Polyphase tectonic reworking of serpentinites and chlorite-tremolite-talc rocks (SW Spain) from the subduction forearc to intracontinental emplacement

IF 3.5 2区 地球科学 Q1 GEOLOGY Journal of Metamorphic Geology Pub Date : 2022-12-14 DOI:10.1111/jmg.12704
Benito Ábalos, Pablo Puelles, José Ignacio Gil Ibarguchi
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引用次数: 1

Abstract

The petrostructural and geochronological study of a poorly known ultramafic unit from SW Spain (Badajoz–Córdoba belt) combined with previous structural data permits disclosure of a history of metasomatism, tectono-metamorphism, reworking and isotopic resetting related to a poly-orogenic evolution in different geodynamic scenarios. The heterogeneous ultramafic unit studied contains antigorite-serpentinites and metasomatized ultramafic rocks (chlorite-talc schists, tremolite-talc-chlorite rocks and magnesio-hornblende-chlorite rocks). Mantle-wedge serpentinization was followed by Si and Al pre- to syn-metamorphic/tectonic metasomatism in a subduction realm. Petrofabrics of selected lithologies reveal variable syn-metamorphic crystal-plastic deformation and recrystallization (assisted by other mechanisms) under relative high pressure, concomitant with the conditions recorded by neighbouring tectonic units that were later intruded by Ordovician granites. The resultant ensemble was reworked and isotopically reset much later in an intracontinental ductile shear zone. Syn- to late-tectonic apatite from chlorite-talc schists provides an anchored Tera–Wassenburg isochron radiometric age of 342.8 ± 12.2 Ma that provides evidence for the decoupling between isotopic systems and microstructures. The results are discussed from a twofold perspective: with regard to the likely tectonic context of this ophiolite (the current analogue of the Mariana forearc) and with regard to regional geological implications.

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蛇纹岩和绿泥石-透闪石-滑石岩(西班牙西南部)从俯冲弧前到陆内侵位的多期构造改造
通过对西班牙西南部一个鲜为人知的超镁铁质单元(Badajoz-Córdoba带)的岩石构造和地质年代学研究,结合以往的构造数据,揭示了在不同地球动力学情景下与多造山演化相关的交代、构造变质、改造和同位素重置史。研究的非均质超镁铁质单元包括反长岩-蛇纹岩和交代超镁铁质岩石(绿泥石-滑石片岩、透闪石-滑石-绿泥石岩石和镁-角闪石-绿泥石岩石)。地幔楔蛇纹岩作用之后是俯冲域中的Si和Al的前-同变质/构造交代作用。所选岩性的岩组在相对高压下显示出可变的同变质晶体塑性变形和再结晶(在其他机制的辅助下),并伴有随后被奥陶系花岗岩侵入的邻近构造单元所记录的条件。由此产生的整体在大陆内韧性剪切带中被重新加工和同位素重置。从绿泥石-滑石片岩中提取的顺-晚期构造磷灰石提供了一个锚定的terra - wassenburg等时辐射年龄为342.8±12.2 Ma,为同位素系统和微观结构之间的解耦提供了证据。结果从两个角度进行了讨论:关于这个蛇绿岩的可能构造背景(目前的马里亚纳前弧的类似物)和关于区域地质意义。
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来源期刊
CiteScore
6.60
自引率
11.80%
发文量
57
审稿时长
6-12 weeks
期刊介绍: The journal, which is published nine times a year, encompasses the entire range of metamorphic studies, from the scale of the individual crystal to that of lithospheric plates, including regional studies of metamorphic terranes, modelling of metamorphic processes, microstructural and deformation studies in relation to metamorphism, geochronology and geochemistry in metamorphic systems, the experimental study of metamorphic reactions, properties of metamorphic minerals and rocks and the economic aspects of metamorphic terranes.
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