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In situ U/Pb dating of impact-produced zircons from the Vargeao Dome (Southern Brazil)
被引:12
|作者:
Nedelec, Anne
[1
,2
]
Paquette, Jean-Louis
[3
]
Yokoyama, Elder
[4
]
Trindade, Ricardo I. F.
[4
]
Aigouy, Thierry
[1
]
Baratoux, David
[2
]
机构:
[1] Univ Toulouse, Geosci Environm Toulouse UMR5563, Toulouse, France
[2] Univ Toulouse, Inst Rech Astrophys & Planetol UMR5577, Toulouse, France
[3] Univ Clermont Ferrand 2, Magmas & Volcans UMR6524, F-63006 Clermont Ferrand, France
[4] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508 Sao Paulo, Brazil
关键词:
U-PB;
FLOOD BASALTS;
AGE;
YELLOWSTONE;
SYSTEMATICS;
EVOLUTION;
PRESSURE;
TITANIQ;
ROCKS;
D O I:
10.1111/maps.12066
中图分类号:
P3 [地球物理学];
P59 [地球化学];
学科分类号:
0708 ;
070902 ;
摘要:
The VargeAo impact structure was formed in the Serra Geral basaltic and rhyodacitic to rhyolitic lava flows of southern Brazil, that belong to the Parana-Etendeka large igneous province. The Chapeco-type rhyodacites contain small baddeleyite crystals recently dated at 134.3 (+/- 0.8) Ma, which is regarded as the age of this acid volcanism coeval to the flood basalt eruption. Inside the impact structure, a brecciated rhyodacitic sample displays fine veinlets containing numerous lithic fragments in a former melt. This impact breccia contains newly formed zircons, either in the veins or at the contact between a vein and the volcanic matrix. The zircons are 1050m in length, clear and nearly unzoned. In situ laser-ablation dating of the zircons provides a concordant Early Aptian age of 123.0 +/- 1.4Ma that is regarded as the age of the impact event. As in situ age determination ensures the best possible selection of the analyzed mineral grains, the methodology employed in this study also represents a promising method for dating other impact structures.
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页码:420 / 431
页数:12
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