Zircon, monazite and titanite U-Pb geochronology revealing Orosirian metamorphic events within the Guiana Shield, Amazonian Craton

IF 3.2 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Precambrian Research Pub Date : 2025-03-27 DOI:10.1016/j.precamres.2025.107766

Matheus Scalabrin, Robert de Lima Muniz, Ticiano José Saraiva dos Santos

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Abstract

Petrography coupled with U-Pb geochronology of migmatites enables the observation of processes and mechanisms involved in continental crust generation and transformation during orogeny. This study focuses on high-grade rocks of four lithostratigraphic units in the Guiana Shield, Amazonian Craton: the Trairão Suite, the Cauarane Group, the Rio Urubu Suite, and the Serra da Prata Suite. Petrographical and geochronological studies of these units reveal that the Orosirian Akawai Orogeny took place from approximately 2.04 to 1.93 Ga. During these 110 million years two high-grade events occurred associated with partial melting and magmatism. Metamorphic event M₁ (2.02 – 1.99 Ga), represented by a grey diatexite of the Trairão Suite, is related to fluid-present partial melting under amphibolite facies conditions. The age of anatexis (2.02 Ma) was obtained for zircon from a dioritic metatexite enclave in the diatexite. The crystallization of the melt generated in this event occurred at 2.00 Ga, obtained for zircon from the grey diatexite. Hornblende-biotite metatexite (Rio Urubu Suite), garnet-sillimanite-K-feldspar metatexite (Cauarane Group), and clinopyroxene-hornblende-orthopyroxene gneiss (Serra da Prata Suite) record the second high-grade metamorphic event M₂ (1.97 – 1.93 Ga). The anatexis of the Cauarane Group occurred by biotite dehydration under high amphibolite to granulite facies conditions. The crystallization of the anatectic melt in the Cauarane Group occurred between ca. 1.96 Ga (metamorphic zircon rims) and 1944 ± 5 Ma (U-Pb monazite). The water-fluxed partial melting in the hornblende-biotite metatexite (Rio Urubu Suite) took place under amphibolite facies conditions, with the crystallization of the anatectic melt occurring at 1938 ± 11 Ma. Granulite facies metamorphism occurred in lenses of clinopyroxene-hornblende-orthopyroxene gneiss of the Serra da Prata Suite at 1949 ± 4 Ma (metamorphic zircon) contemporaneous with dry magma emplacement. Statherian reactivation along NE-SW-trending shear zone in the center of the Guiana Shield was identified in titanite in hornblende-biotite metatexite (Rio Urubu Suite), probably induced by the accretion of the Rio Negro Belt (1.86 – 1.72 Ga).

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锆石、独居石和钛矿U-Pb年代学揭示亚马逊克拉通圭亚那地盾内的奥陶纪变质事件

岩石学与混岩U-Pb年代学相结合，可以观察造山运动期间大陆地壳生成和转化的过程和机制。本文研究了亚马逊河克拉通圭亚那地盾4个岩石地层单元的高等级岩石：trair o套、Cauarane组、里约热内卢Urubu套和Serra da Prata套。这些单元的岩石学和年代学研究表明，奥陶纪阿卡瓦伊造山运动发生在约2.04 ~ 1.93 Ga。在这1.1亿年里，发生了两次与部分熔融和岩浆作用有关的高等级事件。变质事件M1 （2.02 ~ 1.99 Ga）与角闪岩相条件下的流体部分熔融有关，其代表为trair o套的灰色双辉长岩。对角岩中闪长质变质岩包体的锆石进行了深熔年龄测定（2.02 Ma）。在此事件中产生的熔体结晶发生在2.00 Ga，从灰色闪长岩中获得锆石。第二次高变质事件M2 （1.97 ~ 1.93 Ga）为角闪石-黑云母变质岩（里约热内卢Urubu套）、石榴石-硅长石-钾长石变质岩（Cauarane组）和斜辉石-角闪石-正辉石片麻岩（Serra da Prata套）。高角闪岩-麻粒岩相条件下的黑云母脱水形成了Cauarane群的深熔岩。Cauarane群中无晶熔体的结晶发生在约1.96 Ga（变质锆石边缘）和1944±5 Ma （U-Pb独居石）之间。角闪黑云母变质岩（里约热内卢Urubu套）的水溶部分熔融发生在角闪岩相条件下，熔净熔体的结晶发生在1938±11 Ma。麻粒岩相变质作用发生在1949±4 Ma（变质锆石）与干岩浆侵位同时期Serra da Prata套的斜辉石-角闪石-正辉石片麻岩透镜体中。在圭亚那盾中部沿ne - sw向剪切带的角闪黑云母变质岩（里约热内卢Urubu Suite）中的钛铁矿中发现了Statherian再活化，可能是由里约热内卢black Belt （1.86 - 1.72 Ga）的增生引起的。

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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.