Solubility of Ore Minerals in Magmatic-Hydrothermal Deposits: Constraints from Natural and Synthetic Fluid Inclusions

Magmatic-hydrothermal ore deposits are among the most important resources of many elements that are crucial for our technologically oriented civilization. Fluids expelled from crystallizing and cooling plutons are the subject of this study, as they are responsible for the transport and selective concentration of many economically important elements, such as, e.g., Cu, Mo, Sn, W and Au. To understand the potential of such magmatic-hydrothermal fluids to transport elements of interest, the trace element concentrations in fluid inclusions in minerals need to be analyzed quantitatively, and in addition synthetic inclusions need to be prepared and analyzed at relevant geological conditions. To reach these goals a new analytical LA-ICP-MS setup was developed based on the combination of a femtosecond-laser with a fast scanning sector field ICP-MS. An experimental protocol for the formation of synthetic fluid inclusions, trapped from fluids at high temperatures and pressures, was tested and refined to ensure the achievement of equilibrium during syntheses. Concentrations of Mo, W and Au in synthetic fluid inclusions in equilibrium with various ore minerals were determined at different T, P, salinity, fO2 and fS2 conditions and compared to existing natural and experimental data as well as results from thermodynamic modelling. With W being of tremendous economic importance, a particular attention was given to the determination of the solubility of the two most abundant W minerals, i.e., wolframite and scheelite. According to our experiments, T is the most important parameter controlling W transport and deposition, followed by the salinity of the fluid, fO2 and fS2. Pressure has no significant effect in the investigated range of 100-300 MPa. The temperature dependence of wolframite and scheelite solubility is different, which may explain natural observations indicating a decreasing wolframite/scheelite ratio with depth in some W-deposits, or the dominance of ferberite over scheelite in many W-deposits. In addition, geochemical interaction with country-rocks plays an important role in the formation of magmatic-hydrothermal W-deposits, which is supported by our study of natural fluid inclusions from the Panasqueira W-Sn-(Cu-)deposit in Portugal. Fluids from the Main Sulfide Stage at Panasqueira further show a sharp decrease of Cu and As concentrations concomitant to the precipitation of chalcopyrite and arsenopyrite and were likely derived from a single pulse of a rather homogenous magmatic-hydrothermal fluid. The combination of our experimental data with measured W concentrations in natural fluid inclusions from Panasqueira indicate that W concentrations during the mineralization stages (~ 1-70 ppm W) are ca. one to two orders of magnitude higher than previously estimated (~ 0.2 ppm W). This results in a reduction of the required amount of hydrothermal fluid to ca. 10-100 km3 to explain the amount of W precipitated in the Main Oxide Silicate Stage. This finding diminishes, but does not preclude, the necessity of the involvement of meteoric fluids in the formation of the Panasqueira W-Sn-(Cu-)deposit

Molecular evolutionary biology of cetaceans :phylogeny, phylogeography and conservation genetics

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Deciphering river dolphin evolution [4]

SCOPUS: le.jinfo:eu-repo/semantics/publishe

A comparison of methods constructing evolutionary networks from intraspecific DNA sequences

In phylogeography or population genetic studies, evolutionary relationships among DNA haplotypes can be depicted either as a graph, called a ‘network’, with cycles (or ‘loops’), or as a set of phylogenetic trees (i.e. connected graphs with no circuits), possibly with multifurcation(s) and/or ancestral haplotype(s) (both represented by collapsing zero-length branches). For example, several equally optimal trees inferred under the maximum parsimony (MP) criterion display alternative relationships among haplotypes (Fig. 5.1a, b). A strict consensus tree can be used to summarize this set of trees (Fig. 5.1c), but this approach discards much of the historical information. Indeed, a strict consensus tree is typically compatible with many more alternative trees than those used to build it: e.g. the consensus in Fig. 5.1c is compatible with 105 different strictly bifurcating topologies although only two haplotypic trees have been used to build it. Furthermore, the consensus tree cannot easily summarize branch length information (e.g. in Fig. 5.1, taxon 4 is at the tip of a 0 step-long or a 1 steplong branch in trees (a) and (b), respectively). On the contrary, a network graph allows display much of the information contained in the data in a single figure (Fig. 5.1d). Therefore, the major advantage of such graphs over traditional phylogenetic trees is the possibility of using cycles (loops) to represent either ambiguities in the data or genuine reticulate evolution (due to e.g. recombination or horizontal gene transfer). In parsimony networks, sampled and unsampled haplotypes (white circles and black dots, respectively, in Fig. 5.1d) are symbolized by nodes (vertices) that are connected by edges, where each edge represents a single nucleotide substitution. Unsampled haplotypes are inferred to connect sampled haplotypes when the latter are separated by more than a single substitution. The so-called ‘degree’ of a node corresponds to the number of edges to which it is connected (e.g. in Fig. 5.1d, haplotype 2 is a node of degree 4).SCOPUS: ch.binfo:eu-repo/semantics/publishe

