Ultramafic lavas associated with a melange zone of the Romeral fault system
DOI:
https://doi.org/10.32685/0120-1425/bolgeol30.1.1989.149Keywords:
Colombia, Timbío, Q. La Playa, ophiolitic sequence, microspinifex texture, Wehrlite
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Abstract
Systematic geological mapping in the Plancha 364 - Timbío area revealed the presence of ultramafic lavas, associated with a "Melange" zone of the Romeral Fault system, which serves as a boundary between oceanic and continental rocks. The outcrops are in La Playa creek, 6.5 km southwest of Timbío.
The lavas are part of an incomplete ophiolitic sequence of probable Lower Cretaceous age, composed of tuffites and basic breccias, pillow lavas, ultramafic, and sedimentary rocks. Allochthonous blocks of graphitic schists and quartzites are also found in this area. The ultramafic lavas are composed of serpentinized olivine and clinopyroxene, plagioclase, spinels (chromite), and altered glass. The color index is 90. The lava has a porphyritic texture with olivine phenocrysts, amygdules, and a microspinifex texture in the matrix. A wehrlite, which shows amygdules, is associated with the lava, and it is assumed that both rocks belong to the same flow. This new finding confirms once again that this rock type is found in post-Precambrian terrains and brings new insights into the thermal history of the earth.
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