Evolução Tectônica do Quadrilátero Ferrífero, Minas Gerais - Um Modelo

O presente trabalho tem como objetivo apresentar a evolução geológica do Quadrilátero Ferrífero (QF) cuja estruturação é bastante complexa. Essa estruturação resulta principalmente da ação de dois eventos deformacionais: o primeiro de caráter extensional e o segundo compressional, de idades do Proterozóico Inferior e Superior, respectivamente. O primeiro foi o responsável pela formação dos megassinclinais interconectados de Santa Rita, Dom Bosco, da Moeda e da Serra do Curral além dos soerguimentos dos complexos granito-gnáissicos de Santa Rita, Bonfim, do Bação, de Belo Horizonte e Caeté, os quais, em termos gerais, definiram o formato do QF. Durante esse evento foram desenvolvidas megazonas de cisalhamento extensional, identificadas ao longo do contato entre terrenos granito-gnáissicos e rochas supracrustais dos supergrupos Rio das Velhas e Minas. O evento extensional regional, possivelmente ligado a um choque de placas pode ter evoluído em um mecanismo do tipo metamorphic core complex, situado entre 2050 e 1700 Ma, no qual o QF se localizaria na posição de antepaís. Já o evento compressional principal, associado ao fechamento do proto-oceano Brasiliano/Africano a leste do QF, caracteriza-se por constituir a porção intermediária a distal de um cinturão de dobramento com vergência para W. Esse evento afetou principalmente a porção leste do QF, amplificando os megassinclinais, reaproveitando as descontinuidades previamente formadas e gerando novas estruturas.

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MESOZOIC GRANITOIDS IN THE STRUCTURE OF THE BEZYMYANNYI METAMORPHIC-CORE COMPLEX (western Transbaikalia)

Геология и геофизика ◽

10.15372/gig20161105 ◽

2016 ◽

Keyword(s):

Metamorphic Core Complex ◽

Core Complex ◽

Western Transbaikalia ◽

Mesozoic Granitoids ◽

Metamorphic Core

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Laramide to Miocene syn-extensional plutonism in the Puerta del Sol area, central Sonora, Mexico

Revista Mexicana de Ciencias Geológicas ◽

10.22201/cgeo.20072902e.2017.1.401 ◽

2017 ◽

Vol 34 (1) ◽

pp. 45 ◽

Cited By ~ 5

Author(s):

Elizard González-Becuar ◽

Efrén Pérez-Segura ◽

Ricardo Vega-Granillo ◽

Luigi Solari ◽

Carlos Manuel González-León ◽

...

Keyword(s):

Metamorphic Core Complex ◽

Primitive Mantle ◽

Isotopic Ratios ◽

Magmatic Evolution ◽

Calc Alkaline ◽

Core Complex ◽

High K ◽

Sierra Madre ◽

Plutonic Rocks ◽

Metamorphic Core

Plutonic rocks of the Puerta del Sol area, in central Sonora, represent the extension to the south of the El Jaralito batholith, and are part of the footwall of the Sierra Mazatán metamorphic core complex, whose low-angle detachment fault bounds the outcrops of plutonic rocks to the west. Plutons in the area record the magmatic evolution of the Laramide arc and the Oligo-Miocene syn-extensional plutonism in Sonora. The basement of the area is composed by the ca. 1.68 Ga El Palofierral orthogneiss that is part of the Caborca block. The Laramide plutons include the El Gato diorite (71.29 ± 0.45 Ma, U-Pb), the El Pajarito granite (67.9 ± 0.43 Ma, U-Pb), and the Puerta del Sol granodiorite (49.1 ± 0.46 Ma, U-Pb). The younger El Oquimonis granite (41.78 ± 0.32 Ma, U-Pb) is considered part of the scarce magmatism that in Sonora records a transition to the Sierra Madre Occidental magmatic event. The syn-extensional plutons are the El Garambullo gabbro (19.83 ± 0.18 Ma, U-Pb) and the Las Mayitas granodiorite (19.2 ± 1.2 Ma, K-Ar). A migmatitic event that affected the El Palofierral orthogneiss, El Gato diorite, and El Pajarito granite between ca. 68 and 59 Ma might be related to the emplacement of the El Pajarito granite. The plutons are metaluminous to slightly peraluminous, with the exception of El Oquimonis granite, which is a peraluminous two-mica, garnet-bearing granite. They are mostly high-K calc-alkaline with nearly uniform chondrite-normalized REE and primitive-mantle normalized multielemental patterns that are characteristic of continental margin arcs and resemble patterns reported for other Laramide granites of Sonora. The Laramide and syn-extensional plutons also have Sr, Nd and Pb isotopic ratios that plot within the fields reported for Laramide granites emplaced in the Caborca terrane in northwestern and central Sonora. Nevertheless, and despite their geochemical affinity to continental magmatic arcs, the El Garambullo gabbro and Las Mayitas granodiorite are syn-extensional plutons that were emplaced at ca. 20 Ma during development of the Sierra Mazatán metamorphic core complex. The 40Ar/39Ar and K-Ar ages obtained for the El Palofierral orthogneiss, the Puerta del Sol granodiorite, the El Oquimonis granite, and the El Garambullo gabbro range from 26.3 ± 0.6 to 17.4 ± 1.0 Ma and are considered cooling ages associated with the exhumation of the metamorphic core complex.

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