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Статті в журналах з теми "Contact aureole"

Автор: Grafiati

Опубліковано: 10 березня 2023

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1

Owen, J. Victor. "Cordierite + spinel parageneses in pelitic gneiss from the contact aureoles of the Mistastin batholith (Quebec) and the Taylor Brook gabbro complex (Newfoundland)." Canadian Journal of Earth Sciences 28, no. 3 (March 1, 1991): 372–81. http://dx.doi.org/10.1139/e91-034.

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The contact aureoles of the Mistastin batholith and the Taylor Brook gabbro complex contain cordierite + spinel-bearing assemblages derived from quartz-, K-feldspar-, sillimanite-, garnet-, and biotite-bearing pelitic gneiss. Andalusite occurs locally. As a result of continuous, cordierite-forming reactions, garnet and biotite have recrystallized to relatively Fe-rich compositions compared with their counterparts outside the aureoles.Mosaics of fine-grained cordierite and spinel replace sillimanite and biotite throughout the Mistastin aureole. Similar assemblages and textures are preserved in metapelite in the outer part of the Taylor Brook aureole, where garnet adjacent to sillimanite is replaced by cordierite + spinel. The formation of spinel-free cordierite porphyroblasts by garnet-, sillimanite-, biotite-, and quartz-consuming reactions depleted metapelites in both aureoles in quartz, permitting the formation of the undersaturated assemblages. The undersaturated cordierite + spinel assemblages formed on a domainal scale (individually, a few hundred cubic millimetres in volume) and coexist metastably with saturated assemblages elsewhere in the same rock. Peak temperatures (700–750 °C) determined for both aureoles were insufficient to stabilize quartz + spinel parageneses owing to the low gahnite content of the oxide (ZnO < 2 wt.%).Metapelites in the innermost part of the Taylor Brook aureole appear to have been desilicified by the formation and fractionation of anatectic melt, yielding migmatitic rocks virtually devoid of quartz and K-feldspar. In contrast, migmatite in the inner part of the Mistastin aureole retains a quartz + two-feldspar mineralogy, so, as in the nonmigmatitic paragneiss, undersaturated assemblages are present only on a domainal scale.These aureole rocks demonstrate that undersaturated assemblages are not only characteristic of thermally- recrystallized low-grade pelites but also can occur in contact aureoles developed in granulite-facies paragneiss. Aluminous rocks can become undersaturated by subsolidus, quartz-consuming reactions yielding cordierite, or by the formation of anatectic liquids.

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2

Shawwa, Nabil A., Robert P. Raeside, David W. A. McMullin, and Christopher R. M. McFarlane. "Employing contact metamorphism to assess the conditions of pluton emplacement and timing of recrystallization in southwestern Kellys Mountain, Cape Breton Island, Nova Scotia." Canadian Journal of Earth Sciences 54, no. 11 (November 2017): 1165–78. http://dx.doi.org/10.1139/cjes-2017-0052.

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At Kellys Mountain, Cape Breton Island, Nova Scotia, the late Neoproterozoic Glen Tosh formation (a low-grade metapsammite–metapelite unit of the George River Metamorphic Suite) has been intruded by diorite, granodiorite, and granite plutons, and the diorite hosts a narrow contact metamorphic aureole. New mapping and sampling in the contact aureole reveals that the metasedimentary rocks have reached amphibolite-facies metamorphism resulting in the development of neoformed biotite, muscovite, cordierite, ilmenite, garnet, andalusite, sillimanite, monazite, and spinel within the meta-pelite, a mineral assemblage also found in the Kellys Mountain Gneiss as a result of low-pressure regional metamorphism. Neoformed minerals and the disappearance of foliation defines a contact metamorphic aureole within 300 m of the pluton contacts. Petrographic and microprobe analyses of equilibrium assemblages in metapelitic units of the contact aureole yielded metamorphic pressures of 250 MPa, implying an intrusion depth of ∼9 km, with temperatures ranging from 365 to 590 °C. The presence of earlier-formed andalusite and garnet indicates the rocks may have initially undergone a low-pressure regional metamorphic event prior to contact metamorphism. Monazite in the contact aureole was dated using in-situ U–Pb methods and yielded an age of 480.9 ± 3.7 Ma, interpreted as the time of formation of the contact metamorphic aureole.

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3

Selyatitskii, A. Yu, O. P. Polyansky, and R. A. Shelepaev. "A High-Pressure Thermal Aureole of the Bayan-Kol Gabbro–Monzodiorite Intrusion (Western Sangilen, Southeastern Tuva): Evidence for Lower-Crust Mafic Magma Chambers." Russian Geology and Geophysics 62, no. 9 (September 1, 2021): 987–1005. http://dx.doi.org/10.2113/rgg20194157.

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Abstract —Thermal metamorphism produced an aureole near the early Paleozoic Bayan-Kol gabbro–monzodiorite intrusion in the Erzin shear zone of western Sangilen (Tuva–Mongolia microcontinent, Central Asian Orogenic Belt). Field observation of intrusive contact, structure–textural and mineral transformations of metamorphic rocks, regular changes in the chemical composition of minerals with approaching the intrusive contact, and high temperature gradient from intrusive to wallrocks verified the occurrence of a contact aureole near the Bayan-Kol intrusion. The high-gradient thermal metamorphism (M2) affected garnet–staurolite–kyanite schists that formed during earlier regional metamorphism (M1) at 6.2–7.9 kbar and 600–670 ºC. The 0.5 km wide M2 metamorphic aureole mapped along the northwestern intrusion margin consists of a muscovite–sillimanite zone adjacent to the sedimentary country rocks and a cordierite–K-feldspar zone on the side of the intrusion. The M2 metamorphic reactions occurred within the granulite facies temperature range 880–910 ºC along the contact with monzodiorites and at ~950 ºC along the boundary with gabbronorites; the temperature on the aureole periphery was about 640 ºC. Pressure estimates indicate deep-seated high-grade metamorphism at 6.9–7.8 kbar, while the intrusion itself crystallized at 7.7–7.8 kbar. The suggested numerical model implying the formation of a thermal aureole at a depth of 26 km (7 kbar) in the lower crust is consistent with the temperature pattern determined by geothermobarometry for several key points of the metamorphic zoning and confirms its deep-level origin. Thus, the aureole near the Bayan-Kol intrusion represents a rare case of contact metamorphism in the lower continental crust. The obtained results, along with published petrological and geochronological evidence, reveal two depth levels of the early Paleozoic M2 metamorphism in the Sangilen area: upper (7–15 km, 2–4 kbar) and lower (26–30 km, 7–8 kbar) crust. The Bayan-Kol gabbro–monzodiorite intrusion is likely a small apophysis or a fragment of a deep-crust intermediate magma chamber, while the moderate-pressure (7–8 kbar) M2 granulites in the Erzin shear zone are products of high-gradient metamorphism related to the Cambrian–Ordovician collisional mafic magmatism in the Sangilen area.

