INVESTIGATION OF TRACE-ELEMENT DISTRIBUTION IN DETRITAL QUARTZ BY ELECTRON-PARAMAGNETIC-RESONANCE (EPR)

Paramagnetic defects in natural, irradiated (2 kGy, Co-60, 295 K) and etched (40% HE 30 min, 295 K) samples of quartz grains (grain size < 0 .16 mm) from quartz-sand deposits in Weferlingen, HaItern and Frechen (Germany) were investigated by EPR at 9.5 GHz and at 20, 70, and 295 K . In all samples [AlO4](0), [TiO4/Li+](0), [TiO4/H+](0), [TiO4](-), an d Fe3+ paramagnetic centres were detected. Generally, gamma-irradiatio n caused a transformation of diamagnetic precursor centres into these paramagnetic centres, resulting in an increase of the EPR intensity of up to five times. Samples from Weferlingen have similar trace-element contents and show only minor differences in the abundance of paramagn etic centres. In contrast, the abundance of paramagnetic centres in qu artz from the different deposits may differ significantly, especially Fe3+, [AlO4](0) and [TiO4/Li+](0) centres in the gamma-irradiated quar tz samples. The high concentrations of [AlO4](0) and [TiO4/Li+](0) cen tres in the Weferlingen quartz samples reflect higher amounts of igneo us quartz than in the other deposits investigated. These differences i n quartz composition were confirmed by cathodoluminescence microscopy. Etching of quartz samples with hydrofluoric acid (ca. 30% loss of mas s) followed by further EPR measurement revealed that Al centres genera lly show a more or less homogeneous distribution pattern, whereas no F e centres were left in quartz after etching. This indicates that Fe ce ntres are concentrated in the outer rim of the quartz grains.