Mineralogy and geochemistry of a giant agpaitic magma reservoir: The Late Cretaceous Poços de Caldas potassic alkaline complex (SE Brazil)

Guarino, Vincenza; Lustrino, Michele; Zanetti, Alberto; Tassinari, Colombo Celso Gaeta; Ruberti, Excelso; Gennaro, Roberto de; Melluso, Leone

doi:10.1016/j.lithos.2021.106330

Cited by 15 publications

(45 citation statements)

References 58 publications

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“…The magmatic events dated~70-90 Ma [38,45] are the most abundant and widespread ones, assembling all the remaining Brazilian alkaline centers. They include rock bodies of agpaitic affinity, of which the Poços de Caldas [14,[58][59][60][61], Itatiaia [15,40,43], Passa Quatro [19,20], Bom Repouso [21], Monte de Trigo Island [25,62], Lages [63] and Búzios Island [64,65] suites are examples.…”

Section: Alkaline Magmatism In Southern Brazilian Platform: Background Informationmentioning

confidence: 99%

“…The bulk-rock major and trace element geochemistry of nepheline syenites and phonolites, with the marked presence of eudialyte, F-disilicates, aenigmatite and lamprophyllite, indicates the agpaitic affinity of these highly evolved melts. Unlike other agpaitic intrusions, a most peculiar feature in the Poços de Caldas is the absence of pure miaskitic rocks, because the prevailing nepheline syenites and phonolites are characterized by an assemblage showing the contemporaneous presence of minerals typical of miaskitic (e.g., zircon, baddeleyite and titanite) and agpaitic rocks (such as F-disilicates, eudialyte, aenigmatite and astrophyllite), [14] which are defined as a "transitional agpaitic" type, as proposed by [7]. The Poços de Caldas evolved melts are qualitatively derived from mafic-ultramafic melts via clinopyroxene removal in a prolonged fractional crystallization process.…”

Section: Poços De Caldasmentioning

confidence: 99%

“…One of the most remarkable characteristics of the Mesozoic-Cenozoic alkaline magmatism that took place in the southern portion of the Brazilian platform is the abundance of more evolved rock-types [14,15,19,20,[36][37][38][39][40][41]. Silicate alkaline rocks, the most abundant petrographic type present, include evolved nepheline syenites and syenites and their corre-sponding fine-grained varieties, forming large isolated, unique or composite intrusions or even multiple plutons.…”

Section: Introductionmentioning

confidence: 99%

“…Silicate alkaline rocks, the most abundant petrographic type present, include evolved nepheline syenites and syenites and their corre-sponding fine-grained varieties, forming large isolated, unique or composite intrusions or even multiple plutons. Main examples of these massifs are Poços de Caldas [14,42] and Itatiaia [15,43]. A small fraction of these evolved lithologies consists of agpaitic types, such as lujavrites (melanocratic-in this case, M > 30 vol.%-agpaitic variety of nepheline syenite rich in eudialyte, arfvedsonite and/or aegirine with a laminated structure), khibinites (a variety of eudialyte-nepheline syenite with aegirine, alkali amphibole and many accessory minerals, particularly those containing Ti and Zr) and eudialyte/aenigmatite phonolites [12,14,20,26].…”

Section: Introductionmentioning

confidence: 99%

“…Main examples of these massifs are Poços de Caldas [14,42] and Itatiaia [15,43]. A small fraction of these evolved lithologies consists of agpaitic types, such as lujavrites (melanocratic-in this case, M > 30 vol.%-agpaitic variety of nepheline syenite rich in eudialyte, arfvedsonite and/or aegirine with a laminated structure), khibinites (a variety of eudialyte-nepheline syenite with aegirine, alkali amphibole and many accessory minerals, particularly those containing Ti and Zr) and eudialyte/aenigmatite phonolites [12,14,20,26]. However, the amount of information available on the exotic accessory assemblage found in these agpaitic rocks is still limited.…”

Section: Introductionmentioning

confidence: 99%

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Agpaitic Alkaline Rocks in Southern Brazilian Platform: A Review

et al. 2021

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General information is presented on ten agpaitic occurrences located in southern Brazil and at the border between Brazil and Paraguay. All the Brazilian agpaitic rocks are Late Cretaceous in age, whereas the Paraguayan ones are older than Early Triassic. The most significant occurrence is Poços de Caldas, the largest alkaline massif in South America. In general, these agpaitic rocks contain mineral assemblages that indicate presence of typical halogen-bearing Na–Ca–HFSE phases, eudialyte-, rinkite- and wöhlerite-group minerals being the most frequent ones. However, these associations are indeed more complex in terms of composition, with accessory phases in some cases consisting of various minerals, including U–Th oxides/silicates, Nb oxides, REE–Sr–Ba bearing carbonates–fluorocarbonates–phosphates–silicates and Zr–Na rich silicates. They usually form late magmatic stage to hydrothermal/deuteric assemblages linked with coarse and fine-grained, mainly silica-undersaturated evolved rocks. Data also indicate significant differences in type, amount and composition of agpaitic minerals in all investigated occurrences.

