Multi-Stage Evolution of Gold-Bearing Hydrothermal Quartz Veins at the Mokrsko Gold Deposit (Czech Republic) Based on Cathodoluminescence, Spectroscopic, and Trace Elements Analyses

Abstract

We performed a detailed analysis of hydrothermal quartz at the Mokrsko gold deposit (Čelina, Mokrsko-East, and Mokrsko-West deposits). Twenty-one samples were studied by scanning electron microscopy cathodoluminescence (CL) imagining, CL emission spectra and trace elements were measured on six selected samples. Four quartz growth generations Q1 to Q4 were described. Homogeneous early blue CL Q1 with initial emission spectra at 380 and 500 nm was observed at the Čelina deposit with typical titanium concentrations in the range of 20–50 ppm. Hydrothermal quartz at Mokrsko-West, which also includes early Q1, late subhedral faces of yellow CL Q2, and microfissures of greenish CL Q3 (both 570 nm), is characterized by titanium depletion. The titanium concentration is comparable to previous studies of crystallization temperatures proving titanium concentration in quartz as a good geothermal indicator. Q4, developed in microfissures only at Čelina, has no visual CL effect. Mokrsko-West is specific in comparison to Mokrsko-East and Čelina by germanium enrichments in hydrothermal quartz (up to 17 ppm) and the presence of fluorite. Tectonic (sheeted veinlets system, regional tectonic setting) and geochemical (germanium in quartz, the presence of fluorite) characteristics of the quartz veins link the late mineralization stages at the Mokrsko-West deposit to the temporally related Blatná intrusive suite.

Trace-element chemistry of barren and ore-bearing quartz of selected Au, Au-Ag and Sb-Au deposits from the Bohemian Massif

“…Norman et al 1998;Tiepolo et al 2003). We firmly believe that the results for Ti in quartz veins at the Mokrsko-West deposit are in agreement with a recently published independent study (Wertich et al 2018). The following statistical parameters are included for comparison: our dataset (N = 452, min = 2, max = 35, mean = 10.7, median = 9.0) vs. data digitalized from fig.…”

“…The observed zones are related to quartz recrystallization along the grain boundaries, to microfractures, or to rare growth zones (e.g. Wertich et al 2018). These zones represent insignificant fraction of the ablated volume (see below).…”

“…These zones represent insignificant fraction of the ablated volume (see below). Wertich et al (2018) focused on similar types of samples/deposits and also concluded that it is nearly impossible to analyze zones with different CL separately. Distribution of Ti in the hydrothermal quartz veins from the studied deposits; a -all the veins altogether, both ore-bearing and barren; b -ore-bearing veins at the "high-temperature Au" Mokrsko and Petráčkova hora deposits; c -ore-bearing veins at the "medium-to-low temperature Au" Jílové, Kasejovice, and Libčice deposits; d -orebearing veins at the "medium-to-low temperature Au-Ag" Roudný deposit; e -ore-bearing veins at the "medium-to-low temperature Sb-Au" Krásná Hora deposit.…”

“…The following statistical parameters are included for comparison: our dataset (N = 452, min = 2, max = 35, mean = 10.7, median = 9.0) vs. data digitalized from fig. 6 of Wertich et al (2018) (N = 48, min = 1.2, max = 62, mean = 9.1, median = 6.2).…”

Editorial for Special Issue “Mineralogy of Quartz and Silica Minerals”

“…[11] found implications for the formation of bonanza veins in low-sulfidation epithermal deposits from the textural characteristics of non-crystalline silica in sinters and quartz veins. Wertich et al [12] developed a multi-stage model of gold-bearing hydrothermal quartz veins at the Mokrsko gold deposit (Czech Republic) based on cathodoluminescence and trace element data. Based on the results of such studies, the prognosis of potential gold deposits could be significantly improved.…”