Palaeostress and geotectonic interpretation of the Alpine Cycle onset in the Sierra del Guadarrama (eastern Iberian Central System), based on evidence from episyenites

González-Casado, J.M.; Caballero, José María; Casquet, César; Galindo, Carmen; Tornos, Fernando

doi:10.1016/0040-1951(96)00004-2

Cited by 27 publications

(12 citation statements)

References 34 publications

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“…Atuação de fluidos tardi-magmáticos associados aos estágios finais de um plutonismo granítico, como proposto para as ocorrências de Barnesmore, Irlanda (Dempsey et al, 1990), Marche Oeste, Maciço Central Francês (Patrier et al, 1997), Avila-Béjar, Maciço Central Ibérico (Recio et al, 1997), plúton Água Boa, Brasil (Costi et al, 2002;Borges et al, 2009) e Königshain, Maciço Boêmio (Hecht et al, 1999); 2. Ação de fluidos superficiais, que se infiltram durante eventos tectonotermais tardios, como sugerido para os epissienitos de Saint Sylvestre, Maciço Central Francês (Scaillet et al, 1996;Turpin et al, 1990) e Serra de Guadarrama, Maciço Central Ibérico (González-Casado et al, 1996).…”

Section: Epissienitização Potássicaunclassified

Interação entre magmas graníticos e a origem de epissienitos potássicos estaníferos do granito Madeira, mina Pitinga, Amazonas

Borges¹,

Gaia²,

Costi³

et al. 2018

Geol. USP. Sér. cient.

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Disponível on-line no endereço www.igc.usp.br/geologiausp -21 -Resumo O estudo petrográfico de amostras da zona de contato entre as fácies albita-granito de borda e feldspato alcalino-granito hipersolvus porfirítico, na borda oeste do plúton Madeira, identificou rochas com características texturais e composicionais herdadas das duas fácies. Tal feição é interpretada como um processo de interação entre os dois magmas graníticos, colocados e cristalizados contemporaneamente. Em condições subsolidus, fluidos hidrotermais causaram alteração potássica pervasiva, ou epissienitização, caracterizada pela dissolução de quartzo das fácies graníticas, gerando cavidades e aumentando a permeabilidade das rochas alteradas. Paralelamente, a albita da fácies de borda do albita-granito foi desestabilizada e substituída por microclínio hidrotermal e, nos estágios mais tardios, as cavidades foram preenchidas por quartzo, microclínio, fluorita, hematita, cassiterita, fengita, clorita, pirita, esfalerita, galena e calcopirita. Os epissienitos potássicos são rochas de coloração vermelha escura a marrom, granulação fina a média, ricas em microclínio hidrotermal, apresentando-se ora porosas, ora com cavidades preenchidas por quartzo e sulfetos. A cassiterita das rochas epissienitizadas é mais pura e relativamente mais pobre em Nb do que aquela presente no albita-granito magmático. Os fluidos que desencadearam a epissienitização devem ter sido oxidados, ricos em K, alcalinos e subsaturados em sílica. Propõem-se duas hipóteses para a sua origem: 1) por separação de uma fase fluida a partir do líquido magmático formador do granito hipersolvus; 2) pela ação do mesmo fluido que desencadeou o processo de autometassomatismo do albita-granito de núcleo, gerando sua fácies de borda.Palavras-chave: Mina Pitinga; Interação entre magmas graníticos; Processos hidrotermais; Epissienitos potássicos; Cassiterita. AbstractThe petrographic study in samples from the contact zone between the border albite-rich granite and the porphyritic hypersolvus alkali feldspar granite, in the western border of the Madeira pluton, allowed for the recognition of rocks with inherited textural and mineralogical features of both facies. This is interpreted as resulting from the interaction between two coeval granite magmas, which were simultaneously emplaced in the crust. Later, in subsolidus stage, the action of hydrothermal fluids caused a pervasive potassic metassomatism, identified as episyenitization, that initially caused the quartz dissolution of the granitic rocks, generating vugs and increasing the altered rocks' permeability. At the same time, the albite of the border albite-rich granite had been dissolved and replaced for microcline, and, in low-temperature hydrothermal stages, cavities were filled by quartz, microcline, fluorite, hematite, cassiterite, phengite, chlorite, pyrite, sphalerite, galena and chalcopyrite. The potassic episyenites are dark red to brown colored, medium to fine grained, microcline-rich, locally porous rocks and commonly with vugs filled...

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Section: Epissienitização Potássicaunclassified

Interação entre magmas graníticos e a origem de epissienitos potássicos estaníferos do granito Madeira, mina Pitinga, Amazonas

Borges¹,

Gaia²,

Costi³

et al. 2018

Geol. USP. Sér. cient.

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“…Colateralmente, el régimen de paleoesfuerzos deducido para la formación de estas litologías en el Guadarrama, de tipo extensional puro, tiende a reforzar la anterior interpretación González-Casado et al, 1996).…”

Section: Condiciones De Formaciónunclassified

Untitled

Caballero¹

1999

Estud. geol.

