• The Journal of the Petrological Society of Korea
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• v.27 no.2
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• pp.73-84
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• 2018

In the northern Cheongsong, there are occurred igneous intrusions: Cheongsong dike swarm, Jungtaesan laccolith, Galpyeongji stock. The swarm is composed of rhyolitic dikes that have developed many various spherulites. The dikes represent an geometrically radical pattern centering the Galpyeongji stock, but also geochemistry of the intrusions indicate the swarm source. Here we report the compositional data for 28 samples from the three intrusions. All of the intrusions belong to rhyolitic composition, but according to compositional correlation, there are considerable overlaps between intrusion compositions. In particular, the Cheongsong dike swarm is divided into several dike groups by rock color and shows compositional diversity, but the composition of the dikes generally overlap with compositions of other intrusions. The Jungtaesan laccolith is enriched in alkali, $K_2O$ and $Al_2O_3$ and depleted in $Fe_2O_3{^t}$, $TiO_2$ and REE compared to the Cheongsong dike swarm. In contrast, the Galpyeongji stock is narrow in composition range, and commonly has sharp compositional overlaps with the Cheongsong dike swarm. According to the compositional correlations, the stock is considered to be a source of the swarm and it is connected to an episode of volcanism.

• The Journal of the Petrological Society of Korea
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• v.24 no.2
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• pp.91-105
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• 2015

Jungtaesan and Galpyeongji intrusions in the northeastern Cheongsong occur as laccolith and stock which intrude Gasongdong Formation and Dogyedong Formation, respectively. Cheongsong dike swarm, intruding the Dogyedong Formation, is closely associated with this stock. The dike swarm is more radial to focus into Galpyeongji and its outline is oval. The dikes of the dike swarm are only rhyolite dikes with flow banded, spherulitic and rare stony structures, and represents a single intrusive phase of magma. It can be interpretated that orientation of the dikes is controlled by stress states. Therefore, the dikes display a radial pattern through occupying vertical joints that have been generally attributed to radial fractures formed during doming of the sedimentary rocks by the intrusion of the Galpyeongji stock. The dike pattern could sufficiently account for dike injections into these joints.