani, A. V. Bobrov, A. A. Kargal’tsev y Yu A. Ignat’ev. "Phase relations in the model pyrolite at 2.5, 3.0, 7.0 GPа and 1400–1800°c: evidence for the formation of high-chromium garnets". Геохимия 64, n.º 9 (20 de septiembre de 2019): 974–85. http://dx.doi.org/10.31857/s0016-7525649974-985.

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Based on study of partial melting in the model pyrolite, it is shown that garnets synthesized at 7.0 GPa in a temperature range of 1400–1800°C are characterized by an excessive Si content (in relation to 3 f.u.), stable admixture of Cr2O3, and, thus, represent a solid solution of the pyrope–majorite–knorringite composition. Increase in the Cr/Al value in the starting composition results in increase of this ratio in garnet. With increasing temperature, the concentration of Cr2O3 decreases in restite and increases in melt. Cr/Al increases in all garnets from the zone of restite and from the quenched melt aggregate. Estimates of the bulk compositions of restite formed by partial melting of the model pyrolite at 2.5 and 3.0 GPa show that the concentration of Cr in it is higher than that in the starting composition. All minerals from the zone of restite are characterized by the high Cr concentrations, and upon partial melting in the spinel-depth facies, Cr is redistributed to restite. Our results show that the formation of high-chromium garnets relates to the protolith with the high Cr/Al value formed as a residue from partial melting in the spinel-depth facies and further transported to the garnet facies.

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5

Chappell, B. W. "Compositional variation within granite suites of the Lachlan Fold Belt: its causes and implications for the physical state of granite magma". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 87, n.º 1-2 (1996): 159–70. http://dx.doi.org/10.1017/s026359330000657x.

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ABSTRACT:Granites within suites share compositional properties that reflect features of their source rocks. Variation within suites results dominantly from crystal fractionation, either of restite crystals entrained from the source, or by the fractional crystallisation of precipitated crystals. At least in the Lachlan Fold Belt, the processes of magma mixing, assimilation or hydrothermal alteration were insignificant in producing the major compositional variations within suites. Fractional crystallisation produced the complete variation in only one significant group of rocks of that area, the relatively high temperature Boggy Plain Supersuite. Modelling of Sr, Ba and Rb variations in the I-type Glenbog and Moruya suites and the S-type Bullenbalong Suite shows that variation within those suites cannot be the result of fractional crystallisation, but can be readily accounted for by restite fractionation. Direct evidence for the dominance of restite fractionation includes the close chemical equivalence of some plutonic and volcanic rocks, the presence of plagioclase cores that were not derived from a mingled mafic component, and the occurrence of older cores in many zircon crystals. In the Lachlan Fold Belt, granite suites typically evolved through a protracted phase of restite fractionation, with a brief episode of fractional crystallisation sometimes evident in the most felsic rocks. Evolution of the S-type Koetong Suite passed at about 69% SiO2 from a stage dominated by restite separation to one of fractional crystallisation. Other suites exist where felsic rocks evolved in the same way, but the more mafic rocks are absent. In terranes in which tonalitic rocks formed at high temperatures are more common, fractional crystallisation would be a more important process than was the case for the Lachlan Fold Belt.

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6

Burnham, C. Wayne. "Calculated melt and restite compositions of some Australian granites". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 83, n.º 1-2 (1992): 387–97. http://dx.doi.org/10.1017/s0263593300008051.

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ABSTRACTThe thermodynamic relations embodied in the Quasicrystalline Model of Burnham and Nekvasil (1986), as recently extended by the author, have been used to quantitatively assess the feldspar-quartz liquidus relations in two I-type (Jindabyne and Moruya) and two S-type (Bullenbalong and Dalgety) suites of Australian granites, using analytical data provided by B. W. Chappell and co-workers. Among the more notable results obtained from these calculations at a constant pressure of 5·0kbar and = 0·30 (≍2·8 wt% H2O), for purposes of comparison, are that: (1) felsic melts of remarkably uniform, but distinctive composition can be extracted from each suite, leaving solid residues in amounts up to 65 mol%; (2) all melts from both S-type suites have two feldspars plus quartz on their liquidii, whereas both I-type suites have only plagioclase plus quartz on their liquidii; (3) the total solid residue ranges from 27-63% in the Jindabyne suite, from 15–62% in the Moruya suite, from 30–65% in the Bullenbalong suite, and from 27–65% in the Dalgety suite; (4) liquidus temperatures of the S-type Bullenbalong and Dalgety melts are similar (856° and 860°C), reflecting similar feldspar compositions of An53, Or75 and An60, Or77, respectively; (5) liquidus temperatures of the I-type Jindabyne and Moruya melts, however, are distinctly different (950° and 894°C), reflecting correspondingly different plagioclase compositions of An80 and An52; (6) the calculated liquidus plagioclase composition throughout a given suite is very uniform (±1%) and amounts to as much as 46% of the total rock; and (7) these calculated liquidus and residual plagioclase compositions are also the same, within the uncertainty of measurement, as those of the plagioclase crystal-cores determined optically by A. J. R. White. The only plausible explanation for this remarkable consanguinity in plagioclase liquidus, residue, and crystal-core compositions, hence liquidus temperatures, is that the bulk of the residue is restite, in accordance with the model of White and Chappell (1977). This explanation is corroborated by the very systematic variations in the amounts of individual restite minerals with respect to total restite contents. Accordingly, those members of each suite that contain more than 60% total restite probably closely represent the bulk composition of the source rock, which is dioritic or andesitic for the Jindabyne suite, tonalitic or dacitic for the Moruya suite, pelitic metagreywacke for the Bullenbalong suite, and feldspathic metagreywacke for the Dalgety suite. As a corollary, those members with less than 60% restite must have undergone melt-restite segregation (unmixing), probably during ascent and emplacement.

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7

Barbero, L. y C. Villaseca. "The Layos Granite, Hercynian Complex of Toledo (Spain): an example of parautochthonous restite-rich granite in a granulitic area". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 83, n.º 1-2 (1992): 127–38. http://dx.doi.org/10.1017/s0263593300007811.

