ALBERT

Description: The Eastern Sierras Pampeanas were structured by three main events: the Ediacaran to early Cambrian (580–510 Ma) Pampean, the late Cambrian–Ordovician (500–440 Ma) Famatinian and the Devonian-Carboniferous (400–350 Ma) Achalian orogenies. Geochronological and Sm–Nd isotopic evidence combined with petrological and structural features allow to speculate for a major rift event (Ediacaran) dividing into two Mesoproterozoic major crustal blocks (source of the Grenvillian age peaks in the metaclastic rocks).This event would be coeval with the development of arc magmatism along the eastern margin of the eastern block. Closure of this eastern margin led to a Cambrian active margin (Sierra Norte arc) along the western margin of the eastern block in which magmatism reworked the same crustal block. Consumption of a ridge segment (input of OIB signature mafic magmas) which controlled granulite-facies metamorphism led to a final collision (Pampean orogeny) with the western Mesoprotrozoic block. Sm–Nd results for the metamorphic basement suggest that the TDM age interval of 1.8–1.7 Ga, which is associated with the less radiogenic values of εNd(540) (−6 to −8), can be considered as the mean average crustal composition for the Eastern Sierras Pampeanas. Increasing metamorphic grade in rocks with similar detrital sources and metamorphic ages like in the Sierras de Córdoba is associated with a younger TDM age and a more positive εNd(540) value. Pampean pre-540 Ma granitoids form two clusters, one with TDM ages between 2.0 and 1.75 Ga and another between 1.6 and 1.5 Ga. Pampean post-540 Ma granitoids exhibit more homogenous TDM ages ranging from 2.0 to 1.75 Ga. Ordovician re-activation of active margin along the western part of the block that collided in the Cambrian led to arc magmatism (Famatinian orogeny) and related ensialic back-arc basin in which high-grade metamorphism is related to mid-crustal felsic plutonism and mafic magmatism with significant contamination of continental crust. TDM values for the Ordovician Famatinian granitoids define a main interval of 1.8–1.6, except for the Ordovician TTG suites of the Sierras de Córdoba, which show younger TDM ages ranging from 1.3 to 1.0 Ga. In Devonian times (Achalian orogeny), a new subduction regime installed west of the Eastern Sierras Pampeanas. Devonian magmatism in the Sierras exhibit process of mixing/assimilation of depleted mantle signature melts and continental crust. Achalian magmatism exhibits more radiogenic εNd(540) values that range between 0.5 and −4 and TDM ages younger than 1.3 Ga. In pre-Devonian times, crustal reworking is dominant, whereas processes during Devonian times involved different geochemical and isotopic signatures that reflect a major input of juvenile magmatism.

Description: Microbial iron oxyhydroxides are common deposits in natural waters, recent sediments, and mine drainage systems. Along with these minerals, trace and rare earth elements (TREE) are being accumulated within the mineralizing microbial mats. TREE patterns are widely used to characterize minerals and rocks, and to elucidate their evolution and origin. However, whether and which characteristic TREE signatures distinguish between a biological and an abiological origin of iron minerals is still not well-understood. Here we report on long-term flow reactor studies performed in the Tunnel of Äspö (Äspö Hard Rock Laboratory, Sweden). The development of microbial mats dominated by iron-oxidizing bacteria (FeOB), namely Mariprofundus sp. and Gallionella sp were investigated. The feeder fluids of the flow reactors were tapped at 183 and 290 m below sea-level from two brackish, but chemically different aquifers within the surrounding, ~1.8 Ga old, granodioritic rocks. The experiments investigated the accumulation and fractionation of TREE under controlled conditions of the subsurface continental biosphere, and enabled us to assess potential biosignatures evolving within the microbial iron oxyhydroxides. After 2 and 9 months, concentrations of Be, Y, Zn, Zr, Hf, W, Th, Pb, and U in the microbial mats were 103- to 105-fold higher than in the feeder fluids whereas the rare earth elements and Y (REE+Y) contents were 104- and 106-fold enriched. Except for a hydrothermally induced Eu anomaly, the normalized REE+Y patterns of the microbial iron oxyhydroxides were very similar to published REE+Y distributions of Archaean Banded Iron Formations (BIFs). The microbial iron oxyhydroxides from the flow reactors were compared to iron oxyhydroxides that were artificially precipitated from the same feeder fluid. Remarkably, these abiotic and inorganic iron oxyhydroxides show the same REE+Y distribution patterns. Our results indicate that the REE+Y mirror closely the water chemistry, but they do not allow to distinguish microbially mediated from inorganic iron precipitates. Likewise, all TREE studied showed an overall similar fractionation behavior in biogenic, abiotic, and inorganic iron oxyhydroxides. Exceptions are Ni and Tl, which were only accumulated in the microbial iron oxyhydroxides and may point to a potential utility of these elements as microbial biosignatures.

