Armrest slot broken... (Picture inside) // Any recommended glue?

Hi,

See picture : https://imgur.com/a/xVQc0Ux

I bought a used Aeron Classic 5 years ago. I have no idea of the manufacturing date. I've been using it for all this time and am extremely happy with the purchase.

However, after a lot of usage, primarily leaning on the right armrest (and sometimes being a bit rough with it,) a piece of the armrest holding slot broke off, and the entire armrest fell off.

You can see from the picture that it's a fairly clean break. I figure that there should be some way to repair this.

1. Does anybody know what you call the material that the frame is made of?
2. Would there be any recommended way of repairing this? I was thinking some sort of super glue...
3. Any other suggestions?

The rest of the chair is in great condition and I would hate to have to throw the whole thing out. My back and sacrum thank me everyday for using this chair, but now, my elbow is crying murder.

Thank you for your suggestions!