Abstract In spite of hosting one of the most important Pb–Ag–Zn mineralizations in Patagonia, the metamorphic history of the rocks of the Mina Gonzalito Complex (MGC; east of the North Patagonian Massif) is still unclear. The complex consists of schists, para- and ortho-derived gneisses, ranging from greenschist to amphibolite facies, and metamafic rocks. Leucogranites and pegmatites were intruded synkinematically. Field, petrological and thermochronological evidence indicates that the MGC experienced an early prograde path and metamorphic peak during the Early Ordovician (ca. 472 Ma), magmatism and localized post-peak deformation and re-equilibrium at lower pressure, followed by uplift during the Late Permian. The MGC is intruded by the calc-alkaline Santa Rosa Diorite (SiO2 = 58.7–60.4 wt%; LaN/YbN = 7.2–10.5) and trachyte dike swarms in the Late Permian- Early Triassic. The mafic intrusives of the MGC form small schistose, massive and banded bodies interlayered within the gneisses and granites and recorded recrystallization of hornblende + plagioclase + quartz + titanite ± clinopyroxene ± biotite ± ilmenite. The metamafic rocks are mostly tholeiitic gabbros having SiO2 (45.4–52.1 wt%), TiO2 (0.62–2.88 wt%), flat REE patterns (LaN/YbN = 0.48–2.76), although some pyroxene-banded varieties show higher ratios. Initial P–T modelling in the NCKFMASHTO system for the metamafic rocks defined P-T conditions between 550 and 730 °C and 1–4 kbar. Our data suggest that the protolith of the metamafic rocks was emplaced in a shallow environment, associated with underplating of mantle-derived magmas slightly modified by crustal contamination. The intrusion of mantle-derived magmas may have been related either to a magmatic arc or to a continental rift environment. The model involving an Ordovician intracontinental back-arc basin is favored herein because it can reasonably explain many other geological features of Early Paleozoic basement rocks from the northern Patagonia.

中文翻译：

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巴塔哥尼亚北部 Gonzalito 矿区（变）基性岩的地球化学

摘要 尽管巴塔哥尼亚拥有最重要的 Pb-Ag-Zn 矿化之一，但 Mina Gonzalito Complex（MGC；北巴塔哥尼亚地块以东）岩石的变质历史仍不清楚。该复合体由片岩、准和邻位片麻岩组成，范围从绿片岩到角闪岩相，以及变质岩。白花岗岩和伟晶岩是同运动侵入的。现场、岩石学和热年代学证据表明，MGC 在早奥陶世（约 472 Ma）、岩浆作用和局部峰后变形和低压下重新平衡，经历了早期的前进路径和变质峰，随后在晚二叠纪。MGC 被钙碱性圣罗莎闪长岩侵入（SiO2 = 58.7–60.4 wt%；LaN/YbN = 7.2–10。5) 和晚二叠世-早三叠世粗面岩脉群。MGC 的镁铁质侵入体在片麻岩和花岗岩中形成夹层的小片状、块状和带状体，并记录了角闪石 + 斜长石 + 石英 + 钛铁矿 ± 斜辉石 ± 黑云母 ± 钛铁矿的重结晶。变镁铁质岩主要是拉斑辉长岩，具有 SiO2 (45.4–52.1 wt%)、TiO2 (0.62–2.88 wt%)、扁平的 REE 图案（LaN/YbN = 0.48–2.76），尽管一些辉石带状品种显示出更高的比例。NCKFMASHTO 系统中变质岩的初始 P-T 建模定义了 550 至 730 °C 和 1-4 kbar 之间的 PT 条件。我们的数据表明，变质岩的原岩位于浅层环境中，与地壳污染轻微改变的地幔岩浆的底床有关。地幔源岩浆的侵入可能与岩浆弧或大陆裂谷环境有关。奥陶纪陆内弧后盆地模型在本文中受到青睐，因为它可以合理解释巴塔哥尼亚北部早古生代基底岩的许多其他地质特征。