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4

Mouchos, E., L. Papadopoulou, B. J. Williamson, and G. Christofides. "MARIALITIC SCAPOLITE OCCURENCES FROM THE KIMMERIA-LEFKOPETRA METAMORPHIC CONTACT, XANTHI (N. GREECE)." Bulletin of the Geological Society of Greece 50, no. 4 (July 28, 2017): 1943. http://dx.doi.org/10.12681/bgsg.14244.

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Emplacement of the Xanthi Plutonic Complex within the Rhodope Massif of N. Greece created an extensive metamorphic aureole around the plutonite. The aureole contains two areas of intense scapolitization in the contacts between granodiorite and biotitegneiss and between monzonite and sandstone, the latter cross-cut by andesite dykes. This paper reports the results of a mineralogical and geochemical study into the formation of the scapolites and particularly the nature of the plutonite-derived hydrothermal fluids from which scapolites were formed.

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5

FESTA, VINCENZO, ALFREDO CAGGIANELLI, ANTONIO LANGONE, and GIACOMO PROSSER. "Time–space relationships among structural and metamorphic aureoles related to granite emplacement: a case study from the Serre Massif (southern Italy)." Geological Magazine 150, no. 3 (November 16, 2012): 441–54. http://dx.doi.org/10.1017/s0016756812000714.

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AbstractTectonic and thermal perturbations, related to emplacement of granodiorite in the upper continental crust, have been investigated in the late-Hercynian basement exposed in southern Calabria (Italy). Here, the structural aureole is marked by the presence of a major rim fold adjacent to the intrusive contact for a length of at least 20 km. Geometrical analysis of the structural aureole and related foliations, lineations and crenulations reveals that the perturbed zone is at least 3000 m wide and characterized by an open synform trending nearly parallel to the intrusive contact. This pattern is compatible with a laccolith-like mode of magma emplacement, related to the accretion of the pluton that shouldered weak phyllitic and slaty wall rocks. The metamorphic aureole, about 1800 m wide, is characterized by biotite, cordierite and andalusite that appear sequentially in spotted schists and hornfelses approaching the intrusive contact. The peak assemblage equilibrated between 535 and 590°C at pressures between 175 and 200 MPa, confirmed by Al-in-hornblende barometry on granodiorite. Microstructural analysis allowed the inference of a time lag between the thermal and tectonic perturbations. With the aid of thermal modelling it was possible to quantify the time required to reach the peak temperature at a distance from the intrusive contact where cordierite spots and andalusite porphyroblasts clearly overprint crenulations. This estimate represents the time limit to accomplish deformation in the inner portion of the aureole and thus indicates a minimum strain rate of 4 × 10−14 s−1 within the country rocks during granodiorite intrusion.

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6

Zhou, Mei-Fu, John Malpas, Paul T. Robinson, and Peter H. Reynolds. "The dynamothermal aureole of the Donqiao ophiolite (northern Tibet)." Canadian Journal of Earth Sciences 34, no. 1 (January 1, 1997): 59–65. http://dx.doi.org/10.1139/e17-005.

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Metamorphic rocks found at the base of the Jurassic Donqiao ophiolite of northern Tibet are interpreted as a basal dynamothermal aureole produced during obduction of the massif. The rocks form a sequence some 8 m thick, varying from high-grade amphibolites at the contact with overlying harzburgites to greenschist facies metasedimentary rocks lower down. The mineral paragenesis is similar to other such aureoles, and indicates that temperatures in excess of 750 °C may have been reached during metamorphism. The lack of high-pressure minerals suggests that the rocks were produced by subcretion in a relatively shallow dipping subduction zone. Ar–Ar geochronology on amphibole separates provides dates of 175–180 Ma for the displacement of the ophiolite, significantly older than the age of emplacement estimated from stratigraphie relationships. The ophiolite was clearly obducted very soon after its formation in a suprasubduction zone environment.

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7

HIRAJIMA, Takao, Daisuke NAKAMURA, and Katsushi SHIRAHATA. "Winchite from Mt. Hiei contact aureole, Kyoto, Japan." Journal of Mineralogical and Petrological Sciences 95, no. 6 (2000): 107–12. http://dx.doi.org/10.2465/jmps.95.107.

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8

Ings, S. J., and J. V. Owen. "‘Decompressional’ reaction textures formed by isobaric heating: an example from the thermal aureole of the Taylor Brook Gabbro Complex, western Newfoundland." Mineralogical Magazine 66, no. 6 (December 2002): 941–51. http://dx.doi.org/10.1180/0026461026660069.

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Abstract Reaction textures including corona structures in granulites from the Proterozoic Long Range Inlier of western Newfoundland are spatially associated with a Silurian (0.34 Ga) mafic intrusion, the Taylor Brook Gabbro Complex. They comprise, in metabasites and tonalitic gneiss, coronal orthopyroxene and plagioclase on garnet and, in metapelites, cordierite and spinel formed at the expense of sillimanite, garnet and quartz. Although generally interpreted to indicate near-isothermal decompression (ITD) following regional metamorphism, which in the inlier occurred at ˜1.10–1.03 Ga, these features appear to be absent elsewhere. Therefore they are interpreted to be products of contact metamorphism (near-isobaric heating – IBH) within the thermal aureole of the gabbro. Thus, there is a ˜0.7 Ga difference (i.e. mid-Proterozoic vs. mid-Silurian) between the age of the regional metamorphic mineral assemblages and the contact aureole assemblages. The observation that classic ITD features occur in this aureole environment underscores the fact that P-sensitive reactions can progress during IBH as well as by pressure release.

