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Hydrothermal alteration of sediments associated with surface emissions from the Cerro Prieto geothermal field
A study of the mineralogical changes associated with these hydrothermal vents was initiated with the aim of developing possible exploration tools for geothermal resources. The Cerro Prieto reservoir has already been explored by extensive deep drilling so that relationships between surface manifestations and deeper hydrothermal processes could be established directly. Approximately 120 samples of surface sediments were collected both inside and outside of the vents. The mineralogy of the altered sediments studied appears to be controlled by the type of emission. A comparison between the changes in mineralogy due to low temperature hydrothermal activity in the reservoir, seen in samples from boreholes, and mineralogical changes in the surface emission samples shows similar general trends below 180 C: increase of quartz, feldspar and illite, with subsequent disappearance of kaolinite, montmorillonite, calcite and dolomite. These mineral assemblages seem to be characteristic products of the discharge from high intensity geothermal fields
Trace elements in alpine and arctic lake sediments as a record of diffuse atmospheric contamination across Europe
15 páginas, 5 tablas, 3 figuras.1. We surveyed the distribution of several trace elements in contemporary and preindustrial sediment s in 275 lakes in alpine and arctic lake districts across Europe including
the Pyrenees, Alps, the Rila Mountains, Retezat, Julian Alps, Tatras, Scottish mountains,
Central Norway and Greenland.
2. Sediment cores were collected at the deepest part of each lake and analysed at two
depths (surface sediment and at 15–17 cm depth) for Ti, Pb, Cd, Zn, Cu, As, Hg and Se.
3. The concentrations of trace elements found in the lakes included in the survey are
comparable to those reported in aquatic sediments receiving higher contamination loads.
With the exception of Greenland, a large percentage of lakes showed enrichment factors
for most elements well above 1.5, indicating atmospheric contamination. The influence of
contamination has increased the co-distribution of trace elements in sediments, with the
exception of As.
4. Pb is the element that shows the highest contamination level at the European scale,
followed by Hg and As. Zn, Cd, Cu and Se contamination is detectable to a lower degree.
5. The Tatra Mountains and Scotland seem to be most affected. Natural mechanisms
leading to the formation of highly organic, metal-binding sediments may be the cause of
the high levels in Scotland, whereas those in the Tatras appear to be due to elevated
deposition.
6. The Retezat and Central Norway appear to be least polluted.
7. In the Alps, enrichments in Pb, Hg and Zn are higher in southern than in central areas
suggesting a flux of these pollutants from the south. In the Pyrenees, the high natural
levels of As are remarkable. Metal enrichments in the Rila Mountains are comparable to
those in the Tatras, but concentrations are much lower.
8. In general terms, the increase in trace elements in modern with respect to pre-industrial
sediments reflects the history of a long range contamination affecting the remotest
locations in Europe.This study was part of projects funded by the CEC
(EMERGE EVK1-CT-1999-00032) and the CICYT (REN2000-0889 ⁄GLO)Peer reviewe
The founding charter of the Genomic Observatories Network
The co-authors of this paper hereby state the ir intention to work together to launch the Genomic Observatories Network (GOs Network) for which this document will serve as its Founding Charter. We define a Genomic Observatory as an ecosystem and/or site subject to long-term scientific research, including (but not limited to) the sustained study of genomic biodiversity from single-celled microbes to multicellular organisms. An international group of 64 scientists first published the call for a global network of Genomic Observatories in January 2012. The vision for such a network was expanded in a subsequent paper and developed over a series of meetings in Bremen (Germany), Shenzhen (China), Moorea (French Polynesia), Oxford (UK), Pacific Grove (California, USA), Washington (DC, USA), and London (UK). While this commun ity-building process continues, here we express our mutual intent to establish the GOs Network formally, and to describe our shared vision for its future. The views expressed here are ours alone as individual scientists, and do not necessarily represent those of the institutions with which we are affiliated