The El Guijo Pluton: petrology, geochemistry, age and relation to others rocks of Los Pedroches batholith

[Resumen] El plutón de El Guijo es uno de los plutones ácidos circunscritos, intrusivos en las granodioritas que constituyen los tercios central y occidental del batolito de Los Pedroches. Con forma subelíptica, presenta una zonación centrípeta que va desde facies marginales graníticas biotíticas (localmente con microadamellitas porfídicas), marcadamente porfídicas, hasta facies centrales de leucogranitos cordieríticos (± moscovita). Geoquímicamente, las rocas de este plutón definen una asociación peraluminosa, con evolución netamente calcoalcalina. Se presentan los resultados de una datación (Rb-SR, roca total) que definen una isocrona de 300 ± 6 Ma, con (87 Sr/86 Sr) o de 0.704. Finalmente, se discuten sus relaciones y significado en el contexto general del batolito de Los Pedroches.[Abstract] The El Guijo pluton belongs to a group of centred, acidic plutons which intrude the ranodiorites making the most part of the Pedroches Batholith central and western thirds. It has a sub-elliptical shape and shows a centripetal zonation which ranges between marginal, biotite-bearing porphyritic granitic facÍes (locally intruding porphyritic micro-adamellites) and central cordierite -bearing leucogranites (± muscovite). They collectively define a peraluminous association with a neat calcalkaline evolution. The results of a Rb-Sr whole-rock study are presented. These define a 300 ±6 Ma age isochron with (87 Sr/86 Sr) o = 0.704. Finally, its relationships with, and its significance in the context of the overall Pedroches Batholith are discused

Circuit architecture explains functional similarity of bacterial heat shock responses

Heat shock response is a stress response to temperature changes and a consecutive increase in amounts of unfolded proteins. To restore homeostasis, cells upregulate chaperones facilitating protein folding by means of transcription factors (TF). We here investigate two heat shock systems: one characteristic to gram negative bacteria, mediated by transcriptional activator sigma32 in E. coli, and another characteristic to gram positive bacteria, mediated by transcriptional repressor HrcA in L. lactis. We construct simple mathematical model of the two systems focusing on the negative feedbacks, where free chaperons suppress sigma32 activation in the former, while they activate HrcA repression in the latter. We demonstrate that both systems, in spite of the difference at the TF regulation level, are capable of showing very similar heat shock dynamics. We find that differences in regulation impose distinct constrains on chaperone-TF binding affinities: the binding constant of free sigma32 to chaperon DnaK, known to be in 100 nM range, set the lower limit of amount of free chaperon that the system can sense the change at the heat shock, while the binding affinity of HrcA to chaperon GroE set the upper limit and have to be rather large extending into the micromolar range.Comment: 17 pages, 5 figure

Petrology and structure of Campanario-La Haba pluton and Los Berrocales stock (Badajoz): preliminary dates

[Abstract] The Campanario-La Haba pluton and Los Berrocales stock are situated in the southern part ofthe Central-Iberian zone. They form part ofthe late-Hercynian alignement named Caceres-Linares or Pedroches-Alburquerque. During the last years these two granitoids have been related, based on spatial and/or genetic criteria, with Los Pedroches Batholith. These igneous bodies are different. Campanario-La Haba pluton is a coarse grained peraluminous granite with large megaphenocrysts ofcordierite. Three facies are differenciated based on petrographic criteria: coarse grained porfiric granite with megaphenocryst of cordierite, fine grained porfiric granite with megaphenocryst of cordierire and fine-medium granite. Los Berrocales is a zoned stock formed by granodiorites graded to granites in the center. Structure-studies indicates that the Campanario-La Haba pluton has been structurated in magmatic state. The magmatic foliation and lineation direction show the orientation ofN12üE, parallel to the pluton lenghtening. The magnetic susceptibility values show that the magnetic behaviour of the granites is dominated by paramagnetic minerals, fine for apply the Anisotropy ofthe Magnetic Susceptibility. The magnetic structure is rather homogeneous and the magnetic lineation and foliation show the N12üE direction. This paper shows premier dates and conclusions of the work that Mineralogy and Petrology department (University of Basque Country) has being done in conjunction with the Geodinamic department (University ofBasque Country) on the westhern end of the Los Pedroches Batholith

The relationship between the plutonic intrusions and the dyke swarm in the Los Pedroches batholith (Iberian Massif, Spain): Dykes as a paleotectonic and paleostress indicators

[Abstract] The Los Pedroches batholith (Iberian Massif, SW Spain) is composed by a large biotite ±amphibole granodiorite pluton and several, smaller variable porphyritic, biotite ± cordierite granite intrusions. A dyke swarm composed esencially by trachyandesites, dacites and rhyolites cross cut the batholith. The whole set of plutonic and subvolcanic rocks define a K-rich, calc-alkaline alumino-cafemic association; only the trachyandesitic dykes ofshoshonitic affinity, get offthis trend. The dacitic and rhyolitic dykes are cogenetic with and probably comagmatic with thegranodioritic plutonand thegranitic intrusions, respectively. The trachyandesites, locallyshows sin-plutonic relations with thegranodiorite bodyand might becogenetic with mafic microgranular enclaves scattered through the granodiritic unit. The emplacement of the batholith and the dyke swarms is late-hercynian and postcollisional (300 Ma) and, was controled by a transtensional shear zone at acrustal scale. The dyke swarm use the tectonically generated fracture system during cooling and consolidation of the plutonic rocks: (i) R' type Riedel fractures for the trachyandesitic and dacitic dykes emplacement, and (ii) R type Riedel fractures for rhyolitic dykes emplacement. The arrangement ofsome dyke swarms can be use as a paleotectonic and paleostress indicators.

