176 research outputs found
Syn-kinematic magma ascent and batholith inflation (Sierra de San Luis/Argentina)
The measurement of the anisotropy of
the magnetic susceptibility (AMS) is now routinely used since more than four
decades in the analyses of rock fabrics in
granitic rocks (e.g. Stacy 1960, Henry
1975, Gleizes et al. 1993). Even though
the intensity of fabrics in granitoids is
often weakly developed the significance
of orientation and shape of crystals is
the same like in other deformed rock
types. By revealing the distribution of
fabrics in plutonic rocks one of the still
ongoing discussions in granite tectonics
may be addressed: How did those
sometimes voluminous batholiths were
inflated in the middle crust? We are presenting
magnetic fabric data on a series
of Devonian batholiths that intruded
the polyphase deformed metaclastites of
the Sierra de San Luis (32°100– 33°200 S
/ 65°150 – 66°200 W) in central Argentina.
Regional considerations on the
tectonic regime during the emplacement
of the batholiths are inferred from combined
field, microstructural and AMS
observations...conferenc
Laguna Tordillo Formation: Eocene dacitic volcanism in the Deseado Massif, Santa Cruz province
Se determinó una nueva entidad formacional para la provincia geológica Macizo del Deseado. Se trata de rocas volcánicas melanocráticas que se presentan como dos afloramientos en inmediaciones de la laguna Tordillo, en el sector oriental del macizo del Deseado. Son lavas de color negro a rojizo, de textura porfÃrica con fenocristales de labradoritas (An55-57) inmersos en una pasta de textura hialocristalina, de tipo hialofÃtica. Además, poseen xenolitos de roca volcánica de textura glomeroporfÃrica con fenocristales de labradoritas (An56-59) y enstatitas (En56-Fs40-Wo4 ), con rebordes de reacción pigeonÃticos (En44-Fs47-Wo9 ). Los análisis de elementos mayoritarios y traza las definen como lavas dacÃticas, de tipo subalcalino y con afinidad calcoalcalina. Las relaciones estratigráficas evidencian una edad post-Jurásico superior, la cual fue confirmada mediante un fechado radimétrico K/Ar en roca total (fracción vidrio), que resultó en 40,8 ± 2,4 Ma (Eoceno). Teniendo en cuenta el marco paleogeográfico y geotectónico paleógeno para la Patagonia, se propone que estas rocas se generaron como consecuencia de un subplacado básico de magmas, posiblemente vinculados con el Basalto Cerro del Doce o unidades paleógenas correlacionables. Sin embargo, no se descarta una vinculación entre las rocas de la Formación Laguna Tordillo y las piroclastitas de la Formación o Grupo Sarmiento.A new formational entity for the Deseado Massif geological province was determined. They are melanocratic volcanic rocks presented as two outcrops in the proximity of the Tordillo lagoon, in the eastern Deseado Massif. They are black to reddish lava flows, with porphiritic texture composed by labradorite (An55-57) phenocrystals in a hialocrystalline, hialophitic texture matrix. They have also volcanic rock xenoliths with glomeroporphiritic texture composed by labradorite (An56-59) and enstatite (En56-Fs40-Wo4 ), with a pigeonitic rim (En44-Fs47-Wo9 ), phenocrystals. Majority and trace element analysis define them as subalkalic, with calc-alkaline affinities, dacite lavas. The stratigraphic relationships evidence an post-upper Jurassic age for these rocks; this was confirmed by a K/Ar whole rock (vitreous fraction) isotope determination, resulting in a 40.8 ± 2.4 Ma age (Eocene). Considering the Paleogene paleogeographic and geotectonic environment for Patagonia, it is proposed that these rocks were generated as a consequence of a basic magma underplating, possibly linked with the Cerro del Doce Basalt or correlated Paleogene units. Nevertheless, it is not discarded a link between the Laguna Tordillo Formation rocks and the Sarmiento Formation or Group pyroclastic rocks.Fil: Guido, Diego Martin. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones CientÃficas. Instituto de Recursos Minerales; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Escayola, Monica Patricia. Consejo Nacional de Investigaciones CientÃficas y Técnicas; Argentina. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Instituto Geonorte; ArgentinaFil: de Barrio, Raul Ernesto. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones CientÃficas. Instituto de Recursos Minerales; ArgentinaFil: Schalamuk, Bernardo Isidoro. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones CientÃficas. Instituto de Recursos Minerales; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Wemmer, K.. Universitaet Goettingen; Alemani
