John T. Cheney

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Mountain, Skitchewaug and Big Staurolite nappes. Reactivation of A new, detailed tectonic model is presented for the Acadian orogenic this fabric during thrusting is recorded in some rocks of the Big belt of central New England (Vermont and New Hampshire) that Staurolite nappe by rotated garnets that grew during near-isothermal accounts for a wide range of(More)
Integrated studies by Keck Geology Consortium participants have generated many new insights into the Precambrian geology of the Tobacco Root Mountains. We have clarifi ed the tectonic setting and origin of two suites of metamorphic rocks: (1) a quartzofeldspathic gneiss complex with associated metasupracrustal rocks (the combined Indian Creek and(More)
Numerous rod-shaped calcite crystals occur in the blueschist to eclogite facies marbles of Syros, Greece. The rods show a shape-preferred orientation, and the long axes of the rods are oriented at a large angle to foliation. The crystals also have a crystallographic-preferred orientation: calcite c-axes are oriented parallel to the long axes of the rods.(More)
Textures and mineral assemblages of metamorphic rocks of the Tobacco Root Mountains are consistent with metamorphism of all rocks during the Big Sky orogeny (1.77 Ga) at relatively high pressure (P >1.0 GPa) followed by differential Cheney, J.T., Brady, J.B., Tierney, K.A., DeGraff, K.A., Mohlman, H.K., Frisch, J.D., Hatch, C.E., Steiner, M.L., Carmichael,(More)
U-Pb ages measured on zircons from the Tobacco Root Mountains and monazite from the Highland Mountains indicate that the northwestern Wyoming province experienced an episode of high-grade metamorphism at∼1.77 Ga. Leucosome emplaced in Archean gneisses from the Tobacco Root Mountains contains a distinctive population of zircons with an age of 1.77 Ga but(More)
The occurrence of glaucophane-bearing marbles on Syros is noteworthy because reports of marbles that contain glaucophane are rare among descriptions of high-pressure marbles. On Syros, the marbles are composed primarily of calcite with or without dolomite and quartz. Much of the calcite in these marbles shows oriented columnar structures that are(More)
Talc occurs as massive, economic deposits in upper amphibolite facies marbles of Archean age in southwestern Montana. Previous workers have demonstrated that the talc is a replacement of the marble that resulted from interaction with a large volume of fluid. δO (SMOW) values for dolomite and calcite range from 20-25‰ for the unaltered Archean marbles to as(More)
The island of Syros, Greece is part of the Attic-Cycladic blueschist belt, formed during Mesozoic Eurasia-Africa subduction. The rocks of Syros can be broadly divided into three tectono-stratigraphic units: (I) metamorphosed sedimentary and volcanic rocks (marble-schist sequence), (II) remnants of oceanic crust with fault-bounded packages of(More)