Naslov
Geochemical characteristics of Alpine granitoid rocks from the SW part of the Pannonian Basin

Autori
Petrinec, Zorica ; Balen, Dražen

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

Izvornik
33rd International Geological Congress Abstract CD-ROM / - Oslo, 2008

Skup
33rd International Geological Congress

Mjesto i datum
Oslo, Norveška, 06.08.2008. - 14.08.2008

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Moslavačka Gora; Croatia; Pannonian Basin; granitoid rocks; magma mixing and mingling; two-mica granite; leucogranites; muscovite dehydration melting

Sažetak
Field and petrographic studies reveal several types of granitoid rocks which occur in the SW part of Pannonian Basin crystalline basement outcropping in the narrow area on northern part of Moslavacka Gora, Croatia. Geochemical study offers further insight into the generally complex interaction between mingling and mixing of mantle/lower crust material with a crustal material during Cretaceous time. On the basis of trace element distribution (especially REE) a clear distinction has been made between A. two-mica (predominantly biotite) granite, and B. two subgroups of leucogranites. The first group, fine-grained two-mica granite (quartz, feldspar, biotite, muscovite) hosts tourmaline nodules, K-feldspar megacrysts and metapelitic xenoliths. Geochemical analyses yield 72.33-74.29 wt.% SiO2, 13.69-14.67 wt.% Al2O3, low concentrations of Fe2O3 (0.18-1.76 wt.%), MgO (0.07-0.65 wt%), CaO (0.48-1.22 wt.%) and TiO2 (0.12-0.27 wt.%), and relatively high K2O (3.65-6.01 wt.%) and Na2O (2.71-3.85 wt.%). Strong peraluminosity (ASI=1.1-1.2) and high SiO2 content are coupled with low concentrations of ferromagnesian elements together with high LIL trace elements Ba (332-495 ppm), Sr (69-161 ppm), Cs (12-26 ppm), Rb (184-277 ppm), Zr (70-138 ppm). The granite is characterized with moderately flat and fractionated REE chondrite normalized patterns, slight enrichment in the LREE and strongly negative Eu anomaly ((La/Yb)N = 4.62-9.67 ; Eu/Eu* = 0.41-0.81 ; low Σ REE=54.53-121.38 ppm). These rocks show the highest REE abundances among all three groups (La=10.3-26.4, Ce=22.0-52.4, Nd=8.4-20.3 ppm). The two subgroups of pegmatitic and aplitic leucogranites (quartz, albite, K-feldspar, muscovite, biotite, tourmaline, garnet, andalusite) both penetrate two-mica granite and are more difficult to distinguish solely on the basis of trace element data, but show clear differences in REE chondrite normalized patterns. They both exhibit a very high silica content (74.8-76.5 ; 74.7-74.8 wt.%) and a strong peraluminous signature (ASI=1.1-1.6 ; 1.1-1.2), very low contents of TiO2 (0.04-0.05 ; 0.05-0.06 wt.%), Fe2O3 (0.55-0.77 ; 0.62-0.68 wt.%), MgO (0.06-0.07 ; 0.04-0.05 wt.%) and CaO (0.42-0.52 ; 0.19-0.39 wt.%) leading to the absence of mafic minerals (except disseminated tourmaline) and hence a leucocratic appearance. Their trace element distribution is characterized by high Rb (229-244 ; 288-365 ppm), coupled with low Ba (4-11 ; 1-4 ppm), Sr (4-12 ; 2-3 ppm), Cs (11-16 ; 13-15 ppm), Zr (34-35 ; 11-18 ppm), Be, Ta and Th. REE chondrite-normalized patterns are flat ((La/Yb)N=1.9-2.3 ; 2.1-2.4 ; Eu/Eu* = 0.05-0.11 ; 0.01-0.13 ; low Σ REE=21.7-22.5 ; 8.4-9.2 ppm), less fractionated and bear a strong Eu negative anomaly. REE are lower than in the previous group (La=3.2-3.7 ; 1.4-1.6, Ce=6.8-7.7, 2.4-2.9, Nd =3.4 ; 1.2-1.3 ppm). Preliminary model for production of melts indicates muscovite dehydration melting of a (meta)pelitic source combined with differences in formation and emplacement levels.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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