Geochemistry of A Espenuca two-mica granite: origin and evolution

[Abstract] The A Espenuca two-mica granite, situated in the northern sector ofthe Central Iberian Zone, was variably deformed by the Valdoviño Fault. Deformation intensity is observed to increase from W to E, also being more intense in the northern half. Results of the geochemical study of the less deformed granite facies, known in the regionalliterature as the «weakly deformed facies», are presented. Chemical variations are faint (DSi02 z 4%) and reflect a whole composition close to the granite minimum. Analyzed samples correspond to alkali-dch(Na20+K20, x = 8.4 %), CaO-depleted rocks « 0.9 %), showing very low values for the B (=Fe+Mg+Ti) parameter x = 30, and a marked peraluminous character, A/CNK, x =1.16 (range 1.1-1.26), which from the mineralogical point of view is traduced in the occurrence of muscovite (± garnet). The rocks studied are depleted in REE (LREE =75.77-189.83; x = 117.4), notably in the HREE. They exhibit considerably fractionated pattern (La/Lu)n x = 50 as well as important Eu negative anomalies (Eu/Eu*, x = 0.36). These rocks can be linked by fractionated crystallization processes. Massbalance calculations indicate crystallization ratios < 30%, the fractionated minerals being Kfs, Bt, PI. These values to explain the trace element variations observed in the different samples. The chemical-mineralogical composition of analyzed facies suggests an origin by partial melting of crustal rocks (either pelites, schists, meta-greywackes or orthoderived materials) at considerable depths, where garnet constitutes a restite stable phase. Nevertheless, calculated models show that not aH these materials equally adjust as source to the granite magma. The best fits are obtained considering a source similar to 0110 de Sapo gneisses. Key Words: Two-mica granite, fractional crystallization, partia

The Santa Elena stock (Jaén). An intrusion genetically independent fram the magmatic association of the Los Pedroches Batolith

[Abstract] The Santa Elena stock has been classically considered as belonging to the magmatic association ofthe Los Pedroches Batolith. The stock is intrusive into psammo-pelitic materials Ordovician to Carboniferousin age. The Santa Elena stock is composed of biotite granodiorite to tonalite with gabbro-diorite as enclaves ofvariable size outcropping in northern sectors ofthe intrusion. Pelitic xenoliths ofvarious sizes, likely related to magma stopping, are common through the massif. The Santa Elena stock is intruded by a dike complex made of aplite and ore-bearing quartz veins. The two main lithological units exhibit different geochemical features with local evidence ofmagmamixing between acid and basic types. The granodioritetonalite is chemically homogeneous regarding the content of major and trace elements, including REE. These rocks correspond to mildly peraluminous terms ofan alumino-cafemic association ofcalc-alkaline character.The gabbrodiorite enclaves are meta-aluminous and clearly deviate from the geochemical trend defined by granodiorite and tonalite. The rocks from the Santa Elena stock are very different from the common granodiorite types ofthe Los Pedroches Batolith. It appears from the petrological and geochemical data that the Santa Elena stock corresponds to an independent and different magmafrom that at the origin ofthe Los Pedroches to which it had been classically associated

The Linares granite (Jaén): cartography, petrology and geochemistry

[Abstract] Magma emplacement within the Linares granite, a part of the Los Pedroches Batholith, took place in the sequence: biotite granodiorite with microgranular enclaves, biotite monzogranites, and dike swarm complexo Dikes are: WNWESE rhyolite to rhyodacite, aplopegmatite and abundant NE-SW ore-bearing quartz. The Linares intrusion and psamo-pelitic Carboniferous host metasediments (Los Pedroches Culm) are, in part, discordantly covered by Mesozoic (Trias) and Tertiary to Quaternary terrigenous deposits. Bulk rock chemistry of granodiorite shows minor variations in Si02 (64.75... 67 wt %) and REE contents (LREE = 158 -160 ppm), and nearly constant Al CNK (ISA) ratio (1.1 - 1.15). Monzogranites have higher Si02 (66.87 - 68.4 wt %), alkali and REE contents (LREE = 168 - 193 ppm), with A/CNK (ISA) ratio of 1.06 - 1.09. Both granodiorite and monzogranites are peraluminous rocks that may correspond to an aluminous association or to evolved terms of an aluminocafemic association (Debon & Lefort, 1983). Variation diagrams for major and trace elements, including REE, of granodiorite and monzogranites are compatible with magmatic differentiation processes by fractional crystallization starting from a primary granodioritic magma