scholarly journals Epizonal I- and A-type granites and associated ash-flow tuffs, Fogo Island, northeast Newfoundland

1995 ◽  
Vol 32 (11) ◽  
pp. 1835-1844 ◽  
Author(s):  
Hamish A. Sandeman ◽  
John Malpas
Keyword(s):  
Alkali Feldspar ◽  
Granitic Rocks ◽  
Calc Alkaline ◽  
Fine Grained ◽  
Sedimentary Sequences ◽  
Intrusive Rocks ◽  
High Silica ◽  
Composite Nature ◽  
End Members ◽  
Devonian Age

Magmatic activity of Silurian–Devonian age is widespread in the Appalachian–Caledonian Orogen. A marked characteristic of this magmatism is the composite nature of the igneous suites, which range from peridotite to granodiorite in single plutonic bodies. The origin of these suites is still enigmatic, and the assumption that all are the same not proven. Such a suite of intrusive rocks, ranging in composition from minor peridotite to granodiorite, intrudes an openly folded sequence of Silurian volcanogenic sandstones and ash-flow tuffs on Fogo Island, northeast Newfoundland. Two units, the Rogers Cove and Hare Bay microgranites, consist of fine-grained hastingsite granites with spherulitic and flow-banded textures, and exhibit drusy cavities and microfractures that contain the mineral assemblage hastingsitic hornblende + plagioclase + magnetite + zircon. These rocks are characterized by elevated high field strength element contents (e.g., Zr = 74–672 and Y = 21–103 ppm), very high FeO*/MgO ratios (FeO*/MgO = 2.4–93.5), and 10 000 Ga/Al ratios of 1.67–10.52, indicating an A-type granitoid affinity. A third and the most voluminous granitic unit, the Shoal Bay granite, is an alkali-feldspar-phyric, medium-grained, equigranular biotite–hastingsite granite with hastingsite and annitic biotite interstitial to euhedral plagioclase, anhedral quartz, and perthite crystals. The Shoal Bay granite exhibits mineral parageneses similar to the microgranites, but chemical characteristics more typical of calc-alkaline, I-type granitoids. Volcanic–sedimentary sequences spatially associated with the granitic rocks include dense, welded, high-silica, hastingsite-bearing ash-flow tuffs with compositions that suggest they represent erupted equivalents of fractionated end members of the Shoal Bay granite. The rocks making up the Fogo Island batholith have been directly equated with the bimodal, calc-alkaline Mount Peyton batholith of northeast Newfoundland, but the specialized A-type nature of the Fogo granites suggests differing source conditions for the two suites.

scholarly journals Geology and Mineralization of the Bald Hill Molybdenum Occurrence, Buller District, West Nelson, New Zealand

2021 ◽  
Author(s):  
◽  
Allan John Eggers
Keyword(s):  
Large Scale ◽  
Granitic Rocks ◽  
Calc Alkaline ◽  
Southeastern Australia ◽  
Lower Ordovician ◽  
Isotopic Analyses ◽  
Intrusive Rocks ◽  
Normative Quartz ◽  
Granite Batholith ◽  
High Level