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ABSTRACTThe Layos Granite forms elongated massifs within the Toledo Complex of central Spain. It is late-tectonic with respect to the F2 regional phase and simultaneous with the metamorphic peak of the region, which reached a maximum temperature of 800–850°C and pressures of 400–600 MPa. Field studies indicate that this intrusion belongs to the “regional migmatite terrane granite” type. This granite is typically interlayered with sill-like veins and elongated bodies of cordierite/garnet-bearing leucogranites. Enclaves are widespread and comprise restitic types (quartz lumps, biotite, cordierite and sillimanite-rich enclaves) and refractory metamorphic country-rocks including orthogneisses, amphibolites, quartzites, conglomerates and calc-silicate rocks.These granites vary from quartz-rich tonalites to melamonzogranites and define a S-type trend on a QAP plot. Cordierite and biotite are the mafic phases of the rocks. The particularly high percentage of cordierite (10%–30%) varies inversely with the silica content. Sillimanite is a common accessory mineral, always included in cordierite, suggesting a restitic origin. The mineral chemistry of the Layos Granite is similar to that of the leucogranites and country-rock peraluminous granulites (kinzigites), indicating a close approach to equilibrium. The uniform composition of plagioclase (An25), the high albitic content of the K-feldspar, the continuous variation in the Fe/Mg ratios of the mafic minerals, and the high Ti content of the biotites (2.5–6.5%) suggest a genetic relationship.Geochemically, the Layos Granite is strongly peraluminous. Normative corundum lies between 4% and 10% and varies inversely with increase in SiO2. The CaO content is typically low (<1.25%) and shows little variation; similarly the LILE show a limited range. On many variation diagrams, linear trends from peraluminous granulites to the Layos Granite and associated leucogranite can be observed. The chemical characteristics argue against an igneous fractionation or fusion mechanism for the diversification of the Layos Granite. A restite unmixing model between a granulitic pole (represented by the granulites of the Toledo Complex) and a minimum melt (leucogranites) could explain the main chemical variation of the Layos Granite. Melting of a pelitic protolith under anhydrous conditions (biotite dehydration melting) could lead to minimum-temperature melt compositions and a strongly peraluminous residuum.For the most mafic granites (61–63% SiO2), it is estimated that the trapped restite component must have been around 65%. This high proportion of restite is close to the estimated rheological critical melt fraction, but field evidence suggests that this critical value has been exceeded. This high restite component implies high viscosity of the melt which, together with the anhydrous assemblage of the Layos Granite and the associated leucogranites, indicates H2O-undersaturated melting conditions. Under such conditions, the high viscosity magma (crystal-liquid mush) had a restricted movement capacity, leading to the development of parautochthonous plutonic bodies.

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8

CHAPPELL, B. W., A. J. R. WHITE y D. WYBORN. "The Importance of Residual Source Material (Restite) in Granite Petrogenesis". Journal of Petrology 28, n.º 6 (1 de diciembre de 1987): 1111–38. http://dx.doi.org/10.1093/petrology/28.6.1111.

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9

Wolf, Michael B. y Peter J. Wyllie. "Garnet Growth during Amphibolite Anatexis: Implications of a Garnetiferous Restite". Journal of Geology 101, n.º 3 (mayo de 1993): 357–73. http://dx.doi.org/10.1086/648229.

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10

Jumaniyozov, D. I., A. M. Musayev y S. Y. Nematullayev. "Geochemical Criteria Of Ore Content Of Metasomatites Of The Urtalik Deposit (North Nuratau)". American Journal of Social Science and Education Innovations 2, n.º 09 (10 de septiembre de 2020): 79–100. http://dx.doi.org/10.37547/tajssei/volume02issue09-12.

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On the studied site of the Urtalik ore deposit, rare, rare-earth and polymetallic mineralization is shown. Rare elements zirconium and niobium can have restite character which gets a steady state at the recrystallization of ore-bearing minerals. At the same time a rare element zirconium and a rare-earth element ytterbium selectively concentrate in the zircon and apatite respectively.

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11

Yumul, Graciano P. "Zambales Ophiolite Complex (Philippines) Transition-Zone Dunites: Restite, Cumulate, or Replacive Products?" International Geology Review 46, n.º 3 (marzo de 2004): 259–72. http://dx.doi.org/10.2747/0020-6814.46.3.259.

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12

CLEMENS, J. D. "The Importance of Residual Source Material (Restite) in Granite Petrogenesis: A Comment". Journal of Petrology 30, n.º 5 (1 de octubre de 1989): 1313–16. http://dx.doi.org/10.1093/petrology/30.5.1313.

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13

Kriegsman, Leo M. y Bas J. Hensen. "Back reaction between restite and melt: Implications for geothermobarometry and pressure-temperature paths". Geology 26, n.º 12 (1998): 1111. http://dx.doi.org/10.1130/0091-7613(1998)026<1111:brbram>2.3.co;2.

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14

Chappell, B. W. "Towards a unified model for granite genesis". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 95, n.º 1-2 (marzo de 2004): 1–10. http://dx.doi.org/10.1017/s0263593300000870.

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ABSTRACTMost granites result from partial melting within the crust. Granite melts produced at the lowest temperatures of partial melting mainly comprise close to equal amounts of the haplogranite components Qz, Ab and Or, with H2O. Many felsic granites were formed by partial melting under such conditions and are low-temperature types, with crystals of zircon and other restite minerals present in the initial magma. Such magmas evolve in composition, at least initially, through fractionation of that restite. If one of the four haplogranite components either becomes depleted or too low in amount to contribute further to the melt, then melting may proceed to higher temperatures without a contribution from that component. Melting will advance to significantly higher temperatures if there is a critical deficiency in one or more components and a high-temperature granite magma forms, in which zircon is completely soluble. Such magmas are extracted from the source in a completely molten state and may evolve by fractional crystallisation. They are monzonitic, tonalitic or A-type, depending on whether the critical deficiency occurred in the Qz, Or or H2O component. If the Ab component is critically deficient, as in pelitic rocks, the rocks may be infertile for granite production. The control that source rock compositions exert on both the physical and chemical properties of granite magmas provides a unifying element in granite gen

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15

Kohút, Milan, Holly Stein, Pavel Uher, Aaron Aimmerman y L’ubomír Hraško. "Re-Os and U-Th-Pb dating of the Rochovce granite and its mineralization (Western Carpathians, Slovakia)". Geologica Carpathica 64, n.º 1 (1 de febrero de 2013): 71–79. http://dx.doi.org/10.2478/geoca-2013-0005.

