Rheological Aspects of Magma Transport Inferred from Rock Structures

Fernández, Carlos; Castro, Antonio de; Rosa, Jesús Damián de la; Moreno‐Ventas, I.

doi:10.1007/978-94-017-1717-5_5

Cited by 8 publications

(3 citation statements)

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“…1) Gallegos), or coeval granitic intrusions (e.g., Berrocal, Navahermosa, Beced ill as ). The latter also display outcrop-scale structures and textures indicative of mingling processes between the basic and acid magmas (see also : easillas, 1989;Moreno-Ventas et al, 1995;Fernandez et al, 1997 ). The most primitive rocks from these outcrops do not show evidence of magma mixing or crus tal contamination (presence of different intermingled plutonic facies, enclaves, ocellar quartz, spongy plagioclase, and disequilibrium textures around minerals, etc.).…”

Section: Field Relations Petrography and Mineral Chemistrymentioning

confidence: 99%

The Variscan gabbros from the Spanish Central System: A case for crustal recycling in the sub-continental lithospheric mantle?

García

Villaseca

Pérez-Soba

et al. 2009

Lithos

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Keywords: Gabbroic rocks Crustal recycling Variscan orogeny Uthospheric mantle Spanish Central SystemThe gabbroic intrusions that crop out along the Spanish Central System (SCS) are geochemically heterogeneous, including primitive and evolved rocks. Differentiation is mainly related to fractionation of Cr-spinel and olivine, but mixing with coeval granitic magmas or crustal assimilation may have also played a role in the evolution of the most differentiated rocks. The most primitive uncontaminated gabbros show arc like trace element chondrite and primitive-mantle normalised patterns, characterised by large ion Iithophile elements (ULE)-Iigh t rare earth elements (tREE) enrichment, Sr and Pb positive and Nb-Ta-Ti negative anomalies. However, paleogeographic constraints suggest that the SCS was located far from subduction zones, so these geochemical signatures could be better explained by a recycling of continental crustal components within the mantle. The most primitive SCS gabbros expand the Sr-Nd isotopic compositional range of the Variscan basic magmatism in the Central Iberian Zone to more depleted values. This reflects a heterogeneous sub-continental Iithospheric mantle under central Spain ranging from a depleted mantle (ENd = +3.1. 87Sr/86Sr= 0.704) towards an isotopically enriched component (ENd = -1.6, 87Sr/ 86Sr = 0.706). Geochemical modelling suggests that mantle enrichment could be explained by minor lower crustal metapelitic granulite contamination (-2%). Additionally. the Sr-Nd-Pb isotopic ratios of the most primitive gabbros match the composition of the European subcontinental lithospheric mantle recorded in ultramafic xenoliths from western and central Europe.

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Section: Field Relations Petrography and Mineral Chemistrymentioning

confidence: 99%

The Variscan gabbros from the Spanish Central System: A case for crustal recycling in the sub-continental lithospheric mantle?

García

Villaseca

Pérez-Soba

et al. 2009

Lithos

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“…However, the ability for assimilation of granitoid rocks is essentially restricted to local-scale processes. The evidence from field and structural studies (Fernandez et al 1997;Fernandez & Castro 1999a) indicates that large convective movements in large magma chambers, required for large-scale homogenization, are very unlikely in granite batholiths. These field-based studies indicate that emplacement is related to pulse-in-pulse intrusions in association with crustal extension processes rather than to large diapiric bodies, in a way similar to the dyke-in-dyke emplacement of basalts at the midocean ridges.…”

Section: Introductionmentioning

confidence: 97%

The source of granites: inferences from the Lewisian complex

Castro

2004

SJG

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SynopsisThe origin of granitic rocks has been the subject of intense debate. It is broadly accepted that granites are generated in the continental crust. However, the composition of the source rocks and the processes controlling melting reactions remain controversial. Fluid-absent melting is a plausible mechanism for granite generation but is not supported by experimental data. Fluid-present melting is favoured by experiments but the presence of a free water phase is very unlikely in the deep crust. Isotopic ratios are also paradoxical because Nd isotopes indicate a crustal (recycled) source but the low 87 Sr/ 86 Sr ratios displayed by many granite batholiths require a substantial mantle contribution. Furthermore, mantle-crust hybridization mechanisms are difficult to apply in terms of magma mixing and assimilation according to models of the physical/rheological behaviour of silicic magmas. Here I present a new, source-based, genetic approach for granitic rocks in which all these paradoxes are satisfactorily explained. The model is supported by new constraints from laboratory experiments and observations of field relationships in the Lewisian complex of northern Scotland. The process starts with the invasion of crustal regions by water and K-rich monzodiorite (andesite) magmas derived from hybridized regions of the subduction-modified mantle wedge. These intermediate magmas supply the water and potassium necessary for crustal melting and izranite batholith generation.

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“…In this regard, most studies concentrated on various aspects of mafic-felsic interactions in granitoid magma chambers replenished by episodic mafic inputs (e.g., Fernandez and Gasquet 1994;Frost and Mahood 1987;Neves and Vauchez 1995;Fernandez et al 1997;Perugini and Poli 2005;Slaby and Martin 2008;Wada et al 2004;Wiebe 1994;Wiebe et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Magmatic erosion of the solidification front during reintrusion: the eastern margin of the Tuolumne batholith, Sierra Nevada, California

Žák

Paterson

2009

Int J Earth Sci (Geol Rundsch)

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The Tuolumne batholith, Sierra Nevada, California, consists of several nested granitoid units and is an example of upper-crustal normally zoned intrusions. The two outermost units of the batholith are separated by a wide gradational contact in what is interpreted to represent a large magma chamber. In the Potter Point area near the eastern margin of the batholith, the gradational contact is cross-cut by a network of interconnected mafic-felsic sheets, which grade into zones of magmatic erosion by stoping where the host granodiorite between the sheets was entirely removed and replaced by younger enclave-rich quartz diorite. We interpret these features to record disruption of a steep solidification front, which migrated inwards from the eastern batholith margin and separated the mushy to solidified margin from the remaining active magma chamber. When intersecting the gradational contact, the solidification front started to break up via a network of tectonically driven fractures accompanied by simultaneous injection of localized magma pulses. The solidification front break-up is interpreted here as an initial stage of a ''recycling'' process, whereby older magma mush is disrupted and incorporated into younger magma batches, a process we propose to have been widespread along internal contacts in the Tuolumne magma chamber.

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Rheological Aspects of Magma Transport Inferred from Rock Structures

Cited by 8 publications

References 0 publications

The Variscan gabbros from the Spanish Central System: A case for crustal recycling in the sub-continental lithospheric mantle?

The Variscan gabbros from the Spanish Central System: A case for crustal recycling in the sub-continental lithospheric mantle?

The source of granites: inferences from the Lewisian complex

Magmatic erosion of the solidification front during reintrusion: the eastern margin of the Tuolumne batholith, Sierra Nevada, California

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