To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
The Palaeoproterozoic (~2.0−1.8 Ga) Stankuvatske Li deposit (Ukrainian Shield, Central Ukraine) represents an uncommon case of recrystallised, fine-grained petalite ± spodumene meta-pegmatite dykes with LCT affinity hosted in amphibolites and meta-ultrabasic rocks. The meta-pegmatite dykes show remnants of primary, pre-metamorphic zoning, with dominant magmatic albite, K-feldspar, quartz, Li-phases (petalite, spodumene, rarely triphylite and montebrasite), and accessory muscovite, fluorapatite, columbite-(Fe), tantalite-(Fe), cassiterite, Ta-rich rutile, zinco- and ferronigerite, gahnite, pyrite, sphalerite and zircon. The parental magma of the meta-pegmatites was peraluminous, and enriched in Li and P, though relatively poor in B and F during the late-magmatic stage. Metasomatic reactions between residual pegmatite magma and (ultra)basic country rocks resulted in the precipitation of holmquistite, triphylite, fluorapatite, tourmaline and Rb–Cs-rich biotite. Secondary generations of fine-grained petalite, spodumene, albite and K-feldspar were formed during post-magmatic stages, i.e. during hydrothermal–metasomatic alteration and/or subsequent tectono–metamorphic recrystallisation of the primary pegmatites. The initial subsolidus metasomatism of primary feldspars took place in alkaline conditions as a result of Na (partly K) for Li exchange.
The presence of fibrolitic sillimanite and chrysoberyl, together with the scarcity of muscovite and (OH,F)-bearing minerals, point to metamorphic recrystallisation of the former Li-rich granitic pegmatites at relatively high-temperature and medium-pressure (~600±50°C; ~0.3−0.4 GPa) conditions.
Chemical extraction techniques and scanning electron microscopy were used to study the distribution and behavior of actinides and rare earth elements (REE) in hydrothermal veins at Adamello, (Italy). The six samples discussed in this paper were from the phlogopite zone, which is one of the major vein zones. The samples were similar in their bulk chemical composition, mineralogy, and leaching behavior of major elements (determined by extraction with 9M HCl). However, there were major differences in the extractability of REE and actinides. The most significant influence on the leaching characteristics appears to be the amounts of U, Th and REE incorporated in resistant host phases. Uranium and Th are very highly enriched in zirconolite grains. Actinides were more readily leached from samples with a higher content of U and Th, relative to the amount of zirconolite. The results show that REE and actinides present in chemically resistant minerals can be retained under aggressive leaching conditions.
Extensive mineralogical and chemical studies have been carried out on the Ti-rich hydrothermal veins emplaced within the contact aureole of the Adamello batholith. In addition to other actinide and rare earth element host phases, the veins contain both zirconolite and betafite and provide information relevant to ceramic wasteforms designed for the disposal of actinide-rich nuclear wastes. In this paper, we describe the results of element partitioning studies based on dissolution experiments using 9M HCl. Generally, the acid-resistant minerals include allanite, baddeleyite, betafite, chalcopyrite, geikielite, titanite, spinel, and zirconolite. We also found that the major silicate minerals forsterite, phlogopite, and titanian clinohumite and the sulfide mineral pyrrhotite are partially dissolved by the acid treatment, whereas calcite and apatite are highly soluble (as expected). In particular, the distributions of Th and U between the acid-resistant and acid-soluble fractions indicate that they partition mainly between zirconolite, titanite, betafite, and apatite. However, there is a considerable increase in the amounts of Zr, Nb, Th, and U released in certain actinide-rich samples that may result from enhanced dissolution following radiation damage.
Dose-age relationships have been determined by analytical and transmission electron microscopy (AEM and TEM) for the onset dose and critical amorphization dose of a suite of natural zirconolites. Together with a preliminary investigation of the thermal histories of the zirconolite-bearing rocks, the results indicate that valid estimates of D0 (intercept dose at t = 0) and K (annealing rate constant) are obtained and that the host rocks experienced temperatures on the order of 100-200 °C averaged over time. The natural samples are therefore best suited as radiation damage analogues for waste forms stored under deep borehole conditions where temperatures of 100-450 °C are expected. Our results indicate that the critical amorphization (or saturation) dose of zirconolite will increase by a factor of approximately 2 or more as a result of storage at elevated temperature. The effect of long-term annealing on the critical amorphization dose is only important for times in excess of 107-108 years due to the low annealing rate constant of 10−9/yr.
Email your librarian or administrator to recommend adding this to your organisation's collection.