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Abstract The subsurface Rochovce granite intrusion was emplaced into the contact zone between two principal tectonic units (the Veporic Unit and the Gemeric Unit) of the Central Western Carpathians (CWC), Slovakia. The Cretaceous age of this granite and its Mo-W mineralization is shown using two independent methods: U-Pb on zircon and Re-Os on molybdenite. The studied zircons have a typical homogeneous character with oscillatory zoning and scarce restite cores. SHRIMP U-Pb data provide an age of 81.5 ± 0.7 Ma, whereas restite cores suggest a latest Neoproterozoic-Ediacaran age (~565 Ma) source. Zircon εHf(81) values -5.2 to + 0.2 suggest a lower crustal source, whereas one from the Neoproterozoic core εHf(565)= + 7.4 call for the mantle influenced old precursor. Two molybdenite- bearing samples of very different character affirm a genetic relation between W-Mo mineralization and the Rochovce granite. One sample, a quartz-molybdenite vein from the exocontact (altered quartz-sericite schist of the Ochtiná Formation), provides a Re-Os age of 81.4 ± 0.3 Ma. The second molybdenite occurs as 1-2 mm disseminations in finegrained granite, and provides an age of 81.6 ± 0.3 Ma. Both Re-Os ages are identical within their 2-sigma analytical uncertainty and suggest rapid exhumation as a consequence of post-collisional, orogen-parallel extension and unroofing. The Rochovce granite represents the northernmost occurrence of Cretaceous calc-alkaline magmatism with Mo-W mineralization associated with the Alpine-Balkan-Carpathian-Dinaride metallogenic belt.

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16

Hageskov, Bjørn y Bente Mørch. "Adakitic high-Al trondhjemites in the Proterozoic Østfold-Marstrand Belt, W Sweden". Bulletin of the Geological Society of Denmark 46 (25 de junio de 1999): 165–79. http://dx.doi.org/10.37570/bgsd-1999-46-14.

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This paper investigates the first identified intrusives in SE Norway–W Sweden with the specific signature of adakitic arc magmas, which in recent settings are preferably explained as partial melts extracted from subducted oceanic crust. The studied adakitic high–Al trondhjemites occur as sheets in the Koster archipelago, W Sweden, where they form the oldest recognized granitoids in the metasupracrustals of the Stora Le–Marstrand formation. The trondhjemites were intruded during a short ca. 1.59–1.58 Ga interlude between the early and the main orogenic events of the Gothian orogeny (1.6–1.56 Ga, Åhäll et al. 1998). This interlude is otherwise characterized by ‘ordinary’ calcalkaline magmatism which on Koster is predated by the trondhjemites. The typical adakitic signature suggests that the trondhjemitic magma was extracted from a MORB (Mid Ocean Ridge Basalt) like source, and that a hornblende eclogite restite was left in the region of melting. The restite composition indicates melt extraction at PT conditions in the range of 18–25 kb/800°C to 13-15 kb/950–1050°C. These requirement can only be met by subduction of warm (young or shear heated) oceanic crust beneath a crust including early Gothian metamorphosed and deformed Stora Le–Marstrand formation or by melting of metabasaltic material at a deep crustal level. The latter is a less likely possibility and demands that the Stora Le–Marstrand formation at the time of melt extraction was part of a > 45 km thick crust.

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17

Williamson, B. J., H. Downes, M. F. Thirlwall y A. Beard. "Geochemical constraints on restite composition and unmixing in the Velay anatectic granite, French Massif Central". Lithos 40, n.º 2-4 (julio de 1997): 295–319. http://dx.doi.org/10.1016/s0024-4937(97)00033-9.

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18

Huang, Xu-Dong, Jian-Jun Lu, Stanislas Sizaret, Ru-Cheng Wang, Jin-Wei Wu y Dong-Sheng Ma. "Reworked restite enclave: Petrographic and mineralogical constraints from the Tongshanling intrusion, Nanling Range, South China". Journal of Asian Earth Sciences 166 (octubre de 2018): 1–18. http://dx.doi.org/10.1016/j.jseaes.2018.07.001.

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19

COX, K. G. "Postulated restite fragments from Karoo picrite basalts: their bearing on magma segregation and mantle deformation". Journal of the Geological Society 144, n.º 2 (marzo de 1987): 275–80. http://dx.doi.org/10.1144/gsjgs.144.2.0275.

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20

Gorbachev, N. S., A. V. Kostyuk, A. N. Nekrasov, P. N. Gorbachev y D. M. Soultanov. "Experimental study of the system peridotite–basalt–fluid: phase relations at supra- and sepercritical P-T parameters". Петрология 27, n.º 6 (16 de diciembre de 2019): 606–16. http://dx.doi.org/10.31857/s0869-5903276606-616.

