نتایج جستجو برای: geochemical ratios

تعداد نتایج: 134511  

2006
G. H. Jarrar R. J. Stern D. Zachmann

Geochemical, isotopic and age constraints support a comagmatic origin for Ghuweir Mafics and the Feinan A-type granites. The two rocks types, named collectively in this paper as the Feinan Ghuweir Magmatic Suite (FGMS), formed between 556 and 572Ma ago according to Rb–Sr whole-rock dating. FGMS has low Sr initial ratios, which preclude a significant contribution of much older crust in the magma...

Journal: :The Science of the total environment 2015
Bhavna Arora Binayak P Mohanty Jennifer T McGuire

Predicting and controlling the concentrations of redox-sensitive elements are primary concerns for environmental remediation of contaminated sites. These predictions are complicated by dynamic flow processes as hydrologic variability is a governing control on conservative and reactive chemical concentrations. Subsurface heterogeneity in the form of layers and lenses further complicates the flow...

2008
Katharine R. Hendry Rosalind E. M. Rickaby

[1] During the last 50 years, the Antarctic Peninsula has experienced rapid warming with associated retreat of 87% of marine and tidewater glacier fronts. Accelerated glacial retreat and iceberg calving may have a significant impact on the freshwater and nutrient supply to the phytoplankton communities of the highly productive coastal regions. However, commonly used biogenic carbonate proxies f...

2003
S. Mukhopadhyay J. C. Lassiter K. A. Farley S. W. Bogue

[1] We measured He, Sr, Nd, Pb, and Os isotope ratios and major and trace element concentrations in stratigraphically and paleomagnetically controlled shield-stage lavas from Kauai, Hawaii. The range of He/He ratios (17–28 RA) from Kauai is similar to that reported from Loihi and thus challenges the prevailing notion that high He/He ratios are restricted to the preshield stage of Hawaiian magma...

2007
Efrat Farber Avner Vengosh Ittai Gavrieli Amer Marie Thomas D. Bullen Bernhard Mayer Amir Polak Uri Shavit

The chemical composition of groundwater in the Jordan Valley, along the section between the Sea of Galilee and the Dead Sea, is investigated in order to evaluate the origin of the groundwater resources and, in particular, to elucidate the role of deep brines on the chemical composition of the regional groundwater resources in the Jordan Valley. Samples were collected from shallow groundwater in...

2007
Tim Elliott

We present a comprehensive geochemical data set for the most recent volcanics from the Mariana Islands, which provides new constraints on the timing and nature of fluxes from the subducting slab. The lavas display many features typical of island arc volcanics, with all samples showing large negative niobium anomalies and enrichments in alkaline earth elements and lead (e.g., high Ba/La and Pb/C...

2002
Terrence M. Quinn Daniel E. Sampson

[1] We use elemental ratio (Mg/Ca, Sr/Ca, U/Ca and Ba/Ca) and oxygen isotope data from a Porites lutea coral head collected from offshore Amédée Island, New Caledonia (22 290S, 166 280E) to assess the degree to which changes in these geochemical variables reflect variations in sea surface conditions. We have assessed the robustness of each geochemical proxy by comparing 25 years (1992–1968) of ...

2014
N. Walraven P. F. M. van Gaans G. van der Veer B. J. H. van Os G. Th. Klaver S. P. Vriend J. J. Middelburg

Knowledge on the lithologically inherited variation in present day Pb isotope ratios in soils is remarkably limited. Such information is essential to determine the anthropogenic Pb fraction and anthropogenic Pb sources in Pb polluted soils. This study presents results of a survey of subsoil samples of approximately 350 rural locations covering the entire Netherlands, for which the bulk geochemi...

2018
Jennifer S. Harkness Nathaniel R. Warner Ania Ulrich Romain Millot Wolfram Kloppmann Jason M.E. Ahad Martine M. Savard Paul Gammon Avner Vengosh

Oil sands operations in Alberta, Canada generate large volumes (> 840×10m) of oil sands process-affected water (OSPW) that contains contaminants that are toxic to aquatic life. OSPW is stored in open tailings ponds and leakage from the ponds presents a potential long-term environmental risk. However, the presence of naturally occurring saline water in the oil sands region in Alberta presents a ...

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