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Section: Alkaline Magmatism In Southern Brazilian Platform: Background Informationmentioning

confidence: 99%

Section: Poços De Caldasmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Agpaitic Alkaline Rocks in Southern Brazilian Platform: A Review

et al. 2021

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Alkaline rocks of the Bobaomby volcanic field point to a petrogenetic link between Comoros and northern Madagascar lithosphere

Cucciniello

Grifa

de’Gennaro

et al. 2022

Int J Earth Sci (Geol Rundsch)

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The Bobaomby volcanic field (10–11 Ma) is the northernmost volcanic area of Madagascar, and is a monogenetic volcanic field comprising outcrops of lava flows, dykes, scoria cones, tuff rings and plugs, widely scattered over an area of roughly 500 km2. The volcanic rocks range in composition from nephelinite, basanite and tephrite, through tephritic phonolite, to F- and Cl-rich peralkaline phonolite (MgO from 13 to 0.01 wt%), and the serial affinity varies from sodic to potassic. A few mica-amphibole-rich lamprophyric dykes have tephritic composition and ultrapotassic affinity. The mafic lavas host intrusive xenoliths with evident cumulate features (wehrlites, composite olivine gabbros s.l., amphibole clinopyroxenites and “kaersutitites”), as well as various types of mantle-derived xenoliths and xenocrysts in the most primitive rocks. The very wide compositional variations of the observed phases (olivine, clinopyroxene, amphibole, oxides, feldspars, feldspathoids, apatite, titanite, aenigmatite and other accessories) in lavas, dykes and cognate xenoliths are fully consistent with the variable degree of differentiation of the host lavas/dykes, and pointing out to limited open-system or polybaric crystallization. The mafic lavas have marked enrichment in incompatible elements and light rare-earth element (LREE) (e.g., Lan/Ybn = 19–27), whereas concave REE patterns are found in the peralkaline phonolites, as a result of removal of accessory titanite starting from tephritic phonolite magmas. The gabbroic/ultramafic xenoliths are interpreted as crustal cumulates of basanitic and tephritic magmas. Several liquid lines of descent in the basanites and tephrites are evident from the trace-element distribution, and from the differing geochemistry of the evolved rocks. The isotopic compositions reach extreme values (e.g., 206Pb/204Pb = 20.065 in the ultrapotassic lamprophyre) when compared to the rest of the Cenozoic/Recent Madagascan volcanic rocks, but similar to those of the Comoros archipelago, suggesting analogies of mantle sources and enrichment processes in the lithosphere of this volcanic archipelago. The origin of the Bobaomby mafic rocks is compatible from a derivation from low degree partial melting of an incompatible element-enriched peridotite source (possibly located in the lowermost lithospheric mantle) rich in volatile-rich phases (pargasite, locally also phlogopite and possibly carbonates), matching the sources of other Cenozoic volcanic areas throughout Madagascar, and perhaps Comoros.

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Early Cretaceous ultramafic-alkaline-carbonatite magmatism in the Shillong Plateau-Mikir Hills, northeastern India – a synthesis

2022

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A comprehensive mineralogical, geochemical and isotopic review of six ultramafic-alkaline-carbonatite magmatic intrusions of the Shillong Plateau (Sung Valley, Jasra, Swangkre-Rongjeng, and Mawpyut) and Mikir Hills (Samchampi-Samteran and Barpung) is presented here, using the published data. These intrusions emplaced ca. 115–102 Ma ago, thus are significantly younger than the tholeiitic flood basalts erupted in Rajmahal-Sylhet province (ca. 118–115 Ma). The intrusive lithologies vary from ultramafic (dunites, clinopyroxenites, melilitolites) to mafic (ijolites, gabbros sensu lato, shonkinites), to felsic (syenites, nepheline syenites) and carbonatites (mostly calcite-rich varieties). The volcanic-subvolcanic facies (lamprophyres, phonolites) are not abundant. The range of chemical compositions of the magmatic phases in the various assemblages is notable; the intrusive rocks are thus the result of crystallization of magmas from variably evolved, independent liquid-lines-of descent, generally of alkaline/strongly alkaline lineages and sodic-to-potassic in affinity. The large variations of the Sr–Nd isotopic ratios of the silicate intrusive rocks (sensu lato) suggest a role of shallow-level crustal contamination during their formation. The carbonatites of the Sung Valley and Samchampi-Samteran have different isotope ratios than the associated silicate rocks, have some isotopic affinity with the Group I tholeiitic basalts of Rajmahal Traps and have an ultimate genesis in a carbonate-bearing lithospheric mantle.

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Mineralogy and geochemistry of a giant agpaitic magma reservoir: The Late Cretaceous Poços de Caldas potassic alkaline complex (SE Brazil)

Cited by 15 publications

References 58 publications

Agpaitic Alkaline Rocks in Southern Brazilian Platform: A Review

Agpaitic Alkaline Rocks in Southern Brazilian Platform: A Review

Alkaline rocks of the Bobaomby volcanic field point to a petrogenetic link between Comoros and northern Madagascar lithosphere

Early Cretaceous ultramafic-alkaline-carbonatite magmatism in the Shillong Plateau-Mikir Hills, northeastern India – a synthesis

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