241 research outputs found
Rapid eclogitisation of the Dabie–Sulu UHP terrane: Constraints from Lu–Hf garnet geochronology
No full textAbstractThe Qinling–Dabie–Sulu orogenic belt in eastern China is one of the largest ultrahigh-pressure (UHP) terranes worldwide. Mineral Sm–Nd- and zircon U–Pb dating has been widely used to reveal the metamorphic history of this collisional orogen. However, the exact timing of the UHP metamorphic event(s) remains controversial and ages ranging from 245 Ma to 220 Ma have been suggested. We present high precision garnet–cpx Lu–Hf ages for six eclogites from the Dabie and Sulu areas. All ages fall in a narrow range between 219.6 and 224.4 Ma. Five samples define a mean age of 223.0±0.9 Ma and one sample yields a slightly younger age of 219.6±1.4 Ma. This very tight age range is particularly remarkable considering the large regional distribution of sample localities (on the order of 100 km at the time of UHP metamorphism) and the wide variety of garnet and eclogite chemical compositions represented. Two samples yield Sm–Nd ages that are indistinguishable from their Lu–Hf ages, albeit with larger uncertainties.The identical ages of eclogites from both the Dabie and the Sulu region emphasize their close genetic relationship and similar metamorphic histories. The Lu–Hf results appear to date a punctuated event of garnet growth. Alternatively, the Lu–Hf garnet ages may represent the onset of rapid, contemporaneous uplift and subsequent cooling. However, trace element zoning of Lu and Hf is still preserved in garnet porphyroblasts, even in those with a homogeneous major element distribution. Thus, complete re-equilibration of the Lu–Hf system during peak-temperature conditions probably did not occur. The garnet forming event can be placed toward the final stage of the UHP metamorphism, in agreement with some published U–Pb zircon ages. A possible trigger for this short-lived and widespread mineral growth episode may have been a fluid that became available at that stage of the metamorphic history. Although HREE-depleted patterns of older zircon grains may indicate the presence of an older generation of garnet, complete eclogitisation may have been inhibited during the major part of the prograde P–T path due to dry conditions during most of the UHP metamorphism. The uniform Lu–Hf (and Sm–Nd) ages of all investigated Dabie and Sulu eclogites suggest that garnet growth and thus possibly fluid availability were limited to a short time interval over a remarkably large regional scale
Gene loss and lineage specific restriction-modification systems associated with niche differentiation in the Campylobacter jejuni Sequence Type 403 clonal complex
No full textCampylobacter jejuni is a highly diverse species of bacteria commonly associated with infectious intestinal disease of humans and zoonotic carriage in poultry, cattle, pigs, and other animals. The species contains a large number of distinct clonal complexes that vary from host generalist lineages commonly found in poultry, livestock, and human disease cases to host-adapted specialized lineages primarily associated with livestock or poultry. Here, we present novel data on the ST403 clonal complex of C. jejuni, a lineage that has not been reported in avian hosts. Our data show that the lineage exhibits a distinctive pattern of intralineage recombination that is accompanied by the presence of lineage-specific restriction-modification systems. Furthermore, we show that the ST403 complex has undergone gene decay at a number of loci. Our data provide a putative link between the lack of association with avian hosts of C. jejuni ST403 and both gene gain and gene loss through nonsense mutations in coding sequences of genes, resulting in pseudogene formation
Jochen Gerz // Jean Louis Garnell
No full textAlbertini's brief descriptions of Garnell's and Gerz's photo and text based works focus on the temporal and spatial limitations of language and image. Includes short texts by both artists
Religiosity as self-enhancement: a meta-analysis of the relation between socially desirable responding and religiosity
No full textIn a meta-analysis, the authors test the theoretical formulation that religiosity is a means for self-enhancement. The authors operationalized self-enhancement as socially desirable responding (SDR) and focused on three facets of religiosity: intrinsic,extrinsic, and religion-as-quest. Importantly, they assessed two moderators of the relation between SDR and religiosity. Macrolevel culture reflected countries that varied in degree of religiosity (from high to low: United States, Canada, United Kingdom). Micro-level culture reflected U.S. universities high (christian) versus low (secular) on religiosity. The results were generally consistent with the theoretical formulation. Both macro-level and micro-level culture moderated the relation between SDR and religiosity: This relation was more positive in samples that placed higher value on religiosity (United States > Canada >United Kingdom; christian universities > secular universities). The evidence suggests that religiosity is partly in the service of self-enhancement
