No description available.

No description available.

No description available.

Combined Lu-Hf, Sm-Nd and Rb-Sr isotopic studies of continental crustal rocks were undertaken to assess the relative effects of secondary crustal processes on isotopic systematics of whole-rock systems. The processes studied include ductile deformation, and three cases of hydrothermal alteration, involving fluids of varying composition. The Rb-Sr system proved to be easily disturbed during all secondary processes, while Sm-Nd and Lu-Hf systems were, for the most part, resilient. These results show that Nd or Hf isotopic information obtained from old rocks that have undergone typical crustal deformational and alteration events can be counted on to be equally reliable. Nd and Hf isotopic analyses were performed on four suites of Early Archean felsic gneiss complexes from Greenland, Labrador, Swaziland, and Michigan to explore questions associated with Early Archean crustal growth. The Sm-Nd isotopic data yield initial ∊(Nd) values that are mostly consistent with published age data for the suites. Calculations show limited scatter may be attributed to subtle changes in the Sm/Nd ratio or Nd isotopic composition. The Hf isotopic results are more variable and complex than the Nd results. The relevance of the studies on isotopic mobility in the first part of this work is that they have demonstrated that Nd and Hf isotopes are equally resilient during a range of secondary crustal processes. Given the robustness of the Nd isotopic data from the Archean samples, however, it seems unreasonable to attribute the much wider variation in Hf isotopic data to post-Archean isotopic disturbances. Differences in initial Hf isotopic ratios from differing magma sources seem called for. Nd and Hf whole-rock analyses of a Late Archean pristine garnet-bearing granitoid complex from northern Canada point out the importance of garnet in fractionating Lu/Hf ratios, and in developing anomalous ∊(Hf) signatures in potential source regions. Calculations show that even short-lived upper mantle/lower crustal heterogeneities, products of previous partial melting events involving garnet fractionation, can develop the range of positive and negative ∊(Hf) values seen in the Early Archean samples.

Zugl.: Dresden, Techn. Univ., Diss., 2007 u.d.T.: Olsthoorn, Theodora: Kommunikation mit Menschen einer nicht-schriftlichen Kultur

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The Churchill Falls are a second Niagara. They are situated in the interior of Labrador, about 200 miles from the nearest point of the open Atlantic coast, and about 225 miles north of the Gulf of St.Lawrence (figure 1-1). [...]

The peninsule of Labrador-Ungava* (Map 1) is a population desert, having harsh, cold winters and brief, warrn, fly-cursed summers, but offering the glacial geomorphologist ample scope for working on virgin territory, with abundant landforrns often of textbook simplicity. However, it is only in recent years thot extensive aerial photography has been undertaken, and this, together wlth certain military and economie developments within the peninsule, has led to an increasing awareness of the significance of the glacial history of the a rea. These developments led ultimately to the establishment in 1954, of the McGi Il Sub-Arctic Research La bora tory, through which it was proposed to develop a scientific research programme related to this little known a rea. With the establishment of the Laboratory, a Field Director was appointed by McGill University to supervise the studies of the younger workers on the staff. A natural outcome of the system was for an emphasis to develop along the lin es of the research interests of the senior man. Under the direction of Dr. J. D. Ives the system developed into what Matthew (196la) has termed the 1 McGill Programme in relation to the deglaciation of the peninsula. [...]

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