Lavas and pyroclastic products of Nisyros volcano (Aegean arc, Greece) host a wide variety of phenocryst and cumulate assemblages that offer a unique window into the earliest stages of magma ...differentiation. This study presents a detailed petrographic study of lavas, enclaves and cumulates spanning the entire volcanic history of Nisyros to elucidate at which levels in the crust magmas stall and differentiate. We present a new division for the volcanic products into two suites based on field occurrence and petrographic features: a low-porphyricity andesite and a high-porphyricity (rhyo)dacite (HPRD) suite. Cumulate fragments are exclusively found in the HPRD suite and are predominantly derived from upper crustal reservoirs where they crystallised under hydrous conditions from melts that underwent prior differentiation. Rarer cumulate fragments range from (amphibole-)wehrlites to plagioclase-hornblendites and these appear to be derived from the lower crust (0.5–0.8 GPa). The suppressed stability of plagioclase and early saturation of amphibole in these cumulates are indicative of high-pressure crystallisation from primitive hydrous melts (≥ 3 wt% H
2
O). Clinopyroxene in these cumulates has Al
2
O
3
contents up to 9 wt% due to the absence of crystallising plagioclase, and is subsequently consumed in a peritectic reaction to form primitive, Al-rich amphibole (Mg# > 73, 12–15 wt% Al
2
O
3
). The composition of these peritectic amphiboles is distinct from trace element-enriched interstitial amphibole in shallower cumulates. Phenocryst compositions and assemblages in both suites differ markedly from the cumulates. Phenocrysts, therefore, reflect shallow crystallisation and do not record magma differentiation in the deep arc crust.
Hollow tubular structures in subaqueously-emplaced basaltic glass may represent trace fossils caused by microbially-mediated glass dissolution. Mineralized structures of similar morphology and ...spatial distribution in ancient, metamorphosed basaltic rocks have widely been interpreted as ichnofossils, possibly dating to ∼3.5 Ga or greater. Doubts have been raised, however, regarding the biogenicity of the original hollow tubules and granules in basaltic glass. In particular, although elevated levels of biologically-important elements such as C, S, N, and P as well as organic compounds have been detected in association with these structures, a direct detection of unambiguously biogenic organic molecules has not been accomplished. In this study, we describe the direct detection of proteins associated with tubular textures in basaltic glass using synchrotron X-ray spectromicroscopy. Protein-rich organic matter is shown to be associated with the margins of hollow and partly-mineralized tubules. Furthermore, a variety of tubule-infilling secondary minerals, including Ti-rich oxide phases, were observed filling and preserving the microtextures, demonstrating a mechanism whereby cellular materials may be preserved through geologic time.
A new tripodal O-donor ligand, tris(2-N,N-dibutylcarbamoylmethoxyphenyl)phosphine oxide (L), was synthesized. This potentially tetradentate ligand L exhibits variable denticity upon complexation with ...UO2(NO3)2, Nd(NO3)3, and Lu(NO3)3. The complexes were studied by elemental analysis, IR, and 1H, 13C, and 31P NMR spectroscopy. Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental files: Additional text, tables, and figures.
A reduced cardiac output in chronic heart failure (CHF) evokes renal NaCl and water retention, and, therefore, activates mechanisms promoting natriuresis. Atrial natriuretic peptide (ANP) is one such ...factor. We hypothesized that another NaCl sensitive endogenous natriuretic factor, i.e., marinobufagenin (MBG), a specific ligand of the alpha-1 subunit of Na/K ATPase (the main kidney isoform) and also a vasoconstrictor and cardiotonic substance, would be elevated in CHF patients in a graded manner with the severity of CHF.
We measured the plasma levels of MBG, alpha-hANP, ouabain-like compound (OLC) and left ventricular (LV) volumes and ejection fraction in 23 consecutive hypertensive male patients with CHF. Plasma MBG levels exhibited progressive increases (0.59 +/- 0.15, 1.08 +/- 0.20, 1.35 +/- 0.17 and 1.88 +/- 0.05 nmol/l NYHA 1-4, respectively) and paralleled the changes of alpha-hANP. Conversely, plasma OLC did not exhibit such increases. Plasma MBG correlated with alpha-hANP (r = 0.82; P < 0.0001). Both MBG and alpha-hANP correlated with LV systolic (r = 0.55 and r = 0.47; P < 0.01) diameter and inversely with ejection fraction (r = -0.73 and r = -0.60; P < 0.01). OLC did not exhibit correlations with alpha-hANP or LV volumes, but positively correlated with systolic brachial blood pressure and with pulse pressure.