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9

Jamieson, R. A., G. G. Hart, G. G. Chapman, and N. W. Tobey. "The contact aureole of the South Mountain Batholith in Halifax, Nova Scotia: geology, mineral assemblages, and isograds." Canadian Journal of Earth Sciences 49, no. 11 (November 2012): 1280–96. http://dx.doi.org/10.1139/e2012-058.

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The contact aureole at the eastern margin of the South Mountain Batholith (Halifax Pluton) underlies most of the city of Halifax, Nova Scotia. The Halifax Group in the study area includes two lithological units, the Cunard and Bluestone formations. Before intrusion, both had been affected by greenschist facies regional metamorphism and deformed into northeast–southwest-trending, regional upright folds associated with a strong slaty cleavage. Contact metamorphic isograds trend obliquely across the Halifax peninsula, at a high angle to regional structural trends. At 2.5–3 km from the intrusive contact, sparse cordierite spots mark the outer limit of the contact aureole. The biotite-in isograd is marked by the development of biotite within chlorite + muscovite stacks inherited from regional metamorphism. Pyrrhotite is the dominant sulphide mineral throughout the contact aureole. With increasing metamorphic grade, assemblages in both units are marked by increasing modal abundance of cordierite and biotite, with K-feldspar variably developed within ca. 600 m of the contact. However, there is a marked difference in the distribution and appearance of andalusite between the two units. In aluminous pelites of the Cunard formation, idioblastic chiastolite appears before biotite more than 1500 m from the contact. In the less aluminous Bluestone formation, andalusite is present only within ca. 500 m of the contact, where it forms xenoblastic, spongy crystals. In both units, the assemblage andalusite + biotite + K-feldspar ± cordierite is developed near the contact, with local fibrolite and evidence of incipient partial melting. Petrographic constraints suggest pressure–temperature conditions at the contact of ca. 2.5–3.0 kbar (1 kbar = 100 MPa) at ca. 650 °C.

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10

Park, Youngdo, and Changwhan Oh. "CONTACT2: A Macintosh program for calculating heat conduction in a contact aureole." Computers & Geosciences 24, no. 9 (November 1998): 901–4. http://dx.doi.org/10.1016/s0098-3004(97)00135-0.

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11

Mattsson, Tobias, Steffi Burchardt, Karen Mair, and Joachim Place. "Host-rock deformation during the emplacement of the Mourne Mountains granite pluton: Insights from the regional fracture pattern." Geosphere 16, no. 1 (December 16, 2019): 182–209. http://dx.doi.org/10.1130/ges02148.1.

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Abstract The Mourne Mountains magmatic center in Northern Ireland consists of five successively intruded granites emplaced in the upper crust. The Mourne granite pluton has classically been viewed as a type locality of a magma body emplaced by cauldron subsidence. Cauldron subsidence makes space for magma through the emplacement of ring dikes and floor subsidence. However, the Mourne granites were more recently re-interpreted as laccoliths and bysmaliths. Laccolith intrusions form by inflation and dome their host rock. Here we perform a detailed study of the deformation in the host rock to the Mourne granite pluton in order to test its emplacement mechanism. We use the host-rock fracture pattern as a passive marker and microstructures in the contact-metamorphic aureole to constrain large-scale magma emplacement-related deformation. The dip and azimuth of the fractures are very consistent on the roof of the intrusion and can be separated into four steeply inclined sets dominantly striking SE, S, NE, and E, which rules out pluton-wide doming. In contrast, fracture orientations in the northeastern wall to the granites suggest shear parallel to the contact. Additionally, contact-metamorphic segregations along the northeastern contact are brecciated. Based on the host-rock fracture pattern, the contact aureole deformation, and the north-eastward–inclined granite-granite contacts, we propose that mechanisms involving either asymmetric “trap-door” floor subsidence or laccolith and bysmalith intrusion along an inclined or curved floor accommodated the emplacement of the granites and led to deflection of the northeastern wall of the intrusion.

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12

SAKI, A. "Formation of spinel-cordierite-plagioclase symplectites replacing andalusite in metapelitic migmatites of the Alvand aureole, Iran." Geological Magazine 148, no. 3 (October 22, 2010): 423–34. http://dx.doi.org/10.1017/s0016756810000841.

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AbstractSpinel–cordierite–plagioclase symplectites partially replacing andalusite occur in the metapelitic migmatite rocks of the Alvand aureole within the Sanandaj–Sirjan metamorphic belt, Hamadan, Iran. The presence of melt shows that corona development occurred under partial melting conditions. Spinel is predicted to grow with cordierite at around 700°C. Exhaustion of the available SiO2 and/or separation of sillimanite/andalusite from SiO2-rich matrix domains by cordierite resulted in the formation of localized low-silica activity domains and thus triggered the growth of spinel in the rim of andalusite, the reaction Sil/And + Bt = Crd + Spl + Kfs + melt, as the most common reaction for the development of coronas in the metapelitic of Alvand aureole. The breakdown of garnet to plagioclase + sillimanite, dehydration melting and the formation of spinel–plagioclase symplectite could occur during heating or decompression; these textures are limited to the contact aureole in the studied area, so heating is perhaps the more likely explanation for formation of the symplectites in the metapelitic rocks of the Alvand aureole. The P–T diagram, inferred paths and zoning profiles of garnet do not account for the decompression history of the terrane.

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13

Keppie, J. Duncan, and R. D. Dallmeyer. "40Ar/39Ar mineral ages from Kellys Mountain, Cape Breton Island, Nova Scotia: implications for the tectonothermal evolution of the Avalon composite terrane." Canadian Journal of Earth Sciences 26, no. 8 (August 1, 1989): 1509–16. http://dx.doi.org/10.1139/e89-129.

