Petrology, geochemistry, and tectonic setting of granitic rocks from the Ellsworth-Whitmore Mountains crustal block and Thiel Mountains, West Antarctica

Ellsworth‐Whitmore Mountains crustal block (EWM) is a belt of small mountain ranges, hills, and nunataks which trend northward 500 km from the Thiel Mountains of the Transantarctic range to the Ellsworth Mountains. Granitic rocks compose most of the Pirrit Hills, Nash Hills, and Whitmore Mountains, and all of Pagano Nunatak. Mount Woollard is a migmatized complex of biotite schist, amphibolite, pegmatite, and massive biotite granite. A rhyodacite stock crops out in the Martin Hills. The Mount Seelig hornblende‐bearing biotite granite of the Whitmore Mountains and the Mount Woollard biotite granite are metaluminous diopside‐normative granitoids. All other granitic rocks of the EWM are mildly peraluminous, corundum‐normative biotite (locally muscovite‐bearing) leucogranites. Previously published radiometric ages range from 163 to 190 Ma. Petrography, geochemistry, and isotopic data suggest that these rocks are largely highly differentiated leucocratic S‐type granites formed by anatexis of either metasedimentary rocks or more deeply seated, more mafic, plagioclase‐rich granitoids. In these aspects they strongly resemble granites developed in intracontinental terranes such as the Hercynian belt of Europe and in continental collision‐type settings such as the Bhutan and Nepalese Himalaya and the Seward Peninsula of western Alaska. We ascribe their origin to post‐tectonic emplacement in a neutral or extensional (rifted) within‐plate setting following deformation of the EWM. S‐type Cambro‐Ordovician granitic rocks and Precambrian quartz monzonite porphyries of the Thiel Mountains are geochemically similar to the EWM granites, but are correlative with the Granite Harbour Intrusive Series of the Transantarctic Mountains and the Wyatt Formation of the nearby La Gorce Mountains, respectively.

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