The Pariquera Açu K-alkaline complex and southern Brazil lithospheric mantle source characteristics

Morbidelli, L.; Gomes, Celso B.; Brotzu, P.; D’Acquarica, S.; Garbarino, Carlo; Ruberti, Excelso; Traversa, G.

doi:10.1016/s1367-9120(99)00028-0

Cited by 27 publications

(18 citation statements)

References 26 publications

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“…To reach a syenite composition starting from the basanite would require the fractionation of ~7 wt% olivine, ~24 wt% clinopyroxene, ~22 wt% plagioclase, ~13 wt% spinel, and ~3 wt% apatite (~65% fractionation of solid phases; Table 2). Although outcrops of gabbroic cumulates that could corroborate the fractionation models are lacking in Búzios, it should be noted that these types of rocks crop out on the neighboring islands of Monte de Trigo ) and São Sebastião (Bellieni et al 1990) and are also very common in several other alkaline districts from Southeastern Brazil, such as Jacupiranga, Juquiá and Pariquera-Açu (Morbidelli et al 2000;Gomes et al 2011) and Ponte Nova (Azzone et al 2013.…”

Section: Petrologymentioning

confidence: 97%

Geochemistry and petrology of the Búzios Island alkaline massif, SE, Brazil

et al. 2017

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ABSTRACT:The Late Cretaceous Búzios Island alkaline massif intrudes Precambrian charnockites and consists dominantly of syenitic rocks that are cut by a large number of dikes, mostly NE-trending, and representing two distinct suites, a felsic one and a mafic-ultramafic one. Alkali feldspar is the most abundant mineral; other constituents are clinopyroxene, commonly replaced by amphibole/ biotite, and opaques. Accessory minerals include occasionally rare phases bearing Zr, Ti, Nb and Rare Earth Elements (REE). The felsic dikes may also have nepheline (sodalite). The mafic-ultramafic suite, in particular the lamprophyres, shows a primary mineral assemblage with olivine, clinopyroxene and amphibole in addition to a groundmass having glassy material and carbonates (ocelli). The Búzios rocks are chemically evolved, mostly of potassic affinity and mainly belong to the miaskitic series. Variation diagrams for major and trace elements show a bimodal distribution, suggesting an origin from different magmatic pulses. The rocks are interpreted as having been derived by fractional crystallization processes from a basanitic parental magma. The SiO 2 -undersaturated and SiO 2 -oversaturated associations present in the massif are apparently not linked to a single magmatic source, and in the petrogeny residual system two trends are evident: the first one towards the phonolitic minimum and the second one towards the rhyolitic minimum, possibly pointing to amphibole fractionation.KEYWORDS: Igneous petrology; Alkaline rocks; Geochemistry. RESUMO: O maciço alcalino da Ilha dos Búzios, do Cretáceo Superior, é intrusivo em charnockitos precambrianos e consiste predominantemente de rochas sieníticas cortadas por grande número de diques, orientados preferencialmente para NE, representando duas suítes distintas: félsica e máfica-ultramáfica. Feldspato alcalino é o mineral mais abundante; outros constituintes são clinopiroxênio, comumente substituído por anfibólio/biotita, e opacos. Minerais acessórios incluem ocasionalmente fases raras contendo Zr, Ti, Nb e elementos terras raras (ETR). Os diques félsicos podem possuir também nefelina (sodalita). A suíte máfica-ultramáfica, particularmente os lamprófiros, apresenta uma assembleia mineralógica primária com olivina, clinopiroxênio e anfibólio, além de massa fundamental com material vítreo e carbonatos (ocelli

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Section: Petrologymentioning

confidence: 97%

Geochemistry and petrology of the Búzios Island alkaline massif, SE, Brazil

et al. 2017

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“…These rocks are believed to represent the least evolved magmas in the area. In the case of the Early Cretaceous mafic occurrences, ankaratrite is considered to be representative of the parental magma composition for Jacupiranga whereas basanite for Juquiá, PariqueraeAçu and Tunas complexes (Morbidelli et al, 1995(Morbidelli et al, , 2000Ruberti et al, 2005).…”

Section: Fine-grained Rocks (Dikes)mentioning

confidence: 99%

Alkaline magmatism in the Ponta Grossa Arch, SE Brazil: A review

Gomes

Ruberti

Comin-Chiaramontí

et al. 2011

Journal of South American Earth Sciences

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“…The alkaline rocks of this intrusion have not been dated radiometrically; but Morbidelli et al (2000) suggested that based on geological and petrological comparisons with Jacupiranga and Juquiá, as well as structural context, the intrusion must exhibit an age close to 130 My.…”

Section: Resultsmentioning

confidence: 99%