posted on 2015-02-09, 14:12authored byI. Neill, A. C. Kerr, K. R. Chamberlain, A. K. Schmitt, F. Urbani, A. R. Hastie, J. L. Pindell, Tiffany L. Barry, I. L. Millar
Outcrops of volcanic–hypabyssal rocks in Trinidad document the opening of the proto-Caribbean seaway during
Jurassic–Cretaceous break-up of the Americas. The San Souci Group on the northern coast of Trinidad comprises
the San Souci Volcanic Formation (SSVF) and passive margin sediments of the ~130–125 Ma Toco Formation. The
Group was trapped at the leading edge of the Pacific-derived Caribbean Plate during the Cretaceous–Palaeogene,
colliding with the para-autochthonous margin of Trinidad during the Oligocene–Miocene. In-situ U–Pb ion probe
dating of micro-zircons from a mafic volcanic breccia reveal the SSVF crystallised at 135.0 ± 7.3 Ma. The age of the
SSVF is within error of the age of the Toco Formation. Assuming a conformable contact, geodynamic models
indicate a likely origin for the SSVF on the passive margin close to the northern tip of South America. Immobile
element and Nd–Hf radiogenic isotope signatures of the mafic rocks indicate the SSVF was formed by≪10% partial
melting of a heterogeneous spinel peridotite source with no subduction or continental lithospheric mantle
component. Felsic breccias within the SSVF are more enriched in incompatible elements, with isotope signatures
that are less radiogenic than the mafic rocks of the SSVF. The felsic rocks may be derived from re-melting of mafic
crust. Although geochemical comparisons are drawn here with proto-Caribbean igneous outcrops in Venezuela
and elsewhere in the Caribbean more work is needed to elucidate the development of the proto-Caribbean seaway
and its rifted margins. In particular, ion probe dating of micro-zircons may yield valuable insights into
magmatism and metamorphism in the Caribbean, and in altered basaltic terranes more generally
Funding
Open Access funded by Natural Environment Research Council
History
Citation
Tectonophysics , 2014, 626, pp. 170-185 (16)
Author affiliation
/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Geology