Geochemical, Spatial, and Temporal Relationships of the Intrusives and Meta-Intrusives of the Pogo Deposit, Eastern Interior, AK
No full textThe Pogo deposit is an intrusion-related gold deposit (IRGD) located approximately 90 km southeast of Fairbanks, Alaska. It consists mainly of shallowly NW dipping quartz veins hosted in amphibolite facies paragneiss and predominately granite orthogneiss bodies. To date the deposit has produced over 4 million ounces of gold. U-Pb zircon dating of the orthogneisses shows they have Devonian-Mississippian protolith ages. Dates from the metamorphic zircons, established by microprobe Th data and cathodoluminescence studies, constrain a mid-Cretaceous metamorphic event to ~116 Ma. Recrystallization of kyanite to sillimanite and zircon recrystallization indicates this was a large fluid flux event that predated mineralization by 10 million years. Due to the fine-grained nature of the intrusive rocks at Pogo, identifying rocks in hand sample proved problematic. By combining XRF analysis of the rocks’ major and trace elements and age data from this and previous studies, I identified and differentiated several suites of igneous rocks. The oldest is peraluminous granite, emplaced at ~2.5 ± 0.5 kb at ~109-107 Ma, predating mineralization at 104 Ma at a pressure of 2.0 kb. Non-peraluminous granite is less common and of uncertain relationship to the peraluminous granite. Next, temporally, is a body named the Football pluton (and associated dike) of granodioritic to tonalitic composition, emplaced at 2.0 ± 0.5 kb at 103 ± 2 Ma. Not only indistinguishable from age and depth of mineralization, a dike of this body is present downdip underneath the Liese veins (main zone of mineralization), making it the most likely candidate for being the causative pluton for mineralization. The final mid-Cretaceous body is the Liese pluton (and associated dikes), of quartz diorite to tonalite. This forms a large body with E-W dikes cutting the Pogo mineralization and post-dating it at 95.4 ± 0.2 Ma, emplaced at a pressure of 1.0 kb. Thermobarometry and radiometric dating indicate a consistent uplift rate of about 0.6 mm/year during the mid-Cretaceous, 116 to 95 Ma. Initially an extensional event, subduction-related magmatism began at about 105 Ma. At the same time, the thrust faults were re-activated as low angle normal faults that apparently acted as pathways for the Liese mineralization
Jochen Gerz : It Was Easy, 1988-1992
No full textThrough a detailed analysis of Gerz's photo-text series produced since 1988, Pejic investigates notions of reality and the image, citing various iconoclastic controversies throughout history. The author shows that representation is based on the politics of the visible and that an image is a making. 13 bibl. ref
Rotation of irregular staurolite porphyroblasts in a simple shear dominated shear zone controlled by initial growth orientation and aspect ratio
No full textPolymetamorphism and ductile deformation of staurolite-cordierite schist of the Bossost Dome: indication for Variscan extension in the Axial Zone of the central Pyrenees
No full textAbstract – The Bossòst dome is an E–W-trending elongated structural and metamorphic dome developed in Cambro-Ordovician metasedimentary rocks in the Variscan Axial Zone of the central Pyrenees. A steep fault separates a northern half-dome, cored by massif granite, from an E–W-trending doubly plunging antiform with granitic sills and dykes in the core to the south. The main foliation is a flat-lying S1/2 schistosity that grades into a steeper-dipping slaty cleavage at the dome margins. Three major deformational and two metamorphic phases can be differentiated. S1/2 schistosity is an axial planar cleavage to W-vergent recumbent folding that probably occurred in mid-Westphalian time. Peak regional metamorphism M1 is characterized by static growth of staurolite and garnet following thermal relaxation of the previously thickened crust. Strong non-coaxial deformation recording uniform top-to-the-SE extension during D2a is preserved in staurolite–garnet schists in a 1.5 km thick, shallowly SE-dipping zone in the southeastern dome. A 500 m thick contact aureole (M2) was imprinted on the regionally metamorphosed rocks following the intrusion the Bossòst granite during D2b. More coaxial deformation prevailed during synkinematic growth of M2 phases in the inner part of the contact aureole around the northern part of the dome, where it obliterated D2a fabrics. Progressive non-coaxial deformation continued in the southeastern antiform and is recorded by late-synkinemati
CONTRACTIONALLY DEFORMED BELEMNITES AS INDICATORS FOR THRUST FAULTING IN MECHANICALLY WEAK SEDIMENTARY LAYERS – AN EXAMPLE FROM THE LOWER CRETACEOUS OF THE TALKEETNA MTS., CENTRAL ALASKA
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