<p>Molybdenite mineralization occurs within the Bald Hill Prospect (West Nelson) in brecciated and hornfelsed Greenland Group slates and metagreywackes and associated quartz trondhjemite porphyry minor intrusions (Lyell Porphyry). Potassium argon (K-Ar) ages of the Lyell Porphyry, several granites forming part of the adjacent Karamea Granite batholith (Bald Hill Granites) and mineralized hornfelsic country rocks fall in the range 102-120 Ma (mid-Cretaceous). Adjacent lower Ordovician Greenland Group slates yielded four K-Ar ages in the range 112-226 Ma indicating partial argon outgassing of these older metasediments. The Bald Hill Granites and the Lyell Porphyry granitic rocks belong to separate petrogenic provinces. Bald Hill Granites forming the western margin of the Karamea Granite batholith occur as a suite of foliated, medium-grained, muscovite-bearing leucogranites, pink microgranites and biotite-granites. Chemically these rocks are peraluminous-potash granites with 72-75% SiO2, MgONa2O with Rb > Sr and always contain more than 30% normative quartz and 3% normative corundum. In contrast, the Lyell Porphyry rocks intruding both Greenland Group and Bald Hill Granite country rocks, form a series of small, high-level plutons and cross-cutting dykes of quartz trondhjemite, granodiorite, quartz diorite, lamprophyre and quartz-bearing gabbroporphyry. Chemically the Lyell Porphyry intrusive rocks are soda-rich calc-alkaline granitoids containing 46-70% SiO2, >1% MgO, >2.2% CaO, with Na2O>K2O and Sr>Rb with less than 28% normative quartz and less than 2% normative corundum. From their studies of granite batholiths in southeastern Australia, Chappell and White (1974) recognise two contrasting granitoid types called I-type and S-type granites. The Lyell Porphyry and several other intrusive stocks associated with molybdenum mineralization in West Nelson and North Westland are shown to correspond to I-type granites, in contrast to the Karamea batholith granites (including Bald Hill Granites) which conform to S-type granites. Sulphur isotopic analyses of mineralization for ten molybdenum prospects in West Nelson indicate uniformly high temperatures of mineralization in the range 400° to 500°C, with a probable magmatic source for sulphur. The Bald Hill and other S-type granites forming the Karamea batholith were probably formed by the ultrametamorphism of crustal sedimentary material. The Lyell Porphyry and other molybdenum-bearing calc-alkaline intrusive stocks represent melt phases of deeper origin intruding the overlying granites and sediments. The emplacement of these stocks appears to equate with north-south lineaments and large scale circular features in the granite terranes of West Nelson. The geological setting, age, petrological characteristics and molybdenite mineralization of the Lyell Porphyry and Bald Hill Granites are similar to that of other West Nelson occurrences. All are associated with mid-Cretaceous minor granitic porphyry intrusions, emplaced in Paleozoic metasediments, close to the margins of the Karamea and Separation Point batholiths.</p>

scholarly journals Geology and Mineralization of the Bald Hill Molybdenum Occurrence, Buller District, West Nelson, New Zealand

2021 ◽  
Author(s):  
◽  
Allan John Eggers
Keyword(s):  
Large Scale ◽  
Granitic Rocks ◽  
Calc Alkaline ◽  
Southeastern Australia ◽  
Lower Ordovician ◽  
Isotopic Analyses ◽  
Intrusive Rocks ◽  
Normative Quartz ◽  
Granite Batholith ◽  
High Level

<p>Molybdenite mineralization occurs within the Bald Hill Prospect (West Nelson) in brecciated and hornfelsed Greenland Group slates and metagreywackes and associated quartz trondhjemite porphyry minor intrusions (Lyell Porphyry). Potassium argon (K-Ar) ages of the Lyell Porphyry, several granites forming part of the adjacent Karamea Granite batholith (Bald Hill Granites) and mineralized hornfelsic country rocks fall in the range 102-120 Ma (mid-Cretaceous). Adjacent lower Ordovician Greenland Group slates yielded four K-Ar ages in the range 112-226 Ma indicating partial argon outgassing of these older metasediments. The Bald Hill Granites and the Lyell Porphyry granitic rocks belong to separate petrogenic provinces. Bald Hill Granites forming the western margin of the Karamea Granite batholith occur as a suite of foliated, medium-grained, muscovite-bearing leucogranites, pink microgranites and biotite-granites. Chemically these rocks are peraluminous-potash granites with 72-75% SiO2, MgONa2O with Rb > Sr and always contain more than 30% normative quartz and 3% normative corundum. In contrast, the Lyell Porphyry rocks intruding both Greenland Group and Bald Hill Granite country rocks, form a series of small, high-level plutons and cross-cutting dykes of quartz trondhjemite, granodiorite, quartz diorite, lamprophyre and quartz-bearing gabbroporphyry. Chemically the Lyell Porphyry intrusive rocks are soda-rich calc-alkaline granitoids containing 46-70% SiO2, >1% MgO, >2.2% CaO, with Na2O>K2O and Sr>Rb with less than 28% normative quartz and less than 2% normative corundum. From their studies of granite batholiths in southeastern Australia, Chappell and White (1974) recognise two contrasting granitoid types called I-type and S-type granites. The Lyell Porphyry and several other intrusive stocks associated with molybdenum mineralization in West Nelson and North Westland are shown to correspond to I-type granites, in contrast to the Karamea batholith granites (including Bald Hill Granites) which conform to S-type granites. Sulphur isotopic analyses of mineralization for ten molybdenum prospects in West Nelson indicate uniformly high temperatures of mineralization in the range 400° to 500°C, with a probable magmatic source for sulphur. The Bald Hill and other S-type granites forming the Karamea batholith were probably formed by the ultrametamorphism of crustal sedimentary material. The Lyell Porphyry and other molybdenum-bearing calc-alkaline intrusive stocks represent melt phases of deeper origin intruding the overlying granites and sediments. The emplacement of these stocks appears to equate with north-south lineaments and large scale circular features in the granite terranes of West Nelson. The geological setting, age, petrological characteristics and molybdenite mineralization of the Lyell Porphyry and Bald Hill Granites are similar to that of other West Nelson occurrences. All are associated with mid-Cretaceous minor granitic porphyry intrusions, emplaced in Paleozoic metasediments, close to the margins of the Karamea and Separation Point batholiths.</p>

