Which geological processes will destroy plastic?

Question

The geological record at the end of the Anthropocene will undoubtedly contain large volumes of plastic. However, some geological processes will completely destroy plastic (e.g. magmatic or chemical processes). I assume that sedimentary rocks will contain plastic pellets at the least and that igneous rocks will not. Which geological processes that create metamorphic rock will be able to completely destroy plastic molecules?

Answer 1

If the earth gets hot enough, the oxygen in the rocks and soil will cause plastic to eventually carbonize (like turn into oil or coal like material) or even burn if there is enough Oxides near by providing oxygen for combustion. All plastics start with coal, petroleum or natural gas feedstocks, which originated from organic plastics like cellulose, starch and other biomaterials that came from living things in the first place.