{"title":"Late Tonian (c. 735 Ma) A-type granite magmatism on the passive margin of the São Francisco paleocontinent was coeval with outboard subduction","authors":"","doi":"10.1016/j.precamres.2024.107578","DOIUrl":null,"url":null,"abstract":"<div><div>Late Tonian (ca. 735 Ma) A-type granite magmatism accompanied the development of a rifted continental margin in the southwestern portion of the São Francisco paleocontinent. Zircon U-Pb and trace elements, whole-rock lithogeochemistry, and Nd-Sr isotopes enable assessment of the tectonic setting. The Araras Granite shows high silica content (between 73 and 76 %) and ferroan character. The Y + Nb and Yb + Ta parameters vary respectively between 73 to 212 ppm, and 8.3 to 19.1 ppm, and the 1000*Ga/Al ratio varies between 2.6 and 3.4. Zircon U-Pb data indicates a crystallization age of 736 ± 12 Ma. The εNd<sub>(t)</sub> is slightly negative (between −3.6 and −1.7), and the depleted mantle model ages (T<sub>DM</sub>) range between 1.26 and 1.56 Ga. Binary mixing models based on whole-rock element and isotope geochemistry indicate that the granite was formed by mixing melts derived from two sources: a lithospheric mantle component and Paleoproterozoic magmatic arc rocks from the regional basement. The Araras Granite is concluded to represent a late stage of extension-related intraplate magmatism between ca. 840 and 730 Ma, associated with the evolution of a rifted continental margin in the southwestern São Francisco paleocontinent. Intraplate magmatism was partially synchronous with documented magmatic pulses within long-lived island arc systems that surrounded the paleocontinent. Extensional episodes in the rifted passive margin may be related to slab-pull forces driven by the outboard subduction dynamics.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.2000,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Precambrian Research","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0301926824002912","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
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Abstract
Late Tonian (ca. 735 Ma) A-type granite magmatism accompanied the development of a rifted continental margin in the southwestern portion of the São Francisco paleocontinent. Zircon U-Pb and trace elements, whole-rock lithogeochemistry, and Nd-Sr isotopes enable assessment of the tectonic setting. The Araras Granite shows high silica content (between 73 and 76 %) and ferroan character. The Y + Nb and Yb + Ta parameters vary respectively between 73 to 212 ppm, and 8.3 to 19.1 ppm, and the 1000*Ga/Al ratio varies between 2.6 and 3.4. Zircon U-Pb data indicates a crystallization age of 736 ± 12 Ma. The εNd(t) is slightly negative (between −3.6 and −1.7), and the depleted mantle model ages (TDM) range between 1.26 and 1.56 Ga. Binary mixing models based on whole-rock element and isotope geochemistry indicate that the granite was formed by mixing melts derived from two sources: a lithospheric mantle component and Paleoproterozoic magmatic arc rocks from the regional basement. The Araras Granite is concluded to represent a late stage of extension-related intraplate magmatism between ca. 840 and 730 Ma, associated with the evolution of a rifted continental margin in the southwestern São Francisco paleocontinent. Intraplate magmatism was partially synchronous with documented magmatic pulses within long-lived island arc systems that surrounded the paleocontinent. Extensional episodes in the rifted passive margin may be related to slab-pull forces driven by the outboard subduction dynamics.
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.
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