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To obtain new data on the phase relationships in the fluid-containing upper mantle at P up to 4 GPa, T up to 1400C, partial melting of H2O-containing peridotite, basalt, as well as peridotite-basalt association with an alkaline-carbonate fluid was experimentally studied as a model of the mantle reservoir with protoliths of the subdued oceanic crust. At partial melting of H2O-containing peridotite at P = 3.73.9 GPa, T = 10001300C, critical ratios were observed in the whole studied interval P and T. At partial melting of H2O-containing basalt critical relationships between the silicate melt and the aqueous fluid were observed at T = 1000C, P = 3.7 GPa. At T = 1100C, Na-alkaline silicate melt coexisted with garnetite, at T = 1150 and 1300C with clinopyroxenite. Signs of critical relationships between the carbonated silicate melt and the fluid were observed in peridotite-basalt-alkaline-water-carbonate fluid system at Р = 4 GPa, T = 1400C. The reaction ratios among the minerals of peritotite restite with the substitutions of Ol Opx Ca-Cpx K-Amf indicated a high chemical activity of the supercritical fluid melt. The results of the experiments suggest that in the fluid-containing upper mantle with supercritical Р-Т there are areas of partial melting (asthenosphere lenses), containing near-solidus supercritical fluid-melts enriched with incompatible elements, with high reactivity. Mantle reservoirs with supercritical fluid-melts, similar in geochemical terms to the enriched mantle, can serve as a source of magma enriched with incompatible elements. The modal and latent metasomatism of the upper mantle under the influence of supercritical fluid-melts leads to the peridotite refertilization due to the enrichment of restite minerals with incompatible elements and its eclogitization.

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21

Dorais, Michael J. y Christopher J. Spencer. "Revisiting the importance of residual source material (restite) in granite petrogenesis: The Cardigan Pluton, New Hampshire". Lithos 202-203 (agosto de 2014): 237–49. http://dx.doi.org/10.1016/j.lithos.2014.05.007.

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22

Beard, James S., Gary E. Lofgren, A. Krishna Sinha y Richard P. Tollo. "Partial melting of apatite-bearing charnockite, granulite, and diorite: Melt compositions, restite mineralogy, and petrologic implications". Journal of Geophysical Research: Solid Earth 99, B11 (10 de noviembre de 1994): 21591–603. http://dx.doi.org/10.1029/94jb02060.

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23

Gomez, M. D. P. y M. D. R. Alonso. "DUALITY OF CORDIERITE GRANITES RELATED TO MELT RESTITE SEGREGATION IN THE PENA NEGRA ANATECTIC COMPLEX, CENTRAL SPAIN". Canadian Mineralogist 38, n.º 6 (1 de diciembre de 2000): 1329–46. http://dx.doi.org/10.2113/gscanmin.38.6.1329.

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24

Scambos, T. A., M. C. Loiselle y D. R. Wones. "The Center Pond Pluton; the restite of the story (phase separation and melt evolution in granitoid genesis)". American Journal of Science 286, n.º 4 (1 de abril de 1986): 241–80. http://dx.doi.org/10.2475/ajs.286.4.241.

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25

DROOP, G. T. R. "Processes and Conditions During Contact Anatexis, Melt Escape and Restite Formation: the Huntly Gabbro Complex, NE Scotland". Journal of Petrology 44, n.º 6 (1 de junio de 2003): 995–1029. http://dx.doi.org/10.1093/petrology/44.6.995.

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26

Chappell, B. W., A. J. R. White, I. S. Williams y D. Wyborn. "Low- and high-temperature granites". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 95, n.º 1-2 (marzo de 2004): 125–40. http://dx.doi.org/10.1017/s0263593300000973.

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ABSTRACTI-type granites can be assigned to low- and high-temperature groups. The distinction between those groups is formally based on the presence or absence of inherited zircon in relatively mafic rocks of a suite containing less than about 68% SiO2, and shown in many cases by distinctive patterns of compositional variation. Granites of the low-temperature group formed at relatively low magmatic temperatures by the partial melting dominantly of the haplogranite components Qz, Ab and Or in H2O-bearing crustal source rocks. More mafic granites of this type have that character because they contain restite minerals, often including inherited zircon, which were entrained in a more felsic melt. In common with other elements, Zr contents correlate linearly with SiO2, except sometimes in very felsic rocks, and Zr generally decreases as the rocks become more felsic. All S-type granites are apparently low-temperature in origin. After most or all of the restite has been removed from the magma, these granites may evolve further by fractional crystallisation. High-temperature granites formed from a magma that was completely or largely molten, in which zircon crystals were not initially present because the melt was not saturated in that mineral. High-temperature suites commonly evolved compositionally through fractional crystallisation and they may extend to much more mafic compositions through the production of cumulate rocks. However, it is probable that, in some cases, the compositional differences within high-temperature suites arose from varying degrees of partial melting of similar source rocks. Volcanic equivalents of both groups exist and show analogous differences. There are petrographic differences between the two groups and significant mineralisation is much more likely to be associated with the high-temperature granites. The different features of the two groups relate to distinctive source rock compositions. Low-temperature granites were derived from source rocks in which the haplogranite components were present throughout partial melting, whereas the source materials of the high-temperature granites were deficient in one of those components, which therefore, became depleted during the melting, causing the temperatures of melting to rise.

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27

Gorbachev, N. S., A. V. Kostyuk, Yu B. Shapovalov, P. N. Gorbachev, A. N. Nekrasov y D. M. Soultanov. "Critical phenomena and granatization of water-containing eclogite at P = 3,7-4,0 GPa, T = 1000-1300 °C". Доклады Академии наук 489, n.º 4 (10 de diciembre de 2019): 393–98. http://dx.doi.org/10.31857/s0869-56524894393-398.

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The phase relationships have been experimentally studied at eclogitization of basalts and the melting of H2O‑containing eclogite in the basalt-H2O system at P = 3,7-4,0 GPa, T = 1000-1300 C. It is established that the phase relationships depend on temperature. The formation of a supercritical fluid-melt occurs at T = 1000 C, P = 3,7 GPa, conversion eclogite-granatite occurs at T = 1000-1100 C, P = 3,9 GPa, partial melting of eclogite with the formation of Na-alkali silicate melt and clinopyroxenite restite at 1150 C and 1300 C. The supercritical fluid-melt has a high reactivity, resulting in the formation of megacrists of garnet, its enrichment with Ti, the replacement of garnet with clinopyroxene, the formation of ilmenite, K‑containing amphibole, the conversion of eclogite into garnetite as a result of mass crystallization of garnet.

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28

Stone, Maurice. "The Significance of Almandine Garnets in the Lundy and Dartmoor Granites". Mineralogical Magazine 52, n.º 368 (diciembre de 1988): 651–58. http://dx.doi.org/10.1180/minmag.1988.052.368.09.