The phylogeography of dusky dolphins (Lagenorhynchus obscurus): A critical examination of network methods and rooting procedures

We investigated the phylogeography and evolutionary history of dusky dolphins (Lagenorhynchus obscurus) using DNA sequences of the full mitochondrial cytochrome b gene in 124 individuals from the putative stocks off Peru, Argentina and Southwest Africa. While genetic differentiation within oceans is surprisingly low, there is no evidence for recent female gene flow between Atlantic and Pacific waters. Highest genetic variability in terms of sequence divergence and number of haplotypes is found in the Atlantic. Our analyses also indicate that the eastern South Pacific dusky dolphins stock should be considered a separate management unit. Given the high level of mortality experienced by the Peruvian dusky dolphin in local fishery activities, these findings have important implications for an objective management of the species. Furthermore, we analysed our mitochondrial sequence data with several widely used network estimation and rooting methods. The resulting intraspecific gene genealogies and rooting inferences exhibited substantial differences, underlying the limitations of some algorithms. Given that scientific hypotheses and management decisions depend strongly on inferred tree or network topologies, there is a clear need for a systematic comparative analysis of available methods. Finally, the present study indicates that (i) the dusky and the Pacific white-sided dolphins are sister species and (ii) not only the Westwind Drift hypothesis but also other models of dispersion are compatible with the current geographical distribution of dusky dolphins.SCOPUS: ar.jFLWINinfo:eu-repo/semantics/publishe

Evaluating intraspecific Network construction methods using simulated sequence data: do existing algorithms outperform the global maximum parsimony approach ?

In intraspecific studies, reticulated graphs are valuable tools for visualization, within a single figure, of alternative genealogical pathways among haplotypes. As available software packages implementing the global maximum parsimony (MP) approach only give the possibility to merge resulting topologies into less-resolved consensus trees, MP has often been neglected as an alternative approach to purely algorithmic (i.e. methods defined solely on the basis of an algorithm) "network" construction methods. Here, we propose to search tree space using the MP criterion and present a new algorithm for uniting all equally most parsimonious trees into a single (possibly reticulated) graph. Using simulated sequence data, we compare our method with three purely algorithmic and widely used graph construction approaches (minimum-spanning network, statistical parsimony, and median-joining network). We demonstrate that the combination of MP trees into a single graph provides a good estimate of the true genealogy. Moreover, our analyses indicate that, when internal node haplotypes are not sampled, the median-joining and MP methods provide the best estimate of the true genealogy whereas the minimum-spanning algorithm shows very poor performances.Comparative StudyJournal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Independent adaptation to riverine habitats allowed survival of ancient cetacean lineages

The four species of “river dolphins” are associated with six separate great river systems on three subcontinents and have been grouped for more than a century into a single taxon based on their similar appearance. However, several morphologists recently questioned the monophyly of that group. By using phylogenetic analyses of nucleotide sequences from three mitochondrial and two nuclear genes, we demonstrate with statistical significance that extant river dolphins are not monophyletic and suggest that they are relict species whose adaptation to riverine habitats incidentally insured their survival against major environmental changes in the marine ecosystem or the emergence of Delphinidae

Regional Contexts and Family Formation: Evidence from the German Family Panel

Substantial regional variation in marriage and fertility patterns continues to exist in Germany. Following a multilevel approach, we exploit longitudinal data from the German Family Panel (pairfam), enhanced by an array of district-level variables, to investigate the extent to which spatial variations in men's and women's family formation behaviors result from differences in population composition or from 'true' contextual effects. Our multilevel analyses provide evidence for only small-if any-contextual effects on individuals' family formation behaviors (except for a continuation of significant differences between East and West Germany). However, we still find indication that (1) regional economic circumstances matter in determining individuals' fertility intentions as well as their transition to first marriage, (2) regional milieus are associated with individuals' fertility, and that (3) selective family migration takes place. While it seems that social interaction rather than differences in local opportunity structures plays a role here, more research is needed to further substantiate this conclusion