engleski

Petrology and geochemistry of appinite-granodiorite intrusion from the eastern Drava depression (Eastern Croatia).

In the subsurface of the eastern Drava depression, a complex shallow intrusion occurs, which is composed of monzodiorite, granodiorite and hornblende diabase. Hornblende is one of the main mineral phases in mafic and intermediate rocks, which indicates unusually high water content in magma. Consequently, the mafic and intermediate rocks could be defined as appinites. Porphyritic hornblende diabase is composed of plagioclase and hornblende, with occurrence of sporadic biotite and quartz close to the contact with the granodiorite. Hypidiomorphic granular monzodiorite contains plagioclase, hornblende, orthoclase, quartz and biotite. Granodiorite with seriate texture is composed of plagioclase, quartz, orthoclase and biotite, with hornblende that mostly appears near the contact with the hornblende diabase. Textural evidence points to magma mixing and mingling between mafic and felsic end members. The analyzed rocks belong to the calc-alkaline and high-K calc-alkaline series, and are characterized by high FeOt contents relative to MgO. Whole-rock primitive mantle-normalized trace element patterns commonly display Cs positive and Ba negative anomaly. Chondrite-normalized REE patterns are characterized by LREE enrichment relative to MREE and HREE. Trace element geochemistry points to a common lithospheric mantle source, metasomatized by subduction processes. Weak negative Eu anomalies are pronounced in the mafic and intermediate rocks, while granodiorite displays a positive Eu anomaly. These characteristics rule out plagioclase as a fractionating phase, and indicate the importance of hornblende in the evolution of the magma. Textural, mineralogical and geochemical characteristics of the analyzed rocks are clearly distinguishable from the Paleozoic magmatic rocks of the Slavonian mountains. They share common characteristics with Paleogene intrusive rocks of the subsurface of Zala basin in Hungary, which are considered as a continuation of Periadriatic intrusions to the northeast.

appinite, granodiorite, magma mixing, Drava depression

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