Mesoproterozoic evolution of the Río de la Plata Craton in Uruguay: at the heart of Rodinia?
Mesoproterozoic evolution of the Río de la Plata Craton in Uruguay: at the heart of Rodinia?
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DOI：
10.1007/s00531-010-0562-x
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发表时间：
2011-04
影响因子：
2.3
通讯作者：
C. Gaucher;R. Frei;F. Chemale;D. Frei;J. Bossi;G. Martínez;Leticia Chiglino;F. Cernuschi
中科院分区：
文献类型：
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作者：
C. Gaucher;R. Frei;F. Chemale;D. Frei;J. Bossi;G. Martínez;Leticia Chiglino;F. Cernuschi
综述了拉普拉塔克拉通(RPC)中元古代火山沉积单元和构造事件。乌拉圭东部RPC(Nico Pérez Terrane)暴露出一条由显示绿片岩相变质作用的火山沉积序列组成的带。帕尔库特群底部由基性火山岩和辉长岩组成(1492 Ma±14.4 Ma，锆石U-Pb)，中部为碳酸盐岩，顶部为碳酸盐岩、页岩和酸性火山岩(1429 Ma±9.21 Ma，锆石U-Pb)。Mina Verdún群由底部和顶部的流纹岩和酸性火山碎屑岩组成，中间为含康普顿石灰岩和块状白云岩。本文报道了Mina Verdún群(Cerro de las Víboras组)底部的火山灰凝灰岩的锆石U-PbLA-ICPMS年龄为1,433 Ma±7.6 Ma。这一年代表明，米纳Verdún群的时代立即晚于Parque Ute群，这一事实得到了碳同位素化学地层学的支持。K-Ar和Ar-Ar年龄显示，这两个单元在1.25~1.20 Ma之间变形变质。这一构造事件影响了RPC的大部分地区，并导致Nico Pérez Terrane沿Sarandídel Yímeasher沉积到RPC的其余部分。本文报道了拉中国杂岩的锆石U-PbLA-ICPMS年龄(上交点)为3,096 Ma±245 Ma，下交点年龄为1,252 Ma。RPC的埃迪卡拉纪砂岩中含有丰富的中元古代碎屑锆石年龄的中安第斯-中元古代岩带。如果RPC两侧被中元古代格伦维尔时代的带包围，那么它很可能在罗迪尼亚占据了相当中心的位置。建议在劳伦蒂亚和卡拉哈里克拉通之间，在亚马逊以南的一个可能的位置。
Mesoproterozoic volcanosedimentary units and tectonic events occurring in the Río de la Plata Craton (RPC) are reviewed. A belt consisting of volcanosedimentary successions exhibiting greenschist-facies metamorphism is exposed in the eastern RPC (Nico Pérez Terrane) in Uruguay. The Parque UTE Group consists of basic volcanics and gabbros at the base (1,492 ± 4 Ma, U–Pb on zircon), carbonates in its middle part and interbedded carbonates, shales and acid volcanics (1,429 ± 21 Ma, U–Pb on zircon) at the top. The Mina Verdún Group is made up of rhyolites and acid pyroclastics at its base and top, andConophyton-bearing limestones and massive dolostones in the middle. A U–Pb LA-ICP MS zircon age of 1,433 ± 6 Ma is reported here for lapilli-tuffs at the base of the Mina Verdún Group (Cerro de las Víboras Formation). This age shows that the Mina Verdún Group immediately postdates the Parque UTE Group, a fact supported by carbon isotope chemostratigraphy. Both units were deformed and metamorphosed between 1.25 and 1.20 Ga, as shown by K–Ar and Ar–Ar ages. This tectonic event affected most of the RPC and led to the accretion of the Nico Pérez Terrane to the remainder of the RPC along the Sarandí del Yí megashear. We report a U–Pb LA-ICP MS zircon age (upper intercept) of 3,096 ± 45 Ma for metatonalites of the La China Complex (Nico Pérez Terrane), which yield a lower intercept age of 1,252 Ma. A proto-Andean, Mesoproterozoic belt is envisaged to account for abundant Mesoproterozoic detrital zircon ages occurring in Ediacaran sandstones of the RPC. If the RPC is fringed at both sides by Mesoproterozoic, Grenville-aged belts it is likely that it occupied a rather central position in Rodinia. A possible location between Laurentia and the Kalahari Craton, and to the south of Amazonia, is suggested.