Correlation of gabbroic and diabasic rocks from Ellsworth Mountains, Hart Hills, and thiel Mountains, West Antarctica

Gabbroic stocks and/or diabasic sills crop out in the southern Heritage Range of the Ellsworth Moutains, in the Hart Hills 400 km southwest of the Ellsworth Mountains, and in the Thiel Mountains 200 km south of the Hart Hills. In the Ellsworth Mountains and Hart Hills these mafic igneous rocks have undergone pumpellyite‐actinolite and/or greenschist facies regional metamorphism. Relic clinopyroxene compositions, alteration‐resistant trace elements, rare earth element data, and the nature of intruded sedimentary host rocks suggest that (1) gabbroic stocks and diabasic dikes and sills in the southern Ellsworth Mountains were emplaced in a continental area undergoing extensional tectonism and are geochemically dissimilar to both the Ferrar Supergroup of the Transantarctic Mountains and the Hart Hills sill, (2) an unmetamorphosed diabase sill at Lewis Nunatak is correlative with the Ferrar Supergroup, and (3) the Hart Hills sill does not appear to have been emplaced in a withinplate setting, but no further resolution of its tectonic environment is possible. Although geochemical data from the Hart Hills and Lewis Nunatak sills are very similar, the Hart Hills body is not considered to be metamorphosed Ferrar Supergroup. The nearest possible correlatives of the Ellsworth Mountains mafic intrusive rocks are an extensive suite of basaltic and diabasic sills and dikes intrusive into the late Precambrian Patuxent Formation in the Neptune Range of the Pensacola Mountains.

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