نتایج جستجو برای: geochemical ratios

تعداد نتایج: 134511  

2004
Jennifer A. Roberts Philip C. Bennett Luis A. González G. L. Macpherson Kitty L. Milliken

We report low-temperature microbial precipitation of dolomite in dilute natural waters from both field and laboratory experiments. In a freshwater aquifer, microorganisms colonize basalt and nucleate nonstoichiometric dolomite on cell walls. In the laboratory, ordered dolomite formed at near-equilibrium conditions from groundwater with molar Mg:Ca ratios of ,1; dolomite was absent in sterile ex...

2011
Chaosheng Zhang Ya Tang Xianli Xu Ger Kiely

It is challenging to perform spatial geochemical modelling due to the spatial heterogeneity features of geochemical variables. Meanwhile, high quality geochemical maps are needed for better environmental management. Soil organic C (SOC) distribution maps are required for improvements in soil management and for the estimation of C stocks at regional scales. This study investigates the use of a g...

Journal: :Environmental science & technology 2006
M W Fields C E Bagwell S L Carroll T Yan X Liu D B Watson P M Jardine C S Criddle T C Hazen J Zhou

Few studies have demonstrated changes in community structure along a contaminant plume in terms of phylogenetic, functional, and geochemical changes, and such studies are essential to understand how a microbial ecosystem responds to perturbations. Clonal libraries of multiple genes (SSU rDNA, nirK, nirS, amoA, pmoA, and dsrAB) were analyzed from groundwater samples (n = 6) that varied in contam...

Journal: :international journal of mining and geo-engineering 0
samaneh safari shahrood university of technology mansour ziaii shahrood university of technology maliheh ghoorchi ferdowsi university of mashhad

singularity based on fractal and multifractal is a technique for detection of depletion and enrichment for geochemical exploration, while the index of vertical geochemical zonality (vz) of pb.zn/cu.ag is a practical method for exploration of blind porphyry copper mineralization. in this study, these methods are combined for recognition, delineation, and enrichment of vz in jebal- barez in the s...

2002
W. W. Shilts

and Vagners (1971, 1972) expressed this phenomenon elegantly by introducing the concept of "terminal mode" for the optimum grain size to which a mineral can be reduced, given the force and energy typically available in the glacial environment. Thus, hard, uncleaved or poorly cleaved minerals such as quartz, fcldspar, garnet, pyrite and magnetite dominate either the medium or the fine sand fract...

2017
Christophe Thomazo Jean-Francois Buoncristiani Emmanuelle Vennin Pierre Pellenard Theophile Cocquerez Jean L. Mugnier Emmanuelle Gérard

Citation: Thomazo C, Buoncristiani J-F, Vennin E, Pellenard P, Cocquerez T, Mugnier JL and Gérard E (2017) Geochemical Processes Leading to the Precipitation of Subglacial Carbonate Crusts at Bossons Glacier, Mont Blanc Massif (French Alps). Front. Earth Sci. 5:70. doi: 10.3389/feart.2017.00070 Geochemical Processes Leading to the Precipitation of Subglacial Carbonate Crusts at Bossons Glacier,...

2008
S. Sestak P. F. Greenwood

Is UV laser ablation a suitable tool for geochemical analysis of organic rich source materials? Conference Item How to cite: Sestak, Stephen; Watson, Jonathan S.; Sherlock, Sarah; Greenwood, Paul F. and Fuentes, David (2008). Is UV laser ablation a suitable tool for geochemical analysis of organic rich source materials? In: 15th Australian Organic Geochemistry Conference, 8-12 September, Adelaide.

Journal: :Minerals 2023

Geochemical studies of rare earth elements (REEs) as well major and trace were conducted on the beach placer sands from Kanyakumari coastal region, a well-known high background natural radiation area (HBNRA). For first time, uranium isotope ratios (234U/238U 235U/238U) determined in study to investigate provenance leaching U sands. Inductively coupled plasma mass spectrometry was used for measu...

2006
Pedro S. Freitas Leon J. Clarke Hilary Kennedy Christopher A. Richardson Fátima Abrantes

The relationship between potential elemental proxies (Mg/Ca, Sr/Ca and Mn/Ca ratios) and environmental factors was investigated for the bivalve Pecten maximus in a detailed field study undertaken in the Menai Strait, Wales, U.K. An age model constructed for each shell by comparison of measured and predicted oxygen-isotope ratios allowed comparison on a calendar time scale of shell elemental dat...

The most significant aspect of a geochemical exploration program is to define and separate the anomalous values from the background. In the past decades, geochemical anomalies have been identified by means of various methods. Most of the conventional statistical methods aiming at defining the geochemical concentration thresholds for separating anomalies from the background have limited the effi...

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