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

Abstract

In the crystalline basement of the Tatra Mountains (Poland/Slovakia) two types of tourmaline-rich breccia zones are described, both having originated from magmatic fluids and showing a 350 ± 1 Ma Re-Os model age. Both T1 brecciated pegmatites and T2 vein-breccias are cemented by a tourmaline-quartz matrix. In T1 breccias, the metasomatic replacement of feldspars by tourmaline and overgrowths of small Tur 2 tourmalines on the primary pegmatitic Tur 1 tourmaline crystals suggest an important role for metasomatic processes. The microcrystalline nature of the quartz-tourmaline matrix and high vacancy ratios in the X-site in tourmaline from T2 breccias reflect relatively rapid crystallization from an oxidized fluid. The formation of both types of breccias is related to the internal structure of the Tatra granitoid intrusion. The layered character of the granitoid body probably stimulated the formation of pegmatite-like pockets, with local overpressure causing metasomatic alteration, rock brecciation and cementation by tourmaline (T1 breccias), the final hydrofracturing of overburden rocks and fluid escape. The resulting fracture zones (T2) are interpreted as the paths for fluid migration and rapid crystallization as the pressure and temperature dropped from 7.5-6 kbar and 630-570 ºC in the case of the T1 brecciated pegmatites to 2.5-1.5 kbar and 465-430 ºC in the vein T2 breccias.

Mineralogy and origin of coarse-grained segregations in the pyrometallurgical Zn-Pb slags from Katowice-Wełnowiec (Poland)

“…Diaz-Alvarado et al 2013) and, as in the case of the tabular intrusions -prevent volatiles from escaping forming the internal pegmatoidal structures (e.g. Gawęda et al 2013). …”

Experimental Investigation of Biotite-Rich Schist Reacting with B-Bearing Fluids at Upper Crustal Conditions and Correlated Tourmaline Formation

“…Tourmaline is a common accessory mineral in granitoids, mainly in peraluminous leucogranites, in related pegmatites, and in hydrothermal quartz vein and breccia systems that frequently develop around granitoids [1][2][3][4][5][6]. Tourmaline crystallises either as a magmatic mineral, or during the magmatic/hydrothermal transition and as a late post-magmatic hydrothermal mineral.…”

Fossil vs. Active Geothermal Systems: A Field and Laboratory Method to Disclose the Relationships between Geothermal Fluid Flow and Geological Structures at Depth

“…This is not the case for the shallower systems where banded veins can develop exhibiting repeated events of opening and mineral filling (e.g., References [11,114]). Nevertheless, for veins developed at the deeper structural levels, this simplification is also a consequence of the fact that hydrothermal veins are typified by comminution of mineral-filling fractures, hence indications about the evolution of the veins (as, for example, proposed by References [115][116][117]), are not recognizable, generally.…”

“…A mitigation of the k value overestimation is, however, determined by the statistical approach which tends to highlight the most suitable value. Furthermore, it should be taken in account that large veins, such as the hydraulic breccias (burst veins in: Reference [117]) producing instantaneous, co-seismic veins [118], are not compatible with the laminar flow of the parallel plate model, thus being excluded by the database. Similarly, computations resulting in k values > 1 × 10 −12 m 2 are excluded too, since not consistent with the assumptions of the parallel plate model.…”