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Hornblende from a diorite stock within the Kellys Mountain plutonic complex within the Avalon composite terrane, and hornblende, muscovite, and biotite from amphibolite and gneiss within the contact aureole record similar 40Ar/39Ar plateau ages of 493–498 Ma. These data indicate relatively rapid cooling through the contrasting temperatures appropriate for intracrystalline retention of argon in the different minerals. This is consistent with the relatively high level of intrusion of the pluton (3–10 km) suggested previously from the study of mineral assemblages developed in the contact aureole. These relationships suggest that intrusion of the Kellys Mountain complex took place at approximately 500 Ma, indicating an age close to the Cambro-Ordovician boundary. The complex may have formed in the same within-plate rifting regime as the Middle Cambrian Bourinot Group volcanic sequences exposed within the Avalon composite terrane.

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14

Xie, Wenbin, Costantino Sigismondi, Xiaofan Wang, and Paolo Tanga. "Venus transit, aureole and solar diameter." Proceedings of the International Astronomical Union 8, S294 (August 2012): 485–86. http://dx.doi.org/10.1017/s1743921313002986.

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AbstractThe possibility to measure the solar diameter using the transits of Mercury has been exploited to investigate the past three centuries of its evolution and to calibrate these measurements made with satellites. This measurement basically consists to compare the ephemerides of the internal contact timings with the observed timings. The transits of Venus of 2004 and 2012 gave the possibility to apply this method, involving a planet with atmosphere, with the refraction of solar light through it creating a luminous arc all around the disk of the planet. The observations of the 2012 transit made to measure the solar diameter participate to the project Venus Twilight Experiment to study the aureole appearing around it near the ingress/egress phases.

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15

Abart, R., M. Horacek, and E. Povoden. "Stable isotope systematics in the monzoni contact aureole, N-tialy." Chinese Science Bulletin 43, S1 (August 1998): 1. http://dx.doi.org/10.1007/bf02891348.

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16

HOLNESS, M. B. "Contact metamorphism and anatexis of Torridonian arkose by minor intrusions of the Rum Igneous Complex, Inner Hebrides, Scotland." Geological Magazine 136, no. 5 (September 1999): 527–42. http://dx.doi.org/10.1017/s0016756899002988.

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Significant volumes of partial melt developed in the arkosic contact aureoles of two of the numerous mafic and ultramafic minor intrusions found in the northern parts of the Isle of Rum, Scotland. Melting was essentially static, with little movement of melt even on a thin-section scale, and no segregation. The relative proportions of (now inverted) tridymite and high quartz inferred to have crystallized in the silica primary-phase field constrain the pressure of metamorphism to 150 ± 50 bars. Melting attained 95 vol. %, and occurred up to 15 m from the contact with the 50 m diameter gabbro plug. Melting around the adjacent 200 m diameter peridotite plug reached ≈ 70 vol. %, and occurred up to 6 m from the contact. Simple thermal models for the two aureoles, based on the isograds given by the onset of melting, the breakdown of chlorite and the disordering of microcline, support the hypotheses that the peridotite plug was injected as a crystal-rich mush close to its solidus, whereas the gabbro plug was a relatively long-lived feeder conduit. Time scales for the melting events are of the order of forty years for the aureole of the gabbro and ten years for that surrounding the peridotite body. The melt distribution resulting from the heating part of the thermal history is controlled by reaction, and is far from textural equilibrium. Crystallization was abrupt, being complete in ten years for the gabbro, and in only four for the peridotite, resulting in a fine-grained cotectic intergrowth and preservation of the melt distribution.

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17

Hebert, Ronan, Jean-Claude Guézou, Christine Souque, and Michel Ballevre. "Microstructural evolution of metabasalts within a contact metamorphic aureole : a preliminary quantitative bi-dimensional approach." Bulletin de la Société Géologique de France 174, no. 2 (March 1, 2003): 107–14. http://dx.doi.org/10.2113/174.2.107.

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Abstract The emplacement of the Saint-Brieuc diorite (533 ± 12 Ma ; Brittany, France) developed a narrow contact aureole in metabasaltic host-rocks which were previously submitted to a regional-scale deformation and metamorphism at around 590-570 Ma. This study aims to qualify and quantify the microstructural changes of rocks that occur within the contact aureole and that are the result of the static recrystallization due to the thermal effect of the diorite. In order to quantify the textural evolution of rocks, an image analysis has been performed on thin sections. It focused on the measurements of morphological features of hornblende and opaque phases. They are anisotropy shape factors (stretching and elongation) of minerals, the preferred orientation of minerals and the distribution size (areas) of minerals. The quantification of these different parameters shows that the static recrystallization, which increases when approaching the contact with the intrusive, (i) is responsible of a reduction of the anisotropy shape and elongation parameters of grains, (ii) causes coarsening and (iii) is responsible for the disappearance of preferred orientation of minerals. Both together, the qualitative description and quantitative measurements show that the solid-state transformations due to contact metamorphism tend to make the rocks isotropic and equigranular.

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18

Schumacher, Renate. "Zincian staurolite in Glen Doll, Scotland." Mineralogical Magazine 49, no. 353 (September 1985): 561–71. http://dx.doi.org/10.1180/minmag.1985.049.353.10.

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AbstractTextures and relict mineralogy in the Dalradian gneisses from the southern contact aureole of the Glen Doll diorite trace the development of three stages of metamorphism through regional and contact metamorphic phases. Regional metamorphic stage I is characterized by the stability of sillimanite+muscovite; recognition of a subsequent regional metamorphic stage II of lower grade is based on textural criteria, the stability of kyanite and staurolite + quartz, and geothermometry/geobarometry. The breakdown of zincian staurolite occurred under the conditions of contact metamorphism (stage III). Textural evidence from the outer part of the contact aureole suggests that zincian staurolite broke down by the following oxidation reaction:zincian staurolite + muscovite + quartz + O2 → andalusite + Zn-rich spinel + magnetite + biotite + H2O.Various stages of completion of this reaction have been observed in different parts of a sample. Predominance of magnetite over Zn-rich spinel (⩽ 14 wt. % ZnO) as a breakdown product can be explained by the initial breakdown of Fe-staurolite component + muscovite + quartz+O2 to form andalusite+biotite+magnetite. These product phases were joined by the Zn-rich spinel when sufficient Zn-staurolite component had concentrated in the unreacted staurolite. Rare local examples where Zn-rich spinel is dominant over magnetite may reflect lower O2 fugacity and/or higher initial Zn contents of the staurolite.

