The Mineralogical Diversity of Alkaline Igneous Rocks: Critical Factors for the Transition from Miaskitic to Agpaitic Phase Assemblages
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In this paper, the authors discuss two important aspects of the mineralogical evolution of peralkaline plutonic rocks and discuss the transition from miaskitic to agpaitic.Abstract:
Geochemically, the large family of alkaline plutonic rocks (both Qtz-undersaturated and -oversaturated compositions) can be subdivided into metaluminous [(Na
2
O + K
2
O) < Al
2
O
3
] and peralkaline [(Na
2
O + K
2
O) > Al
2
O
3
] types. In this paper, we discuss two important aspects of the mineralogical evolution of such rocks. With respect to their Fe–Mg phases, a major mineralogical transition observed is the precipitation of arfvedsonite or aegirine instead of fayalite or magnetite (± ilmenite). The relative stability of these phases is controlled by oxygen fugacity and Na activity in the crystallizing melts. If Na activity in the melt is high enough, arfvedsonite + aegirine form a common assemblage in peralkaline rocks under both reduced and oxidized conditions. Major mineralogical differences within this rock group exist with respect to their high field strength element (HFSE)-rich minerals: most syenitic rocks, known as miaskites, contain zircon, titanite or ilmenite as HFSE-rich minerals, whereas in agpaites complex Na–K–Ca–(Ti, Zr) silicates incorporate the HFSE. Similarly, only a small group of peralkaline granites are found to lack zircon, titanite or ilmenite but instead contain Na–K–Ca–(Ti, Zr) silicates. Here, we present a detailed phase petrological analysis of the chemical parameters (µNa
2
O, µCaO, µK
2
O) that influence the transition from miaskitic to agpaitic rocks. Based on the occurrence of Ti and Zr minerals, several transitional mineral assemblages are identified and two major evolution trends for agpaites are distinguished: a high-Ca trend, which is exemplified by the alkaline rocks of the Kola Province, Russia, and a Ca-depletion trend, which is displayed by the alkaline rocks of the Gardar Province, South Greenland. Both trends show significant Na-enrichment during magmatic evolution. High-Ca agpaites evolve from nephelinitic parental melts that did not crystallize large amounts of plagioclase. In contrast, agpaites showing Ca-depletion originate by extensive fractionation of plagioclase from basaltic parental melts. In some peralkaline granites evolutionary trends are observed that culminate in agpaite-like HFSE-mineral associations in the most evolved rocks.read more
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The Rare Earth Elements: demand, global resources, and challenges for resourcing future generations
TL;DR: In this paper, the balance of the individual rare earth elements (REE) in each deposit type and how that matches demand is considered, and some of the issues associated with developing these deposits are discussed.
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Europe's rare earth element resource potential: An overview of REE metallogenetic provinces and their geodynamic setting
Kathryn Goodenough,J. Schilling,Erik Jönsson,Erik Jönsson,Per Kalvig,Nicolas Charles,Johann Tuduri,Eimear Deady,Martiya Sadeghi,Henrik Schiellerup,Axel H. E. Müller,Guillaume Bertrand,Nikolaos Arvanitidis,D. G. Eliopoulos,Richard Shaw,Kristine Thrane,Nynke Keulen +16 more
TL;DR: In this article, the potential geological resources of rare earth elements (REE) in Europe are investigated, and the most important European resources are associated with alkaline igneous rocks and carbonatites, although REE deposits are also known from a range of other settings.
Journal ArticleDOI
A global review on agpaitic rocks
Michael A.W. Marks,Gregor Markl +1 more
TL;DR: A review on agpaitic rocks can be found in this article, where the authors provide a summary of the fluid inclusion record of miaskitic and ag paitic assemblages as fluids play a key role in the evolution of peralkaline rocks.
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Evidence of crystallization in residual, Cl–F-rich, agpaitic, trachyphonolitic magmas and primitive Mg-rich basalt–trachyphonolite interaction in the lava domes of the Phlegrean Fields (Italy)
TL;DR: The Cuma and Punta Marmolite trachyphonolitic lava domes are among the oldest Phlegrean products cropping out as mentioned in this paper, and the bulk-rock compositions at Cuma have some of the highest concentrations of Zn, Mn, Zr, Nb, Th, U and lanthanides.
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Geology and market-dependent significance of rare earth element resources
TL;DR: In this paper, the authors proposed that the ideal rare earth element (REE) development targets would be located in a politically stable jurisdiction with a pro-mining disposition such as Canada and Australia.
References
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BookDOI
Igneous Rocks: A Classification and Glossary of Terms
TL;DR: In this paper, Streckeisen presents a glossary of terms and a bibliography of terms of terms for classification and nomenclature of terms in the first edition of the book.
Journal ArticleDOI
On Ferroan (A-type) Granitoids: their Compositional Variability and Modes of Origin
Carol D. Frost,B. Ronald Frost +1 more
TL;DR: In this paper, eight types of ferroan granitoid can be distinguished on the basis of major element chemistry, including calc-alkalic and peraluminous granitoids.
Journal ArticleDOI
Zircon saturation in felsic liquids : Experimental results and applications to trace element geochemistry
TL;DR: For peraluminous melts and melts lying in the quartz-orthoclase-albite composition plane, less than 100 ppm Zr is required for zircon saturation as mentioned in this paper.