Mineral carbonation of peridotite fueled by magmatic degassing and melt impregnation in an oceanic transform fault.

Most of the geologic CO2 entering Earth's atmosphere and oceans is emitted along plate margins. While C-cycling at mid-ocean ridges and subduction zones has been studied for decades, little attention has been paid to degassing of magmatic CO2 and mineral carbonation of mantle rocks in oceanic transform faults. We studied the formation of soapstone (magnesite-talc rock) and other magnesite-bearing assemblages during mineral carbonation of mantle peridotite in the St. Paul's transform fault, equatorial Atlantic. Clumped carbonate thermometry of soapstone yields a formation (or equilibration) temperature of 147 ± 13 °C which, based on thermodynamic constraints, suggests that CO2(aq) concentrations of the hydrothermal fluid were at least an order of magnitude higher than in seawater. The association of magnesite with apatite in veins, magnesite with a δ13C of -3.40 ± 0.04‰, and the enrichment of CO2 in hydrothermal fluids point to magmatic degassing and melt-impregnation as the main source of CO2. Melt-rock interaction related to gas-rich alkali olivine basalt volcanism near the St. Paul's Rocks archipelago is manifested in systematic changes in peridotite compositions, notably a strong enrichment in incompatible elements with decreasing MgO/SiO2. These findings reveal a previously undocumented aspect of the geologic carbon cycle in one of the largest oceanic transform faults: Fueled by magmatism in or below the root zone of the transform fault and subsequent degassing, the fault constitutes a conduit for CO2-rich hydrothermal fluids, while carbonation of peridotite represents a vast sink for the emitted CO2.

Polygonifoliol, a new tirucallane triterpene from the latex of the seaside sandmat Euphorbia polygonifolia.

The genus Euphorbia contains over 2000 species which exhibit a considerable diversity of di- and triterpenes in their latex. The North American species Euphorbia polygonifolia is a low growing plant of Atlantic and Great Lake beaches. The composition of its free and esterified triterpene alcohols was determined by HPLC and (1) H-NMR analyses. An unreported triterpene alcohol was found as 2.6% and 10.3% of the free and esterified fractions, respectively. The structure of the new triterpene alcohol was determined using HMBC, and its configurational assignment was secured by acid-catalyzed isomerization to isotirucallol. The new compound, polygonifoliol, was shown to be Δ(12) -isotirucallol.

Desire: philosophical issues.

To desire something is to want it, wish it, long for it. Various leading theories of this attitude exist, with the most prominent theory holding that to desire something is nothing more than to be inclined to take actions that will obtain that thing. Other important theories tie desires to pleasure and displeasure, to reasons and goodness, or to reward learning. All of these theories leave room for scientific investigation of what causes us to desire, and of what else desires might cause in us. Philosophical speculation on these topics has focused, in the former case, on the generation of new desires from existing desires. In the latter case, it has roamed across topics diverse as the influence of desire on cognition, the relation of desire to mental disorder, and causation of self-knowledge of one's own desires. Copyright © 2010 John Wiley & Sons, Ltd. For further resources related to this article, please visit the WIREs website.