The GEMAS (geochemical mapping of agricultural soil) project collected 2108 Ap horizon soil samples from regularly ploughed fields in 33 European countries, covering 5.6 million km2. The <2 mm fraction of these samples was analysed for 53 elements by ICP-MS and ICP-AES, following a HNO3/HCl/H2O (modified aqua regia) digestion. Results are used here to establish the geochemical background variation and threshold values, derived statistically from the data set, in order to identify unusually high element concentrations for these elements in the Ap samples. Potentially toxic elements (PTEs),

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Monazite from granulite-facies rocks of the Åreskutan Nappe in the Scandinavian Caledonides (Seve Nappe Complex, Sweden) was dated using in-situ U-Th-total Pb chemical geochronology (CHIME). Multi-spot analyses of a non-sheared migmatite neosome yielded an age of 439 ± 3 Ma, whereas a sheared migmatite gave 433 ± 3 Ma (2σ). Although the obtained dates are rather similar, a continuous array of single dates from c. 400 Ma to c. 500 Ma suggests possibly a more complex monazite age pattern in the studied rocks. The grouping and recalculation of the obtained results in respect to Y-Th-U systematics and microtextural context allowed distinguishing several different populations of monazite grains/growth zones. In the migmatite neosome, low-Th and low-Y domains dated at 455 ± 11 Ma are considered to have grown under highgrade sub-solidus conditions, most likely during a progressive burial metamorphic event. The monazites with higher Th and lower Y yielded an age of 439 ± 4 Ma marking the subsequent partial melting event caused by decompression. The youngest (423 ± 13 Ma) Y-enriched monazite reveals features of fluid-assisted growth and is interpreted to date the emplacement of the Åreskutan onto the Lower Seve Nappe. In the sheared migmatite, the high-Th and low-U (high Th/U) monazite with variable Y contents yielded an age of 438 ± 4 Ma, which is interpreted to date the partial melting event. Relatively U-rich rims on some of the monazite grains again reveal features of fluid-assisted growth, and thus their age of 424 ± 6 Ma is interpreted as timing of the nappes emplacement. These results call, however, for further more precise, isotopic (preferably ion microprobe) dating of monazite in the studied rocks.

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Secondary ionization mass spectrometry (SIMS) U-Pb dating of zircons from the Å reskutan Nappe in the central part of the Seve Nappe Complex of western central Jämtland provides new constraints on the timing of granulite-amphibolite-facies metamorphism and tectonic stacking of the nappe during the Caledonian orogeny. Peak-temperature metamorphism in garnet migmatites is constrained to c. 442 + 4 Ma, very similar to the ages of leucogranites at 442 + 3 and 441 + 4 Ma. Within a migmatitic amphibolite, felsic segregations crystallized at 436 + 2 Ma. Pegmatites, cross-cutting the dominant Caledonian foliation in the Nappe, yield 428 + 4 and 430 + 3 Ma ages. The detrital zircon cores in the migmatites and leucogranites provide evidence of Late Palaeoproterozoic, Mesoproterozoic to Early Neoproterozoic source terranes for the metasedimentary rocks. The formation of the ductile and hot Seve migmatites, with their inverted metamorphism and thinning towards the hinterland, can be explained by an extrusion model in which the allochthon stayed ductile for a period of at least 10 million years during cooling from peaktemperature metamorphism early in the Silurian.In our model, Baltica-Laurentia collision occurred in the Late Ordovician-earliest Silurian, with emplacement of the nappes far on to the Baltoscandian platform during the Silurian and early Devonian, Scandian Orogeny lasting until c. 390 Ma.