Contribution of enclave studies to the understanding of origin and evolution of granitic magmas

Didier, Jean

doi:10.1007/bf01820572

Cited by 105 publications

(47 citation statements)

References 9 publications

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“…The frequent presence of basic to intermediate igneous enclaves in granitic rocks, is considered usually as an evidence for hybridization with a mantle-derived component (Vernon, 1984;Didier, 1987;Orsini et al, 1991;Barbarin and Didier, 1992;Dias and Leterrier, 1994;Moreno-Ventas et al, 1995;Bea et al, 1999;Collins et al, 2000;Dias et al, 2002;Bonin, 2004;Janousek et al, 2004;Silva and Neiva, 2004;Renna et al, 2006;Slaby and Martin, 2008). However a simple mixing model (not shown) with a basic pole with a Sr-Nd isotopic composition close to bulk-earth values (as used by Moreno-Ventas et al, 1995) and an acid end-member corresponding to the average of lower crustal xenoliths (Villaseca et al, 1998b) suggest an enormous (Beetsma, 1995); ortogneisses, biotite gneisses and amphibolites (Noronha and Leterrier, 2000); felsic granulites (Villaseca et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

Genesis and emplacement of felsic Variscan plutons within a deep crustal lineation, the Penacova-Régua-Verín fault: An integrated geophysics and geochemical study (NW Iberian Peninsula)

Martins

Sant'Ovaia

Noronha

2009

Lithos

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Multidisciplinary studies integrating, U-Pb geochronology, whole-rock geochemical data, isotope geochemistry, anisotropy of magnetic susceptibility (AMS) studies and gravimetry were carried out on the Vila Pouca de Aguiar and the Águas Frias-Chaves porphyritic biotite granite plutons. Both plutons occur independently in a distance of about 20 km. The Vila Pouca de Aguiar and Águas Frias-Chaves plutons are examples of late to post-orogenic felsic Variscan granites in northern Portugal (NW Iberian Peninsula). The U-Pb zircon analyses yield a consistent age of 299 ± 3 Ma which is considered to be the emplacement age of the two plutons. These granites are weakly peraluminous, show high HREE and Y (and low P) contents which are consistent with them being I-type. This is also supported by their weakly evolved isotopic compositions, 87 Sr/ 86 Sr i = 0.7044-0.7077 and εNd = − 2.0 to − 2.6, as well as by the whole rock oxygen isotope (δ 18 O VSMOW) ranging from + 9.7‰ to + 11.0‰. The emplacement of granite magma took place after the third Variscan deformation phase (D 3 ) in an extensional tectonic regime, large scale uplift and crustal thinning. The integration of different data suggests that both plutons have the same feeding zone aligned within the Penacova-Régua-Verin fault (PRVF) and that both have the same structure which is related to late Variscan phases. The thicker shape for the Águas Frias-Chaves pluton comparing to that of the Vila Pouca de Aguiar pluton is compatible with different depths of PRVF sectors. The available data led us to propose a model of partial melting of a meta-igneous lower crustal source rather than an open-system of mantle-crust interaction. The interaction between the continental crust and invading mafic magmas could have been limited to mere heat transfer and, perhaps, local intermingling.

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Section: Discussionmentioning

confidence: 99%

Genesis and emplacement of felsic Variscan plutons within a deep crustal lineation, the Penacova-Régua-Verín fault: An integrated geophysics and geochemical study (NW Iberian Peninsula)

Martins

Sant'Ovaia

Noronha

2009

Lithos

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“…The enriched nature of subcontinental mantle domains is also present in other sectors within the Variscan Belt (Fernández-Suárez et al, 2011;Janousek et al, 2000;Moreno-Ventas et al, 1995;Orejana et al, 2009;Pin and Duthou, 1990;Villaseca et al, 2011). Further constraints about the hybridisation process in the genesis of granitoids are given by the presence of mafic microgranular enclaves associated with granitic rocks, as they are generally considered as representing a mantle-derived component (Barbarin and Didier, 1992;Bea et al, 1999;Bonin, 2004;Cocherie et al, 1994;Collins et al, 2000;Dias and Leterrier, 1994;Dias et al, 2002;Didier, 1987;Janousek et al, 2004;Moreno-Ventas et al, 1995;Orsini et al, 1991;Renna et al, 2006;Silva and Neiva, 2004;Slaby and Martin, 2008;Vernon, 1984).…”

Section: Nature Of the Granite Sourcesmentioning

confidence: 99%

Late-Variscan emplacement and genesis of the Vieira do Minho composite pluton, Central Iberian Zone: Constraints from U–Pb zircon geochronology, AMS data and Sr–Nd–O isotope geochemistry

