Oxygen isotope sector zoning in natural hydrothermal quartz

Abstract

Oxygen isotope measurements using SIMS and laser-fluorination methods confirm the presence of concentric and sector zoning in low-temperature (200ºC to <400ºC) hydrothermal quartz from Alpine veins. While concentric zoning is most readily explained by changes in the chemical composition of the fluid or temperature of crystallization, the reasons for sector zoning are more difficult to explain. Relative enrichment in 18 O for crystallographically different sectors of quartz corresponds to m >r >z. Sector zoning is, however, largely limited to the exterior zones of crystals and/or to crystals with large Al (>1000 ppm) and trace element contents, probably formed at temperatures <250ºC. Differences in d 18 O between the prismatic (m) relative to the rhombohedral (r and z) growth sectors of up to 2% can be explained by a combination of a face-related crystallographic and/or a growth rate control. In contrast, isotopic sector zoning of up to about 1.5% amongst the different rhombohedral faces increases in parallel with the trace element content and is likely to represent disequilibrium growth. This is indicated by non-systematic, up to 2%, differences within single growth zones and the irregular, larger or smaller, d 18 O values (of several permil) of the exterior compared to the inner zones of the same crystals. Disequilibrium growth may be related to the large trace element content incorporated into the growing quartz at lower temperatures (<250ºC) and/or be related to fluid-vapour separation, allowing crystal growth from both a vapour as well as a liquid phase.

Structural and temporal evolution of a reactivated brittle–ductile fault – Part II: Timing of fault initiation and reactivation by K–Ar dating of synkinematic illite/muscovite

“…6C). The Silurian age of the coarsest size fraction matches well the timing of early thrusting within the Kalak Nappe Complex (470-450 Ma; Kirkland et al, 2009) and final nappe (Dallmeyer et al, 1988;Kirkland et al, 2005). 6C).…”

The titanium-in-quartz (TitaniQ) thermobarometer: A critical examination and re-calibration

“…Diffusivities in hydrothermal fluids are orders of magnitude faster, for which reason boundary layers are unlikely to develop. However, studies on hydrothermal calcite (e.g., Dromgoole and Walter, 1990;Paquette and Reeder, 1995;Barker and Cox, 2011) and hydrothermal quartz (e.g., Ihinger and Zink, 2000;Jourdan et al, 2009) have shown that trace element abundances in hydrothermal minerals nevertheless are influenced by growth rate, which calls for an alternative explanation. In the simplest scenario, fast-growing crystals contain more defects than slowly-grown crystals, leading to a higher abundance of all trace elements (e.g., Martin and Armington, 1983).…”

Origin and significance of the yellow cathodoluminescence (CL) of quartz

“…The great interest in luminescence studies of quartz is due to the fact that information not available by other analytical methods can be obtained. For instance, cathodoluminescence (CL) can be used to reveal internal textures, growth zoning, secondary alteration or different quartz generations, which cannot be discerned by optical or electron microscopy (e.g., Zinkernagel 1978;Ramseyer et al 1988;Owen 1988;Ramseyer and Mullis 1990;Watt et al 1997;Müller 2000;Götze et al 2001a; Van den Kerkhof et al 2004;Rusk et al 2006Rusk et al , 2008Krickl et al 2008;Götze 2009;Müller et al 2009a;Jourdan et al 2009aJourdan et al , 2009bLehmann et al 2009). In addition, CL is an effective method for spatially resolved analysis of extrinsic or intrinsic point defects in quartz by spectral measurements.…”