Relationships between monazite, apatite and chevkinite-group minerals in the rhyolitic Joe Lott Tuff, Utah, USA

Abstract

The high-silica rhyolitic Joe Lott Tuff was erupted at 19.2 ± 0.4 Ma from the Mount Belknap caldera in Utah, USA. Despite having a volume of ca 150 km3 it is compositionally homogeneous and contains ≤3 modal% phenocrysts. The tuff also shows two very unusual aspects of the REE-bearing phases, monazite and the chevkinite-group minerals (CGM): (i) the presence of perrierite-(Ce) in a high-silica rhyolite, and (ii) the replacement of CGM in the stratigraphic sequence by monazite, with a subsequent return to a CGM. Evidence from CGM distribution and variations in monazite and apatite-group composition with stratigraphic height in the deposit are used to infer that prior to eruption the magma was compositionally zoned, the zonation being partially obliterated by convective overturn in the reservoir.

Chevkinite-group minerals in selected intrusions of the Mazury Complex, North-Eastern Poland: insights into the formation of a titanite-like phase by hydrothermal alteration

“…The exceptionally high values of ThO 2 in a crystal in sample Kr-6-33, ≤ 9.10 wt% (Table S1; Fig. 2a), match those in perrierite-(Ce) from the rhyolitic Joe Lott Tuff, Utah (Galanciak et al 2020) in being among the highest yet recorded in the CGM. An important feature is that Al is the dominant cation in the C site.…”

Hydrothermal alteration of chevkinite: insights from natural rocks and experiments

“…Material for these studies comes mainly from two sources. First, as part of our own field and petrological studies, e.g., UK Palaeogene granites (Macdonald et al 2013), high-K trachyandesites from Moravia (Macdonald et al 2017), the Kłodzko-Złoty Stok intrusion, Sudetes (Nejbert et al 2020), the Joe Lott Tuff, Utah (Galanciak et al 2020), the Gold Flat Tuff, Nevada (Macdonald et al 2021) and the Krasnopol intrusion, Mazury Complex (Domańska-Siuda et al 2022). Second, through ongoing collaborations with other organizations, e.g., the U.S. Geological Survey, GFZ Potsdam, the Russian Academy of Sciences (Mos cow and Apatity), the Polish Academy of Sciences (Kraków), and the Universities of Edin burgh and Milan.…”