Nitrogen and carbon partitioning in diagenetic and hydrothermal minerals from Paleozoic Black Shales, (Selwyn Basin, Yukon Territories, Canada)

摘要: Abstract Selected mineralized black shales of Devonian age from the Selwyn Basin, Northwest Territories (Canada) were analyzed by Nuclear Reaction Analyses (NRA) and electron microprobe for nitrogen carbon in silicates, sulfides, phosphates organic matter order to give new insights on fractionation processes during diagenesis hydrothermal infiltration. Hydrothermal feldspars show tri-modal composition: albite, high nitrogen-bearing K-feldspar (∼56 mol% buddingtonite (NH4AlSi3O8·1/2H2O, hydrous ammonium-feldspar, ∼51 orthoclase) hyalophane (∼32 celsian). Barium-rich (hyalophane) contain lowest contents. Potassium are positively correlated, while barium negatively correlated due replacement monovalent NH4+ divalent Ba2+. The Ba-rich rim shows penetrative textures towards an internal K–N-rich core that is interpreted as diffusive overgrowth. These be deposited hot Ba-bearing fluids. second important carrier (from 0.6 0.66 wt.%). quartz (N=527 ppm), diagenetic biogenic F-rich apatite (conodonts: N=468 ppm,), Fe–Ni sulfides (N=380–620 ppm) abiogenic Ni–Fe (N>440 homogeneously distributed with amounts 10-fold lower than those measured matter. A two-step nitrogen-release model suggested explain nitrogen-partitioning these minerals. Primary breakdown considered liberate nitrogen, phosphate sulfur pore fluids water column, providing nutrients vent fauna growth. Sulfurization, microbial sulfate reduction, silicification releases a step. Minor was trapped molecules conodonts, majority transported incorporated ammonium substituting potassium.