The Ediacaran margin of the proterozoic MARA block and the sedimentary basins of the Clymene Ocean: Insights from U-Pb zircon geochronology in the Puna-Sierras Pampeanas transition, NW Argentina

IF 3.2 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Precambrian Research Pub Date : 2025-04-28 DOI:10.1016/j.precamres.2025.107792

C.D. Ramacciotti , M.A. Larrovere , C. Casquet , C.I.Lembo Wuest , M.Morales Cámera , P.H. Alasino , J.A. Murra , A. Riveros , M.A.S. Basei , L. Herazo , E.G. Baldo

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Abstract

The basement of the sierras of Fiambalá and Altohuasi, in the Puna-Sierras Pampeanas transition (NW Argentina), consists mainly of early Cambrian metamorphic rocks (Fiambalá Metasedimentary Complex; new name) and granitoids (Loconte Intrusive Complex; new name). The metasedimentary complex consists of: 1) the Tatón Unit (gneisses, metatexites, diatexites and mylonites); and 2) the Laguna Helada Unit (low- to medium-grade fine-grained metaconglomerates with subordinated metapsammites, slates, phyllites, schists, mylonites and marbles). U-Pb zircon geochronology performed in the two units yields similar results suggesting that they were sourced from the same basements and probably belong to a continuous stratigraphic pile prior to metamorphism and ductile shearing. These units show a main group of ages between ca. 0.95 and 1.10 Ga, and a secondary group at ca. 1.15–1.25 Ga, with a minor peak at ca. 1.33 Ga, and few Paleoproterozoic-Neoarchean ages. This, along with zircon metamorphic overgrowths of 526 ± 4 Ma found in the Tatón Unit, and regional correlations, indicate that sedimentation took place in Ediacaran to early Cambrian times, in a mixed carbonate-siliciclastic platform bordering the extinct Clymene Ocean. Comparisons (lithology, Sr-isotopes and detrital zircon data) with similar successions recognized elsewhere in the Sierras Pampeanas, southern Puna, Cordillera Frontal, and Cordillera Oriental suggest that the sediments came from the same source areas and that they were part of a common sedimentary environment, i.e., the Difunta Correa Basin. The main source areas were the Grenville and the Granite-Rhyolite provinces of Laurentia and the MARA block. This basin – now dismembered by Paleozoic deformation – is one of the many basins formed along the margins of the Clymene Ocean lying in NW Argentina, southern Brazil, Paraguay, and Río de la Plata craton. The closure of this ocean, during the early Cambrian Pampean orogeny resulted in the low- to high-grade metamorphism of the Fiambalá Metasedimentary Complex.

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元古代MARA地块埃迪卡拉纪边缘与Clymene洋沉积盆地：来自阿根廷西北部Puna-Sierras Pampeanas过渡带U-Pb锆石年代学的启示

在阿根廷西北部的Puna-Sierras Pampeanas过渡中，fiambal和Altohuasi山脉的基底主要由早寒武世变质岩(fiambal变质沉积杂岩；新名称)和花岗岩类(Loconte侵入杂岩；新名称)。变质沉积岩杂岩包括：1)Tatón单元（片麻岩、变质岩、闪长岩和糜棱岩）；2)拉古纳海拉达组（中低品位细粒变质砾岩，次生变质砾岩、板岩、千层岩、片岩、糜棱岩和大理岩）。两个单元的U-Pb锆石年代学结果相似，表明它们来自同一基底，可能属于变质作用和韧性剪切作用之前的连续地层堆。这些单元的主要年龄群在约0.95 - 1.10 Ga之间，次要年龄群在约1.15-1.25 Ga之间，其中约1.33 Ga为小高峰，古元古代-新太古代年龄较少。这与Tatón单元中发现的526±4 Ma的锆石变质过度生长以及区域对比表明，沉积发生在埃迪卡拉纪至早寒武纪，在与已灭绝的Clymene海洋相邻的混合碳酸盐-硅屑台地中。与其他地区的类似序列进行比较（岩性、sr同位素和碎屑锆石数据）表明，这些沉积物来自相同的源区，并且它们是一个共同沉积环境的一部分，即Difunta Correa盆地。主要烃源区为Laurentia的Grenville省、花岗流纹岩省和MARA地块。这个盆地——现在被古生代的变形肢解了——是沿克莱门尼洋边缘形成的众多盆地之一，克莱门尼洋位于阿根廷西北部、巴西南部、巴拉圭和Río德拉普拉塔克拉通。早寒武纪造山运动期间，该洋的闭合导致了fiambal变质杂岩的低至高变质作用。

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来源期刊

Precambrian Research 地学-地球科学综合

CiteScore

7.20

自引率

28.90%

发文量

325

审稿时长

12 months

期刊介绍： Precambrian Research publishes studies on all aspects of the early stages of the composition, structure and evolution of the Earth and its planetary neighbours. With a focus on process-oriented and comparative studies, it covers, but is not restricted to, subjects such as: (1) Chemical, biological, biochemical and cosmochemical evolution; the origin of life; the evolution of the oceans and atmosphere; the early fossil record; palaeobiology; (2) Geochronology and isotope and elemental geochemistry; (3) Precambrian mineral deposits; (4) Geophysical aspects of the early Earth and Precambrian terrains; (5) Nature, formation and evolution of the Precambrian lithosphere and mantle including magmatic, depositional, metamorphic and tectonic processes. In addition, the editors particularly welcome integrated process-oriented studies that involve a combination of the above fields and comparative studies that demonstrate the effect of Precambrian evolution on Phanerozoic earth system processes. Regional and localised studies of Precambrian phenomena are considered appropriate only when the detail and quality allow illustration of a wider process, or when significant gaps in basic knowledge of a particular area can be filled.