237 research outputs found
Structural Controls on Crustal Fluid Circulation and Hot Spring Geochemistry Above a FlatâSlab Subduction Zone, Peru
Hot spring geochemistry from the Cordillera Blanca and Cordillera Huayhuash, Peru, reveal the influence of crustalâscale structures on geothermal fluid circulation in an amagmatic region located above a flatâslab subduction zone. To test the influence of contrasting modes of faulting in these regions, springs were targeted along the Cordillera Blanca detachment fault, within its hanging wall, in the footwall of the detachment, and in the Cordillera Huayhuash. Hot springs along the Cordillera Blanca detachment fault zone are associated with recent extension and normal faulting, and those in its footwall and the Cordillera Huayhuash are located in the Marañon fold and thrust belt where compressional structures dominate. Springs along and in the hanging wall of the Cordillera Blanca detachment fault yield brackishâsaline, alkalineâchloride waters, with oxygen, hydrogen, carbon, and chlorine stable isotope values that suggest mixing between meteoric groundwater and saline brine affected by high waterârock interaction. Geothermometry reservoir temperature estimates (RTEs) of 91â226°C indicate maximum flow path depths of 8.7 or 11 km, depending on geothermal gradient, associated with the Cordillera Blanca detachment fault. In contrast, springs in the footwall and in the Cordillera Huayhuash exhibit a wide range of water types with an isotopic affinity to meteoric water, suggesting a greater influence from shallow groundwater and less waterârock interaction. For these springs, RTEs of 40â98°C correspond to much shallower circulation (1.6â4 km). Results indicate that the Cordillera Blanca detachment system accommodates significantly deeper circulation of crustal fluids compared to other regional compressional structures
Deep structure of the Ionian Sea and Sicily Dionysus - Cruise No. M111, October 10 - November 1, 2014, Catania (Italy) â Catania (Italy)
Summary
The origin of the Ionian Sea lithosphere and the deep structure of its margins remain a little
investigated part of the Mediterranean Sea. To shed light on the plate tectonic setting in this
central part of southern Europe, R/V METEOR cruise M111 set out to acquire deep penetrating
seismic data in the Ionian Sea. M111 formed the core of an amphibious investigation covering
the Ionian Sea and island of Sicily. A total of 153 OBS/OBH deployments using French and
German instruments were successfully carried out, in addition to 12 land stations installed on
Sicily, which recorded the offshore air gun shots.
The aim of this onshore-offshore study is to quantify the deep geometry and architecture of the
Calabria subduction zone and Ionian Sea lithosphere and to shed light on the nature of the Ionian
Sea crust (oceanic crust vs. thinned continental crust). Investigating the structure of the Ionian
crust and lithospheric mantle will contribute to unravel the unknown ocean-continent transition
and Tethys margin. Analyzing the tectonic activity and active deformation zones is essential for
understanding the subduction processes that underlie the neotectonics of the Calabrian
subduction zone and earthquake hazard of the Calabria/Sicily region, especially in the vicinity of
local decoupling zones
Ionian Abyssal Plain: a window into the Tethys oceanic lithosphere
The nature of the Ionian Sea crust has been the subject
of scientific debate for more than 30Â years, mainly because seismic imaging
of the deep crust and upper mantle of the Ionian Abyssal Plain (IAP) has not
been conclusive to date. The IAP is sandwiched between the Calabrian and
Hellenic subduction zones in the central Mediterranean. A NNEâSSW-oriented
131 km long seismic refraction and wide-angle reflection profile, consisting
of eight ocean bottom seismometers and hydrophones, was acquired in 2014.
The profile was designed to univocally confirm the proposed oceanic nature
of the IAP crust as a remnant of the Tethys and to confute its
interpretation as a strongly thinned part of the African continental crust.