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AbstractAlmandine garnets in the cordierite-bearing granite of Sweltor Quarry, Dartmoor, contain < 10 mol. % of the spessartine end-member, whilst those in the Lundy granite have c. 10 mol. % spessartine. Experimental work indicates that such compositions can grow in equilibrium with siliceous melts at depths of 18–25 km. This evidence, reaction rims, lack of marked zoning and comparison with garnets in other siliceous calc-alkaline siliceous rocks point to a genesis involving partial melting of the ‘local’ lower crust. A restite origin rather than direct crystallization from magma is favoured but the evidence is equivocal. The Dartmoor granite (Hercynian) is a typical peraluminous late- to post-tectonic S-type granite. The S-type character of the Lundy (Tertiary) granite is revealed by the occurrence of garnet and topaz together with biotite enriched in Rb, Cs and F, despite its close association with Tertiary basic magmatism in an anorogenic setting.

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29

Kanaris-Sotiriou, Raymond. "Graphite-bearing peraluminous dacites from the Erlend volcanic complex, Faeroe-Shetland Basin, North Atlantic". Mineralogical Magazine 61, n.º 405 (abril de 1997): 175–84. http://dx.doi.org/10.1180/minmag.1997.061.405.02.

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AbstractStrongly peraluminous, cordierite-bearing anatectic dacites from the offshore Tertiary Erlend volcanic centre, north of the Shetland Isles, are shown to contain graphite which is interpreted as being essentially a restite phase inherited from carbonaceous pelitic source rocks. The form and characteristics of the graphite are documented and graphite geothermometry applied to establish that the graphite records a minimum peak temperature of ∼800°C, confirming that temperatures at which anatexis occurs were attained. The different morphological forms of graphite observed suggest the possibility that minor amounts of fluid-deposited graphite may also be present. The chemistry of the Erlend dacites is compared with that of other known examples of graphite-bearing peraluminous silicic igneous rocks and briefly with experimentally generated peraluminous liquid compositions. The Erlend source rocks were probably subjected to a higher degree of partial melting than has occurred in the petrogenesis of many other anatectic peraluminous silicic rocks.

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30

Vernon, R. H. "PROBLEMS IN IDENTIFYING RESTITE IN S-TYPE GRANITES OF SOUTHEASTERN AUSTRALIA, WITH SPECULATIONS ON SOURCES OF MAGMA AND ENCLAVES". Canadian Mineralogist 45, n.º 1 (1 de febrero de 2007): 147–78. http://dx.doi.org/10.2113/gscanmin.45.1.147.

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31

Stephens, W. E. "Polycrystalline amphibole aggregates (clots) in granites as potential I‐type restite: An ion microprobe study of rare‐earth distributions". Australian Journal of Earth Sciences 48, n.º 4 (agosto de 2001): 591–601. http://dx.doi.org/10.1046/j.1440-0952.2001.00880.x.

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32

HOLTZ, F. y P. BARBEY. "Genesis of Peraluminous Granites II. Mineralogy and Chemistry of the Tourem Complex (North Portugal). Sequential Melting vs. Restite Unmixing". Journal of Petrology 32, n.º 5 (1 de octubre de 1991): 959–78. http://dx.doi.org/10.1093/petrology/32.5.959.

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33

Yamamoto, Michiko y Jason Phipps Morgan. "North Arch volcanic fields near Hawaii are evidence favouring the restite-root hypothesis for the origin of hotspot swells". Terra Nova 21, n.º 6 (diciembre de 2009): 452–66. http://dx.doi.org/10.1111/j.1365-3121.2009.00902.x.

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34

Jeon, Heejin y Ian S. Williams. "Trace inheritance—Clarifying the zircon O-Hf isotopic fingerprint of I-type granite sources: Implications for the restite model". Chemical Geology 476 (enero de 2018): 456–68. http://dx.doi.org/10.1016/j.chemgeo.2017.11.041.

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35

Clarke, D. Barrie. "The Origins of Strongly Peraluminous Granitoid Rocks". Canadian Mineralogist 57, n.º 4 (15 de julio de 2019): 529–50. http://dx.doi.org/10.3749/canmin.1800075.

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Abstract Strongly peraluminous granites (SPAGs), with 1.20 < A/CNK < 1.30, are relatively rare rocks. They contain significant modal abundances of AFM minerals such as Bt-Ms-Crd-Grt-And-Toz-Tur-Spl-Crn of potentially magmatic, peritectic, restitic, and xenocrystic origin. Determining the origin of a SPAG depends to a large extent on establishing the correct origin of these AFM minerals. Strongly peraluminous granitic rocks can form in eight distinctly different ways: (1) as the melt fraction resulting from dehydration partial melting of peraluminous metasedimentary rocks; (2) as the bulk composition of diatexitic migmatite resulting from extensive partial melting of peraluminous metasedimentary rock; (3) as a diatexite modified by incomplete restite unmixing; (4) by bulk contamination of a less strongly peraluminous granite magma with highly peraluminous metasedimentary rocks; (5) by selective acquisition or concentration of AFM minerals by a less strongly peraluminous granite magma; (6) by fractional crystallization of quartz and feldspar from a less strongly peraluminous granite magma; (7) by removal of alkalies (Ca, Na, K) by release of a suprasolidus aqueous fluid from a less strongly peraluminous granite magma; and (8) by subsolidus hydrothermal alteration of a less strongly peraluminous granite rock. Contamination by pelitic material is the most effective process for creating SPAG plutons. A detailed case study of the South Mountain Batholith shows that its early SPAGs contain high modal abundances of Bt-Crd-Grt, largely of external origin, whereas its later SPAGs contain high modal abundances of Ms-And-Toz, largely the products of fluido-magmatic processes.

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36

Williams, Ian S. y Kenton S. W. Campbell. "Bruce William Chappell 1936–2012". Historical Records of Australian Science 28, n.º 2 (2017): 146. http://dx.doi.org/10.1071/hr17012.