scholarly journals Geotermobarometria y Quimica Mineral del Pluton Sienito "Pajeú" Serra Talhada, Pernambuco, NE de Brasil

1998 ◽  
Vol 25 (1) ◽  
pp. 61
Author(s):  
CRISTINA NANCY REYES
Keyword(s):  
Alkali Feldspar ◽  
Mineral Chemistry ◽  
Northeastern Brazil ◽  
Calc Alkaline ◽  
Calcic Plagioclase ◽  
Perfect Agreement ◽  
Fine Grained ◽  
Microgranular Enclaves ◽  
High Alkali ◽  
Opaque Minerals

The Pajeu Syenitic Complex, Serra Talhada, Pernambuco province, northeastern Brazil is tectonically emplaced within the framework of Neoproterozoic (Brasiliano). In the present work were studied whole rock and specific mineral chemical data (85’24” – 816’31” S and 3819’8” – 3836’2” W). Two distinct petrographic facies have been identified. The predominant porphyritic syenite facies is characterized by perthite microcline megacrysts (up to 8 cm long) and fine grained syenite; both facies have distributed melanocratic microgranular enclaves of syenitic composition. The mineral assemblage comprising alkali feldspar, plagioclase, quartz, biotite, hornblende and accessory amounts of zircon, opaque minerals, epidote, allanite, sphene etc. the geochemical signatures define overlapping calc-alkaline and shoshonitic affinities and metaluminous to peraluminous nature. The complex is characterized by silica enrichment (62.2% - 72.4%), moderate alumina (14% - 16.6%) and high alkali abundance (8.6% - 9.1%). The enclaves have low silica (54.2% - 56.4%) and corresponding enrichment in mafic phases. High alkali abundance, preponderance of K2O over Na2O and TiO2 variation between 0.22% to 0.57% are in agreement with shoshonitic affinities. Mineral chemistry of amphiboles enables their classification as edenite – magnesian hornblende. The micas are mainly magnesian biotite. Plagioclase is usually oligoclase (An20) and K-feldspar is orthoclase. The geochemical signatures of biotite and amphibole are in perfect agreement with the other shoshonitic rocks of northeastern of Brazil. Temperatures estimateds for calcic plagioclase and amphibole pairs indicate a temperature range of 646-671C for porphyritic syenite and 629-650C for enclaves. Geobarometric estimates, using Al in amphiboles indicate equation pressure of 1,48 Kbar to 2,26 Kbar for porphyritic syenite and 1,01 Kbar for enclaves. Other pressure estimates yielding 2,25 Kbar to 2,91 Kbar and 1,76 Kbar respectively, though at variance with the earlier estimates correspond with epizonal emplacement of the pluton.

scholarly journals The Upper Cretaceous intrusive rocks with extensive crustal contribution in Hacımahmutuşağı Area (Aksaray/Turkey)

2019 ◽  
Vol 70 (3) ◽  
pp. 261-276
Author(s):  
Serhat Köksal
Keyword(s):  
Mafic Magma ◽  
The Other ◽  
Granitic Rocks ◽  
Geochemical Data ◽  
Magma Source ◽  
Accessory Zircon ◽  
Fine Grained ◽  
Intrusive Rocks ◽  
Crustal Contribution ◽  
Opaque Minerals

