ALLANITE-(Ce) FROM THE EOCENE CASTO GRANITE, IDAHO: RESPONSE TO HYDROTHERMAL ALTERATION

Wood, Scott A.; Ricketts, Alice

doi:10.2113/gscanmin.38.1.81

Cited by 68 publications

(23 citation statements)

References 43 publications

(49 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…the measured composition of this mineral (see table 4) is consistent with thorite or huttonite (both thsiO 4 ). In general, th contents of allanites commonly range between 0.2-1.7 wt% thO 2 , (e.g., Deer et al 1982;catlos et al 2000;Wood & ricketts 2000;Poitrasson 2002). the allanites from the protolith contain 1.4-1.7 wt% thO 2 which is close to the maximum values of th contents reported in the literature (see above; Fig.…”

Section: Composition Of Accessory Phasessupporting

confidence: 81%

Stability and isotopic dating of monazite and allanite in partially molten rocks: examples from the Central Alps

2009

View full text Add to dashboard Cite

We investigated the stability of monazite and allanite as a function of bulk rock composition within several types of tertiary Alpine anatexites, characterized by different compositions and melting reactions, but similar P-t conditions of melting. the investigated rocks consist of: (1) orthogneisses in which the melting reaction was triggered by water infiltration from the bergell pluton; (2) anatectic tonalites, which were affected by water-assisted melting; and (3) metapelitic migmatites, which underwent muscovite dehydration melting. the studied anatexites cover a large range of ca contents and water activities during partial melting, and allow an assessment of how much these parameters affect the stability of accessory phases. the different melting reactions that affected these rocks generated different water activities during the meltpresent stage; they were highest in the water-saturated, contact metamorphic anatexites, and lowest in the metapelitic anatexites that underwent dehydration melting. these differences go together with different accessory phases within the migmatites. Whereas metapelitic anatexites only contain monazite, anatexites derived from tonalitic and granodioritic protoliths mainly contain allanite. this is consistent with observations made on tertiary Alpine anatexites, suggesting that the growth of specific accessory phases is determined by the water activity and ca content during melting.We measured single-grain monazite U/Pb isotope ages. One grain has relics of old cores, which have also been detected in Y-zonation patterns of the monazite. the data of unzoned monazites indicate partial melting in the southern steep belt between 30.78 ± 0.14 and 28.10 ± 0.28 Ma. Introductionthe stability of accessory minerals is a key to understand the geochemical evolution of crustal rocks during melting and crystallization, because rEE are almost completely hosted in these minerals (e.g., Miller & Mittlefehldt 1982;Watt et al. 1996). some of these minerals, e.g., allanite, zircon and monazite, are frequently used geochronometers; hence a good petrologic constraint on their formation has important implications for the correct interpretation of isotopic ages. Whereas analytical errors of age determinations have become increasingly small, the geologic interpretation of these isotopic ages still remains uncertain, because the criteria relating a specific geologic event to a measured datum are generally lacking. the problem concerns the distinction between mineral phases formed during melting or during crystallization of migmatites. this distinction is fundamental when dating these minerals from migmatites, because the long residence time of melt in the deeper crust (10 6 -10 7 yr, rosenberg et al. 2007) makes it difficult to attribute the analytically precise ages to a specific geologic process within a long-lasting period of crustal melting. better constraints on the phase relationships of accessory minerals are needed before isotopic ages can be accurately coupled to specific, possibly short...

show abstract

Section: Composition Of Accessory Phasessupporting

confidence: 81%

Stability and isotopic dating of monazite and allanite in partially molten rocks: examples from the Central Alps

2009

View full text Add to dashboard Cite

show abstract

“…4e). Allanite has been shown to be prone to hydrothermal alteration (Morin 1977;Wood and Ricketts 2000;Poitrasson 2002), Fig. 4 and all allanite generations in the Cnoc nan Cuilean samples show evidence of alteration, particularly the biotite-magnetite vein allanite.…”

