Low-δ18Ο in mississippian los leones granite (46°S). Tectonic implications for the understanding of late paleozoic evolution in patagonia

IF 1.7 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of South American Earth Sciences Pub Date : 2024-09-21 DOI:10.1016/j.jsames.2024.105174

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Abstract

Los Leones Granite represents a calc-alkaline tonalite-granodiorite tabular stock of ∼3 km² intruded within Paleozoic metasedimentary rocks from the Eastern Andean Metamorphic Complex. Two newly obtained zircon SHRIMP U-Pb ages reveal a Middle Mississippian (340-335 Ma) crystallization age, contrasting with previously accepted K-Ar Pennsylvanian age. Isotopic analysis indicate derivation from a depleted source with minimal influence of continental crust contamination (eHf_(i) ∼14), which experienced hydrothermal alteration at high temperatures (δ¹⁸O ∼4.13). New data coupled with contemporaneous subduction-related rocks in Western Patagonia and Antarctica suggest the existence a broader Lower Carboniferous subduction zone extending at least from Northern Patagonia, to Western Antarctica. On the other hand, isotopic signatures depict a tectono-magmatic framework with a thermal configuration of the margin that was modified by the presence of a local slab tear or the progressive horizontalization of the isotherms as result of the ∼20 myr. of magmatic quiescence in the area.

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密西西比时期洛斯莱昂斯花岗岩（南纬 46°）中的低δ18Ο。构造对了解巴塔哥尼亚晚古生代演化的影响

洛斯莱昂内斯花岗岩是一个面积约为 3 平方公里的钙碱性碳酸盐岩-花岗闪长岩岩体，侵入于东安第斯变质岩群的古生代变质岩中。新获得的两个锆石 SHRIMP U-Pb 年龄显示了中密西西比（340-335 Ma）结晶年龄，与之前公认的 K-Ar 宾夕法尼亚年龄形成对比。同位素分析表明，该矿石来自贫化源，受大陆地壳污染的影响极小（eHf(i) ∼14），在高温下经历了热液蚀变（δ18O ∼4.13）。新的数据以及西巴塔哥尼亚和南极洲与俯冲有关的同期岩石表明，存在一个更广泛的下石炭统俯冲带，至少从北巴塔哥尼亚一直延伸到南极洲西部。另一方面，同位素特征描绘了一个构造-岩浆框架，其边缘的热构造因当地板块撕裂的存在或该地区岩浆静止 20 万年左右导致的等温线逐渐水平化而发生了变化。

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来源期刊

Journal of South American Earth Sciences 地学-地球科学综合

CiteScore

3.70

自引率

22.20%

发文量

364

审稿时长

6-12 weeks

期刊介绍： Papers must have a regional appeal and should present work of more than local significance. Research papers dealing with the regional geology of South American cratons and mobile belts, within the following research fields: -Economic geology, metallogenesis and hydrocarbon genesis and reservoirs. -Geophysics, geochemistry, volcanology, igneous and metamorphic petrology. -Tectonics, neo- and seismotectonics and geodynamic modeling. -Geomorphology, geological hazards, environmental geology, climate change in America and Antarctica, and soil research. -Stratigraphy, sedimentology, structure and basin evolution. -Paleontology, paleoecology, paleoclimatology and Quaternary geology. New developments in already established regional projects and new initiatives dealing with the geology of the continent will be summarized and presented on a regular basis. Short notes, discussions, book reviews and conference and workshop reports will also be included when relevant.