Abstract The Hacımahmutuşağı area (Aksaray/Turkey) is located in the western part of the Central Anatolian Crystalline Complex (CACC). Gneiss and marble compose the basement units, while intrusive rocks are gabbros and granitoids. The pegmatitic hornblende gabbros contain pegmatitic to fine-grained hornblendes, plagioclase, clinopyroxene, and accessory opaque minerals. The fine-grained gabbros, on the other hand, are composed of plagioclase, hornblende, and biotite as major components whereas the apatite and opaque minerals are present in accessory content. Granitic– granodioritic rocks are the common intrusive rock types in the area, and constitute quartz, orthoclase, plagioclase and biotite, and accessory zircon and opaque minerals. Leucogranites, comprising quartz, orthoclase, plagioclase with minor biotite, hornblende, and with accessory apatite and opaque minerals, are found as dykes intruding the marble and the granitic–granodioritic rocks. Strontium–neodymium isotope data of gabbros and granitoids have high 87Sr/86Sr(i) ratios (0.7076 to 0.7117) and low ɛNd(i) values (−5.0 to −9.8) point out enriched source and pronounced crustal contribution in their genesis. In the Hacımahmutuşağı area, it is plausible that the heat increase caused by the hot zone, which was generated by underplating mafic magma along with the hydrous mafic sills in the lower crust, might have resulted in partial melts from crystallized mafic sills and older crustal rocks. It can be suggested that these hybrid melts adiabatically rose to the shallow crust, ponded and crystallized there and formed the magma source of the intrusive rocks within the Hacımahmutuşağı area and the other hybrid granitic rocks with crustal signatures in the CACC. Geochemical data indicate that granitoids and gabbros are collision to post-collision related sub-alkaline rocks derived from an enriched source with extensive crustal inputs.

Major- and trace-element composition of REE-rich turkestanite from peralkaline granites of the Morro Redondo Complex, Graciosa Province, south Brazil

2010 ◽  
Vol 74 (4) ◽  
pp. 645-658 ◽  
Author(s):  
F. C. J. Vilalva ◽  
S. R. F. Vlach
Keyword(s):  
Trace Element ◽  
Inductively Coupled Plasma ◽  
Alkali Feldspar ◽  
Trace Element Composition ◽  
Inductively Coupled ◽  
Coupled Substitution ◽  
Plasma Mass Spectrometry ◽  
Compositional Variations ◽  
End Members ◽  
South Brazil

AbstractTurkestanite, a rare Th- and REE-bearing cyclosilicate in the ekanite–steacyite group was found in evolved peralkaline granitesfrom the Morro Redondo Complex, south Brazil. It occurswith quartz, alkali feldspar and an unnamed Y-bearing silicate. Electron microprobe analysis indicates relatively homogeneous compositions with maximum ThO2, Na2O and K2O contentsof 22.4%, 2.93% and 3.15 wt.%, respectively, and significant REE2O3 abundances(5.21 to 11.04 wt.%). The REE patterns show enrichment of LREE over HREE, a strong negative Eu anomaly and positive Ce anomaly, the latter in the most transformed crystals. Laser ablation inductively coupled plasma mass spectrometry trace element patterns display considerable depletions in Nb, Zr, Hf, Ti and Li relative to whole-rock sample compositions. Observed compositional variations suggest the influence of coupled substitution mechanisms involving steacyite, a Na-dominant analogue of turkestanite, iraqite, a REE-bearing end-member in the ekanite–steacyite group, ekanite and some theoretical end-members. Turkestanite crystals were interpreted as having precipitated during post-magmatic stages in the presence of residual HFSE-rich fluidscarrying Ca, the circulation of which wasenhanced by deformational events.

scholarly journals Petrogenesis of the synplutonic high-magnesian porphyritic dykes from the mafic-granitoid plutons of the East-European Craton, Voronezh crystalline massif

2019 ◽  
Vol 64 (4) ◽  
pp. 356-371
Author(s):  
R. A. Terentiev
Keyword(s):  
Trace Elements ◽  
Magma Chamber ◽  
Earth Element ◽  
Parent Magma ◽  
Chrome Spinel ◽  
Calc Alkaline ◽  
East European ◽  
Fine Grained ◽  
Mineral Inclusions ◽  
Metasomatized Mantle