Martins

Ovaia

Noronha

2013

Lithos

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In the Central Iberian Zone synorogenic (syn-and late-D 3 , the last deformation phase) composite batholiths of biotite-rich granitods with peraluminous character are well represented. We report here U-Pb zircon and monazite ages, geochemical, Sr-Nd-O isotopic data and Anisotropy of Magnetic Susceptibility (AMS) studies for the late-D 3 Vieira do Minho pluton, in northern Portugal. AMS reveals the paramagnetic behaviour of these granites and the magnetic fabric enhances the major role of NW-SE regional anisotropies on controlling the ascent and emplacement of the magmas. Magnetic anisotropy and medium temperature microstructures also point out the evolution of regional tectonics during crystallization of the magma. U-Pb zircon and monazite analyses yield consistent ages of 310 ± 2 Ma and 312 ± 2 Ma, interpreted as emplacement age. The Vieira do Minho pluton consists of two peraluminous monzogranites, the VMG and the MRG. Both have similar ε Nd values (VMG= −5.2 to −5.7; MRG =−4.98 to −5.96) but the VMG is slightly enriched in 87 Sr/ 86 i = 0.7087-0.7098 as well as in δ 18 O in the range of 10.6‰ to 11.0‰ than the MRG with 87 Sr/ 86 i =0.7064-0.7075 and δ 18 O=9.9‰-10.5‰. These granites are associated with coeval scarce grabroic intrusions and/or mafic microgranular enclaves which are not considered as mafic precursors of the associated granitic magmatism. Instead, a lower metaigneous crustal source, at different levels, is proposed based on the available data set.

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“…The megacrysts of the sparsely porphyritic granite -alkali feldspar, plagioclase, and quartz -are commonly rounded and have a slightly corroded appearance, which is one of the features indicative of mingling of mafic and felsic components in a bimodal magmatic association (e.g. Cantagrel et al 1984, Didier 1987, Salonsaari & Haapala 1994, Salonsaari 1995. Among the other features typical of the hybrid rocks, needle-like apatite is found in the granitoids of Obbnäsudden, but corona textures (amphibole rims around quartz grains and micrographic pla- gioclase-quartz mantles surrounding alkali feldspar grains) are not present.…”

Section: Evidence Of Interaction Of Two Magmas: Hybrid Granitoids Andmentioning

confidence: 99%

The rapakivi granite plutons of Bodom and Obbnäs, southern Finland: petrography and geochemistry

Kosunen¹

1999

Bull Geol Soc Finland

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KOSUNEN, PAULA 1999. The rapakivi granite plutons of Bodom and Obbnäs, southern Finland: petrography and geochemistry. Bulletin of the Geological Society of Finland 71, Part 2,.The Obbnäs and Bodom granite plutons of southernmost Finland show the typical petrographic and geochemical features of the Proterozoic rapakivi granites in Finland and elsewhere: they cut sharply across the 1900 Ma Svecofennian metamorphic bedrock and have the geochemical characteristics of subalkaline A-type granites. The Bodom pluton is composed of porphyritic granites (hornblende-, hornblende-biotite-, and biotite-bearing varieties) and an evengrained granite that probably represent two separate intrusive phases. This lithologic variation does not occur in the Obbnäs pluton, which is almost entirely composed of porphyritic hornblende-biotite granite that gradually becomes more mafic to the southwest. Three types of hybrid granitoids resulting from magma mingling and mixing occur on the southwestern tip of the Obbnäs peninsula. The Bodom granites are syenogranites, whereas the composition of the Obbnäs granite varies from syeno-to monzogranite. The main silicates of both the Bodom and Obbnäs granites are quartz, microcline, plagioclase (An 1541 ), biotite (siderophyllite), and generally also amphibole (ferropargasite or hastingsite). Plagioclase-mantled alkali feldspar megacrysts are absent or rare. The accessory minerals are fluorite, allanite, zircon, apatite, and iron-titanium oxides; the Obbnäs granite also contains titanite. The Bodom and Obbnäs granites are metaluminous to weakly peraluminous, with average A/CNK of 1.00 and 1.05, respectively, have high Fe/Mg (average FeO tot /[FeO tot +MgO] is 0.94 for the Bodom and 0.87 for the Obbnäs granites), and high Ga/Al (3.78 to 5.22 in Bodom and 2.46 to 4.18 in Obbnäs). The REE contents are high with LREE-enriched chondrite-normalized patterns and moderate (Obbnäs) to relatively strong (Bodom) negative Eu-anomalies. The Obbnäs granite is enriched in CaO, TiO z , MgO, and FeO, and depleted in Si0 2 and K 2 0 compared to the Bodom granites. Also, there are differences in the Ba, Rb, and Sr contents of the two plutons (Ba and Sr higher, Rb lower in Obbnäs) that cannot easily be traced to single parental granite magma. These features, together with the presence of titanite in the Obbnäs pluton, suggest different sources for the granites of the two plutons: a potassium feldspar-rich source for Bodom and potassium feldspar-poor for Obbnäs.

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Contribution of enclave studies to the understanding of origin and evolution of granitic magmas

Cited by 105 publications

References 9 publications

Genesis and emplacement of felsic Variscan plutons within a deep crustal lineation, the Penacova-Régua-Verín fault: An integrated geophysics and geochemical study (NW Iberian Peninsula)

Genesis and emplacement of felsic Variscan plutons within a deep crustal lineation, the Penacova-Régua-Verín fault: An integrated geophysics and geochemical study (NW Iberian Peninsula)

Late-Variscan emplacement and genesis of the Vieira do Minho composite pluton, Central Iberian Zone: Constraints from U–Pb zircon geochronology, AMS data and Sr–Nd–O isotope geochemistry

The rapakivi granite plutons of Bodom and Obbnäs, southern Finland: petrography and geochemistry

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