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19

Todd, Clifford S. "Bleaching of limestones in the Notch Peak contact-metamorphic aureole, Utah." Geology 18, no. 1 (1990): 83. http://dx.doi.org/10.1130/0091-7613(1990)018<0083:bolitn>2.3.co;2.

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20

Hilchie, L. J., and R. A. Jamieson. "Graphite thermometry in a low-pressure contact aureole, Halifax, Nova Scotia." Lithos 208-209 (November 2014): 21–33. http://dx.doi.org/10.1016/j.lithos.2014.08.015.

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21

Gier�, Reto. "Titanian clinohumite and geikielite in marbles from the Bergell contact aureole." Contributions to Mineralogy and Petrology 96, no. 4 (1987): 496–502. http://dx.doi.org/10.1007/bf01166694.

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22

Süssenberger, Annette, Susanne Theodora Schmidt, Florian H. Schmidt, and Manuel F. G. Weinkauf. "Reaction progress of clay minerals and carbonaceous matter in a contact metamorphic aureole (Torres del Paine intrusion, Chile)." European Journal of Mineralogy 32, no. 6 (December 9, 2020): 653–71. http://dx.doi.org/10.5194/ejm-32-653-2020.

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Abstract. This study reports on reaction processes in a transition zone from contact to regional metamorphism by using Raman spectroscopy on carbonaceous matter (RSCM), illite “crystallinity” (Kübler index, KI), chlorite geothermometry, and thermal modeling. The thermal effect due to the emplacement of the Torres del Paine intrusion (TPI, assembly time of ca. 150 kyr) had different consequences for inorganic and organic compounds of the host rock. The thermal alteration of the pre-intrusive regional metamorphosed host rock is documented by elevated RSCM temperatures, high-temperature chlorite generations, and the appearance of epidote and retrograde Fe-rich chlorite. Microprobe analysis on chlorite indicates incomplete re-equilibration as evidenced by various chlorite populations of individual contact metamorphic samples. This study indicates that the maturity of organic matter is the most reliable and unequivocal indicator on timescales of several thousand years to determine the lateral extension of the TPI contact aureole. Raman geothermometry reveals that the lateral extension of the contact-influenced zone expands up to a distance of 1.5 km and, thus, expands to ca. 1.1 km further out than the macroscopically mappable hornfels contact aureole. The best match between measured (Raman geothermometry) and calculated (thermal modeling) ΔTmax values (ΔT=54 ∘C) is achieved with a total intrusion assembly time of 150 kyr, a magmatic temperature of 800 ∘C, a two-batch model (batch repose time of 10 kyr) with five pulses per batch, short heating durations (3 kyr), and long pulse repose times (15 kyr).

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23

Tettelaar, Tanya, and Aphrodite Indares. "Granulite-facies regional and contact metamorphism of the Tasiuyak paragneiss, northern Labrador: textural evolution and interpretation." Canadian Journal of Earth Sciences 44, no. 10 (October 1, 2007): 1413–37. http://dx.doi.org/10.1139/e07-029.

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The Tasiuyak paragneiss at the western margin of the Nain Plutonic Suite has been subjected to two granulite-facies metamorphic events: (i) regional metamorphism during the Paleoproterozoic Torngat orogeny, and (ii) contact metamorphism due to emplacement of the Mesoproterozoic Nain Plutonic Suite. Regional metamorphism led to partial melting of pelitic rocks and the development of a locally well-preserved sequence of prograde and retrograde textures. These textures are partly controlled by bulk composition and formed in the pressure–temperature (P–T) field of the continuous reaction: biotite + sillimanite + plagioclase + quartz = garnet + K-feldspar + melt, along a hairpin P–T path with peak conditions of ~8–10 kbar (0.8–1.0 GPa) and up to 870 °C in the NaKFMASH (Na2O–K2O–FeO–MgO–Al2O3–SiO2–H2O) system. These textures controlled the development of the contact metamorphic assemblages. Contact metamorphism of the pelitic rocks between the Tessiarsuyungoakh intrusion and the Makhavinekh Lake pluton led to growth of orthopyroxene-cordierite symplectite after garnet–biotite, and cordierite–spinel symplectite after garnet–sillimanite. These phase associations attest to reactions in specific microtextural settings, some of which produced a second generation of partial melt. Maximum temperatures were above ~750 °C and pressures were lower than those of the regional metamorphism. The aureole around the Makhavinekh Lake pluton is ~4 km wide and shows a progressive development of the contact metamorphic assemblages toward the pluton. In contrast, the contact metamorphic overprint is incipient around the Tessiarsuyungoakh intrusion, which developed a ~20 m wide contact aureole and is most prominent in screens of paragneiss within that intrusion.

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24

Ferguson, Colin C., and Sanaa I. Al-Ameen. "Muscovite breakdown and corundum growth at anomalously low fH2o: a study of contact metamorphism and convective fluid movement around the Omey granite, Connemara, Ireland." Mineralogical Magazine 49, no. 353 (September 1985): 505–14. http://dx.doi.org/10.1180/minmag.1985.049.353.03.

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AbstractIn the aureole of the late Caledonian Omey granite corundum develops in the Dalradian country rocks in a zone up to 250 m from the granite contact. The distribution of andalusite and K-feldspar in pelites and calcite+wollastonite+grossularite in marbles is consistent with inner-aureole metamorphic conditions of 615±25°C at 2.5±0.25 kbar, and ⋍ 0.85. Corundum develops from the reaction muscovite → corundum + K-feldspar+H2O and first appears over 100 m further from the granite than the assemblage wollastonite + grossularite + anorthite. Experimentally determined equilibria can be satisfied only if for the corundum-producing reaction was less than 0.6 and perhaps as low as 0.4. Corundum always grows within large muscovite crystals;fH2O within the crystal lattice is unrelated to that in the grain-boundary fluid of the surrounding rock.Although whole-rock oxidation ratios are irregularly distributed within the aureole they are uniformly low in corundum-bearing rocks. Reducing conditions probably resulted from localized flow of H2O-rich fluid away from the granite in a diffuse channelway that contains most of the corundum localities and also a distinctive skarn. Although corundum growth within muscovite is sealed off from the external water vapour conditions, it is suggested that movement of H2O down a thermal gradient (and hence down an fH2O gradient at constant pressure) promotes the escape of (OH)− from the muscovite lattice and so allows the corundum reaction to proceed.

