Sediment-redox dynamics in an oligotrophic deep-water lake in Tierra del Fuego: insights from Fe isotopes.

Unlabelled: For long time in the history of Earth, ferruginous conditions governed the oceans. With the rise of oxygen during the Proterozoic era and the subsequent evolution of living organisms, worldwide deposition of iron formations occurred. These sedimentary units reveal the transition into oxic oceans, passing by local and transitory euxinic conditions, especially in coastal shelves.

Mercury isotope evidence for the importance of recycled fluids in collisional ore systems.

The sources of fluids and metals in porphyry systems of continental-collision settings are poorly constrained. Mercury isotopes display unique mass-independent fractionation (expressed as ΔHg) and may provide important constraints on metal and volatile sources given that Hg is a highly volatile metal. Here, we report Hg isotope data on ore-forming porphyries, barren magmatic rocks, and mantle-derived mafic magmas from southern Tibet.

Identifying crustal contributions in the Patagonian Chon Aike Silicic Large Igneous Province.

Unlabelled: The volcanic rocks of the Chon Aike Silicic Large Igneous Province (CASP) are recognized as magmas dominantly produced by crustal anatexis. Investigating the zircon of the CASP provides an opportunity to gain further insight into geochemical and isotopic differences of the potential magmatic sources (i.e.

Data on the arc magmatism developed in the Antarctic Peninsula and Patagonia during the Late Triassic-Jurassic: A compilation of new and previous geochronology, geochemistry and isotopic tracing results.

We present the results of U-Pb zircon dating conducted using laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), isotopic tracing analyses of Hf in zircon and Sr-Nd in whole-rock and whole-rock major oxides, and trace element abundances of 12 plutonic and volcanic rocks present on the Antarctic Peninsula. The dataset is presented in combination with the results of previous studies conducted in both Patagonia and the Antarctic Peninsula. These results were filtered for concordant Pb-U zircon ages and topology of the Ar/Ar age spectra.

Gold endowments of porphyry deposits controlled by precipitation efficiency.

Porphyry deposits are natural suppliers of most copper and significant gold to our society. Whereas the Cu-richest (Au-poor) porphyries are related to Andean-type subduction and typical calc-alkaline magmatism, the Au-richest porphyries are associated with high-K calc-alkaline to alkaline magmatism in late to post-subduction or post-collision and extensional settings, and subordinately with calc-alkaline magmatism. The reasons behind these associations and the large variations in metal endowments of porphyry Cu-Au deposits remain obscure.

Petroleum as source and carrier of metals in epigenetic sediment-hosted mineralization.

Sediment-hosted ore deposits contribute a significant amount (up to 65%) of the global resources of lead and zinc. Among them, the Mississippi-Valley type deposits and related oil fields often comprise large-scale hydrothermal systems where regional host rocks are stained with disseminated liquid petroleum (crude oil) and other organic compounds. Current models for the formation of those epigenetic Pb-Zn sulphide deposits consider that metals are mostly leached from basement rocks and their detrital erosional products, and transported by oxidized basinal hydrothermal fluids as chloride complexes.

Stochastic modelling of deep magmatic controls on porphyry copper deposit endowment.

Porphyry deposits, our main source of copper and of significant amounts of Mo, Re and Au, form at convergent margins in association with intermediate-felsic magmas. Although it is accepted that copper is transported and precipitated by fluids released by these magmas, the magmatic processes leading to the formation of economic deposits remain elusive. Here we perform Monte Carlo petrological and geochemical modelling to quantitatively link crustal magmatic processes and the geochemical signatures of magmas (i.

Monitoring steel bridge renovation using lead isotopic tracing.

Monitoring removal of lead (Pb) paint from steel structures usually involves analysis of environmental samples for total lead and determination of blood Pb levels of employees involved in the Pb paint removal. We used high precision Pb isotopic tracing for a bridge undergoing Pb paint removal to determine if Pb in the environmental and blood samples originated from the bridge paint. The paint system on the bridge consisted of an anti-corrosive red Pb primer top-coated with a Micaceous Iron Oxide (MIO) alkyd.

Impact on the environment from steel bridge paint deterioration using lead isotopic tracing, paint compositions and soil deconstruction.

Deterioration and repair of lead paint on steel structures can result in contamination of the ambient environment but other sources of lead such as from past use of leaded paint and gasoline and industrial activities can also contribute to the contamination. Using a combination of high precision lead isotopic tracing, detailed paint examination, including with scanning electron microscopy, and soil deconstruction we have compared paint on a steel bridge and bulk soil and lead-rich particles separated from soil. The majority of Pb found in the paint derives from Australian sources but some also has a probable US origin.

Crustal thickness control on Sr/Y signatures of recent arc magmas: an Earth scale perspective.

Arc magmas originate in subduction zones as partial melts of the mantle, induced by aqueous fluids/melts liberated by the subducted slab. Subsequently, they rise through and evolve within the overriding plate crust. Aside from broadly similar features that distinguish them from magmas of other geodynamic settings (e.

Mass spectrometry in Earth sciences: the precise and accurate measurement of time.

Precise determinations of the isotopic compositions of a variety of elements is a widely applied tool in Earth sciences. Isotope ratios are used to quantify rates of geological processes that occurred during the previous 4.5 billion years, and also at the present time.

Why large porphyry Cu deposits like high Sr/Y magmas?

Porphyry systems supply most copper and significant gold to our economy. Recent studies indicate that they are frequently associated with high Sr/Y magmatic rocks, but the meaning of this association remains elusive. Understanding the association between high Sr/Y magmatic rocks and porphyry-type deposits is essential to develop genetic models that can be used for exploration purposes.

Local to regional scale industrial heavy metal pollution recorded in sediments of large freshwater lakes in central Europe (lakes Geneva and Lucerne) over the last centuries.

This research first focuses on the spatial and temporal patterns of heavy metals from contrasting environments (highly polluted to deepwater sites) of Lake Geneva. The mercury (Hg) and lead (Pb) records from two deepwater sites show that the heavy metal variations before the industrial period are primarily linked to natural weathering input of trace elements. By opposition, the discharge of industrial treated wastewaters into Vidy Bay of Lake Geneva during the second part of the 20th century, involved the sedimentation of highly metal-contaminated sediments in the area surrounding the WWTP outlet pipe discharge.