Janus Pannonius Múzeum Évkönyve 43 (1998)( Pécs, 1999)

Régészet - Schléder, Zsolt–T. Biró, Katalin. Petroarchaeological studies on polished stone artifacts from Baranya county, Hungary

SCHLÉDER, ZS. & К. T. BIRÓ: PETROARCHEOLOGICAL STUDIES ON POLISHED STONE ARTIFACTS FROM BARANYA COUNTRY 77 Analytical methods Petrographical studies Standard petrographical analysis techniques were used (KUBOVics 1993). Thin sections of rock slices of 30 urn thickness were studied under Reichert petrographical microscope. Electron microprobe analysis Analyses were performed using an AMRAY 1830 I/T6 scanning electron microprobe analysator (20 keV, 12 nA) equipped with ED AX PV 9800 X-ray spectrometer at the Eötvös Loránd University, Dept. of Petrology and Geochemistry

5 on flat polished surface of the cut samples. Neutron activation analysis Powder of tools were used for NAA. Radiation of the samples were carried out at the nuclear reactor of BME. (8 hours radiation time, 100 kW maximal capacity, 2x1012 neutron x cm"

2 x s"

1 maximal neutron flux). The 7-radiation of samples was measured by Márta В alla (Budapest Technical University), after a cooling time of one week (time of measurement: 5000s) and one month (time of measurement: 10,000 s), respectively. Petrographical description The basis of dividing samples into groups Samples with similar mineral composition and texture were divided into smaller groups laying stress upon the differences. Some samples are very similar concerning both texture and mineral composition. Samples bearing similar petrographical characteristics can be studied together, mentioning the slight differences as well Igneous rocks Tephritic rocks The group of tephritic rocks (different variants of alkaline basalts) - including samples no. 2, 3, 8,13 - are described together, emphasising similarities and differences as well. Macroscopic features. Coarse-grained, porphyritic texture rock with the following porphyritic components: cca. 5 mm large dark brown-black amphiboles and pale pink-red plagioclases of the same size. Sample no. 8 is significantly different from the others; its colour is red because of alteration caused by burial. Microscopic features. Name of rock: tephrite. Texture: hypidiomorphic - panidiomorphic granular. Mineral composition: amphibole, pyroxene, (rarely olivine), feldspar, analcime, biotite, apatite, opaque mineral. In sample no. 3 only, a few olivine crystals can be found as well. It is idiomorphic with a size of 0.5-1 mm. It always turns into calcite and serpentine pseudomorphs. All the thin sections contain kaersutite (idiomorphic amphibole with strong - light and dark brown - pleochroism, pyroxene inclusions, the y/c extinction angle is about 6°). Size is about 1 mm in samples no. 2, 13 and about 0.5 mm in samples no. 3, 8. The amount of pyroxene is smaller than that of kaersutite. Size is about 0.5 mm in samples no. 2, 13 and about 1 mm in samples no. 3, 8. Pyroxene is often zoned: augite in the core, Tiaugite in the rim. The Y/C angle is 40°, dispersion is strong. Pyroxene has idio-hypidiomorphic shape, often with inclusions. It usually turns to fine-grained amphiboles (uralization). Kaersutite and augite often grow together, especially in samples no. 2, 13. Most frequent mineral is the 0.5-1 mm sized, hypidiomorphic-xenomorphic feldspar lath that contains inclusions as well (composition: oligoclase-andesine according to the MichelLévy extinction method). Mainly in sample no. 2, it turns to chlorite, calcite. Biotite occurs in every sample as tiny, 50-100 urn sized, idiomorphic-hypidiomorphic tabular crystals. High Ti- and Fe-content is indicated by strong pleochroism. It usually turns to opaque minerals. Every thin section contains idiomorphic apatite laths, even as large as 1 mm. It often occurs as inclusion in feldspar, kaersutite, but may grow into them as well. Opaque minerals are frequent in every thin section. Size about 0.5 mm. Ilmenite and titanomagnetite were determined under the microscope. They always tum into leucoxene (Photo Plate IV1

1, 2). Basalt Samples no. 4, 9, 10, 16, 17 were made of basalt. These samples can be divided into three subgroups, based on mineral composition and texture observed in the microscope. Macroscopic features. Grey, on weathered surface light brownish grey rock. In some cases, 0.2 mm large black pyroxene and dark green olivine can be seen in the fine-grained matrix, rarely with black xenoliths of even 1 cm size as in sample no. 17.