NMR characterization of hairpin polyamide complexes with the minor groove of DNA
Polyamides containing N-methylimidazole (Im) and N-methylpyrrole (Py) amino acids can be combined in antiparallel side-by-side dimeric complexes for sequence-specific recognition in the minor groove of DNA. Covalently linking polyamide subunits has led to designed ligands with both increased affinity and specificity. Simple aliphatic amino acid linkers serve as internal guide residues for turn vs extended binding in a head-to-tail-linked polyamide motif. Polyamides of sequence composition ImPyPy-X-PyPyPy containing linkers of incremental length (X = 3-aminopropionic acid (β), 4-aminobutyric acid (γ), or 5-aminovaleric acid (δ)) in complex with an undecamer DNA duplex containing a 5'-(A,T)G(A,T)(3)-3' target site were structurally characterized using NMR spectroscopy. Previous quantitative DNase I footprinting studies identified gamma as the highest affinity of these "turn" linkers. NMR titrations and 2D NOESY data combined with restrained molecular modeling reveal that polyamides with β, γ, and δ linkers all may adopt a hairpin structure. Modeling supports the idea that the linkers in the βand δcomplexes adopt an energetically less favorable turn geometry than the γlinker and confirms that the three-carbon γ linker is sufficient and optimal for the hairpin conformation
The Conlara metamorphic complex: Lithology, provenance, metamorphic constraints on the metabasic rocks, and chime monazite dating
The Conlara Metamorphic Complex, the easternmost complex of the Sierra de San Luis, is a key unit to understand the relationship between the late Proterozoic-Early Cambrian Pampean and the Upper Cambrian-Middle Ordovician Famatinian orogenies of the Eastern Sierras Pampeanas. The Conlara Metamorphic Complex extends to the east to the foothills of the Sierra de Comechingones and to the west up the RÃo Guzmán shear zone. The main rock types of the CMC are metaclastic and metaigneous rocks that are intruded by Ordovician and Devonian granitoids. The metaclastic units comprise fine to medium-grained metagreywackes and scarce metapelites with lesser amounts of tourmaline schists and tourmalinites whereas the metaigneous rocks encompass basic and granitoids rocks. The former occur as rare amphibolite interlayered within the metasedimentary rocks. The granitic component corresponds to a series of orthogneisses and migmatites (stromatite and diatexite). The CMC is divided in four groups based on the dominant lithological associations: San Martin and La Cocha correspond mainly to schists and some gneisses and Santa Rosa and San Felipe encompass mainly paragneisses, migmatites and orthogneisses. The Conlara Metamoprphic Complex underwent a polyphase metamorphic evolution. The penetrative D2-S2 foliation was affected by upright, generally isoclinal, N-NE trending D3 folds that control the NNE outcrop patterns of the different groups. An earlier, relic S1 is preserved in microlithons. Discontinuous high-T shear zones within the schists and migmatites are related with D4 whereas some fine-grained discontinuous shear bands attest for a D5 deformation phase. Geochemistry of both non-migmatitic metaclastic units and amphibolites suggest that the Conlara Metamorphic Complex represents an arc related basin. Maximun depositional ages indicate a pre- 570 Ma deposition of the sediments. An ample interval between sedimentation and granite emplacement in the already metamorphic complex is indicated by the 497 ± 8 Ma age of El Peñon granite. D1-D2 history took place at 564 ± 21 Ma as indicated by one PbSL age calculated for the M2 garnet of La Cocha Group. D3 is constrained by the pervasively solid-state deformed Early Ordovician granitoids which exhibits folded xenoliths