Química Mineral E Evolução Petrológica Do Sienito Piquiri: Magmatismo Shoshonítico, Neoproterozóico, Pós-Colisional No Sul Do Brasil

Stabel, Larissa Zitto; Nardi, Lauro Valentim Stoll; Cid, Jorge Plá

doi:10.25249/0375-7536.200131221122

Cited by 16 publications

(23 citation statements)

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“…They have been reported by several authors (e.g. Holm et al 1982, Thompson and Fowler 1986, Laflèche et al 1991, Corriveau and Gorton 1993, Janasi et al 1993, Eklund et al 1998, Stabel et al 2001, particularly in one of the largest syenitic provinces in the world, situated in northeastern and eastern Brazil (e.g. Silva Filho et al 1987, Ferreira and Sial 1993, Conceição 1993, Plá Cid et al 1999, Conceição et al 2000a.…”

Section: Introductionmentioning

confidence: 88%

“…The fine-to medium-grained syenites and quartzmonzonites are petrographically distinct from the dominant alkali feldspar syenites due to their finer texture, to the presence of quartz and preserved plagioclase crystals, and potassic feldspar with perthite contents lower than 25 vol% (Stabel et al 2001). Diopside is the dominant pyroxene, whilst in the dominant alkali feldspar syenites, augite is more abundant.…”

Section: Geology Of the Piquiri Syenite Massifmentioning

confidence: 94%

“…Plagioclase from the alkali feldspar syenites occurs mostly as partially resorbed inclusions in alkali feldspar, as discussed by Nekvasil (1990) for similar syenitic compositions. Stabel et al (2001) interpreted the fine-to medium-grained rocks as co-magmatic with the alkali feldspar syenites, resulting from rapidlycrystallized liquids of compositions close to the parental magma. The phlogopite-bearing alkali feldspar syenites were found in drill cores, intimately associated with lamprophyric rocks.…”

Section: Geology Of the Piquiri Syenite Massifmentioning

confidence: 99%

“…Potassic and ultrapotassic syenitic or trachytic rocks from post-orogenic or postcollisional settings have been described by several authors (e.g. Civetta et al 1981, Holm et al 1982, Thompson and Fowler 1986, Silva Filho et al 1987, Nardi and Bonin 1991, Ferreira and Sial 1993, Conceição 1993, 2000a, Eklund et al 1998, Plá Cid et al 1999, Sommer et al 1999, Wildner et al 1999, Miller et al 1999, Stabel et al 2001, Ilbeyli et al 2004, and in some Archaean terranes (Laflèche et al 1991, Bourne and L'Heureux 1991, Corriveau and Gorton 1993. Pliocene ultrapotassic lavas and minettes in a typical post-collisional setting have been described in Sierra Nevada, California, by Feldstain and Lange (1999).…”

Section: Introductionmentioning

confidence: 99%

“…In many cases, they are related to minettes (Leat et al 1989, Stabel et al 2001, Paim et al 2002, Plá Cid et al 2005, among other authors).…”

Section: Introductionmentioning

confidence: 99%

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Geochemistry and petrogenesis of post-collisional ultrapotassic syenites and granites from southernmost Brazil: the Piquiri Syenite Massif

Nardi

Plá-Cid

Bitencourt

et al. 2008

An. Acad. Bras. Ciênc.

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The Piquiri Syenite Massif, southernmost Brazil, is part of the post-collisional magmatism related to the Neoproterozoic Brasiliano-Pan-African Orogenic Cycle. The massif is about 12 km in diameter and is composed of syenites, granites, monzonitic rocks and lamprophyres. Diopside-phlogopite, diopside-biotite-augite-calcic-amphibole, are the main ferro-magnesian paragenesis in the syenitic rocks. Syenitic and granitic rocks are co-magmatic and related to an ultrapotassic, silica-saturated magmatism. Their trace element patterns indicate a probable mantle source modified by previous, subduction-related metasomatism. The ultrapotassic granites of this massif were produced by fractional crystallization of syenitic magmas, and may be considered as a particular group of hypersolvus and subsolvus A-type granites. Based upon textural, structural and geochemical data most of the syenitic rocks, particularly the fine-grained types, are considered as crystallized liquids, in spite of the abundance of cumulatic layers, schlieren, and compositional banding. Most of the studied samples are metaluminous, with K 2 O/Na 2 O ratios higher than 2. The ultrapotassic syenitic and lamprophyric rocks in the Piquiri massif are interpreted to have been produced from enriched mantle sources, OIB-type, like most of the post-collisional shoshonitic, sodic alkaline and high-K tholeiitic magmatism in southernmost Brazil. The source of the ultrapotassic and lamprophyric magmas is probably the same veined mantle, with abundant phlogopite + apatite + amphibole that reflects a previous subduction-related metasomatism.

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