林波波杂岩中央区热构造演化综述及其对已发表的地球动力学模型的影响

IF 1.2 4区 地球科学 Q2 GEOLOGY
D. van REENEN, M. Clark, C. Smit, T. Tsunogae, O. Safonov
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引用次数: 1

摘要

本文讨论了用于支持最近提出的非洲南部林波波复合体(LC)在新太古代和古元古代地球动力学演化的相互矛盾模型的已发表数据的可信度。本文主要讨论了影响陆相中央带(CZ)的构造和变质作用过程,同时也考虑了陆相南缘带(SMZ)与Kaapvaal克拉通(KVC)花岗岩-绿岩地体在陡峭北倾的侯特河剪切带(HRSZ)位置的热构造相互作用时间的意义。在与KVC接触处,与HRSZ相关的构造活动表现为一个狭窄的“热铁带”,其直接年代为2.72 ~ 2.69 Ga,发育于北倾的HRSZ下盘。与hrsz相关的构造活动间歇性地持续到2.65 ~ 2.62 Ga,没有构造变质或年代学证据表明SMZ和KVC的其余部分在约2.68 Ga之后受到区域热构造(造山)活动的影响。布来花岗岩体在2.612 Ga侵位前2.72 ~ 2.62 Ga CZ的互补演化分别表现为2.72 ~ 2.66 Ga和2.65 ~ 2.62 Ga两个热构造事件。早2.72 ~ 2.66 Ga事件与CZ从上升的地壳尺度麻粒岩底辟中近垂直掘出有关,并伴随着在地壳中(20 km深度)陡倾等斜褶皱和麻粒母粒结构的CZ麻粒岩侵位。在2.65 ~ 2.62 Ga的新太古代,一个中等(~45°)的东北方向剪切变形事件,伴随着广泛的花岗质底辟作用,控制了CZ在2.612 Ga布莱岩体侵入之前的最终侵位。第二次构造-热事件表现为主要的剪切构造特征,包括巨型封闭褶皱、巨型南北走向褶皱和宽29 km的西南-东北走向、适度东南倾、东北向外延的Tshipise矫直带(TSZ)。CZ最终在600 Myr后(约2.02 Ga)的区域性高温古元古代热事件中被挖掘出来并位于地壳上层,该热事件与主要的近垂直走滑剪切带重叠在新太古代斜滑剪切带上。与这一主要热事件相关的CZ热构造活动被认为是大约2.02 Ga的离散陡倾狭窄织物平行剪切带,覆盖了较旧的构造。利用重力驱动的地壳尺度底辟模型解释了林波波造山运动2.72 ~ 2.62 Ga时期LC的SMZ和CZ的演化。所提出和讨论的数据与其他已发表的模型相矛盾,这些模型提出了2.65至2.62 Ga的大陆-大陆碰撞造山运动,涉及SMZ和KVC,随后在600 Myr之后的2.02 Ga发生了与近水平逆冲构造相关的跨洋造山运动。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Review of the thermo-tectonic evolution of the Central Zone of the Limpopo Complex with implications for conflicting published geodynamic models
This paper addresses the credibility of published data utilised to underpin conflicting models recently proposed for the geodynamic evolution of the Limpopo Complex (LC), Southern Africa, in the Neoarchaean and Palaeoproterozoic. We are mainly focused on the tectonic and metamorphic processes that affected the Central Zone (CZ) of the LC, but also consider the significance of the timing of the thermo-tectonic interaction of the Southern Marginal Zone (SMZ) of the LC with the granite-greenstone terrane of the Kaapvaal Craton (KVC) at the position of the steep north-dipping Hout River Shear Zone (HRSZ). HRSZ-linked tectonism at the contact with the KVC is expressed as a narrow “hot-iron zone” directly dated at 2.72 to 2.69 Ga and developed in the footwall of the north-dipping HRSZ. HRSZ-linked tectonic activity intermittently continued up to 2.65 to 2.62 Ga with no structural-metamorphic or geochronological evidence that the SMZ and the rest of the KVC were affected by regional thermo-tectonic (orogenic) activity after ca. 2.68 Ga. The complementary evolution of the CZ at 2.72 to 2.62 Ga prior to emplacement at 2.612 Ga of the Bulai granitic pluton is expressed by two thermo-tectonic events, at 2.72 to 2.66 Ga and 2.65 to 2.62 Ga, respectively. The early 2.72 to 2.66 Ga event was associated with near-vertical exhumation of the CZ from a rising crustal-scale granulite diapir, accompanied by emplacement of steeply-dipping isoclinal folded and granoblastic-textured CZ granulites at the mid-crustal level (20 km depth). A moderately (~45°) northeast-directed shear deformational event, accompanied by extensive granitic diapirism, controlled the final emplacement of the CZ in the Neoarchaean at 2.65 to 2.62 Ga prior to intrusion of the 2.612 Ga Bulai pluton. This second tectono-thermal event is expressed by major sheared structural features that include mega-closed folds, mega-north-south trending folds, and the 29 km-wide southwest-northeast-trending and moderately southeast-dipping and northeast-verging Tshipise Straightening Zone (TSZ) that bounds the CZ in the south. The CZ was finally exhumed and emplaced at the upper crustal level 600 Myr later (at ca. 2.02 Ga) during a regional high-temperature Palaeoproterozoic thermal event associated with major near-vertical strike-slip shear zones that overprint Neoarchaean oblique slip shear zones that bound the CZ. Thermo-tectonic activity in the CZ that is associated with this mainly thermal event is recognised as discrete steeply-dipping narrow fabric-parallel shear zones dated at ca. 2.02 Ga that overprint older structures. A gravity-driven crustal-scale diapiric model is utilised to explain the evolution of the SMZ and CZ of the LC at 2.72 to 2.62 Ga during the Limpopo Orogeny. Data presented and discussed contradict alternative published models that propose a continent-continent collisional orogeny at 2.65 to 2.62 Ga involving the SMZ and KVC, followed 600 Myr later at 2.02 Ga by a transpressional orogeny associated with near-horizontal thrust tectonics.
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来源期刊
CiteScore
3.60
自引率
5.60%
发文量
18
审稿时长
>12 weeks
期刊介绍: The South African Journal of Geology publishes scientific papers, notes, stratigraphic descriptions and discussions in the broadly defined fields of geoscience that are related directly or indirectly to the geology of Africa. Contributions relevant to former supercontinental entities such as Gondwana and Rodinia are also welcome as are topical studies on any geoscience-related discipline. Review papers are welcome as long as they represent original, new syntheses. Special issues are also encouraged but terms for these must be negotiated with the Editors.
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