Nitrogen isotopic evolution of carbonaceous matter during metamorphism: Methodology and preliminary results | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Nitrogen isotopic evolution of carbonaceous matter during metamorphism: Methodology and preliminary results

Publication Type:

Journal Article

Source:

Chemical Geology, Volume 232, Issue 3-4, p.152-169 (2006)

ISBN:

0009-2541

URL:

http://www.sciencedirect.com/science/journal/00092541

Keywords:

Sedimentary-organic-matter; resolution-electron-microscopy; municipal-waste-plastics; graphite-formation; high-pressure; metasedimentary-rocks; nutrient-utilization; nanomole-quantities; molecular-nitrogen; mass-spectrometry

Abstract:

Nitrogen content and isotopic composition of carbonaceous-rich metasediments were determined by on-line and sealed-tube combustion using ultra-high vacuum line and static mass spectrometer adapted to analyse nitrogen nanomoles. Accurate measurements showed that nitrogen amount released by on-line combustion technique was underestimated to various extents. As a result, the nitrogen isotopic composition was not correctly determined. In contrast, sealed-tube combustion appeared to yield the most reproducible and accurate measurements, except for nitrogen depleted carbonaceous matter (semi-graphite to graphite transition) containing less than around 60 ppm of nitrogen, which were contaminated during their extraction from the rock. In view of that, a preliminary sealed-tube investigation of the organic nitrogen content and isotopic composition in a homogenous series of low-grade metasediments was undertaken: in spite of an important nitrogen loss, the carbonaceous matter nitrogen isotopic composition remains about the same during the meta-anthracite and semi-graphitisation stages. Inferences on the process of organic nitrogen mineralization during carbonaceous matter metamorphism can be drawn and several paleo-biogeochemical implications envisaged. (c) 2006 Elsevier B.V. All rights reserved.

Notes:

Inst Phys Globe, Equipe Physicochim Fluides Geol, F-75251 Paris 05, France; Univ Paris 06, UMR 7618, Lab BioEMCo, F-75232 Paris, France; KIGAM, Taejon 305350, South Korea; Inst Europeen Membranes Montpellier, F-34095 Montpellier 05, FranceReviewEnglish