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首页> 外文期刊>Journal of Iberian geology >Origin and provenance of igneous clasts from late Palaeozoic conglomerate formations (Del Ratón and El Planchón) in the Andean Precordillera of San Juan, Argentina
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Origin and provenance of igneous clasts from late Palaeozoic conglomerate formations (Del Ratón and El Planchón) in the Andean Precordillera of San Juan, Argentina

机译：阿根廷圣胡安安第斯山脉的古生代砾岩晚期地层（DelRatón和ElPlanchón）的火成岩起源和起源

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Late Palaeozoic conglomerate formations (Del Ratón and El Planchón) from the Andean Precordillera (Argentina) were studied to unravel their age, composition and provenance. The conglomerates from the Del Ratón Formation are formed by igneous clasts of acid, intermediate and basic compositions (volcanic and plutonic). Laser Ablation (ICP-MS) zircon U-Pb study has yielded an age of 348±2 Ma (late Tournaisian) for the crystallization of a granitic clast, interpreted as a maximum deposition age for the Del Ratón Formation. Geochemistry of these clasts (high LILE/HFSE and La/Yb ratios, negative Nb-Ta anomalies) suggests a calc-alkaline batholithic source, probably located along the Andean Frontal Cordillera currently to the west, where similar calc-alkaline igneous rocks have been described. The El Planchón Formation overlies the Del Ratón Formation and, in the studied conglomerates, there are only igneous clasts of mafic composition (volcanic/subvolcanic). These mafic clasts have a very similar petrography and geochemistry to the Late Ordovician mafic igneous rocks of the Western Precordillera (low LILE/HFSE and La/Yb ratios, no negative Nb-Ta anomalies). Therefore we suggest that the El Planchón conglomerate clasts were probably delivered mainly from northern sources within the Precordillera terrane. This change in clast provenance is tentatively related to a shift in mountain uplift from the Frontal Cordillera (in the west) to the Precordillera (in the east) after the early Visean.
机译：研究了来自安第斯山脉（阿根廷）的古生代砾岩构造（DelRatón和ElPlanchón），以揭示其年龄，成分和出处。 DelRatón组的砾岩是由酸，中间和碱性成分（火山岩和深成岩）的火成岩碎片形成的。激光烧蚀（ICP-MS）锆石U-Pb研究表明，花岗岩碎屑的结晶年龄为348±2 Ma（吐纳晚期），这被解释为DelRatón组的最大沉积年龄。这些岩屑的地球化学特征（高LILE / HFSE和La / Yb比，负Nb-Ta异常）表明钙碱性碱性岩源可能位于安第斯前额山脉，目前位于西部，那里曾经有类似的钙碱性火成岩描述。 ElPlanchón组覆盖着DelRatón组，在研究的集团公司中，只有火成岩碎屑组成（火山岩/次火山岩）。这些镁铁质岩屑的岩石学和地球化学特征与西部Precordillera的晚奥陶纪镁铁质火成岩（LILE / HFSE和La / Yb比低，Nb-Ta异常无负值）相似。因此，我们认为ElPlanchón砾岩碎屑可能主要来自Precordillera地貌内的北部来源。震源起源的这种变化暂时与早期Visean之后山隆起从额叶山脉（西部）到Precordillera（东部）的变化有关。

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