The Richtersveld Igneous Complex, South Africa: U‐Pb Zircon and Geochemical Evidence for the Beginning of Neoproterozoic Continental Breakup
The Richtersveld Igneous Complex, South Africa: U‐Pb Zircon and Geochemical Evidence for the Beginning of Neoproterozoic Continental Breakup
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DOI：
10.1086/320795
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发表时间：
2001-07
期刊：
影响因子：
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通讯作者：
H. Frimmel;R. Zartman;Andreas Späth
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文献类型：
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作者：
H. Frimmel;R. Zartman;Andreas Späth
南非 1.03-1.06-Ga 纳马夸-纳塔尔变质带最西端的 Richtersveld 火成岩杂岩体 (RIC) 和相关岩石的新 U-Pb 锆石年龄和地球化学数据表明，该杂岩体与后纳马夸造山塌陷无关，而是在伸展应力场中地幔衍生的碱性岩浆作用的产物，该岩浆作用导致了到新元古代超大陆的分裂。花岗岩到正长岩熔体结晶的最古老年龄为 \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$833\pm 2$$ \end{document} Ma.地壳的持续变薄反映在波士顿石岩脉的侵入和相关的喷出阶段，其日期为 \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$801\pm 8$$ \end{document} Ma.这个火成岩省的岩浆活动沿着西南-东北线性趋势延伸约200公里，至少持续到 \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$771\pm 6$$ \end{document} Ma，这是现在裂痕开始的最佳约束。随后的裂谷沉积物沉积伴随着区域性广泛的基性岩脉和双峰式的、主要是长英质的火山活动，沿着发展中的裂谷盆地的生长断层，位于 \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$741\pm 6$$ \end{document} Ma.协和图上一致的较低截距年龄（意思是： \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$282\pm 28$$ \end{document} Ma) 建议抬升并可能暴露于地下水流，以响应更南边的海角褶皱带的晚古生代构造运动。 RIC 的成因与地幔柱上方的地壳变薄一致，该地幔柱在约 100 m.yr 的长时间内导致地幔岩浆添加到地壳中。与其他地方现有的地质年代学和岩石学/地球化学数据进行比较，人们猜测在超大陆古盘古大陆的中心是否存在从非洲东南部延伸到中国南部的超级地幔柱。
New U‐Pb zircon ages and geochemical data for felsic intrusive and extrusive rocks from the Richtersveld Igneous Complex (RIC) and related rocks in the westernmost part of the 1.03–1.06‐Ga Namaqua‐Natal metamorphic belt, South Africa, indicate that this complex is not related to post‐Namaqua orogenic collapse but is the product of mantle‐derived alkaline magmatism in an extensional stress field that led to the breakup of a Neoproterozoic supercontinent. The oldest age obtained for the crystallization of granitic to syenitic melts is \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$833\pm 2$$ \end{document} Ma. Continued thinning of the crust is reflected by the intrusion of bostonite dikes and a related extrusive phase dated at \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$801\pm 8$$ \end{document} Ma. Magmatism in this igneous province, which stretches for about 200 km along a southwest‐northeast linear trend, lasted at least until \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$771\pm 6$$ \end{document} Ma, which is now the best constraint on the beginning of rifting. Subsequent rift sediment deposition was accompanied by the emplacement of regionally extensive mafic dikes and bimodal, predominantly felsic volcanism along growth faults in the evolving rift basin at \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$741\pm 6$$ \end{document} Ma. Consistent lower intercept ages on concordia diagrams (mean: \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$282\pm 28$$ \end{document} Ma) suggest uplift and possible exposure to groundwater flow in response to late Paleozoic tectonism in the Cape Fold Belt farther south. The genesis of the RIC is in accordance with crustal thinning above a mantle plume that contributed to a mantle‐derived magma addition to the crust over a prolonged period of some 100 m.yr. Comparison with existing geochronological and petrological/geochemical data from elsewhere invites speculation as to the existence of a superplume stretching from southeastern Africa to South China in the heart of a supercontinent Palaeopangea.