scholarly journals Volatiles in basaltic glasses from the Easter-Salas y Gomez Seamount Chain and Easter Microplate: Implications for geochemical cycling of volatile elements

2002 ◽  
Vol 3 (7) ◽  
pp. 1-29 ◽  
Author(s):  
Kyla Simons ◽  
Jacqueline Dixon ◽  
Jean-Guy Schilling ◽  
Richard Kingsley ◽  
Robert Poreda
Keyword(s):  
Volatile Elements ◽  
Geochemical Cycling ◽  
Easter Microplate ◽  
Seamount Chain

Illite-smectites and the influence of burial diagenesis on the geochemical cycling of nitrogen

Clay Minerals ◽  
1998 ◽  
Vol 33 (4) ◽  
pp. 539-546 ◽  
Author(s):  
P. A. Schroeder ◽  
A. A. McLain
Keyword(s):  
Reaction Mechanisms ◽  
Ostwald Ripening ◽  
Precipitation Reaction ◽  
Oil Well ◽  
Burial Diagenesis ◽  
Fixed Nitrogen ◽  
Geochemical Cycling ◽  
Oil Generation ◽  
Fraction Increase ◽  
Changing Rate

AbstractFixed nitrogen in illite-smectites (I-S) has been measured for Miocene shales from a Gulf of Mexico oil well. Fixed N values for the <0.2 µm fraction increase with depth from 150 ppm (1000 m) to a maximum of 360 ppm (3841 m). This increase is coincident with illitization from 41% I in I-S to 75% I in I-S. Below 3841 m, fixed N values decrease to 190 ppm (4116 m) while I-S is maintained with a slight increase from 77 to 82%. The changes in fixed N with increasing illitization are consistent with the notion that illitization proceeds via both transformation and dissolution/ precipitation reaction mechanisms. The trend of decreasing fixed N in illitic I-S is compatible with surface-controlled crystal growth and Ostwald ripening mechanisms for illitization. The trend may also be linked to the timing of maximum NH] release from kerogen maturation during oil generation. The changing rate of NH+4 liberation from organic matter and multiple illitization reaction mechanisms can result in complex N geochemical cycling pathways throughout early diagenesis to metamorphism.

scholarly journals Substrate-dependent competition and cooperation relationships between Geobacter and Dehalococcoides for their organohalide respiration

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Yongyi Liang ◽  
Qihong Lu ◽  
Zhiwei Liang ◽  
Xiaokun Liu ◽  
Wenwen Fang ◽  
...  
Keyword(s):  
Electron Donors ◽  
Community Stability ◽  
Organohalide Respiration ◽  
Competition And Cooperation ◽  
Free Competition ◽  
Isolation And Characterization ◽  
Geochemical Cycling ◽  
New Strategy ◽  
Insight Into

AbstractObligate and non-obligate organohalide-respiring bacteria (OHRB) play central roles in the geochemical cycling and environmental bioremediation of organohalides. Their coexistence and interactions may provide functional redundancy and community stability to assure organohalide respiration efficiency but, at the same time, complicate isolation and characterization of specific OHRB. Here, we employed a growth rate/yield tradeoff strategy to enrich and isolate a rare non-obligate tetrachloroethene (PCE)-respiring Geobacter from a Dehalococcoides-predominant microcosm, providing experimental evidence for the rate/yield tradeoff theory in population selection. Surprisingly, further physiological and genomic characterizations, together with co-culture experiments, revealed three unique interactions (i.e., free competition, conditional competition and syntrophic cooperation) between Geobacter and Dehalococcoides for their respiration of PCE and polychlorinated biphenyls (PCBs), depending on both the feeding electron donors (acetate/H2 vs. propionate) and electron acceptors (PCE vs. PCBs). This study provides the first insight into substrate-dependent interactions between obligate and non-obligate OHRB, as well as a new strategy to isolate fastidious microorganisms, for better understanding of the geochemical cycling and bioremediation of organohalides.

Petrology of the Easter microplate region in the South Pacific

1996 ◽  
Vol 72 (3-4) ◽  
pp. 259-289 ◽  
Author(s):  
R. Hekinian ◽  
J. Francheteau ◽  
R. Armijo ◽  
J.P. Cogné ◽  
M. Constantin ◽  
...  
Keyword(s):  
South Pacific ◽  
The South ◽  
Easter Microplate

The Projectile of the Lappajärvi Impact Crater

1980 ◽  
Vol 35 (2) ◽  
pp. 197-203 ◽  
Author(s):  
Elke Göbel ◽  
Uwe Reimold ◽  
Hildegard Baddenhausen ◽  
Herbert Palme
Keyword(s):  
Impact Crater ◽  
Carbonaceous Chondrite ◽  
Volatile Elements ◽  
Rich Phase ◽  
Impact Melt ◽  
Siderophile Elements ◽  
High Concentrations ◽  
Impact Melts

Abstract Two impact melt samples from the Lappajärvi crater (Scandinavia) are highly enriched in siderophile elements, such as Ir, Re, and Os. This indicates the presence of a meteoritic component. The simultaneous enrichments of Ni, Co, Cr, and Se suggest a chondritic projectile. Because of the relatively large indigenous contributions to Ni, Co, and Cr, it is not possible to distinguish between a normal and a carbonaceous chondrite. The high concentrations of relatively volatile elements could point towards a volatile-rich projectile.The two melt samples have high Re/Ir ratios compared to chondritic ratios. Enrichment of Re relative to Ir is very unusual in terrestrial impact melts. Loss of Re, because of volatilisation under oxidizing conditions or by weathering is frequently observed.The high Re/Ir ratios and the high abundances of relatively volatile elements either indicate the presence of a volatile rich phase or they characterize a type of meteorite, which has not been sampled. Some lunar highland rocks have a pattern of meteoritic elements rather similar to that observed for the Lappajärvi meteorite.The Lappajärvi crater is, after Rocheehouart, the second European crater where a significant amount of meteoritic component has been found.A melt sample from the Lake St. Martin crater (Manitoba), did not show any enrichment in meteoritic elements.

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