The evolution of late-Hercynian granites and rhyolites documented by quartz – a review

Abstract

The potential of igneous quartz for providing a better understanding of magmatic processes is demonstrated by studying late-Hercynian rhyolites and granites from central and western Europe. Cathodoluminescence (CL) reveals growth patterns and alteration structures within igneous quartz reflecting the magma crystallisation history. The relatively stable and blue-dominant CL of zoned phenocrysts is principally related to variations in the Ti concentration, which is a function of the crystallisation temperature. The Al/Ti ratio of igneous quartz increases with progressive magma differentiation, as Ti is more compatible, compared to Al, Li, K, Ge, B, Fe, P during magma evolution. The red-dominant CL of the anhedral groundmass quartz in granite is unstable during electron bombardment and associated with OH-and H 2 O-bearing lattice defects. Thus, CL properties of quartz are different for rocks formed from H 2 O-poor and H 2 O-rich melts. Both groundmass and phenocrysts in granites are rich in alteration structures as a result of interaction with deuteric fluids during cooling, whereas phenocrysts in extrusive rocks do not usually contain such structures. The combined study of trace elements along with the analysis of quartz textures and melt inclusion inventories may reveal detailed PTX-paths of granite magmas. This study shows that quartz is a sensitive indicator for physico-chemical changes during the evolution of silica-rich magmas. Common growth textures show a wide variety in quartz phenocrysts in rhyolites and some granites. We present a classification of textures, which formed as a result of heterogeneous intra-granular lattice defects and impurities. The alternation of growth and resorption microtextures reflects stepwise adiabatic and non-adiabatic magma ascent, temporary storage of magma in reservoirs and mixing with more mafic, hotter magma. The anhedral groundmass quartz overgrowing early-magmatic phenocrysts in granites is free of growth zoning.

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

“…Götze et al 2001;Müller et al 2003), is low in both samples, with similar concentrations compared to published Al data from magmatic and hydrothermal quartz elsewhere (e.g. Jourdan et al 2009;Müller et al 2010b). The differences in Ti contents rank among the most conspicuous features distinguishing both samples quartz from the T2 breccia is poorer in Ti (2.2 and 3.7 ppm).…”

A Study of Cathodoluminescence and Trace Element Compositional Zoning in Natural Quartz from Volcanic Rocks: Mapping Titanium Content in Quartz

“…or combinations thereof could possibly produce the sharp transition~cf. Liu et al, 2006;Müller et al, 2009;Thomas et al, 2010;Thomas & Watson, 2012!. Finally, the thin outermost rim is characterized by a sharp decrease in Ti to levels near 100 ppm; the map best illustrates this, as it was difficult to obtain LA-ICPMS data near the crystal edge.…”

“…involves decompression along a hypothetical path, during which partial resorption of the core occurs~cf. Müller et al, 2009!, followed by storage of the magma at low pressure~ca. Յ3 kbar!…”

The Chemistry of Quartz in Granitic Pegmatites of Southern Norway: Petrogenetic and Economic Implications

“…However, comparatively little of this type of work has been carried out on the chemistry of pegmatite quartz. The limited number of publications is in contrast to the abundant studies dealing with trace elements of hydrothermal (e.g., Rusk et al 2006Rusk et al , 2008Rusk et al , 2011Rusk, 2012Rusk, , 2014Tanner et al, 2013;Maydagán et al, 2015), volcanic (e.g., Watt et al, 1997;Wark et al, 2007;Audétat, 2013), plutonic (e.g., Müller et al, 2000Müller et al, , 2010bWiebe et al, 2007;Jacamon and Larsen, 2009;Breiter et al, 2013), metamorphic (e.g., Van den Kerkhof et al, 2004;Spear and Wark, 2009;Kidder et al, 2013), and sedimentary quartz (e.g., Götze and Plötze, 1997;Götze, 2012;Götte et al, 2013;Müller and Knies, 2013).…”