Chemical and structural study of the Zr, Ti-disilicates in the venanzite from Pian di Celle, Umbria, Italy

Bellezza, Marco; Merlino, Stefano; Perchiazzi, Natale

doi:10.1127/0935-1221/2004/0016-0957

Cited by 16 publications

(15 citation statements)

References 27 publications

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“…Niocalite is a monoclinic disilicate mineral belonging to the låvenite−cuspidine group, and is a rare accessory mineral in carbonatite, nepheline syenite, and metamorphosed carbonatite (Bellezza et al 2004, Casillas et al 2008. The minerals belonging to the låvenite−cuspidine group are important repositories for high field strength elements (HFSEs), specifically Nb, Zr, and Ti (Chakhmouradian et al 2008).…”

Section: Introductionmentioning

confidence: 99%

“…The minerals belonging to the låvenite−cuspidine group are important repositories for high field strength elements (HFSEs), specifically Nb, Zr, and Ti (Chakhmouradian et al 2008). The general chemical formula for this group is M 16 (Si 2 O 7 ) 4 (O,OH,F) 8 (Bellezza et al 2004, Merlino & Perchiazzi 1988, where M represents sites for cations with coordination number from VI to VIII; this includes high-charge and small-radius cations (e.g., Nb 5+ , Zr 4+ , Ti 4+ , REE 3+ , Mn 2+ , Fe 2+ ), and low-charge and large-radius Ca 2+ and Na + cations. Detailed chemical formulae of the låvenite-cuspidine group minerals are listed in Bellezza et al (2004).…”

Section: Introductionmentioning

confidence: 99%

“…The general chemical formula for this group is M 16 (Si 2 O 7 ) 4 (O,OH,F) 8 (Bellezza et al 2004, Merlino & Perchiazzi 1988, where M represents sites for cations with coordination number from VI to VIII; this includes high-charge and small-radius cations (e.g., Nb 5+ , Zr 4+ , Ti 4+ , REE 3+ , Mn 2+ , Fe 2+ ), and low-charge and large-radius Ca 2+ and Na + cations. Detailed chemical formulae of the låvenite-cuspidine group minerals are listed in Bellezza et al (2004). The crystal structure for this group consists of a wall of edge-sharing Ca(O,F) n polyhedra ('octahedral') parallel to the c-axis and the diorthosilicate groups, which are corner-linked to the walls (Merlino & Perchiazzi 1988).…”

Section: Introductionmentioning

confidence: 99%

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A Combined Geochemical and Geochronological Investigation of Niocalite From the Oka Carbonatite Complex, Canada

2013

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This study is the first to report a detailed geochemical investigation and in situ U-Pb ages for niocalite, which occurs within carbonatite from the Bond Zone area of the Oka Carbonatite Complex (Canada). Niocalite is a Nb-disilicate member of the låvenite−cuspidine group. The major element composition of the niocalite studied here is relatively homogeneous with the average formula of: (Na . Niocalite is enriched in minor and trace elements [i.e., Ta, Ti, and rare earth elements (REEs) up to 4.35 wt.%], with double-and triple-valenced elements (i.e., Sr, Y, REEs) substituting at different Ca-occupied lattice sites. The chondrite-normalized REE patterns for niocalite are LREE-enriched (~10 4 times chondrite) and negatively sloped. In addition, niocalite has higher HREE contents compared to those for co-existing apatite from the identical carbonatite sample. This result is expected based on bond valence data because of differing cation sizes. In situ U-Pb ages for niocalite from three carbonatite samples obtained by LA-ICP-MS define a wide range of ages, between ~111 and ~133 Ma. Niocalite from one carbonatite sample yields a bimodal distribution with weighted mean 206 Pb/ 238 U ages of 110.1 ± 5.0 Ma and 133.2 ± 6.1 Ma, and overlap those of co-existing apatite for the same sample. Two other samples of carbonatite yield weighted mean 206 Pb/ 238 U ages of 110.6 ± 1.2 Ma and 115.0 ± 1.9 Ma. The geochronological data for niocalite reported here suggests a protracted petrogenetic history for Oka, which corroborates the relatively large range of ages (~20 Myr) previously determined for apatite from the Oka complex. In situ 87 Sr/ 86 Sr isotope ratios for niocalite obtained by LA-MC-ICP-MS are variable and range between 0.70314 (±7) and 0.70343 (±8). Based on the combined U-Pb ages, major and trace element abundances, and Sr isotope ratios, the history of niocalite formation cannot be attributed to either simple closed-system fractional crystallization or carbonate-silicate liquid immiscibility. Rather, these are consistent with periodic carbonatite melt derivation from a heterogeneous mantle source, and suggest that some of niocalite investigated here represent cognate crystals.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Combined Geochemical and Geochronological Investigation of Niocalite From the Oka Carbonatite Complex, Canada

