Strontium isotope geochemistry of late cretaceous granodiorites, Jamaica and Haiti, greater Antilles

• Published in: Earth and Planetary Science Letters
• Main Authors: Jones, Lois M., Walker, Raymond L., Kesler, Stephen E., Lewis, John F.
• Other Authors: Department of Geology, University of Michigan, Ann Arbor, MI 48109, U.S.A., Research and Development Department, Continental Oil Company, Ponca City, OK 74601, U.S.A., Oak Ridge National Laboratory, Oak Ridge, TN 37830, U.S.A., Department of Geology, George Washington University, Washington, DC 20052, U.S.A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 1979
• Subjects: Geology and Earth Sciences; Science; Terre-Neuve
• Online Access: https://hdl.handle.net/2027.42/23675; http://www.sciencedirect.com/science/article/B6V61-472BF8W-49/2/e0afc858c86d61ae46a89782c94aaec6; https://doi.org/10.1016/0012-821X(79)90160-2

Initial 87Sr/86Sr ratios have been determined for a representative suite of Upper Cretaceous granodiorites and associated rocks from the Above Rocks composite stock in central Jamaica and the Terre-Neuve pluton in northwestern Haiti. The average initial 87Sr/86Sr ratio for severn samples of the Terre-Neuve intrusion is 0.7036, with a range of 0.7026-0.7047. For two samples of the Above Rocks the initial ratios are 0.7033 and 0.7034. A third sample from this intrusive has an initial ratio of 0.7084, which is tenatively attributed to contamination. The initial 87Sr/86Sr ratios indicate that neither ancient sialic crust nor sediments carried down a Benioff zone can be the primary source of the granodioritic magma. K/Rb ratios for these rocks range from 178 to 247, which are much lower than the average values (>=1000) for tholeiitic basalts. It is concluded that the magmas originated primarily by melting of downthrust oceanic crust or adjacent mantle material. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/23675/1/0000644.pdf