Journal
BRAZILIAN JOURNAL OF GEOLOGY
Volume 48, Issue 2, Pages 403-414Publisher
SOC BRASILEIRA GEOLOGIA
DOI: 10.1590/2317-4889201820170094
Keywords
Alkaline rocks; Ponta Grossa Arch; Geochronology
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Funding
- Fapesp [2012/06082-6, 2016/23399-4]
- Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [12/06082-6] Funding Source: FAPESP
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New age determinations by Ar-Ar and U-Pb SHRIMP for the alkaline complexes of Banhadao and Itapirapua that occur in the Ribeira Valley are in agreement with the previously radiometric K-Ar ages available in literature. Ar-Ar ages on biotite for Banhadao range in the 106-110 Ma interval, and suggest a minimum age of 106 Ma for the complex. Ar-Ar data on biotite for Itapirapua are more uniform, indicating an age of 102 Ma for the complex. U-Pb SHRIMP determinations on titanite from Itapirapua melanite syenitic rocks yielded an age of similar to 106 Ma. Thus, the age interval of 100 and 110 Ma does exist indeed, suggesting an intermediate magmatic pulse between the already well-defined peaks of 80-90 Ma and 130-140 Ma for the alkaline rocks in southern Brazil, confirming the periodicity of the magmatism.
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