documenta naturae Nr. 151
VOUDOURIS, P. & KATERINOPOULOS, A.:
New Occurrences of Mineral Megacrysts in Tertiary Magmatic-hydrothermal and Epithermal Environments in
Greece
p.1-21, 2 tabs., 4 pls.,
P. VOUDOURIS, P., KATERINOPOULOS, A. & MELFOS, V.:
Alpine-type Fissure Minerals in Greece:
p. 23-45, 2 figs., 2 tabs., 4 pls.
München 2004
ISBN 3-86544-151-3
39 EUR
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Bestellübersicht
New Occurrences of Mineral Megacrysts in Tertiary Magmatic-hydrothermal and Epithermal Environments in Greece Recent fieldwork in Greece resulted in new discoveries of mineral species most of which in very large and well formed crystals. Hostrocks are volcanics, intrusive bodies, contact metamorphic zones, and minor pegmatites of Tertiary age. Over twenty different species (among them quartz varieties, garnet, vesuvianite, diopside, epidote, alunite, fluorite, and the silica microcrystalline species) are presented and geologically determined. The volcanic-hosted, epithermal altered environments in Evros region, Limnos, Lesvos, Samos and Milos Islands are excellent places to collect gem-quality amethysts, beautiful crystals of alunite and fluorite, as well as chalcedony and opal. The intrusive bodies exposed at Samothraki, Maronia, Kimmeria and Limnos Island are crosscut by numerous quartz veins including K-feldspar, muscovite and magnetite in well-shaped crystals. Garnet, tourmaline, muscovite and epidote are some of the minerals related to pegmatite bodies outcropped in northern Greece. Very rich in megacryst mineral samples are the scarn environments in northern Greece (Maronia, Kimmeria) and Seriphos Island. The minerals quartz, garnet, epidote, vesuvianite and diopside from the above localities are world-class, some of them reaching gem qualities. All the mineral specimens discovered in the present work are related to the development of Tertiary magmatic centers: The mineral depositing processes can be regarded as integral parts of magmatic-hydrothermal and epithermal systems. Some of the minerals described above are unique in Europe and probably in the world. Areas like Seriphos, Kimmeria and Maronia should be protected from mineral exploitation, and characterized as European mineralogical geotopes. Alpine-type Fissure Minerals in Greece A systematic mineralogical research of the metamorphic complexes in Greece led to the localization of large crystals (megacrysts), mainly quartz, and other minerals such as adularia, albite, chlorite, byssolith, hematite, muscovite, rutile and epidote within alpine-type fissures. As a result, Greece can be regarded as an alpine-type mineralogical province. Alpine-type fissure minerals in Greece are identified in a wide range of rock lithologies (gneisses, amphibolites, quartzites, metapegmatites, schists, etc) mainly within three tectono-metamorphic provinces: the Rhodope Massif, the Attico-Cycladic Massif, and the metamorphic complex of Crete Island. Quartz crystals were found in an enormous variety of colors and forms with excellent material coming from Attica, Evia, Ios, Thassos and Drama areas. Gem-quality smoky- and rocky crystal quartz varieties, green-colored quartz and amethyst were found in several localities reaching sizes up to 40cm. Different crystal habits, as prismatic quartz, Tessin-habit quartz, fiber quartz, gwindle, sceptre- and window-shaped forms are of world-class quality. In addition adularia crystals (up to 3cm in size), albite (up to 6cm), hematite in iron roses (up to 5cm), chlorite (idiomorphic crystals up to 2cm in diameter), byssolith, calcite, epidote (up to 5cm in size), pyrite, white mica (flakes up to 3cm in diameter), rutile (needles up to 3cm) are localized for the first time in Greece. Based on the existing data, it can be proposed that the formation of alpine-type fissures in Greece and their mineralogy are closely related to the extensional tectonics accompanying the exhumation of the metamorphic core complexes. Initial formation probably took place close to the brittle-ductile transition but most of the veins are clearly late-stage, filling subvertical fractures. Preexisting pegmatites and quartz veins in the Variscan and Mesozoic granitoids and associated rocks were probably involved in recrystallization processes and redistribution of chemical components in the fissures during the Miocene stage of extension in Greece. Alpine-type fissure minerals are not only of great scientific interest, they can also be considered as mineralogical treasures, unique in Greece and in Europe. Areas like Evia, Thassos, Drama, Attika and Andros Island should be characterized as European mineralogical geotopes.