Magma hybridization in the Western Tatra Mts. granitoid intrusion (S-Poland, Western Carpathians)

Abstract

In the Variscan Western Tatra granites hybridization phenomena such as mixing and mingling can be observed at the contact of mafic precursors of dioritic composition and more felsic granitic host rocks. The textural evidence of hybridization include: plagioclase–K-feldspar–sphene ocelli, hornblende- and biotite-rimmed quartz ocelli, plagioclase with Ca-rich spike zonation, inversely zoned K-feldspar crystals, mafic clots, poikilitic plagioclase and quartz crystals, mixed apatite morphologies, zoned K-feldspar phenocrysts. The apparent pressure range of the magma hybridization event was calculated at 6.1 kbar to 4.6 kbar, while the temperature, calculated by independent methods, is in the range of 810°C−770°C. U-Pb age data of the hybrid rocks were obtained by in-situ LA-MC-ICP-MS analysis of zircon. The oscillatory zoned zircon crystals yield a concordia age of 368 ± 8 Ma (MSWD = 1.1), interpreted as the age of magma hybridization and timing of formation of the magmatic precursors. It is the oldest Variscan magmatic event in that part of the Tatra Mountains.

Age and origin of the tourmaline-rich hydraulic breccias in the Tatra Granite, Western Carpathians

“…The granitoid intrusion shows internal layering, formed as a result of mixing of mafic and felsic magma batches during flow (Burda et al 2011;Gawęda and Szopa 2011). The formation of sedimentary-like structures in the granite was facilitated by the high content of volatiles, including H 2 O, B, CO 2 , P 2 O 5 , and locally CH 4 (Gawęda and Szopa 2011;Szopa et al in print).…”

“…The tongue-shaped Tatra granitoid intrusion (Kohút and Janák 1994) consists of several magmatic pulses, all dated by the U-Pb method on zircon: I-type mingled hybrid quartz diorite, interpreted as a mafic precursor and dated at 368 ± 8 Ma, tonalite-granodiorite showing an age interval of 360-370 Ma, syenogranite-monzogranite, locally porphyritic, rich in xenoliths and mafic microgranular enclaves, dated from 350 ± 5 Ma to 337 ± 6 Ma (Poller et al 2000;Gawęda et al 2005;Gawęda 2008Gawęda , 2009Burda et al 2011Burda et al , 2013. Formerly, these granites were dated at 314 ± 4 Ma (Poller and Todt 2000) but this age was later interpreted as to be influenced by the Pb-loss caused by post-magmatic shearing (Gawęda 2009).…”

“…8). Given that the calibrated pressure for different parts of the Tatra granite Pluton was 4.5-6 kbar (Ludhová and Janák 1999;Gawęda et al 2005;Gawęda 2009;Burda et al 2011;Gawęda and Szopa 2011), it could have exceeded the lithostatic pressure, favouring hydrofracturing of the internal pegmatitic components as well as of the host granite. Crystallization inside the distant fracture zones (T2), calibrated for the unzoned, syntectonic muscovite (Fig.…”

The petrogenesis of granitoid rocks unusually rich in apatite in the Western Tatra Mts. (S-Poland, Western Carpathians)

“…In the Western Tatra Mts., an EarlyVariscan hybridization episode is imprinted on I-type quartzdiorite precursors, occurring as sills in the metamorphic envelope and at the bottom of a granodiorite-tonalite intrusion (Gawęda et al 2005). The mingling-mixing processes between the granodioritic common Tatra type and quartzdiorite precursors were dated at 368±8 Ma by zircon U-Pb method (Burda et al 2011).…”

“…1). The rocks occur at the bottom of a tongue-shaped granitoid pluton formed by multiple injections of magma of different chemistry and origin (Kohut and Janak 1994;Gawęda 2009;Burda et al 2011;Gawęda and Szopa 2011) in the northern slopes of Starorobociański Mt. (Fig.…”