Textural and mineralogical study of sandstones from the onshore Gulf of Alaska Tertiary Province, southern Alaska

1976 ◽  
Author(s):  
Gary R. Winkler ◽  
Hugh McLean ◽  
George Plafker
Keyword(s):  
Gulf Of Alaska ◽  
Mineralogical Study

Spatial and temporal dynamics of Pacific capelin Mallotus catervarius in the Gulf of Alaska: implications for ecosystem-based fisheries management

2020 ◽  
Vol 637 ◽  
pp. 117-140 ◽  
Author(s):  
DW McGowan ◽  
ED Goldstein ◽  
ML Arimitsu ◽  
AL Deary ◽  
O Ormseth ◽  
...  
Keyword(s):  
Temporal Dynamics ◽  
Marine Ecosystem ◽  
Gulf Of Alaska ◽  
Data Series ◽  
Limited Information ◽  
Important Species ◽  
Multiple Data ◽  
Spatial And Temporal Dynamics ◽  
Spawning Areas ◽  
Spatio Temporal

Pacific capelin Mallotus catervarius are planktivorous small pelagic fish that serve an intermediate trophic role in marine food webs. Due to the lack of a directed fishery or monitoring of capelin in the Northeast Pacific, limited information is available on their distribution and abundance, and how spatio-temporal fluctuations in capelin density affect their availability as prey. To provide information on life history, spatial patterns, and population dynamics of capelin in the Gulf of Alaska (GOA), we modeled distributions of spawning habitat and larval dispersal, and synthesized spatially indexed data from multiple independent sources from 1996 to 2016. Potential capelin spawning areas were broadly distributed across the GOA. Models of larval drift show the GOA’s advective circulation patterns disperse capelin larvae over the continental shelf and upper slope, indicating potential connections between spawning areas and observed offshore distributions that are influenced by the location and timing of spawning. Spatial overlap in composite distributions of larval and age-1+ fish was used to identify core areas where capelin consistently occur and concentrate. Capelin primarily occupy shelf waters near the Kodiak Archipelago, and are patchily distributed across the GOA shelf and inshore waters. Interannual variations in abundance along with spatio-temporal differences in density indicate that the availability of capelin to predators and monitoring surveys is highly variable in the GOA. We demonstrate that the limitations of individual data series can be compensated for by integrating multiple data sources to monitor fluctuations in distributions and abundance trends of an ecologically important species across a large marine ecosystem.

A mineralogical study of the Guanajuato, Mexico, silver ores

1975 ◽  
Author(s):  
Ivan Franklin Wilson ◽  
Charles Milton ◽  
Joseph Rollins Houston
Keyword(s):  
Mineralogical Study

Bathymetric map of the western Gulf of Alaska

1980 ◽  
Author(s):  
J.M. Dunlavey ◽  
J. R. Childs ◽  
Roland E. von Huene
Keyword(s):  
Gulf Of Alaska ◽  
Bathymetric Map

scholarly journals Development of a predation index to assess trophic stability in the Gulf of Alaska

2020 ◽  
Vol 30 (7) ◽  
Author(s):  
Cheryl L. Barnes ◽  
Anne H. Beaudreau ◽  
Martin W. Dorn ◽  
Kirstin K. Holsman ◽  
Franz J. Mueter
Keyword(s):  
Gulf Of Alaska

scholarly journals Phlogopite-pargasite coexistence in an oxygen reduced spinel-peridotite ambient

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Costanza Bonadiman ◽  
Valentina Brombin ◽  
Giovanni B. Andreozzi ◽  
Piera Benna ◽  
Massimo Coltorti ◽  
...  
Keyword(s):  
Oxygen Fugacity ◽  
Upper Mantle ◽  
Mantle Xenoliths ◽  
Spinel Peridotite ◽  
Simultaneous Formation ◽  
Empirical Potentials ◽  
Elastic Data ◽  
Mineralogical Study ◽  
Semi Empirical ◽  
T Locus

AbstractThe occurrence of phlogopite and amphibole in mantle ultramafic rocks is widely accepted as the modal effect of metasomatism in the upper mantle. However, their simultaneous formation during metasomatic events and the related sub-solidus equilibrium with the peridotite has not been extensively studied. In this work, we discuss the geochemical conditions at which the pargasite-phlogopite assemblage becomes stable, through the investigation of two mantle xenoliths from Mount Leura (Victoria State, Australia) that bear phlogopite and the phlogopite + amphibole (pargasite) pair disseminated in a harzburgite matrix. Combining a mineralogical study and thermodynamic modelling, we predict that the P–T locus of the equilibrium reaction pargasite + forsterite = Na-phlogopite + 2 diopside + spinel, over the range 1.3–3.0 GPa/540–1500 K, yields a negative Clapeyron slope of -0.003 GPa K–1 (on average). The intersection of the P–T locus of supposed equilibrium with the new mantle geotherm calculated in this work allowed us to state that the Mount Leura xenoliths achieved equilibrium at 2.3 GPa /1190 K, that represents a plausible depth of ~ 70 km. Metasomatic K-Na-OH rich fluids stabilize hydrous phases. This has been modelled by the following equilibrium equation: 2 (K,Na)-phlogopite + forsterite = 7/2 enstatite + spinel + fluid (components: Na2O,K2O,H2O). Using quantum-mechanics, semi-empirical potentials, lattice dynamics and observed thermo-elastic data, we concluded that K-Na-OH rich fluids are not effective metasomatic agents to convey alkali species across the upper mantle, as the fluids are highly reactive with the ultramafic system and favour the rapid formation of phlogopite and amphibole. In addition, oxygen fugacity estimates of the Mount Leura mantle xenoliths [Δ(FMQ) = –1.97 ± 0.35; –1.83 ± 0.36] indicate a more reducing mantle environment than what is expected from the occurrence of phlogopite and amphibole in spinel-bearing peridotites. This is accounted for by our model of full molecular dissociation of the fluid and incorporation of the O-H-K-Na species into (OH)-K-Na-bearing mineral phases (phlogopite and amphibole), that leads to a peridotite metasomatized ambient characterized by reduced oxygen fugacity.

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