marvel - Vulnerability of Adamantium and Vibranium

Vibranium and Adamantium are two of the rarest as well as near-indestructible materials in Marvel universe. Although they possess immense durability, both materials have some weaknesses too.

So, are either of these materials vulnerable to magic? I'm talking about the Comic book versions only.

Answer

First things first, Adamantium have slightly more complicated histories than just becoming a metal or finding a metal one day. The first "version" of Adamantium was Proto-Adamantium, which was accidentally discovered by Dr. Myron MacLain during the Second World War. It was then recreated in the 60s, but using a combinations of Resin as opposed to the Vibranium in the proto-Adamantium. More about Adamantium can be read at the bottom of this answer ¹

Through a metallurgic accident, MacLain created the indestructible Vibranium-steel compound that was used to create the shield used by the super-soldier Captain America. MacLain spent decades attempting to duplicate the process, and although unsuccessful, he instead created True Adamantium in the 1960s.
_{Adamantium - Marvel.com}

Vibranium has a simpler history, existing as a naturally occurring meteoric metal, which although rare exists naturally in the universe. Of which most of the Earth's Vibranium exists exclusively in Wakanda.

Now onto the question at hand. I found on example of magic breaking Captain America's shield, a iron-Vibranium alloy. It was destroyed by King Thor in Thor Vol. 2 #73. Thor, wielding the power of the Odinforce destroys the shield and kills Captain America, the timeline is however restored in #79. In the same comic just a few panels earlier, Thor melts Wolverine's Adamantium Beta with the Odin force.

_{(Click all images to embiggen)}

On another Earth, where the Adamantium is noted as being weaker, Valkyrie, under the power of Enchantress shatters Cap's shield with a magic Sword. (Ultimate Comics Vol. 1 New Ultimate #2)

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¹ This metallurgical accident was shaped into a disc and used to make Captain America's shield. As stated above, MacLain continued to attempt to recreate the "proto-Adamantium" however was unsuccessful. True Adamantium was instead discovered in the 1960s and would become the standard for Adamantium, however, while proto-Adamantium was formed with Steel, Vibranium and an unknown catalyst, True Adamantium is created through the mixing of certain chemical resins whose exact composition is a closely guarded government secret, and exists in a mould-able state for 8 minutes before hardening no matter the temperature. The only known substance able to pierce Adamantium is the compound known as Antarctic Vibranium, also called "anti-metal".

There also exists Secondary Adamantium, which is far weaker and can be broken by those with Superhuman strength.

Due to the prohibitive cost of Adamantium’s creation, many parties have resorted to the use of a somewhat weaker compound named Secondary Adamantium, which was once used to coat the sentient computer named F.A.U.S.T..
_{Adamantium - Marvel.com}

Adamantium Beta, which formed after True Adamantium merged with Wolverine's bones and was changed on the molecular level by his Healing Factor:

Wolverine's mutant healing factor allowed him to survive the process and induced a molecular change in the metal, transforming it into a wholly new metal, named Adamantium Beta that does not inhibit the biological processes of bone.
_ibid.

There also exists various variations for Adamantium for different Earths, such as Earth-1610 (Ultimate Earth), which isn't as strong as that of Earth-616, etc. Finally, as noted in the above link, the Soviet Union attempted to create Adamantium but weren't exactly successful:

Attempts by the former Solviet Union to reproduce the metal resulted in the creation of Carbonadium, a weaker yet far more malleable form that was used to create retractable coils wielded by the Russian super-soldier Omega Red.
_ibid.