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Bruce Chappell was one of the most distinguished geologists of his generation whose contributions to understanding the origins of granites are both insightful and profound. A pioneer in the application of X-ray fluorescence spectrography to the analysis of geological materials, his radical ideas about magma genesis, still the subject of vigorous debate, have dominated and largely determined the global directions of subsequent research on granites. His restite model, the recognition that most granite magmas move bodily away from their source regions as a mixture of melt and solid residual material, the progressive separation of which determines the magma composition, underlies his tenet that granites are images of their source. His consequent recognition, with Allan White, that there are two fundamentally different types of granite magma, I-type (derived from igneous sources) and S-type (derived from weathered sedimentary sources), each with its distinctive evolutionary path and associated mineralization, continues to underpin research into granites worldwide, and the search for granite-related mineral deposits.

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37

Bateman, R., T. A. Scambos y M. C. Loiselle. "The Center Pond Pluton; the restite of the story (phase separation and melt evolution in granitoid genesis); discussion and reply". American Journal of Science 288, n.º 3 (1 de marzo de 1988): 282–87. http://dx.doi.org/10.2475/ajs.288.3.282.

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38

Wang, Luo-Juan, Jing-Hui Guo, Changqing Yin, Peng Peng, Jian Zhang, Christopher J. Spencer y Jia-Hui Qian. "High-temperature S-type granitoids (charnockites) in the Jining complex, North China Craton: Restite entrainment and hybridization with mafic magma". Lithos 320-321 (noviembre de 2018): 435–53. http://dx.doi.org/10.1016/j.lithos.2018.09.035.

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39

Cesare, B. "Incongruent melting of biotite to spinel in a quartz-free restite at El Joyazo (SE Spain): Textures and reaction characterization". Contributions to Mineralogy and Petrology 139, n.º 3 (julio de 2000): 273–84. http://dx.doi.org/10.1007/s004100000137.

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40

Surin, T. N. "Late-devonian sakhara dunite-clinopiroxenite-gabbro complex (East Magnitogorsk zone, South Urals): petrological-mineralogical features and geodynamic setting". МИНЕРАЛОГИЯ (MINERALOGY) 7 (abril de 2021): 40–53. http://dx.doi.org/10.35597/2313-545x-2021-7-1-3.

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The relevance of the work is caused by necessary regional analysis of magmatic evolution of the East Magnitogorsk belt and refnement of ideas on geodynamics of the South Urals. The geology and petrochemical-mineralogical features of the Sakhara dunite-clinopyroxenite-gabbro complex in the South Urals are characterized in the paper. Its late Frasnian age is substantiated. The composition of olivine, clinopyroxene and chromite in rocks of the complex are determined. The restite nature of dunites is proved. It is shown that rocks of the complex are similar to those of the Urals platinum belt and belong to Ural-Alaskan type. It is concluded that the complex formed in island-arc geodynamic setting and in the beginning of the formation of a mature island arc. The location of massifs of the complex is an additional argument in favor of a western dip (in the present-day coordinates) of a subduction paleozone at the moment of its formation. Crystallization diferentiation was a leading mechanism of petrogenesis of rocks of the complex.

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41

Osipova, T. A., G. A. Kallistov, D. A. Zamyatin y V. A. Bulatov. "Zr-Th-U MINERALS IN HIGH-MG DIORITE OF THE CHELYABINSK MASSIF (SOUTH URALS) – EVIDENCE FOR CRUST–MANTLE INTERACTION". Geodynamics & Tectonophysics 12, n.º 2 (23 de junio de 2021): 350–64. http://dx.doi.org/10.5800/gt-2021-12-2-0528.

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Zr-Th-U minerals, namely baddeleyite, zircon and U-Th-oxide, were found in high-Mg diorite from the Late Devonian – Early Carboniferous synplutonic dyke in granodiorites of the Chelyabinsk massif, South Urals. Micron-sized minerals were investigated by electron microscopy and cathodoluminescence spectroscopy. Their chemical compositions were determined by electron probe microanalysis that was optimized to ensure more precise measurements of the composition of minerals. Baddeleyite grains are found as inclusions in amphibole crystals and reside in intergranular areas. The former retain their composition and show no traces of corrosion or substitution. In the intergranular areas, baddeleyite grains were replaced by polycrystalline zircon due to the reaction with an acid melt, and the U-Th-oxide precipitated inside baddeleyite simultaneously, which suggests the restite origin of baddeleyite. The main features of the baddeleyite composition are extremely high concentrations of ThO2 and UO2 (to 0.03 wt. % and 1.0 wt. %, respectively), which may be due to the metasomatic interaction between the mantle peridotite and the crustal or carbonatite fluid or melt.

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42

Maksimov, S. O., V. G. Sakhno, N. A. Ekimova y V. M. Chubarov. "Selective contamination of basaltic magmas and buchite genesis (on the example of Shufan plateau, Primorye)". Доклады Академии наук 489, n.º 5 (20 de diciembre de 2019): 490–96. http://dx.doi.org/10.31857/s0869-56524895490-496.

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The article discusses the problem of large-scale contamination of the Shufan volcanic plateaus basalts (Primorye) by selective melts from xenoliths. Silicic and alkaline liquids, selectively extracted from xenoliths, mix in a limited way with basaltic melts forming bands of granophyre that give lavas a taxitic structure. The article describes the unique compositions of buchites that were chemically modified by the diffusion interaction with basaltic magma and selectively molten politic xenoliths. Their mineral associations are represented by a high ferriferous cordierite (sekaninaite), ultra-ferriferous hercynite, (Al, Zr) Fe-armalcolite, Zr-ilmenite, mullite, sillimanite, high-lanthanum monazite, and barium-phosphate-aluminosilicate phase. The chemical and mineral compositions of buchites reflect the accumulation of refractory elements (Al, Fe, Ti, Zr, Ni, Cr) in the restite material of xenoliths. It is followed by the formation of ultra-alumina, ultra-ferruginous, initially immiscible metal-silicate composition. Low Pb isotopic ratios in Shufan basalts suggest a selective contamination by an ancient cratonic basements material. A consecutive increase of the isotopic ratios is observed the basalts contaminated by the upper crustal material, which is also shown by buchites isotopic composition.