This paper documents the data on high-Mg porphyrite dykes (PDs) from the mafic to felsic (~2.09 Ma) plutons of Elan complex (EC). The low-thickness (first centimeters) synplutonic dykes are characterized by sharp straight contacts without visible chilling zones, in contrast to the larger (up to 119 m) dykes that have gradual transitions. The dykes are fresh, porphyritic (bronzite, Al-enstatite, labradorite) and has fine-grained mainly quartzo-feldspathic (+biotite, sulfides, accessories, ±hypersthene) matrix. Based on geochemistry data the PDs are intermediate rocks (SiO2 = 58.9–60.3 wt. %) and plot into calc-alkaline series with high magnesian of whole rock (Mg# ~0.7) and felsic (68.9–70.2 wt. %) matrix (Mg# ~0.5). The PDs show differentiated rare-earth element patterns with negligible Eu anomalies. The bronzite phenocrysts varying sizes are characterized by block zoning and contain irregular inclusions of olivine (Mg# ~0.85), clinopyroxene (Mg# ~0.88), phlogopite (Mg# up to 0.94), labradorite, chrome spinel, graphite and sulfides. The Al-enstatite phenocrysts are practically sterile with respect to trace elements and mineral inclusions. The geochemical features as well as diffusion zones, reaction rims, and resorbed faces of the phenocrysts such as orthopyroxene and plagioclase indicate processes of recrystallization and/or partial dissolution of nonequilibrium crystals in the melt and indicate intratelluric nature of the dyke phenocrysts that cores are inherited from the EC derivatives/cumulate. The mineral thermometry estimates are: (1) the parent magma starting temperatures of 1200–1400 °С and (2) the EC crystallization temperatures 1080–1155 °С, (3) the PD emplacement temperatures 910–1070 °С. The petrogenetic model supposes the generation of EC high-temperature magmas similar to boninites from an upper metasomatized mantle. The melt is contaminated with continental crust lithologies. It implies the half-way evolved magma chamber in the crust. The PD melt, as a result of ending of the half-way magma chamber evolution, was emplaced into the still unheated EC plutons.

scholarly journals Effects of Separated Fractions of Fbc Bottom Ash on Selected Properties of Cement Mortars

2020 ◽  
Vol 30 (4) ◽  
pp. 1-20
Author(s):  
Zbigniew Kledyński ◽  
Łukasz Krysiak
Keyword(s):  
Power Plants ◽  
Activity Index ◽  
Bottom Ash ◽  
High Water ◽  
Coarse Grained ◽  
Partial Replacement ◽  
Fine Grained ◽  
Cement Mortars ◽  
Inert Additive ◽  
High Silica

Abstract This paper discusses the effects of partial replacement of cement with fluidized bed bottom ash on the properties of mortars. The analyzed ash samples originating from four Polish power plants were separated by grain size selection into fine and coarse-grained fractions. This process leads to a creation of derivative samples of differing physical properties and, partially, phase compositions, as tested in XRD and TG analyses. Despite its high water demand, the obtained fine-grained fraction has the potential for application in cementbased composites as a reactive, pozzolanic additive. An acceptable activity index may be reached when the sulfate content is limited, implying benefits of combining the ash with low gypsum cements. The coarse-grained fraction is significantly less reactive, while a high silica and aluminate content is related to improved mechanical properties of the composite. It can, therefore, potentially be used as a quasi-inert additive or a substitute for sand.

scholarly journals Análise e Avaliação dos Problemas Existentes na Fachada de Arenito do Museu Júlio de Castilhos, Porto Alegre, RS

2007 ◽  
Vol 34 (1) ◽  
pp. 63
Author(s):  
VERÔNICA DI BENEDETTI ◽  
RUY PAULO PHILIPP ◽  
ROBERTO SACKS DE CAMPOS
Keyword(s):  
Chemical Deposition ◽  
Alkali Feldspar ◽  
Mineralogical Composition ◽  
Granitic Rocks ◽  
Porto Alegre ◽  
Urban Architecture ◽  
Weathering Processes ◽  
Military Engineer ◽  
Petrographic Analyses ◽  
The City

The Júlio de Castilhos museum of Porto Alegre, formerly used as residence, was built in 1877 by a military engineer Catão Roxo. This building is one of the few examples of urban architecture from the last part of the nineteenth century. Its façade is covered by arenitic and granitic rocks quarried near the city. The covering shows the effects of weathering processes occurred during many years. Some of these were observed during a façade mapping as loss of rocky materials, discoloration, chemical deposition, desintegration and fracturing. Petrographic analyses of the arenite indicate an arcosean composition, rich in quartz, with plagioclase and alkali-feldspar (microcline) and opaque minerals in lesser amounts. The grains have a fine layer of iron oxide (hematite) clad, with a fringe of siliceous cement. The remained pores are filled by clay minerals, mainly illite. The elevated degree of compactation and diagenesis are responsible for the high coherence of the rock, allowing its use as covering rock. The petrographic features (textures and mineralogical composition) indicate that the arenites used on the façade’s museum, comes from the Botucatu Formation. The recognition of the mineral constituents and the knowledge of regional geology allow the façade’s recuperation through the replacing of unrecoverable pieces by new ones.

