Feathery and network-like filamentous textures as indicators for the re-crystallization of quartz from a metastable silica precursor at the Rusey Fault Zone, Cornwall, UK

Abstract

Abstract. Hydrothermal quartz crystals, which occur in the Rusey Fault Zone (Cornwall, UK), show feathery textures and network-like filamentous textures. Optical hot-cathodoluminescence (CL) analysis and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) investigations on quartz samples revealed that positions exhibiting feathery textures (violet luminescence) contain higher amounts of Al and Li than quartz positions without feathery textures (blue luminescence), while concentrations of Al and Li are significantly lower in feathery textures. Both Al and Li correlate negatively with Si. Raman spectroscopy investigations revealed the presence of a weak peak at 507–509 cm−1 in quartz affected by feathery textures, which we attribute to the presence of ≤ 5 % moganite, a microcrystalline silica polymorph, intergrown with chalcedony. The combined occurrence of feathery textures and network-like filamentous textures in quartz samples from the Rusey Fault Zone points to the presence of a metastable silica precursor (i.e., amorphous silica or silica gel) before or during the crystallization.

Hydrothermal genesis and growth of the banded agates from the Allumiere-Tolfa volcanic district (Latium, Italy)

“…It is worth noting that the positive correlation between Al and Li in the hyaline quartz (and chalcedony) from the investigated sample. Similar relationship has been reported by i.e., Yilmaz et al (2016) or Perny et al (1992) and can be attributed to Si ↔ Al(+ Li) substitution in the crystal lattice during the crystal growth in hydrothermal environment. Moreover, according to this author, the presence of feathery quartz may also account for variable amounts of Al and Li in hydrothermal quartz.…”

“…The hydrothermal Bambauer quartz with typical µm-sized growth lamellae indicates a lower temperature of hydrothermal fluids characterized by strong fluctuations in silica concentrations and/or pH conditions (Bambauer et al 1961;Richter et al 2015;Powolny et al 2019;Götze et al 2020;Pršek et al 2020) or episodic crystallization, with periods of stasis alternating with periods of growth. Lastly the local evidence of feathery/splintery extinction of some quartz crystals agrees with subsequent recrystallization of metastable silica phases such as chalcedony or amorphous silica (Fournier 1985;Yilmaz et al 2016;Powolny et al 2019;Götze et al 2020;Pršek et al 2020).…”

Trace and Macro Element Contaminations in Tissues of Vimba persa and Alosa braschnikowi From the South Caspian Sea and Potential Human Health Risk Assessment

“…In their study, Zn, Cu, Ca, and iron were reported to be at higher levels of accumulation in the fish liver (38), similar to the results obtained for the Cu and Fe in the present study. The results of the present study are also consistent with the results of a study conducted by Yilmaz et al (39) who investigated the element accumulations in the tissue of Tinca tinca. They found that the Cu and Fe levels in the fish liver were higher than in other tissues.…”

Agates from Western Atlas (Morocco)—Constraints from Mineralogical and Microtextural Characteristics

“…The presence of boiling could be further responsible for the formation of ore-related phases, such as Fe and Cu sulfides found within the silica matrix of agates. The feathery and jigsaw puzzle quartz microtextures found within agate nodules provide, in turn, strong evidence for the recrystallization of pre-existing massive chalcedony or amorphous silica [52][53][54].…”