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43

Tichomirowa, Marion, Axel Gerdes, Manuel Lapp, Dietmar Leonhardt y Martin Whitehouse. "The Chemical Evolution from Older (323–318 Ma) towards Younger Highly Evolved Tin Granites (315–314 Ma)—Sources and Metal Enrichment in Variscan Granites of the Western Erzgebirge (Central European Variscides, Germany)". Minerals 9, n.º 12 (11 de diciembre de 2019): 769. http://dx.doi.org/10.3390/min9120769.

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The sources and critical enrichment processes for granite related tin ores are still not well understood. The Erzgebirge represents one of the classical regions for tin mineralization. We investigated the four largest plutons from the Western Erzgebirge (Germany) for the geochemistry of bulk rocks and autocrystic zircons and relate this information to their intrusion ages. The source rocks of the Variscan granites were identified as high-grade metamorphic rocks based on the comparison of Hf-O isotope data on zircons, the abundance of xenocrystic zircon ages as well as Nd and Hf model ages. Among these rocks, restite is the most likely candidate for later Variscan melts. Based on the evolution with time, we could reconstruct enrichment factors for tin and tungsten starting from the protoliths (575 Ma) that were later converted to high-grade metamorphic rocks (340 Ma) and served as sources for the older biotite granites (323–318 Ma) and the tin granites (315–314 Ma). This evolution involved a continuous enrichment of both tin and tungsten with an enrichment factor of ~15 for tin and ~7 for tungsten compared to the upper continental crust (UCC). Ore level concentrations (>10–100 times enrichment) were achieved only in the greisen bodies and dykes by subsequent hydrothermal processes.

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44

Ramirez, J. A. y L. G. Menendez. "A geochemical study of two peraluminous granites from south-central Iberia: the Nisa-Albuquerque and Jalama batholiths". Mineralogical Magazine 63, n.º 1 (febrero de 1999): 85–104. http://dx.doi.org/10.1180/002646199548330.

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AbstractIn this paper we present new petrological and geochemical data for two peraluminous granite batholiths (Nisa Alburquerque and Jalama batholiths) representative of the ‘Araya-type’ granites of the Central-Iberian Zone. Both granites are composite with several facies (monzogranites and leucogranites) that can be grouped into two main granite units: the external units and central units. Intrusive relationships and lack of geochemical coherence between the central and external units indicate that they are not comagmatic but represent different pulses. The central units of both batholiths are petrologically and geochemically different. On the other hand, external units show a lot of similarities and are the main object of this study. The main characteristics of the external granites can be interpreted in terms of an incomplete fractional crystallization process of early mineral phases (plg + Kf + bt) which probably took place at the level of emplacement. Other possible mechanisms of magmatic differentiation (magma mixing, restite unmixing, sequential melting) can be discarded based on field, petrography and geochemical data. We propose that the ‘Araya-type’ granites are formed by the intrusion of distinct magma pulses (central and external). Further evolution within each pulse can be due to incomplete fractional crystallization possibly taking place at the emplacement level.

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45

White, A. J. R., B. W. Chappell y D. Wyborn. "Application of the Restite Model to the Deddick Granodiorite and its Enclaves --a Reinterpretation of the Observations and Data of Maas et al. (1997)". Journal of Petrology 40, n.º 3 (1 de marzo de 1999): 413–21. http://dx.doi.org/10.1093/petroj/40.3.413.

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46

Sawka, Wayne N. "REE and trace element variations in accessory minerals and hornblende from the strongly zoned McMurry Meadows Pluton, California". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 79, n.º 2-3 (1988): 157–68. http://dx.doi.org/10.1017/s0263593300014188.

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ABSTRACTThe zoned McMurry Meadows Pluton has been examined for REE and trace element variations in hornblende, sphene, apatite, allanite and zircon. Mineral separates (17), were analysed by INAA from four granitoids spanning the compositional range of the pluton (60%–75% SiO2). All of the phases examined exhibit significant compositional variations, with sphene having the largest changes in chondrite normalised REE patterns. Compositional variations in these minerals are related to paragenetic sequence and, as the whole rocks become more evolved, increases in partition coefficients; not subsolidus re-equilibration. Hornblende is only a dominant site for REE in granites where sphene is a later crystallising phase, otherwise allanite (LREE only) and sphene are the dominant whole rock sites for REE. Zircon and apatite normally contribute less than 10% each to the whole rock abundance of REE. Three zircon samples contain only small compositional differences and are interpreted as having crystallised from the bulk magma prior to differentiation. Zr variation in the pluton is nonlinear, first increasing and then decreasing with whole rock fractionation. A simple process, analogous to “restite unmixing” applied to the Zr variation, defines a bulk magma composition of about 63% SiO2, before differentiation of the zoned pluton. The modelled bulk magma need only have evolved by about 2·5% silica and still have produced the entire compositional range (60–75% SiO2) observed in the pluton.

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47

Huppert, Herbert E., R. Stephen y J. Sparks. "The fluid dynamics of crustal melting by injection of basaltic sills". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 79, n.º 2-3 (1988): 237–43. http://dx.doi.org/10.1017/s0263593300014243.

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ABSTRACTWhen basaltic magma is emplaced into continental crust, melting and generation of granitic magma can occur. We present experimental and theoretical investigations of the fluid dynamical and heat transfer processes at the roof and floor of a basaltic sill in which the wall rocks melt. At the floor, relatively low density crustal melt rises and mixes into the overlying magma, which would form hybrid andesitic magma. Below the roof the low-density melt forms a stable layer with negligible mixing between it and the underlying hotter, denser magma. Our calculations applied to basaltic sills in hot crust predict that sills from 10-1500 m thick require only 2-200 years to solidify, during which time large volumes of overlying layers of convecting silicic magma are formed. These time scales are very short compared with the lifetimes of large silicic magma systems of around 106 years, and also with the time scale of 107 years for thermal relaxation of the continental crust. An important feature of the process is that crystallisation and melting occur simultaneously, though in different spots of the source region. The granitic magmas formed are thus a mixture of igneous phenocrysts and lesser amounts of restite crystals. Several features of either plutonic or volcanic silicic systems can be explained without requiring large, high-level, long-lived magma chambers.