2013

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“…Minerals of this group have complex general formulas with high HFSE and REE as well as Mn, Fe, Na, and Ca [46][47][48], and include the wöhlerite and rinkite groups.…”

Section: Na-zr-ti Sorosilicatesmentioning

confidence: 99%

Nb and REE Distribution in the Monte Verde Carbonatite–Alkaline–Agpaitic Complex (Angola)

et al. 2019

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The Angolan alkaline–carbonatite complex of Monte Verde has a semi-circular shape and is comprised of a central intrusion of foidolite rocks surrounded by concentrically arranged minor bodies of other alkaline rocks and carbonatite magmatic breccias. This rock association is hosted by fenitized Eburnean granites. Concentric swarms of alkaline dykes of late formation, mostly of nepheline trachyte composition, crosscut the previous units. Most high-field strength elements (HFSE) and rare earth elements (REE) are concentrated in pyrochlore crystals in the carbonatite and alkaline breccias. Magmatic fluornatropyrochlore is replaced and overgrown by five secondary generations of pyrochlore formed during subsolidus stages and have higher Th, REE, Si, U, Sr, Ba, Zr, and Ti contents. The second, third, and fourth pyrochlore generations are associated with late fluids also producing quartz and REE rich minerals; whereas fifth and sixth pyrochlore generations are linked to the fenitization process. On the other hand, minerals of the rinkite, rosenbuschite, wöhlerite, eudialyte groups, as well as loparite-(Ce), occur in accessory amounts in nepheline trachyte, recording low to moderate agpaicity. In addition, minor REE-bearing carbonates, silicates, and phosphates crystallize as late minor secondary minerals into carbonatite breccia and alkaline dykes. In conclusion, the scarcity of HFSE and REE minerals at the Monte Verde carbonatite-alkaline-agpaitic complex suggests low metallogenetic interest and economic potential for the outcrops analysed in this study. However, the potential for buried resources should not be neglected.

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“…Some insufficiently studied phases of melilitolite include Ca-Fe-H 2 O-and Mg-H 2 O-silicates, a macdonaldite-like mineral, a hydrodelhayelite-like mineral and a CuFe sulphide [16]. Abundant large ocelli of calcite (up to vol.20% of the rock) and green or brown silicate glass are an important constituent of the rock [11,12,[16][17][18]. Crystallisation order: chromian spinel, perovskite ≈ olivine, nepheline, melilite ≈ apatite, magnetite, leucite, phlogopite, clinopyroxene ≈ kalsilite, götzenite, REE-rich perovskite, cuspidine, calcite ≈ khibinskite, sulphides, umbrianite, delhayelite, macdonaldite ≈ Ca-Fe-hydrosilicate ≈zeolites.…”

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confidence: 99%

Extreme chemical conditions of crystallisation of Umbrian Melilitolites and wealth of rare, late stage/hydrothermal minerals

Stoppa

Schiazza

2014

Open Geosciences

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Melilitolites of the Umbria Latium Ultra-alkaline District display a complete crystallisation sequence of peculiar, late-stage mineral phases and hydrothermal/cement minerals, analogous to fractionated mineral associations from the Kola Peninsula. This paper summarises 20 years of research which has resulted in the identification of a large number of mineral species, some very rare or completely new and some not yet classified. The progressive increasing alkalinity of the residual liquid allowed the formation of Zr-Ti phases and further delhayelitemacdonaldite mineral crystallisation in the groundmass. The presence of leucite and kalsilite in the igneous assemblage is unusual and gives a kamafugitic nature to the rocks. Passage to non-igneous temperatures (T<600 • C) is marked by the metastable reaction and formation of a rare and complex zeolite association (T<300 • C). Circulation of low-temperature (T<100 • C) K-Ca-Ba-CO 2 -SO 2 -fluids led to the precipitation of sulphates and hydrated and/or hydroxylated silicate-sulphate-carbonates. As a whole, this mineral assemblage can be considered typical of ultra-alkaline carbonatitic rocks.

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Chemical and structural study of the Zr, Ti-disilicates in the venanzite from Pian di Celle, Umbria, Italy

Cited by 16 publications

References 27 publications

A Combined Geochemical and Geochronological Investigation of Niocalite From the Oka Carbonatite Complex, Canada

A Combined Geochemical and Geochronological Investigation of Niocalite From the Oka Carbonatite Complex, Canada

Nb and REE Distribution in the Monte Verde Carbonatite–Alkaline–Agpaitic Complex (Angola)

Extreme chemical conditions of crystallisation of Umbrian Melilitolites and wealth of rare, late stage/hydrothermal minerals

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