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25

Longridge, Luke, Roger L. Gibson, and Paul A. M. Nex. "Structural controls on melt segregation and migration related to the formation of the diapiric Schwerin Fold in the contact aureole of the Bushveld Complex, South Africa." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 100, no. 1-2 (March 2009): 61–76. http://dx.doi.org/10.1017/s1755691009016119.

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ABSTRACTPartial melting of metapelitic rocks beneath the mafic–ultramafic Rustenburg Layered Suite of the Bushveld Complex in the vicinity of the periclinal Schwerin Fold resulted in a structurally controlled distribution of granitic leucosomes in the upper metamorphic aureole. In the core of the pericline, subvertical structures facilitated the rise of buoyant leucosome through the aureole towards the contact with the Bushveld Complex, with leucosomes accumulating in en-echelon tension gashes. In a subhorizontal syn-metamorphic shear zone to the southeast of the pericline, leucosomes accumulated in subhorizontal dilational structural sites. The kinematics of this shear zone are consistent with slumping of material off the southeastern limb of the rising Schwerin pericline. The syndeformational timing of leucosome emplacement supports a syn-intrusive, density-driven origin for the Schwerin Fold. Modelling of the cooling of the Rustenburg Layered Suite and heating of the floor rocks using a multiple intrusion model indicates that temperatures above the solidus were maintained for >600,000 years up to 300 m from the contact, in agreement with rheological modelling of floor-rock diapirs that indicate growth rates on the order of 8 mm/year for the Schwerin Fold.

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26

Likhanov, Igor I., Vladimir V. Reverdatto, and Isabella Memmi. "The origin of arfvedsonite in metabasites from the contact aureole of the Kharlovo gabbro intrusion (Russia)." European Journal of Mineralogy 7, no. 2 (March 29, 1995): 379–90. http://dx.doi.org/10.1127/ejm/7/2/0379.

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27

Roselle, Gregory T., Lukas P. Baumgartner, and John A. Chapman. "Nucleation-dominated crystallization of forsterite in the Ubehebe Peak contact aureole, California." Geology 25, no. 9 (1997): 823. http://dx.doi.org/10.1130/0091-7613(1997)025<0823:ndcofi>2.3.co;2.

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28

OKUYAMA-KUSUNOSE, YASUKO, and TETSUMARU ITAYA. "Metamorphism of carbonaceous material in the Tono contact aureole, Kitakami Mountains, Japan." Journal of Metamorphic Geology 5, no. 2 (April 1987): 121–39. http://dx.doi.org/10.1111/j.1525-1314.1987.tb00375.x.

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29

SAWAKI, TAKAYUKI. "PERICLASE IN THE CONTACT AUREOLE OF THE NOGO-HAKUSAN AREA, CENTRAL JAPAN." Journal of the Geological Society of Japan 95, no. 2 (1989): 137–40. http://dx.doi.org/10.5575/geosoc.95.137.

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30

MCFARLANE, C., and T. MARKHARRISON. "Pb-diffusion in monazite: Constraints from a high-T contact aureole setting." Earth and Planetary Science Letters 250, no. 1-2 (October 15, 2006): 376–84. http://dx.doi.org/10.1016/j.epsl.2006.06.050.

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31

Sokol, E. V., A. S. Deviatiiarova, S. N. Kokh, V. V. Reverdatto, D. A. Artemyev, and V. Yu Kolobov. "Sulfides in the marbles of spurrite-merwinite facies: the Kochumdek River, East Siberia." Доклады Академии наук 489, no. 2 (November 20, 2019): 174–78. http://dx.doi.org/10.31857/s0869-56524892174-178.

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In the marbles of the Kochumdek contact metamorphic aureole pyrrhotite, rasvumite, sphalerite, alabandite, wurtzite, galena, acanthite have been identified. Mineralogical diversity of sulphides is the consequence of the efficient crystal-chemical fractionation of trace elements under the PT‑conditions of spurrite-merwinite metamorphic facies. Trace element and isotope fingerprints of sulfides indicate that sedimentary parent rocks were the main source of sulfur and metals for sulfides mineralization.

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32

Marfin, Alexander E., Alexei V. Ivanov, Vadim S. Kamenetsky, Adam Abersteiner, Tamara Yu Yakich, and Timur V. Dudkin. "Contact Metamorphic and Metasomatic Processes at the Kharaelakh Intrusion, Oktyabrsk Deposit, Norilsk-Talnakh Ore District: Application of LA-ICP-MS Dating of Perovskite, Apatite, Garnet, and Titanite." Economic Geology 115, no. 6 (September 1, 2020): 1213–26. http://dx.doi.org/10.5382/econgeo.4744.

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Abstract The Norilsk-Talnakh ore district in the northwestern Siberian platform contains globally unique reserves of Cu-Ni-sulfides with Pt and, especially, Pd. The Oktyabrsk deposit, which is one of the largest in the district, is spatially and genetically associated with the Kharaelakh mafic-ultramafic intrusion and its exceptionally large metamorphic and metasomatic aureoles. In this study, we employed in situ laser ablation-inductively coupled plasma-mass spectrometry U-Pb isotope dating of apatite, titanite, garnet, and perovskite that cocrystallize with disseminated sulfides within the aureole of metasomatic and contact metamorphic rocks. The calculated isotopic ages for apatite (257.3 ± 4.5 and 248.9 ± 5.1 Ma), titanite (248.6 ± 6.8 and 249.1 ± 2.9 Ma), garnet (260.0 ± 11.0 Ma), and perovskite (247.3 ± 8.2 Ma), though with large uncertainties, indicate that sulfide mineralization within metasomatic and contact-metamorphic rocks is coeval with the emplacement of the Kharaelakh intrusion. These isotopic dates are in complete agreement with the published isotope dilution-thermal ionization mass spectrometry U-Pb zircon ages for the Norilsk intrusions and, at the same time, notably older than available Re-Os isochron ages of sulfides. The latter ages have been long interpreted as evidence for a prolonged duration of magmatic ore-forming processes; however, our data narrow their life span. Trace elements in titanite and garnet allow distinguishing late- and postmagmatic grains, which show indistinguishable U-Pb isotope ages.

