Abstract The provenance of sandstones deposited in the late Paleozoic Tepuel-Genoa Basin is analyzed in this paper. Five sections were sampled in Esquel, Sierra de Tepuel, Sierra de Tecka, El Molle, and Rio Genoa areas for petrographic and geochemical studies. The sandstones in the Tepuel-Genoa Basin are dominated by feldspathic litharenites and litharenites, showing lithic fragments of volcanic and sedimentary rocks in the Valle Chico Formation and medium-to high-grade metamorphic rock clasts in the rest of the units. Detrital modes of seventy-five sandstones samples from the Valle Chico, Pampa de Tepuel, Mojon de Hierro, and Rio Genoa formations were counted and analyzed. Seven modal components have discriminant value for identifying provenance areas (Qm, Qi, Lv, Lmm-h, Lm-Lp, Lm, Qpm). These modal components allow identification of three petrofacies: 1. Quartzose-lithic (Qm69Lv2Lm29), 2. Quartzose (Qm89Lv4Lm7) and 3. Volcanic-sedimentary (Qm60Lv38Lm1). The quartzose-lithic petrofacies is mainly composed of monocrystalline quartz, medium- and high-grade metamorphic clasts and polycrystalline quartz with cataclastic texture, this assemblage is interpreted as being derived from the crystalline rocks that form the Deseado Massif. The quartzose petrofacies is composed of monocrystalline quartz with scarce contributions of metamorphic clasts and traces of volcanic fragments; the provenance area is ascribed to sedimentary terrains, which most likely covered part of the Deseado Massif. The volcanic-sedimentary petrofacies is comprised of volcanic (acidic and intermediate rocks) and sedimentary (sandstone and mudstone) clasts, with discrete amounts of quartz grains with idiomorph shapes and embayments. This assemblage may correspond to material supply from the Devonian-Early Carboniferous accretionary complex developed in Chile or the unroofing of the western volcanic arc located in the central part of Patagonia. The validity of the three defined petrofacies was evaluated using Principal Component Analysis and triangular compositional diagrams; both methods show good separation and lack of overlap between the three petrofacies. Major (Si, Al, Fe, Na, K) and trace-REE elements (Zr, Th, Sc, Hf) were used to improve the petrographic information. The relation SiO2 against K2O/Na2O indicates that the Pampa de Tepuel and the Mojon de Hierro formations correspond to a passive margin, while the Valle Chico and Rio Genoa formations represent different types of active continental margins. The Th/Sc and Zr/Sc ratios and the Th-Hf-Co distributions indicate that the sandstones of the Tepuel Group were formed from rocks compatibles with the average composition of the upper continental crust.

中文翻译：

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解释晚古生代特普尔-热那亚盆地砂岩的碎屑模式和地球化学：古地理意义（巴塔哥尼亚，阿根廷）

摘要 对晚古生代特普尔-热那亚盆地沉积的砂岩物源进行了分析。在 Esquel、Sierra de Tepuel、Sierra de Tecka、El Molle 和 Rio Genoa 地区对五个剖面进行了岩相和地球化学研究。特普尔-热那亚盆地砂岩以长石岩屑岩和岩屑岩为主，Valle Chico组为火山岩和沉积岩岩屑，其余单元为中高品位变质岩碎屑。对来自 Valle Chico、Pampa de Tepuel、Mojon de Hierro 和 Rio Genoa 地层的 75 个砂岩样品的碎屑模式进行了计数和分析。七个模态分量具有识别来源区域的判别值（Qm、Qi、Lv、Lmm-h、Lm-Lp、Lm、Qpm）。这些模态分量可以识别三种岩相：1. 石英岩相 (Qm69Lv2Lm29)，2. 石英岩 (Qm89Lv4Lm7) 和 3. 火山沉积岩 (Qm60Lv38Lm1)。石英岩岩相主要由单晶石英、中高品位变质碎屑和多晶石英组成，具有碎裂结构，这种组合被解释为来自形成德塞多地块的结晶岩。石英岩相由单晶石英组成，变质碎屑和火山碎屑的痕迹很少；起源区属于沉积地形，很可能覆盖了 Deseado 地块的一部分。火山-沉积岩相由火山（酸性和中性岩）和沉积（砂岩和泥岩）碎屑组成，具有离散量的具有自形形状和凹坑的石英颗粒。这种组合可能对应于智利开发的泥盆纪-早石炭世增生杂岩的物质供应或位于巴塔哥尼亚中部的西部火山弧的开顶。使用主成分分析和三角成分图评估了三个定义的岩相的有效性；两种方法都显示出三个岩相之间的良好分离和不重叠。主要（Si、Al、Fe、Na、K）和痕量 REE 元素（Zr、Th、Sc、Hf）用于改善岩相信息。SiO2 与 K2O/Na2O 的关系表明 Pampa de Tepuel 和 Mojon de Hierro 地层对应于被动边缘，而 Valle Chico 和 Rio Genoa 地层代表了不同类型的活动大陆边缘。Th/Sc 和 Zr/Sc 比值和 Th-Hf-Co 分布表明，特普尔群砂岩是由与上大陆地壳的平均成分相容的岩石形成的。