scholarly journals Age and origin of the Cannon Point syenite, Essex County, New York: southernmost expression of Monteregian Hills magmatism?

2017 ◽  
Vol 54 (4) ◽  
pp. 379-392
Author(s):  
David G. Bailey ◽  
Marian Lupulescu ◽  
Jeffrey Chiarenzelli ◽  
Jonathan P. Traylor
Keyword(s):  
New York ◽  
New York State ◽  
Alkali Feldspar ◽  
Crustal Material ◽  
Lake Champlain ◽  
Essex County ◽  
York State ◽  
Fine Grained ◽  
The North ◽  
Basement Faults

Two syenite sills intrude the local Paleozoic strata of eastern New York State and are exposed along the western shore of Lake Champlain. The sills are fine-grained, alkali feldspar syenites and quartz syenites, with phenocrysts of sanidine and albite. The two sills are compositionally distinct, with crossing rare earth element profiles and different incompatible element ratios, which eliminates the possibility of a simple petrogenetic relationship. Zircon extracted from the upper sill yields a U–Pb age of 131.1 ± 1.7 Ma, making the sills the youngest known igneous rocks in New York State. This age is similar to that of the earliest intrusions in the Monteregian Hills of Quebec, >100 km to the north. Sr and Nd radiogenic isotope ratios are also similar to those observed in some of the syenitic rocks of the eastern Monteregian Hills. The Cannon Point syenites have compositions typical of A-type, within-plate granitoids. They exhibit unusually high Ta and Nb concentrations, resulting in distinct trace element signatures that are similar to those of the silicic rocks of the Valles Caldera, a large, rift-related magmatic system. We suggest that the Cannon Point syenites were melts derived primarily by anatexis of old, primitive, lower crustal material in response to Mesozoic rifting and to the intrusion of mantle-derived magmas. The sills indicate that the effects of continental rifting were spatially and temporally extensive, resulting in the reactivation of basement faults in the Lake Champlain Valley hundreds of kilometers west of the active rift boundary, and crustal melting >50 Ma after the initiation of rifting.

Exemples de mélange de magmas en contexte plutonique: les enclaves des tonalites–granodiorites du massif de Bono (Sardaigne septentrionale)

1989 ◽  
Vol 26 (6) ◽  
pp. 1264-1281 ◽  
Author(s):  
C. Cocirta ◽  
J. B. Orsini ◽  
C. Coulon
Keyword(s):  
Geochemical Data ◽  
Mixing Process ◽  
Calc Alkaline ◽  
Specific Group ◽  
Mineralogical Analysis ◽  
Magmatic Origin ◽  
Interaction Mechanisms ◽  
Compositional Variations ◽  
End Members ◽  
Host Rocks

In calc-alkaline orogenic plutons, the dark xenoliths and their host rocks must be considered the expression of partial mixing of magma.Three associations of this type have been investigated and are illustrated by the Bono pluton (northern Sardinia)— a composite pluton including three intrusives of different nature (tonalitic to granodioritic) and containing a very large number of basaltic xenoliths of magmatic origin. Detailed mineralogical analysis of the two end members in each association, coupled with geochemical data, has determined the major petrogenetic mechanisms intervening in the mixing process in a plutonic setting: temperature equilibration, mechanical exchanges of crystals, chemical exchanges, etc. The most important result of this article, however, is to show that each intrusion is related to a specific group of xenoliths that is characterized by constant FeOt/MgO. The latter reflects the different composition of basaltic components, and it is concluded that each intrusive event is associated with a unique mixing episode. As in volcanic settings, the mixing process may have initiated the intrusion.The extreme compositional variations in the magmatic xenoliths, recognized in several series of orogenic plutons, is explained here by different initial basaltic end members and by variation in the intensity of the interaction mechanisms. [Journal Translation]

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