Involvement of the Argentine Precordillera terrane in the Famatinian mobile belt: U-Pb SHRIMP and metamorphic evidence from the Sierra de Pie de Palo
Involvement of the Argentine Precordillera terrane in the Famatinian mobile belt: U-Pb SHRIMP and metamorphic evidence from the Sierra de Pie de Palo
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阿根廷前记录地体参与法马提尼运动带：U-Pb SHRIMP 和来自 Sierra de Pie de Palo 的变质证据
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
J. Saavedra
中科院分区：
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作者：
C. Casquet;E. Baldo;R. Pankhurst;C. Rapela;C. Galindo;C. Fanning;J. Saavedra
新资料表明，阿根廷前科迪勒拉地体东缘由格伦维里亚基底和由其衍生的沉积盖层组成，它们共同受到冈瓦纳边缘增生过程中奥陶世变形变质作用的影响。基底首先发生了低压/低温（P/T）型变质作用，在某些地方（686±40 MPa, 790±17℃）达到了高级别混染条件，与假定的Laurentian地块对应的Grenvillian M2变质作用相当。第二次变质作用在盖层中被识别，发生在高P/T条件下，顺时针P-T路径（压力峰值：1300±100 Mpa， 600±50°C）。随着压力从峰值下降，低铀锆石过度生长在碎屑岩心中，产生的U-Pb SHRIMP年龄约为460 Ma。这被解释为韧性逆冲时代与早期隆升相吻合；冈瓦纳的初始吸积一定发生在此之前。晚新元古代碎屑锆石的缺失与阿根廷Precordillera地体的Laurentian起源一致。
New data suggest that the eastern margin of the Argentine Precordillera terrane comprises Grenvillian basement and a sedimentary cover derived from it that were together affected by Middle Ordovician deformation and metamorphism during accretion to the Gondwana margin. The basement first underwent low pressure/temperature ( P/T ) type metamorphism, reaching high-grade migmatitic conditions in places (686 ± 40 MPa, 790 ± 17 °C), comparable to the Grenvillian M2 metamorphism of the supposed Laurentian counterpart of the terrane. The second metamorphism, recognized in the cover sequence, is of Famatinian age and took place under higher P/T conditions, following a clockwise P-T path (baric peak: 1300 ± 100 Mpa, 600 ± 50 °C). Low-U zircon overgrew detrital Grenvillian cores as pressure fell from its peak, and yields U-Pb SHRIMP ages of ca. 460 Ma. This is interpreted as the age of ductile thrusting coincident with early uplift; initial accretion to Gondwana must have occurred before this. The absence of late Neoproterozoic detrital zircons is consistent with a Laurentian origin of the Argentine Precordillera terrane.