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Milovanović D., Tucci P., Morbideli P., Popović D.

Milovanović D., Tucci P., Morbideli P., Popović D. Petrology of mafic granulites from Bistrica, southern part of Zlatibor ultramafic massif (Dinaridic ophiolite belt, Serbia). K A R. P A. T H. O. B A L K. A. N I. D. E S. General position. A L P S.

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Milovanović D., Tucci P., Morbideli P., Popović D.

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  1. Milovanović D., Tucci P., Morbideli P., Popović D. Petrology of mafic granulites from Bistrica, southern part of Zlatibor ultramafic massif (Dinaridic ophiolite belt, Serbia)

  2. K A R P A T H O B A L K A N I D E S General position A L P S D I N A R I D E S A P E N I N E S

  3. GEOLOGICAL MAP OF SERBIA&MONTENEGRO 1:500 000 Ultramafites TISSIA Pillow lavas Concept of terranes by Prof Stevan Karamata VZWT Melanges KBT Limestones RVOT VČMT HT JB SMCT DIT KT VZWT DIT VZCT SPPT DOT EBDT KBT RVOT DHCT

  4. Definition of term - mafic granulite (A proposal on behalf of the IUGS Subcommision on the Systematics of Metamorphic Rocks,(Web version of 31.10.2002) The basis of the rocks names is their mineralogy and structure. Granulite is a high-grade metamorphic rock in which Fe-Mg-silikates are dominantly hydroxil- free.... The rocks with >30% mafic mineral may be called mafic granulites. The term should not be applied to calcsilicate rocks, marbl, ironstones and quartzites.

  5. Amph Py Grt Plg Ultramafic rocks Mafic granulites

  6. Chemistry of minerals Grt Py Amph Plagioclase is Anorthite

  7. Degrees of metamorphism

  8. Experimental constraints S&D 94 P (kbar) W&N 91 Qtz-absent Grt Qtz-present 16 Hbl Cpx Pl Qtz L Cpx Qtz R 93 Hbl Grt P&B 95 Pl Pl L C 88 Qtz 12 Opx V E&T 86 R 91 W&W 94 8 N&C 00b N&C 00a P 68, J 78 and WW 93 Hbl Opx Pl Cpx Qtz 4 L P&B 95 Hbl+Qtz= Opx+Cpx+Pl+V B&L 91 B 69 CWT 67 S 81 0 400 T (0C) 800 600 1000 Degrees of metamorphism Opx-free Grt+Cpx+Pl±Qtz assemblages Grt-Py = 900-10000C, 10 kbars Grt-Ho = 830-8800C, 8-10 kbars Eclogite P Grt+Cpx+Pl ±(Hbl or Qtz) Cpx+Grt ±Amph±Qtz) Grt+Cpx+Opx+Pl ±(Hbl or Qtz) Grt+Cpx+Pl +Hbl+Qtz Reactions: Grt+Cpx+Pl +Hbl+Qtz Pl Baz.Pl+PyI+H2O=Grt+PyII±HoII+An or Amph Amphibolite There are significant discrepancies between experimental and naturalconstraints on the P–T conditions of opy-free grt + cpy+ pl ± Q bearing mineral assemblages and therefore on theP–T position of this reaction. Granulite Hbl+Pl+Qtz ±(Grt or Cpx) Baz.Pl+ HoI±PyI=Grt+PyII±HoII +An+H2O Py Opx+Cpx+Pl+Hbl+ Qtz) Grt T

  9. Protolith

  10. Protolith Contamination, Partial melting ? No fractionation of Pl Subduction ? ?

  11. Experimental constraints P (kbar) S&D 94 W&N 91 Qtz-absent Grt Qtz-present 16 Hbl Cpx Pl Qtz L Cpx Qtz R 93 Hbl Grt P&B 95 Pl Pl L C 88 Qtz 12 Opx V E&T 86 R 91 W&W 94 8 N&C 00b N&C 00a P 68, J 78 and WW 93 Hbl Opx Pl Cpx Qtz 4 L P&B 95 Hbl+Qtz= Opx+Cpx+Pl+V B&L 91 B 69 CWT 67 S 81 0 400 T (0C) 600 800 1000 CONCLUSIONS METAMORPHISM Major and trace element whole-rock geochemical data indicatethat metamorphism was broadly izochemical Garnet-clinopyroxene-hornblende-plagioclasethermo-barometry indicatespeak metamorphic conditions of about 900-1000°C and 830-880°C at pressures 8-10 kbars Difference in temperature most probably represents asuccesion of mineral formingin a cooling period under which hornblende was formed. Gr+Py Gr+Ho Absence of thermal relaxation features in mafic granulites require metamorphism withrapid exhumation Fabrics of ultramafic rocks and mafic granulites suggestthat development of the Grt-Cpx-Ho-Pl assemblages is connect withophiolite emplacement, subduction,rather than having been causedby heat from the ophiolite.

  12. CONCLUSIONS PROTOLITH The trace element, rare earth element data suggest that Mafic granulites of Bistrica have protolith features resemblingmid-ocean ridge basalt (MORB). Lack of sheeted dyke complexes in investigated area may suggest also anoceanic plateau(ophiolitesformed in back arc basins?) Distinguishing oceanic plateau basalts from MORB is more difficult, because all geochemically gradations exist between these basalts. Whole rock compositions, with well defined positive Eu anomalies indicate that protoliths of mafic granulitesfrom Bistrica have acumulus origin. Partial melting or dehydration of the subducted oceanic crust causes loss of LREE The low silica content could be due to loss ofa silicic melt (or fluid) during subduction, or loss of SiO2 during seafloor alteration Mafic granulites could representdeep cumulus portions ofsubducted oceanic crust(olivine gabbros ?)

  13. CONCLUSIONS Metamorphic changes are most probably relatedwith subduction off oceanic crust(basaltic rocks) during formation of Dinaridic ophiolite belt in Jurassic (?)

  14. THANK YOU

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