These older rocks are metasedimentary rocks, which means they’re sedimentary rocks that have been changed by heat and pressure.
这些更古老的岩石是变质沉积岩，这意味着它们是经过热量和压力改变的沉积岩。
英语百科
Metasediment
（重定向自Metasedimentary）
In geology, metasediment is sediment or sedimentary rock that appears to have been altered by metamorphism. The overall composition of a metasediment can be used to identify the original sedimentary rock, even where they have been subject to high-grade metamorphism and intense deformation.