Section: Allanitementioning

confidence: 99%

Enrichment of Rare Earth Elements during magmatic and post-magmatic processes: a case study from the Loch Loyal Syenite Complex, northern Scotland

Walters

Goodenough

Hughes

et al. 2013

Contrib Mineral Petrol

View full text Add to dashboard Cite

Concern about security of supply of critical elements used in new technologies, such as the Rare Earth Elements (REE), means that it is increasingly important to understand the processes by which they are enriched in crustal settings. High REE contents are found in syenitedominated alkaline complexes intruded along the Moine Thrust Zone, a major collisional zone in north-west Scotland. The most northerly of these is the Loch Loyal Syenite Complex, which comprises three separate intrusions. One of these, the Cnoc nan Cuilean intrusion, contains two mappable zones: a Mixed Syenite Zone in which mafic melasyenite is mixed and mingled with leucosyenite and a Massive Leucosyenite Zone. Within the Mixed Syenite Zone, hydrothermal activity is evident in the form of narrow altered veins dominated by biotite and magnetite; these are poorly exposed and their lateral extent is uncertain. The REE mineral allanite is relatively abundant in the melasyenite and is extremely enriched in the biotite-magnetite veins, which have up to 2 % total rare earth oxides in bulk rock analyses. An overall model for development of this intrusion can be divided into three episodes: (1) generation of a Light Rare Earth Element (LREE)-enriched parental magma due to enrichment of the mantle source by subduction of pelagic carbonates; (2) early crystallisation of allanite in melasyenite, due to the saturation of the magma in the LREE; and (3) hydrothermal alteration, in three different episodes identified by petrography and mineral chemistry, generating the intense enrichment of REE in the biotite-magnetite veins. Dating of allanite and titanite in the biotite-magnetite veins gives ages of c. 426 Ma, overlapping with previously published crystallisation ages for zircon in the syenite.

show abstract

“…Mineralogical evidences suggest that REEs can be mobilized in a very limited degree (Wood and Ricketts 2000) due to the secondary mineralization during water-rock interactions. It is known that REEs can readily precipitate in various forms of minerals, among which phosphate minerals such as monazite, rhabdophane, or silica-phosphates such as, britholite are often considered as potential candidates to immobilize the long-lived radionuclides of the REEs and tri-and tetravalent actinides.…”

Section: Introductionmentioning

confidence: 99%

The influence of pH and temperature on the aqueous geochemistry of neodymium in near surface conditions

Çetiner

2008

Environ Monit Assess

View full text Add to dashboard Cite

Geochemical calculations were employed for the solubility and speciation of neodymium in a model soil solution as a function of pH. The calculations were based on the recently determined stability constants for Nd and solubility product for the Nd end-member of mineral monazite (NdPO(4)). Simulations were carried out at near neutral pH (pH 6.0 to pH 7.5) and 25 degrees C at the atmospheric CO(2) partial pressure. Additional calculations were also performed to assess Nd mobility at the extreme temperature conditions (300 degrees C) at neutral pH. Our results suggest that relatively dilute (Ionic Strength, I = 0.1), low-temperature waters may transport very small quantities of rare earth elements and actinides to the surficial environment at near neutral pH conditions. Evidently, higher temperature or extreme fluid composition may have a greater potential for mobilization of these elements. The results are pertinent to researchers interested in engineering applications for the precipitation of Nd and surrogate actinides from aqueous nuclear wastes.

show abstract

ALLANITE-(Ce) FROM THE EOCENE CASTO GRANITE, IDAHO: RESPONSE TO HYDROTHERMAL ALTERATION

Cited by 68 publications

References 43 publications

Stability and isotopic dating of monazite and allanite in partially molten rocks: examples from the Central Alps

Stability and isotopic dating of monazite and allanite in partially molten rocks: examples from the Central Alps

Enrichment of Rare Earth Elements during magmatic and post-magmatic processes: a case study from the Loch Loyal Syenite Complex, northern Scotland

The influence of pH and temperature on the aqueous geochemistry of neodymium in near surface conditions

Contact Info

Product

Resources

About