In CHF, MBG exhibits progressive increases similar to ANP, varies with CHF severity and correlates with LV systolic function. We hypothesize, that, in CHF, the concurrent production of these two natriuretic hormones, a vasorelaxant, ANP, and a vasoconstrictor, MBG, potentiate each other's natriuretic effects, but may offset their vasoactive actions.
Melt inclusions in olivine are source of unique information about primitive mantle melts. Here we report results of an experimental study aimed at evaluating the ability of olivine to isolate ...chemically melt inclusions from the host magma after their entrapment. We demonstrate that nearly ‘dry’ melt inclusions from Galapagos Plateau basalt can gain up to 2.5 wt.% of water if they are placed for 2 days in a water-bearing melt at 200 MPa and 1140 °C. The major element composition of melt inclusions also changed significantly, as a result of a re-equilibration with the olivine host mineral, whereas no significant changes were detected for incompatible trace elements. Our results indicate that inclusions in olivine can rapidly and selectively exchange water with the matrix melt, probably, through combination of proton diffusion and molecular water transport along dislocations in olivine. The fast water transport explains element fractionation, which is not predictable from the theory of magmatic processes. An efficient re-equilibration of melt inclusions with matrix melt can explain the decoupling of water and incompatible trace elements (e.g., H
2O vs. K
2O) reported for suites of primitive inclusions from mid-ocean-ridge setting and island arcs. Rare cases of well preservation of initial water content in suites of co-genetic inclusions imply very short residence time (a few hours) of the olivine phenocrysts in magma with contrasting water content during fractionation and transport to the surface and rapid quenching upon eruption.
In this paper we deal with Seifert fibre spaces, which are compact 3-manifolds admitting a foliation by circles. We give a combinatorial description for these manifolds in all the possible cases: ...orientable, non-orientable, closed, and with boundary. Moreover, we compute a potentially sharp upper bound for their complexity in terms of the invariants of the combinatorial description, extending to the non-orientable case results by Fominykh and Wiest for the orientable case with boundary and by Martelli and Petronio for the closed orientable case. Our upper bound is indeed sharp for all Seifert fibre spaces contained in the census of non-orientable closed 3-manifolds classified with respect to complexity.
The differences in FeO mantle contents and core masses between the terrestrial planets suggest the oxygen fugacity (fO2) during their differentiation likely varied significantly. The metal-silicate ...partitioning of siderophile (iron-loving) elements is a function of fO2 and of their valence state(s) in silicate melts. Silicon (Si) is known to partition into metal at low fO2 and has been proposed as a possible light element in the cores of Mercury and the aubrite parent body (AuPB).
To systematically study the metal-silicate partitioning behavior of siderophile elements into Si-bearing metal, 69 high pressure (P) – temperature (T) metal-silicate partitioning experiments were performed under moderately to highly reducing conditions. Oxygen fugacities ranged between 1 and 7 units below the iron-wüstite buffer (ΔIW). Experimental pressures and temperatures ranged between 1 and 5 GPa and 1883 to 2273 K, respectively. A comparison of the ΔIW values and the fO2 based on the Si-SiO2 buffer (ΔSi-SiO2) indicates that the activity coefficient of FeO in silicate melts decreases significantly from reducing to highly reducing conditions under C-saturated conditions. It was found that at conditions more reducing than ΔIW = −3 to −4, the metal-silicate partitioning behavior of the majority of the siderophile elements deviates significantly from values corresponding to their expected valence state(s). These results indicate that the activity in metal of the elements considered, including that of Si itself, is decreased as a function of Si metal content, and a thermodynamic approach was used to quantify these effects. Interaction coefficients of trace elements in Si-bearing, Fe-rich alloys (εMSi) derived from the new experiments are in good agreement with previously proposed values at similar pressures below 5 GPa. However, εMSi values obtained for C-free systems decrease within the 1 to 11 GPa range, suggesting extrapolation of lower-pressure parameters may yield erroneous results at much higher pressures. Altogether, the new results provide an extensive experimental foundation for future studies of planetary differentiation under (highly) reduced conditions.
•The activity coefficient of FeO decreases with decreasing oxygen fugacity.•Silicon in metal decreases activities of trace elements in Fe-rich alloys.•Interaction coefficients of trace elements in Fe−Si alloys vary with pressure.
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