In the Fore-Sudetic Block, basaltoid exposures have been described from the Jawor, Legnica and Zlotoryja, as well as Niemcza and Kowalskie-Zelowice, Targowica, and Ziebice areas.
The aim of our paper is to present preliminary results of new K-Ar datings and petrological studies of basaltoid rocks exposed between Zlotoryja in the NW and Nowa Cerekiew in the SE of Lower Silesia.
Basaltoid rocks are represented here by predominant tephrites and basanites, rare foidites, and singular basalts and trachybasalts (Bolewski and Parachoniak, 1982; Kozlowska-Koch, 1987; Wierzcholowski, 1993; Lorenc et al., 2004).
The magnetic and gravimetric data show that the Cenozoic basaltoid occurrences are associated with the so-called "basalt anomalies" which may point to a relatively shallow depth of volcanic rocks, whose subsurface extent is much more greater than the surfacicial one (Cwojdzinski and Jodlowski, 1982; Badura and Przybylski, 2000).
The results of geochemical studies indicate that the majority of Lower Silesian basaltoid rocks originated in the upper mantle at depths ranging between 75 and 90 km (Wierzcholowski, 1993), whereas more alkaline varieties were formed due to magma differentiation at depths of 30-45 km.
The basaltoid rocks studied have dark-grey, nearly black colour, and are massive and very fine-grained.
Olivine phenocrysts in both types of basaltoid rocks are represented mainly by Mg-rich (core [Fo.sub.88-80], rim [Fo.sub.78-71]) chrysolite.
In the groundmass of the basaltoid rock samples, clinopyroxenes and opaque minerals (iron oxides, ilmenite) were mainly observed.
Both the Sudetic and Fore-Sudetic blocks, separated by the SMF, bear numerous exposures of Oligocene-Miocene basaltoids (Birkenmajer et al., 1977, 2002a, 2002b, 2004; see also Badura et al., 2005), some of them being located on the fault zone (Figs.
and Przybylski, B.: 2005, New age and petrological constraints on Lower Silesian basaltoids, SW Poland, Acta Geodyn.