Carbonatite metasomatized peridotite xenoliths from southern Patagonia: implications for lithospheric processes and Neogene plateau magmatism
摘要:
The mineral chemistry, major and trace element, and Sr-Nd isotopic composition of Cr-diopside, spinel peridotite xenoliths from the Estancia Lote 17 locality in southern Patagonia document a strong carbonatitic metasomatism of the backarc continental lithosphere. The Lote 17 peridotite xenolith suite consists of hydrous spinel Iherzolite, wehrlite, and olivine websterite, and anhydrous harzburgite and Iherzolite. Two-pyroxene thermometry indicates equilibration temperatures ranging from 870 to 1015 degreesC and the lack of plagioclase or garnet suggests the xenoliths originated from between similar to 40 and 60 km depth. All of the xenoliths are LILE- and LREE-enriched, but have relatively low Sr-87/Sr-86 (0.70294 to 0.70342) and high epsilon (Nd) (+3.0 to +6.6), indicating recent trace element enrichment (similar to 25 Ma, based on the low Sr-87/Sr-86 and high Rb concentrations of phlogopite separates) in the long-term, melt-depleted Patagonian lithosphere. Lote 17 peridotite xenoliths are divided into two basic groups. Group 1 xenoliths consist of fertile peridotites that contain hydrous phases (amphibole +/- phlogopite +/- apatite). Group 1 xenoliths are further subdivided into three groups (a, b, and c) based on distinctive textures and whole-rock chemistry. Group 1 xenolith mineralogy and chemistry are consistent with a complex metasomatic history involving variable extents of recent carbonatite metasomatism (high Ca/Al, Nb/La, Zr/Hf, low Ti/Eu) that has overprinted earlier metasomatic events. Group 2 xenoliths consist of infertile, anhydrous harzburgites and record cryptic metasomatism that is attributed to CO2-rich fluids liberated from Group 1 carbonatite metasomatic reactions. Extremely variable incompatible trace element ratios and depleted Sr-Nd isotopic compositions of Lote 17 peridotite xenoliths indicate that the continental lithosphere was neither the primary source nor an enriched lithospheric contaminant for Neogene Patagonian plateau lavas. Neogene plateau magmatism associated with formation of asthenospheric slab windows may have triggered this occurrence of "intraplate-type" carbonatite metasomatism in an active continental backarc setting.
Decarboxylative Allylation of Amino Alkanoic Acids and Esters via Dual Catalysis
作者:Simon B. Lang、Kathryn M. O’Nele、Jon A. Tunge
DOI:10.1021/ja508317j
日期:2014.10.1
temperature decarboxylative allylation of recalcitrant α-amino and phenylacetic allyl esters. This operationally simple process produces CO2 as the only byproduct and provides direct access to allylated alkanes. After photochemical oxidation, the carboxylate undergoes radical decarboxylation to site-specifically generate radical intermediates which undergo allylation. A radical dual catalysis mechanism
光氧化还原和钯催化的组合已被用于促进顽固的 α-氨基和苯乙酸烯丙酯的室温脱羧烯丙基化。这个操作简单的过程产生 CO2 作为唯一的副产品,并提供直接获取烯丙基化烷烃的途径。光化学氧化后,羧酸盐发生自由基脱羧作用,以位点特异性地生成自由基中间体,然后进行烯丙基化。提出了一种自由基双催化机制。游离苯乙酸也使用类似的反应条件进行烯丙基化。
Towards Highly Fluorescent and Water-Soluble Perylene Dyes
A systematic approach towards highlyfluorescent, water-soluble perylene-3,4:9,10-tetracarboxylic acid diimide chromophores is presented. Water solubility was introduced first through the attachment of four hydrophilic substituents onto the bay region of the perylene dye. Positively and negatively charged groups were then applied to the chromophore, and their number and their distance from the aromatic
sacrificial electrondonors that facilitate proton-coupled electron transfer. Repeated photochemical reduction and chemical oxida-tion reveals that the complex retained a charging capacity of 72% after four cycles. We demonstrate a chemical system that can decouple photochemical processes from the day-night cycle, which has been a barrier to realizing utilization of solar energy in photochemical processes
Novel routes to 4-substituted N,N-dialkylanilines, N-alkylanilines and anilines
作者:Alan R. Katritzky、Hengyuan Lang、Xiangfu Lan
DOI:10.1016/s0040-4020(01)87221-5
日期:1993.8
N-dialkylanilines, -N-alkylanilines, -anilines and some substituted analogs obtained via lithiation are converted by lithium aluminum hydride or Grignard reagents into 4-substituted N,N-dialkylanilines, N-alkylanilines and anilines, respectively, in good yields.
Kinetics of the Decay Reactions of the <i>N</i>,<i>N-</i>Dimethyl-<i>p-</i>Toluidine Cation Radical in Acetonitrile. Acid−Base Interaction to Promote the CH<sub>2</sub>−CH<sub>2</sub> Bonding
The decay reaction of N,N-dimethyl-p-toluidine (DMT) cationradical (DMT + ) in acetonitrile (AN) was analyzed using an electron-transfer stopped-flow (ETSF) method. In the ETSF method, DMT + is generated by mixing AN solutions of DMT and tris(p-bromophenyl)amine cationradical (TBPA + ). When DMT + was generated quantitatively without DMT via 1:1 mixing of DMT and TBPA + , it was found that DMT +