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RESUMENSe modeliza teóricamente la formación de las episienitas de la Sierra de Guadarrama, consistente básicamente en un proceso acoplado de decuarcificación-albitización. El modelo se basa en un esquema de transporte de masas advectivo en un medio continuo, donde el proceso reactivo se formula desde un punto de vista cinético.Se demuestra la factibilidad de la formación de estas litologías a partir de fluidos hiposalinos (2,32 % peso NaCl equivalente) en equilibrio parcial con un monzogranito biotíti-co, asociados a trayectorias de reacción isobáricas y gradientes geotérmicos negativos, enmarcadas en el campo de solubilidad retrógrada del cuarzo y ligadas a la rápida movilización del fluido residente en el medio a alterar durante la apertura tectónica de éste.El modelo explica el carácter albítico de la alteración a diferencia de esquemas previos, que predicen microclinización en base a las relaciones dlogKmicldT > dlogKaJdT (0,05739 y 0,05735) Y dlogKKCI/dT < dlogKNac¡/dT (-0,038 Y -0,036). La formación de albita deriva de la presencia de un componente anortítico, dado que dlogKan/dT =0,1293Las relaciones de desequilibrio son muy moderadas, implicando que la intensidad de la alteración sea resultado de la circulación de grandes volúmenes de fluido. Esta característica conlleva, para las constantes de reacción consideradas, la escasa modificación, espacial y temporal, del fluido, siendo prácticamente nula para sus componentes mayoritarios (Na, K y, subordinadamente, el pH).El modelo demuestra la necesidad del tratamiento de sistemas complejos. En este sentido, el esquema de especiación propuesto demuestra que la evolución del pH a temperatura decreciente no es necesariamente acidificante, sino dependiente del pH del fluido inicial, dado que las concentraciones calculadas implican un control tanto por la disociación del HCI, como de la base NaOH. ABSTRACTThe development of episyenites from Sierra de Guadarrama has been modelized. The process mainly consists in a coupled process of dequartzfication-albitization. The model is based on pure advective mass transport in a continuum medium, where the reactive process is formulated from a kinetic point of view.It is demonstrated the possibility of its formation through the action of low-salinity tluids (2,32 wt % NaCl equiv.), partially equilibrated with a biotite monzogranite, linked to isobaric reaction paths across negative geothermal gradients, intersecting the quartz retrograde solubility field, and associated to a quick tluid-resident mobilization due to the environment tectonic opening.The model explains the albitic nature of the alteration against former models. These predict microcline formation from the gradient relations dlogKmic/dT > dlogKab/dT (0.05739 and 0.05735) and dlogKKCI/dT < dlogKNaCI/dT (-0.038 and -0.036). Albite formation arises from the anortite component presence, because dlogKan/dT = 0.1293 » dlogKmicldT.

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“…This is mainly composed of Hercynian granitoids (344-285 Ma; Ibarrola et al, 1987) and highto medium-grade metamorphic rocks. Granitoids form the Guadarrama Batholith, consisting primarily of peraluminous monzogranites to leucogranites, with minor rocks of more basic composition (González-Casado et al, 1996). Post-Hercynian intrusive rocks are also common in the area, mainly in the form of dykes.…”

Section: Geological Settingmentioning

confidence: 99%

Characterisation of monzogranitic batholiths as a supply source for heritage construction in the northwest of Madrid

Fort

Buergo

Pérez-Monserrat

et al. 2010

Engineering Geology

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The Church of the Assumption of Our Lady, in Valdemorillo (Madrid, Spain) is almost entirely built with granitoids. The studies and analyses were focused on the oldest part of the building (Ghosts Corner), which will be restored and rehabilitated in the near future. Homogeneous monzogranite is the predominant granitoid used in the Ghosts Corner, followed by granitic porphyry, porphyrytic monzogranite, gneiss and leucogranite. The original quarries that supplied homogeneous monzogranites for the first construction stages correspond to blocks present in the monument's surroundings. Quarries that supplied the granitic porphyries correspond to the dykes located to east-southeast of Valdemorillo, which are oriented N-S in relation to their intrusion direction. The combined use of ultrasonic velocity and Schmidt hammer techniques allowed, first, selection of the most representative blocks and ashlars for sampling. This reduced sampling to a minimum, but yielded representative results for the whole building. Second, the combined values were used to compare results for the building stones of the church to rocks from the surrounding quarries. Stones from the building showed lower ultrasonic and Schmidt hammer values, and higher porosity and water saturation values compared to the original quarry rocks. The anisotropy indices are directly related to the decay processes in the stone: spalling of homogeneous monzogranite and grain disintegration in granitic porphyries. Finally, the methods applied are inexpensive, easy to use and non-destructive techniques, very advisable properties when working with built heritage.

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Palaeostress and geotectonic interpretation of the Alpine Cycle onset in the Sierra del Guadarrama (eastern Iberian Central System), based on evidence from episyenites

Cited by 27 publications

References 34 publications

Interação entre magmas graníticos e a origem de epissienitos potássicos estaníferos do granito Madeira, mina Pitinga, Amazonas

Interação entre magmas graníticos e a origem de epissienitos potássicos estaníferos do granito Madeira, mina Pitinga, Amazonas

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Characterisation of monzogranitic batholiths as a supply source for heritage construction in the northwest of Madrid

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