Naslov
MICROSTRUCTURAL CHARACTERISTICS OF STAUROLITE FROM MICA SCHIST OF THE DRAVA DEPRESSION BASEMENT (CROATIA)

Autori
Matošević, Mario ; Šuica, Sanja

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
13th Multinational Congress on Microscopy: BOOK OF ABSTRACTS / Gajović, Andreja ; Weber, Igor ; Kovačević, Goran ; Čadež, Vida ; Šegota, Suzana ; Peharec Štefanić, Petra ; Vidoš, Ana - Zagreb : Institut Ruđer Bošković ; Hrvatsko mikroskopijsko društvo, 2017, 520-521

ISBN
978-953-7941-19-2

Skup
13th Multinational Congress on Microscopy

Mjesto i datum
Rovinj, Hrvatska, 24.09.2017. - 29.09.2017

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
staurolit, tinjčasti škriljavac, dinamički metamorfizam, Tisia, Dravska depresija
(staurolite, mica schist, dynamic metamorphism, Tisia, Drava Depression)

Sažetak
Staurolite, with the chemical formula (Fe, Mg, Zn)2Al9Si4O22(OH)2, is a nesosillicate mineral formed during regional metamorphism in the amphibolite facies (medium grade metamorphism), usually as a porphyroblast. Atypical staurolite has been found in the garnet-staurolite-muscovite-biotite schist of the SW part of the Pannonian Basin System's crystalline basement, in the exploration wells of the Grubišno Polje field, located in the Drava Depression, Croatia. The analyzed rock can be correlated with biotite-muscovite gneisses of the Ravna Gora progressive-metamorphic series (Raffaelli, 1965), a part of the Papuk complex (Jamičić, 1983, 1988) or Hercynian progressive-metamorphic complex of the Slavonian mountains (Pamić & Lanphere, 1991). This is in accordance with Pamić (1999), who claims that the rocks of the surrounding area of Grubišno Polje are connected to the crystalline complex of the Slavonian mountains. Based on modern regional-geological concepts, the Slavonian mountains, along with the area of Grubišno Polje, are a part of the Tisia microplate (e.g. Schmid et al., 2008 and references therein). The rock is characterized by augen structure with mylonitic foliation. The peak metamorphic assemblage includes quartz, biotite, muscovite, staurolite, garnet, K-feldspar and plagioclase. Accessory minerals are apatite and zircon, while tourmaline, carbonate, hematite and chlorite represent retrograde mineral phases. Foliation is defined by the arrangement of quartz and phyllosilicates into distinct elongated and lenticular domains (Q and P domains). Garnet and rare feldspars occur as porphyroclasts, while staurolite appears as an aggregate of finer clasts with sericite-muscovite in intergranular space. The staurolite in the garnet-staurolite-muscovite-biotite schist has been confirmed optically, by using polarizing microscope Olympus BX51, as well as chemically and mineralogically, by the scanning electron microscope (SEM) JEOL JSM-6510 LV with Energy-dispersive X-ray spectrometry (EDS). The staurolite grains are mainly prismatic, elongated along the c axis, with rarely developed twins. Individual grains and fragments (50-400 µm) are formed as a result of cleavage along the b axis, along with irregular fracturing. They typically display pleochroism, from colorless to pale yellow. The porphyroblastic schist was developed during regional metamorphism in the amphibolite facies from pelitic protolith enriched with iron and potassium. Later episode of dynamic metamorphism resulted in recrystallization and the occurence of retrograde assemblage. Anastomosing of quartz and phillosilicate domains around staurolite aggregates indicates that the staurolite initially represented porphyroblast as well. The shear stress led to the segmentation and a fracturing of staurolite porhyroblasts, rotation and recrystallization of newly-formed grains and crystallization of sericite-muscovite in fractures between staurolite grains.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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