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33

Cui, Xiaojun, Peter I. Nabelek, and Mian Liu. "Heat and fluid flow in contact metamorphic aureoles with layered and transient permeability, with application to the Notch Peak aureole, Utah." Journal of Geophysical Research: Solid Earth 106, B4 (April 10, 2001): 6477–91. http://dx.doi.org/10.1029/2000jb900418.

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34

VOLDMAN, GUSTAVO G., GUILLERMO L. ALBANESI, and MARGARITA DO CAMPO. "Conodont palaeothermometry of contact metamorphism in Middle Ordovician rocks from the Precordillera of western Argentina." Geological Magazine 145, no. 4 (March 27, 2008): 449–62. http://dx.doi.org/10.1017/s001675680800455x.

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AbstractThe Yerba Loca Formation (Middle–Upper Ordovician), exposed in the Western Precordillera, San Juan, Argentina, is made up of clastic–carbonate turbidites, and basic–ultrabasic rocks. It is affected by regional Siluro-Devonian very low-grade metamorphism that locally reaches greenschist facies. At Ancaucha creek, 45 conodont samples were taken from two sections that include 30 to 50 m thick sills. In order to analyse the thermal alteration patterns produced by these intrusive bodies, conodont Colour Alteration Index (CAI) is contrasted with optical petrography and X-ray diffraction analyses of clay minerals. The intrusions are dated as post-Darriwilian (Da2), as determined by conodont biostratigraphy of the host rock, which indicates theParoistodus horridusSubzone of theLenodus variabilisZone. The distribution of CAI values defines a thermal aureole of about 2.5 times intrusion thickness that prevailed over the later very low-grade metamorphism. Metasomatism at Ancaucha creek is recorded by CAI values of 4 to 7, particularly restricted to a few layers close to the intrusions, as indicated by conodont textures and rock fabric. One-dimensional thermal computer simulation conforms to empirical data indicating temperatures greater than 600 °C for the contact zone, although it points out slightly narrower thermal aureoles. The clay mineral assemblage of most of the analysed samples (chlorite, illite, smectite and I/S mixed-layers) is complex and probably derives from several superimposed processes, thus representing non-equilibrium assemblages. In turn, KI values (0.27–0.32) indicate anchizone metamorphism, in agreement with regional CAI values of 4; consequently, the occurrence of smectite and I/S probably resulted from retrograde diagenesis processes.

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35

BARBOZA, SCOTT A., and GEORGE W. BERGANTZ. "Metamorphism and Anatexis in the Mafic Complex Contact Aureole, Ivrea Zone, Northern Italy." Journal of Petrology 41, no. 8 (August 1, 2000): 1307–27. http://dx.doi.org/10.1093/petrology/41.8.1307.

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36

Yardley, B. W. D. "Equilibrium and Kinetics in Contact Metamorphism. The Ballachulish Igneous Complex and its Aureole." Lithos 30, no. 1 (April 1993): 91–92. http://dx.doi.org/10.1016/0024-4937(93)90008-z.

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37

JOESTEN, RAYMOND, and GEORGE FISHER. "Kinetics of diffusion-controlled mineral growth in the Christmas Mountains (Texas) contact aureole." Geological Society of America Bulletin 100, no. 5 (May 1988): 714–32. http://dx.doi.org/10.1130/0016-7606(1988)100<0714:kodcmg>2.3.co;2.

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38

Moazzen, M., and M. Modjarrad. "Contact metamorphism and crystal size distribution studies in the Shivar aureole, NW Iran." Geological Journal 40, no. 5 (2005): 499–517. http://dx.doi.org/10.1002/gj.1025.

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39

Nabelek, Peter I., and Theodore C. Labotka. "Implications of geochemical fronts in the Notch Peak contact-metamorphic aureole, Utah, USA." Earth and Planetary Science Letters 119, no. 4 (October 1993): 539–59. http://dx.doi.org/10.1016/0012-821x(93)90061-d.

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40

Yoder, H. S. "Equilibrium and kinetics in contact metamorphism: The ballachulish igneous complex and its aureole." Geochimica et Cosmochimica Acta 56, no. 7 (July 1992): 2965–66. http://dx.doi.org/10.1016/0016-7037(92)90378-v.

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41

Wilkinson, J. J. "The role of metamorphic fluids in the development of the Cornubian orefield: fluid inclusion evidence from south Cornwall." Mineralogical Magazine 54, no. 375 (June 1990): 219–30. http://dx.doi.org/10.1180/minmag.1990.054.375.08.

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AbstractVeins developed during contact metamorphism associated with the emplacement of the Cornubian granite batholith contain both H2O-rich and CO2-rich fluid inclusions. Microthermometric data indicate that unmixing of a low-CO2, low-salinity fluid occurred at 400–200°C and 1000–500 bars to produce low-density CO2-rich vapour and saline aqueous fluids (8–42 wt. % NaCl equivalent). Decrepitation-linked ICP analyses show that the cation composition of the brines is dominated by Na, K and Ca, but that significant amounts of Li, Sr, Ba, Fe, Mn, Zn and B are also present. Bulk volatile analyses confirm the dominance of CO2 over N2 and CH4 in the vapour phase, with CO2/N2 molar ratios of 15.3–28.7 and CO2/CH4 molar ratios of 66.9–292. The relative abundance of nitrogen suggests an aureole-derived ‘organic’ component is present.The source of the fluids is ambiguous as they are intermediate in composition between ideal ‘magmatic’ and ‘metamorphic’ end-members. It is proposed that this is due to mixing of the two types of fluid in the contact aureole during granite intrusion. A model is suggested in which magmatic-metamorphic circulation occurred synchronously with granite emplacement and subsequently evolved to a meteoric-dominated system with the bulk of the ore deposits forming in response to the influx of meteoric fluids.

