Petrography of the Payandé stock and associated metamorphic rocks
DOI:
https://doi.org/10.32685/0120-1425/bolgeol17.1-3.1969.313Keywords:
Colombia, Payánde, Tolima Department , metamorphic facies, igneous bodies, Cretaceous
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Abstract
The present work aims to report on the quantitative petrography of the Payandé stock and associated metamorphic s.
The Jura-Triassic sediments and Precambrian metamorphic rocks of the area were intruded by the Payandé stock, a composite igneous body of late Jurassic or early Cretaceous age which produced thermal metamorphism in the overlying rocks.
Petrographic studies of the stock proved that two different intrusions form it: a small quartz diorite intrusion that was followed by a larger intrusion of granodiorite separated by a very small-time span. These two intrusions were followed by emplacement of pegmatite- aplite, andesite- dacite, and lamprophyre dykes.
The characteristics of the thermal metamorphism were studied using a combined system of petrographic, chemical and X-ray diffraction methods. As a result, two metamorphic facies, the hornblende hornfels facies and the Albite- epidote- hornfels facies, were found to be asymmetrically distributed around the stock.
On the geological map, the representative mineral associations were located, and at the same time, the isograds were plotted. An effort is made to give some idea about the temperature-pressure conditions that prevailed during metamorphism by taking individual minerals or mineral associations with special characteristics as a basis for analysis.
Based on the isograd distribution, the shape of the stock is interpreted, and it is concluded that the Payandé stock is an irregular thin sheet that dips to the west.
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