The origin of magmatic layering in the High Tatra granite, Central Western Carpathians – implications for the formation of granitoid plutons

Abstract

The High Tatra granite intrusion is an example of a Variscan syn-tectonic, tongue-shaped intrusion. In some portions of the intrusion, structures occur which appear to be of sedimentary origin. These include structures similar to graded bedding, cross-bedding, troughs and flame structures, K-feldspar-rich cumulates and magmatic breccias. Formation of these structures might be related to changing magma properties, including crystal fraction, development of a crystal mush and a decrease in magma viscosity, stimulated by influx of mafic magma and high volatile content. The suggested processes in operation are: gravity-controlled separation, magma flow segregation, deposition on the magma-chamber floor, filter pressing and density currents stimulated by tectonic activity.%The formation of the sedimentary structures was also aided by the presence of large numbers of xenoliths that acted as a heat sink and influenced the thermal field in the intrusion, stimulating rapid cooling and crystal nucleation. Sinking xenoliths deformed the layering and, to some extent, protected the unconsolidated crystal mush from erosion by magma flowing past.%Areas with well-developed sedimentary magmatic structures can be viewed as having involved magma rich in crystals locally forming closely-packed networks from which residual melt was extracted by filter pressing, and preserved in leucocratic pods and dykes. Interleaved, non-layered granite may be interpreted to have formed from the magma with initially low crystal fractions.%It is suggested that the intrusion was formed from numerous magma injections representing different stages in the mixing and mingling of felsic and mafic sources. It solidified by gravitation-driven crystal accumulation and flow sorting on the magma chamber floor and on the surfaces of large numbers of xenoliths. Shear stress acting during intrusion might have influenced the formation of magmatic structures.

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).…”

U-Pb zircon age of the youngest magmatic activity in the High Tatra granites (Central Western Carpathians)

“…2a, b) Sikorska, 2009 andSzopa, 2011), quartz, biotite (fm = 0.541-0.587), muscovite (both magmatic and post-magmatic ones). Mghornblende occurs in rock-portions showing mixingmingling features (Gawęda and Szopa, 2011).…”

“…Recent geological mapping enlarges that area further to the north in Poland, to Mięguszowieckie Peaks and further to Kozie Peaks in NW (Gawęda, 2009). This area is currently interpreted as the mixing-mingling zone, additionally complicated by the presence of numerous xenoliths (Gawęda, 2009 andSzopa, 2011).…”

“…crystallization in the range of 720-890°C and pressure at 4-6 kbar (Gawęda and Szopa, 2011). Epidote, Ca-garnet, chlorite, titanite, sericite, sporadically prehnite and Fepumpellyite are secondary minerals linked to lowtemperature post-magmatic alterations (Leichman et al, 2009 andWłodyka, 2013).…”

Sequential granite emplacement: a structural study of the late Variscan Strzelin intrusion, SW Poland

“…The fracturation started after the crystallization of schlieren that surround xenoliths, but still in the presence of granitic melt. This is supported by the offset schlieren, but without submagmatic deformation of minerals close to the fractures Gawęda and Szopa 2011), and by the fact that some fractures cutting the xenolith were healed by the granite magma. Even younger fractures, cutting through the xenoliths without displacement of the surrounding schlieren, have been filled with aplite and quartz (Fig.…”