scholarly journals The occurrence of wakefieldite, a rare earth element vanadate, in the rhyolitic Joe Lott Tuff, Utah, USA

2019 ◽  
Vol 84 (1) ◽  
pp. 109-116
Author(s):  
Bogusław Bagiński ◽  
Ray Macdonald ◽  
Harvey E. Belkin ◽  
Jakub Kotowski ◽  
Petras Jokubauskas ◽  
...  
Keyword(s):  
Solid Solution ◽  
Rare Earth ◽  
Rare Earth Element ◽  
Hydrothermal Fluid ◽  
Earth Element ◽  
Hydrothermal Fluids ◽  
Fe Oxide ◽  
Uranium Mineralisation ◽  
High Silica

AbstractThe high-silica rhyolitic Joe Lott Tuff was erupted at 19.2 ± 0.4 Ma from the Mount Belknap caldera, SW Utah. Certain units in the tuff contain two species of wakefieldite, the Nd- and Y-dominant types. They occur in disseminated streaks and patches in association with rhodochrosite, calcite, Fe oxide, cerite-(Ce), and a Mn silicate (caryopilite?), thought to have been deposited from hydrothermal fluids. The wakefieldites contain the highest levels of As (≤15.34 wt.% As2O5) and P (≤5.7 wt.% P2O5) yet recorded in this mineral, indicating significant solid solution towards chernovite-(Y) and xenotime-(Y). Thorium levels are also unusually high (≤14.2 wt.% ThO2). The source of the hydrothermal fluid(s) is unknown but might be related to uranium mineralisation in the region, in that As, V and U are commonly associated in such deposits.

Multiple-stage hydrothermal alteration in porphyry copper systems in northern Turkey: the temporal interplay of potassic, propylitic, and phyllic fluids

1980 ◽  
Vol 17 (7) ◽  
pp. 901-926 ◽  
Author(s):  
R. P. Taylor ◽  
B. J. Fryer
Keyword(s):  
Rare Earth ◽  
Hydrothermal Alteration ◽  
Rare Earth Element ◽  
Earth Element ◽  
Root Zone ◽  
Porphyry Copper ◽  
Hydrothermal Fluids ◽  
New Mineral ◽  
Potassic Alteration ◽  
Different Levels

The Bakircay and Ulutas Cu–Mo prospects represent the first occurrences of porphyry mineralization to be described in Turkey.Differences observed in the two prospects in terms of hydrothermal alteration (in particular, alteration overprinting), igneous textures, abundance of xenoliths, breccia phenomena, and style and intensity of fracturing may relate to different levels of exposure within a model porphyry system, Bakircay representing the deep root zone of such a system and Ulutas reflecting much higher levels close to the apex of such a system, or may simply reflect different levels of emplacement.The alteration assemblages present at the Bakircay prospect lend themselves to a geochemical study of the temporal variations in the hydrothermal fluids responsible for single- and multiple-stage alteration–mineralization. The chemical changes involved during single-stage potassic alteration are related to amphibole breakdown and the deposition of hydrothermal biotite (and chalcopyrite). These changes are manifested in light rare-earth element (LREE) enrichment and heavy rare-earth element (HREE) depletion reflecting the high K+ and Cl− activity of the hydrothermal fluids. During propylitic overprinting of potassic alteration changes in whole-rock geochemistry relate to the destruction of biotite (both igneous and hydrothermal) and the formation of chlorite, epidote, calcite, and apatite. These changes result in the loss of ail rare-earth elements (REE) due to increasing fluid/rock ratios and further changes within the HREE relating to zircon stability and the deposition of new mineral phases, e.g., epidote. Conversion of preexisting alteration types lo the quartz–sericite–pyrite ± rutile, calcite assemblages, typical of phyllic alteration, results in the loss of all elements not accommodated in these phases. The high fluid/rock ratios and low pH of the fluids cause progressive leaching of all REE, particularly the lightest (La and Ce).

Rare earth element mobility associated with uranium mineralisation

Nature ◽  
1979 ◽  
Vol 282 (5736) ◽  
pp. 247-250 ◽  
Author(s):  
Scott M. McLennan ◽  
S. R. Taylor
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Element Mobility ◽  
Uranium Mineralisation

Effect of Conjoint Additions of Rare Earth Element Oxides on the Phase Stability of Zirconia

1995 ◽  
Vol 412 ◽  
Author(s):  
Ewan R. Maddrell
Keyword(s):  
Solid Solution ◽  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Oxide Phase ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Zirconium Butoxide ◽  
Pyrochlore Type

AbstractThe ability of the cubic phase of zirconia to accommodate in solid solution the oxides of rare earth elements with differing cationic radii has been investigated. Mixed oxide phase assemblages were prepared by hydrolysing zirconium butoxide with solutions of rare earth element nitrates followed by drying, calcining and sintering. The resulting products were characterised by X-ray diffraction and energy dispersive spectroscopy. The cubic zirconia phase can accept into solid solution the larger, non-cubic stabilising, rare earth element ions such as lanthanum in the presence of the cubic stabilising oxides of yttrium and samarium. As the proportion of the larger rare earth element ions is increased the formation of pyrochlore type compounds is favoured.

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