Description: Due to its extreme salinity and high Mg concentration the Dead Sea is characterized by a very low density of cells most of which are Archaea. We discovered several underwater fresh to brackish water springs in the Dead Sea harboring dense microbial communities. We provide the first characterization of these communities, discuss their possible origin, hydrochemical environment, energetic resources and the putative biogeochemical pathways they are mediating. Pyrosequencing of the 16S rRNA gene and community fingerprinting methods showed that the spring community originates from the Dead Sea sediments and not from the aquifer. Furthermore, it suggested that there is a dense Archaeal community in the shoreline pore water of the lake. Sequences of bacterial sulfate reducers, nitrifiers iron oxidizers and iron reducers were identified as well. Analysis of white and green biofilms suggested that sulfide oxidation through chemolitotrophy and phototrophy is highly significant. Hyperspectral analysis showed a tight association between abundant green sulfur bacteria and cyanobacteria in the green biofilms. Together, our findings show that the Dead Sea floor harbors diverse microbial communities, part of which is not known from other hypersaline environments. Analysis of the water’s chemistry shows evidence of microbial activity along the path and suggests that the springs supply nitrogen, phosphorus and organic matter to the microbial communities in the Dead Sea. The underwater springs are a newly recognized water source for the Dead Sea. Their input of microorganisms and nutrients needs to be considered in the assessment of possible impact of dilution events of the lake surface waters, such as those that will occur in the future due to the intended establishment of the Red Sea - Dead Sea water conduit.

Description: Organic molecules, such as pharmaceuticals, agro-chemicals and pigments, frequently form several crystal polymorphs with different physicochemical properties. Finding polymorphs has long been a purely experimental game of trial-and-error. Here we utilize in silico polymorph screening in combination with rationally planned crystallization experiments to study the polymorphism of the pharmaceutical compound Dalcetrapib, with 10 torsional degrees of freedom one of the most flexible molecules ever studied computationally. The experimental crystal polymorphs are found at the bottom of the calculated lattice energy landscape, and two predicted structures are identified as candidates for a missing, thermodynamically more stable polymorph. Pressure-dependent stability calculations suggested high pressure as a means to bring these polymorphs into existence. Subsequently, one of them could indeed be crystallized in the 0.02 to 0.50 GPa pressure range and was found to be metastable at ambient pressure, effectively derisking the appearance of a more stable polymorph during late-stage development of Dalcetrapib.

Description: The application of the SHRIMP U/Pb dating technique to zircon and monazite of different rock types of the Sierras de Córdoba provides an important insight into the metamorphic history of the basement domains. Additional constraints on the Pampean metamorphic episode were gained by Pb/Pb stepwise leaching (PbSL) experiments on two titanite and garnet separates. Results indicate that the metamorphic history recorded by Crd-free gneisses (M2) started in the latest Neoproterozoic/earliest Cambrian (553 and 543 Ma) followed by the M4 metamorphism at ~530 Ma that is documented in the diatexites. Zircon ages of 492 Ma in the San Carlos Massif correlate partly with rather low Th/U ratios (〈0.1) suggesting their growth by metamorphic fluids. This age is even younger than the PbSL titanite ages of 506 Ma. It is suggested that the fluid alteration relates to the beginning of the Famatinien metamorphic cycle in the neighbouring Sierra de San Luis and has not affected the titanite ages. The PTt evolution can be correlated with the plate tectonic processes responsible for the formation of the Pampean orogene, i.e., the accretion of the Pampean basement to the Río de La Plata craton (M2) and the later collision of the Western Pampean basement with the Pampean basement.

