Abstract
Metabasites belonging to the Arquia Complex and outcropping along the Pijao-Genova strip (western edge of the Central Cordillera of the Colombian Andes) consist of chlorite schists, actinolite schists with and without garnet, amphibolites, garnet-amphibolites, eclogites and metabasalts. Some bodies of serpentinized peridotites are observed along with metabasites. Both rock types are confined to the tectonic block bordered by the Cauca-Almaguer and Silvia-Pijao fault systems and their satellite faults. Metabasites were affected by a regional metamorphism, reaching their peak of metamorphism at the amphibolite facies. The Rare Earth Elements (REEs) (normalized to the C1 chondrite) from the studied rocks show a Light REEs depletion and a flat or no-fractionated Heavy REEs patterns. The metabasites´ REEs patterns, along with their La/Sm ratio < 0.6 and positive Nb, Ta and Ti anomalies, may suggest their protoliths are MORBtype related. The lithologic association between metabasites, few metapelites and deformed ultramafic rocks suggest that the rocks of the Complex Arquia can represent remnants of an ophiolite sequence of N-MORB type series. The whole rock-garnet Lu-Hf geochronology from metabasites yield an age of 128.7±3.5 Ma. This age has been interpreted as the age at which these rocks reached the eclogite facies, which in turn coincides with the roll-back process of the subducted ocean lithosphere and the Quebradagrande magmatic arc formation. Keywords: Petrology; metabasites; Arquia Complex; Cordillera Central; Colombia.
Highlights
Las metabasitas del Complejo Arquía en la franja Pijao-Génova, borde occidental de la Cordillera Central de los Andes &RORPELDQRV FRQVLVWHQ HQ HVTXLVWRV FORUtWLFRV HVTXLVWRV DFWLQROtWLFRV FRQ \ VLQ JUDQDWH DQ¿EROLWDV DQ¿EROLWDV JUDQDWtIHUDV HFORJLWDV \ PHWDEDVDOWRV $OJXQRV FXHUSRV GH SHULGRWLWDV VHUSHQWLQL]DGDV DÀRUDQ D OR ODUJR GH IDOODV GHO VLVWHPD &DXFD $OPDJXHU \ 6LOYLD3LMDR DVt FRPR VXV IDOODV VDWpOLWHV /DV PHWDEDVLWDV IXHURQ DIHFWDGDV SRU XQ PHWDPRU¿VPR UHJLRQDO DOFDQ]DQGR VX SLFR PHWDPyU¿FR HQ IDFLHV DQ¿EROLWD /RV HOHPHQWRV GH WLHUUDV UDUDV (75V QRUPDOL]DGRV DO FRQGULWR C1) de las rocas estudiadas muestran un empobrecimiento en ETRs Ligeros y patrones planos a poco fraccionados de ETRs Pesados
These regions are the result of processes of accretion and amalgamation to the South American margin of Mesozoic rocks formed in ocean environments, such as island arcs, oceanic plateaus and mid-ocean ridges (Kerr et al, 1997; Moreno-Sánchez and Pardo-Trujillo, 2003; Pindell and Kennan, 2009; Cediel et al, 2003; Villagómez et al, 2011; Ruiz et al, 2012; Bustamante et al, 2011)
The limit of the continental and oceanic crust in Colombia has been previously discussed as the Cretaceous boundary in the western Colombia, which KDV EHHQ GH¿QHG E\ WKH &DXFD$OPDJXHU IDXOW V\VWHP +RZHYHU IXUWKHU HDVW SURWROLWKV RI RFHDQLF DI¿QLW\ for metabasites of the Arquía Complex and volcanic rocks of the Quebradagrande Complex (Ruiz et al, 2012; Villagómez et al, 2011; Rodríguez and Arango, 2013)
Summary
Las metabasitas del Complejo Arquía en la franja Pijao-Génova, borde occidental de la Cordillera Central de los Andes &RORPELDQRV FRQVLVWHQ HQ HVTXLVWRV FORUtWLFRV HVTXLVWRV DFWLQROtWLFRV FRQ \ VLQ JUDQDWH DQ¿EROLWDV DQ¿EROLWDV JUDQDWtIHUDV HFORJLWDV \ PHWDEDVDOWRV $OJXQRV FXHUSRV GH SHULGRWLWDV VHUSHQWLQL]DGDV DÀRUDQ D OR ODUJR GH IDOODV GHO VLVWHPD &DXFD $OPDJXHU \ 6LOYLD3LMDR DVt FRPR VXV IDOODV VDWpOLWHV /DV PHWDEDVLWDV IXHURQ DIHFWDGDV SRU XQ PHWDPRU¿VPR UHJLRQDO DOFDQ]DQGR VX SLFR PHWDPyU¿FR HQ IDFLHV DQ¿EROLWD /RV HOHPHQWRV GH WLHUUDV UDUDV (75V QRUPDOL]DGRV DO FRQGULWR C1) de las rocas estudiadas muestran un empobrecimiento en ETRs Ligeros y patrones planos a poco fraccionados de ETRs Pesados. Metabasites and associated rocks of the Arquía Complex in the study area are mainly represented by chlorite and actinolite to amphibole schists, the last of them with or without garnet porphyroblasts, with minor garnet-bearing or -absent amphibolites and subordinate amounts of serpentinized peridotites and metabasalts.
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