Juha Köykkä - Oulu

Res Terrae, Ser. A 32, J. Köykkä, Sedimentology of the Mesoproterozoic Telemark basin-fills, South Norway: implications for
sedimentation processes, depositional environments and tectonic evolution
for minimizing the grain-size effect. The advantage of the Dickinson-Gazzi technique
is that sandstone maturity effects are minimized, and sandstones of different grain siz-
es can be compared. From a modal point-count analysis, the percentages of various
combinations of grains are plotted on ternary diagrams, which are based on quartz-
feldspar-lithic fragment proportions that reflect different provenance terranes (Dickin-
son and Suzek, 1978; Dickinson et al., 1985). These terranes are subdivided as fol-
lows: (i) stable craton, (ii) basement uplift, (iii) magmatic arc, and (iv) recycled oroge-
ny.
Clastic petrofacies analysis was used in Paper II as supplementary data to identify
the tectonic setting of the provenance area. A total of 500 grains were counted from
each thin section by the method described above.
4.5 Geochemistry
Geochemistry and geochemical data were used to identifying the geochemical signa-
tures of the (i) geological process, (ii) depositional basin tectonic evolution, and (iii)
provenance of the sampled rocks. The main geochemical tools used in this thesis (Pa-
pers II and IV) included an X-ray fluorescence spectrometer (XRF) and laser ablation
with an inductively coupled plasma mass spectrometer (LA-ICP-MS).
4.5.1 XRF analysis
XRF analysis can be used as an analytical tool to determine the major and trace ele-
ment geochemistry of rock samples. XRF analysis is based on the theory that a prima-
ry X-ray beam excites secondary X-rays, which have wavelength characteristics of the
elements present in the analyzed rock samples. The intensity of the secondary X-rays
is used to determine the concentrations of the elements present by reference to calibra-
tion standards, with appropriate corrections being made for instrumental errors and the
effects the rock samples have on the X-ray emission intensities (matrix effects).
The rock samples used in this thesis were crushed, milled and analyzed at the Uni-
versity of Oulu, Institute of Electron Optics, using the Siemens SRS 303AS X-ray flu-
orescence spectrometer with a cobalt tube and pressed powders. The loss of ignition
was determined from the total weight of loss after ignition at 950 o C for 2 hours. The
accuracy of the measurements was within