An overview of monogenetic carbonatitic magmatism from Uganda, Italy, China and Spain: Volcanologic and geochemical features

Stoppa, Francesco; Schiazza, Mariangela

doi:10.1016/j.jsames.2012.10.004

Cited by 45 publications

(24 citation statements)

References 73 publications

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“…Ap/crb D Zr = 1.6-2.2 and Ap/crb D Nb  0.1), apatite fractionation would lead to appreciable changes in the Rb and HFSE budget of the evolving carbonatitic magma. Simple calculations based on the composition of primitive carbonatitic magmas worldwide (Rilley et al, 1998;Ying et al, 2004;Chakhmouradian et al, 2009;Eby et al, 2009;Stoppa and Schiazza, 2013) show that apatites with tens of ppm Rb and Nb and a few hundred ppm Zr should be common in these rocks, which is clearly not the case (Mao et al, 2016; this work). Thus, our data indicate that apatite has a negligible effect on the fate of Rb or HFSE in natural magmas and that the Ap/crb D Rb and Ap/crb D HFSE values of Hammouda et al (2010) are overestimated and should not be used to model natural systems.…”

Section: Apatite Fractionation and Its Effects On Carbonatite Evolutionmentioning

confidence: 76%

Apatite in carbonatitic rocks: Compositional variation, zoning, element partitioning and petrogenetic significance

Chakhmouradian

Reguir

Zaitsev

et al. 2017

Lithos

178

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Apatite-group phosphates are nearly ubiquitous in carbonatites, but our understanding of these minerals is inadequate, particularly in the areas of element partitioning and petrogenetic interpretation of their compositional variation among spatially associated rocks and within individual crystals. In the present work, the mode of occurrence, and major-and trace-element chemistry of apatite (sensu lato) from calcite and dolomite carbonatites, their associated cumulate rocks (including phoscorites) and hydrothermal parageneses were studied using a set of 80 samples from 50 localities worldwide. The majority of this set represents material for which no analytical data are available in the literature. Electron-microprobe and laser-ablation mass-spectrometry data (~600 and 400 analyses, respectively), accompanied by back-scattered-electron and cathodoluminescence images and Raman spectra, were used to identify the key compositional characteristics and zoning patterns of carbonatitic apatite. These data are placed in the context of phosphorus geochemistry in carbonatitic systems and carbonatite evolution, and compared to the models proposed by previous workers. The documented variations in apatite morphology and zoning represent a detailed record of a wide range of evolutionary processes, both magmatic and fluid-driven. The majority of igneous apatite from the examined rocks is Cl-poor fluorapatite or F-rich hydroxylapatite ( 0.3 apfu F) with 0.2-2.7 wt.% SrO, 0-4.5 wt.% LREE 2 O 3 , 0-0.8 wt.% Na 2 O, and low levels of other cations accommodated in the Ca site (up to 1000 ppm Mn, 2300 ppm Fe, 200 ppm Ba, 150 ppm Pb, 700 ppm Th and 150 ppm U), none of which show meaningful correlation with the host-rock type. Silicate, (SO 4) 2and (VO 4) 3anions, substituting for (PO 4) 3-, tend to occur in greater abundance in crystals from calcite carbonatites (up to 4.2 wt.% SiO 2 , 1.5 wt.% SO 3 and 660 ppm V). Although (CO 3) 2groups are very likely present in some samples, Raman micro-spectroscopy proved inconclusive for apatites with small P-site deficiencies and other substituent elements in this site. Indicator REE ratios sensitive to redox conditions (Ce, Eu) and hydrothermal overprint (Y) form a fairly tight cluster of values (0.8-1.3, 0.8-1.1 and 0.6-0.9, respectively) and may be used in combination with trace-element abundances for the development of geochemical exploration tools. Hydrothermal apatite forms in carbonatites as the product of replacement of primary apatite, or is deposited in fractures and interstices as euhedral crystals and aggregates associated with typical late-stage minerals (e.g., quartz and chlorite). Hydrothermal apatite is typically depleted in Sr, REE, Mn and Th, but enriched in F (up to 4.8 wt.%) relative to its igneous precursor, and also differs from the latter in at least some of key REE ratios [e.g., shows (La/Yb) cn  25, or a negative Ce anomaly]. The only significant exception is Sr(REE,Na)-rich replacement zones and overgrowths on igneous apatite from some dolomite(-bearing) carbonati...

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Section: Apatite Fractionation and Its Effects On Carbonatite Evolutionmentioning

confidence: 76%

Apatite in carbonatitic rocks: Compositional variation, zoning, element partitioning and petrogenetic significance

Chakhmouradian

Reguir

Zaitsev

et al. 2017

Lithos

178

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“…Young rocks emplaced extrusively or near the surface and unaffected by postmagmatic processes exhibit a variety of readily recognizable textures. Their characterization is beyond the scope of the present work; interested readers are addressed to the reviews and case studies by Keller (1989), Mitchell (1997), Zaitsev et al (2008), Eby et al (2009), Stoppa and Schiazza (2013). Recognition and petrogenetic analysis of old and/or deformed intrusive carbonatites generally requires detailed knowledge of their trace-element and isotopic characteristics (e.g., Fig.…”

Section: Interpretation Of Carbonatite Textures: Challenges and Limitmentioning

confidence: 99%

Calcite and dolomite in intrusive carbonatites. I. Textural variations

2015

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Carbonatites are nominally igneous rocks, whose evolution commonly involves also a variety of postmagmatic processes, including exsolution, subsolidus re-equilibration of igneous mineral assemblages with fluids of different provenance, hydrothermal crystallization, recrystallization and tectonic mobilization. Petrogenetic interpretation of carbonatites and assessment of their mineral potential are impossible without understanding the textural and compositional effects of both magmatic and postmagmatic processes on the principal constituents of these rocks. In the present work, we describe the major (micro)textural characteristics of carbonatitic calcite and dolomite in the context of magma evolution, fluid-rock interaction, or deformation, and provide information on the compositional variation of these minerals and its relation to specific evolutionary processes.

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“…Commonly, those lapilli contain at their centres a single, relatively large euhedral crystal or crystal fragment. These cores or kernels typically consist of olivine and, more rarely, phlogopite, clinopyroxene (Stoppa et al, 2000;Stoppa and Schiazza, 2013), titaniferous magnetite (Campeny et al, 2014) or also country rock microxenoliths (Rosatelli et al, 2003;Campeny et al, 2014). Mantles, or rims, are composed of fine-grained microphenocryst material in which prismatic minerals are commonly flow-aligned (e.g., Mitchell, 1997).…”

Section: Introductionmentioning

confidence: 99%

Silicate glass micro and nanospherules generated in explosive eruptions of ultrabasic magmas: Implications for the origin of pelletal lapilli

Sánchez

Sarrionandia

Aróstegui

et al. 2015

Journal of Volcanology and Geothermal Research

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An overview of monogenetic carbonatitic magmatism from Uganda, Italy, China and Spain: Volcanologic and geochemical features

Cited by 45 publications

References 73 publications

Apatite in carbonatitic rocks: Compositional variation, zoning, element partitioning and petrogenetic significance

Apatite in carbonatitic rocks: Compositional variation, zoning, element partitioning and petrogenetic significance

Calcite and dolomite in intrusive carbonatites. I. Textural variations

Silicate glass micro and nanospherules generated in explosive eruptions of ultrabasic magmas: Implications for the origin of pelletal lapilli

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