Geochronological constraints on the evolution of the southern Dom Feliciano Belt (Uruguay)

New U–Pb sensitive high-resolution ion microprobe, K–Ar and Ar–Ar data from the southernmost Dom Feliciano Belt allow the identification of four major events. Orthogneisses from the Punta del Este Terrane indicate a magmatic episode at c. 770 Ma and high-grade metamorphism at 641 ± 17 Ma. Granitoid emplacement at 627 ± 23 Ma was roughly coeval with peak metamorphism. Volcaniclastic rocks of the Las Ventanas Formation dated at 573 ± 11 Ma can be correlated with the peripheral foreland basin (571 ± 8 Ma). Transpression and coeval high-K calc-alkaline magmatism is recorded in the Maldonado granite dated at 564 ± 7 Ma. The following events are postulated: (1) magmatism at 850–750 Ma related to rifting; (2) metamorphism and granite emplacement at 650–600 Ma; (3) molasse sequences and foreland basins at c. 573 Ma; (4) late magmatism at 580–560 Ma associated with transpression. The data indicate that (1) the Punta del Este Terrane could be a portion of the Coastal Terrane of the Kaoko Belt, (2) granitoid emplacement at 650–600 Ma in the Punta del Este and Nico Pérez terranes favours westward subduction, and (3) widespread post-collisional synkinematic magmatism occurred in the Dom Feliciano and Kaoko belts between 580 and 550 Ma.对最南端多姆·费利西亚诺造山带（Dom Feliciano Belt）获取的新型U-Pb高灵敏度高分辨率离子探针（sensitive high-resolution ion microprobe）、K-Ar及Ar-Ar同位素定年数据，可识别出四大主要构造-热事件。埃斯特角地体（Punta del Este Terrane）的正片麻岩记录了约770 Ma的岩浆事件，以及641 ± 17 Ma的高级变质作用。627 ± 23 Ma的花岗岩类侵位，与峰期变质作用大致同期。定年结果为573 ± 11 Ma的拉斯文塔纳组（Las Ventanas Formation）火山碎屑岩，可与571 ± 8 Ma形成的周缘前陆盆地进行时代对比。定年结果为564 ± 7 Ma的马尔多纳多花岗岩，记录了走滑挤压作用及同期的高钾钙碱性岩浆作用。 本次研究提出以下四大构造事件：(1) 850~750 Ma期间与裂谷作用相关的岩浆作用；(2) 650~600 Ma期间的变质作用与花岗岩侵位；(3) 约573 Ma的磨拉石序列与前陆盆地发育；(4) 580~560 Ma期间与走滑挤压作用伴生的晚期岩浆作用。 研究数据表明：(1) 埃斯特角地体可能属于卡奥科造山带（Kaoko Belt）沿海地体的一部分；(2) 埃斯特角地体与尼科·佩雷斯地体（Nico Pérez Terrane）在650~600 Ma发生的花岗岩类侵位，支持西向俯冲作用；(3) 580~550 Ma期间，多姆·费利西亚诺造山带与卡奥科造山带广泛发育碰撞后同构造岩浆作用。