Final answer:
Cementation is the weak form of chemical alteration of sediment during the lithification process, involving precipitation of minerals like calcite, quartz, and pyrite in the sediment's pore spaces.
Step-by-step explanation:
A weak form of chemical alteration of sediment during the lithification process is called cementation. The lithification process involves the transformation of loose grains of sediment into rock through several steps including compaction and cementation.
Cementation occurs when minerals precipitate from groundwater moving through the pore spaces between sediment grains, acting as a glue that binds the particles together. Common cementing agents include calcite, quartz, and pyrite, which contribute to the formation of sedimentary rocks as the sediments are buried and compacted over time due to the accumulation of more material.