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42

Wang, Wei-(RZ), Geoffrey Clarke, Nathan R. Daczko, and Yue Zhao. "Modelling the partial melting of metasediments in a low-pressure regional contact aureole: the effect of water and whole-rock composition." Geological Magazine 156, no. 08 (December 3, 2018): 1400–1424. http://dx.doi.org/10.1017/s001675681800078x.

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AbstractLow-pressure regional aureoles with steep metamorphic field gradients are critical to understanding progressive metamorphism in high-temperature metasedimentary rocks. Delicately layered pelitic and psammitic metasedimentary rocks at Mt Stafford, central Australia, record a greenschist- to granulite-facies Palaeoproterozoic regional aureole, associated with S-type granite plutons, reflecting metamorphism in the range 500–800 °C and at ∼3 kbar. The rocks experienced minimal deformation during metamorphism and partial melting. Partial melting textures evolve progressively along the steep metamorphic field gradient from the incipient stages of melting marked by cuspate grains with low dihedral angles, to melt proportions sufficient to form diatexite with schollen. Phase equilibria modelling in the NCKFMASHTO system for pelitic, semi-pelitic and high- and low-ferromagnesian psammitic samples quantitatively illustrates the dependence of partial melting on rock composition and water volume. Pelitic compositions are more fertile than psammitic compositions when the water content in the rocks is low, especially during the early stages of melting. The whole-rock ferromagnesian component additionally influences melt fertility, with ferromagnesian-rich psammite being more fertile than psammite with a lower ferromagnesian component. Subtle variations in free water content can result in obvious changes in melt volume but limited variation in melt composition. Distinct melting histories of pelitic and psammitic rocks inferred from field relationships may be partially attributed to potential differences in water volume retained to super-solidus conditions. Melt composition is more dependent on the rock composition than the variation in water content.

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43

Gallien, F., R. Abart, and S. Wyhlidal. "Contact metamorphism and selective metasomatism of the layered Bellerophon Formation in the eastern Monzoni contact aureole, northern Italy." Mineralogy and Petrology 91, no. 1-2 (March 26, 2007): 25–53. http://dx.doi.org/10.1007/s00710-007-0184-6.

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44

Likhanov, Igor I., Vladimir V. Reverdatto, and Isabella Memmi. "Short-range mobilization of elements in the biotite zone of contact aureole of the Kharlovo gabbro intrusion (Russia)." European Journal of Mineralogy 6, no. 1 (February 4, 1994): 133–44. http://dx.doi.org/10.1127/ejm/6/1/0133.

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45

Renzulli, Alberto, Mario Tribaudino, Emma Salvioli-Mariani, Giancarlo Serri, and Paul M. Holm. "Cordierite-anorthoclase hornfels xenoliths in Stromboli lavas (Aeolian Islands, Sicily): an example of a fast cooled contact aureole." European Journal of Mineralogy 15, no. 4 (July 28, 2003): 665–79. http://dx.doi.org/10.1127/0935-1221/2003/0015-0665.

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46

Yu, Yang, and S. A. Morse. "40Ar/39Ar chronology of the Nain anorthosites, Canada." Canadian Journal of Earth Sciences 30, no. 6 (June 1, 1993): 1166–78. http://dx.doi.org/10.1139/e93-099.

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A hornblende 40Ar/39Ar age of 1328 ± 8 Ma has been obtained from the contact aureole of the Bird Lake Massif, confirming it as one of the oldest members of the Nain plutonic suite. This age constrains the timing of the early stage magma activity of the Nain plutonic suite.Plagioclase samples from the intrusions yield either U-shaped, or staircase-shaped 40Ar/39Ar age spectra, and most of them have two isochrons of similar age but greatly different initial argon composition. Most plagioclase closure ages are >95% of either the hornblende age from a contact aureole or coexisting biotite ages, and appear to reflect single cooling events for each intrusion. Two major stages of emplacement for the Nain anorthosites are identified: an older anorthosite event and a main anorthosite event, in agreement with results from earlier field studies. The Port Manvers Run, Paul Island, and Nukasorsuktokh Island intrusions yield much younger plagioclase ages than any previously established intrusion ages, probably reflecting previously unknown later, local heating events.The total duration of the major anorthositic magma activity in the Nain region is about 23 Ma, estimated from the Bird Lake massif margin at 1328 ± 8 Ma and the Kiglapait intrusion at 1305 ± 2 Ma (Sm/Nd, U/Pb), implying an emplacement rate of about 0.0022 km3/year. This rate is far less than the effusion rate of magma on some of the Phanerozoic rifted margins and supports the "aborted rifting" model for the generation of massif anorthosite.

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47

Horacek, M. "Lithologic Control on Fluid Evolution During Contact Metamorphism in the Eastern Monzoni Thermal Aureole." Mineralogical Magazine 62A, no. 2 (1998): 650. http://dx.doi.org/10.1180/minmag.1998.62a.2.09.

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48

Hobson, A., F. Bussy, and J. Hernandez. "Shallow-Level Migmatization of Gabbrosin a Metamorphic Contact Aureole, Fuerteventura Basal Complex, Canary Islands." Journal of Petrology 39, no. 5 (May 1, 1998): 1025–37. http://dx.doi.org/10.1093/petroj/39.5.1025.

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49

WHEELER, J. "Disequilibrium in the Ross of Mull Contact Metamorphic Aureole, Scotland: a Consequence of Polymetamorphism." Journal of Petrology 45, no. 4 (April 1, 2004): 835–53. http://dx.doi.org/10.1093/petrology/egg113.

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50

LINKLATER, C. M., B. HARTE, and A. E. FALLICK. "A stable isotope study of the migmatitic rocks in the Ballachulish contact aureole, Scotland." Journal of Metamorphic Geology 12, no. 3 (May 1994): 273–83. http://dx.doi.org/10.1111/j.1525-1314.1994.tb00022.x.

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