Petrological, geochemical and isotopic data of Neoproterozoic rock units from Uruguay and South Africa: Correlation of basement terranes across the South Atlantic
Petrological, geochemical and isotopic data of Neoproterozoic rock units from Uruguay and South Africa: Correlation of basement terranes across the South Atlantic
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DOI：
10.1016/j.gr.2019.10.012
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发表时间：
2020-04
影响因子：
6.1
通讯作者：
T. Will;S. Höhn;H. Frimmel;C. Gaucher;P. L. Roux;P. Macey
中科院分区：
文献类型：
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作者：
T. Will;S. Höhn;H. Frimmel;C. Gaucher;P. L. Roux;P. Macey
来自乌拉圭Cuchilla Dionisio（或埃斯特角）地体（CDT）和巴西南部Várzea do Capivarita杂岩（VCC）的长英质至中等火成岩被侵位于Tonian期，并在接近Cryogenian末期经历了高级变质作用。地质和地球化学数据表明，S型起源和形成在大陆板内设置回收的下地壳物质，最初从地幔中提取的古元古代。类似的托尼时代长英质火成岩出现在南非最西部和纳米比亚南部的Richtersveld火成杂岩以及Vredefontein和Rosh Pinah地层中，并与乌拉圭和巴西的假定同类岩石进行了对比。在非洲西南部的大部分未变质的长英质火成岩的地球化学和同位素数据意味着板内起源和形成的部分熔融或分离结晶的镁铁质岩石，从地幔中提取的元古代。来自南美洲和非洲西南部的所有这些Tonian火成岩的母岩熔体形成于卡拉哈里盆地西缘的非造山大陆环境中，并在与源区分离后被纳马夸省型基底侵位和/或污染。新的岩石学资料表明，CDT高级片麻岩的地温梯度为c. 20-25 °C/km，这意味着在今天南美洲东部边缘的活动大陆边缘，在低温纪晚期至埃迪卡拉纪早期，俯冲和洋盆闭合之后，发生了大陆碰撞构造。相关的缝合线可以通过CDT中的高级片麻岩和角闪岩相基性岩来追踪，并可能继续向北延伸至巴西南部的大阿罗约杂岩和VCC。
Felsic to intermediate igneous rocks from the Cuchilla Dionisio (or Punta del Este) Terrane (CDT) in Uruguay and the Várzea do Capivarita Complex (VCC) in southern Brazil were emplaced in the Tonian and experienced high-grade metamorphism towards the end of the Cryogenian. Geological and geochemical data indicate an S-type origin and formation in a continental within-plate setting by recycling of lower crustal material that was initially extracted from the mantle in the Palaeoproterozoic. Similar felsic igneous rocks of Tonian age occur in the Richtersveld Igneous Complex and the Vredefontein and Rosh Pinah formations in westernmost South Africa and southern Namibia and have been correlated with their supposed equivalents in Uruguay and Brazil. Geochemical and isotope data of the largely unmetamorphosed felsic igneous rocks in southwestern Africa imply a within-plate origin and formation by partial melting or fractional crystallization of mafic rocks that were extracted from the mantle in the Proterozoic. The parental melts of all of these Tonian igneous rocks from South America and southwestern Africa formed in an anorogenic continental setting at the western margin of the Kalahari Craton and were emplaced in, and/or contaminated by, Namaqua Province-type basement after separation from their source region. However, the source regions and the time of extractions thereof are different and, moreover, occurred at different palaeogeographical latitudes.New petrological data of CDT high-grade gneiss indicate a geothermal gradient of c. 20–25 °C/km, implying continental collisional tectonics following subduction and ocean basin closure at an active continental margin at the eastern edge of present-day South America in the late Cryogenian to early Ediacaran. The associated suture may be traced by the high-grade gneiss and amphibolite-facies mafic rocks in the CDT and probably continues northwards to the Arroio Grande Complex and the VCC in southern Brazil.