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

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

80 A JANUS PANNONIUS MÚZEUM ÉVKÖNYVE 41^2 (1996-97) Metamagmatite (1) Sample nr. 11 was described as metamagmatite. Macroscopic features. Hard, fine grained, homogenous, dark green rock. Microscopic features. Name of rock: metamagmatite Texture: originally porphyritic, now intergranular. Mineral composition: pyroxene, plagioclase, apatite, opaque mineral. Idiomorphic 0.125-0.25 mm large pyroxene of augitic composition based on a Y/C extinction angle of 35°. It tends to turn into chlorite and amphibole. As a result of uralitization, 0.1-0.2 mm large amphiboles appear as inclusion in pyroxene. Brown, brownish green amphibole of 0.125 mm size can also be found in the rock. It was determined as hornblende, based on the 1520° Y/C extinction angle. Idiomorphic-hypidiomorphic strongly altered plagioclase occurs as 0.5-1 mm large porphyritic grains. It turns into sericite, zoisite, clinozoisite and epidote (saussuritisation). Monocrystalline xenomorphic 0.2-0.5 mm large quartz crystals appear as a result of metamorphosis. Apatite crystals are approximately 0.1 mm large in this sample. Ilmenite can be found in the form of 0.1 mm large skeletal crystals. Metamagmatite (2) Sample nr. 18 was described also as metamagmatite. Macroscopic features. Hard, fine-grained, dark green rock with black mottles. Microscopic features. Name of rock: metamagmatite. Texture: originally рофпутис-по1осгу81аШпе. Mineral composition: pyroxene, amphibole, plagioclase, opaque mineral. Idiomorphic 1 mm large porphyrin^ pyroxene with augitic composition (based on the 40° Y/c extinction angle). Chloritisation can rarely be observed. The idiomorphic 0.5-1 mm large amphibole fully turned into chlorite. Chlorite sometimes contains brown amphibole that can be either relict mineral or secondary particles. The hypidiomorphic 0.125 mm large plagioclase has oligoclasic composition based on the MichelLévy extinction method. It contains zoisite and clinozoisite as a result of strong saussuritisation. Monocrystalline quartz with undulatory extinction occurs in the form of 0.25 mm large crystals as secondary mineral. Small idiomorphic fibres of apatite can be found as inclusions of plagioclase. Skeletal crystals of 0.125 mm large ilmenite turn into titanite. The rock contains 1-2 mm large gabbroitic xenoliths as well consisting of 0.5 mm large pyroxene (diallage-augite) and plagioclase (oligoclase) crystals. Hornfels Sample nr. 12 was described as hornfels. Macroscopic features. Fine grained, homogenous light grey, brownish grey rock. Microscopic features. Name of rock: hornfels. Texture: poikiloblastic. Mineral composition: pyroxene, feldspar, titanite. Pyroxene is a frequent component in the rock. It occurs as xenomorphic 0.1-0.2 mm large inclusions in feldspar crystals. Based on the 30° ylc extinction angle, its composition is diopsidic. The feldspar occurs as hipidiomorphic tables containing pyroxene and titanite inclusions. Size of the tables is 0.5 mm. Based on small 2V, its composition is sanidinic. Secondary minerals among the feldspars are titanite (smaller than 0.1 mm) and limonite (Photo Plate Villi). Metagabbro Sample nr. 15 was described as metagabbro. Macroscopic features. Coarse-grained rock with large off-white plagioclases of 1 cm size and dark green amphiboles among the plagioclases. Microscopic features. Name of rock: metagabbro. Texture: hypidiomorphic. Mineral composition: pyroxene (turned into amphibole), plagioclase. Pyroxene fully turned into tremolite laths accumulated in 1-2 mm nests, rimmed by 0.1-0.2 mm thick-chlorite. The hypidiomorphic 2-3 mm large plagioclase crystals are of labradoritic composition, based on Michel-Levy extinction method. It often turns into clinozoisite and prehnite as a result of saussuritisation (Photo Plate VII 12). Investigation of trace elements The trace element content (Table 3) of the samples was determined by NAA. Unaltered basaltic rocks were selected for the investigation, because these rocks are homogeneous enough to be representative in spite of the small amount. Investigation was carried out on the three basalt types (samples 4,9 and 17). Values were normalised according to NA KAMURA (1974) and thus compared to reference data and each other. Based on petrographical studies, young - Pliocene - basalts were chosen as a reference (EMBEY-ISZTIN et al. 1993, HARANGI et al. 1995). Young alcaline basalts in the Pannonian-basin can be