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| Titel |
Magmatic evolution and reconstruction of the Central American land-bridge since Late Cretaceous |
| VerfasserIn |
W. Wegner, G. Wörner, R. S. Harmon, B. Jicha |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250023811
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| Zusammenfassung |
| We document by major- and trace elements, selected 40Ar/39Ar dating, 143Nd/144Nd,
87Sr/86Sr, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb as well as δ18O isotopes on 310
samples from the Cordillera de Panama and the Peninsulas of Sona and Azuero the
magmatic evolution and oceanic plate interactions over the last 100 Ma in western
Panama.
A first phase of magmatism formed the oceanic basement of the Caribbean Large Igneous
Plateau (CLIP). These Basalts were erupted from 95 to 69 Ma (Hoernle et al. 2004). Flat
trace element patterns are - apart from some alteration effects - characteristic for the
intraplate Galapagos plume (head-) source. Younger accreted terranes with enriched patterns
were amalgamated between 70 and 20 Ma (CLIP-OIB). Nd and Pb isotopes from these
CLIP-OIBs also argue for an origin from the Galapagos hot spot (Hoernle et al.
2002).
The second major phase partly overlaps the first phase in time. Their arc trace element
patterns (depletion in Nb and Ta plus enrichment of the fluid mobile elements such as Ba, K,
Pb, and Sr) indicate the initiation of subduction at 71 to 69 Ma (CLIP-ARC) in the region of
Azuero and Sona Peninsulas. The EARLY-ARC comprises two major pulses from
68-60 Ma (Chagres Igneous Complex) and 50 to 40 Ma from the length of the
Cordillera de Panama. These low K tholeiites and andesites have large variations
in Nb, Ta implying that mantle sources region at this time were heterogeneous
and variable in incompatible elements prior to fluid enrichment. Their Nd isotopes
(-¥0.512636) are lowest in this region. Nd-, Sr- and Pb- isotopes shows the EARLY-ARC
as a distinct group with mantle sources that is not documented in older or later
magmas.
Andesites of the third phase (YOUNGER-ARC, 19-5 Ma) form discrete volcanic centers
across the Cordillera de Panama with progressive enrichment from varied tholeiites to more
uniform medium-K arc character. These come from a homogeneous and matured source as
Nb and Ta depletion is more uniform, only few samples show depleted patterns comparable
to the EARLY-ARC. Nd-, Sr- and Pb-isotopes are similar to the present Central American
Arc (CENTAM).
The youngest phase consists of isolated adakitic centers along the Cordillera de Panama
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