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source terrains, changes in the sedimentation pattern, and the cooling history of the
hinterland. Figure 2.1 shows the work routine, which was applied to the rock samples
and Appendix A, Tab. A1 summarises sample descriptions and locations.
2.2 X-ray fluorescence spectroscopy (XRF) and Instrumental Neutron Activation
Analysis (INAA) on whole rock
Major and trace element concentrations of 38 rock samples were measured by XRF
(X-ray fluorescence spectrometry) at the Institut für Geowissenschaften, Universität
Tübingen, Germany, with a Siemens S 200 spectrometer. Three basalt samples were
analysed on a Philips PW 2400 spectrometer at the University of Fribourg, Switzerland.
Pulverised sample material was dried at 110°C to remove adsorbed water (H 2O - ).
Sample tablets were formed by melting of 7.5 g lithium metaborate and 1.5 g whole
rock powder. The weight of crystal water (H 2O + ) was determined on 1 g sample
powder at 1050°C after 15 hours.
INAA was performed on 38 samples by Activation Laboratories Ltd. in Ancaster,
Ontario, Canada. A 0.5-2.0 g sample was weighed into a small custom-made
polyethylene vial to totally fill the vial. For every 11 samples, a CANMET MRG-1
standard was co-irradiated with flux wires at a thermal neutron flux of 7 x 10 12
neutron/cm 2 s for 15 minutes in the RIFLS site of the McMaster Nuclear Reactor. After 7
days of decay time the samples were counted on a high purity co-axial Ge Detector
with a resolution of > 1.7 keV for the 1332 keV Co-60 photopeak. The data were
corrected for decay and compared with a calibrated value developed from multiple
international reference materials (approximately 50) using the flux wire monitors. The
CANMET standard MRG-1 was used solely for verification of the procedure and not for
calibration purposes. Selected samples were recounted and compared with the original
as part of the QA/QC procedure. Gamma-ray energies are listed in Hoffman (1992). A
summary of XRF and INAA is given in Appendix A, Tab. A2. For chondrite normalised
rare earth element (REE) diagrams, normalisation values for the Sedy meteorite of
Masuda et al. (1973) were used. Ocean ridge granite (ORG) REE patterns are
normalised with values after Pearce et al. (1974).
2.3 Mica and amphibole separation for K/Ar, Ar/Ar and Rb/Sr dating
Sericites of low-grade metamorphic clastic sediments were measured from the
fraction < 2 �m. For sericite separation the samples were ground for 20 s in an agatemill.
Rocks containing small amounts of carbonate were treated with 5% acetic acid.
The insoluble residue was washed several times with distilled water. Separation of the
< 2 �m clay-fraction was achieved in Atterberg cylinders. If necessary, sodium
(Calgon � ) was used as dispersing agent. Biotite and white mica were separated using
streaming tubes (Mica Jet), heavy liquids (sodium polytungstate, � = 2.9 g/cm 3 ) and
magnetic separation. Quality of separation was enhanced by paper sticking and
handpicking. Amphibole separation was performed by crushing, sieving, magnetic
separation, and handpicking. Yury D. Pushkarev, Institute of Geology and
Geochronology of the Precambrian, Russian Academy of Sciences, St. Petersburg,
Russia, performed the K/Ar age determinations. All basalt whole rock samples were
crushed for destruction of bubbles, which may contain excess 40 Ar. The content of