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Protolith Ages and Timing of Metasomatism Related to the Formation of Whiteschists at Mautia Hill, Tanzania: Implications for the Assembly of Gondwana

Huntly Cutten, Simon P. Johnson and Bert De Waele
The Journal of Geology
Vol. 114, No. 6 (November 2006), pp. 683-698
DOI: 10.1086/507614
Stable URL: http://www.jstor.org/stable/10.1086/507614
Page Count: 16
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Abstract

Abstract Mautia Hill, situated in the Mozambique Belt of East Africa, is a locality famous for its unique high‐pressure whiteschist mineral assemblages. The rocks are located in a complex regional tectonic setting that is critical to understanding the amalgamation history of Gondwana.The timing of the Pan‐African Gondwana collision in this region is still a topic of considerable debate, especially because the age of the Mautia high‐pressure metamorphism/metasomatism has yet to be established. We have extracted detrital zircons with extensive low‐U overgrowths and dated them using the U‐Pb SHRIMP method. Detrital zircon cores indicate that the sediments came from a region identical to the adjacent Tanzania Craton and adjacent Western Mozambique Belt. One detrital grain has a 207Pb/206Pb age of ca. 3.5 Ga and is the oldest dated zircon in the region. The zircon rims provide 207‐corrected 206Pb/238U and 208Pb/232Th weighted mean ages of \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 $549\pm 41$ \end{document} and \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 $535\pm 40$ \end{document} Ma, respectively, dating the age of collision between the Tanzania Craton and Madagascar‐India during the assembly of Gondwana. This new age indicates that collisional orogenesis in this part of the East African Orogen occurred in a similar time frame as in many other parts of Gondwana, including South America, southern Africa, India, Australia, and Antarctica, but later than a ∼640‐Ma age previously attributed to the collision in this area by some authors.

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