A P-wave velocity model developed from travel-time forward modelling is
refined by gravimetric data and synthetic modelling of the seismic data. A
roughly 6â7 km thick crust with velocities ranging from 5.1 to 7.2 km sâ1, top to bottom, can be traced throughout the IAP. In the vicinity of
the Medina seamounts at the southern IAP boundary, the crust thickens to
about 9 km and seismic velocities decrease to 6.8 km sâ1 at the crustâmantle
boundary. The seismic velocity distribution and depth of the crustâmantle
boundary in the IAP document its oceanic nature and support the
interpretation of the IAP as a remnant of the Tethys lithosphere with the
Malta Escarpment as a transform margin and a Tethys opening in the NNWâSSE
direction.</p
Limits of the seismogenic zone in the epicentral region of the 26 December 2004 great Sumatra-Andaman earthquake: Results from seismic refraction and wide-angle reflection surveys and thermal modeling
The 26 December 2004 Sumatra earthquake (Mw = 9.1) initiated around 30 km
depth and ruptured 1300 km of the Indo-Australian Sunda plate boundary. During
the Sumatra OBS (ocean bottom seismometer) survey, a wide angle seismic profile
was acquired across the epicentral region. A seismic velocity model was
obtained from combined travel time tomography and forward modeling. Together
with reflection seismic data from the SeaCause II cruise, the deep structure of
the source region of the great earthquake is revealed. Four to five kilometers
of sediments overlie the oceanic crust at the trench, and the subducting slab
can be imaged down to a depth of 35 km. We find a crystalline backstop 120 km
from the trench axis, below the fore arc basin. A high velocity zone at the
lower landward limit of the raycovered domain, at 22 km depth, marks a shallow
continental Moho, 170 km from the trench. The deep structure obtained from the
seismic data was used to construct a thermal model of the fore arc in order to
predict the limits of the seismogenic zone along the plate boundary fault.
Assuming 100C-150C as its updip limit, the seismogenic zone is predicted to
begin 530 km from the trench. The downdip limit of the 2004 rupture as inferred
from aftershocks is within the 350C 450C temperature range, but this limit is
210-250 km from the trench axis and is much deeper than the fore arc Moho. The
deeper part of the rupture occurred along the contact between the mantle wedge
and the downgoing plate
Marine transform faults and fracture zones: A joint perspective integrating seismicity, fluid flow and life
Landscape genomics and biased FST approaches reveal single nucleotide polymorphisms under selection in goat breeds of North-East Mediterranean
<p>Abstract</p> <p>Background</p> <p>In this study we compare outlier loci detected using a <it>F<smcaps>ST </smcaps></it>based method with those identified by a recently described method based on spatial analysis (SAM). We tested a panel of single nucleotide polymorphisms (SNPs) previously genotyped in individuals of goat breeds of southern areas of the Mediterranean basin (Italy, Greece and Albania). We evaluate how the SAM method performs with SNPs, which are increasingly employed due to their high number, low cost and easy of scoring.</p> <p>Results</p> <p>The combined use of the two outlier detection approaches, never tested before using SNP polymorphisms, resulted in the identification of the same three loci involved in milk and meat quality data by using the two methods, while the <it>F<smcaps>ST </smcaps></it>based method identified 3 more loci as under selection sweep in the breeds examined.</p> <p>Conclusion</p> <p>Data appear congruent by using the two methods for <it>F<smcaps>ST </smcaps></it>values exceeding the 99% confidence limits. The methods of <it>F<smcaps>ST </smcaps></it>and SAM can independently detect signatures of selection and therefore can reduce the probability of finding false positives if employed together. The outlier loci identified in this study could indicate adaptive variation in the analysed species, characterized by a large range of climatic conditions in the rearing areas and by a history of intense trade, that implies plasticity in adapting to new environments.</p
The Amino-Terminus of Nitric Oxide Sensitive Guanylyl Cyclase α1 Does Not Affect Dimerization but Influences Subcellular Localization
