The scientist pointed out the magma on Dr. Williams' sketch.
Notice that the magma is not following the original channels.
Now, two magma areas were showing where only one had shown before.
The tunnel would have to be done before the magma started to move.
At any rate, it is somewhat above this discontinuity that magma is formed.
On the other hand, the magma could find weaknesses we haven't detected.
According to what we have, this is the shape of a magma front.
And the magma'll be thick, viscous stuff, like basalt on Terra.
If the initial composition of the magma is represented by a point between the two eutectic points, orthoclase will separate first.
They were not so much torn off and incorporated in the magma, as they were thoroughly injected and metamorphosed.