of the D1-D2 deformed metaclastic rocks. Pressure-temperature pseudosections were calculated for one amphibolite using the geologically realistic system MnNCKFMASHTO (MnO–Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3). Peak metamophic conditions (M2) indicate 6 kbar and 620 °C. Late chlorite on the rims and in cracks of garnet, along with titanite rims on ilmenite and matrix plagioclase breaking down to albite suggests that the P-T path moved back down. Monazite analyses yield isochron Th–U–Pb ages ranging from 446 to 418 Ma. The oldest age of 446 ± 5 Ma correspond to a migmatite from the Santa Rosa Group. Monazites in samples from the La Cocha and the San Martin group crystallized at decreasing temperatures, followed by the 418 ± 10 Ma low-Y2O3 monazites in one sample of the la Cocha Group that was also obtained from a migmatite, and would likely mark a later stage of a retrograde metamorphism New CHIME monazite ages presented here likely represent post-peak fluid assisted recrystallization that are similar to amphibole and muscovite cooling ages. Therefore the monazite ages may represent a re-equilibration of the monazite on the cooling path of the basement complex.Fil: López de Luchi, Mónica G.. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de GeocronologÃa y GeologÃa Isotópica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de GeocronologÃa y GeologÃa Isotópica; ArgentinaFil: MartÃnez Dopico, Carmen Irene. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de GeocronologÃa y GeologÃa Isotópica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de GeocronologÃa y GeologÃa Isotópica; ArgentinaFil: Cutts, Kathryn Ann. Universidade do Estado de Rio do Janeiro; BrasilFil: Schulz, Bernhard. Institute of Mineralogy; AlemaniaFil: Siegesmund, Siegfried. Universität Göttingen; AlemaniaFil: Wemmer, Klaus. Universität Göttingen; AlemaniaFil: Montenegro, Teresita Francisca. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentin
NMR characterization of hairpin polyamide complexes with the minor groove of DNA
Polyamides containing N-methylimidazole (Im) and N-methylpyrrole (Py) amino acids can be combined in antiparallel side-by-side dimeric complexes for sequence-specific recognition in the minor groove of DNA. Covalently linking polyamide subunits has led to designed ligands with both increased affinity and specificity. Simple aliphatic amino acid linkers serve as internal guide residues for turn vs extended binding in a head-to-tail-linked polyamide motif. Polyamides of sequence composition ImPyPy-X-PyPyPy containing linkers of incremental length (X = 3-aminopropionic acid (β), 4-aminobutyric acid (γ), or 5-aminovaleric acid (δ)) in complex with an undecamer DNA duplex containing a 5'-(A,T)G(A,T)(3)-3' target site were structurally characterized using NMR spectroscopy. Previous quantitative DNase I footprinting studies identified gamma as the highest affinity of these "turn" linkers. NMR titrations and 2D NOESY data combined with restrained molecular modeling reveal that polyamides with β, γ, and δ linkers all may adopt a hairpin structure. Modeling supports the idea that the linkers in the βand δcomplexes adopt an energetically less favorable turn geometry than the γlinker and confirms that the three-carbon γ linker is sufficient and optimal for the hairpin conformation
Jurassic cooling ages in Paleozoic to early Mesozoic granitoids of northeastern Patagonia : 40Ar/39Ar, 40K–40Ar mica and U–Pb zircon evidence
University of Buenos Aires (PICTUBACYT X183), CONICET and ANPCYT (PICT20131162) financial support is acknowledged.U–Pb SHRIMP zircon crystallization ages and Ar–Ar and K–Ar mica cooling ages for basement rocks of the Yaminué and Nahuel Niyeu areas in northeastern Patagonia are presented. Granitoids that cover the time span from Ordovician to Early Triassic constitute the main outcrops of the western sector of the Yaminué block. The southern Yaminué Metaigneous Complex comprises highly deformed Ordovician and Permian granitoids crosscut by undeformed leucogranite dikes (U–Pb SHRIMP zircon age of 254 ± 2 Ma). Mica separates from highly deformed granitoids from the southern sector yielded an Ar–Ar muscovite