BACKGROUND: Nitric oxide sensitive guanylyl cyclase (NOsGC) is a heterodimeric enzyme formed by an α- and a ÎČâ-subunit. A splice variant (C-αâ) of the αâ-subunit, lacking at least the first 236 amino acids has been described by Sharina et al. 2008 and has been shown to be expressed in differentiating human embryonic cells. Wagner et al. 2005 have shown that the amino acids 61-128 of the αâ-subunit are mandatory for quantitative heterodimerization implying that the C-αâ-splice variant should lose its capacity to dimerize quantitatively. METHODOLOGY/PRINCIPAL FINDINGS: In the current study we demonstrate preserved quantitative dimerization of the C-αâ-splice by co-purification with the ÎČâ-subunit. In addition we used fluorescence resonance energy transfer (FRET) based on fluorescence lifetime imaging (FLIM) using fusion proteins of the ÎČâ-subunit and the αâ-subunit or the C-αâ variant with ECFP or EYFP. Analysis of the respective combinations in HEK-293 cells showed that the fluorescence lifetime was significantly shorter (â0.3 ns) for αâ/ÎČâ and C-αâ/ÎČâ than the negative control. In addition we show that lack of the amino-terminus in the αâ splice variant directs it to a more oxidized subcellular compartment. CONCLUSIONS/SIGNIFICANCE: We conclude that the amino-terminus of the αâ-subunit is dispensable for dimerization in-vivo and ex-vivo, but influences the subcellular trafficking
The role of changing geodynamics in the progressive contamination of Late Cretaceous to Late Miocene arc magmas in the southern Central Andes
The tectonic and geodynamic setting of the southern Central Andean convergent margin changed significantly between the Late Cretaceous and the Late Miocene, influencing magmatic activity and its geochemical composition. Here we investigate how these changes, which include changing slab-dip angle and convergence angles and rates, have influenced the contamination of the arc magmas with crustal material. Whole rock geochemical data for a suite of Late Cretaceous to Late Miocene arc rocks from the Pampean flat-slab segment (29â31 °S) of the southern Central Andes is presented alongside petrographic observations and high resolution age dating. In-situ UâPb dating of magmatic zircon, combined with ArâAr dating of plagioclase, has led to an improved regional stratigraphy and provides an accurate temporal constraint for the geochemical data.
A generally higher content of incompatible trace elements (e.g. Nb/Zr ratios from 0.019 to 0.083 and Nb/Yb from 1.5 to 16.4) is observed between the Late Cretaceous (~ 72 Ma), when the southern Central Andean margin is suggested to have been in extension, and the Miocene when the thickness of the continental crust increased and the angle of the subducting Nazca plate shallowed. Trace and rare earth element compositions obtained for the Late Cretaceous to Late Eocene arc magmatic rocks from the Principal Cordillera of Chile, combined with a lack of zircon inheritance, suggest limited assimilation of the overlying continental crust by arc magmas derived from the mantle wedge. A general increase in incompatible, fluid-mobile/immobile (e.g., Ba/Nb) and fluid-immobile/immobile (e.g., Nb/Zr) trace element ratios is attributed to the influence of the subducting slab on the melt source region and/or the influx of asthenospheric mantle.
The Late Oligocene (~ 26 Ma) to Early Miocene (~ 17 Ma), and Late Miocene (~ 6 Ma) arc magmatic rocks present in the Frontal Cordillera show evidence for the bulk assimilation of the PermianâTriassic (PâT) basement, both on the basis of their trace and rare earth element compositions and the presence of PâT inherited zircon cores. Crustal reworking is also identified in the Argentinean Precordillera; Late Miocene (12â9 Ma) arc magmatic rocks display distinct trace element signatures (specifically low Th, U and REE concentrations) and contain inherited zircon cores with Proterozoic and PâT ages, suggesting the assimilation of both the PâT basement and a Grenville-aged basement. We conclude that changing geodynamics play an important role in determining the geochemical evolution of magmatic rocks at convergent margins and should be given due consideration when evaluating the petrogenesis of arc magmas.</p
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