Description: Arquitectura sísmica-estratigráfica de la Formación Camaná del Oligoceno-Plioceno, Antearco del sur de Perú (Provincia de Arequipa). La Cuenca Camaná-Mollendo es una depresión de margen activo en el sur de Perú, la cual es elongada en sentido ~NW-SE y se extendiende desde la cordillera de la Costa hasta la fosa Perú-Chile. Esta cuenca consiste en un sistema de graben y semigrábenes y está rellenada con rocas sedimentarias de edad Oligoceno a Plioceno, correspondientes a la Formación Camaná (deltaico y fluvial, ~500 m de espesor). Una integración de datos provenientes de columnas estratigráficas, sísmica de reflexión 2D costa afuera, proveniencia sedimentaria, y geocronología de U-Pb en zircones volcanoclásticos ayudó a elaborar un cuadro tectono-cronoestratigráfico de toda la Cuenca Camaná-Mollendo. Para llevar a cabo esta integración, en primer lugar se requirió reinterpretar geológicamente la data sísmica 2D costa afuera y resaltar las características estratigráficas más prominentes (i.e., superficies erosivas), las cuales son atribuibles a la Formación Camaná. Estas características lograron ser correlacionadas con las superficies erosivas definidas en la Formación Camaná costa adentro y dieron como resultado la siguiente división: (i) “Unidad CamA” de la Formación Camaná (deltas de grano grueso) y (ii) “Unidad CamB” de la Formación Camaná (depósitos fluviales). La Unidad CamA se subdividió en tres subunidades en base a discontinuidades estratigráficas menores y diferencias en su geometría depositacional (i.e., A1: Oligoceno; A2: Mioceno inferior; y A3: Mioceno medio). La Unidad CamA refleja geometría progradante (A1 y A2) y “onlapante” (A3). La Unidad CamB (Mioceno superior a Plioceno) comprende conglomerados fluviales e hiperpícnicos de alta energía. Cada una de estas unidades y subunidades se extienden costa afuera de Camaná y mantienen similares geometrías depositacionales y los mismos límites secuenciales. En los depósitos costa afuera, las subunidades A1 y A2 (Oligoceno a Mioceno Inferior) están agrupadas como “A1+A2” debido a que ambos muestran similares geometrías progradacionales y es difícil diferenciarlos. Un sistema regresivo (RST) representa estas subunidades. Estos depósitos alcanzan ~2,5 km de espesor, y están intensamente afectados por fallas normales y lístricas asociados a geometrías depositacionales pinch-out. Los estratos de la subunidad A3 (Mioceno Medio) reflejan un sistema transgresivo (TST), y cubren toda la cuenca con sedimentos finos. La subunidad A3 alcanza ~1 km de espesor, y se caracteriza por su geometría “onlapante”, y menor proporción de tectónica sinsedimentaria. Finalmente, la depositación de la Unidad CamB (Mioceno Superior a Plioceno) ocurrió durante un nuevo episodio regresivo (RST), la cual se vuelve deltaica y progradacional costa afuera y está mucho menos afectada por fallas sinsedimentarias. Los límites estratigráficos entre “A1+A2” y A3, y entre A3 y CamB observados costa adentro se utilizan para diferenciar, correlacionar y predecir las principales geometrías depositacionales y sistemas depositacionales encadenados interpretados para los depósitos costa afuera. Los reflectores sísmicos de alta frecuencia representan tales límites y apoyan la subdivisión de la Formación Camaná costa afuera. Estos límites son además utilizados para definir depocentros a lo largo de la Cuenca Camaná- Mollendo, donde los depocentros más voluminosos están ubicados en las cercanías de los grandes valles (e.g., Planchada, Camaná y Punta de Bombón). Los depósitos de las subunidades “A1+A2” son considerados como un potencial reservorio de hidrocarburos debido a su alta tasa de sedimentación. Los depósitos de la subunidad A3 son transgresivos y considerados como una potencial roca sello. Estructuralmente, la Cuenca Camaná-Mollendo está compuesta por elementos estructurales propios de sistemas de grábenes y semi-grábenes, los cuales están orientados preferencialmente ~NW-SE (orientación andina)