age of 182 ± 3 Ma and a K–Ar biotite age of 186 ± 2 Ma. Moderately to highly deformed Permian to Early Triassic granitoids made up the northern Yaminué Complex. The Late Permian to Early Triassic (U–Pb SHRIMP zircon age of 252 ± 6 Ma) Cabeza de Vaca Granite of the Yaminué block yielded Jurassic mica K–Ar cooling ages (198 ± 2, 191 ± 1, and 190 ± 2 Ma). At the boundary between the Yaminué and Nahuel Niyeu blocks, K–Ar muscovite ages of 188 ± 3 and 193 ± 5 Ma were calculated for the Flores Granite, whereas the Early Permian Navarrete granodiorite, located in the Nahuel Niyeu block, yielded a K–Ar biotite age of 274 ± 4 Ma. The Jurassic thermal history is not regionally uniform. In the supracrustal exposures of the Nahuel Niyeu block, the Early Permian granitoids of its western sector as well as other Permian plutons and Ordovician leucogranites located further east show no evidence of cooling age reset since mica ages suggest cooling in the wake of crystallization of these intrusive rocks. In contrast, deeper crustal levels are inferred for Permian–Early Triassic granitoids in the Yaminué block since cooling ages for these rocks are of Jurassic age (198–182 Ma). Jurassic resetting is contemporaneous with the massive Lower Jurassic Flores Granite, and the Marifil and Chon Aike volcanic provinces. This intraplate deformational pulse that affected northeastern Patagonia during the Early Jurassic (Sinemurian–Pliensbachian) was responsible for the partial (re)exhumation of the mid-crustal Paleozoic basement along reactivated discrete NE–SW to ENE–WSW lineaments and the resetting of isotopic systems. These new thermochronological data indicate that Early Permian magmatic rocks of the Nahuel Niyeu block were below 300 °C for ca. 20 Ma prior to the onset of the main magmatic episode of the Late Permian to Triassic igneous and metaigneous rocks of the Yaminué block.PostprintPeer reviewe
NMR Characterization of the Aliphatic β/β Pairing for Recognition of A·T/T·A Base Pairs in the Minor Groove of DNA
Polyamides containing N-methylimidazole (Im) and N-methylpyrrole (Py) amino acids can be combined in antiparallel side-by-side dimeric complexes for sequence-specific recognition in the minor groove of DNA. Because the curvature of four or five contiguous Im−Py rings does not perfectly match the canonical B-helix, β-alanine (β) residues have been inserted to reset the register. Complexes of three pyrrole−imidazole polyamides of sequence composition ImPyPy-X-PyPyPy-Dp, where X = Py, β, or glycine (G), bound to a 13 base pair DNA duplex containing a 9 base pair 5‘-TGTATATCA-3‘ match site were characterized by NMR. NMR titrations and NOESY data combined with restrained molecular modeling show that each polyamide adopts an extended antiparallel dimeric conformation with the ligands fully overlapped around a central Py/Py, G/G, or β/β pair. Conformational exchange is seen near the linker for the G-linked complex, but not with the β or Py linkers. In addition to providing the first direct structural evidence for formation of the aliphatic β/β pairing in the minor groove, models support the idea that the β linker of ImPyPy-β-PyPyPy-Dp provides an optimal combination of size, flexibility, and alignment of the polyamide-paired aromatic subunits in extended, dimeric 2:1 complexes
Photon Reconstruction in the Belle II Calorimeter Using Graph Neural Networks
We present the study of a fuzzy clustering algorithm for the Belle II
electromagnetic calorimeter using Graph Neural Networks. We use a realistic
detector simulation including simulated beam backgrounds and focus on the
reconstruction of both isolated and overlapping photons. We find significant
improvements of the energy resolution compared to the currently used
reconstruction algorithm for both isolated and overlapping photons of more than
30% for photons with energies E < 0.5 GeV and high levels of beam backgrounds.
Overall, the GNN reconstruction improves the resolution and reduces the tails
of the reconstructed energy distribution and therefore is a promising option
for the upcoming high luminosity running of Belle II.Comment: 18 pages, 11 figure
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