U–Pb SHRIMP data constraints on calc-alkaline granitoids with 1.3–1.6 Ga Nd Tub>DMub> model ages from the central domain of the Borborema province, NE Brazil

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• 作者：I.P. Guimarã ; esup>aup>up> ; up>up>ignez@ufpe.br"" rel=""nofollowup> ; A.F. Silva Filhoup>aup> ; C.N. Almeidaup>bup> ; M.B. Macambiraup>cup> ; R. Armstrongup>dup>
• 关键词：Granitoids ; Brasiliano ; Source rock ; U&#x2013 ; Pb SHRIMP data
• 刊名：Journal of South American Earth Sciences
• 出版年：2011
• 出版时间：April 2011
• 年：2011
• 卷：31
• 期：4
• 页码：383-396
• 全文大小：1685 K

文摘

The Tabira, Itapetim and Timbaúba granitoids are intruded into metasedimentary sequences and Cariris Velhos (Tonian) orthogneisses from the Central Domain of the Borborema Province, NE Brazil. They have U–Pb SHRIMP ages of 593 ± 7 Ma; 615 ± 9 Ma and 616 ± 5 Ma respectively. The studied granitoids have zircon cores inherited from the protholith, with a large number of analyses showing up>206up>Pb/up>238up>U ages ranging from 950 to 1200 Ma. Oscillatory zoning typical of magmatic zircon is common, although it is faint in some inherited cores.

The studied granitoids are calc-alkaline and show Nd Tub>DMub> model ages ranging from 1.30 to 1.56 Ga and Nd (600 Ma) ranging from −2.40 to −5.34. These values are similar to those recorded in the country rocks. The lowest values of Nd (600 Ma) were recorded in enclaves of dioritic composition. Nd and U–Pb SHRIMP data suggest a significant participation of the metasedimentary rocks in the protholith of these granitoids. The Mesoproterozoic Nd Tub>DMub> model ages recorded in the studied granitoids are interpreted as the result of a hybrid source involving melting of metagraywackes, metamafic rocks of Tonian ages and/or biotite – bearing orthogneisses (Cariris Velhos Orthogneisses). The resulted melting was modified by mingling with juvenile Brasiliano melts, diorite in composition.

The Timbaúba granitoids intrusions are coeval with high-T metamorphism and flat-lying foliation forming event in an intracontinental setting, during the Brasiliano convergence and contractional deformation. The Itapetim Pluton was emplaced in the convergence - lateral escape setting and the Tabira granitoids were intruded after the flat-lying foliation event, representing sin transcurrent intrusions.

Our data show that within the Central Domain of the Borborema Province, granitoids with similar petrographic and geochemical compositions can have distinct ages and be intruded in distinct tectonic regimes.