The Siuna terrane, defined here for the first time, is composed of slices of limey sedimentary strata, intermediate volcanic rock, serpentinite, and ultramafic cumulates, thrust together in the lower Upper Cretaceous. The terrane is intruded by intermediate dikes, plugs and plutons dated from 75 to 60 Ma, and is cut by Tertiary normal and strike-slip faults. The Siuna terrane volcanic and sedimentary strata probably formed in a Lower Cretaceous volcanic arc and associated back-arc or inter-arc basin. They host a Zn-Cu-Au volcanogenic massive sulfide occurrence and a Au-Cu skarn (the Siuna Mine), as well as several Au prospects. The serpentinite bodies host podiform chromite and disseminated Au occurrences. The Siuna terrane is distinct from the Chortis block to the north, and may have formed far from it. Evidence to date indicates that the low grade metamorphic "continental" basement of the Chortis block does not extend beneath the Siuna area. Isotopic evidence, as well as the presence of fragments of oceanic crust (serpentinite and ultramafic cumulates), indicate that the Siuna belt represents a fragment underlain by oceanic crust, appended to the Chortis block in the Upper Cretaceous; it may originally have been part of Greater Antilles Arc. The interpretation of the Siuna terrane presented here constitutes a significant departure from previous interpretations of the geology and tectonics history of the area.
|Venable, Margaret Ellen.
|Titley, Spencer, Page, Norman
|The University of Arizona.
|University of Arizona
|text, Dissertation-Reproduction (electronic)
|Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Page generated in 0.0022 seconds