The Kennack Gneiss of the Lizard Peninsula, Cornwall, SW England: Commingling and mixing of mafic and felsic magmas accompanying Givetian continental incorporation of the Lizard ophiolite

The Kennack Gneiss comprises a suite of interlayered mafic and felsic igneous rocks that intruded the 397 Ma Lizard Ophiolite Complex, Cornwall, at 376.4 ± 1.7 Ma (U-Pb single-zircon date) and were shortly thereafter (c. 370 Ma) metamorphosed to the amphibolite facies. Weakly deformed examples at the type-locality of Kennack Sands reveal net-veining of the mafic by the felsic component, dispersed enclaves of the former in the latter and flame-like interfingering of the two, features indicative of magmatic commingling and mixing. The silicic components of the Kennack Gneiss range from granodiorite to syenogranite and from metaluminous to peraluminous, the least silicic rocks being the most peraluminous. They were generated through anatexis of a predominantly metasedimentary crustal source having trace element and isotopic compositions comparable to those of the Devonian Gramscatho Group of South Cornwall. The mafic component of the gneiss includes members (group 1) which are weakly enriched in light REE, have minor negative Ta, Nb, P and Ti anomalies in extended trace element plots, and display primitive, time-corrected 143Nd/ 144Nd and 87Sr/ 86Sr values, and others (group 2) which are more strongly enriched in all incompatible trace elements, exhibit more prominent negative Ta, Nb, P and Ti anomalies, and have isotopic ratios intermediate between group 1 mafic components and the associated felsic gneiss. Group 2 represents mixtures of group 1 and granitic melts, whereas group 1 rocks are comparable to EMORB and were probably generated through partial melting of a weakly enriched mantle source. Emplacement of two commingled magmas into the base of the Lizard ophiolite, one representing the products of crustal anatexis, implies that the ophiolite was removed from its oceanic setting and was in the process of obduction in the Givetian.published_or_final_versio

In Silico Evidence for Gluconeogenesis from Fatty Acids in Humans

The question whether fatty acids can be converted into glucose in humans has a long standing tradition in biochemistry, and the expected answer is “No”. Using recent advances in Systems Biology in the form of large-scale metabolic reconstructions, we reassessed this question by performing a global investigation of a genome-scale human metabolic network, which had been reconstructed on the basis of experimental results. By elementary flux pattern analysis, we found numerous pathways on which gluconeogenesis from fatty acids is feasible in humans. On these pathways, four moles of acetyl-CoA are converted into one mole of glucose and two moles of CO2. Analyzing the detected pathways in detail we found that their energetic requirements potentially limit their capacity. This study has many other biochemical implications: effect of starvation, sports physiology, practically carbohydrate-free diets of inuit, as well as survival of hibernating animals and embryos of egg-laying animals. Moreover, the energetic loss associated to the usage of gluconeogenesis from fatty acids can help explain the efficiency of carbohydrate reduced and ketogenic diets such as the Atkins diet

Geochemistry and U-Pb and 40Ar- 39Ar geochronology of The Man of War Gneiss, Lizard complex, SW England: Pre-Hercynian arc-type crust with a Sudeten-Iberian connection

The Man of War Gneiss is a variably deformed meta-igneous body that ranges in composition from gabbro to tonalite and comprises part of the basal structural slice of the Lizard ophiolite complex, SW England. U-Pb dating of zircon demonstrates that the parental magmas crystallized in the earliest Ordovician (499 +8 -3 Ma), but 40Ar- 39Ar step-heating analysis of amphiboles suggests that at least the northernmost zone of the gneiss was subjected to an amphibolite-grade metamorphic event at c. 374 Ma, probably associated with thrust emplacement of the ophiolite. The gneiss exhibits major, trace and rare earth element variations in conformity with an origin through partial melting of an amphibolitic source containing hornblende and plagioclase, probably with minor garnet and zircon. The elemental abundances and variations are characteristic of granitoids formed in supra-subduction zone environments. A granitoid sill within the adjacent Old Lizard Head Series schists, previously inferred to be related to the Man of War Gneiss, is trondhjemitic and exhibits higher SiO 2, TiO 2 and MgO, but lower Zr, V, Ba, and Sr contents, and therefore is probably not genetically related to the latter. The sill may record local melting during ophiolite emplacement. The Man of War Gneiss probably represents a structural inlier of pre-Hercynian basement incorporated in the Hercynian nappes of SW England during NNW-directed thrusting. We emphasize the geological and geochronological similarities between variably deformed granitoid units of the Lizard complex, the Sudeten Massif of southern Poland, and the allochthonous complexes of northern Portugal and NW Spain. These granitoid rocks may represent dispersed remnants of Tremadoc arcs that formed oceanward from the northern margin of Gondwana. This is further convincing evidence that at this time Eastern Avalonia was separated from northern Gondwana by an ocean basin that may have been connected with the Tornquist Sea.link_to_subscribed_fulltex