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48

Fazlnia, Abdolnaser. "Geochemical characteristics and conditions of formation of the Chah-Bazargan peraluminous granitic patches, ShahrBabak, Iran". Geologica Carpathica 68, n.º 5 (26 de octubre de 2017): 445–63. http://dx.doi.org/10.1515/geoca-2017-0029.

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Abstract Xenoliths of garnet-biotite-kyanite schist from the Qori metamorphic complex (southern part of the Sanandaj-Sirjan zone, northeast Neyriz, Zagros orogen in Iran) in the 173.0±1.6 Ma Chah-Bazargan leuco-quartz diorite intrusion were studied. This intrusion caused these schist xenoliths to be metamorphosed to the pyroxene hornfels facies (approximately 4.5±1.0 kbar and 760±35 °C), converting them to diatexite migmatite as a result of partial melting of the xenoliths. These melts are granites in composition. Melt volumes of 20 to 30 vol. % were calculated for small patches of the peraluminous granites. It is possible that anatectic melting affected only the leucosome, such that melting was more than 20 to 30 vol. %. It is possible that a large amount of melt was not extracted due to balanced in situ crystallization, the adhesion force between melt and crystal (restite), and high viscosity of the leucosome. The Chah-Bazargan peraluminous granites are depleted in trace elements such as REEs, HFSE (Ti, Zr, Ta, Nb, Th, U, Hf, Y), Ba, Pb, and Sr. These elements are largely insensitive to source enrichment, but sensitive to the amounts of main and accessory minerals. These elements were hosted by minerals such as garnet, biotite, muscovite, K-feldspar, plagioclase, ilmenite, apatite, monazite, and zircon in the source (diatexitic migmatitic xenoliths).

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49

Grew, E. S., A. T. Rao, K. K. V. S. Raju, C. Hejny, J. M. Moore, D. J. Waters, M. G. Yates y C. K. Shearer. "Prismatine and ferrohögbomite-2N2S in granulite-facies Fe-oxide lenses in the Eastern Ghats Belt at Venugopalapuram, Vizianagaram district, Andhra Pradesh, India: do such lenses have a tourmaline-enriched lateritic precursor?" Mineralogical Magazine 67, n.º 5 (octubre de 2003): 1081–98. http://dx.doi.org/10.1180/0026461036750144.

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AbstractFluorine-rich prismatine, (□,Fe,Mg)(Mg,Al,Fe)5Al4(Si,B,Al)5O21(OH,F), with F/(OH+F) = 0.36–0.40 and hercynite are major constituents of a Fe-Al-B-rich lens in ultrahigh-temperature granulite-facies quartz-sillimanite-hypersthene-cordierite gneisses of the Eastern Ghats belt, Andhra Pradesh, India. Hemo-ilmenite, sapphirine, magnetite, biotite and sillimanite are subordinate. Lithium, Be and B are concentrated in prismatine (140 ppm Li, 170 ppm Be, and 2.8 –3.0 wt.% B2O3). Another Fe-rich lens is dominantly magnetite, which encloses fine-grained zincian ferrohögbomite-2N2S, (Fe2+,Mg,Zn,Al)6 (Al,Fe3+,Ti)16O30(OH)2, containing minor Ga2O3 (0.30 –0.92 wt.%). Fe-Al-B-rich lenses with prismatine (or kornerupine) constitute a distinctive type of B-enrichment in granulite-facies rocks and have been reported from four other localities worldwide. A scenario involving a tourmalineenriched lateritic precursor affected by dehydration melting is our preferred explanation for the origin of the Fe-Al-B-rich lenses at the five localities. Whole-rock analyses and field relationships at another of these localities, Bok se Puts, Namaqualand, South Africa, are consistent with this scenario. Under granulite-facies conditions, tourmaline would have broken down to give kornerupine-prismatine (±other borosilicates) plus a sodic melt containing H2O and B. Removal of this melt depleted the rock in Na and B, but the formation of ferromagnesian borosilicate phases in the restite prevented total loss of B.

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50

Bea, F. "Controls on the trace element composition of crustal melts". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 87, n.º 1-2 (1996): 33–41. http://dx.doi.org/10.1017/s0263593300006453.

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ABSTRACT:The behaviour of trace elements during partial melting depends primarily on their mode of occurrence. For elements occurring as trace constituents of major phases (e.g. Li, Rb, Cs, Eu, Sr, Ba, Ga, etc.), slow intracrystalline diffusion (D ≍ 10−16 cm2 s−1) at the temperature range of crustal anatexis causes all effective crystal-melt partition coefficients to have a value close to unity and impedes further melt-restite re-equilibration. Usually, therefore, the trace element composition of crustal melts simply depends on the mass balance between the proportion and composition of phases that melt and the proportion and composition of newly formed phases. The behaviour of trace elements occurring as essential structural components in accessory phases (e.g. P, La-Sm, Gd-Lu, Y, Th, U, Zr, Hf, etc.) depends on the solubility, solution kinetics, grain size and the textural position of accessory phases. In common crustal protoliths a significant mass fraction of monazite, zircon, xenotime, Th-orthosilicates, uraninite; etc.—but not apatite—is included within other major and accessory phases. During low melt fraction anatexis the amount of accessory phases available for the melt is not sufficient for saturation, thus producing leucosomes with concentrations of La-Sm, Gd-Lu, Y, Th, U and Zr lower than expected from solubility equations. Low concentrations of these elements may also occur if the melt is prevented from reaching equilibrium with the accessories due to fast segregation. However, the first mechanism seems more feasible as leucosomes that are undersaturated with respect to monazite and zircon are frequently saturated, even oversaturated, with respect to apatite.

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