Topic
Feldspathoid
About: Feldspathoid is a research topic. Over the lifetime, 42 publications have been published within this topic receiving 1361 citations.
Papers
TL;DR: In this paper, the range of feldspathic igneous rocks using five geochemical variables: the FeO/(FeO þMgO) ratio or Fe-index, the modified alkali^lime index, the aluminum-saturation index, and the alkalinity index, were classified.
Abstract: In this paper we classify the range of feldspathic igneous rocks using five geochemical variables: the FeO/(FeO þMgO) ratio or Fe-index, the modified alkali^lime index, the aluminum-saturation index, the alkalinity index, and the feldspathoid silica-saturation index.The Fe-index distinguishes between melts that have undergone extensive iron enrichment during differentiation from those that have not. The transition from tholeiite to ferrobasalt allows us to extend this boundary to silica values as low as 48 wt %. We introduce the feldspathoid silica-saturation index, which, coupled with the alkalinity index, allows us to extend the geochemical classification to alkaline rocks. We show that most alkaline rocks are ferroan and that this probably reflects extensive fractional crystallization of olivine and pyroxene with minimal participation of Fe^Ti oxides. The expanded classification allows us to illustrate the geochemical and petrogenetic relationship of the plutonic rocks from ferroan granites to nepheline syenites that commonly occur in intracratonic environments. It also allows us to distinguish four families of feldspathic rocks: (1) magnesian rocks, which are exemplified by Caledonian and Cordilleran batholiths and are characterized by differentiation under oxidizing and relatively hydrous conditions; (2) ferroan rocks, which include fayalite granites, alkali granites, and nepheline syenites and are characterized by differentiation under reducing and relatively dry conditions; (3) leucogranites, which commonly form by crustal melting; (4) potassic and ultrapotassic rocks, which originate from mantle that has been enriched in K2O.
548 citations
TL;DR: In this article, the authors compare the geochemical and mineralogical characteristics of rare earth elements (REEs) mineralization in carbonatites, peralkaline feldspathoid rocks, and granites, and find that the differences in the extent of postmagmatic reworking of primary REE minerals by hydrothermal fluids reflect different sources and evolutionary pathways of their parental magmas.
Abstract: Deposits of rare earth elements (REEs) in igneous rocks have played an instrumental role in meeting the growing industrial demand for these elements since the 1960s. Among the many different igneous rocks containing appreciable concentrations of REEs, carbonatites and peralkaline silicate rocks are the most important sources of these elements, both historically and for meeting the anticipated growth in REE demand. The contrasting geochemical and mineralogical characteristics of REE mineralization in carbonatites, peralkaline feldspathoid rocks, and peralkaline granites reflect different sources and evolutionary pathways of their parental magmas, as well as differences in the extent of postmagmatic reworking of primary REE minerals by hydrothermal fluids.
240 citations
TL;DR: In this paper, the infrared spectra in the 300-1400 cm−1 region indicate that the non-crystalline products of interaction between hydroxyaluminium species and orthosilicic acid in dilute aqueous solutions of pH 6.5 have an infrared spectrum similar to imogolite, and are termed hydrous feldspathoids.
192 citations
TL;DR: In this article, the authors defined two classes of alkaline rocks: those relatively rich in soda, in potash, or in both; and those which, with relatively low total of alkalies, yet carry essential amounts of minerals specially characteristic of alkali-rich eruptives, such as nephelite, leucite, analcite, etcetera.
Abstract: Definition Alkaline rocks include two classes: first, those relatively rich in soda, in potash, or in both; and, secondly, those which, with relatively low total of alkalies, yet carry essential amounts of minerals specially characteristic of alkali-rich eruptives, such as nephelite, leucite, analcite, etcetera. Field (genetic) association is also a criterion generally used in separating any alkaline type from the subalkaline or lime-alkali group of igneous rocks. Thus, monzonite may not be rich in alkalies nor carry any feldspathoid, yet it is regarded as of the alkaline group largely because it is often in comagmatic relation to nephelite syenite or the alkaline feldspar syenites. For the same reason, camptonite, alnoite, limburgite, and melilite basalt with, on the average, only 4.1 to 5.4 per cent of alkalies for each, are considered as belonging in the alkaline groups, though no feldspathoid is an essential constituent of any one of these rocks. On . . .
66 citations
Book•
1 Jan 1984
TL;DR: In this article, the average structures of Alkali and Plagioclase Feldspars are analyzed and compared to real Feldspathoids and their average and real structures.
Abstract: Feldspars.- 1. Average Structures of Alkali and Plagioclase Feldspars : Systematics and Applications.- 2. Phase Relations of Plagioclase Feldspars.- 3. The Modulated Structure of the Intermediate Plagioclases and Its Change with Composition.- 4. Spectroscopy of Feldspars.- 5. Thermal Expansion of Alkali Feldspars.- 6. Mechanical Properties of Feldspars.- 7. The Exchange Equilibrium Distribution of Alkali and Alkaline-Earth Elements Between Feldspars and Hydrothermal Solutions.- 8. Alkali Feldspar Exsolution : Kinetics and Dependence on Alkali Interdiffusion.- 9. Feldspars and the Thermal History of Igneous Rocks.- 10. Transmission Electron Microscope Investigations of the Microstructures of Microclines.- 11. Massif Anorthosites : Another Partisan Review.- Feldspathoids.- 12. Feldspathoids : Their Average and Real Structures.- 13. Feldspathoid Stabilities and Phase Inversions - A Review.- 14. Chemistry, Occurrence and Paragenesis of Feldspathoids : A Review.
46 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
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| 2021 | 1 |
| 2020 | 3 |
| 2019 | 1 |
| 2017 | 1 |
| 2015 | 4 |
| 2014 | 3 |