Age and petrogenesis of the Sarmiento ophiolite complex of southern Chile

• Published in: Journal of South American Earth Sciences
• Main Authors: Stern, C. R., Mukasa, Samuel B., Fuenzalida P. , R.
• Other Authors: Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109-1063, USA, Department of Geological Sciences, University of Colorado, Boulder, CO 80309-0250, USA, Empresa Nacional del Petroleo, Casilla 11135, Santiago, Chile
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 1992
• Subjects: Geology and Earth Sciences; Science; South Georgia Island; Rocas; Sarmiento
• Online Access: http://hdl.handle.net/2027.42/29957; http://www.sciencedirect.com/science/article/B6VDS-48B0P51-23/2/16d4ffe896c5a08829cd6a8953ec3e85; https://doi.org/10.1016/0895-9811(92)90020-Y

Zircon fractions separated from fine-grained plagiogranites, interpreted to be cogenetic with the mafic rocks of the Sarmiento ophiolite complex in southern Chile, yield slightly to grossly discordant age patterns for which the lower concordia intercept U-Pb ages of 140.7 +/- 0.7 Ma (Lolos Fjord) and 137.1 +/- 0.6 Ma (Encuentro Fjord) are well constrained. These dates are interpreted as formation ages for the northern portion of the igneous floor of the Rocas Verdes basin, and they are younger than the age of 150 Ma determined for a more southern portion of the floor of this basin on South Georgia Island. Coarse-grained trondjemites within the gabbro units of the Sarmiento complex yield a lower concordia intercept U-Pb age of 147 +/- 10 Ma and a poorly defined upper intercept reflecting an inherited zircon component, possibly of Proterozoic age. These rocks are interpreted as remobilized fragments of country rocks entrapped within the essentially mantle-derived rocks of the ophiolite complex. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/29957/1/0000318.pdf